ATP2B3

ATP2B3 (PMCA3) is a plasma membrane Ca²⁺-ATPase that extrudes cytoplasmic Ca²⁺ to maintain intracellular calcium homeostasis, with critical roles in neuronal signaling and adrenal aldosterone regulation. In the brain, PMCA3 localizes to cerebellar granule cell processes and hippocampal dendritic fields, where it controls sub-plasma membrane Ca²⁺ microdomains; mutations in its catalytic P-domain (G733R) or calmodulin-binding region (E1081Q) impair Ca²⁺ extrusion in a splice variant–dependent manner and cause cerebellar ataxia (PMID:28807751, PMID:36207321, PMID:7770003). In adrenal aldosterone-producing adenomas, somatic loss-of-function mutations near transmembrane codons 416–426 abolish Ca²⁺ export, generate Na⁺-dependent inward currents that depolarize the plasma membrane, elevate intracellular Ca²⁺, and drive CYP11B2 (aldosterone synthase) expression and autonomous aldosterone production (PMID:23416519, PMID:27035656, PMID:24082052). PMCA3 activity is negatively regulated by phosphorylation-independent binding of 14-3-3ε, which reduces Ca²⁺ clearance following intracellular Ca²⁺ transients (PMID:18029012).

1. 1994 Medium

   Mapping ATP2B3 to Xq28 established it as an X-linked candidate for neurological disease, framing subsequent genetic studies.

   Evidence FISH, somatic cell hybrid, and linkage analysis in human samples

   PMID:8187550

   Open questions at the time

   • No disease-causing mutations identified at this stage
   • Functional relevance of chromosomal position not tested
2. 1995 Medium

   Demonstrating that PMCA3 protein localizes to cerebellar granule cell processes and hippocampal dendritic fields revealed its neuron-specific Ca²⁺ extrusion role, distinguishing it from ubiquitous PMCA isoforms.

   Evidence Immunohistochemistry and in situ hybridization in rat brain

   PMID:7770003

   Open questions at the time

   • Localization shown only in rat; human tissue confirmation lacking
   • No functional consequence of regional expression tested
3. 2007 High

   Identification of 14-3-3ε as a phosphorylation-independent inhibitor of PMCA3 pump activity established the first known regulatory partner that attenuates Ca²⁺ clearance.

   Evidence Two-hybrid, co-immunoprecipitation, GST pull-down, aequorin-based Ca²⁺ measurements in CHO cells

   PMID:18029012

   Open questions at the time

   • Physiological context of 14-3-3ε regulation (e.g., neuronal vs. adrenal) not addressed
   • Binding site on PMCA3 not mapped
4. 2012 Medium

   Showing that PMCA3 knockdown in PC12 cells accelerates neurite outgrowth and triggers compensatory upregulation of PMCA1/4 and SERCA demonstrated that PMCA3 loss remodels Ca²⁺ signaling networks during neuronal differentiation.

   Evidence Antisense stable transfection in PC12 cells with differentiation assays and immunoblot

   PMID:22921123

   Open questions at the time

   • Relevance to in vivo neuronal development not tested
   • Compensatory mechanisms complicate isolation of PMCA3-specific roles
5. 2013 High

   Discovery of recurrent somatic ATP2B3 mutations in aldosterone-producing adenomas, coupled with electrophysiological evidence for membrane depolarization and CYP11B2/NR4A2 upregulation, established a direct mechanistic link between PMCA3 loss-of-function and autonomous aldosterone secretion.

   Evidence Exome sequencing of APA cohort; patch-clamp on primary adenoma cells; overexpression in HAC15 cells with gene expression readout

   PMID:23416519 PMID:24082052

   Open questions at the time

   • Precise structural basis for mutation-induced ion leak not resolved
   • Whether mutations act purely through loss of Ca²⁺ extrusion or also gain-of-function Na⁺ conductance remained unclear
6. 2016 High

   Mechanistic dissection of the L425_V426del mutation resolved that APA-linked ATP2B3 mutations simultaneously abolish Ca²⁺ pump function and introduce a Na⁺-dependent inward current, explaining both elevated intracellular Ca²⁺ and membrane depolarization.

   Evidence Ca²⁺ imaging in NCI-H295R and HEK-293 cells, patch-clamp electrophysiology, aldosterone production assays

   PMID:27035656

   Open questions at the time

   • Na⁺ conductance pathway through the mutant pump not structurally characterized
   • In vivo confirmation of dual mechanism lacking
7. 2017 Medium

   Identification of the catalytic P-domain G733R mutation as impairing Ca²⁺ handling, supported by molecular dynamics, linked PMCA3 catalytic domain integrity to cerebellar ataxia pathogenesis.

   Evidence Cellular Ca²⁺ assays combined with homology modeling and molecular dynamics

   PMID:28807751

   Open questions at the time

   • No patient genotype–phenotype segregation data provided
   • Structural model based on homology, not experimental structure
8. 2022 Medium

   Demonstrating that the ataxia-linked E1081Q mutation near the calmodulin-binding domain has opposite effects in the 'a' versus 'b' splice variants revealed that PMCA3 splice context determines whether a mutation causes gain or loss of sub-PM Ca²⁺ extrusion.

   Evidence Sub-plasma membrane Ca²⁺ microdomain measurements and pump activity assays comparing splice variants

   PMID:36207321

   Open questions at the time

   • Relative expression of splice variants in cerebellar neurons not quantified
   • How splice-specific effects translate to selective cerebellar vulnerability unknown

• Key unresolved questions include the high-resolution structural basis for mutation-induced Na⁺ leak through PMCA3, the in vivo contribution of 14-3-3ε regulation to neuronal or adrenal Ca²⁺ homeostasis, and whether PMCA3 splice variant ratios explain cell-type-specific disease manifestations.
• No cryo-EM or crystal structure of PMCA3 available
• In vivo knockout/knockin mouse models with neuronal or adrenal phenotyping not reported in the timeline
• Relative pathogenic contribution of Ca²⁺ extrusion loss versus Na⁺ leak in APA not resolved