Affinage

PPP3CA

Protein phosphatase 3 catalytic subunit alpha · UniProt Q08209

Length
521 aa
Mass
58.7 kDa
Annotated
2026-06-10
26 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PPP3CA encodes the catalytic subunit of calcineurin, a Ca2+/calmodulin-regulated serine-threonine phosphatase that functions as a heterodimer with a Ca2+-binding regulatory subunit to couple calcium signals to substrate dephosphorylation (PMID:8978785). Its evolutionarily conserved role as a calmodulin-regulated phosphatase was established through the yeast ortholog CNA1, where loss of catalytic activity disrupts the regulation of the mating-pheromone response (PMID:1651503). Substrate selection depends on an acidic recruitment pocket (the E282 pocket) adjacent to the active site that binds basophilic substrates via arginine contacts; the disease-causing E282K variant inverts the charge of this pocket and shifts substrate preference from basic to acidic targets, as shown by structure determination, in vitro dephosphorylation, and cellular phosphoproteomics (PMID:41698888). Through its phosphatase activity, PPP3CA dephosphorylates NFAT-family transcription factors—including NFATc4, with which it associates in competition with CAMTA1—to regulate downstream transcription (PMID:35332122, PMID:8978785), and it negatively regulates HIF transcriptional activity in an activity-dependent manner without changing HIF-alpha protein levels (PMID:30776328). PPP3CA further modulates AKT/mTOR signaling and autophagy, including TFEB nuclear translocation, downstream of receptor inputs (PMID:41214150). Loss-of-function variants in the catalytic domain cause epileptic encephalopathy whereas auto-inhibitory domain gain-of-function variants cause multiple congenital abnormalities, defining a domain-dependent functional dichotomy (PMID:29432562).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1991 High

    Established that the calcineurin catalytic subunit is a conserved calmodulin-regulated phosphatase with a defined biological role, providing the foundational identity for mammalian PPP3CA.

    Evidence Yeast CNA1/CNA2 cloning with calmodulin and human calcineurin probes and double-null pheromone-response epistasis

    PMID:1651503

    Open questions at the time
    • Does not identify mammalian substrates
    • Mechanism inferred from yeast orthologs rather than human protein
  2. 1996 Low

    Defined PPP3CA's subunit architecture and linked it to NF-AT dephosphorylation in transcriptional regulation, framing its role in immune gene expression.

    Evidence Chromosome mapping and biochemical subunit characterization with literature synthesis of NF-AT dephosphorylation

    PMID:8978785

    Open questions at the time
    • NF-AT dephosphorylation cited from prior literature, not demonstrated here
    • No direct enzymatic assay in this study
  3. 2018 Medium

    Resolved how distinct PPP3CA domain mutations produce opposite clinical outcomes, establishing a gain-of-function versus loss-of-function dichotomy.

    Evidence Clinical exome sequencing with yeast functional assays of catalytic versus auto-inhibitory domain mutations

    PMID:29432562

    Open questions at the time
    • Functional readouts in yeast, not human neurons
    • Does not define the affected substrates per disorder
  4. 2019 Medium

    Showed that PPP3CA acts as a phosphatase-dependent negative regulator of HIF transcriptional output independent of HIF-alpha stability, expanding its transcriptional reach beyond NFAT.

    Evidence siRNA phosphatase screen, active versus catalytically inactive overexpression, ionomycin activation, and HIF reporter assays in HeLa cells

    PMID:30776328

    Open questions at the time
    • Direct HIF-pathway substrate not identified
    • Single cell-line system
  5. 2020 Low

    Linked PPP3CA to ERK1/2 dephosphorylation and control of proliferation, migration, and apoptosis in metanephric mesenchyme cells.

    Evidence Lentiviral knockdown with proliferation/migration/apoptosis assays and ERK1/2 phospho-western blot in mK4 cells

    PMID:33169579

    Open questions at the time
    • Single knockdown approach
    • Direct dephosphorylation of ERK1/2 not biochemically demonstrated
  6. 2021 Medium

    Demonstrated that truncating variants in a regulatory-domain hotspot abolish mutant protein and cause more severe seizures than catalytic missense variants, refining genotype-severity relationships.

    Evidence Exome sequencing with RNA and protein expression studies in patient cells

    PMID:33963760

    Open questions at the time
    • Mechanism of protein loss not defined
    • Single lab
  7. 2022 Medium

    Identified competitive NFATc4 binding between CAMTA1 and PPP3CA as a switch controlling NFATc4 dephosphorylation and chemoresistance, placing PPP3CA in a tunable transcriptional module.

    Evidence Co-IP, siRNA knockdown rescue, luciferase reporters, and xenograft model in colorectal cancer

    PMID:35332122

    Open questions at the time
    • Competitive binding inferred, not structurally resolved
    • Single lab
  8. 2022 Low

    Connected PPP3CA to TRIM72-driven glycolytic and PI3K/Akt/mTOR signaling in breast cancer.

    Evidence Co-IP, PPP3CA siRNA, MCT4 promoter luciferase assay, and xenograft model

    PMID:35324524

    Open questions at the time
    • Single Co-IP without reciprocal validation
    • Direct phosphatase substrate in this axis unknown
  9. 2025 Medium

    Showed PPP3CA stability and activity are regulated by OR2T6 via calcium influx, with downstream suppression of AKT/mTOR and dual control of autophagy through TFEB translocation.

    Evidence Co-IP/MS, ubiquitin-proteasome and calcium influx assays, AKT/mTOR western blot, and TFEB translocation assays with tumor models

    PMID:41214150

    Open questions at the time
    • Whether TFEB is a direct PPP3CA substrate not established
    • Single lab
  10. 2025 Low

    Placed PPP3CA under transcriptional repression by MAZ, with loss activating ERK/MAPK and NFATc1/MMP9 to drive osteoclast differentiation.

    Evidence Promoter binding assay, OVX mouse model, RANKL osteoclast differentiation, and PPP3CA overexpression with phospho-ERK western blot

    PMID:40602229

    Open questions at the time
    • Limited direct PPP3CA biochemistry
    • Single lab
  11. 2026 High

    Provided the structural basis for substrate recruitment, showing an acidic E282 pocket selects basophilic substrates and that the E282K disease variant inverts this selectivity.

    Evidence CNE282K structure determination, in vitro dephosphorylation, active-site mutagenesis, and cellular phosphoproteomics

    PMID:41698888

    Open questions at the time
    • Full repertoire of acidic substrates gained by E282K not catalogued
    • Link to specific disease phenotype at organ level not established

Open questions

Synthesis pass · forward-looking unresolved questions
  • How calcineurin substrate selection, domain-specific dysfunction, and the diverse downstream pathways (HIF, ERK, AKT/mTOR, autophagy) integrate into the distinct disease phenotypes remains unresolved.
  • No unified substrate map across tissues
  • Mechanistic basis distinguishing epileptic encephalopathy from congenital abnormalities at substrate level unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0016787 hydrolase activity 3
Pathway
R-HSA-74160 Gene expression (Transcription) 3 R-HSA-162582 Signal Transduction 2 R-HSA-9612973 Autophagy 1
Partners
CAMTA1NFATC4OR2T6PPP3R1TRIM72
Complex memberships
calcineurin

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1991 Yeast CNA1 encodes a calmodulin-regulated phosphoprotein phosphatase (calcineurin/PP2B homolog) whose catalytic subunit is 54% identical to the mammalian counterpart; genetic deletion of both yeast calcineurin catalytic subunit genes (cna1 cna2) causes hypersensitivity to mating pheromone alpha-factor and failure to resume growth during continuous pheromone exposure, placing calcineurin as an antagonist of the mating-pheromone response pathway. Yeast library screening with calmodulin and human calcineurin cDNA probes; PCR cloning; null mutant construction and pheromone-response epistasis assay Proceedings of the National Academy of Sciences of the United States of America High 1651503
2018 Mutations in different functional domains of PPP3CA cause distinct clinical disorders: catalytic domain mutations and frameshift (loss-of-function) result in epileptic encephalopathy, while auto-inhibitory (AI) domain mutations cause multiple congenital abnormalities. Yeast model experiments demonstrated that catalytic domain mutations decrease calcineurin signaling whereas AI domain mutations increase calcineurin signaling, establishing a gain-of-function vs. loss-of-function dichotomy. Clinical exome sequencing; yeast model functional assays for calcineurin signaling activity Human molecular genetics Medium 29432562
2019 PPP3CA (calcineurin Aα) negatively regulates hypoxia-inducible factor (HIF) transcriptional activity in a phosphatase-activity-dependent manner: a constitutively active PPP3CA inhibited HIF target gene expression without altering HIF-1α or HIF-2α protein levels, while a catalytically inactive mutant had no effect. Ionomycin-activated endogenous PPP3CA phenocopied the effect, and PPP3CA silencing abolished this ionomycin effect. siRNA screen of 25 phosphatase catalytic subunits; constitutively active vs. catalytically inactive PPP3CA overexpression; ionomycin pharmacological activation; HIF transcriptional reporter assays in HeLa cells Archives of biochemistry and biophysics Medium 30776328
2021 PPP3CA truncating variants clustered within a 26-amino acid region in the regulatory domain (RD) produce no detectable mutant protein (expression studies showed RNA from mutant allele but absence of mutant protein), causing more severe early-onset seizures than loss-of-function missense variants in the catalytic domain. Exome sequencing; expression studies (RNA and protein analysis) of truncating variant in patient cells Clinical genetics Medium 33963760
2022 CAMTA1 and PPP3CA competitively bind to NFATc4; CAMTA1 knockdown promotes PPP3CA-mediated dephosphorylation of NFATc4, upregulating NFATc4 activity and increasing colorectal cancer chemoresistance to oxaliplatin. PPP3CA is essential for the NFATc4 dephosphorylation and chemoresistance phenotype caused by CAMTA1 knockdown. Co-immunoprecipitation (Co-IP); siRNA knockdown of PPP3CA and CAMTA1; luciferase reporter assays; xenograft tumor model Cell death discovery Medium 35332122
2022 TRIM72 interacts with PPP3CA (shown by Co-IP); PPP3CA mediates the effects of TRIM72 on hypoxia-induced lactate production and MCT4 (monocarboxylate transporter 4) promoter activity, as well as PI3K/Akt/mTOR pathway signaling in breast cancer cells. Co-immunoprecipitation (Co-IP); siRNA knockdown of PPP3CA; luciferase reporter assay; western blot; xenograft model Anti-cancer drugs Low 35324524
2020 PPP3CA knockdown in metanephric mesenchyme mK4 cells promoted E-cadherin expression, cell apoptosis, and reduced cell proliferation and migration; the underlying mechanism was associated with dephosphorylation of ERK1/2 by PPP3CA. Lentiviral knockdown; flow cytometry; EdU/CCK-8 assay; wound healing assay; western blot for ERK1/2 phosphorylation Sheng wu gong cheng xue bao = Chinese journal of biotechnology Low 33169579
2025 OR2T6 physically binds PPP3CA (Co-IP and mass spectrometry); OR2T6 promotes PPP3CA protein stability and enzyme activity through the ubiquitin-proteasome system and by promoting calcium ion influx via the Gs/cAMP/PKA channel signaling axis. PPP3CA activity downstream of OR2T6 suppresses the AKT/mTOR pathway, inhibiting tumor proliferation and promoting autophagy initiation; PPP3CA also facilitates nuclear translocation of TFEB, leading to transcriptional inactivation of lysosomal target genes and blocking autophagic flux. Co-immunoprecipitation and mass spectrometry; ubiquitin-proteasome pathway analysis; calcium influx assays; AKT/mTOR pathway western blot; TFEB nuclear translocation assay; in vitro and in vivo tumor assays Cell death and differentiation Medium 41214150
2025 MAZ transcriptionally represses PPP3CA by binding to its promoter; reduced PPP3CA leads to activation of the ERK/MAPK pathway, increased NFATc1 and MMP9 levels, and promotion of osteoclast differentiation and osteoporosis progression in vivo. Bioinformatics; OVX mouse model; RANKL-induced osteoclast differentiation; PPP3CA overexpression; promoter binding assay; ERK1/2 phosphorylation western blot; in vivo animal experiments Tissue & cell Low 40602229
2026 The disease-causing E282K missense variant in PPP3CA/calcineurin alters substrate dephosphorylation by disrupting an acidic substrate recruitment pocket (the 'E282 pocket') adjacent to the active site that normally binds basophilic substrates via arginine residues. The CNE282K structure shows that the pocket transforms from acidic to basic and is blocked by a E282K-E237 salt bridge, shifting substrate preference from basic to acidic substrates as confirmed by in vitro assays and cellular phosphoproteomics. Crystal/structural analysis of CNE282K; in vitro dephosphorylation assays; active-site mutagenesis; cell phosphoproteomics; molecular/cellular techniques Nature communications High 41698888
1996 Calcineurin (PPP3CA/calcineurin Aα) is a heterodimer consisting of a 58-59 kDa calmodulin-binding catalytic subunit (calcineurin A) and a 19 kDa Ca2+-binding regulatory subunit (calcineurin B); it functions in transcriptional regulation in T lymphocytes by dephosphorylating NF-AT, which is essential for interleukin-2 gene transcription. Chromosomal localization of PPP3CA confirmed to chromosome 4. Chromosome mapping; biochemical characterization of subunit composition; functional literature synthesis with NF-AT dephosphorylation Cytogenetics and cell genetics Low 8978785
2024 PPP3CA pathogenic variants within the calmodulin-binding domain result in childhood-onset epilepsy with focal and generalized seizures, while variants within the regulatory domain lead to early-onset drug-resistant severe epilepsy, indicating that variant location within PPP3CA determines the severity of calcineurin dysfunction and clinical phenotype. Clinical case series with literature review; electro-clinical characterization; genotype-phenotype correlation analysis Seizure Low 39305655

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1991 Yeast has homologs (CNA1 and CNA2 gene products) of mammalian calcineurin, a calmodulin-regulated phosphoprotein phosphatase. Proceedings of the National Academy of Sciences of the United States of America 280 1651503
2005 The CNA1 histone of the ciliate Tetrahymena thermophila is essential for chromosome segregation in the germline micronucleus. Molecular biology of the cell 51 16251352
2017 De Novo Mutations in PPP3CA Cause Severe Neurodevelopmental Disease with Seizures. American journal of human genetics 49 28942967
2018 Loss-of-function and gain-of-function mutations in PPP3CA cause two distinct disorders. Human molecular genetics 41 29432562
1996 Calcineurin A alpha (PPP3CA), calcineurin A beta (PPP3CB) and calcineurin B (PPP3R1) are located on human chromosomes 4, 10q21-->q22 and 2p16-->p15 respectively. Cytogenetics and cell genetics 40 8978785
2010 Fine mapping of calcineurin (PPP3CA) gene reveals novel alternative splicing patterns, association of 5'UTR trinucleotide repeat with addiction vulnerability, and differential isoform expression in Alzheimer's disease. Substance use & misuse 21 20590401
2021 PPP3CA truncating variants clustered in the regulatory domain cause early-onset refractory epilepsy. Clinical genetics 16 33963760
2022 Investigation of Copy Number Variations (CNVs) of the Goat PPP3CA Gene and Their Effect on Litter Size and Semen Quality. Animals : an open access journal from MDPI 13 35203154
2021 Deletion mutation within the goat PPP3CA gene identified by GWAS significantly affects litter size. Reproduction, fertility, and development 13 33883061
2019 Protein phosphatase PPP3CA (calcineurin A) down-regulates hypoxia-inducible factor transcriptional activity. Archives of biochemistry and biophysics 13 30776328
2018 Early-onset infant epileptic encephalopathy associated with a de novo PPP3CA gene mutation. Cold Spring Harbor molecular case studies 13 30455226
2014 Molecular cloning, structural analysis and tissue expression of protein phosphatase 3 catalytic subunit alpha isoform (PPP3CA) gene in Tianfu goat muscle. International journal of molecular sciences 13 24514563
2022 TRIM72 exerts antitumor effects in breast cancer and modulates lactate production and MCT4 promoter activity by interacting with PPP3CA. Anti-cancer drugs 11 35324524
2019 Dominant mutants of the calcineurin catalytic subunit (CNA-1) showed developmental defects, increased sensitivity to stress conditions, and CNA-1 interacts with CaM and CRZ-1 in Neurospora crassa. Archives of microbiology 9 31807806
2020 Clinical and Genetic Study on a Chinese Patient with Infantile Onset Epileptic Encephalopathy carrying a PPP3CA Null Variant: a case report. BMC pediatrics 7 32593294
2003 Expression of the yeast calcineurin subunits CNA1 and CNA2 during growth and hyper-osmotic stress. FEMS microbiology letters 7 12725927
2022 CAMTA1-PPP3CA-NFATc4 multi-protein complex mediates the resistance of colorectal cancer to oxaliplatin. Cell death discovery 6 35332122
2024 PPP3CA gene-related developmental and epileptic encephalopathy: Expanding the electro-clinical phenotype. Seizure 3 39305655
2024 Expanding the clinical spectrum of PPP3CA variants - alternative isoforms matter. Orphanet journal of rare diseases 3 39707491
2022 Case report: A novel PPP3CA truncating mutation within the regulatory domain causes severe developmental and epileptic encephalopathy in a Chinese patient. Frontiers in neurology 3 36158964
2025 New variants and genotype-phenotype correlation of PPP3CA-related developmental and epileptic encephalopathy. Frontiers in neuroscience 1 40548073
2025 Circular RNA hsa_circ_0099188 regulates inducible nitric oxide synthase and chemokine transcription in macrophages by targeting the hsa-miR-381-3p/PPP3CA and hsa-miR-381-3p/KLF4 pathways in response to 4,4'-methylene diphenyl diisocyanate-glutathione conjugate exposure. Toxicological sciences : an official journal of the Society of Toxicology 1 40796177
2026 The clinical missense variant E282K in PPP3CA/calcineurin shifts substrate dephosphorylation by altering active site recruitment. Nature communications 0 41698888
2025 Activation of ERK/MAPK signaling by MAZ through transcriptional repression of PPP3CA to promote osteoclastogenesis and osteoporosis progression: Functions and mechanisms. Tissue & cell 0 40602229
2025 OR2T6 modulates autophagy through the PPP3CA-mediated pathways to suppress gastric cancer. Cell death and differentiation 0 41214150
2020 [PPP3CA silence regulates MET process, cell apoptosis, proliferation and migration in metanephric mesenchyme cells]. Sheng wu gong cheng xue bao = Chinese journal of biotechnology 0 33169579

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