{"gene":"PPP1R3G","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2013,"finding":"PPP1R3G functions as a glycogen-targeting subunit (G subunit) of protein phosphatase 1 (PP1) in liver, where it stimulates glycogen synthase activity and promotes hepatic glycogenesis. Liver-specific overexpression increases hepatic glycogen accumulation, accelerates postprandial blood glucose clearance, and reduces hepatic triglyceride levels. The glycogen-binding domain of PPP1R3G is indispensable for its effects on glucose metabolism and triglyceride accumulation.","method":"Liver-specific transgenic mouse overexpression, primary hepatocyte assays, glycogen synthase activity measurement, domain deletion (glycogen-binding domain mutant)","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic model combined with primary cell assays and domain-deletion mutagenesis, multiple orthogonal functional readouts","pmids":["24264575"],"is_preprint":false},{"year":2016,"finding":"Whole-body deletion of PPP1R3G reduces glycogen deposition in adipose tissue, decreases fat accumulation, and increases metabolic rate in high-fat diet-fed mice, linking PPP1R3G-mediated glycogen synthesis to lipid metabolism. In 3T3L1 cells, PPP1R3G overexpression increases both glycogen and triglyceride levels.","method":"Whole-body PPP1R3G knockout mouse model, high-fat diet feeding, metabolic rate measurement (O2/CO2), 3T3L1 cell overexpression assays","journal":"Molecular and cellular endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse model with multiple metabolic phenotype readouts plus cell-based validation","pmids":["27815211"],"is_preprint":false},{"year":2021,"finding":"PPP1R3G recruits its catalytic subunit PP1γ to complex I (TNFR1 signaling complex) to dephosphorylate inhibitory phosphorylation sites on RIPK1 (including serine 25), thereby activating RIPK1 kinase activity and promoting apoptosis and necroptosis. A PPP1R3G mutant that cannot bind PP1γ fails to rescue RIPK1 activation. Ppp1r3g-/- mice are protected from TNF-induced systemic inflammatory response syndrome.","method":"CRISPR whole-genome knockout screen, PPP1R3G-PP1γ binding mutant rescue experiments, RIPK1 S25A mutation rescue, Ppp1r3g knockout mice with TNF-induced SIRS model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide CRISPR screen, epistasis via RIPK1 phospho-mutants, PP1γ-binding mutant, and in vivo KO validation across multiple orthogonal approaches","pmids":["34862394"],"is_preprint":false},{"year":2023,"finding":"PPP1R3G knockdown in HTR-8/SVneo trophoblasts decreases p-Akt/Akt expression and reduces MMP-9 levels, inhibiting trophoblast migration, invasion, and proliferation via the Akt/MMP-9 signaling pathway.","method":"Lentiviral knockdown, wound-healing assay, Transwell invasion assay, CCK-8 proliferation assay, western blotting for Akt and MMP-9 pathway components","journal":"Experimental biology and medicine (Maywood, N.J.)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — loss-of-function with defined cellular phenotypes and pathway placement, but single lab with no rescue or mutagenesis validation","pmids":["37642261"],"is_preprint":false},{"year":2025,"finding":"PPP1R3G deletion in oligodendrocyte precursor cells (OPCs) inhibits OPC differentiation and myelination. Mechanistically, PPP1R3G loss inhibits AMPK, which normally suppresses Drp1 phosphorylation; reduced AMPK activity permits Drp1-mediated mitochondrial fission, disrupting mitochondrial dynamics (reduced length/number, impaired membrane potential and ATP production), thereby impairing OPC differentiation. AMPK activation rescues the fission defects.","method":"Ppp1r3g KO mice, primary OPC culture, immunohistochemistry, TEM, RNA-seq, mitochondrial functional assays, AMPK activation rescue experiment","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mice with TEM structural analysis plus AMPK rescue, but single lab and mechanistic link between PPP1R3G and AMPK not biochemically reconstituted","pmids":["40834529"],"is_preprint":false},{"year":2026,"finding":"In doxorubicin-induced cardiotoxicity, DOX triggers p38-mediated inhibitory phosphorylation of RIPK1 as a transient brake. PPP1R3G is recruited to dephosphorylate RIPK1, activating it and triggering early-stage apoptosis. Activated RIPK1 promotes cytosolic release of mitochondrial DNA, inducing ZBP1 expression via IFN-β signaling, which amplifies late-stage necroptosis in a feed-forward loop. Ppp1r3g knockout mice are protected from DOX-induced cardiac dysfunction and mortality.","method":"Ppp1r3g genetic KO mice, doxorubicin cardiotoxicity model, in vitro cell death assays, cytokine measurement (TNFα, IFN-β, IFN-γ), mtDNA release assay, ZBP1/IFN-β pathway analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO model with multiple orthogonal mechanistic readouts (apoptosis, necroptosis, mtDNA release, IFN-β/ZBP1 pathway) and cardiac functional endpoints","pmids":["41984837"],"is_preprint":false}],"current_model":"PPP1R3G is a regulatory subunit of protein phosphatase 1 (PP1) with at least two distinct mechanistic roles: (1) as a glycogen-targeting G subunit in liver and adipose tissue, it recruits PP1 to dephosphorylate and activate glycogen synthase, promoting glycogenesis and linking glycogen metabolism to lipid homeostasis; and (2) in cell death signaling, it recruits its catalytic partner PP1γ to complex I to dephosphorylate inhibitory sites on RIPK1 (including S25), activating RIPK1 kinase activity and driving apoptosis and necroptosis downstream of TNF and doxorubicin stimulation, with activated RIPK1 further promoting mtDNA release and ZBP1/necroptosis amplification."},"narrative":{"mechanistic_narrative":"PPP1R3G is a regulatory targeting subunit of protein phosphatase 1 (PP1) that operates in two distinct biological contexts: glycogen metabolism and cell death signaling [PMID:24264575, PMID:34862394]. As a glycogen-targeting (G) subunit in liver and adipose tissue, PPP1R3G directs PP1 to activate glycogen synthase, promoting glycogenesis, accelerating postprandial glucose clearance, and lowering hepatic triglyceride levels; its glycogen-binding domain is indispensable for these metabolic effects [PMID:24264575], and its activity couples glycogen synthesis to systemic lipid metabolism, since its loss reduces adipose glycogen and fat accumulation while raising metabolic rate [PMID:27815211]. In a mechanistically separate role, PPP1R3G recruits its catalytic partner PP1γ to complex I of the TNFR1 signaling complex to dephosphorylate inhibitory sites on RIPK1, including serine 25, thereby activating RIPK1 kinase activity and driving apoptosis and necroptosis; a PP1γ-binding-deficient mutant fails to support RIPK1 activation, and Ppp1r3g-deficient mice are protected from TNF-induced systemic inflammatory response syndrome [PMID:34862394]. This RIPK1-activating function extends to doxorubicin cardiotoxicity, where PPP1R3G removes a transient p38-imposed phosphorylation brake on RIPK1 to trigger early apoptosis, with activated RIPK1 then promoting cytosolic mitochondrial DNA release and ZBP1/IFN-β-driven amplification of late necroptosis [PMID:41984837]. Additional cell-context roles in trophoblast migration via Akt/MMP-9 signaling [PMID:37642261] and in oligodendrocyte precursor differentiation via AMPK-Drp1-dependent mitochondrial dynamics [PMID:40834529] have been reported.","teleology":[{"year":2013,"claim":"Established that PPP1R3G is a glycogen-targeting PP1 subunit controlling hepatic glucose handling, answering what cellular function the protein serves.","evidence":"Liver-specific transgenic overexpression, primary hepatocyte glycogen synthase assays, and glycogen-binding-domain deletion mutant in mice","pmids":["24264575"],"confidence":"High","gaps":["Direct biochemical reconstitution of the PPP1R3G-PP1-glycogen synthase complex not shown","Identity of the PP1 catalytic isoform engaged in liver not defined here"]},{"year":2016,"claim":"Connected PPP1R3G-driven glycogen synthesis to whole-body lipid metabolism, showing its metabolic role extends beyond glucose storage.","evidence":"Whole-body Ppp1r3g knockout mice on high-fat diet with metabolic rate measurement plus 3T3L1 adipocyte overexpression","pmids":["27815211"],"confidence":"High","gaps":["Mechanistic link between glycogen accumulation and triglyceride levels not resolved","Tissue-specific contributions (adipose vs liver) not separated genetically"]},{"year":2021,"claim":"Revealed a second, signaling role: PPP1R3G recruits PP1γ to dephosphorylate and activate RIPK1, defining it as a positive regulator of TNF-induced cell death.","evidence":"Genome-wide CRISPR knockout screen, PP1γ-binding mutant rescue, RIPK1 S25A epistasis, and Ppp1r3g KO mice in a TNF-induced SIRS model","pmids":["34862394"],"confidence":"High","gaps":["How PPP1R3G is itself recruited to complex I is not defined","Full set of RIPK1 inhibitory sites dephosphorylated beyond S25 not enumerated","Relationship between the metabolic and cell-death roles unaddressed"]},{"year":2023,"claim":"Implicated PPP1R3G in trophoblast migration and proliferation through Akt/MMP-9 signaling, extending its roles to cell motility.","evidence":"Lentiviral knockdown in HTR-8/SVneo trophoblasts with wound-healing, Transwell, CCK-8 assays and Akt/MMP-9 western blotting","pmids":["37642261"],"confidence":"Medium","gaps":["Single lab with no rescue or mutagenesis validation","Whether the effect requires PP1 binding is untested","Direct link between PPP1R3G and Akt phosphorylation not established"]},{"year":2025,"claim":"Linked PPP1R3G to oligodendrocyte precursor differentiation via an AMPK-Drp1 axis controlling mitochondrial fission.","evidence":"Ppp1r3g KO mice and primary OPC culture with TEM, RNA-seq, mitochondrial functional assays, and AMPK-activation rescue","pmids":["40834529"],"confidence":"Medium","gaps":["Biochemical link between PPP1R3G and AMPK not reconstituted","Single lab; PP1-dependence of the effect untested","How a glycogen/PP1 subunit modulates AMPK activity is unexplained"]},{"year":2026,"claim":"Extended the RIPK1-activating function to doxorubicin cardiotoxicity and defined a feed-forward amplification loop, showing PPP1R3G drives both apoptosis and necroptosis in vivo.","evidence":"Ppp1r3g KO mice in a doxorubicin cardiotoxicity model with cell death assays, mtDNA release assays, and ZBP1/IFN-β pathway analysis","pmids":["41984837"],"confidence":"High","gaps":["Whether PP1γ recruitment mediates the cardiac effect not directly tested here","Trigger that recruits PPP1R3G after p38 phosphorylation not defined","Therapeutic relevance of targeting PPP1R3G not established"]},{"year":null,"claim":"How a single PP1 targeting subunit is partitioned between glycogen metabolism and RIPK1-dependent cell death, and what determines its context-specific engagement, remains unresolved.","evidence":"No discovery in the corpus reconciles the metabolic and cell-death roles or defines the recruitment logic across tissues","pmids":[],"confidence":"Low","gaps":["No unifying model linking glycogen-targeting and RIPK1-regulating functions","No structural model of PPP1R3G complexes","Regulation of PPP1R3G expression and localization across tissues uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,5]}],"complexes":["PP1 holoenzyme","TNFR1 signaling complex (complex I)"],"partners":["PPP1CC","RIPK1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"B7ZBB8","full_name":"Protein phosphatase 1 regulatory subunit 3G","aliases":[],"length_aa":358,"mass_kda":38.0,"function":"Glycogen-targeting subunit for protein phosphatase 1 (PP1). Involved in the regulation of hepatic glycogenesis in a manner coupled to the fasting-feeding cycle and distinct from other glycogen-targeting subunits (By similarity)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/B7ZBB8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PPP1R3G","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PPP1R3G","total_profiled":1310},"omim":[{"mim_id":"619541","title":"PROTEIN PHOSPHATASE 1, REGULATORY SUBUNIT 3G; PPP1R3G","url":"https://www.omim.org/entry/619541"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"liver","ntpm":6.0}],"url":"https://www.proteinatlas.org/search/PPP1R3G"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"B7ZBB8","domains":[{"cath_id":"2.60.40.2440","chopping":"197-271_294-307_323-353","consensus_level":"high","plddt":90.3061,"start":197,"end":353}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/B7ZBB8","model_url":"https://alphafold.ebi.ac.uk/files/AF-B7ZBB8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-B7ZBB8-F1-predicted_aligned_error_v6.png","plddt_mean":67.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PPP1R3G","jax_strain_url":"https://www.jax.org/strain/search?query=PPP1R3G"},"sequence":{"accession":"B7ZBB8","fasta_url":"https://rest.uniprot.org/uniprotkb/B7ZBB8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/B7ZBB8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/B7ZBB8"}},"corpus_meta":[{"pmid":"24264575","id":"PMC_24264575","title":"Regulation of glucose homeostasis and lipid metabolism by PPP1R3G-mediated hepatic glycogenesis.","date":"2013","source":"Molecular endocrinology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/24264575","citation_count":42,"is_preprint":false},{"pmid":"34862394","id":"PMC_34862394","title":"RIPK1 dephosphorylation and kinase activation by PPP1R3G/PP1γ promote apoptosis and necroptosis.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34862394","citation_count":33,"is_preprint":false},{"pmid":"27815211","id":"PMC_27815211","title":"Ablation of PPP1R3G reduces glycogen deposition and mitigates high-fat diet induced obesity.","date":"2016","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/27815211","citation_count":19,"is_preprint":false},{"pmid":"37642261","id":"PMC_37642261","title":"Decreased PPP1R3G in pre-eclampsia impairs human trophoblast invasion and migration via Akt/MMP-9 signaling pathway.","date":"2023","source":"Experimental biology and medicine (Maywood, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/37642261","citation_count":3,"is_preprint":false},{"pmid":"39790903","id":"PMC_39790903","title":"Corrigendum: Decreased PPP1R3G in pre-eclampsia impairs human trophoblast invasion and migration via Akt/MMP-9 signaling pathway.","date":"2024","source":"Experimental biology and medicine (Maywood, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/39790903","citation_count":1,"is_preprint":false},{"pmid":"40834529","id":"PMC_40834529","title":"PPP1R3G inhibition impairs OPCs differentiation and myelination in aged mice.","date":"2025","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40834529","citation_count":0,"is_preprint":false},{"pmid":"41040151","id":"PMC_41040151","title":"PPP1R3G Deletion Blocks RIPK1-Mediated Apoptosis and Necroptosis in Doxorubicin-Induced Cardiotoxicity.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41040151","citation_count":0,"is_preprint":false},{"pmid":"41984837","id":"PMC_41984837","title":"PPP1R3G-RIPK1-ZBP1 axis activates early-stage apoptosis and late-stage necroptosis to promote doxorubicin-induced cardiotoxicity.","date":"2026","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/41984837","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5849,"output_tokens":1942,"usd":0.023339,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8938,"output_tokens":2921,"usd":0.058858,"stage2_stop_reason":"end_turn"},"total_usd":0.082197,"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\": 2013,\n      \"finding\": \"PPP1R3G functions as a glycogen-targeting subunit (G subunit) of protein phosphatase 1 (PP1) in liver, where it stimulates glycogen synthase activity and promotes hepatic glycogenesis. Liver-specific overexpression increases hepatic glycogen accumulation, accelerates postprandial blood glucose clearance, and reduces hepatic triglyceride levels. The glycogen-binding domain of PPP1R3G is indispensable for its effects on glucose metabolism and triglyceride accumulation.\",\n      \"method\": \"Liver-specific transgenic mouse overexpression, primary hepatocyte assays, glycogen synthase activity measurement, domain deletion (glycogen-binding domain mutant)\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic model combined with primary cell assays and domain-deletion mutagenesis, multiple orthogonal functional readouts\",\n      \"pmids\": [\"24264575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Whole-body deletion of PPP1R3G reduces glycogen deposition in adipose tissue, decreases fat accumulation, and increases metabolic rate in high-fat diet-fed mice, linking PPP1R3G-mediated glycogen synthesis to lipid metabolism. In 3T3L1 cells, PPP1R3G overexpression increases both glycogen and triglyceride levels.\",\n      \"method\": \"Whole-body PPP1R3G knockout mouse model, high-fat diet feeding, metabolic rate measurement (O2/CO2), 3T3L1 cell overexpression assays\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse model with multiple metabolic phenotype readouts plus cell-based validation\",\n      \"pmids\": [\"27815211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PPP1R3G recruits its catalytic subunit PP1γ to complex I (TNFR1 signaling complex) to dephosphorylate inhibitory phosphorylation sites on RIPK1 (including serine 25), thereby activating RIPK1 kinase activity and promoting apoptosis and necroptosis. A PPP1R3G mutant that cannot bind PP1γ fails to rescue RIPK1 activation. Ppp1r3g-/- mice are protected from TNF-induced systemic inflammatory response syndrome.\",\n      \"method\": \"CRISPR whole-genome knockout screen, PPP1R3G-PP1γ binding mutant rescue experiments, RIPK1 S25A mutation rescue, Ppp1r3g knockout mice with TNF-induced SIRS model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide CRISPR screen, epistasis via RIPK1 phospho-mutants, PP1γ-binding mutant, and in vivo KO validation across multiple orthogonal approaches\",\n      \"pmids\": [\"34862394\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PPP1R3G knockdown in HTR-8/SVneo trophoblasts decreases p-Akt/Akt expression and reduces MMP-9 levels, inhibiting trophoblast migration, invasion, and proliferation via the Akt/MMP-9 signaling pathway.\",\n      \"method\": \"Lentiviral knockdown, wound-healing assay, Transwell invasion assay, CCK-8 proliferation assay, western blotting for Akt and MMP-9 pathway components\",\n      \"journal\": \"Experimental biology and medicine (Maywood, N.J.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — loss-of-function with defined cellular phenotypes and pathway placement, but single lab with no rescue or mutagenesis validation\",\n      \"pmids\": [\"37642261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PPP1R3G deletion in oligodendrocyte precursor cells (OPCs) inhibits OPC differentiation and myelination. Mechanistically, PPP1R3G loss inhibits AMPK, which normally suppresses Drp1 phosphorylation; reduced AMPK activity permits Drp1-mediated mitochondrial fission, disrupting mitochondrial dynamics (reduced length/number, impaired membrane potential and ATP production), thereby impairing OPC differentiation. AMPK activation rescues the fission defects.\",\n      \"method\": \"Ppp1r3g KO mice, primary OPC culture, immunohistochemistry, TEM, RNA-seq, mitochondrial functional assays, AMPK activation rescue experiment\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mice with TEM structural analysis plus AMPK rescue, but single lab and mechanistic link between PPP1R3G and AMPK not biochemically reconstituted\",\n      \"pmids\": [\"40834529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In doxorubicin-induced cardiotoxicity, DOX triggers p38-mediated inhibitory phosphorylation of RIPK1 as a transient brake. PPP1R3G is recruited to dephosphorylate RIPK1, activating it and triggering early-stage apoptosis. Activated RIPK1 promotes cytosolic release of mitochondrial DNA, inducing ZBP1 expression via IFN-β signaling, which amplifies late-stage necroptosis in a feed-forward loop. Ppp1r3g knockout mice are protected from DOX-induced cardiac dysfunction and mortality.\",\n      \"method\": \"Ppp1r3g genetic KO mice, doxorubicin cardiotoxicity model, in vitro cell death assays, cytokine measurement (TNFα, IFN-β, IFN-γ), mtDNA release assay, ZBP1/IFN-β pathway analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO model with multiple orthogonal mechanistic readouts (apoptosis, necroptosis, mtDNA release, IFN-β/ZBP1 pathway) and cardiac functional endpoints\",\n      \"pmids\": [\"41984837\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PPP1R3G is a regulatory subunit of protein phosphatase 1 (PP1) with at least two distinct mechanistic roles: (1) as a glycogen-targeting G subunit in liver and adipose tissue, it recruits PP1 to dephosphorylate and activate glycogen synthase, promoting glycogenesis and linking glycogen metabolism to lipid homeostasis; and (2) in cell death signaling, it recruits its catalytic partner PP1γ to complex I to dephosphorylate inhibitory sites on RIPK1 (including S25), activating RIPK1 kinase activity and driving apoptosis and necroptosis downstream of TNF and doxorubicin stimulation, with activated RIPK1 further promoting mtDNA release and ZBP1/necroptosis amplification.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PPP1R3G is a regulatory targeting subunit of protein phosphatase 1 (PP1) that operates in two distinct biological contexts: glycogen metabolism and cell death signaling [#0, #2]. As a glycogen-targeting (G) subunit in liver and adipose tissue, PPP1R3G directs PP1 to activate glycogen synthase, promoting glycogenesis, accelerating postprandial glucose clearance, and lowering hepatic triglyceride levels; its glycogen-binding domain is indispensable for these metabolic effects [#0], and its activity couples glycogen synthesis to systemic lipid metabolism, since its loss reduces adipose glycogen and fat accumulation while raising metabolic rate [#1]. In a mechanistically separate role, PPP1R3G recruits its catalytic partner PP1\\u03b3 to complex I of the TNFR1 signaling complex to dephosphorylate inhibitory sites on RIPK1, including serine 25, thereby activating RIPK1 kinase activity and driving apoptosis and necroptosis; a PP1\\u03b3-binding-deficient mutant fails to support RIPK1 activation, and Ppp1r3g-deficient mice are protected from TNF-induced systemic inflammatory response syndrome [#2]. This RIPK1-activating function extends to doxorubicin cardiotoxicity, where PPP1R3G removes a transient p38-imposed phosphorylation brake on RIPK1 to trigger early apoptosis, with activated RIPK1 then promoting cytosolic mitochondrial DNA release and ZBP1/IFN-\\u03b2-driven amplification of late necroptosis [#5]. Additional cell-context roles in trophoblast migration via Akt/MMP-9 signaling [#3] and in oligodendrocyte precursor differentiation via AMPK-Drp1-dependent mitochondrial dynamics [#4] have been reported.\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established that PPP1R3G is a glycogen-targeting PP1 subunit controlling hepatic glucose handling, answering what cellular function the protein serves.\",\n      \"evidence\": \"Liver-specific transgenic overexpression, primary hepatocyte glycogen synthase assays, and glycogen-binding-domain deletion mutant in mice\",\n      \"pmids\": [\"24264575\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct biochemical reconstitution of the PPP1R3G-PP1-glycogen synthase complex not shown\",\n        \"Identity of the PP1 catalytic isoform engaged in liver not defined here\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected PPP1R3G-driven glycogen synthesis to whole-body lipid metabolism, showing its metabolic role extends beyond glucose storage.\",\n      \"evidence\": \"Whole-body Ppp1r3g knockout mice on high-fat diet with metabolic rate measurement plus 3T3L1 adipocyte overexpression\",\n      \"pmids\": [\"27815211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanistic link between glycogen accumulation and triglyceride levels not resolved\",\n        \"Tissue-specific contributions (adipose vs liver) not separated genetically\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a second, signaling role: PPP1R3G recruits PP1\\u03b3 to dephosphorylate and activate RIPK1, defining it as a positive regulator of TNF-induced cell death.\",\n      \"evidence\": \"Genome-wide CRISPR knockout screen, PP1\\u03b3-binding mutant rescue, RIPK1 S25A epistasis, and Ppp1r3g KO mice in a TNF-induced SIRS model\",\n      \"pmids\": [\"34862394\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How PPP1R3G is itself recruited to complex I is not defined\",\n        \"Full set of RIPK1 inhibitory sites dephosphorylated beyond S25 not enumerated\",\n        \"Relationship between the metabolic and cell-death roles unaddressed\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Implicated PPP1R3G in trophoblast migration and proliferation through Akt/MMP-9 signaling, extending its roles to cell motility.\",\n      \"evidence\": \"Lentiviral knockdown in HTR-8/SVneo trophoblasts with wound-healing, Transwell, CCK-8 assays and Akt/MMP-9 western blotting\",\n      \"pmids\": [\"37642261\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab with no rescue or mutagenesis validation\",\n        \"Whether the effect requires PP1 binding is untested\",\n        \"Direct link between PPP1R3G and Akt phosphorylation not established\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked PPP1R3G to oligodendrocyte precursor differentiation via an AMPK-Drp1 axis controlling mitochondrial fission.\",\n      \"evidence\": \"Ppp1r3g KO mice and primary OPC culture with TEM, RNA-seq, mitochondrial functional assays, and AMPK-activation rescue\",\n      \"pmids\": [\"40834529\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Biochemical link between PPP1R3G and AMPK not reconstituted\",\n        \"Single lab; PP1-dependence of the effect untested\",\n        \"How a glycogen/PP1 subunit modulates AMPK activity is unexplained\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended the RIPK1-activating function to doxorubicin cardiotoxicity and defined a feed-forward amplification loop, showing PPP1R3G drives both apoptosis and necroptosis in vivo.\",\n      \"evidence\": \"Ppp1r3g KO mice in a doxorubicin cardiotoxicity model with cell death assays, mtDNA release assays, and ZBP1/IFN-\\u03b2 pathway analysis\",\n      \"pmids\": [\"41984837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether PP1\\u03b3 recruitment mediates the cardiac effect not directly tested here\",\n        \"Trigger that recruits PPP1R3G after p38 phosphorylation not defined\",\n        \"Therapeutic relevance of targeting PPP1R3G not established\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single PP1 targeting subunit is partitioned between glycogen metabolism and RIPK1-dependent cell death, and what determines its context-specific engagement, remains unresolved.\",\n      \"evidence\": \"No discovery in the corpus reconciles the metabolic and cell-death roles or defines the recruitment logic across tissues\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No unifying model linking glycogen-targeting and RIPK1-regulating functions\",\n        \"No structural model of PPP1R3G complexes\",\n        \"Regulation of PPP1R3G expression and localization across tissues uncharacterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"complexes\": [\n      \"PP1 holoenzyme\",\n      \"TNFR1 signaling complex (complex I)\"\n    ],\n    \"partners\": [\n      \"PPP1CC\",\n      \"RIPK1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}