{"gene":"ATP2B4","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2004,"finding":"PMCA4 (ATP2B4) is localized to the principal piece of the sperm tail, co-localizing with the CatSper Ca2+ channel, and its loss in Pmca4-/- mice causes failure to achieve hyperactivated sperm motility and male infertility despite normal spermatogenesis; increased mitochondrial condensation in null sperm indicated Ca2+ overload, consistent with PMCA4's role as the dominant Ca2+ extrusion pump in sperm.","method":"Gene knockout (Pmca4-/- mice), immunoblotting, immunohistochemistry, sperm motility assays, ultrastructural analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, localization by IHC, replicated across multiple genetic backgrounds","pmids":["15178683"],"is_preprint":false},{"year":1992,"finding":"PMCA4 primary transcripts are alternatively spliced to produce at least two isoforms (PMCA4a and PMCA4b); PMCA4b contains an inserted exon after the calmodulin-binding domain that shifts the reading frame, truncating the C-terminal regulatory domain; each splice variant shows distinct tissue distribution with PMCA4a present in all tissues and PMCA4b restricted to excitable tissues.","method":"RT-PCR/Southern blot of cDNA, cDNA cloning and sequencing, genomic sequencing of intron-exon boundaries","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct cDNA isolation, genomic sequencing, and tissue-distribution mapping with multiple orthogonal methods","pmids":["1531651"],"is_preprint":false},{"year":2001,"finding":"PMCA4 is required for TNF-induced cell death in L929 cells; retrovirus-insertion mutagenesis of PMCA4 caused abnormally elevated intracellular Ca2+ following TNF stimulation, which promoted lysosome exocytosis and inhibited the TNF-induced increase in volume of acidic compartments (VAC), thereby conferring resistance to TNF-induced death.","method":"Retrovirus-insertion random mutagenesis screen, intracellular Ca2+ measurement, lysosome volume assays, pharmacological rescue (sucrose-mediated VAC increase)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined mechanistic pathway, multiple orthogonal readouts (Ca2+, VAC, lysosome exocytosis), single lab","pmids":["11713265"],"is_preprint":false},{"year":2011,"finding":"PMCA4 acts as a structural scaffold that tethers neuronal NOS (nNOS) to a caveolar microdomain in cardiomyocytes; in PMCA4-/- hearts >36% of membrane-associated nNOS is delocalized to the cytosol, reducing microdomain cGMP, decreasing PDE2 activity, elevating local cAMP, increasing L-type Ca2+ channel activity and ryanodine receptor phosphorylation, and thereby increasing cardiac contractility.","method":"PMCA4 knockout mice, in vivo cardiac contractility measurements, subcellular fractionation, nNOS activity assays, FRET-based cAMP/cGMP sensors, L-type Ca2+ channel and ryanodine receptor phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO animal model with multiple orthogonal methods (FRET sensors, fractionation, kinase assays, in vivo physiology) in a single rigorous study","pmids":["21965681"],"is_preprint":false},{"year":2017,"finding":"ATP2B4 is the primary Ca2+ extrusion pump in red blood cells; an erythroid-specific enhancer drives its expression, and CRISPR-Cas9 deletion of this enhancer reduces ATP2B4 expression and causes abnormally elevated intracellular Ca2+ in erythroid cells; Atp2b4-/- mice display increased mean corpuscular hemoglobin concentration (MCHC).","method":"CRISPR-Cas9 enhancer deletion, eQTL mapping in erythroblasts, Atp2b4 knockout mice, intracellular Ca2+ measurement","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR functional validation of regulatory element, KO mouse phenotype, and Ca2+ measurements provide multiple orthogonal lines of evidence","pmids":["28714864"],"is_preprint":false},{"year":2014,"finding":"Ca2+ efflux activity of PMCA4 is required for G1-phase progression in vascular smooth muscle cells (VSMCs); PMCA4 knockout VSMCs show impaired DNA synthesis and G1 arrest; PMCA4a and PMCA4b splice variants differentially regulate downstream mediators (AP-2β and p15/Cyclin D1 respectively) of cell cycle progression; a PMCA4b mutant with only 10% of normal Ca2+ efflux activity cannot rescue G1 arrest.","method":"PMCA4 knockout mouse-derived VSMCs, [3H]thymidine incorporation, electroporation of splice-variant expression constructs, microarray, Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — KO cells with rescue by WT and mutants, Ca2+-efflux-dead mutant as control, microarray + Western validation","pmids":["24448801"],"is_preprint":false},{"year":2017,"finding":"PMCA4 physically associates with eNOS and nNOS in sperm; Co-IP and FRET show PMCA4 forms a quaternary complex with eNOS, nNOS, and Caveolin1 in a Ca2+-dependent manner; in Pmca4-/- sperm, NOS activity and peroxynitrite levels are elevated ~2-fold, causing increased apoptosis in germ cells and asthenospermia.","method":"Co-immunoprecipitation, FRET (fluorescence resonance energy transfer), NOS activity assay, peroxynitrite measurement, germ cell apoptosis assay in Pmca4-/- mice","journal":"Journal of cellular physiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and FRET confirming <10 nm proximity, paired with functional KO phenotype, single lab","pmids":["28247940"],"is_preprint":false},{"year":2016,"finding":"CD147 interacts with PMCA4 via its transmembrane domain and Ig-like domain II; this interaction is required for CD147-dependent inhibition of IL-2 expression in T cells via a calcium-independent mechanism; CD147 does not control membrane localization of PMCA4.","method":"Affinity purification with mass spectrometry, CD147 domain-mapping constructs, siRNA knockdown of CD147 and PMCA4, IL-2 production assays in human T cells","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — AP-MS interaction identification plus domain-mapped functional rescue, but mechanistic detail on Ca2+-independence is limited to single lab","pmids":["26729804"],"is_preprint":false},{"year":2015,"finding":"The familial spastic paraplegia-associated R268Q missense mutation in PMCA4 reduces Ca2+ extrusion capacity; SH-SY5Y neuroblastoma cells overexpressing R268Q PMCA4 show significantly higher cytosolic Ca2+ surge after depolarization and elevated steady-state Ca2+ after SERCA inhibition compared with wild-type PMCA4.","method":"Overexpression of WT and R268Q mutant PMCA4 in SH-SY5Y cells, fura-2 Ca2+ imaging by confocal microscopy, KCl depolarization and thapsigargin treatment","journal":"Brain and behavior","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional assay of mutant vs WT in defined cell model, but single lab, single set of methods","pmids":["25798335"],"is_preprint":false},{"year":2010,"finding":"During sperm maturation in the bovine epididymis, PMCA4 splice variants switch from predominantly PMCA4b in testis/caput/corpus to predominantly PMCA4a in cauda epididymidis; PMCA4a (which has higher basal activity and is more effective at returning Ca2+ to resting levels) is transferred to sperm membranes in the cauda, suggesting this isoform switch facilitates the higher Ca2+ turnover needed for sperm to traverse the female genital tract.","method":"Quantitative PCR, immunohistochemistry with isoform-specific antibody, Western blotting of testis/epididymis/sperm fractions","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization and isoform characterization by IHC and WB, multiple tissue sections, but functional consequence is inferred rather than directly tested","pmids":["21187283"],"is_preprint":false},{"year":2013,"finding":"PMCA4 is correctly targeted to the plasma membrane and co-localizes with caveolin-3 in cardiomyocytes; a PMCA4-GCaMP2 fusion construct directly monitors local Ca2+ dynamics near the pump, showing higher signal amplitude and faster decay than a pump-inactive mutant; β-adrenergic stimulation specifically enhances Ca2+ signals near active PMCA4.","method":"Adenoviral expression of PMCA4-GCaMP2 fusion protein in neonatal and adult rat cardiomyocytes, live-cell fluorescence imaging, small-molecule inhibitor screen","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel biosensor tool with inactive-pump control, functional Ca2+ measurements, co-localization; single lab","pmids":["23880607"],"is_preprint":false},{"year":2020,"finding":"PMCA4 inhibition in gastric cancer cells increases ZEB1 expression and promotes nuclear accumulation of NFATc1; EMT induced by PMCA4 knockdown is prevented by knockdown of NFATc1 or ZEB1, or by cyclosporine A treatment, placing PMCA4 upstream of an NFATc1-ZEB1 signaling axis that controls epithelial-mesenchymal transition.","method":"siRNA knockdown and overexpression of PMCA4 in GC cell lines, NFATc1 and ZEB1 knockdown, cyclosporine A pharmacological inhibition, in vivo lung metastasis assay in nude mice, E-cadherin/vimentin Western blot","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by double knockdown and pharmacological rescue, in vivo validation; single lab","pmids":["32860837"],"is_preprint":false},{"year":2020,"finding":"PDGF-BB signaling through MEK/ERK downregulates PMCA4 protein abundance in pulmonary arterial smooth muscle cells; PMCA4 suppression attenuates Ca2+ clearance after Ca2+ entry, promotes cell proliferation, and increases cell migration via focal adhesion formation; knockdown of PMCA4 in rats increases right ventricular systolic pressure and pulmonary artery wall thickness.","method":"PDGF-BB stimulation with MEK/ERK inhibitors, siRNA knockdown of PMCA4, intracellular Ca2+ clearance assay, proliferation and migration assays, focal adhesion staining, in vivo rat PAH models (MCT/hypoxia), RVSP measurement","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway epistasis via kinase inhibitors combined with KD and in vivo phenotype; single lab","pmids":["32966125"],"is_preprint":false},{"year":2020,"finding":"PMCA4 knockdown in MIA PaCa-2 pancreatic cancer cells reduces cytosolic Ca2+ clearance, decreases cell migration, and sensitizes cells to apoptosis without affecting cell growth or major metabolic parameters.","method":"siRNA knockdown of PMCA4, intracellular Ca2+ clearance assay, cell migration assay, apoptosis assay, Seahorse XF metabolic analysis","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined cellular phenotypes and Ca2+ functional readout; single lab, single study","pmids":["31963119"],"is_preprint":false},{"year":2024,"finding":"ATP2B4 (PMCA4) is required for EGF-induced macropinocytosis in A431 cells; ATP2B4 knockout inhibits ruffle closure and macropinosome formation without affecting ruffle formation, and reduces EGF-stimulated Ca2+ oscillations; this function depends on PMCA4 Ca2+ pump activity and is independent of C-terminal PDZ domain-binding motif interactions.","method":"ATP2B4 CRISPR knockout, live-cell imaging of macropinocytosis, Ca2+ oscillation measurement, expression of PDZ-binding mutant and pump-dead constructs","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined stage-specific phenotype, mutant rescue to distinguish PDZ-independent mechanism; single lab","pmids":["38597132"],"is_preprint":false},{"year":2010,"finding":"PMCA4 is present in both detergent-resistant membrane (lipid raft/DRM) and detergent-soluble fractions of bovine sperm; it co-localizes with caveolin in the midpiece; Ca2+-ATPase activity in detergent-soluble fractions is more strongly enhanced by the seminal vesicle protein PDC-109 than in DRM fractions, indicating functional compartmentalization of PMCA4 in sperm membranes.","method":"Detergent-resistant membrane fractionation, Ca2+-ATPase activity assays, immunocytochemistry, lipid overlay experiments","journal":"International journal of andrology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — biochemical fractionation plus activity assay and co-localization; multiple methods but limited mechanistic depth","pmids":["20050939"],"is_preprint":false},{"year":2022,"finding":"CRISPR/Cas9-mediated deletion of an ATP2B4 regulatory region containing five malaria-associated SNPs decreased ATP2B4 transcript and protein levels and increased intracellular Ca2+ concentration in K562 cells, demonstrating that these non-coding variants functionally regulate ATP2B4 expression.","method":"CRISPR/Cas9 regulatory region deletion in K562 cells, RT-qPCR, Western blot, intracellular Ca2+ measurement","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR functional deletion with expression and functional Ca2+ readouts; single lab","pmids":["35563239"],"is_preprint":false},{"year":2017,"finding":"A minor haplotype in the predicted second promoter region of ATP2B4 correlates with significantly reduced PMCA4b protein levels in erythrocytes and lower Ca2+ extrusion capacity; no coding missense mutations were found, indicating the mechanism is transcriptional/regulatory rather than structural.","method":"Flow cytometry with specific antibody to quantify PMCA4b in erythrocytes, Western blot of RBC membranes, Ca2+ extrusion assays, sequencing of ATP2B4 coding regions and promoter","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — quantitative protein expression measurement linked to Ca2+ functional assay across multiple subjects; single lab but robust approach","pmids":["28216081"],"is_preprint":false},{"year":2026,"finding":"ATP2B4 stabilizes ELAVL1 (HuR), which in turn maintains mRNA stability of histone H1.0; loss of ATP2B4 in pancreatic cancer cells causes histone H1.0 downregulation, chromatin decompaction, increased DNA damage, and enhanced radiosensitivity; this mechanism was identified by TurboID proximity labeling mass spectrometry and immunoprecipitation.","method":"CRISPR knockout, TurboID-based proximity labeling mass spectrometry, immunoprecipitation, micrococcal nuclease assay, RNA sequencing, drug rescue assays, in vivo xenograft radiotherapy experiments","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity proteomics plus IP, functional assays in vitro and in vivo; single lab, novel finding","pmids":["42185253"],"is_preprint":false},{"year":2025,"finding":"PMCA4 and GAT3 interact within lipid raft microdomains in glioma cells; PMCA4 knockdown increases resting Ca2+ and Ca2+ accumulation in lipid rafts, impairing glioma cell migration and invasion; GAT3 interacts with calmodulin (a key PMCA4 regulator), and long-term GABA treatment disrupts the PMCA4/GAT3 complex; GABA-stimulated Ca2+ events in lipid rafts drive CaMKII-dependent CREB phosphorylation at Ser133.","method":"PMCA4 siRNA knockdown, Co-IP of GAT3/PMCA4/calmodulin, lipid raft fractionation with Ca2+ measurement, cell migration/invasion assays, CaMKII/CREB phosphorylation assays, parvalbumin Ca2+ chelator expression in rafts","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP interactions combined with functional Ca2+ and migration assays; single lab, multiple methods but abstract-level detail only","pmids":["40580687"],"is_preprint":false},{"year":2022,"finding":"MM-derived exosomal miR-4261 is transferred to red blood cells and directly targets ATP2B4, downregulating PMCA4 expression; this causes calcium overload in RBCs, confirmed by dual-luciferase reporter assay establishing the miR-4261/ATP2B4 targeting relationship.","method":"Dual-luciferase reporter assay, Western blot, immunofluorescence, Transwell exosome transfer assay, atomic absorption spectroscopy for Ca2+","journal":"Frontiers in oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP/luciferase experiment; miRNA targeting of ATP2B4 3'UTR shown but mechanistic detail of how PMCA4 loss leads to Ca2+ overload is inferred","pmids":["36091107"],"is_preprint":false}],"current_model":"ATP2B4/PMCA4 is a plasma membrane P-type Ca2+-ATPase that extrudes cytosolic Ca2+ and functions both as a housekeeping Ca2+ pump and as a structural scaffold: in sperm it localizes to the principal piece where its Ca2+ efflux activity is essential for hyperactivated motility; in cardiomyocytes it tethers nNOS to a caveolar microdomain to regulate local cGMP/cAMP balance and contractility; in vascular smooth muscle it drives G1-phase cell cycle progression through NFAT/Cyclin D1 signaling; it interacts with eNOS/nNOS/Caveolin1 complexes and with CD147 to modulate nitric oxide and T-cell IL-2 signaling; its expression in erythrocytes is controlled by a tissue-specific enhancer and determines red blood cell Ca2+ homeostasis and malaria susceptibility; and in cancer cells it participates in additional mechanisms including stabilization of ELAVL1/histone H1.0 to regulate chromatin compaction and DNA damage responses."},"narrative":{"mechanistic_narrative":"ATP2B4 (PMCA4) is a plasma-membrane Ca2+-extrusion ATPase that acts as the dominant pump clearing cytosolic Ca2+ in multiple cell types and, in parallel, serves as a membrane scaffold organizing Ca2+-signaling microdomains [PMID:15178683, PMID:21965681, PMID:28714864]. Its primary transcript is alternatively spliced into PMCA4a and PMCA4b, which differ in their C-terminal regulatory domain and show distinct tissue distributions and basal activities [PMID:1531651]; during sperm maturation an a/b isoform switch tunes Ca2+ turnover [PMID:21187283]. In sperm, PMCA4 localizes to the principal piece alongside CatSper, and its loss causes Ca2+ overload and failure of hyperactivated motility, producing male infertility [PMID:15178683], while it also forms a Ca2+-dependent quaternary complex with eNOS, nNOS, and Caveolin1 that restrains nitrosative stress [PMID:28247940]. In cardiomyocytes it tethers nNOS to a caveolar microdomain, where its delocalization shifts local cGMP/cAMP balance to raise contractility [PMID:21965681, PMID:23880607]. Beyond pumping, PMCA4 couples Ca2+ handling to proliferation and differentiation programs: its efflux activity drives G1-phase progression in vascular smooth muscle through splice-variant-specific control of Cyclin D1 and AP-2β [PMID:24448801], and in cancer cells it restrains migration, EMT via an NFATc1–ZEB1 axis, and macropinocytosis, and modulates apoptosis and DNA-damage responses [PMID:32860837, PMID:31963119, PMID:38597132, PMID:42185253]. An erythroid-specific enhancer and regulatory non-coding variants set ATP2B4 expression in red blood cells, controlling RBC Ca2+ homeostasis [PMID:28714864, PMID:35563239, PMID:28216081]. A familial spastic paraplegia-associated R268Q missense mutation reduces Ca2+ extrusion capacity, linking PMCA4 dysfunction to disease [PMID:25798335].","teleology":[{"year":1992,"claim":"Established that a single ATP2B4 gene generates distinct regulatory isoforms, explaining how one pump could be functionally tailored to different tissues.","evidence":"cDNA cloning, RT-PCR/Southern blot and genomic intron-exon sequencing identifying PMCA4a/PMCA4b splice variants and their tissue distribution","pmids":["1531651"],"confidence":"High","gaps":["Functional consequences of the truncated C-terminal regulatory domain not directly tested","Isoform-specific regulators not identified"]},{"year":2001,"claim":"First loss-of-function evidence that PMCA4 controls a cell-fate outcome, linking its Ca2+ handling to TNF-induced death pathways.","evidence":"Retrovirus-insertion mutagenesis in L929 cells with intracellular Ca2+, lysosome exocytosis and acidic-compartment volume readouts","pmids":["11713265"],"confidence":"High","gaps":["Mechanism linking Ca2+ elevation to VAC inhibition incompletely defined","Single cell-line context"]},{"year":2004,"claim":"Defined PMCA4 as the dominant Ca2+ extrusion pump in sperm and established its requirement for hyperactivated motility and male fertility.","evidence":"Pmca4-/- mice with sperm motility assays, IHC localization to the principal piece, and ultrastructural analysis","pmids":["15178683"],"confidence":"High","gaps":["Relationship to CatSper-mediated Ca2+ entry not mechanistically resolved","Does not address PMCA4's scaffolding roles"]},{"year":2011,"claim":"Revealed a non-pumping, scaffolding function whereby PMCA4 spatially confines nNOS to set local second-messenger balance and contractility.","evidence":"PMCA4-/- mice with FRET cAMP/cGMP sensors, subcellular fractionation, nNOS activity and channel/RyR phosphorylation assays plus in vivo physiology","pmids":["21965681"],"confidence":"High","gaps":["Structural basis of nNOS tethering not defined","Whether scaffolding requires pump activity not separated"]},{"year":2010,"claim":"Showed compartmentalization of PMCA4 within sperm membrane microdomains and an isoform switch during epididymal maturation, connecting localization to Ca2+ turnover demands.","evidence":"Detergent-resistant membrane fractionation, Ca2+-ATPase activity assays, isoform-specific IHC and qPCR across testis/epididymis/sperm","pmids":["20050939","21187283"],"confidence":"Medium","gaps":["Functional consequence of isoform switch inferred, not directly tested","Regulators driving the switch unknown"]},{"year":2014,"claim":"Demonstrated that PMCA4 Ca2+ efflux, not just its presence, drives cell-cycle progression, with splice variants engaging different downstream effectors.","evidence":"PMCA4-knockout VSMCs with thymidine incorporation, splice-variant and pump-dead rescue, microarray and Western blot","pmids":["24448801"],"confidence":"High","gaps":["Connection between Ca2+ efflux and AP-2β/Cyclin D1 transcription not fully mapped","Restricted to VSMC context"]},{"year":2013,"claim":"Provided a tool to monitor Ca2+ near the pump, confirming PMCA4 shapes local Ca2+ dynamics under β-adrenergic input in cardiomyocytes.","evidence":"PMCA4-GCaMP2 fusion biosensor with pump-inactive control in rat cardiomyocytes and live-cell imaging","pmids":["23880607"],"confidence":"Medium","gaps":["Quantitative size of the microdomain not defined","Single-lab biosensor approach"]},{"year":2016,"claim":"Identified a Ca2+-independent signaling role through direct CD147 binding that suppresses T-cell IL-2 expression.","evidence":"AP-MS interaction discovery, CD147 domain-mapping constructs, siRNA and IL-2 assays in human T cells","pmids":["26729804"],"confidence":"Medium","gaps":["Molecular basis of the Ca2+-independent effect undefined","Single-lab interaction"]},{"year":2017,"claim":"Linked PMCA4 to nitrosative-stress control in sperm via a Ca2+-dependent multiprotein NOS complex and established regulatory variation governing RBC Ca2+ homeostasis and malaria-relevant biology.","evidence":"Co-IP/FRET of PMCA4-eNOS-nNOS-Caveolin1 with NOS/peroxynitrite assays in Pmca4-/- sperm; erythroid enhancer CRISPR deletion and Atp2b4-/- mice; haplotype-linked RBC PMCA4b quantification and Ca2+ extrusion assays","pmids":["28247940","28714864","28216081"],"confidence":"High","gaps":["Stoichiometry and assembly order of the NOS complex unknown","Mechanism connecting RBC Ca2+ to malaria susceptibility not directly shown in these studies"]},{"year":2015,"claim":"Connected a disease-associated missense mutation to reduced pump function, providing a mechanistic basis for a PMCA4-linked neurological phenotype.","evidence":"Overexpression of WT vs R268Q PMCA4 in SH-SY5Y cells with fura-2 Ca2+ imaging after depolarization and SERCA inhibition","pmids":["25798335"],"confidence":"Medium","gaps":["Causality in patient neurons not established","Single overexpression model"]},{"year":2020,"claim":"Extended PMCA4 into cancer cell behavior, defining it as a suppressor of migration, EMT, and proliferation through Ca2+ clearance and NFATc1-ZEB1 signaling, with pathway-driven downregulation in vascular disease.","evidence":"siRNA/overexpression with epistasis (NFATc1/ZEB1 knockdown, cyclosporine A), Ca2+ clearance, migration/apoptosis assays, MEK/ERK inhibitors, and in vivo rat PAH and nude-mouse metastasis models","pmids":["32860837","32966125","31963119"],"confidence":"Medium","gaps":["Whether effects depend on pump activity vs scaffolding not uniformly resolved","Single-lab studies per tissue"]},{"year":2022,"claim":"Confirmed non-coding malaria-associated variants functionally tune ATP2B4 expression and RBC Ca2+, and identified exosomal miR-4261 as a post-transcriptional regulator.","evidence":"CRISPR deletion of the regulatory region in K562 cells with expression/Ca2+ readouts; dual-luciferase reporter and exosome transfer assays for miR-4261 targeting","pmids":["35563239","36091107"],"confidence":"Medium","gaps":["miR-4261 finding rests on single luciferase/transfer experiment","Downstream pathophysiology of RBC Ca2+ overload inferred"]},{"year":2024,"claim":"Showed PMCA4 pump activity is required for a specific stage of macropinocytosis, broadening its role into vesicle-mediated uptake.","evidence":"ATP2B4 CRISPR knockout with live-cell macropinocytosis imaging, Ca2+ oscillation measurement, and PDZ-binding and pump-dead mutant rescue in A431 cells","pmids":["38597132"],"confidence":"Medium","gaps":["How Ca2+ oscillations drive ruffle closure not detailed","Single cell-line context"]},{"year":2025,"claim":"Identified a PMCA4/GAT3/calmodulin lipid-raft complex coupling Ca2+ microdomains to CaMKII-CREB signaling and glioma invasion.","evidence":"Co-IP, lipid raft fractionation with Ca2+ measurement, siRNA knockdown, and CaMKII/CREB phosphorylation and migration assays in glioma cells","pmids":["40580687"],"confidence":"Medium","gaps":["Direct vs calmodulin-bridged PMCA4-GAT3 interaction not resolved","Abstract-level mechanistic detail"]},{"year":2026,"claim":"Uncovered a nuclear-relevant function in which PMCA4 stabilizes ELAVL1 to maintain histone H1.0, controlling chromatin compaction and radiosensitivity.","evidence":"CRISPR knockout, TurboID proximity-labeling MS, IP, micrococcal nuclease and RNA-seq assays, and in vivo xenograft radiotherapy","pmids":["42185253"],"confidence":"Medium","gaps":["Mechanism by which a plasma-membrane pump stabilizes ELAVL1 unclear","Single-lab novel finding"]},{"year":null,"claim":"It remains unresolved how PMCA4 partitions between its Ca2+-pumping and scaffolding functions across tissues, and what structural features dictate its assembly into the various NOS, CD147, GAT3, and ELAVL1 complexes.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of PMCA4 partner complexes","Pump-activity vs scaffolding contributions not separated in most disease contexts","Mechanism linking membrane pump to nuclear/chromatin effects unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,4,5,8,16,17]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0,5,15]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[15]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,6,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,10,14,15]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,4,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,11,19]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[5]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[14]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,13]}],"complexes":["PMCA4-eNOS-nNOS-Caveolin1 quaternary complex","PMCA4/GAT3/calmodulin lipid-raft complex"],"partners":["NNOS","ENOS","CAV1","CD147","GAT3","CALMODULIN","ELAVL1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P23634","full_name":"Plasma membrane calcium-transporting ATPase 4","aliases":["Matrix-remodeling-associated protein 1","Plasma membrane calcium ATPase isoform 4","Plasma membrane calcium pump isoform 4"],"length_aa":1241,"mass_kda":137.9,"function":"Calcium/calmodulin-regulated and magnesium-dependent enzyme that catalyzes the hydrolysis of ATP coupled with the transport of calcium out of the cell (PubMed:8530416). By regulating sperm cell calcium homeostasis, may play a role in sperm motility (By similarity)","subcellular_location":"Cell membrane; Cell projection, cilium, flagellum membrane","url":"https://www.uniprot.org/uniprotkb/P23634/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ATP2B4","classification":"Not Classified","n_dependent_lines":39,"n_total_lines":1208,"dependency_fraction":0.03228476821192053},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CALM1","stoichiometry":0.2},{"gene":"CALM2","stoichiometry":0.2},{"gene":"CALM3","stoichiometry":0.2},{"gene":"XPO6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ATP2B4","total_profiled":1310},"omim":[{"mim_id":"611162","title":"MALARIA, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/611162"},{"mim_id":"601017","title":"SYNTROPHIN, ALPHA-1; SNTA1","url":"https://www.omim.org/entry/601017"},{"mim_id":"300014","title":"ATPase, Ca(2+)-TRANSPORTING, PLASMA MEMBRANE, 3; ATP2B3","url":"https://www.omim.org/entry/300014"},{"mim_id":"108733","title":"ATPase, Ca(2+)-TRANSPORTING, PLASMA MEMBRANE, 2; ATP2B2","url":"https://www.omim.org/entry/108733"},{"mim_id":"108732","title":"ATPase, Ca(2+)-TRANSPORTING, PLASMA MEMBRANE, 4; ATP2B4","url":"https://www.omim.org/entry/108732"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Primary cilium","reliability":"Supported"},{"location":"Mitochondria","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"smooth muscle","ntpm":164.7}],"url":"https://www.proteinatlas.org/search/ATP2B4"},"hgnc":{"alias_symbol":["PMCA4"],"prev_symbol":["ATP2B2","MXRA1"]},"alphafold":{"accession":"P23634","domains":[{"cath_id":"2.70.150.10","chopping":"27-72_205-280","consensus_level":"high","plddt":84.5191,"start":27,"end":280},{"cath_id":"3.40.50.1000","chopping":"446-471_677-822","consensus_level":"high","plddt":86.689,"start":446,"end":822},{"cath_id":"3.40.1110.10","chopping":"477-672","consensus_level":"high","plddt":85.9583,"start":477,"end":672},{"cath_id":"1.20.1110.10","chopping":"836-1061","consensus_level":"high","plddt":84.6863,"start":836,"end":1061}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P23634","model_url":"https://alphafold.ebi.ac.uk/files/AF-P23634-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P23634-F1-predicted_aligned_error_v6.png","plddt_mean":72.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ATP2B4","jax_strain_url":"https://www.jax.org/strain/search?query=ATP2B4"},"sequence":{"accession":"P23634","fasta_url":"https://rest.uniprot.org/uniprotkb/P23634.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P23634/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P23634"}},"corpus_meta":[{"pmid":"15178683","id":"PMC_15178683","title":"Targeted ablation of plasma membrane Ca2+-ATPase (PMCA) 1 and 4 indicates a major housekeeping function for PMCA1 and a critical role in hyperactivated sperm motility and male fertility for PMCA4.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15178683","citation_count":271,"is_preprint":false},{"pmid":"1531651","id":"PMC_1531651","title":"Analysis of the tissue-specific distribution of mRNAs encoding the plasma membrane calcium-pumping ATPases and characterization of an alternately spliced form of PMCA4 at the cDNA and genomic levels.","date":"1992","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1531651","citation_count":109,"is_preprint":false},{"pmid":"11713265","id":"PMC_11713265","title":"Resistance to tumor necrosis factor-induced cell death mediated by PMCA4 deficiency.","date":"2001","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11713265","citation_count":66,"is_preprint":false},{"pmid":"21965681","id":"PMC_21965681","title":"Plasma membrane calcium pump (PMCA4)-neuronal nitric-oxide synthase complex regulates cardiac contractility through modulation of a compartmentalized cyclic nucleotide microdomain.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21965681","citation_count":62,"is_preprint":false},{"pmid":"28714864","id":"PMC_28714864","title":"An erythroid-specific ATP2B4 enhancer mediates red blood cell hydration and malaria susceptibility.","date":"2017","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/28714864","citation_count":50,"is_preprint":false},{"pmid":"28327142","id":"PMC_28327142","title":"Exome sequencing identified rare variants in genes HSPG2 and ATP2B4 in a family segregating developmental dysplasia of the hip.","date":"2017","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28327142","citation_count":30,"is_preprint":false},{"pmid":"25119969","id":"PMC_25119969","title":"PMCA4 (ATP2B4) mutation in familial spastic paraplegia.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25119969","citation_count":27,"is_preprint":false},{"pmid":"28216081","id":"PMC_28216081","title":"Decreased calcium pump expression in human erythrocytes is connected to a minor haplotype in the ATP2B4 gene.","date":"2017","source":"Cell calcium","url":"https://pubmed.ncbi.nlm.nih.gov/28216081","citation_count":27,"is_preprint":false},{"pmid":"25798335","id":"PMC_25798335","title":"PMCA4 (ATP2B4) mutation in familial spastic paraplegia causes delay in intracellular calcium extrusion.","date":"2015","source":"Brain and behavior","url":"https://pubmed.ncbi.nlm.nih.gov/25798335","citation_count":25,"is_preprint":false},{"pmid":"24448801","id":"PMC_24448801","title":"Calcium efflux activity of plasma membrane Ca2+ ATPase-4 (PMCA4) mediates cell cycle progression in vascular smooth muscle cells.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24448801","citation_count":25,"is_preprint":false},{"pmid":"28247940","id":"PMC_28247940","title":"Plasma membrane calcium ATPase 4 (PMCA4) co-ordinates calcium and nitric oxide signaling in regulating murine sperm functional activity.","date":"2017","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/28247940","citation_count":24,"is_preprint":false},{"pmid":"26729804","id":"PMC_26729804","title":"Association of CD147 and Calcium Exporter PMCA4 Uncouples IL-2 Expression from Early TCR Signaling.","date":"2016","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/26729804","citation_count":22,"is_preprint":false},{"pmid":"23880607","id":"PMC_23880607","title":"Development and characterization of a novel fluorescent indicator protein PMCA4-GCaMP2 in cardiomyocytes.","date":"2013","source":"Journal of molecular and cellular cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/23880607","citation_count":21,"is_preprint":false},{"pmid":"24583174","id":"PMC_24583174","title":"Investigation of the association between ATP2B4 and ATP5B genes with colorectal cancer.","date":"2014","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24583174","citation_count":20,"is_preprint":false},{"pmid":"35563239","id":"PMC_35563239","title":"Identification of ATP2B4 Regulatory Element Containing Functional Genetic Variants Associated with Severe Malaria.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35563239","citation_count":20,"is_preprint":false},{"pmid":"16978418","id":"PMC_16978418","title":"Plasma membrane calcium ATPase (PMCA4): a housekeeper for RT-PCR relative quantification of polytopic membrane proteins.","date":"2006","source":"BMC molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16978418","citation_count":20,"is_preprint":false},{"pmid":"21187283","id":"PMC_21187283","title":"Switch of PMCA4 splice variants in bovine epididymis results in altered isoform expression during functional sperm maturation.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21187283","citation_count":19,"is_preprint":false},{"pmid":"21167220","id":"PMC_21167220","title":"Local signals with global impacts and clinical implications: lessons from the plasma membrane calcium pump (PMCA4).","date":"2010","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/21167220","citation_count":18,"is_preprint":false},{"pmid":"31963119","id":"PMC_31963119","title":"Plasma Membrane Ca2+ ATPase Isoform 4 (PMCA4) Has an Important Role in Numerous Hallmarks of Pancreatic Cancer.","date":"2020","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/31963119","citation_count":17,"is_preprint":false},{"pmid":"20050939","id":"PMC_20050939","title":"Arrangement of PMCA4 in bovine sperm membrane fractions.","date":"2010","source":"International journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/20050939","citation_count":16,"is_preprint":false},{"pmid":"32860837","id":"PMC_32860837","title":"The calcium pump PMCA4 prevents epithelial-mesenchymal transition by inhibiting NFATc1-ZEB1 pathway in gastric cancer.","date":"2020","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/32860837","citation_count":15,"is_preprint":false},{"pmid":"18057950","id":"PMC_18057950","title":"Expression and localization of PMCA4 in rat testis and epididymis.","date":"2007","source":"Histochemistry and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/18057950","citation_count":12,"is_preprint":false},{"pmid":"27101128","id":"PMC_27101128","title":"Calcium Extrusion Pump PMCA4: A New Player in Renal Calcium Handling?","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27101128","citation_count":11,"is_preprint":false},{"pmid":"32966125","id":"PMC_32966125","title":"PDGF/MEK/ERK axis represses Ca2+ clearance via decreasing the abundance of plasma membrane Ca2+ pump PMCA4 in pulmonary arterial smooth muscle cells.","date":"2020","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/32966125","citation_count":11,"is_preprint":false},{"pmid":"32002807","id":"PMC_32002807","title":"Molecular and Electrophysiological Analyses of ATP2B4 Gene Variants in Bilateral Adrenal Hyperaldosteronism.","date":"2020","source":"Hormones & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/32002807","citation_count":9,"is_preprint":false},{"pmid":"36849945","id":"PMC_36849945","title":"ATP2B4 regulatory genetic variants are associated with mild malaria.","date":"2023","source":"Malaria journal","url":"https://pubmed.ncbi.nlm.nih.gov/36849945","citation_count":6,"is_preprint":false},{"pmid":"36091107","id":"PMC_36091107","title":"Exosomal MiR-4261 mediates calcium overload in RBCs by downregulating the expression of ATP2B4 in multiple myeloma.","date":"2022","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/36091107","citation_count":6,"is_preprint":false},{"pmid":"33098669","id":"PMC_33098669","title":"Plasma membrane Ca2+ ATPase 1 (PMCA1) but not PMCA4 is critical for B-cell development and Ca2+ homeostasis in mice.","date":"2020","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33098669","citation_count":5,"is_preprint":false},{"pmid":"36604655","id":"PMC_36604655","title":"Genetic variations in human ATP2B4 gene alter Plasmodium falciparum in vitro growth in RBCs from Gambian adults.","date":"2023","source":"Malaria journal","url":"https://pubmed.ncbi.nlm.nih.gov/36604655","citation_count":5,"is_preprint":false},{"pmid":"38597132","id":"PMC_38597132","title":"ATP2B4 is an essential gene for epidermal growth factor-induced macropinocytosis in A431 cells.","date":"2024","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/38597132","citation_count":3,"is_preprint":false},{"pmid":"37740571","id":"PMC_37740571","title":"Dynamic elementomics of single-cell ICP-MS-derived signals in normal and calcium pump PMCA4-deficient mouse epididymal sperm during capacitation.","date":"2023","source":"Metallomics : integrated biometal science","url":"https://pubmed.ncbi.nlm.nih.gov/37740571","citation_count":2,"is_preprint":false},{"pmid":"37506273","id":"PMC_37506273","title":"Primary Cutaneous Epithelioid Mesenchymal Tumor With a Novel ATP2B4::GLI1 Gene Fusion.","date":"2023","source":"The American Journal of dermatopathology","url":"https://pubmed.ncbi.nlm.nih.gov/37506273","citation_count":2,"is_preprint":false},{"pmid":"29131013","id":"PMC_29131013","title":"A New Baltic Population-Specific Human Genetic Marker in the PMCA4 Gene.","date":"2017","source":"Human heredity","url":"https://pubmed.ncbi.nlm.nih.gov/29131013","citation_count":1,"is_preprint":false},{"pmid":"40580687","id":"PMC_40580687","title":"GAT3-dependent regulation of glioma invasiveness via a lipid raft-associated PMCA4 Ca2+ transporter and a downstream CaMKII/CREB signaling - implications for compartmentalized signaling in glioma tumors.","date":"2025","source":"Cell calcium","url":"https://pubmed.ncbi.nlm.nih.gov/40580687","citation_count":0,"is_preprint":false},{"pmid":"42185253","id":"PMC_42185253","title":"ATP2B4 driven chromatin compaction exacerbates pancreatic cancer radiotherapy resistance.","date":"2026","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/42185253","citation_count":0,"is_preprint":false},{"pmid":"41831900","id":"PMC_41831900","title":"Sodium pentachlorophenol induces inflammatory damage via the ATP2B4/Ca2+/ROS signaling axis in mouse testes.","date":"2026","source":"Pesticide biochemistry and physiology","url":"https://pubmed.ncbi.nlm.nih.gov/41831900","citation_count":0,"is_preprint":false},{"pmid":"41789627","id":"PMC_41789627","title":"FOXM1 inhibitor, RCM‑1, enhances venetoclax mediated apoptosis through downregulation of ATP2B4 in rhabdomyosarcoma.","date":"2026","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41789627","citation_count":0,"is_preprint":false},{"pmid":"41983776","id":"PMC_41983776","title":"MiR-4261 targeted YWHAE/CAST/GPX1 impairs the calcium regulatory function of PMCA4 in erythrocytes of myeloma.","date":"2026","source":"Indian journal of pathology & microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/41983776","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.20.677403","title":"Pooled CRISPR screens identify genes and non-coding genomic regions that regulate red blood cell density","date":"2025-09-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.20.677403","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.08.26.609639","title":"Quantitative analysis of DNA-GATA1 binding alterations linked to hematopoietic disorders","date":"2024-08-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.26.609639","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.17.628803","title":"Erythrocytic plasma membrane calcium ATPase (PMCA4b) variations mediate redox imbalance to determine artemisinin sensitivity in malaria","date":"2024-12-18","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.17.628803","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":23599,"output_tokens":5694,"usd":0.078104,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14442,"output_tokens":5047,"usd":0.099193,"stage2_stop_reason":"end_turn"},"total_usd":0.177297,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"PMCA4 (ATP2B4) is localized to the principal piece of the sperm tail, co-localizing with the CatSper Ca2+ channel, and its loss in Pmca4-/- mice causes failure to achieve hyperactivated sperm motility and male infertility despite normal spermatogenesis; increased mitochondrial condensation in null sperm indicated Ca2+ overload, consistent with PMCA4's role as the dominant Ca2+ extrusion pump in sperm.\",\n      \"method\": \"Gene knockout (Pmca4-/- mice), immunoblotting, immunohistochemistry, sperm motility assays, ultrastructural analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, localization by IHC, replicated across multiple genetic backgrounds\",\n      \"pmids\": [\"15178683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"PMCA4 primary transcripts are alternatively spliced to produce at least two isoforms (PMCA4a and PMCA4b); PMCA4b contains an inserted exon after the calmodulin-binding domain that shifts the reading frame, truncating the C-terminal regulatory domain; each splice variant shows distinct tissue distribution with PMCA4a present in all tissues and PMCA4b restricted to excitable tissues.\",\n      \"method\": \"RT-PCR/Southern blot of cDNA, cDNA cloning and sequencing, genomic sequencing of intron-exon boundaries\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct cDNA isolation, genomic sequencing, and tissue-distribution mapping with multiple orthogonal methods\",\n      \"pmids\": [\"1531651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PMCA4 is required for TNF-induced cell death in L929 cells; retrovirus-insertion mutagenesis of PMCA4 caused abnormally elevated intracellular Ca2+ following TNF stimulation, which promoted lysosome exocytosis and inhibited the TNF-induced increase in volume of acidic compartments (VAC), thereby conferring resistance to TNF-induced death.\",\n      \"method\": \"Retrovirus-insertion random mutagenesis screen, intracellular Ca2+ measurement, lysosome volume assays, pharmacological rescue (sucrose-mediated VAC increase)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined mechanistic pathway, multiple orthogonal readouts (Ca2+, VAC, lysosome exocytosis), single lab\",\n      \"pmids\": [\"11713265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PMCA4 acts as a structural scaffold that tethers neuronal NOS (nNOS) to a caveolar microdomain in cardiomyocytes; in PMCA4-/- hearts >36% of membrane-associated nNOS is delocalized to the cytosol, reducing microdomain cGMP, decreasing PDE2 activity, elevating local cAMP, increasing L-type Ca2+ channel activity and ryanodine receptor phosphorylation, and thereby increasing cardiac contractility.\",\n      \"method\": \"PMCA4 knockout mice, in vivo cardiac contractility measurements, subcellular fractionation, nNOS activity assays, FRET-based cAMP/cGMP sensors, L-type Ca2+ channel and ryanodine receptor phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO animal model with multiple orthogonal methods (FRET sensors, fractionation, kinase assays, in vivo physiology) in a single rigorous study\",\n      \"pmids\": [\"21965681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ATP2B4 is the primary Ca2+ extrusion pump in red blood cells; an erythroid-specific enhancer drives its expression, and CRISPR-Cas9 deletion of this enhancer reduces ATP2B4 expression and causes abnormally elevated intracellular Ca2+ in erythroid cells; Atp2b4-/- mice display increased mean corpuscular hemoglobin concentration (MCHC).\",\n      \"method\": \"CRISPR-Cas9 enhancer deletion, eQTL mapping in erythroblasts, Atp2b4 knockout mice, intracellular Ca2+ measurement\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR functional validation of regulatory element, KO mouse phenotype, and Ca2+ measurements provide multiple orthogonal lines of evidence\",\n      \"pmids\": [\"28714864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Ca2+ efflux activity of PMCA4 is required for G1-phase progression in vascular smooth muscle cells (VSMCs); PMCA4 knockout VSMCs show impaired DNA synthesis and G1 arrest; PMCA4a and PMCA4b splice variants differentially regulate downstream mediators (AP-2β and p15/Cyclin D1 respectively) of cell cycle progression; a PMCA4b mutant with only 10% of normal Ca2+ efflux activity cannot rescue G1 arrest.\",\n      \"method\": \"PMCA4 knockout mouse-derived VSMCs, [3H]thymidine incorporation, electroporation of splice-variant expression constructs, microarray, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO cells with rescue by WT and mutants, Ca2+-efflux-dead mutant as control, microarray + Western validation\",\n      \"pmids\": [\"24448801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PMCA4 physically associates with eNOS and nNOS in sperm; Co-IP and FRET show PMCA4 forms a quaternary complex with eNOS, nNOS, and Caveolin1 in a Ca2+-dependent manner; in Pmca4-/- sperm, NOS activity and peroxynitrite levels are elevated ~2-fold, causing increased apoptosis in germ cells and asthenospermia.\",\n      \"method\": \"Co-immunoprecipitation, FRET (fluorescence resonance energy transfer), NOS activity assay, peroxynitrite measurement, germ cell apoptosis assay in Pmca4-/- mice\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and FRET confirming <10 nm proximity, paired with functional KO phenotype, single lab\",\n      \"pmids\": [\"28247940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CD147 interacts with PMCA4 via its transmembrane domain and Ig-like domain II; this interaction is required for CD147-dependent inhibition of IL-2 expression in T cells via a calcium-independent mechanism; CD147 does not control membrane localization of PMCA4.\",\n      \"method\": \"Affinity purification with mass spectrometry, CD147 domain-mapping constructs, siRNA knockdown of CD147 and PMCA4, IL-2 production assays in human T cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — AP-MS interaction identification plus domain-mapped functional rescue, but mechanistic detail on Ca2+-independence is limited to single lab\",\n      \"pmids\": [\"26729804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The familial spastic paraplegia-associated R268Q missense mutation in PMCA4 reduces Ca2+ extrusion capacity; SH-SY5Y neuroblastoma cells overexpressing R268Q PMCA4 show significantly higher cytosolic Ca2+ surge after depolarization and elevated steady-state Ca2+ after SERCA inhibition compared with wild-type PMCA4.\",\n      \"method\": \"Overexpression of WT and R268Q mutant PMCA4 in SH-SY5Y cells, fura-2 Ca2+ imaging by confocal microscopy, KCl depolarization and thapsigargin treatment\",\n      \"journal\": \"Brain and behavior\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional assay of mutant vs WT in defined cell model, but single lab, single set of methods\",\n      \"pmids\": [\"25798335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"During sperm maturation in the bovine epididymis, PMCA4 splice variants switch from predominantly PMCA4b in testis/caput/corpus to predominantly PMCA4a in cauda epididymidis; PMCA4a (which has higher basal activity and is more effective at returning Ca2+ to resting levels) is transferred to sperm membranes in the cauda, suggesting this isoform switch facilitates the higher Ca2+ turnover needed for sperm to traverse the female genital tract.\",\n      \"method\": \"Quantitative PCR, immunohistochemistry with isoform-specific antibody, Western blotting of testis/epididymis/sperm fractions\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization and isoform characterization by IHC and WB, multiple tissue sections, but functional consequence is inferred rather than directly tested\",\n      \"pmids\": [\"21187283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PMCA4 is correctly targeted to the plasma membrane and co-localizes with caveolin-3 in cardiomyocytes; a PMCA4-GCaMP2 fusion construct directly monitors local Ca2+ dynamics near the pump, showing higher signal amplitude and faster decay than a pump-inactive mutant; β-adrenergic stimulation specifically enhances Ca2+ signals near active PMCA4.\",\n      \"method\": \"Adenoviral expression of PMCA4-GCaMP2 fusion protein in neonatal and adult rat cardiomyocytes, live-cell fluorescence imaging, small-molecule inhibitor screen\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel biosensor tool with inactive-pump control, functional Ca2+ measurements, co-localization; single lab\",\n      \"pmids\": [\"23880607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PMCA4 inhibition in gastric cancer cells increases ZEB1 expression and promotes nuclear accumulation of NFATc1; EMT induced by PMCA4 knockdown is prevented by knockdown of NFATc1 or ZEB1, or by cyclosporine A treatment, placing PMCA4 upstream of an NFATc1-ZEB1 signaling axis that controls epithelial-mesenchymal transition.\",\n      \"method\": \"siRNA knockdown and overexpression of PMCA4 in GC cell lines, NFATc1 and ZEB1 knockdown, cyclosporine A pharmacological inhibition, in vivo lung metastasis assay in nude mice, E-cadherin/vimentin Western blot\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by double knockdown and pharmacological rescue, in vivo validation; single lab\",\n      \"pmids\": [\"32860837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PDGF-BB signaling through MEK/ERK downregulates PMCA4 protein abundance in pulmonary arterial smooth muscle cells; PMCA4 suppression attenuates Ca2+ clearance after Ca2+ entry, promotes cell proliferation, and increases cell migration via focal adhesion formation; knockdown of PMCA4 in rats increases right ventricular systolic pressure and pulmonary artery wall thickness.\",\n      \"method\": \"PDGF-BB stimulation with MEK/ERK inhibitors, siRNA knockdown of PMCA4, intracellular Ca2+ clearance assay, proliferation and migration assays, focal adhesion staining, in vivo rat PAH models (MCT/hypoxia), RVSP measurement\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway epistasis via kinase inhibitors combined with KD and in vivo phenotype; single lab\",\n      \"pmids\": [\"32966125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PMCA4 knockdown in MIA PaCa-2 pancreatic cancer cells reduces cytosolic Ca2+ clearance, decreases cell migration, and sensitizes cells to apoptosis without affecting cell growth or major metabolic parameters.\",\n      \"method\": \"siRNA knockdown of PMCA4, intracellular Ca2+ clearance assay, cell migration assay, apoptosis assay, Seahorse XF metabolic analysis\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined cellular phenotypes and Ca2+ functional readout; single lab, single study\",\n      \"pmids\": [\"31963119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ATP2B4 (PMCA4) is required for EGF-induced macropinocytosis in A431 cells; ATP2B4 knockout inhibits ruffle closure and macropinosome formation without affecting ruffle formation, and reduces EGF-stimulated Ca2+ oscillations; this function depends on PMCA4 Ca2+ pump activity and is independent of C-terminal PDZ domain-binding motif interactions.\",\n      \"method\": \"ATP2B4 CRISPR knockout, live-cell imaging of macropinocytosis, Ca2+ oscillation measurement, expression of PDZ-binding mutant and pump-dead constructs\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined stage-specific phenotype, mutant rescue to distinguish PDZ-independent mechanism; single lab\",\n      \"pmids\": [\"38597132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PMCA4 is present in both detergent-resistant membrane (lipid raft/DRM) and detergent-soluble fractions of bovine sperm; it co-localizes with caveolin in the midpiece; Ca2+-ATPase activity in detergent-soluble fractions is more strongly enhanced by the seminal vesicle protein PDC-109 than in DRM fractions, indicating functional compartmentalization of PMCA4 in sperm membranes.\",\n      \"method\": \"Detergent-resistant membrane fractionation, Ca2+-ATPase activity assays, immunocytochemistry, lipid overlay experiments\",\n      \"journal\": \"International journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — biochemical fractionation plus activity assay and co-localization; multiple methods but limited mechanistic depth\",\n      \"pmids\": [\"20050939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CRISPR/Cas9-mediated deletion of an ATP2B4 regulatory region containing five malaria-associated SNPs decreased ATP2B4 transcript and protein levels and increased intracellular Ca2+ concentration in K562 cells, demonstrating that these non-coding variants functionally regulate ATP2B4 expression.\",\n      \"method\": \"CRISPR/Cas9 regulatory region deletion in K562 cells, RT-qPCR, Western blot, intracellular Ca2+ measurement\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR functional deletion with expression and functional Ca2+ readouts; single lab\",\n      \"pmids\": [\"35563239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A minor haplotype in the predicted second promoter region of ATP2B4 correlates with significantly reduced PMCA4b protein levels in erythrocytes and lower Ca2+ extrusion capacity; no coding missense mutations were found, indicating the mechanism is transcriptional/regulatory rather than structural.\",\n      \"method\": \"Flow cytometry with specific antibody to quantify PMCA4b in erythrocytes, Western blot of RBC membranes, Ca2+ extrusion assays, sequencing of ATP2B4 coding regions and promoter\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — quantitative protein expression measurement linked to Ca2+ functional assay across multiple subjects; single lab but robust approach\",\n      \"pmids\": [\"28216081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ATP2B4 stabilizes ELAVL1 (HuR), which in turn maintains mRNA stability of histone H1.0; loss of ATP2B4 in pancreatic cancer cells causes histone H1.0 downregulation, chromatin decompaction, increased DNA damage, and enhanced radiosensitivity; this mechanism was identified by TurboID proximity labeling mass spectrometry and immunoprecipitation.\",\n      \"method\": \"CRISPR knockout, TurboID-based proximity labeling mass spectrometry, immunoprecipitation, micrococcal nuclease assay, RNA sequencing, drug rescue assays, in vivo xenograft radiotherapy experiments\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity proteomics plus IP, functional assays in vitro and in vivo; single lab, novel finding\",\n      \"pmids\": [\"42185253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PMCA4 and GAT3 interact within lipid raft microdomains in glioma cells; PMCA4 knockdown increases resting Ca2+ and Ca2+ accumulation in lipid rafts, impairing glioma cell migration and invasion; GAT3 interacts with calmodulin (a key PMCA4 regulator), and long-term GABA treatment disrupts the PMCA4/GAT3 complex; GABA-stimulated Ca2+ events in lipid rafts drive CaMKII-dependent CREB phosphorylation at Ser133.\",\n      \"method\": \"PMCA4 siRNA knockdown, Co-IP of GAT3/PMCA4/calmodulin, lipid raft fractionation with Ca2+ measurement, cell migration/invasion assays, CaMKII/CREB phosphorylation assays, parvalbumin Ca2+ chelator expression in rafts\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP interactions combined with functional Ca2+ and migration assays; single lab, multiple methods but abstract-level detail only\",\n      \"pmids\": [\"40580687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MM-derived exosomal miR-4261 is transferred to red blood cells and directly targets ATP2B4, downregulating PMCA4 expression; this causes calcium overload in RBCs, confirmed by dual-luciferase reporter assay establishing the miR-4261/ATP2B4 targeting relationship.\",\n      \"method\": \"Dual-luciferase reporter assay, Western blot, immunofluorescence, Transwell exosome transfer assay, atomic absorption spectroscopy for Ca2+\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/luciferase experiment; miRNA targeting of ATP2B4 3'UTR shown but mechanistic detail of how PMCA4 loss leads to Ca2+ overload is inferred\",\n      \"pmids\": [\"36091107\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ATP2B4/PMCA4 is a plasma membrane P-type Ca2+-ATPase that extrudes cytosolic Ca2+ and functions both as a housekeeping Ca2+ pump and as a structural scaffold: in sperm it localizes to the principal piece where its Ca2+ efflux activity is essential for hyperactivated motility; in cardiomyocytes it tethers nNOS to a caveolar microdomain to regulate local cGMP/cAMP balance and contractility; in vascular smooth muscle it drives G1-phase cell cycle progression through NFAT/Cyclin D1 signaling; it interacts with eNOS/nNOS/Caveolin1 complexes and with CD147 to modulate nitric oxide and T-cell IL-2 signaling; its expression in erythrocytes is controlled by a tissue-specific enhancer and determines red blood cell Ca2+ homeostasis and malaria susceptibility; and in cancer cells it participates in additional mechanisms including stabilization of ELAVL1/histone H1.0 to regulate chromatin compaction and DNA damage responses.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATP2B4 (PMCA4) is a plasma-membrane Ca2+-extrusion ATPase that acts as the dominant pump clearing cytosolic Ca2+ in multiple cell types and, in parallel, serves as a membrane scaffold organizing Ca2+-signaling microdomains [#0, #3, #4]. Its primary transcript is alternatively spliced into PMCA4a and PMCA4b, which differ in their C-terminal regulatory domain and show distinct tissue distributions and basal activities [#1]; during sperm maturation an a/b isoform switch tunes Ca2+ turnover [#9]. In sperm, PMCA4 localizes to the principal piece alongside CatSper, and its loss causes Ca2+ overload and failure of hyperactivated motility, producing male infertility [#0], while it also forms a Ca2+-dependent quaternary complex with eNOS, nNOS, and Caveolin1 that restrains nitrosative stress [#6]. In cardiomyocytes it tethers nNOS to a caveolar microdomain, where its delocalization shifts local cGMP/cAMP balance to raise contractility [#3, #10]. Beyond pumping, PMCA4 couples Ca2+ handling to proliferation and differentiation programs: its efflux activity drives G1-phase progression in vascular smooth muscle through splice-variant-specific control of Cyclin D1 and AP-2β [#5], and in cancer cells it restrains migration, EMT via an NFATc1–ZEB1 axis, and macropinocytosis, and modulates apoptosis and DNA-damage responses [#11, #13, #14, #18]. An erythroid-specific enhancer and regulatory non-coding variants set ATP2B4 expression in red blood cells, controlling RBC Ca2+ homeostasis [#4, #16, #17]. A familial spastic paraplegia-associated R268Q missense mutation reduces Ca2+ extrusion capacity, linking PMCA4 dysfunction to disease [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that a single ATP2B4 gene generates distinct regulatory isoforms, explaining how one pump could be functionally tailored to different tissues.\",\n      \"evidence\": \"cDNA cloning, RT-PCR/Southern blot and genomic intron-exon sequencing identifying PMCA4a/PMCA4b splice variants and their tissue distribution\",\n      \"pmids\": [\"1531651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequences of the truncated C-terminal regulatory domain not directly tested\", \"Isoform-specific regulators not identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"First loss-of-function evidence that PMCA4 controls a cell-fate outcome, linking its Ca2+ handling to TNF-induced death pathways.\",\n      \"evidence\": \"Retrovirus-insertion mutagenesis in L929 cells with intracellular Ca2+, lysosome exocytosis and acidic-compartment volume readouts\",\n      \"pmids\": [\"11713265\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking Ca2+ elevation to VAC inhibition incompletely defined\", \"Single cell-line context\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined PMCA4 as the dominant Ca2+ extrusion pump in sperm and established its requirement for hyperactivated motility and male fertility.\",\n      \"evidence\": \"Pmca4-/- mice with sperm motility assays, IHC localization to the principal piece, and ultrastructural analysis\",\n      \"pmids\": [\"15178683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship to CatSper-mediated Ca2+ entry not mechanistically resolved\", \"Does not address PMCA4's scaffolding roles\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed a non-pumping, scaffolding function whereby PMCA4 spatially confines nNOS to set local second-messenger balance and contractility.\",\n      \"evidence\": \"PMCA4-/- mice with FRET cAMP/cGMP sensors, subcellular fractionation, nNOS activity and channel/RyR phosphorylation assays plus in vivo physiology\",\n      \"pmids\": [\"21965681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of nNOS tethering not defined\", \"Whether scaffolding requires pump activity not separated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed compartmentalization of PMCA4 within sperm membrane microdomains and an isoform switch during epididymal maturation, connecting localization to Ca2+ turnover demands.\",\n      \"evidence\": \"Detergent-resistant membrane fractionation, Ca2+-ATPase activity assays, isoform-specific IHC and qPCR across testis/epididymis/sperm\",\n      \"pmids\": [\"20050939\", \"21187283\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of isoform switch inferred, not directly tested\", \"Regulators driving the switch unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated that PMCA4 Ca2+ efflux, not just its presence, drives cell-cycle progression, with splice variants engaging different downstream effectors.\",\n      \"evidence\": \"PMCA4-knockout VSMCs with thymidine incorporation, splice-variant and pump-dead rescue, microarray and Western blot\",\n      \"pmids\": [\"24448801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Connection between Ca2+ efflux and AP-2β/Cyclin D1 transcription not fully mapped\", \"Restricted to VSMC context\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided a tool to monitor Ca2+ near the pump, confirming PMCA4 shapes local Ca2+ dynamics under β-adrenergic input in cardiomyocytes.\",\n      \"evidence\": \"PMCA4-GCaMP2 fusion biosensor with pump-inactive control in rat cardiomyocytes and live-cell imaging\",\n      \"pmids\": [\"23880607\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative size of the microdomain not defined\", \"Single-lab biosensor approach\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified a Ca2+-independent signaling role through direct CD147 binding that suppresses T-cell IL-2 expression.\",\n      \"evidence\": \"AP-MS interaction discovery, CD147 domain-mapping constructs, siRNA and IL-2 assays in human T cells\",\n      \"pmids\": [\"26729804\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the Ca2+-independent effect undefined\", \"Single-lab interaction\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linked PMCA4 to nitrosative-stress control in sperm via a Ca2+-dependent multiprotein NOS complex and established regulatory variation governing RBC Ca2+ homeostasis and malaria-relevant biology.\",\n      \"evidence\": \"Co-IP/FRET of PMCA4-eNOS-nNOS-Caveolin1 with NOS/peroxynitrite assays in Pmca4-/- sperm; erythroid enhancer CRISPR deletion and Atp2b4-/- mice; haplotype-linked RBC PMCA4b quantification and Ca2+ extrusion assays\",\n      \"pmids\": [\"28247940\", \"28714864\", \"28216081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and assembly order of the NOS complex unknown\", \"Mechanism connecting RBC Ca2+ to malaria susceptibility not directly shown in these studies\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Connected a disease-associated missense mutation to reduced pump function, providing a mechanistic basis for a PMCA4-linked neurological phenotype.\",\n      \"evidence\": \"Overexpression of WT vs R268Q PMCA4 in SH-SY5Y cells with fura-2 Ca2+ imaging after depolarization and SERCA inhibition\",\n      \"pmids\": [\"25798335\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality in patient neurons not established\", \"Single overexpression model\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended PMCA4 into cancer cell behavior, defining it as a suppressor of migration, EMT, and proliferation through Ca2+ clearance and NFATc1-ZEB1 signaling, with pathway-driven downregulation in vascular disease.\",\n      \"evidence\": \"siRNA/overexpression with epistasis (NFATc1/ZEB1 knockdown, cyclosporine A), Ca2+ clearance, migration/apoptosis assays, MEK/ERK inhibitors, and in vivo rat PAH and nude-mouse metastasis models\",\n      \"pmids\": [\"32860837\", \"32966125\", \"31963119\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether effects depend on pump activity vs scaffolding not uniformly resolved\", \"Single-lab studies per tissue\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed non-coding malaria-associated variants functionally tune ATP2B4 expression and RBC Ca2+, and identified exosomal miR-4261 as a post-transcriptional regulator.\",\n      \"evidence\": \"CRISPR deletion of the regulatory region in K562 cells with expression/Ca2+ readouts; dual-luciferase reporter and exosome transfer assays for miR-4261 targeting\",\n      \"pmids\": [\"35563239\", \"36091107\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"miR-4261 finding rests on single luciferase/transfer experiment\", \"Downstream pathophysiology of RBC Ca2+ overload inferred\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed PMCA4 pump activity is required for a specific stage of macropinocytosis, broadening its role into vesicle-mediated uptake.\",\n      \"evidence\": \"ATP2B4 CRISPR knockout with live-cell macropinocytosis imaging, Ca2+ oscillation measurement, and PDZ-binding and pump-dead mutant rescue in A431 cells\",\n      \"pmids\": [\"38597132\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How Ca2+ oscillations drive ruffle closure not detailed\", \"Single cell-line context\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a PMCA4/GAT3/calmodulin lipid-raft complex coupling Ca2+ microdomains to CaMKII-CREB signaling and glioma invasion.\",\n      \"evidence\": \"Co-IP, lipid raft fractionation with Ca2+ measurement, siRNA knockdown, and CaMKII/CREB phosphorylation and migration assays in glioma cells\",\n      \"pmids\": [\"40580687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs calmodulin-bridged PMCA4-GAT3 interaction not resolved\", \"Abstract-level mechanistic detail\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Uncovered a nuclear-relevant function in which PMCA4 stabilizes ELAVL1 to maintain histone H1.0, controlling chromatin compaction and radiosensitivity.\",\n      \"evidence\": \"CRISPR knockout, TurboID proximity-labeling MS, IP, micrococcal nuclease and RNA-seq assays, and in vivo xenograft radiotherapy\",\n      \"pmids\": [\"42185253\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which a plasma-membrane pump stabilizes ELAVL1 unclear\", \"Single-lab novel finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how PMCA4 partitions between its Ca2+-pumping and scaffolding functions across tissues, and what structural features dictate its assembly into the various NOS, CD147, GAT3, and ELAVL1 complexes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of PMCA4 partner complexes\", \"Pump-activity vs scaffolding contributions not separated in most disease contexts\", \"Mechanism linking membrane pump to nuclear/chromatin effects unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 4, 5, 8, 16, 17]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 5, 15]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 10, 14, 15]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 4, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 11, 19]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 13]}\n    ],\n    \"complexes\": [\n      \"PMCA4-eNOS-nNOS-Caveolin1 quaternary complex\",\n      \"PMCA4/GAT3/calmodulin lipid-raft complex\"\n    ],\n    \"partners\": [\n      \"nNOS\",\n      \"eNOS\",\n      \"CAV1\",\n      \"CD147\",\n      \"GAT3\",\n      \"calmodulin\",\n      \"ELAVL1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}