{"gene":"ARPP19","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2010,"finding":"ARPP19, when phosphorylated by Greatwall kinase, associates with and inhibits PP2A, promoting mitotic entry. In Xenopus egg extracts, endogenous ARPP19 (but not α-Endosulfine/ENSA) is responsible for PP2A inhibition at mitotic entry. Without Greatwall activity, ARPP19 is dephosphorylated and loses its capacity to bind and inhibit PP2A.","method":"Biochemical identification of Greatwall substrates in Xenopus egg extracts; co-immunoprecipitation; phosphatase activity assays; depletion/add-back experiments","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution in egg extracts with depletion/add-back, multiple orthogonal assays; independently replicated in subsequent studies","pmids":["21164014"],"is_preprint":false},{"year":2013,"finding":"Phosphorylation of ARPP19 at S67 by Greatwall kinase promotes its binding to PP2A-B55δ, inhibiting PP2A activity. This process is controlled by Cdk1 and plays an essential role within the Cdk1 auto-amplification loop for entry into the first meiotic division. Once phosphorylated by Greatwall at S67, ARPP19 escapes negative regulation by PKA.","method":"Xenopus oocyte microinjection; phospho-specific mutants; PP2A activity assays; co-immunoprecipitation","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstitution in physiologically intact Xenopus oocytes, phospho-mutant analysis, PP2A activity measurements, single lab with multiple orthogonal methods","pmids":["23781026"],"is_preprint":false},{"year":2014,"finding":"ARPP19 phosphorylation at serine 109 by PKA is necessary and sufficient for maintaining Xenopus oocytes arrested in prophase. Progesterone promotes partial dephosphorylation of ARPP19 at S109, enabling a threshold level of active Cdk1 to form. Active Cdk1 then initiates the MPF auto-amplification loop requiring Greatwall-dependent phosphorylation of ARPP19 at S67. Thus ARPP19 integrates opposing PKA and Greatwall signals at a crossroads in meiotic M-phase control.","method":"Xenopus oocyte microinjection; phospho-specific mutants (S109A, S109D); kinase activity assays; PKA manipulation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — phosphomutant rescue/dominant experiments in intact oocytes with multiple readouts; single lab but multiple orthogonal methods","pmids":["24525567"],"is_preprint":false},{"year":2017,"finding":"ARPP-16 (the striatum-enriched splice variant sharing the ARPP19 locus) is phosphorylated at Ser46 by MAST3 kinase in vitro and in vivo. This phosphorylation converts ARPP-16 into a selective inhibitor of B55α- and B56δ-containing PP2A heterotrimers. ARPP-16 interacts directly with the PP2A scaffolding A subunit. PKA phosphorylation at Ser88 opposes MAST3, causing dephosphorylation of Ser46 and disinhibition of PP2A. Conditional knockout of ARPP-16 results in dephosphorylation of PP2A substrates including phospho-Thr75-DARPP-32, phospho-T308-Akt, and phospho-T202/Y204-ERK.","method":"In vitro kinase assay; co-immunoprecipitation; conditional knockout mouse (CaMKIIα::cre/floxed ARPP-16/19); phospho-specific antibodies; PP2A activity assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assays plus conditional KO with defined substrate phenotypes, multiple orthogonal methods","pmids":["28167675"],"is_preprint":false},{"year":2017,"finding":"PKA phosphorylation and MAST3 phosphorylation of ARPP-16/19 are mutually suppressive: phosphorylation by PKA prevents MAST3 from acting and prevents PP2A inhibition by MAST3-phosphorylated ARPP-16. PKA also phosphorylates MAST3 at multiple sites, inhibiting MAST3 kinase activity. Together these interactions create a switch-like response to cAMP regulating PP2A activity in striatal neurons.","method":"In vitro kinase assays; mass spectrometry; mathematical modeling; phospho-mutant analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assays with phospho-mutants, MS, and quantitative mathematical modeling; single lab, multiple orthogonal methods","pmids":["28613156"],"is_preprint":false},{"year":2019,"finding":"Using conditional knockout mouse models, ARPP19 (but not ENSA) was found essential for mouse embryogenesis. Arpp19 ablation dramatically decreased MEF viability by perturbing the temporal pattern of protein dephosphorylation during mitotic progression, consistent with a drop in PP2A-B55 activity inhibition. ENSA could not compensate for ARPP19 loss in mitotic division. By contrast, ENSA ablation (but not ARPP19 ablation) perturbed S phase.","method":"Conditional knockout mouse models (Arpp19 and Ensa); mouse embryonic fibroblast viability assays; cell cycle analysis; phospho-protein timing analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO mouse models with defined cellular phenotypes; distinct roles established for ARPP19 vs ENSA by genetic comparison","pmids":["30626720"],"is_preprint":false},{"year":2021,"finding":"Molecular determinants of ARPP19's S67 phosphorylation confer high affinity and slow dephosphorylation kinetics when bound to PP2A-B55, enabling it to act as a competitive inhibitor of PP2A-B55 substrates. Phospho-S109 (PKA site) restricts S67 phosphorylation by increasing PP2A-B55-catalyzed dephosphorylation of S67, and a double feedback loop between S67 and S109 phosphorylation sites coordinates PP2A-B55 inhibition with Cyclin B/Cdk1 activation during cell division.","method":"In vitro phosphatase kinetics assays; phospho-mutant analysis; binding affinity measurements; Xenopus egg extract reconstitution","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with kinetic measurements, phosphomutant analysis, and cell-free extract functional assays; single lab, multiple orthogonal methods","pmids":["34117214"],"is_preprint":false},{"year":2021,"finding":"PP2A-B55δ is the phosphatase responsible for dephosphorylating ARPP19 at S109 (the PKA site) to initiate prophase release in Xenopus oocytes. In prophase, PKA and PP2A-B55δ are simultaneously active. When progesterone reduces PKA activity, PP2A-B55δ dephosphorylates S109, unlocking the prophase block. Thus PP2A-B55δ acts at two distinct ARPP19 sites—opposing PKA (at S109) and being inhibited by Gwl-phosphorylated ARPP19 (at S67).","method":"Xenopus oocyte microinjection; phosphatase inhibitor experiments; PP2A-B55δ immunodepletion; phospho-specific assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — genetic and biochemical identification of the phosphatase acting on S109 in intact oocytes, multiple approaches; single lab","pmids":["33758202"],"is_preprint":false},{"year":2023,"finding":"Cryo-EM structures of PP2A:B55 bound to phosphorylated ARPP19 reveal that the intrinsically disordered ARPP19 binds PP2A:B55 using multiple distinct binding sites on the B55 subunit, explaining how both substrates and inhibitors are recruited to PP2A:B55. Complementary NMR spectroscopy confirmed the structural findings. The structures provide a molecular mechanism for PP2A:B55 inhibition by ARPP19.","method":"Single-particle cryo-EM; NMR spectroscopy; biophysical/biochemical assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution cryo-EM structure with complementary NMR validation and biochemical assays; published in peer-reviewed journal","pmids":["38123684"],"is_preprint":false},{"year":2025,"finding":"ARPP19 is phosphorylated in a Cdk1-dependent manner at serine 23 (a site absent in mammalian ENSA) in mitotic human cells, and dephosphorylated at S23 during mitotic exit by the phosphatase Fcp1 (resistant to okadaic acid). Substituting endogenous ARPP19 with a S23-phosphorylation-resistant mutant increased chromosome segregation errors and accelerated mitotic exit; a phosphomimetic S23 mutant delayed mitotic exit. This phosphorylation switch grants timely mitotic exit and chromosome stability.","method":"Phospho-specific antibodies in human cells; CRISPR/endogenous substitution with phospho-mutants; phosphatase inhibitor experiments (okadaic acid); chromosome segregation assays; mitotic timing assays","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — endogenous mutant substitution in human cells with multiple functional readouts (chromosome segregation, mitotic timing), phosphatase identification; single lab, multiple orthogonal methods","pmids":["40447768"],"is_preprint":false},{"year":2001,"finding":"ARPP-16 and ARPP-19 are substrates for PKA; both proteins contain a conserved consensus PKA phosphorylation site (RKPSLVA). In striatal slices, ARPP-16 phosphorylation increases in response to D1 dopamine receptor activation and decreases with D2 dopamine receptor activation. In non-neuronal cells, ARPP-19 is highly phosphorylated in response to PKA activation.","method":"In vitro kinase assay; phospho-specific antibody immunoblotting; striatal slice pharmacology","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal use of phospho-specific antibodies in intact cells and slices plus in vitro kinase assays; single lab, two methods","pmids":["11279279"],"is_preprint":false},{"year":1990,"finding":"ARPP-16 and ARPP-19 were purified to homogeneity and identified as substrates for cAMP-dependent protein kinase (PKA). ARPP-19 contains 16 additional NH2-terminal amino acids compared to ARPP-16; both are encoded by related cDNA clones sharing identical 3'-untranslated sequences, suggesting they arise from alternative transcription/splicing.","method":"Protein purification; cDNA cloning and sequencing; in vitro PKA phosphorylation assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct biochemical purification and in vitro kinase assay; single lab, foundational biochemical characterization","pmids":["2160982"],"is_preprint":false},{"year":2002,"finding":"ARPP-19 mediates NGF-dependent regulation of GAP-43 mRNA stability. In an NGF-dependent manner, ARPP-19 binds to the 3' region of GAP-43 mRNA that controls its half-life. Mutation of serine 104 (the PKA phosphorylation site) to alanine or aspartate abolished regulation of GAP-43 mRNA reporter expression in PC12 cells, demonstrating that PKA-dependent phosphorylation of ARPP-19 is required for this post-transcriptional function.","method":"RNA-protein binding assay; PC12 cell overexpression; reporter assays with 3'UTR constructs; site-directed mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA binding, reporter assay, and phospho-site mutagenesis in intact cells; single lab, multiple orthogonal methods","pmids":["12221279"],"is_preprint":false},{"year":2017,"finding":"Greatwall kinase-dependent phosphorylation of ARPP19 at S67 is dominant over PKA-dependent phosphorylation at S109 in controlling Cdk1 activation. Both PKA and Gwl phosphorylate ARPP19 independently of each other. Cdk1 is not directly involved in regulating the biological activity of ARPP19.","method":"Xenopus oocyte microinjection; phospho-specific mutants; kinase activity assays","journal":"Cell cycle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — intact oocyte phosphomutant epistasis experiments; single lab, two orthogonal phospho-site mutations tested functionally","pmids":["28722544"],"is_preprint":false},{"year":2020,"finding":"In human platelets, ARPP19 S62 is phosphorylated by MASTL (or a related kinase) and both S62 and S104 are dephosphorylated by platelet PP2A. Only S62-phosphorylated ARPP19 (but not S104-phosphorylated) acts as a PP2A inhibitor in this context. The entire MASTL-ENSA/ARPP19-PP2A pathway is present and active in anucleate platelets.","method":"Proteomic analysis; recombinant protein phosphorylation assays with MASTL, PKA, PKG; phospho-mutant analysis; PP2A activity assays in platelets","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and phospho-mutants in human platelets; single lab, multiple methods","pmids":["32085646"],"is_preprint":false},{"year":2021,"finding":"ARPP-19 and ARPP-16 are intrinsically disordered proteins. Their interaction with PP2A is mediated by a linear motif interacting with the PP2A A subunit (modest affinity), and both proteins transiently interact with the B56 subunit weakly via multiple interaction motifs.","method":"NMR spectroscopy; SAXS; microscale thermophoresis","journal":"Frontiers in molecular biosciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — structural characterization by NMR+SAXS with direct binding measurements; single lab, multiple biophysical methods","pmids":["33842550"],"is_preprint":false},{"year":2025,"finding":"SF3B1 K700E mutation increases inclusion of ARPP19 exon 2, producing an ARPP19-long isoform that sustains PP2A-B55 inhibition and promotes mitotic progression. Ectopic expression of ARPP19-long accelerated mitotic exit. Pharmacological inhibition of DYRK1A or broad serine/threonine phosphatases shifted ARPP19 exon 2 inclusion in the same direction as SF3B1 K700E, indicating a kinase-phosphatase signaling axis influences this splice event.","method":"RNA-seq in K562 cells expressing SF3B1 K700E; siRNA knockdown of SF3B1 in HeLa cells; ectopic ARPP19-long overexpression; mitotic timing assays; pharmacological inhibition","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional assay with ectopic isoform expression and mitotic timing readout; preprint, single lab","pmids":["bio_10.1101_2025.05.08.652831"],"is_preprint":true}],"current_model":"ARPP19 is an intrinsically disordered protein that acts as a central integrator of mitotic/meiotic signaling: when phosphorylated at S67 by Greatwall kinase, it binds and potently inhibits PP2A:B55 (through multiple contacts on the B55 subunit as revealed by cryo-EM) to sustain Cdk1 activation and mitotic entry; when phosphorylated at S109 by PKA, it maintains prophase arrest in oocytes; PP2A-B55δ itself dephosphorylates S109 to initiate meiotic resumption, while the phosphatase Fcp1 dephosphorylates a Cdk1-dependent S23 site to ensure timely mitotic exit and chromosome stability; in striatal neurons, the related ARPP-16 isoform is phosphorylated at S46 by MAST3 kinase to basally inhibit PP2A, an effect opposed by PKA-mediated S88 phosphorylation, creating a cAMP-regulated switch in PP2A activity; additionally, ARPP19 binds the 3' end of GAP-43 mRNA in a PKA-phosphorylation-dependent manner to regulate mRNA stability downstream of NGF signaling."},"narrative":{"mechanistic_narrative":"ARPP19 is an intrinsically disordered protein that functions as a regulatable inhibitor of protein phosphatase PP2A, integrating opposing kinase inputs to control the timing of mitotic and meiotic transitions [PMID:21164014, PMID:24525567]. Upon phosphorylation at S67 by Greatwall kinase, ARPP19 binds PP2A-B55δ and inhibits its activity, sustaining Cdk1 activation and driving M-phase entry; this step is essential within the Cdk1 auto-amplification loop [PMID:21164014, PMID:23781026]. The phospho-S67 mark confers high affinity and slow dephosphorylation kinetics, allowing ARPP19 to act as a competitive inhibitor of PP2A-B55 substrates, and cryo-EM and NMR show the disordered protein engages multiple distinct sites on the B55 subunit [PMID:34117214, PMID:38123684]. A second, antagonistic input is provided by PKA, which phosphorylates ARPP19 at S109 to maintain prophase arrest in oocytes; this PKA site is itself dephosphorylated by PP2A-B55δ to initiate meiotic resumption, and reciprocal feedback between S67 and S109 coordinates phosphatase inhibition with Cyclin B/Cdk1 activation [PMID:24525567, PMID:34117214, PMID:33758202]. ARPP19 is genetically essential for mouse embryogenesis and for proper mitotic dephosphorylation timing, a role its paralog ENSA cannot substitute [PMID:30626720]. A Cdk1-dependent S23 phosphorylation, removed by Fcp1 at mitotic exit, tunes the timing of exit and safeguards chromosome segregation [PMID:40447768]. The striatum-enriched isoform ARPP-16 is phosphorylated at S46 by MAST3 to inhibit PP2A and is opposed by PKA-mediated S88 phosphorylation, establishing a cAMP-regulated switch governing PP2A activity in neurons [PMID:28167675, PMID:28613156]. Beyond cell-cycle control, ARPP-19 binds the 3' region of GAP-43 mRNA in a PKA-phosphorylation-dependent manner to regulate its stability downstream of NGF [PMID:12221279].","teleology":[{"year":1990,"claim":"Established ARPP-16/ARPP-19 as a pair of PKA substrates differing only by an N-terminal extension, defining the protein and its regulatory phosphoacceptor.","evidence":"Protein purification, cDNA cloning, and in vitro PKA phosphorylation assays","pmids":["2160982"],"confidence":"Medium","gaps":["No cellular function assigned at this stage","Phosphatase target PP2A not yet identified"]},{"year":2001,"claim":"Linked ARPP phosphorylation to dopamine receptor signaling, showing PKA-site phosphorylation is dynamically regulated by D1/D2 receptor activity in striatum.","evidence":"In vitro kinase assays, phospho-specific immunoblotting, and striatal slice pharmacology","pmids":["11279279"],"confidence":"Medium","gaps":["Downstream effector of phosphorylated ARPP unknown","No mechanistic link to PP2A yet"]},{"year":2002,"claim":"Revealed an RNA-regulatory role distinct from phosphatase control, showing PKA-phosphorylated ARPP-19 binds GAP-43 mRNA to control its stability under NGF.","evidence":"RNA-protein binding, 3'UTR reporter assays, and phospho-site mutagenesis in PC12 cells","pmids":["12221279"],"confidence":"Medium","gaps":["RNA-binding determinants not mapped","Generality beyond GAP-43 mRNA untested","Relation to PP2A function unresolved"]},{"year":2010,"claim":"Defined ARPP19's core mitotic function: Greatwall-phosphorylated ARPP19 inhibits PP2A to promote mitotic entry, with endogenous ARPP19 (not ENSA) responsible in egg extracts.","evidence":"Greatwall-substrate identification, co-IP, and depletion/add-back in Xenopus egg extracts","pmids":["21164014"],"confidence":"High","gaps":["Specific phosphosite and PP2A holoenzyme not yet pinned down","Structural basis of inhibition unknown"]},{"year":2013,"claim":"Identified S67 as the Greatwall site and PP2A-B55δ as the target, placing ARPP19 inside the Cdk1 auto-amplification loop and showing S67 phosphorylation escapes PKA control.","evidence":"Phospho-mutant analysis, PP2A activity assays, and co-IP in Xenopus oocytes","pmids":["23781026"],"confidence":"High","gaps":["Kinetic basis of inhibition not quantified","Crosstalk with the PKA site mechanistically undefined"]},{"year":2014,"claim":"Established the antagonistic PKA arm: S109 phosphorylation maintains prophase arrest, and progesterone-driven partial dephosphorylation permits Cdk1 activation, positioning ARPP19 as an integrator of PKA and Greatwall signals.","evidence":"S109A/S109D phospho-mutants, kinase assays, and PKA manipulation in Xenopus oocytes","pmids":["24525567"],"confidence":"High","gaps":["Phosphatase removing S109 not yet identified","Quantitative coupling of S67 and S109 unresolved"]},{"year":2017,"claim":"Extended the model to neurons, showing MAST3 phosphorylates ARPP-16 at S46 to selectively inhibit B55α/B56δ-PP2A, with PKA at S88 opposing this, defined by direct A-subunit interaction and a conditional-KO substrate phenotype.","evidence":"In vitro kinase assays, co-IP, and CaMKIIα::cre conditional ARPP-16/19 knockout mouse with phospho-substrate readouts","pmids":["28167675"],"confidence":"High","gaps":["Full set of neuronal PP2A substrates incomplete","Physiological/behavioral consequences not fully mapped"]},{"year":2017,"claim":"Resolved the PKA-MAST3 logic as a mutually suppressive, switch-like circuit controlling neuronal PP2A activity in response to cAMP.","evidence":"In vitro kinase assays, mass spectrometry, phospho-mutants, and mathematical modeling","pmids":["28613156","28722544"],"confidence":"High","gaps":["In vivo demonstration of switch dynamics limited","Cell-cycle vs neuronal Greatwall/MAST3 division of labor not unified"]},{"year":2019,"claim":"Demonstrated genetic necessity and non-redundancy: ARPP19 is essential for embryogenesis and mitotic dephosphorylation timing, while ENSA acts in S phase, separating paralog functions.","evidence":"Conditional Arpp19 and Ensa knockout mice with MEF viability and cell-cycle phospho-timing analyses","pmids":["30626720"],"confidence":"High","gaps":["Molecular basis of ARPP19/ENSA functional divergence unclear","S-phase mechanism of ENSA not addressed for ARPP19"]},{"year":2021,"claim":"Provided the kinetic and feedback mechanism: phospho-S67 confers slow-turnover competitive inhibition of PP2A-B55, S109 restricts S67 via accelerated dephosphorylation, and PP2A-B55δ dephosphorylates S109 to release prophase arrest.","evidence":"In vitro phosphatase kinetics, binding affinity measurements, phospho-mutants, and Xenopus extract/oocyte reconstitution","pmids":["34117214","33758202"],"confidence":"High","gaps":["Atomic-level basis of multivalent binding not yet visualized","Regulation of PP2A-B55δ dual targeting of S67 vs S109 incompletely defined"]},{"year":2021,"claim":"Characterized ARPP19/ARPP-16 as intrinsically disordered proteins engaging PP2A through a linear A-subunit motif plus weak multivalent B56 contacts, framing the structural basis of recognition.","evidence":"NMR, SAXS, and microscale thermophoresis binding measurements","pmids":["33842550"],"confidence":"Medium","gaps":["Affinity in isolation is modest; phospho-dependent contacts not fully resolved","Functional weight of individual motifs untested"]},{"year":2023,"claim":"Delivered the structural mechanism: cryo-EM and NMR show phospho-ARPP19 occupies multiple distinct B55 sites, explaining how PP2A:B55 recruits both substrates and inhibitors.","evidence":"Single-particle cryo-EM, NMR, and biophysical assays of PP2A:B55-ARPP19","pmids":["38123684"],"confidence":"High","gaps":["Dynamics of the disordered regions in the complex not fully captured","Structural comparison with ENSA-bound state absent"]},{"year":2025,"claim":"Identified an additional Cdk1-dependent S23 phosphorylation, removed by Fcp1, that tunes mitotic exit timing and chromosome segregation fidelity.","evidence":"Phospho-specific antibodies, CRISPR endogenous phospho-mutant substitution, okadaic-acid-resistant phosphatase assays, and segregation/timing readouts in human cells","pmids":["40447768"],"confidence":"High","gaps":["How S23 phosphorylation alters PP2A inhibition mechanistically unclear","Kinase identity beyond Cdk1-dependence not defined"]},{"year":2025,"claim":"Connected splicing regulation to ARPP19 output, showing SF3B1 K700E favors exon-2 inclusion to produce an ARPP19-long isoform that sustains PP2A-B55 inhibition and accelerates mitotic exit.","evidence":"RNA-seq and SF3B1 knockdown, ectopic ARPP19-long expression with mitotic timing, and DYRK1A/phosphatase inhibition (preprint)","pmids":["bio_10.1101_2025.05.08.652831"],"confidence":"Medium","gaps":["Preprint; isoform mechanism not independently confirmed","Physiological relevance in SF3B1-mutant disease not established"]},{"year":null,"claim":"How ARPP19's distinct functional modes—mitotic PP2A inhibition, neuronal cAMP switching, and RNA-stability control—are coordinated within a single cell, and what distinguishes ARPP19 from ENSA at the molecular level, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model reconciling cell-cycle and neuronal roles","Structural/sequence basis of ARPP19 vs ENSA divergence undefined","RNA-binding mechanism uncharacterized at residue level"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3,6,8]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[12]}],"localization":[],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,1,5,9]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4,10]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[2,7]}],"complexes":[],"partners":["PP2A","PPP2R2D","PPP2R1A","MASTL","MAST3","PRKACA","FCP1","GAP-43"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P56211","full_name":"cAMP-regulated phosphoprotein 19","aliases":[],"length_aa":112,"mass_kda":12.3,"function":"Protein phosphatase inhibitor that specifically inhibits protein phosphatase 2A (PP2A) during mitosis (PubMed:38123684). Inhibition of PP2A is enhanced when ARPP19 is phosphorylated (PubMed:38123684). When phosphorylated at Ser-62 during mitosis, specifically interacts with PPP2R2D (PR55-delta) and inhibits its activity, leading to inactivation of PP2A, an essential condition to keep cyclin-B1-CDK1 activity high during M phase (PubMed:21164014). May indirectly enhance GAP-43 expression (By similarity)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P56211/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARPP19","classification":"Not Classified","n_dependent_lines":163,"n_total_lines":1208,"dependency_fraction":0.13493377483443708},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ARPP19","total_profiled":1310},"omim":[{"mim_id":"608221","title":"MICROTUBULE-ASSOCIATED SERINE/THREONINE KINASE-LIKE; MASTL","url":"https://www.omim.org/entry/608221"},{"mim_id":"605488","title":"cAMP-REGULATED PHOSPHOPROTEIN 21; ARPP21","url":"https://www.omim.org/entry/605488"},{"mim_id":"605487","title":"cAMP-REGULATED PHOSPHOPROTEIN 19; ARPP19","url":"https://www.omim.org/entry/605487"},{"mim_id":"603061","title":"ENDOSULFINE, ALPHA; ENSA","url":"https://www.omim.org/entry/603061"},{"mim_id":"176915","title":"PROTEIN PHOSPHATASE 2, CATALYTIC SUBUNIT, ALPHA ISOFORM; PPP2CA","url":"https://www.omim.org/entry/176915"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Basal body","reliability":"Approved"},{"location":"Nucleoli","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":481.4}],"url":"https://www.proteinatlas.org/search/ARPP19"},"hgnc":{"alias_symbol":["ARPP-19","ARPP-16","ARPP16","ENSAL"],"prev_symbol":[]},"alphafold":{"accession":"P56211","domains":[{"cath_id":"-","chopping":"11-69","consensus_level":"medium","plddt":71.8366,"start":11,"end":69}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P56211","model_url":"https://alphafold.ebi.ac.uk/files/AF-P56211-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P56211-F1-predicted_aligned_error_v6.png","plddt_mean":68.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARPP19","jax_strain_url":"https://www.jax.org/strain/search?query=ARPP19"},"sequence":{"accession":"P56211","fasta_url":"https://rest.uniprot.org/uniprotkb/P56211.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P56211/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P56211"}},"corpus_meta":[{"pmid":"21164014","id":"PMC_21164014","title":"The substrate of Greatwall kinase, Arpp19, controls mitosis by inhibiting protein phosphatase 2A.","date":"2010","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/21164014","citation_count":354,"is_preprint":false},{"pmid":"25736597","id":"PMC_25736597","title":"MicroRNA-320a sensitizes tamoxifen-resistant breast cancer cells to tamoxifen by targeting ARPP-19 and ERRγ.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/25736597","citation_count":80,"is_preprint":false},{"pmid":"2158525","id":"PMC_2158525","title":"Differential expression of ARPP-16 and ARPP-19, two highly related cAMP-regulated phosphoproteins, one of which is specifically associated with dopamine-innervated brain regions.","date":"1990","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/2158525","citation_count":57,"is_preprint":false},{"pmid":"8120638","id":"PMC_8120638","title":"Expression of mRNAs encoding ARPP-16/19, ARPP-21, and DARPP-32 in human brain tissue.","date":"1994","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/8120638","citation_count":53,"is_preprint":false},{"pmid":"12221279","id":"PMC_12221279","title":"Nerve growth factor controls GAP-43 mRNA stability via the phosphoprotein ARPP-19.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12221279","citation_count":50,"is_preprint":false},{"pmid":"11279279","id":"PMC_11279279","title":"ARPP-16/ARPP-19: a highly conserved family of cAMP-regulated phosphoproteins.","date":"2001","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11279279","citation_count":47,"is_preprint":false},{"pmid":"2160982","id":"PMC_2160982","title":"Purification and cDNA cloning of ARPP-16, a cAMP-regulated phosphoprotein enriched in basal ganglia, and of a related phosphoprotein, ARPP-19.","date":"1990","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2160982","citation_count":46,"is_preprint":false},{"pmid":"11771749","id":"PMC_11771749","title":"Decreased levels of ARPP-19 and PKA in brains of Down syndrome and Alzheimer's disease.","date":"2001","source":"Journal of neural transmission. 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conserved across plants and most eukaryotes.","date":"2015","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25666948","citation_count":14,"is_preprint":false},{"pmid":"21630148","id":"PMC_21630148","title":"Greatwall kinase, ARPP-19 and protein phosphatase 2A: shifting the mitosis paradigm.","date":"2011","source":"Results and problems in cell differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/21630148","citation_count":13,"is_preprint":false},{"pmid":"31717978","id":"PMC_31717978","title":"Arpp19 Promotes Myc and Cip2a Expression and Associates with Patient Relapse in Acute Myeloid Leukemia.","date":"2019","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/31717978","citation_count":12,"is_preprint":false},{"pmid":"34117214","id":"PMC_34117214","title":"The study of the determinants controlling Arpp19 phosphatase-inhibitory activity reveals an Arpp19/PP2A-B55 feedback loop.","date":"2021","source":"Nature 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In Xenopus egg extracts, endogenous ARPP19 (but not α-Endosulfine/ENSA) is responsible for PP2A inhibition at mitotic entry. Without Greatwall activity, ARPP19 is dephosphorylated and loses its capacity to bind and inhibit PP2A.\",\n      \"method\": \"Biochemical identification of Greatwall substrates in Xenopus egg extracts; co-immunoprecipitation; phosphatase activity assays; depletion/add-back experiments\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution in egg extracts with depletion/add-back, multiple orthogonal assays; independently replicated in subsequent studies\",\n      \"pmids\": [\"21164014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Phosphorylation of ARPP19 at S67 by Greatwall kinase promotes its binding to PP2A-B55δ, inhibiting PP2A activity. This process is controlled by Cdk1 and plays an essential role within the Cdk1 auto-amplification loop for entry into the first meiotic division. Once phosphorylated by Greatwall at S67, ARPP19 escapes negative regulation by PKA.\",\n      \"method\": \"Xenopus oocyte microinjection; phospho-specific mutants; PP2A activity assays; co-immunoprecipitation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstitution in physiologically intact Xenopus oocytes, phospho-mutant analysis, PP2A activity measurements, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"23781026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ARPP19 phosphorylation at serine 109 by PKA is necessary and sufficient for maintaining Xenopus oocytes arrested in prophase. Progesterone promotes partial dephosphorylation of ARPP19 at S109, enabling a threshold level of active Cdk1 to form. Active Cdk1 then initiates the MPF auto-amplification loop requiring Greatwall-dependent phosphorylation of ARPP19 at S67. Thus ARPP19 integrates opposing PKA and Greatwall signals at a crossroads in meiotic M-phase control.\",\n      \"method\": \"Xenopus oocyte microinjection; phospho-specific mutants (S109A, S109D); kinase activity assays; PKA manipulation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — phosphomutant rescue/dominant experiments in intact oocytes with multiple readouts; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"24525567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ARPP-16 (the striatum-enriched splice variant sharing the ARPP19 locus) is phosphorylated at Ser46 by MAST3 kinase in vitro and in vivo. This phosphorylation converts ARPP-16 into a selective inhibitor of B55α- and B56δ-containing PP2A heterotrimers. ARPP-16 interacts directly with the PP2A scaffolding A subunit. PKA phosphorylation at Ser88 opposes MAST3, causing dephosphorylation of Ser46 and disinhibition of PP2A. Conditional knockout of ARPP-16 results in dephosphorylation of PP2A substrates including phospho-Thr75-DARPP-32, phospho-T308-Akt, and phospho-T202/Y204-ERK.\",\n      \"method\": \"In vitro kinase assay; co-immunoprecipitation; conditional knockout mouse (CaMKIIα::cre/floxed ARPP-16/19); phospho-specific antibodies; PP2A activity assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assays plus conditional KO with defined substrate phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"28167675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PKA phosphorylation and MAST3 phosphorylation of ARPP-16/19 are mutually suppressive: phosphorylation by PKA prevents MAST3 from acting and prevents PP2A inhibition by MAST3-phosphorylated ARPP-16. PKA also phosphorylates MAST3 at multiple sites, inhibiting MAST3 kinase activity. Together these interactions create a switch-like response to cAMP regulating PP2A activity in striatal neurons.\",\n      \"method\": \"In vitro kinase assays; mass spectrometry; mathematical modeling; phospho-mutant analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assays with phospho-mutants, MS, and quantitative mathematical modeling; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28613156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Using conditional knockout mouse models, ARPP19 (but not ENSA) was found essential for mouse embryogenesis. Arpp19 ablation dramatically decreased MEF viability by perturbing the temporal pattern of protein dephosphorylation during mitotic progression, consistent with a drop in PP2A-B55 activity inhibition. ENSA could not compensate for ARPP19 loss in mitotic division. By contrast, ENSA ablation (but not ARPP19 ablation) perturbed S phase.\",\n      \"method\": \"Conditional knockout mouse models (Arpp19 and Ensa); mouse embryonic fibroblast viability assays; cell cycle analysis; phospho-protein timing analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO mouse models with defined cellular phenotypes; distinct roles established for ARPP19 vs ENSA by genetic comparison\",\n      \"pmids\": [\"30626720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Molecular determinants of ARPP19's S67 phosphorylation confer high affinity and slow dephosphorylation kinetics when bound to PP2A-B55, enabling it to act as a competitive inhibitor of PP2A-B55 substrates. Phospho-S109 (PKA site) restricts S67 phosphorylation by increasing PP2A-B55-catalyzed dephosphorylation of S67, and a double feedback loop between S67 and S109 phosphorylation sites coordinates PP2A-B55 inhibition with Cyclin B/Cdk1 activation during cell division.\",\n      \"method\": \"In vitro phosphatase kinetics assays; phospho-mutant analysis; binding affinity measurements; Xenopus egg extract reconstitution\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with kinetic measurements, phosphomutant analysis, and cell-free extract functional assays; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"34117214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PP2A-B55δ is the phosphatase responsible for dephosphorylating ARPP19 at S109 (the PKA site) to initiate prophase release in Xenopus oocytes. In prophase, PKA and PP2A-B55δ are simultaneously active. When progesterone reduces PKA activity, PP2A-B55δ dephosphorylates S109, unlocking the prophase block. Thus PP2A-B55δ acts at two distinct ARPP19 sites—opposing PKA (at S109) and being inhibited by Gwl-phosphorylated ARPP19 (at S67).\",\n      \"method\": \"Xenopus oocyte microinjection; phosphatase inhibitor experiments; PP2A-B55δ immunodepletion; phospho-specific assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — genetic and biochemical identification of the phosphatase acting on S109 in intact oocytes, multiple approaches; single lab\",\n      \"pmids\": [\"33758202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cryo-EM structures of PP2A:B55 bound to phosphorylated ARPP19 reveal that the intrinsically disordered ARPP19 binds PP2A:B55 using multiple distinct binding sites on the B55 subunit, explaining how both substrates and inhibitors are recruited to PP2A:B55. Complementary NMR spectroscopy confirmed the structural findings. The structures provide a molecular mechanism for PP2A:B55 inhibition by ARPP19.\",\n      \"method\": \"Single-particle cryo-EM; NMR spectroscopy; biophysical/biochemical assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution cryo-EM structure with complementary NMR validation and biochemical assays; published in peer-reviewed journal\",\n      \"pmids\": [\"38123684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARPP19 is phosphorylated in a Cdk1-dependent manner at serine 23 (a site absent in mammalian ENSA) in mitotic human cells, and dephosphorylated at S23 during mitotic exit by the phosphatase Fcp1 (resistant to okadaic acid). Substituting endogenous ARPP19 with a S23-phosphorylation-resistant mutant increased chromosome segregation errors and accelerated mitotic exit; a phosphomimetic S23 mutant delayed mitotic exit. This phosphorylation switch grants timely mitotic exit and chromosome stability.\",\n      \"method\": \"Phospho-specific antibodies in human cells; CRISPR/endogenous substitution with phospho-mutants; phosphatase inhibitor experiments (okadaic acid); chromosome segregation assays; mitotic timing assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — endogenous mutant substitution in human cells with multiple functional readouts (chromosome segregation, mitotic timing), phosphatase identification; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40447768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ARPP-16 and ARPP-19 are substrates for PKA; both proteins contain a conserved consensus PKA phosphorylation site (RKPSLVA). In striatal slices, ARPP-16 phosphorylation increases in response to D1 dopamine receptor activation and decreases with D2 dopamine receptor activation. In non-neuronal cells, ARPP-19 is highly phosphorylated in response to PKA activation.\",\n      \"method\": \"In vitro kinase assay; phospho-specific antibody immunoblotting; striatal slice pharmacology\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal use of phospho-specific antibodies in intact cells and slices plus in vitro kinase assays; single lab, two methods\",\n      \"pmids\": [\"11279279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"ARPP-16 and ARPP-19 were purified to homogeneity and identified as substrates for cAMP-dependent protein kinase (PKA). ARPP-19 contains 16 additional NH2-terminal amino acids compared to ARPP-16; both are encoded by related cDNA clones sharing identical 3'-untranslated sequences, suggesting they arise from alternative transcription/splicing.\",\n      \"method\": \"Protein purification; cDNA cloning and sequencing; in vitro PKA phosphorylation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct biochemical purification and in vitro kinase assay; single lab, foundational biochemical characterization\",\n      \"pmids\": [\"2160982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ARPP-19 mediates NGF-dependent regulation of GAP-43 mRNA stability. In an NGF-dependent manner, ARPP-19 binds to the 3' region of GAP-43 mRNA that controls its half-life. Mutation of serine 104 (the PKA phosphorylation site) to alanine or aspartate abolished regulation of GAP-43 mRNA reporter expression in PC12 cells, demonstrating that PKA-dependent phosphorylation of ARPP-19 is required for this post-transcriptional function.\",\n      \"method\": \"RNA-protein binding assay; PC12 cell overexpression; reporter assays with 3'UTR constructs; site-directed mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA binding, reporter assay, and phospho-site mutagenesis in intact cells; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"12221279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Greatwall kinase-dependent phosphorylation of ARPP19 at S67 is dominant over PKA-dependent phosphorylation at S109 in controlling Cdk1 activation. Both PKA and Gwl phosphorylate ARPP19 independently of each other. Cdk1 is not directly involved in regulating the biological activity of ARPP19.\",\n      \"method\": \"Xenopus oocyte microinjection; phospho-specific mutants; kinase activity assays\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — intact oocyte phosphomutant epistasis experiments; single lab, two orthogonal phospho-site mutations tested functionally\",\n      \"pmids\": [\"28722544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In human platelets, ARPP19 S62 is phosphorylated by MASTL (or a related kinase) and both S62 and S104 are dephosphorylated by platelet PP2A. Only S62-phosphorylated ARPP19 (but not S104-phosphorylated) acts as a PP2A inhibitor in this context. The entire MASTL-ENSA/ARPP19-PP2A pathway is present and active in anucleate platelets.\",\n      \"method\": \"Proteomic analysis; recombinant protein phosphorylation assays with MASTL, PKA, PKG; phospho-mutant analysis; PP2A activity assays in platelets\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and phospho-mutants in human platelets; single lab, multiple methods\",\n      \"pmids\": [\"32085646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ARPP-19 and ARPP-16 are intrinsically disordered proteins. Their interaction with PP2A is mediated by a linear motif interacting with the PP2A A subunit (modest affinity), and both proteins transiently interact with the B56 subunit weakly via multiple interaction motifs.\",\n      \"method\": \"NMR spectroscopy; SAXS; microscale thermophoresis\",\n      \"journal\": \"Frontiers in molecular biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural characterization by NMR+SAXS with direct binding measurements; single lab, multiple biophysical methods\",\n      \"pmids\": [\"33842550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SF3B1 K700E mutation increases inclusion of ARPP19 exon 2, producing an ARPP19-long isoform that sustains PP2A-B55 inhibition and promotes mitotic progression. Ectopic expression of ARPP19-long accelerated mitotic exit. Pharmacological inhibition of DYRK1A or broad serine/threonine phosphatases shifted ARPP19 exon 2 inclusion in the same direction as SF3B1 K700E, indicating a kinase-phosphatase signaling axis influences this splice event.\",\n      \"method\": \"RNA-seq in K562 cells expressing SF3B1 K700E; siRNA knockdown of SF3B1 in HeLa cells; ectopic ARPP19-long overexpression; mitotic timing assays; pharmacological inhibition\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional assay with ectopic isoform expression and mitotic timing readout; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.05.08.652831\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ARPP19 is an intrinsically disordered protein that acts as a central integrator of mitotic/meiotic signaling: when phosphorylated at S67 by Greatwall kinase, it binds and potently inhibits PP2A:B55 (through multiple contacts on the B55 subunit as revealed by cryo-EM) to sustain Cdk1 activation and mitotic entry; when phosphorylated at S109 by PKA, it maintains prophase arrest in oocytes; PP2A-B55δ itself dephosphorylates S109 to initiate meiotic resumption, while the phosphatase Fcp1 dephosphorylates a Cdk1-dependent S23 site to ensure timely mitotic exit and chromosome stability; in striatal neurons, the related ARPP-16 isoform is phosphorylated at S46 by MAST3 kinase to basally inhibit PP2A, an effect opposed by PKA-mediated S88 phosphorylation, creating a cAMP-regulated switch in PP2A activity; additionally, ARPP19 binds the 3' end of GAP-43 mRNA in a PKA-phosphorylation-dependent manner to regulate mRNA stability downstream of NGF signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARPP19 is an intrinsically disordered protein that functions as a regulatable inhibitor of protein phosphatase PP2A, integrating opposing kinase inputs to control the timing of mitotic and meiotic transitions [#0, #2]. Upon phosphorylation at S67 by Greatwall kinase, ARPP19 binds PP2A-B55\\u03b4 and inhibits its activity, sustaining Cdk1 activation and driving M-phase entry; this step is essential within the Cdk1 auto-amplification loop [#0, #1]. The phospho-S67 mark confers high affinity and slow dephosphorylation kinetics, allowing ARPP19 to act as a competitive inhibitor of PP2A-B55 substrates, and cryo-EM and NMR show the disordered protein engages multiple distinct sites on the B55 subunit [#6, #8]. A second, antagonistic input is provided by PKA, which phosphorylates ARPP19 at S109 to maintain prophase arrest in oocytes; this PKA site is itself dephosphorylated by PP2A-B55\\u03b4 to initiate meiotic resumption, and reciprocal feedback between S67 and S109 coordinates phosphatase inhibition with Cyclin B/Cdk1 activation [#2, #6, #7]. ARPP19 is genetically essential for mouse embryogenesis and for proper mitotic dephosphorylation timing, a role its paralog ENSA cannot substitute [#5]. A Cdk1-dependent S23 phosphorylation, removed by Fcp1 at mitotic exit, tunes the timing of exit and safeguards chromosome segregation [#9]. The striatum-enriched isoform ARPP-16 is phosphorylated at S46 by MAST3 to inhibit PP2A and is opposed by PKA-mediated S88 phosphorylation, establishing a cAMP-regulated switch governing PP2A activity in neurons [#3, #4]. Beyond cell-cycle control, ARPP-19 binds the 3' region of GAP-43 mRNA in a PKA-phosphorylation-dependent manner to regulate its stability downstream of NGF [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established ARPP-16/ARPP-19 as a pair of PKA substrates differing only by an N-terminal extension, defining the protein and its regulatory phosphoacceptor.\",\n      \"evidence\": \"Protein purification, cDNA cloning, and in vitro PKA phosphorylation assays\",\n      \"pmids\": [\"2160982\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cellular function assigned at this stage\", \"Phosphatase target PP2A not yet identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Linked ARPP phosphorylation to dopamine receptor signaling, showing PKA-site phosphorylation is dynamically regulated by D1/D2 receptor activity in striatum.\",\n      \"evidence\": \"In vitro kinase assays, phospho-specific immunoblotting, and striatal slice pharmacology\",\n      \"pmids\": [\"11279279\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effector of phosphorylated ARPP unknown\", \"No mechanistic link to PP2A yet\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Revealed an RNA-regulatory role distinct from phosphatase control, showing PKA-phosphorylated ARPP-19 binds GAP-43 mRNA to control its stability under NGF.\",\n      \"evidence\": \"RNA-protein binding, 3'UTR reporter assays, and phospho-site mutagenesis in PC12 cells\",\n      \"pmids\": [\"12221279\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RNA-binding determinants not mapped\", \"Generality beyond GAP-43 mRNA untested\", \"Relation to PP2A function unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined ARPP19's core mitotic function: Greatwall-phosphorylated ARPP19 inhibits PP2A to promote mitotic entry, with endogenous ARPP19 (not ENSA) responsible in egg extracts.\",\n      \"evidence\": \"Greatwall-substrate identification, co-IP, and depletion/add-back in Xenopus egg extracts\",\n      \"pmids\": [\"21164014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific phosphosite and PP2A holoenzyme not yet pinned down\", \"Structural basis of inhibition unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified S67 as the Greatwall site and PP2A-B55\\u03b4 as the target, placing ARPP19 inside the Cdk1 auto-amplification loop and showing S67 phosphorylation escapes PKA control.\",\n      \"evidence\": \"Phospho-mutant analysis, PP2A activity assays, and co-IP in Xenopus oocytes\",\n      \"pmids\": [\"23781026\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetic basis of inhibition not quantified\", \"Crosstalk with the PKA site mechanistically undefined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established the antagonistic PKA arm: S109 phosphorylation maintains prophase arrest, and progesterone-driven partial dephosphorylation permits Cdk1 activation, positioning ARPP19 as an integrator of PKA and Greatwall signals.\",\n      \"evidence\": \"S109A/S109D phospho-mutants, kinase assays, and PKA manipulation in Xenopus oocytes\",\n      \"pmids\": [\"24525567\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphatase removing S109 not yet identified\", \"Quantitative coupling of S67 and S109 unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended the model to neurons, showing MAST3 phosphorylates ARPP-16 at S46 to selectively inhibit B55\\u03b1/B56\\u03b4-PP2A, with PKA at S88 opposing this, defined by direct A-subunit interaction and a conditional-KO substrate phenotype.\",\n      \"evidence\": \"In vitro kinase assays, co-IP, and CaMKII\\u03b1::cre conditional ARPP-16/19 knockout mouse with phospho-substrate readouts\",\n      \"pmids\": [\"28167675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of neuronal PP2A substrates incomplete\", \"Physiological/behavioral consequences not fully mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Resolved the PKA-MAST3 logic as a mutually suppressive, switch-like circuit controlling neuronal PP2A activity in response to cAMP.\",\n      \"evidence\": \"In vitro kinase assays, mass spectrometry, phospho-mutants, and mathematical modeling\",\n      \"pmids\": [\"28613156\", \"28722544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo demonstration of switch dynamics limited\", \"Cell-cycle vs neuronal Greatwall/MAST3 division of labor not unified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated genetic necessity and non-redundancy: ARPP19 is essential for embryogenesis and mitotic dephosphorylation timing, while ENSA acts in S phase, separating paralog functions.\",\n      \"evidence\": \"Conditional Arpp19 and Ensa knockout mice with MEF viability and cell-cycle phospho-timing analyses\",\n      \"pmids\": [\"30626720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of ARPP19/ENSA functional divergence unclear\", \"S-phase mechanism of ENSA not addressed for ARPP19\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided the kinetic and feedback mechanism: phospho-S67 confers slow-turnover competitive inhibition of PP2A-B55, S109 restricts S67 via accelerated dephosphorylation, and PP2A-B55\\u03b4 dephosphorylates S109 to release prophase arrest.\",\n      \"evidence\": \"In vitro phosphatase kinetics, binding affinity measurements, phospho-mutants, and Xenopus extract/oocyte reconstitution\",\n      \"pmids\": [\"34117214\", \"33758202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-level basis of multivalent binding not yet visualized\", \"Regulation of PP2A-B55\\u03b4 dual targeting of S67 vs S109 incompletely defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Characterized ARPP19/ARPP-16 as intrinsically disordered proteins engaging PP2A through a linear A-subunit motif plus weak multivalent B56 contacts, framing the structural basis of recognition.\",\n      \"evidence\": \"NMR, SAXS, and microscale thermophoresis binding measurements\",\n      \"pmids\": [\"33842550\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Affinity in isolation is modest; phospho-dependent contacts not fully resolved\", \"Functional weight of individual motifs untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Delivered the structural mechanism: cryo-EM and NMR show phospho-ARPP19 occupies multiple distinct B55 sites, explaining how PP2A:B55 recruits both substrates and inhibitors.\",\n      \"evidence\": \"Single-particle cryo-EM, NMR, and biophysical assays of PP2A:B55-ARPP19\",\n      \"pmids\": [\"38123684\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of the disordered regions in the complex not fully captured\", \"Structural comparison with ENSA-bound state absent\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified an additional Cdk1-dependent S23 phosphorylation, removed by Fcp1, that tunes mitotic exit timing and chromosome segregation fidelity.\",\n      \"evidence\": \"Phospho-specific antibodies, CRISPR endogenous phospho-mutant substitution, okadaic-acid-resistant phosphatase assays, and segregation/timing readouts in human cells\",\n      \"pmids\": [\"40447768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How S23 phosphorylation alters PP2A inhibition mechanistically unclear\", \"Kinase identity beyond Cdk1-dependence not defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected splicing regulation to ARPP19 output, showing SF3B1 K700E favors exon-2 inclusion to produce an ARPP19-long isoform that sustains PP2A-B55 inhibition and accelerates mitotic exit.\",\n      \"evidence\": \"RNA-seq and SF3B1 knockdown, ectopic ARPP19-long expression with mitotic timing, and DYRK1A/phosphatase inhibition (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.05.08.652831\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint; isoform mechanism not independently confirmed\", \"Physiological relevance in SF3B1-mutant disease not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ARPP19's distinct functional modes\\u2014mitotic PP2A inhibition, neuronal cAMP switching, and RNA-stability control\\u2014are coordinated within a single cell, and what distinguishes ARPP19 from ENSA at the molecular level, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model reconciling cell-cycle and neuronal roles\", \"Structural/sequence basis of ARPP19 vs ENSA divergence undefined\", \"RNA-binding mechanism uncharacterized at residue level\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3, 6, 8]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [12]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 1, 5, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4, 10]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PP2A\", \"PPP2R2D\", \"PPP2R1A\", \"MASTL\", \"MAST3\", \"PRKACA\", \"Fcp1\", \"GAP-43\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}