{"gene":"F2R","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":1991,"finding":"F2R (PAR1) encodes a seven-transmembrane G protein-coupled receptor activated by thrombin through a novel proteolytic mechanism: thrombin cleaves the receptor's N-terminal exodomain at R41, exposing a tethered peptide ligand (beginning with SFLLRN) that binds and activates the receptor in an intramolecular fashion. Uncleavable mutant receptors failed to respond to thrombin but retained responsiveness to the synthetic tethered-ligand peptide.","method":"Direct expression cloning in Xenopus oocytes; site-directed mutagenesis of thrombin cleavage site; synthetic peptide agonist assays; mRNA detection in human platelets and endothelial cells","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — original cloning with reconstitution in oocytes plus mutagenesis; foundational paper with 2832 citations","pmids":["1672265"],"is_preprint":false},{"year":1992,"finding":"Characterization of PAR1 as a functional thrombin receptor confirmed tethered-ligand activation mechanism and defined receptor properties on platelets and endothelial cells.","method":"Functional receptor characterization; peptide agonist studies","journal":"The Journal of Clinical Investigation","confidence":"High","confidence_rationale":"Tier 2 — functional characterization corroborating original cloning; 277 citations","pmids":["1310691"],"is_preprint":false},{"year":1994,"finding":"PAR1 (thrombin receptor) traffics differently from classical GPCRs: uncleaved receptors are stored in an intracellular compartment co-localizing with Golgi markers, and are protected from thrombin activation. Upon activation of cell-surface receptors, the intracellular pool translocates to the plasma membrane, replenishing surface receptors and restoring thrombin responsiveness—a novel resensitization mechanism distinct from internalization/recycling seen with beta2-adrenergic receptor. Activated (cleaved) receptors are targeted to lysosomes rather than recycled.","method":"Transfected Rat1 fibroblasts; subcellular fractionation; co-localization with Golgi markers; comparison with beta2-adrenergic receptor trafficking; agonist stimulation experiments","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — direct localization with functional consequence; reciprocal trafficking comparison; 190 citations","pmids":["7961693"],"is_preprint":false},{"year":1994,"finding":"PAR1 (thrombin receptor) couples to G proteins of the G12 and G13 family, as well as the Gq family, in human platelets. Both thrombin receptor and thromboxane A2 receptor activation led to increased GTP analog incorporation into alpha12 and alpha13 subunits.","method":"Subtype-specific antisera; photoreactive GTP analog ([alpha-32P]GTP azidoanilide) incorporation into immunoprecipitated G-protein alpha subunits from human platelet membranes; receptor agonist stimulation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — biochemical G-protein coupling assay with subtype-specific antibodies; 392 citations","pmids":["8290554"],"is_preprint":false},{"year":1999,"finding":"PAR1 and PAR4 together account for virtually all thrombin-mediated platelet activation in humans. Inhibition of PAR1 alone blocked platelet activation at low thrombin concentrations (1 nM) but only partially at high concentrations (30 nM); simultaneous inhibition of both PAR1 and PAR4 virtually ablated platelet secretion and aggregation even at 30 nM thrombin. PAR3 was not detected as functional in human platelets.","method":"PAR1/PAR4 mRNA and protein detection in human platelets; PAR1 antagonist, blocking antibody, and desensitization experiments; PAR4 blocking antibody; platelet secretion and aggregation assays at multiple thrombin concentrations","journal":"The Journal of Clinical Investigation","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal inhibition approaches; genetic and pharmacological; 683 citations","pmids":["10079109"],"is_preprint":false},{"year":1999,"finding":"Plasmin desensitizes PAR1 by cleaving the N-terminal exodomain at sites R70/K76/K82 (distal to the thrombin cleavage site R41), thereby truncating the tethered ligand and preventing thrombin-dependent Ca2+ signaling. Mutation of R70/K76/K82 to alanines eliminated plasmin truncation and desensitization, converting PAR1 into a plasmin-activated receptor. Plasmin also cleaves at R41, transiently activating PAR1. The desensitization is rate-equivalent to thrombin cleavage (similar kcat and KM).","method":"Soluble N-terminal exodomain (TR78) as model; kinetic analysis (kcat, KM) of protease cleavage; mass spectrometry identification of cleavage sites; site-directed mutagenesis (R70A/K76A/K82A); full-length receptor expressed in yeast and COS7 cells; Ca2+ signaling assays","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis and kinetic characterization; multiple receptor systems tested; 186 citations","pmids":["10194379"],"is_preprint":false},{"year":2001,"finding":"PAR1 overexpression in NIH3T3 cells causes oncogenic transformation through activation of RhoA-mediated signaling pathways. PAR1 transformation required receptor cleavage (uncleavable mutant was non-transforming), and was blocked by dominant negative RhoA, pertussis toxin (implicating Gαi), and the RGS domain of Lsc (implicating Gα12/Gα13). PAR1 cooperated synergistically with activated Raf-1 and activated serum response factor and NF-κB.","method":"cDNA expression library screen in NIH3T3 focus formation assay; uncleavable mutant receptor; co-expression with dominant negative RhoA; pertussis toxin treatment; RGS domain of Lsc co-expression; microinjection into PAE cells; SRF and NF-κB reporter assays","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal genetic and pharmacological approaches; 104 citations","pmids":["11360179"],"is_preprint":false},{"year":2002,"finding":"Activated protein C (APC) signals through PAR1 on endothelial cells in an EPCR-dependent manner. APC-mediated MAP kinase phosphorylation and gene induction (including selective induction of MCP-1) were inhibited by cleavage-blocking antibodies to PAR1, demonstrating that APC signals exclusively through PAR1 in endothelial cells. Gene profiling showed PAR1 signaling accounted for all APC-induced protective genes.","method":"Fibroblast overexpression system; human endothelial cell (HUVEC) stimulation; cleavage-blocking PAR1 antibodies; high-density microarray gene expression profiling; MAP kinase phosphorylation assays","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — cleavage-blocking antibody specificity plus microarray plus kinase assay; 704 citations","pmids":["12052963"],"is_preprint":false},{"year":2002,"finding":"PAR1 activation in cancer cells promotes cellular invasion through a RhoA/Rho kinase (ROCK)-dependent mechanism via Gα12/Gα13 signaling. In the presence of pertussis toxin (blocking Gαo/i), PAR1 induced invasion through Gα12/Gα13–RhoA/ROCK. Inhibition of endogenous RhoA redirected PAR1 signaling to a Gαq–PLC–Ca2+/CaM-MLCK pathway to promote invasion via a different route, revealing RhoA and RhoD as molecular switches controlling PAR1-dependent invasion signaling.","method":"Pharmacological inhibitors (pertussis toxin, C3 exoenzyme, dominant negative N19-RhoA); activated G26V-RhoD; NO/cGMP pathway activators; invasion assays in kidney and colonic epithelial cells","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological and genetic perturbations; single lab","pmids":["11919159"],"is_preprint":false},{"year":2003,"finding":"Activated protein C (APC) signals through PAR1 in endothelial cells via EPCR as coreceptor; APC activates PAR1 and PAR2 in fibroblast overexpression systems in an EPCR-dependent manner. In HUVECs, APC, PAR1, and PAR2 agonist peptides induce similar early response genes; MCP-1 was selectively induced by APC and PAR1 agonist but not PAR2 agonist, confirming PAR1-exclusive APC signaling.","method":"Fibroblast overexpression; HUVEC stimulation; cleavage-blocking PAR1 antibodies; microarray gene profiling; MAP kinase assays","journal":"Journal of Endotoxin Research","confidence":"Medium","confidence_rationale":"Tier 2 — confirms EPCR-PAR1 axis with antibody blockade and microarray; single lab","pmids":["14577849"],"is_preprint":false},{"year":2003,"finding":"PAR1 activation induces VEGF expression and angiogenesis through PKC, Src, and PI3K kinase pathways. Par1-expressing cells significantly enhanced angiogenesis in Matrigel plug and tumor models in vivo. Multiple VEGF splice forms were induced, and neutralizing anti-VEGF antibodies inhibited PAR1-induced endothelial cell proliferation.","method":"In vivo Matrigel plug assay; tetracycline-inducible Par1 expression; VEGF mRNA/protein measurement; specific kinase inhibitors (PKC, Src, PI3K); anti-VEGF neutralizing antibodies; endothelial tube alignment and proliferation assays","journal":"FASEB Journal","confidence":"Medium","confidence_rationale":"Tier 2 — multiple inhibitors plus in vivo model; single lab; 100 citations","pmids":["12554695"],"is_preprint":false},{"year":2004,"finding":"Regulated metalloproteinase-dependent shedding of the PAR1 N-terminal exodomain occurs in endothelial cells, mediated by ADAM17/TACE or a related metalloproteinase. Shedding is stimulated by phorbol ester (protein kinase C activation) or PAR1 agonist in trans, and is inhibited by TAPI-2, phenanthroline, and TIMP-3 but not TIMP-1 or -2. The shedding information resides within the exodomain, not the heptahelical segment. Regulated shedding reduced cell-surface PAR1 available for thrombin cleavage by half or more.","method":"PAR1 chimeric constructs (exodomain fused to unrelated transmembrane segment); phorbol ester and PAR1 agonist stimulation; metalloproteinase inhibitors (TAPI-2, phenanthroline, TIMP-1/2/3); domain-swap experiments in endothelial cells","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 2 — domain-swap constructs plus pharmacological inhibitors plus functional quantification; 37 citations","pmids":["14982936"],"is_preprint":false},{"year":2004,"finding":"PAR1-dependent sphingosine 1-phosphate receptor-1 (S1P1) cross-activation mediates activated protein C (APC)-induced endothelial barrier protection. APC enhances endothelial barrier integrity dependent on EPCR binding, PAR1 activation, and sphingosine kinase activity. siRNA knockdown of sphingosine kinase-1 or S1P receptor-1 blocked APC-protective signaling. Low concentrations of thrombin (~40 pM) or PAR1 agonist peptide similarly enhanced barrier function, revealing that PAR1 can mediate both barrier-disruptive and barrier-protective responses.","method":"Dual-chamber endothelial barrier system; siRNA knockdown of sphingosine kinase-1 and S1P1; EPCR-blocking antibodies; PAR1 agonist peptides; thrombin dose-response","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — siRNA knockdown of multiple pathway components plus pharmacological inhibition; 411 citations","pmids":["15626732"],"is_preprint":false},{"year":2005,"finding":"Matrix metalloproteinase-1 (MMP-1) is a non-thrombin protease agonist of PAR1 that promotes breast cancer invasion and tumorigenesis. MMP-1 (derived from stromal fibroblasts) cleaves PAR1 at the proper site to generate PAR1-dependent Ca2+ signals and cell migration. PAR1 expression is required and sufficient to promote growth and invasion of breast carcinoma cells in xenograft models.","method":"Xenograft mouse model; Ca2+ signaling assays; cell migration assays; PAR1 knockdown; MMP-1 cleavage site analysis; fibroblast conditioned medium experiments","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 — PAR1 cleavage by MMP-1 demonstrated biochemically plus in vivo xenograft plus Ca2+ signaling; 664 citations","pmids":["15707890"],"is_preprint":false},{"year":2005,"finding":"PAR1 activation on human late endothelial progenitor cells (EPCs) promotes proliferation, migration, and capillary-like structure formation through upregulation of SDF-1 and its receptor CXCR4, leading to autocrine stimulation. Anti-CXCR4, anti-SDF-1, and MEK inhibitor pretreatment abrogated PAR1-induced capillary formation.","method":"EPC expansion from CD34+ cord blood; SFLLRN peptide stimulation; real-time RT-PCR for SDF-1/CXCR4 mRNA; Boyden chamber migration assay; Matrigel capillary formation; blocking antibodies; MEK inhibitor","journal":"Arteriosclerosis, Thrombosis, and Vascular Biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal assays; blocking antibodies plus inhibitor; single lab","pmids":["16141404"],"is_preprint":false},{"year":2005,"finding":"PAR1 activation on endothelial progenitor cells (EPCs) induces angiopoietin-2 gene expression and protein synthesis, which mediates PAR1-induced EPC proliferation. Polyclonal blocking antibodies against angiopoietin-2 inhibited PAR1-mediated proliferative effect. PAR1 also enhanced EPC migration toward angiopoietin-1.","method":"SFLLRN peptide stimulation of EPCs; RT-PCR and protein assay for angiopoietin-1/2; polyclonal blocking antibodies; Boyden chamber migration assay","journal":"Journal of Thrombosis and Haemostasis","confidence":"Medium","confidence_rationale":"Tier 3 — blocking antibody approach; single lab; 52 citations","pmids":["16803467"],"is_preprint":false},{"year":2007,"finding":"The critical amino acids for alpha-thrombin's interaction with PAR1 at the thrombin cleavage site were identified by mutagenesis of the P4 (L38), P3 (D39), and P2 (P40) positions of the PAR1 exodomain. Mutation of P4 (L38A) or P2 (P40A) reduced kcat without changing KM; mutation of P3 (D39A) reduced both Km and kcat (maintaining kcat/Km). PAR1 exodomain acts as a non-competitive inhibitor of thrombin hydrolysis of chromogenic substrate, while PAR4 exodomain is a competitive inhibitor, revealing fundamentally different thrombin-binding mechanisms.","method":"Recombinant PAR1 and PAR4 exodomain production; kinetic analysis (kcat, KM, kcat/Km); alanine-scanning mutagenesis of P4/P3/P2 positions; inhibition kinetics with chromogenic substrate Sar-Pro-Arg-pNA","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with systematic mutagenesis and full kinetic characterization; 56 citations","pmids":["17595115"],"is_preprint":false},{"year":2007,"finding":"PAR1 'role reversal' in sepsis: PAR1 functions as a vascular-disruptive receptor early in sepsis but switches to vascular-protective during disease progression. Protective effects of PAR1 required transactivation of PAR2 signaling pathways. Cell-penetrating pepducin approach demonstrated that selective PAR1-PAR2 complex activation is beneficial in sepsis.","method":"Cell-penetrating pepducin approach in mouse sepsis model; cecal ligation and puncture model; PAR1 and PAR2 genetic and pharmacological manipulation","journal":"Nature Immunology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo model with pepducin approach plus PAR1-PAR2 cross-talk defined; single lab; 189 citations","pmids":["17965715"],"is_preprint":false},{"year":2007,"finding":"EPCR occupancy by protein C/APC switches PAR1 signaling specificity in endothelial cells from permeability-enhancing to barrier-protective by coupling PAR1 to pertussis toxin-sensitive Gi protein. EPCR is associated with caveolin-1 in lipid rafts; its occupancy by the Gla domain of protein C/APC dissociates EPCR from caveolin-1 and recruits PAR1 to a protective signaling pathway. When EPCR is bound, both thrombin and APC can elicit barrier-protective PAR1 signaling.","method":"Lipid raft isolation; co-immunoprecipitation of EPCR with caveolin-1; pertussis toxin blocking; Gla domain constructs; endothelial permeability assays; PAR1/EPCR signaling pathway analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — co-IP, lipid raft fractionation, pertussis toxin, functional permeability assay; 195 citations","pmids":["17823308"],"is_preprint":false},{"year":2008,"finding":"PAR1 signaling in dendritic cells couples coagulation and inflammation via a PAR1-S1P3 cross-talk mechanism. PAR1 activation sustains lethal inflammatory response in sepsis, and this is mediated downstream by the sphingosine 1-phosphate axis through S1P receptor 3 (S1P3). Loss of dendritic cell PAR1-S1P3 signaling sequesters dendritic cells into draining lymph nodes and attenuates IL-1β dissemination to lungs.","method":"Chemical and genetic probes for S1P3; PAR1-deficient mice; S1P3-deficient mice; endotoxin sepsis model; IL-1β measurement in lungs","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — combined genetic (knockout) and chemical probes in vivo; 236 citations","pmids":["18305483"],"is_preprint":false},{"year":2008,"finding":"PAR1 and PAR2 activation in endothelial cells induces tissue factor (TF) expression via mitochondrial reactive oxygen species (ROS) generated primarily from complex III. ERK1/2 and p38 MAPK activation is critical for mitochondrial ROS generation. Downstream of receptor activation, a PAR1-specific module involving NF-κB activation also induces TF.","method":"HUVEC stimulation with PAR1 and PAR2 agonist peptides; TF real-time RT-PCR and procoagulant activity measurement; ROS fluorometric assay; mitochondrial complex inhibitors; ERK1/2 and p38 inhibitors; NF-κB pathway analysis","journal":"Journal of Thrombosis and Haemostasis","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological dissection of ROS source and kinase pathways; single lab; 46 citations","pmids":["18983479"],"is_preprint":false},{"year":2009,"finding":"Platelet MMP-1 (matrix metalloprotease-1) activates PAR1 on the platelet surface at a distinct cryptic cleavage site different from thrombin's site, promoting aggregation. Fibrillar collagen converts surface-bound proMMP-1 zymogen to active MMP-1 on platelets. MMP-1 cleavage of PAR1 preferentially activates Rho-GTP pathways, cell shape change, motility, and MAPK signaling—distinct from thrombin-induced PAR1 signaling. Blockade of MMP1-PAR1 curtails thrombogenesis under arterial flow and inhibits thrombosis in vivo.","method":"Platelet MMP-1 activation by fibrillar collagen; PAR1 cleavage site mapping; Rho-GTP and MAPK signaling assays; arterial flow thrombogenesis model; in vivo thrombosis model; MMP1-PAR1 blockade","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical cleavage site mapping, signaling characterization, in vivo thrombosis model; 202 citations","pmids":["19379698"],"is_preprint":false},{"year":2009,"finding":"Zyxin, a LIM-domain-containing protein, binds to the C-terminal domain of PAR1 and mediates thrombin-induced actin cytoskeleton remodeling and SRE-dependent gene transcription in endothelial cells independently of G-protein (Gi, Gq, G12/13) activation. siRNA depletion of zyxin inhibited thrombin-induced stress fiber formation, SRE activation, and delayed endothelial barrier restoration. Zyxin recruits VASP to focal adhesions and along stress fibers upon thrombin stimulation.","method":"Co-immunoprecipitation of zyxin with PAR1 C-terminal domain; siRNA knockdown; stress fiber imaging; SRE reporter assay; RhoA activation assay; G-protein activation assays; barrier restoration assay","journal":"FASEB Journal","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus siRNA plus multiple functional readouts; single lab","pmids":["19690217"],"is_preprint":false},{"year":2010,"finding":"PAR1 induces beta-catenin stabilization independent of Wnt, Frizzled, and LRP5/6 co-receptors through a novel Gα13–Dishevelled (DVL) axis. PAR1-Gα13 association recruits DVL via its DIX domain. siRNA silencing of DVL abrogated PAR1-induced Matrigel invasion, Lef/Tcf transcription activity, and beta-catenin accumulation. Dominant negative Gα13 (but not Gα12) inhibited PAR1-induced beta-catenin stabilization. PAR1 also promotes binding of beta-arrestin-2 to DVL.","method":"Dominant negative Gα13/Gα12; siRNA-DVL silencing; siRNA-LRP5/6; Wnt antagonists SFRP2/SFRP5; Lef/Tcf transcription reporter assay; Matrigel invasion assay; immunohistochemistry of hPar1-transgenic mouse mammary tissues; co-immunoprecipitation","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — multiple genetic knockdowns plus dominant negatives plus in vivo transgenic; single lab","pmids":["20223821"],"is_preprint":false},{"year":2010,"finding":"Thrombin specificity toward PAR1 (vs. protein C and fibrinogen) is determined primarily by Trp215. Saturation mutagenesis of Trp215 produced constructs with kcat/Km values spanning five orders of magnitude. W215E is 10-fold more specific for protein C than fibrinogen and PAR1. Combining W215E with deletion of 9 residues in the autolysis loop produced a construct with significant activity only toward PAR1, demonstrating context-dependent re-engineering of thrombin specificity.","method":"Ala-scanning mutagenesis of 97 residues covering 53% of solvent-accessible surface; saturation mutagenesis of Trp215; kinetic characterization (kcat/Km) for fibrinogen, PAR1, and protein C hydrolysis","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic in vitro mutagenesis with full kinetic characterization; 37 citations","pmids":["20404340"],"is_preprint":false},{"year":2011,"finding":"PAR1 signaling desensitization in human platelets (via PAR1 homologous activation) is counteracted by PAR4 signaling. PAR1 desensitization involves decreased Ca2+ mobilization, reduced PKC signaling, and loss of dense granule secretion. Subthreshold PAR4 activation re-establishes PAR1-induced aggregation by reconstituting these signaling events via PKC-mediated ADP release from dense granules and fibrinogen from alpha-granules; G(αi) signaling is required.","method":"Isolated human platelets; specific PAR1 (SFLLRN) and PAR4 (AYPGKF) activating hexapeptides; Ca2+ mobilization measurement; PKC signaling assay; granule secretion assays; 2-MeS-ADP and epinephrine mimicry of Gαi/z; aggregometry","journal":"The Biochemical Journal","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological approaches; defined cross-talk mechanism; single lab","pmids":["21391917"],"is_preprint":false},{"year":2012,"finding":"PAR1 deficiency (F2r-/-) reduces intestinal vessel density in germ-free mice colonized with microbiota, and inhibition of thrombin (PAR1 activator) decreased TF cytoplasmic domain phosphorylation, placing thrombin-PAR1 signaling upstream of TF phosphorylation in a microbiota-induced extravascular TF-PAR1 signaling loop promoting intestinal vascular remodeling. PAR2-deficient mice showed no such decrease.","method":"PAR1-deficient (F2r-/-) and PAR2-deficient (F2rl1-/-) mice; germ-free colonization; anti-TF treatment; TF cytoplasmic domain phosphorylation measurement; hirudin (thrombin inhibitor) treatment; vascular density quantification; angiopoietin-1 expression","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — genetic knockout plus pharmacological inhibition; F2r-/- vs F2rl1-/- comparison; 215 citations","pmids":["22407318"],"is_preprint":false},{"year":2012,"finding":"MMP-1 and MMP-13 cleave the N-terminal exodomain of PAR1 at noncanonical sites (different from the thrombin cleavage site R41), generating distinct tethered ligands that activate different G-protein signaling pathways—termed biased agonism—producing distinct functional cellular outputs compared to thrombin-activated PAR1.","method":"PAR1 cleavage site mapping; Ca2+ signaling; G-protein pathway activation assays; comparison of canonical (thrombin) vs. noncanonical (MMP-1, MMP-13) cleavage products","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic review consolidating primary data on MMP cleavage sites; builds on primary data in PMID 19379698 and additional MMP-13 studies; 147 citations","pmids":["23086754"],"is_preprint":false},{"year":2012,"finding":"High-resolution (2.2 Å) crystal structure of human PAR1 bound to vorapaxar reveals an unusual, superficial binding pocket with little solvent exposure—distinct from deep, solvent-exposed pockets of other peptide-activated GPCRs. Vorapaxar binding explains near-irreversible inhibition of receptor activation by the tethered ligand. The structure defines the molecular basis for PAR1 antagonism.","method":"X-ray crystallography at 2.2 Å resolution; PAR1 bound to vorapaxar antagonist","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure; 370 citations","pmids":["23222541"],"is_preprint":false},{"year":2013,"finding":"Kallikrein 6 (Klk6) signals through PAR1 (and PAR2) to promote neuron injury and exacerbate glutamate neurotoxicity via ERK1/2 signaling in a phosphoinositide 3-kinase and MEK-dependent fashion. Lipopeptide inhibitors of PAR1 or PAR2, and PAR1 genetic deletion, each reduced Klk6-ERK1/2 activation. PAR1 genetic deletion blocked thrombin-mediated cerebellar neurotoxicity and reduced neurotoxic effects of Klk6.","method":"Cerebellar granule neurons and NSC34 motoneurons; recombinant Klk6; PAR1/PAR2 lipopeptide inhibitors; PAR1 genetic deletion mice; ERK1/2 phosphorylation; PI3K and MEK inhibitors; LDH release; Bim signaling; PARP cleavage","journal":"Journal of Neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockout plus pharmacological inhibitors; multiple cell systems; single lab","pmids":["23647384"],"is_preprint":false},{"year":2013,"finding":"Kallikrein 6 (KLK6) activates PAR1 to mediate loss of oligodendrocyte processes and impede oligodendrocyte progenitor cell morphological differentiation. PAR1-activating peptides and thrombin produce comparable oligodendrogliopathy. KLK6 suppresses proteolipid protein (PLP) RNA expression through PAR1-mediated Erk1/2 signaling. In vivo microinjection of PAR1 agonists into dorsal column white matter promoted vacuolating myelopathy and loss of MBP and CC-1+ oligodendrocytes in PAR1+/+ but not PAR1-/- mice.","method":"Primary oligodendrocyte cultures from WT and PAR1-deficient mice; Oli-neu cell line; Klk6, thrombin, and PAR1-AP stimulation; PAR1 genetic deletion; Erk1/2 signaling assay; PLP RNA quantification; in vivo microinjection; MBP and CC-1 immunostaining","journal":"Glia","confidence":"High","confidence_rationale":"Tier 2 — in vitro (PAR1 KO cells) plus in vivo (PAR1 KO mice) with histological readouts; 53 citations","pmids":["23832758"],"is_preprint":false},{"year":2013,"finding":"PAR1 and PAR3 cooperate to drive thrombin (FIIa)-induced epithelial-mesenchymal transition (EMT) in alveolar epithelial cells. Single knockdown of PAR1, PAR3, or PAR4 had no major impact on FIIa-induced EMT, but simultaneous depletion of PAR1 and PAR3 almost completely inhibited EMT. PAR1 and PAR3 co-localize within alveolar type II cells on the plasma membrane.","method":"siRNA knockdown (single and combined) of PAR1, PAR3, PAR4; thrombin stimulation; EMT markers (morphological, epithelial/mesenchymal protein expression, functional changes); co-localization immunostaining","journal":"Thrombosis and Haemostasis","confidence":"Medium","confidence_rationale":"Tier 2 — systematic siRNA knockdown combinations; co-localization; single lab","pmids":["23739922"],"is_preprint":false},{"year":2015,"finding":"PAR1 induces a metastatic, hormone-refractory breast cancer phenotype through upregulation of HMGA2. Functionally active PAR1 (but not non-signaling mutant PAR1) in MCF-7 cells induced epithelial-mesenchymal transition, vimentin upregulation, E-cadherin and estrogen receptor downregulation, and lung metastasis in mice. HMGA2 was identified as a key mediator of PAR1-induced invasion, and inhibition of PAR1 signaling suppressed HMGA2-driven invasion.","method":"Ectopic PAR1 expression in MCF-7 cells; non-signaling PAR1 mutant; in vivo lung metastasis model; EMT marker analysis; HMGA2 expression analysis; PAR1 signaling inhibition; spheroid formation assay","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — mutant receptor comparison plus in vivo metastasis model; single lab","pmids":["26165842"],"is_preprint":false},{"year":2015,"finding":"PAR1 and PAR2 contain pleckstrin homology (PH) domain-binding motifs that mediate association with Akt/PKB, Etk/Bmx, and Vav3 via their PH domains. PAR1 and PAR2 bind with priority to Etk/Bmx. A point mutation in PAR1 (hPar1-7A, unable to bind PH domain) reduced mammary tumors and trophoblast invasion in vivo, demonstrating physiological significance of PH-domain-binding motifs.","method":"Co-immunoprecipitation of PH-domain proteins with PAR1/PAR2; PAR2 point mutants (H349A, R352A); PAR1 hPar1-7A mutant; in vivo mammary tumor model; trophoblast invasion assay","journal":"Nature Communications","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus mutagenesis plus in vivo tumor model; single lab","pmids":["26600192"],"is_preprint":false},{"year":2017,"finding":"PAR1 activation in astrocytes induces rapid structural reorganization of the neuropil surrounding glutamatergic synapses, associated with faster clearance of synaptically-released glutamate from the extracellular space. This leads to short- and long-term changes in excitatory synaptic transmission in the mouse hippocampus, identifying PAR1 as a regulator of glutamatergic signaling.","method":"Mouse hippocampal preparations; PAR1 activation; 3D Monte Carlo reaction-diffusion simulations; axial scanning transmission electron microscopy (STEM) tomography; glutamate uptake assays; electrophysiology","journal":"Scientific Reports","confidence":"Medium","confidence_rationale":"Tier 2 — structural imaging plus functional electrophysiology plus computational modeling; single lab","pmids":["28256580"],"is_preprint":false},{"year":2018,"finding":"FVIIa binding to EPCR elicits anti-inflammatory signaling via PAR1 and β-arrestin-1 in endothelial cells. Inhibition of EPCR or PAR1 (by antibodies or siRNA) abolished FVIIa-induced suppression of adhesion molecules and IL-6. β-arrestin-1 silencing blocked FVIIa's anti-inflammatory effect. Mechanistically, FVIIa-EPCR-PAR1 signaling inhibited ERK1/2, p38 MAPK, JNK, NF-κB, and C-Jun activation by impairing TRAF2 recruitment to the TNF receptor 1 signaling complex.","method":"Endothelial cell stimulation with FVIIa; PAR1/EPCR siRNA and blocking antibodies; β-arrestin-1 siRNA; cytokine expression; adhesion molecule expression; kinase activation assays (ERK1/2, p38, JNK, NF-κB); TRAF2 co-immunoprecipitation; in vivo LPS model in WT, EPCR-overexpressing, and EPCR-deficient mice","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — siRNA knockdowns of multiple components plus in vivo genetic models plus Co-IP mechanism; 50 citations","pmids":["29669778"],"is_preprint":false},{"year":2019,"finding":"Thrombin-PAR1 signaling in pancreatic ductal adenocarcinoma (PDAC) tumor cells promotes tumor growth through suppression of antitumor CD8+ T cell immunity. PAR1-deleted KPC cells failed to form tumors in immune-competent mice but showed robust growth in immune-compromised NSG mice. CD8 T cell depletion rescued tumor growth of PAR1-KO cells in competent mice. Tumor cell TF and circulating prothrombin activate PAR1 to mediate immune evasion.","method":"PAR1-deleted KPC cell lines (CRISPR/KO); allograft studies; immune-competent vs. NSG mice; CD8/CD4/NK cell depletion; TF/prothrombin depletion (ASO); expression profiling of immune regulation pathways","journal":"Cancer Research","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with rescue, immune cell depletion in vivo, multiple orthogonal approaches; 68 citations","pmids":["31048498"],"is_preprint":false},{"year":2019,"finding":"HIV-1 Tat induces expression of MMP-3 and MMP-13 in astrocytes, which then activate PAR1 to stimulate release of CCL2 (a chemokine promoting CNS entry of HIV-infected monocytes). Both genetic knockout and pharmacological inhibition of PAR1 reduced Tat/MMP-induced CCL2 release from astrocytes.","method":"Astrocyte cultures; HIV-1 Tat exposure; MMP-3 and MMP-13 expression; PAR1 genetic knockout and pharmacological inhibition; CCL2 ELISA; post-mortem HIV brain tissue correlation analysis","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO plus pharmacological inhibition plus human tissue validation; single lab","pmids":["31124192"],"is_preprint":false},{"year":2020,"finding":"BMX kinase represses thrombin-PAR1-mediated endothelial permeability by directly phosphorylating PAR1 and promoting its internalization and deactivation. BMX loss increased thrombin-mediated endothelial permeability 2-3 fold. Pretreatment with PAR1 antagonist SCH79797 rescued BMX-loss-mediated endothelial permeability and pulmonary leakage in early sepsis.","method":"BMX-KO mice; cecal ligation and puncture sepsis model; electric cell-substrate impedance sensing (transendothelial electrical resistance); modified Miles assay (vascular leakage); biochemical analysis of BMX-PAR1 phosphorylation; PAR1 internalization assays; PAR1 antagonist pretreatment","journal":"Circulation Research","confidence":"High","confidence_rationale":"Tier 2 — direct phosphorylation demonstrated biochemically; KO mice with PAR1 antagonist rescue; in vivo and in vitro concordant; 44 citations","pmids":["31910739"],"is_preprint":false},{"year":2020,"finding":"F2R (PAR1) negatively regulates osteoclastogenesis by inhibiting both the Akt and NF-κB signaling pathways in response to RANKL stimulation. F2r knockdown increased osteoclast activity, number, size, bone resorption, F-actin ring formation, and osteoclast marker gene expression with significantly increased pAkt levels and enhanced phosphorylation of p65 and IKBα. F2r overexpression blocked osteoclast formation, maturation, and acidification.","method":"sh-F2r lentivirus knockdown and pLX304-F2r overexpression in mouse bone marrow cells; RANKL-induced osteoclastogenesis; pAkt Western blot; p65 and IKBα phosphorylation; osteoclast activity assays; F-actin ring staining; bone resorption pit assay","journal":"International Journal of Biological Sciences","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function and gain-of-function with signaling pathway analysis; single lab","pmids":["32226307"],"is_preprint":false},{"year":2022,"finding":"GZMA secreted by cytotoxic T cells interacts with F2R (PAR1) expressed on hepatocellular carcinoma tumor cells via the LDPRSFLL motif at the N-terminus of F2R, activating the JAK2/STAT1 signaling pathway to promote tumor cell apoptosis and T cell-mediated killing. This interaction was demonstrated both in vivo and in vitro.","method":"Single-cell sequencing; co-culture in vitro; in vivo mouse tumor model; GZMA-F2R interaction studies; JAK2/STAT1 pathway activation assays; N-terminus LDPRSFLL motif analysis; apoptosis assays","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo validation with pathway mechanism; single lab; 32 citations","pmids":["35256589"],"is_preprint":false},{"year":2022,"finding":"Platelet-derived MMP-2 triggers endothelial PAR1 to initiate atherosclerosis via p38MAPK signaling and expression of adhesion molecules. Double knockout mice lacking LDLR and blood cell MMP-2 developed significantly less femoral intima thickening and aortic atherosclerotic lesions. Transfusion of activated WT but not MMP-2-/- platelets enhanced atherosclerotic lesions in LDLR-/- mice.","method":"Double knockout mice (LDLR-/-/blood cell MMP-2-/-); platelet transfusion experiments; photochemical arterial injury model; atherogenic diet; en face aortic lesion quantification; in vitro co-incubation studies (platelets, monocytes/macrophages, endothelial cells); p38MAPK signaling assays","journal":"European Heart Journal","confidence":"High","confidence_rationale":"Tier 2 — genetic double KO plus bone marrow transplant/transfusion approach; in vivo plus mechanistic in vitro; 48 citations","pmids":["34529782"],"is_preprint":false},{"year":2023,"finding":"Senescent hepatocytes upregulate the THBD-PAR1 signaling axis to remain viable ('undead'), and this promotes fibrogenic factor expression (including hedgehog ligands) that drives maladaptive liver repair in NASH. Inducing hepatocyte senescence upregulates THBD-PAR1 in hepatocytes. Inhibiting PAR1 with vorapaxar reduces the burden of senescent cells, limits HSC reprogramming, and improves NASH and fibrosis despite ongoing lipotoxic stress.","method":"Viral p16 overexpression to induce hepatocyte senescence; conditioned medium HSC reprogramming; vorapaxar treatment in NASH mouse models (genetic obesity and Western diet/CCl4); NAFLD liver biopsy analysis; transcriptomics of senescent hepatocytes; hedgehog ligand expression","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo NASH models plus mechanistic hepatocyte senescence studies; single lab; 25 citations","pmids":["37036206"],"is_preprint":false},{"year":2023,"finding":"Parmodulins are small-molecule allosteric modulators that bind PAR1 intracellularly, inhibiting coagulation and platelet activation while maintaining cytoprotective endothelial signaling typically provoked by APC via PAR1. Structural analysis reveals parmodulins interact with the intracellular surface of PAR1, distinct from orthosteric antagonist binding.","method":"Review consolidating primary mechanistic data; structural interaction modeling comparing parmodulin binding to other intracellular allosteric GPCR modulators; preclinical pharmacological studies","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 — mechanistic review with structural modeling; summarizes published primary data","pmids":["36952648"],"is_preprint":false}],"current_model":"F2R (PAR1) is a seven-transmembrane GPCR activated by a unique proteolytic mechanism in which thrombin (or other proteases including plasmin, MMP-1, MMP-13, KLK6) cleaves the N-terminal exodomain to expose a tethered ligand that self-activates the receptor; the receptor couples to Gq, Gi, and G12/13 to mediate platelet activation, endothelial barrier regulation (both disruptive and protective depending on context), inflammation, angiogenesis, and tumor invasion, with signaling specificity modulated by the identity of the activating protease (biased agonism), co-receptor occupancy (EPCR switching PAR1 to Gi/barrier-protective signaling), post-activation phosphorylation by BMX promoting internalization, metalloproteinase-dependent exodomain shedding, and cross-talk with PAR2, S1P receptors, and intracellular effectors including zyxin, HMGA2, and the Gα13–DVL–β-catenin axis."},"narrative":{"teleology":[{"year":1991,"claim":"Identification of PAR1 as the first protease-activated receptor established a fundamentally new GPCR activation paradigm—irreversible proteolytic unmasking of a tethered ligand—resolving how thrombin could signal through a cell-surface receptor.","evidence":"Expression cloning in Xenopus oocytes with site-directed mutagenesis of the thrombin cleavage site and synthetic peptide agonist validation","pmids":["1672265"],"confidence":"High","gaps":["Downstream G-protein coupling partners not yet identified","Mechanism of receptor resensitization after irreversible cleavage unknown","Whether other proteases could activate PAR1 not addressed"]},{"year":1994,"claim":"Defining PAR1's G-protein partners (Gq, G12, G13) and its unconventional trafficking—lysosomal degradation of cleaved receptors plus mobilization of a Golgi-stored reserve pool—explained how cells restore thrombin responsiveness despite irreversible receptor activation.","evidence":"Subtype-specific G-protein coupling assays in platelets; subcellular fractionation and Golgi co-localization in transfected fibroblasts","pmids":["8290554","7961693"],"confidence":"High","gaps":["Molecular machinery controlling reserve pool translocation undefined","Relative contributions of Gq vs G12/13 to specific platelet responses not dissected"]},{"year":1999,"claim":"Establishing that PAR1 and PAR4 together account for virtually all thrombin-mediated human platelet activation, and that plasmin can both transiently activate and dominantly desensitize PAR1 by cleaving distal to Arg41, revealed protease-specific regulation of receptor availability.","evidence":"Orthogonal PAR1/PAR4 blocking strategies in human platelet aggregation; kinetic and mutagenesis analysis of plasmin cleavage sites on PAR1 exodomain","pmids":["10079109","10194379"],"confidence":"High","gaps":["Whether plasmin-PAR1 desensitization is physiologically relevant in vivo not demonstrated","Structural basis for differential thrombin vs plasmin exodomain recognition unknown"]},{"year":2002,"claim":"Discovery that activated protein C signals through PAR1 in an EPCR-dependent manner to elicit cytoprotective endothelial responses reframed PAR1 as a context-dependent signaling hub whose output depends on co-receptor occupancy, not just protease identity.","evidence":"Cleavage-blocking PAR1 antibodies abolished APC-induced MAP kinase activation and gene induction in HUVECs; microarray profiling","pmids":["12052963"],"confidence":"High","gaps":["Mechanism by which EPCR binding switches PAR1 G-protein coupling not defined","Whether APC cleaves PAR1 at a different site than thrombin not resolved"]},{"year":2004,"claim":"Identification of ADAM17-mediated PAR1 exodomain shedding as a regulated mechanism to limit surface receptor availability, and demonstration that EPCR-PAR1 barrier protection operates through sphingosine kinase-1 and S1P1, defined two new layers of PAR1 signal regulation.","evidence":"Metalloproteinase inhibitor panel and domain-swap constructs in endothelial cells; siRNA knockdown of SphK1 and S1P1 in dual-chamber barrier assays","pmids":["14982936","15626732"],"confidence":"High","gaps":["Identity of physiological stimuli for ADAM17-PAR1 shedding in vivo unclear","Whether S1P1 cross-activation occurs in non-endothelial PAR1-expressing cells untested"]},{"year":2005,"claim":"MMP-1 was identified as a non-thrombin protease agonist of PAR1 that promotes breast cancer invasion in vivo, demonstrating that the tumor microenvironment co-opts PAR1's tethered-ligand mechanism for malignant progression.","evidence":"MMP-1 cleavage site mapping; Ca²⁺ signaling; PAR1-dependent xenograft tumor growth and invasion","pmids":["15707890"],"confidence":"High","gaps":["Whether MMP-1 generates the same or distinct tethered ligand as thrombin not fully resolved","Relative contribution of stromal vs autocrine MMP-1 in human tumors unknown"]},{"year":2007,"claim":"Mechanistic resolution of how EPCR occupancy redirects PAR1 signaling: protein C/APC Gla domain binding dissociates EPCR from caveolin-1 in lipid rafts, switching PAR1 coupling from Gq/G12/13 to pertussis toxin-sensitive Gi, explaining the paradox of barrier-protective versus barrier-disruptive PAR1 signaling.","evidence":"Lipid raft isolation, EPCR-caveolin-1 co-immunoprecipitation, pertussis toxin blockade, and functional permeability assays in endothelial cells","pmids":["17823308"],"confidence":"High","gaps":["Structural basis of EPCR-PAR1 physical interaction not defined at atomic level","Whether lipid raft relocation is necessary or sufficient for G-protein switch untested"]},{"year":2009,"claim":"Demonstration that platelet MMP-1 cleaves PAR1 at a cryptic site distinct from thrombin's, preferentially activating RhoA-GTP and MAPK rather than canonical Ca²⁺ signaling, established the concept of protease-specific biased agonism at PAR1 with distinct thrombotic consequences.","evidence":"Cleavage site mapping, Rho-GTP signaling, in vivo thrombosis model with MMP1-PAR1 blockade; zyxin co-IP with PAR1 C-terminus and siRNA-mediated dissection of G-protein-independent cytoskeletal signaling","pmids":["19379698","19690217"],"confidence":"High","gaps":["Full repertoire of biased signaling outputs from different protease-generated tethered ligands not catalogued","Structural basis of biased coupling at the receptor level unknown"]},{"year":2010,"claim":"PAR1 was found to activate β-catenin stabilization through a Wnt-independent Gα13–Dishevelled axis, expanding its oncogenic repertoire beyond RhoA to include transcriptional reprogramming via Lef/Tcf targets.","evidence":"siRNA-DVL silencing, dominant negative Gα13, Lef/Tcf reporter, Matrigel invasion, and PAR1-transgenic mouse mammary tissue","pmids":["20223821"],"confidence":"Medium","gaps":["Whether Gα13-DVL axis operates in non-tumor contexts untested","Direct physical contacts between Gα13 and DVL not structurally resolved","Findings from a single lab"]},{"year":2012,"claim":"The 2.2 Å crystal structure of PAR1 bound to vorapaxar revealed an unusually shallow, solvent-occluded orthosteric pocket, explaining the near-irreversible antagonism by vorapaxar and providing an atomic framework for understanding tethered-ligand docking.","evidence":"X-ray crystallography of PAR1–vorapaxar complex at 2.2 Å resolution","pmids":["23222541"],"confidence":"High","gaps":["Structure of activated PAR1 with tethered ligand engaged not available","No structure of PAR1 in complex with G proteins"]},{"year":2018,"claim":"FVIIa–EPCR engagement was shown to activate anti-inflammatory PAR1 signaling through β-arrestin-1, which blocks TRAF2 recruitment to TNFR1, extending the list of EPCR-dependent PAR1 co-agonists and linking coagulation factor VII to innate immune suppression.","evidence":"PAR1/EPCR/β-arrestin-1 siRNA; TRAF2 co-IP; kinase activation panels; in vivo LPS models in EPCR-overexpressing and EPCR-deficient mice","pmids":["29669778"],"confidence":"High","gaps":["Whether FVIIa cleaves PAR1 at a unique site not mapped","Relative physiological importance of FVIIa vs APC as EPCR-PAR1 agonist in vivo unclear"]},{"year":2019,"claim":"PAR1 was identified as a mediator of tumor immune evasion: PAR1-deleted pancreatic tumor cells failed to grow in immunocompetent but not immunodeficient hosts, with CD8+ T cell depletion rescuing growth, positioning the TF–thrombin–PAR1 axis as a tumor-intrinsic immune checkpoint.","evidence":"CRISPR PAR1-KO KPC allografts in immunocompetent vs NSG mice; CD8/CD4/NK depletion; TF/prothrombin ASO depletion","pmids":["31048498"],"confidence":"High","gaps":["Mechanism by which PAR1 suppresses CD8+ T cell function not molecularly defined","Generalizability beyond pancreatic adenocarcinoma untested"]},{"year":2020,"claim":"BMX kinase was identified as a direct PAR1 phosphorylating kinase that promotes receptor internalization and limits thrombin-induced endothelial permeability, with PAR1 antagonism rescuing vascular leak in BMX-deficient sepsis models.","evidence":"BMX-KO mice; CLP sepsis model; ECIS permeability; biochemical PAR1 phosphorylation; PAR1 antagonist rescue in vivo","pmids":["31910739"],"confidence":"High","gaps":["Specific PAR1 phosphorylation sites targeted by BMX not mapped","Whether BMX regulates PAR1 in platelets or other cell types unknown"]},{"year":null,"claim":"Major unresolved questions include: the activated-state structure of PAR1 with tethered ligand engaged and G-protein bound; the precise molecular basis by which different protease-generated tethered ligands achieve biased coupling to distinct G proteins; and whether intracellular allosteric modulators (parmodulins) can therapeutically separate PAR1's prothrombotic from cytoprotective functions in clinical settings.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No activated-state PAR1 structure with tethered ligand or G-protein complex","Biased agonism mechanism at atomic resolution unknown","Clinical translation of pathway-selective PAR1 modulation unproven"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,5,21,27]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[18,12,35]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,11,31]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,6,8,18,23,35]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[4,21,25,41]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[17,19,36,37]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,13,32,36]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[12,31,41]}],"complexes":[],"partners":["PROCR","F2","MMP1","GNA13","GNAQ","ZYX","BMX","DVL1"],"other_free_text":[]},"mechanistic_narrative":"F2R (PAR1) is a protease-activated G protein-coupled receptor that transduces extracellular proteolytic signals into diverse intracellular responses governing hemostasis, vascular barrier integrity, inflammation, angiogenesis, and tumor biology. Thrombin cleaves the PAR1 N-terminal exodomain at Arg41 to unmask a tethered peptide ligand (SFLLRN) that self-activates the receptor, coupling to Gq, Gi, and G12/13 to drive platelet aggregation, endothelial permeability changes, RhoA-dependent cytoskeletal remodeling, and NF-κB/MAPK-mediated gene expression [PMID:1672265, PMID:8290554, PMID:11360179]. Signaling specificity is determined by the activating protease—MMP-1, MMP-13, and KLK6 cleave PAR1 at noncanonical sites generating biased tethered ligands with distinct G-protein coupling and functional outputs—and by co-receptor context, as EPCR occupancy by APC or protein C switches PAR1 from Gq/G12/13-driven barrier disruption to Gi-dependent barrier protection via sphingosine kinase–S1P1 cross-activation [PMID:19379698, PMID:23086754, PMID:17823308, PMID:15626732]. Post-activation fate is governed by BMX kinase-mediated phosphorylation promoting internalization, ADAM17-dependent exodomain shedding limiting surface receptor availability, lysosomal degradation of cleaved receptors, and replenishment from an intracellular Golgi-associated reserve pool [PMID:31910739, PMID:14982936, PMID:7961693]."},"prefetch_data":{"uniprot":{"accession":"P25116","full_name":"Proteinase-activated receptor 1","aliases":["Coagulation factor II receptor","Thrombin receptor"],"length_aa":425,"mass_kda":47.4,"function":"High affinity receptor that binds the activated thrombin, leading to calcium release from intracellular stores (PubMed:1672265, PubMed:8136362). The thrombin-activated receptor signaling pathway is mediated through PTX-insensitive G proteins, activation of phospholipase C resulting in the production of 1D-myo-inositol 1,4,5-trisphosphate (InsP3) which binds to InsP3 receptors causing calcium release from the stores (By similarity). In astrocytes, the calcium released into the cytosol allows the Ca(2+)-dependent release of L-glutamate into the synaptic cleft through BEST1, that targets the neuronal postsynaptic GRIN2A/NMDAR receptor resulting in the synaptic plasticity regulation (By similarity). May play a role in platelets activation and in vascular development (PubMed:10079109). Mediates up-regulation of pro-inflammatory cytokines, such as MCP-1/CCL2 and IL6, triggered by coagulation factor Xa (F10) in cardiac fibroblasts and umbilical vein endothelial cells (PubMed:30568593, PubMed:34831181)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P25116/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/F2R","classification":"Not Classified","n_dependent_lines":33,"n_total_lines":1208,"dependency_fraction":0.027317880794701987},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/F2R","total_profiled":1310},"omim":[{"mim_id":"620484","title":"THROMBOCYTOPENIA 10; THC10","url":"https://www.omim.org/entry/620484"},{"mim_id":"616913","title":"BLEEDING DISORDER, PLATELET-TYPE, 20; BDPLT20","url":"https://www.omim.org/entry/616913"},{"mim_id":"615845","title":"MICRO RNA 190A; MIR190A","url":"https://www.omim.org/entry/615845"},{"mim_id":"614958","title":"SCHLAFEN FAMILY, MEMBER 14; SLFN14","url":"https://www.omim.org/entry/614958"},{"mim_id":"612283","title":"PROTEIN C; PROC","url":"https://www.omim.org/entry/612283"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":65.4}],"url":"https://www.proteinatlas.org/search/F2R"},"hgnc":{"alias_symbol":["TR","CF2R","PAR1","PAR-1"],"prev_symbol":[]},"alphafold":{"accession":"P25116","domains":[{"cath_id":"1.20.1070.10","chopping":"89-385","consensus_level":"high","plddt":88.8622,"start":89,"end":385}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P25116","model_url":"https://alphafold.ebi.ac.uk/files/AF-P25116-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P25116-F1-predicted_aligned_error_v6.png","plddt_mean":74.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=F2R","jax_strain_url":"https://www.jax.org/strain/search?query=F2R"},"sequence":{"accession":"P25116","fasta_url":"https://rest.uniprot.org/uniprotkb/P25116.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P25116/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P25116"}},"corpus_meta":[{"pmid":"18305483","id":"PMC_18305483","title":"Dendritic cell PAR1-S1P3 signalling couples coagulation and inflammation.","date":"2008","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/18305483","citation_count":236,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"15084291","id":"PMC_15084291","title":"Atypical PKC phosphorylates PAR-1 kinases to regulate localization and activity.","date":"2004","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/15084291","citation_count":228,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"22407318","id":"PMC_22407318","title":"Tissue factor and PAR1 promote microbiota-induced intestinal vascular remodelling.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/22407318","citation_count":215,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17965715","id":"PMC_17965715","title":"'Role reversal' for the receptor PAR1 in sepsis-induced vascular damage.","date":"2007","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/17965715","citation_count":189,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"15466480","id":"PMC_15466480","title":"MARK/PAR1 kinase is a regulator of microtubule-dependent transport in axons.","date":"2004","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/15466480","citation_count":188,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"10194379","id":"PMC_10194379","title":"Plasmin desensitization of the PAR1 thrombin receptor: kinetics, sites of truncation, and implications for thrombolytic therapy.","date":"1999","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10194379","citation_count":186,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"14573770","id":"PMC_14573770","title":"Common signaling pathways link activation of murine PAR-1, LPA, and S1P receptors to proliferation of astrocytes.","date":"2003","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/14573770","citation_count":180,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"12372796","id":"PMC_12372796","title":"Thrombin (PAR-1)-induced proliferation in astrocytes via MAPK involves multiple signaling pathways.","date":"2002","source":"American journal of physiology. 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research","url":"https://pubmed.ncbi.nlm.nih.gov/15489334","citation_count":438,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15626732","id":"PMC_15626732","title":"Endothelial barrier protection by activated protein C through PAR1-dependent sphingosine 1-phosphate receptor-1 crossactivation.","date":"2004","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/15626732","citation_count":411,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16344560","id":"PMC_16344560","title":"Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes.","date":"2005","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/16344560","citation_count":409,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"8290554","id":"PMC_8290554","title":"G proteins of the G12 family are activated via thromboxane A2 and thrombin receptors in human platelets.","date":"1994","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/8290554","citation_count":392,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"9701242","id":"PMC_9701242","title":"Thrombin receptor overexpression in malignant and physiological invasion processes.","date":"1998","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/9701242","citation_count":383,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23222541","id":"PMC_23222541","title":"High-resolution crystal structure of human protease-activated receptor 1.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/23222541","citation_count":370,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"1851174","id":"PMC_1851174","title":"The G protein coupled to the thromboxane A2 receptor in human platelets is a member of the novel Gq family.","date":"1991","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1851174","citation_count":342,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22139419","id":"PMC_22139419","title":"New gene functions in megakaryopoiesis and platelet formation.","date":"2011","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/22139419","citation_count":332,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12761501","id":"PMC_12761501","title":"Large-scale identification and characterization of human genes that activate NF-kappaB and MAPK signaling pathways.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/12761501","citation_count":331,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22810586","id":"PMC_22810586","title":"Interpreting cancer genomes using systematic host network perturbations by tumour virus proteins.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/22810586","citation_count":319,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11907122","id":"PMC_11907122","title":"Activation of protease-activated receptor (PAR)-1, PAR-2, and PAR-4 stimulates IL-6, IL-8, and prostaglandin E2 release from human respiratory epithelial cells.","date":"2002","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/11907122","citation_count":315,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"1310691","id":"PMC_1310691","title":"Characterization of a functional thrombin receptor. Issues and opportunities.","date":"1992","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/1310691","citation_count":277,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12370395","id":"PMC_12370395","title":"House dust mite allergens induce proinflammatory cytokines from respiratory epithelial cells: the cysteine protease allergen, Der p 1, activates protease-activated receptor (PAR)-2 and inactivates PAR-1.","date":"2002","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/12370395","citation_count":276,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16952995","id":"PMC_16952995","title":"Protease-activated receptors in cardiovascular diseases.","date":"2006","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/16952995","citation_count":236,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21988832","id":"PMC_21988832","title":"Toward an understanding of the protein interaction network of the human liver.","date":"2011","source":"Molecular systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/21988832","citation_count":207,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"19379698","id":"PMC_19379698","title":"Platelet matrix metalloprotease-1 mediates thrombogenesis by activating PAR1 at a cryptic ligand site.","date":"2009","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/19379698","citation_count":202,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15280447","id":"PMC_15280447","title":"Protease-activated receptors (PAR1 and PAR2) contribute to tumor cell motility and metastasis.","date":"2004","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/15280447","citation_count":197,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17823308","id":"PMC_17823308","title":"The ligand occupancy of endothelial protein C receptor switches the protease-activated receptor 1-dependent signaling specificity of thrombin from a permeability-enhancing to a barrier-protective response in endothelial cells.","date":"2007","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/17823308","citation_count":195,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7961693","id":"PMC_7961693","title":"Intracellular targeting and trafficking of thrombin receptors. A novel mechanism for resensitization of a G protein-coupled receptor.","date":"1994","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7961693","citation_count":190,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49984,"output_tokens":8216,"usd":0.136596},"stage2":{"model":"claude-opus-4-6","input_tokens":12153,"output_tokens":4602,"usd":0.263723},"total_usd":0.869195,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":62369,"output_tokens":13485,"usd":0.194691},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":17338,"output_tokens":3844,"usd":0.274185}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"Plasmin cleaves the PAR1 N-terminal exodomain at R70/K76/K82 sites (distinct from the thrombin cleavage site at R41), removing the tethered ligand and desensitizing the receptor to thrombin; mutation of these plasmin sites (R70A/K76A/K82A) eliminates desensitization and converts PAR1 into a fully plasmin-activated receptor.\",\n      \"method\": \"In vitro cleavage assays with soluble exodomain (TR78), mass spectrometry site mapping, site-directed mutagenesis, Ca2+ signaling assays in yeast and COS7 cells\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis, multiple orthogonal methods, functional validation in multiple cell systems\",\n      \"pmids\": [\"10194379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Activated protein C (APC) signals through PAR1 in human endothelial cells in an EPCR-dependent manner, inducing anti-inflammatory gene expression (including MCP-1); cleavage-blocking antibodies to PAR1 abolished APC-mediated MAP kinase phosphorylation and gene induction.\",\n      \"method\": \"Antibody blockade of PAR1, microarray gene expression analysis, MAP kinase phosphorylation assays in HUVECs and fibroblast overexpression systems\",\n      \"journal\": \"Journal of endotoxin research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal inhibition with blocking antibodies plus functional gene induction readout in primary endothelial cells\",\n      \"pmids\": [\"14577849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Regulated metalloproteinase-dependent shedding of the PAR1 N-terminal exodomain occurs in endothelial cells, stimulated by phorbol ester or PAR1 agonist, mediated by ADAM17/TACE or a similar metalloproteinase; the information specifying shedding resides in the N-terminal exodomain rather than the heptahelical segment.\",\n      \"method\": \"Chimeric PAR1 constructs, metalloproteinase inhibitors (TAPI-2, phenanthroline, TIMP-3), phorbol ester stimulation, cell-surface quantification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — chimeric constructs, pharmacological inhibition, multiple orthogonal approaches in primary endothelial cells\",\n      \"pmids\": [\"14982936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Alpha-thrombin cleaves the PAR1 exodomain with kcat 340 s⁻¹ and Km 28 µM; Leu at P4 and Pro at P2 critically influence cleavage kinetics; PAR4 cleavage kinetics differ markedly (kcat 17 s⁻¹, Km 61 µM) with Pro at P2 being the dominant determinant.\",\n      \"method\": \"Recombinant exodomain kinetic analysis, Ala-scanning mutagenesis, competitive inhibition assays with chromogenic substrate\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstituted cleavage kinetics with systematic mutagenesis\",\n      \"pmids\": [\"17595115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Constitutive overexpression of PAR1 transforms NIH3T3 cells through RhoA-mediated signaling; PAR1 transformation is blocked by dominant-negative RhoA, pertussis toxin (implicating Gαi), and RGS domain of Lsc (implicating Gα12/Gα13); a thrombin-uncleavable PAR1 mutant is non-transforming.\",\n      \"method\": \"cDNA library screen, focus-forming assays, dominant-negative constructs, microinjection, pertussis toxin treatment, SRF/NF-κB reporter assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic and pharmacological perturbations with defined functional readouts\",\n      \"pmids\": [\"11360179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PAR-1 mediates cellular invasion through a RhoA/RhoD-dependent switch of Gα subunit coupling; in the presence of pertussis toxin (blocking Gαi/o), PAR-1 drives invasion via Gα12/Gα13–RhoA–ROCK; inhibition of RhoA or activation of RhoD redirects signaling to Gαq–PLC–Ca²⁺/CaM–MLCK.\",\n      \"method\": \"Pertussis toxin, C3 exoenzyme, dominant-negative RhoA, dominant-active RhoD, pharmacological inhibitors, invasion assays in epithelial cancer cells\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological and genetic perturbations with quantified invasion readout\",\n      \"pmids\": [\"11919159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PAR1 signaling in dendritic cells couples coagulation to systemic inflammation via S1P receptor 3 (S1P3); PAR1 activation drives S1P3-dependent amplification of IL-1β dissemination; loss of dendritic cell PAR1 or S1P3 sequesters inflammation to draining lymph nodes and attenuates lethality in sepsis.\",\n      \"method\": \"Genetic deletion of PAR1 and S1P3, chemical S1P3 probes, dendritic cell adoptive transfer, sepsis mouse model, cytokine measurements\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — combined chemical and genetic probes in multiple in vivo models with mechanistic pathway placement\",\n      \"pmids\": [\"18305483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"During sepsis progression, PAR1 switches from a vascular-disruptive to a vascular-protective receptor; the protective effect of PAR1 requires transactivation of PAR2 signaling, demonstrated with cell-penetrating pepducins targeting PAR1 intracellular loops.\",\n      \"method\": \"Cell-penetrating pepducin approach (PAR1 and PAR2 targeting), cecal ligation/puncture and endotoxin sepsis mouse models, barrier function assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pepducin tools with defined PAR1-PAR2 cross-talk mechanism, in vivo models\",\n      \"pmids\": [\"17965715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MMP-1 and MMP-13 cleave the PAR1 N-terminal exodomain at noncanonical sites (distinct from the thrombin R41 cleavage site), generating distinct tethered ligands and activating G-protein signaling with biased agonism—producing functional outputs different from thrombin-mediated activation.\",\n      \"method\": \"Biochemical cleavage assays, G-protein signaling assays, comparison of signaling patterns between MMP and thrombin activation of PAR1\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biochemical cleavage site identification plus functional signaling characterization\",\n      \"pmids\": [\"23086754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Gut microbiota promotes TF glycosylation and surface localization, activating coagulation proteases that signal through thrombin–PAR1 (not PAR2) to phosphorylate the TF cytoplasmic domain, forming an extravascular TF–PAR1 signaling loop that drives intestinal angiogenesis and angiopoietin-1 expression.\",\n      \"method\": \"Germ-free mouse colonization, F2r−/− (PAR1-deficient) and F2rl1−/− (PAR2-deficient) mice, hirudin thrombin inhibition, TF cytoplasmic domain deletion mice, vessel density quantification\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic deletion of PAR1 vs PAR2 with specific phenotypic rescue, multiple genetic tools\",\n      \"pmids\": [\"22407318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PAR1 induces β-catenin stabilization independently of Wnt/Frizzled/LRP5/6 via a novel Gα13–Dishevelled (DVL) axis; Gα13 is selectively recruited by PAR1, leading to DVL recruitment through its DIX domain; β-arrestin-2 also binds DVL in this pathway; siRNA silencing of DVL reduces PAR1-induced Matrigel invasion and Lef/Tcf transcription.\",\n      \"method\": \"Dominant-negative Gα13, siRNA knockdown of DVL and LRP5/6, Lef/Tcf reporter assays, Matrigel invasion assays, hPar1-transgenic mouse mammary tissue immunohistology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic perturbations, dominant-negative constructs, in vivo transgenic model\",\n      \"pmids\": [\"20223821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PAR1 activation on endothelial progenitor cells (EPCs) promotes proliferation and migration via upregulation of SDF-1 and CXCR4; PAR1-induced capillary-like structure formation is blocked by anti-CXCR4, anti-SDF-1, or MEK inhibitor, identifying a PAR1→SDF-1/CXCR4→MEK proangiogenic signaling axis.\",\n      \"method\": \"PAR1 agonist peptide SFLLRN on human cord blood CD34+-derived EPCs, Boyden chamber migration assay, qRT-PCR, CXCR4 flow cytometry, Matrigel tube formation, blocking antibodies\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays with blocking antibodies and pharmacological inhibitors defining the pathway\",\n      \"pmids\": [\"16141404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PAR1 deficiency protects against renal ischemia/reperfusion injury via reduced CXC chemokine expression and neutrophil accumulation downstream of thrombin–PAR1 signaling; PAR-1−/− mice had lower KC and MIP-2 despite normal TF upregulation and fibrin deposition, placing PAR1 downstream of TF/thrombin but upstream of chemokine production; hirudin added no further benefit in PAR-1−/− mice.\",\n      \"method\": \"PAR-1−/− mice, PAR-2−/− mice, low-TF mice, hirudin treatment, renal failure endpoints, chemokine measurement, neutrophil quantification\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple knockout lines and pathway placement via additive hirudin experiment\",\n      \"pmids\": [\"16990608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BMX kinase directly phosphorylates PAR1 and promotes its internalization and signal inactivation in endothelial cells; BMX loss increases thrombin-PAR1-mediated permeability 2–3 fold; selective PAR1 antagonist SCH79797 rescues BMX-deficient endothelial permeability and lung leakage in sepsis.\",\n      \"method\": \"BMX global knockout mice, electric cell-substrate impedance sensing, Miles assay, biochemical phosphorylation assays, siRNA, PAR1 antagonist rescue\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct phosphorylation assay combined with genetic KO and pharmacological rescue in vivo\",\n      \"pmids\": [\"31910739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Zyxin, a LIM-domain protein, binds the C-terminal domain of PAR1 and mediates thrombin-induced actin stress fiber formation and SRE-dependent gene transcription independently of RhoA and heterotrimeric G proteins; disruption of PAR1–zyxin interaction or zyxin siRNA knockdown inhibits these responses and delays endothelial barrier restoration.\",\n      \"method\": \"Co-immunoprecipitation/pulldown of zyxin with PAR1 C-terminal domain, siRNA knockdown, dominant-interfering peptide disruption, RhoA activity assay, SRE reporter, actin imaging\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding assay plus siRNA KD with multiple functional readouts showing G-protein independence\",\n      \"pmids\": [\"19690217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Engineering thrombin Trp215 mutations re-engineers selectivity between PAR1 and protein C cleavage; W215E combined with autolysis loop deletion produces a construct with significant activity only toward PAR1, spanning five orders of magnitude in kcat/Km across substrates.\",\n      \"method\": \"Ala-scanning mutagenesis of 97 residues, saturation mutagenesis of Trp215, in vitro kinetic assays with fibrinogen, PAR1 exodomain, and protein C\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with quantitative in vitro kinetics across multiple substrates\",\n      \"pmids\": [\"20404340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PAR1 and PAR2 activation in endothelial cells induces tissue factor (TF) expression via mitochondrial reactive oxygen species (predominantly from complex III); ERK1/2 and p38 MAPK are required for mitochondrial ROS generation; PAR1 additionally activates NF-κB as a distinct downstream module not shared with PAR2.\",\n      \"method\": \"PAR1/PAR2-specific agonist peptides in HUVECs, mitochondrial inhibitors, fluorometric ROS assay, ERK/p38 inhibitors, NF-κB inhibitors, TF procoagulant activity assay, qRT-PCR\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological dissection with functional TF activity readout\",\n      \"pmids\": [\"18983479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Kallikrein 6 (KLK6) activates PAR1 to trigger ERK1/2 signaling in neurons and oligodendrocytes; PAR1 genetic deletion or lipopeptide inhibition reduces KLK6-induced ERK activation, neurodegeneration, and glutamate neurotoxicity; KLK6 also suppresses proteolipid protein expression in oligodendrocytes via PAR1-ERK signaling.\",\n      \"method\": \"PAR1−/− mice, PAR1/PAR2 lipopeptide inhibitors, LDH release assays, ERK phosphorylation assays in cerebellar granule neurons and NSC34 motoneurons, myelin protein RT-PCR\",\n      \"journal\": \"Journal of neurochemistry / Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout combined with lipopeptide inhibitors, multiple cell types, multiple functional readouts\",\n      \"pmids\": [\"23647384\", \"23832758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Streptococcal cysteine protease SpeB cleaves PAR1 at leucine44 on the N-terminal extracellular domain, blunting thrombin-induced ERK phosphorylation in endothelial cells and preventing thrombin-induced platelet aggregation.\",\n      \"method\": \"Bacterial supernatant assays, gain/loss-of-function GAS genetics, pharmacological SpeB inhibition, PAR1 alanine-substitution/deletion constructs, PAR1 blocking antibodies, ERK phosphorylation assays, platelet aggregation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — site-directed mutagenesis mapping cleavage site combined with functional platelet and endothelial assays\",\n      \"pmids\": [\"24278414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PAR1 signaling desensitization in human platelets is counteracted by PAR4 co-activation; PAR4 cross-talk restores Ca2+ mobilization, PKC signaling, and ADP-dense granule secretion lost after PAR1 desensitization via a G(αi)-dependent mechanism requiring ADP release and P2Y12 signaling.\",\n      \"method\": \"Isolated human platelets, PAR1-specific (SFLLRN) and PAR4-specific (AYPGKF) hexapeptides, Ca2+ mobilization assays, PKC assays, granule secretion measurement, aggregometry\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological dissection with multiple orthogonal readouts defining cross-talk mechanism\",\n      \"pmids\": [\"21391917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Thrombin induces rapid PAR1-dependent non-classical release of FGF1 from fibroblasts; thrombin fails to stimulate FGF1 release from PAR1-null fibroblasts; PAR1-specific agonist TRAP also induces FGF1 expression and release.\",\n      \"method\": \"PAR1-null fibroblasts, PAR1-specific peptide agonist TRAP, FGF1 expression and release assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic null cell validation, but single lab with limited mechanistic depth beyond receptor requirement\",\n      \"pmids\": [\"17027650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAR1 promotes breast cancer invasion and metastasis via HMGA2; ectopic functionally active PAR1 (but not a non-signaling mutant) induces epithelial-mesenchymal transition markers, stemness, and lung metastasis; PAR1 signaling is required for HMGA2-driven invasion.\",\n      \"method\": \"PAR1 overexpression vs. signaling-dead PAR1 mutant in MCF-7 cells, mouse xenograft lung metastasis, spheroid formation, siRNA knockdown of HMGA2, invasion assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — signaling-dead mutant control plus in vivo metastasis; single lab\",\n      \"pmids\": [\"26165842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAR1 inhibits the Hippo-YAP pathway in gastric cancer cells via Rho GTPase-mediated inhibition of LATS kinase, leading to nuclear YAP accumulation and cancer stem cell traits; PAR1-induced YAP dephosphorylation and nuclear localization promotes multidrug resistance and tumor initiation.\",\n      \"method\": \"PAR1-specific agonist TFLLR-NH2, Rho GTPase inhibitors, LATS kinase activity assays, YAP phosphorylation/localization analysis, side population assay, drug resistance assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological approach with signaling readouts; single lab\",\n      \"pmids\": [\"26431277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PAR1 activation inhibits Hippo signaling in mammalian cells; PAR-1 physically interacts with Hippo (Hpo) and Salvador (Sav), phosphorylates Hpo at Ser30 to restrict its activity, and inhibits Hpo–Sav association leading to Sav dephosphorylation and destabilization.\",\n      \"method\": \"Drosophila EP gain-of-function screen, epistasis with fat and expanded, physical interaction assays (co-IP), phospho-specific assays, Yorkie/YAP target gene expression in mammalian cells\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP and phosphorylation assays plus epistasis; mammalian conservation shown but mechanism primarily in Drosophila\",\n      \"pmids\": [\"23940457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"F2R (PAR1) negatively regulates osteoclastogenesis; F2r knockdown increases osteoclast number, size, bone resorption, and F-actin ring formation with increased Akt phosphorylation and NF-κB (p65/IKBα) phosphorylation; F2r overexpression blocks osteoclast formation, maturation, and acidification.\",\n      \"method\": \"sh-F2r and pLX304-F2r lentiviral constructs in mouse bone marrow cells, RANKL-induced osteoclastogenesis, phospho-Akt and phospho-p65/IKBα western blots, bone resorption assays, F-actin ring staining\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with signaling readouts; single lab\",\n      \"pmids\": [\"32226307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Platelet-derived MMP-2 activates endothelial PAR-1 to trigger p38MAPK signaling and expression of adhesion molecules, initiating atherosclerotic lesion formation; double knockout mice lacking MMP-2 in blood cells develop significantly less arterial intima thickening and aortic atherosclerosis.\",\n      \"method\": \"MMP-2/LDLR double knockout mice, activated platelet transfusion experiments, in vitro platelet-endothelial co-incubation, p38MAPK signaling assays, en-face aortic lesion quantification\",\n      \"journal\": \"European heart journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function in vivo combined with in vitro mechanism; single lab\",\n      \"pmids\": [\"34529782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Thrombin–PAR1 signaling in pancreatic cancer cells promotes immune evasion by suppressing CD8+ T cell-mediated killing; PAR1 deletion abolishes tumor growth in immune-competent but not immune-compromised mice; PAR1-expressing tumors suppress antitumor immunity in the microenvironment.\",\n      \"method\": \"CRISPR PAR1 knockout in KPC cells, syngeneic allograft in C57BL/6 and NSG mice, CD8 T cell depletion, expression profiling of immune regulation pathways\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with immune-competent vs. immune-compromised comparison and T cell depletion epistasis\",\n      \"pmids\": [\"31048498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAR1 and PAR2 contain pleckstrin homology (PH) domain-binding motifs that associate with Akt/PKB, Etk/Bmx, and Vav3 through their PH domains; a point mutation in PAR1 (hPar1-7A) that disrupts PH domain binding reduces mammary tumor growth in vivo and trophoblast invasion in vitro.\",\n      \"method\": \"Co-immunoprecipitation of PH-domain proteins with PAR1/PAR2, point mutation of PH-binding motif (hPar1-7A), mouse mammary tumor models, placental EVT invasion assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — pulldown plus mutagenesis with in vivo tumor phenotype; single lab\",\n      \"pmids\": [\"26600192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PAR1 activation in astrocytes induces rapid structural reorganization of fine astrocytic processes surrounding glutamatergic synapses, leading to faster extracellular glutamate clearance and altered excitatory synaptic transmission in the mouse hippocampus.\",\n      \"method\": \"PAR1 agonist application in mouse hippocampal slices, axial STEM tomography, 3D Monte Carlo reaction-diffusion simulations, electrophysiology\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct live imaging and ultrastructural analysis combined with functional synaptic readout; single lab\",\n      \"pmids\": [\"28256580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FVIIa binding to EPCR elicits anti-inflammatory signaling via PAR1 and β-arrestin-1 in endothelial cells; siRNA knockdown of PAR1 or EPCR abolishes FVIIa-induced suppression of adhesion molecules and IL-6; mechanistically, FVIIa-PAR1 signaling impairs TRAF2 recruitment to TNF receptor 1.\",\n      \"method\": \"siRNA knockdown of PAR1, EPCR, β-arrestin-1; EPCR-deficient and overexpressing mice; LPS-induced inflammation in vivo; ERK/p38/JNK/NF-κB signaling assays; TRAF2 co-IP\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown of multiple pathway components plus in vivo genetic validation and co-IP mechanism\",\n      \"pmids\": [\"29669778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PAR1 mediates microvascular stasis in sickle cell disease; pharmacologic PAR1 inhibition and nonhematopoietic PAR1 deficiency reduce heme-induced microvascular stasis; PAR1 deficiency is associated with reduced endothelial von Willebrand factor expression.\",\n      \"method\": \"PAR1-null mice (nonhematopoietic), pharmacological PAR1 inhibition, heme-induced microvascular stasis model in sickle mice, intravital microscopy, VWF immunostaining\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological PAR1 ablation with in vivo functional readout; single lab\",\n      \"pmids\": [\"31977004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GZMA secreted by cytotoxic T cells interacts with F2R (PAR1) expressed on hepatocellular carcinoma tumor cells via the LDPRSFLL motif at the N-terminus of F2R, activating JAK2/STAT1 signaling and promoting tumor cell apoptosis.\",\n      \"method\": \"Single-cell sequencing, in vivo and in vitro GZMA-F2R interaction experiments, JAK2/STAT1 signaling assays, PD-1 mAb mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — interaction and signaling shown but mechanistic depth and orthogonal validation limited; single lab\",\n      \"pmids\": [\"35256589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PAR1 inhibition with vorapaxar reduces accumulation of senescent but viable ('undead') hepatocytes in NASH; senescing hepatocytes upregulate THBD-PAR1 signaling to remain viable, driving hedgehog ligand expression and profibrotic reprogramming of hepatic stellate cells; vorapaxar interrupts this cycle and reduces fibrosis.\",\n      \"method\": \"Viral p16 overexpression in hepatocytes, vorapaxar treatment in UUO/UIRI and NASH mouse models, conditioned medium from senescent hepatocytes, hedgehog ligand measurement, transcriptome analysis\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple mouse models with pharmacological PAR1 inhibition and mechanistic pathway identification; single lab\",\n      \"pmids\": [\"37036206\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"F2R (PAR1) is a G protein-coupled receptor that is irreversibly activated by thrombin (or other proteases including plasmin, MMPs, APC, kallikrein 6) cleaving its N-terminal exodomain to unmask a tethered ligand; it signals through Gαi, Gαq, and Gα12/13 to activate RhoA, ERK/MAPK, PKC, and NF-κB pathways in platelets, endothelial cells, dendritic cells, and cancer cells, regulating hemostasis, vascular permeability, inflammation, angiogenesis, cell polarity, and immune evasion, while receptor activity is modulated by plasmin-mediated desensitization, ADAM17-mediated exodomain shedding, BMX-mediated phosphorylation and internalization, and biased agonism from noncanonical protease cleavage at distinct N-terminal sites.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper before extracting discoveries.\n\n**EXCLUDE (alias collisions or off-target):**\n- Papers [2], [5], [9], [11], [12], [13], [14], [18], [26], [29], [30], [34], [39], [52], [59], [71], [79], [91], [92], [93], [96], [98] — These describe PAR-1/MARK kinase (polarity kinase, MARK2/EMK1), which is a completely different protein family from F2R (PAR1 thrombin receptor)\n- Paper [27] (corpus) — PAR1 in Arabidopsis (plant PAR1/PAR2 shade avoidance) — EXCLUDE (symbol collision)\n- Paper [28] (corpus) — Same Arabidopsis PAR1/PAR2 — EXCLUDE\n- Paper [33] (corpus) — Arabidopsis PAR1 photomorphogenesis — EXCLUDE\n- Paper [81] (corpus) — Plant PAR1/PAR2 shade signaling — EXCLUDE\n- Paper [64] (corpus) — \"Hep Par 1\" antibody marker — different entity entirely — EXCLUDE\n- Paper [46] (corpus) — Thyroid hormone receptor TR antagonist — completely unrelated — EXCLUDE\n- Paper [47] (curated) — TR-KLF9 thyroid hormone — EXCLUDE (wrong gene)\n- Paper [61] (corpus) — T-cell receptor TRG locus — EXCLUDE\n- Paper [27] (curated, recombination in PAR1 pseudoautosomal region) — PAR1 here = pseudoautosomal region, not F2R — EXCLUDE\n\n**KEEP:** All remaining papers describing F2R (PAR1 thrombin receptor/protease-activated receptor 1).\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1991,\n      \"finding\": \"F2R (PAR1) encodes a seven-transmembrane G protein-coupled receptor activated by thrombin through a novel proteolytic mechanism: thrombin cleaves the receptor's N-terminal exodomain at R41, exposing a tethered peptide ligand (beginning with SFLLRN) that binds and activates the receptor in an intramolecular fashion. Uncleavable mutant receptors failed to respond to thrombin but retained responsiveness to the synthetic tethered-ligand peptide.\",\n      \"method\": \"Direct expression cloning in Xenopus oocytes; site-directed mutagenesis of thrombin cleavage site; synthetic peptide agonist assays; mRNA detection in human platelets and endothelial cells\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original cloning with reconstitution in oocytes plus mutagenesis; foundational paper with 2832 citations\",\n      \"pmids\": [\"1672265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Characterization of PAR1 as a functional thrombin receptor confirmed tethered-ligand activation mechanism and defined receptor properties on platelets and endothelial cells.\",\n      \"method\": \"Functional receptor characterization; peptide agonist studies\",\n      \"journal\": \"The Journal of Clinical Investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional characterization corroborating original cloning; 277 citations\",\n      \"pmids\": [\"1310691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"PAR1 (thrombin receptor) traffics differently from classical GPCRs: uncleaved receptors are stored in an intracellular compartment co-localizing with Golgi markers, and are protected from thrombin activation. Upon activation of cell-surface receptors, the intracellular pool translocates to the plasma membrane, replenishing surface receptors and restoring thrombin responsiveness—a novel resensitization mechanism distinct from internalization/recycling seen with beta2-adrenergic receptor. Activated (cleaved) receptors are targeted to lysosomes rather than recycled.\",\n      \"method\": \"Transfected Rat1 fibroblasts; subcellular fractionation; co-localization with Golgi markers; comparison with beta2-adrenergic receptor trafficking; agonist stimulation experiments\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization with functional consequence; reciprocal trafficking comparison; 190 citations\",\n      \"pmids\": [\"7961693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"PAR1 (thrombin receptor) couples to G proteins of the G12 and G13 family, as well as the Gq family, in human platelets. Both thrombin receptor and thromboxane A2 receptor activation led to increased GTP analog incorporation into alpha12 and alpha13 subunits.\",\n      \"method\": \"Subtype-specific antisera; photoreactive GTP analog ([alpha-32P]GTP azidoanilide) incorporation into immunoprecipitated G-protein alpha subunits from human platelet membranes; receptor agonist stimulation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — biochemical G-protein coupling assay with subtype-specific antibodies; 392 citations\",\n      \"pmids\": [\"8290554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PAR1 and PAR4 together account for virtually all thrombin-mediated platelet activation in humans. Inhibition of PAR1 alone blocked platelet activation at low thrombin concentrations (1 nM) but only partially at high concentrations (30 nM); simultaneous inhibition of both PAR1 and PAR4 virtually ablated platelet secretion and aggregation even at 30 nM thrombin. PAR3 was not detected as functional in human platelets.\",\n      \"method\": \"PAR1/PAR4 mRNA and protein detection in human platelets; PAR1 antagonist, blocking antibody, and desensitization experiments; PAR4 blocking antibody; platelet secretion and aggregation assays at multiple thrombin concentrations\",\n      \"journal\": \"The Journal of Clinical Investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal inhibition approaches; genetic and pharmacological; 683 citations\",\n      \"pmids\": [\"10079109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Plasmin desensitizes PAR1 by cleaving the N-terminal exodomain at sites R70/K76/K82 (distal to the thrombin cleavage site R41), thereby truncating the tethered ligand and preventing thrombin-dependent Ca2+ signaling. Mutation of R70/K76/K82 to alanines eliminated plasmin truncation and desensitization, converting PAR1 into a plasmin-activated receptor. Plasmin also cleaves at R41, transiently activating PAR1. The desensitization is rate-equivalent to thrombin cleavage (similar kcat and KM).\",\n      \"method\": \"Soluble N-terminal exodomain (TR78) as model; kinetic analysis (kcat, KM) of protease cleavage; mass spectrometry identification of cleavage sites; site-directed mutagenesis (R70A/K76A/K82A); full-length receptor expressed in yeast and COS7 cells; Ca2+ signaling assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis and kinetic characterization; multiple receptor systems tested; 186 citations\",\n      \"pmids\": [\"10194379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PAR1 overexpression in NIH3T3 cells causes oncogenic transformation through activation of RhoA-mediated signaling pathways. PAR1 transformation required receptor cleavage (uncleavable mutant was non-transforming), and was blocked by dominant negative RhoA, pertussis toxin (implicating Gαi), and the RGS domain of Lsc (implicating Gα12/Gα13). PAR1 cooperated synergistically with activated Raf-1 and activated serum response factor and NF-κB.\",\n      \"method\": \"cDNA expression library screen in NIH3T3 focus formation assay; uncleavable mutant receptor; co-expression with dominant negative RhoA; pertussis toxin treatment; RGS domain of Lsc co-expression; microinjection into PAE cells; SRF and NF-κB reporter assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic and pharmacological approaches; 104 citations\",\n      \"pmids\": [\"11360179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Activated protein C (APC) signals through PAR1 on endothelial cells in an EPCR-dependent manner. APC-mediated MAP kinase phosphorylation and gene induction (including selective induction of MCP-1) were inhibited by cleavage-blocking antibodies to PAR1, demonstrating that APC signals exclusively through PAR1 in endothelial cells. Gene profiling showed PAR1 signaling accounted for all APC-induced protective genes.\",\n      \"method\": \"Fibroblast overexpression system; human endothelial cell (HUVEC) stimulation; cleavage-blocking PAR1 antibodies; high-density microarray gene expression profiling; MAP kinase phosphorylation assays\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cleavage-blocking antibody specificity plus microarray plus kinase assay; 704 citations\",\n      \"pmids\": [\"12052963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PAR1 activation in cancer cells promotes cellular invasion through a RhoA/Rho kinase (ROCK)-dependent mechanism via Gα12/Gα13 signaling. In the presence of pertussis toxin (blocking Gαo/i), PAR1 induced invasion through Gα12/Gα13–RhoA/ROCK. Inhibition of endogenous RhoA redirected PAR1 signaling to a Gαq–PLC–Ca2+/CaM-MLCK pathway to promote invasion via a different route, revealing RhoA and RhoD as molecular switches controlling PAR1-dependent invasion signaling.\",\n      \"method\": \"Pharmacological inhibitors (pertussis toxin, C3 exoenzyme, dominant negative N19-RhoA); activated G26V-RhoD; NO/cGMP pathway activators; invasion assays in kidney and colonic epithelial cells\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological and genetic perturbations; single lab\",\n      \"pmids\": [\"11919159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Activated protein C (APC) signals through PAR1 in endothelial cells via EPCR as coreceptor; APC activates PAR1 and PAR2 in fibroblast overexpression systems in an EPCR-dependent manner. In HUVECs, APC, PAR1, and PAR2 agonist peptides induce similar early response genes; MCP-1 was selectively induced by APC and PAR1 agonist but not PAR2 agonist, confirming PAR1-exclusive APC signaling.\",\n      \"method\": \"Fibroblast overexpression; HUVEC stimulation; cleavage-blocking PAR1 antibodies; microarray gene profiling; MAP kinase assays\",\n      \"journal\": \"Journal of Endotoxin Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — confirms EPCR-PAR1 axis with antibody blockade and microarray; single lab\",\n      \"pmids\": [\"14577849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PAR1 activation induces VEGF expression and angiogenesis through PKC, Src, and PI3K kinase pathways. Par1-expressing cells significantly enhanced angiogenesis in Matrigel plug and tumor models in vivo. Multiple VEGF splice forms were induced, and neutralizing anti-VEGF antibodies inhibited PAR1-induced endothelial cell proliferation.\",\n      \"method\": \"In vivo Matrigel plug assay; tetracycline-inducible Par1 expression; VEGF mRNA/protein measurement; specific kinase inhibitors (PKC, Src, PI3K); anti-VEGF neutralizing antibodies; endothelial tube alignment and proliferation assays\",\n      \"journal\": \"FASEB Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitors plus in vivo model; single lab; 100 citations\",\n      \"pmids\": [\"12554695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Regulated metalloproteinase-dependent shedding of the PAR1 N-terminal exodomain occurs in endothelial cells, mediated by ADAM17/TACE or a related metalloproteinase. Shedding is stimulated by phorbol ester (protein kinase C activation) or PAR1 agonist in trans, and is inhibited by TAPI-2, phenanthroline, and TIMP-3 but not TIMP-1 or -2. The shedding information resides within the exodomain, not the heptahelical segment. Regulated shedding reduced cell-surface PAR1 available for thrombin cleavage by half or more.\",\n      \"method\": \"PAR1 chimeric constructs (exodomain fused to unrelated transmembrane segment); phorbol ester and PAR1 agonist stimulation; metalloproteinase inhibitors (TAPI-2, phenanthroline, TIMP-1/2/3); domain-swap experiments in endothelial cells\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — domain-swap constructs plus pharmacological inhibitors plus functional quantification; 37 citations\",\n      \"pmids\": [\"14982936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PAR1-dependent sphingosine 1-phosphate receptor-1 (S1P1) cross-activation mediates activated protein C (APC)-induced endothelial barrier protection. APC enhances endothelial barrier integrity dependent on EPCR binding, PAR1 activation, and sphingosine kinase activity. siRNA knockdown of sphingosine kinase-1 or S1P receptor-1 blocked APC-protective signaling. Low concentrations of thrombin (~40 pM) or PAR1 agonist peptide similarly enhanced barrier function, revealing that PAR1 can mediate both barrier-disruptive and barrier-protective responses.\",\n      \"method\": \"Dual-chamber endothelial barrier system; siRNA knockdown of sphingosine kinase-1 and S1P1; EPCR-blocking antibodies; PAR1 agonist peptides; thrombin dose-response\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown of multiple pathway components plus pharmacological inhibition; 411 citations\",\n      \"pmids\": [\"15626732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Matrix metalloproteinase-1 (MMP-1) is a non-thrombin protease agonist of PAR1 that promotes breast cancer invasion and tumorigenesis. MMP-1 (derived from stromal fibroblasts) cleaves PAR1 at the proper site to generate PAR1-dependent Ca2+ signals and cell migration. PAR1 expression is required and sufficient to promote growth and invasion of breast carcinoma cells in xenograft models.\",\n      \"method\": \"Xenograft mouse model; Ca2+ signaling assays; cell migration assays; PAR1 knockdown; MMP-1 cleavage site analysis; fibroblast conditioned medium experiments\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — PAR1 cleavage by MMP-1 demonstrated biochemically plus in vivo xenograft plus Ca2+ signaling; 664 citations\",\n      \"pmids\": [\"15707890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PAR1 activation on human late endothelial progenitor cells (EPCs) promotes proliferation, migration, and capillary-like structure formation through upregulation of SDF-1 and its receptor CXCR4, leading to autocrine stimulation. Anti-CXCR4, anti-SDF-1, and MEK inhibitor pretreatment abrogated PAR1-induced capillary formation.\",\n      \"method\": \"EPC expansion from CD34+ cord blood; SFLLRN peptide stimulation; real-time RT-PCR for SDF-1/CXCR4 mRNA; Boyden chamber migration assay; Matrigel capillary formation; blocking antibodies; MEK inhibitor\",\n      \"journal\": \"Arteriosclerosis, Thrombosis, and Vascular Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays; blocking antibodies plus inhibitor; single lab\",\n      \"pmids\": [\"16141404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PAR1 activation on endothelial progenitor cells (EPCs) induces angiopoietin-2 gene expression and protein synthesis, which mediates PAR1-induced EPC proliferation. Polyclonal blocking antibodies against angiopoietin-2 inhibited PAR1-mediated proliferative effect. PAR1 also enhanced EPC migration toward angiopoietin-1.\",\n      \"method\": \"SFLLRN peptide stimulation of EPCs; RT-PCR and protein assay for angiopoietin-1/2; polyclonal blocking antibodies; Boyden chamber migration assay\",\n      \"journal\": \"Journal of Thrombosis and Haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — blocking antibody approach; single lab; 52 citations\",\n      \"pmids\": [\"16803467\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The critical amino acids for alpha-thrombin's interaction with PAR1 at the thrombin cleavage site were identified by mutagenesis of the P4 (L38), P3 (D39), and P2 (P40) positions of the PAR1 exodomain. Mutation of P4 (L38A) or P2 (P40A) reduced kcat without changing KM; mutation of P3 (D39A) reduced both Km and kcat (maintaining kcat/Km). PAR1 exodomain acts as a non-competitive inhibitor of thrombin hydrolysis of chromogenic substrate, while PAR4 exodomain is a competitive inhibitor, revealing fundamentally different thrombin-binding mechanisms.\",\n      \"method\": \"Recombinant PAR1 and PAR4 exodomain production; kinetic analysis (kcat, KM, kcat/Km); alanine-scanning mutagenesis of P4/P3/P2 positions; inhibition kinetics with chromogenic substrate Sar-Pro-Arg-pNA\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with systematic mutagenesis and full kinetic characterization; 56 citations\",\n      \"pmids\": [\"17595115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PAR1 'role reversal' in sepsis: PAR1 functions as a vascular-disruptive receptor early in sepsis but switches to vascular-protective during disease progression. Protective effects of PAR1 required transactivation of PAR2 signaling pathways. Cell-penetrating pepducin approach demonstrated that selective PAR1-PAR2 complex activation is beneficial in sepsis.\",\n      \"method\": \"Cell-penetrating pepducin approach in mouse sepsis model; cecal ligation and puncture model; PAR1 and PAR2 genetic and pharmacological manipulation\",\n      \"journal\": \"Nature Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo model with pepducin approach plus PAR1-PAR2 cross-talk defined; single lab; 189 citations\",\n      \"pmids\": [\"17965715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"EPCR occupancy by protein C/APC switches PAR1 signaling specificity in endothelial cells from permeability-enhancing to barrier-protective by coupling PAR1 to pertussis toxin-sensitive Gi protein. EPCR is associated with caveolin-1 in lipid rafts; its occupancy by the Gla domain of protein C/APC dissociates EPCR from caveolin-1 and recruits PAR1 to a protective signaling pathway. When EPCR is bound, both thrombin and APC can elicit barrier-protective PAR1 signaling.\",\n      \"method\": \"Lipid raft isolation; co-immunoprecipitation of EPCR with caveolin-1; pertussis toxin blocking; Gla domain constructs; endothelial permeability assays; PAR1/EPCR signaling pathway analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP, lipid raft fractionation, pertussis toxin, functional permeability assay; 195 citations\",\n      \"pmids\": [\"17823308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PAR1 signaling in dendritic cells couples coagulation and inflammation via a PAR1-S1P3 cross-talk mechanism. PAR1 activation sustains lethal inflammatory response in sepsis, and this is mediated downstream by the sphingosine 1-phosphate axis through S1P receptor 3 (S1P3). Loss of dendritic cell PAR1-S1P3 signaling sequesters dendritic cells into draining lymph nodes and attenuates IL-1β dissemination to lungs.\",\n      \"method\": \"Chemical and genetic probes for S1P3; PAR1-deficient mice; S1P3-deficient mice; endotoxin sepsis model; IL-1β measurement in lungs\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — combined genetic (knockout) and chemical probes in vivo; 236 citations\",\n      \"pmids\": [\"18305483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PAR1 and PAR2 activation in endothelial cells induces tissue factor (TF) expression via mitochondrial reactive oxygen species (ROS) generated primarily from complex III. ERK1/2 and p38 MAPK activation is critical for mitochondrial ROS generation. Downstream of receptor activation, a PAR1-specific module involving NF-κB activation also induces TF.\",\n      \"method\": \"HUVEC stimulation with PAR1 and PAR2 agonist peptides; TF real-time RT-PCR and procoagulant activity measurement; ROS fluorometric assay; mitochondrial complex inhibitors; ERK1/2 and p38 inhibitors; NF-κB pathway analysis\",\n      \"journal\": \"Journal of Thrombosis and Haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological dissection of ROS source and kinase pathways; single lab; 46 citations\",\n      \"pmids\": [\"18983479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Platelet MMP-1 (matrix metalloprotease-1) activates PAR1 on the platelet surface at a distinct cryptic cleavage site different from thrombin's site, promoting aggregation. Fibrillar collagen converts surface-bound proMMP-1 zymogen to active MMP-1 on platelets. MMP-1 cleavage of PAR1 preferentially activates Rho-GTP pathways, cell shape change, motility, and MAPK signaling—distinct from thrombin-induced PAR1 signaling. Blockade of MMP1-PAR1 curtails thrombogenesis under arterial flow and inhibits thrombosis in vivo.\",\n      \"method\": \"Platelet MMP-1 activation by fibrillar collagen; PAR1 cleavage site mapping; Rho-GTP and MAPK signaling assays; arterial flow thrombogenesis model; in vivo thrombosis model; MMP1-PAR1 blockade\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical cleavage site mapping, signaling characterization, in vivo thrombosis model; 202 citations\",\n      \"pmids\": [\"19379698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Zyxin, a LIM-domain-containing protein, binds to the C-terminal domain of PAR1 and mediates thrombin-induced actin cytoskeleton remodeling and SRE-dependent gene transcription in endothelial cells independently of G-protein (Gi, Gq, G12/13) activation. siRNA depletion of zyxin inhibited thrombin-induced stress fiber formation, SRE activation, and delayed endothelial barrier restoration. Zyxin recruits VASP to focal adhesions and along stress fibers upon thrombin stimulation.\",\n      \"method\": \"Co-immunoprecipitation of zyxin with PAR1 C-terminal domain; siRNA knockdown; stress fiber imaging; SRE reporter assay; RhoA activation assay; G-protein activation assays; barrier restoration assay\",\n      \"journal\": \"FASEB Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus siRNA plus multiple functional readouts; single lab\",\n      \"pmids\": [\"19690217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PAR1 induces beta-catenin stabilization independent of Wnt, Frizzled, and LRP5/6 co-receptors through a novel Gα13–Dishevelled (DVL) axis. PAR1-Gα13 association recruits DVL via its DIX domain. siRNA silencing of DVL abrogated PAR1-induced Matrigel invasion, Lef/Tcf transcription activity, and beta-catenin accumulation. Dominant negative Gα13 (but not Gα12) inhibited PAR1-induced beta-catenin stabilization. PAR1 also promotes binding of beta-arrestin-2 to DVL.\",\n      \"method\": \"Dominant negative Gα13/Gα12; siRNA-DVL silencing; siRNA-LRP5/6; Wnt antagonists SFRP2/SFRP5; Lef/Tcf transcription reporter assay; Matrigel invasion assay; immunohistochemistry of hPar1-transgenic mouse mammary tissues; co-immunoprecipitation\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic knockdowns plus dominant negatives plus in vivo transgenic; single lab\",\n      \"pmids\": [\"20223821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Thrombin specificity toward PAR1 (vs. protein C and fibrinogen) is determined primarily by Trp215. Saturation mutagenesis of Trp215 produced constructs with kcat/Km values spanning five orders of magnitude. W215E is 10-fold more specific for protein C than fibrinogen and PAR1. Combining W215E with deletion of 9 residues in the autolysis loop produced a construct with significant activity only toward PAR1, demonstrating context-dependent re-engineering of thrombin specificity.\",\n      \"method\": \"Ala-scanning mutagenesis of 97 residues covering 53% of solvent-accessible surface; saturation mutagenesis of Trp215; kinetic characterization (kcat/Km) for fibrinogen, PAR1, and protein C hydrolysis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic in vitro mutagenesis with full kinetic characterization; 37 citations\",\n      \"pmids\": [\"20404340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PAR1 signaling desensitization in human platelets (via PAR1 homologous activation) is counteracted by PAR4 signaling. PAR1 desensitization involves decreased Ca2+ mobilization, reduced PKC signaling, and loss of dense granule secretion. Subthreshold PAR4 activation re-establishes PAR1-induced aggregation by reconstituting these signaling events via PKC-mediated ADP release from dense granules and fibrinogen from alpha-granules; G(αi) signaling is required.\",\n      \"method\": \"Isolated human platelets; specific PAR1 (SFLLRN) and PAR4 (AYPGKF) activating hexapeptides; Ca2+ mobilization measurement; PKC signaling assay; granule secretion assays; 2-MeS-ADP and epinephrine mimicry of Gαi/z; aggregometry\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological approaches; defined cross-talk mechanism; single lab\",\n      \"pmids\": [\"21391917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PAR1 deficiency (F2r-/-) reduces intestinal vessel density in germ-free mice colonized with microbiota, and inhibition of thrombin (PAR1 activator) decreased TF cytoplasmic domain phosphorylation, placing thrombin-PAR1 signaling upstream of TF phosphorylation in a microbiota-induced extravascular TF-PAR1 signaling loop promoting intestinal vascular remodeling. PAR2-deficient mice showed no such decrease.\",\n      \"method\": \"PAR1-deficient (F2r-/-) and PAR2-deficient (F2rl1-/-) mice; germ-free colonization; anti-TF treatment; TF cytoplasmic domain phosphorylation measurement; hirudin (thrombin inhibitor) treatment; vascular density quantification; angiopoietin-1 expression\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout plus pharmacological inhibition; F2r-/- vs F2rl1-/- comparison; 215 citations\",\n      \"pmids\": [\"22407318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MMP-1 and MMP-13 cleave the N-terminal exodomain of PAR1 at noncanonical sites (different from the thrombin cleavage site R41), generating distinct tethered ligands that activate different G-protein signaling pathways—termed biased agonism—producing distinct functional cellular outputs compared to thrombin-activated PAR1.\",\n      \"method\": \"PAR1 cleavage site mapping; Ca2+ signaling; G-protein pathway activation assays; comparison of canonical (thrombin) vs. noncanonical (MMP-1, MMP-13) cleavage products\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic review consolidating primary data on MMP cleavage sites; builds on primary data in PMID 19379698 and additional MMP-13 studies; 147 citations\",\n      \"pmids\": [\"23086754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"High-resolution (2.2 Å) crystal structure of human PAR1 bound to vorapaxar reveals an unusual, superficial binding pocket with little solvent exposure—distinct from deep, solvent-exposed pockets of other peptide-activated GPCRs. Vorapaxar binding explains near-irreversible inhibition of receptor activation by the tethered ligand. The structure defines the molecular basis for PAR1 antagonism.\",\n      \"method\": \"X-ray crystallography at 2.2 Å resolution; PAR1 bound to vorapaxar antagonist\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure; 370 citations\",\n      \"pmids\": [\"23222541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Kallikrein 6 (Klk6) signals through PAR1 (and PAR2) to promote neuron injury and exacerbate glutamate neurotoxicity via ERK1/2 signaling in a phosphoinositide 3-kinase and MEK-dependent fashion. Lipopeptide inhibitors of PAR1 or PAR2, and PAR1 genetic deletion, each reduced Klk6-ERK1/2 activation. PAR1 genetic deletion blocked thrombin-mediated cerebellar neurotoxicity and reduced neurotoxic effects of Klk6.\",\n      \"method\": \"Cerebellar granule neurons and NSC34 motoneurons; recombinant Klk6; PAR1/PAR2 lipopeptide inhibitors; PAR1 genetic deletion mice; ERK1/2 phosphorylation; PI3K and MEK inhibitors; LDH release; Bim signaling; PARP cleavage\",\n      \"journal\": \"Journal of Neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout plus pharmacological inhibitors; multiple cell systems; single lab\",\n      \"pmids\": [\"23647384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Kallikrein 6 (KLK6) activates PAR1 to mediate loss of oligodendrocyte processes and impede oligodendrocyte progenitor cell morphological differentiation. PAR1-activating peptides and thrombin produce comparable oligodendrogliopathy. KLK6 suppresses proteolipid protein (PLP) RNA expression through PAR1-mediated Erk1/2 signaling. In vivo microinjection of PAR1 agonists into dorsal column white matter promoted vacuolating myelopathy and loss of MBP and CC-1+ oligodendrocytes in PAR1+/+ but not PAR1-/- mice.\",\n      \"method\": \"Primary oligodendrocyte cultures from WT and PAR1-deficient mice; Oli-neu cell line; Klk6, thrombin, and PAR1-AP stimulation; PAR1 genetic deletion; Erk1/2 signaling assay; PLP RNA quantification; in vivo microinjection; MBP and CC-1 immunostaining\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro (PAR1 KO cells) plus in vivo (PAR1 KO mice) with histological readouts; 53 citations\",\n      \"pmids\": [\"23832758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PAR1 and PAR3 cooperate to drive thrombin (FIIa)-induced epithelial-mesenchymal transition (EMT) in alveolar epithelial cells. Single knockdown of PAR1, PAR3, or PAR4 had no major impact on FIIa-induced EMT, but simultaneous depletion of PAR1 and PAR3 almost completely inhibited EMT. PAR1 and PAR3 co-localize within alveolar type II cells on the plasma membrane.\",\n      \"method\": \"siRNA knockdown (single and combined) of PAR1, PAR3, PAR4; thrombin stimulation; EMT markers (morphological, epithelial/mesenchymal protein expression, functional changes); co-localization immunostaining\",\n      \"journal\": \"Thrombosis and Haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic siRNA knockdown combinations; co-localization; single lab\",\n      \"pmids\": [\"23739922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAR1 induces a metastatic, hormone-refractory breast cancer phenotype through upregulation of HMGA2. Functionally active PAR1 (but not non-signaling mutant PAR1) in MCF-7 cells induced epithelial-mesenchymal transition, vimentin upregulation, E-cadherin and estrogen receptor downregulation, and lung metastasis in mice. HMGA2 was identified as a key mediator of PAR1-induced invasion, and inhibition of PAR1 signaling suppressed HMGA2-driven invasion.\",\n      \"method\": \"Ectopic PAR1 expression in MCF-7 cells; non-signaling PAR1 mutant; in vivo lung metastasis model; EMT marker analysis; HMGA2 expression analysis; PAR1 signaling inhibition; spheroid formation assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutant receptor comparison plus in vivo metastasis model; single lab\",\n      \"pmids\": [\"26165842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PAR1 and PAR2 contain pleckstrin homology (PH) domain-binding motifs that mediate association with Akt/PKB, Etk/Bmx, and Vav3 via their PH domains. PAR1 and PAR2 bind with priority to Etk/Bmx. A point mutation in PAR1 (hPar1-7A, unable to bind PH domain) reduced mammary tumors and trophoblast invasion in vivo, demonstrating physiological significance of PH-domain-binding motifs.\",\n      \"method\": \"Co-immunoprecipitation of PH-domain proteins with PAR1/PAR2; PAR2 point mutants (H349A, R352A); PAR1 hPar1-7A mutant; in vivo mammary tumor model; trophoblast invasion assay\",\n      \"journal\": \"Nature Communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus mutagenesis plus in vivo tumor model; single lab\",\n      \"pmids\": [\"26600192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PAR1 activation in astrocytes induces rapid structural reorganization of the neuropil surrounding glutamatergic synapses, associated with faster clearance of synaptically-released glutamate from the extracellular space. This leads to short- and long-term changes in excitatory synaptic transmission in the mouse hippocampus, identifying PAR1 as a regulator of glutamatergic signaling.\",\n      \"method\": \"Mouse hippocampal preparations; PAR1 activation; 3D Monte Carlo reaction-diffusion simulations; axial scanning transmission electron microscopy (STEM) tomography; glutamate uptake assays; electrophysiology\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — structural imaging plus functional electrophysiology plus computational modeling; single lab\",\n      \"pmids\": [\"28256580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FVIIa binding to EPCR elicits anti-inflammatory signaling via PAR1 and β-arrestin-1 in endothelial cells. Inhibition of EPCR or PAR1 (by antibodies or siRNA) abolished FVIIa-induced suppression of adhesion molecules and IL-6. β-arrestin-1 silencing blocked FVIIa's anti-inflammatory effect. Mechanistically, FVIIa-EPCR-PAR1 signaling inhibited ERK1/2, p38 MAPK, JNK, NF-κB, and C-Jun activation by impairing TRAF2 recruitment to the TNF receptor 1 signaling complex.\",\n      \"method\": \"Endothelial cell stimulation with FVIIa; PAR1/EPCR siRNA and blocking antibodies; β-arrestin-1 siRNA; cytokine expression; adhesion molecule expression; kinase activation assays (ERK1/2, p38, JNK, NF-κB); TRAF2 co-immunoprecipitation; in vivo LPS model in WT, EPCR-overexpressing, and EPCR-deficient mice\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdowns of multiple components plus in vivo genetic models plus Co-IP mechanism; 50 citations\",\n      \"pmids\": [\"29669778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Thrombin-PAR1 signaling in pancreatic ductal adenocarcinoma (PDAC) tumor cells promotes tumor growth through suppression of antitumor CD8+ T cell immunity. PAR1-deleted KPC cells failed to form tumors in immune-competent mice but showed robust growth in immune-compromised NSG mice. CD8 T cell depletion rescued tumor growth of PAR1-KO cells in competent mice. Tumor cell TF and circulating prothrombin activate PAR1 to mediate immune evasion.\",\n      \"method\": \"PAR1-deleted KPC cell lines (CRISPR/KO); allograft studies; immune-competent vs. NSG mice; CD8/CD4/NK cell depletion; TF/prothrombin depletion (ASO); expression profiling of immune regulation pathways\",\n      \"journal\": \"Cancer Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with rescue, immune cell depletion in vivo, multiple orthogonal approaches; 68 citations\",\n      \"pmids\": [\"31048498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HIV-1 Tat induces expression of MMP-3 and MMP-13 in astrocytes, which then activate PAR1 to stimulate release of CCL2 (a chemokine promoting CNS entry of HIV-infected monocytes). Both genetic knockout and pharmacological inhibition of PAR1 reduced Tat/MMP-induced CCL2 release from astrocytes.\",\n      \"method\": \"Astrocyte cultures; HIV-1 Tat exposure; MMP-3 and MMP-13 expression; PAR1 genetic knockout and pharmacological inhibition; CCL2 ELISA; post-mortem HIV brain tissue correlation analysis\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO plus pharmacological inhibition plus human tissue validation; single lab\",\n      \"pmids\": [\"31124192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BMX kinase represses thrombin-PAR1-mediated endothelial permeability by directly phosphorylating PAR1 and promoting its internalization and deactivation. BMX loss increased thrombin-mediated endothelial permeability 2-3 fold. Pretreatment with PAR1 antagonist SCH79797 rescued BMX-loss-mediated endothelial permeability and pulmonary leakage in early sepsis.\",\n      \"method\": \"BMX-KO mice; cecal ligation and puncture sepsis model; electric cell-substrate impedance sensing (transendothelial electrical resistance); modified Miles assay (vascular leakage); biochemical analysis of BMX-PAR1 phosphorylation; PAR1 internalization assays; PAR1 antagonist pretreatment\",\n      \"journal\": \"Circulation Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct phosphorylation demonstrated biochemically; KO mice with PAR1 antagonist rescue; in vivo and in vitro concordant; 44 citations\",\n      \"pmids\": [\"31910739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"F2R (PAR1) negatively regulates osteoclastogenesis by inhibiting both the Akt and NF-κB signaling pathways in response to RANKL stimulation. F2r knockdown increased osteoclast activity, number, size, bone resorption, F-actin ring formation, and osteoclast marker gene expression with significantly increased pAkt levels and enhanced phosphorylation of p65 and IKBα. F2r overexpression blocked osteoclast formation, maturation, and acidification.\",\n      \"method\": \"sh-F2r lentivirus knockdown and pLX304-F2r overexpression in mouse bone marrow cells; RANKL-induced osteoclastogenesis; pAkt Western blot; p65 and IKBα phosphorylation; osteoclast activity assays; F-actin ring staining; bone resorption pit assay\",\n      \"journal\": \"International Journal of Biological Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function and gain-of-function with signaling pathway analysis; single lab\",\n      \"pmids\": [\"32226307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GZMA secreted by cytotoxic T cells interacts with F2R (PAR1) expressed on hepatocellular carcinoma tumor cells via the LDPRSFLL motif at the N-terminus of F2R, activating the JAK2/STAT1 signaling pathway to promote tumor cell apoptosis and T cell-mediated killing. This interaction was demonstrated both in vivo and in vitro.\",\n      \"method\": \"Single-cell sequencing; co-culture in vitro; in vivo mouse tumor model; GZMA-F2R interaction studies; JAK2/STAT1 pathway activation assays; N-terminus LDPRSFLL motif analysis; apoptosis assays\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo validation with pathway mechanism; single lab; 32 citations\",\n      \"pmids\": [\"35256589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Platelet-derived MMP-2 triggers endothelial PAR1 to initiate atherosclerosis via p38MAPK signaling and expression of adhesion molecules. Double knockout mice lacking LDLR and blood cell MMP-2 developed significantly less femoral intima thickening and aortic atherosclerotic lesions. Transfusion of activated WT but not MMP-2-/- platelets enhanced atherosclerotic lesions in LDLR-/- mice.\",\n      \"method\": \"Double knockout mice (LDLR-/-/blood cell MMP-2-/-); platelet transfusion experiments; photochemical arterial injury model; atherogenic diet; en face aortic lesion quantification; in vitro co-incubation studies (platelets, monocytes/macrophages, endothelial cells); p38MAPK signaling assays\",\n      \"journal\": \"European Heart Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic double KO plus bone marrow transplant/transfusion approach; in vivo plus mechanistic in vitro; 48 citations\",\n      \"pmids\": [\"34529782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Senescent hepatocytes upregulate the THBD-PAR1 signaling axis to remain viable ('undead'), and this promotes fibrogenic factor expression (including hedgehog ligands) that drives maladaptive liver repair in NASH. Inducing hepatocyte senescence upregulates THBD-PAR1 in hepatocytes. Inhibiting PAR1 with vorapaxar reduces the burden of senescent cells, limits HSC reprogramming, and improves NASH and fibrosis despite ongoing lipotoxic stress.\",\n      \"method\": \"Viral p16 overexpression to induce hepatocyte senescence; conditioned medium HSC reprogramming; vorapaxar treatment in NASH mouse models (genetic obesity and Western diet/CCl4); NAFLD liver biopsy analysis; transcriptomics of senescent hepatocytes; hedgehog ligand expression\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo NASH models plus mechanistic hepatocyte senescence studies; single lab; 25 citations\",\n      \"pmids\": [\"37036206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Parmodulins are small-molecule allosteric modulators that bind PAR1 intracellularly, inhibiting coagulation and platelet activation while maintaining cytoprotective endothelial signaling typically provoked by APC via PAR1. Structural analysis reveals parmodulins interact with the intracellular surface of PAR1, distinct from orthosteric antagonist binding.\",\n      \"method\": \"Review consolidating primary mechanistic data; structural interaction modeling comparing parmodulin binding to other intracellular allosteric GPCR modulators; preclinical pharmacological studies\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — mechanistic review with structural modeling; summarizes published primary data\",\n      \"pmids\": [\"36952648\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"F2R (PAR1) is a seven-transmembrane GPCR activated by a unique proteolytic mechanism in which thrombin (or other proteases including plasmin, MMP-1, MMP-13, KLK6) cleaves the N-terminal exodomain to expose a tethered ligand that self-activates the receptor; the receptor couples to Gq, Gi, and G12/13 to mediate platelet activation, endothelial barrier regulation (both disruptive and protective depending on context), inflammation, angiogenesis, and tumor invasion, with signaling specificity modulated by the identity of the activating protease (biased agonism), co-receptor occupancy (EPCR switching PAR1 to Gi/barrier-protective signaling), post-activation phosphorylation by BMX promoting internalization, metalloproteinase-dependent exodomain shedding, and cross-talk with PAR2, S1P receptors, and intracellular effectors including zyxin, HMGA2, and the Gα13–DVL–β-catenin axis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"F2R (PAR1) is a protease-activated G protein-coupled receptor that links extracellular proteolysis to intracellular signaling across hemostasis, inflammation, vascular biology, neuronal remodeling, and cancer. Thrombin cleaves the PAR1 N-terminal exodomain at Arg41 to unmask a tethered ligand, while noncanonical cleavage by plasmin, MMP-1/MMP-13, APC, KLK6, FVIIa, or bacterial SpeB at distinct sites produces biased signaling outputs or receptor desensitization [PMID:10194379, PMID:23086754, PMID:14577849, PMID:23647384, PMID:24278414]. Activated PAR1 couples to Gα12/13–RhoA, Gαi, and Gαq to drive cytoskeletal reorganization, ERK/MAPK and NF-κB activation, β-catenin stabilization via a Gα13–Dishevelled axis, and Hippo–YAP pathway inhibition, with signaling modulated by BMX kinase-mediated phosphorylation and internalization, ADAM17-dependent exodomain shedding, and PAR4/PAR2 cross-talk [PMID:11360179, PMID:11919159, PMID:20223821, PMID:31910739, PMID:14982936, PMID:17965715]. In vivo, PAR1 controls vascular barrier integrity, intestinal angiogenesis, sepsis-associated inflammation via dendritic cell S1P3 co-signaling, renal ischemia–reperfusion injury through chemokine production, and tumor immune evasion by suppressing CD8+ T cell killing [PMID:18305483, PMID:22407318, PMID:16990608, PMID:31048498].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Resolved how plasmin disarms PAR1 rather than activating it: plasmin cleaves the exodomain at R70/K76/K82 (downstream of the thrombin site), removing the tethered ligand and desensitizing the receptor — establishing the principle of protease-specific exodomain processing as a regulatory mechanism.\",\n      \"evidence\": \"In vitro cleavage/mass spectrometry with site-directed mutagenesis and Ca²⁺ signaling in yeast and COS7 cells\",\n      \"pmids\": [\"10194379\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether plasmin desensitization occurs at physiological concentrations on platelets in vivo\", \"Structural basis of differential cleavage site accessibility\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Established that PAR1 oncogenic transformation requires thrombin cleavage and operates through Gα12/13–RhoA and Gαi signaling, positioning PAR1 as a multi-G-protein-coupled oncogene rather than a simple hemostatic receptor.\",\n      \"evidence\": \"Focus-forming assays with dominant-negative RhoA, pertussis toxin, RGS-Lsc, and thrombin-uncleavable PAR1 mutant in NIH3T3 cells\",\n      \"pmids\": [\"11360179\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which G-protein pathway dominates in specific tumor contexts\", \"Whether endogenous thrombin levels in tumor microenvironment suffice for chronic activation\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrated that PAR1 drives cellular invasion through a RhoA/RhoD-dependent switch between Gα12/13–ROCK and Gαq–PLC–MLCK, revealing how a single receptor generates context-dependent invasive behaviors.\",\n      \"evidence\": \"Pertussis toxin, C3 exoenzyme, dominant-negative/active Rho constructs with invasion assays in epithelial cancer cells\",\n      \"pmids\": [\"11919159\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of signals that toggle the RhoA/RhoD switch in vivo\", \"Whether this switch operates in non-epithelial invasion contexts\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed that APC signals through PAR1 in an EPCR-dependent manner to induce anti-inflammatory gene programs in endothelial cells, establishing PAR1 as a conduit for the cytoprotective arm of the protein C pathway.\",\n      \"evidence\": \"PAR1 cleavage-blocking antibodies abolish APC-induced MAPK phosphorylation and gene induction in HUVECs\",\n      \"pmids\": [\"14577849\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise APC cleavage site on PAR1 exodomain relative to thrombin site\", \"Mechanism of biased signaling from APC versus thrombin\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified ADAM17/TACE-dependent metalloproteinase shedding of the PAR1 exodomain as a distinct regulatory mechanism, with structural determinants residing in the N-terminal domain rather than the transmembrane core.\",\n      \"evidence\": \"Chimeric PAR1 constructs, metalloproteinase inhibitors (TAPI-2, TIMP-3), phorbol ester stimulation in endothelial cells\",\n      \"pmids\": [\"14982936\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact ADAM17 cleavage site on PAR1\", \"Physiological triggers beyond PMA/agonist stimulation\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated that PAR1 deficiency protects from renal ischemia–reperfusion injury by reducing CXC chemokine production and neutrophil recruitment, placing PAR1 downstream of TF/thrombin generation and upstream of inflammatory chemokine expression in vivo.\",\n      \"evidence\": \"PAR1⁻/⁻ and PAR2⁻/⁻ mice with hirudin epistasis in renal I/R model\",\n      \"pmids\": [\"16990608\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell type(s) in kidney expressing the critical PAR1 pool\", \"Whether PAR1 blockade is therapeutic post-injury\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Quantified the kinetic basis of thrombin's selectivity for PAR1 (kcat 340 s⁻¹, Km 28 μM) versus PAR4, identifying P4 Leu and P2 Pro as critical determinants — providing a biophysical framework for differential receptor activation kinetics on platelets.\",\n      \"evidence\": \"Recombinant exodomain kinetics with systematic Ala-scanning mutagenesis\",\n      \"pmids\": [\"17595115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How membrane environment and cofactors alter these kinetics\", \"Structural explanation for P4/P2 contributions\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Revealed that PAR1 switches from vascular-disruptive to vascular-protective during sepsis progression via transactivation of PAR2, establishing receptor cross-talk as a mechanism for context-dependent PAR1 signaling.\",\n      \"evidence\": \"PAR1- and PAR2-targeting pepducins in cecal ligation/puncture and endotoxin sepsis mouse models\",\n      \"pmids\": [\"17965715\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of PAR1-to-PAR2 transactivation\", \"Whether PAR1–PAR2 heterodimer formation is required\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected PAR1 to systemic innate immune amplification: PAR1 on dendritic cells couples coagulation to S1P3-dependent IL-1β dissemination, and loss of either receptor confines inflammation to draining lymph nodes.\",\n      \"evidence\": \"PAR1⁻/⁻ and S1P3⁻/⁻ mice, dendritic cell adoptive transfer, sepsis models with cytokine measurement\",\n      \"pmids\": [\"18305483\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PAR1–S1P3 crosstalk involves physical receptor interaction or shared downstream effectors\", \"Relevance to human sepsis\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified mitochondrial complex III-derived ROS as a required intermediary in PAR1-induced tissue factor expression in endothelial cells, with NF-κB as a PAR1-selective (not PAR2-shared) downstream module.\",\n      \"evidence\": \"Mitochondrial inhibitors, ERK/p38 inhibitors, NF-κB inhibitors with TF activity readout in HUVECs\",\n      \"pmids\": [\"18983479\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PAR1 signals to mitochondria\", \"Whether mitochondrial ROS pathway operates in non-endothelial cells\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified zyxin as a direct PAR1 C-terminal binding partner that mediates thrombin-induced actin stress fibers and SRE-dependent transcription independently of RhoA and heterotrimeric G proteins, revealing a G-protein-independent signaling arm.\",\n      \"evidence\": \"Co-immunoprecipitation, siRNA knockdown, dominant-interfering peptide in endothelial cells\",\n      \"pmids\": [\"19690217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PAR1 C-tail–zyxin interaction\", \"Whether zyxin pathway is active in platelets\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Uncovered a Wnt-independent β-catenin stabilization pathway: PAR1 selectively engages Gα13 to recruit Dishevelled via its DIX domain, activating Lef/Tcf transcription and invasion without requiring Frizzled/LRP5/6.\",\n      \"evidence\": \"Dominant-negative Gα13, DVL/LRP5/6 siRNA, Lef/Tcf reporters, invasion assays, PAR1-transgenic mouse mammary tissue\",\n      \"pmids\": [\"20223821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Gα13 physically recruits DVL\", \"Whether this pathway operates in normal tissue homeostasis\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed that PAR4 co-activation rescues PAR1 desensitization in human platelets through a Gαi/P2Y12-dependent mechanism, explaining why dual PAR signaling sustains platelet activation despite rapid PAR1 internalization.\",\n      \"evidence\": \"PAR1- and PAR4-specific peptides with Ca²⁺, PKC, granule secretion, and aggregation readouts in isolated human platelets\",\n      \"pmids\": [\"21391917\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PAR1–PAR4 heterodimers form on platelets\", \"Quantitative threshold of PAR1 desensitization triggering PAR4 dominance\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that MMP-1/MMP-13 cleave PAR1 at noncanonical sites generating biased tethered ligands with distinct signaling outputs from thrombin, providing a molecular basis for protease-specific PAR1 agonism in disease.\",\n      \"evidence\": \"Biochemical cleavage assays and comparative G-protein signaling profiles\",\n      \"pmids\": [\"23086754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the specific noncanonical cleavage sites at amino acid resolution\", \"In vivo relevance of MMP-biased PAR1 signaling\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Placed PAR1 in a gut microbiota–TF–thrombin signaling axis driving intestinal angiogenesis: commensal colonization promotes TF-dependent thrombin generation that signals specifically through PAR1 (not PAR2) to induce angiopoietin-1 and vascular remodeling.\",\n      \"evidence\": \"Germ-free colonization, F2r⁻/⁻ vs F2rl1⁻/⁻ mice, hirudin, TF cytoplasmic domain deletion mice, vessel quantification\",\n      \"pmids\": [\"22407318\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which intestinal cell type is the primary PAR1-expressing target\", \"Whether this pathway contributes to tumor angiogenesis in the gut\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended PAR1's protease repertoire to KLK6 in the nervous system: KLK6 activates PAR1–ERK signaling to drive neurodegeneration and suppress myelin protein expression, linking PAR1 to neuroinflammatory demyelination.\",\n      \"evidence\": \"PAR1⁻/⁻ mice, PAR1/PAR2 lipopeptide inhibitors, ERK assays in cerebellar and motor neurons, oligodendrocyte myelin gene expression\",\n      \"pmids\": [\"23647384\", \"23832758\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KLK6 cleaves PAR1 at a unique or canonical site\", \"Therapeutic window for PAR1 inhibition in demyelinating disease\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed that FVIIa–EPCR signals anti-inflammatory effects through PAR1 and β-arrestin-1 by impairing TRAF2 recruitment to TNFR1, establishing a second EPCR-dependent biased PAR1 signaling pathway distinct from the APC–EPCR axis.\",\n      \"evidence\": \"siRNA of PAR1/EPCR/β-arrestin-1, EPCR-deficient and overexpressing mice, TRAF2 co-IP, LPS inflammation model\",\n      \"pmids\": [\"29669778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FVIIa and APC compete for PAR1 on the same cell\", \"Structural basis for β-arrestin-1-biased versus G-protein signaling from PAR1\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated that tumor cell-intrinsic PAR1 promotes immune evasion: PAR1 CRISPR knockout abolishes pancreatic tumor growth in immunocompetent but not immunodeficient mice, with suppression of CD8⁺ T cell killing as the mechanism.\",\n      \"evidence\": \"CRISPR PAR1 KO in KPC cells, syngeneic vs NSG mouse allografts, CD8 depletion epistasis\",\n      \"pmids\": [\"31048498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which PAR1 suppresses CD8 T cell function\", \"Whether PAR1 inhibitors can synergize with checkpoint immunotherapy\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified BMX kinase as a direct PAR1 phosphorylation partner that promotes receptor internalization and signal termination; BMX loss amplifies thrombin-PAR1 permeability, rescuable by PAR1 antagonist — establishing a kinase-dependent desensitization mechanism.\",\n      \"evidence\": \"BMX KO mice, impedance sensing, Miles assay, biochemical phosphorylation, PAR1 antagonist SCH79797 rescue\",\n      \"pmids\": [\"31910739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific PAR1 residues phosphorylated by BMX\", \"Whether BMX-mediated desensitization is specific to PAR1 or applies to other PARs\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for how different proteases generate biased tethered ligands at distinct cleavage sites, the molecular mechanism of PAR1-to-PAR2 transactivation, the cell-type-specific determinants of Gα-subunit coupling choice, and whether PAR1 inhibition can be harnessed for cancer immunotherapy.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No co-crystal structure of PAR1 with any activating protease\", \"Mechanism of PAR1–PAR2 transactivation undefined at molecular level\", \"No systematic mapping of cell-type-specific G-protein coupling preferences\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 3, 4, 5, 8, 17]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [23, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 13, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 5, 10, 16, 22, 29]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [3, 9, 19]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6, 12, 26, 29]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [21, 22, 26, 32]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RHOA\", \"BMX\", \"ZYX\", \"DVL2\", \"S1PR3\", \"EPCR\", \"ADAM17\", \"GNA13\"],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"F2R (PAR1) is a protease-activated G protein-coupled receptor that transduces extracellular proteolytic signals into diverse intracellular responses governing hemostasis, vascular barrier integrity, inflammation, angiogenesis, and tumor biology. Thrombin cleaves the PAR1 N-terminal exodomain at Arg41 to unmask a tethered peptide ligand (SFLLRN) that self-activates the receptor, coupling to Gq, Gi, and G12/13 to drive platelet aggregation, endothelial permeability changes, RhoA-dependent cytoskeletal remodeling, and NF-κB/MAPK-mediated gene expression [PMID:1672265, PMID:8290554, PMID:11360179]. Signaling specificity is determined by the activating protease—MMP-1, MMP-13, and KLK6 cleave PAR1 at noncanonical sites generating biased tethered ligands with distinct G-protein coupling and functional outputs—and by co-receptor context, as EPCR occupancy by APC or protein C switches PAR1 from Gq/G12/13-driven barrier disruption to Gi-dependent barrier protection via sphingosine kinase–S1P1 cross-activation [PMID:19379698, PMID:23086754, PMID:17823308, PMID:15626732]. Post-activation fate is governed by BMX kinase-mediated phosphorylation promoting internalization, ADAM17-dependent exodomain shedding limiting surface receptor availability, lysosomal degradation of cleaved receptors, and replenishment from an intracellular Golgi-associated reserve pool [PMID:31910739, PMID:14982936, PMID:7961693].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Identification of PAR1 as the first protease-activated receptor established a fundamentally new GPCR activation paradigm—irreversible proteolytic unmasking of a tethered ligand—resolving how thrombin could signal through a cell-surface receptor.\",\n      \"evidence\": \"Expression cloning in Xenopus oocytes with site-directed mutagenesis of the thrombin cleavage site and synthetic peptide agonist validation\",\n      \"pmids\": [\"1672265\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream G-protein coupling partners not yet identified\", \"Mechanism of receptor resensitization after irreversible cleavage unknown\", \"Whether other proteases could activate PAR1 not addressed\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defining PAR1's G-protein partners (Gq, G12, G13) and its unconventional trafficking—lysosomal degradation of cleaved receptors plus mobilization of a Golgi-stored reserve pool—explained how cells restore thrombin responsiveness despite irreversible receptor activation.\",\n      \"evidence\": \"Subtype-specific G-protein coupling assays in platelets; subcellular fractionation and Golgi co-localization in transfected fibroblasts\",\n      \"pmids\": [\"8290554\", \"7961693\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery controlling reserve pool translocation undefined\", \"Relative contributions of Gq vs G12/13 to specific platelet responses not dissected\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing that PAR1 and PAR4 together account for virtually all thrombin-mediated human platelet activation, and that plasmin can both transiently activate and dominantly desensitize PAR1 by cleaving distal to Arg41, revealed protease-specific regulation of receptor availability.\",\n      \"evidence\": \"Orthogonal PAR1/PAR4 blocking strategies in human platelet aggregation; kinetic and mutagenesis analysis of plasmin cleavage sites on PAR1 exodomain\",\n      \"pmids\": [\"10079109\", \"10194379\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether plasmin-PAR1 desensitization is physiologically relevant in vivo not demonstrated\", \"Structural basis for differential thrombin vs plasmin exodomain recognition unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Discovery that activated protein C signals through PAR1 in an EPCR-dependent manner to elicit cytoprotective endothelial responses reframed PAR1 as a context-dependent signaling hub whose output depends on co-receptor occupancy, not just protease identity.\",\n      \"evidence\": \"Cleavage-blocking PAR1 antibodies abolished APC-induced MAP kinase activation and gene induction in HUVECs; microarray profiling\",\n      \"pmids\": [\"12052963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which EPCR binding switches PAR1 G-protein coupling not defined\", \"Whether APC cleaves PAR1 at a different site than thrombin not resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of ADAM17-mediated PAR1 exodomain shedding as a regulated mechanism to limit surface receptor availability, and demonstration that EPCR-PAR1 barrier protection operates through sphingosine kinase-1 and S1P1, defined two new layers of PAR1 signal regulation.\",\n      \"evidence\": \"Metalloproteinase inhibitor panel and domain-swap constructs in endothelial cells; siRNA knockdown of SphK1 and S1P1 in dual-chamber barrier assays\",\n      \"pmids\": [\"14982936\", \"15626732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of physiological stimuli for ADAM17-PAR1 shedding in vivo unclear\", \"Whether S1P1 cross-activation occurs in non-endothelial PAR1-expressing cells untested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"MMP-1 was identified as a non-thrombin protease agonist of PAR1 that promotes breast cancer invasion in vivo, demonstrating that the tumor microenvironment co-opts PAR1's tethered-ligand mechanism for malignant progression.\",\n      \"evidence\": \"MMP-1 cleavage site mapping; Ca²⁺ signaling; PAR1-dependent xenograft tumor growth and invasion\",\n      \"pmids\": [\"15707890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MMP-1 generates the same or distinct tethered ligand as thrombin not fully resolved\", \"Relative contribution of stromal vs autocrine MMP-1 in human tumors unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Mechanistic resolution of how EPCR occupancy redirects PAR1 signaling: protein C/APC Gla domain binding dissociates EPCR from caveolin-1 in lipid rafts, switching PAR1 coupling from Gq/G12/13 to pertussis toxin-sensitive Gi, explaining the paradox of barrier-protective versus barrier-disruptive PAR1 signaling.\",\n      \"evidence\": \"Lipid raft isolation, EPCR-caveolin-1 co-immunoprecipitation, pertussis toxin blockade, and functional permeability assays in endothelial cells\",\n      \"pmids\": [\"17823308\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of EPCR-PAR1 physical interaction not defined at atomic level\", \"Whether lipid raft relocation is necessary or sufficient for G-protein switch untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstration that platelet MMP-1 cleaves PAR1 at a cryptic site distinct from thrombin's, preferentially activating RhoA-GTP and MAPK rather than canonical Ca²⁺ signaling, established the concept of protease-specific biased agonism at PAR1 with distinct thrombotic consequences.\",\n      \"evidence\": \"Cleavage site mapping, Rho-GTP signaling, in vivo thrombosis model with MMP1-PAR1 blockade; zyxin co-IP with PAR1 C-terminus and siRNA-mediated dissection of G-protein-independent cytoskeletal signaling\",\n      \"pmids\": [\"19379698\", \"19690217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full repertoire of biased signaling outputs from different protease-generated tethered ligands not catalogued\", \"Structural basis of biased coupling at the receptor level unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"PAR1 was found to activate β-catenin stabilization through a Wnt-independent Gα13–Dishevelled axis, expanding its oncogenic repertoire beyond RhoA to include transcriptional reprogramming via Lef/Tcf targets.\",\n      \"evidence\": \"siRNA-DVL silencing, dominant negative Gα13, Lef/Tcf reporter, Matrigel invasion, and PAR1-transgenic mouse mammary tissue\",\n      \"pmids\": [\"20223821\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Gα13-DVL axis operates in non-tumor contexts untested\", \"Direct physical contacts between Gα13 and DVL not structurally resolved\", \"Findings from a single lab\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The 2.2 Å crystal structure of PAR1 bound to vorapaxar revealed an unusually shallow, solvent-occluded orthosteric pocket, explaining the near-irreversible antagonism by vorapaxar and providing an atomic framework for understanding tethered-ligand docking.\",\n      \"evidence\": \"X-ray crystallography of PAR1–vorapaxar complex at 2.2 Å resolution\",\n      \"pmids\": [\"23222541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of activated PAR1 with tethered ligand engaged not available\", \"No structure of PAR1 in complex with G proteins\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"FVIIa–EPCR engagement was shown to activate anti-inflammatory PAR1 signaling through β-arrestin-1, which blocks TRAF2 recruitment to TNFR1, extending the list of EPCR-dependent PAR1 co-agonists and linking coagulation factor VII to innate immune suppression.\",\n      \"evidence\": \"PAR1/EPCR/β-arrestin-1 siRNA; TRAF2 co-IP; kinase activation panels; in vivo LPS models in EPCR-overexpressing and EPCR-deficient mice\",\n      \"pmids\": [\"29669778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether FVIIa cleaves PAR1 at a unique site not mapped\", \"Relative physiological importance of FVIIa vs APC as EPCR-PAR1 agonist in vivo unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"PAR1 was identified as a mediator of tumor immune evasion: PAR1-deleted pancreatic tumor cells failed to grow in immunocompetent but not immunodeficient hosts, with CD8+ T cell depletion rescuing growth, positioning the TF–thrombin–PAR1 axis as a tumor-intrinsic immune checkpoint.\",\n      \"evidence\": \"CRISPR PAR1-KO KPC allografts in immunocompetent vs NSG mice; CD8/CD4/NK depletion; TF/prothrombin ASO depletion\",\n      \"pmids\": [\"31048498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PAR1 suppresses CD8+ T cell function not molecularly defined\", \"Generalizability beyond pancreatic adenocarcinoma untested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"BMX kinase was identified as a direct PAR1 phosphorylating kinase that promotes receptor internalization and limits thrombin-induced endothelial permeability, with PAR1 antagonism rescuing vascular leak in BMX-deficient sepsis models.\",\n      \"evidence\": \"BMX-KO mice; CLP sepsis model; ECIS permeability; biochemical PAR1 phosphorylation; PAR1 antagonist rescue in vivo\",\n      \"pmids\": [\"31910739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific PAR1 phosphorylation sites targeted by BMX not mapped\", \"Whether BMX regulates PAR1 in platelets or other cell types unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include: the activated-state structure of PAR1 with tethered ligand engaged and G-protein bound; the precise molecular basis by which different protease-generated tethered ligands achieve biased coupling to distinct G proteins; and whether intracellular allosteric modulators (parmodulins) can therapeutically separate PAR1's prothrombotic from cytoprotective functions in clinical settings.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No activated-state PAR1 structure with tethered ligand or G-protein complex\", \"Biased agonism mechanism at atomic resolution unknown\", \"Clinical translation of pathway-selective PAR1 modulation unproven\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 5, 21, 27]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [18, 12, 35]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 11, 31]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 6, 8, 18, 23, 35]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [4, 21, 25, 41]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [17, 19, 36, 37]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 13, 32, 36]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [12, 31, 41]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PROCR\",\n      \"F2\",\n      \"MMP1\",\n      \"GNA13\",\n      \"GNAQ\",\n      \"ZYX\",\n      \"BMX\",\n      \"DVL1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}