{"gene":"PPP2R2D","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2009,"finding":"Greatwall kinase (Gwl), activated by Cdk1/cyclin B during M phase, promotes inactivation of PP2A/B55delta (PP2A containing the B55delta/PPP2R2D regulatory subunit), a phosphatase that targets CDK phosphosites. Once activated, Gwl promotes PP2A/B55delta inhibition without further requirement for MPF. Removal of PP2A/B55delta activity rescues the inability of Gwl-depleted Xenopus egg extracts to enter M phase, placing PP2A/B55delta downstream of Gwl in the pathway controlling mitotic entry.","method":"Xenopus egg extract biochemistry, immunodepletion of Gwl and PP2A/B55delta, epistasis rescue experiments","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal depletion epistasis in a reconstituted extract system, multiple orthogonal functional rescue experiments, replicated across labs in subsequent work","pmids":["19793917"],"is_preprint":false},{"year":2021,"finding":"PP2A-B55delta (PPP2R2D-containing complex) is the phosphatase responsible for dephosphorylating Arpp19 at serine 109 (the PKA site) in Xenopus oocytes. In prophase, PKA and PP2A-B55delta are simultaneously active; the drop in PKA activity induced by progesterone allows PP2A-B55delta to dephosphorylate Arpp19-S109, releasing the prophase arrest. PP2A-B55delta thus acts on two distinct Arpp19 sites: opposing PKA (S109 dephosphorylation to initiate meiosis) and being inhibited by Greatwall-phosphorylated Arpp19 (S67) to permit Cdk1 activation at M-phase entry.","method":"Xenopus oocyte meiosis assays, phosphatase identification biochemistry, site-specific Arpp19 phosphorylation/dephosphorylation assays, epistasis with PKA and Greatwall","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct biochemical identification of PP2A-B55delta as the Arpp19-S109 phosphatase with multiple functional assays in a single rigorous study","pmids":["33758202"],"is_preprint":false},{"year":2018,"finding":"In yeast (Saccharomyces cerevisiae), the TORC1–Greatwall(Rim15)–PP2A-B55delta (Cdc55) pathway controls alcoholic fermentation rate. Deletion of CDC55 (encoding B55delta) abolished high fermentation performance in Rim15-deficient yeast, placing PP2A-B55delta downstream of Greatwall/Rim15 and upstream of glycolytic control. The pathway is conserved in fission yeast (Schizosaccharomyces pombe).","method":"Yeast genetics, fermentation assays with CDC55 deletion mutants, TORC1 pathway epistasis","journal":"Applied and environmental microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in yeast with functional fermentation readout, confirmed in two yeast species; yeast ortholog study","pmids":["30341081"],"is_preprint":false},{"year":2020,"finding":"PPP2R2D in T cells suppresses IL-2 production by maintaining the IL-2 gene and IL-2-enhancing transcription factor loci in a closed chromatin state and keeping phosphorylated CREB (an IL-2 enhancer) at low levels. T cell-specific PPP2R2D knockout mice produce more IL-2, show elevated pCREB, and display increased Treg suppressive function in vitro and in vivo, with reduced systemic autoimmunity upon TLR7 stimulation.","method":"T cell-specific conditional knockout (LckCre), chromatin accessibility assays, IL-2 production measurement, in vitro and in vivo Treg suppression assays, autoimmunity model","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with multiple orthogonal cellular readouts; single lab, no biochemical reconstitution of direct substrate","pmids":["32897879"],"is_preprint":false},{"year":2022,"finding":"Alcohol consumption induces hepatic AhR activation, which transcriptionally upregulates Ppp2r2d. Elevated PPP2R2D then dephosphorylates/inactivates AMPKalpha, causing autophagy inhibition and mitochondrial dysfunction, and altering phospho-/sphingo-lipid metabolism. Hepatocyte-specific AhR ablation reverses steatosis and restores phospholipid content, confirming the AhR→PPP2R2D→AMPKalpha dephosphorylation axis.","method":"Alcohol-fed mouse model, hepatocyte-specific AhR knockout, PPP2R2D overexpression/knockdown, AMPKalpha phosphorylation assays, autophagy markers, lipidomics, AhR chromatin-binding (transcriptional target identification)","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (KO, overexpression, phosphorylation assays, lipidomics) in single lab; PPP2R2D identified as direct AhR transcriptional target dephosphorylating AMPKalpha","pmids":["36241614"],"is_preprint":false},{"year":2016,"finding":"PPP2R2D (PP2A-B55delta) counteracts CDK1 activation in hepatocellular carcinoma cells treated with cisplatin, modulating G2/M cell cycle transitions. miR-133b suppresses PP2A-B55delta expression by binding to the 3'-UTR of PPP2R2D mRNA. Overexpression of B55delta enhances cisplatin sensitivity, while knockdown reduces it.","method":"Luciferase reporter assay (miR-133b binding to PPP2R2D 3'UTR), PPP2R2D stable knockdown/overexpression cell lines, cell cycle analysis, apoptosis assays, in vivo tumorigenicity assay","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — luciferase validation of miR-133b/PPP2R2D interaction plus functional rescue experiments; single lab","pmids":["27074866"],"is_preprint":false},{"year":2022,"finding":"In T cells, PPP2R2D acts as a negative regulator of immune checkpoint receptor expression (PD-1, LAG3, TIM3, CTLA4): T cell-specific PPP2R2D-deficient mice show open chromatin at exhaustion marker loci and greater intratumoral T cell exhaustion. PPP2R2D deficiency also leads to expansion of Foxp3+ Treg cells within tumors, enhancing Treg-mediated suppression of antitumor immunity.","method":"Conditional T cell-specific KO (LckCreR2Dfl/fl), melanoma xenograft model, chromatin accessibility assays at exhaustion marker loci, adoptive T cell transfer, flow cytometry","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with chromatin accessibility and in vivo adoptive transfer experiments; single lab, builds on prior work","pmids":["35831019"],"is_preprint":false},{"year":2018,"finding":"PPP2R2D promotes gastric cancer cell proliferation and migration through activation of mTOR signaling: PPP2R2D knockdown decreases mTOR phosphorylation, while overexpression promotes proliferation and migration in vitro.","method":"siRNA knockdown and overexpression in gastric cancer cell lines, mTOR phosphorylation assays, proliferation/migration assays, in vivo tumor growth and metastasis model","journal":"International journal of oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single phosphorylation readout without direct substrate validation or reconstitution; mTOR pathway placement inferred from phospho-mTOR levels only","pmids":["29568966"],"is_preprint":false},{"year":2024,"finding":"PPP2R2D modulates AMPKalpha phosphorylation in renal tubular epithelial cells: miR-5010-5p targets PPP2R2D (validated by dual-luciferase assay), and miR-5010-5p transfection reduces PPP2R2D expression, restores phosphorylated AMPK, and decreases NF-kappaB phosphorylation, reducing inflammatory cytokine production under high-glucose conditions.","method":"Dual-luciferase reporter assay, miRNA mimic transfection, western blotting for AMPKalpha phosphorylation and NF-kappaB phosphorylation, cytokine measurement","journal":"BMJ open diabetes research & care","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, luciferase validation of miRNA target plus downstream phosphorylation assays; indirect evidence that PPP2R2D dephosphorylates AMPKalpha","pmids":["38442987"],"is_preprint":false}],"current_model":"PPP2R2D encodes the B55delta regulatory subunit of PP2A, a serine/threonine phosphatase complex that targets CDK phosphosites during mitotic/meiotic regulation: it is inactivated downstream of Greatwall kinase (which phosphorylates the PP2A inhibitor Arpp19-S67) to permit Cdk1-driven M-phase entry, and it dephosphorylates Arpp19-S109 (opposing PKA) to initiate meiotic progression; beyond cell cycle control, PPP2R2D dephosphorylates AMPKalpha (regulated by AhR-dependent transcription and by miRNAs including miR-133b and miR-5010-5p), suppresses IL-2 production and chromatin accessibility at immune checkpoint loci in T cells, and modulates mTOR signaling in cancer contexts."},"narrative":{"mechanistic_narrative":"PPP2R2D encodes the B55delta regulatory subunit that directs the PP2A serine/threonine phosphatase toward CDK phosphosites during cell-cycle and meiotic control [PMID:19793917, PMID:33758202]. During mitotic entry, PP2A-B55delta opposes Cdk1-driven phosphorylation and is itself inactivated downstream of Greatwall kinase, such that removing PP2A-B55delta activity rescues M-phase entry in Greatwall-depleted extracts [PMID:19793917]. In meiosis, PP2A-B55delta acts on two distinct Arpp19 sites: it dephosphorylates Arpp19-S109 (the PKA site) to release prophase arrest upon the progesterone-induced fall in PKA activity, while being inhibited by Greatwall-phosphorylated Arpp19-S67 to permit Cdk1 activation at M-phase entry [PMID:33758202]. This TORC1–Greatwall–PP2A-B55delta module is conserved to yeast, where it governs fermentation rate [PMID:30341081]. Beyond the cell cycle, PPP2R2D dephosphorylates and inactivates AMPKalpha; hepatic AhR transcriptionally upregulates Ppp2r2d to drive this axis, inhibiting autophagy and causing mitochondrial dysfunction in alcohol-induced steatosis [PMID:36241614]. In T cells, PPP2R2D restrains immune activation by maintaining closed chromatin at the IL-2 locus and at immune-checkpoint/exhaustion loci, suppressing IL-2 and pCREB and limiting Treg expansion [PMID:32897879, PMID:35831019]. Its expression is tuned post-transcriptionally by miRNAs in cancer and disease contexts [PMID:27074866, PMID:38442987].","teleology":[{"year":2009,"claim":"Placed PP2A-B55delta in the mitotic-entry pathway as the CDK-phosphosite phosphatase inactivated downstream of Greatwall kinase, explaining how M-phase phosphorylations are stabilized.","evidence":"Xenopus egg extract immunodepletion and epistasis rescue of Gwl and PP2A-B55delta","pmids":["19793917"],"confidence":"High","gaps":["Mechanism by which Greatwall output inactivates the B55delta holoenzyme not resolved at this step","Specific CDK substrates dephosphorylated by B55delta not enumerated"]},{"year":2021,"claim":"Identified PP2A-B55delta as the Arpp19-S109 (PKA-site) phosphatase, showing it integrates PKA and Greatwall inputs through two distinct Arpp19 sites to control meiotic resumption.","evidence":"Xenopus oocyte meiosis assays with site-specific Arpp19 phosphorylation biochemistry and PKA/Greatwall epistasis","pmids":["33758202"],"confidence":"High","gaps":["Structural basis for dual-site recognition of Arpp19 unresolved","Whether the same holoenzyme acts on both sites simultaneously in vivo not established"]},{"year":2018,"claim":"Demonstrated conservation of the TORC1–Greatwall–PP2A-B55delta module by linking it to metabolic (fermentation) control in yeast, extending its role beyond animal cell-cycle regulation.","evidence":"S. cerevisiae genetics with CDC55 deletion and fermentation assays, confirmed in S. pombe","pmids":["30341081"],"confidence":"Medium","gaps":["Molecular substrate linking B55delta to glycolytic control not identified","Relevance to mammalian metabolism not tested here"]},{"year":2016,"claim":"Connected PPP2R2D-mediated CDK1 counteraction to chemosensitivity, and showed its expression is set post-transcriptionally by miR-133b.","evidence":"Luciferase 3'UTR reporter for miR-133b, knockdown/overexpression cell lines, cisplatin cell-cycle and in vivo tumorigenicity assays in hepatocellular carcinoma","pmids":["27074866"],"confidence":"Medium","gaps":["Direct CDK1 dephosphorylation by B55delta not reconstituted in this context","Single cancer type"]},{"year":2020,"claim":"Established an immunoregulatory role: PPP2R2D restrains IL-2 production by keeping the IL-2 locus and pCREB low, linking the phosphatase subunit to T-cell tolerance.","evidence":"T cell-specific conditional KO (LckCre), chromatin accessibility, IL-2 and pCREB measurement, Treg suppression and TLR7 autoimmunity models","pmids":["32897879"],"confidence":"Medium","gaps":["Direct substrate at the IL-2 locus not biochemically defined","Single lab, no reconstitution"]},{"year":2022,"claim":"Defined a hepatic AhR→PPP2R2D→AMPKalpha axis, showing PPP2R2D dephosphorylates AMPKalpha to inhibit autophagy and drive alcohol-induced steatosis.","evidence":"Alcohol-fed mouse model, hepatocyte-specific AhR KO, PPP2R2D gain/loss, AMPKalpha phosphorylation assays and lipidomics","pmids":["36241614"],"confidence":"Medium","gaps":["Direct PP2A-B55delta dephosphorylation of AMPKalpha not reconstituted in vitro","Single lab"]},{"year":2022,"claim":"Extended the T-cell role to checkpoint and exhaustion control, showing PPP2R2D loss opens chromatin at exhaustion loci and expands intratumoral Tregs.","evidence":"T cell-specific conditional KO, melanoma xenograft, chromatin accessibility at exhaustion loci, adoptive transfer, flow cytometry","pmids":["35831019"],"confidence":"Medium","gaps":["Mechanistic link between phosphatase activity and chromatin state at checkpoint loci undefined","Direct substrate unknown"]},{"year":2024,"claim":"Reinforced the PPP2R2D–AMPKalpha link in renal epithelium and added miR-5010-5p as a second post-transcriptional regulator tuning the axis under high glucose.","evidence":"Dual-luciferase reporter, miRNA mimic transfection, AMPKalpha and NF-kappaB phosphorylation western blots, cytokine measurement","pmids":["38442987"],"confidence":"Low","gaps":["Indirect evidence that PPP2R2D dephosphorylates AMPKalpha — no direct biochemistry","Single lab"]},{"year":null,"claim":"The molecular determinants of B55delta substrate selection across its cell-cycle (CDK/Arpp19) and metabolic/immune (AMPKalpha, chromatin) roles remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of how B55delta recruits distinct substrates","Direct reconstitution of AMPKalpha dephosphorylation lacking","Mechanism connecting phosphatase activity to chromatin accessibility at immune loci unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1]}],"localization":[],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,6]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,4]}],"complexes":["PP2A holoenzyme (B55delta-containing)"],"partners":["ARPP19","AMPK (PRKAA)","MASTL","AHR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q66LE6","full_name":"Serine/threonine-protein phosphatase 2A 55 kDa regulatory subunit B delta isoform","aliases":["PP2A subunit B isoform B55-delta","PP2A subunit B isoform PR55-delta","PP2A subunit B isoform R2-delta","PP2A subunit B isoform delta"],"length_aa":453,"mass_kda":52.0,"function":"Substrate-recognition subunit of protein phosphatase 2A (PP2A) that plays a key role in cell cycle by controlling mitosis entry and exit. Involved in chromosome clustering during late mitosis by mediating dephosphorylation of MKI67 (By similarity). The activity of PP2A complexes containing PPP2R2D (PR55-delta) fluctuate during the cell cycle: the activity is high in interphase and low in mitosis (By similarity)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q66LE6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PPP2R2D","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":74,"dependency_fraction":0.013513513513513514},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PPP2R2D","total_profiled":1310},"omim":[{"mim_id":"613992","title":"PROTEIN PHOSPHATASE 2, REGULATORY SUBUNIT B, DELTA; PPP2R2D","url":"https://www.omim.org/entry/613992"},{"mim_id":"608221","title":"MICROTUBULE-ASSOCIATED SERINE/THREONINE KINASE-LIKE; MASTL","url":"https://www.omim.org/entry/608221"},{"mim_id":"605487","title":"cAMP-REGULATED PHOSPHOPROTEIN 19; ARPP19","url":"https://www.omim.org/entry/605487"},{"mim_id":"604147","title":"PTTG1 REGULATOR OF SISTER CHROMATID SEPARATION, SECURIN; PTTG1","url":"https://www.omim.org/entry/604147"},{"mim_id":"603061","title":"ENDOSULFINE, ALPHA; ENSA","url":"https://www.omim.org/entry/603061"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"pancreas","ntpm":15.0}],"url":"https://www.proteinatlas.org/search/PPP2R2D"},"hgnc":{"alias_symbol":["MDS026","B55delta","B55D"],"prev_symbol":[]},"alphafold":{"accession":"Q66LE6","domains":[{"cath_id":"2.130.10.10","chopping":"17-449","consensus_level":"medium","plddt":93.2785,"start":17,"end":449}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q66LE6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q66LE6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q66LE6-F1-predicted_aligned_error_v6.png","plddt_mean":91.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PPP2R2D","jax_strain_url":"https://www.jax.org/strain/search?query=PPP2R2D"},"sequence":{"accession":"Q66LE6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q66LE6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q66LE6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q66LE6"}},"corpus_meta":[{"pmid":"19793917","id":"PMC_19793917","title":"The M phase kinase Greatwall (Gwl) promotes inactivation of PP2A/B55delta, a phosphatase directed against CDK phosphosites.","date":"2009","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19793917","citation_count":160,"is_preprint":false},{"pmid":"27074866","id":"PMC_27074866","title":"Protein phosphatase 2A-B55δ enhances chemotherapy sensitivity of human hepatocellular carcinoma under the regulation of microRNA-133b.","date":"2016","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/27074866","citation_count":35,"is_preprint":false},{"pmid":"36241614","id":"PMC_36241614","title":"Induction of the hepatic aryl hydrocarbon receptor by alcohol dysregulates autophagy and phospholipid metabolism via PPP2R2D.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36241614","citation_count":29,"is_preprint":false},{"pmid":"30341081","id":"PMC_30341081","title":"Nutrient Signaling via the TORC1-Greatwall-PP2AB55δ Pathway Is Responsible for the High Initial Rates of Alcoholic Fermentation in Sake Yeast Strains of Saccharomyces cerevisiae.","date":"2018","source":"Applied and environmental microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30341081","citation_count":22,"is_preprint":false},{"pmid":"32897879","id":"PMC_32897879","title":"PPP2R2D suppresses IL-2 production and Treg function.","date":"2020","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/32897879","citation_count":17,"is_preprint":false},{"pmid":"29568966","id":"PMC_29568966","title":"PPP2R2D, a regulatory subunit of protein phosphatase 2A, promotes gastric cancer growth and metastasis via mechanistic target of rapamycin activation.","date":"2018","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/29568966","citation_count":15,"is_preprint":false},{"pmid":"33758202","id":"PMC_33758202","title":"The M-phase regulatory phosphatase PP2A-B55δ opposes protein kinase A on Arpp19 to initiate meiotic division.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/33758202","citation_count":9,"is_preprint":false},{"pmid":"38442987","id":"PMC_38442987","title":"MicroRNA-5010-5p ameliorates high-glucose induced inflammation in renal tubular epithelial cells by modulating the expression of PPP2R2D.","date":"2024","source":"BMJ open diabetes research & care","url":"https://pubmed.ncbi.nlm.nih.gov/38442987","citation_count":6,"is_preprint":false},{"pmid":"35831019","id":"PMC_35831019","title":"PPP2R2D Suppresses Effector T Cell Exhaustion and Regulatory T Cell Expansion and Inhibits Tumor Growth in Melanoma.","date":"2022","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/35831019","citation_count":5,"is_preprint":false},{"pmid":"40256259","id":"PMC_40256259","title":"LncRNA SNHG25 facilitates colorectal cancer progression by upregulating PPP2R2D expression through sponging miR-329-3p.","date":"2025","source":"Cytotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/40256259","citation_count":4,"is_preprint":false},{"pmid":"30211417","id":"PMC_30211417","title":"Cd induces G2/M cell cycle arrest by up-regulating miR-133b via directly targeting PPP2R2D in L02 hepatocytes.","date":"2018","source":"Metallomics : integrated biometal science","url":"https://pubmed.ncbi.nlm.nih.gov/30211417","citation_count":3,"is_preprint":false},{"pmid":"24596207","id":"PMC_24596207","title":"An in vivo screen implicates PPP2R2D as an inhibitor of T-cell function.","date":"2014","source":"Cancer discovery","url":"https://pubmed.ncbi.nlm.nih.gov/24596207","citation_count":2,"is_preprint":false},{"pmid":"30357203","id":"PMC_30357203","title":"Retraction: Cd induces G2/M cell cycle arrest by up-regulating miR-133b via directly targeting PPP2R2D in L02 hepatocytes.","date":"2018","source":"Metallomics : integrated biometal science","url":"https://pubmed.ncbi.nlm.nih.gov/30357203","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8602,"output_tokens":2835,"usd":0.034166,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10136,"output_tokens":3032,"usd":0.06324,"stage2_stop_reason":"end_turn"},"total_usd":0.097406,"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\": 2009,\n      \"finding\": \"Greatwall kinase (Gwl), activated by Cdk1/cyclin B during M phase, promotes inactivation of PP2A/B55delta (PP2A containing the B55delta/PPP2R2D regulatory subunit), a phosphatase that targets CDK phosphosites. Once activated, Gwl promotes PP2A/B55delta inhibition without further requirement for MPF. Removal of PP2A/B55delta activity rescues the inability of Gwl-depleted Xenopus egg extracts to enter M phase, placing PP2A/B55delta downstream of Gwl in the pathway controlling mitotic entry.\",\n      \"method\": \"Xenopus egg extract biochemistry, immunodepletion of Gwl and PP2A/B55delta, epistasis rescue experiments\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal depletion epistasis in a reconstituted extract system, multiple orthogonal functional rescue experiments, replicated across labs in subsequent work\",\n      \"pmids\": [\"19793917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PP2A-B55delta (PPP2R2D-containing complex) is the phosphatase responsible for dephosphorylating Arpp19 at serine 109 (the PKA site) in Xenopus oocytes. In prophase, PKA and PP2A-B55delta are simultaneously active; the drop in PKA activity induced by progesterone allows PP2A-B55delta to dephosphorylate Arpp19-S109, releasing the prophase arrest. PP2A-B55delta thus acts on two distinct Arpp19 sites: opposing PKA (S109 dephosphorylation to initiate meiosis) and being inhibited by Greatwall-phosphorylated Arpp19 (S67) to permit Cdk1 activation at M-phase entry.\",\n      \"method\": \"Xenopus oocyte meiosis assays, phosphatase identification biochemistry, site-specific Arpp19 phosphorylation/dephosphorylation assays, epistasis with PKA and Greatwall\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct biochemical identification of PP2A-B55delta as the Arpp19-S109 phosphatase with multiple functional assays in a single rigorous study\",\n      \"pmids\": [\"33758202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In yeast (Saccharomyces cerevisiae), the TORC1–Greatwall(Rim15)–PP2A-B55delta (Cdc55) pathway controls alcoholic fermentation rate. Deletion of CDC55 (encoding B55delta) abolished high fermentation performance in Rim15-deficient yeast, placing PP2A-B55delta downstream of Greatwall/Rim15 and upstream of glycolytic control. The pathway is conserved in fission yeast (Schizosaccharomyces pombe).\",\n      \"method\": \"Yeast genetics, fermentation assays with CDC55 deletion mutants, TORC1 pathway epistasis\",\n      \"journal\": \"Applied and environmental microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in yeast with functional fermentation readout, confirmed in two yeast species; yeast ortholog study\",\n      \"pmids\": [\"30341081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PPP2R2D in T cells suppresses IL-2 production by maintaining the IL-2 gene and IL-2-enhancing transcription factor loci in a closed chromatin state and keeping phosphorylated CREB (an IL-2 enhancer) at low levels. T cell-specific PPP2R2D knockout mice produce more IL-2, show elevated pCREB, and display increased Treg suppressive function in vitro and in vivo, with reduced systemic autoimmunity upon TLR7 stimulation.\",\n      \"method\": \"T cell-specific conditional knockout (LckCre), chromatin accessibility assays, IL-2 production measurement, in vitro and in vivo Treg suppression assays, autoimmunity model\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with multiple orthogonal cellular readouts; single lab, no biochemical reconstitution of direct substrate\",\n      \"pmids\": [\"32897879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Alcohol consumption induces hepatic AhR activation, which transcriptionally upregulates Ppp2r2d. Elevated PPP2R2D then dephosphorylates/inactivates AMPKalpha, causing autophagy inhibition and mitochondrial dysfunction, and altering phospho-/sphingo-lipid metabolism. Hepatocyte-specific AhR ablation reverses steatosis and restores phospholipid content, confirming the AhR→PPP2R2D→AMPKalpha dephosphorylation axis.\",\n      \"method\": \"Alcohol-fed mouse model, hepatocyte-specific AhR knockout, PPP2R2D overexpression/knockdown, AMPKalpha phosphorylation assays, autophagy markers, lipidomics, AhR chromatin-binding (transcriptional target identification)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (KO, overexpression, phosphorylation assays, lipidomics) in single lab; PPP2R2D identified as direct AhR transcriptional target dephosphorylating AMPKalpha\",\n      \"pmids\": [\"36241614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PPP2R2D (PP2A-B55delta) counteracts CDK1 activation in hepatocellular carcinoma cells treated with cisplatin, modulating G2/M cell cycle transitions. miR-133b suppresses PP2A-B55delta expression by binding to the 3'-UTR of PPP2R2D mRNA. Overexpression of B55delta enhances cisplatin sensitivity, while knockdown reduces it.\",\n      \"method\": \"Luciferase reporter assay (miR-133b binding to PPP2R2D 3'UTR), PPP2R2D stable knockdown/overexpression cell lines, cell cycle analysis, apoptosis assays, in vivo tumorigenicity assay\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — luciferase validation of miR-133b/PPP2R2D interaction plus functional rescue experiments; single lab\",\n      \"pmids\": [\"27074866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In T cells, PPP2R2D acts as a negative regulator of immune checkpoint receptor expression (PD-1, LAG3, TIM3, CTLA4): T cell-specific PPP2R2D-deficient mice show open chromatin at exhaustion marker loci and greater intratumoral T cell exhaustion. PPP2R2D deficiency also leads to expansion of Foxp3+ Treg cells within tumors, enhancing Treg-mediated suppression of antitumor immunity.\",\n      \"method\": \"Conditional T cell-specific KO (LckCreR2Dfl/fl), melanoma xenograft model, chromatin accessibility assays at exhaustion marker loci, adoptive T cell transfer, flow cytometry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with chromatin accessibility and in vivo adoptive transfer experiments; single lab, builds on prior work\",\n      \"pmids\": [\"35831019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PPP2R2D promotes gastric cancer cell proliferation and migration through activation of mTOR signaling: PPP2R2D knockdown decreases mTOR phosphorylation, while overexpression promotes proliferation and migration in vitro.\",\n      \"method\": \"siRNA knockdown and overexpression in gastric cancer cell lines, mTOR phosphorylation assays, proliferation/migration assays, in vivo tumor growth and metastasis model\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single phosphorylation readout without direct substrate validation or reconstitution; mTOR pathway placement inferred from phospho-mTOR levels only\",\n      \"pmids\": [\"29568966\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PPP2R2D modulates AMPKalpha phosphorylation in renal tubular epithelial cells: miR-5010-5p targets PPP2R2D (validated by dual-luciferase assay), and miR-5010-5p transfection reduces PPP2R2D expression, restores phosphorylated AMPK, and decreases NF-kappaB phosphorylation, reducing inflammatory cytokine production under high-glucose conditions.\",\n      \"method\": \"Dual-luciferase reporter assay, miRNA mimic transfection, western blotting for AMPKalpha phosphorylation and NF-kappaB phosphorylation, cytokine measurement\",\n      \"journal\": \"BMJ open diabetes research & care\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, luciferase validation of miRNA target plus downstream phosphorylation assays; indirect evidence that PPP2R2D dephosphorylates AMPKalpha\",\n      \"pmids\": [\"38442987\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PPP2R2D encodes the B55delta regulatory subunit of PP2A, a serine/threonine phosphatase complex that targets CDK phosphosites during mitotic/meiotic regulation: it is inactivated downstream of Greatwall kinase (which phosphorylates the PP2A inhibitor Arpp19-S67) to permit Cdk1-driven M-phase entry, and it dephosphorylates Arpp19-S109 (opposing PKA) to initiate meiotic progression; beyond cell cycle control, PPP2R2D dephosphorylates AMPKalpha (regulated by AhR-dependent transcription and by miRNAs including miR-133b and miR-5010-5p), suppresses IL-2 production and chromatin accessibility at immune checkpoint loci in T cells, and modulates mTOR signaling in cancer contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PPP2R2D encodes the B55delta regulatory subunit that directs the PP2A serine/threonine phosphatase toward CDK phosphosites during cell-cycle and meiotic control [#0, #1]. During mitotic entry, PP2A-B55delta opposes Cdk1-driven phosphorylation and is itself inactivated downstream of Greatwall kinase, such that removing PP2A-B55delta activity rescues M-phase entry in Greatwall-depleted extracts [#0]. In meiosis, PP2A-B55delta acts on two distinct Arpp19 sites: it dephosphorylates Arpp19-S109 (the PKA site) to release prophase arrest upon the progesterone-induced fall in PKA activity, while being inhibited by Greatwall-phosphorylated Arpp19-S67 to permit Cdk1 activation at M-phase entry [#1]. This TORC1–Greatwall–PP2A-B55delta module is conserved to yeast, where it governs fermentation rate [#2]. Beyond the cell cycle, PPP2R2D dephosphorylates and inactivates AMPKalpha; hepatic AhR transcriptionally upregulates Ppp2r2d to drive this axis, inhibiting autophagy and causing mitochondrial dysfunction in alcohol-induced steatosis [#4]. In T cells, PPP2R2D restrains immune activation by maintaining closed chromatin at the IL-2 locus and at immune-checkpoint/exhaustion loci, suppressing IL-2 and pCREB and limiting Treg expansion [#3, #6]. Its expression is tuned post-transcriptionally by miRNAs in cancer and disease contexts [#5, #8].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Placed PP2A-B55delta in the mitotic-entry pathway as the CDK-phosphosite phosphatase inactivated downstream of Greatwall kinase, explaining how M-phase phosphorylations are stabilized.\",\n      \"evidence\": \"Xenopus egg extract immunodepletion and epistasis rescue of Gwl and PP2A-B55delta\",\n      \"pmids\": [\"19793917\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Greatwall output inactivates the B55delta holoenzyme not resolved at this step\", \"Specific CDK substrates dephosphorylated by B55delta not enumerated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified PP2A-B55delta as the Arpp19-S109 (PKA-site) phosphatase, showing it integrates PKA and Greatwall inputs through two distinct Arpp19 sites to control meiotic resumption.\",\n      \"evidence\": \"Xenopus oocyte meiosis assays with site-specific Arpp19 phosphorylation biochemistry and PKA/Greatwall epistasis\",\n      \"pmids\": [\"33758202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for dual-site recognition of Arpp19 unresolved\", \"Whether the same holoenzyme acts on both sites simultaneously in vivo not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated conservation of the TORC1–Greatwall–PP2A-B55delta module by linking it to metabolic (fermentation) control in yeast, extending its role beyond animal cell-cycle regulation.\",\n      \"evidence\": \"S. cerevisiae genetics with CDC55 deletion and fermentation assays, confirmed in S. pombe\",\n      \"pmids\": [\"30341081\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular substrate linking B55delta to glycolytic control not identified\", \"Relevance to mammalian metabolism not tested here\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected PPP2R2D-mediated CDK1 counteraction to chemosensitivity, and showed its expression is set post-transcriptionally by miR-133b.\",\n      \"evidence\": \"Luciferase 3'UTR reporter for miR-133b, knockdown/overexpression cell lines, cisplatin cell-cycle and in vivo tumorigenicity assays in hepatocellular carcinoma\",\n      \"pmids\": [\"27074866\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CDK1 dephosphorylation by B55delta not reconstituted in this context\", \"Single cancer type\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established an immunoregulatory role: PPP2R2D restrains IL-2 production by keeping the IL-2 locus and pCREB low, linking the phosphatase subunit to T-cell tolerance.\",\n      \"evidence\": \"T cell-specific conditional KO (LckCre), chromatin accessibility, IL-2 and pCREB measurement, Treg suppression and TLR7 autoimmunity models\",\n      \"pmids\": [\"32897879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrate at the IL-2 locus not biochemically defined\", \"Single lab, no reconstitution\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a hepatic AhR→PPP2R2D→AMPKalpha axis, showing PPP2R2D dephosphorylates AMPKalpha to inhibit autophagy and drive alcohol-induced steatosis.\",\n      \"evidence\": \"Alcohol-fed mouse model, hepatocyte-specific AhR KO, PPP2R2D gain/loss, AMPKalpha phosphorylation assays and lipidomics\",\n      \"pmids\": [\"36241614\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PP2A-B55delta dephosphorylation of AMPKalpha not reconstituted in vitro\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the T-cell role to checkpoint and exhaustion control, showing PPP2R2D loss opens chromatin at exhaustion loci and expands intratumoral Tregs.\",\n      \"evidence\": \"T cell-specific conditional KO, melanoma xenograft, chromatin accessibility at exhaustion loci, adoptive transfer, flow cytometry\",\n      \"pmids\": [\"35831019\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between phosphatase activity and chromatin state at checkpoint loci undefined\", \"Direct substrate unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Reinforced the PPP2R2D–AMPKalpha link in renal epithelium and added miR-5010-5p as a second post-transcriptional regulator tuning the axis under high glucose.\",\n      \"evidence\": \"Dual-luciferase reporter, miRNA mimic transfection, AMPKalpha and NF-kappaB phosphorylation western blots, cytokine measurement\",\n      \"pmids\": [\"38442987\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Indirect evidence that PPP2R2D dephosphorylates AMPKalpha — no direct biochemistry\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular determinants of B55delta substrate selection across its cell-cycle (CDK/Arpp19) and metabolic/immune (AMPKalpha, chromatin) roles remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of how B55delta recruits distinct substrates\", \"Direct reconstitution of AMPKalpha dephosphorylation lacking\", \"Mechanism connecting phosphatase activity to chromatin accessibility at immune loci unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [\"PP2A holoenzyme (B55delta-containing)\"],\n    \"partners\": [\"ARPP19\", \"AMPK (PRKAA)\", \"MASTL\", \"AHR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}