{"gene":"AVPR2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":1992,"finding":"Point mutations in the AVPR2 gene (encoding the renal vasopressin V2 receptor) cause X-linked nephrogenic diabetes insipidus (NDI); missense mutations in conserved extracellular regions of AVPR2 co-segregate with NDI, establishing AVPR2 loss-of-function as the molecular basis of the disorder.","method":"Genomic sequencing, genetic mapping, co-segregation analysis in NDI families","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-segregation in multiple independent families, replicated extensively in subsequent studies","pmids":["1303271"],"is_preprint":false},{"year":2001,"finding":"Calnexin, an ER chaperone, associates with precursor forms of both wild-type and mutant AVPR2 receptors; ER-retained NDI mutants (e.g., W71X, R337X) show prolonged calnexin association compared to wild-type, indicating calnexin participates in quality control and ER retention of misfolded AVPR2.","method":"Sequential co-immunoprecipitation, immunofluorescence, confocal microscopy, Western blot, endoglycosidase H treatment in transfected cells","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP with functional follow-up (glycosylation maturation, localization), single lab with multiple orthogonal methods","pmids":["11389590"],"is_preprint":false},{"year":1997,"finding":"The NDI-causing truncation mutant V2R-R337ter is non-functional because it is retained in the ER and fails to reach the plasma membrane; a minimum C-terminal length (requiring at least residues up to position 341, with identity of residue 340 being important) is required for ER export and plasma membrane expression of AVPR2.","method":"ELISA on surface-tagged receptors, endoglycosidase H assay, adenylyl cyclase activity, binding assays, metabolic labeling in COS.M6 and HEK293 cells","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal biochemical assays (binding, signaling, glycosylation, surface ELISA) with systematic truncation mutagenesis, single lab","pmids":["9171234"],"is_preprint":false},{"year":2006,"finding":"After vasopressin (VP) stimulation of renal epithelial cells, V2R is rapidly internalized into endosomes while AQP2 accumulates at the cell surface in endocytosis-resistant membrane domains; V2R endocytosis and AQP2 trafficking are spatially and temporally separable events, and the initial burst of endocytosis upon VP addition is due to V2R internalization rather than cAMP elevation.","method":"Confocal live-cell imaging, epitope-tagged V2R and AQP2 in LLC-PK1 cells, forskolin control, FITC-dextran fluid-phase marker, polarized filter-grown cells","journal":"Biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple imaging and pharmacological approaches in the same system, clear functional separation of V2R and AQP2 trafficking, single lab","pmids":["16563128"],"is_preprint":false},{"year":2007,"finding":"Alix (AIP1) directly interacts with the last 29 amino acids of the V2R C-terminus; upon vasopressin stimulation, Alix accelerates lysosomal (not proteasomal) degradation of V2R, providing a mechanism for VP-induced receptor downregulation in kidney principal cells.","method":"Yeast two-hybrid screening, GST pull-down assay, co-immunolocalization, V2R-GFP transfection in LLC-PK1 cells, Western blot, chloroquine and MG132 inhibitor experiments","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus GST pull-down plus functional cell imaging with specific inhibitors, single lab with multiple orthogonal methods","pmids":["17287200"],"is_preprint":false},{"year":2008,"finding":"Vasopressin reduces LPS-induced pulmonary inflammation (IL-6 levels and NF-κB/IκB phosphorylation) through the V2R; pre-treatment with a V2R antagonist completely abolished vasopressin's immunosuppressive effects, placing V2R as the mediator of vasopressin's anti-inflammatory action in the lung.","method":"In vivo mouse LPS sepsis model, receptor-selective antagonist pre-treatment, immunoblotting for phospho-IκB, IL-6 ELISA","journal":"Resuscitation","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — pharmacological epistasis with selective antagonist in vivo, single lab, single study","pmids":["18951114"],"is_preprint":false},{"year":2008,"finding":"V2R promoter activity is increased by hypertonicity via JNK and PKA pathways, and is suppressed by V1aR stimulation (Ca2+ pathway); hypertonicity enhances V1aR-mediated suppression of V2R expression, revealing a counteracting regulatory mechanism between V1aR and V2R signaling.","method":"Luciferase reporter assays with rV2R promoter in LLC-PK1/rV1aR cells, JNK inhibitor (SP600125), PKA inhibitor (H89), intracellular Ca2+ measurements","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter reporter assay with kinase inhibitors and Ca2+ measurements in stable cell line, single lab","pmids":["18701631"],"is_preprint":false},{"year":2011,"finding":"V2R antagonists (OPC41061, OPC31260) act as protean agonists: they function as pharmacological chaperones that rescue membrane trafficking of inactivating NDI mutants (Ser-333del, Y128S) whose defect is defective membrane trafficking rather than internalization, while acting as inverse agonists of wild-type V2R.","method":"COS-7 cell expression, cAMP accumulation assay, immunofluorescence for subcellular localization, internalization inhibition experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cAMP assay combined with localization imaging and pharmacological rescue, single lab","pmids":["22144672"],"is_preprint":false},{"year":2015,"finding":"The I130N gain-of-function mutation in AVPR2 causes constitutive cAMP generation (nephrogenic syndrome of inappropriate antidiuresis, NSIAD); this constitutive activity does not lead to β-arrestin interaction, causing constitutive dynamin-dependent, β-arrestin-independent internalization, whereas agonist-induced endocytosis remains β-arrestin dependent.","method":"cAMP assay in HEK293 cells, dominant-negative dynamin transfection, surface expression ELISA, tolvaptan (inverse agonist) treatment","journal":"Kidney international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional cAMP and endocytosis assays with dominant-negative constructs and pharmacological tools, single lab","pmids":["26131744"],"is_preprint":false},{"year":2021,"finding":"Crystal structures of arrestin-2 in complex with four different phosphopeptides derived from the V2R C-tail revealed that single phospho-interaction changes cause conformational changes at remote arrestin sites; interdependent phospho-binding between different sites was demonstrated, providing a mechanism by which V2R phosphorylation patterns encode selective arrestin functions.","method":"X-ray crystallography, FRET, 1H NMR with genetic code expansion, multiple phosphopeptide complexes","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of four complexes with orthogonal validation by FRET and NMR, rigorous structural and functional characterization in one study","pmids":["33888704"],"is_preprint":false},{"year":2000,"finding":"A84D mutation near conserved D85 in AVPR2 causes receptor misfolding and ER retention, affecting both ligand binding and G protein coupling; W99R mutation at the start of the first extracellular loop greatly impairs ligand binding with minor effect on intracellular routing, indicating W99 is critical for high-affinity agonist binding.","method":"Functional expression in transfected cells, radioligand binding assays, adenylyl cyclase coupling assays, subcellular localization analysis","journal":"Journal of the American Society of Nephrology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — binding and signaling assays combined with localization, two mutations characterized, single lab","pmids":["10820167"],"is_preprint":false},{"year":2024,"finding":"The V2R-βarrestin complex scaffolds Gβγ at the plasma membrane through a direct βarrestin-Gβγ interaction, enabling Gβγ transport to endosomes; endosomal Gβγ then potentiates Gαs translocation to endosomes, regenerating an endosomal pool of heterotrimeric Gs for sustained non-canonical endosomal G protein signaling.","method":"GPCR signaling assays, protein-protein interaction studies, endosomal fractionation, V2R as model GPCR","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct interaction and endosomal translocation demonstrated with V2R as the model receptor, single lab","pmids":["38972875"],"is_preprint":false},{"year":2020,"finding":"NDI-causing AVPR2 mutants L86P, M272R, and W323_I324insR are retained in the ER with immature glycosylation and reduced stability; tolvaptan rescued M272R by restoring glycosylation maturation, membrane sorting, and dDAVP-stimulated cAMP response, demonstrating tolvaptan's pharmacochaperone activity for this specific mutant.","method":"MDCK cell expression, immunofluorescence, glycosylation maturation assay, cAMP assay, pharmacological rescue with tolvaptan, VX-809, sildenafil, ibuprofen","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical readouts (glycosylation, localization, cAMP) with pharmacological rescue, single lab","pmids":["33009446"],"is_preprint":false},{"year":2016,"finding":"Non-peptide V2R agonist OPC51803 acts both as a pharmacochaperone that promotes ER-retained mutant V2R maturation and trafficking to plasma membrane, and as a conventional agonist causing β-arrestin-dependent desensitization at the cell surface; a peptide antagonist blocked OPC51803-stimulated cAMP, indicating the agonist primarily activates cell-surface receptors.","method":"COS-7 and MDCK cell expression, cAMP accumulation assay, peptide antagonist blocking experiments, T273M and other mutant characterization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological dissection with antagonist blocking and cAMP assays, single lab","pmids":["27601473"],"is_preprint":false},{"year":2011,"finding":"A novel NDI-causing AVPR2 mutation L170P is retained in the ER; inhibition of the lysosome (but not proteasome) increased intracellular accumulation of L170P, whereas proteasome inhibition resulted in plasma membrane localization, revealing that misfolded AVPR2 is degraded via the lysosomal pathway and that proteasome inhibition can redirect it to the plasma membrane.","method":"MDCK cell culture, immunofluorescence, lysosomal inhibitor (chloroquine/bafilomycin) and proteasome inhibitor (MG132) treatment, expression level comparison","journal":"NDT plus","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological pathway dissection with orthogonal inhibitors, localization imaging, single lab","pmids":["21629670"],"is_preprint":false},{"year":2021,"finding":"A novel AVPR2 missense mutation (c.530T>A, L177Q) results in normal cell-surface expression of the receptor but significantly impaired cAMP accumulation in response to AVP stimulation, classifying it as a type III receptor mutant with a signaling defect rather than a trafficking defect.","method":"Immunofluorescence for subcellular localization in HEK-293T cells, cAMP assay after AVP stimulation, wild-type vs mutant comparison","journal":"Frontiers in pediatrics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single mutation, localization and cAMP only, no mechanistic follow-up of coupling defect","pmids":["34956990"],"is_preprint":false},{"year":2009,"finding":"Renal carcinoma cells (CAKI-2 and A498) express functional V2R; DDAVP (V2R agonist) induced cell proliferation, and this effect was completely blocked by selective V2R antagonist SR121463B, demonstrating that V2R activation drives proliferation in renal cancer cells via a cAMP-dependent mechanism.","method":"Immunofluorescence, RT-PCR for V2R expression, cell proliferation assay with DDAVP and SR121463B in cancer cell lines","journal":"Urologic oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pharmacological antagonism without deeper mechanistic dissection of downstream pathway","pmids":["19217806"],"is_preprint":false},{"year":2012,"finding":"V2R-mediated siRNA delivery is feasible: dDAVP conjugated to nine D-arginines (dDAVP-9r) bound V2R on IMCD cells, induced AQP2 phosphorylation at Ser256, and delivered siRNA specifically into V2R-expressing cells (MDCK, LLC-PK1) but not V2R-negative COS-7 cells, demonstrating ligand-induced V2R internalization can be exploited for receptor-mediated cargo delivery.","method":"Peptide synthesis, polyplex formation assay, fluorescein-labeled siRNA delivery, AQP2 phosphorylation immunoblot, V2R-negative cell control","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional receptor internalization demonstrated but mechanistic details of intracellular trafficking not resolved, single lab","pmids":["22761946"],"is_preprint":false}],"current_model":"AVPR2 (V2R) is a Gs-coupled GPCR expressed in renal collecting duct principal cells that, upon arginine vasopressin binding, activates adenylyl cyclase to generate cAMP, driving AQP2 phosphorylation and apical membrane insertion for water reabsorption; receptor quality control involves calnexin-assisted ER folding, with misfolded mutants undergoing lysosomal degradation, while correctly folded receptor at the plasma membrane is internalized in a dynamin/β-arrestin-dependent manner after agonist stimulation, with Alix accelerating lysosomal downregulation; the V2R–β-arrestin complex also scaffolds Gβγ for transport to endosomes where sustained Gαs signaling occurs; phosphorylation patterns on the V2R C-tail encode selective β-arrestin conformational states as revealed by crystal structures, and gain-of-function mutations cause constitutive cAMP production (NSIAD) via β-arrestin-independent constitutive internalization, while loss-of-function mutations cause NDI predominantly through ER retention and trafficking defects."},"narrative":{"mechanistic_narrative":"AVPR2 (V2R) is a Gs-coupled vasopressin receptor of renal collecting duct epithelia whose activation by arginine vasopressin drives cAMP-dependent AQP2 phosphorylation and apical insertion for water reabsorption; loss-of-function point mutations cause X-linked nephrogenic diabetes insipidus (NDI) [PMID:1303271]. High-affinity agonist binding and productive G protein coupling depend on specific residues in the extracellular and transmembrane regions, with mutations there separately impairing ligand binding, coupling, or folding [PMID:10820167]. A large class of NDI mutants are not signaling-defective but trafficking-defective: they misfold and are retained in the ER, where calnexin engages both wild-type and mutant precursors and shows prolonged association with ER-retained mutants as part of receptor quality control [PMID:11389590, PMID:9171234]. ER-retained misfolded V2R is cleared predominantly through the lysosomal rather than the proteasomal route [PMID:21629670], and small-molecule V2R ligands act as pharmacochaperones that restore glycosylation maturation, membrane trafficking, and agonist-stimulated cAMP signaling of trafficking-defective mutants [PMID:22144672, PMID:33009446, PMID:27601473]. After agonist stimulation, surface V2R is internalized into endosomes as a process separable from AQP2 surface accumulation [PMID:16563128], with Alix binding the V2R C-terminus to accelerate ligand-induced lysosomal downregulation [PMID:17287200]. The phosphorylated V2R C-tail encodes selective β-arrestin conformations, and the V2R–β-arrestin complex scaffolds Gβγ to drive sustained endosomal Gs signaling [PMID:33888704, PMID:38972875]. Gain-of-function mutation causes constitutive β-arrestin-independent, dynamin-dependent internalization underlying nephrogenic syndrome of inappropriate antidiuresis (NSIAD) [PMID:26131744].","teleology":[{"year":1992,"claim":"Established that AVPR2 itself is the disease gene, defining loss of V2R function as the molecular basis of X-linked NDI and grounding all subsequent mechanistic work in a clinical phenotype.","evidence":"Genomic sequencing and co-segregation analysis of missense mutations in NDI families","pmids":["1303271"],"confidence":"High","gaps":["Did not resolve at which step (binding, coupling, trafficking) each mutation fails","No structural basis for the affected conserved residues"]},{"year":1997,"claim":"Identified ER retention and failure to reach the plasma membrane as a mechanism of NDI mutation pathogenicity, distinguishing trafficking defects from signaling defects and defining a minimum C-terminal length required for ER export.","evidence":"Surface ELISA, endoglycosidase H, adenylyl cyclase and binding assays with truncation mutants in COS.M6/HEK293 cells","pmids":["9171234"],"confidence":"High","gaps":["Did not identify the chaperone machinery enforcing retention","Did not address how misfolded receptor is degraded"]},{"year":2000,"claim":"Mapped specific residues to discrete functional roles, separating folding/ER-retention defects from pure ligand-binding defects, refining the genotype-to-mechanism map for NDI.","evidence":"Radioligand binding, adenylyl cyclase coupling, and localization of A84D and W99R mutants in transfected cells","pmids":["10820167"],"confidence":"Medium","gaps":["Only two mutations characterized","No structural model of binding pocket"]},{"year":2001,"claim":"Implicated calnexin in AVPR2 ER quality control, providing the chaperone mechanism that retains misfolded NDI mutants in the ER.","evidence":"Sequential co-IP, glycosylation maturation, and confocal localization of WT and mutant receptors in transfected cells","pmids":["11389590"],"confidence":"High","gaps":["Did not define the degradative fate of calnexin-retained mutants","Other co-chaperones not characterized"]},{"year":2006,"claim":"Separated V2R endocytosis from AQP2 trafficking in space and time, showing the agonist-induced endocytic burst reflects receptor internalization rather than cAMP elevation.","evidence":"Live-cell confocal imaging of tagged V2R and AQP2 in polarized LLC-PK1 cells with forskolin controls","pmids":["16563128"],"confidence":"High","gaps":["Endocytic adaptors driving V2R internalization not identified here","Fate of internalized receptor unresolved"]},{"year":2007,"claim":"Identified Alix as a direct V2R C-terminal partner that accelerates agonist-induced lysosomal degradation, defining a mechanism for vasopressin-induced receptor downregulation.","evidence":"Yeast two-hybrid, GST pull-down, co-localization, and chloroquine/MG132 inhibitor experiments in LLC-PK1 cells","pmids":["17287200"],"confidence":"High","gaps":["Whether Alix acts via ESCRT for V2R sorting not resolved","In vivo contribution to renal V2R turnover untested"]},{"year":2008,"claim":"Extended V2R biology beyond the kidney by implicating it in vasopressin's anti-inflammatory action in the lung, and defined transcriptional regulation of V2R by hypertonicity and counteracting V1aR signaling.","evidence":"In vivo LPS sepsis model with V2R antagonist; V2R promoter luciferase reporter with JNK/PKA inhibitors and Ca2+ measurements","pmids":["18951114","18701631"],"confidence":"Medium","gaps":["Cell type mediating lung anti-inflammatory effect not identified","Promoter regulation shown in cell line, not validated in vivo"]},{"year":2011,"claim":"Demonstrated that V2R antagonists can act as pharmacochaperones (protean agonists) rescuing trafficking-defective mutants, and clarified that misfolded V2R is degraded lysosomally with proteasome inhibition redirecting it to the surface.","evidence":"cAMP assays, localization imaging, and inverse-agonist rescue (OPC compounds); lysosome vs proteasome inhibitor dissection of L170P in MDCK cells","pmids":["22144672","21629670"],"confidence":"Medium","gaps":["Generalizability across mutant classes incomplete","Mechanism by which ligand binding promotes folding not structurally defined"]},{"year":2015,"claim":"Defined the gain-of-function NSIAD mechanism, showing constitutive cAMP generation with β-arrestin-independent, dynamin-dependent internalization, contrasting with agonist-induced β-arrestin-dependent endocytosis.","evidence":"cAMP assays, dominant-negative dynamin, surface ELISA, and tolvaptan treatment of I130N in HEK293 cells","pmids":["26131744"],"confidence":"Medium","gaps":["Structural basis of constitutive activity not resolved","How constitutive activity escapes β-arrestin engagement unexplained"]},{"year":2016,"claim":"Showed a single non-peptide ligand can both rescue ER-retained mutant maturation and act as a surface agonist driving β-arrestin-dependent desensitization, illustrating dual pharmacochaperone/agonist behavior.","evidence":"cAMP assays with peptide antagonist blocking and mutant characterization in COS-7/MDCK cells","pmids":["27601473"],"confidence":"Medium","gaps":["Balance of intracellular rescue versus surface activation not quantified per mutant","Therapeutic window untested in vivo"]},{"year":2020,"claim":"Validated tolvaptan pharmacochaperone rescue across multiple ER-retained NDI mutants by restoring glycosylation maturation, sorting, and cAMP response.","evidence":"Glycosylation, localization, and cAMP assays with multiple rescue compounds for L86P/M272R/W323_I324insR in MDCK cells","pmids":["33009446"],"confidence":"Medium","gaps":["Mutant-specific responsiveness not predictable a priori","In vivo efficacy not established"]},{"year":2021,"claim":"Provided the structural logic for biased signaling by showing V2R C-tail phosphorylation patterns encode distinct β-arrestin conformations through interdependent phospho-binding; separately identified a pure signaling-defect (type III) NDI mutant.","evidence":"X-ray crystallography of four arrestin-2/phosphopeptide complexes with FRET/NMR; localization and cAMP assay of L177Q in HEK-293T cells","pmids":["33888704","34956990"],"confidence":"High","gaps":["Full-length phosphorylated V2R–arrestin structure not solved","L177Q coupling defect not mechanistically dissected (Low confidence)"]},{"year":2024,"claim":"Established that the V2R–β-arrestin complex scaffolds Gβγ to regenerate an endosomal Gs pool, explaining sustained non-canonical endosomal Gαs signaling.","evidence":"Protein-protein interaction studies and endosomal fractionation using V2R as a model GPCR","pmids":["38972875"],"confidence":"Medium","gaps":["Physiological consequence of endosomal signaling for renal water handling not established","Structural basis of the β-arrestin–Gβγ interaction undefined"]},{"year":null,"claim":"How distinct C-tail phosphorylation barcodes and endosomal Gs signaling translate into the divergent physiological and disease outcomes of V2R activation in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No in vivo link between endosomal signaling and AQP2-mediated water reabsorption","Predictive mutation-to-mechanism-to-therapy mapping incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2,10]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,9,11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,3,8]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1,2,14]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[3,11]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[4,14]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,8,11]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2,12]}],"complexes":[],"partners":["ARRB2","PDCD6IP","CANX","GNB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P30518","full_name":"Vasopressin V2 receptor","aliases":["AVPR V2","Antidiuretic hormone receptor","Renal-type arginine vasopressin receptor"],"length_aa":371,"mass_kda":40.3,"function":"G-protein-coupled receptor for arginine vasopressin, an antidiuretic that promotes renal water reabsorption (PubMed:1534149, PubMed:19440390, PubMed:33664408, PubMed:33742150). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of downstream effectors, such as adenylate cyclase (cAMP) (PubMed:33664408, PubMed:33742150). AVPR2 is coupled to G(s) G alpha proteins and mediates activation of adenylate cyclase activity (PubMed:33664408, PubMed:33742150)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P30518/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/AVPR2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/AVPR2","total_profiled":1310},"omim":[{"mim_id":"621542","title":"ARRESTIN DOMAIN-CONTAINING PROTEIN 2; ARRDC2","url":"https://www.omim.org/entry/621542"},{"mim_id":"619788","title":"ARRESTIN DOMAIN-CONTAINING PROTEIN 4; ARRDC4","url":"https://www.omim.org/entry/619788"},{"mim_id":"618537","title":"ARGININE VASOPRESSIN-INDUCED PROTEIN 1; AVPI1","url":"https://www.omim.org/entry/618537"},{"mim_id":"612464","title":"ARRESTIN DOMAIN-CONTAINING PROTEIN 3; ARRDC3","url":"https://www.omim.org/entry/612464"},{"mim_id":"610365","title":"C1q- AND TUMOR NECROSIS FACTOR-RELATED PROTEIN 1; C1QTNF1","url":"https://www.omim.org/entry/610365"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose tissue","ntpm":9.6},{"tissue":"kidney","ntpm":12.5}],"url":"https://www.proteinatlas.org/search/AVPR2"},"hgnc":{"alias_symbol":["V2R"],"prev_symbol":["DIR3","DIR"]},"alphafold":{"accession":"P30518","domains":[{"cath_id":"1.20.1070.10","chopping":"36-237_263-341","consensus_level":"high","plddt":87.0785,"start":36,"end":341}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P30518","model_url":"https://alphafold.ebi.ac.uk/files/AF-P30518-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P30518-F1-predicted_aligned_error_v6.png","plddt_mean":76.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=AVPR2","jax_strain_url":"https://www.jax.org/strain/search?query=AVPR2"},"sequence":{"accession":"P30518","fasta_url":"https://rest.uniprot.org/uniprotkb/P30518.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P30518/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P30518"}},"corpus_meta":[{"pmid":"9245589","id":"PMC_9245589","title":"Sequence of the human immunoglobulin diversity (D) segment locus: a systematic analysis provides no evidence for the use of DIR segments, inverted D segments, \"minor\" D segments or D-D recombination.","date":"1997","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/9245589","citation_count":221,"is_preprint":false},{"pmid":"12628182","id":"PMC_12628182","title":"Functional expression of murine V2R pheromone receptors involves selective association with the M10 and M1 families of MHC class Ib molecules.","date":"2003","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/12628182","citation_count":212,"is_preprint":false},{"pmid":"1303271","id":"PMC_1303271","title":"Mutations in the vasopressin type 2 receptor gene (AVPR2) associated with nephrogenic diabetes insipidus.","date":"1992","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/1303271","citation_count":162,"is_preprint":false},{"pmid":"17382427","id":"PMC_17382427","title":"V2R gene families degenerated in primates, dog and cow, but expanded in opossum.","date":"2007","source":"Trends in genetics : TIG","url":"https://pubmed.ncbi.nlm.nih.gov/17382427","citation_count":128,"is_preprint":false},{"pmid":"20399016","id":"PMC_20399016","title":"A comparative study of human health risks via consumption of food crops grown on wastewater irrigated soil (Peshawar) and relatively clean water irrigated soil (lower Dir).","date":"2010","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/20399016","citation_count":128,"is_preprint":false},{"pmid":"8037205","id":"PMC_8037205","title":"Nature and recurrence of AVPR2 mutations in X-linked nephrogenic diabetes insipidus.","date":"1994","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8037205","citation_count":125,"is_preprint":false},{"pmid":"16463097","id":"PMC_16463097","title":"Dirigent proteins in conifer defense: gene discovery, phylogeny, and differential wound- and 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reports","url":"https://pubmed.ncbi.nlm.nih.gov/28165501","citation_count":8,"is_preprint":false},{"pmid":"30952965","id":"PMC_30952965","title":"Longitudinal monitoring of cancer cell subpopulations in monolayers, 3D spheroids, and xenografts using the photoconvertible dye DiR.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30952965","citation_count":8,"is_preprint":false},{"pmid":"27117808","id":"PMC_27117808","title":"A novel mutation affecting the arginine-137 residue of AVPR2 in dizygous twins leads to nephrogenic diabetes insipidus and attenuated urine exosome aquaporin-2.","date":"2016","source":"Physiological reports","url":"https://pubmed.ncbi.nlm.nih.gov/27117808","citation_count":8,"is_preprint":false},{"pmid":"7868891","id":"PMC_7868891","title":"Recombination potential of the human DIR elements.","date":"1995","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/7868891","citation_count":8,"is_preprint":false},{"pmid":"3265307","id":"PMC_3265307","title":"Giemsa-11 technique elucidating three structurally altered nonfluorescent Y chromosomes: r (Y), idic (Yp), dir tan dup (Yp).","date":"1988","source":"Annales de genetique","url":"https://pubmed.ncbi.nlm.nih.gov/3265307","citation_count":8,"is_preprint":false},{"pmid":"33721131","id":"PMC_33721131","title":"β-Arrestin inhibition induces autophagy, apoptosis, G0/G1 cell cycle arrest in agonist-activated V2R receptor in breast cancer cells.","date":"2021","source":"Medical oncology (Northwood, London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/33721131","citation_count":7,"is_preprint":false},{"pmid":"34101133","id":"PMC_34101133","title":"Novel AVPR2 mutations and clinical characteristics in 28 Chinese families with congenital nephrogenic diabetes insipidus.","date":"2021","source":"Journal of endocrinological investigation","url":"https://pubmed.ncbi.nlm.nih.gov/34101133","citation_count":7,"is_preprint":false},{"pmid":"31691500","id":"PMC_31691500","title":"Periconceptional ethanol exposure induces a sex specific diuresis and increase in AQP2 and AVPR2 in the kidneys of aged rat offspring.","date":"2019","source":"Physiological reports","url":"https://pubmed.ncbi.nlm.nih.gov/31691500","citation_count":7,"is_preprint":false},{"pmid":"29472987","id":"PMC_29472987","title":"Adult female with symptomatic AVPR2-related nephrogenic syndrome of inappropriate antidiuresis (NSIAD).","date":"2018","source":"Endocrinology, diabetes & metabolism case reports","url":"https://pubmed.ncbi.nlm.nih.gov/29472987","citation_count":7,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":49113,"output_tokens":4572,"usd":0.107959,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12704,"output_tokens":4305,"usd":0.085572,"stage2_stop_reason":"end_turn"},"total_usd":0.193531,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1992,\n      \"finding\": \"Point mutations in the AVPR2 gene (encoding the renal vasopressin V2 receptor) cause X-linked nephrogenic diabetes insipidus (NDI); missense mutations in conserved extracellular regions of AVPR2 co-segregate with NDI, establishing AVPR2 loss-of-function as the molecular basis of the disorder.\",\n      \"method\": \"Genomic sequencing, genetic mapping, co-segregation analysis in NDI families\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-segregation in multiple independent families, replicated extensively in subsequent studies\",\n      \"pmids\": [\"1303271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Calnexin, an ER chaperone, associates with precursor forms of both wild-type and mutant AVPR2 receptors; ER-retained NDI mutants (e.g., W71X, R337X) show prolonged calnexin association compared to wild-type, indicating calnexin participates in quality control and ER retention of misfolded AVPR2.\",\n      \"method\": \"Sequential co-immunoprecipitation, immunofluorescence, confocal microscopy, Western blot, endoglycosidase H treatment in transfected cells\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP with functional follow-up (glycosylation maturation, localization), single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11389590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The NDI-causing truncation mutant V2R-R337ter is non-functional because it is retained in the ER and fails to reach the plasma membrane; a minimum C-terminal length (requiring at least residues up to position 341, with identity of residue 340 being important) is required for ER export and plasma membrane expression of AVPR2.\",\n      \"method\": \"ELISA on surface-tagged receptors, endoglycosidase H assay, adenylyl cyclase activity, binding assays, metabolic labeling in COS.M6 and HEK293 cells\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal biochemical assays (binding, signaling, glycosylation, surface ELISA) with systematic truncation mutagenesis, single lab\",\n      \"pmids\": [\"9171234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"After vasopressin (VP) stimulation of renal epithelial cells, V2R is rapidly internalized into endosomes while AQP2 accumulates at the cell surface in endocytosis-resistant membrane domains; V2R endocytosis and AQP2 trafficking are spatially and temporally separable events, and the initial burst of endocytosis upon VP addition is due to V2R internalization rather than cAMP elevation.\",\n      \"method\": \"Confocal live-cell imaging, epitope-tagged V2R and AQP2 in LLC-PK1 cells, forskolin control, FITC-dextran fluid-phase marker, polarized filter-grown cells\",\n      \"journal\": \"Biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple imaging and pharmacological approaches in the same system, clear functional separation of V2R and AQP2 trafficking, single lab\",\n      \"pmids\": [\"16563128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Alix (AIP1) directly interacts with the last 29 amino acids of the V2R C-terminus; upon vasopressin stimulation, Alix accelerates lysosomal (not proteasomal) degradation of V2R, providing a mechanism for VP-induced receptor downregulation in kidney principal cells.\",\n      \"method\": \"Yeast two-hybrid screening, GST pull-down assay, co-immunolocalization, V2R-GFP transfection in LLC-PK1 cells, Western blot, chloroquine and MG132 inhibitor experiments\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus GST pull-down plus functional cell imaging with specific inhibitors, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"17287200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Vasopressin reduces LPS-induced pulmonary inflammation (IL-6 levels and NF-κB/IκB phosphorylation) through the V2R; pre-treatment with a V2R antagonist completely abolished vasopressin's immunosuppressive effects, placing V2R as the mediator of vasopressin's anti-inflammatory action in the lung.\",\n      \"method\": \"In vivo mouse LPS sepsis model, receptor-selective antagonist pre-treatment, immunoblotting for phospho-IκB, IL-6 ELISA\",\n      \"journal\": \"Resuscitation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — pharmacological epistasis with selective antagonist in vivo, single lab, single study\",\n      \"pmids\": [\"18951114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"V2R promoter activity is increased by hypertonicity via JNK and PKA pathways, and is suppressed by V1aR stimulation (Ca2+ pathway); hypertonicity enhances V1aR-mediated suppression of V2R expression, revealing a counteracting regulatory mechanism between V1aR and V2R signaling.\",\n      \"method\": \"Luciferase reporter assays with rV2R promoter in LLC-PK1/rV1aR cells, JNK inhibitor (SP600125), PKA inhibitor (H89), intracellular Ca2+ measurements\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter reporter assay with kinase inhibitors and Ca2+ measurements in stable cell line, single lab\",\n      \"pmids\": [\"18701631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"V2R antagonists (OPC41061, OPC31260) act as protean agonists: they function as pharmacological chaperones that rescue membrane trafficking of inactivating NDI mutants (Ser-333del, Y128S) whose defect is defective membrane trafficking rather than internalization, while acting as inverse agonists of wild-type V2R.\",\n      \"method\": \"COS-7 cell expression, cAMP accumulation assay, immunofluorescence for subcellular localization, internalization inhibition experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cAMP assay combined with localization imaging and pharmacological rescue, single lab\",\n      \"pmids\": [\"22144672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The I130N gain-of-function mutation in AVPR2 causes constitutive cAMP generation (nephrogenic syndrome of inappropriate antidiuresis, NSIAD); this constitutive activity does not lead to β-arrestin interaction, causing constitutive dynamin-dependent, β-arrestin-independent internalization, whereas agonist-induced endocytosis remains β-arrestin dependent.\",\n      \"method\": \"cAMP assay in HEK293 cells, dominant-negative dynamin transfection, surface expression ELISA, tolvaptan (inverse agonist) treatment\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional cAMP and endocytosis assays with dominant-negative constructs and pharmacological tools, single lab\",\n      \"pmids\": [\"26131744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structures of arrestin-2 in complex with four different phosphopeptides derived from the V2R C-tail revealed that single phospho-interaction changes cause conformational changes at remote arrestin sites; interdependent phospho-binding between different sites was demonstrated, providing a mechanism by which V2R phosphorylation patterns encode selective arrestin functions.\",\n      \"method\": \"X-ray crystallography, FRET, 1H NMR with genetic code expansion, multiple phosphopeptide complexes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of four complexes with orthogonal validation by FRET and NMR, rigorous structural and functional characterization in one study\",\n      \"pmids\": [\"33888704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"A84D mutation near conserved D85 in AVPR2 causes receptor misfolding and ER retention, affecting both ligand binding and G protein coupling; W99R mutation at the start of the first extracellular loop greatly impairs ligand binding with minor effect on intracellular routing, indicating W99 is critical for high-affinity agonist binding.\",\n      \"method\": \"Functional expression in transfected cells, radioligand binding assays, adenylyl cyclase coupling assays, subcellular localization analysis\",\n      \"journal\": \"Journal of the American Society of Nephrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — binding and signaling assays combined with localization, two mutations characterized, single lab\",\n      \"pmids\": [\"10820167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The V2R-βarrestin complex scaffolds Gβγ at the plasma membrane through a direct βarrestin-Gβγ interaction, enabling Gβγ transport to endosomes; endosomal Gβγ then potentiates Gαs translocation to endosomes, regenerating an endosomal pool of heterotrimeric Gs for sustained non-canonical endosomal G protein signaling.\",\n      \"method\": \"GPCR signaling assays, protein-protein interaction studies, endosomal fractionation, V2R as model GPCR\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct interaction and endosomal translocation demonstrated with V2R as the model receptor, single lab\",\n      \"pmids\": [\"38972875\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NDI-causing AVPR2 mutants L86P, M272R, and W323_I324insR are retained in the ER with immature glycosylation and reduced stability; tolvaptan rescued M272R by restoring glycosylation maturation, membrane sorting, and dDAVP-stimulated cAMP response, demonstrating tolvaptan's pharmacochaperone activity for this specific mutant.\",\n      \"method\": \"MDCK cell expression, immunofluorescence, glycosylation maturation assay, cAMP assay, pharmacological rescue with tolvaptan, VX-809, sildenafil, ibuprofen\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical readouts (glycosylation, localization, cAMP) with pharmacological rescue, single lab\",\n      \"pmids\": [\"33009446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Non-peptide V2R agonist OPC51803 acts both as a pharmacochaperone that promotes ER-retained mutant V2R maturation and trafficking to plasma membrane, and as a conventional agonist causing β-arrestin-dependent desensitization at the cell surface; a peptide antagonist blocked OPC51803-stimulated cAMP, indicating the agonist primarily activates cell-surface receptors.\",\n      \"method\": \"COS-7 and MDCK cell expression, cAMP accumulation assay, peptide antagonist blocking experiments, T273M and other mutant characterization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological dissection with antagonist blocking and cAMP assays, single lab\",\n      \"pmids\": [\"27601473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A novel NDI-causing AVPR2 mutation L170P is retained in the ER; inhibition of the lysosome (but not proteasome) increased intracellular accumulation of L170P, whereas proteasome inhibition resulted in plasma membrane localization, revealing that misfolded AVPR2 is degraded via the lysosomal pathway and that proteasome inhibition can redirect it to the plasma membrane.\",\n      \"method\": \"MDCK cell culture, immunofluorescence, lysosomal inhibitor (chloroquine/bafilomycin) and proteasome inhibitor (MG132) treatment, expression level comparison\",\n      \"journal\": \"NDT plus\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological pathway dissection with orthogonal inhibitors, localization imaging, single lab\",\n      \"pmids\": [\"21629670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A novel AVPR2 missense mutation (c.530T>A, L177Q) results in normal cell-surface expression of the receptor but significantly impaired cAMP accumulation in response to AVP stimulation, classifying it as a type III receptor mutant with a signaling defect rather than a trafficking defect.\",\n      \"method\": \"Immunofluorescence for subcellular localization in HEK-293T cells, cAMP assay after AVP stimulation, wild-type vs mutant comparison\",\n      \"journal\": \"Frontiers in pediatrics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single mutation, localization and cAMP only, no mechanistic follow-up of coupling defect\",\n      \"pmids\": [\"34956990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Renal carcinoma cells (CAKI-2 and A498) express functional V2R; DDAVP (V2R agonist) induced cell proliferation, and this effect was completely blocked by selective V2R antagonist SR121463B, demonstrating that V2R activation drives proliferation in renal cancer cells via a cAMP-dependent mechanism.\",\n      \"method\": \"Immunofluorescence, RT-PCR for V2R expression, cell proliferation assay with DDAVP and SR121463B in cancer cell lines\",\n      \"journal\": \"Urologic oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pharmacological antagonism without deeper mechanistic dissection of downstream pathway\",\n      \"pmids\": [\"19217806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"V2R-mediated siRNA delivery is feasible: dDAVP conjugated to nine D-arginines (dDAVP-9r) bound V2R on IMCD cells, induced AQP2 phosphorylation at Ser256, and delivered siRNA specifically into V2R-expressing cells (MDCK, LLC-PK1) but not V2R-negative COS-7 cells, demonstrating ligand-induced V2R internalization can be exploited for receptor-mediated cargo delivery.\",\n      \"method\": \"Peptide synthesis, polyplex formation assay, fluorescein-labeled siRNA delivery, AQP2 phosphorylation immunoblot, V2R-negative cell control\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional receptor internalization demonstrated but mechanistic details of intracellular trafficking not resolved, single lab\",\n      \"pmids\": [\"22761946\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"AVPR2 (V2R) is a Gs-coupled GPCR expressed in renal collecting duct principal cells that, upon arginine vasopressin binding, activates adenylyl cyclase to generate cAMP, driving AQP2 phosphorylation and apical membrane insertion for water reabsorption; receptor quality control involves calnexin-assisted ER folding, with misfolded mutants undergoing lysosomal degradation, while correctly folded receptor at the plasma membrane is internalized in a dynamin/β-arrestin-dependent manner after agonist stimulation, with Alix accelerating lysosomal downregulation; the V2R–β-arrestin complex also scaffolds Gβγ for transport to endosomes where sustained Gαs signaling occurs; phosphorylation patterns on the V2R C-tail encode selective β-arrestin conformational states as revealed by crystal structures, and gain-of-function mutations cause constitutive cAMP production (NSIAD) via β-arrestin-independent constitutive internalization, while loss-of-function mutations cause NDI predominantly through ER retention and trafficking defects.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AVPR2 (V2R) is a Gs-coupled vasopressin receptor of renal collecting duct epithelia whose activation by arginine vasopressin drives cAMP-dependent AQP2 phosphorylation and apical insertion for water reabsorption; loss-of-function point mutations cause X-linked nephrogenic diabetes insipidus (NDI) [#0]. High-affinity agonist binding and productive G protein coupling depend on specific residues in the extracellular and transmembrane regions, with mutations there separately impairing ligand binding, coupling, or folding [#10]. A large class of NDI mutants are not signaling-defective but trafficking-defective: they misfold and are retained in the ER, where calnexin engages both wild-type and mutant precursors and shows prolonged association with ER-retained mutants as part of receptor quality control [#1, #2]. ER-retained misfolded V2R is cleared predominantly through the lysosomal rather than the proteasomal route [#14], and small-molecule V2R ligands act as pharmacochaperones that restore glycosylation maturation, membrane trafficking, and agonist-stimulated cAMP signaling of trafficking-defective mutants [#7, #12, #13]. After agonist stimulation, surface V2R is internalized into endosomes as a process separable from AQP2 surface accumulation [#3], with Alix binding the V2R C-terminus to accelerate ligand-induced lysosomal downregulation [#4]. The phosphorylated V2R C-tail encodes selective \\u03b2-arrestin conformations, and the V2R\\u2013\\u03b2-arrestin complex scaffolds G\\u03b2\\u03b3 to drive sustained endosomal Gs signaling [#9, #11]. Gain-of-function mutation causes constitutive \\u03b2-arrestin-independent, dynamin-dependent internalization underlying nephrogenic syndrome of inappropriate antidiuresis (NSIAD) [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that AVPR2 itself is the disease gene, defining loss of V2R function as the molecular basis of X-linked NDI and grounding all subsequent mechanistic work in a clinical phenotype.\",\n      \"evidence\": \"Genomic sequencing and co-segregation analysis of missense mutations in NDI families\",\n      \"pmids\": [\"1303271\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve at which step (binding, coupling, trafficking) each mutation fails\", \"No structural basis for the affected conserved residues\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identified ER retention and failure to reach the plasma membrane as a mechanism of NDI mutation pathogenicity, distinguishing trafficking defects from signaling defects and defining a minimum C-terminal length required for ER export.\",\n      \"evidence\": \"Surface ELISA, endoglycosidase H, adenylyl cyclase and binding assays with truncation mutants in COS.M6/HEK293 cells\",\n      \"pmids\": [\"9171234\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the chaperone machinery enforcing retention\", \"Did not address how misfolded receptor is degraded\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Mapped specific residues to discrete functional roles, separating folding/ER-retention defects from pure ligand-binding defects, refining the genotype-to-mechanism map for NDI.\",\n      \"evidence\": \"Radioligand binding, adenylyl cyclase coupling, and localization of A84D and W99R mutants in transfected cells\",\n      \"pmids\": [\"10820167\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only two mutations characterized\", \"No structural model of binding pocket\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Implicated calnexin in AVPR2 ER quality control, providing the chaperone mechanism that retains misfolded NDI mutants in the ER.\",\n      \"evidence\": \"Sequential co-IP, glycosylation maturation, and confocal localization of WT and mutant receptors in transfected cells\",\n      \"pmids\": [\"11389590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the degradative fate of calnexin-retained mutants\", \"Other co-chaperones not characterized\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Separated V2R endocytosis from AQP2 trafficking in space and time, showing the agonist-induced endocytic burst reflects receptor internalization rather than cAMP elevation.\",\n      \"evidence\": \"Live-cell confocal imaging of tagged V2R and AQP2 in polarized LLC-PK1 cells with forskolin controls\",\n      \"pmids\": [\"16563128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endocytic adaptors driving V2R internalization not identified here\", \"Fate of internalized receptor unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified Alix as a direct V2R C-terminal partner that accelerates agonist-induced lysosomal degradation, defining a mechanism for vasopressin-induced receptor downregulation.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, co-localization, and chloroquine/MG132 inhibitor experiments in LLC-PK1 cells\",\n      \"pmids\": [\"17287200\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Alix acts via ESCRT for V2R sorting not resolved\", \"In vivo contribution to renal V2R turnover untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Extended V2R biology beyond the kidney by implicating it in vasopressin's anti-inflammatory action in the lung, and defined transcriptional regulation of V2R by hypertonicity and counteracting V1aR signaling.\",\n      \"evidence\": \"In vivo LPS sepsis model with V2R antagonist; V2R promoter luciferase reporter with JNK/PKA inhibitors and Ca2+ measurements\",\n      \"pmids\": [\"18951114\", \"18701631\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell type mediating lung anti-inflammatory effect not identified\", \"Promoter regulation shown in cell line, not validated in vivo\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated that V2R antagonists can act as pharmacochaperones (protean agonists) rescuing trafficking-defective mutants, and clarified that misfolded V2R is degraded lysosomally with proteasome inhibition redirecting it to the surface.\",\n      \"evidence\": \"cAMP assays, localization imaging, and inverse-agonist rescue (OPC compounds); lysosome vs proteasome inhibitor dissection of L170P in MDCK cells\",\n      \"pmids\": [\"22144672\", \"21629670\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generalizability across mutant classes incomplete\", \"Mechanism by which ligand binding promotes folding not structurally defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the gain-of-function NSIAD mechanism, showing constitutive cAMP generation with \\u03b2-arrestin-independent, dynamin-dependent internalization, contrasting with agonist-induced \\u03b2-arrestin-dependent endocytosis.\",\n      \"evidence\": \"cAMP assays, dominant-negative dynamin, surface ELISA, and tolvaptan treatment of I130N in HEK293 cells\",\n      \"pmids\": [\"26131744\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of constitutive activity not resolved\", \"How constitutive activity escapes \\u03b2-arrestin engagement unexplained\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed a single non-peptide ligand can both rescue ER-retained mutant maturation and act as a surface agonist driving \\u03b2-arrestin-dependent desensitization, illustrating dual pharmacochaperone/agonist behavior.\",\n      \"evidence\": \"cAMP assays with peptide antagonist blocking and mutant characterization in COS-7/MDCK cells\",\n      \"pmids\": [\"27601473\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Balance of intracellular rescue versus surface activation not quantified per mutant\", \"Therapeutic window untested in vivo\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Validated tolvaptan pharmacochaperone rescue across multiple ER-retained NDI mutants by restoring glycosylation maturation, sorting, and cAMP response.\",\n      \"evidence\": \"Glycosylation, localization, and cAMP assays with multiple rescue compounds for L86P/M272R/W323_I324insR in MDCK cells\",\n      \"pmids\": [\"33009446\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mutant-specific responsiveness not predictable a priori\", \"In vivo efficacy not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the structural logic for biased signaling by showing V2R C-tail phosphorylation patterns encode distinct \\u03b2-arrestin conformations through interdependent phospho-binding; separately identified a pure signaling-defect (type III) NDI mutant.\",\n      \"evidence\": \"X-ray crystallography of four arrestin-2/phosphopeptide complexes with FRET/NMR; localization and cAMP assay of L177Q in HEK-293T cells\",\n      \"pmids\": [\"33888704\", \"34956990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length phosphorylated V2R\\u2013arrestin structure not solved\", \"L177Q coupling defect not mechanistically dissected (Low confidence)\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established that the V2R\\u2013\\u03b2-arrestin complex scaffolds G\\u03b2\\u03b3 to regenerate an endosomal Gs pool, explaining sustained non-canonical endosomal G\\u03b1s signaling.\",\n      \"evidence\": \"Protein-protein interaction studies and endosomal fractionation using V2R as a model GPCR\",\n      \"pmids\": [\"38972875\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological consequence of endosomal signaling for renal water handling not established\", \"Structural basis of the \\u03b2-arrestin\\u2013G\\u03b2\\u03b3 interaction undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How distinct C-tail phosphorylation barcodes and endosomal Gs signaling translate into the divergent physiological and disease outcomes of V2R activation in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo link between endosomal signaling and AQP2-mediated water reabsorption\", \"Predictive mutation-to-mechanism-to-therapy mapping incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2, 10]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 9, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 3, 8]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1, 2, 14]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [3, 11]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [4, 14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 8, 11]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2, 12]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ARRB2\", \"PDCD6IP\", \"CANX\", \"GNB1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}