{"gene":"PPP3R2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2005,"finding":"PPP3R2 (PPP3RL) is a testis-specific regulatory subunit (Calcineurin B, type II) of protein phosphatase 3 (calcineurin), containing four EF-hand calcium-binding domains; its tissue-specific expression in testis is due to demethylation of its promoter region in testis.","method":"Gene cloning, sequence analysis, RT-PCR tissue expression profiling, promoter methylation analysis","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct experimental characterization of promoter methylation and expression specificity in a single focused study with multiple methods","pmids":["15865209"],"is_preprint":false},{"year":2017,"finding":"PPP3R2 is a direct target of miR-146a in chondrocytes; miR-146a suppresses Ppp3r2 expression to impair cartilage matrix homeostasis, and miR-146a inhibition in mouse OA models alleviates cartilage destruction via restoration of Ppp3r2 (and Camk2d) expression.","method":"miR-146a knockout mice, surgical OA mouse models, miR-146a inhibitor treatment, target validation (luciferase reporter / target identification implied), gene expression analysis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO and inhibitor rescue experiments in two OA models, single lab, target identification stated but full luciferase details not explicit in abstract","pmids":["28383548"],"is_preprint":false},{"year":2020,"finding":"PPP3R2 (testis-specific calcineurin regulatory subunit) is essential for sperm maturation and capacitation in mice; knockout of Ppp3r2 causes male sterility with impaired sperm motility, morphological defects, increased sperm membrane stiffness, disrupted membrane diffusion barrier at the annulus, and impaired cholesterol efflux during capacitation.","method":"Ppp3r2 knockout mice, sperm motility and morphology analysis, membrane stiffness measurements, annulus integrity assays, cholesterol efflux assays","journal":"Journal of molecular cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function KO with multiple orthogonal phenotypic readouts (motility, morphology, membrane stiffness, cholesterol efflux) establishing a defined cellular role","pmids":["31900494"],"is_preprint":false},{"year":2021,"finding":"PPP3R2 forms a sperm-specific calcineurin complex with the catalytic subunit PPP3CC; SPATA33 interacts with this PPP3CC/PPP3R2 complex via a PQIIIT (PxIxIT) motif and localizes calcineurin to the mitochondria in sperm. Loss of SPATA33 causes calcineurin to disappear from the mitochondria and phenocopies Ppp3r2 knockout (reduced motility, inflexible midpiece, impaired fertility). Sperm calcineurin also interacts with mitochondrial protein VDAC2.","method":"In silico PxIxIT motif screening, Spata33 knockout mice, immunoprecipitation (Co-IP), sperm motility and morphology analysis, immunofluorescence localization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, KO mouse phenocopy of Ppp3r2 KO, subcellular localization with functional consequence, multiple orthogonal methods in single rigorous study","pmids":["34446558"],"is_preprint":false},{"year":2025,"finding":"The FK506-FKBP12.6 complex preferentially binds and inhibits the sperm-specific calcineurin composed of PPP3CC and PPP3R2; this inhibition disrupts Ca2+ homeostasis (blocking calcineurin-mediated dephosphorylation of RyR2) and mitochondrial homeostasis (via Drp1 hyperphosphorylation), causing male infertility. FKBP12.6 deficiency alleviates FK506-induced reduction of PPP3CC and PPP3R2 expression and restores sperm motility.","method":"FKBP12.6 knockout mice, sperm motility assays, Co-immunoprecipitation, phosphorylation analysis of RyR2 and Drp1, mitochondrial function assays","journal":"Molecular biomedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO rescue experiment with Co-IP and phosphorylation mechanistic readouts, single lab, multiple methods","pmids":["41428164"],"is_preprint":false}],"current_model":"PPP3R2 is a testis-specific regulatory subunit (Calcineurin B type II) that heterodimerizes with the catalytic subunit PPP3CC to form sperm-specific calcineurin, a calcium-dependent phosphatase localized to the mitochondria via the adaptor SPATA33 (which binds via a PxIxIT motif) and also interacting with VDAC2; this complex is essential for sperm motility, midpiece flexibility, membrane remodeling, and cholesterol efflux during capacitation, with its inhibition by FK506-FKBP12.6 disrupting Ca2+ and mitochondrial homeostasis and causing male infertility, and its expression in chondrocytes is suppressed by miR-146a to impair cartilage matrix homeostasis."},"narrative":{"mechanistic_narrative":"PPP3R2 (Calcineurin B, type II) is a testis-specific regulatory subunit of protein phosphatase 3 (calcineurin) whose four EF-hand calcium-binding domains confer Ca2+ sensitivity, and whose restricted expression arises from demethylation of its promoter selectively in testis [PMID:15865209]. It heterodimerizes with the catalytic subunit PPP3CC to assemble a sperm-specific calcineurin holoenzyme that is essential for sperm maturation and capacitation: loss of PPP3R2 causes male sterility with impaired motility, morphological defects, increased membrane stiffness, a disrupted diffusion barrier at the annulus, and defective cholesterol efflux [PMID:31900494]. This complex is targeted to sperm mitochondria by the adaptor SPATA33, which engages the PPP3CC/PPP3R2 complex through a PxIxIT (PQIIIT) motif and additionally interacts with the mitochondrial channel VDAC2; SPATA33 loss removes calcineurin from mitochondria and phenocopies the PPP3R2 knockout [PMID:34446558]. The phosphatase activity of this complex maintains Ca2+ and mitochondrial homeostasis—dephosphorylating RyR2 and limiting Drp1 phosphorylation—and is selectively inhibited by the FK506-FKBP12.6 complex, linking its blockade to male infertility [PMID:41428164]. Beyond its reproductive role, PPP3R2 is a direct target of miR-146a in chondrocytes, where its suppression impairs cartilage matrix homeostasis [PMID:28383548].","teleology":[{"year":2005,"claim":"Established that PPP3R2 is a distinct, testis-restricted calcineurin regulatory subunit, defining it as a tissue-specific paralog rather than a ubiquitous phosphatase component.","evidence":"Gene cloning, sequence/EF-hand domain analysis, RT-PCR tissue profiling and promoter methylation analysis","pmids":["15865209"],"confidence":"Medium","gaps":["No functional phosphatase activity demonstrated for the encoded subunit","Catalytic partner and substrates not identified at this stage","Physiological role in testis untested"]},{"year":2017,"claim":"Identified a non-reproductive regulatory context by showing PPP3R2 is a direct miR-146a target whose suppression impairs cartilage matrix homeostasis, implicating it in osteoarthritis pathology.","evidence":"miR-146a knockout and surgical OA mouse models with inhibitor rescue and target validation","pmids":["28383548"],"confidence":"Medium","gaps":["Direct luciferase 3'UTR binding not fully detailed","Mechanism linking PPP3R2 levels to matrix homeostasis not resolved","Whether chondrocyte expression reflects a calcineurin complex unknown"]},{"year":2020,"claim":"Defined the in vivo cellular requirement for PPP3R2, showing it is essential for sperm motility, membrane mechanics, the annulus diffusion barrier, and capacitation-associated cholesterol efflux.","evidence":"Ppp3r2 knockout mice with motility, morphology, membrane stiffness, annulus integrity and cholesterol efflux assays","pmids":["31900494"],"confidence":"High","gaps":["Catalytic partner not yet identified","Subcellular localization of the active complex not established","Direct phosphatase substrates unknown"]},{"year":2021,"claim":"Resolved the molecular architecture of the active complex, showing PPP3R2 pairs with PPP3CC and is recruited to mitochondria by the PxIxIT-motif adaptor SPATA33, which also contacts VDAC2.","evidence":"In silico PxIxIT screening, Spata33 knockout mice, reciprocal Co-IP, and immunofluorescence localization with phenocopy analysis","pmids":["34446558"],"confidence":"High","gaps":["Direct dephosphorylation substrates of the mitochondrial complex not defined here","Structural basis of SPATA33-calcineurin and VDAC2 interactions unresolved","Functional consequence of VDAC2 association not dissected"]},{"year":2025,"claim":"Connected complex activity to downstream Ca2+ and mitochondrial homeostasis by showing FK506-FKBP12.6 selectively inhibits the PPP3CC/PPP3R2 phosphatase, altering RyR2 and Drp1 phosphorylation and causing infertility.","evidence":"FKBP12.6 knockout mice with sperm motility, Co-IP, RyR2/Drp1 phosphorylation and mitochondrial function assays","pmids":["41428164"],"confidence":"Medium","gaps":["Direct dephosphorylation of RyR2/Drp1 by PPP3R2-containing calcineurin not biochemically reconstituted","Single-lab mechanistic readouts","Relationship between Ca2+ and mitochondrial branches not fully ordered"]},{"year":null,"claim":"Whether PPP3R2-containing calcineurin acts directly on RyR2 and Drp1 and the structural basis of its mitochondrial recruitment remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted phosphatase-substrate assay for the sperm complex","No structural model of the PPP3CC/PPP3R2/SPATA33 assembly","Functional role of PPP3R2 in chondrocytes not connected to a defined complex"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4]}],"complexes":["sperm-specific calcineurin (PPP3CC/PPP3R2)"],"partners":["PPP3CC","SPATA33","VDAC2","FKBP12.6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96LZ3","full_name":"Calcineurin subunit B type 2","aliases":["Calcineurin B-like protein","CBLP","Calcineurin BII","CNBII","PPP3R1-like","Protein phosphatase 2B regulatory subunit 2","Protein phosphatase 3 regulatory subunit B beta isoform"],"length_aa":170,"mass_kda":19.5,"function":"Regulatory subunit of calcineurin, a calcium-dependent, calmodulin stimulated protein phosphatase. Confers calcium sensitivity","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q96LZ3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PPP3R2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PPP3R2","total_profiled":1310},"omim":[{"mim_id":"613821","title":"PROTEIN PHOSPHATASE 3, REGULATORY SUBUNIT B, BETA; PPP3R2","url":"https://www.omim.org/entry/613821"},{"mim_id":"114107","title":"PROTEIN PHOSPHATASE 3, CATALYTIC SUBUNIT, GAMMA ISOFORM; PPP3CC","url":"https://www.omim.org/entry/114107"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Primary cilium","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"testis","ntpm":76.0}],"url":"https://www.proteinatlas.org/search/PPP3R2"},"hgnc":{"alias_symbol":["PPP3RL"],"prev_symbol":[]},"alphafold":{"accession":"Q96LZ3","domains":[{"cath_id":"1.10.238.10","chopping":"18-82","consensus_level":"high","plddt":94.5734,"start":18,"end":82},{"cath_id":"1.10.238.10","chopping":"89-165","consensus_level":"high","plddt":94.9096,"start":89,"end":165}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96LZ3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96LZ3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96LZ3-F1-predicted_aligned_error_v6.png","plddt_mean":91.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PPP3R2","jax_strain_url":"https://www.jax.org/strain/search?query=PPP3R2"},"sequence":{"accession":"Q96LZ3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96LZ3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96LZ3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96LZ3"}},"corpus_meta":[{"pmid":"17684544","id":"PMC_17684544","title":"Systematic association mapping identifies NELL1 as a novel IBD disease gene.","date":"2007","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/17684544","citation_count":106,"is_preprint":false},{"pmid":"28383548","id":"PMC_28383548","title":"miR-146a facilitates osteoarthritis by regulating cartilage homeostasis via targeting Camk2d and Ppp3r2.","date":"2017","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/28383548","citation_count":87,"is_preprint":false},{"pmid":"27831554","id":"PMC_27831554","title":"The control of male fertility by spermatid-specific factors: searching for contraceptive targets from spermatozoon's head to tail.","date":"2016","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/27831554","citation_count":49,"is_preprint":false},{"pmid":"34446558","id":"PMC_34446558","title":"SPATA33 localizes calcineurin to the mitochondria and regulates sperm motility in mice.","date":"2021","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/34446558","citation_count":43,"is_preprint":false},{"pmid":"15865209","id":"PMC_15865209","title":"Characterization of a human regulatory subunit of protein phosphatase 3 gene (PPP3RL) expressed specifically in testis.","date":"2005","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/15865209","citation_count":30,"is_preprint":false},{"pmid":"21233773","id":"PMC_21233773","title":"Are calcineurin genes associated with athletic status? A function, replication study.","date":"2011","source":"Medicine and science in sports and exercise","url":"https://pubmed.ncbi.nlm.nih.gov/21233773","citation_count":17,"is_preprint":false},{"pmid":"31900494","id":"PMC_31900494","title":"Dependence of sperm structural and functional integrity on testicular calcineurin isoform PPP3R2 expression.","date":"2020","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/31900494","citation_count":16,"is_preprint":false},{"pmid":"20107831","id":"PMC_20107831","title":"Are calcineurin genes associated with endurance phenotype traits?","date":"2010","source":"European journal of applied physiology","url":"https://pubmed.ncbi.nlm.nih.gov/20107831","citation_count":10,"is_preprint":false},{"pmid":"25201034","id":"PMC_25201034","title":"Gene profiling of human VEGF signaling pathways in human endothelial and retinal pigment epithelial cells after anti VEGF treatment.","date":"2014","source":"BMC research notes","url":"https://pubmed.ncbi.nlm.nih.gov/25201034","citation_count":8,"is_preprint":false},{"pmid":"37841933","id":"PMC_37841933","title":"Isolation and characterization of ZK002, a novel dual function snake venom protein from Deinagkistrodon acutus with anti-angiogenic and anti-inflammatory properties.","date":"2023","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/37841933","citation_count":6,"is_preprint":false},{"pmid":"39655393","id":"PMC_39655393","title":"Genomic Effects of Biomechanical Loading in Adolescent Human Growth Plate Cartilage: A Pilot Study.","date":"2024","source":"Cartilage","url":"https://pubmed.ncbi.nlm.nih.gov/39655393","citation_count":3,"is_preprint":false},{"pmid":"40867601","id":"PMC_40867601","title":"The Role of miRNA167 in Skin Improvement: Insight from Extracellular Vesicles Derived from Rock Samphire (Crithmum maritimum).","date":"2025","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/40867601","citation_count":3,"is_preprint":false},{"pmid":"41428164","id":"PMC_41428164","title":"FK506 binding protein 12.6-mediated inhibition of sperm-specific calcineurin is essential for FK506-induced male infertility by disturbing the homeostasis of calcium and mitochondria.","date":"2025","source":"Molecular biomedicine","url":"https://pubmed.ncbi.nlm.nih.gov/41428164","citation_count":0,"is_preprint":false},{"pmid":"42002767","id":"PMC_42002767","title":"Genome-wide mapping of stress-responsive lncRNA, uc.104, reveals the chromatin-mediated regulation of stress and plasticity-related genes in the hippocampus of chronic restraint rats.","date":"2026","source":"Molecular brain","url":"https://pubmed.ncbi.nlm.nih.gov/42002767","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9745,"output_tokens":1565,"usd":0.026355,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8280,"output_tokens":2446,"usd":0.051275,"stage2_stop_reason":"end_turn"},"total_usd":0.07763,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"PPP3R2 (PPP3RL) is a testis-specific regulatory subunit (Calcineurin B, type II) of protein phosphatase 3 (calcineurin), containing four EF-hand calcium-binding domains; its tissue-specific expression in testis is due to demethylation of its promoter region in testis.\",\n      \"method\": \"Gene cloning, sequence analysis, RT-PCR tissue expression profiling, promoter methylation analysis\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct experimental characterization of promoter methylation and expression specificity in a single focused study with multiple methods\",\n      \"pmids\": [\"15865209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PPP3R2 is a direct target of miR-146a in chondrocytes; miR-146a suppresses Ppp3r2 expression to impair cartilage matrix homeostasis, and miR-146a inhibition in mouse OA models alleviates cartilage destruction via restoration of Ppp3r2 (and Camk2d) expression.\",\n      \"method\": \"miR-146a knockout mice, surgical OA mouse models, miR-146a inhibitor treatment, target validation (luciferase reporter / target identification implied), gene expression analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO and inhibitor rescue experiments in two OA models, single lab, target identification stated but full luciferase details not explicit in abstract\",\n      \"pmids\": [\"28383548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PPP3R2 (testis-specific calcineurin regulatory subunit) is essential for sperm maturation and capacitation in mice; knockout of Ppp3r2 causes male sterility with impaired sperm motility, morphological defects, increased sperm membrane stiffness, disrupted membrane diffusion barrier at the annulus, and impaired cholesterol efflux during capacitation.\",\n      \"method\": \"Ppp3r2 knockout mice, sperm motility and morphology analysis, membrane stiffness measurements, annulus integrity assays, cholesterol efflux assays\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function KO with multiple orthogonal phenotypic readouts (motility, morphology, membrane stiffness, cholesterol efflux) establishing a defined cellular role\",\n      \"pmids\": [\"31900494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PPP3R2 forms a sperm-specific calcineurin complex with the catalytic subunit PPP3CC; SPATA33 interacts with this PPP3CC/PPP3R2 complex via a PQIIIT (PxIxIT) motif and localizes calcineurin to the mitochondria in sperm. Loss of SPATA33 causes calcineurin to disappear from the mitochondria and phenocopies Ppp3r2 knockout (reduced motility, inflexible midpiece, impaired fertility). Sperm calcineurin also interacts with mitochondrial protein VDAC2.\",\n      \"method\": \"In silico PxIxIT motif screening, Spata33 knockout mice, immunoprecipitation (Co-IP), sperm motility and morphology analysis, immunofluorescence localization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, KO mouse phenocopy of Ppp3r2 KO, subcellular localization with functional consequence, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"34446558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The FK506-FKBP12.6 complex preferentially binds and inhibits the sperm-specific calcineurin composed of PPP3CC and PPP3R2; this inhibition disrupts Ca2+ homeostasis (blocking calcineurin-mediated dephosphorylation of RyR2) and mitochondrial homeostasis (via Drp1 hyperphosphorylation), causing male infertility. FKBP12.6 deficiency alleviates FK506-induced reduction of PPP3CC and PPP3R2 expression and restores sperm motility.\",\n      \"method\": \"FKBP12.6 knockout mice, sperm motility assays, Co-immunoprecipitation, phosphorylation analysis of RyR2 and Drp1, mitochondrial function assays\",\n      \"journal\": \"Molecular biomedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO rescue experiment with Co-IP and phosphorylation mechanistic readouts, single lab, multiple methods\",\n      \"pmids\": [\"41428164\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PPP3R2 is a testis-specific regulatory subunit (Calcineurin B type II) that heterodimerizes with the catalytic subunit PPP3CC to form sperm-specific calcineurin, a calcium-dependent phosphatase localized to the mitochondria via the adaptor SPATA33 (which binds via a PxIxIT motif) and also interacting with VDAC2; this complex is essential for sperm motility, midpiece flexibility, membrane remodeling, and cholesterol efflux during capacitation, with its inhibition by FK506-FKBP12.6 disrupting Ca2+ and mitochondrial homeostasis and causing male infertility, and its expression in chondrocytes is suppressed by miR-146a to impair cartilage matrix homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PPP3R2 (Calcineurin B, type II) is a testis-specific regulatory subunit of protein phosphatase 3 (calcineurin) whose four EF-hand calcium-binding domains confer Ca2+ sensitivity, and whose restricted expression arises from demethylation of its promoter selectively in testis [#0]. It heterodimerizes with the catalytic subunit PPP3CC to assemble a sperm-specific calcineurin holoenzyme that is essential for sperm maturation and capacitation: loss of PPP3R2 causes male sterility with impaired motility, morphological defects, increased membrane stiffness, a disrupted diffusion barrier at the annulus, and defective cholesterol efflux [#2]. This complex is targeted to sperm mitochondria by the adaptor SPATA33, which engages the PPP3CC/PPP3R2 complex through a PxIxIT (PQIIIT) motif and additionally interacts with the mitochondrial channel VDAC2; SPATA33 loss removes calcineurin from mitochondria and phenocopies the PPP3R2 knockout [#3]. The phosphatase activity of this complex maintains Ca2+ and mitochondrial homeostasis—dephosphorylating RyR2 and limiting Drp1 phosphorylation—and is selectively inhibited by the FK506-FKBP12.6 complex, linking its blockade to male infertility [#4]. Beyond its reproductive role, PPP3R2 is a direct target of miR-146a in chondrocytes, where its suppression impairs cartilage matrix homeostasis [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that PPP3R2 is a distinct, testis-restricted calcineurin regulatory subunit, defining it as a tissue-specific paralog rather than a ubiquitous phosphatase component.\",\n      \"evidence\": \"Gene cloning, sequence/EF-hand domain analysis, RT-PCR tissue profiling and promoter methylation analysis\",\n      \"pmids\": [\"15865209\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No functional phosphatase activity demonstrated for the encoded subunit\",\n        \"Catalytic partner and substrates not identified at this stage\",\n        \"Physiological role in testis untested\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified a non-reproductive regulatory context by showing PPP3R2 is a direct miR-146a target whose suppression impairs cartilage matrix homeostasis, implicating it in osteoarthritis pathology.\",\n      \"evidence\": \"miR-146a knockout and surgical OA mouse models with inhibitor rescue and target validation\",\n      \"pmids\": [\"28383548\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct luciferase 3'UTR binding not fully detailed\",\n        \"Mechanism linking PPP3R2 levels to matrix homeostasis not resolved\",\n        \"Whether chondrocyte expression reflects a calcineurin complex unknown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the in vivo cellular requirement for PPP3R2, showing it is essential for sperm motility, membrane mechanics, the annulus diffusion barrier, and capacitation-associated cholesterol efflux.\",\n      \"evidence\": \"Ppp3r2 knockout mice with motility, morphology, membrane stiffness, annulus integrity and cholesterol efflux assays\",\n      \"pmids\": [\"31900494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Catalytic partner not yet identified\",\n        \"Subcellular localization of the active complex not established\",\n        \"Direct phosphatase substrates unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved the molecular architecture of the active complex, showing PPP3R2 pairs with PPP3CC and is recruited to mitochondria by the PxIxIT-motif adaptor SPATA33, which also contacts VDAC2.\",\n      \"evidence\": \"In silico PxIxIT screening, Spata33 knockout mice, reciprocal Co-IP, and immunofluorescence localization with phenocopy analysis\",\n      \"pmids\": [\"34446558\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct dephosphorylation substrates of the mitochondrial complex not defined here\",\n        \"Structural basis of SPATA33-calcineurin and VDAC2 interactions unresolved\",\n        \"Functional consequence of VDAC2 association not dissected\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected complex activity to downstream Ca2+ and mitochondrial homeostasis by showing FK506-FKBP12.6 selectively inhibits the PPP3CC/PPP3R2 phosphatase, altering RyR2 and Drp1 phosphorylation and causing infertility.\",\n      \"evidence\": \"FKBP12.6 knockout mice with sperm motility, Co-IP, RyR2/Drp1 phosphorylation and mitochondrial function assays\",\n      \"pmids\": [\"41428164\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct dephosphorylation of RyR2/Drp1 by PPP3R2-containing calcineurin not biochemically reconstituted\",\n        \"Single-lab mechanistic readouts\",\n        \"Relationship between Ca2+ and mitochondrial branches not fully ordered\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether PPP3R2-containing calcineurin acts directly on RyR2 and Drp1 and the structural basis of its mitochondrial recruitment remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No reconstituted phosphatase-substrate assay for the sperm complex\",\n        \"No structural model of the PPP3CC/PPP3R2/SPATA33 assembly\",\n        \"Functional role of PPP3R2 in chondrocytes not connected to a defined complex\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [\"sperm-specific calcineurin (PPP3CC/PPP3R2)\"],\n    \"partners\": [\"PPP3CC\", \"SPATA33\", \"VDAC2\", \"FKBP12.6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}