{"gene":"S1PR3","run_date":"2026-04-28T20:42:06","timeline":{"discoveries":[{"year":1999,"finding":"S1PR3 (EDG-3) couples to Gi, Gq, and G13 families of heterotrimeric G proteins, in contrast to S1PR1 (EDG-1) which couples only to Gi. This was demonstrated directly using a subunit-selective [35S]GTPgammaS binding assay in Sf9 and HEK293 cells.","method":"Subunit-selective [35S]GTPgammaS binding assay in Sf9 and HEK293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro G-protein activation assay, replicated across two cell systems","pmids":["10488065"],"is_preprint":false},{"year":1999,"finding":"S1PR3 (EDG-3) expressed in Xenopus oocytes confers SPP-responsive intracellular calcium transients coupled to Gq pathway; suramin selectively antagonizes SPP-activated calcium responses in EDG-3-expressing oocytes with IC50 of 22 µM, establishing EDG-3 as a pharmacologically distinct GPCR subtype.","method":"Xenopus oocyte expression system; Ca2+ measurements; chimeric Galphaqi co-expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — heterologous reconstitution in Xenopus oocytes with pharmacological validation","pmids":["10383399"],"is_preprint":false},{"year":1999,"finding":"S1PR3 (EDG-3) overexpression confers specific [32P]S1P binding (displaced by S1P and sphingosylphosphorylcholine but not LPA), mediates inositol phosphate production and [Ca2+]i increase partially sensitive to pertussis toxin, activates MAPK in PTX-sensitive/Ras-dependent manner, and decreases cellular cAMP, establishing distinct signaling characteristics compared to EDG-1 and EDG-5.","method":"Radioligand binding, inositol phosphate assay, Ca2+ measurements, MAPK activation assay, cAMP measurement in EDG-3-overexpressing cells","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal in vitro assays in reconstituted system","pmids":["10381367"],"is_preprint":false},{"year":1999,"finding":"S1PR3 (EDG-3) activates the phospholipase C-Ca2+ system in transfected CHO cells; S1P-induced Ca2+ response was enhanced and associated with significant inositol phosphate production in EDG-3-transfected versus vector-transfected cells, inhibited by the PLC inhibitor U73122.","method":"Ca2+ measurement and inositol phosphate assay in EDG-3-transfected CHO cells","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — reconstituted overexpression system with pharmacological inhibitor confirmation","pmids":["9928946"],"is_preprint":false},{"year":2000,"finding":"S1PR3 (EDG-3) expressed in CHO cells promotes S1P-induced chemotaxis and membrane ruffling via PI3K- and Rac-dependent mechanisms, inducing a biphasic increase in GTP-bound Rac; this is in contrast to EDG-5 which inhibits Rac activation.","method":"Chemotaxis assay, membrane ruffling imaging, Rac-GTP pulldown in CHO cells expressing EDG-3","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean receptor-specific overexpression with multiple functional readouts and mechanistic dissection","pmids":["11094076"],"is_preprint":false},{"year":2001,"finding":"S1PR3 (EDG-3) is required together with EDG-1 for S1P-induced Rho activation and integrin (αvβ3 and β1) clustering into focal contacts in human umbilical vein endothelial cells; antisense knockdown of EDG-3 inhibits S1P-induced cell migration on fibronectin, vitronectin and Matrigel.","method":"Antisense phosphothioate oligonucleotides, C3 exotoxin inhibition, integrin blocking antibodies, Rho activation assay, HUVEC migration assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function with multiple orthogonal methods and defined cellular phenotype","pmids":["11150298"],"is_preprint":false},{"year":2001,"finding":"S1PR3 (LP(B3)/EDG-3) deletion in mouse embryonic fibroblasts causes significant decreases in S1P-induced phospholipase C activation and slight decreases in adenylyl cyclase inhibition, with no change in Rho activation, demonstrating nonredundant coupling of S1PR3 to PLC/Ca2+ pathway; retroviral re-expression of LP(B3) rescued PLC activation.","method":"Gene knockout in mice, MEF preparation, PLC activation assay, adenylyl cyclase inhibition assay, Rho activation assay, retroviral rescue","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic knockout with rescue experiment and multiple pathway readouts","pmids":["11443127"],"is_preprint":false},{"year":2002,"finding":"In S1P2/S1P3 double-knockout MEFs, Rho activation is completely lost and PLC activation and calcium mobilization are significantly decreased compared to wild-type, establishing preferential coupling of S1PR3 to PLC/Ca2+ pathways and S1PR2 to Rho; double-null pups show perinatal lethality demonstrating essential combined role.","method":"Double gene knockout in mice, MEF signaling assays (Rho, PLC, Ca2+, adenylyl cyclase)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis via double knockout with multiple signaling readouts","pmids":["12006579"],"is_preprint":false},{"year":2001,"finding":"S1PR3 (EDG-3) and EDG-5, but not EDG-1, mediate S1P-induced NF-κB activation in HEK293 cells through a mechanism requiring protein kinase C and Ca2+ downstream of Gq; Rho activation alone through Gq or G13 is insufficient for NF-κB activation.","method":"NF-κB reporter assay, PKC inhibitor treatment, Ca2+ chelation, overexpression of EDG receptor subtypes in HEK293 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — receptor-specific overexpression with mechanistic dissection of G protein pathway","pmids":["11673450"],"is_preprint":false},{"year":2001,"finding":"S1PR3 (EDG-3) mediates S1P-induced PI3K and Akt activation in CHO cells through phospholipase D; PLD2 is required downstream of EDG-3, as catalytically inactive PLD2 mutant eliminates S1P-induced Akt activation, and 1-butanol (PLD inhibitor) blocks PI3K/Akt activation and Rac-dependent membrane ruffling.","method":"PLD activity assay, PI3K assay, Akt phosphorylation, dominant-negative PLD2 co-expression, 1-butanol inhibition in EDG-3-overexpressing CHO cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis of PLD2 plus multiple pathway assays in reconstituted system","pmids":["11468290"],"is_preprint":false},{"year":2000,"finding":"S1PR3 (EDG-3) mediates S1P-induced cell proliferation, survival, ERK/MAP kinase activation, and c-Jun/c-Fos induction via Gi/o- and Rho-dependent pathways; pertussis toxin and C3 exoenzyme inhibit EDG-3-mediated serum response element activation.","method":"Stable transfection in HTC4 hepatoma cells, thymidine incorporation, apoptosis assay, ERK activation, reporter gene assay, PTX and C3 exoenzyme inhibition","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — stable transfection with multiple functional readouts and pharmacological pathway dissection","pmids":["10617617"],"is_preprint":false},{"year":2000,"finding":"S1PR3 (EDG-3) mediates S1P-induced activation of IK.ACh (muscarinic-type inward rectifier K+ current) in human atrial cardiomyocytes; this is blocked by the EDG-3-selective antagonist suramin but not affected by carbachol, and EDG-3 transcript is detected in human atrial cells.","method":"Patch-clamp electrophysiology in freshly isolated atrial myocytes, suramin antagonist, RT-PCR for receptor transcripts","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 2 — electrophysiology with receptor-selective pharmacological blockade in native cardiac tissue","pmids":["10908314"],"is_preprint":false},{"year":2003,"finding":"A synthetic peptide (KRX-725) from the second intracellular loop of S1PR3 mimics S1P by triggering Gi-dependent MEK-ERK signaling, induces receptor internalization of S1PR3 but not S1PR1, and promotes angiogenesis ex vivo and in vivo; demonstrating that the second intracellular loop of S1PR3 is sufficient to activate specific downstream signaling.","method":"Peptide synthesis, ERK activation assay, receptor internalization assay, aortic ring ex vivo angiogenesis, mouse corneal pocket assay","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 — functional peptide assay with receptor-specific internalization, single lab","pmids":["12763936"],"is_preprint":false},{"year":2002,"finding":"S1PR3 (EDG-3) mediates S1P-induced Ca2+ mobilization in C2C12 myoblasts; antisense oligodeoxynucleotides against EDG-3 significantly reduced SPP-induced Ca2+ response, and combined inhibition of EDG-3 and EDG-5 abolished the response, whereas antisense against EDG-1 had no effect.","method":"Antisense ODN knockdown, Ca2+ imaging (confocal, spectrophotofluorimeter) in C2C12 myoblasts","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 — antisense knockdown with quantitative Ca2+ readout, single lab","pmids":["11853542"],"is_preprint":false},{"year":2006,"finding":"Estrogen (E2) transactivates EGFR in breast cancer cells via a mechanism involving SphK1 activation, S1P release, and subsequent activation of S1PR3 (EDG-3), which leads to EGFR transactivation in a matrix metalloprotease-dependent manner.","method":"SphK1 activity assay, S1P ELISA, S1PR3 signaling assay, EGFR phosphorylation, MMP inhibitor treatment in breast cancer cells","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical assays in a single lab demonstrating the signaling axis","pmids":["16636149"],"is_preprint":false},{"year":2006,"finding":"S1PR3 (Edg3/S1P3) expression is necessary and sufficient for VEGF-dependent upregulation of Akt3 in primary endothelial cells; VEGF stimulates S1P3 expression via a Gi-protein-dependent mechanism (pertussis toxin-sensitive), and knockdown of S1P3 blocks VEGF-stimulated Akt3 induction.","method":"siRNA knockdown, pertussis toxin inhibition, Akt3 mRNA/protein measurement, overexpression in primary endothelial cells","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — loss- and gain-of-function in primary cells with defined molecular readout, single lab","pmids":["16527273"],"is_preprint":false},{"year":2014,"finding":"S1PR3 mediates S1P-induced expansion of cancer stem cells (ALDH-positive) via ligand-independent Notch activation; S1PR3 knockdown or S1PR3 antagonist inhibits tumorigenicity of SphK1-overexpressing CSCs in nude mice.","method":"ALDH flow cytometry, S1PR3 siRNA knockdown, S1PR3 antagonist, xenograft mouse model, Notch pathway activation assay","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological loss-of-function with in vivo validation, single lab","pmids":["25254944"],"is_preprint":false},{"year":2015,"finding":"S1PR3 contributes to the egress of Gna13-mutant germinal center B cells from lymph nodes; dissemination of Gna13-deficient GC B cells in mouse models depends on S1PR3, placing S1PR3 downstream of Gα13 signaling in GC B cell retention/egress.","method":"Genetic mouse models (Gna13 conditional KO, S1PR3 KO), lymph node egress assays, flow cytometry","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in mouse model, single lab","pmids":["26573295"],"is_preprint":false},{"year":2017,"finding":"S1PR3 is required for macrophage bactericidal function in sepsis; S1pr3-/- mice show increased bacterial burden and mortality; S1PR3 regulates ROS production and phagosome maturation by controlling recruitment of VPS34 (vacuolar protein-sorting 34) to phagosomes.","method":"S1PR3 knockout mice, bone marrow transfer, bacterial killing assay, ROS measurement, phagosome maturation assay, VPS34 recruitment to phagosomes","journal":"American journal of respiratory and critical care medicine","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with mechanistic rescue (BM transfer) and defined molecular mechanism (VPS34 recruitment), multiple readouts","pmids":["28850247"],"is_preprint":false},{"year":2017,"finding":"S1PR3 is a direct target of miR-127 in myogenic cells; overexpression of miR-127 enhances myogenic differentiation and S1PR3 is required for this effect, as S1PR3 knockdown mimics miR-127 overexpression and S1PR3 restoration reverses the pro-differentiation phenotype.","method":"miRNA overexpression, luciferase reporter assay, C2C12 differentiation assay, transgenic mice, satellite cell assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — validated miRNA target with functional in vitro and in vivo phenotype, single lab","pmids":["28358363"],"is_preprint":false},{"year":2018,"finding":"S1PR3 signals via TRPA1 to mediate S1P-induced itch in pruriceptors, and via TRPV1 to mediate S1P-induced pain in nociceptors; S1P-evoked itch is lost in TRPA1-null mice and pain/heat hypersensitivity is lost in TRPV1-null mice, with S1PR3 required for both responses.","method":"Ca2+ imaging, electrophysiology in sensory neurons, S1PR3-KO mice, TRPA1-KO and TRPV1-KO mice, behavioral itch and pain assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic KO models with electrophysiology and behavioral validation establishing distinct cellular mechanisms","pmids":["30082422"],"is_preprint":false},{"year":2018,"finding":"S1P/S1PR3 axis promotes aerobic glycolysis in osteosarcoma by inhibiting YAP phosphorylation and promoting YAP nuclear translocation, leading to formation of a YAP-c-MYC complex that enhances PGAM1 transcription; co-immunoprecipitation confirmed YAP-c-MYC interaction and ChIP showed their binding to PGAM1 promoter.","method":"S1PR3 knockdown, co-immunoprecipitation, chromatin immunoprecipitation, luciferase reporter, metabolic flux analysis, xenograft mouse model","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods including Co-IP, ChIP, and in vivo validation, single lab","pmids":["30587459"],"is_preprint":false},{"year":2019,"finding":"S1PR3 activation in mouse vagal airway afferent nodose C-fibers mediates S1P-induced action potential generation; S1P fails to activate airway nodose C-fibers in S1PR3 knockout mice, and an S1PR3 antagonist (TY52156) inhibits S1P-evoked action potentials.","method":"Single-cell RT-PCR, two-photon Ca2+ imaging of nodose ganglia in transgenic GCaMP6s mice, single-fiber electrophysiology, S1PR3-KO mice, S1PR3 antagonist","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO confirmed by pharmacological blockade with electrophysiology, strong evidence","pmids":["30793318"],"is_preprint":false},{"year":2021,"finding":"Crystal structure of active human S1PR3 in complex with its natural agonist S1P determined at 3.2-Å resolution; S1P adopts an unbent conformation in a long tunnel traversing the receptor obliquely; four residues surrounding the alkyl tail of S1P (the 'quartet core') undergo coordinated rotamer changes to accommodate S1P and induce active conformation; the quartet core also determines G protein selectivity of S1PR3.","method":"X-ray crystallography, active S1PR3-S1P complex structure at 3.2 Å; mutagenesis of quartet core residues; comparison with inactive S1PR1 structure","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with mutagenesis validation of key mechanistic residues","pmids":["34108205"],"is_preprint":false},{"year":2021,"finding":"S1PR3 is a G12-biased agonist target; ALESIA compound acts as an S1PR3-G12-biased agonist (identified by TGFα shedding assay), promoting nitric oxide production and oxidative stress leading to cancer cell death under low-glucose conditions.","method":"TGFα shedding assay (DREADD-based G protein activation), nitric oxide measurement, oxidative stress assay, NADPH measurement, in vivo peritoneal tumor model","journal":"Cell chemical biology","confidence":"Medium","confidence_rationale":"Tier 1-2 — functional GPCR assay with biased signaling characterization, single lab","pmids":["33561428"],"is_preprint":false},{"year":2020,"finding":"S1P lyase inhibition protects against sepsis by increasing S1P levels that stimulate S1PR3, activating p38 and ERK MAPK pathways, reducing tissue damage; the protective effects are absent in S1PR3-deficient mice, establishing S1PR3 as essential for this protective pathway.","method":"S1P lyase inhibitor treatment, S1PR3-KO mice, cytokine measurement, lung permeability assay, p38/ERK phosphorylation, survival studies","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO confirms receptor requirement, single lab","pmids":["32711251"],"is_preprint":false},{"year":2009,"finding":"EDG3 (S1PR3) protein co-immunoprecipitates with SHC3 protein from human ependymoma tissue, and EDG3 protein was found to be N-glycosylated (confirmed by N-glycosidase-F digestion), indicating proper post-translational processing and plasma membrane trafficking.","method":"Co-immunoprecipitation from tumor tissue, N-glycosidase-F digestion, qPCR gene amplification analysis","journal":"Cancer letters","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP from tumor tissue without functional follow-up of the interaction","pmids":["19748727"],"is_preprint":false},{"year":2018,"finding":"S1PR3 mediates S1P-induced CCL20 release from human bronchial epithelial cells; siRNA knockdown of S1PR3 suppresses S1P-induced CCL20 expression, and S1PR1/3 antagonist VPC23019 attenuates eosinophilic inflammation in OVA-challenged mice.","method":"Transcriptome analysis, siRNA knockdown, ELISA, OVA-challenged asthma mouse model, VPC23019 antagonist","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with in vitro and in vivo confirmation, single lab","pmids":["30192865"],"is_preprint":false},{"year":2018,"finding":"S1PR3 mediates fingolimod phosphate (pFTY720)-dependent protection of astrocytes against OGD-induced neuroinflammation by inhibiting TLR2/4-PI3K-NFκB signaling; S1PR3 knockdown reverses the protective effects of pFTY720.","method":"S1PR3 siRNA knockdown, OGD model in astrocytes, TLR2/PI3K/NFκB pathway assays, cytokine measurement","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA-mediated loss-of-function with defined pathway readout, single lab","pmids":["29536648"],"is_preprint":false},{"year":2019,"finding":"FTY720-P stimulates the Na+/K+ ATPase in HepG2 liver cells via S1PR3, acting sequentially through PKC, ERK, NF-κB, and COX-2 to induce PGE2 release; the effect was blocked by the specific S1PR3 antagonist CAY10444 and reproduced by the S1PR3 agonist CYM5541.","method":"Na+/K+ ATPase activity assay, S1PR3-specific antagonist and agonist, PKC/ERK inhibitors, COX inhibitor, IκB expression western blot in HepG2 cells","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological dissection with multiple pathway inhibitors and receptor-specific tools, single lab","pmids":["31502430"],"is_preprint":false},{"year":2024,"finding":"Extracellular α-synuclein causes S1PR3 uncoupling from G protein in HeLa cells, leading to impaired retrograde trafficking of IGF-II/M6P receptor (which is under S1PR3 regulation), reduced cathepsin D lysosomal delivery, and enhanced secretion of immature pro-cathepsin D.","method":"S1PR3 G-protein coupling assay, cathepsin D activity assay, pro-cathepsin D secretion measurement, IGF-II/M6P receptor retrograde trafficking assay in HeLa cells","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional readouts linking S1PR3 uncoupling to lysosomal pathway, single lab","pmids":["38163647"],"is_preprint":false},{"year":2022,"finding":"S1PR3 promotes aerobic glycolysis in septic macrophages via HIF-1α, HK2, and PFKFB3; S1PR3 knockdown dampens glycolysis-associated markers, retrieves LPS-modulated M1/M2 polarization balance, and attenuates NF-κB p65 activation.","method":"S1PR3 siRNA, glycolytic flux assay, macrophage polarization markers, NF-κB p65 activation, LPS-induced sepsis mouse model","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 — genetic silencing with multiple metabolic and inflammatory readouts in vitro and in vivo, single lab","pmids":["39549732"],"is_preprint":false},{"year":2025,"finding":"S1PR3 activates STAT3 via a Gαi/PKA-mediated Src activation pathway in keratinocytes; activated STAT3 in turn directly upregulates S1PR3 expression forming a positive feedback loop; S1PR3 genetic deletion or pharmacological inhibition attenuates psoriasis-like skin inflammation in mice.","method":"Genetic S1pr3 deletion, S1PR3 pharmacological inhibition, Src/STAT3 phosphorylation assays, Gαi/PKA pathway dissection, STAT3 ChIP on S1PR3 promoter, skin inflammation mouse model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — combined genetic and pharmacological evidence with defined Gαi/PKA-Src-STAT3 mechanism and feedback loop, single lab","pmids":["39833165"],"is_preprint":false},{"year":2025,"finding":"S1PR3 regulates hippocampal synaptic plasticity and depression-like behavior via downregulation of RhoA/ROCK1; AAV-mediated S1PR3 overexpression in hippocampal neurons alleviates CUMS-induced depressive behavior and synaptic deficits, and these effects are normalized by RhoA expression, placing RhoA/ROCK1 downstream of S1PR3.","method":"AAV-mediated S1PR3 overexpression in hippocampal neurons, RhoA rescue experiment, behavioral tests (SPT, FST, OFT), synaptic spine density analysis, electron microscopy of synaptic ultrastructure","journal":"Progress in neuro-psychopharmacology & biological psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — genetic gain-of-function with epistasis rescue experiment and defined pathway, single lab","pmids":["39828081"],"is_preprint":false},{"year":2023,"finding":"CEACAM1-long isoform in neutrophils regulates susceptibility to NET formation by controlling the S1P/S1PR2/S1PR3 axis via autophagy signaling; CC1-L ablation aggravated hepatic IRI by promoting NETs in a mouse liver transplant model.","method":"Conditional knockout mouse model (CC1-L), NETosis assay, autophagy signaling assays, S1PR2/S1PR3 pathway analysis in mouse and human OLT samples","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined pathway, but S1PR3 role is part of a dual receptor axis, single lab","pmids":["36719377"],"is_preprint":false},{"year":2023,"finding":"ApoM-bound S1P shows a tendency to induce prolonged activation of Akt via S1PR1 and S1PR3 compared to albumin- or ApoA4-bound S1P, correlating with greater S1P stability and more efficient S1P release from endothelial cells.","method":"S1P stability assay, S1P release from endothelial cells, Akt phosphorylation kinetics with different S1P carrier proteins and receptor comparisons","journal":"Journal of biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — single lab, indirect evidence for S1PR3 role in signaling duration, no direct S1PR3 mutagenesis or KO","pmids":["37098187"],"is_preprint":false}],"current_model":"S1PR3 is a G protein-coupled receptor for sphingosine 1-phosphate that couples to Gi, Gq, and G13, activating downstream pathways including PLC/Ca2+, PI3K/Akt (via PLD), RhoA, Rac, ERK/MAPK, and NF-κB; its crystal structure reveals S1P binds in an unbent conformation in a transmembrane tunnel with a 'quartet core' of residues controlling both receptor activation and G protein subtype selectivity; functionally, S1PR3 drives endothelial cell migration (via Rho-integrin signaling), cardiac IK.ACh activation, macrophage bactericidal activity (via VPS34-phagosome recruitment), sensory neuron activation of itch (via TRPA1) and pain (via TRPV1), cancer stem cell expansion (via Notch), aerobic glycolysis (via YAP/c-MYC/PGAM1), and vascular resistance (via RhoA/ROCK), while also being subject to feedback regulation where STAT3 activation upregulates S1PR3 expression."},"narrative":{"teleology":[{"year":1999,"claim":"Establishing S1PR3 as a multi-G-protein-coupled S1P receptor resolved how a single lipid could activate divergent intracellular pathways through different receptor subtypes, distinguishing S1PR3 (Gi/Gq/G13 coupling) from S1PR1 (Gi-only).","evidence":"Subunit-selective [³⁵S]GTPγS binding in Sf9/HEK293 cells, Ca²⁺ transients in Xenopus oocytes, radioligand binding and IP/cAMP assays in CHO cells","pmids":["10488065","10383399","10381367","9928946"],"confidence":"High","gaps":["Structural basis of differential G protein selectivity unknown","Relative contribution of each G protein arm in native tissues not established"]},{"year":2001,"claim":"Delineating the downstream effector architecture showed that S1PR3 preferentially couples to PLC/Ca²⁺ (confirmed by genetic knockout with rescue), activates PI3K/Akt through PLD2, and mediates NF-κB activation through PKC/Ca²⁺, while also activating Rho/Rac for migration and integrin clustering in endothelial cells.","evidence":"S1PR3-KO MEFs with retroviral rescue; dominant-negative PLD2 in CHO cells; NF-κB reporter with PKC/Ca²⁺ inhibition in HEK293; antisense knockdown with Rho/integrin assays in HUVECs","pmids":["11443127","11468290","11673450","11150298","11094076"],"confidence":"High","gaps":["Mechanism of PLD2 coupling to S1PR3 not determined","Whether Rho activation is direct through G13 or indirect in endothelial cells not resolved"]},{"year":2000,"claim":"Discovery that S1PR3 activates cardiac IK.ACh in human atrial myocytes established a physiological role beyond cell lines, showing receptor-mediated ion channel regulation in native tissue.","evidence":"Patch-clamp electrophysiology with suramin blockade in freshly isolated atrial cardiomyocytes","pmids":["10908314"],"confidence":"High","gaps":["Whether S1PR3-mediated IK.ACh contributes to cardiac arrhythmogenesis not tested","Downstream G protein subtype mediating the ionic effect not identified"]},{"year":2002,"claim":"S1PR2/S1PR3 double-knockout epistasis revealed that S1PR3 preferentially drives PLC/Ca²⁺ while S1PR2 preferentially drives Rho, and that their combined loss causes perinatal lethality, establishing essential combined developmental roles.","evidence":"Double-KO mice with MEF signaling assays for Rho, PLC, Ca²⁺, and adenylyl cyclase","pmids":["12006579"],"confidence":"High","gaps":["Cause of perinatal lethality not characterized","Organ-specific contributions of each receptor not dissected"]},{"year":2006,"claim":"Linking S1PR3 to estrogen-EGFR transactivation in breast cancer and VEGF-dependent Akt3 induction in endothelial cells placed S1PR3 at the intersection of growth factor and sphingolipid signaling networks.","evidence":"SphK1 activation/S1P release leading to EGFR phosphorylation via MMP in breast cancer cells; siRNA knockdown showing VEGF-S1PR3-Akt3 axis in primary endothelial cells","pmids":["16636149","16527273"],"confidence":"Medium","gaps":["Direct physical interaction between S1PR3 and EGFR not demonstrated","Physiological relevance in vivo for estrogen-EGFR axis not established"]},{"year":2014,"claim":"Identification of S1PR3 as a driver of cancer stem cell expansion via ligand-independent Notch activation revealed a non-canonical signaling mechanism, with in vivo validation showing S1PR3 loss reduces tumorigenicity.","evidence":"ALDH flow cytometry, S1PR3 siRNA/antagonist, Notch activation assay, nude mouse xenograft","pmids":["25254944"],"confidence":"Medium","gaps":["Mechanism of ligand-independent Notch activation by S1PR3 not defined","Whether direct S1PR3-Notch physical interaction occurs not tested"]},{"year":2017,"claim":"Demonstration that S1PR3 controls macrophage bactericidal function by recruiting VPS34 to phagosomes for ROS production and phagosome maturation established a direct role in innate immunity, with S1PR3-KO mice showing increased bacterial burden and sepsis mortality.","evidence":"S1PR3-KO mice, bone marrow transfer, bacterial killing assay, VPS34 recruitment to phagosomes","pmids":["28850247"],"confidence":"High","gaps":["How S1PR3 signaling connects to VPS34 recruitment molecularly unknown","Whether specific G protein arm mediates phagosome function not defined"]},{"year":2018,"claim":"Genetic studies in knockout mice revealed that S1PR3 mediates S1P-induced itch via TRPA1 in pruriceptors and pain via TRPV1 in nociceptors, establishing cell-type-specific coupling to distinct TRP channels as the basis for dual somatosensory functions.","evidence":"Ca²⁺ imaging and electrophysiology in sensory neurons; behavioral assays in S1PR3-KO, TRPA1-KO, and TRPV1-KO mice","pmids":["30082422"],"confidence":"High","gaps":["Intracellular signaling cascade linking S1PR3 to TRPA1 versus TRPV1 activation not resolved","Whether PLC or other second messengers gate TRP channels downstream of S1PR3 not established"]},{"year":2018,"claim":"S1PR3 was shown to promote aerobic glycolysis in osteosarcoma through YAP nuclear translocation and YAP-c-MYC complex formation driving PGAM1 transcription, broadening S1PR3's role to metabolic reprogramming in cancer.","evidence":"Co-IP of YAP-c-MYC, ChIP on PGAM1 promoter, metabolic flux analysis, xenograft model","pmids":["30587459"],"confidence":"Medium","gaps":["Whether S1PR3-YAP axis operates through Hippo kinase inhibition or parallel pathway not determined","Generalizability to other cancer types not tested"]},{"year":2021,"claim":"The crystal structure of active S1PR3 bound to S1P resolved how the ligand adopts an unbent conformation in a transmembrane tunnel and identified a 'quartet core' of residues whose coordinated rotamer changes control both receptor activation and G protein subtype selectivity, providing a structural basis for the multi-G-protein coupling first observed in 1999.","evidence":"X-ray crystallography at 3.2 Å resolution; mutagenesis of quartet core residues; structural comparison with inactive S1PR1","pmids":["34108205"],"confidence":"High","gaps":["Cryo-EM structure of S1PR3-G protein ternary complex not yet obtained","How quartet core conformational changes propagate to the intracellular G protein binding surface not resolved"]},{"year":2025,"claim":"Discovery of a Gαi/PKA–Src–STAT3 positive feedback loop where STAT3 directly upregulates S1PR3 transcription in keratinocytes revealed an autoamplification mechanism relevant to psoriasis-like inflammation, and S1PR3's regulation of hippocampal synaptic plasticity via RhoA/ROCK1 was established.","evidence":"S1PR3 genetic deletion/pharmacological inhibition with STAT3 ChIP on S1PR3 promoter in skin inflammation model; AAV-mediated S1PR3 overexpression with RhoA rescue in hippocampal neurons","pmids":["39833165","39828081"],"confidence":"Medium","gaps":["Whether the STAT3 feedback loop operates in cell types beyond keratinocytes not tested","Direct assessment of S1PR3 in human psoriasis tissue not performed"]},{"year":null,"claim":"Key unresolved questions include the cryo-EM structure of S1PR3 in complex with different G protein subtypes, the molecular mechanism linking S1PR3 to VPS34 phagosomal recruitment, how cell-type-specific G protein coupling is determined, and whether biased agonism at S1PR3 can be therapeutically exploited.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No ternary complex structure of S1PR3 with any G protein","Mechanism of cell-type-specific effector selection unknown","No clinical data on S1PR3-selective therapeutics"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,2,3,23]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,23]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,2,26]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,8,9,10,23,32]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[18,27,31]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[20,22,33]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[21,31]}],"complexes":[],"partners":["GNAI1","GNAQ","GNA13","PLD2","VPS34","TRPA1","TRPV1","STAT3"],"other_free_text":[]},"mechanistic_narrative":"S1PR3 is a G protein-coupled receptor for sphingosine 1-phosphate that transduces signals through Gi, Gq, and G12/13 heterotrimeric G proteins, activating PLC/Ca²⁺, PI3K/Akt (via PLD2), Rac, Rho, ERK/MAPK, and NF-κB pathways to regulate diverse cellular responses including migration, proliferation, survival, and metabolic reprogramming [PMID:10488065, PMID:10617617, PMID:11468290, PMID:11673450]. The crystal structure of the active S1PR3–S1P complex reveals the ligand in an unbent conformation within a transmembrane tunnel, where a 'quartet core' of residues undergoes coordinated rotamer changes that control both receptor activation and G protein subtype selectivity [PMID:34108205]. Physiologically, S1PR3 drives endothelial cell migration through Rho-dependent integrin clustering [PMID:11150298], macrophage bactericidal function via VPS34 recruitment to phagosomes [PMID:28850247], sensory neuron activation of itch and pain through TRPA1 and TRPV1 channels respectively [PMID:30082422], cardiac IK.ACh current activation in atrial myocytes [PMID:10908314], and cancer stem cell expansion via Notch signaling [PMID:25254944]. S1PR3 also participates in a positive feedback loop in keratinocytes where Gαi/PKA–Src–STAT3 signaling upregulates S1PR3 expression, contributing to psoriasis-like inflammation [PMID:39833165]."},"prefetch_data":{"uniprot":{"accession":"Q99500","full_name":"Sphingosine 1-phosphate receptor 3","aliases":["Endothelial differentiation G-protein coupled receptor 3","Sphingosine 1-phosphate receptor Edg-3","S1P receptor Edg-3"],"length_aa":378,"mass_kda":42.2,"function":"Receptor for the lysosphingolipid sphingosine 1-phosphate (S1P). S1P is a bioactive lysophospholipid that elicits diverse physiological effect on most types of cells and tissues. When expressed in rat HTC4 hepatoma cells, is capable of mediating S1P-induced cell proliferation and suppression of apoptosis","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q99500/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/S1PR3","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/S1PR3","total_profiled":1310},"omim":[{"mim_id":"614451","title":"ELONGATION OF VERY LONG CHAIN FATTY ACIDS-LIKE 7; ELOVL7","url":"https://www.omim.org/entry/614451"},{"mim_id":"601965","title":"SPHINGOSINE-1-PHOSPHATE RECEPTOR 3; S1PR3","url":"https://www.omim.org/entry/601965"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"blood vessel","ntpm":59.3}],"url":"https://www.proteinatlas.org/search/S1PR3"},"hgnc":{"alias_symbol":["EDG-3","FLJ37523","bA791O21.3"],"prev_symbol":["EDG3","C9orf47","C9orf108"]},"alphafold":{"accession":"Q99500","domains":[{"cath_id":"1.20.1070.10","chopping":"14-225_243-320","consensus_level":"high","plddt":89.3687,"start":14,"end":320}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99500","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q99500-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q99500-F1-predicted_aligned_error_v6.png","plddt_mean":79.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=S1PR3","jax_strain_url":"https://www.jax.org/strain/search?query=S1PR3"},"sequence":{"accession":"Q99500","fasta_url":"https://rest.uniprot.org/uniprotkb/Q99500.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q99500/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99500"}},"corpus_meta":[{"pmid":"10488065","id":"PMC_10488065","title":"Differential 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treating coronary heart disease complicated with major depressive disorder through S1PR3 regulation.","date":"2025","source":"Computers in biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40472508","citation_count":0,"is_preprint":false},{"pmid":"40410851","id":"PMC_40410851","title":"S1PR3 inhibition impairs cell cycle checkpoint via the AKT/WEE1 pathway in oral squamous cell carcinoma.","date":"2025","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40410851","citation_count":0,"is_preprint":false},{"pmid":"42001307","id":"PMC_42001307","title":"S1PR3 expression independently predicts the cumulative incidence of relapse in adult B-cell acute lymphoblastic leukemia: a single-center retrospective analysis.","date":"2026","source":"American journal of clinical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/42001307","citation_count":0,"is_preprint":false},{"pmid":"38163647","id":"PMC_38163647","title":"Extracellular α-synuclein impairs sphingosine 1-phosphate receptor type 3 (S1PR3)-regulated lysosomal delivery of cathepsin D in HeLa cells.","date":"2024","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/38163647","citation_count":0,"is_preprint":false},{"pmid":"41623209","id":"PMC_41623209","title":"S1PR3 Inactivation Aggravates Cerebrovascular Endothelial Cell Permeability Mediated by cPLA2 and STAT3 Phosphorylation Under Oxidative Stress.","date":"2026","source":"Basic & clinical pharmacology & toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/41623209","citation_count":0,"is_preprint":false},{"pmid":"41387860","id":"PMC_41387860","title":"S1PR3 Inhibition in alveolar epithelial cells alleviates pulmonary fibrosis by enhancing alveolar barrier function.","date":"2025","source":"Respiratory research","url":"https://pubmed.ncbi.nlm.nih.gov/41387860","citation_count":0,"is_preprint":false},{"pmid":"40782218","id":"PMC_40782218","title":"Effects of sphingolipid metabolism related genes-SPTLC1, ORMDL3, SPHK1 and S1PR3 polymorphisms on susceptibility to hashimoto's thyroiditis.","date":"2025","source":"Journal of endocrinological investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40782218","citation_count":0,"is_preprint":false},{"pmid":"41806939","id":"PMC_41806939","title":"S1P/S1PR3 axis drives epithelial dysfunction and type 2 inflammation in chronic rhinosinusitis with nasal polyps.","date":"2026","source":"Mucosal immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41806939","citation_count":0,"is_preprint":false},{"pmid":"41691873","id":"PMC_41691873","title":"S1PR3 antagonism ameliorates endothelial dysfunction in septic acute kidney injury through the ROCK1-Drp1 signalling pathway.","date":"2026","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41691873","citation_count":0,"is_preprint":false},{"pmid":"41573902","id":"PMC_41573902","title":"S1PR3 mediates glial stimulated tumor invasion in response 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This was demonstrated directly using a subunit-selective [35S]GTPgammaS binding assay in Sf9 and HEK293 cells.\",\n      \"method\": \"Subunit-selective [35S]GTPgammaS binding assay in Sf9 and HEK293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro G-protein activation assay, replicated across two cell systems\",\n      \"pmids\": [\"10488065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"S1PR3 (EDG-3) expressed in Xenopus oocytes confers SPP-responsive intracellular calcium transients coupled to Gq pathway; suramin selectively antagonizes SPP-activated calcium responses in EDG-3-expressing oocytes with IC50 of 22 µM, establishing EDG-3 as a pharmacologically distinct GPCR subtype.\",\n      \"method\": \"Xenopus oocyte expression system; Ca2+ measurements; chimeric Galphaqi co-expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — heterologous reconstitution in Xenopus oocytes with pharmacological validation\",\n      \"pmids\": [\"10383399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"S1PR3 (EDG-3) overexpression confers specific [32P]S1P binding (displaced by S1P and sphingosylphosphorylcholine but not LPA), mediates inositol phosphate production and [Ca2+]i increase partially sensitive to pertussis toxin, activates MAPK in PTX-sensitive/Ras-dependent manner, and decreases cellular cAMP, establishing distinct signaling characteristics compared to EDG-1 and EDG-5.\",\n      \"method\": \"Radioligand binding, inositol phosphate assay, Ca2+ measurements, MAPK activation assay, cAMP measurement in EDG-3-overexpressing cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal in vitro assays in reconstituted system\",\n      \"pmids\": [\"10381367\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"S1PR3 (EDG-3) activates the phospholipase C-Ca2+ system in transfected CHO cells; S1P-induced Ca2+ response was enhanced and associated with significant inositol phosphate production in EDG-3-transfected versus vector-transfected cells, inhibited by the PLC inhibitor U73122.\",\n      \"method\": \"Ca2+ measurement and inositol phosphate assay in EDG-3-transfected CHO cells\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted overexpression system with pharmacological inhibitor confirmation\",\n      \"pmids\": [\"9928946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"S1PR3 (EDG-3) expressed in CHO cells promotes S1P-induced chemotaxis and membrane ruffling via PI3K- and Rac-dependent mechanisms, inducing a biphasic increase in GTP-bound Rac; this is in contrast to EDG-5 which inhibits Rac activation.\",\n      \"method\": \"Chemotaxis assay, membrane ruffling imaging, Rac-GTP pulldown in CHO cells expressing EDG-3\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean receptor-specific overexpression with multiple functional readouts and mechanistic dissection\",\n      \"pmids\": [\"11094076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"S1PR3 (EDG-3) is required together with EDG-1 for S1P-induced Rho activation and integrin (αvβ3 and β1) clustering into focal contacts in human umbilical vein endothelial cells; antisense knockdown of EDG-3 inhibits S1P-induced cell migration on fibronectin, vitronectin and Matrigel.\",\n      \"method\": \"Antisense phosphothioate oligonucleotides, C3 exotoxin inhibition, integrin blocking antibodies, Rho activation assay, HUVEC migration assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with multiple orthogonal methods and defined cellular phenotype\",\n      \"pmids\": [\"11150298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"S1PR3 (LP(B3)/EDG-3) deletion in mouse embryonic fibroblasts causes significant decreases in S1P-induced phospholipase C activation and slight decreases in adenylyl cyclase inhibition, with no change in Rho activation, demonstrating nonredundant coupling of S1PR3 to PLC/Ca2+ pathway; retroviral re-expression of LP(B3) rescued PLC activation.\",\n      \"method\": \"Gene knockout in mice, MEF preparation, PLC activation assay, adenylyl cyclase inhibition assay, Rho activation assay, retroviral rescue\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout with rescue experiment and multiple pathway readouts\",\n      \"pmids\": [\"11443127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In S1P2/S1P3 double-knockout MEFs, Rho activation is completely lost and PLC activation and calcium mobilization are significantly decreased compared to wild-type, establishing preferential coupling of S1PR3 to PLC/Ca2+ pathways and S1PR2 to Rho; double-null pups show perinatal lethality demonstrating essential combined role.\",\n      \"method\": \"Double gene knockout in mice, MEF signaling assays (Rho, PLC, Ca2+, adenylyl cyclase)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis via double knockout with multiple signaling readouts\",\n      \"pmids\": [\"12006579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"S1PR3 (EDG-3) and EDG-5, but not EDG-1, mediate S1P-induced NF-κB activation in HEK293 cells through a mechanism requiring protein kinase C and Ca2+ downstream of Gq; Rho activation alone through Gq or G13 is insufficient for NF-κB activation.\",\n      \"method\": \"NF-κB reporter assay, PKC inhibitor treatment, Ca2+ chelation, overexpression of EDG receptor subtypes in HEK293 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — receptor-specific overexpression with mechanistic dissection of G protein pathway\",\n      \"pmids\": [\"11673450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"S1PR3 (EDG-3) mediates S1P-induced PI3K and Akt activation in CHO cells through phospholipase D; PLD2 is required downstream of EDG-3, as catalytically inactive PLD2 mutant eliminates S1P-induced Akt activation, and 1-butanol (PLD inhibitor) blocks PI3K/Akt activation and Rac-dependent membrane ruffling.\",\n      \"method\": \"PLD activity assay, PI3K assay, Akt phosphorylation, dominant-negative PLD2 co-expression, 1-butanol inhibition in EDG-3-overexpressing CHO cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis of PLD2 plus multiple pathway assays in reconstituted system\",\n      \"pmids\": [\"11468290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"S1PR3 (EDG-3) mediates S1P-induced cell proliferation, survival, ERK/MAP kinase activation, and c-Jun/c-Fos induction via Gi/o- and Rho-dependent pathways; pertussis toxin and C3 exoenzyme inhibit EDG-3-mediated serum response element activation.\",\n      \"method\": \"Stable transfection in HTC4 hepatoma cells, thymidine incorporation, apoptosis assay, ERK activation, reporter gene assay, PTX and C3 exoenzyme inhibition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — stable transfection with multiple functional readouts and pharmacological pathway dissection\",\n      \"pmids\": [\"10617617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"S1PR3 (EDG-3) mediates S1P-induced activation of IK.ACh (muscarinic-type inward rectifier K+ current) in human atrial cardiomyocytes; this is blocked by the EDG-3-selective antagonist suramin but not affected by carbachol, and EDG-3 transcript is detected in human atrial cells.\",\n      \"method\": \"Patch-clamp electrophysiology in freshly isolated atrial myocytes, suramin antagonist, RT-PCR for receptor transcripts\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology with receptor-selective pharmacological blockade in native cardiac tissue\",\n      \"pmids\": [\"10908314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A synthetic peptide (KRX-725) from the second intracellular loop of S1PR3 mimics S1P by triggering Gi-dependent MEK-ERK signaling, induces receptor internalization of S1PR3 but not S1PR1, and promotes angiogenesis ex vivo and in vivo; demonstrating that the second intracellular loop of S1PR3 is sufficient to activate specific downstream signaling.\",\n      \"method\": \"Peptide synthesis, ERK activation assay, receptor internalization assay, aortic ring ex vivo angiogenesis, mouse corneal pocket assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional peptide assay with receptor-specific internalization, single lab\",\n      \"pmids\": [\"12763936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"S1PR3 (EDG-3) mediates S1P-induced Ca2+ mobilization in C2C12 myoblasts; antisense oligodeoxynucleotides against EDG-3 significantly reduced SPP-induced Ca2+ response, and combined inhibition of EDG-3 and EDG-5 abolished the response, whereas antisense against EDG-1 had no effect.\",\n      \"method\": \"Antisense ODN knockdown, Ca2+ imaging (confocal, spectrophotofluorimeter) in C2C12 myoblasts\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — antisense knockdown with quantitative Ca2+ readout, single lab\",\n      \"pmids\": [\"11853542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Estrogen (E2) transactivates EGFR in breast cancer cells via a mechanism involving SphK1 activation, S1P release, and subsequent activation of S1PR3 (EDG-3), which leads to EGFR transactivation in a matrix metalloprotease-dependent manner.\",\n      \"method\": \"SphK1 activity assay, S1P ELISA, S1PR3 signaling assay, EGFR phosphorylation, MMP inhibitor treatment in breast cancer cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical assays in a single lab demonstrating the signaling axis\",\n      \"pmids\": [\"16636149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"S1PR3 (Edg3/S1P3) expression is necessary and sufficient for VEGF-dependent upregulation of Akt3 in primary endothelial cells; VEGF stimulates S1P3 expression via a Gi-protein-dependent mechanism (pertussis toxin-sensitive), and knockdown of S1P3 blocks VEGF-stimulated Akt3 induction.\",\n      \"method\": \"siRNA knockdown, pertussis toxin inhibition, Akt3 mRNA/protein measurement, overexpression in primary endothelial cells\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss- and gain-of-function in primary cells with defined molecular readout, single lab\",\n      \"pmids\": [\"16527273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"S1PR3 mediates S1P-induced expansion of cancer stem cells (ALDH-positive) via ligand-independent Notch activation; S1PR3 knockdown or S1PR3 antagonist inhibits tumorigenicity of SphK1-overexpressing CSCs in nude mice.\",\n      \"method\": \"ALDH flow cytometry, S1PR3 siRNA knockdown, S1PR3 antagonist, xenograft mouse model, Notch pathway activation assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological loss-of-function with in vivo validation, single lab\",\n      \"pmids\": [\"25254944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"S1PR3 contributes to the egress of Gna13-mutant germinal center B cells from lymph nodes; dissemination of Gna13-deficient GC B cells in mouse models depends on S1PR3, placing S1PR3 downstream of Gα13 signaling in GC B cell retention/egress.\",\n      \"method\": \"Genetic mouse models (Gna13 conditional KO, S1PR3 KO), lymph node egress assays, flow cytometry\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in mouse model, single lab\",\n      \"pmids\": [\"26573295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"S1PR3 is required for macrophage bactericidal function in sepsis; S1pr3-/- mice show increased bacterial burden and mortality; S1PR3 regulates ROS production and phagosome maturation by controlling recruitment of VPS34 (vacuolar protein-sorting 34) to phagosomes.\",\n      \"method\": \"S1PR3 knockout mice, bone marrow transfer, bacterial killing assay, ROS measurement, phagosome maturation assay, VPS34 recruitment to phagosomes\",\n      \"journal\": \"American journal of respiratory and critical care medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with mechanistic rescue (BM transfer) and defined molecular mechanism (VPS34 recruitment), multiple readouts\",\n      \"pmids\": [\"28850247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"S1PR3 is a direct target of miR-127 in myogenic cells; overexpression of miR-127 enhances myogenic differentiation and S1PR3 is required for this effect, as S1PR3 knockdown mimics miR-127 overexpression and S1PR3 restoration reverses the pro-differentiation phenotype.\",\n      \"method\": \"miRNA overexpression, luciferase reporter assay, C2C12 differentiation assay, transgenic mice, satellite cell assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — validated miRNA target with functional in vitro and in vivo phenotype, single lab\",\n      \"pmids\": [\"28358363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"S1PR3 signals via TRPA1 to mediate S1P-induced itch in pruriceptors, and via TRPV1 to mediate S1P-induced pain in nociceptors; S1P-evoked itch is lost in TRPA1-null mice and pain/heat hypersensitivity is lost in TRPV1-null mice, with S1PR3 required for both responses.\",\n      \"method\": \"Ca2+ imaging, electrophysiology in sensory neurons, S1PR3-KO mice, TRPA1-KO and TRPV1-KO mice, behavioral itch and pain assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic KO models with electrophysiology and behavioral validation establishing distinct cellular mechanisms\",\n      \"pmids\": [\"30082422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"S1P/S1PR3 axis promotes aerobic glycolysis in osteosarcoma by inhibiting YAP phosphorylation and promoting YAP nuclear translocation, leading to formation of a YAP-c-MYC complex that enhances PGAM1 transcription; co-immunoprecipitation confirmed YAP-c-MYC interaction and ChIP showed their binding to PGAM1 promoter.\",\n      \"method\": \"S1PR3 knockdown, co-immunoprecipitation, chromatin immunoprecipitation, luciferase reporter, metabolic flux analysis, xenograft mouse model\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including Co-IP, ChIP, and in vivo validation, single lab\",\n      \"pmids\": [\"30587459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"S1PR3 activation in mouse vagal airway afferent nodose C-fibers mediates S1P-induced action potential generation; S1P fails to activate airway nodose C-fibers in S1PR3 knockout mice, and an S1PR3 antagonist (TY52156) inhibits S1P-evoked action potentials.\",\n      \"method\": \"Single-cell RT-PCR, two-photon Ca2+ imaging of nodose ganglia in transgenic GCaMP6s mice, single-fiber electrophysiology, S1PR3-KO mice, S1PR3 antagonist\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO confirmed by pharmacological blockade with electrophysiology, strong evidence\",\n      \"pmids\": [\"30793318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structure of active human S1PR3 in complex with its natural agonist S1P determined at 3.2-Å resolution; S1P adopts an unbent conformation in a long tunnel traversing the receptor obliquely; four residues surrounding the alkyl tail of S1P (the 'quartet core') undergo coordinated rotamer changes to accommodate S1P and induce active conformation; the quartet core also determines G protein selectivity of S1PR3.\",\n      \"method\": \"X-ray crystallography, active S1PR3-S1P complex structure at 3.2 Å; mutagenesis of quartet core residues; comparison with inactive S1PR1 structure\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with mutagenesis validation of key mechanistic residues\",\n      \"pmids\": [\"34108205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"S1PR3 is a G12-biased agonist target; ALESIA compound acts as an S1PR3-G12-biased agonist (identified by TGFα shedding assay), promoting nitric oxide production and oxidative stress leading to cancer cell death under low-glucose conditions.\",\n      \"method\": \"TGFα shedding assay (DREADD-based G protein activation), nitric oxide measurement, oxidative stress assay, NADPH measurement, in vivo peritoneal tumor model\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — functional GPCR assay with biased signaling characterization, single lab\",\n      \"pmids\": [\"33561428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"S1P lyase inhibition protects against sepsis by increasing S1P levels that stimulate S1PR3, activating p38 and ERK MAPK pathways, reducing tissue damage; the protective effects are absent in S1PR3-deficient mice, establishing S1PR3 as essential for this protective pathway.\",\n      \"method\": \"S1P lyase inhibitor treatment, S1PR3-KO mice, cytokine measurement, lung permeability assay, p38/ERK phosphorylation, survival studies\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO confirms receptor requirement, single lab\",\n      \"pmids\": [\"32711251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"EDG3 (S1PR3) protein co-immunoprecipitates with SHC3 protein from human ependymoma tissue, and EDG3 protein was found to be N-glycosylated (confirmed by N-glycosidase-F digestion), indicating proper post-translational processing and plasma membrane trafficking.\",\n      \"method\": \"Co-immunoprecipitation from tumor tissue, N-glycosidase-F digestion, qPCR gene amplification analysis\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP from tumor tissue without functional follow-up of the interaction\",\n      \"pmids\": [\"19748727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"S1PR3 mediates S1P-induced CCL20 release from human bronchial epithelial cells; siRNA knockdown of S1PR3 suppresses S1P-induced CCL20 expression, and S1PR1/3 antagonist VPC23019 attenuates eosinophilic inflammation in OVA-challenged mice.\",\n      \"method\": \"Transcriptome analysis, siRNA knockdown, ELISA, OVA-challenged asthma mouse model, VPC23019 antagonist\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with in vitro and in vivo confirmation, single lab\",\n      \"pmids\": [\"30192865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"S1PR3 mediates fingolimod phosphate (pFTY720)-dependent protection of astrocytes against OGD-induced neuroinflammation by inhibiting TLR2/4-PI3K-NFκB signaling; S1PR3 knockdown reverses the protective effects of pFTY720.\",\n      \"method\": \"S1PR3 siRNA knockdown, OGD model in astrocytes, TLR2/PI3K/NFκB pathway assays, cytokine measurement\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA-mediated loss-of-function with defined pathway readout, single lab\",\n      \"pmids\": [\"29536648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FTY720-P stimulates the Na+/K+ ATPase in HepG2 liver cells via S1PR3, acting sequentially through PKC, ERK, NF-κB, and COX-2 to induce PGE2 release; the effect was blocked by the specific S1PR3 antagonist CAY10444 and reproduced by the S1PR3 agonist CYM5541.\",\n      \"method\": \"Na+/K+ ATPase activity assay, S1PR3-specific antagonist and agonist, PKC/ERK inhibitors, COX inhibitor, IκB expression western blot in HepG2 cells\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological dissection with multiple pathway inhibitors and receptor-specific tools, single lab\",\n      \"pmids\": [\"31502430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Extracellular α-synuclein causes S1PR3 uncoupling from G protein in HeLa cells, leading to impaired retrograde trafficking of IGF-II/M6P receptor (which is under S1PR3 regulation), reduced cathepsin D lysosomal delivery, and enhanced secretion of immature pro-cathepsin D.\",\n      \"method\": \"S1PR3 G-protein coupling assay, cathepsin D activity assay, pro-cathepsin D secretion measurement, IGF-II/M6P receptor retrograde trafficking assay in HeLa cells\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional readouts linking S1PR3 uncoupling to lysosomal pathway, single lab\",\n      \"pmids\": [\"38163647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"S1PR3 promotes aerobic glycolysis in septic macrophages via HIF-1α, HK2, and PFKFB3; S1PR3 knockdown dampens glycolysis-associated markers, retrieves LPS-modulated M1/M2 polarization balance, and attenuates NF-κB p65 activation.\",\n      \"method\": \"S1PR3 siRNA, glycolytic flux assay, macrophage polarization markers, NF-κB p65 activation, LPS-induced sepsis mouse model\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic silencing with multiple metabolic and inflammatory readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"39549732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"S1PR3 activates STAT3 via a Gαi/PKA-mediated Src activation pathway in keratinocytes; activated STAT3 in turn directly upregulates S1PR3 expression forming a positive feedback loop; S1PR3 genetic deletion or pharmacological inhibition attenuates psoriasis-like skin inflammation in mice.\",\n      \"method\": \"Genetic S1pr3 deletion, S1PR3 pharmacological inhibition, Src/STAT3 phosphorylation assays, Gαi/PKA pathway dissection, STAT3 ChIP on S1PR3 promoter, skin inflammation mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — combined genetic and pharmacological evidence with defined Gαi/PKA-Src-STAT3 mechanism and feedback loop, single lab\",\n      \"pmids\": [\"39833165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"S1PR3 regulates hippocampal synaptic plasticity and depression-like behavior via downregulation of RhoA/ROCK1; AAV-mediated S1PR3 overexpression in hippocampal neurons alleviates CUMS-induced depressive behavior and synaptic deficits, and these effects are normalized by RhoA expression, placing RhoA/ROCK1 downstream of S1PR3.\",\n      \"method\": \"AAV-mediated S1PR3 overexpression in hippocampal neurons, RhoA rescue experiment, behavioral tests (SPT, FST, OFT), synaptic spine density analysis, electron microscopy of synaptic ultrastructure\",\n      \"journal\": \"Progress in neuro-psychopharmacology & biological psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic gain-of-function with epistasis rescue experiment and defined pathway, single lab\",\n      \"pmids\": [\"39828081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CEACAM1-long isoform in neutrophils regulates susceptibility to NET formation by controlling the S1P/S1PR2/S1PR3 axis via autophagy signaling; CC1-L ablation aggravated hepatic IRI by promoting NETs in a mouse liver transplant model.\",\n      \"method\": \"Conditional knockout mouse model (CC1-L), NETosis assay, autophagy signaling assays, S1PR2/S1PR3 pathway analysis in mouse and human OLT samples\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined pathway, but S1PR3 role is part of a dual receptor axis, single lab\",\n      \"pmids\": [\"36719377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ApoM-bound S1P shows a tendency to induce prolonged activation of Akt via S1PR1 and S1PR3 compared to albumin- or ApoA4-bound S1P, correlating with greater S1P stability and more efficient S1P release from endothelial cells.\",\n      \"method\": \"S1P stability assay, S1P release from endothelial cells, Akt phosphorylation kinetics with different S1P carrier proteins and receptor comparisons\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, indirect evidence for S1PR3 role in signaling duration, no direct S1PR3 mutagenesis or KO\",\n      \"pmids\": [\"37098187\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"S1PR3 is a G protein-coupled receptor for sphingosine 1-phosphate that couples to Gi, Gq, and G13, activating downstream pathways including PLC/Ca2+, PI3K/Akt (via PLD), RhoA, Rac, ERK/MAPK, and NF-κB; its crystal structure reveals S1P binds in an unbent conformation in a transmembrane tunnel with a 'quartet core' of residues controlling both receptor activation and G protein subtype selectivity; functionally, S1PR3 drives endothelial cell migration (via Rho-integrin signaling), cardiac IK.ACh activation, macrophage bactericidal activity (via VPS34-phagosome recruitment), sensory neuron activation of itch (via TRPA1) and pain (via TRPV1), cancer stem cell expansion (via Notch), aerobic glycolysis (via YAP/c-MYC/PGAM1), and vascular resistance (via RhoA/ROCK), while also being subject to feedback regulation where STAT3 activation upregulates S1PR3 expression.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"S1PR3 is a G protein-coupled receptor for sphingosine 1-phosphate that transduces signals through Gi, Gq, and G12/13 heterotrimeric G proteins, activating PLC/Ca²⁺, PI3K/Akt (via PLD2), Rac, Rho, ERK/MAPK, and NF-κB pathways to regulate diverse cellular responses including migration, proliferation, survival, and metabolic reprogramming [PMID:10488065, PMID:10617617, PMID:11468290, PMID:11673450]. The crystal structure of the active S1PR3–S1P complex reveals the ligand in an unbent conformation within a transmembrane tunnel, where a 'quartet core' of residues undergoes coordinated rotamer changes that control both receptor activation and G protein subtype selectivity [PMID:34108205]. Physiologically, S1PR3 drives endothelial cell migration through Rho-dependent integrin clustering [PMID:11150298], macrophage bactericidal function via VPS34 recruitment to phagosomes [PMID:28850247], sensory neuron activation of itch and pain through TRPA1 and TRPV1 channels respectively [PMID:30082422], cardiac IK.ACh current activation in atrial myocytes [PMID:10908314], and cancer stem cell expansion via Notch signaling [PMID:25254944]. S1PR3 also participates in a positive feedback loop in keratinocytes where Gαi/PKA–Src–STAT3 signaling upregulates S1PR3 expression, contributing to psoriasis-like inflammation [PMID:39833165].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing S1PR3 as a multi-G-protein-coupled S1P receptor resolved how a single lipid could activate divergent intracellular pathways through different receptor subtypes, distinguishing S1PR3 (Gi/Gq/G13 coupling) from S1PR1 (Gi-only).\",\n      \"evidence\": \"Subunit-selective [³⁵S]GTPγS binding in Sf9/HEK293 cells, Ca²⁺ transients in Xenopus oocytes, radioligand binding and IP/cAMP assays in CHO cells\",\n      \"pmids\": [\"10488065\", \"10383399\", \"10381367\", \"9928946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of differential G protein selectivity unknown\", \"Relative contribution of each G protein arm in native tissues not established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Delineating the downstream effector architecture showed that S1PR3 preferentially couples to PLC/Ca²⁺ (confirmed by genetic knockout with rescue), activates PI3K/Akt through PLD2, and mediates NF-κB activation through PKC/Ca²⁺, while also activating Rho/Rac for migration and integrin clustering in endothelial cells.\",\n      \"evidence\": \"S1PR3-KO MEFs with retroviral rescue; dominant-negative PLD2 in CHO cells; NF-κB reporter with PKC/Ca²⁺ inhibition in HEK293; antisense knockdown with Rho/integrin assays in HUVECs\",\n      \"pmids\": [\"11443127\", \"11468290\", \"11673450\", \"11150298\", \"11094076\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PLD2 coupling to S1PR3 not determined\", \"Whether Rho activation is direct through G13 or indirect in endothelial cells not resolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Discovery that S1PR3 activates cardiac IK.ACh in human atrial myocytes established a physiological role beyond cell lines, showing receptor-mediated ion channel regulation in native tissue.\",\n      \"evidence\": \"Patch-clamp electrophysiology with suramin blockade in freshly isolated atrial cardiomyocytes\",\n      \"pmids\": [\"10908314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether S1PR3-mediated IK.ACh contributes to cardiac arrhythmogenesis not tested\", \"Downstream G protein subtype mediating the ionic effect not identified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"S1PR2/S1PR3 double-knockout epistasis revealed that S1PR3 preferentially drives PLC/Ca²⁺ while S1PR2 preferentially drives Rho, and that their combined loss causes perinatal lethality, establishing essential combined developmental roles.\",\n      \"evidence\": \"Double-KO mice with MEF signaling assays for Rho, PLC, Ca²⁺, and adenylyl cyclase\",\n      \"pmids\": [\"12006579\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cause of perinatal lethality not characterized\", \"Organ-specific contributions of each receptor not dissected\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linking S1PR3 to estrogen-EGFR transactivation in breast cancer and VEGF-dependent Akt3 induction in endothelial cells placed S1PR3 at the intersection of growth factor and sphingolipid signaling networks.\",\n      \"evidence\": \"SphK1 activation/S1P release leading to EGFR phosphorylation via MMP in breast cancer cells; siRNA knockdown showing VEGF-S1PR3-Akt3 axis in primary endothelial cells\",\n      \"pmids\": [\"16636149\", \"16527273\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction between S1PR3 and EGFR not demonstrated\", \"Physiological relevance in vivo for estrogen-EGFR axis not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of S1PR3 as a driver of cancer stem cell expansion via ligand-independent Notch activation revealed a non-canonical signaling mechanism, with in vivo validation showing S1PR3 loss reduces tumorigenicity.\",\n      \"evidence\": \"ALDH flow cytometry, S1PR3 siRNA/antagonist, Notch activation assay, nude mouse xenograft\",\n      \"pmids\": [\"25254944\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of ligand-independent Notch activation by S1PR3 not defined\", \"Whether direct S1PR3-Notch physical interaction occurs not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstration that S1PR3 controls macrophage bactericidal function by recruiting VPS34 to phagosomes for ROS production and phagosome maturation established a direct role in innate immunity, with S1PR3-KO mice showing increased bacterial burden and sepsis mortality.\",\n      \"evidence\": \"S1PR3-KO mice, bone marrow transfer, bacterial killing assay, VPS34 recruitment to phagosomes\",\n      \"pmids\": [\"28850247\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How S1PR3 signaling connects to VPS34 recruitment molecularly unknown\", \"Whether specific G protein arm mediates phagosome function not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Genetic studies in knockout mice revealed that S1PR3 mediates S1P-induced itch via TRPA1 in pruriceptors and pain via TRPV1 in nociceptors, establishing cell-type-specific coupling to distinct TRP channels as the basis for dual somatosensory functions.\",\n      \"evidence\": \"Ca²⁺ imaging and electrophysiology in sensory neurons; behavioral assays in S1PR3-KO, TRPA1-KO, and TRPV1-KO mice\",\n      \"pmids\": [\"30082422\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Intracellular signaling cascade linking S1PR3 to TRPA1 versus TRPV1 activation not resolved\", \"Whether PLC or other second messengers gate TRP channels downstream of S1PR3 not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"S1PR3 was shown to promote aerobic glycolysis in osteosarcoma through YAP nuclear translocation and YAP-c-MYC complex formation driving PGAM1 transcription, broadening S1PR3's role to metabolic reprogramming in cancer.\",\n      \"evidence\": \"Co-IP of YAP-c-MYC, ChIP on PGAM1 promoter, metabolic flux analysis, xenograft model\",\n      \"pmids\": [\"30587459\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether S1PR3-YAP axis operates through Hippo kinase inhibition or parallel pathway not determined\", \"Generalizability to other cancer types not tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The crystal structure of active S1PR3 bound to S1P resolved how the ligand adopts an unbent conformation in a transmembrane tunnel and identified a 'quartet core' of residues whose coordinated rotamer changes control both receptor activation and G protein subtype selectivity, providing a structural basis for the multi-G-protein coupling first observed in 1999.\",\n      \"evidence\": \"X-ray crystallography at 3.2 Å resolution; mutagenesis of quartet core residues; structural comparison with inactive S1PR1\",\n      \"pmids\": [\"34108205\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cryo-EM structure of S1PR3-G protein ternary complex not yet obtained\", \"How quartet core conformational changes propagate to the intracellular G protein binding surface not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Discovery of a Gαi/PKA–Src–STAT3 positive feedback loop where STAT3 directly upregulates S1PR3 transcription in keratinocytes revealed an autoamplification mechanism relevant to psoriasis-like inflammation, and S1PR3's regulation of hippocampal synaptic plasticity via RhoA/ROCK1 was established.\",\n      \"evidence\": \"S1PR3 genetic deletion/pharmacological inhibition with STAT3 ChIP on S1PR3 promoter in skin inflammation model; AAV-mediated S1PR3 overexpression with RhoA rescue in hippocampal neurons\",\n      \"pmids\": [\"39833165\", \"39828081\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the STAT3 feedback loop operates in cell types beyond keratinocytes not tested\", \"Direct assessment of S1PR3 in human psoriasis tissue not performed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the cryo-EM structure of S1PR3 in complex with different G protein subtypes, the molecular mechanism linking S1PR3 to VPS34 phagosomal recruitment, how cell-type-specific G protein coupling is determined, and whether biased agonism at S1PR3 can be therapeutically exploited.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No ternary complex structure of S1PR3 with any G protein\", \"Mechanism of cell-type-specific effector selection unknown\", \"No clinical data on S1PR3-selective therapeutics\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 2, 3, 23]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2, 26]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 8, 9, 10, 23, 32]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [18, 27, 31]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [20, 22, 33]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [21, 31]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"GNAI1\",\n      \"GNAQ\",\n      \"GNA13\",\n      \"PLD2\",\n      \"VPS34\",\n      \"TRPA1\",\n      \"TRPV1\",\n      \"STAT3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}