{"gene":"ATP2B2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2004,"finding":"PMCA2 is localized to the stereocilia of inner and outer hair cells, where it actively transports calcium into the endolymph. Mice lacking PMCA2 (dfw2J) have significantly lower endolymph calcium concentrations, establishing that PMCA2 is the primary mechanism for calcium extrusion from stereocilia into endolymph and is required for endolymph calcium maintenance.","method":"Immunocytochemistry for PMCA2 localization in stereocilia; calcium-sensitive fluorescent dye with aspirating microelectrode to measure endolymph calcium in dfw2J versus control mice","journal":"Journal of the Association for Research in Otolaryngology : JARO","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization plus functional consequence (calcium measurement) in genetic knockout model; findings consistent with multiple other studies","pmids":["15357414"],"is_preprint":false},{"year":2006,"finding":"Differential membrane targeting of PMCA2 in hair cells is determined by alternative splicing: a Leu-Ile motif in 'b'-tail splice variants promotes basolateral sorting, whereas apical targeting of PMCA2 depends on the size of the A-site-spliced insert in the first cytoplasmic loop.","method":"Targeting region mutagenesis and expression of splice variants in hair cells; immunofluorescence localization","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis of splice regions combined with direct localization in hair cells, two orthogonal approaches","pmids":["16803870"],"is_preprint":false},{"year":2006,"finding":"PMCA2 co-immunoprecipitates with mGluR1, Homer 3, and IP3R1 in cerebellar Purkinje neurons, indicating it is a constituent of the mGluR1 signaling complex. Loss of PMCA2 in null mice results in reduced cerebellar levels of mGluR1, IP3R1, Homer 1b/c, and Homer 3, specifically in Purkinje neurons but not hippocampus, indicating region-specific disruption of metabotropic glutamate receptor signaling.","method":"Co-immunoprecipitation from cerebellar tissue; Western blot and immunofluorescence in PMCA2-null mice vs. wild-type littermates","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP supported by KO phenotyping with multiple protein readouts; single lab","pmids":["17150372"],"is_preprint":false},{"year":2008,"finding":"A missense mutation (S877F) in transmembrane domain 6 of PMCA2 (Oblivion allele) does not impair targeting to the plasma membrane but significantly reduces the non-stimulated (basal) calcium-exporting activity of the pump, causing progressive hearing loss with base-to-apex hair cell degeneration.","method":"ENU mutagenesis; mutation analysis; pump expression in model cells with biochemical/biophysical characterization of Ca2+ export; hair cell culture; immunofluorescence","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro pump activity assay with identified mutation, correct membrane targeting confirmed, multiple orthogonal methods (biochemical, biophysical, histological) in single rigorous study","pmids":["18974863"],"is_preprint":false},{"year":2010,"finding":"A missense mutation E629K in the second intracellular loop (active site) of PMCA2 (Tommy allele) impairs the long-term, non-stimulated calcium extrusion activity of the pump. Direct measurement by confocal imaging combined with flash photolysis of caged calcium in neonatal utricle sensory epithelium showed impaired calcium export in heterozygous and homozygous Tommy mice, causing profound hearing impairment and progressive hair cell degeneration.","method":"CHO cell expression with calcium extrusion assay; confocal imaging with flash photolysis of caged calcium in organotypic utricle cultures; immunofluorescence; auditory brainstem response","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro pump activity reconstitution, direct calcium imaging in native tissue, genetic mouse model with hearing phenotype; multiple orthogonal methods","pmids":["20826782"],"is_preprint":false},{"year":2010,"finding":"PMCA2 is expressed at the apical surface of mammary epithelial cells during lactation and transports calcium into milk. Loss of PMCA2 expression during mammary gland involution raises intracellular calcium levels and sensitizes mammary epithelial cells to apoptosis. Conversely, overexpression of PMCA2 in T47D breast cancer cells lowers intracellular calcium and protects them from apoptosis.","method":"PMCA2 knockout mice phenotyping; siRNA knockdown and overexpression in T47D cells with intracellular calcium measurement and apoptosis assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function and gain-of-function with calcium measurement and apoptosis readouts; genetic mouse model plus cell culture validation","pmids":["20534448"],"is_preprint":false},{"year":2010,"finding":"In cerebellar Purkinje neurons, reducing PMCA2 to 50% (heterozygous knockout) nearly doubles the time constant for calcium transient recovery in dendrites, prolongs calcium-dependent K+ currents, weakens climbing fiber responses, and slows action potential firing frequency, demonstrating that PMCA2 is required for the kinetics of calcium clearance that determines Purkinje neuron electrical output and motor coordination precision.","method":"Two-photon calcium imaging in Purkinje dendrites; whole-cell patch clamp in PMCA2+/- versus wild-type mice; Western blot for PMCA2 levels; narrow-beam behavioral assay","journal":"The Journal of physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal electrophysiological and imaging methods, direct causal link between protein level and calcium dynamics and neuronal output","pmids":["20083513"],"is_preprint":false},{"year":2011,"finding":"The PMCA2w/a splice variant (expressed in stereocilia) increases its activity only marginally in response to rapid cytoplasmic Ca2+ elevation (unlike other PMCA2 variants that are strongly stimulated), allowing constitutive calcium extrusion in stereocilia. A human mutant (V586M) failed to impair the pump's calcium ejection activity, while a murine mutant displayed evident defects in both basal activity and long-range calcium ejection.","method":"In vitro pump activity assays in model cells overexpressing wild-type or mutant PMCA2 variants; calcium ejection measured by aequorin-based assay","journal":"Cell calcium","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with site-specific mutants, direct enzymatic activity measurement, multiple variants compared","pmids":["22047666"],"is_preprint":false},{"year":2012,"finding":"PMCA2 interacts with calcineurin in breast cancer cells (inhibitory interaction). Disruption of the PMCA2/calcineurin interaction activates the calcineurin/NFAT pathway, upregulates the pro-apoptotic protein Fas Ligand, and induces apoptotic cell death; this effect is potentiated when combined with paclitaxel.","method":"Co-immunoprecipitation; disruption of PMCA2/calcineurin interaction with competing peptides; NFAT pathway reporter assay; Fas Ligand Western blot; viability and apoptosis assays in multiple breast cancer cell lines","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal functional interaction validated by peptide disruption and pathway readout; single lab, multiple cell lines","pmids":["22962307"],"is_preprint":false},{"year":2012,"finding":"PMCA2 is physically associated with α7-nicotinic acetylcholine receptors (α7-nAChRs) and the scaffold protein PSD-95 in hippocampal interneurons. PMCA2 activity limits the duration of calcium elevations produced by α7-nAChR activation. Inhibition of PMCA2 triggers rapid CaMKII- and proteasome-dependent removal of α7-nAChR clusters in a PSD-95-dependent manner, without affecting other calcium-permeable receptors on the same neurons.","method":"Functional proteomics (co-immunoprecipitation/mass spectrometry) from rat brain; calcium imaging in hippocampal interneuron cultures; PMCA2 inhibitor carboxyeosin; single-particle tracking of α7-nAChR; CaMKII inhibitor and proteasome inhibitor experiments","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — proteomic identification plus functional imaging, pharmacological dissection with multiple inhibitors, single-particle tracking; multiple orthogonal methods","pmids":["22593058"],"is_preprint":false},{"year":2012,"finding":"The w-splice insert in the first intracellular loop of PMCA2 is sufficient to direct apical membrane targeting when inserted into the normally basolateral PMCA4 isoform. Optimizing the PDZ ligand site to interact with scaffolding protein NHERF2 further enhances apical localization of the chimeric pump, demonstrating that the w-insert provides autonomous apical targeting information.","method":"Chimeric pump construction (PMCA4 with PMCA2 w-insert); polarized epithelial cell transfection; immunofluorescence localization; PDZ ligand mutagenesis; calcium signaling assays","journal":"Cell calcium","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution of targeting with chimeric construct, mutagenesis of targeting motif, localization validated in polarized cells","pmids":["22252018"],"is_preprint":false},{"year":2016,"finding":"PMCA2 physically interacts with HER2 in actin-rich membrane domains of breast cancer cells. Knockdown of PMCA2 increases intracellular calcium, disrupts HER2-HSP90 interactions, inhibits HER2 signaling, and causes internalization and degradation of HER2. Knockout of PMCA2 inhibits mammary tumor formation in MMTV-Neu mice, placing PMCA2 upstream of HER2 membrane retention and signaling.","method":"Co-immunoprecipitation; siRNA knockdown; reverse-phase protein array; confocal microscopy; PMCA2 knockout in MMTV-Neu mice; tumor formation assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, KD with multiple downstream readouts (calcium, HER2 signaling, localization), in vivo genetic knockout tumor model; multiple orthogonal methods","pmids":["26729871"],"is_preprint":false},{"year":2016,"finding":"Silencing of PMCA2 (but not PMCA1 or PMCA4) reduces MDA-MB-231 breast cancer cell proliferation and sensitizes cells to doxorubicin-induced cytotoxicity, demonstrating an isoform-specific role for PMCA2 in breast cancer cell survival.","method":"siRNA-mediated knockdown of PMCA2, PMCA1, and PMCA4; cell proliferation and viability assays; calcium signaling measurement; flow cytometry","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific siRNA with proliferation and drug sensitivity readouts, specificity confirmed by testing related isoforms; single lab","pmids":["27148852"],"is_preprint":false},{"year":2017,"finding":"PMCA2 activity is regulated by the cortical cytoskeleton: disruption of F-actin with cytochalasin D increases PMCA2-mediated Ca2+ extrusion (~50-100%), while stabilization of F-actin with jasplakinolide fully inhibits it. Microtubule disruption with colchicine decreases PMCA activity (~40-60%). These effects occur without changes in surface expression, indicating regulation of specific activity.","method":"Live cell calcium imaging in HEK293 cells expressing PMCA2; pharmacological manipulation of actin (cytochalasin D, jasplakinolide) and microtubules (colchicine); surface expression quantification","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live cell functional assay with pharmacological agents and surface expression control; single lab","pmids":["28527708"],"is_preprint":false},{"year":2019,"finding":"NHERF1 interacts with PMCA2 at the apical membrane of lactating mammary epithelial cells and is required for PMCA2's proper apical localization. Loss of NHERF1 in knockout mice displaces PMCA2 from the apical membrane, disrupts apical-basal polarity, and triggers premature Stat3 activation and lysosome-mediated cell death. PMCA2 also interacts with NHERF2, which partially compensates for NHERF1 loss.","method":"Co-immunoprecipitation; NHERF1 knockout mice; immunofluorescence localization; Western blot for Stat3 activation; mammary gland histology","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic KO mouse with defined localization and signaling consequences, multiple orthogonal methods","pmids":["31087002"],"is_preprint":false},{"year":2019,"finding":"PMCA2 expression in the dorsal horn is required for normal nociceptive processing in a sex-specific manner: female (but not male) PMCA2+/- mice show increased mechanical pain sensitivity and reduced heat sensitivity, accompanied by female-specific changes in mGluR1, NMDA receptor subunits, AMPA receptor subunit GluR1, GABA receptor subunits, and glutamate transporter levels in the dorsal horn.","method":"Behavioral pain assays (von Frey, Hargreaves) in PMCA2+/- vs. wild-type mice; Western blot for receptor and transporter levels in dorsal horn; sex-stratified analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic haploinsufficiency with behavioral and molecular readouts, sex-specificity established; single lab","pmids":["27702770"],"is_preprint":false},{"year":2019,"finding":"Decreased PMCA2 expression in the dorsal horn parallels increased neuropathic pain in EAE (multiple sclerosis model) and spinal cord injury mice. IL-1β, acting directly on spinal cord neurons in culture, specifically downregulates PMCA2 protein levels (SERCA and NCX remained unaltered), identifying IL-1β as an effector that reduces PMCA2 expression to increase neuronal calcium and pain sensitivity.","method":"Western blot of PMCA2 in dorsal horn of EAE and SCI mice; pure spinal cord neuronal cultures treated with cytokines (IL-1β, TNFα, IL-6); behavioral pain assays","journal":"Journal of neuroinflammation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct neuronal culture experiment showing IL-1β-specific effect on PMCA2 (with negative results for SERCA and NCX), correlated with in vivo pain models; single lab","pmids":["31703709"],"is_preprint":false},{"year":2018,"finding":"PMCA2 is required for adequate ERα signaling in the female dorsal horn: ERα agonist induces ERα signaling in PMCA2+/+ but not PMCA2+/- female mice, and estradiol analgesia is lost in PMCA2+/- females. This sex-specific link between PMCA2 and ERα is absent in male mice.","method":"Ovariectomy and estradiol replacement in PMCA2+/+ vs. PMCA2+/- mice; intrathecal ERα agonist administration; Western blot for ERα signaling in dorsal horn; behavioral pain assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic haploinsufficiency combined with pharmacological and hormonal manipulation, sex-stratified; single lab","pmids":["30467368"],"is_preprint":false},{"year":2013,"finding":"PMCA2 activity is required for Purkinje cell dendritic growth: pharmacological inhibition of PMCA2 with carboxyeosin reduces Purkinje cell dendritic tree size in cerebellar organotypic slice cultures. PMCA2 inhibition also partially rescues dendritic morphology when combined with mGluR1 stimulation, likely via compensatory inactivation of voltage-gated calcium channels.","method":"Organotypic cerebellar slice cultures; carboxyeosin inhibition of PMCA2; immunofluorescence for Purkinje cell morphology; pharmacological combinations with mGluR1 agonists and calcium channel blockers","journal":"Neural plasticity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with morphological quantification and mechanistic follow-up; single lab","pmids":["24288624"],"is_preprint":false},{"year":2013,"finding":"Downregulation of PMCA2 in PC12 cells accelerates neuronal differentiation, promotes longer neurite formation, and leads to apoptosis with DNA laddering. PMCA2 suppression triggers compensatory upregulation of PMCA1, PMCA4, and SERCA, and alters voltage-dependent calcium channel expression and contribution to calcium influx.","method":"Stable antisense transfection of PC12 cells; cAMP-induced differentiation; Western blot for calcium handling proteins; calcium influx measurements; apoptosis assays (DNA laddering)","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — stable knockdown with multiple functional readouts; single lab, single method per readout","pmids":["22921123"],"is_preprint":false},{"year":2017,"finding":"PMCA2-interacting complex in kidney cells includes 474 proteins identified by immunoprecipitation-mass spectrometry. Functional validation revealed a novel role for PMCA2 as a calcium oxalate monohydrate (COM) crystal-binding protein: neutralization with anti-PMCA2 antibody reduces COM crystal-cell adhesion and crystal internalization, implicating PMCA2 in kidney stone pathogenesis.","method":"Immunoprecipitation followed by nanoLC-ESI-Qq-TripleTOF MS/MS; quantitative immuno-co-localization; COM crystal-protein binding assay; crystal-cell adhesion and internalization assays with antibody neutralization","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — IP-MS for interactome plus functional crystal-binding assays with antibody neutralization as specificity control; single lab","pmids":["29085954"],"is_preprint":false},{"year":2025,"finding":"A splice variant of PMCA2 localizes to the lysosome (not only the plasma membrane) where it forms an evolutionarily conserved complex with NPC1. This lysosomal PMCA2 mediates calcium uptake into lysosomes. Disruption of the NPC1-PMCA2 complex contributes to lysosomal calcium dysregulation in Niemann-Pick disease type C and Parkinson's disease.","method":"Subcellular fractionation/localization; co-immunoprecipitation with NPC1; lysosomal calcium measurements; disease model validation (NPC, Parkinson's disease models)","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel splice-variant-dependent localization with Co-IP and lysosomal calcium functional assays; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.10.01.679724"],"is_preprint":true},{"year":2025,"finding":"Cryo-EM structure of human calcium-bound ATP2B2 at 2.64 Å resolution was determined. Structural analysis revealed that neuropsychiatric disease-associated missense variants cluster near the Ca2+ pore and ATP:Mg2+ coordination site. In vitro assays confirmed that missense variants at these structural hotspots impair ATP2B2-mediated Ca2+ extrusion in cellular and biochemical assays.","method":"Cryo-EM structure determination at 2.64 Å; 3D-neighborhood missense variant clustering analysis on AlphaFold3-predicted structures validated by the cryo-EM map; in vitro Ca2+ extrusion assays with disease-associated missense mutants","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — near-atomic cryo-EM structure with functional mutagenesis validation; preprint, not yet peer-reviewed, but multiple orthogonal methods","pmids":["bio_10.1101_2025.08.25.672202"],"is_preprint":true},{"year":2023,"finding":"De novo missense ATP2B2 variants (including variants at Ca2+ transport domain residues) cause both loss-of-function and gain-of-function alterations in cytosolic calcium handling in cell-based studies, demonstrating that precise ATP2B2-mediated calcium regulation is required for neurodevelopment and cerebellar function.","method":"Exome/genome sequencing; in silico structural analysis; cell-based cytosolic calcium handling assays for each variant; clinical phenotyping","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional calcium assays for multiple distinct variants; single report with multiple affected individuals","pmids":["37675773"],"is_preprint":false}],"current_model":"ATP2B2/PMCA2 is a plasma membrane calcium-extruding ATPase whose w/a splice variant constitutively pumps Ca2+ from hair cell stereocilia into endolymph to maintain endolymph calcium homeostasis and hair cell mechanotransduction; its subcellular targeting (apical vs. basolateral) is directed by alternative splicing at the first intracellular loop (w-insert confers apical targeting) and is stabilized by interaction with PDZ-scaffold proteins NHERF1/NHERF2; in mammary epithelial and breast cancer cells PMCA2 lowers cytosolic Ca2+ to suppress apoptosis and, by interacting with HER2 in actin-rich membrane domains and maintaining HER2-HSP90 stability, promotes HER2 signaling and tumor growth; in neurons PMCA2 clears dendritic Ca2+ transients to shape Purkinje neuron firing and cerebellar output, participates in the mGluR1-Homer-IP3R1 signaling complex, and via PSD-95 controls α7-nAChR cluster stability; a lysosomal splice variant additionally forms a complex with NPC1 to mediate lysosomal Ca2+ uptake; cytoskeletal state (F-actin polymerization) directly modulates PMCA2 specific activity; and loss-of-function or gain-of-function variants in the Ca2+ pore or ATP:Mg2+ coordination domain cause deafness, vestibular dysfunction, and neurodevelopmental/movement disorders."},"narrative":{"mechanistic_narrative":"ATP2B2 (PMCA2) is a plasma-membrane Ca2+-extruding ATPase that sets and shapes cytosolic and luminal calcium across sensory, neuronal, and epithelial tissues, with its subcellular targeting and activity tuned by alternative splicing and partner proteins [PMID:15357414, PMID:20826782, PMID:22252018]. In cochlear and vestibular hair cells PMCA2 resides in stereocilia and pumps Ca2+ into endolymph, acting as the primary determinant of endolymph calcium homeostasis required for mechanotransduction [PMID:15357414]. Its membrane polarity is splice-controlled: a Leu-Ile motif in 'b'-tail variants drives basolateral sorting while the size of the A-site insert directs apical targeting, and the w-insert in the first cytoplasmic loop carries autonomous apical-targeting information further reinforced by PDZ-scaffold interactions with NHERF1/NHERF2 [PMID:16803870, PMID:22252018, PMID:31087002]. The w/a stereociliar variant is largely uncoupled from acute Ca2+ stimulation, enabling constitutive calcium extrusion [PMID:22047666]. Disease-associated missense variants cluster near the Ca2+ pore and ATP:Mg2+ coordination site and impair pump activity, producing both loss- and gain-of-function effects that underlie progressive hearing loss, hair cell degeneration, and neurodevelopmental/cerebellar disorders [PMID:18974863, PMID:20826782, PMID:bio_10.1101_2025.08.25.672202, PMID:37675773]. In Purkinje neurons PMCA2 clears dendritic Ca2+ transients to set firing kinetics and dendritic growth, and is a constituent of the mGluR1-Homer-IP3R1 complex [PMID:17150372, PMID:20083513, PMID:24288624]; in hippocampal interneurons it associates with α7-nAChRs and PSD-95 to control receptor cluster stability [PMID:22593058]. In mammary epithelium and breast cancer PMCA2 lowers cytosolic calcium to suppress apoptosis, interacts with HER2 in actin-rich domains to maintain HER2-HSP90 stability and signaling, and promotes tumor formation [PMID:20534448, PMID:26729871, PMID:27148852]. Pump specific activity is directly modulated by the cortical cytoskeleton, with F-actin polymerization inhibiting and disruption enhancing Ca2+ extrusion [PMID:28527708].","teleology":[{"year":2004,"claim":"Established the core physiological role of PMCA2 by showing it is the dominant calcium-extrusion route from hair cell stereocilia into endolymph, settling where and why the pump matters for hearing.","evidence":"Immunocytochemistry plus endolymph calcium measurement in dfw2J knockout vs control mice","pmids":["15357414"],"confidence":"High","gaps":["Does not resolve splice-variant identity or molecular targeting mechanism in stereocilia","No structural basis for pump activity"]},{"year":2006,"claim":"Answered how a single gene achieves polarized membrane targeting, showing splice variation encodes basolateral versus apical sorting signals.","evidence":"Targeting-region mutagenesis and splice-variant expression with immunofluorescence in hair cells","pmids":["16803870"],"confidence":"High","gaps":["Did not identify the scaffold proteins that read the apical signal","Mechanism of the A-site insert size effect unresolved"]},{"year":2006,"claim":"Placed PMCA2 within the neuronal mGluR1 signaling machinery, linking calcium clearance to metabotropic glutamate receptor signaling integrity in Purkinje neurons.","evidence":"Co-immunoprecipitation from cerebellum and protein-level analysis in PMCA2-null vs wild-type mice","pmids":["17150372"],"confidence":"Medium","gaps":["Single-lab Co-IP without reciprocal validation of each partner","Direct versus indirect association within the complex not distinguished"]},{"year":2008,"claim":"Separated targeting from catalytic defects, showing a TM6 missense mutation reduces basal pump activity without mislocalization and causes progressive hair cell loss.","evidence":"ENU Oblivion (S877F) allele with in vitro pump activity assay, hair cell culture and histology","pmids":["18974863"],"confidence":"High","gaps":["Mechanism by which reduced basal activity drives base-to-apex degeneration not defined","No structural model of the mutation site at the time"]},{"year":2010,"claim":"Extended the genotype-function map with an active-site mutation impairing long-term calcium extrusion, confirmed by direct calcium imaging in native sensory epithelium.","evidence":"Tommy (E629K) allele; CHO extrusion assay plus flash photolysis of caged calcium in utricle cultures and ABR","pmids":["20826782"],"confidence":"High","gaps":["Dominant heterozygous mechanism not fully explained","Relationship to splice variant context unaddressed"]},{"year":2010,"claim":"Defined a non-sensory role, showing apical PMCA2 transports calcium into milk and that its loss raises cytosolic calcium to sensitize epithelial cells to apoptosis, with the reverse protecting cancer cells.","evidence":"PMCA2 knockout mouse mammary phenotyping plus siRNA and overexpression in T47D cells with calcium and apoptosis readouts","pmids":["20534448"],"confidence":"High","gaps":["Downstream apoptotic effectors not identified at this stage","Did not address HER2 or calcineurin coupling"]},{"year":2010,"claim":"Quantified the neuronal calcium-clearance function, showing PMCA2 dosage controls dendritic calcium transient kinetics and thereby Purkinje neuron firing and motor precision.","evidence":"Two-photon calcium imaging and patch clamp in PMCA2+/- vs wild-type cerebellum with behavioral testing","pmids":["20083513"],"confidence":"High","gaps":["Molecular partners mediating dendritic localization not defined here","Link to specific behavioral circuits incomplete"]},{"year":2011,"claim":"Explained how the stereociliar w/a variant supports constitutive extrusion, showing it is only marginally stimulated by acute calcium and that species-specific mutants differ in activity impact.","evidence":"In vitro aequorin-based calcium ejection assays of wild-type and mutant PMCA2 variants","pmids":["22047666"],"confidence":"High","gaps":["Structural basis for stimulation-independence not resolved","Discordance between human V586M and murine mutant phenotypes unexplained"]},{"year":2012,"claim":"Connected PMCA2 anti-apoptotic function to a defined effector pathway, showing it restrains calcineurin/NFAT/FasL signaling in breast cancer cells.","evidence":"Co-IP, peptide disruption of the PMCA2/calcineurin interaction, NFAT reporter and apoptosis assays across cell lines","pmids":["22962307"],"confidence":"Medium","gaps":["Single-lab interaction not independently confirmed","Whether the interaction is direct or scaffold-mediated unresolved"]},{"year":2012,"claim":"Identified a neuronal scaffold function, showing PMCA2 with PSD-95 limits α7-nAChR calcium signals and controls receptor cluster stability via CaMKII/proteasome turnover.","evidence":"Co-IP/MS from brain, calcium imaging, single-particle tracking and pharmacological dissection in hippocampal interneurons","pmids":["22593058"],"confidence":"High","gaps":["Direct binding interface among PMCA2, PSD-95 and α7-nAChR not mapped","Generalizability beyond interneurons untested"]},{"year":2012,"claim":"Demonstrated that the w-insert is an autonomous apical targeting determinant, transferable to a normally basolateral isoform and enhanced by NHERF2-binding PDZ optimization.","evidence":"PMCA4/PMCA2-w chimera expression in polarized epithelial cells with localization and PDZ-ligand mutagenesis","pmids":["22252018"],"confidence":"High","gaps":["Trafficking machinery recognizing the w-insert not identified","Quantitative contribution of PDZ versus insert in native cells unresolved"]},{"year":2013,"claim":"Linked PMCA2 calcium clearance to neuronal morphogenesis, showing its activity is required for Purkinje dendritic growth.","evidence":"Carboxyeosin inhibition in organotypic cerebellar slices with morphological quantification and pharmacological combinations","pmids":["24288624"],"confidence":"Medium","gaps":["Carboxyeosin specificity for PMCA2 limited","Mechanistic coupling to mGluR1 and calcium channels only partially defined"]},{"year":2013,"claim":"Showed PMCA2 level controls neuronal differentiation and survival, with knockdown accelerating neurite outgrowth and triggering apoptosis alongside compensatory calcium-handler upregulation.","evidence":"Stable antisense PC12 cells with differentiation, calcium influx and apoptosis assays","pmids":["22921123"],"confidence":"Medium","gaps":["Compensation by PMCA1/4 and SERCA confounds interpretation","Direct causal pathway to apoptosis not isolated"]},{"year":2016,"claim":"Defined a pro-tumorigenic mechanism upstream of HER2, showing PMCA2 maintains HER2-HSP90 stability and membrane retention in actin-rich domains and is required for HER2-driven tumor formation.","evidence":"Reciprocal Co-IP, siRNA with multiple readouts, RPPA, and PMCA2 knockout in MMTV-Neu mice","pmids":["26729871"],"confidence":"High","gaps":["Whether HER2 interaction is direct or calcium/actin-dependent not fully separated","Structural interface unmapped"]},{"year":2016,"claim":"Established isoform specificity in cancer, showing only PMCA2 (not PMCA1/4) supports proliferation and chemoresistance.","evidence":"Isoform-specific siRNA with proliferation, viability and doxorubicin-sensitivity assays in MDA-MB-231 cells","pmids":["27148852"],"confidence":"Medium","gaps":["Single-lab study","Mechanism linking PMCA2 to drug resistance not defined"]},{"year":2017,"claim":"Revealed cytoskeletal control of pump output, showing F-actin state directly modulates PMCA2 specific activity independent of surface expression.","evidence":"Live-cell calcium imaging in HEK293 with actin and microtubule pharmacology plus surface-expression controls","pmids":["28527708"],"confidence":"Medium","gaps":["Molecular link between cytoskeleton and pump conformation unknown","Physiological context of regulation untested"]},{"year":2017,"claim":"Uncovered an extracellular/adhesion function, identifying PMCA2 as a calcium oxalate crystal-binding protein relevant to kidney stone pathogenesis.","evidence":"IP-MS interactome plus COM crystal-binding, adhesion and internalization assays with antibody neutralization in kidney cells","pmids":["29085954"],"confidence":"Medium","gaps":["Whether crystal binding depends on pump activity unclear","Single-lab functional validation"]},{"year":2018,"claim":"Linked PMCA2 to sex-specific hormonal signaling, showing it is required for ERα signaling and estradiol analgesia in female dorsal horn.","evidence":"Ovariectomy/estradiol replacement and ERα agonist in PMCA2+/- vs wild-type mice with signaling and pain readouts","pmids":["30467368"],"confidence":"Medium","gaps":["Mechanism connecting calcium handling to ERα signaling undefined","Male-female divergence unexplained"]},{"year":2019,"claim":"Defined PMCA2's role in nociceptive processing, showing haploinsufficiency alters pain sensitivity and dorsal-horn receptor/transporter levels in a sex-specific manner.","evidence":"Behavioral pain assays and Western blots in PMCA2+/- mice with sex stratification","pmids":["27702770"],"confidence":"Medium","gaps":["Causality between receptor changes and pain phenotype not established","Cell-type origin of changes unresolved"]},{"year":2019,"claim":"Identified an upstream regulator of PMCA2 in pathological pain, showing IL-1β specifically downregulates PMCA2 to raise neuronal calcium.","evidence":"Western blot of PMCA2 in EAE/SCI dorsal horn and cytokine treatment of spinal neuron cultures with negative controls for SERCA/NCX","pmids":["31703709"],"confidence":"Medium","gaps":["Transcriptional vs post-translational mechanism of downregulation unknown","Single-lab correlation with in vivo pain"]},{"year":2019,"claim":"Established the apical scaffolding requirement, showing NHERF1 retains PMCA2 at the apical membrane and that its loss disrupts polarity and triggers cell death.","evidence":"Reciprocal Co-IP, NHERF1 knockout mice, localization, Stat3 readout and histology in lactating mammary gland","pmids":["31087002"],"confidence":"High","gaps":["Relative contributions of NHERF1 vs NHERF2 not quantified","Whether cell death is a direct consequence of PMCA2 mislocalization unclear"]},{"year":2023,"claim":"Connected PMCA2 to human neurodevelopmental disease, showing de novo variants cause both loss- and gain-of-function calcium-handling changes.","evidence":"Exome/genome sequencing, in silico structural analysis and cell-based cytosolic calcium assays for multiple variants","pmids":["37675773"],"confidence":"Medium","gaps":["Mechanism by which gain-of-function variants cause disease unresolved","Genotype-phenotype correlation across variants incomplete"]},{"year":2025,"claim":"Provided the structural framework, determining a cryo-EM structure that localizes neuropsychiatric variants to the Ca2+ pore and ATP:Mg2+ site and confirms their functional impact.","evidence":"Cryo-EM at 2.64 Å with 3D variant-clustering analysis and in vitro Ca2+ extrusion assays of disease mutants (preprint)","pmids":["bio_10.1101_2025.08.25.672202"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Structure does not capture splice-variant or partner-bound states"]},{"year":2025,"claim":"Expanded the localization repertoire, showing a lysosomal splice variant forms a conserved complex with NPC1 to mediate lysosomal calcium uptake relevant to NPC and Parkinson's disease.","evidence":"Subcellular fractionation, Co-IP with NPC1 and lysosomal calcium measurements in disease models (preprint)","pmids":["bio_10.1101_2025.10.01.679724"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Splice-variant determinant of lysosomal targeting not mapped","Direct vs indirect NPC1 association unconfirmed"]},{"year":null,"claim":"How distinct splice variants, partner scaffolds, and cytoskeletal state are integrated to select PMCA2 localization (apical, basolateral, lysosomal) and tune activity in a tissue-specific manner remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking splice variant to trafficking machinery","Structural basis of partner and cytoskeletal regulation undefined","Mechanism distinguishing loss- vs gain-of-function disease outcomes unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[3,4,7,22]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,5,7,21]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[3,4,22]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,3,10,11]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[21]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,5,7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,9,11]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5,8,19]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[6,9,18]}],"complexes":["mGluR1-Homer-IP3R1 signaling complex","PMCA2-NPC1 lysosomal complex"],"partners":["NHERF1","NHERF2","HER2","HSP90","CALCINEURIN","PSD-95","CHRNA7","NPC1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q01814","full_name":"Plasma membrane calcium-transporting ATPase 2","aliases":["Plasma membrane calcium ATPase isoform 2","Plasma membrane calcium pump isoform 2"],"length_aa":1243,"mass_kda":136.9,"function":"ATP-driven Ca(2+) ion pump involved in the maintenance of basal intracellular Ca(2+) levels in specialized cells of cerebellar circuit and vestibular and cochlear systems (PubMed:15829536, PubMed:17234811). Uses ATP as an energy source to transport cytosolic Ca(2+) ions across the plasma membrane to the extracellular compartment (PubMed:15829536, PubMed:17234811). Has fast activation and Ca(2+) clearance rate suited to control fast neuronal Ca(2+) dynamics. At parallel fiber to Purkinje neuron synapse, mediates presynaptic Ca(2+) efflux in response to climbing fiber-induced Ca(2+) rise. Provides for fast return of Ca(2+) concentrations back to their resting levels, ultimately contributing to long-term depression induction and motor learning (By similarity). Plays an essential role in hearing and balance (PubMed:15829536, PubMed:17234811). In cochlear hair cells, shuttles Ca(2+) ions from stereocilia to the endolymph and dissipates Ca(2+) transients generated by the opening of the mechanoelectrical transduction channels. Regulates Ca(2+) levels in the vestibular system, where it contributes to the formation of otoconia (PubMed:15829536, PubMed:17234811). In non-excitable cells, regulates Ca(2+) signaling through spatial control of Ca(2+) ions extrusion and dissipation of Ca(2+) transients generated by store-operated channels (PubMed:25690014). In lactating mammary gland, allows for the high content of Ca(2+) ions in the milk (By similarity)","subcellular_location":"Basolateral cell membrane","url":"https://www.uniprot.org/uniprotkb/Q01814/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ATP2B2","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/ATP2B2","total_profiled":1310},"omim":[{"mim_id":"619804","title":"DEAFNESS, AUTOSOMAL DOMINANT 82; DFNA82","url":"https://www.omim.org/entry/619804"},{"mim_id":"613792","title":"CHROMOSOME 3pter-p25 DELETION SYNDROME","url":"https://www.omim.org/entry/613792"},{"mim_id":"607806","title":"OTOPETRIN 1; OTOP1","url":"https://www.omim.org/entry/607806"},{"mim_id":"605516","title":"CADHERIN 23; CDH23","url":"https://www.omim.org/entry/605516"},{"mim_id":"603963","title":"INTEGRIN, ALPHA-9; ITGA9","url":"https://www.omim.org/entry/603963"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":88.0},{"tissue":"choroid plexus","ntpm":61.0},{"tissue":"salivary gland","ntpm":31.3},{"tissue":"skeletal muscle","ntpm":35.1}],"url":"https://www.proteinatlas.org/search/ATP2B2"},"hgnc":{"alias_symbol":["PMCA2"],"prev_symbol":[]},"alphafold":{"accession":"Q01814","domains":[{"cath_id":"2.70.150.10","chopping":"31-86_209-289","consensus_level":"high","plddt":84.4845,"start":31,"end":289},{"cath_id":"1.20.1110.10","chopping":"386-473_867-928_950-1097","consensus_level":"medium","plddt":83.8227,"start":386,"end":1097},{"cath_id":"3.40.50.1000","chopping":"480-505_712-857","consensus_level":"medium","plddt":86.4566,"start":480,"end":857},{"cath_id":"3.40.1110.10","chopping":"511-707","consensus_level":"high","plddt":86.9423,"start":511,"end":707},{"cath_id":"1.10.287","chopping":"98-128_149-188","consensus_level":"high","plddt":74.0665,"start":98,"end":188}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q01814","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q01814-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q01814-F1-predicted_aligned_error_v6.png","plddt_mean":73.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ATP2B2","jax_strain_url":"https://www.jax.org/strain/search?query=ATP2B2"},"sequence":{"accession":"Q01814","fasta_url":"https://rest.uniprot.org/uniprotkb/Q01814.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q01814/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q01814"}},"corpus_meta":[{"pmid":"15829536","id":"PMC_15829536","title":"Modification 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Mice lacking PMCA2 (dfw2J) have significantly lower endolymph calcium concentrations, establishing that PMCA2 is the primary mechanism for calcium extrusion from stereocilia into endolymph and is required for endolymph calcium maintenance.\",\n      \"method\": \"Immunocytochemistry for PMCA2 localization in stereocilia; calcium-sensitive fluorescent dye with aspirating microelectrode to measure endolymph calcium in dfw2J versus control mice\",\n      \"journal\": \"Journal of the Association for Research in Otolaryngology : JARO\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization plus functional consequence (calcium measurement) in genetic knockout model; findings consistent with multiple other studies\",\n      \"pmids\": [\"15357414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Differential membrane targeting of PMCA2 in hair cells is determined by alternative splicing: a Leu-Ile motif in 'b'-tail splice variants promotes basolateral sorting, whereas apical targeting of PMCA2 depends on the size of the A-site-spliced insert in the first cytoplasmic loop.\",\n      \"method\": \"Targeting region mutagenesis and expression of splice variants in hair cells; immunofluorescence localization\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of splice regions combined with direct localization in hair cells, two orthogonal approaches\",\n      \"pmids\": [\"16803870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PMCA2 co-immunoprecipitates with mGluR1, Homer 3, and IP3R1 in cerebellar Purkinje neurons, indicating it is a constituent of the mGluR1 signaling complex. Loss of PMCA2 in null mice results in reduced cerebellar levels of mGluR1, IP3R1, Homer 1b/c, and Homer 3, specifically in Purkinje neurons but not hippocampus, indicating region-specific disruption of metabotropic glutamate receptor signaling.\",\n      \"method\": \"Co-immunoprecipitation from cerebellar tissue; Western blot and immunofluorescence in PMCA2-null mice vs. wild-type littermates\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP supported by KO phenotyping with multiple protein readouts; single lab\",\n      \"pmids\": [\"17150372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"A missense mutation (S877F) in transmembrane domain 6 of PMCA2 (Oblivion allele) does not impair targeting to the plasma membrane but significantly reduces the non-stimulated (basal) calcium-exporting activity of the pump, causing progressive hearing loss with base-to-apex hair cell degeneration.\",\n      \"method\": \"ENU mutagenesis; mutation analysis; pump expression in model cells with biochemical/biophysical characterization of Ca2+ export; hair cell culture; immunofluorescence\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro pump activity assay with identified mutation, correct membrane targeting confirmed, multiple orthogonal methods (biochemical, biophysical, histological) in single rigorous study\",\n      \"pmids\": [\"18974863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A missense mutation E629K in the second intracellular loop (active site) of PMCA2 (Tommy allele) impairs the long-term, non-stimulated calcium extrusion activity of the pump. Direct measurement by confocal imaging combined with flash photolysis of caged calcium in neonatal utricle sensory epithelium showed impaired calcium export in heterozygous and homozygous Tommy mice, causing profound hearing impairment and progressive hair cell degeneration.\",\n      \"method\": \"CHO cell expression with calcium extrusion assay; confocal imaging with flash photolysis of caged calcium in organotypic utricle cultures; immunofluorescence; auditory brainstem response\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro pump activity reconstitution, direct calcium imaging in native tissue, genetic mouse model with hearing phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"20826782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PMCA2 is expressed at the apical surface of mammary epithelial cells during lactation and transports calcium into milk. Loss of PMCA2 expression during mammary gland involution raises intracellular calcium levels and sensitizes mammary epithelial cells to apoptosis. Conversely, overexpression of PMCA2 in T47D breast cancer cells lowers intracellular calcium and protects them from apoptosis.\",\n      \"method\": \"PMCA2 knockout mice phenotyping; siRNA knockdown and overexpression in T47D cells with intracellular calcium measurement and apoptosis assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function and gain-of-function with calcium measurement and apoptosis readouts; genetic mouse model plus cell culture validation\",\n      \"pmids\": [\"20534448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In cerebellar Purkinje neurons, reducing PMCA2 to 50% (heterozygous knockout) nearly doubles the time constant for calcium transient recovery in dendrites, prolongs calcium-dependent K+ currents, weakens climbing fiber responses, and slows action potential firing frequency, demonstrating that PMCA2 is required for the kinetics of calcium clearance that determines Purkinje neuron electrical output and motor coordination precision.\",\n      \"method\": \"Two-photon calcium imaging in Purkinje dendrites; whole-cell patch clamp in PMCA2+/- versus wild-type mice; Western blot for PMCA2 levels; narrow-beam behavioral assay\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal electrophysiological and imaging methods, direct causal link between protein level and calcium dynamics and neuronal output\",\n      \"pmids\": [\"20083513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The PMCA2w/a splice variant (expressed in stereocilia) increases its activity only marginally in response to rapid cytoplasmic Ca2+ elevation (unlike other PMCA2 variants that are strongly stimulated), allowing constitutive calcium extrusion in stereocilia. A human mutant (V586M) failed to impair the pump's calcium ejection activity, while a murine mutant displayed evident defects in both basal activity and long-range calcium ejection.\",\n      \"method\": \"In vitro pump activity assays in model cells overexpressing wild-type or mutant PMCA2 variants; calcium ejection measured by aequorin-based assay\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with site-specific mutants, direct enzymatic activity measurement, multiple variants compared\",\n      \"pmids\": [\"22047666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PMCA2 interacts with calcineurin in breast cancer cells (inhibitory interaction). Disruption of the PMCA2/calcineurin interaction activates the calcineurin/NFAT pathway, upregulates the pro-apoptotic protein Fas Ligand, and induces apoptotic cell death; this effect is potentiated when combined with paclitaxel.\",\n      \"method\": \"Co-immunoprecipitation; disruption of PMCA2/calcineurin interaction with competing peptides; NFAT pathway reporter assay; Fas Ligand Western blot; viability and apoptosis assays in multiple breast cancer cell lines\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal functional interaction validated by peptide disruption and pathway readout; single lab, multiple cell lines\",\n      \"pmids\": [\"22962307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PMCA2 is physically associated with α7-nicotinic acetylcholine receptors (α7-nAChRs) and the scaffold protein PSD-95 in hippocampal interneurons. PMCA2 activity limits the duration of calcium elevations produced by α7-nAChR activation. Inhibition of PMCA2 triggers rapid CaMKII- and proteasome-dependent removal of α7-nAChR clusters in a PSD-95-dependent manner, without affecting other calcium-permeable receptors on the same neurons.\",\n      \"method\": \"Functional proteomics (co-immunoprecipitation/mass spectrometry) from rat brain; calcium imaging in hippocampal interneuron cultures; PMCA2 inhibitor carboxyeosin; single-particle tracking of α7-nAChR; CaMKII inhibitor and proteasome inhibitor experiments\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proteomic identification plus functional imaging, pharmacological dissection with multiple inhibitors, single-particle tracking; multiple orthogonal methods\",\n      \"pmids\": [\"22593058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The w-splice insert in the first intracellular loop of PMCA2 is sufficient to direct apical membrane targeting when inserted into the normally basolateral PMCA4 isoform. Optimizing the PDZ ligand site to interact with scaffolding protein NHERF2 further enhances apical localization of the chimeric pump, demonstrating that the w-insert provides autonomous apical targeting information.\",\n      \"method\": \"Chimeric pump construction (PMCA4 with PMCA2 w-insert); polarized epithelial cell transfection; immunofluorescence localization; PDZ ligand mutagenesis; calcium signaling assays\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution of targeting with chimeric construct, mutagenesis of targeting motif, localization validated in polarized cells\",\n      \"pmids\": [\"22252018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PMCA2 physically interacts with HER2 in actin-rich membrane domains of breast cancer cells. Knockdown of PMCA2 increases intracellular calcium, disrupts HER2-HSP90 interactions, inhibits HER2 signaling, and causes internalization and degradation of HER2. Knockout of PMCA2 inhibits mammary tumor formation in MMTV-Neu mice, placing PMCA2 upstream of HER2 membrane retention and signaling.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; reverse-phase protein array; confocal microscopy; PMCA2 knockout in MMTV-Neu mice; tumor formation assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, KD with multiple downstream readouts (calcium, HER2 signaling, localization), in vivo genetic knockout tumor model; multiple orthogonal methods\",\n      \"pmids\": [\"26729871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Silencing of PMCA2 (but not PMCA1 or PMCA4) reduces MDA-MB-231 breast cancer cell proliferation and sensitizes cells to doxorubicin-induced cytotoxicity, demonstrating an isoform-specific role for PMCA2 in breast cancer cell survival.\",\n      \"method\": \"siRNA-mediated knockdown of PMCA2, PMCA1, and PMCA4; cell proliferation and viability assays; calcium signaling measurement; flow cytometry\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific siRNA with proliferation and drug sensitivity readouts, specificity confirmed by testing related isoforms; single lab\",\n      \"pmids\": [\"27148852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PMCA2 activity is regulated by the cortical cytoskeleton: disruption of F-actin with cytochalasin D increases PMCA2-mediated Ca2+ extrusion (~50-100%), while stabilization of F-actin with jasplakinolide fully inhibits it. Microtubule disruption with colchicine decreases PMCA activity (~40-60%). These effects occur without changes in surface expression, indicating regulation of specific activity.\",\n      \"method\": \"Live cell calcium imaging in HEK293 cells expressing PMCA2; pharmacological manipulation of actin (cytochalasin D, jasplakinolide) and microtubules (colchicine); surface expression quantification\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live cell functional assay with pharmacological agents and surface expression control; single lab\",\n      \"pmids\": [\"28527708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NHERF1 interacts with PMCA2 at the apical membrane of lactating mammary epithelial cells and is required for PMCA2's proper apical localization. Loss of NHERF1 in knockout mice displaces PMCA2 from the apical membrane, disrupts apical-basal polarity, and triggers premature Stat3 activation and lysosome-mediated cell death. PMCA2 also interacts with NHERF2, which partially compensates for NHERF1 loss.\",\n      \"method\": \"Co-immunoprecipitation; NHERF1 knockout mice; immunofluorescence localization; Western blot for Stat3 activation; mammary gland histology\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic KO mouse with defined localization and signaling consequences, multiple orthogonal methods\",\n      \"pmids\": [\"31087002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PMCA2 expression in the dorsal horn is required for normal nociceptive processing in a sex-specific manner: female (but not male) PMCA2+/- mice show increased mechanical pain sensitivity and reduced heat sensitivity, accompanied by female-specific changes in mGluR1, NMDA receptor subunits, AMPA receptor subunit GluR1, GABA receptor subunits, and glutamate transporter levels in the dorsal horn.\",\n      \"method\": \"Behavioral pain assays (von Frey, Hargreaves) in PMCA2+/- vs. wild-type mice; Western blot for receptor and transporter levels in dorsal horn; sex-stratified analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic haploinsufficiency with behavioral and molecular readouts, sex-specificity established; single lab\",\n      \"pmids\": [\"27702770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Decreased PMCA2 expression in the dorsal horn parallels increased neuropathic pain in EAE (multiple sclerosis model) and spinal cord injury mice. IL-1β, acting directly on spinal cord neurons in culture, specifically downregulates PMCA2 protein levels (SERCA and NCX remained unaltered), identifying IL-1β as an effector that reduces PMCA2 expression to increase neuronal calcium and pain sensitivity.\",\n      \"method\": \"Western blot of PMCA2 in dorsal horn of EAE and SCI mice; pure spinal cord neuronal cultures treated with cytokines (IL-1β, TNFα, IL-6); behavioral pain assays\",\n      \"journal\": \"Journal of neuroinflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct neuronal culture experiment showing IL-1β-specific effect on PMCA2 (with negative results for SERCA and NCX), correlated with in vivo pain models; single lab\",\n      \"pmids\": [\"31703709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PMCA2 is required for adequate ERα signaling in the female dorsal horn: ERα agonist induces ERα signaling in PMCA2+/+ but not PMCA2+/- female mice, and estradiol analgesia is lost in PMCA2+/- females. This sex-specific link between PMCA2 and ERα is absent in male mice.\",\n      \"method\": \"Ovariectomy and estradiol replacement in PMCA2+/+ vs. PMCA2+/- mice; intrathecal ERα agonist administration; Western blot for ERα signaling in dorsal horn; behavioral pain assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic haploinsufficiency combined with pharmacological and hormonal manipulation, sex-stratified; single lab\",\n      \"pmids\": [\"30467368\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PMCA2 activity is required for Purkinje cell dendritic growth: pharmacological inhibition of PMCA2 with carboxyeosin reduces Purkinje cell dendritic tree size in cerebellar organotypic slice cultures. PMCA2 inhibition also partially rescues dendritic morphology when combined with mGluR1 stimulation, likely via compensatory inactivation of voltage-gated calcium channels.\",\n      \"method\": \"Organotypic cerebellar slice cultures; carboxyeosin inhibition of PMCA2; immunofluorescence for Purkinje cell morphology; pharmacological combinations with mGluR1 agonists and calcium channel blockers\",\n      \"journal\": \"Neural plasticity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with morphological quantification and mechanistic follow-up; single lab\",\n      \"pmids\": [\"24288624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Downregulation of PMCA2 in PC12 cells accelerates neuronal differentiation, promotes longer neurite formation, and leads to apoptosis with DNA laddering. PMCA2 suppression triggers compensatory upregulation of PMCA1, PMCA4, and SERCA, and alters voltage-dependent calcium channel expression and contribution to calcium influx.\",\n      \"method\": \"Stable antisense transfection of PC12 cells; cAMP-induced differentiation; Western blot for calcium handling proteins; calcium influx measurements; apoptosis assays (DNA laddering)\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — stable knockdown with multiple functional readouts; single lab, single method per readout\",\n      \"pmids\": [\"22921123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PMCA2-interacting complex in kidney cells includes 474 proteins identified by immunoprecipitation-mass spectrometry. Functional validation revealed a novel role for PMCA2 as a calcium oxalate monohydrate (COM) crystal-binding protein: neutralization with anti-PMCA2 antibody reduces COM crystal-cell adhesion and crystal internalization, implicating PMCA2 in kidney stone pathogenesis.\",\n      \"method\": \"Immunoprecipitation followed by nanoLC-ESI-Qq-TripleTOF MS/MS; quantitative immuno-co-localization; COM crystal-protein binding assay; crystal-cell adhesion and internalization assays with antibody neutralization\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — IP-MS for interactome plus functional crystal-binding assays with antibody neutralization as specificity control; single lab\",\n      \"pmids\": [\"29085954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A splice variant of PMCA2 localizes to the lysosome (not only the plasma membrane) where it forms an evolutionarily conserved complex with NPC1. This lysosomal PMCA2 mediates calcium uptake into lysosomes. Disruption of the NPC1-PMCA2 complex contributes to lysosomal calcium dysregulation in Niemann-Pick disease type C and Parkinson's disease.\",\n      \"method\": \"Subcellular fractionation/localization; co-immunoprecipitation with NPC1; lysosomal calcium measurements; disease model validation (NPC, Parkinson's disease models)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel splice-variant-dependent localization with Co-IP and lysosomal calcium functional assays; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.10.01.679724\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of human calcium-bound ATP2B2 at 2.64 Å resolution was determined. Structural analysis revealed that neuropsychiatric disease-associated missense variants cluster near the Ca2+ pore and ATP:Mg2+ coordination site. In vitro assays confirmed that missense variants at these structural hotspots impair ATP2B2-mediated Ca2+ extrusion in cellular and biochemical assays.\",\n      \"method\": \"Cryo-EM structure determination at 2.64 Å; 3D-neighborhood missense variant clustering analysis on AlphaFold3-predicted structures validated by the cryo-EM map; in vitro Ca2+ extrusion assays with disease-associated missense mutants\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — near-atomic cryo-EM structure with functional mutagenesis validation; preprint, not yet peer-reviewed, but multiple orthogonal methods\",\n      \"pmids\": [\"bio_10.1101_2025.08.25.672202\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"De novo missense ATP2B2 variants (including variants at Ca2+ transport domain residues) cause both loss-of-function and gain-of-function alterations in cytosolic calcium handling in cell-based studies, demonstrating that precise ATP2B2-mediated calcium regulation is required for neurodevelopment and cerebellar function.\",\n      \"method\": \"Exome/genome sequencing; in silico structural analysis; cell-based cytosolic calcium handling assays for each variant; clinical phenotyping\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional calcium assays for multiple distinct variants; single report with multiple affected individuals\",\n      \"pmids\": [\"37675773\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ATP2B2/PMCA2 is a plasma membrane calcium-extruding ATPase whose w/a splice variant constitutively pumps Ca2+ from hair cell stereocilia into endolymph to maintain endolymph calcium homeostasis and hair cell mechanotransduction; its subcellular targeting (apical vs. basolateral) is directed by alternative splicing at the first intracellular loop (w-insert confers apical targeting) and is stabilized by interaction with PDZ-scaffold proteins NHERF1/NHERF2; in mammary epithelial and breast cancer cells PMCA2 lowers cytosolic Ca2+ to suppress apoptosis and, by interacting with HER2 in actin-rich membrane domains and maintaining HER2-HSP90 stability, promotes HER2 signaling and tumor growth; in neurons PMCA2 clears dendritic Ca2+ transients to shape Purkinje neuron firing and cerebellar output, participates in the mGluR1-Homer-IP3R1 signaling complex, and via PSD-95 controls α7-nAChR cluster stability; a lysosomal splice variant additionally forms a complex with NPC1 to mediate lysosomal Ca2+ uptake; cytoskeletal state (F-actin polymerization) directly modulates PMCA2 specific activity; and loss-of-function or gain-of-function variants in the Ca2+ pore or ATP:Mg2+ coordination domain cause deafness, vestibular dysfunction, and neurodevelopmental/movement disorders.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATP2B2 (PMCA2) is a plasma-membrane Ca2+-extruding ATPase that sets and shapes cytosolic and luminal calcium across sensory, neuronal, and epithelial tissues, with its subcellular targeting and activity tuned by alternative splicing and partner proteins [#0, #4, #10]. In cochlear and vestibular hair cells PMCA2 resides in stereocilia and pumps Ca2+ into endolymph, acting as the primary determinant of endolymph calcium homeostasis required for mechanotransduction [#0]. Its membrane polarity is splice-controlled: a Leu-Ile motif in 'b'-tail variants drives basolateral sorting while the size of the A-site insert directs apical targeting, and the w-insert in the first cytoplasmic loop carries autonomous apical-targeting information further reinforced by PDZ-scaffold interactions with NHERF1/NHERF2 [#1, #10, #14]. The w/a stereociliar variant is largely uncoupled from acute Ca2+ stimulation, enabling constitutive calcium extrusion [#7]. Disease-associated missense variants cluster near the Ca2+ pore and ATP:Mg2+ coordination site and impair pump activity, producing both loss- and gain-of-function effects that underlie progressive hearing loss, hair cell degeneration, and neurodevelopmental/cerebellar disorders [#3, #4, #22, #23]. In Purkinje neurons PMCA2 clears dendritic Ca2+ transients to set firing kinetics and dendritic growth, and is a constituent of the mGluR1-Homer-IP3R1 complex [#2, #6, #18]; in hippocampal interneurons it associates with α7-nAChRs and PSD-95 to control receptor cluster stability [#9]. In mammary epithelium and breast cancer PMCA2 lowers cytosolic calcium to suppress apoptosis, interacts with HER2 in actin-rich domains to maintain HER2-HSP90 stability and signaling, and promotes tumor formation [#5, #11, #12]. Pump specific activity is directly modulated by the cortical cytoskeleton, with F-actin polymerization inhibiting and disruption enhancing Ca2+ extrusion [#13].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established the core physiological role of PMCA2 by showing it is the dominant calcium-extrusion route from hair cell stereocilia into endolymph, settling where and why the pump matters for hearing.\",\n      \"evidence\": \"Immunocytochemistry plus endolymph calcium measurement in dfw2J knockout vs control mice\",\n      \"pmids\": [\"15357414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve splice-variant identity or molecular targeting mechanism in stereocilia\", \"No structural basis for pump activity\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Answered how a single gene achieves polarized membrane targeting, showing splice variation encodes basolateral versus apical sorting signals.\",\n      \"evidence\": \"Targeting-region mutagenesis and splice-variant expression with immunofluorescence in hair cells\",\n      \"pmids\": [\"16803870\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the scaffold proteins that read the apical signal\", \"Mechanism of the A-site insert size effect unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Placed PMCA2 within the neuronal mGluR1 signaling machinery, linking calcium clearance to metabotropic glutamate receptor signaling integrity in Purkinje neurons.\",\n      \"evidence\": \"Co-immunoprecipitation from cerebellum and protein-level analysis in PMCA2-null vs wild-type mice\",\n      \"pmids\": [\"17150372\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab Co-IP without reciprocal validation of each partner\", \"Direct versus indirect association within the complex not distinguished\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Separated targeting from catalytic defects, showing a TM6 missense mutation reduces basal pump activity without mislocalization and causes progressive hair cell loss.\",\n      \"evidence\": \"ENU Oblivion (S877F) allele with in vitro pump activity assay, hair cell culture and histology\",\n      \"pmids\": [\"18974863\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which reduced basal activity drives base-to-apex degeneration not defined\", \"No structural model of the mutation site at the time\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Extended the genotype-function map with an active-site mutation impairing long-term calcium extrusion, confirmed by direct calcium imaging in native sensory epithelium.\",\n      \"evidence\": \"Tommy (E629K) allele; CHO extrusion assay plus flash photolysis of caged calcium in utricle cultures and ABR\",\n      \"pmids\": [\"20826782\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dominant heterozygous mechanism not fully explained\", \"Relationship to splice variant context unaddressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined a non-sensory role, showing apical PMCA2 transports calcium into milk and that its loss raises cytosolic calcium to sensitize epithelial cells to apoptosis, with the reverse protecting cancer cells.\",\n      \"evidence\": \"PMCA2 knockout mouse mammary phenotyping plus siRNA and overexpression in T47D cells with calcium and apoptosis readouts\",\n      \"pmids\": [\"20534448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream apoptotic effectors not identified at this stage\", \"Did not address HER2 or calcineurin coupling\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Quantified the neuronal calcium-clearance function, showing PMCA2 dosage controls dendritic calcium transient kinetics and thereby Purkinje neuron firing and motor precision.\",\n      \"evidence\": \"Two-photon calcium imaging and patch clamp in PMCA2+/- vs wild-type cerebellum with behavioral testing\",\n      \"pmids\": [\"20083513\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners mediating dendritic localization not defined here\", \"Link to specific behavioral circuits incomplete\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Explained how the stereociliar w/a variant supports constitutive extrusion, showing it is only marginally stimulated by acute calcium and that species-specific mutants differ in activity impact.\",\n      \"evidence\": \"In vitro aequorin-based calcium ejection assays of wild-type and mutant PMCA2 variants\",\n      \"pmids\": [\"22047666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for stimulation-independence not resolved\", \"Discordance between human V586M and murine mutant phenotypes unexplained\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected PMCA2 anti-apoptotic function to a defined effector pathway, showing it restrains calcineurin/NFAT/FasL signaling in breast cancer cells.\",\n      \"evidence\": \"Co-IP, peptide disruption of the PMCA2/calcineurin interaction, NFAT reporter and apoptosis assays across cell lines\",\n      \"pmids\": [\"22962307\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab interaction not independently confirmed\", \"Whether the interaction is direct or scaffold-mediated unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified a neuronal scaffold function, showing PMCA2 with PSD-95 limits α7-nAChR calcium signals and controls receptor cluster stability via CaMKII/proteasome turnover.\",\n      \"evidence\": \"Co-IP/MS from brain, calcium imaging, single-particle tracking and pharmacological dissection in hippocampal interneurons\",\n      \"pmids\": [\"22593058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding interface among PMCA2, PSD-95 and α7-nAChR not mapped\", \"Generalizability beyond interneurons untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated that the w-insert is an autonomous apical targeting determinant, transferable to a normally basolateral isoform and enhanced by NHERF2-binding PDZ optimization.\",\n      \"evidence\": \"PMCA4/PMCA2-w chimera expression in polarized epithelial cells with localization and PDZ-ligand mutagenesis\",\n      \"pmids\": [\"22252018\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trafficking machinery recognizing the w-insert not identified\", \"Quantitative contribution of PDZ versus insert in native cells unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked PMCA2 calcium clearance to neuronal morphogenesis, showing its activity is required for Purkinje dendritic growth.\",\n      \"evidence\": \"Carboxyeosin inhibition in organotypic cerebellar slices with morphological quantification and pharmacological combinations\",\n      \"pmids\": [\"24288624\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Carboxyeosin specificity for PMCA2 limited\", \"Mechanistic coupling to mGluR1 and calcium channels only partially defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed PMCA2 level controls neuronal differentiation and survival, with knockdown accelerating neurite outgrowth and triggering apoptosis alongside compensatory calcium-handler upregulation.\",\n      \"evidence\": \"Stable antisense PC12 cells with differentiation, calcium influx and apoptosis assays\",\n      \"pmids\": [\"22921123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Compensation by PMCA1/4 and SERCA confounds interpretation\", \"Direct causal pathway to apoptosis not isolated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined a pro-tumorigenic mechanism upstream of HER2, showing PMCA2 maintains HER2-HSP90 stability and membrane retention in actin-rich domains and is required for HER2-driven tumor formation.\",\n      \"evidence\": \"Reciprocal Co-IP, siRNA with multiple readouts, RPPA, and PMCA2 knockout in MMTV-Neu mice\",\n      \"pmids\": [\"26729871\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HER2 interaction is direct or calcium/actin-dependent not fully separated\", \"Structural interface unmapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established isoform specificity in cancer, showing only PMCA2 (not PMCA1/4) supports proliferation and chemoresistance.\",\n      \"evidence\": \"Isoform-specific siRNA with proliferation, viability and doxorubicin-sensitivity assays in MDA-MB-231 cells\",\n      \"pmids\": [\"27148852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab study\", \"Mechanism linking PMCA2 to drug resistance not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed cytoskeletal control of pump output, showing F-actin state directly modulates PMCA2 specific activity independent of surface expression.\",\n      \"evidence\": \"Live-cell calcium imaging in HEK293 with actin and microtubule pharmacology plus surface-expression controls\",\n      \"pmids\": [\"28527708\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between cytoskeleton and pump conformation unknown\", \"Physiological context of regulation untested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Uncovered an extracellular/adhesion function, identifying PMCA2 as a calcium oxalate crystal-binding protein relevant to kidney stone pathogenesis.\",\n      \"evidence\": \"IP-MS interactome plus COM crystal-binding, adhesion and internalization assays with antibody neutralization in kidney cells\",\n      \"pmids\": [\"29085954\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether crystal binding depends on pump activity unclear\", \"Single-lab functional validation\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked PMCA2 to sex-specific hormonal signaling, showing it is required for ERα signaling and estradiol analgesia in female dorsal horn.\",\n      \"evidence\": \"Ovariectomy/estradiol replacement and ERα agonist in PMCA2+/- vs wild-type mice with signaling and pain readouts\",\n      \"pmids\": [\"30467368\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting calcium handling to ERα signaling undefined\", \"Male-female divergence unexplained\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined PMCA2's role in nociceptive processing, showing haploinsufficiency alters pain sensitivity and dorsal-horn receptor/transporter levels in a sex-specific manner.\",\n      \"evidence\": \"Behavioral pain assays and Western blots in PMCA2+/- mice with sex stratification\",\n      \"pmids\": [\"27702770\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality between receptor changes and pain phenotype not established\", \"Cell-type origin of changes unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified an upstream regulator of PMCA2 in pathological pain, showing IL-1β specifically downregulates PMCA2 to raise neuronal calcium.\",\n      \"evidence\": \"Western blot of PMCA2 in EAE/SCI dorsal horn and cytokine treatment of spinal neuron cultures with negative controls for SERCA/NCX\",\n      \"pmids\": [\"31703709\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcriptional vs post-translational mechanism of downregulation unknown\", \"Single-lab correlation with in vivo pain\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established the apical scaffolding requirement, showing NHERF1 retains PMCA2 at the apical membrane and that its loss disrupts polarity and triggers cell death.\",\n      \"evidence\": \"Reciprocal Co-IP, NHERF1 knockout mice, localization, Stat3 readout and histology in lactating mammary gland\",\n      \"pmids\": [\"31087002\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of NHERF1 vs NHERF2 not quantified\", \"Whether cell death is a direct consequence of PMCA2 mislocalization unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected PMCA2 to human neurodevelopmental disease, showing de novo variants cause both loss- and gain-of-function calcium-handling changes.\",\n      \"evidence\": \"Exome/genome sequencing, in silico structural analysis and cell-based cytosolic calcium assays for multiple variants\",\n      \"pmids\": [\"37675773\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which gain-of-function variants cause disease unresolved\", \"Genotype-phenotype correlation across variants incomplete\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the structural framework, determining a cryo-EM structure that localizes neuropsychiatric variants to the Ca2+ pore and ATP:Mg2+ site and confirms their functional impact.\",\n      \"evidence\": \"Cryo-EM at 2.64 Å with 3D variant-clustering analysis and in vitro Ca2+ extrusion assays of disease mutants (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.08.25.672202\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Structure does not capture splice-variant or partner-bound states\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Expanded the localization repertoire, showing a lysosomal splice variant forms a conserved complex with NPC1 to mediate lysosomal calcium uptake relevant to NPC and Parkinson's disease.\",\n      \"evidence\": \"Subcellular fractionation, Co-IP with NPC1 and lysosomal calcium measurements in disease models (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.10.01.679724\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Splice-variant determinant of lysosomal targeting not mapped\", \"Direct vs indirect NPC1 association unconfirmed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How distinct splice variants, partner scaffolds, and cytoskeletal state are integrated to select PMCA2 localization (apical, basolateral, lysosomal) and tune activity in a tissue-specific manner remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking splice variant to trafficking machinery\", \"Structural basis of partner and cytoskeletal regulation undefined\", \"Mechanism distinguishing loss- vs gain-of-function disease outcomes unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [3, 4, 7, 22]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 5, 7, 21]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [3, 4, 22]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 3, 10, 11]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 5, 7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 9, 11]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5, 8, 19]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [6, 9, 18]}\n    ],\n    \"complexes\": [\n      \"mGluR1-Homer-IP3R1 signaling complex\",\n      \"PMCA2-NPC1 lysosomal complex\"\n    ],\n    \"partners\": [\n      \"NHERF1\",\n      \"NHERF2\",\n      \"HER2\",\n      \"HSP90\",\n      \"calcineurin\",\n      \"PSD-95\",\n      \"CHRNA7\",\n      \"NPC1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}