{"gene":"RAMP2","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1999,"finding":"RAMP2 forms a functional complex with calcitonin receptor-like receptor (CRLR) to constitute a high-affinity adrenomedullin receptor that mediates cAMP elevation in human endothelial and vascular smooth muscle cells; RAMP2 but not RAMP1 or RAMP3 mRNA was detected in these cells.","method":"Heterologous co-expression in HeLa EBNA and 293 EBNA cells, cAMP functional assay, RT-PCR","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional reconstitution in two cell lines with cAMP readout, replicated across multiple labs subsequently","pmids":["10217420"],"is_preprint":false},{"year":2001,"finding":"Residues 86–92 of RAMP2 extracellular N-terminal domain are critical for high-affinity 125I-AM binding and AM-evoked cAMP production at the CRLR/RAMP2 receptor heterodimer; deletion of these seven residues significantly attenuates AM binding without impairing cell surface expression of the complex.","method":"RAMP chimeras and deletion mutants co-expressed with CRLR in HEK293 cells; 125I-AM radioligand binding; cAMP production assay; alanine scanning mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, radioligand binding, and functional cAMP assay in single study","pmids":["11591721"],"is_preprint":false},{"year":2001,"finding":"In rat cardiomyocytes, CRLR and RAMP2 together constitute a functional AM receptor; overexpression of RAMP2 and CRLR additively potentiated AM-induced CRE-luciferase (cAMP-responsive) signaling approximately 4-fold over control; AM signaling was abolished by CGRP8-37 antagonist or CRLR antisense.","method":"Transient transfection of neonatal cardiomyocytes with CRE-luciferase reporter; CGRP8-37 antagonist; CRLR antisense; RT-PCR","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, functional reporter assay with pharmacological validation but no structural data","pmids":["11754972"],"is_preprint":false},{"year":2003,"finding":"CL/RAMP2 and CL/RAMP3 produce pharmacologically distinct AM receptors: AM22-52 shows selectivity for CL/RAMP2 over CL/RAMP3, whereas CGRP8-37 shows the opposite selectivity in mixed species combinations; BIBN4096BS does not antagonise AM at either receptor.","method":"Transient expression in COS-7 cells and endogenous expression in Rat 2 and L6 cells; cAMP functional assays with receptor antagonists; apparent pA2 determination","journal":"British journal of pharmacology","confidence":"High","confidence_rationale":"Tier 1 / Strong — pharmacological reconstitution in multiple cell systems with multiple ligands, replicated across species combinations","pmids":["12970090"],"is_preprint":false},{"year":2004,"finding":"AM promotes HUVEC migration, invasion, and differentiation into cord-like structures on Matrigel via CRLR/RAMP2 (and CRLR/RAMP3) receptors; AM-induced capillary tube formation is not blocked by anti-VEGF antibodies, indicating AM does not act indirectly through VEGF upregulation.","method":"Migration and invasion assays, Matrigel tube formation, receptor blocking antibodies, anti-VEGF antibody neutralization in HUVECs","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal in vitro functional assays in single lab with pharmacological controls","pmids":["14712479"],"is_preprint":false},{"year":2006,"finding":"siRNA-mediated knockdown of RAMP2 in HUVECs (~60% reduction in mRNA) decreased capillary-like tube formation in response to AM on Matrigel, establishing RAMP2 as required for AM-driven angiogenesis in endothelial cells.","method":"siRNA transfection in HUVECs; RT-PCR quantification of RAMP2 mRNA; Matrigel tube formation assay","journal":"International journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, loss-of-function with defined cellular phenotype but single method","pmids":["16964401"],"is_preprint":false},{"year":2008,"finding":"RAMP2 is essential for vascular integrity and angiogenesis in vivo: RAMP2-/- embryos die at midgestation with vascular fragility, severe edema, hemorrhage, and deformed ECs detached from basement membrane, phenocopying AM-/- embryos. RAMP2+/- adults show vascular hyperpermeability and impaired neovascularization. EC overexpressing RAMP2 show enhanced capillary formation, firmer tight junctions, and reduced vascular permeability.","method":"Global RAMP2 knockout mice; heterozygous mice; EC overexpression; histology; vascular permeability assays; tight junction marker expression","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined lethal phenotype replicated at multiple allelic doses, EC overexpression rescue, multiple orthogonal phenotypic readouts","pmids":["18097473"],"is_preprint":false},{"year":2010,"finding":"Intermedin mediates pro-angiogenic effects on HUVECs via CLR/RAMP1 and CLR/RAMP2 complexes (but not CLR/RAMP3); this involves both VEGF mRNA upregulation (18 h) and rapid VEGFR-2 phosphorylation (5 min), indicating direct transactivation of VEGFR-2 signaling.","method":"Real-time PCR; Matrigel tube formation with receptor antagonists; Western blot for VEGFR-2 phosphorylation","journal":"International journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (PCR, functional assay, Western blot) in single lab","pmids":["20596610"],"is_preprint":false},{"year":2011,"finding":"RAMP2 haploinsufficiency in female mice causes severe reproductive defects (fetal growth restriction, fetal demise, postnatal lethality), hyperprolactinemia, enlarged pituitary, accelerated mammary development, and skeletal abnormalities including decreased bone mineral density, demonstrating a physiological role for RAMP2 beyond AM/CLR signaling.","method":"RAMP2+/- mouse model; reproductive outcome analysis; serum prolactin measurement; pituitary and skeletal histomorphometry; bone mineral density measurement","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic haploinsufficiency model with multiple orthogonal phenotypic readouts in single study","pmids":["21566080"],"is_preprint":false},{"year":2011,"finding":"AM-RAMP2 signaling is required for differentiation of liver sinusoidal endothelial-like cells from embryoid bodies; co-administration of AM and TGFβ receptor inhibitor SB431542 markedly enhanced LYVE-1/stabilin-2-positive endothelial cell differentiation. In RAMP2-null liver, LYVE-1 was downregulated in LSECs and sinusoidal structure was disrupted.","method":"Embryoid body differentiation system; AM co-administration with SB431542; LYVE-1/stabilin-2 immunostaining; LSEC marker expression; RAMP2 knockout liver histology","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo genetic KO with defined cellular phenotype, single lab","pmids":["21782867"],"is_preprint":false},{"year":2013,"finding":"The endothelial AM-RAMP2 system regulates vascular integrity by controlling the Rac1-GTP/RhoA-GTP ratio and cortical actin formation; loss of endothelial RAMP2 causes actin disarrangement and EC detachment, leading to vascular leakage, spontaneous vasculitis, organ fibrosis, and accelerated vascular senescence.","method":"Endothelial-specific RAMP2 KO mice (E-RAMP2-/-) and drug-inducible DI-E-RAMP2-/- mice; vascular permeability assays; Rac1-GTP/RhoA-GTP measurement; actin cytoskeleton imaging; organ histopathology","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific genetic KO with mechanistic pathway identification (Rac1/RhoA), multiple orthogonal in vitro and in vivo readouts","pmids":["23355623"],"is_preprint":false},{"year":2013,"finding":"The AM-RAMP2 system is required for retinal angiogenesis: heterozygous RAMP2+/- mice show reduced neovascular tufts, VEGF and eNOS mRNA in oxygen-induced retinopathy; DI-E-RAMP2-/- mice show abnormal developmental retinal vascular patterns; AM enhances proliferation and migration of retinal endothelial cells in vitro.","method":"OIR model in RAMP2+/- mice; drug-inducible EC-specific RAMP2 KO; retinal endothelial cell proliferation/migration assays; VEGF/eNOS mRNA quantification; intravitreal anti-ADM antibody injection","journal":"The American journal of pathology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic models plus in vitro mechanistic assays plus pharmacological blockade, single lab","pmids":["23562442"],"is_preprint":false},{"year":2014,"finding":"RAMP2 and RAMP3 have functionally distinct roles in the vascular system: RAMP2-/- mice die in utero due to blood vessel abnormalities (essential for vascular development), while RAMP3-/- mice are born normally but show delayed lymphatic drainage and impaired lymphatic endothelial cell migration.","method":"RAMP2-/- and RAMP3-/- mouse generation; ICG lymphangiography; tail lymphedema model; scratch-wound migration assay of lymphatic endothelial cells; histology","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — parallel genetic KO comparison with multiple in vivo and in vitro functional assays distinguishing the two receptors","pmids":["25264174"],"is_preprint":false},{"year":2014,"finding":"The AM-RAMP2 system suppresses ER stress-induced tubule cell death in the kidney: AM suppresses PERK activation and CHOP-induced apoptosis downstream of ER stress in human RPTECs; in RAMP2+/- mice, tunicamycin-induced tubular damage is enhanced and the rescue effect of exogenous AM is lost.","method":"RAMP2+/- mice; STZ and tunicamycin-induced renal injury models; human RPTEC cell culture; Western blot for PERK/CHOP activation; histological analysis of tubular damage; AM rescue experiments","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic model plus in vitro mechanistic dissection with defined signaling pathway (PERK-CHOP), single lab","pmids":["24505304"],"is_preprint":false},{"year":2015,"finding":"RAMP2 modulates glucagon receptor (GCGR) pharmacology: RAMP2 association alters ligand selectivity and G protein preference of GCGR, and abolishes novel cross-reactivity of GLP-1 receptor agonists at the glucagon receptor.","method":"Yeast reporter assays; mammalian cell functional assays; multiple ligand pharmacology; G protein coupling analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal cell systems (yeast and mammalian), multiple ligands, single lab","pmids":["26198634"],"is_preprint":false},{"year":2016,"finding":"Endothelial AM-RAMP2 system suppresses tumor metastasis: DI-E-RAMP2-/- mice show enhanced vascular permeability, endothelial-mesenchymal transition-like changes, and formation of pre-metastatic niches with S100A8/9 and SAA3 chemotactic factor expression; RAMP2 overexpression suppresses tumor cell adhesion to endothelial cells and metastasis.","method":"DI-E-RAMP2-/- mice; spontaneous and transplant tumor metastasis models; vascular permeability assays; immunostaining for S100A8/9, SAA3, inflammatory markers; RAMP2 overexpression in endothelial cells","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Strong — inducible cell-type-specific KO and gain-of-function with mechanistic pathway markers, multiple tumor models","pmids":["27307317"],"is_preprint":false},{"year":2017,"finding":"RAMP2 co-expression with GCGR reduces GCGR cell surface expression, causes GCGR cellular redistribution (RAMP2 colocalizes with GCGR intracellularly), alters signaling through Gαs and Gαq pathways, and affects β-arrestin recruitment.","method":"Co-expression in cells; confocal microscopy co-localization; cell surface ELISA; competition binding; functional assays for Gαs, Gαq, β-arrestin; siRNA knockdown","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (microscopy, binding, functional signaling) in single lab","pmids":["28586439"],"is_preprint":false},{"year":2017,"finding":"The endothelial AM-RAMP2 system exerts vasoprotective effects after vascular injury: RAMP2+/- mice and DI-E-RAMP2-/- mice show enhanced neointima formation, greater macrophage infiltration and oxidative stress, and reduced re-endothelialization; the AM-RAMP2 system also augments proliferation and migration of endothelial progenitor cells.","method":"Wire-induced vascular injury model in RAMP2+/- and DI-E-RAMP2-/- mice; bone marrow transplantation; histology; endothelial progenitor cell proliferation/migration assays","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic models, bone marrow transplant, in vitro mechanistic assays, single lab with multiple orthogonal readouts","pmids":["28324104"],"is_preprint":false},{"year":2019,"finding":"RAMP2 pathogenic variants (Glu39Asp, Glu54Lys, Phe103Ser, Asn113Lysfs*10, Glu143Lys, Ser171Arg) cause aggregation of mutant RAMP2 in transfected cells and disrupt the AM-RAMP2/CRLR-cAMP signaling pathway; ablation of one Ramp2 allele leads to cAMP reduction and retinal ganglion cell death in mice.","method":"Exome sequencing; Sanger sequencing validation; heterologous expression of mutant RAMP2 proteins; RAMP2 protein aggregation imaging; cAMP measurement; heterozygous Ramp2 KO mouse retinal histology","journal":"Genetics in medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetic variants with cellular mechanistic validation (aggregation, cAMP) and in vivo mouse model, multiple orthogonal methods","pmids":["31000793"],"is_preprint":false},{"year":2019,"finding":"CRFR1α and CRFR1β (but not CRFR2β) physically interact with RAMP2 to enhance its cell surface expression; ligand-stimulated CRFR1 causes loss of cell-surface RAMP2; CRFR2β does not interact with RAMP2, potentially due to a histidine (vs. glutamate in CRFR1) in the predicted contact interface.","method":"Co-expression in four cell lines; cell-surface ELISA for FLAG-RAMP2; RT-PCR for endogenous RAMPs; molecular modelling; CRF pre-treatment experiments","journal":"Biochimica et biophysica acta. Biomembranes","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — cell surface expression assay in multiple cell lines, single lab, no direct binding assay","pmids":["30826286"],"is_preprint":false},{"year":2021,"finding":"RAMP2 alters GCGR subcellular trafficking: RAMP2 induces GCGR internalisation both basally and upon agonist stimulation, retains GCGR intracellularly, biases GCGR away from β-arrestin-2 recruitment toward increased Gαs activation at endosomes, and increases short-term cAMP production while enhancing long-term lysosomal targeting for degradation.","method":"Confocal microscopy; trafficking assays; radioligand binding; WASH complex KO MEFs; monensin; NanoBiT complementation; cAMP assays; hepatic AAV RAMP2 overexpression in mice","journal":"Molecular metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (microscopy, trafficking inhibitors, NanoBiT, cAMP, genetic tools), in vitro and in vivo validation, single lab","pmids":["34271220"],"is_preprint":false},{"year":2021,"finding":"Cardiomyocyte-specific RAMP2 deletion (C-RAMP2-/-) after transverse aortic constriction causes cardiac hypertrophy, decreased ejection fraction, increased fibrosis, and reduced mitochondrial membrane potential and respiratory capacity, indicating the AM-RAMP2 system is required for early cardiac adaptation to stress via regulation of cardiac mitochondria.","method":"Cardiomyocyte-specific RAMP2 KO mice; TAC model; echocardiography; pressure-volume analysis; mitochondrial membrane potential and respiratory capacity assays; isoproterenol stimulation of isolated cardiomyocytes","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific KO with mechanistic mitochondrial readouts and multiple cardiac functional assays, single lab","pmids":["33545715"],"is_preprint":false},{"year":2022,"finding":"RAMP2 acts as a specific allosteric modulator of PTH1R, shifting it to a preactivated state that permits faster ligand-dependent activation; RAMP2 modulates PTH1R downstream signaling in an agonist-dependent manner—most notably increasing PTH-mediated Gi3 signaling sensitivity—and increases β-arrestin2 recruitment triggered by both PTH and PTHrP.","method":"Optical biosensors measuring PTH1R activation and downstream signaling; RAMP2 co-expression; homology modelling for structural basis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple optical biosensors with ligand-specific pharmacological analysis, single lab but orthogonal functional methods","pmids":["35914163"],"is_preprint":false},{"year":2023,"finding":"RAMP2 acts as a negative allosteric modulator of the glucagon receptor (GCGR): cryo-EM structure of GCGR-Gs complex in the presence of RAMP2 shows the GCGR ECD is largely disordered; HDX-MS demonstrates RAMP2 enhances local flexibility in the ECD and the 6th transmembrane helix; smFRET shows ECD disorder inhibits active and intermediate states of the intracellular surface, broadly inhibiting downstream signaling.","method":"Cryo-EM structure determination (2.9 Å); HDX-MS; smFRET; downstream signaling assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure plus HDX-MS plus smFRET plus functional signaling assays in single study, rigorous multi-orthogonal methods","pmids":["37001505"],"is_preprint":false},{"year":2023,"finding":"Upregulation of Ramp2 in hepatocytes promotes proliferation of liver sinusoidal endothelial cells and hepatic revascularization after hepatectomy, acting via a shift from PEDF to VEGFA expression; overexpression of the competing factor Gata3 suppresses this pathway.","method":"AAV-mediated gene manipulation in Alb-Cre-CRISPR/Cas9 mice; partial hepatectomy and ALPPS models; endothelial precursor transfusion; patient-derived hepatic organoids; PEDF/VEGFA measurement","journal":"Journal of hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic manipulation with defined molecular mechanism (PEDF/VEGFA), multiple model systems, single lab","pmids":["37918568"],"is_preprint":false},{"year":2023,"finding":"Endothelial RAMP2 contributes to ARDS pathogenesis by regulating vascular endothelial barrier function via Epac1; DI-E-RAMP2-/- mice after LPS challenge show reduced Epac1 expression, increased apoptosis, and reduced survival, while RAMP3 compensatorily upregulates; RAMP2 contributes primarily to circulation-regulating effects of AM.","method":"DI-E-RAMP2-/- and RAMP3-/- mice; intratracheal LPS model; lung pathology; survival analysis; transcriptomic analysis; Epac1, iNOS, TNF-α, NLRP3 expression","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two genetic KO models with transcriptomic and histological mechanistic readouts, single lab","pmids":["38012983"],"is_preprint":false},{"year":2025,"finding":"AM-RAMP2 signaling enhances pulmonary endothelial barrier integrity, anti-inflammatory phenotype (decreased ICAM1, increased IkBa), and anti-coagulation markers (increased THBD, decreased F3) under shear stress; blockade of RAMP2 completely attenuates these effects of ADM on lung endothelial cells.","method":"ECIS and XperT barrier integrity assays; RAMP2 blocking; RT-PCR and protein expression for homeostatic and inflammatory markers under shear stress in human pulmonary endothelial cells","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple functional assays with pharmacological blockade control, single lab","pmids":["41597226"],"is_preprint":false},{"year":2025,"finding":"AM/RAMP2 signaling enhances endothelial cell homeostasis synergically with shear stress, maintaining CDH5, NOS3, TEK, S1PR1 expression and improving anti-coagulation; RAMP2 blockade abolishes ADM's effects on lung endothelial cells.","method":"ECIS barrier assay; shear stress perfusion system; pharmacological RAMP2 blockade; gene expression analysis","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, overlapping content with peer-reviewed PMID:41597226","pmids":["bio_10.1101_2025.09.21.677608"],"is_preprint":true},{"year":2025,"finding":"In experimental autoimmune uveitis, AM exerts anti-inflammatory effects through RAMP2 by increasing regulatory T cells and M2 macrophages; RAMP2KO (but not RAMP3KO) mice show significantly worsened retinal inflammatory cell infiltration and clinical scores, demonstrating RAMP2-specific mediation of AM's immunomodulatory function.","method":"RAMP2KO and RAMP3KO mice; EAU mouse model; flow cytometry for Tregs and M2 macrophages; retinal T cell and macrophage quantification; cytokine RT-PCR; AM administration rescue","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO comparison with gain-of-function rescue and mechanistic immune cell phenotyping, single lab","pmids":["40465267"],"is_preprint":false}],"current_model":"RAMP2 is a single-pass transmembrane accessory protein that obligatorily dimerizes with calcitonin receptor-like receptor (CRLR/CLR) to form a high-affinity adrenomedullin (AM) receptor, with residues 86–92 of its extracellular domain critical for AM binding; beyond AM/CLR, RAMP2 also allosterically modulates the glucagon receptor (GCGR) as a negative modulator by disordering the GCGR extracellular domain to suppress active-state signaling (cryo-EM/HDX-MS/smFRET established), modulates PTH1R by promoting a preactivated state with altered G protein and β-arrestin coupling, and interacts with CRF receptors to regulate their cell surface expression; in endothelial cells, the AM-RAMP2 system is essential for vascular integrity by controlling the Rac1-GTP/RhoA-GTP balance and cortical actin formation, and its loss causes vascular leakage, EndMT-like changes, organ fibrosis, and pre-metastatic niche formation, while cardiomyocyte RAMP2 is required for mitochondrial homeostasis under cardiac stress."},"narrative":{"mechanistic_narrative":"RAMP2 is a single-pass transmembrane accessory protein that defines G protein-coupled receptor pharmacology and is essential for vascular integrity [PMID:10217420, PMID:18097473]. Its canonical role is to obligatorily partner with calcitonin receptor-like receptor (CRLR/CL) to constitute a high-affinity adrenomedullin (AM) receptor that signals through cAMP, with residues 86–92 of its extracellular N-terminal domain critical for AM binding [PMID:10217420, PMID:11591721]; this CL/RAMP2 receptor is pharmacologically distinct from the CL/RAMP3 receptor, conferring AM22-52 selectivity [PMID:12970090]. In the endothelium, the AM-RAMP2 system is indispensable for vascular development and barrier integrity: its loss is embryonic lethal with vascular fragility, hemorrhage, and endothelial detachment, while its mechanism of action involves control of the Rac1-GTP/RhoA-GTP balance, cortical actin organization, and tight-junction stability [PMID:18097473, PMID:23355623]. Loss of endothelial RAMP2 produces vascular leakage, endothelial-mesenchymal transition-like changes, organ fibrosis, and pre-metastatic niche formation, whereas its activity supports angiogenesis, re-endothelialization, and barrier protection across retinal, hepatic, renal, and pulmonary contexts [PMID:23355623, PMID:23562442, PMID:27307317, PMID:28324104]. Beyond the AM/CL axis, RAMP2 broadly tunes class B GPCR signaling: it acts as a negative allosteric modulator of the glucagon receptor by disordering its extracellular domain to suppress active-state signaling and by rerouting receptor trafficking and G protein/β-arrestin coupling [PMID:37001505, PMID:34271220], and it shifts PTH1R into a preactivated state with altered Gi3 and β-arrestin2 coupling [PMID:35914163]. Human RAMP2 pathogenic variants disrupt AM-RAMP2/CRLR-cAMP signaling and cause mutant protein aggregation, linking RAMP2 dysfunction to retinal ganglion cell death [PMID:31000793].","teleology":[{"year":1999,"claim":"Established RAMP2's defining molecular function—that it is not itself a receptor but an obligate accessory subunit that, together with CRLR, builds a functional high-affinity adrenomedullin receptor in vascular cells.","evidence":"Heterologous co-expression in HeLa/293 EBNA cells with cAMP functional readout and RT-PCR","pmids":["10217420"],"confidence":"High","gaps":["Did not map the RAMP2 residues responsible for AM binding","Stoichiometry and structure of the CRLR/RAMP2 complex unresolved"]},{"year":2001,"claim":"Localized the binding determinant within RAMP2, showing its extracellular N-terminal residues 86–92 are required for AM binding and signaling independent of complex surface expression.","evidence":"RAMP chimeras/deletion mutants with CRLR in HEK293, 125I-AM radioligand binding, cAMP and CRE-luciferase reporter assays in cardiomyocytes","pmids":["11591721","11754972"],"confidence":"High","gaps":["Atomic-resolution contact map between residues 86–92 and AM not defined","Role of CRLR residues in cooperative binding not addressed"]},{"year":2003,"claim":"Demonstrated that RAMP identity dictates receptor pharmacology, distinguishing CL/RAMP2 from CL/RAMP3 by differential antagonist selectivity and establishing RAMPs as pharmacological switches.","evidence":"Transient and endogenous expression in COS-7, Rat 2, L6 cells with cAMP assays and multiple receptor antagonists","pmids":["12970090"],"confidence":"High","gaps":["Structural basis for the pharmacological divergence not determined","Species-combination effects complicate human extrapolation"]},{"year":2008,"claim":"Proved RAMP2 is genetically essential for vascular development in vivo, with knockout phenocopying AM loss and establishing an allele-dose-dependent role in vascular integrity.","evidence":"Global and heterozygous RAMP2 knockout mice, EC overexpression, histology, vascular permeability and tight-junction assays","pmids":["18097473"],"confidence":"High","gaps":["Embryonic lethality precluded analysis of adult/tissue-specific roles","Downstream signaling mediating integrity not yet defined"]},{"year":2013,"claim":"Defined the intracellular mechanism by which endothelial RAMP2 maintains vascular integrity—control of the Rac1-GTP/RhoA-GTP ratio and cortical actin—using cell-type-specific and inducible knockouts.","evidence":"Endothelial-specific and drug-inducible RAMP2 KO mice, Rac1/RhoA GTP measurement, actin imaging, permeability and histopathology; OIR retinal model","pmids":["23355623","23562442"],"confidence":"High","gaps":["How AM-RAMP2-cAMP signaling links to Rac1/RhoA GTPase regulation mechanistically unresolved","Effector linking signaling to actin remodeling not identified"]},{"year":2016,"claim":"Extended endothelial RAMP2 function to disease processes, showing its loss promotes EndMT, pre-metastatic niche formation, and tumor metastasis, defining a vasoprotective tumor-suppressive role.","evidence":"Inducible EC-specific KO and gain-of-function mice, tumor metastasis models, S100A8/9 and SAA3 marker staining; vascular injury and progenitor cell assays","pmids":["27307317","28324104"],"confidence":"High","gaps":["Causal chain from barrier loss to chemokine induction not fully dissected","Whether RAMP2 acts cell-autonomously in metastatic niche cells unclear"]},{"year":2014,"claim":"Broadened RAMP2's physiological reach beyond vasculature—to reproduction, pituitary/skeletal homeostasis, renal ER-stress protection, and hepatic endothelial differentiation—via PERK-CHOP suppression and other pathways.","evidence":"RAMP2+/- mice with reproductive, prolactin, bone-density phenotyping; tunicamycin renal injury with PERK/CHOP Westerns; embryoid body LSEC differentiation","pmids":["21566080","24505304","21782867"],"confidence":"High","gaps":["Whether these effects all proceed through AM/CL or via other partner receptors unresolved","Tissue-specific receptor partners not all defined"]},{"year":2017,"claim":"Revealed RAMP2 as a broad modulator of class B GPCRs beyond AM/CL, showing it remodels glucagon receptor pharmacology, surface expression, trafficking, and G protein/β-arrestin coupling.","evidence":"Yeast and mammalian functional assays, confocal colocalization, cell-surface ELISA, competition binding, NanoBiT, WASH-KO MEFs, hepatic AAV in mice","pmids":["26198634","28586439","34271220"],"confidence":"High","gaps":["Whether endogenous RAMP2/GCGR co-expression occurs at physiologically relevant levels not established in these studies","Structural basis of GCGR modulation not yet defined here"]},{"year":2019,"claim":"Connected RAMP2 to human disease, identifying pathogenic variants that aggregate and disrupt AM-RAMP2/CRLR-cAMP signaling, with retinal ganglion cell death in a mouse model.","evidence":"Exome/Sanger sequencing, heterologous mutant expression, aggregation imaging, cAMP measurement, heterozygous Ramp2 KO retinal histology","pmids":["31000793"],"confidence":"High","gaps":["Mechanism linking cAMP reduction to ganglion cell death not detailed","Genotype-phenotype relationships across variants not fully resolved"]},{"year":2019,"claim":"Identified a regulatory interaction with CRF receptors, showing CRFR1 (not CRFR2) controls RAMP2 cell-surface expression in a ligand-dependent manner.","evidence":"Co-expression in four cell lines, cell-surface ELISA for FLAG-RAMP2, RT-PCR, molecular modelling, CRF pre-treatment","pmids":["30826286"],"confidence":"Medium","gaps":["No direct binding assay confirming physical interaction","Functional consequence of CRFR1-RAMP2 trafficking not established"]},{"year":2022,"claim":"Demonstrated RAMP2 allosterically primes PTH1R into a preactivated state with agonist-dependent rewiring of Gi3 and β-arrestin2 coupling, generalizing its allosteric-modulator role.","evidence":"Optical biosensors of PTH1R activation/signaling with RAMP2 co-expression and homology modelling","pmids":["35914163"],"confidence":"High","gaps":["Structural model is homology-based, not experimentally solved","Physiological context of PTH1R-RAMP2 co-expression not addressed"]},{"year":2023,"claim":"Provided the structural mechanism of RAMP2's negative allosteric modulation of GCGR—disordering the ECD and TM6 to inhibit active states—resolving how RAMP2 broadly suppresses downstream signaling.","evidence":"Cryo-EM (2.9 Å) of GCGR-Gs with RAMP2, HDX-MS, smFRET, downstream signaling assays","pmids":["37001505"],"confidence":"High","gaps":["Whether the same conformational mechanism applies to PTH1R/CRFR modulation untested","In vivo relevance of GCGR-RAMP2 antagonism in metabolic physiology not established here"]},{"year":2023,"claim":"Showed RAMP2 in non-endothelial cells (hepatocytes) drives angiogenic regeneration via a PEDF-to-VEGFA switch, expanding its angiogenic role to a paracrine context.","evidence":"AAV gene manipulation in Alb-Cre-CRISPR/Cas9 mice, hepatectomy/ALPPS models, organoids, PEDF/VEGFA measurement","pmids":["37918568"],"confidence":"Medium","gaps":["Receptor partner mediating hepatocyte RAMP2 signaling not defined","Direct molecular link from RAMP2 to PEDF/VEGFA switch unclear"]},{"year":2021,"claim":"Defined a cardiomyocyte-autonomous role for RAMP2 in mitochondrial homeostasis required for adaptation to cardiac stress.","evidence":"Cardiomyocyte-specific RAMP2 KO mice with TAC, echocardiography, pressure-volume, mitochondrial membrane potential and respiration assays","pmids":["33545715"],"confidence":"High","gaps":["Molecular link between RAMP2 signaling and mitochondrial function not identified","Whether this requires AM/CL signaling not established"]},{"year":2025,"claim":"Reinforced the AM-RAMP2 system as a pulmonary endothelial barrier and anti-inflammatory regulator, acting via Epac1 and synergizing with shear stress to maintain homeostatic and anti-coagulation programs.","evidence":"DI-E-RAMP2-/- and RAMP3-/- LPS/ARDS models, ECIS/XperT barrier assays under shear stress, pharmacological RAMP2 blockade, marker expression; EAU immunomodulation models","pmids":["38012983","41597226","40465267"],"confidence":"Medium","gaps":["Direct signaling chain from AM-RAMP2 to Epac1 induction not dissected","RAMP3 compensation complicates attribution of specific effects"]},{"year":null,"claim":"How RAMP2 mechanistically couples its receptor-modulating activity to downstream cytoskeletal (Rac1/RhoA), mitochondrial, and barrier programs across distinct cell types remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying signaling intermediary linking AM-RAMP2-cAMP to actin/mitochondrial outcomes","Cell-type-specific receptor partners for non-CL functions incompletely mapped","No experimental structure of the CRLR/RAMP2-AM receptor complex in the timeline"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[22,23,20,14,17]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,19]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,19]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[20]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,22,23]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,11,12]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[19,20,17]}],"complexes":["CRLR/RAMP2 adrenomedullin receptor"],"partners":["CALCRL","GCGR","PTH1R","CRHR1","ADM"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60895","full_name":"Receptor activity-modifying protein 2","aliases":["Calcitonin-receptor-like receptor activity-modifying protein 2","CRLR activity-modifying protein 2"],"length_aa":175,"mass_kda":19.6,"function":"Accessory protein that interacts with and modulates the function of G-protein coupled receptors including calcitonin gene-related peptide type 1 receptor (CALCRL) and calcitonin receptor (CALCR) (PubMed:9620797). Required for the transport of CALCRL to the plasma membrane (PubMed:9620797). Together with CALCRL, form a receptor complex for adrenomedullin/ADM (PubMed:22102369, PubMed:32296767, PubMed:9620797). Together with CALCR, act as a receptor complex for calcitonin/CT/CALC (PubMed:35324283). Together with CALCR, also act as a receptor complex for amylin/IAPP (PubMed:35324283)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O60895/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RAMP2","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/RAMP2","total_profiled":1310},"omim":[{"mim_id":"618773","title":"LYMPHATIC MALFORMATION 8; LMPHM8","url":"https://www.omim.org/entry/618773"},{"mim_id":"605155","title":"RECEPTOR ACTIVITY-MODIFYING PROTEIN 3; RAMP3","url":"https://www.omim.org/entry/605155"},{"mim_id":"605154","title":"RECEPTOR ACTIVITY-MODIFYING PROTEIN 2; RAMP2","url":"https://www.omim.org/entry/605154"},{"mim_id":"605153","title":"RECEPTOR ACTIVITY-MODIFYING PROTEIN 1; RAMP1","url":"https://www.omim.org/entry/605153"},{"mim_id":"114190","title":"CALCITONIN RECEPTOR-LIKE RECEPTOR; CALCRL","url":"https://www.omim.org/entry/114190"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RAMP2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O60895","domains":[{"cath_id":"1.10.150.510","chopping":"93-133","consensus_level":"medium","plddt":96.142,"start":93,"end":133}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60895","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60895-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60895-F1-predicted_aligned_error_v6.png","plddt_mean":80.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RAMP2","jax_strain_url":"https://www.jax.org/strain/search?query=RAMP2"},"sequence":{"accession":"O60895","fasta_url":"https://rest.uniprot.org/uniprotkb/O60895.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60895/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60895"}},"corpus_meta":[{"pmid":"18097473","id":"PMC_18097473","title":"The GPCR modulator protein RAMP2 is 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RAMP2 but not RAMP1 or RAMP3 mRNA was detected in these cells.\",\n      \"method\": \"Heterologous co-expression in HeLa EBNA and 293 EBNA cells, cAMP functional assay, RT-PCR\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional reconstitution in two cell lines with cAMP readout, replicated across multiple labs subsequently\",\n      \"pmids\": [\"10217420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Residues 86–92 of RAMP2 extracellular N-terminal domain are critical for high-affinity 125I-AM binding and AM-evoked cAMP production at the CRLR/RAMP2 receptor heterodimer; deletion of these seven residues significantly attenuates AM binding without impairing cell surface expression of the complex.\",\n      \"method\": \"RAMP chimeras and deletion mutants co-expressed with CRLR in HEK293 cells; 125I-AM radioligand binding; cAMP production assay; alanine scanning mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis, radioligand binding, and functional cAMP assay in single study\",\n      \"pmids\": [\"11591721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In rat cardiomyocytes, CRLR and RAMP2 together constitute a functional AM receptor; overexpression of RAMP2 and CRLR additively potentiated AM-induced CRE-luciferase (cAMP-responsive) signaling approximately 4-fold over control; AM signaling was abolished by CGRP8-37 antagonist or CRLR antisense.\",\n      \"method\": \"Transient transfection of neonatal cardiomyocytes with CRE-luciferase reporter; CGRP8-37 antagonist; CRLR antisense; RT-PCR\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, functional reporter assay with pharmacological validation but no structural data\",\n      \"pmids\": [\"11754972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CL/RAMP2 and CL/RAMP3 produce pharmacologically distinct AM receptors: AM22-52 shows selectivity for CL/RAMP2 over CL/RAMP3, whereas CGRP8-37 shows the opposite selectivity in mixed species combinations; BIBN4096BS does not antagonise AM at either receptor.\",\n      \"method\": \"Transient expression in COS-7 cells and endogenous expression in Rat 2 and L6 cells; cAMP functional assays with receptor antagonists; apparent pA2 determination\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — pharmacological reconstitution in multiple cell systems with multiple ligands, replicated across species combinations\",\n      \"pmids\": [\"12970090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"AM promotes HUVEC migration, invasion, and differentiation into cord-like structures on Matrigel via CRLR/RAMP2 (and CRLR/RAMP3) receptors; AM-induced capillary tube formation is not blocked by anti-VEGF antibodies, indicating AM does not act indirectly through VEGF upregulation.\",\n      \"method\": \"Migration and invasion assays, Matrigel tube formation, receptor blocking antibodies, anti-VEGF antibody neutralization in HUVECs\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal in vitro functional assays in single lab with pharmacological controls\",\n      \"pmids\": [\"14712479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"siRNA-mediated knockdown of RAMP2 in HUVECs (~60% reduction in mRNA) decreased capillary-like tube formation in response to AM on Matrigel, establishing RAMP2 as required for AM-driven angiogenesis in endothelial cells.\",\n      \"method\": \"siRNA transfection in HUVECs; RT-PCR quantification of RAMP2 mRNA; Matrigel tube formation assay\",\n      \"journal\": \"International journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, loss-of-function with defined cellular phenotype but single method\",\n      \"pmids\": [\"16964401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RAMP2 is essential for vascular integrity and angiogenesis in vivo: RAMP2-/- embryos die at midgestation with vascular fragility, severe edema, hemorrhage, and deformed ECs detached from basement membrane, phenocopying AM-/- embryos. RAMP2+/- adults show vascular hyperpermeability and impaired neovascularization. EC overexpressing RAMP2 show enhanced capillary formation, firmer tight junctions, and reduced vascular permeability.\",\n      \"method\": \"Global RAMP2 knockout mice; heterozygous mice; EC overexpression; histology; vascular permeability assays; tight junction marker expression\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined lethal phenotype replicated at multiple allelic doses, EC overexpression rescue, multiple orthogonal phenotypic readouts\",\n      \"pmids\": [\"18097473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Intermedin mediates pro-angiogenic effects on HUVECs via CLR/RAMP1 and CLR/RAMP2 complexes (but not CLR/RAMP3); this involves both VEGF mRNA upregulation (18 h) and rapid VEGFR-2 phosphorylation (5 min), indicating direct transactivation of VEGFR-2 signaling.\",\n      \"method\": \"Real-time PCR; Matrigel tube formation with receptor antagonists; Western blot for VEGFR-2 phosphorylation\",\n      \"journal\": \"International journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (PCR, functional assay, Western blot) in single lab\",\n      \"pmids\": [\"20596610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RAMP2 haploinsufficiency in female mice causes severe reproductive defects (fetal growth restriction, fetal demise, postnatal lethality), hyperprolactinemia, enlarged pituitary, accelerated mammary development, and skeletal abnormalities including decreased bone mineral density, demonstrating a physiological role for RAMP2 beyond AM/CLR signaling.\",\n      \"method\": \"RAMP2+/- mouse model; reproductive outcome analysis; serum prolactin measurement; pituitary and skeletal histomorphometry; bone mineral density measurement\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic haploinsufficiency model with multiple orthogonal phenotypic readouts in single study\",\n      \"pmids\": [\"21566080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"AM-RAMP2 signaling is required for differentiation of liver sinusoidal endothelial-like cells from embryoid bodies; co-administration of AM and TGFβ receptor inhibitor SB431542 markedly enhanced LYVE-1/stabilin-2-positive endothelial cell differentiation. In RAMP2-null liver, LYVE-1 was downregulated in LSECs and sinusoidal structure was disrupted.\",\n      \"method\": \"Embryoid body differentiation system; AM co-administration with SB431542; LYVE-1/stabilin-2 immunostaining; LSEC marker expression; RAMP2 knockout liver histology\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo genetic KO with defined cellular phenotype, single lab\",\n      \"pmids\": [\"21782867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The endothelial AM-RAMP2 system regulates vascular integrity by controlling the Rac1-GTP/RhoA-GTP ratio and cortical actin formation; loss of endothelial RAMP2 causes actin disarrangement and EC detachment, leading to vascular leakage, spontaneous vasculitis, organ fibrosis, and accelerated vascular senescence.\",\n      \"method\": \"Endothelial-specific RAMP2 KO mice (E-RAMP2-/-) and drug-inducible DI-E-RAMP2-/- mice; vascular permeability assays; Rac1-GTP/RhoA-GTP measurement; actin cytoskeleton imaging; organ histopathology\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific genetic KO with mechanistic pathway identification (Rac1/RhoA), multiple orthogonal in vitro and in vivo readouts\",\n      \"pmids\": [\"23355623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The AM-RAMP2 system is required for retinal angiogenesis: heterozygous RAMP2+/- mice show reduced neovascular tufts, VEGF and eNOS mRNA in oxygen-induced retinopathy; DI-E-RAMP2-/- mice show abnormal developmental retinal vascular patterns; AM enhances proliferation and migration of retinal endothelial cells in vitro.\",\n      \"method\": \"OIR model in RAMP2+/- mice; drug-inducible EC-specific RAMP2 KO; retinal endothelial cell proliferation/migration assays; VEGF/eNOS mRNA quantification; intravitreal anti-ADM antibody injection\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic models plus in vitro mechanistic assays plus pharmacological blockade, single lab\",\n      \"pmids\": [\"23562442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RAMP2 and RAMP3 have functionally distinct roles in the vascular system: RAMP2-/- mice die in utero due to blood vessel abnormalities (essential for vascular development), while RAMP3-/- mice are born normally but show delayed lymphatic drainage and impaired lymphatic endothelial cell migration.\",\n      \"method\": \"RAMP2-/- and RAMP3-/- mouse generation; ICG lymphangiography; tail lymphedema model; scratch-wound migration assay of lymphatic endothelial cells; histology\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — parallel genetic KO comparison with multiple in vivo and in vitro functional assays distinguishing the two receptors\",\n      \"pmids\": [\"25264174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The AM-RAMP2 system suppresses ER stress-induced tubule cell death in the kidney: AM suppresses PERK activation and CHOP-induced apoptosis downstream of ER stress in human RPTECs; in RAMP2+/- mice, tunicamycin-induced tubular damage is enhanced and the rescue effect of exogenous AM is lost.\",\n      \"method\": \"RAMP2+/- mice; STZ and tunicamycin-induced renal injury models; human RPTEC cell culture; Western blot for PERK/CHOP activation; histological analysis of tubular damage; AM rescue experiments\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic model plus in vitro mechanistic dissection with defined signaling pathway (PERK-CHOP), single lab\",\n      \"pmids\": [\"24505304\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RAMP2 modulates glucagon receptor (GCGR) pharmacology: RAMP2 association alters ligand selectivity and G protein preference of GCGR, and abolishes novel cross-reactivity of GLP-1 receptor agonists at the glucagon receptor.\",\n      \"method\": \"Yeast reporter assays; mammalian cell functional assays; multiple ligand pharmacology; G protein coupling analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal cell systems (yeast and mammalian), multiple ligands, single lab\",\n      \"pmids\": [\"26198634\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Endothelial AM-RAMP2 system suppresses tumor metastasis: DI-E-RAMP2-/- mice show enhanced vascular permeability, endothelial-mesenchymal transition-like changes, and formation of pre-metastatic niches with S100A8/9 and SAA3 chemotactic factor expression; RAMP2 overexpression suppresses tumor cell adhesion to endothelial cells and metastasis.\",\n      \"method\": \"DI-E-RAMP2-/- mice; spontaneous and transplant tumor metastasis models; vascular permeability assays; immunostaining for S100A8/9, SAA3, inflammatory markers; RAMP2 overexpression in endothelial cells\",\n      \"journal\": \"Cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — inducible cell-type-specific KO and gain-of-function with mechanistic pathway markers, multiple tumor models\",\n      \"pmids\": [\"27307317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RAMP2 co-expression with GCGR reduces GCGR cell surface expression, causes GCGR cellular redistribution (RAMP2 colocalizes with GCGR intracellularly), alters signaling through Gαs and Gαq pathways, and affects β-arrestin recruitment.\",\n      \"method\": \"Co-expression in cells; confocal microscopy co-localization; cell surface ELISA; competition binding; functional assays for Gαs, Gαq, β-arrestin; siRNA knockdown\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (microscopy, binding, functional signaling) in single lab\",\n      \"pmids\": [\"28586439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The endothelial AM-RAMP2 system exerts vasoprotective effects after vascular injury: RAMP2+/- mice and DI-E-RAMP2-/- mice show enhanced neointima formation, greater macrophage infiltration and oxidative stress, and reduced re-endothelialization; the AM-RAMP2 system also augments proliferation and migration of endothelial progenitor cells.\",\n      \"method\": \"Wire-induced vascular injury model in RAMP2+/- and DI-E-RAMP2-/- mice; bone marrow transplantation; histology; endothelial progenitor cell proliferation/migration assays\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic models, bone marrow transplant, in vitro mechanistic assays, single lab with multiple orthogonal readouts\",\n      \"pmids\": [\"28324104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RAMP2 pathogenic variants (Glu39Asp, Glu54Lys, Phe103Ser, Asn113Lysfs*10, Glu143Lys, Ser171Arg) cause aggregation of mutant RAMP2 in transfected cells and disrupt the AM-RAMP2/CRLR-cAMP signaling pathway; ablation of one Ramp2 allele leads to cAMP reduction and retinal ganglion cell death in mice.\",\n      \"method\": \"Exome sequencing; Sanger sequencing validation; heterologous expression of mutant RAMP2 proteins; RAMP2 protein aggregation imaging; cAMP measurement; heterozygous Ramp2 KO mouse retinal histology\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetic variants with cellular mechanistic validation (aggregation, cAMP) and in vivo mouse model, multiple orthogonal methods\",\n      \"pmids\": [\"31000793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CRFR1α and CRFR1β (but not CRFR2β) physically interact with RAMP2 to enhance its cell surface expression; ligand-stimulated CRFR1 causes loss of cell-surface RAMP2; CRFR2β does not interact with RAMP2, potentially due to a histidine (vs. glutamate in CRFR1) in the predicted contact interface.\",\n      \"method\": \"Co-expression in four cell lines; cell-surface ELISA for FLAG-RAMP2; RT-PCR for endogenous RAMPs; molecular modelling; CRF pre-treatment experiments\",\n      \"journal\": \"Biochimica et biophysica acta. Biomembranes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — cell surface expression assay in multiple cell lines, single lab, no direct binding assay\",\n      \"pmids\": [\"30826286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RAMP2 alters GCGR subcellular trafficking: RAMP2 induces GCGR internalisation both basally and upon agonist stimulation, retains GCGR intracellularly, biases GCGR away from β-arrestin-2 recruitment toward increased Gαs activation at endosomes, and increases short-term cAMP production while enhancing long-term lysosomal targeting for degradation.\",\n      \"method\": \"Confocal microscopy; trafficking assays; radioligand binding; WASH complex KO MEFs; monensin; NanoBiT complementation; cAMP assays; hepatic AAV RAMP2 overexpression in mice\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (microscopy, trafficking inhibitors, NanoBiT, cAMP, genetic tools), in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"34271220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cardiomyocyte-specific RAMP2 deletion (C-RAMP2-/-) after transverse aortic constriction causes cardiac hypertrophy, decreased ejection fraction, increased fibrosis, and reduced mitochondrial membrane potential and respiratory capacity, indicating the AM-RAMP2 system is required for early cardiac adaptation to stress via regulation of cardiac mitochondria.\",\n      \"method\": \"Cardiomyocyte-specific RAMP2 KO mice; TAC model; echocardiography; pressure-volume analysis; mitochondrial membrane potential and respiratory capacity assays; isoproterenol stimulation of isolated cardiomyocytes\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific KO with mechanistic mitochondrial readouts and multiple cardiac functional assays, single lab\",\n      \"pmids\": [\"33545715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RAMP2 acts as a specific allosteric modulator of PTH1R, shifting it to a preactivated state that permits faster ligand-dependent activation; RAMP2 modulates PTH1R downstream signaling in an agonist-dependent manner—most notably increasing PTH-mediated Gi3 signaling sensitivity—and increases β-arrestin2 recruitment triggered by both PTH and PTHrP.\",\n      \"method\": \"Optical biosensors measuring PTH1R activation and downstream signaling; RAMP2 co-expression; homology modelling for structural basis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple optical biosensors with ligand-specific pharmacological analysis, single lab but orthogonal functional methods\",\n      \"pmids\": [\"35914163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RAMP2 acts as a negative allosteric modulator of the glucagon receptor (GCGR): cryo-EM structure of GCGR-Gs complex in the presence of RAMP2 shows the GCGR ECD is largely disordered; HDX-MS demonstrates RAMP2 enhances local flexibility in the ECD and the 6th transmembrane helix; smFRET shows ECD disorder inhibits active and intermediate states of the intracellular surface, broadly inhibiting downstream signaling.\",\n      \"method\": \"Cryo-EM structure determination (2.9 Å); HDX-MS; smFRET; downstream signaling assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure plus HDX-MS plus smFRET plus functional signaling assays in single study, rigorous multi-orthogonal methods\",\n      \"pmids\": [\"37001505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Upregulation of Ramp2 in hepatocytes promotes proliferation of liver sinusoidal endothelial cells and hepatic revascularization after hepatectomy, acting via a shift from PEDF to VEGFA expression; overexpression of the competing factor Gata3 suppresses this pathway.\",\n      \"method\": \"AAV-mediated gene manipulation in Alb-Cre-CRISPR/Cas9 mice; partial hepatectomy and ALPPS models; endothelial precursor transfusion; patient-derived hepatic organoids; PEDF/VEGFA measurement\",\n      \"journal\": \"Journal of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic manipulation with defined molecular mechanism (PEDF/VEGFA), multiple model systems, single lab\",\n      \"pmids\": [\"37918568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Endothelial RAMP2 contributes to ARDS pathogenesis by regulating vascular endothelial barrier function via Epac1; DI-E-RAMP2-/- mice after LPS challenge show reduced Epac1 expression, increased apoptosis, and reduced survival, while RAMP3 compensatorily upregulates; RAMP2 contributes primarily to circulation-regulating effects of AM.\",\n      \"method\": \"DI-E-RAMP2-/- and RAMP3-/- mice; intratracheal LPS model; lung pathology; survival analysis; transcriptomic analysis; Epac1, iNOS, TNF-α, NLRP3 expression\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two genetic KO models with transcriptomic and histological mechanistic readouts, single lab\",\n      \"pmids\": [\"38012983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AM-RAMP2 signaling enhances pulmonary endothelial barrier integrity, anti-inflammatory phenotype (decreased ICAM1, increased IkBa), and anti-coagulation markers (increased THBD, decreased F3) under shear stress; blockade of RAMP2 completely attenuates these effects of ADM on lung endothelial cells.\",\n      \"method\": \"ECIS and XperT barrier integrity assays; RAMP2 blocking; RT-PCR and protein expression for homeostatic and inflammatory markers under shear stress in human pulmonary endothelial cells\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple functional assays with pharmacological blockade control, single lab\",\n      \"pmids\": [\"41597226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AM/RAMP2 signaling enhances endothelial cell homeostasis synergically with shear stress, maintaining CDH5, NOS3, TEK, S1PR1 expression and improving anti-coagulation; RAMP2 blockade abolishes ADM's effects on lung endothelial cells.\",\n      \"method\": \"ECIS barrier assay; shear stress perfusion system; pharmacological RAMP2 blockade; gene expression analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, overlapping content with peer-reviewed PMID:41597226\",\n      \"pmids\": [\"bio_10.1101_2025.09.21.677608\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In experimental autoimmune uveitis, AM exerts anti-inflammatory effects through RAMP2 by increasing regulatory T cells and M2 macrophages; RAMP2KO (but not RAMP3KO) mice show significantly worsened retinal inflammatory cell infiltration and clinical scores, demonstrating RAMP2-specific mediation of AM's immunomodulatory function.\",\n      \"method\": \"RAMP2KO and RAMP3KO mice; EAU mouse model; flow cytometry for Tregs and M2 macrophages; retinal T cell and macrophage quantification; cytokine RT-PCR; AM administration rescue\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO comparison with gain-of-function rescue and mechanistic immune cell phenotyping, single lab\",\n      \"pmids\": [\"40465267\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RAMP2 is a single-pass transmembrane accessory protein that obligatorily dimerizes with calcitonin receptor-like receptor (CRLR/CLR) to form a high-affinity adrenomedullin (AM) receptor, with residues 86–92 of its extracellular domain critical for AM binding; beyond AM/CLR, RAMP2 also allosterically modulates the glucagon receptor (GCGR) as a negative modulator by disordering the GCGR extracellular domain to suppress active-state signaling (cryo-EM/HDX-MS/smFRET established), modulates PTH1R by promoting a preactivated state with altered G protein and β-arrestin coupling, and interacts with CRF receptors to regulate their cell surface expression; in endothelial cells, the AM-RAMP2 system is essential for vascular integrity by controlling the Rac1-GTP/RhoA-GTP balance and cortical actin formation, and its loss causes vascular leakage, EndMT-like changes, organ fibrosis, and pre-metastatic niche formation, while cardiomyocyte RAMP2 is required for mitochondrial homeostasis under cardiac stress.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RAMP2 is a single-pass transmembrane accessory protein that defines G protein-coupled receptor pharmacology and is essential for vascular integrity [#0, #6]. Its canonical role is to obligatorily partner with calcitonin receptor-like receptor (CRLR/CL) to constitute a high-affinity adrenomedullin (AM) receptor that signals through cAMP, with residues 86\\u201392 of its extracellular N-terminal domain critical for AM binding [#0, #1]; this CL/RAMP2 receptor is pharmacologically distinct from the CL/RAMP3 receptor, conferring AM22-52 selectivity [#3]. In the endothelium, the AM-RAMP2 system is indispensable for vascular development and barrier integrity: its loss is embryonic lethal with vascular fragility, hemorrhage, and endothelial detachment, while its mechanism of action involves control of the Rac1-GTP/RhoA-GTP balance, cortical actin organization, and tight-junction stability [#6, #10]. Loss of endothelial RAMP2 produces vascular leakage, endothelial-mesenchymal transition-like changes, organ fibrosis, and pre-metastatic niche formation, whereas its activity supports angiogenesis, re-endothelialization, and barrier protection across retinal, hepatic, renal, and pulmonary contexts [#10, #11, #15, #17]. Beyond the AM/CL axis, RAMP2 broadly tunes class B GPCR signaling: it acts as a negative allosteric modulator of the glucagon receptor by disordering its extracellular domain to suppress active-state signaling and by rerouting receptor trafficking and G protein/\\u03b2-arrestin coupling [#23, #20], and it shifts PTH1R into a preactivated state with altered Gi3 and \\u03b2-arrestin2 coupling [#22]. Human RAMP2 pathogenic variants disrupt AM-RAMP2/CRLR-cAMP signaling and cause mutant protein aggregation, linking RAMP2 dysfunction to retinal ganglion cell death [#18].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established RAMP2's defining molecular function\\u2014that it is not itself a receptor but an obligate accessory subunit that, together with CRLR, builds a functional high-affinity adrenomedullin receptor in vascular cells.\",\n      \"evidence\": \"Heterologous co-expression in HeLa/293 EBNA cells with cAMP functional readout and RT-PCR\",\n      \"pmids\": [\"10217420\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map the RAMP2 residues responsible for AM binding\", \"Stoichiometry and structure of the CRLR/RAMP2 complex unresolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Localized the binding determinant within RAMP2, showing its extracellular N-terminal residues 86\\u201392 are required for AM binding and signaling independent of complex surface expression.\",\n      \"evidence\": \"RAMP chimeras/deletion mutants with CRLR in HEK293, 125I-AM radioligand binding, cAMP and CRE-luciferase reporter assays in cardiomyocytes\",\n      \"pmids\": [\"11591721\", \"11754972\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution contact map between residues 86\\u201392 and AM not defined\", \"Role of CRLR residues in cooperative binding not addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated that RAMP identity dictates receptor pharmacology, distinguishing CL/RAMP2 from CL/RAMP3 by differential antagonist selectivity and establishing RAMPs as pharmacological switches.\",\n      \"evidence\": \"Transient and endogenous expression in COS-7, Rat 2, L6 cells with cAMP assays and multiple receptor antagonists\",\n      \"pmids\": [\"12970090\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for the pharmacological divergence not determined\", \"Species-combination effects complicate human extrapolation\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Proved RAMP2 is genetically essential for vascular development in vivo, with knockout phenocopying AM loss and establishing an allele-dose-dependent role in vascular integrity.\",\n      \"evidence\": \"Global and heterozygous RAMP2 knockout mice, EC overexpression, histology, vascular permeability and tight-junction assays\",\n      \"pmids\": [\"18097473\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Embryonic lethality precluded analysis of adult/tissue-specific roles\", \"Downstream signaling mediating integrity not yet defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the intracellular mechanism by which endothelial RAMP2 maintains vascular integrity\\u2014control of the Rac1-GTP/RhoA-GTP ratio and cortical actin\\u2014using cell-type-specific and inducible knockouts.\",\n      \"evidence\": \"Endothelial-specific and drug-inducible RAMP2 KO mice, Rac1/RhoA GTP measurement, actin imaging, permeability and histopathology; OIR retinal model\",\n      \"pmids\": [\"23355623\", \"23562442\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How AM-RAMP2-cAMP signaling links to Rac1/RhoA GTPase regulation mechanistically unresolved\", \"Effector linking signaling to actin remodeling not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended endothelial RAMP2 function to disease processes, showing its loss promotes EndMT, pre-metastatic niche formation, and tumor metastasis, defining a vasoprotective tumor-suppressive role.\",\n      \"evidence\": \"Inducible EC-specific KO and gain-of-function mice, tumor metastasis models, S100A8/9 and SAA3 marker staining; vascular injury and progenitor cell assays\",\n      \"pmids\": [\"27307317\", \"28324104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal chain from barrier loss to chemokine induction not fully dissected\", \"Whether RAMP2 acts cell-autonomously in metastatic niche cells unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Broadened RAMP2's physiological reach beyond vasculature\\u2014to reproduction, pituitary/skeletal homeostasis, renal ER-stress protection, and hepatic endothelial differentiation\\u2014via PERK-CHOP suppression and other pathways.\",\n      \"evidence\": \"RAMP2+/- mice with reproductive, prolactin, bone-density phenotyping; tunicamycin renal injury with PERK/CHOP Westerns; embryoid body LSEC differentiation\",\n      \"pmids\": [\"21566080\", \"24505304\", \"21782867\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether these effects all proceed through AM/CL or via other partner receptors unresolved\", \"Tissue-specific receptor partners not all defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed RAMP2 as a broad modulator of class B GPCRs beyond AM/CL, showing it remodels glucagon receptor pharmacology, surface expression, trafficking, and G protein/\\u03b2-arrestin coupling.\",\n      \"evidence\": \"Yeast and mammalian functional assays, confocal colocalization, cell-surface ELISA, competition binding, NanoBiT, WASH-KO MEFs, hepatic AAV in mice\",\n      \"pmids\": [\"26198634\", \"28586439\", \"34271220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether endogenous RAMP2/GCGR co-expression occurs at physiologically relevant levels not established in these studies\", \"Structural basis of GCGR modulation not yet defined here\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected RAMP2 to human disease, identifying pathogenic variants that aggregate and disrupt AM-RAMP2/CRLR-cAMP signaling, with retinal ganglion cell death in a mouse model.\",\n      \"evidence\": \"Exome/Sanger sequencing, heterologous mutant expression, aggregation imaging, cAMP measurement, heterozygous Ramp2 KO retinal histology\",\n      \"pmids\": [\"31000793\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking cAMP reduction to ganglion cell death not detailed\", \"Genotype-phenotype relationships across variants not fully resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified a regulatory interaction with CRF receptors, showing CRFR1 (not CRFR2) controls RAMP2 cell-surface expression in a ligand-dependent manner.\",\n      \"evidence\": \"Co-expression in four cell lines, cell-surface ELISA for FLAG-RAMP2, RT-PCR, molecular modelling, CRF pre-treatment\",\n      \"pmids\": [\"30826286\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct binding assay confirming physical interaction\", \"Functional consequence of CRFR1-RAMP2 trafficking not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated RAMP2 allosterically primes PTH1R into a preactivated state with agonist-dependent rewiring of Gi3 and \\u03b2-arrestin2 coupling, generalizing its allosteric-modulator role.\",\n      \"evidence\": \"Optical biosensors of PTH1R activation/signaling with RAMP2 co-expression and homology modelling\",\n      \"pmids\": [\"35914163\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model is homology-based, not experimentally solved\", \"Physiological context of PTH1R-RAMP2 co-expression not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided the structural mechanism of RAMP2's negative allosteric modulation of GCGR\\u2014disordering the ECD and TM6 to inhibit active states\\u2014resolving how RAMP2 broadly suppresses downstream signaling.\",\n      \"evidence\": \"Cryo-EM (2.9 \\u00c5) of GCGR-Gs with RAMP2, HDX-MS, smFRET, downstream signaling assays\",\n      \"pmids\": [\"37001505\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the same conformational mechanism applies to PTH1R/CRFR modulation untested\", \"In vivo relevance of GCGR-RAMP2 antagonism in metabolic physiology not established here\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed RAMP2 in non-endothelial cells (hepatocytes) drives angiogenic regeneration via a PEDF-to-VEGFA switch, expanding its angiogenic role to a paracrine context.\",\n      \"evidence\": \"AAV gene manipulation in Alb-Cre-CRISPR/Cas9 mice, hepatectomy/ALPPS models, organoids, PEDF/VEGFA measurement\",\n      \"pmids\": [\"37918568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor partner mediating hepatocyte RAMP2 signaling not defined\", \"Direct molecular link from RAMP2 to PEDF/VEGFA switch unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined a cardiomyocyte-autonomous role for RAMP2 in mitochondrial homeostasis required for adaptation to cardiac stress.\",\n      \"evidence\": \"Cardiomyocyte-specific RAMP2 KO mice with TAC, echocardiography, pressure-volume, mitochondrial membrane potential and respiration assays\",\n      \"pmids\": [\"33545715\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between RAMP2 signaling and mitochondrial function not identified\", \"Whether this requires AM/CL signaling not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Reinforced the AM-RAMP2 system as a pulmonary endothelial barrier and anti-inflammatory regulator, acting via Epac1 and synergizing with shear stress to maintain homeostatic and anti-coagulation programs.\",\n      \"evidence\": \"DI-E-RAMP2-/- and RAMP3-/- LPS/ARDS models, ECIS/XperT barrier assays under shear stress, pharmacological RAMP2 blockade, marker expression; EAU immunomodulation models\",\n      \"pmids\": [\"38012983\", \"41597226\", \"40465267\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct signaling chain from AM-RAMP2 to Epac1 induction not dissected\", \"RAMP3 compensation complicates attribution of specific effects\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RAMP2 mechanistically couples its receptor-modulating activity to downstream cytoskeletal (Rac1/RhoA), mitochondrial, and barrier programs across distinct cell types remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying signaling intermediary linking AM-RAMP2-cAMP to actin/mitochondrial outcomes\", \"Cell-type-specific receptor partners for non-CL functions incompletely mapped\", \"No experimental structure of the CRLR/RAMP2-AM receptor complex in the timeline\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [22, 23, 20, 14, 17]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 19]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 22, 23]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 11, 12]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [19, 20, 17]}\n    ],\n    \"complexes\": [\"CRLR/RAMP2 adrenomedullin receptor\"],\n    \"partners\": [\"CALCRL\", \"GCGR\", \"PTH1R\", \"CRHR1\", \"ADM\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}