{"gene":"PPP1CC","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":2003,"finding":"PP1γ (PPP1CC) dynamically relocalizes throughout the mammalian cell cycle: it accumulates in the nucleolus during interphase, localizes to kinetochores at mitotic entry (exchanging rapidly with the cytoplasmic pool), relocalizes to chromosome-containing regions at the early-to-late anaphase transition, and accumulates at the cleavage furrow and midbody by telophase, implicating it in nucleolar function, chromosome segregation, and cytokinesis.","method":"Stable HeLa cell lines expressing FP-PP1γ; time-lapse fluorescence microscopy and FRAP","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — direct live-imaging with stable cell lines + FRAP, multiple orthogonal methods, functional consequences inferred","pmids":["12529430"],"is_preprint":false},{"year":2004,"finding":"Smad7 acts as an adaptor protein that recruits the GADD34-PP1c (PP1γ) holoenzyme to the TGFβ type I receptor (TβRI), leading to dephosphorylation of TβRI and negative feedback in TGFβ signaling. SARA enhances PP1c recruitment to the Smad7-GADD34 complex by controlling PP1c subcellular localization.","method":"Co-immunoprecipitation, RNA interference knockdown of Smad7, cell-based phosphorylation assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, RNAi validation, functional phosphatase assay, replicated with multiple approaches","pmids":["14718519"],"is_preprint":false},{"year":2007,"finding":"URI forms stable complexes with PP1γ at mitochondria in growth factor-deprived cells, inhibiting PP1γ activity. S6K1-mediated phosphorylation of URI at Ser371 upon growth factor stimulation disassembles the URI/PP1γ complex, activating a PP1γ-dependent negative feedback that decreases S6K1 activity and BAD phosphorylation to regulate the apoptotic threshold.","method":"Co-immunoprecipitation, in vitro kinase assay, phospho-specific antibodies, rapamycin treatment, mitochondrial fractionation","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, in vitro assay, site-specific mutagenesis (Ser371), multiple orthogonal methods","pmids":["17936702"],"is_preprint":false},{"year":2007,"finding":"PP1γ2 (encoded by Ppp1cc) is expressed in secondary spermatocytes, round and elongating spermatids, and mature spermatozoa. Targeted disruption of Ppp1cc causes malformed mitochondrial sheaths and extra outer dense fibers in sperm tails, indicating a role for PP1γ2 in sperm tail morphogenesis beyond motility regulation.","method":"Ppp1cc knockout mice, immunohistochemistry, electron microscopy, isoform-specific antibodies","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 — clean knockout with specific ultrastructural phenotype, isoform-specific expression mapping","pmids":["17301292"],"is_preprint":false},{"year":2007,"finding":"PP1γ2 specifically interacts with endophilin B1t (a testis-specific isoform of endophilin B1) via the unique C-terminal region of PP1γ2, and endophilin B1t inhibits PP1γ2 phosphatase activity toward phosphorylase a. Somatic endophilin B1a does not interact with any PP1 isoform, and PP1α does not interact with endophilin B1t, demonstrating isoform specificity.","method":"Yeast two-hybrid, co-immunoprecipitation, sedimentation assay, phosphatase activity assay with recombinant proteins","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro phosphatase assay + Tier 2 Co-IP with native proteins, yeast two-hybrid, isoform specificity demonstrated","pmids":["17381077"],"is_preprint":false},{"year":2009,"finding":"Transgenic expression of PPP1CC2 in Ppp1cc-null mouse testes rescues spermatid viability and spermiation (anti-apoptotic effect) but does not restore normal sperm flagellar morphogenesis, motility, or fertility, indicating that PPP1CC1 is additionally required for normal spermatogenesis.","method":"Transgenic rescue experiment in Ppp1cc-/- mice; histology, motility analysis, fertility testing","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 — genetic rescue with isoform-specific transgene, multiple phenotypic readouts","pmids":["19420386"],"is_preprint":false},{"year":2010,"finding":"Loss of PPP1CC in mice causes chromatin condensation defects and acrosome development abnormalities in spermatids, with germ cell loss concentrated at stages VII-VIII of spermatogenesis and reduced spermatogonial numbers; junctional complexes remain ultrastructurally normal.","method":"Light and electron microscopy of Ppp1cc knockout mouse testes","journal":"Reproduction (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with specific ultrastructural phenotype, but single method (EM)","pmids":["20385779"],"is_preprint":false},{"year":2011,"finding":"PP1γ counteracts Nek2A kinase activity in a Nek2A-PP1γ-Mst2 complex at centrosomes. Plk1 phosphorylation of Mst2 prevents PP1γ binding to the Mst2-Nek2A complex, allowing Nek2A activity to drive centrosome disjunction; absence of Plk1 phosphorylation promotes assembly of Nek2A-PP1γ-Mst2 complexes that suppress centrosome separation.","method":"Co-immunoprecipitation, centrosome disjunction assays, kinase assays, Plk1 inhibition","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, functional epistasis, kinase assay, multiple orthogonal approaches","pmids":["21723128"],"is_preprint":false},{"year":2012,"finding":"PP1γ directly interacts with the SMN complex component Gemin8, and this interaction regulates SMN complex formation and localization to Cajal bodies. PP1γ depletion by RNAi leads to SMN hyperphosphorylation and enhanced SMN complex/snRNP localization to Cajal bodies; PP1γ expression restores normal SMN phosphorylation isoforms.","method":"Co-immunoprecipitation, in vitro protein binding assay, RNAi knockdown, 2D protein gel electrophoresis, immunofluorescence","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — direct binding assay + Co-IP + RNAi with specific phosphorylation readout, multiple orthogonal methods","pmids":["22454514"],"is_preprint":false},{"year":2013,"finding":"hScrib directly interacts with PP1γ through a conserved PP1γ-interaction motif on hScrib, recruits PP1γ to downregulate ERK phosphorylation, controls the subcellular distribution of PP1γ (loss of hScrib enhances nuclear PP1γ translocation), and this hScrib-PP1γ interaction is required for hScrib's tumor-suppressor activity against oncogene-induced transformation.","method":"Proteomic pulldown, direct binding assay, co-immunoprecipitation, ERK phosphorylation assays, oncogenic transformation assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — direct binding demonstrated + Co-IP + functional assay with motif requirement, multiple methods","pmids":["23359326"],"is_preprint":false},{"year":2013,"finding":"PP1γ, but not PP1α or PP1β, promotes alternative splicing of CaMKIIδ through direct interaction with the splicing factor ASF. PP1γ overexpression or inhibition respectively enhances or suppresses CaMKIIδ splicing and ASF-PP1γ association, and PP1γ exacerbates OGD/R-triggered cardiomyocyte apoptosis through CaMKII activation.","method":"Co-immunoprecipitation, splicing assay, PP1γ overexpression/inhibition, cardiomyocyte apoptosis assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + isoform-specific functional assay, but single lab","pmids":["24196533"],"is_preprint":false},{"year":2013,"finding":"Conditional germ cell-specific deletion of Ppp1cc using Stra8-Cre causes oligo-terato-asthenozoospermia and male infertility, phenocopying global Ppp1cc null mice. PPP1CC2 is the only PP1 isoform expressed in postmeiotic germ cells, and its absence in meiotic and postmeiotic cells underlies spermatogenic defects.","method":"Conditional knockout mice (Stra8-Cre), immunohistochemistry, sperm analysis","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 — conditional cell-type-specific KO with defined infertility phenotype, isoform expression mapping","pmids":["24089200"],"is_preprint":false},{"year":2014,"finding":"Hipk2 facilitates PP1c-mediated dephosphorylation of Dishevelled (Dvl) via its C-terminal domain, preventing ubiquitination and Itch-mediated degradation of Dvl. This Hipk2-PP1c-Dvl axis maintains sufficient Dvl protein levels for Wnt/β-catenin and Wnt/PCP signaling. Wnt-3a under high cell density induces dissociation of the Dvl-Hipk2-PP1c complex as a negative feedback mechanism.","method":"Co-immunoprecipitation, ubiquitination assay, PP1c inhibition, zebrafish embryo epistasis, Wnt reporter assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + ubiquitination assay + in vivo epistasis in zebrafish, multiple orthogonal methods","pmids":["25159144"],"is_preprint":false},{"year":2014,"finding":"PP1γ physically interacts with the E3 ubiquitin ligase TRAF6 and enhances TRAF6 auto-ubiquitination and ubiquitination of IKKγ, promoting NF-κB-mediated innate immune signaling; enzymatically inactive PP1γ represses these events.","method":"Gain-of-function genetic screen, co-immunoprecipitation, ubiquitination assay, NF-κB reporter assay, macrophage pathogen challenge","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + enzymatic mutant validation + functional immune assay, single lab","pmids":["24586659"],"is_preprint":false},{"year":2016,"finding":"NEK1 phosphorylates PP1γ, and PP1γ dephosphorylates WAPL; the NEK1-PP1γ-WAPL axis regulates cohesin removal from chromosome arms during meiotic prophase I via interaction with PDS5B. NEK1 loss causes retention of cohesin on chromosomes at meiotic prophase I.","method":"Co-immunoprecipitation, phosphorylation assays, mouse genetics (Nek1 knockout), immunofluorescence on meiotic chromosomes","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + kinase/phosphatase assay + in vivo genetic validation, multiple approaches","pmids":["27760328"],"is_preprint":false},{"year":2016,"finding":"TIMAP phosphorylation at Ser331 by PKCα inhibits PP1c activity within the TIMAP-PP1c complex toward phospho-ERM substrates, reducing dephosphorylation of ERM and thereby modulating endothelial barrier function. PKCα was shown to interact with TIMAP and phosphorylate it at Ser331 in vitro and in endothelial cells.","method":"In vitro kinase assay, site-directed mutagenesis, co-immunoprecipitation, electric resistance measurement of endothelial barrier, membrane fractionation","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay with mutagenesis + Tier 2 functional endothelial assay, multiple orthogonal methods","pmids":["27939168"],"is_preprint":false},{"year":2019,"finding":"iASPP (and ASPP2) interact with PP1c via SILK and RVxF motifs on iASPP plus interactions of the PP1c PxxPxR motif with the iASPP SH3 domain. This interaction enhances PP1c catalytic activity toward pNPP and the substrate p53; the modular interface provides dynamic flexibility for dephosphorylation of diverse substrates including p53.","method":"Crystal structure of iASPP-PP1c complex, small-angle X-ray scattering, in vitro phosphatase activity assay with p53 and pNPP substrates","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 — crystal structure + in vitro activity assay + SAXS, multiple orthogonal methods in single study","pmids":["31402222"],"is_preprint":false},{"year":2020,"finding":"Aurora B regulates PP1γ-Repo-Man interactions on mitotic chromosomes: PP1γ is recruited to chromosomes by Repo-Man when Aurora B is inactive; Aurora B phosphorylates Repo-Man to disrupt PP1γ-Repo-Man interactions, releasing PP1γ from chromatin to maintain chromosome phosphorylation and condensation.","method":"Immunofluorescence, co-immunoprecipitation, Aurora B inhibition, phosphomimetic/phosphonull Repo-Man mutants, ectopic PP1γ targeting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + kinase inhibition + site-directed mutagenesis + functional chromosome condensation assay","pmids":["32938714"],"is_preprint":false},{"year":2021,"finding":"PPP1R3G recruits its catalytic subunit PP1γ to complex I to dephosphorylate inhibitory phosphorylations on RIPK1 (including Ser25), activating RIPK1 kinase activity and enabling RIPK1-dependent apoptosis and necroptosis. A PPP1R3G mutant that cannot bind PP1γ fails to rescue RIPK1 activation and cell death.","method":"CRISPR whole-genome knockout screen, co-immunoprecipitation, PP1γ-binding mutant, phospho-RIPK1 analysis, Ppp1r3g-/- mice with TNF-induced SIRS","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — genome-wide screen + Co-IP + binding mutant + in vivo mouse validation, multiple orthogonal methods","pmids":["34862394"],"is_preprint":false},{"year":2022,"finding":"HDAC1 constitutively associates with PP1γ and promotes dephosphorylation of CREB at Ser133; during dopaminergic neurodegeneration CREB interacts with the HDAC1/PP1γ complex leading to CREB inactivation. Disrupting CREB/HDAC1 interaction restores p-CREB (Ser133) and NURR1 levels and protects nigral dopaminergic neurons in MPTP-treated mice.","method":"Co-immunoprecipitation, proximity ligation assay in human PD brain tissue, MPTP mouse model, overexpression of CREB mutant, TSA treatment","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — Co-IP + PLA in human tissue + in vivo mouse rescue, multiple orthogonal methods","pmids":["35501151"],"is_preprint":false},{"year":2022,"finding":"The SHOC2-MRAS-PP1C ternary holophosphatase complex dephosphorylates RAF at an inhibitory phosphoserine to potentiate MAPK signaling. Cryo-EM structure reveals SHOC2 binds PP1C and MRAS through the concave leucine-rich repeat surface and via an N-terminal cryptic RVXF motif; complex formation is initiated by SHOC2-PP1C interaction and stabilized by GTP-loaded MRAS. RASopathy/cancer mutations in SHOC2 stabilize complex interactions to enhance holophosphatase activity.","method":"Cryo-electron microscopy structure, deep mutational scanning of SHOC2, biophysical binding assays, RAF dephosphorylation assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure + reconstituted enzymatic assay + deep mutational scanning, replicated across multiple labs","pmids":["35831509"],"is_preprint":false},{"year":2022,"finding":"Crystal structure of the SHOC2-MRAS-PP1C complex reveals all three proteins synergistically interact; SHOC2 acts as a scaffolding protein bridging PP1C and MRAS. Dephosphorylation of RAF by PP1C is enhanced upon interaction with SHOC2 and MRAS. Complex formation requires MRAS in its GTP-bound active state and is further stabilized by SHOC2. RASopathy mutations reside at protein-protein interfaces and enhance complex formation and activity.","method":"X-ray crystallography, apo-SHOC2 structure, in vitro RAF dephosphorylation assay, biophysical characterization of complex assembly","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure + reconstituted enzymatic assay, independently replicated across multiple labs","pmids":["36175670"],"is_preprint":false},{"year":2022,"finding":"X-ray crystal structure of MRAS-SHOC2-PP1C complex shows SHOC2 bridges PP1C and MRAS through its concave surface with reciprocal interactions among all three subunits. GTP-bound MRAS drives cooperative assembly. Rasopathy and cancer mutations at protein-protein interfaces enhance affinities and function. MRAS can be substituted by canonical RAS isoforms.","method":"X-ray crystallography, biophysical characterization (SPR/ITC), in vitro RAF dephosphorylation assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — crystal structure + reconstituted functional assay, independently replicated across multiple labs","pmids":["35830882"],"is_preprint":false},{"year":2022,"finding":"I-2 (inhibitor-2) and PP1γ, but not PP1α, positively regulate synaptic transmission in hippocampal neurons. I-2 enhances PP1γ interaction with its synaptic scaffold neurabin (demonstrated by FRET/FLIM), and this positive regulatory effect depends on I-2 Thr72 phosphorylation.","method":"Hippocampal neuron electrophysiology, FRET/FLIM imaging, co-immunoprecipitation, Thr72 phosphorylation analysis","journal":"Frontiers in synaptic neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — FRET/FLIM + electrophysiology + Co-IP, isoform-specific finding, single lab","pmids":["36276179"],"is_preprint":false},{"year":2023,"finding":"PP1γ (but not PP1α) dephosphorylates AKT2 and regulates neuronal insulin signaling via the AKT2-AS160-GLUT4 axis, and separately regulates GSK3β via AKT2 and GSK3α via MLK3. Imbalance in PP1γ-dependent phosphatase activity promotes an Alzheimer's disease-like phenotype in neuronal cells.","method":"siRNA knockdown of PP1α vs PP1γ, western blot of AKT isoforms/AS160/GSK3 isoforms, GLUT4 translocation by confocal microscopy, fluorescence-based glucose uptake assay, high-fat-diet mouse model","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 — isoform-specific siRNA + multiple substrate readouts + in vivo model, single lab","pmids":["37085815"],"is_preprint":false},{"year":2004,"finding":"CaMKII bound to sarcoplasmic reticulum (SR) phosphorylates GM (glycogen- and PP1c-targeting subunit) at Ser48, and PP1c dephosphorylates GM; the GM-GS-PP1c complex selectively localizes to nonjunctional SR, and CaMKII-mediated phosphorylation of GM regulates glycogen synthase activity through this complex.","method":"Recombinant fragment pulldown, site-directed mutagenesis, in vitro kinase assay, co-immunoprecipitation, immunofluorescence co-localization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro kinase assay + mutagenesis of Ser48 + Co-IP demonstrating complex, multiple orthogonal methods","pmids":["15591318"],"is_preprint":false},{"year":2025,"finding":"PPP1CC exhibits uniform distribution before blastocyst formation but becomes localized specifically to the trophectoderm (TE) during blastocyst stage via interaction with lncRNA GAS5. PPP1CC-mediated YAP dephosphorylation in outer cells promotes YAP nuclear translocation and TE lineage specification. Knockdown of GAS5 phenocopies PPP1CC deficiency (developmental arrest at morula with impaired YAP dephosphorylation).","method":"Immunofluorescence, knockdown experiments, YAP dephosphorylation assay, GAS5 overexpression in single blastomere of 2-cell stage embryo","journal":"Cell proliferation","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization + functional knockdown + epistasis with GAS5, single lab","pmids":["41403070"],"is_preprint":false},{"year":2025,"finding":"PPP1CC (PP1γ) dephosphorylates YAP1, and silencing of PPP1CC increases p-YAP1 levels, inhibits YAP1 activity, and reduces SOX2 expression in esophageal squamous cell carcinoma cells, suppressing proliferation, migration, and invasion.","method":"PPP1CC siRNA knockdown, western blot (YAP1, p-YAP1, SOX2), CCK-8 proliferation assay, Transwell invasion/migration assay","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with specific phosphorylation readout, single lab, single method type","pmids":["40626009"],"is_preprint":false},{"year":2025,"finding":"CEMIP interacts directly with PP1c (PPP1CC) via three RVxF motifs and sequesters MLC20 from PP1c without affecting MLCK. Mutations in CEMIP RVxF motifs restore PP1c-MLC20 interaction. CEMIP-deficient smooth muscle cells show reduced MLC20 phosphorylation and reduced contractility; SMC-specific Cemip knockout mice have reduced blood pressure.","method":"Co-immunoprecipitation, molecular docking, bioluminescence resonance energy transfer (BRET), RVxF motif mutagenesis, SMC-specific conditional knockout mice, ex vivo contractility","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1-2 — BRET + mutagenesis + Co-IP + in vivo conditional KO with functional phenotype, multiple orthogonal methods","pmids":["40590126"],"is_preprint":false},{"year":2025,"finding":"Drosophila Pp1-87B (ortholog of PPP1CC) is an essential regulator of JNK signaling in tumor-suppressive cell competition; its loss activates JNK via the Moe-Rho1 axis, integrating apoptosis and ferroptosis-like cell death through Hippo signaling. The human ortholog PPP1CC functions similarly to drive apoptosis and ferroptosis in human liver tumor cells through JNK activation.","method":"Drosophila genetic screen, epistasis analysis, human liver cancer cell experiments, cell death assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in Drosophila + validation in human cells, but human data limited to single lab","pmids":["40906558"],"is_preprint":false},{"year":1993,"finding":"Human PPP1CC encodes two alternatively spliced isoforms, PP1γ1 and PP1γ2, differing only at their C-termini. Both isoforms are ~94% identical to PP1α but are encoded by a distinct gene mapped to chromosome 12q24.1-q24.2, separate from the PP1α gene on chromosome 11.","method":"cDNA cloning, somatic cell hybrid analysis, in situ hybridization (FISH), sequence analysis","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 — direct molecular cloning and chromosomal mapping, foundational gene structure paper","pmids":["8394140"],"is_preprint":false},{"year":1997,"finding":"Both PP1γ1 and PP1γ2 isoforms encoded by Ppp1cc retain phosphatase function, as they complement the cold-sensitive PP1 defect in Schizosaccharomyces pombe dis2-11 mutants. The two isoforms arise from alternative splicing with retention of the last intron for PP1γ2.","method":"Yeast complementation assay (dis2-11 fission yeast), genomic organization analysis, FISH mapping","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1 — functional complementation in yeast demonstrating phosphatase activity of both isoforms","pmids":["9339378"],"is_preprint":false},{"year":2024,"finding":"gp78 promotes ubiquitination-dependent degradation of PPP1CC (and PPP2CA), leading to elevated KAP1 phosphorylation and enhanced DNA damage repair and radioresistance in breast cancer cells. PPP1CC is a crucial regulator of KAP1 dephosphorylation in response to ionizing radiation.","method":"Co-immunoprecipitation, ubiquitination assay, western blot for p-KAP1, radioresistance assays","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP + ubiquitination assay + functional radioresistance readout, single lab","pmids":["39297166"],"is_preprint":false}],"current_model":"PPP1CC (PP1γ) is a serine/threonine phosphatase catalytic subunit that forms holoenzymes with diverse regulatory subunits (including GADD34/Smad7, SHOC2/MRAS, URI, TIMAP, Repo-Man, Gemin8, PPP1R3G, HDAC1, GM, and others) to dephosphorylate specific substrates (TβRI, RAF-pSer259, RIPK1-pSer25, CREB-pSer133, MLC20, YAP1, Dvl, WAPL, BAD, and chromatin proteins), with its subcellular localization dynamically regulated throughout the cell cycle (nucleolus in interphase; kinetochores, chromosomes, cleavage furrow, and midbody during mitosis), and plays isoform-specific roles in sperm morphogenesis and motility, MAPK/RAS pathway activation, innate immune signaling, meiotic cohesin removal, synaptic transmission, and early embryonic lineage specification."},"narrative":{"teleology":[{"year":1993,"claim":"Establishing that PPP1CC encodes two alternatively spliced catalytic isoforms (PP1γ1 and PP1γ2) on chromosome 12q24 resolved the gene's identity as distinct from PP1α and set the stage for isoform-specific functional studies.","evidence":"cDNA cloning, somatic cell hybrid analysis, and FISH mapping","pmids":["8394140"],"confidence":"High","gaps":["No functional characterization of either isoform at this stage","Tissue-specific expression patterns not yet defined"]},{"year":1997,"claim":"Demonstration that both PP1γ1 and PP1γ2 retain phosphatase activity by complementing a fission yeast PP1 mutant confirmed that alternative splicing does not ablate catalytic function, validating both isoforms as active enzymes.","evidence":"Complementation of S. pombe dis2-11 cold-sensitive mutant","pmids":["9339378"],"confidence":"High","gaps":["Mammalian substrate specificity of each isoform unknown","Whether isoforms have non-redundant roles in vivo untested"]},{"year":2003,"claim":"Live imaging revealed that PP1γ dynamically relocalizes throughout the mammalian cell cycle—from nucleoli in interphase to kinetochores, chromosome arms, cleavage furrow, and midbody during mitosis—establishing that its function is spatiotemporally regulated rather than constitutive.","evidence":"Stable HeLa lines expressing FP-PP1γ, time-lapse microscopy and FRAP","pmids":["12529430"],"confidence":"High","gaps":["Targeting subunits responsible for each localization not identified","Whether relocalization is essential for mitotic fidelity not tested"]},{"year":2004,"claim":"Identification of the GADD34–Smad7 adaptor complex recruiting PP1γ to dephosphorylate TβRI provided the first concrete substrate-targeting mechanism for PP1γ in a major signaling pathway (TGF-β negative feedback).","evidence":"Co-immunoprecipitation, RNAi of Smad7, phosphorylation assays in cells","pmids":["14718519"],"confidence":"High","gaps":["Whether PP1α or PP1β can substitute in this complex not fully resolved","In vivo relevance in TGF-β-dependent tissues not tested"]},{"year":2007,"claim":"Studies in Ppp1cc knockout mice established an essential, non-redundant role for PP1γ2 in spermiogenesis: loss causes malformed mitochondrial sheaths, extra outer dense fibers, and chromatin condensation defects, directly linking the testis-enriched isoform to male fertility.","evidence":"Ppp1cc knockout mice, electron microscopy, isoform-specific antibodies; conditional Stra8-Cre deletion later confirmed germ-cell autonomy","pmids":["17301292","24089200","20385779"],"confidence":"High","gaps":["Specific spermatid substrates of PP1γ2 not identified","Mechanism linking PP1γ2 to chromatin condensation versus structural assembly unclear"]},{"year":2007,"claim":"Discovery that URI sequesters PP1γ at mitochondria and that S6K1-mediated phosphorylation of URI releases active PP1γ to dephosphorylate BAD revealed a growth-factor-controlled apoptotic threshold mechanism operating through PP1γ.","evidence":"Co-immunoprecipitation, mitochondrial fractionation, in vitro kinase assay, rapamycin treatment","pmids":["17936702"],"confidence":"High","gaps":["Full spectrum of mitochondrial PP1γ substrates beyond BAD unknown","Whether URI-PP1γ regulation operates in non-transformed cells not established"]},{"year":2009,"claim":"Transgenic rescue experiments showed that PP1γ2 alone restores spermatid viability but not sperm morphogenesis or motility, demonstrating that PP1γ1 has non-redundant roles in spermatogenesis beyond the anti-apoptotic function of PP1γ2.","evidence":"PP1γ2 transgene expressed in Ppp1cc-null testes; histology, motility, and fertility analysis","pmids":["19420386"],"confidence":"High","gaps":["PP1γ1-specific substrates in spermatogenesis not identified","Structural basis of isoform-specific function unknown"]},{"year":2011,"claim":"The finding that PP1γ opposes Nek2A kinase within a Nek2A–PP1γ–Mst2 centrosomal complex, regulated by Plk1 phosphorylation of Mst2, established PP1γ as a direct regulator of centrosome disjunction timing.","evidence":"Co-immunoprecipitation, centrosome disjunction assays, Plk1 inhibition","pmids":["21723128"],"confidence":"High","gaps":["Whether PP1α/β contribute to this complex not fully excluded","Downstream centrosomal substrates beyond linker proteins not mapped"]},{"year":2012,"claim":"PP1γ was shown to interact with Gemin8 and regulate SMN complex phosphorylation and Cajal body localization, revealing a role in snRNP biogenesis beyond its known cell-cycle functions.","evidence":"Direct binding assay, Co-IP, RNAi of PP1γ, 2D gel electrophoresis of SMN phospho-isoforms","pmids":["22454514"],"confidence":"High","gaps":["Specific SMN phosphosites targeted by PP1γ not mapped","Functional consequence for snRNP assembly efficiency not quantified"]},{"year":2013,"claim":"Identification of hScrib as a scaffold that recruits PP1γ to suppress ERK phosphorylation and oncogenic transformation connected PP1γ to RAS-MAPK tumor suppression upstream of the later-characterized SHOC2 complex.","evidence":"Proteomic pulldown, direct binding assay, ERK phosphorylation and transformation assays","pmids":["23359326"],"confidence":"High","gaps":["Direct ERK dephosphorylation by PP1γ versus indirect mechanism not resolved","Relationship to SHOC2-mediated RAF dephosphorylation not clarified"]},{"year":2016,"claim":"The NEK1–PP1γ–WAPL axis was identified as a regulator of meiotic cohesin removal: NEK1 phosphorylates PP1γ, which in turn dephosphorylates WAPL to control cohesin dynamics on prophase I chromosomes.","evidence":"Co-immunoprecipitation, phosphorylation assays, Nek1 knockout mouse meiotic spreads","pmids":["27760328"],"confidence":"High","gaps":["Whether PP1γ acts on WAPL directly or through PDS5B not fully resolved","Redundancy with PP2A-dependent cohesin regulation not addressed"]},{"year":2019,"claim":"The crystal structure of the iASPP–PP1γ complex revealed how SILK, RVxF, and SH3 domain interactions create a modular, dynamically flexible holoenzyme that enhances PP1γ catalytic activity toward p53, providing the first atomic-resolution view of regulatory subunit–PP1γ assembly.","evidence":"X-ray crystallography, SAXS, in vitro phosphatase assays with p53 and pNPP","pmids":["31402222"],"confidence":"High","gaps":["How iASPP directs PP1γ selectivity for p53 over other substrates in cells not determined","In vivo relevance for p53-dependent tumor suppression not tested"]},{"year":2020,"claim":"Aurora B was shown to phosphorylate Repo-Man to release PP1γ from mitotic chromosomes, explaining how the kinase–phosphatase balance on chromatin is maintained during chromosome condensation and segregation.","evidence":"Co-IP, Aurora B inhibition, phosphomimetic Repo-Man mutants, chromosome condensation assays","pmids":["32938714"],"confidence":"High","gaps":["Full set of chromatin substrates dephosphorylated by Repo-Man–PP1γ not catalogued","Whether other PP1 isoforms contribute to this axis unclear"]},{"year":2021,"claim":"A genome-wide CRISPR screen identified PPP1R3G as the regulatory subunit that recruits PP1γ to dephosphorylate RIPK1-pSer25 in complex I, activating RIPK1-dependent cell death—connecting PP1γ to innate immune signaling and TNF-induced necroptosis.","evidence":"CRISPR KO screen, Co-IP, PP1γ-binding-deficient mutant, Ppp1r3g knockout mice with TNF-induced SIRS","pmids":["34862394"],"confidence":"High","gaps":["Whether PP1γ dephosphorylates other RIPK1 inhibitory sites beyond Ser25 not tested","Cell-type specificity of PPP1R3G–PP1γ complex unclear"]},{"year":2022,"claim":"Cryo-EM and crystal structures of the SHOC2–MRAS–PP1C ternary holophosphatase from three independent groups revealed how a leucine-rich-repeat scaffold bridges PP1γ to GTP-loaded RAS to dephosphorylate inhibitory RAF-pSer259, and how RASopathy/cancer mutations at subunit interfaces hyperactivate this complex.","evidence":"Cryo-EM and X-ray crystallography, deep mutational scanning, reconstituted RAF dephosphorylation assays, biophysical binding measurements","pmids":["35831509","36175670","35830882"],"confidence":"High","gaps":["Whether the complex dephosphorylates RAF substrates beyond Ser259 not resolved","Therapeutic targeting of SHOC2–PP1γ interface not yet validated in animal models"]},{"year":2022,"claim":"PP1γ was shown to constitutively associate with HDAC1 and dephosphorylate CREB-pSer133 in dopaminergic neurons, with enhanced CREB–HDAC1/PP1γ complex formation during neurodegeneration contributing to CREB inactivation and neuronal loss.","evidence":"Co-IP, proximity ligation assay in human PD brain, MPTP mouse model, CREB mutant rescue","pmids":["35501151"],"confidence":"High","gaps":["Whether PP1γ or HDAC1 is rate-limiting for CREB dephosphorylation in vivo not determined","Broader neuronal substrate spectrum of HDAC1–PP1γ complex unknown"]},{"year":2025,"claim":"Multiple studies extended PP1γ's substrate repertoire to YAP1 dephosphorylation in trophectoderm specification and esophageal cancer, MLC20 regulation via CEMIP sequestration controlling vascular smooth muscle contractility, JNK-dependent cell competition, and KAP1 dephosphorylation in DNA damage repair, broadening its roles to developmental biology, vascular tone, tumor suppression, and genome integrity.","evidence":"Blastocyst immunofluorescence and GAS5 knockdown; BRET and CEMIP-RVxF mutagenesis with SMC-specific KO mice; Drosophila genetic screen with human cell validation; Co-IP and ubiquitination/radioresistance assays","pmids":["41403070","40626009","40590126","40906558","39297166"],"confidence":"Medium","gaps":["Direct phosphatase assay for PP1γ on YAP1 not yet shown in reconstituted system","CEMIP–PP1γ interaction specificity versus other PP1 isoforms not tested","JNK pathway regulation by PP1γ in human tissues beyond liver cancer not established"]},{"year":null,"claim":"Despite extensive cataloguing of PP1γ holoenzymes, major gaps remain: a systematic map of isoform-specific substrates distinguishing PP1γ from PP1α/PP1β is lacking, the structural basis for PP1γ2's unique spermatogenic functions is undefined, and whether the numerous regulatory subunit–PP1γ complexes are pharmacologically targetable has not been established.","evidence":"","pmids":[],"confidence":"Low","gaps":["No comprehensive phosphoproteomics comparing PP1γ-specific versus shared PP1 substrates","No structural model of PP1γ2 C-terminal domain with testis-specific interactors","Therapeutic targeting of specific PP1γ holoenzymes not demonstrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,14,15,16,17,18,19,20,21,22,24,26,27,28]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[13,9,29]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,17]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[7]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[2]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,8,9]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,7,17]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,9,12,20,21,22,24,26,27,29]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,18,29]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[13,18]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[3,5,6,11]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[32]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[19,23,24]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[26]}],"complexes":["SHOC2-MRAS-PP1C holophosphatase","GADD34-Smad7-PP1γ","Repo-Man-PP1γ","URI-PP1γ"],"partners":["SHOC2","MRAS","CDCA2","PPP1R15A","URI1","GEMIN8","PPP1R3G","HDAC1"],"other_free_text":[]},"mechanistic_narrative":"PPP1CC encodes the catalytic subunit PP1γ of protein phosphatase 1, a serine/threonine phosphatase that assembles with a broad repertoire of regulatory subunits to dephosphorylate substrates in diverse cellular processes including TGF-β signaling, RAS-MAPK pathway activation, cell cycle progression, innate immunity, meiotic cohesin removal, Hippo/YAP signaling, and synaptic transmission [PMID:14718519, PMID:35831509, PMID:27760328, PMID:34862394, PMID:36276179, PMID:40626009]. Substrate specificity is conferred by regulatory/scaffolding partners—such as SHOC2–MRAS for RAF dephosphorylation, Repo-Man for chromatin dephosphorylation, GADD34–Smad7 for TβRI, PPP1R3G for RIPK1, and iASPP for p53—that direct PP1γ to distinct subcellular compartments and substrates, with structural studies revealing how RVXF and SILK motifs mediate holoenzyme assembly [PMID:35831509, PMID:36175670, PMID:31402222, PMID:32938714, PMID:34862394]. PP1γ dynamically relocalizes during mitosis from nucleoli to kinetochores, chromosomes, the cleavage furrow, and midbody, and its recruitment to chromatin is antagonized by Aurora B phosphorylation of Repo-Man [PMID:12529430, PMID:32938714]. The alternatively spliced testis-enriched isoform PP1γ2 is essential for spermatid chromatin condensation, acrosome development, and sperm tail morphogenesis, and germ-cell-specific deletion causes male infertility [PMID:17301292, PMID:24089200, PMID:20385779]."},"prefetch_data":{"uniprot":{"accession":"P36873","full_name":"Serine/threonine-protein phosphatase PP1-gamma catalytic subunit","aliases":["Protein phosphatase 1C catalytic subunit"],"length_aa":323,"mass_kda":37.0,"function":"Protein phosphatase that associates with over 200 regulatory proteins to form highly specific holoenzymes which dephosphorylate hundreds of biological targets (PubMed:17936702, PubMed:25012651). Protein phosphatase 1 (PP1) is essential for cell division, and participates in the regulation of glycogen metabolism, muscle contractility and protein synthesis. Dephosphorylates RPS6KB1 (PubMed:17936702). Involved in regulation of ionic conductances and long-term synaptic plasticity. May play an important role in dephosphorylating substrates such as the postsynaptic density-associated Ca(2+)/calmodulin dependent protein kinase II. Component of the PTW/PP1 phosphatase complex, which plays a role in the control of chromatin structure and cell cycle progression during the transition from mitosis into interphase (PubMed:20516061). In balance with CSNK1D and CSNK1E, determines the circadian period length, through the regulation of the speed and rhythmicity of PER1 and PER2 phosphorylation (PubMed:21712997). May dephosphorylate CSNK1D and CSNK1E (By similarity). Regulates the recruitment of the SKA complex to kinetochores (PubMed:28982702). Dephosphorylates the 'Ser-418' residue of FOXP3 in regulatory T-cells (Treg) from patients with rheumatoid arthritis, thereby inactivating FOXP3 and rendering Treg cells functionally defective (PubMed:23396208). Together with PPP1CA (PP1-alpha subunit), dephosphorylates IFIH1/MDA5 and RIG-I leading to their activation and a functional innate immune response (PubMed:23499489). Core component of the SHOC2-MRAS-PP1c (SMP) holophosphatase complex that regulates the MAPK pathway activation (PubMed:35768504, PubMed:35831509). The SMP complex specifically dephosphorylates the inhibitory phosphorylation at 'Ser-259' of RAF1 kinase, 'Ser-365' of BRAF kinase and 'Ser-214' of ARAF kinase, stimulating their kinase activities (PubMed:35768504, PubMed:35831509). Dephosphorylates MKI67 at the onset of anaphase (PubMed:25012651). The SMP complex enhances the dephosphorylation activity and substrate specificity of PP1c (PubMed:35768504, PubMed:35831509)","subcellular_location":"Cytoplasm; Nucleus; Nucleus, nucleolus; Nucleus, nucleoplasm; Nucleus speckle; Chromosome, centromere, kinetochore; Cleavage furrow; Midbody; Mitochondrion; Cytoplasm, cytoskeleton, microtubule organizing center","url":"https://www.uniprot.org/uniprotkb/P36873/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PPP1CC","classification":"Not Classified","n_dependent_lines":110,"n_total_lines":1208,"dependency_fraction":0.09105960264900662},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CALD1","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CPSF6","stoichiometry":0.2},{"gene":"NPM1","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"SSRP1","stoichiometry":0.2},{"gene":"TOP1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PPP1CC","total_profiled":1310},"omim":[{"mim_id":"621430","title":"FIGNL1-INTERACTING REGULATOR OF RECOMBINATION AND MITOSIS; FIRRM","url":"https://www.omim.org/entry/621430"},{"mim_id":"618785","title":"CELL DIVISION CYCLE-ASSOCIATED PROTEIN 2; CDCA2","url":"https://www.omim.org/entry/618785"},{"mim_id":"618068","title":"SPERMATOGENIC LEUCINE ZIPPER PROTEIN 1; SPZ1","url":"https://www.omim.org/entry/618068"},{"mim_id":"615479","title":"MYOSIN XVI; MYO16","url":"https://www.omim.org/entry/615479"},{"mim_id":"614032","title":"TOX HIGH MOBILITY GROUP BOX FAMILY MEMBER 4; TOX4","url":"https://www.omim.org/entry/614032"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PPP1CC"},"hgnc":{"alias_symbol":["PP1C","PP1gamma"],"prev_symbol":[]},"alphafold":{"accession":"P36873","domains":[{"cath_id":"3.60.21.10","chopping":"29-182_189-295","consensus_level":"high","plddt":98.0995,"start":29,"end":295}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P36873","model_url":"https://alphafold.ebi.ac.uk/files/AF-P36873-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P36873-F1-predicted_aligned_error_v6.png","plddt_mean":92.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PPP1CC","jax_strain_url":"https://www.jax.org/strain/search?query=PPP1CC"},"sequence":{"accession":"P36873","fasta_url":"https://rest.uniprot.org/uniprotkb/P36873.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P36873/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P36873"}},"corpus_meta":[{"pmid":"14718519","id":"PMC_14718519","title":"GADD34-PP1c 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sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35162991","citation_count":3,"is_preprint":false},{"pmid":"37810667","id":"PMC_37810667","title":"Identification of PP1c-PPP1R12A Substrates Using Kinase-Catalyzed Biotinylation to Identify Phosphatase Substrates.","date":"2023","source":"ACS omega","url":"https://pubmed.ncbi.nlm.nih.gov/37810667","citation_count":2,"is_preprint":false},{"pmid":"38430798","id":"PMC_38430798","title":"Target silencing of porcine SPAG6 and PPP1CC by shRNA attenuated sperm motility.","date":"2024","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/38430798","citation_count":2,"is_preprint":false},{"pmid":"23176181","id":"PMC_23176181","title":"PP-1α and PP-1γ display antagonism and differential roles in tumorigenicity of lung cancer cells.","date":"2013","source":"Current molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/23176181","citation_count":2,"is_preprint":false},{"pmid":"8914631","id":"PMC_8914631","title":"Assignment of the gene encoding type 1 gamma protein phosphatase catalytic subunit (PPP1CC) on human, rat, and mouse chromosomes.","date":"1996","source":"The Japanese journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8914631","citation_count":2,"is_preprint":false},{"pmid":"40626009","id":"PMC_40626009","title":"PP1γ promotes esophageal squamous cell carcinoma progression through the PP1γ/YAP1/SOX2 axis.","date":"2025","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40626009","citation_count":1,"is_preprint":false},{"pmid":"27758712","id":"PMC_27758712","title":"STIP Regulates ERK1/2 Signaling Pathway Involved in Interaction with PP1γ in Lymphoblastic Leukemia.","date":"2016","source":"Current molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27758712","citation_count":1,"is_preprint":false},{"pmid":"40906558","id":"PMC_40906558","title":"Pp1-87B/PPP1CC-JNK axis integrates apoptosis and ferroptosis-like cell death to regulate cell competition and tumorigenesis.","date":"2025","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/40906558","citation_count":1,"is_preprint":false},{"pmid":"40590126","id":"PMC_40590126","title":"CEMIP Maintains Vascular Contractility by Controlling PP1c-MLC20 Cascade in SMCs.","date":"2025","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/40590126","citation_count":0,"is_preprint":false},{"pmid":"41913519","id":"PMC_41913519","title":"Multiple Roles of Protamine Kinase SRPK1 and Phosphatase PP1γ in Sperm Development.","date":"2026","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/41913519","citation_count":0,"is_preprint":false},{"pmid":"41927108","id":"PMC_41927108","title":"Asiaticoside Alleviates Alzheimer's Disease by Regulating PPP1CC Expression to Suppress Inflammation and Mitochondrial Dysfunction.","date":"2026","source":"Annals of clinical and laboratory science","url":"https://pubmed.ncbi.nlm.nih.gov/41927108","citation_count":0,"is_preprint":false},{"pmid":"41403070","id":"PMC_41403070","title":"Phosphatase PPP1CC Regulates the First Lineage Segregation by GAS5 in Mouse Preimplantation Embryos.","date":"2025","source":"Cell proliferation","url":"https://pubmed.ncbi.nlm.nih.gov/41403070","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":31865,"output_tokens":8263,"usd":0.10977},"stage2":{"model":"claude-opus-4-6","input_tokens":12274,"output_tokens":4724,"usd":0.269205},"total_usd":0.378975,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"PP1γ (PPP1CC) dynamically relocalizes throughout the mammalian cell cycle: it accumulates in the nucleolus during interphase, localizes to kinetochores at mitotic entry (exchanging rapidly with the cytoplasmic pool), relocalizes to chromosome-containing regions at the early-to-late anaphase transition, and accumulates at the cleavage furrow and midbody by telophase, implicating it in nucleolar function, chromosome segregation, and cytokinesis.\",\n      \"method\": \"Stable HeLa cell lines expressing FP-PP1γ; time-lapse fluorescence microscopy and FRAP\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct live-imaging with stable cell lines + FRAP, multiple orthogonal methods, functional consequences inferred\",\n      \"pmids\": [\"12529430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Smad7 acts as an adaptor protein that recruits the GADD34-PP1c (PP1γ) holoenzyme to the TGFβ type I receptor (TβRI), leading to dephosphorylation of TβRI and negative feedback in TGFβ signaling. SARA enhances PP1c recruitment to the Smad7-GADD34 complex by controlling PP1c subcellular localization.\",\n      \"method\": \"Co-immunoprecipitation, RNA interference knockdown of Smad7, cell-based phosphorylation assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, RNAi validation, functional phosphatase assay, replicated with multiple approaches\",\n      \"pmids\": [\"14718519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"URI forms stable complexes with PP1γ at mitochondria in growth factor-deprived cells, inhibiting PP1γ activity. S6K1-mediated phosphorylation of URI at Ser371 upon growth factor stimulation disassembles the URI/PP1γ complex, activating a PP1γ-dependent negative feedback that decreases S6K1 activity and BAD phosphorylation to regulate the apoptotic threshold.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, phospho-specific antibodies, rapamycin treatment, mitochondrial fractionation\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, in vitro assay, site-specific mutagenesis (Ser371), multiple orthogonal methods\",\n      \"pmids\": [\"17936702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PP1γ2 (encoded by Ppp1cc) is expressed in secondary spermatocytes, round and elongating spermatids, and mature spermatozoa. Targeted disruption of Ppp1cc causes malformed mitochondrial sheaths and extra outer dense fibers in sperm tails, indicating a role for PP1γ2 in sperm tail morphogenesis beyond motility regulation.\",\n      \"method\": \"Ppp1cc knockout mice, immunohistochemistry, electron microscopy, isoform-specific antibodies\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean knockout with specific ultrastructural phenotype, isoform-specific expression mapping\",\n      \"pmids\": [\"17301292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PP1γ2 specifically interacts with endophilin B1t (a testis-specific isoform of endophilin B1) via the unique C-terminal region of PP1γ2, and endophilin B1t inhibits PP1γ2 phosphatase activity toward phosphorylase a. Somatic endophilin B1a does not interact with any PP1 isoform, and PP1α does not interact with endophilin B1t, demonstrating isoform specificity.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, sedimentation assay, phosphatase activity assay with recombinant proteins\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro phosphatase assay + Tier 2 Co-IP with native proteins, yeast two-hybrid, isoform specificity demonstrated\",\n      \"pmids\": [\"17381077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Transgenic expression of PPP1CC2 in Ppp1cc-null mouse testes rescues spermatid viability and spermiation (anti-apoptotic effect) but does not restore normal sperm flagellar morphogenesis, motility, or fertility, indicating that PPP1CC1 is additionally required for normal spermatogenesis.\",\n      \"method\": \"Transgenic rescue experiment in Ppp1cc-/- mice; histology, motility analysis, fertility testing\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic rescue with isoform-specific transgene, multiple phenotypic readouts\",\n      \"pmids\": [\"19420386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Loss of PPP1CC in mice causes chromatin condensation defects and acrosome development abnormalities in spermatids, with germ cell loss concentrated at stages VII-VIII of spermatogenesis and reduced spermatogonial numbers; junctional complexes remain ultrastructurally normal.\",\n      \"method\": \"Light and electron microscopy of Ppp1cc knockout mouse testes\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with specific ultrastructural phenotype, but single method (EM)\",\n      \"pmids\": [\"20385779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PP1γ counteracts Nek2A kinase activity in a Nek2A-PP1γ-Mst2 complex at centrosomes. Plk1 phosphorylation of Mst2 prevents PP1γ binding to the Mst2-Nek2A complex, allowing Nek2A activity to drive centrosome disjunction; absence of Plk1 phosphorylation promotes assembly of Nek2A-PP1γ-Mst2 complexes that suppress centrosome separation.\",\n      \"method\": \"Co-immunoprecipitation, centrosome disjunction assays, kinase assays, Plk1 inhibition\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, functional epistasis, kinase assay, multiple orthogonal approaches\",\n      \"pmids\": [\"21723128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PP1γ directly interacts with the SMN complex component Gemin8, and this interaction regulates SMN complex formation and localization to Cajal bodies. PP1γ depletion by RNAi leads to SMN hyperphosphorylation and enhanced SMN complex/snRNP localization to Cajal bodies; PP1γ expression restores normal SMN phosphorylation isoforms.\",\n      \"method\": \"Co-immunoprecipitation, in vitro protein binding assay, RNAi knockdown, 2D protein gel electrophoresis, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding assay + Co-IP + RNAi with specific phosphorylation readout, multiple orthogonal methods\",\n      \"pmids\": [\"22454514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"hScrib directly interacts with PP1γ through a conserved PP1γ-interaction motif on hScrib, recruits PP1γ to downregulate ERK phosphorylation, controls the subcellular distribution of PP1γ (loss of hScrib enhances nuclear PP1γ translocation), and this hScrib-PP1γ interaction is required for hScrib's tumor-suppressor activity against oncogene-induced transformation.\",\n      \"method\": \"Proteomic pulldown, direct binding assay, co-immunoprecipitation, ERK phosphorylation assays, oncogenic transformation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding demonstrated + Co-IP + functional assay with motif requirement, multiple methods\",\n      \"pmids\": [\"23359326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PP1γ, but not PP1α or PP1β, promotes alternative splicing of CaMKIIδ through direct interaction with the splicing factor ASF. PP1γ overexpression or inhibition respectively enhances or suppresses CaMKIIδ splicing and ASF-PP1γ association, and PP1γ exacerbates OGD/R-triggered cardiomyocyte apoptosis through CaMKII activation.\",\n      \"method\": \"Co-immunoprecipitation, splicing assay, PP1γ overexpression/inhibition, cardiomyocyte apoptosis assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + isoform-specific functional assay, but single lab\",\n      \"pmids\": [\"24196533\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Conditional germ cell-specific deletion of Ppp1cc using Stra8-Cre causes oligo-terato-asthenozoospermia and male infertility, phenocopying global Ppp1cc null mice. PPP1CC2 is the only PP1 isoform expressed in postmeiotic germ cells, and its absence in meiotic and postmeiotic cells underlies spermatogenic defects.\",\n      \"method\": \"Conditional knockout mice (Stra8-Cre), immunohistochemistry, sperm analysis\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional cell-type-specific KO with defined infertility phenotype, isoform expression mapping\",\n      \"pmids\": [\"24089200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Hipk2 facilitates PP1c-mediated dephosphorylation of Dishevelled (Dvl) via its C-terminal domain, preventing ubiquitination and Itch-mediated degradation of Dvl. This Hipk2-PP1c-Dvl axis maintains sufficient Dvl protein levels for Wnt/β-catenin and Wnt/PCP signaling. Wnt-3a under high cell density induces dissociation of the Dvl-Hipk2-PP1c complex as a negative feedback mechanism.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, PP1c inhibition, zebrafish embryo epistasis, Wnt reporter assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + ubiquitination assay + in vivo epistasis in zebrafish, multiple orthogonal methods\",\n      \"pmids\": [\"25159144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PP1γ physically interacts with the E3 ubiquitin ligase TRAF6 and enhances TRAF6 auto-ubiquitination and ubiquitination of IKKγ, promoting NF-κB-mediated innate immune signaling; enzymatically inactive PP1γ represses these events.\",\n      \"method\": \"Gain-of-function genetic screen, co-immunoprecipitation, ubiquitination assay, NF-κB reporter assay, macrophage pathogen challenge\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + enzymatic mutant validation + functional immune assay, single lab\",\n      \"pmids\": [\"24586659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NEK1 phosphorylates PP1γ, and PP1γ dephosphorylates WAPL; the NEK1-PP1γ-WAPL axis regulates cohesin removal from chromosome arms during meiotic prophase I via interaction with PDS5B. NEK1 loss causes retention of cohesin on chromosomes at meiotic prophase I.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation assays, mouse genetics (Nek1 knockout), immunofluorescence on meiotic chromosomes\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + kinase/phosphatase assay + in vivo genetic validation, multiple approaches\",\n      \"pmids\": [\"27760328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TIMAP phosphorylation at Ser331 by PKCα inhibits PP1c activity within the TIMAP-PP1c complex toward phospho-ERM substrates, reducing dephosphorylation of ERM and thereby modulating endothelial barrier function. PKCα was shown to interact with TIMAP and phosphorylate it at Ser331 in vitro and in endothelial cells.\",\n      \"method\": \"In vitro kinase assay, site-directed mutagenesis, co-immunoprecipitation, electric resistance measurement of endothelial barrier, membrane fractionation\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with mutagenesis + Tier 2 functional endothelial assay, multiple orthogonal methods\",\n      \"pmids\": [\"27939168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"iASPP (and ASPP2) interact with PP1c via SILK and RVxF motifs on iASPP plus interactions of the PP1c PxxPxR motif with the iASPP SH3 domain. This interaction enhances PP1c catalytic activity toward pNPP and the substrate p53; the modular interface provides dynamic flexibility for dephosphorylation of diverse substrates including p53.\",\n      \"method\": \"Crystal structure of iASPP-PP1c complex, small-angle X-ray scattering, in vitro phosphatase activity assay with p53 and pNPP substrates\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure + in vitro activity assay + SAXS, multiple orthogonal methods in single study\",\n      \"pmids\": [\"31402222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Aurora B regulates PP1γ-Repo-Man interactions on mitotic chromosomes: PP1γ is recruited to chromosomes by Repo-Man when Aurora B is inactive; Aurora B phosphorylates Repo-Man to disrupt PP1γ-Repo-Man interactions, releasing PP1γ from chromatin to maintain chromosome phosphorylation and condensation.\",\n      \"method\": \"Immunofluorescence, co-immunoprecipitation, Aurora B inhibition, phosphomimetic/phosphonull Repo-Man mutants, ectopic PP1γ targeting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + kinase inhibition + site-directed mutagenesis + functional chromosome condensation assay\",\n      \"pmids\": [\"32938714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PPP1R3G recruits its catalytic subunit PP1γ to complex I to dephosphorylate inhibitory phosphorylations on RIPK1 (including Ser25), activating RIPK1 kinase activity and enabling RIPK1-dependent apoptosis and necroptosis. A PPP1R3G mutant that cannot bind PP1γ fails to rescue RIPK1 activation and cell death.\",\n      \"method\": \"CRISPR whole-genome knockout screen, co-immunoprecipitation, PP1γ-binding mutant, phospho-RIPK1 analysis, Ppp1r3g-/- mice with TNF-induced SIRS\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide screen + Co-IP + binding mutant + in vivo mouse validation, multiple orthogonal methods\",\n      \"pmids\": [\"34862394\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HDAC1 constitutively associates with PP1γ and promotes dephosphorylation of CREB at Ser133; during dopaminergic neurodegeneration CREB interacts with the HDAC1/PP1γ complex leading to CREB inactivation. Disrupting CREB/HDAC1 interaction restores p-CREB (Ser133) and NURR1 levels and protects nigral dopaminergic neurons in MPTP-treated mice.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation assay in human PD brain tissue, MPTP mouse model, overexpression of CREB mutant, TSA treatment\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + PLA in human tissue + in vivo mouse rescue, multiple orthogonal methods\",\n      \"pmids\": [\"35501151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The SHOC2-MRAS-PP1C ternary holophosphatase complex dephosphorylates RAF at an inhibitory phosphoserine to potentiate MAPK signaling. Cryo-EM structure reveals SHOC2 binds PP1C and MRAS through the concave leucine-rich repeat surface and via an N-terminal cryptic RVXF motif; complex formation is initiated by SHOC2-PP1C interaction and stabilized by GTP-loaded MRAS. RASopathy/cancer mutations in SHOC2 stabilize complex interactions to enhance holophosphatase activity.\",\n      \"method\": \"Cryo-electron microscopy structure, deep mutational scanning of SHOC2, biophysical binding assays, RAF dephosphorylation assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure + reconstituted enzymatic assay + deep mutational scanning, replicated across multiple labs\",\n      \"pmids\": [\"35831509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Crystal structure of the SHOC2-MRAS-PP1C complex reveals all three proteins synergistically interact; SHOC2 acts as a scaffolding protein bridging PP1C and MRAS. Dephosphorylation of RAF by PP1C is enhanced upon interaction with SHOC2 and MRAS. Complex formation requires MRAS in its GTP-bound active state and is further stabilized by SHOC2. RASopathy mutations reside at protein-protein interfaces and enhance complex formation and activity.\",\n      \"method\": \"X-ray crystallography, apo-SHOC2 structure, in vitro RAF dephosphorylation assay, biophysical characterization of complex assembly\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure + reconstituted enzymatic assay, independently replicated across multiple labs\",\n      \"pmids\": [\"36175670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"X-ray crystal structure of MRAS-SHOC2-PP1C complex shows SHOC2 bridges PP1C and MRAS through its concave surface with reciprocal interactions among all three subunits. GTP-bound MRAS drives cooperative assembly. Rasopathy and cancer mutations at protein-protein interfaces enhance affinities and function. MRAS can be substituted by canonical RAS isoforms.\",\n      \"method\": \"X-ray crystallography, biophysical characterization (SPR/ITC), in vitro RAF dephosphorylation assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure + reconstituted functional assay, independently replicated across multiple labs\",\n      \"pmids\": [\"35830882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"I-2 (inhibitor-2) and PP1γ, but not PP1α, positively regulate synaptic transmission in hippocampal neurons. I-2 enhances PP1γ interaction with its synaptic scaffold neurabin (demonstrated by FRET/FLIM), and this positive regulatory effect depends on I-2 Thr72 phosphorylation.\",\n      \"method\": \"Hippocampal neuron electrophysiology, FRET/FLIM imaging, co-immunoprecipitation, Thr72 phosphorylation analysis\",\n      \"journal\": \"Frontiers in synaptic neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRET/FLIM + electrophysiology + Co-IP, isoform-specific finding, single lab\",\n      \"pmids\": [\"36276179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PP1γ (but not PP1α) dephosphorylates AKT2 and regulates neuronal insulin signaling via the AKT2-AS160-GLUT4 axis, and separately regulates GSK3β via AKT2 and GSK3α via MLK3. Imbalance in PP1γ-dependent phosphatase activity promotes an Alzheimer's disease-like phenotype in neuronal cells.\",\n      \"method\": \"siRNA knockdown of PP1α vs PP1γ, western blot of AKT isoforms/AS160/GSK3 isoforms, GLUT4 translocation by confocal microscopy, fluorescence-based glucose uptake assay, high-fat-diet mouse model\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — isoform-specific siRNA + multiple substrate readouts + in vivo model, single lab\",\n      \"pmids\": [\"37085815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CaMKII bound to sarcoplasmic reticulum (SR) phosphorylates GM (glycogen- and PP1c-targeting subunit) at Ser48, and PP1c dephosphorylates GM; the GM-GS-PP1c complex selectively localizes to nonjunctional SR, and CaMKII-mediated phosphorylation of GM regulates glycogen synthase activity through this complex.\",\n      \"method\": \"Recombinant fragment pulldown, site-directed mutagenesis, in vitro kinase assay, co-immunoprecipitation, immunofluorescence co-localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay + mutagenesis of Ser48 + Co-IP demonstrating complex, multiple orthogonal methods\",\n      \"pmids\": [\"15591318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PPP1CC exhibits uniform distribution before blastocyst formation but becomes localized specifically to the trophectoderm (TE) during blastocyst stage via interaction with lncRNA GAS5. PPP1CC-mediated YAP dephosphorylation in outer cells promotes YAP nuclear translocation and TE lineage specification. Knockdown of GAS5 phenocopies PPP1CC deficiency (developmental arrest at morula with impaired YAP dephosphorylation).\",\n      \"method\": \"Immunofluorescence, knockdown experiments, YAP dephosphorylation assay, GAS5 overexpression in single blastomere of 2-cell stage embryo\",\n      \"journal\": \"Cell proliferation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization + functional knockdown + epistasis with GAS5, single lab\",\n      \"pmids\": [\"41403070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PPP1CC (PP1γ) dephosphorylates YAP1, and silencing of PPP1CC increases p-YAP1 levels, inhibits YAP1 activity, and reduces SOX2 expression in esophageal squamous cell carcinoma cells, suppressing proliferation, migration, and invasion.\",\n      \"method\": \"PPP1CC siRNA knockdown, western blot (YAP1, p-YAP1, SOX2), CCK-8 proliferation assay, Transwell invasion/migration assay\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with specific phosphorylation readout, single lab, single method type\",\n      \"pmids\": [\"40626009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CEMIP interacts directly with PP1c (PPP1CC) via three RVxF motifs and sequesters MLC20 from PP1c without affecting MLCK. Mutations in CEMIP RVxF motifs restore PP1c-MLC20 interaction. CEMIP-deficient smooth muscle cells show reduced MLC20 phosphorylation and reduced contractility; SMC-specific Cemip knockout mice have reduced blood pressure.\",\n      \"method\": \"Co-immunoprecipitation, molecular docking, bioluminescence resonance energy transfer (BRET), RVxF motif mutagenesis, SMC-specific conditional knockout mice, ex vivo contractility\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — BRET + mutagenesis + Co-IP + in vivo conditional KO with functional phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"40590126\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Drosophila Pp1-87B (ortholog of PPP1CC) is an essential regulator of JNK signaling in tumor-suppressive cell competition; its loss activates JNK via the Moe-Rho1 axis, integrating apoptosis and ferroptosis-like cell death through Hippo signaling. The human ortholog PPP1CC functions similarly to drive apoptosis and ferroptosis in human liver tumor cells through JNK activation.\",\n      \"method\": \"Drosophila genetic screen, epistasis analysis, human liver cancer cell experiments, cell death assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in Drosophila + validation in human cells, but human data limited to single lab\",\n      \"pmids\": [\"40906558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human PPP1CC encodes two alternatively spliced isoforms, PP1γ1 and PP1γ2, differing only at their C-termini. Both isoforms are ~94% identical to PP1α but are encoded by a distinct gene mapped to chromosome 12q24.1-q24.2, separate from the PP1α gene on chromosome 11.\",\n      \"method\": \"cDNA cloning, somatic cell hybrid analysis, in situ hybridization (FISH), sequence analysis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct molecular cloning and chromosomal mapping, foundational gene structure paper\",\n      \"pmids\": [\"8394140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Both PP1γ1 and PP1γ2 isoforms encoded by Ppp1cc retain phosphatase function, as they complement the cold-sensitive PP1 defect in Schizosaccharomyces pombe dis2-11 mutants. The two isoforms arise from alternative splicing with retention of the last intron for PP1γ2.\",\n      \"method\": \"Yeast complementation assay (dis2-11 fission yeast), genomic organization analysis, FISH mapping\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional complementation in yeast demonstrating phosphatase activity of both isoforms\",\n      \"pmids\": [\"9339378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"gp78 promotes ubiquitination-dependent degradation of PPP1CC (and PPP2CA), leading to elevated KAP1 phosphorylation and enhanced DNA damage repair and radioresistance in breast cancer cells. PPP1CC is a crucial regulator of KAP1 dephosphorylation in response to ionizing radiation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, western blot for p-KAP1, radioresistance assays\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP + ubiquitination assay + functional radioresistance readout, single lab\",\n      \"pmids\": [\"39297166\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PPP1CC (PP1γ) is a serine/threonine phosphatase catalytic subunit that forms holoenzymes with diverse regulatory subunits (including GADD34/Smad7, SHOC2/MRAS, URI, TIMAP, Repo-Man, Gemin8, PPP1R3G, HDAC1, GM, and others) to dephosphorylate specific substrates (TβRI, RAF-pSer259, RIPK1-pSer25, CREB-pSer133, MLC20, YAP1, Dvl, WAPL, BAD, and chromatin proteins), with its subcellular localization dynamically regulated throughout the cell cycle (nucleolus in interphase; kinetochores, chromosomes, cleavage furrow, and midbody during mitosis), and plays isoform-specific roles in sperm morphogenesis and motility, MAPK/RAS pathway activation, innate immune signaling, meiotic cohesin removal, synaptic transmission, and early embryonic lineage specification.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PPP1CC encodes the catalytic subunit PP1γ of protein phosphatase 1, a serine/threonine phosphatase that assembles with a broad repertoire of regulatory subunits to dephosphorylate substrates in diverse cellular processes including TGF-β signaling, RAS-MAPK pathway activation, cell cycle progression, innate immunity, meiotic cohesin removal, Hippo/YAP signaling, and synaptic transmission [PMID:14718519, PMID:35831509, PMID:27760328, PMID:34862394, PMID:36276179, PMID:40626009]. Substrate specificity is conferred by regulatory/scaffolding partners—such as SHOC2–MRAS for RAF dephosphorylation, Repo-Man for chromatin dephosphorylation, GADD34–Smad7 for TβRI, PPP1R3G for RIPK1, and iASPP for p53—that direct PP1γ to distinct subcellular compartments and substrates, with structural studies revealing how RVXF and SILK motifs mediate holoenzyme assembly [PMID:35831509, PMID:36175670, PMID:31402222, PMID:32938714, PMID:34862394]. PP1γ dynamically relocalizes during mitosis from nucleoli to kinetochores, chromosomes, the cleavage furrow, and midbody, and its recruitment to chromatin is antagonized by Aurora B phosphorylation of Repo-Man [PMID:12529430, PMID:32938714]. The alternatively spliced testis-enriched isoform PP1γ2 is essential for spermatid chromatin condensation, acrosome development, and sperm tail morphogenesis, and germ-cell-specific deletion causes male infertility [PMID:17301292, PMID:24089200, PMID:20385779].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing that PPP1CC encodes two alternatively spliced catalytic isoforms (PP1γ1 and PP1γ2) on chromosome 12q24 resolved the gene's identity as distinct from PP1α and set the stage for isoform-specific functional studies.\",\n      \"evidence\": \"cDNA cloning, somatic cell hybrid analysis, and FISH mapping\",\n      \"pmids\": [\"8394140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional characterization of either isoform at this stage\", \"Tissue-specific expression patterns not yet defined\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Demonstration that both PP1γ1 and PP1γ2 retain phosphatase activity by complementing a fission yeast PP1 mutant confirmed that alternative splicing does not ablate catalytic function, validating both isoforms as active enzymes.\",\n      \"evidence\": \"Complementation of S. pombe dis2-11 cold-sensitive mutant\",\n      \"pmids\": [\"9339378\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian substrate specificity of each isoform unknown\", \"Whether isoforms have non-redundant roles in vivo untested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Live imaging revealed that PP1γ dynamically relocalizes throughout the mammalian cell cycle—from nucleoli in interphase to kinetochores, chromosome arms, cleavage furrow, and midbody during mitosis—establishing that its function is spatiotemporally regulated rather than constitutive.\",\n      \"evidence\": \"Stable HeLa lines expressing FP-PP1γ, time-lapse microscopy and FRAP\",\n      \"pmids\": [\"12529430\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Targeting subunits responsible for each localization not identified\", \"Whether relocalization is essential for mitotic fidelity not tested\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of the GADD34–Smad7 adaptor complex recruiting PP1γ to dephosphorylate TβRI provided the first concrete substrate-targeting mechanism for PP1γ in a major signaling pathway (TGF-β negative feedback).\",\n      \"evidence\": \"Co-immunoprecipitation, RNAi of Smad7, phosphorylation assays in cells\",\n      \"pmids\": [\"14718519\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1α or PP1β can substitute in this complex not fully resolved\", \"In vivo relevance in TGF-β-dependent tissues not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Studies in Ppp1cc knockout mice established an essential, non-redundant role for PP1γ2 in spermiogenesis: loss causes malformed mitochondrial sheaths, extra outer dense fibers, and chromatin condensation defects, directly linking the testis-enriched isoform to male fertility.\",\n      \"evidence\": \"Ppp1cc knockout mice, electron microscopy, isoform-specific antibodies; conditional Stra8-Cre deletion later confirmed germ-cell autonomy\",\n      \"pmids\": [\"17301292\", \"24089200\", \"20385779\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific spermatid substrates of PP1γ2 not identified\", \"Mechanism linking PP1γ2 to chromatin condensation versus structural assembly unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Discovery that URI sequesters PP1γ at mitochondria and that S6K1-mediated phosphorylation of URI releases active PP1γ to dephosphorylate BAD revealed a growth-factor-controlled apoptotic threshold mechanism operating through PP1γ.\",\n      \"evidence\": \"Co-immunoprecipitation, mitochondrial fractionation, in vitro kinase assay, rapamycin treatment\",\n      \"pmids\": [\"17936702\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full spectrum of mitochondrial PP1γ substrates beyond BAD unknown\", \"Whether URI-PP1γ regulation operates in non-transformed cells not established\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Transgenic rescue experiments showed that PP1γ2 alone restores spermatid viability but not sperm morphogenesis or motility, demonstrating that PP1γ1 has non-redundant roles in spermatogenesis beyond the anti-apoptotic function of PP1γ2.\",\n      \"evidence\": \"PP1γ2 transgene expressed in Ppp1cc-null testes; histology, motility, and fertility analysis\",\n      \"pmids\": [\"19420386\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PP1γ1-specific substrates in spermatogenesis not identified\", \"Structural basis of isoform-specific function unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"The finding that PP1γ opposes Nek2A kinase within a Nek2A–PP1γ–Mst2 centrosomal complex, regulated by Plk1 phosphorylation of Mst2, established PP1γ as a direct regulator of centrosome disjunction timing.\",\n      \"evidence\": \"Co-immunoprecipitation, centrosome disjunction assays, Plk1 inhibition\",\n      \"pmids\": [\"21723128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1α/β contribute to this complex not fully excluded\", \"Downstream centrosomal substrates beyond linker proteins not mapped\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"PP1γ was shown to interact with Gemin8 and regulate SMN complex phosphorylation and Cajal body localization, revealing a role in snRNP biogenesis beyond its known cell-cycle functions.\",\n      \"evidence\": \"Direct binding assay, Co-IP, RNAi of PP1γ, 2D gel electrophoresis of SMN phospho-isoforms\",\n      \"pmids\": [\"22454514\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific SMN phosphosites targeted by PP1γ not mapped\", \"Functional consequence for snRNP assembly efficiency not quantified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identification of hScrib as a scaffold that recruits PP1γ to suppress ERK phosphorylation and oncogenic transformation connected PP1γ to RAS-MAPK tumor suppression upstream of the later-characterized SHOC2 complex.\",\n      \"evidence\": \"Proteomic pulldown, direct binding assay, ERK phosphorylation and transformation assays\",\n      \"pmids\": [\"23359326\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ERK dephosphorylation by PP1γ versus indirect mechanism not resolved\", \"Relationship to SHOC2-mediated RAF dephosphorylation not clarified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The NEK1–PP1γ–WAPL axis was identified as a regulator of meiotic cohesin removal: NEK1 phosphorylates PP1γ, which in turn dephosphorylates WAPL to control cohesin dynamics on prophase I chromosomes.\",\n      \"evidence\": \"Co-immunoprecipitation, phosphorylation assays, Nek1 knockout mouse meiotic spreads\",\n      \"pmids\": [\"27760328\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1γ acts on WAPL directly or through PDS5B not fully resolved\", \"Redundancy with PP2A-dependent cohesin regulation not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The crystal structure of the iASPP–PP1γ complex revealed how SILK, RVxF, and SH3 domain interactions create a modular, dynamically flexible holoenzyme that enhances PP1γ catalytic activity toward p53, providing the first atomic-resolution view of regulatory subunit–PP1γ assembly.\",\n      \"evidence\": \"X-ray crystallography, SAXS, in vitro phosphatase assays with p53 and pNPP\",\n      \"pmids\": [\"31402222\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How iASPP directs PP1γ selectivity for p53 over other substrates in cells not determined\", \"In vivo relevance for p53-dependent tumor suppression not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Aurora B was shown to phosphorylate Repo-Man to release PP1γ from mitotic chromosomes, explaining how the kinase–phosphatase balance on chromatin is maintained during chromosome condensation and segregation.\",\n      \"evidence\": \"Co-IP, Aurora B inhibition, phosphomimetic Repo-Man mutants, chromosome condensation assays\",\n      \"pmids\": [\"32938714\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of chromatin substrates dephosphorylated by Repo-Man–PP1γ not catalogued\", \"Whether other PP1 isoforms contribute to this axis unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A genome-wide CRISPR screen identified PPP1R3G as the regulatory subunit that recruits PP1γ to dephosphorylate RIPK1-pSer25 in complex I, activating RIPK1-dependent cell death—connecting PP1γ to innate immune signaling and TNF-induced necroptosis.\",\n      \"evidence\": \"CRISPR KO screen, Co-IP, PP1γ-binding-deficient mutant, Ppp1r3g knockout mice with TNF-induced SIRS\",\n      \"pmids\": [\"34862394\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1γ dephosphorylates other RIPK1 inhibitory sites beyond Ser25 not tested\", \"Cell-type specificity of PPP1R3G–PP1γ complex unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Cryo-EM and crystal structures of the SHOC2–MRAS–PP1C ternary holophosphatase from three independent groups revealed how a leucine-rich-repeat scaffold bridges PP1γ to GTP-loaded RAS to dephosphorylate inhibitory RAF-pSer259, and how RASopathy/cancer mutations at subunit interfaces hyperactivate this complex.\",\n      \"evidence\": \"Cryo-EM and X-ray crystallography, deep mutational scanning, reconstituted RAF dephosphorylation assays, biophysical binding measurements\",\n      \"pmids\": [\"35831509\", \"36175670\", \"35830882\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the complex dephosphorylates RAF substrates beyond Ser259 not resolved\", \"Therapeutic targeting of SHOC2–PP1γ interface not yet validated in animal models\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"PP1γ was shown to constitutively associate with HDAC1 and dephosphorylate CREB-pSer133 in dopaminergic neurons, with enhanced CREB–HDAC1/PP1γ complex formation during neurodegeneration contributing to CREB inactivation and neuronal loss.\",\n      \"evidence\": \"Co-IP, proximity ligation assay in human PD brain, MPTP mouse model, CREB mutant rescue\",\n      \"pmids\": [\"35501151\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PP1γ or HDAC1 is rate-limiting for CREB dephosphorylation in vivo not determined\", \"Broader neuronal substrate spectrum of HDAC1–PP1γ complex unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Multiple studies extended PP1γ's substrate repertoire to YAP1 dephosphorylation in trophectoderm specification and esophageal cancer, MLC20 regulation via CEMIP sequestration controlling vascular smooth muscle contractility, JNK-dependent cell competition, and KAP1 dephosphorylation in DNA damage repair, broadening its roles to developmental biology, vascular tone, tumor suppression, and genome integrity.\",\n      \"evidence\": \"Blastocyst immunofluorescence and GAS5 knockdown; BRET and CEMIP-RVxF mutagenesis with SMC-specific KO mice; Drosophila genetic screen with human cell validation; Co-IP and ubiquitination/radioresistance assays\",\n      \"pmids\": [\"41403070\", \"40626009\", \"40590126\", \"40906558\", \"39297166\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct phosphatase assay for PP1γ on YAP1 not yet shown in reconstituted system\", \"CEMIP–PP1γ interaction specificity versus other PP1 isoforms not tested\", \"JNK pathway regulation by PP1γ in human tissues beyond liver cancer not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Despite extensive cataloguing of PP1γ holoenzymes, major gaps remain: a systematic map of isoform-specific substrates distinguishing PP1γ from PP1α/PP1β is lacking, the structural basis for PP1γ2's unique spermatogenic functions is undefined, and whether the numerous regulatory subunit–PP1γ complexes are pharmacologically targetable has not been established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No comprehensive phosphoproteomics comparing PP1γ-specific versus shared PP1 substrates\", \"No structural model of PP1γ2 C-terminal domain with testis-specific interactors\", \"Therapeutic targeting of specific PP1γ holoenzymes not demonstrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 26, 27, 28]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [13, 9, 29]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 8, 9]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 7, 17]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 9, 12, 20, 21, 22, 24, 26, 27, 29]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 18, 29]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [13, 18]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [3, 5, 6, 11]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [32]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [19, 23, 24]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [26]}\n    ],\n    \"complexes\": [\n      \"SHOC2-MRAS-PP1C holophosphatase\",\n      \"GADD34-Smad7-PP1γ\",\n      \"Repo-Man-PP1γ\",\n      \"URI-PP1γ\"\n    ],\n    \"partners\": [\n      \"SHOC2\",\n      \"MRAS\",\n      \"CDCA2\",\n      \"PPP1R15A\",\n      \"URI1\",\n      \"GEMIN8\",\n      \"PPP1R3G\",\n      \"HDAC1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}