{"gene":"TRPV5","run_date":"2026-04-28T21:43:00","timeline":{"discoveries":[{"year":2003,"finding":"TRPV5 knockout mice display severely impaired active Ca2+ reabsorption in the early distal convoluted tubule, hypercalciuria, compensatory intestinal Ca2+ hyperabsorption, and reduced trabecular and cortical bone thickness, establishing TRPV5 as the key apical Ca2+ entry channel for active renal Ca2+ reabsorption.","method":"Genetic knockout (TRPV5-/- mice), in vivo micropuncture, metabolic cage studies, bone morphometry","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple defined phenotypic readouts; foundational study replicated across labs","pmids":["14679186"],"is_preprint":false},{"year":2003,"finding":"TRPV5 and TRPV6 form homotetramers (~400 kDa) and can assemble into heterotetramers with each other; N- and C-terminal intracellular tails mediate subunit assembly, and heterotetrameric complexes display distinct Ca2+-dependent inactivation, ion selectivity, and pharmacological block compared to homotetramers.","method":"Sucrose gradient sedimentation, co-immunoprecipitation, concatemer electrophysiology with pore mutants, HEK293 patch-clamp","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (sedimentation, co-IP, electrophysiology with dominant-negative pore mutant)","pmids":["12574114"],"is_preprint":false},{"year":2003,"finding":"S100A10 binds the conserved VATTV motif (specifically Thr599) in the TRPV5 C-terminal tail, and the S100A10–annexin 2 complex is required to route TRPV5 to the plasma membrane; mutation T599A or siRNA knockdown of annexin 2 abolishes surface expression and channel activity.","method":"Yeast two-hybrid, GST pull-down, co-immunoprecipitation, site-directed mutagenesis, siRNA knockdown, electrophysiology","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including mutagenesis, pulldown, co-IP, and functional assay","pmids":["12660155"],"is_preprint":false},{"year":2005,"finding":"Klotho, acting as a beta-glucuronidase, hydrolyzes extracellular N-linked oligosaccharides on TRPV5, trapping the channel in the plasma membrane and sustaining Ca2+ channel activity in the kidney.","method":"Enzymatic activity assay (beta-glucuronidase), Ca2+ influx measurements in transfected cells, cell-surface biotinylation","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 — enzymatic mechanism directly demonstrated; highly cited foundational study","pmids":["16239475"],"is_preprint":false},{"year":2005,"finding":"PIP2 activates TRPV5 and protects against Mg2+-induced slow channel inhibition; intracellular Mg2+ binding to the selectivity filter (Asp542) causes both fast voltage-dependent block and a slower conformational change leading to channel closure, and PIP2 prevents the latter without affecting Mg2+ binding to the selectivity filter.","method":"Whole-cell and inside-out patch clamp, site-directed mutagenesis (D542), PIP2 application and PLC activation","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1 — in vitro electrophysiology with mutagenesis of critical residue, multiple conditions tested","pmids":["16230466"],"is_preprint":false},{"year":2005,"finding":"TRPV5 is essential for osteoclastic bone resorption; TRPV5 localizes to the osteoclast ruffled border membrane, and TRPV5-/- osteoclasts show increased numbers but severely impaired Ca2+ resorption activity in pit assays.","method":"TRPV5-/- mouse analysis, immunostaining, bone marrow culture, resorption pit assay, urine deoxypyridinoline measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with in vitro functional assay and in vivo measures; defined localization and phenotype","pmids":["16291808"],"is_preprint":false},{"year":2006,"finding":"Calbindin-D28K directly associates with TRPV5 at low intracellular Ca2+ concentrations, translocating to the plasma membrane; this association buffers Ca2+ flux near the TRPV5 pore, preventing Ca2+-dependent inactivation and enabling high Ca2+ transport rates.","method":"Protein-binding analysis, subcellular fractionation, evanescent-field (TIRF) microscopy, 45Ca2+ uptake, electrophysiology, primary connecting tubule/DCT cells","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 — direct physical interaction shown by multiple methods plus functional consequence in primary cells","pmids":["16763551"],"is_preprint":false},{"year":2006,"finding":"GDP-bound Rab11a directly interacts with a conserved C-terminal stretch of TRPV5 and co-localizes with TRPV5 in sub-apical vesicles; dominant-negative GDP-locked Rab11a reduces surface expression and Ca2+ uptake, identifying Rab11a as a direct cargo-interacting trafficking GTPase for TRPV5.","method":"GST pulldown, co-immunoprecipitation, live imaging, 45Ca2+ uptake, surface biotinylation","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal pulldown/co-IP, localization, and functional loss-of-function with defined phenotype","pmids":["16354700"],"is_preprint":false},{"year":2006,"finding":"Tissue kallikrein (TK) stimulates Ca2+ reabsorption via bradykinin receptor type 2 → PLC/DAG/PKC pathway, phosphorylating TRPV5 at Ser299 and Ser654 to increase its plasma membrane abundance by delaying retrieval; mutation of these PKC sites abolishes the effect.","method":"Primary renal epithelial cell cultures, pharmacological inhibitors, site-directed mutagenesis (S299A, S654A), cell-surface labeling, 45Ca2+ assays, electrophysiology","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — defined signaling pathway with mutagenesis and functional readout in primary cells","pmids":["17006539"],"is_preprint":false},{"year":2006,"finding":"Extracellular pH dynamically controls TRPV5 surface abundance via vesicular 'kiss and linger' interactions: alkalinization recruits TRPV5-containing vesicles to the membrane increasing activity, while acidification retrieves them, as demonstrated by TIRF microscopy and functional assays.","method":"TIRF microscopy, cell-surface protein labeling, electrophysiology, 45Ca2+ uptake, functional channel recovery after chemobleaching","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal imaging and functional methods; mechanism clearly defined","pmids":["17178838"],"is_preprint":false},{"year":2003,"finding":"Extracellular glutamate 522 (E522) in the pore region of TRPV5 acts as the pH sensor; its mutation (E522Q) selectively abolishes proton-induced reduction of open probability without affecting Mg2+-dependent block, and E522 is accessible from the extracellular face as shown by MTSET reactivity of the E522C mutant.","method":"Whole-cell and single-channel patch clamp, site-directed mutagenesis, substituted cysteine accessibility (MTS reagents)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with single-channel analysis and SCAM identifies specific residue mechanism","pmids":["14525991"],"is_preprint":false},{"year":2005,"finding":"Internal protons cause a clockwise rotation of the pore helix in TRPV5 (detected by SCAM), which facilitates closing of the selectivity filter gate by external protons; intra- and extracellular pH sensors cooperate through this conformational change.","method":"Substituted cysteine accessibility method (SCAM), whole-cell patch clamp, site-directed mutagenesis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — conformational change mapped by SCAM combined with mutagenesis and electrophysiology","pmids":["16121193"],"is_preprint":false},{"year":2004,"finding":"The N-tail (residues 64–77) and C-tail (residues 596–601) of TRPV5 mediate channel subunit assembly via N-N, C-C, and N-C interactions; deletion of either tail alone exerts dominant-negative effects on surface trafficking, whereas dual deletion does not, establishing these domains as assembly signals required for plasma membrane targeting.","method":"GST pulldown, co-immunoprecipitation, patch clamp, 45Ca2+ uptake in Xenopus oocytes, surface expression analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — mutagenesis of specific domains with biochemical interaction and functional readout","pmids":["15489237"],"is_preprint":false},{"year":2004,"finding":"80K-H, a Ca2+-binding protein with two EF-hand structures, directly binds TRPV5 and acts as a Ca2+ sensor controlling channel activity; inactivation of its EF-hands reduces TRPV5-mediated Ca2+ current and accelerates Ca2+-dependent feedback inhibition without altering TRPV5 surface expression.","method":"cDNA microarray, co-immunoprecipitation, electrophysiology, site-directed mutagenesis of EF-hands","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — binding demonstrated by co-IP, mechanism confirmed by mutagenesis with electrophysiological readout","pmids":["15100231"],"is_preprint":false},{"year":2008,"finding":"Klotho removes alpha2,6-linked sialic acids from TRPV5 N-glycan chains via its sialidase activity, exposing galactose-N-acetylglucosamine that then binds galectin-1 to form a cell-surface lattice retaining functional TRPV5 at the plasma membrane; knockdown of ST6Gal-1 or use of hamster cells lacking ST6Gal-1 abolishes the effect.","method":"siRNA knockdown of sialyltransferases, heterologous expression in cells lacking ST6Gal-1, Ca2+ influx measurements, surface abundance assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — mechanism dissected with genetic knockdown and complementation in multiple cell systems","pmids":["18606998"],"is_preprint":false},{"year":2008,"finding":"TRPV5 undergoes constitutive caveolae-mediated endocytosis; PKC activation (via OAG or PTH) phosphorylates TRPV5 at Ser299 and Ser654 to inhibit this endocytosis, increasing surface abundance; caveolin-1 knockdown or knockout abolishes the PKC-mediated upregulation.","method":"Dominant-negative dynamin, siRNA knockdown of caveolin-1 and clathrin, caveolin-1 KO cells, site-directed mutagenesis, patch clamp, surface biotinylation","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 2 — mechanism defined by multiple genetic manipulations, mutagenesis, and functional assays","pmids":["18305097"],"is_preprint":false},{"year":2009,"finding":"PTH activates TRPV5 via the adenylyl cyclase–cAMP–PKA cascade; PKA directly phosphorylates Thr709 on TRPV5, increasing channel open probability without changing surface expression; alanine substitution at T709 abolishes both in vitro phosphorylation and PTH-mediated stimulation.","method":"FRET (cAMP and Ca2+ dynamics), cell-surface biotinylation, patch clamp with PKA catalytic subunit application, site-directed mutagenesis (T709A), in vitro phosphorylation assay","journal":"Journal of the American Society of Nephrology","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro phosphorylation plus mutagenesis plus electrophysiology; replicated across methods","pmids":["19423690"],"is_preprint":false},{"year":2007,"finding":"TRPV5 is constitutively internalized via dynamin- and clathrin-dependent endocytosis into Rab11a-positive perinuclear recycling vesicles; after internalization, TRPV5 is stable (>3 h) and recycles back to the surface, and this recycling is Ca2+-dependent (BAPTA-AM reduces recycling kinetics).","method":"Dynamin and clathrin inhibition, Rab11a colocalization, pulse-chase experiments, Ca2+ chelation (BAPTA-AM), brefeldin A block","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple pharmacological and molecular tools defining the endocytic and recycling pathway","pmids":["18077461"],"is_preprint":false},{"year":2011,"finding":"Calmodulin (CaM) binds Ca2+-dependently to the last ~30 residues of the TRPV5 C-terminus (W702, R706), with one CaM bridging two TRPV5 C-termini; this interaction mediates Ca2+-dependent inactivation of the channel. PTH-induced PKA phosphorylation of T709 reduces CaM binding, thereby increasing TRPV5 open probability.","method":"NMR spectroscopy (residue-level interaction mapping), site-directed mutagenesis (W702A, R706E, T709), patch clamp electrophysiology","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — NMR structure of interaction combined with mutagenesis and electrophysiology","pmids":["21576356"],"is_preprint":false},{"year":2018,"finding":"Cryo-EM structures of TRPV5 bound to PI(4,5)P2 or calmodulin reveal: PI(4,5)P2 binds between the N-linker, S4-S5 linker, and S6 helix, inducing conformational changes that open the lower gate; CaM binds two TRPV5 C-terminal peptides simultaneously, and Ca2+-activated CaM Lys116 forms a cation-π interaction with Trp583 at the intracellular gate to mediate channel inhibition.","method":"Cryo-electron microscopy (cryo-EM), molecular dynamics simulations, functional validation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — atomic-resolution cryo-EM structures with mechanistic interpretation of gating","pmids":["30305626"],"is_preprint":false},{"year":2018,"finding":"Cryo-EM structure of full-length rabbit TRPV5 in complex with econazole reveals that econazole occupies a hydrophobic pocket analogous to the phosphatidylinositide/vanilloid pocket of TRPV1, locking TRPV5 in a closed conformation with a distinct lower gate that occludes Ca2+ permeation.","method":"Cryo-electron microscopy (cryo-EM), molecular dynamics simulations","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — high-resolution structure directly demonstrating inhibitor binding pocket and closed-state mechanism","pmids":["29323279"],"is_preprint":false},{"year":2019,"finding":"Cryo-EM structures of full-length TRPV5 in lipid nanodiscs and in complex with CaM reveal flexible CaM binding stoichiometry; the W583A gate mutant structure provides mechanistic insight into Ca2+-dependent regulation and confirms W583 as the intracellular gate.","method":"Cryo-electron microscopy in lipid nanodiscs, site-directed mutagenesis (W583A)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM with mutagenesis validation","pmids":["30975749"],"is_preprint":false},{"year":2014,"finding":"FGF23 promotes renal Ca2+ reabsorption and increases apical membrane abundance of TRPV5 via a signaling cascade involving FGF receptor–αKlotho complex, ERK1/2, SGK1, and WNK4; Fgf23 knockout mice show reduced TRPV5 membrane abundance and Ca2+ reabsorption similar to αKlotho knockouts.","method":"Fgf23 KO mouse analysis, pharmacological pathway dissection (ERK1/2, SGK1, WNK4 inhibitors/activators), immunostaining, colocalization studies","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — KO mouse phenotype with defined signaling pathway via multiple inhibitors","pmids":["24434184"],"is_preprint":false},{"year":2014,"finding":"NDPK-B (histidine kinase) activates TRPV5 channel activity and Ca2+ flux by phosphorylating histidine 711 in the C-terminal tail; PHPT1 (histidine phosphatase) reverses this activation. NDPK-B knockdown reduces TRPV5 activity, and NDPK-B-/- mice have increased urinary Ca2+ excretion.","method":"Inside-out patch clamp, site-directed mutagenesis (H711), shRNA knockdown, NDPK-B-/- mouse urinary Ca2+ measurement","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 — direct in vitro patch clamp with specific residue mutagenesis plus in vivo validation","pmids":["24523290"],"is_preprint":false},{"year":2006,"finding":"WNK4 increases TRPV5-mediated Ca2+ uptake twofold by enhancing TRPV5 surface expression when co-expressed in Xenopus oocytes; this effect requires complex N-glycosylation of TRPV5 and is abolished by blocking the secretory pathway or by the N358Q glycosylation-null mutant.","method":"Xenopus oocyte expression, 45Ca2+ uptake, surface expression analysis, N-glycosylation mutant (N358Q), syntaxin 6 blockade","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 — functional assay in oocytes with mechanistic dissection, single lab","pmids":["17018846","18703016"],"is_preprint":false},{"year":2009,"finding":"Ca2+-sensing receptor (CaR) co-localizes with TRPV5 at the DCT/CNT luminal membrane and activates TRPV5-mediated Ca2+ influx via PMA-insensitive PKC isoforms targeting Ser299 and Ser654; mutation of these residues or dominant-negative CaR abolishes stimulation.","method":"Co-localization immunostaining, patch clamp, Fura-2 Ca2+ imaging, site-directed mutagenesis (S299A, S654A), dominant-negative CaR(R185Q)","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 — functional pathway defined with mutagenesis, single lab","pmids":["19157541"],"is_preprint":false},{"year":2005,"finding":"FKBP52 specifically interacts with TRPV5 and inhibits channel activity; the peptidyl-prolyl cis-trans isomerase (PPIase) catalytic domain of FKBP52 is required for this inhibition, as shown by PPIase-domain mutation and FK-506 pharmacological block.","method":"Co-immunoprecipitation, 45Ca2+ uptake, electrophysiology, siRNA knockdown, pharmacological blockade (FK-506), PPIase domain mutagenesis","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays with domain mutagenesis, single lab","pmids":["16352746"],"is_preprint":false},{"year":2004,"finding":"SGK1 (but not SGK2) and the scaffold protein NHERF2 cooperate to stimulate TRPV5-mediated Ca2+ transport by increasing TRPV5 plasma membrane abundance; the second PDZ domain of NHERF2 is required for this effect, and the TRPV5 C-tail interacts with NHERF2 in a Ca2+-independent manner.","method":"Xenopus oocyte expression, 45Ca2+ uptake, electrophysiology, pull-down/overlay assays, PDZ domain deletion mutants","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — functional assay combined with domain mapping, two complementary papers","pmids":["15319523","15665527"],"is_preprint":false},{"year":2013,"finding":"Uromodulin (UMOD) upregulates TRPV5 current density and surface abundance by impeding caveolin-1-mediated endocytosis from the extracellular side; UMOD has no effect in caveolin-1 null cells and requires caveolin-1 re-expression to restore regulation. Disease mutant UMOD fails to upregulate TRPV5.","method":"Patch clamp, surface biotinylation, caveolin-1 KO cells, extracellular UMOD application, immunofluorescence in Umod-/- mice","journal":"Kidney international","confidence":"Medium","confidence_rationale":"Tier 2 — KO cell line and in vivo immunostaining with functional assay, single lab","pmids":["23466996"],"is_preprint":false},{"year":2016,"finding":"MUC1 physically interacts with TRPV5 (co-immunoprecipitation) and upregulates its activity by impairing dynamin-2- and caveolin-1-mediated endocytosis; this effect requires TRPV5 N-glycan and is mediated through a galectin-3 lattice binding to MUC1 VNTRs; disease-mutant MUC1 fails to increase TRPV5 activity.","method":"Patch clamp, co-immunoprecipitation, siRNA knockdown of galectin-1 and galectin-3, dynamin-2/caveolin-1 inhibition, VNTR-deletion mutant","journal":"Journal of the American Society of Nephrology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple molecular tools with functional readout and mutant comparison, single lab","pmids":["27036738"],"is_preprint":false},{"year":2003,"finding":"The C-terminus of TRPV5 (specifically residues 649–701) controls Ca2+-dependent inactivation; deletion of the last 30 amino acids (G701X) or truncation at positions 650–653 decreases Ca2+ sensitivity, while E649X abolishes Ca2+-dependent inactivation entirely.","method":"C-terminal truncation mutagenesis, patch clamp electrophysiology, HEK293 heterologous expression","journal":"Pflugers Archiv","confidence":"Medium","confidence_rationale":"Tier 1 — systematic mutagenesis with electrophysiology, single lab","pmids":["12634930"],"is_preprint":false},{"year":2017,"finding":"Trp583 at the intracellular pore terminus of TRPV5 acts as a gate hinge for Ca2+ permeation; W583 mutants display massively increased Ca2+ influx, and structural modeling combined with electrophysiology indicates a glycine residue above W583 provides flexibility for gate rearrangement; this gate also functionally interacts with the C-terminus involved in CaM-mediated inactivation.","method":"Site-directed mutagenesis, patch clamp electrophysiology, homology modeling, biochemical analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — mutagenesis with functional consequence and structural modeling, single lab","pmids":["28374795"],"is_preprint":false},{"year":2022,"finding":"Cryo-EM shows low extracellular pH inhibits TRPV5 by precluding PI(4,5)P2 binding/activation and captures intermediate conformations during the open-to-closed transition; PKA phosphorylation controls TRPV5 activity by preventing CaM binding rather than directly activating gating, and PI(4,5)P2 is the primary gating modulator.","method":"Cryo-electron microscopy, electrophysiology","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 — atomic-resolution cryo-EM structures capturing mechanism of pH inhibition and PKA/CaM interplay","pmids":["35476976"],"is_preprint":false},{"year":2013,"finding":"Inflammatory cytokines (TNF-α, IFN-γ, IL-1β) reduce TRPV5 surface expression by promoting its interaction with UBR4 E3 ubiquitin ligase, leading to ubiquitin-dependent degradation; klotho protects TRPV5 from this cytokine-induced endocytosis and degradation.","method":"Co-immunoprecipitation (TRPV5-UBR4), UBR4 siRNA knockdown, adenoviral TRPV5 expression in mIMCD3 cells, transgenic Klotho overexpression mouse model","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP identifies E3 ligase, siRNA rescue confirms mechanism, validated in vivo","pmids":["23747339"],"is_preprint":false},{"year":2014,"finding":"Klotho upregulates TRPV5 from both inside and outside the cell: extracellular (secreted) Klotho inhibits TRPV5 endocytosis (blocked by dominant-negative dynamin), while intracellular (membrane-bound) Klotho enhances forward trafficking (blocked by brefeldin A); both effects require the putative sialidase activity of Klotho.","method":"Patch clamp, dominant-negative dynamin II, brefeldin A, sialidase-activity site mutagenesis, HEK293 coexpression","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic dissection with multiple pharmacological and genetic tools, single lab","pmids":["25378396"],"is_preprint":false},{"year":2013,"finding":"Klotho and sialidase stimulate TRPV5 by two distinct mechanisms: klotho acts via the TRPV5 N-glycan (N358Q mutant abolishes klotho effect) to inhibit endocytosis, while sialidase increases TRPV5 activity by inhibiting lipid raft-mediated internalization independently of N-glycosylation; galectin-3 (not galectin-1) is expressed in DCT and activates TRPV5.","method":"Biochemical glycan assays, 45Ca2+ uptake, TIRF microscopy, N-glycosylation mutant (N358Q), galectin-3 application","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — orthogonal approaches with glycan mutant to dissect two mechanisms, single lab","pmids":["23970553"],"is_preprint":false},{"year":2003,"finding":"SCAM mapping of the TRPV5 outer pore reveals that the S5-to-pore region (L520C, G521C, E522C) is accessible from the extracellular medium, the pore helix (Pro527–Ile541) adopts an alpha-helical structure with a cation-selective interior, and Asp542 is at the center of the selectivity filter.","method":"Substituted cysteine accessibility method (SCAM) with MTSET/MTSES, whole-cell patch clamp, 44 position cysteine scan","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 — systematic SCAM mapping defining outer pore topology, single lab","pmids":["14630907"],"is_preprint":false},{"year":2019,"finding":"Structure-based virtual screening identified novel specific TRPV5 inhibitors; cryo-EM of TRPV5 with the selective inhibitor revealed binding sites distinct from the econazole pocket, enabling a proposed mechanism of selective TRPV5 inhibition over TRPV6.","method":"Structure-based virtual screening, cryo-electron microscopy, patch clamp electrophysiology","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 1 — cryo-EM structures with functional validation, single lab","pmids":["31647410"],"is_preprint":false}],"current_model":"TRPV5 is a constitutively active, highly Ca2+-selective tetrameric TRP channel localized to the apical membrane of renal distal convoluted tubule cells, where it functions as the rate-limiting Ca2+ entry step in transcellular reabsorption; its activity and surface abundance are regulated by a multi-layered network including PKA-mediated phosphorylation of T709 (activated by PTH, preventing calmodulin binding), PKC-mediated phosphorylation of S299/S654 (stimulated by tissue kallikrein, CaR, and PTH, inhibiting caveolae-mediated endocytosis), PI(4,5)P2 binding to the S4-S5/S6 interface (primary gating activator), calmodulin binding to W702/R706 in the C-terminus (Ca2+-dependent inactivation via a cation-π interaction with the W583 intracellular gate), NDPK-B histidine phosphorylation at H711, extracellular glycan modification by klotho (sialic acid removal exposing galectin-binding sites that retain the channel at the surface), Rab11a-mediated clathrin-dependent recycling, association with the S100A10–annexin 2 complex and calbindin-D28K for membrane targeting and local Ca2+ buffering, and regulation by FGF23 via the FGFR–αKlotho–ERK1/2–SGK1–WNK4 signaling axis."},"narrative":{"teleology":[{"year":2003,"claim":"TRPV5 knockout mice established TRPV5 as the essential apical Ca²⁺ entry channel for renal transcellular Ca²⁺ reabsorption, resolving a long-standing question about the molecular identity of the rate-limiting entry step.","evidence":"TRPV5⁻/⁻ mice with micropuncture, metabolic cage studies, and bone morphometry","pmids":["14679186"],"confidence":"High","gaps":["Human loss-of-function genetics not reported","Relative contribution of TRPV5 vs TRPV6 in kidney not fully delineated"]},{"year":2003,"claim":"Defining the tetrameric architecture, subunit assembly domains, and pore topology resolved fundamental questions about TRPV5 channel stoichiometry and ion permeation pathway.","evidence":"Sucrose gradient sedimentation, co-IP, concatemer electrophysiology, systematic SCAM mapping of S5-pore-S6, and N/C-tail assembly domain mutagenesis","pmids":["12574114","14630907","15489237"],"confidence":"High","gaps":["Full atomic structure of the channel was not yet available","Heterotetramer stoichiometry with TRPV6 in native tissue unknown"]},{"year":2003,"claim":"Identification of Glu522 as the extracellular pH sensor and the C-terminus (residues 649–701) as the Ca²⁺-dependent inactivation domain established the two key regulatory inputs controlling TRPV5 open probability.","evidence":"SCAM and single-channel recording with E522Q mutagenesis; C-terminal truncation series with patch clamp","pmids":["14525991","12634930"],"confidence":"High","gaps":["Structural basis of pH-induced gating unknown","Identity of the C-terminal Ca²⁺ sensor (later shown to be calmodulin) not yet determined"]},{"year":2003,"claim":"Discovery that S100A10–annexin 2 binds the TRPV5 C-tail at Thr599 and is required for surface delivery established the first trafficking partner essential for channel function.","evidence":"Yeast two-hybrid, GST pull-down, co-IP, T599A mutagenesis, annexin 2 siRNA knockdown with electrophysiology","pmids":["12660155"],"confidence":"High","gaps":["Whether S100A10–annexin 2 acts in regulated vs constitutive trafficking unclear"]},{"year":2004,"claim":"Identification of 80K-H as a Ca²⁺-sensing modulator and SGK1/NHERF2 as trafficking regulators expanded the accessory protein network controlling TRPV5 activity and surface abundance.","evidence":"Co-IP and EF-hand mutagenesis for 80K-H; oocyte expression and PDZ domain deletions for NHERF2/SGK1","pmids":["15100231","15319523"],"confidence":"Medium","gaps":["Direct binding site of 80K-H on TRPV5 not mapped","In vivo relevance of NHERF2 scaffold not tested"]},{"year":2005,"claim":"Three discoveries collectively established PI(4,5)P₂ as a key gating activator, klotho-mediated glycan remodeling as a membrane retention mechanism, and TRPV5 as essential for osteoclast bone resorption, broadening the channel's functional context beyond renal epithelium.","evidence":"Inside-out patch clamp with PIP₂/Mg²⁺ and D542 mutagenesis; β-glucuronidase assay and surface biotinylation for klotho; TRPV5⁻/⁻ osteoclast resorption pit assays","pmids":["16230466","16239475","16291808"],"confidence":"High","gaps":["Structural basis of PIP₂ binding unknown at this point","Specific glycan residues modified by klotho unresolved","TRPV5 role in osteoblasts not addressed"]},{"year":2005,"claim":"Internal pH-driven pore helix rotation cooperates with the extracellular E522 pH sensor, revealing a two-sided conformational gating mechanism for proton inhibition.","evidence":"SCAM on pore helix residues combined with intracellular and extracellular pH manipulation and electrophysiology","pmids":["16121193"],"confidence":"High","gaps":["Atomic details of the rotation not resolved until cryo-EM"]},{"year":2006,"claim":"Defining the calbindin-D28K association, Rab11a-mediated recycling, PKC phosphorylation sites (S299/S654) via tissue kallikrein, and pH-dependent vesicular trafficking built a comprehensive picture of how TRPV5 surface abundance is dynamically regulated.","evidence":"TIRF microscopy and primary DCT cells for calbindin-D28K; GST pulldown and dominant-negative Rab11a for recycling; site-directed mutagenesis S299A/S654A with primary cell Ca²⁺ assays for kallikrein/PKC; TIRF and surface labeling for pH-dependent trafficking","pmids":["16763551","16354700","17006539","17178838"],"confidence":"High","gaps":["Whether calbindin-D28K binding is direct or involves intermediates debated","Endosomal sorting signals for recycling vs degradation not identified"]},{"year":2007,"claim":"Demonstration that TRPV5 undergoes constitutive clathrin/dynamin-dependent endocytosis into Rab11a-positive recycling compartments, with Ca²⁺-dependent recycling kinetics, unified earlier trafficking observations into a coherent constitutive cycling model.","evidence":"Dynamin/clathrin inhibition, Rab11a colocalization, pulse-chase, BAPTA-AM Ca²⁺ chelation","pmids":["18077461"],"confidence":"High","gaps":["Molecular link between intracellular Ca²⁺ and recycling machinery not identified"]},{"year":2008,"claim":"The klotho mechanism was refined to sialidase-mediated removal of α2,6-linked sialic acids exposing galectin-1 binding sites, and PKC-mediated phosphorylation was shown to specifically inhibit caveolae-dependent endocytosis, distinguishing two parallel surface-retention pathways.","evidence":"ST6Gal-1 siRNA and complementation for galectin lattice; caveolin-1 KO cells and site-directed mutagenesis for caveolae pathway","pmids":["18606998","18305097"],"confidence":"High","gaps":["Whether galectin-1 or galectin-3 is the physiologically relevant lectin in DCT was debated"]},{"year":2009,"claim":"PTH was shown to activate TRPV5 via cAMP–PKA phosphorylation of Thr709, increasing open probability without changing surface expression—a mechanism distinct from the PKC/surface-retention pathway—while CaR was found to activate TRPV5 through PKC at the same S299/S654 sites.","evidence":"FRET-based cAMP/Ca²⁺ sensors, in vitro PKA phosphorylation, T709A mutagenesis with patch clamp for PTH; Fura-2 imaging and mutagenesis for CaR","pmids":["19423690","19157541"],"confidence":"High","gaps":["How PTH coordinates dual PKA and PKC arms at the channel level in vivo not resolved"]},{"year":2011,"claim":"NMR-based mapping of the calmodulin–TRPV5 C-terminal interaction at residue resolution (W702, R706) and demonstration that PKA phosphorylation of T709 reduces CaM affinity provided the molecular logic linking hormonal stimulation to relief of Ca²⁺-dependent inactivation.","evidence":"NMR spectroscopy with mutagenesis (W702A, R706E, T709) and patch clamp","pmids":["21576356"],"confidence":"High","gaps":["Structural basis of how CaM occupancy gates the pore not yet visualized"]},{"year":2013,"claim":"Additional surface-retention mechanisms were identified: uromodulin inhibits caveolin-1-mediated endocytosis extracellularly, galectin-3 (not just galectin-1) activates TRPV5 in DCT, and inflammatory cytokines promote UBR4 E3 ligase-mediated ubiquitination and degradation counteracted by klotho.","evidence":"Caveolin-1 KO cells with UMOD application; N358Q glycan mutant and galectin-3 application; UBR4 co-IP and siRNA with klotho overexpression mouse model","pmids":["23466996","23970553","23747339"],"confidence":"Medium","gaps":["Direct ubiquitination sites on TRPV5 not mapped","Relative importance of galectin-1 vs galectin-3 in vivo unresolved","UMOD mechanism confirmed only in cell lines"]},{"year":2014,"claim":"FGF23 was shown to promote TRPV5 apical membrane abundance via FGFR–αKlotho–ERK1/2–SGK1–WNK4, and NDPK-B histidine phosphorylation of H711 was identified as a novel activating modification reversed by PHPT1, adding two new regulatory axes.","evidence":"Fgf23 KO mouse with pathway inhibitor dissection; inside-out patch clamp with H711 mutagenesis and NDPK-B⁻/⁻ mouse","pmids":["24434184","24523290"],"confidence":"High","gaps":["How WNK4 mechanistically increases TRPV5 surface expression not defined","Whether NDPK-B and PKA pathways converge at the C-terminus not tested"]},{"year":2018,"claim":"Cryo-EM structures of TRPV5 with PI(4,5)P₂, calmodulin, and the inhibitor econazole revealed the atomic basis of gating: PIP₂ opens the lower gate at the S4-S5/S6 interface, CaM closes it via a Lys116–Trp583 cation-π interaction, and econazole occupies a vanilloid-like pocket to lock the channel shut.","evidence":"Cryo-EM at near-atomic resolution with molecular dynamics simulations and functional validation","pmids":["30305626","29323279"],"confidence":"High","gaps":["Open-state structure not captured","Lipid nanodisc structures needed for native-like context"]},{"year":2019,"claim":"Lipid nanodisc cryo-EM structures and the W583A gate mutant confirmed Trp583 as the intracellular gate and revealed flexible CaM binding stoichiometry, while structure-based screening identified novel selective TRPV5 inhibitors binding at a site distinct from the econazole pocket.","evidence":"Cryo-EM in lipid nanodiscs with W583A mutagenesis; virtual screening with cryo-EM validation and patch clamp","pmids":["30975749","31647410"],"confidence":"High","gaps":["Full open-state structure still lacking","Pharmacokinetics and in vivo efficacy of novel inhibitors not reported"]},{"year":2022,"claim":"Cryo-EM at low pH captured intermediate conformations of the open-to-closed transition and showed that acidification inhibits by precluding PIP₂ binding, confirming PIP₂ as the primary gating modulator and reinterpreting PKA's role as preventing CaM binding rather than directly activating gating.","evidence":"Cryo-EM structures at different pH values with electrophysiology","pmids":["35476976"],"confidence":"High","gaps":["Complete gating cycle with all modulators simultaneously bound not captured","Native tetrameric composition (homo vs hetero with TRPV6) in DCT not structurally resolved"]},{"year":null,"claim":"Major open questions include the full open-state structure, the in vivo stoichiometry of TRPV5/TRPV6 heterotetramers in native tissue, the direct ubiquitination sites mediating cytokine-induced degradation, human genetic validation of TRPV5 loss-of-function phenotypes, and the therapeutic potential of selective TRPV5 modulators.","evidence":"","pmids":[],"confidence":"Low","gaps":["Full open-state cryo-EM structure not yet captured","No human Mendelian disease mutation reported","In vivo pharmacology of TRPV5-selective inhibitors untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,4,19,20]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[4,19,32]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,3,7,8,9,14,15,22]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[7,9,17]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,4,5,19]}],"complexes":["TRPV5 homotetramer","TRPV5-TRPV6 heterotetramer","S100A10-annexin 2 complex"],"partners":["TRPV6","S100A10","ANXA2","CALM1","RAB11A","KL","CALB1","NHERF2"],"other_free_text":[]},"mechanistic_narrative":"TRPV5 is a constitutively active, highly Ca²⁺-selective tetrameric channel that serves as the rate-limiting apical Ca²⁺ entry step in active transcellular Ca²⁺ reabsorption in the renal distal convoluted tubule, and additionally participates in osteoclastic bone resorption [PMID:14679186, PMID:16291808]. Channel gating is primarily controlled by PI(4,5)P₂ binding at the S4-S5/S6 interface, which opens the lower gate defined by Trp583, while Ca²⁺-dependent inactivation is mediated by calmodulin binding to the C-terminus (W702/R706), with CaM Lys116 forming a cation-π interaction with W583 to close the intracellular gate; PTH-stimulated PKA phosphorylation of Thr709 counteracts inactivation by displacing calmodulin [PMID:30305626, PMID:21576356, PMID:19423690, PMID:35476976]. Surface abundance is regulated by a multi-layered trafficking network: klotho removes sialic acids from TRPV5 N-glycans to expose galectin-binding sites that retain the channel at the plasma membrane, PKC phosphorylation of Ser299/Ser654 inhibits caveolae-mediated endocytosis, the S100A10–annexin 2 complex is required for membrane targeting, Rab11a mediates clathrin-dependent recycling from perinuclear vesicles, and FGF23 signals through FGFR–αKlotho–ERK1/2–SGK1–WNK4 to promote apical TRPV5 expression [PMID:16239475, PMID:18606998, PMID:17006539, PMID:18305097, PMID:12660155, PMID:16354700, PMID:24434184]. Extracellular protons inhibit gating via the pH sensor Glu522, which cooperates with intracellular pH-driven pore helix rotation and, at the structural level, by precluding PI(4,5)P₂ binding [PMID:14525991, PMID:16121193, PMID:35476976]."},"prefetch_data":{"uniprot":{"accession":"Q9NQA5","full_name":"Transient receptor potential cation channel subfamily V member 5","aliases":["Calcium transport protein 2","CaT2","Epithelial calcium channel 1","ECaC","ECaC1","Osm-9-like TRP channel 3","OTRPC3"],"length_aa":729,"mass_kda":82.6,"function":"Constitutively active calcium selective cation channel thought to be involved in Ca(2+) reabsorption in kidney and intestine (PubMed:11549322, PubMed:18768590). Required for normal Ca(2+) reabsorption in the kidney distal convoluted tubules (By similarity). The channel is activated by low internal calcium level and the current exhibits an inward rectification (PubMed:11549322, PubMed:18768590). A Ca(2+)-dependent feedback regulation includes fast channel inactivation and slow current decay (By similarity). Heteromeric assembly with TRPV6 seems to modify channel properties. TRPV5-TRPV6 heteromultimeric concatemers exhibit voltage-dependent gating (By similarity)","subcellular_location":"Apical cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9NQA5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TRPV5","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/TRPV5","total_profiled":1310},"omim":[{"mim_id":"619683","title":"B-BOX- AND SPRY DOMAIN-CONTAINING PROTEIN; BSPRY","url":"https://www.omim.org/entry/619683"},{"mim_id":"606680","title":"TRANSIENT RECEPTOR POTENTIAL CATION CHANNEL, SUBFAMILY V, MEMBER 6; TRPV6","url":"https://www.omim.org/entry/606680"},{"mim_id":"606679","title":"TRANSIENT RECEPTOR POTENTIAL CATION CHANNEL, SUBFAMILY V, MEMBER 5; TRPV5","url":"https://www.omim.org/entry/606679"},{"mim_id":"604824","title":"KLOTHO; KL","url":"https://www.omim.org/entry/604824"},{"mim_id":"600968","title":"SOLUTE CARRIER FAMILY 12 (SODIUM/CHLORIDE TRANSPORTER), MEMBER 3; SLC12A3","url":"https://www.omim.org/entry/600968"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":1.6},{"tissue":"kidney","ntpm":4.0}],"url":"https://www.proteinatlas.org/search/TRPV5"},"hgnc":{"alias_symbol":["CaT2"],"prev_symbol":["ECAC1"]},"alphafold":{"accession":"Q9NQA5","domains":[{"cath_id":"1.25.40.20","chopping":"48-259","consensus_level":"medium","plddt":92.8126,"start":48,"end":259},{"cath_id":"-","chopping":"314-358_367-469","consensus_level":"high","plddt":91.1326,"start":314,"end":469},{"cath_id":"1.10.287","chopping":"481-608","consensus_level":"medium","plddt":89.7791,"start":481,"end":608}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQA5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQA5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQA5-F1-predicted_aligned_error_v6.png","plddt_mean":82.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TRPV5","jax_strain_url":"https://www.jax.org/strain/search?query=TRPV5"},"sequence":{"accession":"Q9NQA5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQA5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQA5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQA5"}},"corpus_meta":[{"pmid":"16239475","id":"PMC_16239475","title":"The 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distal convoluted tubule, hypercalciuria, compensatory intestinal Ca2+ hyperabsorption, and reduced trabecular and cortical bone thickness, establishing TRPV5 as the key apical Ca2+ entry channel for active renal Ca2+ reabsorption.\",\n      \"method\": \"Genetic knockout (TRPV5-/- mice), in vivo micropuncture, metabolic cage studies, bone morphometry\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple defined phenotypic readouts; foundational study replicated across labs\",\n      \"pmids\": [\"14679186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"TRPV5 and TRPV6 form homotetramers (~400 kDa) and can assemble into heterotetramers with each other; N- and C-terminal intracellular tails mediate subunit assembly, and heterotetrameric complexes display distinct Ca2+-dependent inactivation, ion selectivity, and pharmacological block compared to homotetramers.\",\n      \"method\": \"Sucrose gradient sedimentation, co-immunoprecipitation, concatemer electrophysiology with pore mutants, HEK293 patch-clamp\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (sedimentation, co-IP, electrophysiology with dominant-negative pore mutant)\",\n      \"pmids\": [\"12574114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"S100A10 binds the conserved VATTV motif (specifically Thr599) in the TRPV5 C-terminal tail, and the S100A10–annexin 2 complex is required to route TRPV5 to the plasma membrane; mutation T599A or siRNA knockdown of annexin 2 abolishes surface expression and channel activity.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down, co-immunoprecipitation, site-directed mutagenesis, siRNA knockdown, electrophysiology\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including mutagenesis, pulldown, co-IP, and functional assay\",\n      \"pmids\": [\"12660155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Klotho, acting as a beta-glucuronidase, hydrolyzes extracellular N-linked oligosaccharides on TRPV5, trapping the channel in the plasma membrane and sustaining Ca2+ channel activity in the kidney.\",\n      \"method\": \"Enzymatic activity assay (beta-glucuronidase), Ca2+ influx measurements in transfected cells, cell-surface biotinylation\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — enzymatic mechanism directly demonstrated; highly cited foundational study\",\n      \"pmids\": [\"16239475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIP2 activates TRPV5 and protects against Mg2+-induced slow channel inhibition; intracellular Mg2+ binding to the selectivity filter (Asp542) causes both fast voltage-dependent block and a slower conformational change leading to channel closure, and PIP2 prevents the latter without affecting Mg2+ binding to the selectivity filter.\",\n      \"method\": \"Whole-cell and inside-out patch clamp, site-directed mutagenesis (D542), PIP2 application and PLC activation\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro electrophysiology with mutagenesis of critical residue, multiple conditions tested\",\n      \"pmids\": [\"16230466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TRPV5 is essential for osteoclastic bone resorption; TRPV5 localizes to the osteoclast ruffled border membrane, and TRPV5-/- osteoclasts show increased numbers but severely impaired Ca2+ resorption activity in pit assays.\",\n      \"method\": \"TRPV5-/- mouse analysis, immunostaining, bone marrow culture, resorption pit assay, urine deoxypyridinoline measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with in vitro functional assay and in vivo measures; defined localization and phenotype\",\n      \"pmids\": [\"16291808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Calbindin-D28K directly associates with TRPV5 at low intracellular Ca2+ concentrations, translocating to the plasma membrane; this association buffers Ca2+ flux near the TRPV5 pore, preventing Ca2+-dependent inactivation and enabling high Ca2+ transport rates.\",\n      \"method\": \"Protein-binding analysis, subcellular fractionation, evanescent-field (TIRF) microscopy, 45Ca2+ uptake, electrophysiology, primary connecting tubule/DCT cells\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct physical interaction shown by multiple methods plus functional consequence in primary cells\",\n      \"pmids\": [\"16763551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GDP-bound Rab11a directly interacts with a conserved C-terminal stretch of TRPV5 and co-localizes with TRPV5 in sub-apical vesicles; dominant-negative GDP-locked Rab11a reduces surface expression and Ca2+ uptake, identifying Rab11a as a direct cargo-interacting trafficking GTPase for TRPV5.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, live imaging, 45Ca2+ uptake, surface biotinylation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal pulldown/co-IP, localization, and functional loss-of-function with defined phenotype\",\n      \"pmids\": [\"16354700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Tissue kallikrein (TK) stimulates Ca2+ reabsorption via bradykinin receptor type 2 → PLC/DAG/PKC pathway, phosphorylating TRPV5 at Ser299 and Ser654 to increase its plasma membrane abundance by delaying retrieval; mutation of these PKC sites abolishes the effect.\",\n      \"method\": \"Primary renal epithelial cell cultures, pharmacological inhibitors, site-directed mutagenesis (S299A, S654A), cell-surface labeling, 45Ca2+ assays, electrophysiology\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — defined signaling pathway with mutagenesis and functional readout in primary cells\",\n      \"pmids\": [\"17006539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Extracellular pH dynamically controls TRPV5 surface abundance via vesicular 'kiss and linger' interactions: alkalinization recruits TRPV5-containing vesicles to the membrane increasing activity, while acidification retrieves them, as demonstrated by TIRF microscopy and functional assays.\",\n      \"method\": \"TIRF microscopy, cell-surface protein labeling, electrophysiology, 45Ca2+ uptake, functional channel recovery after chemobleaching\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal imaging and functional methods; mechanism clearly defined\",\n      \"pmids\": [\"17178838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Extracellular glutamate 522 (E522) in the pore region of TRPV5 acts as the pH sensor; its mutation (E522Q) selectively abolishes proton-induced reduction of open probability without affecting Mg2+-dependent block, and E522 is accessible from the extracellular face as shown by MTSET reactivity of the E522C mutant.\",\n      \"method\": \"Whole-cell and single-channel patch clamp, site-directed mutagenesis, substituted cysteine accessibility (MTS reagents)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with single-channel analysis and SCAM identifies specific residue mechanism\",\n      \"pmids\": [\"14525991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Internal protons cause a clockwise rotation of the pore helix in TRPV5 (detected by SCAM), which facilitates closing of the selectivity filter gate by external protons; intra- and extracellular pH sensors cooperate through this conformational change.\",\n      \"method\": \"Substituted cysteine accessibility method (SCAM), whole-cell patch clamp, site-directed mutagenesis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — conformational change mapped by SCAM combined with mutagenesis and electrophysiology\",\n      \"pmids\": [\"16121193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The N-tail (residues 64–77) and C-tail (residues 596–601) of TRPV5 mediate channel subunit assembly via N-N, C-C, and N-C interactions; deletion of either tail alone exerts dominant-negative effects on surface trafficking, whereas dual deletion does not, establishing these domains as assembly signals required for plasma membrane targeting.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, patch clamp, 45Ca2+ uptake in Xenopus oocytes, surface expression analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis of specific domains with biochemical interaction and functional readout\",\n      \"pmids\": [\"15489237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"80K-H, a Ca2+-binding protein with two EF-hand structures, directly binds TRPV5 and acts as a Ca2+ sensor controlling channel activity; inactivation of its EF-hands reduces TRPV5-mediated Ca2+ current and accelerates Ca2+-dependent feedback inhibition without altering TRPV5 surface expression.\",\n      \"method\": \"cDNA microarray, co-immunoprecipitation, electrophysiology, site-directed mutagenesis of EF-hands\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — binding demonstrated by co-IP, mechanism confirmed by mutagenesis with electrophysiological readout\",\n      \"pmids\": [\"15100231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Klotho removes alpha2,6-linked sialic acids from TRPV5 N-glycan chains via its sialidase activity, exposing galactose-N-acetylglucosamine that then binds galectin-1 to form a cell-surface lattice retaining functional TRPV5 at the plasma membrane; knockdown of ST6Gal-1 or use of hamster cells lacking ST6Gal-1 abolishes the effect.\",\n      \"method\": \"siRNA knockdown of sialyltransferases, heterologous expression in cells lacking ST6Gal-1, Ca2+ influx measurements, surface abundance assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mechanism dissected with genetic knockdown and complementation in multiple cell systems\",\n      \"pmids\": [\"18606998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TRPV5 undergoes constitutive caveolae-mediated endocytosis; PKC activation (via OAG or PTH) phosphorylates TRPV5 at Ser299 and Ser654 to inhibit this endocytosis, increasing surface abundance; caveolin-1 knockdown or knockout abolishes the PKC-mediated upregulation.\",\n      \"method\": \"Dominant-negative dynamin, siRNA knockdown of caveolin-1 and clathrin, caveolin-1 KO cells, site-directed mutagenesis, patch clamp, surface biotinylation\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mechanism defined by multiple genetic manipulations, mutagenesis, and functional assays\",\n      \"pmids\": [\"18305097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PTH activates TRPV5 via the adenylyl cyclase–cAMP–PKA cascade; PKA directly phosphorylates Thr709 on TRPV5, increasing channel open probability without changing surface expression; alanine substitution at T709 abolishes both in vitro phosphorylation and PTH-mediated stimulation.\",\n      \"method\": \"FRET (cAMP and Ca2+ dynamics), cell-surface biotinylation, patch clamp with PKA catalytic subunit application, site-directed mutagenesis (T709A), in vitro phosphorylation assay\",\n      \"journal\": \"Journal of the American Society of Nephrology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro phosphorylation plus mutagenesis plus electrophysiology; replicated across methods\",\n      \"pmids\": [\"19423690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TRPV5 is constitutively internalized via dynamin- and clathrin-dependent endocytosis into Rab11a-positive perinuclear recycling vesicles; after internalization, TRPV5 is stable (>3 h) and recycles back to the surface, and this recycling is Ca2+-dependent (BAPTA-AM reduces recycling kinetics).\",\n      \"method\": \"Dynamin and clathrin inhibition, Rab11a colocalization, pulse-chase experiments, Ca2+ chelation (BAPTA-AM), brefeldin A block\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological and molecular tools defining the endocytic and recycling pathway\",\n      \"pmids\": [\"18077461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Calmodulin (CaM) binds Ca2+-dependently to the last ~30 residues of the TRPV5 C-terminus (W702, R706), with one CaM bridging two TRPV5 C-termini; this interaction mediates Ca2+-dependent inactivation of the channel. PTH-induced PKA phosphorylation of T709 reduces CaM binding, thereby increasing TRPV5 open probability.\",\n      \"method\": \"NMR spectroscopy (residue-level interaction mapping), site-directed mutagenesis (W702A, R706E, T709), patch clamp electrophysiology\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structure of interaction combined with mutagenesis and electrophysiology\",\n      \"pmids\": [\"21576356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-EM structures of TRPV5 bound to PI(4,5)P2 or calmodulin reveal: PI(4,5)P2 binds between the N-linker, S4-S5 linker, and S6 helix, inducing conformational changes that open the lower gate; CaM binds two TRPV5 C-terminal peptides simultaneously, and Ca2+-activated CaM Lys116 forms a cation-π interaction with Trp583 at the intracellular gate to mediate channel inhibition.\",\n      \"method\": \"Cryo-electron microscopy (cryo-EM), molecular dynamics simulations, functional validation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — atomic-resolution cryo-EM structures with mechanistic interpretation of gating\",\n      \"pmids\": [\"30305626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-EM structure of full-length rabbit TRPV5 in complex with econazole reveals that econazole occupies a hydrophobic pocket analogous to the phosphatidylinositide/vanilloid pocket of TRPV1, locking TRPV5 in a closed conformation with a distinct lower gate that occludes Ca2+ permeation.\",\n      \"method\": \"Cryo-electron microscopy (cryo-EM), molecular dynamics simulations\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution structure directly demonstrating inhibitor binding pocket and closed-state mechanism\",\n      \"pmids\": [\"29323279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cryo-EM structures of full-length TRPV5 in lipid nanodiscs and in complex with CaM reveal flexible CaM binding stoichiometry; the W583A gate mutant structure provides mechanistic insight into Ca2+-dependent regulation and confirms W583 as the intracellular gate.\",\n      \"method\": \"Cryo-electron microscopy in lipid nanodiscs, site-directed mutagenesis (W583A)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM with mutagenesis validation\",\n      \"pmids\": [\"30975749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FGF23 promotes renal Ca2+ reabsorption and increases apical membrane abundance of TRPV5 via a signaling cascade involving FGF receptor–αKlotho complex, ERK1/2, SGK1, and WNK4; Fgf23 knockout mice show reduced TRPV5 membrane abundance and Ca2+ reabsorption similar to αKlotho knockouts.\",\n      \"method\": \"Fgf23 KO mouse analysis, pharmacological pathway dissection (ERK1/2, SGK1, WNK4 inhibitors/activators), immunostaining, colocalization studies\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse phenotype with defined signaling pathway via multiple inhibitors\",\n      \"pmids\": [\"24434184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NDPK-B (histidine kinase) activates TRPV5 channel activity and Ca2+ flux by phosphorylating histidine 711 in the C-terminal tail; PHPT1 (histidine phosphatase) reverses this activation. NDPK-B knockdown reduces TRPV5 activity, and NDPK-B-/- mice have increased urinary Ca2+ excretion.\",\n      \"method\": \"Inside-out patch clamp, site-directed mutagenesis (H711), shRNA knockdown, NDPK-B-/- mouse urinary Ca2+ measurement\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct in vitro patch clamp with specific residue mutagenesis plus in vivo validation\",\n      \"pmids\": [\"24523290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"WNK4 increases TRPV5-mediated Ca2+ uptake twofold by enhancing TRPV5 surface expression when co-expressed in Xenopus oocytes; this effect requires complex N-glycosylation of TRPV5 and is abolished by blocking the secretory pathway or by the N358Q glycosylation-null mutant.\",\n      \"method\": \"Xenopus oocyte expression, 45Ca2+ uptake, surface expression analysis, N-glycosylation mutant (N358Q), syntaxin 6 blockade\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assay in oocytes with mechanistic dissection, single lab\",\n      \"pmids\": [\"17018846\", \"18703016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Ca2+-sensing receptor (CaR) co-localizes with TRPV5 at the DCT/CNT luminal membrane and activates TRPV5-mediated Ca2+ influx via PMA-insensitive PKC isoforms targeting Ser299 and Ser654; mutation of these residues or dominant-negative CaR abolishes stimulation.\",\n      \"method\": \"Co-localization immunostaining, patch clamp, Fura-2 Ca2+ imaging, site-directed mutagenesis (S299A, S654A), dominant-negative CaR(R185Q)\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional pathway defined with mutagenesis, single lab\",\n      \"pmids\": [\"19157541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FKBP52 specifically interacts with TRPV5 and inhibits channel activity; the peptidyl-prolyl cis-trans isomerase (PPIase) catalytic domain of FKBP52 is required for this inhibition, as shown by PPIase-domain mutation and FK-506 pharmacological block.\",\n      \"method\": \"Co-immunoprecipitation, 45Ca2+ uptake, electrophysiology, siRNA knockdown, pharmacological blockade (FK-506), PPIase domain mutagenesis\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays with domain mutagenesis, single lab\",\n      \"pmids\": [\"16352746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SGK1 (but not SGK2) and the scaffold protein NHERF2 cooperate to stimulate TRPV5-mediated Ca2+ transport by increasing TRPV5 plasma membrane abundance; the second PDZ domain of NHERF2 is required for this effect, and the TRPV5 C-tail interacts with NHERF2 in a Ca2+-independent manner.\",\n      \"method\": \"Xenopus oocyte expression, 45Ca2+ uptake, electrophysiology, pull-down/overlay assays, PDZ domain deletion mutants\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assay combined with domain mapping, two complementary papers\",\n      \"pmids\": [\"15319523\", \"15665527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Uromodulin (UMOD) upregulates TRPV5 current density and surface abundance by impeding caveolin-1-mediated endocytosis from the extracellular side; UMOD has no effect in caveolin-1 null cells and requires caveolin-1 re-expression to restore regulation. Disease mutant UMOD fails to upregulate TRPV5.\",\n      \"method\": \"Patch clamp, surface biotinylation, caveolin-1 KO cells, extracellular UMOD application, immunofluorescence in Umod-/- mice\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO cell line and in vivo immunostaining with functional assay, single lab\",\n      \"pmids\": [\"23466996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MUC1 physically interacts with TRPV5 (co-immunoprecipitation) and upregulates its activity by impairing dynamin-2- and caveolin-1-mediated endocytosis; this effect requires TRPV5 N-glycan and is mediated through a galectin-3 lattice binding to MUC1 VNTRs; disease-mutant MUC1 fails to increase TRPV5 activity.\",\n      \"method\": \"Patch clamp, co-immunoprecipitation, siRNA knockdown of galectin-1 and galectin-3, dynamin-2/caveolin-1 inhibition, VNTR-deletion mutant\",\n      \"journal\": \"Journal of the American Society of Nephrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple molecular tools with functional readout and mutant comparison, single lab\",\n      \"pmids\": [\"27036738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The C-terminus of TRPV5 (specifically residues 649–701) controls Ca2+-dependent inactivation; deletion of the last 30 amino acids (G701X) or truncation at positions 650–653 decreases Ca2+ sensitivity, while E649X abolishes Ca2+-dependent inactivation entirely.\",\n      \"method\": \"C-terminal truncation mutagenesis, patch clamp electrophysiology, HEK293 heterologous expression\",\n      \"journal\": \"Pflugers Archiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis with electrophysiology, single lab\",\n      \"pmids\": [\"12634930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Trp583 at the intracellular pore terminus of TRPV5 acts as a gate hinge for Ca2+ permeation; W583 mutants display massively increased Ca2+ influx, and structural modeling combined with electrophysiology indicates a glycine residue above W583 provides flexibility for gate rearrangement; this gate also functionally interacts with the C-terminus involved in CaM-mediated inactivation.\",\n      \"method\": \"Site-directed mutagenesis, patch clamp electrophysiology, homology modeling, biochemical analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutagenesis with functional consequence and structural modeling, single lab\",\n      \"pmids\": [\"28374795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cryo-EM shows low extracellular pH inhibits TRPV5 by precluding PI(4,5)P2 binding/activation and captures intermediate conformations during the open-to-closed transition; PKA phosphorylation controls TRPV5 activity by preventing CaM binding rather than directly activating gating, and PI(4,5)P2 is the primary gating modulator.\",\n      \"method\": \"Cryo-electron microscopy, electrophysiology\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — atomic-resolution cryo-EM structures capturing mechanism of pH inhibition and PKA/CaM interplay\",\n      \"pmids\": [\"35476976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Inflammatory cytokines (TNF-α, IFN-γ, IL-1β) reduce TRPV5 surface expression by promoting its interaction with UBR4 E3 ubiquitin ligase, leading to ubiquitin-dependent degradation; klotho protects TRPV5 from this cytokine-induced endocytosis and degradation.\",\n      \"method\": \"Co-immunoprecipitation (TRPV5-UBR4), UBR4 siRNA knockdown, adenoviral TRPV5 expression in mIMCD3 cells, transgenic Klotho overexpression mouse model\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP identifies E3 ligase, siRNA rescue confirms mechanism, validated in vivo\",\n      \"pmids\": [\"23747339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Klotho upregulates TRPV5 from both inside and outside the cell: extracellular (secreted) Klotho inhibits TRPV5 endocytosis (blocked by dominant-negative dynamin), while intracellular (membrane-bound) Klotho enhances forward trafficking (blocked by brefeldin A); both effects require the putative sialidase activity of Klotho.\",\n      \"method\": \"Patch clamp, dominant-negative dynamin II, brefeldin A, sialidase-activity site mutagenesis, HEK293 coexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic dissection with multiple pharmacological and genetic tools, single lab\",\n      \"pmids\": [\"25378396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Klotho and sialidase stimulate TRPV5 by two distinct mechanisms: klotho acts via the TRPV5 N-glycan (N358Q mutant abolishes klotho effect) to inhibit endocytosis, while sialidase increases TRPV5 activity by inhibiting lipid raft-mediated internalization independently of N-glycosylation; galectin-3 (not galectin-1) is expressed in DCT and activates TRPV5.\",\n      \"method\": \"Biochemical glycan assays, 45Ca2+ uptake, TIRF microscopy, N-glycosylation mutant (N358Q), galectin-3 application\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — orthogonal approaches with glycan mutant to dissect two mechanisms, single lab\",\n      \"pmids\": [\"23970553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SCAM mapping of the TRPV5 outer pore reveals that the S5-to-pore region (L520C, G521C, E522C) is accessible from the extracellular medium, the pore helix (Pro527–Ile541) adopts an alpha-helical structure with a cation-selective interior, and Asp542 is at the center of the selectivity filter.\",\n      \"method\": \"Substituted cysteine accessibility method (SCAM) with MTSET/MTSES, whole-cell patch clamp, 44 position cysteine scan\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — systematic SCAM mapping defining outer pore topology, single lab\",\n      \"pmids\": [\"14630907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Structure-based virtual screening identified novel specific TRPV5 inhibitors; cryo-EM of TRPV5 with the selective inhibitor revealed binding sites distinct from the econazole pocket, enabling a proposed mechanism of selective TRPV5 inhibition over TRPV6.\",\n      \"method\": \"Structure-based virtual screening, cryo-electron microscopy, patch clamp electrophysiology\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structures with functional validation, single lab\",\n      \"pmids\": [\"31647410\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TRPV5 is a constitutively active, highly Ca2+-selective tetrameric TRP channel localized to the apical membrane of renal distal convoluted tubule cells, where it functions as the rate-limiting Ca2+ entry step in transcellular reabsorption; its activity and surface abundance are regulated by a multi-layered network including PKA-mediated phosphorylation of T709 (activated by PTH, preventing calmodulin binding), PKC-mediated phosphorylation of S299/S654 (stimulated by tissue kallikrein, CaR, and PTH, inhibiting caveolae-mediated endocytosis), PI(4,5)P2 binding to the S4-S5/S6 interface (primary gating activator), calmodulin binding to W702/R706 in the C-terminus (Ca2+-dependent inactivation via a cation-π interaction with the W583 intracellular gate), NDPK-B histidine phosphorylation at H711, extracellular glycan modification by klotho (sialic acid removal exposing galectin-binding sites that retain the channel at the surface), Rab11a-mediated clathrin-dependent recycling, association with the S100A10–annexin 2 complex and calbindin-D28K for membrane targeting and local Ca2+ buffering, and regulation by FGF23 via the FGFR–αKlotho–ERK1/2–SGK1–WNK4 signaling axis.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TRPV5 is a constitutively active, highly Ca²⁺-selective tetrameric channel that serves as the rate-limiting apical Ca²⁺ entry step in active transcellular Ca²⁺ reabsorption in the renal distal convoluted tubule, and additionally participates in osteoclastic bone resorption [PMID:14679186, PMID:16291808]. Channel gating is primarily controlled by PI(4,5)P₂ binding at the S4-S5/S6 interface, which opens the lower gate defined by Trp583, while Ca²⁺-dependent inactivation is mediated by calmodulin binding to the C-terminus (W702/R706), with CaM Lys116 forming a cation-π interaction with W583 to close the intracellular gate; PTH-stimulated PKA phosphorylation of Thr709 counteracts inactivation by displacing calmodulin [PMID:30305626, PMID:21576356, PMID:19423690, PMID:35476976]. Surface abundance is regulated by a multi-layered trafficking network: klotho removes sialic acids from TRPV5 N-glycans to expose galectin-binding sites that retain the channel at the plasma membrane, PKC phosphorylation of Ser299/Ser654 inhibits caveolae-mediated endocytosis, the S100A10–annexin 2 complex is required for membrane targeting, Rab11a mediates clathrin-dependent recycling from perinuclear vesicles, and FGF23 signals through FGFR–αKlotho–ERK1/2–SGK1–WNK4 to promote apical TRPV5 expression [PMID:16239475, PMID:18606998, PMID:17006539, PMID:18305097, PMID:12660155, PMID:16354700, PMID:24434184]. Extracellular protons inhibit gating via the pH sensor Glu522, which cooperates with intracellular pH-driven pore helix rotation and, at the structural level, by precluding PI(4,5)P₂ binding [PMID:14525991, PMID:16121193, PMID:35476976].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"TRPV5 knockout mice established TRPV5 as the essential apical Ca²⁺ entry channel for renal transcellular Ca²⁺ reabsorption, resolving a long-standing question about the molecular identity of the rate-limiting entry step.\",\n      \"evidence\": \"TRPV5⁻/⁻ mice with micropuncture, metabolic cage studies, and bone morphometry\",\n      \"pmids\": [\"14679186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human loss-of-function genetics not reported\", \"Relative contribution of TRPV5 vs TRPV6 in kidney not fully delineated\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defining the tetrameric architecture, subunit assembly domains, and pore topology resolved fundamental questions about TRPV5 channel stoichiometry and ion permeation pathway.\",\n      \"evidence\": \"Sucrose gradient sedimentation, co-IP, concatemer electrophysiology, systematic SCAM mapping of S5-pore-S6, and N/C-tail assembly domain mutagenesis\",\n      \"pmids\": [\"12574114\", \"14630907\", \"15489237\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full atomic structure of the channel was not yet available\", \"Heterotetramer stoichiometry with TRPV6 in native tissue unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identification of Glu522 as the extracellular pH sensor and the C-terminus (residues 649–701) as the Ca²⁺-dependent inactivation domain established the two key regulatory inputs controlling TRPV5 open probability.\",\n      \"evidence\": \"SCAM and single-channel recording with E522Q mutagenesis; C-terminal truncation series with patch clamp\",\n      \"pmids\": [\"14525991\", \"12634930\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of pH-induced gating unknown\", \"Identity of the C-terminal Ca²⁺ sensor (later shown to be calmodulin) not yet determined\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Discovery that S100A10–annexin 2 binds the TRPV5 C-tail at Thr599 and is required for surface delivery established the first trafficking partner essential for channel function.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, co-IP, T599A mutagenesis, annexin 2 siRNA knockdown with electrophysiology\",\n      \"pmids\": [\"12660155\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether S100A10–annexin 2 acts in regulated vs constitutive trafficking unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of 80K-H as a Ca²⁺-sensing modulator and SGK1/NHERF2 as trafficking regulators expanded the accessory protein network controlling TRPV5 activity and surface abundance.\",\n      \"evidence\": \"Co-IP and EF-hand mutagenesis for 80K-H; oocyte expression and PDZ domain deletions for NHERF2/SGK1\",\n      \"pmids\": [\"15100231\", \"15319523\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding site of 80K-H on TRPV5 not mapped\", \"In vivo relevance of NHERF2 scaffold not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Three discoveries collectively established PI(4,5)P₂ as a key gating activator, klotho-mediated glycan remodeling as a membrane retention mechanism, and TRPV5 as essential for osteoclast bone resorption, broadening the channel's functional context beyond renal epithelium.\",\n      \"evidence\": \"Inside-out patch clamp with PIP₂/Mg²⁺ and D542 mutagenesis; β-glucuronidase assay and surface biotinylation for klotho; TRPV5⁻/⁻ osteoclast resorption pit assays\",\n      \"pmids\": [\"16230466\", \"16239475\", \"16291808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PIP₂ binding unknown at this point\", \"Specific glycan residues modified by klotho unresolved\", \"TRPV5 role in osteoblasts not addressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Internal pH-driven pore helix rotation cooperates with the extracellular E522 pH sensor, revealing a two-sided conformational gating mechanism for proton inhibition.\",\n      \"evidence\": \"SCAM on pore helix residues combined with intracellular and extracellular pH manipulation and electrophysiology\",\n      \"pmids\": [\"16121193\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic details of the rotation not resolved until cryo-EM\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defining the calbindin-D28K association, Rab11a-mediated recycling, PKC phosphorylation sites (S299/S654) via tissue kallikrein, and pH-dependent vesicular trafficking built a comprehensive picture of how TRPV5 surface abundance is dynamically regulated.\",\n      \"evidence\": \"TIRF microscopy and primary DCT cells for calbindin-D28K; GST pulldown and dominant-negative Rab11a for recycling; site-directed mutagenesis S299A/S654A with primary cell Ca²⁺ assays for kallikrein/PKC; TIRF and surface labeling for pH-dependent trafficking\",\n      \"pmids\": [\"16763551\", \"16354700\", \"17006539\", \"17178838\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether calbindin-D28K binding is direct or involves intermediates debated\", \"Endosomal sorting signals for recycling vs degradation not identified\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstration that TRPV5 undergoes constitutive clathrin/dynamin-dependent endocytosis into Rab11a-positive recycling compartments, with Ca²⁺-dependent recycling kinetics, unified earlier trafficking observations into a coherent constitutive cycling model.\",\n      \"evidence\": \"Dynamin/clathrin inhibition, Rab11a colocalization, pulse-chase, BAPTA-AM Ca²⁺ chelation\",\n      \"pmids\": [\"18077461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between intracellular Ca²⁺ and recycling machinery not identified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"The klotho mechanism was refined to sialidase-mediated removal of α2,6-linked sialic acids exposing galectin-1 binding sites, and PKC-mediated phosphorylation was shown to specifically inhibit caveolae-dependent endocytosis, distinguishing two parallel surface-retention pathways.\",\n      \"evidence\": \"ST6Gal-1 siRNA and complementation for galectin lattice; caveolin-1 KO cells and site-directed mutagenesis for caveolae pathway\",\n      \"pmids\": [\"18606998\", \"18305097\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether galectin-1 or galectin-3 is the physiologically relevant lectin in DCT was debated\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"PTH was shown to activate TRPV5 via cAMP–PKA phosphorylation of Thr709, increasing open probability without changing surface expression—a mechanism distinct from the PKC/surface-retention pathway—while CaR was found to activate TRPV5 through PKC at the same S299/S654 sites.\",\n      \"evidence\": \"FRET-based cAMP/Ca²⁺ sensors, in vitro PKA phosphorylation, T709A mutagenesis with patch clamp for PTH; Fura-2 imaging and mutagenesis for CaR\",\n      \"pmids\": [\"19423690\", \"19157541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PTH coordinates dual PKA and PKC arms at the channel level in vivo not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"NMR-based mapping of the calmodulin–TRPV5 C-terminal interaction at residue resolution (W702, R706) and demonstration that PKA phosphorylation of T709 reduces CaM affinity provided the molecular logic linking hormonal stimulation to relief of Ca²⁺-dependent inactivation.\",\n      \"evidence\": \"NMR spectroscopy with mutagenesis (W702A, R706E, T709) and patch clamp\",\n      \"pmids\": [\"21576356\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of how CaM occupancy gates the pore not yet visualized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Additional surface-retention mechanisms were identified: uromodulin inhibits caveolin-1-mediated endocytosis extracellularly, galectin-3 (not just galectin-1) activates TRPV5 in DCT, and inflammatory cytokines promote UBR4 E3 ligase-mediated ubiquitination and degradation counteracted by klotho.\",\n      \"evidence\": \"Caveolin-1 KO cells with UMOD application; N358Q glycan mutant and galectin-3 application; UBR4 co-IP and siRNA with klotho overexpression mouse model\",\n      \"pmids\": [\"23466996\", \"23970553\", \"23747339\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination sites on TRPV5 not mapped\", \"Relative importance of galectin-1 vs galectin-3 in vivo unresolved\", \"UMOD mechanism confirmed only in cell lines\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"FGF23 was shown to promote TRPV5 apical membrane abundance via FGFR–αKlotho–ERK1/2–SGK1–WNK4, and NDPK-B histidine phosphorylation of H711 was identified as a novel activating modification reversed by PHPT1, adding two new regulatory axes.\",\n      \"evidence\": \"Fgf23 KO mouse with pathway inhibitor dissection; inside-out patch clamp with H711 mutagenesis and NDPK-B⁻/⁻ mouse\",\n      \"pmids\": [\"24434184\", \"24523290\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How WNK4 mechanistically increases TRPV5 surface expression not defined\", \"Whether NDPK-B and PKA pathways converge at the C-terminus not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Cryo-EM structures of TRPV5 with PI(4,5)P₂, calmodulin, and the inhibitor econazole revealed the atomic basis of gating: PIP₂ opens the lower gate at the S4-S5/S6 interface, CaM closes it via a Lys116–Trp583 cation-π interaction, and econazole occupies a vanilloid-like pocket to lock the channel shut.\",\n      \"evidence\": \"Cryo-EM at near-atomic resolution with molecular dynamics simulations and functional validation\",\n      \"pmids\": [\"30305626\", \"29323279\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Open-state structure not captured\", \"Lipid nanodisc structures needed for native-like context\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Lipid nanodisc cryo-EM structures and the W583A gate mutant confirmed Trp583 as the intracellular gate and revealed flexible CaM binding stoichiometry, while structure-based screening identified novel selective TRPV5 inhibitors binding at a site distinct from the econazole pocket.\",\n      \"evidence\": \"Cryo-EM in lipid nanodiscs with W583A mutagenesis; virtual screening with cryo-EM validation and patch clamp\",\n      \"pmids\": [\"30975749\", \"31647410\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full open-state structure still lacking\", \"Pharmacokinetics and in vivo efficacy of novel inhibitors not reported\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Cryo-EM at low pH captured intermediate conformations of the open-to-closed transition and showed that acidification inhibits by precluding PIP₂ binding, confirming PIP₂ as the primary gating modulator and reinterpreting PKA's role as preventing CaM binding rather than directly activating gating.\",\n      \"evidence\": \"Cryo-EM structures at different pH values with electrophysiology\",\n      \"pmids\": [\"35476976\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Complete gating cycle with all modulators simultaneously bound not captured\", \"Native tetrameric composition (homo vs hetero with TRPV6) in DCT not structurally resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include the full open-state structure, the in vivo stoichiometry of TRPV5/TRPV6 heterotetramers in native tissue, the direct ubiquitination sites mediating cytokine-induced degradation, human genetic validation of TRPV5 loss-of-function phenotypes, and the therapeutic potential of selective TRPV5 modulators.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Full open-state cryo-EM structure not yet captured\", \"No human Mendelian disease mutation reported\", \"In vivo pharmacology of TRPV5-selective inhibitors untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 4, 19, 20]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [4, 19, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 3, 7, 8, 9, 14, 15, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [7, 9, 17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [8, 16, 22, 25]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 4, 5, 19]}\n    ],\n    \"complexes\": [\n      \"TRPV5 homotetramer\",\n      \"TRPV5-TRPV6 heterotetramer\",\n      \"S100A10-annexin 2 complex\"\n    ],\n    \"partners\": [\n      \"TRPV6\",\n      \"S100A10\",\n      \"ANXA2\",\n      \"CALM1\",\n      \"RAB11A\",\n      \"KL\",\n      \"CALB1\",\n      \"NHERF2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}