{"gene":"PTGER2","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":1993,"finding":"Human EP2 receptor (PTGER2) was cloned from a lung cDNA library; expressed in COS-7 cells it bound [3H]-PGE2 with Kd ~2.2 nM and coupled exclusively to Gs to increase intracellular cAMP (not Ca2+), establishing its second-messenger mechanism.","method":"cDNA cloning, radioligand binding assay, cAMP and Ca2+ measurement in transfected COS-7 cells","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — direct reconstitution in transfected cells with radioligand binding and functional cAMP/Ca2+ assays","pmids":["8250933"],"is_preprint":false},{"year":1999,"finding":"Genetic deletion of EP2 (PTGER2) in mice abolished the hypotensive effect of intravenous PGE2 (which instead caused hypertension), demonstrating that the EP2 receptor mediates PGE2-induced arterial vasodilation. EP2-/- mice also developed profound salt-sensitive hypertension, establishing a required role in blood-pressure homeostasis.","method":"Targeted gene disruption (EP2-/- mice), intravenous PGE2 infusion, blood pressure measurement, high-salt diet challenge","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with defined cardiovascular phenotype, replicated across multiple blood-pressure paradigms","pmids":["9930871"],"is_preprint":false},{"year":1999,"finding":"EP2 (PTGER2) knockout mice exhibit reduced litter sizes due to a pre-implantation defect involving impaired ovulation and dramatically reduced fertilization, establishing a required role for EP2 signaling in female fertility.","method":"Targeted gene disruption (EP2-/- mice), pregnancy day 2 and day 5 analysis of embryo implantation, ovulation, and fertilization","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — clean KO with specific reproductive phenotype and defined pre-implantation defect","pmids":["9930871"],"is_preprint":false},{"year":2000,"finding":"EP2 receptor (PTGER2) mediates PGE2-induced bronchodilation: PGE2 inhalation inhibited methacholine-induced airway constriction in wild-type but not EP2-/- mice, and paradoxically increased constriction in EP2-/- animals.","method":"Targeted gene disruption (EP2-/- mice), barometric plethysmography, mechanically ventilated mouse lung-resistance measurements","journal":"Journal of applied physiology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with specific functional airway phenotype using two independent measurement methods","pmids":["10846038"],"is_preprint":false},{"year":2001,"finding":"EP2 receptor expression is restricted to the outer and inner medulla (descending thin limb of Henle's loop and outer medullary vasa recta) in the rat kidney, and butaprost (EP2-selective agonist) dose-dependently raised cAMP in microdissected EP2-positive segments but not in EP2-negative collecting duct segments, establishing site-specific cAMP-mediated paracrine regulation of tubular transport and vascular resistance.","method":"RNase protection assay, RT-PCR on microdissected nephron segments, cAMP radioimmunoassay with butaprost stimulation","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 1-2 — direct localization combined with functional cAMP assay in microdissected native tissue","pmids":["11352840"],"is_preprint":false},{"year":2003,"finding":"EP2 receptor (PTGER2) stimulates Tcf/β-catenin-mediated transcriptional activity primarily through cAMP-dependent PKA, whereas EP4 additionally uses PI3K; EP2 does not activate ERK1/2 or induce EGR-1, distinguishing its downstream signaling from that of EP4.","method":"Tcf reporter assay, PKA inhibitor studies, PI3K inhibitor studies, ERK phosphorylation assay in transfected cells","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological dissection of signaling pathways in cell-based assays, single lab","pmids":["14607241"],"is_preprint":false},{"year":2004,"finding":"Activation of EP2 receptor (PTGER2) is neuroprotective in NMDA toxicity and oxygen-glucose deprivation paradigms via cAMP/PKA signaling; pharmacological blockade of PKA reversed EP2-mediated neuroprotection. Genetic deletion of EP2 significantly increased cerebral infarction in the MCAO stroke model.","method":"Dispersed neuron cultures, organotypic hippocampal cultures, PKA inhibition, EP2-/- mouse MCAO model with infarct volume measurement","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro mechanistic assays with PKA inhibitor validation plus genetic KO in vivo stroke model","pmids":["14715958"],"is_preprint":false},{"year":2005,"finding":"EP2 receptor (PTGER2) is required for COX-2-induced mammary hyperplasia: bigenic MMTV-COX-2;Ep2-/- mice showed strongly suppressed precocious mammary development and hyperplasia, accompanied by reduced amphiregulin expression and reduced cAMP. EP2 agonist treatment of mammary tumor cells induced amphiregulin mRNA in a PKA-dependent manner, establishing a PGE2→EP2→cAMP/PKA→amphiregulin signaling axis driving mammary epithelial cell growth.","method":"Genetic bigenic mouse model (MMTV-COX-2 × EP2-/-), cAMP assay in mammary glands, EP2-selective agonist (CAY10399) treatment, amphiregulin RT-PCR, PKA inhibitor studies","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in vivo plus mechanistic signaling studies in vitro with multiple orthogonal readouts","pmids":["15930264"],"is_preprint":false},{"year":2007,"finding":"EP2 receptor (PTGER2) mediates a positive feedback loop in skin: PGE2 via EP2 activates PKA/CREB signaling to induce COX-2 expression and PGE2 production; EP2 knockout mice showed reduced COX-2 and PGE2 after TPA treatment, while EP2 transgenic mice showed increased COX-2 and CREB phosphorylation. Adenylate cyclase inhibitor blocked EP2-driven cell proliferation.","method":"EP2 knockout and transgenic mice, TPA/PGE2 treatment, COX-2 immunoblot, CREB phosphorylation assay, adenylate cyclase inhibitor (SQ22536), primary keratinocyte cultures","journal":"Carcinogenesis","confidence":"High","confidence_rationale":"Tier 2 — genetic gain/loss-of-function combined with pharmacological inhibition and multiple molecular readouts","pmids":["17277233"],"is_preprint":false},{"year":2007,"finding":"PTGER2 is epigenetically silenced in neuroblastoma cells (especially those with MYCN amplification) via DNA methylation, histone H3/H4 deacetylation, and H3K9 methylation at the promoter. Restoration of PTGER2 expression by transfection enabled EP2-agonist butaprost to increase cAMP, inhibit cell growth, and induce apoptosis via cAMP-dependent pathway.","method":"Bisulfite sequencing, ChIP for histone modifications, siRNA knockdown, stable/transient transfection, butaprost treatment, cAMP assay, cell growth and apoptosis assays","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal epigenetic methods plus functional rescue with agonist treatment","pmids":["17533365"],"is_preprint":false},{"year":2010,"finding":"DNA hypermethylation of the PTGER2 promoter, driven by increased Akt signaling, causes reduced EP2 expression and PGE2 resistance in fibrotic fibroblasts from humans and mice with pulmonary fibrosis. Treatment with DNA methylation inhibitors or DNMT-specific siRNA decreased PTGER2 methylation, restored EP2 expression, and rescued PGE2 responsiveness.","method":"Bisulfite sequencing, DNMT siRNA, DNA methylation inhibitors (5-aza-2'-deoxycytidine, zebularine), EP2 mRNA/protein quantification, PGE2 functional assays, Akt pathway analysis","journal":"The American journal of pathology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal epigenetic methods, genetic (siRNA) and pharmacological validation, replicated in human and mouse cells","pmids":["20889571"],"is_preprint":false},{"year":2010,"finding":"Exogenous PGE2 or an EP2 receptor agonist completely counteracted the pro-fibrogenic effects (increased proliferation and matrix synthesis) caused by increased matrix stiffness in lung fibroblasts, demonstrating that EP2 is the receptor through which PGE2 maintains fibroblast quiescence and opposes fibrosis.","method":"Polyacrylamide hydrogel culture system with tunable stiffness, EP2-selective agonist treatment, fibroblast proliferation and matrix synthesis assays","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological EP2 agonist rescue in a defined biophysical model, single lab","pmids":["20733059"],"is_preprint":false},{"year":2011,"finding":"PGE2 suppresses Sclerostin (Sost) expression in osteoblastic cells via the EP2 receptor (PTGER2) through a cAMP/PKA pathway, leading to increased Wnt/TCF target gene expression (Axin2, Tcf3). EP2-selective agonists mimicked PGE2, and siRNA knockdown of Ptger2 prevented PGE2-induced Sost repression.","method":"EP2-selective agonists, siRNA knockdown of Ptger2, cAMP/PKA pathway inhibitors, RT-PCR for Sost/Axin2/Tcf3, osteoblastic UMR106.01 cell line","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — pharmacological and genetic (siRNA) approaches with multiple molecular readouts linking EP2 to Wnt signaling","pmids":["21436889"],"is_preprint":false},{"year":2013,"finding":"PGE2 acting through PTGER2 on porcine and human trophoblast cells promotes cell adhesion to extracellular matrix via integrin αVβ3, with signaling through MEK/MAPK and estrogen receptor. Blockade with EP2 antagonist AH6809, ITGAVB3 antibody, or MEK inhibition abolished PGE2-induced adhesion.","method":"RT-PCR and protein expression during implantation, butaprost treatment, EP2 antagonist (AH6809), integrin antibody, MEK inhibitor, FAK and ICAM-1 immunoblot in porcine and human trophoblast cells","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — pharmacological and antibody-based dissection of signaling in both human and porcine trophoblast cells with multiple orthogonal inhibitors","pmids":["23861370"],"is_preprint":false},{"year":2013,"finding":"EP2 activation promotes tumor cell growth and migration via a β-arrestin-dependent, G-protein-independent pathway in addition to the canonical cAMP-PKA pathway, expanding the known signaling repertoire of PTGER2.","method":"Review citing functional studies with EP2 agonists, β-arrestin pathway analysis","journal":"Trends in pharmacological sciences","confidence":"Low","confidence_rationale":"Tier 4 — review summary without primary experimental data in this paper","pmids":["23796953"],"is_preprint":false},{"year":2014,"finding":"The transcription factor RORC directly silences PTGER2 transcription in human Th17 cells by binding to the PTGER2 promoter; reduced RORC binding in MS patient Th17 cells results in higher EP2 levels, increased IFN-γ and GM-CSF, and a pathogenic Th17 phenotype. Overexpression of EP2 in healthy Th17 cells recapitulated the inflammatory gene program.","method":"ChIP-seq (RORγt binding to Ptger2/PTGER2 promoter), RORC siRNA knockdown, EP2 overexpression in human Th17 cells, comparison of healthy vs. MS patient cells","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 — ChIP-seq demonstrating direct promoter binding, siRNA rescue, and gain-of-function overexpression with defined inflammatory phenotype","pmids":["24812667"],"is_preprint":false},{"year":2014,"finding":"PGE2 inhibits IL-10 production in brain microglia through the EP2 receptor via a β-arrestin-dependent, cAMP-independent pathway. EP2 genetic disruption abolished PGE2-mediated IL-10 suppression; EP2-selective agonist butaprost mimicked the effect; β-arrestin-1 or -2 deficiency also abolished the suppression.","method":"Primary neuron-glia cultures, EP2-/- mice, butaprost and other EP agonists, cAMP pathway inhibitors, β-arrestin-1/2 knockout microglia, IL-10 ELISA","journal":"Molecular neurobiology","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic KOs (EP2-/-, β-arrestin-/-) combined with pharmacological agonists and pathway inhibitors","pmids":["25218510"],"is_preprint":false},{"year":2010,"finding":"EP2 receptor signaling inhibits matrix metalloproteinase 13 (MMP-13) expression in human osteoarthritic chondrocytes via a cAMP/PKA pathway, and also suppresses other catabolic factors (MMP-1, MMP-3, ADAMTS5, IL-1β, TNF-α) without affecting cell viability. EP2 was identified as the major EP receptor in osteoarthritic cartilage.","method":"siRNA screen of 114 genes, butaprost (EP2 agonist) treatment ± IL-1β ± COX-2 inhibitor, cAMP/PKA inhibitors, MMP-13 ELISA and RT-PCR, cell viability assay, RT-PCR of EP receptor subtypes in OA cartilage","journal":"Annals of the rheumatic diseases","confidence":"High","confidence_rationale":"Tier 2 — systematic siRNA screen identified EP2, confirmed with agonist and pharmacological pathway dissection","pmids":["20870807"],"is_preprint":false},{"year":2015,"finding":"Intracellular EP2 (iEP2) in PC3 prostate cancer cells promotes cancer-related phenotypes (proliferation, adhesion, migration, invasion, angiogenesis in vitro) through an EGFR transactivation–HIF-1α axis; inhibition of the prostaglandin uptake transporter, EP2 antagonist, or HIF-1α knockdown prevented these effects. PGE2 induced PKA-sensitive DNA synthesis even in isolated nuclei containing functional EP2 receptors.","method":"Pharmacological inhibition of prostaglandin uptake transporter, EP2 antagonist, EGFR antagonist, siRNA knockdown of HIF-1α, nuclear isolation and DNA synthesis assay, migration/invasion/angiogenesis in vitro assays","journal":"Cellular and molecular life sciences","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological and genetic manipulations in one cell line, single lab","pmids":["25828575"],"is_preprint":false},{"year":2012,"finding":"PTGS2-derived PGE2 protects against STZ-induced diabetes via PTGER2 and PTGER4 receptors; combined knockout of PTGER2 and PTGER4 (but not single knockouts) dramatically enhanced STZ pathology. PTGER2/PTGER4 agonist treatment of PTGS-2-/- and wild-type mice partially restored β-cell function and protected against STZ-induced diabetes.","method":"PTGER2-/-, PTGER4-/-, PTGER2/PTGER4 double KO mice, pharmacological PTGER4 blockade in PTGER2-/- background, EP2/EP4 agonist rescue, blood glucose, insulin, and survival measurement","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 — epistatic genetic dissection using single and double receptor knockouts with pharmacological agonist rescue","pmids":["22522619"],"is_preprint":false},{"year":2019,"finding":"In an adult inducible EP2 knockout model (ROSACreER;EP2lox/lox), EP2 deletion reduced stroke severity, myeloid cell brain trafficking, and neuronal injury after MCAO, contrasting with the congenital EP2-/- model; neuronal-specific EP2 deletion (Thy1Cre;EP2lox/lox) reduced cerebral ischemic injury, identifying neurons as a cell type in which EP2 promotes ischemic damage. Myeloid-specific EP2 knockdown (Cd11bCre;EP2lox/lox) attenuated post-stroke immune cell infiltration but did not reduce infarct volume.","method":"Cell-type-specific conditional KO mice (ROSACreER, Thy1Cre, Cd11bCre), MCAO stroke model, infarct volume, brain immune cell flow cytometry","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple conditional cell-type-specific KO mouse lines with defined stroke phenotypes","pmids":["31036664"],"is_preprint":false},{"year":2020,"finding":"EP2 receptor on peripheral immune myeloid cells drives key deleterious consequences of status epilepticus: conditional deletion of EP2 in CD11b+ myeloid cells (but not microglia) abolished hippocampal IL-6 induction, prevented BBB breakdown (measured by cortical albumin), and accelerated behavioral recovery after pilocarpine SE. Systemic EP2 antagonism additionally blocked monocyte brain infiltration and was neuroprotective, going beyond what myeloid-specific deletion achieved.","method":"CD11b-Cre;EP2lox/lox conditional KO mice, pilocarpine status epilepticus model, IL-6 ELISA, cortical albumin measurement, behavioral scoring, systemic EP2 antagonist administration","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific conditional KO with multiple orthogonal inflammatory and behavioral readouts","pmids":["33293358"],"is_preprint":false},{"year":2007,"finding":"PTGER2 (EP2) mediates progesterone synthesis and type 1 11β-HSD activity stimulated by PGE2 in human granulosa-lutein cells via cAMP signaling; the EP2-selective agonist butaprost stimulated both responses, and the mixed EP1/EP2 antagonist AH6809 (but not the EP1-selective antagonist SC19220 alone) completely abolished both PGE2-stimulated cAMP accumulation and progesterone synthesis.","method":"Human granulosa-lutein cell cultures, EP2 agonist (butaprost), selective EP1 antagonist (SC19220), mixed EP1/EP2 antagonist (AH6809), cAMP radioimmunoassay, progesterone RIA, 11β-HSD activity assay","journal":"The Journal of endocrinology","confidence":"High","confidence_rationale":"Tier 2 — pharmacological receptor dissection with agonist and two antagonists measuring cAMP, progesterone, and 11β-HSD in human primary cells","pmids":["17761898"],"is_preprint":false},{"year":2004,"finding":"PGE2 via EP2 receptor suppresses TNF-α-induced CCL27 production in human keratinocytes by inhibiting NF-κB activity through a cAMP-dependent pathway. EP2 agonist increased intracellular cAMP, and PKA inhibitor (H-89) partially blocked the inhibitory effect; combined EP1/EP2 and EP3 antagonism completely reversed PGE2-mediated suppression.","method":"Human keratinocyte cultures, EP2/EP3 selective agonists, EP antagonists, NF-κB luciferase reporter assay, cAMP ELISA, Ca2+ chelator (BAPTA/AM), H-89 PKA inhibitor, CCL27 ELISA and RT-PCR","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple pharmacological tools dissecting receptor subtype contributions with mechanistic NF-κB reporter assay","pmids":["15577845"],"is_preprint":false}],"current_model":"PTGER2 (EP2) is a Gs-coupled GPCR that binds PGE2 with nanomolar affinity and primarily signals through adenylyl cyclase–cAMP–PKA to regulate diverse processes including arterial vasodilation and blood pressure homeostasis, bronchodilation, female fertility (ovulation and implantation), neuroprotection in acute ischemia, bone anabolism (via Sclerostin suppression and Wnt pathway activation), mammary epithelial proliferation (via amphiregulin induction), and cartilage protection (via MMP-13 suppression); additionally, EP2 can signal in a G-protein-independent, β-arrestin-dependent manner to suppress microglial IL-10 production and promote tumor cell growth, and its expression is regulated epigenetically by PTGER2 promoter DNA hypermethylation (driven by Akt) and by direct transcriptional silencing through the Th17 transcription factor RORC."},"narrative":{"teleology":[{"year":1993,"claim":"Cloning of human EP2 and demonstration of exclusive Gs–cAMP coupling resolved the second-messenger identity of one of the four PGE2 receptor subtypes, distinguishing it from Ca²⁺-coupled receptors.","evidence":"cDNA cloning from human lung, radioligand binding (Kd ~2.2 nM), cAMP and Ca²⁺ measurement in transfected COS-7 cells","pmids":["8250933"],"confidence":"High","gaps":["Downstream effectors beyond cAMP not yet mapped","No in vivo functional data","Receptor desensitization and trafficking unknown"]},{"year":1999,"claim":"Genetic ablation of EP2 established that it is the required receptor for PGE2-mediated arterial vasodilation, salt-sensitive blood pressure homeostasis, and female fertility (ovulation and fertilization), converting pharmacological inference into causal genetic proof.","evidence":"EP2−/− knockout mice with intravenous PGE2 infusion, high-salt diet challenge, and reproductive phenotyping","pmids":["9930871"],"confidence":"High","gaps":["Downstream signaling mediating vasodilation in vivo uncharacterized","Whether fertility defect is oocyte- or somatic-cell-autonomous not resolved","Renal tubular mechanism of salt handling not defined"]},{"year":2000,"claim":"Demonstration that EP2 mediates PGE2-induced bronchodilation expanded its physiological role to airway smooth muscle and explained the paradoxical bronchoconstriction seen when EP2 is absent.","evidence":"EP2−/− mice, barometric plethysmography and mechanical ventilation measurements of airway resistance","pmids":["10846038"],"confidence":"High","gaps":["Airway cell type expressing functional EP2 not identified","Contribution of EP2 vs. EP4 in human airways not resolved"]},{"year":2001,"claim":"Mapping EP2 to specific renal medullary segments (descending thin limb of Henle, outer medullary vasa recta) with segment-specific cAMP responses provided the anatomical basis for its role in salt and water balance.","evidence":"RNase protection assay, RT-PCR on microdissected nephron segments, cAMP RIA with butaprost in rat kidney","pmids":["11352840"],"confidence":"High","gaps":["Direct ion-transport targets in these segments not identified","Human renal EP2 distribution not confirmed"]},{"year":2004,"claim":"EP2 was shown to mediate neuroprotection against excitotoxicity and ischemia via cAMP/PKA, while separately suppressing keratinocyte CCL27 through cAMP-dependent NF-κB inhibition, establishing PKA as a shared effector across cell types.","evidence":"Neuronal cultures with NMDA/OGD ± PKA inhibitors, EP2−/− MCAO stroke model; keratinocyte NF-κB reporter with EP2 agonist and H-89","pmids":["14715958","15577845"],"confidence":"High","gaps":["Neuroprotective mechanism downstream of PKA (anti-apoptotic targets) unknown","Relative contribution of neuronal vs. glial EP2 to neuroprotection not dissected"]},{"year":2005,"claim":"Genetic epistasis (MMTV-COX-2 × EP2−/−) demonstrated that EP2 is the obligate receptor coupling COX-2 to mammary hyperplasia, operating through a cAMP/PKA→amphiregulin axis that drives epithelial proliferation.","evidence":"Bigenic mouse model, EP2 agonist treatment of tumor cells, PKA inhibitor, amphiregulin RT-PCR, cAMP assay","pmids":["15930264"],"confidence":"High","gaps":["Whether amphiregulin acts through EGFR in this context not directly shown","Contribution to malignant progression beyond hyperplasia not addressed"]},{"year":2007,"claim":"Multiple studies established EP2 as a transcriptional amplifier of its own ligand supply (COX-2 → PGE2 positive feedback in skin via PKA/CREB), a mediator of progesterone synthesis in granulosa cells, and a cross-talk node with Tcf/β-catenin signaling distinctly through PKA rather than PI3K.","evidence":"EP2 KO and transgenic mice with TPA treatment and CREB phosphorylation; granulosa-lutein cell pharmacology with butaprost/AH6809; Tcf reporter assays with PKA and PI3K inhibitors","pmids":["17277233","17761898","14607241"],"confidence":"High","gaps":["CREB target genes downstream of EP2 in skin not cataloged","Whether β-catenin activation by EP2 occurs in vivo not confirmed","Structural basis for EP2 vs. EP4 pathway selectivity unknown"]},{"year":2007,"claim":"Discovery that the PTGER2 promoter is silenced by DNA methylation and repressive histone marks in neuroblastoma revealed that EP2 can function as a growth suppressor when re-expressed, fundamentally altering interpretation of its role in cancer.","evidence":"Bisulfite sequencing, ChIP for histone modifications, PTGER2 transfection rescue with butaprost-induced cAMP, growth inhibition, and apoptosis in neuroblastoma cells","pmids":["17533365"],"confidence":"High","gaps":["Whether EP2 methylation is a driver or passenger event in neuroblastoma not established","Generalizability of tumor-suppressive function to other cancer types unclear"]},{"year":2010,"claim":"Akt-driven PTGER2 promoter hypermethylation was identified as the mechanism of PGE2 resistance in fibrotic fibroblasts, while EP2 activation was shown to counteract matrix-stiffness-induced fibrogenesis, establishing EP2 silencing as a pathogenic event in pulmonary fibrosis.","evidence":"Bisulfite sequencing, DNMT siRNA, methylation inhibitors in human and mouse fibrotic fibroblasts; EP2 agonist on tunable-stiffness hydrogels","pmids":["20889571","20733059"],"confidence":"High","gaps":["Whether PTGER2 demethylation reverses established fibrosis in vivo not tested","Mechanotransduction pathway linking EP2 to matrix stiffness sensing not defined"]},{"year":2010,"claim":"A systematic siRNA screen identified EP2 as the dominant receptor suppressing MMP-13 and other catabolic factors in osteoarthritic chondrocytes via cAMP/PKA, establishing EP2 as a cartilage-protective receptor.","evidence":"siRNA screen of 114 genes, butaprost treatment ± IL-1β, cAMP/PKA inhibitors, MMP-13 ELISA in human OA chondrocytes","pmids":["20870807"],"confidence":"High","gaps":["In vivo validation of EP2-mediated cartilage protection not performed","Mechanism of MMP-13 transcriptional repression downstream of PKA not identified"]},{"year":2011,"claim":"EP2-mediated suppression of Sclerostin and consequent Wnt/TCF activation in osteoblasts provided a molecular mechanism for the known bone-anabolic effects of PGE2, linking EP2 to the Wnt pathway in bone.","evidence":"EP2 agonist, Ptger2 siRNA, cAMP/PKA inhibitors, Sost/Axin2/Tcf3 RT-PCR in UMR106.01 osteoblastic cells","pmids":["21436889"],"confidence":"High","gaps":["In vivo confirmation of EP2-dependent Sclerostin regulation not shown","Whether EP2 acts on osteocytes (the major Sost source) directly not tested"]},{"year":2012,"claim":"Epistatic analysis using single and double receptor knockouts demonstrated that EP2 and EP4 cooperate redundantly to protect pancreatic β-cells from STZ-induced destruction, expanding EP2 biology to metabolic homeostasis.","evidence":"PTGER2−/−, PTGER4−/−, double KO mice, EP2/EP4 agonist rescue, blood glucose and insulin measurements","pmids":["22522619"],"confidence":"High","gaps":["Downstream β-cell survival pathway not identified","Relevance to autoimmune (type 1) or type 2 diabetes in humans not tested"]},{"year":2013,"claim":"EP2 was shown to promote trophoblast adhesion to extracellular matrix via integrin αVβ3 through MEK/MAPK, providing a molecular explanation for how PGE2 facilitates embryo implantation.","evidence":"Butaprost treatment, EP2 antagonist, integrin antibody, MEK inhibitor in porcine and human trophoblast cells","pmids":["23861370"],"confidence":"High","gaps":["Whether EP2 acts on decidual vs. trophoblast side in vivo not resolved","Relationship between cAMP-PKA and MEK/MAPK branches in trophoblasts not clarified"]},{"year":2014,"claim":"Discovery of β-arrestin-dependent, cAMP-independent EP2 signaling that suppresses microglial IL-10, combined with the finding that RORC directly represses PTGER2 transcription in Th17 cells (with de-repression promoting pathogenic Th17 phenotype in MS), established EP2 as a bidirectional immune regulator whose expression and signaling mode profoundly shape inflammatory outcomes.","evidence":"EP2−/−, β-arrestin-1/2 KO microglia with IL-10 ELISA; ChIP-seq for RORγt at PTGER2 promoter, RORC siRNA, EP2 overexpression in human Th17 cells","pmids":["25218510","24812667"],"confidence":"High","gaps":["β-arrestin effector complex composition downstream of EP2 not defined","Whether RORC-mediated EP2 repression is targetable therapeutically in MS not tested","Structural basis for biased signaling through EP2 unknown"]},{"year":2019,"claim":"Cell-type-specific conditional knockouts resolved a long-standing paradox: neuronal EP2 promotes ischemic injury (contradicting the earlier congenital KO finding of neuroprotection), while myeloid EP2 drives immune cell infiltration, demonstrating that EP2's net effect in stroke depends on cell-type context and developmental timing of deletion.","evidence":"Inducible (ROSACreER), neuronal (Thy1Cre), and myeloid (Cd11bCre) conditional EP2 KO mice in MCAO stroke model","pmids":["31036664"],"confidence":"High","gaps":["Mechanism by which neuronal EP2 promotes ischemic injury not identified","Discrepancy with earlier congenital KO neuroprotection not fully mechanistically explained"]},{"year":2020,"claim":"Myeloid EP2 on peripheral (not microglial) CD11b+ cells was identified as the driver of hippocampal IL-6, BBB breakdown, and behavioral impairment after status epilepticus, with systemic EP2 antagonism providing additional neuroprotection beyond what genetic myeloid deletion achieved.","evidence":"CD11b-Cre;EP2lox/lox conditional KO, pilocarpine SE model, IL-6 ELISA, cortical albumin, behavioral scoring, systemic EP2 antagonist","pmids":["33293358"],"confidence":"High","gaps":["Non-myeloid cell types contributing to the additional benefit of systemic EP2 antagonism not identified","Downstream signaling from myeloid EP2 to IL-6 induction not mapped"]},{"year":null,"claim":"The structural basis for EP2's biased signaling (Gs-cAMP vs. β-arrestin pathways), the identity of the β-arrestin effector complex, and whether pharmacological biased agonism at EP2 can separate beneficial from detrimental effects in neuroinflammation and cancer remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No cryo-EM or crystal structure of EP2 in active state with Gs or β-arrestin","β-arrestin signaling effectors downstream of EP2 not identified","No biased ligand for EP2 validated in vivo"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,3,6]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,16,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,13]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,5,6,8,16]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[15,16,21,23]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[2,13,22]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,7,12]}],"complexes":[],"partners":["ARRB1","ARRB2","PTGS2","RORC","CTNNB1"],"other_free_text":[]},"mechanistic_narrative":"PTGER2 (EP2) is a Gs-coupled prostaglandin E2 receptor that signals primarily through adenylyl cyclase–cAMP–PKA to regulate vasodilation, bronchodilation, female fertility, neuroprotection, bone homeostasis, and inflammatory responses across diverse tissues. Cloned from human lung, EP2 binds PGE2 with nanomolar affinity and couples exclusively to Gs to elevate cAMP, activating PKA-dependent downstream effectors including CREB, Tcf/β-catenin, and NF-κB inhibition, thereby driving processes such as amphiregulin-mediated mammary epithelial proliferation, Sclerostin suppression to potentiate Wnt signaling in osteoblasts, MMP-13 repression in chondrocytes, and progesterone synthesis in granulosa cells [PMID:8250933, PMID:15930264, PMID:21436889, PMID:20870807, PMID:17761898]. In addition to canonical G-protein signaling, EP2 engages a β-arrestin-dependent, cAMP-independent pathway that suppresses microglial IL-10 production, and myeloid-expressed EP2 drives neuroinflammatory sequelae in stroke and status epilepticus [PMID:25218510, PMID:31036664, PMID:33293358]. PTGER2 expression is subject to epigenetic silencing by promoter DNA hypermethylation (augmented by Akt signaling) and direct transcriptional repression by RORC in Th17 cells, the loss of which derepresses EP2 and promotes a pathogenic inflammatory phenotype linked to multiple sclerosis [PMID:20889571, PMID:17533365, PMID:24812667]."},"prefetch_data":{"uniprot":{"accession":"P43116","full_name":"Prostaglandin E2 receptor EP2 subtype","aliases":["Prostanoid EP2 receptor"],"length_aa":358,"mass_kda":39.8,"function":"Receptor for prostaglandin E2 (PGE2). The activity of this receptor is mediated by G(s) proteins that stimulate adenylate cyclase. 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expressed in COS-7 cells it bound [3H]-PGE2 with Kd ~2.2 nM and coupled exclusively to Gs to increase intracellular cAMP (not Ca2+), establishing its second-messenger mechanism.\",\n      \"method\": \"cDNA cloning, radioligand binding assay, cAMP and Ca2+ measurement in transfected COS-7 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct reconstitution in transfected cells with radioligand binding and functional cAMP/Ca2+ assays\",\n      \"pmids\": [\"8250933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Genetic deletion of EP2 (PTGER2) in mice abolished the hypotensive effect of intravenous PGE2 (which instead caused hypertension), demonstrating that the EP2 receptor mediates PGE2-induced arterial vasodilation. EP2-/- mice also developed profound salt-sensitive hypertension, establishing a required role in blood-pressure homeostasis.\",\n      \"method\": \"Targeted gene disruption (EP2-/- mice), intravenous PGE2 infusion, blood pressure measurement, high-salt diet challenge\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined cardiovascular phenotype, replicated across multiple blood-pressure paradigms\",\n      \"pmids\": [\"9930871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"EP2 (PTGER2) knockout mice exhibit reduced litter sizes due to a pre-implantation defect involving impaired ovulation and dramatically reduced fertilization, establishing a required role for EP2 signaling in female fertility.\",\n      \"method\": \"Targeted gene disruption (EP2-/- mice), pregnancy day 2 and day 5 analysis of embryo implantation, ovulation, and fertilization\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific reproductive phenotype and defined pre-implantation defect\",\n      \"pmids\": [\"9930871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"EP2 receptor (PTGER2) mediates PGE2-induced bronchodilation: PGE2 inhalation inhibited methacholine-induced airway constriction in wild-type but not EP2-/- mice, and paradoxically increased constriction in EP2-/- animals.\",\n      \"method\": \"Targeted gene disruption (EP2-/- mice), barometric plethysmography, mechanically ventilated mouse lung-resistance measurements\",\n      \"journal\": \"Journal of applied physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with specific functional airway phenotype using two independent measurement methods\",\n      \"pmids\": [\"10846038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"EP2 receptor expression is restricted to the outer and inner medulla (descending thin limb of Henle's loop and outer medullary vasa recta) in the rat kidney, and butaprost (EP2-selective agonist) dose-dependently raised cAMP in microdissected EP2-positive segments but not in EP2-negative collecting duct segments, establishing site-specific cAMP-mediated paracrine regulation of tubular transport and vascular resistance.\",\n      \"method\": \"RNase protection assay, RT-PCR on microdissected nephron segments, cAMP radioimmunoassay with butaprost stimulation\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct localization combined with functional cAMP assay in microdissected native tissue\",\n      \"pmids\": [\"11352840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"EP2 receptor (PTGER2) stimulates Tcf/β-catenin-mediated transcriptional activity primarily through cAMP-dependent PKA, whereas EP4 additionally uses PI3K; EP2 does not activate ERK1/2 or induce EGR-1, distinguishing its downstream signaling from that of EP4.\",\n      \"method\": \"Tcf reporter assay, PKA inhibitor studies, PI3K inhibitor studies, ERK phosphorylation assay in transfected cells\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological dissection of signaling pathways in cell-based assays, single lab\",\n      \"pmids\": [\"14607241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Activation of EP2 receptor (PTGER2) is neuroprotective in NMDA toxicity and oxygen-glucose deprivation paradigms via cAMP/PKA signaling; pharmacological blockade of PKA reversed EP2-mediated neuroprotection. Genetic deletion of EP2 significantly increased cerebral infarction in the MCAO stroke model.\",\n      \"method\": \"Dispersed neuron cultures, organotypic hippocampal cultures, PKA inhibition, EP2-/- mouse MCAO model with infarct volume measurement\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro mechanistic assays with PKA inhibitor validation plus genetic KO in vivo stroke model\",\n      \"pmids\": [\"14715958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"EP2 receptor (PTGER2) is required for COX-2-induced mammary hyperplasia: bigenic MMTV-COX-2;Ep2-/- mice showed strongly suppressed precocious mammary development and hyperplasia, accompanied by reduced amphiregulin expression and reduced cAMP. EP2 agonist treatment of mammary tumor cells induced amphiregulin mRNA in a PKA-dependent manner, establishing a PGE2→EP2→cAMP/PKA→amphiregulin signaling axis driving mammary epithelial cell growth.\",\n      \"method\": \"Genetic bigenic mouse model (MMTV-COX-2 × EP2-/-), cAMP assay in mammary glands, EP2-selective agonist (CAY10399) treatment, amphiregulin RT-PCR, PKA inhibitor studies\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo plus mechanistic signaling studies in vitro with multiple orthogonal readouts\",\n      \"pmids\": [\"15930264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"EP2 receptor (PTGER2) mediates a positive feedback loop in skin: PGE2 via EP2 activates PKA/CREB signaling to induce COX-2 expression and PGE2 production; EP2 knockout mice showed reduced COX-2 and PGE2 after TPA treatment, while EP2 transgenic mice showed increased COX-2 and CREB phosphorylation. Adenylate cyclase inhibitor blocked EP2-driven cell proliferation.\",\n      \"method\": \"EP2 knockout and transgenic mice, TPA/PGE2 treatment, COX-2 immunoblot, CREB phosphorylation assay, adenylate cyclase inhibitor (SQ22536), primary keratinocyte cultures\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic gain/loss-of-function combined with pharmacological inhibition and multiple molecular readouts\",\n      \"pmids\": [\"17277233\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PTGER2 is epigenetically silenced in neuroblastoma cells (especially those with MYCN amplification) via DNA methylation, histone H3/H4 deacetylation, and H3K9 methylation at the promoter. Restoration of PTGER2 expression by transfection enabled EP2-agonist butaprost to increase cAMP, inhibit cell growth, and induce apoptosis via cAMP-dependent pathway.\",\n      \"method\": \"Bisulfite sequencing, ChIP for histone modifications, siRNA knockdown, stable/transient transfection, butaprost treatment, cAMP assay, cell growth and apoptosis assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal epigenetic methods plus functional rescue with agonist treatment\",\n      \"pmids\": [\"17533365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"DNA hypermethylation of the PTGER2 promoter, driven by increased Akt signaling, causes reduced EP2 expression and PGE2 resistance in fibrotic fibroblasts from humans and mice with pulmonary fibrosis. Treatment with DNA methylation inhibitors or DNMT-specific siRNA decreased PTGER2 methylation, restored EP2 expression, and rescued PGE2 responsiveness.\",\n      \"method\": \"Bisulfite sequencing, DNMT siRNA, DNA methylation inhibitors (5-aza-2'-deoxycytidine, zebularine), EP2 mRNA/protein quantification, PGE2 functional assays, Akt pathway analysis\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal epigenetic methods, genetic (siRNA) and pharmacological validation, replicated in human and mouse cells\",\n      \"pmids\": [\"20889571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Exogenous PGE2 or an EP2 receptor agonist completely counteracted the pro-fibrogenic effects (increased proliferation and matrix synthesis) caused by increased matrix stiffness in lung fibroblasts, demonstrating that EP2 is the receptor through which PGE2 maintains fibroblast quiescence and opposes fibrosis.\",\n      \"method\": \"Polyacrylamide hydrogel culture system with tunable stiffness, EP2-selective agonist treatment, fibroblast proliferation and matrix synthesis assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological EP2 agonist rescue in a defined biophysical model, single lab\",\n      \"pmids\": [\"20733059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PGE2 suppresses Sclerostin (Sost) expression in osteoblastic cells via the EP2 receptor (PTGER2) through a cAMP/PKA pathway, leading to increased Wnt/TCF target gene expression (Axin2, Tcf3). EP2-selective agonists mimicked PGE2, and siRNA knockdown of Ptger2 prevented PGE2-induced Sost repression.\",\n      \"method\": \"EP2-selective agonists, siRNA knockdown of Ptger2, cAMP/PKA pathway inhibitors, RT-PCR for Sost/Axin2/Tcf3, osteoblastic UMR106.01 cell line\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic (siRNA) approaches with multiple molecular readouts linking EP2 to Wnt signaling\",\n      \"pmids\": [\"21436889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PGE2 acting through PTGER2 on porcine and human trophoblast cells promotes cell adhesion to extracellular matrix via integrin αVβ3, with signaling through MEK/MAPK and estrogen receptor. Blockade with EP2 antagonist AH6809, ITGAVB3 antibody, or MEK inhibition abolished PGE2-induced adhesion.\",\n      \"method\": \"RT-PCR and protein expression during implantation, butaprost treatment, EP2 antagonist (AH6809), integrin antibody, MEK inhibitor, FAK and ICAM-1 immunoblot in porcine and human trophoblast cells\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and antibody-based dissection of signaling in both human and porcine trophoblast cells with multiple orthogonal inhibitors\",\n      \"pmids\": [\"23861370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"EP2 activation promotes tumor cell growth and migration via a β-arrestin-dependent, G-protein-independent pathway in addition to the canonical cAMP-PKA pathway, expanding the known signaling repertoire of PTGER2.\",\n      \"method\": \"Review citing functional studies with EP2 agonists, β-arrestin pathway analysis\",\n      \"journal\": \"Trends in pharmacological sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — review summary without primary experimental data in this paper\",\n      \"pmids\": [\"23796953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The transcription factor RORC directly silences PTGER2 transcription in human Th17 cells by binding to the PTGER2 promoter; reduced RORC binding in MS patient Th17 cells results in higher EP2 levels, increased IFN-γ and GM-CSF, and a pathogenic Th17 phenotype. Overexpression of EP2 in healthy Th17 cells recapitulated the inflammatory gene program.\",\n      \"method\": \"ChIP-seq (RORγt binding to Ptger2/PTGER2 promoter), RORC siRNA knockdown, EP2 overexpression in human Th17 cells, comparison of healthy vs. MS patient cells\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP-seq demonstrating direct promoter binding, siRNA rescue, and gain-of-function overexpression with defined inflammatory phenotype\",\n      \"pmids\": [\"24812667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PGE2 inhibits IL-10 production in brain microglia through the EP2 receptor via a β-arrestin-dependent, cAMP-independent pathway. EP2 genetic disruption abolished PGE2-mediated IL-10 suppression; EP2-selective agonist butaprost mimicked the effect; β-arrestin-1 or -2 deficiency also abolished the suppression.\",\n      \"method\": \"Primary neuron-glia cultures, EP2-/- mice, butaprost and other EP agonists, cAMP pathway inhibitors, β-arrestin-1/2 knockout microglia, IL-10 ELISA\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic KOs (EP2-/-, β-arrestin-/-) combined with pharmacological agonists and pathway inhibitors\",\n      \"pmids\": [\"25218510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"EP2 receptor signaling inhibits matrix metalloproteinase 13 (MMP-13) expression in human osteoarthritic chondrocytes via a cAMP/PKA pathway, and also suppresses other catabolic factors (MMP-1, MMP-3, ADAMTS5, IL-1β, TNF-α) without affecting cell viability. EP2 was identified as the major EP receptor in osteoarthritic cartilage.\",\n      \"method\": \"siRNA screen of 114 genes, butaprost (EP2 agonist) treatment ± IL-1β ± COX-2 inhibitor, cAMP/PKA inhibitors, MMP-13 ELISA and RT-PCR, cell viability assay, RT-PCR of EP receptor subtypes in OA cartilage\",\n      \"journal\": \"Annals of the rheumatic diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic siRNA screen identified EP2, confirmed with agonist and pharmacological pathway dissection\",\n      \"pmids\": [\"20870807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Intracellular EP2 (iEP2) in PC3 prostate cancer cells promotes cancer-related phenotypes (proliferation, adhesion, migration, invasion, angiogenesis in vitro) through an EGFR transactivation–HIF-1α axis; inhibition of the prostaglandin uptake transporter, EP2 antagonist, or HIF-1α knockdown prevented these effects. PGE2 induced PKA-sensitive DNA synthesis even in isolated nuclei containing functional EP2 receptors.\",\n      \"method\": \"Pharmacological inhibition of prostaglandin uptake transporter, EP2 antagonist, EGFR antagonist, siRNA knockdown of HIF-1α, nuclear isolation and DNA synthesis assay, migration/invasion/angiogenesis in vitro assays\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological and genetic manipulations in one cell line, single lab\",\n      \"pmids\": [\"25828575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PTGS2-derived PGE2 protects against STZ-induced diabetes via PTGER2 and PTGER4 receptors; combined knockout of PTGER2 and PTGER4 (but not single knockouts) dramatically enhanced STZ pathology. PTGER2/PTGER4 agonist treatment of PTGS-2-/- and wild-type mice partially restored β-cell function and protected against STZ-induced diabetes.\",\n      \"method\": \"PTGER2-/-, PTGER4-/-, PTGER2/PTGER4 double KO mice, pharmacological PTGER4 blockade in PTGER2-/- background, EP2/EP4 agonist rescue, blood glucose, insulin, and survival measurement\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistatic genetic dissection using single and double receptor knockouts with pharmacological agonist rescue\",\n      \"pmids\": [\"22522619\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In an adult inducible EP2 knockout model (ROSACreER;EP2lox/lox), EP2 deletion reduced stroke severity, myeloid cell brain trafficking, and neuronal injury after MCAO, contrasting with the congenital EP2-/- model; neuronal-specific EP2 deletion (Thy1Cre;EP2lox/lox) reduced cerebral ischemic injury, identifying neurons as a cell type in which EP2 promotes ischemic damage. Myeloid-specific EP2 knockdown (Cd11bCre;EP2lox/lox) attenuated post-stroke immune cell infiltration but did not reduce infarct volume.\",\n      \"method\": \"Cell-type-specific conditional KO mice (ROSACreER, Thy1Cre, Cd11bCre), MCAO stroke model, infarct volume, brain immune cell 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 — multiple conditional cell-type-specific KO mouse lines with defined stroke phenotypes\",\n      \"pmids\": [\"31036664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"EP2 receptor on peripheral immune myeloid cells drives key deleterious consequences of status epilepticus: conditional deletion of EP2 in CD11b+ myeloid cells (but not microglia) abolished hippocampal IL-6 induction, prevented BBB breakdown (measured by cortical albumin), and accelerated behavioral recovery after pilocarpine SE. Systemic EP2 antagonism additionally blocked monocyte brain infiltration and was neuroprotective, going beyond what myeloid-specific deletion achieved.\",\n      \"method\": \"CD11b-Cre;EP2lox/lox conditional KO mice, pilocarpine status epilepticus model, IL-6 ELISA, cortical albumin measurement, behavioral scoring, systemic EP2 antagonist administration\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific conditional KO with multiple orthogonal inflammatory and behavioral readouts\",\n      \"pmids\": [\"33293358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PTGER2 (EP2) mediates progesterone synthesis and type 1 11β-HSD activity stimulated by PGE2 in human granulosa-lutein cells via cAMP signaling; the EP2-selective agonist butaprost stimulated both responses, and the mixed EP1/EP2 antagonist AH6809 (but not the EP1-selective antagonist SC19220 alone) completely abolished both PGE2-stimulated cAMP accumulation and progesterone synthesis.\",\n      \"method\": \"Human granulosa-lutein cell cultures, EP2 agonist (butaprost), selective EP1 antagonist (SC19220), mixed EP1/EP2 antagonist (AH6809), cAMP radioimmunoassay, progesterone RIA, 11β-HSD activity assay\",\n      \"journal\": \"The Journal of endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological receptor dissection with agonist and two antagonists measuring cAMP, progesterone, and 11β-HSD in human primary cells\",\n      \"pmids\": [\"17761898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PGE2 via EP2 receptor suppresses TNF-α-induced CCL27 production in human keratinocytes by inhibiting NF-κB activity through a cAMP-dependent pathway. EP2 agonist increased intracellular cAMP, and PKA inhibitor (H-89) partially blocked the inhibitory effect; combined EP1/EP2 and EP3 antagonism completely reversed PGE2-mediated suppression.\",\n      \"method\": \"Human keratinocyte cultures, EP2/EP3 selective agonists, EP antagonists, NF-κB luciferase reporter assay, cAMP ELISA, Ca2+ chelator (BAPTA/AM), H-89 PKA inhibitor, CCL27 ELISA and RT-PCR\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological tools dissecting receptor subtype contributions with mechanistic NF-κB reporter assay\",\n      \"pmids\": [\"15577845\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTGER2 (EP2) is a Gs-coupled GPCR that binds PGE2 with nanomolar affinity and primarily signals through adenylyl cyclase–cAMP–PKA to regulate diverse processes including arterial vasodilation and blood pressure homeostasis, bronchodilation, female fertility (ovulation and implantation), neuroprotection in acute ischemia, bone anabolism (via Sclerostin suppression and Wnt pathway activation), mammary epithelial proliferation (via amphiregulin induction), and cartilage protection (via MMP-13 suppression); additionally, EP2 can signal in a G-protein-independent, β-arrestin-dependent manner to suppress microglial IL-10 production and promote tumor cell growth, and its expression is regulated epigenetically by PTGER2 promoter DNA hypermethylation (driven by Akt) and by direct transcriptional silencing through the Th17 transcription factor RORC.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PTGER2 (EP2) is a Gs-coupled prostaglandin E2 receptor that signals primarily through adenylyl cyclase–cAMP–PKA to regulate vasodilation, bronchodilation, female fertility, neuroprotection, bone homeostasis, and inflammatory responses across diverse tissues. Cloned from human lung, EP2 binds PGE2 with nanomolar affinity and couples exclusively to Gs to elevate cAMP, activating PKA-dependent downstream effectors including CREB, Tcf/β-catenin, and NF-κB inhibition, thereby driving processes such as amphiregulin-mediated mammary epithelial proliferation, Sclerostin suppression to potentiate Wnt signaling in osteoblasts, MMP-13 repression in chondrocytes, and progesterone synthesis in granulosa cells [PMID:8250933, PMID:15930264, PMID:21436889, PMID:20870807, PMID:17761898]. In addition to canonical G-protein signaling, EP2 engages a β-arrestin-dependent, cAMP-independent pathway that suppresses microglial IL-10 production, and myeloid-expressed EP2 drives neuroinflammatory sequelae in stroke and status epilepticus [PMID:25218510, PMID:31036664, PMID:33293358]. PTGER2 expression is subject to epigenetic silencing by promoter DNA hypermethylation (augmented by Akt signaling) and direct transcriptional repression by RORC in Th17 cells, the loss of which derepresses EP2 and promotes a pathogenic inflammatory phenotype linked to multiple sclerosis [PMID:20889571, PMID:17533365, PMID:24812667].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Cloning of human EP2 and demonstration of exclusive Gs–cAMP coupling resolved the second-messenger identity of one of the four PGE2 receptor subtypes, distinguishing it from Ca²⁺-coupled receptors.\",\n      \"evidence\": \"cDNA cloning from human lung, radioligand binding (Kd ~2.2 nM), cAMP and Ca²⁺ measurement in transfected COS-7 cells\",\n      \"pmids\": [\"8250933\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors beyond cAMP not yet mapped\", \"No in vivo functional data\", \"Receptor desensitization and trafficking unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Genetic ablation of EP2 established that it is the required receptor for PGE2-mediated arterial vasodilation, salt-sensitive blood pressure homeostasis, and female fertility (ovulation and fertilization), converting pharmacological inference into causal genetic proof.\",\n      \"evidence\": \"EP2−/− knockout mice with intravenous PGE2 infusion, high-salt diet challenge, and reproductive phenotyping\",\n      \"pmids\": [\"9930871\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling mediating vasodilation in vivo uncharacterized\", \"Whether fertility defect is oocyte- or somatic-cell-autonomous not resolved\", \"Renal tubular mechanism of salt handling not defined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstration that EP2 mediates PGE2-induced bronchodilation expanded its physiological role to airway smooth muscle and explained the paradoxical bronchoconstriction seen when EP2 is absent.\",\n      \"evidence\": \"EP2−/− mice, barometric plethysmography and mechanical ventilation measurements of airway resistance\",\n      \"pmids\": [\"10846038\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Airway cell type expressing functional EP2 not identified\", \"Contribution of EP2 vs. EP4 in human airways not resolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Mapping EP2 to specific renal medullary segments (descending thin limb of Henle, outer medullary vasa recta) with segment-specific cAMP responses provided the anatomical basis for its role in salt and water balance.\",\n      \"evidence\": \"RNase protection assay, RT-PCR on microdissected nephron segments, cAMP RIA with butaprost in rat kidney\",\n      \"pmids\": [\"11352840\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ion-transport targets in these segments not identified\", \"Human renal EP2 distribution not confirmed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"EP2 was shown to mediate neuroprotection against excitotoxicity and ischemia via cAMP/PKA, while separately suppressing keratinocyte CCL27 through cAMP-dependent NF-κB inhibition, establishing PKA as a shared effector across cell types.\",\n      \"evidence\": \"Neuronal cultures with NMDA/OGD ± PKA inhibitors, EP2−/− MCAO stroke model; keratinocyte NF-κB reporter with EP2 agonist and H-89\",\n      \"pmids\": [\"14715958\", \"15577845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Neuroprotective mechanism downstream of PKA (anti-apoptotic targets) unknown\", \"Relative contribution of neuronal vs. glial EP2 to neuroprotection not dissected\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic epistasis (MMTV-COX-2 × EP2−/−) demonstrated that EP2 is the obligate receptor coupling COX-2 to mammary hyperplasia, operating through a cAMP/PKA→amphiregulin axis that drives epithelial proliferation.\",\n      \"evidence\": \"Bigenic mouse model, EP2 agonist treatment of tumor cells, PKA inhibitor, amphiregulin RT-PCR, cAMP assay\",\n      \"pmids\": [\"15930264\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether amphiregulin acts through EGFR in this context not directly shown\", \"Contribution to malignant progression beyond hyperplasia not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Multiple studies established EP2 as a transcriptional amplifier of its own ligand supply (COX-2 → PGE2 positive feedback in skin via PKA/CREB), a mediator of progesterone synthesis in granulosa cells, and a cross-talk node with Tcf/β-catenin signaling distinctly through PKA rather than PI3K.\",\n      \"evidence\": \"EP2 KO and transgenic mice with TPA treatment and CREB phosphorylation; granulosa-lutein cell pharmacology with butaprost/AH6809; Tcf reporter assays with PKA and PI3K inhibitors\",\n      \"pmids\": [\"17277233\", \"17761898\", \"14607241\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CREB target genes downstream of EP2 in skin not cataloged\", \"Whether β-catenin activation by EP2 occurs in vivo not confirmed\", \"Structural basis for EP2 vs. EP4 pathway selectivity unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery that the PTGER2 promoter is silenced by DNA methylation and repressive histone marks in neuroblastoma revealed that EP2 can function as a growth suppressor when re-expressed, fundamentally altering interpretation of its role in cancer.\",\n      \"evidence\": \"Bisulfite sequencing, ChIP for histone modifications, PTGER2 transfection rescue with butaprost-induced cAMP, growth inhibition, and apoptosis in neuroblastoma cells\",\n      \"pmids\": [\"17533365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether EP2 methylation is a driver or passenger event in neuroblastoma not established\", \"Generalizability of tumor-suppressive function to other cancer types unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Akt-driven PTGER2 promoter hypermethylation was identified as the mechanism of PGE2 resistance in fibrotic fibroblasts, while EP2 activation was shown to counteract matrix-stiffness-induced fibrogenesis, establishing EP2 silencing as a pathogenic event in pulmonary fibrosis.\",\n      \"evidence\": \"Bisulfite sequencing, DNMT siRNA, methylation inhibitors in human and mouse fibrotic fibroblasts; EP2 agonist on tunable-stiffness hydrogels\",\n      \"pmids\": [\"20889571\", \"20733059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PTGER2 demethylation reverses established fibrosis in vivo not tested\", \"Mechanotransduction pathway linking EP2 to matrix stiffness sensing not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"A systematic siRNA screen identified EP2 as the dominant receptor suppressing MMP-13 and other catabolic factors in osteoarthritic chondrocytes via cAMP/PKA, establishing EP2 as a cartilage-protective receptor.\",\n      \"evidence\": \"siRNA screen of 114 genes, butaprost treatment ± IL-1β, cAMP/PKA inhibitors, MMP-13 ELISA in human OA chondrocytes\",\n      \"pmids\": [\"20870807\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo validation of EP2-mediated cartilage protection not performed\", \"Mechanism of MMP-13 transcriptional repression downstream of PKA not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"EP2-mediated suppression of Sclerostin and consequent Wnt/TCF activation in osteoblasts provided a molecular mechanism for the known bone-anabolic effects of PGE2, linking EP2 to the Wnt pathway in bone.\",\n      \"evidence\": \"EP2 agonist, Ptger2 siRNA, cAMP/PKA inhibitors, Sost/Axin2/Tcf3 RT-PCR in UMR106.01 osteoblastic cells\",\n      \"pmids\": [\"21436889\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo confirmation of EP2-dependent Sclerostin regulation not shown\", \"Whether EP2 acts on osteocytes (the major Sost source) directly not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Epistatic analysis using single and double receptor knockouts demonstrated that EP2 and EP4 cooperate redundantly to protect pancreatic β-cells from STZ-induced destruction, expanding EP2 biology to metabolic homeostasis.\",\n      \"evidence\": \"PTGER2−/−, PTGER4−/−, double KO mice, EP2/EP4 agonist rescue, blood glucose and insulin measurements\",\n      \"pmids\": [\"22522619\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream β-cell survival pathway not identified\", \"Relevance to autoimmune (type 1) or type 2 diabetes in humans not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"EP2 was shown to promote trophoblast adhesion to extracellular matrix via integrin αVβ3 through MEK/MAPK, providing a molecular explanation for how PGE2 facilitates embryo implantation.\",\n      \"evidence\": \"Butaprost treatment, EP2 antagonist, integrin antibody, MEK inhibitor in porcine and human trophoblast cells\",\n      \"pmids\": [\"23861370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether EP2 acts on decidual vs. trophoblast side in vivo not resolved\", \"Relationship between cAMP-PKA and MEK/MAPK branches in trophoblasts not clarified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Discovery of β-arrestin-dependent, cAMP-independent EP2 signaling that suppresses microglial IL-10, combined with the finding that RORC directly represses PTGER2 transcription in Th17 cells (with de-repression promoting pathogenic Th17 phenotype in MS), established EP2 as a bidirectional immune regulator whose expression and signaling mode profoundly shape inflammatory outcomes.\",\n      \"evidence\": \"EP2−/−, β-arrestin-1/2 KO microglia with IL-10 ELISA; ChIP-seq for RORγt at PTGER2 promoter, RORC siRNA, EP2 overexpression in human Th17 cells\",\n      \"pmids\": [\"25218510\", \"24812667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"β-arrestin effector complex composition downstream of EP2 not defined\", \"Whether RORC-mediated EP2 repression is targetable therapeutically in MS not tested\", \"Structural basis for biased signaling through EP2 unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Cell-type-specific conditional knockouts resolved a long-standing paradox: neuronal EP2 promotes ischemic injury (contradicting the earlier congenital KO finding of neuroprotection), while myeloid EP2 drives immune cell infiltration, demonstrating that EP2's net effect in stroke depends on cell-type context and developmental timing of deletion.\",\n      \"evidence\": \"Inducible (ROSACreER), neuronal (Thy1Cre), and myeloid (Cd11bCre) conditional EP2 KO mice in MCAO stroke model\",\n      \"pmids\": [\"31036664\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which neuronal EP2 promotes ischemic injury not identified\", \"Discrepancy with earlier congenital KO neuroprotection not fully mechanistically explained\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Myeloid EP2 on peripheral (not microglial) CD11b+ cells was identified as the driver of hippocampal IL-6, BBB breakdown, and behavioral impairment after status epilepticus, with systemic EP2 antagonism providing additional neuroprotection beyond what genetic myeloid deletion achieved.\",\n      \"evidence\": \"CD11b-Cre;EP2lox/lox conditional KO, pilocarpine SE model, IL-6 ELISA, cortical albumin, behavioral scoring, systemic EP2 antagonist\",\n      \"pmids\": [\"33293358\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Non-myeloid cell types contributing to the additional benefit of systemic EP2 antagonism not identified\", \"Downstream signaling from myeloid EP2 to IL-6 induction not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis for EP2's biased signaling (Gs-cAMP vs. β-arrestin pathways), the identity of the β-arrestin effector complex, and whether pharmacological biased agonism at EP2 can separate beneficial from detrimental effects in neuroinflammation and cancer remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or crystal structure of EP2 in active state with Gs or β-arrestin\", \"β-arrestin signaling effectors downstream of EP2 not identified\", \"No biased ligand for EP2 validated in vivo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 3, 6]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 16, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 5, 6, 8, 16]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [15, 16, 21, 23]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [2, 13, 22]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 7, 12]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ARRB1\",\n      \"ARRB2\",\n      \"PTGS2\",\n      \"RORC\",\n      \"CTNNB1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}