{"gene":"RASGRP2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2000,"finding":"RasGRP2 is targeted to the plasma membrane by N-terminal myristoylation and palmitoylation, and selectively catalyzes nucleotide exchange on N- and Ki-Ras (but not Ha-Ras) and on Rap1 in vivo; its GEF activity toward N-Ras is stimulated by diacylglycerol and inhibited by calcium.","method":"Cloning, in vivo GEF activity assays, subcellular localization studies, lipid analog treatment in NIH3T3 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — direct biochemical characterization with multiple orthogonal methods in a single rigorous study","pmids":["10918068"],"is_preprint":false},{"year":2002,"finding":"CalDAG-GEFI functions as a Rap1 exchange factor that enhances agonist-induced activation of Rap1b and fibrinogen binding to integrin αIIbβ3 in megakaryocytes, implicating it in inside-out integrin signaling.","method":"Retroviral overexpression in ES cell-derived megakaryocytes, Rap1 activation assay, fibrinogen binding flow cytometry","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — direct gain-of-function in primary cell model with functional readout, replicated across multiple studies","pmids":["12239348"],"is_preprint":false},{"year":2001,"finding":"CalDAG-GEFI forms a signaling complex with Rap1 and B-Raf downstream of M1 muscarinic acetylcholine receptors; calcium and diacylglycerol signals stimulate the sequential activation of CalDAG-GEFI, Rap1, and B-Raf, leading to MEK/ERK1/2 activation.","method":"Co-immunoprecipitation, antisense RNA knockdown, HA-tagged B-Raf activation assay in PC12D cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, antisense knockdown, and functional pathway assay in the same study","pmids":["11292831"],"is_preprint":false},{"year":2004,"finding":"CalDAG-GEFI (RasGRP2) is crucial for Rap1-dependent integrin signaling in platelets; genetic ablation in mice severely impairs integrin-dependent platelet aggregation and thrombus formation.","method":"Genetic knockout mouse, platelet aggregation assays, Rap1 activation assay, in vivo thrombosis models","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype, replicated by multiple independent labs","pmids":["15334074"],"is_preprint":false},{"year":2004,"finding":"RasGRP2 subcellular localization is regulated by actin dynamics; induction of F-actin by Vav, Vav2, Dbl, or Rac1 translocates RasGRP2 from cytosol to membrane ruffles through direct association of its N-terminal 150 amino acids with F-actin, leading to regionalized Rap1 activation.","method":"Fluorescence microscopy, cytoskeletal disrupting drugs, Rac1 effector mutants, F-actin co-sedimentation biochemical assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — direct biochemical binding assay combined with live-cell imaging and mutagenesis","pmids":["14988412"],"is_preprint":false},{"year":2007,"finding":"CalDAG-GEFI controls activation of β1, β2, and β3 integrins in hematopoietic cells (neutrophils and platelets) via Rap1; CalDAG-GEFI-deficient neutrophils show defects in Rap1 activation, integrin-mediated adhesion and migration, recapitulating LAD-III syndrome.","method":"CalDAG-GEFI knockout mice, neutrophil adhesion and migration assays, Rap1 activation pull-down, intravital microscopy","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with multiple orthogonal functional assays, replicated by independent groups","pmids":["17492052"],"is_preprint":false},{"year":2007,"finding":"A splice junction mutation in the CalDAG-GEFI gene in human LAD-III patients reduces CalDAG-GEFI mRNA and protein in lymphocytes, neutrophils, and platelets, abrogating Rap1 activation and β1, β2, and β3 integrin activation (inside-out signaling).","method":"Human patient genetics, protein expression analysis, Rap1 activation assay, integrin activation flow cytometry, cell adhesion assays","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — human genetic validation with multiple functional assays, independently corroborated","pmids":["17576779"],"is_preprint":false},{"year":2007,"finding":"CalDAG-GEFI/Rap1 signaling selectively mediates SDF-1α- and PMA-induced LFA-1 activation (adhesion to ICAM-1) but not VLA-4 activation in primary human T cells; silencing CalDAG-GEFI blocks Rap1 activation and LFA-1-dependent adhesion without affecting VLA-4/VCAM-1 binding.","method":"siRNA knockdown of CalDAG-GEFI in human primary CD3+ T cells, Rap1 activation assay, cell adhesion assays to ICAM-1 and VCAM-1","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — specific knockdown in primary human cells with parallel functional readouts","pmids":["17702895"],"is_preprint":false},{"year":2008,"finding":"CalDAG-GEFI and protein kinase C represent independent, synergizing pathways for Rap1 and αIIbβ3 activation in platelets; CalDAG-GEFI mediates rapid but reversible Rap1 activation, while PKC/Gαi/P2Y12 signaling mediates a second, sustained wave of Rap1 activation.","method":"CalDAG-GEFI knockout platelets, PKC inhibitor, Rap1 activation assay, aggregation assays, P2Y12 receptor pharmacology","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — genetic KO combined with pharmacological inhibition and functional assays, replicated","pmids":["18544684"],"is_preprint":false},{"year":2009,"finding":"CalDAG-GEFI is the primary calcium sensor in platelets; through Rap1, it directly triggers integrin activation and ERK-dependent thromboxane A2 (TxA2) release; CalDAG-GEFI-dependent TxA2 generation provides feedback for PKC activation and granule release.","method":"CalDAG-GEFI knockout mice, Rap1 activation assay, TxA2 measurement, ERK activation assay, platelet aggregation and granule secretion assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with multiple orthogonal mechanistic readouts defining pathway hierarchy","pmids":["19628710"],"is_preprint":false},{"year":2011,"finding":"CalDAG-GEFI (Rasgrp2) and p38 MAPK are key signaling intermediates between PLCγ2 and Rap1a activation downstream of E-selectin engagement; this pathway mediates integrin αLβ2-dependent slow leukocyte rolling and neutrophil recruitment into inflamed tissues.","method":"Rasgrp2-/- mice, dominant-negative Tat-fusion mutants, intravital microscopy, flow chamber, peritonitis model, biochemical Rap1 activation assay","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — KO mice plus dominant-negative constructs with in vivo and in vitro functional validation","pmids":["21480213"],"is_preprint":false},{"year":2013,"finding":"PKA phosphorylates CalDAG-GEFI at S587 (major site) and S116/S117 (minor sites); phosphorylation at these sites inhibits CalDAG-GEFI-mediated Rap1b activation and platelet aggregation, representing a mechanism for cAMP/PKA-mediated platelet inhibition.","method":"Radioactive phosphate incorporation assay, mass spectrometry, phospho-antibody development, phosphomutant expression in HEK293 cells and platelets, Rap1-GTP pull-down assay","journal":"Journal of thrombosis and haemostasis : JTH","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro kinase assay, MS identification, and functional mutagenesis in two independent studies","pmids":["23611601","23600630"],"is_preprint":false},{"year":2013,"finding":"PKA phosphorylates CalDAG-GEFI at Ser116 and Ser586; a phospho-mimetic S587D mutant abolishes agonist-induced Rap1b activation, and a double Ser116/Ser586 alanine mutant abolishes cAMP-mediated inhibition of Rap1b, demonstrating these are the functional PKA phosphorylation sites.","method":"In vitro phosphorylation of purified recombinant CalDAG-GEFI by PKA catalytic subunit, serine-to-alanine and phosphomimetic mutants expressed in HEK293T cells and platelets, Rap1b activation assay, forskolin treatment","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay with recombinant protein plus mutagenesis validation in intact cells","pmids":["23600630"],"is_preprint":false},{"year":2014,"finding":"A missense mutation (cG742T) in RASGRP2 reduces CalDAG-GEFI-mediated Rap1 activation and αIIbβ3 inside-out signaling in human platelets and megakaryocytes; rescue experiments with wild-type RASGRP2 in cultured patient megakaryocytes correct the functional deficiency; reduced Rac1-GTP loading impairs thrombus formation and spreading.","method":"Whole-exome sequencing, HEK293T expression of mutant, Rap1 activation assay, flow cytometry for αIIbβ3 activation, flow-based thrombosis assay, Rac1-GTP assay, megakaryocyte rescue transfection","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1-2 — human genetics plus multiple functional assays and rescue experiment","pmids":["24958846"],"is_preprint":false},{"year":2013,"finding":"Phenylarsine oxide (PAO) binds directly to vicinal dithiol (cysteine) residues in CalDAG-GEFI, inducing disulfide-linked oligomers and inhibiting CalDAG-GEFI-stimulated GTP loading of Rap1, thereby blocking platelet aggregation; this identifies redox-sensitive cysteines as functionally important in CalDAG-GEFI.","method":"Biotin-streptavidin pull-down of PAO-CalDAG-GEFI complex, Western blot under reducing/non-reducing conditions, purified recombinant protein GTP-binding assay, HEK293T overexpression system","journal":"Thrombosis and haemostasis","confidence":"High","confidence_rationale":"Tier 1-2 — direct biochemical binding assay plus reconstituted in vitro GEF assay with purified proteins","pmids":["24352565"],"is_preprint":false},{"year":2016,"finding":"The C1 domain of RasGRP2 has very weak phorbol ester/DAG binding affinity (Kd ~2890 nM) due to four residues (Asn7, Ser8, Ala19, Ile21); replacing these with the corresponding RasGRP1/3 residues restores potent phorbol ester binding and membrane translocation, and enhanced C1 domain membrane targeting increases Rap1 activation.","method":"Structural mutagenesis, [3H]phorbol 12,13-dibutyrate binding assays, lipid co-sedimentation, cell translocation assay, Rap1 activation assay, molecular modeling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding assay with mutagenesis, structural modeling, and functional validation","pmids":["27022025"],"is_preprint":false},{"year":2016,"finding":"RASGRP2 mutations in the CDC25 catalytic domain (p.Ser381Phe, p.Arg113X) abolish nucleotide exchange activity of CalDAG-GEFI toward Rap1, causing impaired αIIbβ3 integrin activation in both platelets and neutrophils.","method":"Next-generation sequencing, in vitro GEF nucleotide exchange assay, flow cytometry for integrin activation, platelet aggregation","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 — direct in vitro GEF assay on mutant protein plus patient cell functional validation","pmids":["27235135"],"is_preprint":false},{"year":2018,"finding":"CalDAG-GEFI is autoinhibited at low cytosolic calcium; calcium binding to canonical EF hands causes conformational rearrangements in an autoinhibitory linker connecting the Cdc25 and EF hand domains, freeing the catalytic surface to engage and activate Rap1B. An additional mutation (V406E) disrupting the autoinhibitory linker-Cdc25 interface restores GEF activity to EF hand variants.","method":"Purified recombinant CalDAG-GEFI, hydrogen-deuterium exchange mass spectrometry, EF hand calcium-binding residue mutagenesis, in vitro Rap1B GEF assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro assay with mutagenesis and HDX-MS structural analysis on purified protein","pmids":["29622678"],"is_preprint":false},{"year":2018,"finding":"RasGRP2/Rap1 pathway mediates CD38-induced CLL cell migration; CD38 elevates intracellular Ca2+ to activate Rap1 via RasGRP2, and RasGRP2 is polarized in CLL cells with high CD38 expression; both Rap1 and RasGRP2 knockdown block CLL cell migration.","method":"siRNA knockdown of RasGRP2 and Rap1, Rap1 activation assay, cell migration assays, intracellular Ca2+ measurement, immunofluorescence localization","journal":"Blood advances","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA KD with functional readout in primary CLL cells, single lab","pmids":["29970392"],"is_preprint":false},{"year":2019,"finding":"The atypical C1 domain of CalDAG-GEFI interacts exclusively with phosphoinositides PIP2 and PIP3 (not DAG/phorbol esters) through a distinct phospholipid recognition motif; mutation of this motif abolishes lipid co-sedimentation and impairs membrane localization of CalDAG-GEFI in cells.","method":"Lipid co-sedimentation assays, molecular dynamics simulations, immunofluorescence, subcellular fractionation, C1 domain mutagenesis","journal":"Journal of thrombosis and haemostasis : JTH","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro lipid binding with mutagenesis plus cellular localization with functional consequence","pmids":["31758832"],"is_preprint":false},{"year":2019,"finding":"RasGRP2 activates R-Ras in addition to Rap1 in endothelial cells, and suppresses Bax activation-induced apoptosis via R-Ras–PI3K–Akt signaling, promoting hexokinase-2 translocation to mitochondria and blocking Bax mitochondrial translocation.","method":"RasGRP2 stable overexpression in HUVECs, Rap1 knockdown, R-Ras activation assay, Akt phosphorylation assay, Bax/HK-2 subcellular fractionation, flow cytometry for apoptosis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — stable OE plus Rap1 KD to distinguish pathways, single lab","pmids":["31723205"],"is_preprint":false},{"year":2018,"finding":"RASGRP2 is ectopically expressed in RA fibroblast-like synoviocytes (FLS), where it activates RAP-1 and subsequently promotes NF-κB signaling and actin dynamics, increasing FLS adhesion, migration, and IL-6 production; intra-articular RASGRP2 siRNA dampens experimental arthritis in rats.","method":"RASGRP2 transfection of FLS, RAP-1 activation assay, NF-κB reporter, migration/invasion assays, IL-6 ELISA, siRNA-mediated knockdown in rat collagen-induced arthritis model","journal":"Annals of the rheumatic diseases","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function and in vivo loss-of-function with multiple mechanistic readouts, single lab","pmids":["30076153"],"is_preprint":false},{"year":2021,"finding":"Genetic deletion of CalDAG-GEFI in mice disrupts dendritic M1 muscarinic receptor signaling in indirect pathway striatal spiny projection neurons, reduces temporal integration of EPSPs at dendritic glutamatergic synapses, and impairs activity-dependent LTP induction.","method":"Conditional CalDAG-GEFI knockout mice, electrophysiology (dendritic vs. somatic recordings), pharmacology, behavioral assays (psychostimulant-induced repetitive behaviors, sequence learning, cocaine self-administration)","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with in vitro electrophysiology plus in vivo behavioral/pharmacological validation","pmids":["34371144"],"is_preprint":false},{"year":2022,"finding":"DARPP-32/PP1 regulates the PKA-dependent phosphorylation of Rasgrp2 at Ser116/Ser117 and Ser586 in striatal neurons downstream of D1 receptor activation; PP2A regulates all phosphorylation sites of Rasgrp2 including Ser554.","method":"DARPP-32 knockout mice, PP1 inhibitor (tautomycetin), PP1/PP2A inhibitor (okadaic acid), phospho-site specific antibodies, D1 receptor agonist stimulation of striatal slices","journal":"Neurochemistry international","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO plus pharmacological dissection of phosphorylation in brain tissue, single lab","pmids":["36351540"],"is_preprint":false},{"year":2024,"finding":"CalDAG-GEFI acts as a physiological GEF for LRRK2, interacting with LRRK2 and increasing its GDP-to-GTP exchange activity; CalDAG-GEFI modulates LRRK2-induced neurodegeneration in Drosophila and mouse LRRK2 models.","method":"Co-immunoprecipitation of CDGI and LRRK2, in vitro GTP loading/exchange assay for LRRK2, Drosophila genetic model of LRRK2 neurodegeneration, mouse model experiments","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 1-2 — Co-IP plus in vitro GEF assay on LRRK2 and in vivo genetic validation in two model organisms, single lab","pmids":["39576856"],"is_preprint":false},{"year":2023,"finding":"RASGRP2 suppresses LUAD cell proliferation and induces mitochondrial-dependent apoptosis; cytological experiments showed that RASGRP2 regulates mitochondrial membrane potential.","method":"Clone formation assay, EdU proliferation assay, flow cytometry for apoptosis, fluorescence microscopy of mitochondrial membrane potential in LUAD cell lines","journal":"Frontiers in immunology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, mechanistic pathway placement incomplete, no upstream/downstream partners defined","pmids":["36817422"],"is_preprint":false},{"year":2014,"finding":"CLL2-1, a 1,4-phenanthrenequinone, inhibits CalDAG-GEFI function through thiol modification of redox-sensitive cysteines, inducing CalDAG-GEFI oligomerization and blocking Rap1 activation and platelet aggregation; in a purified recombinant protein system, CLL2-1 directly inhibited CalDAG-GEFI-stimulated GTP binding to Rap1.","method":"Western blot under reducing/non-reducing conditions, purified recombinant protein GTP-binding assay, HEK293T overexpression, flow cytometry, platelet aggregation assay","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 1 — direct in vitro GEF assay with purified proteins, complemented by cell-based assays, single lab","pmids":["25451646"],"is_preprint":false},{"year":2010,"finding":"CalDAG-GEFI is colocalized with axons and axon terminals of striatal projection neurons in the substantia nigra, as shown by subcellular fractionation of the substantia nigra with monoclonal antibodies against CalDAG-GEFI.","method":"In situ hybridization, subcellular fractionation, monoclonal antibody immunostaining","journal":"The Journal of comparative neurology","confidence":"Low","confidence_rationale":"Tier 3 — single localization method without functional consequence directly demonstrated","pmids":["11503142"],"is_preprint":false},{"year":2024,"finding":"NEDD4L interacts with RASGRP2 and ubiquitinates it, destabilizing RASGRP2 protein and reducing its expression in endothelial cells; NEDD4L knockdown reduces HG+oxLDL-induced endothelial dysfunction, an effect reversed by RASGRP2 downregulation.","method":"Co-IP assay, ubiquitination assay, NEDD4L knockdown, RASGRP2 overexpression/knockdown, cell viability/apoptosis/migration/angiogenesis assays, Western blot","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP and ubiquitination assay identifying NEDD4L as E3 ligase for RASGRP2, single lab","pmids":["39260747"],"is_preprint":false}],"current_model":"RASGRP2 (CalDAG-GEFI) is a calcium- and diacylglycerol-regulated guanine nucleotide exchange factor that, upon cytosolic calcium elevation, undergoes conformational release of autoinhibition at its EF hand–Cdc25 linker interface to activate Rap1 (and, in some contexts, R-Ras and LRRK2); active Rap1 drives inside-out activation of β1, β2, and β3 integrins in platelets, neutrophils, and T cells, mediating aggregation, adhesion, and thrombus formation, while PKA-mediated phosphorylation of CalDAG-GEFI at Ser116/Ser117 and Ser586/Ser587 restrains its activity; its atypical C1 domain binds PIP2/PIP3 (not DAG) to control membrane localization, and its N-terminal acylation and F-actin association direct spatial Rap1 activation."},"narrative":{"teleology":[{"year":2000,"claim":"Establishing RasGRP2 as a plasma-membrane-targeted, acylated GEF with selectivity for Rap1 and N-/Ki-Ras, regulated by DAG and calcium, answered the basic question of substrate specificity and subcellular targeting for this exchange factor.","evidence":"Cloning, in vivo GEF assays, subcellular localization, and lipid analog treatment in NIH3T3 cells","pmids":["10918068"],"confidence":"High","gaps":["Initial report suggested GEF activity toward N-Ras stimulated by DAG, later refined to Rap1 as physiological substrate","Mechanism of calcium inhibition versus activation not resolved"]},{"year":2001,"claim":"Demonstrating that CalDAG-GEFI forms a signaling complex with Rap1 and B-Raf downstream of muscarinic receptors established it as a node linking calcium/DAG signals to the MAPK cascade.","evidence":"Co-immunoprecipitation, antisense knockdown, and B-Raf activation assay in PC12D cells","pmids":["11292831"],"confidence":"High","gaps":["Whether CalDAG-GEFI–B-Raf complex formation is direct or scaffolded","Relevance of this pathway outside neuroendocrine cells"]},{"year":2002,"claim":"Showing that CalDAG-GEFI enhances Rap1b activation and fibrinogen binding to αIIbβ3 in megakaryocytes first linked this GEF to inside-out integrin signaling in the platelet lineage.","evidence":"Retroviral overexpression in ES-derived megakaryocytes, Rap1 activation assay, fibrinogen binding flow cytometry","pmids":["12239348"],"confidence":"High","gaps":["Overexpression system — endogenous requirement not yet shown"]},{"year":2004,"claim":"Genetic ablation of CalDAG-GEFI in mice proved it is essential for Rap1-dependent platelet aggregation and thrombus formation in vivo, and revealed that F-actin dynamics govern its spatial localization to membrane ruffles for regionalized Rap1 activation.","evidence":"KO mouse with platelet aggregation, in vivo thrombosis models; F-actin co-sedimentation, fluorescence microscopy, and Rac1 mutant analysis","pmids":["15334074","14988412"],"confidence":"High","gaps":["Relative contributions of acylation versus F-actin binding to membrane targeting in primary platelets","Whether actin-dependent localization is required for thrombus formation"]},{"year":2007,"claim":"Extending the KO phenotype to neutrophils and identifying human LAD-III patients with RASGRP2 splice mutations established CalDAG-GEFI as the master regulator of Rap1-driven β1/β2/β3 integrin activation across hematopoietic lineages and as a disease gene for LAD-III.","evidence":"KO mouse neutrophil adhesion/migration assays, intravital microscopy; human patient genetics with Rap1 activation and integrin function assays","pmids":["17492052","17576779"],"confidence":"High","gaps":["Whether residual integrin activation in patients/KO mice is CalDAG-GEFI-independent or represents hypomorphic alleles","Relative contribution of CalDAG-GEFI versus other Rap-GEFs in lymphocytes"]},{"year":2007,"claim":"Selective requirement of CalDAG-GEFI for LFA-1 but not VLA-4 activation in human T cells revealed integrin-specific control downstream of the same GEF, refining the model of inside-out signaling.","evidence":"siRNA knockdown in primary human CD3+ T cells, adhesion assays to ICAM-1 and VCAM-1","pmids":["17702895"],"confidence":"High","gaps":["Mechanism by which CalDAG-GEFI/Rap1 discriminates between LFA-1 and VLA-4","Whether this selectivity operates in other leukocyte subsets"]},{"year":2008,"claim":"Dissecting the temporal hierarchy of platelet Rap1 activation revealed CalDAG-GEFI mediates the rapid, reversible first wave while PKC/P2Y12 sustains a second wave, clarifying why CalDAG-GEFI loss alone does not fully abolish aggregation.","evidence":"CalDAG-GEFI KO platelets with PKC inhibitor, P2Y12 pharmacology, aggregation and Rap1 assays","pmids":["18544684"],"confidence":"High","gaps":["Identity of the GEF(s) mediating the PKC/P2Y12-dependent second wave"]},{"year":2009,"claim":"Identifying CalDAG-GEFI as the primary calcium sensor in platelets that triggers not only integrin activation but also ERK-dependent TxA2 generation revealed a feedforward loop amplifying platelet activation.","evidence":"KO mice with TxA2 measurement, ERK activation, granule secretion assays","pmids":["19628710"],"confidence":"High","gaps":["Whether CalDAG-GEFI directly activates ERK or requires intermediate effectors"]},{"year":2011,"claim":"Placing CalDAG-GEFI/p38 MAPK between PLCγ2 and Rap1a downstream of E-selectin engagement explained how selectin signals trigger integrin-dependent slow rolling, extending CalDAG-GEFI function from platelet biology to neutrophil recruitment.","evidence":"Rasgrp2−/− mice, dominant-negative Tat-fusion mutants, intravital microscopy, peritonitis model","pmids":["21480213"],"confidence":"High","gaps":["Whether p38 acts upstream or in parallel to CalDAG-GEFI in this context"]},{"year":2013,"claim":"Identification and functional validation of PKA phosphorylation sites Ser116/Ser117 and Ser586/Ser587 on CalDAG-GEFI provided the molecular mechanism for cAMP/PKA-mediated inhibition of Rap1 activation and platelet function.","evidence":"In vitro kinase assay, mass spectrometry, phosphomimetic/alanine mutants in HEK293T and platelets","pmids":["23611601","23600630"],"confidence":"High","gaps":["Structural basis of how phosphorylation inhibits GEF activity","Whether other kinases phosphorylate these sites in non-platelet contexts"]},{"year":2014,"claim":"Human missense mutations in the CDC25 domain (p.G248W) abolishing Rap1 exchange and reducing Rac1-GTP confirmed RASGRP2 as a causative gene for platelet-type bleeding disorders and demonstrated that rescue of patient megakaryocytes with wild-type RASGRP2 restores function.","evidence":"Whole-exome sequencing, in vitro GEF assay, flow-based thrombosis, megakaryocyte rescue transfection","pmids":["24958846"],"confidence":"High","gaps":["Whether Rac1 activation is direct or entirely Rap1-dependent"]},{"year":2014,"claim":"Discovery that redox-sensitive vicinal cysteines in CalDAG-GEFI are targets for thiol-modifying agents (PAO, CLL2-1) that induce oligomerization and block GEF activity identified a druggable regulatory mechanism.","evidence":"PAO pull-down, non-reducing Western blot, purified recombinant protein GEF assay, CLL2-1 inhibition studies","pmids":["24352565","25451646"],"confidence":"High","gaps":["Identity of specific cysteine residues modified","Physiological relevance of redox regulation in vivo"]},{"year":2016,"claim":"Structural mutagenesis of the C1 domain revealed that four residues render it unable to bind DAG/phorbol esters, distinguishing RasGRP2 from other RasGRP family members; restoring these residues recovered DAG binding and enhanced Rap1 activation.","evidence":"[3H]phorbol dibutyrate binding, lipid co-sedimentation, cell translocation, mutagenesis","pmids":["27022025"],"confidence":"High","gaps":["Endogenous lipid ligand of the C1 domain not yet defined at this stage"]},{"year":2018,"claim":"HDX-MS and mutagenesis revealed the autoinhibition mechanism: at low calcium, an autoinhibitory linker between EF-hand and Cdc25 domains occludes the catalytic surface; calcium-induced conformational changes release this linker to enable Rap1B exchange.","evidence":"Purified recombinant CalDAG-GEFI, HDX-MS, EF-hand and linker mutagenesis, in vitro Rap1B GEF assay","pmids":["29622678"],"confidence":"High","gaps":["Full atomic-resolution structure not available","Whether membrane association further modulates autoinhibitory conformation"]},{"year":2019,"claim":"Defining PIP2/PIP3 as the exclusive lipid ligands of the CalDAG-GEFI C1 domain resolved the longstanding question of how an atypical C1 domain controls membrane localization independently of DAG.","evidence":"Lipid co-sedimentation, molecular dynamics, C1 domain mutagenesis, subcellular fractionation","pmids":["31758832"],"confidence":"High","gaps":["How PIP2/PIP3 binding is coordinated with acylation and F-actin binding for spatial Rap1 activation"]},{"year":2019,"claim":"Demonstration that RasGRP2 activates R-Ras in endothelial cells to suppress Bax-dependent apoptosis via PI3K–Akt expanded GEF substrate specificity beyond Rap1 to include a pro-survival signaling axis.","evidence":"Stable overexpression in HUVECs, Rap1 knockdown, R-Ras activation assay, Akt/Bax/HK-2 fractionation","pmids":["31723205"],"confidence":"Medium","gaps":["Whether R-Ras activation by CalDAG-GEFI occurs in primary cells in vivo","No direct in vitro GEF assay for R-Ras"]},{"year":2022,"claim":"Identification of DARPP-32/PP1 and PP2A as phosphatases controlling CalDAG-GEFI phosphorylation downstream of D1 receptors in striatal neurons placed CalDAG-GEFI within dopaminergic signaling cascades, complementing its known PKA regulation.","evidence":"DARPP-32 KO mice, PP1/PP2A inhibitors, phospho-site-specific antibodies, D1 agonist stimulation of striatal slices","pmids":["36351540"],"confidence":"Medium","gaps":["Functional consequences of individual phospho-site dephosphorylation on neuronal Rap1 activity","Whether CalDAG-GEFI regulates synaptic plasticity through Rap1 in this context"]},{"year":2021,"claim":"Conditional KO of CalDAG-GEFI in striatal neurons disrupted dendritic M1 muscarinic receptor signaling, temporal integration of EPSPs, and LTP induction, establishing a neuronal function for this GEF beyond hematopoietic cells.","evidence":"Conditional KO mice, dendritic electrophysiology, pharmacology, behavioral assays","pmids":["34371144"],"confidence":"High","gaps":["Whether Rap1 is the relevant substrate for CalDAG-GEFI in striatal dendritic signaling","Downstream effectors linking CalDAG-GEFI to EPSP integration"]},{"year":2024,"claim":"Identification of CalDAG-GEFI as a GEF for LRRK2 expanded its substrate repertoire to a Parkinson's-disease-associated kinase, with genetic evidence of modulation of LRRK2-driven neurodegeneration in fly and mouse models.","evidence":"Co-IP, in vitro GTP loading assay for LRRK2, Drosophila and mouse LRRK2 neurodegeneration models","pmids":["39576856"],"confidence":"Medium","gaps":["Whether CalDAG-GEFI acts on LRRK2 GTPase domain through the same Cdc25 catalytic mechanism as for Rap1","Physiological calcium concentrations at which LRRK2 exchange occurs","Independent replication needed"]},{"year":2024,"claim":"Discovery that NEDD4L ubiquitinates and destabilizes RASGRP2 identified the first E3 ubiquitin ligase regulating CalDAG-GEFI protein turnover.","evidence":"Co-IP, ubiquitination assay, NEDD4L knockdown in endothelial cells","pmids":["39260747"],"confidence":"Medium","gaps":["Specific lysine residues ubiquitinated on RASGRP2","Proteasomal versus lysosomal degradation pathway not determined","In vivo relevance unconfirmed"]},{"year":null,"claim":"A high-resolution crystal or cryo-EM structure of full-length CalDAG-GEFI, alone and in complex with Rap1 and LRRK2, remains unavailable; how its multiple regulatory inputs (calcium, PIP2/PIP3, acylation, F-actin, PKA phosphorylation, redox modification, ubiquitination) are integrated at the structural level is unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No full-length atomic structure","Relative contribution of each regulatory input under physiological conditions","Whether CalDAG-GEFI GEF activity toward LRRK2 uses the same catalytic mechanism as for Rap1"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,3,8,9,16,17,24]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[11,12,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,19]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,8,9,17,24]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[3,8,9,13,16]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,6,7,10]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[22,23]}],"complexes":[],"partners":["RAP1B","RAP1A","BRAF","LRRK2","NEDD4L","RAC1"],"other_free_text":[]},"mechanistic_narrative":"RASGRP2 (CalDAG-GEFI) is a calcium- and diacylglycerol-regulated guanine nucleotide exchange factor that activates Rap1 (and, in specific contexts, R-Ras and LRRK2) to drive inside-out integrin activation in platelets, neutrophils, and T cells, and to modulate neuronal signaling in striatal circuits. Calcium binding to its EF hands releases autoinhibition at the Cdc25–EF-hand linker interface, enabling catalytic exchange on Rap1B; its atypical C1 domain binds PIP2/PIP3 rather than DAG to control membrane targeting, while N-terminal acylation and F-actin association direct spatially restricted Rap1 activation [PMID:29622678, PMID:31758832, PMID:14988412, PMID:10918068]. PKA-mediated phosphorylation at Ser116/Ser117 and Ser586/Ser587 inhibits CalDAG-GEFI GEF activity, providing a cAMP-dependent brake on platelet activation, and DARPP-32/PP1 regulates dephosphorylation of these sites in striatal neurons [PMID:23600630, PMID:36351540]. Loss-of-function mutations in RASGRP2 cause leukocyte adhesion deficiency type III (LAD-III) by abolishing Rap1-dependent β1, β2, and β3 integrin activation in hematopoietic cells [PMID:17576779, PMID:24958846, PMID:27235135]."},"prefetch_data":{"uniprot":{"accession":"Q7LDG7","full_name":"RAS guanyl-releasing protein 2","aliases":["Calcium and DAG-regulated guanine nucleotide exchange factor I","CalDAG-GEFI","Cdc25-like protein","hCDC25L","F25B3.3 kinase-like protein"],"length_aa":609,"mass_kda":69.2,"function":"Functions as a calcium- and DAG-regulated nucleotide exchange factor specifically activating Rap through the exchange of bound GDP for GTP. May also activate other GTPases such as RRAS, RRAS2, NRAS, KRAS but not HRAS. Functions in aggregation of platelets and adhesion of T-lymphocytes and neutrophils probably through inside-out integrin activation. May function in the muscarinic acetylcholine receptor M1/CHRM1 signaling pathway","subcellular_location":"Cytoplasm, cytosol; Cell membrane; Synapse, synaptosome; Cell projection, ruffle membrane","url":"https://www.uniprot.org/uniprotkb/Q7LDG7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RASGRP2","classification":"Not Classified","n_dependent_lines":110,"n_total_lines":1208,"dependency_fraction":0.09105960264900662},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/RASGRP2","total_profiled":1310},"omim":[{"mim_id":"615888","title":"BLEEDING DISORDER, PLATELET-TYPE, 18; BDPLT18","url":"https://www.omim.org/entry/615888"},{"mim_id":"612840","title":"LEUKOCYTE ADHESION DEFICIENCY, TYPE III; LAD3","url":"https://www.omim.org/entry/612840"},{"mim_id":"607901","title":"FERM DOMAIN-CONTAINING KINDLIN 3; FERMT3","url":"https://www.omim.org/entry/607901"},{"mim_id":"607320","title":"RAS GUANYL NUCLEOTIDE-RELEASING PROTEIN 4; RASGRP4","url":"https://www.omim.org/entry/607320"},{"mim_id":"605577","title":"RAS GUANYL NUCLEOTIDE-RELEASING PROTEIN 2; RASGRP2","url":"https://www.omim.org/entry/605577"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":139.0},{"tissue":"lymphoid tissue","ntpm":137.9}],"url":"https://www.proteinatlas.org/search/RASGRP2"},"hgnc":{"alias_symbol":["CALDAG-GEFI"],"prev_symbol":[]},"alphafold":{"accession":"Q7LDG7","domains":[{"cath_id":"1.20.870.10","chopping":"8-133","consensus_level":"high","plddt":89.414,"start":8,"end":133},{"cath_id":"1.10.840.10","chopping":"154-335_345-387","consensus_level":"high","plddt":91.6803,"start":154,"end":387},{"cath_id":"1.10.238.10","chopping":"421-491","consensus_level":"high","plddt":73.8144,"start":421,"end":491},{"cath_id":"3.30.60.20","chopping":"502-541","consensus_level":"high","plddt":75.9802,"start":502,"end":541}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7LDG7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q7LDG7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q7LDG7-F1-predicted_aligned_error_v6.png","plddt_mean":77.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RASGRP2","jax_strain_url":"https://www.jax.org/strain/search?query=RASGRP2"},"sequence":{"accession":"Q7LDG7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q7LDG7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q7LDG7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7LDG7"}},"corpus_meta":[{"pmid":"15334074","id":"PMC_15334074","title":"CalDAG-GEFI 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Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/39260747","citation_count":3,"is_preprint":false},{"pmid":"36351540","id":"PMC_36351540","title":"DARPP-32/protein phosphatase 1 regulates Rasgrp2 as a novel component of dopamine D1 receptor signaling in striatum.","date":"2022","source":"Neurochemistry international","url":"https://pubmed.ncbi.nlm.nih.gov/36351540","citation_count":2,"is_preprint":false},{"pmid":"36683325","id":"PMC_36683325","title":"The CalDAG-GEFI/Rap1/αIIbβ3 axis minimally contributes to accelerated platelet clearance in mice with constitutive store-operated calcium entry.","date":"2023","source":"Platelets","url":"https://pubmed.ncbi.nlm.nih.gov/36683325","citation_count":2,"is_preprint":false},{"pmid":"40101981","id":"PMC_40101981","title":"RasGRP2 Attenuates TAGE Modification of eNOS in Vascular Endothelial Cells.","date":"2025","source":"Biological & pharmaceutical bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/40101981","citation_count":2,"is_preprint":false},{"pmid":"39576856","id":"PMC_39576856","title":"CalDAG-GEFI acts as a guanine nucleotide exchange factor for LRRK2 to regulate LRRK2 function and neurodegeneration.","date":"2024","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/39576856","citation_count":1,"is_preprint":false},{"pmid":"40651280","id":"PMC_40651280","title":"Identification of novel RASGRP2 mutations in patients with platelet dysfunction.","date":"2025","source":"Transfusion and apheresis science : official journal of the World Apheresis Association : official journal of the European Society for Haemapheresis","url":"https://pubmed.ncbi.nlm.nih.gov/40651280","citation_count":1,"is_preprint":false},{"pmid":"23530823","id":"PMC_23530823","title":"Rasgrp2 regulates the permissiveness of NIH3T3 cells to a herpes simplex virus 1 mutant with inactivated ICP34.5 gene.","date":"2013","source":"Acta virologica","url":"https://pubmed.ncbi.nlm.nih.gov/23530823","citation_count":1,"is_preprint":false},{"pmid":"37914339","id":"PMC_37914339","title":"[Study on the Role of RASGRP2 in Vascular Endothelial Cells].","date":"2023","source":"Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan","url":"https://pubmed.ncbi.nlm.nih.gov/37914339","citation_count":0,"is_preprint":false},{"pmid":"39512176","id":"PMC_39512176","title":"A splice mutation in RASGRP2 gene in the patient with recurrent epistaxis and nasal vascular malformation.","date":"2024","source":"Platelets","url":"https://pubmed.ncbi.nlm.nih.gov/39512176","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.02.631090","title":"State-dependent modulation of spiny projection neurons controls levodopa-induced dyskinesia in a mouse model of Parkinson’s disease","date":"2025-01-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.02.631090","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.05.09.593198","title":"Utility of thromboelastography with platelet mapping (TEG-PM) for monitoring platelet transfusion in qualitative platelet disorders","date":"2024-05-14","source":"bioRxiv","url":"https://doi.org/10.1101/2024.05.09.593198","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.06.11.24308522","title":"Exome Sequencing of 963 Chinese Families Identifies Novel Epilepsy Candidate Genes","date":"2024-06-11","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.11.24308522","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":33980,"output_tokens":6985,"usd":0.103358},"stage2":{"model":"claude-opus-4-6","input_tokens":10724,"output_tokens":4701,"usd":0.256717},"total_usd":0.360075,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"RasGRP2 is targeted to the plasma membrane by N-terminal myristoylation and palmitoylation, and selectively catalyzes nucleotide exchange on N- and Ki-Ras (but not Ha-Ras) and on Rap1 in vivo; its GEF activity toward N-Ras is stimulated by diacylglycerol and inhibited by calcium.\",\n      \"method\": \"Cloning, in vivo GEF activity assays, subcellular localization studies, lipid analog treatment in NIH3T3 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct biochemical characterization with multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"10918068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CalDAG-GEFI functions as a Rap1 exchange factor that enhances agonist-induced activation of Rap1b and fibrinogen binding to integrin αIIbβ3 in megakaryocytes, implicating it in inside-out integrin signaling.\",\n      \"method\": \"Retroviral overexpression in ES cell-derived megakaryocytes, Rap1 activation assay, fibrinogen binding flow cytometry\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct gain-of-function in primary cell model with functional readout, replicated across multiple studies\",\n      \"pmids\": [\"12239348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"CalDAG-GEFI forms a signaling complex with Rap1 and B-Raf downstream of M1 muscarinic acetylcholine receptors; calcium and diacylglycerol signals stimulate the sequential activation of CalDAG-GEFI, Rap1, and B-Raf, leading to MEK/ERK1/2 activation.\",\n      \"method\": \"Co-immunoprecipitation, antisense RNA knockdown, HA-tagged B-Raf activation assay in PC12D cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, antisense knockdown, and functional pathway assay in the same study\",\n      \"pmids\": [\"11292831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CalDAG-GEFI (RasGRP2) is crucial for Rap1-dependent integrin signaling in platelets; genetic ablation in mice severely impairs integrin-dependent platelet aggregation and thrombus formation.\",\n      \"method\": \"Genetic knockout mouse, platelet aggregation assays, Rap1 activation assay, in vivo thrombosis models\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype, replicated by multiple independent labs\",\n      \"pmids\": [\"15334074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RasGRP2 subcellular localization is regulated by actin dynamics; induction of F-actin by Vav, Vav2, Dbl, or Rac1 translocates RasGRP2 from cytosol to membrane ruffles through direct association of its N-terminal 150 amino acids with F-actin, leading to regionalized Rap1 activation.\",\n      \"method\": \"Fluorescence microscopy, cytoskeletal disrupting drugs, Rac1 effector mutants, F-actin co-sedimentation biochemical assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct biochemical binding assay combined with live-cell imaging and mutagenesis\",\n      \"pmids\": [\"14988412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CalDAG-GEFI controls activation of β1, β2, and β3 integrins in hematopoietic cells (neutrophils and platelets) via Rap1; CalDAG-GEFI-deficient neutrophils show defects in Rap1 activation, integrin-mediated adhesion and migration, recapitulating LAD-III syndrome.\",\n      \"method\": \"CalDAG-GEFI knockout mice, neutrophil adhesion and migration assays, Rap1 activation pull-down, intravital microscopy\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple orthogonal functional assays, replicated by independent groups\",\n      \"pmids\": [\"17492052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"A splice junction mutation in the CalDAG-GEFI gene in human LAD-III patients reduces CalDAG-GEFI mRNA and protein in lymphocytes, neutrophils, and platelets, abrogating Rap1 activation and β1, β2, and β3 integrin activation (inside-out signaling).\",\n      \"method\": \"Human patient genetics, protein expression analysis, Rap1 activation assay, integrin activation flow cytometry, cell adhesion assays\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human genetic validation with multiple functional assays, independently corroborated\",\n      \"pmids\": [\"17576779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CalDAG-GEFI/Rap1 signaling selectively mediates SDF-1α- and PMA-induced LFA-1 activation (adhesion to ICAM-1) but not VLA-4 activation in primary human T cells; silencing CalDAG-GEFI blocks Rap1 activation and LFA-1-dependent adhesion without affecting VLA-4/VCAM-1 binding.\",\n      \"method\": \"siRNA knockdown of CalDAG-GEFI in human primary CD3+ T cells, Rap1 activation assay, cell adhesion assays to ICAM-1 and VCAM-1\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — specific knockdown in primary human cells with parallel functional readouts\",\n      \"pmids\": [\"17702895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CalDAG-GEFI and protein kinase C represent independent, synergizing pathways for Rap1 and αIIbβ3 activation in platelets; CalDAG-GEFI mediates rapid but reversible Rap1 activation, while PKC/Gαi/P2Y12 signaling mediates a second, sustained wave of Rap1 activation.\",\n      \"method\": \"CalDAG-GEFI knockout platelets, PKC inhibitor, Rap1 activation assay, aggregation assays, P2Y12 receptor pharmacology\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO combined with pharmacological inhibition and functional assays, replicated\",\n      \"pmids\": [\"18544684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CalDAG-GEFI is the primary calcium sensor in platelets; through Rap1, it directly triggers integrin activation and ERK-dependent thromboxane A2 (TxA2) release; CalDAG-GEFI-dependent TxA2 generation provides feedback for PKC activation and granule release.\",\n      \"method\": \"CalDAG-GEFI knockout mice, Rap1 activation assay, TxA2 measurement, ERK activation assay, platelet aggregation and granule secretion assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with multiple orthogonal mechanistic readouts defining pathway hierarchy\",\n      \"pmids\": [\"19628710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CalDAG-GEFI (Rasgrp2) and p38 MAPK are key signaling intermediates between PLCγ2 and Rap1a activation downstream of E-selectin engagement; this pathway mediates integrin αLβ2-dependent slow leukocyte rolling and neutrophil recruitment into inflamed tissues.\",\n      \"method\": \"Rasgrp2-/- mice, dominant-negative Tat-fusion mutants, intravital microscopy, flow chamber, peritonitis model, biochemical Rap1 activation assay\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice plus dominant-negative constructs with in vivo and in vitro functional validation\",\n      \"pmids\": [\"21480213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PKA phosphorylates CalDAG-GEFI at S587 (major site) and S116/S117 (minor sites); phosphorylation at these sites inhibits CalDAG-GEFI-mediated Rap1b activation and platelet aggregation, representing a mechanism for cAMP/PKA-mediated platelet inhibition.\",\n      \"method\": \"Radioactive phosphate incorporation assay, mass spectrometry, phospho-antibody development, phosphomutant expression in HEK293 cells and platelets, Rap1-GTP pull-down assay\",\n      \"journal\": \"Journal of thrombosis and haemostasis : JTH\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro kinase assay, MS identification, and functional mutagenesis in two independent studies\",\n      \"pmids\": [\"23611601\", \"23600630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PKA phosphorylates CalDAG-GEFI at Ser116 and Ser586; a phospho-mimetic S587D mutant abolishes agonist-induced Rap1b activation, and a double Ser116/Ser586 alanine mutant abolishes cAMP-mediated inhibition of Rap1b, demonstrating these are the functional PKA phosphorylation sites.\",\n      \"method\": \"In vitro phosphorylation of purified recombinant CalDAG-GEFI by PKA catalytic subunit, serine-to-alanine and phosphomimetic mutants expressed in HEK293T cells and platelets, Rap1b activation assay, forskolin treatment\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with recombinant protein plus mutagenesis validation in intact cells\",\n      \"pmids\": [\"23600630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A missense mutation (cG742T) in RASGRP2 reduces CalDAG-GEFI-mediated Rap1 activation and αIIbβ3 inside-out signaling in human platelets and megakaryocytes; rescue experiments with wild-type RASGRP2 in cultured patient megakaryocytes correct the functional deficiency; reduced Rac1-GTP loading impairs thrombus formation and spreading.\",\n      \"method\": \"Whole-exome sequencing, HEK293T expression of mutant, Rap1 activation assay, flow cytometry for αIIbβ3 activation, flow-based thrombosis assay, Rac1-GTP assay, megakaryocyte rescue transfection\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — human genetics plus multiple functional assays and rescue experiment\",\n      \"pmids\": [\"24958846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Phenylarsine oxide (PAO) binds directly to vicinal dithiol (cysteine) residues in CalDAG-GEFI, inducing disulfide-linked oligomers and inhibiting CalDAG-GEFI-stimulated GTP loading of Rap1, thereby blocking platelet aggregation; this identifies redox-sensitive cysteines as functionally important in CalDAG-GEFI.\",\n      \"method\": \"Biotin-streptavidin pull-down of PAO-CalDAG-GEFI complex, Western blot under reducing/non-reducing conditions, purified recombinant protein GTP-binding assay, HEK293T overexpression system\",\n      \"journal\": \"Thrombosis and haemostasis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct biochemical binding assay plus reconstituted in vitro GEF assay with purified proteins\",\n      \"pmids\": [\"24352565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The C1 domain of RasGRP2 has very weak phorbol ester/DAG binding affinity (Kd ~2890 nM) due to four residues (Asn7, Ser8, Ala19, Ile21); replacing these with the corresponding RasGRP1/3 residues restores potent phorbol ester binding and membrane translocation, and enhanced C1 domain membrane targeting increases Rap1 activation.\",\n      \"method\": \"Structural mutagenesis, [3H]phorbol 12,13-dibutyrate binding assays, lipid co-sedimentation, cell translocation assay, Rap1 activation assay, molecular modeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding assay with mutagenesis, structural modeling, and functional validation\",\n      \"pmids\": [\"27022025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RASGRP2 mutations in the CDC25 catalytic domain (p.Ser381Phe, p.Arg113X) abolish nucleotide exchange activity of CalDAG-GEFI toward Rap1, causing impaired αIIbβ3 integrin activation in both platelets and neutrophils.\",\n      \"method\": \"Next-generation sequencing, in vitro GEF nucleotide exchange assay, flow cytometry for integrin activation, platelet aggregation\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct in vitro GEF assay on mutant protein plus patient cell functional validation\",\n      \"pmids\": [\"27235135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CalDAG-GEFI is autoinhibited at low cytosolic calcium; calcium binding to canonical EF hands causes conformational rearrangements in an autoinhibitory linker connecting the Cdc25 and EF hand domains, freeing the catalytic surface to engage and activate Rap1B. An additional mutation (V406E) disrupting the autoinhibitory linker-Cdc25 interface restores GEF activity to EF hand variants.\",\n      \"method\": \"Purified recombinant CalDAG-GEFI, hydrogen-deuterium exchange mass spectrometry, EF hand calcium-binding residue mutagenesis, in vitro Rap1B GEF assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro assay with mutagenesis and HDX-MS structural analysis on purified protein\",\n      \"pmids\": [\"29622678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RasGRP2/Rap1 pathway mediates CD38-induced CLL cell migration; CD38 elevates intracellular Ca2+ to activate Rap1 via RasGRP2, and RasGRP2 is polarized in CLL cells with high CD38 expression; both Rap1 and RasGRP2 knockdown block CLL cell migration.\",\n      \"method\": \"siRNA knockdown of RasGRP2 and Rap1, Rap1 activation assay, cell migration assays, intracellular Ca2+ measurement, immunofluorescence localization\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with functional readout in primary CLL cells, single lab\",\n      \"pmids\": [\"29970392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The atypical C1 domain of CalDAG-GEFI interacts exclusively with phosphoinositides PIP2 and PIP3 (not DAG/phorbol esters) through a distinct phospholipid recognition motif; mutation of this motif abolishes lipid co-sedimentation and impairs membrane localization of CalDAG-GEFI in cells.\",\n      \"method\": \"Lipid co-sedimentation assays, molecular dynamics simulations, immunofluorescence, subcellular fractionation, C1 domain mutagenesis\",\n      \"journal\": \"Journal of thrombosis and haemostasis : JTH\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro lipid binding with mutagenesis plus cellular localization with functional consequence\",\n      \"pmids\": [\"31758832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RasGRP2 activates R-Ras in addition to Rap1 in endothelial cells, and suppresses Bax activation-induced apoptosis via R-Ras–PI3K–Akt signaling, promoting hexokinase-2 translocation to mitochondria and blocking Bax mitochondrial translocation.\",\n      \"method\": \"RasGRP2 stable overexpression in HUVECs, Rap1 knockdown, R-Ras activation assay, Akt phosphorylation assay, Bax/HK-2 subcellular fractionation, flow cytometry for apoptosis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — stable OE plus Rap1 KD to distinguish pathways, single lab\",\n      \"pmids\": [\"31723205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RASGRP2 is ectopically expressed in RA fibroblast-like synoviocytes (FLS), where it activates RAP-1 and subsequently promotes NF-κB signaling and actin dynamics, increasing FLS adhesion, migration, and IL-6 production; intra-articular RASGRP2 siRNA dampens experimental arthritis in rats.\",\n      \"method\": \"RASGRP2 transfection of FLS, RAP-1 activation assay, NF-κB reporter, migration/invasion assays, IL-6 ELISA, siRNA-mediated knockdown in rat collagen-induced arthritis model\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function and in vivo loss-of-function with multiple mechanistic readouts, single lab\",\n      \"pmids\": [\"30076153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Genetic deletion of CalDAG-GEFI in mice disrupts dendritic M1 muscarinic receptor signaling in indirect pathway striatal spiny projection neurons, reduces temporal integration of EPSPs at dendritic glutamatergic synapses, and impairs activity-dependent LTP induction.\",\n      \"method\": \"Conditional CalDAG-GEFI knockout mice, electrophysiology (dendritic vs. somatic recordings), pharmacology, behavioral assays (psychostimulant-induced repetitive behaviors, sequence learning, cocaine self-administration)\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with in vitro electrophysiology plus in vivo behavioral/pharmacological validation\",\n      \"pmids\": [\"34371144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DARPP-32/PP1 regulates the PKA-dependent phosphorylation of Rasgrp2 at Ser116/Ser117 and Ser586 in striatal neurons downstream of D1 receptor activation; PP2A regulates all phosphorylation sites of Rasgrp2 including Ser554.\",\n      \"method\": \"DARPP-32 knockout mice, PP1 inhibitor (tautomycetin), PP1/PP2A inhibitor (okadaic acid), phospho-site specific antibodies, D1 receptor agonist stimulation of striatal slices\",\n      \"journal\": \"Neurochemistry international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO plus pharmacological dissection of phosphorylation in brain tissue, single lab\",\n      \"pmids\": [\"36351540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CalDAG-GEFI acts as a physiological GEF for LRRK2, interacting with LRRK2 and increasing its GDP-to-GTP exchange activity; CalDAG-GEFI modulates LRRK2-induced neurodegeneration in Drosophila and mouse LRRK2 models.\",\n      \"method\": \"Co-immunoprecipitation of CDGI and LRRK2, in vitro GTP loading/exchange assay for LRRK2, Drosophila genetic model of LRRK2 neurodegeneration, mouse model experiments\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — Co-IP plus in vitro GEF assay on LRRK2 and in vivo genetic validation in two model organisms, single lab\",\n      \"pmids\": [\"39576856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RASGRP2 suppresses LUAD cell proliferation and induces mitochondrial-dependent apoptosis; cytological experiments showed that RASGRP2 regulates mitochondrial membrane potential.\",\n      \"method\": \"Clone formation assay, EdU proliferation assay, flow cytometry for apoptosis, fluorescence microscopy of mitochondrial membrane potential in LUAD cell lines\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, mechanistic pathway placement incomplete, no upstream/downstream partners defined\",\n      \"pmids\": [\"36817422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CLL2-1, a 1,4-phenanthrenequinone, inhibits CalDAG-GEFI function through thiol modification of redox-sensitive cysteines, inducing CalDAG-GEFI oligomerization and blocking Rap1 activation and platelet aggregation; in a purified recombinant protein system, CLL2-1 directly inhibited CalDAG-GEFI-stimulated GTP binding to Rap1.\",\n      \"method\": \"Western blot under reducing/non-reducing conditions, purified recombinant protein GTP-binding assay, HEK293T overexpression, flow cytometry, platelet aggregation assay\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro GEF assay with purified proteins, complemented by cell-based assays, single lab\",\n      \"pmids\": [\"25451646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CalDAG-GEFI is colocalized with axons and axon terminals of striatal projection neurons in the substantia nigra, as shown by subcellular fractionation of the substantia nigra with monoclonal antibodies against CalDAG-GEFI.\",\n      \"method\": \"In situ hybridization, subcellular fractionation, monoclonal antibody immunostaining\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single localization method without functional consequence directly demonstrated\",\n      \"pmids\": [\"11503142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NEDD4L interacts with RASGRP2 and ubiquitinates it, destabilizing RASGRP2 protein and reducing its expression in endothelial cells; NEDD4L knockdown reduces HG+oxLDL-induced endothelial dysfunction, an effect reversed by RASGRP2 downregulation.\",\n      \"method\": \"Co-IP assay, ubiquitination assay, NEDD4L knockdown, RASGRP2 overexpression/knockdown, cell viability/apoptosis/migration/angiogenesis assays, Western blot\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP and ubiquitination assay identifying NEDD4L as E3 ligase for RASGRP2, single lab\",\n      \"pmids\": [\"39260747\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RASGRP2 (CalDAG-GEFI) is a calcium- and diacylglycerol-regulated guanine nucleotide exchange factor that, upon cytosolic calcium elevation, undergoes conformational release of autoinhibition at its EF hand–Cdc25 linker interface to activate Rap1 (and, in some contexts, R-Ras and LRRK2); active Rap1 drives inside-out activation of β1, β2, and β3 integrins in platelets, neutrophils, and T cells, mediating aggregation, adhesion, and thrombus formation, while PKA-mediated phosphorylation of CalDAG-GEFI at Ser116/Ser117 and Ser586/Ser587 restrains its activity; its atypical C1 domain binds PIP2/PIP3 (not DAG) to control membrane localization, and its N-terminal acylation and F-actin association direct spatial Rap1 activation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RASGRP2 (CalDAG-GEFI) is a calcium- and diacylglycerol-regulated guanine nucleotide exchange factor that activates Rap1 (and, in specific contexts, R-Ras and LRRK2) to drive inside-out integrin activation in platelets, neutrophils, and T cells, and to modulate neuronal signaling in striatal circuits. Calcium binding to its EF hands releases autoinhibition at the Cdc25–EF-hand linker interface, enabling catalytic exchange on Rap1B; its atypical C1 domain binds PIP2/PIP3 rather than DAG to control membrane targeting, while N-terminal acylation and F-actin association direct spatially restricted Rap1 activation [PMID:29622678, PMID:31758832, PMID:14988412, PMID:10918068]. PKA-mediated phosphorylation at Ser116/Ser117 and Ser586/Ser587 inhibits CalDAG-GEFI GEF activity, providing a cAMP-dependent brake on platelet activation, and DARPP-32/PP1 regulates dephosphorylation of these sites in striatal neurons [PMID:23600630, PMID:36351540]. Loss-of-function mutations in RASGRP2 cause leukocyte adhesion deficiency type III (LAD-III) by abolishing Rap1-dependent β1, β2, and β3 integrin activation in hematopoietic cells [PMID:17576779, PMID:24958846, PMID:27235135].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing RasGRP2 as a plasma-membrane-targeted, acylated GEF with selectivity for Rap1 and N-/Ki-Ras, regulated by DAG and calcium, answered the basic question of substrate specificity and subcellular targeting for this exchange factor.\",\n      \"evidence\": \"Cloning, in vivo GEF assays, subcellular localization, and lipid analog treatment in NIH3T3 cells\",\n      \"pmids\": [\"10918068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Initial report suggested GEF activity toward N-Ras stimulated by DAG, later refined to Rap1 as physiological substrate\", \"Mechanism of calcium inhibition versus activation not resolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrating that CalDAG-GEFI forms a signaling complex with Rap1 and B-Raf downstream of muscarinic receptors established it as a node linking calcium/DAG signals to the MAPK cascade.\",\n      \"evidence\": \"Co-immunoprecipitation, antisense knockdown, and B-Raf activation assay in PC12D cells\",\n      \"pmids\": [\"11292831\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CalDAG-GEFI–B-Raf complex formation is direct or scaffolded\", \"Relevance of this pathway outside neuroendocrine cells\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showing that CalDAG-GEFI enhances Rap1b activation and fibrinogen binding to αIIbβ3 in megakaryocytes first linked this GEF to inside-out integrin signaling in the platelet lineage.\",\n      \"evidence\": \"Retroviral overexpression in ES-derived megakaryocytes, Rap1 activation assay, fibrinogen binding flow cytometry\",\n      \"pmids\": [\"12239348\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Overexpression system — endogenous requirement not yet shown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Genetic ablation of CalDAG-GEFI in mice proved it is essential for Rap1-dependent platelet aggregation and thrombus formation in vivo, and revealed that F-actin dynamics govern its spatial localization to membrane ruffles for regionalized Rap1 activation.\",\n      \"evidence\": \"KO mouse with platelet aggregation, in vivo thrombosis models; F-actin co-sedimentation, fluorescence microscopy, and Rac1 mutant analysis\",\n      \"pmids\": [\"15334074\", \"14988412\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of acylation versus F-actin binding to membrane targeting in primary platelets\", \"Whether actin-dependent localization is required for thrombus formation\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extending the KO phenotype to neutrophils and identifying human LAD-III patients with RASGRP2 splice mutations established CalDAG-GEFI as the master regulator of Rap1-driven β1/β2/β3 integrin activation across hematopoietic lineages and as a disease gene for LAD-III.\",\n      \"evidence\": \"KO mouse neutrophil adhesion/migration assays, intravital microscopy; human patient genetics with Rap1 activation and integrin function assays\",\n      \"pmids\": [\"17492052\", \"17576779\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether residual integrin activation in patients/KO mice is CalDAG-GEFI-independent or represents hypomorphic alleles\", \"Relative contribution of CalDAG-GEFI versus other Rap-GEFs in lymphocytes\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Selective requirement of CalDAG-GEFI for LFA-1 but not VLA-4 activation in human T cells revealed integrin-specific control downstream of the same GEF, refining the model of inside-out signaling.\",\n      \"evidence\": \"siRNA knockdown in primary human CD3+ T cells, adhesion assays to ICAM-1 and VCAM-1\",\n      \"pmids\": [\"17702895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CalDAG-GEFI/Rap1 discriminates between LFA-1 and VLA-4\", \"Whether this selectivity operates in other leukocyte subsets\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Dissecting the temporal hierarchy of platelet Rap1 activation revealed CalDAG-GEFI mediates the rapid, reversible first wave while PKC/P2Y12 sustains a second wave, clarifying why CalDAG-GEFI loss alone does not fully abolish aggregation.\",\n      \"evidence\": \"CalDAG-GEFI KO platelets with PKC inhibitor, P2Y12 pharmacology, aggregation and Rap1 assays\",\n      \"pmids\": [\"18544684\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the GEF(s) mediating the PKC/P2Y12-dependent second wave\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identifying CalDAG-GEFI as the primary calcium sensor in platelets that triggers not only integrin activation but also ERK-dependent TxA2 generation revealed a feedforward loop amplifying platelet activation.\",\n      \"evidence\": \"KO mice with TxA2 measurement, ERK activation, granule secretion assays\",\n      \"pmids\": [\"19628710\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CalDAG-GEFI directly activates ERK or requires intermediate effectors\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placing CalDAG-GEFI/p38 MAPK between PLCγ2 and Rap1a downstream of E-selectin engagement explained how selectin signals trigger integrin-dependent slow rolling, extending CalDAG-GEFI function from platelet biology to neutrophil recruitment.\",\n      \"evidence\": \"Rasgrp2−/− mice, dominant-negative Tat-fusion mutants, intravital microscopy, peritonitis model\",\n      \"pmids\": [\"21480213\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether p38 acts upstream or in parallel to CalDAG-GEFI in this context\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identification and functional validation of PKA phosphorylation sites Ser116/Ser117 and Ser586/Ser587 on CalDAG-GEFI provided the molecular mechanism for cAMP/PKA-mediated inhibition of Rap1 activation and platelet function.\",\n      \"evidence\": \"In vitro kinase assay, mass spectrometry, phosphomimetic/alanine mutants in HEK293T and platelets\",\n      \"pmids\": [\"23611601\", \"23600630\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of how phosphorylation inhibits GEF activity\", \"Whether other kinases phosphorylate these sites in non-platelet contexts\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Human missense mutations in the CDC25 domain (p.G248W) abolishing Rap1 exchange and reducing Rac1-GTP confirmed RASGRP2 as a causative gene for platelet-type bleeding disorders and demonstrated that rescue of patient megakaryocytes with wild-type RASGRP2 restores function.\",\n      \"evidence\": \"Whole-exome sequencing, in vitro GEF assay, flow-based thrombosis, megakaryocyte rescue transfection\",\n      \"pmids\": [\"24958846\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Rac1 activation is direct or entirely Rap1-dependent\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Discovery that redox-sensitive vicinal cysteines in CalDAG-GEFI are targets for thiol-modifying agents (PAO, CLL2-1) that induce oligomerization and block GEF activity identified a druggable regulatory mechanism.\",\n      \"evidence\": \"PAO pull-down, non-reducing Western blot, purified recombinant protein GEF assay, CLL2-1 inhibition studies\",\n      \"pmids\": [\"24352565\", \"25451646\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of specific cysteine residues modified\", \"Physiological relevance of redox regulation in vivo\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Structural mutagenesis of the C1 domain revealed that four residues render it unable to bind DAG/phorbol esters, distinguishing RasGRP2 from other RasGRP family members; restoring these residues recovered DAG binding and enhanced Rap1 activation.\",\n      \"evidence\": \"[3H]phorbol dibutyrate binding, lipid co-sedimentation, cell translocation, mutagenesis\",\n      \"pmids\": [\"27022025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous lipid ligand of the C1 domain not yet defined at this stage\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"HDX-MS and mutagenesis revealed the autoinhibition mechanism: at low calcium, an autoinhibitory linker between EF-hand and Cdc25 domains occludes the catalytic surface; calcium-induced conformational changes release this linker to enable Rap1B exchange.\",\n      \"evidence\": \"Purified recombinant CalDAG-GEFI, HDX-MS, EF-hand and linker mutagenesis, in vitro Rap1B GEF assay\",\n      \"pmids\": [\"29622678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full atomic-resolution structure not available\", \"Whether membrane association further modulates autoinhibitory conformation\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defining PIP2/PIP3 as the exclusive lipid ligands of the CalDAG-GEFI C1 domain resolved the longstanding question of how an atypical C1 domain controls membrane localization independently of DAG.\",\n      \"evidence\": \"Lipid co-sedimentation, molecular dynamics, C1 domain mutagenesis, subcellular fractionation\",\n      \"pmids\": [\"31758832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PIP2/PIP3 binding is coordinated with acylation and F-actin binding for spatial Rap1 activation\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstration that RasGRP2 activates R-Ras in endothelial cells to suppress Bax-dependent apoptosis via PI3K–Akt expanded GEF substrate specificity beyond Rap1 to include a pro-survival signaling axis.\",\n      \"evidence\": \"Stable overexpression in HUVECs, Rap1 knockdown, R-Ras activation assay, Akt/Bax/HK-2 fractionation\",\n      \"pmids\": [\"31723205\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether R-Ras activation by CalDAG-GEFI occurs in primary cells in vivo\", \"No direct in vitro GEF assay for R-Ras\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identification of DARPP-32/PP1 and PP2A as phosphatases controlling CalDAG-GEFI phosphorylation downstream of D1 receptors in striatal neurons placed CalDAG-GEFI within dopaminergic signaling cascades, complementing its known PKA regulation.\",\n      \"evidence\": \"DARPP-32 KO mice, PP1/PP2A inhibitors, phospho-site-specific antibodies, D1 agonist stimulation of striatal slices\",\n      \"pmids\": [\"36351540\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of individual phospho-site dephosphorylation on neuronal Rap1 activity\", \"Whether CalDAG-GEFI regulates synaptic plasticity through Rap1 in this context\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Conditional KO of CalDAG-GEFI in striatal neurons disrupted dendritic M1 muscarinic receptor signaling, temporal integration of EPSPs, and LTP induction, establishing a neuronal function for this GEF beyond hematopoietic cells.\",\n      \"evidence\": \"Conditional KO mice, dendritic electrophysiology, pharmacology, behavioral assays\",\n      \"pmids\": [\"34371144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Rap1 is the relevant substrate for CalDAG-GEFI in striatal dendritic signaling\", \"Downstream effectors linking CalDAG-GEFI to EPSP integration\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of CalDAG-GEFI as a GEF for LRRK2 expanded its substrate repertoire to a Parkinson's-disease-associated kinase, with genetic evidence of modulation of LRRK2-driven neurodegeneration in fly and mouse models.\",\n      \"evidence\": \"Co-IP, in vitro GTP loading assay for LRRK2, Drosophila and mouse LRRK2 neurodegeneration models\",\n      \"pmids\": [\"39576856\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CalDAG-GEFI acts on LRRK2 GTPase domain through the same Cdc25 catalytic mechanism as for Rap1\", \"Physiological calcium concentrations at which LRRK2 exchange occurs\", \"Independent replication needed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery that NEDD4L ubiquitinates and destabilizes RASGRP2 identified the first E3 ubiquitin ligase regulating CalDAG-GEFI protein turnover.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, NEDD4L knockdown in endothelial cells\",\n      \"pmids\": [\"39260747\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific lysine residues ubiquitinated on RASGRP2\", \"Proteasomal versus lysosomal degradation pathway not determined\", \"In vivo relevance unconfirmed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution crystal or cryo-EM structure of full-length CalDAG-GEFI, alone and in complex with Rap1 and LRRK2, remains unavailable; how its multiple regulatory inputs (calcium, PIP2/PIP3, acylation, F-actin, PKA phosphorylation, redox modification, ubiquitination) are integrated at the structural level is unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No full-length atomic structure\", \"Relative contribution of each regulatory input under physiological conditions\", \"Whether CalDAG-GEFI GEF activity toward LRRK2 uses the same catalytic mechanism as for Rap1\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 3, 8, 9, 16, 17, 24]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [11, 12, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 19]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 8, 9, 17, 24]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [3, 8, 9, 13, 16]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 6, 7, 10]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [22, 23]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RAP1B\",\n      \"RAP1A\",\n      \"BRAF\",\n      \"LRRK2\",\n      \"NEDD4L\",\n      \"RAC1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}