{"gene":"PIK3R1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1999,"finding":"Genetic disruption of p85alpha (and its splice variants p55alpha/p50alpha) in mice causes defects in B cell development and proliferation, with reduced peripheral mature B cells and decreased proliferative responses to anti-IgM, anti-CD40, and LPS, while T cell development remains normal, demonstrating a specific role for PIK3R1 in B cell signaling.","method":"RAG2-deficient blastocyst complementation system with p85alpha-p55alpha-p50alpha knockout mice","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with specific cellular phenotype, replicated across lymphocyte populations with defined functional readouts","pmids":["9888855"],"is_preprint":false},{"year":1999,"finding":"Pik3r1-/- mice show increased insulin sensitivity and hypoglycemia due to increased glucose transport in skeletal muscle and adipocytes; the isoform switch from p85alpha to p50alpha in knockout mice is associated with increased PtdIns(3,4,5)P3 generation and facilitated Glut4 translocation from low-density microsomes to the plasma membrane.","method":"Targeted gene disruption in mice; insulin-stimulated PI3K activity assay; PtdIns(3,4,5)P3 measurement; subcellular fractionation of Glut4","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple orthogonal biochemical readouts (PI3K activity, PIP3 levels, Glut4 fractionation), defined metabolic phenotype","pmids":["9988280"],"is_preprint":false},{"year":2001,"finding":"Somatic deletions in the inter-SH2 region of PIK3R1 proximal to the Ser608 autoregulatory site (e.g., a 23-amino-acid deletion) result in constitutive PI3K activation, establishing PIK3R1 as an oncogene in colon and ovarian tumors.","method":"SSCP/heteroduplex mutation analysis of primary tumors; expression of mutant p85alpha protein in cells with PI3K activity assay","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct functional assay of mutant protein activation, supported by primary tumor mutation data","pmids":["11606375"],"is_preprint":false},{"year":2002,"finding":"Heterozygous disruption of Pik3r1 reduces free p85alpha levels, restores the molecular balance between p85, p110, and IRS proteins, maintains normal PI3K activation while increasing insulin-stimulated Akt activity, and improves glucose tolerance and insulin sensitivity; this protects insulin-resistant mice from developing diabetes.","method":"Heterozygous Pik3r1 knockout in normal and insulin-resistant mice; PI3K activity assay; Akt phosphorylation; glucose tolerance tests","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic model with multiple orthogonal biochemical and metabolic readouts across multiple mouse models","pmids":["11781359"],"is_preprint":false},{"year":2003,"finding":"p85alpha-/- brown adipocyte cells show 70% reduction in p85 protein with parallel reduction of p110, 50% decrease in PI3K activity, and 30% decrease in Akt activity leading to decreased insulin-induced glucose uptake; p85alpha (but not p85beta) is required for insulin-stimulated JNK activation via cdc42 and MKK4, demonstrating a PI3K-independent signaling function.","method":"Gene-disrupted brown adipocyte cell lines; PI3K activity assay; Akt phosphorylation; glucose uptake; JNK activity; reconstitution with p85 mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal assays in defined KO cell lines, reconstitution experiments with domain mutants","pmids":["14504291"],"is_preprint":false},{"year":2004,"finding":"p85alpha possesses GTPase-activating protein (GAP) activity toward Rab5, Rab4, Cdc42, and Rac1 (with little activity toward Rab11), mediated by its BH domain; purified recombinant p85alpha directly binds Rab5; cells expressing BH domain mutants of p85 show reduced PDGFR degradation rates and sustained MAPK and Akt pathway activation.","method":"In vitro GAP assay with purified recombinant proteins; direct binding assay; BH domain mutant expression in cells; PDGFR degradation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted in vitro enzymatic assay with purified proteins, mutagenesis with functional cellular readout","pmids":["15377662"],"is_preprint":false},{"year":2005,"finding":"p85alpha-/- macrophages show 50% reduction in proliferation in response to M-CSF and GM-CSF, reduced migration and adhesion on fibronectin and VCAM-1, and defective phagocytosis; these are associated with reduced Akt and Rac activation (but not Erk activation), demonstrating a specific role for p85alpha in actin- and growth-based macrophage functions.","method":"Bone marrow-derived macrophages from p85alpha-/- mice; proliferation assays; wound-healing and chemotaxis assays; phagocytosis assay; Akt/Rac/Erk phosphorylation","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with multiple orthogonal functional and biochemical readouts in primary cells","pmids":["15769893"],"is_preprint":false},{"year":1997,"finding":"The p85alpha gene generates three regulatory subunit isoforms (p85alpha, p55alpha, p50alpha) via alternative splicing; p50alpha forms heterodimers with p110 but uniquely with both wortmannin-sensitive and wortmannin-insensitive forms, exhibits markedly higher capacity for PI3K activation by insulin, and has higher affinity for tyrosine-phosphorylated IRS-1 than p85alpha or p55alpha.","method":"Expression cloning using 32P-labeled IRS-1; Northern blotting; co-immunoprecipitation; PI3K activity assay; wortmannin labeling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical characterization across multiple methods (binding, activity, isoform-specific antibodies), replicated in multiple tissues","pmids":["9065454"],"is_preprint":false},{"year":2010,"finding":"p85alpha and p85beta form heterodimers that are disrupted by insulin treatment; the resulting p85 monomers interact with and increase nuclear translocation of the spliced form of XBP-1 (XBP-1s), promoting resolution of ER stress; this interaction is lost in ob/ob mice and restored by p85 overexpression in liver.","method":"Co-immunoprecipitation; nuclear fractionation; p85alpha/p85beta overexpression in ob/ob mice liver; XBP-1s nuclear localization assay","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, nuclear fractionation with functional consequence, in vivo rescue experiment","pmids":["20348926"],"is_preprint":false},{"year":2011,"finding":"PIK3R1 mutations in the nSH2 and iSH2 domains (e.g., delH450-E451, delK459, delY463-L466, delR574-T576, N564D) bind p110alpha and increase pAKT(Ser473) levels, demonstrating gain-of-function PI3K activation; truncation mutations (R348X, K511VfsX2) do not bind p110alpha and show no change in pAKT.","method":"Stable expression of mutant p85alpha in U2OS cells; co-immunoprecipitation of p110alpha; Western blot of phospho-AKT(Ser473)","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional assay of multiple mutants with co-IP and signaling readout, clear structure-function relationship established","pmids":["21478295"],"is_preprint":false},{"year":2011,"finding":"Multiple PIK3R1 and PIK3R2 mutations demonstrate gain-of-function PI3K pathway activation; p85alpha dimers bind and stabilize PTEN, and disruption of this interaction by mutations leads to PTEN destabilization and pathway activation, revealing a novel regulatory mechanism.","method":"Functional characterization of mutant proteins; co-immunoprecipitation of p85alpha dimers with PTEN; PI3K pathway signaling assays","journal":"Cancer discovery","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP of p85alpha dimer-PTEN complex, functional signaling assays, multiple mutations tested","pmids":["21984976"],"is_preprint":false},{"year":2013,"finding":"Heterozygous mutations in PIK3R1 (including c.1906_1907insC and c.1945C>T p.Arg649Trp) cause SHORT syndrome; functional studies in lymphoblastoid cells with the PIK3R1 frameshift mutation show decreased phosphorylation of the downstream S6 target, indicating downregulation of PI3K-AKT-mTOR pathway signaling.","method":"Whole-exome sequencing; Sanger sequencing; functional phosphorylation assay in patient-derived lymphoblastoid cells","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — patient-derived cells with downstream phosphorylation readout, replicated in multiple families but limited to single downstream marker","pmids":["23810382"],"is_preprint":false},{"year":2014,"finding":"A heterozygous splice site mutation in PIK3R1 (causing deletion of residues 434-475 in the inter-SH2 domain) activates PI3K signaling in T cells due to qualitative and quantitative binding changes in the p85alpha-p110delta complex and failure of the C-terminal region to properly inhibit p110delta catalytic activity.","method":"Patient cell studies; T cell overexpression of mutant p85alpha; PI3K signaling assays; p85alpha-p110delta complex analysis","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mechanistic dissection of p85-p110 interaction with functional signaling readout in patient and healthy cells","pmids":["25488983"],"is_preprint":false},{"year":2014,"finding":"Two heterozygous PIK3R1 splice site mutations causing deletion of exon 10 (part of the p110-binding domain) produce a shortened p85alpha protein that causes elevated AKT phosphorylation in patient T cell blasts, consistent with loss of p85alpha-mediated inhibition of p110 activity.","method":"Whole-exome sequencing; Western blot of phospho-AKT in patient T cell blasts; PI3Kδ inhibitor rescue experiment","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient-derived cells with AKT phosphorylation readout and pharmacological rescue, single lab","pmids":["25133428"],"is_preprint":false},{"year":2014,"finding":"ICOS activation in CD4+ T cells promotes interaction of p85alpha with intracellular osteopontin (OPN-i), followed by OPN-i nuclear translocation, interaction with Bcl-6, and protection of Bcl-6 from ubiquitin-dependent proteasomal degradation, sustaining TFH and TFR cell differentiation.","method":"Co-immunoprecipitation; nuclear fractionation; Bcl-6 stability assay; genetic loss-of-function studies in TFH/TFR cells","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP of p85alpha-OPN-i complex, nuclear localization, protein stability assay with defined functional consequence","pmids":["25436971"],"is_preprint":false},{"year":2014,"finding":"BRD7 binds to the iSH2 domain of p85alpha and facilitates nuclear translocation of p85alpha; BRD7-dependent depletion of p85 from the cytosol impairs p85/p110 complex formation, decreasing p110 protein levels and PI3K pathway signaling; BRD7 and p110 compete for p85 binding.","method":"Co-immunoprecipitation; nuclear fractionation; RNAi knockdown; Akt phosphorylation assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP identifying interaction surface, nuclear fractionation showing localization change, competition assay, RNAi with signaling readout","pmids":["24657164"],"is_preprint":false},{"year":2014,"finding":"Naturally occurring PIK3R1 truncation mutations PIK3R1(R348*) and PIK3R1(L370fs) localize to the nucleus (unlike wild-type p85alpha) and unexpectedly increase JNK and ERK phosphorylation; these mutant proteins scaffold multiple JNK pathway components in the nucleus to facilitate nuclear JNK pathway activation.","method":"Expression of mutant PIK3R1 in cancer cells; nuclear localization studies; JNK/ERK phosphorylation assays; in vitro and in vivo MEK/JNK inhibitor response","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — subcellular localization experiments directly tied to functional signaling consequence, in vitro and in vivo drug response validation","pmids":["25284480"],"is_preprint":false},{"year":2015,"finding":"p110alpha-free p85alpha homodimerizes via two intermolecular interactions (SH3:proline-rich region and BH:BH) to selectively bind unphosphorylated activated PTEN; homodimeric p85alpha protects PTEN from E3 ligase WWP2-mediated proteasomal degradation and enhances PTEN lipid phosphatase activity and membrane association; cancer-derived oncogenic p85alpha mutations disrupt homodimerization or the PTEN interaction surface.","method":"Biochemical pulldown; co-immunoprecipitation; in vitro PTEN lipid phosphatase assay; proteasomal degradation assay; domain mutant analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution of PTEN-p85alpha interaction, enzymatic activity assay, proteasomal degradation assay, multiple orthogonal methods","pmids":["26222500"],"is_preprint":false},{"year":1999,"finding":"p85alpha dimerizes via intermolecular SH3 domain-proline-rich motif interactions and BH-BH domain interactions both in vitro and in vivo; competition experiments show these are intermolecular interactions; binding of SH2 domain ligands does not affect the dimeric state.","method":"Deletion and point mutants; native PAGE for apparent molecular mass; competition experiments; in vitro and in vivo dimerization assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple domain mutants tested in vitro and in vivo, competition experiments with defined interaction surfaces","pmids":["10212202"],"is_preprint":false},{"year":2008,"finding":"Crystal structure of p110alpha/p85alpha reveals that oncogenic mutations predominantly occur at interfaces between p110 domains and between p110 and p85 domains; these mutations disrupt stabilizing interactions at the p110alpha-p85alpha interface; the iSH2 domain of p85alpha mediates membrane interaction.","method":"X-ray crystallography; structural analysis of oncogenic mutation positions","journal":"Cell cycle","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with structural analysis of mutation positions, but functional validation is limited within the abstract","pmids":["18418043"],"is_preprint":false},{"year":2017,"finding":"TRAF6 polyubiquitylates p85alpha on Lys513 and Lys519 in the iSH2 domain (Lys63-linked) in response to TGF-beta, promoting formation of a complex between TGF-beta type I receptor (TbetaRI) and p85alpha, leading to PI3K and AKT activation and cell motility; this activation is independent of TbetaRI kinase activity.","method":"In situ proximity ligation assay; co-immunoprecipitation; ubiquitination assay; mutagenesis of Lys513/Lys519; cell migration assay; prostate cancer tissue analysis","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — site-specific mutagenesis identifying ubiquitination sites, Co-IP of receptor-p85alpha complex, functional migration assay, tissue validation","pmids":["28676490"],"is_preprint":false},{"year":2017,"finding":"APDS2 mutation in p85alpha (deletion 434-475) leads to >300-fold basal activation of p110delta but only ~2-fold activation of p110alpha when associated with mutated p85alpha; the mutation disrupts inhibitory interactions from the nSH2, iSH2, and cSH2 domains of p85; all APDS mutations are inhibited by idelalisib.","method":"Biochemical kinase assays; hydrogen-deuterium exchange mass spectrometry; comparison of p110alpha vs p110delta activation by mutant p85alpha","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assay with HDX-MS structural analysis, quantitative comparison across isoforms","pmids":["28167755"],"is_preprint":false},{"year":2019,"finding":"The oncogenic PIK3R1 Q572* truncation in the iSH2 domain disrupts all p85-inhibitory inputs and hyper-activates p110alpha more than p110delta; the R649W mutation in the cSH2 domain of PIK3R1 decreases sensitivity to activation by receptor tyrosine kinases.","method":"Biochemical kinase assays; hydrogen-deuterium exchange mass spectrometry","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay combined with HDX-MS structural analysis, isoform-specific mechanistic distinction","pmids":["31831213"],"is_preprint":false},{"year":2015,"finding":"p85alpha undergoes rapidly reversible concentration-dependent monomer-dimer assembly in vitro and in vivo; dimerization involves both SH3-PR1 and cSH2-cSH2 intermolecular interactions; the structural architecture of the p85alpha homodimer was determined by integrative methods including SAXS and chemical cross-linking.","method":"Analytical ultracentrifugation; fluorescence fluctuation spectroscopy (in vivo); SAXS; chemical cross-linking; integrative structure determination","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple biophysical methods with structural determination, in vitro and in vivo validation of dimerization","pmids":["26475863"],"is_preprint":false},{"year":2006,"finding":"Activated Galpha(q) directly binds p110alpha/p85alpha PI3K (not p110gamma) in a GTP-dependent manner with approximately 7-fold stronger affinity than GDP-bound Galpha(q); Galpha(q) competes with Ras for binding to p110alpha/p85alpha by binding to the p85-binding domain of p110alpha (not the Ras-binding domain), inhibiting Ras activation of the PI3K/Akt pathway.","method":"Purified protein fluorescence spectroscopy; co-precipitation with deletion mutants; constitutively active Galpha(q)Q209L expression; PI3K/Akt signaling assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro binding assay with purified proteins, affinity measurement, domain mapping by deletion mutants, functional cellular assay","pmids":["16268778"],"is_preprint":false},{"year":2005,"finding":"The N-terminal SH2, C-terminal SH2, and SH3 domains of p85alpha are required for interaction with the BCR/ABL protein network; a triple domain mutant of p85alpha (p85mut) disrupts binding to BCR/ABL and other fusion tyrosine kinases while retaining p110alpha binding, reducing PI3K and Akt activation and inhibiting BCR/ABL-dependent leukemogenic transformation.","method":"Point mutations in SH2 and SH3 domains; co-immunoprecipitation; PI3K activity assay; Akt phosphorylation; hematopoietic transformation assay; SCID mouse model","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain-specific mutagenesis with co-IP, enzymatic activity, and in vivo leukemogenesis validation","pmids":["16135792"],"is_preprint":false},{"year":2007,"finding":"p85alpha (but not p85beta) is required for JNK activation in states of insulin resistance (high-fat diet-induced obesity, JNK1 overexpression); p85alpha activates JNK via cdc42 and MKK4, independently of its role as a PI3K heterodimer component and only in response to insulin and ER stress-inducing stimuli; both an intact N terminus and functional SH2 domains are required.","method":"p85alpha-/- and p85beta-/- cell lines; JNK activity assay; p85alpha domain mutant reconstitution; cdc42/MKK4 epistasis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO, domain mutant reconstitution, epistasis analysis identifying pathway components","pmids":["17283057"],"is_preprint":false},{"year":2008,"finding":"p85alpha (regulatory) and p110beta (catalytic) isoforms, but not p110alpha, are specifically required for androgen-stimulated androgen receptor transactivation and cell proliferation in prostate cancer cells; p110beta lipid kinase activity (not protein kinase activity) is required; p110beta is indispensable for androgen-induced AR-DNA interaction.","method":"siRNA knockdown of p85alpha/p110alpha/p110beta; AR transactivation assay; chromatin immunoprecipitation; tumor xenograft","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific siRNA knockdown with ChIP readout, kinase-dead mutant analysis, but PI3K-independent role of p85alpha not directly demonstrated","pmids":["18372911"],"is_preprint":false},{"year":2008,"finding":"p85alpha deficiency in osteoclasts results in impaired growth, differentiation, adhesion, and migration via integrin alphavbeta3, with reduced Akt and Erk1/2 activation; full-length p85alpha (but not SH3-domain-deleted version) is required for osteoclast maturation; p85alpha regulates expression of MITF, TRAP, cathepsin K, and beta3 integrin.","method":"p85alpha-/- osteoclast progenitors; in vivo bone histomorphometry; in vitro differentiation/adhesion/migration assays; microarray; reconstitution with SH3-deleted mutant","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO with multiple cellular assays, in vivo bone phenotype, reconstitution with domain mutant identifying functional requirement for SH3 domain","pmids":["18809581"],"is_preprint":false},{"year":2007,"finding":"IREM-1 (CD300f) recruits p85alpha of PI3K (via tyrosine residues Y236 and Y263) and SHP-1 upon immunoprecipitation; PI3K recruitment through these residues (when Y205 and Y249 ITIM sites are mutated) drives degranulation in RBL cells, demonstrating dual inhibitory/activating signaling capacity of IREM-1 depending on p85alpha recruitment.","method":"Immunoprecipitation in transfected cells and U937 cells; IREM-1 tyrosine mutants; RBL cell degranulation assay; PI3K inhibitor treatment","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP in transfected and endogenous cells, functional degranulation assay with site-specific mutants","pmids":["17202342"],"is_preprint":false},{"year":2008,"finding":"p85alpha deficiency impairs NK cell lineage commitment (reducing NK cellularity in bone marrow and liver), Ly49 subset specification, NKG2D and NK1.1 receptor-mediated cytokine/chemokine generation, and NK-mediated cytotoxicity against tumor cells.","method":"p85alpha-/- mice; flow cytometric analysis of NK subset specification; NK cytotoxicity assays; cytokine measurement","journal":"Genes and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with multiple cellular phenotype readouts in primary NK cells, single lab","pmids":["18548087"],"is_preprint":false},{"year":2007,"finding":"p85alpha deficiency specifically impairs Kit ligand/SCF-induced (but not FcepsilonRI-initiated) mast cell secretory granule exocytosis, proliferation, and Akt phosphorylation, demonstrating receptor-specific usage of different PI3K family members in a single cell type.","method":"p85alpha-/- mast cells; Kit and FcepsilonRI cross-linking; exocytosis and proliferation assays; Akt phosphorylation; PI3K inhibitor (LY294002)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO with receptor-specific functional dissection, pharmacological validation","pmids":["10681597"],"is_preprint":false},{"year":2012,"finding":"PIK3R1 loss in ovarian cancer cells activates AKT through enhanced p110alpha kinase activity, decreased PTEN levels, and p110-independent JAK2/STAT3 signaling through deregulated Gab2 phosphorylation; PIK3R1 loss relieves negative inhibition on AKT and promotes assembly of JAK2/STAT3 signalosome.","method":"PIK3R1 knockdown in ovarian cancer cells; phosphoproteomics; Gab2 phosphorylation analysis; JAK2/STAT3 signaling assays; combination inhibitor treatment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — systematic knockdown with phosphoproteomic analysis identifying Gab2 as mediator, multiple orthogonal signaling readouts","pmids":["30755611"],"is_preprint":false},{"year":1993,"finding":"Both p85alpha and p85beta isoforms associate with p110 and PI3K activity in T cells; upon TCR/CD3 or PKC stimulation, the p110 complexed to p85alpha becomes rapidly phosphorylated on serine, while p85beta undergoes rapid increase in threonine phosphorylation, revealing differential regulation of the two PI3K isoforms.","method":"Phosphopeptide pulldown; isoform-specific monoclonal antibodies; T cell activation assays; phosphorylation analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific antibodies with differential phosphorylation readout, single lab","pmids":["8388374"],"is_preprint":false},{"year":2014,"finding":"p85alpha deficiency in osteoclast progenitors (using p85alpha-/- mice) demonstrates that genetic disruption of p85alpha but not p85beta normalizes KITD814V oncogenic KIT-induced ligand-independent hyperproliferation and promiscuous cytokine responses in HSC/Ps and mast cell progenitors.","method":"Genetic disruption of p85alpha vs p85beta in KITD814V-expressing hematopoietic cells; proliferation assays; Rac inhibitor and rapamycin treatment","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific genetic disruption with functional proliferation readout, pharmacological validation","pmids":["17483298"],"is_preprint":false},{"year":2016,"finding":"C-terminal PIK3R1 mutations (SHORT syndrome) show severely reduced insulin-stimulated association of mutant but not WT p85alpha with IRS1; mutant p85alpha overexpression in 3T3-L1 preadipocytes attenuates insulin-induced AKT phosphorylation and adipocyte differentiation.","method":"Patient-derived cells (p.Tyr657X mutation); co-immunoprecipitation of p85alpha-IRS1; mutant p85alpha overexpression in 3T3-L1 cells; AKT phosphorylation; adipocyte differentiation assay","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP in patient-derived cells and reconstitution in 3T3-L1 cells, single lab","pmids":["27766312"],"is_preprint":false},{"year":2021,"finding":"CBL mutations drive PI3K/AKT signaling via increased LYN activation and interaction with mutant CBL, leading to enhanced CBL phosphorylation, PIK3R1 recruitment, and downstream PI3K/AKT signaling; LYN inhibition (genetic or dasatinib) reduces CBL-PIK3R1 interaction and PI3K/AKT signaling.","method":"Global mass spectrometry phosphoproteomics; CBL interactome by MS; functional signaling assays; genetic ablation and dasatinib inhibition of LYN; in vitro and in vivo antiproliferative assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Moderate — MS-defined interactome, genetic and pharmacological dissection of pathway, in vivo validation","pmids":["33512474"],"is_preprint":false},{"year":2012,"finding":"PKA phosphorylates p85alpha on Ser83 adjacent to the N-terminal SH3 domain in vivo and in vitro; Ser83 phosphorylation is crucial for synergistic RARα/p85alpha binding induced by cAMP/RA co-treatment, and controls MCF7 cell proliferation, RA-induced inhibition of proliferation, migration, and RA-induced reduction of motility.","method":"PKA phosphorylation assay in vivo and in vitro; Ser83Ala and Ser83Asp p85alpha mutants; co-immunoprecipitation of RARα/p85alpha; cell growth and migration assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro phosphorylation assay with site-directed mutagenesis and functional cellular readout, single lab","pmids":["22366926"],"is_preprint":false},{"year":2016,"finding":"p85alpha promotes nucleolin (NCL) transcription via c-Jun activation; NCL binds EGFR mRNA and increases its stability; p85alpha thereby upregulates EGFR protein expression and promotes malignant cellular transformation in a PI3K-independent manner.","method":"p85alpha knockdown and knockout cells; EGFR mRNA stability assay; NCL overexpression rescue; c-Jun activation analysis","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD/KO with rescue experiment identifying NCL as intermediary, mRNA stability assay, single lab","pmids":["26918608"],"is_preprint":false},{"year":2023,"finding":"NLRP6 binds p85alpha and recruits E3 ligase RBX1 to ubiquitinate p85alpha on Lys256; this ubiquitination is recognized by autophagy cargo receptor OPTN, causing selective autophagic degradation of p85alpha, subsequent reduction of PTEN stability, and activation of the PI3K/AKT pathway.","method":"Co-immunoprecipitation; ubiquitination assay with site-specific mutagenesis (K256); autophagy flux assay; OPTN interaction; PTEN stability assay; tumor xenograft","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — site-specific ubiquitination with mutagenesis, autophagy receptor identification, PTEN stability consequence, in vivo validation","pmids":["37770465"],"is_preprint":false},{"year":2017,"finding":"PAK4 specifically interacts with p85alpha (the regulatory subunit of PI3K), and PAK4-deficient pancreatic cancer cells exhibit reduced AKT phosphorylation downstream of HGF signaling, implicating PAK4 in PI3K pathway activation via p85alpha interaction.","method":"Co-immunoprecipitation of PAK4 and p85alpha; PAK4 knockdown; AKT phosphorylation assay; HGF stimulation","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP identifying interaction, functional KD with signaling readout, single lab","pmids":["28205613"],"is_preprint":false},{"year":2014,"finding":"p85alpha deficiency in beta-cells markedly delays onset and severity of ER stress-induced diabetic phenotype in Akita+/- mice by decreasing activation of ER stress-dependent apoptotic pathways and preserving beta-cell mass; this is linked to p85alpha's role in promoting nuclear localization of XBP-1.","method":"p85alpha-deficient Akita+/- mice; beta-cell mass quantification; ER stress pathway assays; XBP-1 nuclear localization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with defined cellular phenotype (beta-cell apoptosis), mechanistic link to XBP-1 nuclear localization","pmids":["24395790"],"is_preprint":false},{"year":2007,"finding":"p85alpha deficiency in thymocytes impairs pre-TCR-controlled beta-selection (DN to DP transition) without affecting positive or negative selection; inhibition of p110delta blocks DN-to-DP transition in fetal thymic organ culture; PTEN deficiency (amplifying PI3K signals) accelerates this transition.","method":"p85alpha-/- Rag-2-/- mice with anti-CD3epsilon injection; p110delta inhibitor (IC87114) in fetal thymic organ culture; PTEN-/- thymic organ culture; flow cytometry of thymocyte subsets","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO with pharmacological and epistatic validation across multiple experimental systems","pmids":["17237381"],"is_preprint":false}],"current_model":"PIK3R1 (p85alpha) is the predominant regulatory subunit of class IA PI3K that binds, stabilizes, and inhibits the p110 catalytic subunit via its nSH2, iSH2, and cSH2 domains; it also functions as an adaptor linking phosphotyrosine-containing receptors/IRS proteins to p110 activation, forms homodimers that bind and protect PTEN from proteasomal degradation, acts as a GAP for Rab5/Rab4 to regulate receptor trafficking, facilitates nuclear translocation of XBP-1s to resolve ER stress, participates in PI3K-independent JNK activation via cdc42/MKK4, can be ubiquitinated (by TRAF6 on Lys513/519 or by RBX1 on Lys256) to modulate its activity and stability, and undergoes PKA-mediated phosphorylation on Ser83 to integrate cAMP signaling; loss-of-function mutations cause immunodeficiency (APDS2) and SHORT syndrome via impaired p110 inhibition or disrupted IRS1 association, while gain-of-function mutations in the iSH2/nSH2 domains constitutively activate PI3K in cancer."},"narrative":{"mechanistic_narrative":"PIK3R1 encodes p85alpha, the predominant regulatory subunit of class IA PI3K, which binds the p110 catalytic subunit to stabilize and constitutively inhibit it while coupling its activation to phosphotyrosine-containing receptors and adaptors such as IRS proteins [PMID:9065454, PMID:21478295, PMID:28167755]. The inhibitory function is mediated by the nSH2, iSH2, and cSH2 domains contacting p110; disruption of these contacts by deletions or truncations in the iSH2/nSH2 region releases p110 from inhibition and drives constitutive lipid-kinase activity [PMID:11606375, PMID:21478295, PMID:28167755, PMID:31831213]. The gene is functionally pleiotropic: full-length p85alpha forms homodimers through SH3-proline-rich and BH-BH (and cSH2-cSH2) intermolecular contacts, and these p110-free dimers bind, stabilize, and enhance the activity of PTEN, so that loss of p85alpha or its dimerization destabilizes PTEN and de-represses PI3K/AKT signaling [PMID:21984976, PMID:26222500, PMID:10212202, PMID:26475863]. Beyond its canonical lipid-kinase scaffold role, p85alpha carries BH-domain GAP activity toward Rab5/Rab4 and Cdc42/Rac1 that controls receptor (PDGFR) trafficking and degradation [PMID:15377662], drives PI3K-independent JNK activation via Cdc42/MKK4 in insulin resistance and ER stress [PMID:14504291, PMID:17283057], and promotes nuclear translocation of XBP-1s to resolve ER stress [PMID:20348926, PMID:24395790]. Genetically, p85alpha is required for B-cell development, thymocyte beta-selection, NK and macrophage function, mast-cell and osteoclast signaling, and for insulin-stimulated GLUT4-mediated glucose uptake, where its dosage tunes metabolic sensitivity [PMID:9888855, PMID:9988280, PMID:11781359, PMID:15769893, PMID:18809581, PMID:17237381]. Heterozygous loss-of-function splice/truncation mutations cause the immunodeficiency APDS2 (via failed inhibition of p110delta) and SHORT syndrome (via disrupted IRS1 association and reduced PI3K-AKT-mTOR signaling), while iSH2/nSH2 gain-of-function mutations constitutively activate PI3K in cancer [PMID:23810382, PMID:25488983, PMID:28167755, PMID:31831213, PMID:27766312]. Its activity is further modulated by post-translational modification, including TRAF6-mediated K63 ubiquitination on Lys513/519 promoting TGF-beta receptor coupling, RBX1/NLRP6-driven K256 ubiquitination targeting it for autophagic degradation, and PKA phosphorylation on Ser83 integrating cAMP signaling [PMID:28676490, PMID:22366926, PMID:37770465].","teleology":[{"year":1997,"claim":"Establishing that PIK3R1 generates multiple regulatory isoforms with distinct receptor-coupling properties answered how a single gene tunes PI3K responsiveness to insulin.","evidence":"Expression cloning with 32P-IRS-1, co-IP, and PI3K activity assays defining p85alpha/p55alpha/p50alpha isoforms","pmids":["9065454"],"confidence":"High","gaps":["Tissue-specific physiological roles of each isoform not resolved","Structural basis of differential IRS-1 affinity not defined"]},{"year":1999,"claim":"Genetic ablation in mice defined the in vivo cellular requirements for p85alpha, separating an essential role in B-cell development from dispensability in T-cell development.","evidence":"RAG2 blastocyst complementation with p85alpha/p55alpha/p50alpha knockout mice and lymphocyte functional readouts","pmids":["9888855"],"confidence":"High","gaps":["Molecular signal downstream of receptors not mapped","Does not address adaptor vs catalytic-scaffold contribution"]},{"year":1999,"claim":"Demonstrating that p85alpha dosage controls insulin sensitivity revealed the regulatory subunit as a rate-limiting tuner of metabolic PI3K signaling rather than merely a permissive scaffold.","evidence":"Targeted knockout mice with insulin-stimulated PI3K activity, PIP3 measurement, and GLUT4 fractionation; later confirmed by heterozygous models","pmids":["9988280","11781359"],"confidence":"High","gaps":["Mechanism of isoform switch (p85alpha to p50alpha) not fully defined","Liver vs muscle vs adipose contributions partly separable"]},{"year":1999,"claim":"Mapping the p85alpha homodimerization interfaces established that the protein self-associates independently of SH2 ligand binding, anticipating a p110-free pool.","evidence":"Deletion/point mutants, native PAGE, and competition experiments in vitro and in vivo","pmids":["10212202"],"confidence":"High","gaps":["Functional consequence of dimerization not yet known at this stage","Stoichiometry in cells not quantified"]},{"year":2001,"claim":"Finding constitutively activating iSH2 deletions in tumors reclassified PIK3R1 as an oncogene, not solely a negative regulator.","evidence":"Mutation analysis of primary colon/ovarian tumors plus PI3K activity assay of mutant protein","pmids":["11606375"],"confidence":"High","gaps":["Precise structural mechanism of activation deferred to later HDX-MS work","Frequency across cancer types not established here"]},{"year":2003,"claim":"Showing p85alpha is required for insulin-stimulated JNK activation via Cdc42/MKK4 uncovered a PI3K-catalysis-independent signaling output of the regulatory subunit.","evidence":"p85alpha-/- brown adipocyte lines with reconstitution by domain mutants and JNK/Akt/glucose-uptake readouts","pmids":["14504291"],"confidence":"High","gaps":["Direct biochemical link between p85alpha and Cdc42 not reconstituted","Physiological relevance addressed later in insulin resistance"]},{"year":2004,"claim":"Identifying BH-domain GAP activity toward Rab5/Rab4/Cdc42/Rac1 assigned p85alpha a direct role in receptor trafficking distinct from PI3K regulation.","evidence":"In vitro GAP assays with purified protein, direct Rab5 binding, and BH-mutant PDGFR degradation assays","pmids":["15377662"],"confidence":"High","gaps":["Cellular GAP targets in vivo not exhaustively validated","Regulation of the GAP activity unknown"]},{"year":2006,"claim":"Defining Galpha(q) as a GTP-dependent binder of the p110alpha/p85alpha complex linked GPCR signaling to PI3K regulation via competition with Ras.","evidence":"Purified-protein fluorescence spectroscopy, deletion-mutant co-precipitation, and constitutively active Galpha(q) signaling assays","pmids":["16268778"],"confidence":"High","gaps":["Physiological GPCR contexts not established","Net signaling outcome (inhibition vs activation) context-dependent"]},{"year":2010,"claim":"Linking insulin-disrupted p85 monomers to XBP-1s nuclear translocation established a non-catalytic role in resolving ER stress.","evidence":"Reciprocal Co-IP, nuclear fractionation, and in vivo p85 overexpression rescue in ob/ob liver","pmids":["20348926"],"confidence":"High","gaps":["Direct binding region on XBP-1s not mapped","Relationship to dimer-monomer equilibrium not quantified"]},{"year":2011,"claim":"Distinguishing gain-of-function SH2-domain mutations from loss-of-binding truncations clarified that PIK3R1 cancer mutations act by p110 retention with failed inhibition.","evidence":"Stable mutant expression in U2OS cells with p110alpha co-IP and phospho-AKT readout","pmids":["21478295"],"confidence":"High","gaps":["Quantitative activation per mutant not measured biochemically here","Isoform selectivity (p110alpha vs delta) addressed later"]},{"year":2011,"claim":"Discovering that p85alpha dimers bind and stabilize PTEN defined a second tumor-suppressive axis lost in cancer mutations.","evidence":"Co-IP of p85alpha dimer-PTEN complex with functional signaling assays across multiple mutations","pmids":["21984976"],"confidence":"High","gaps":["Mechanism of PTEN protection deferred to later reconstitution","In vivo contribution to tumor suppression not quantified"]},{"year":2013,"claim":"Identifying heterozygous PIK3R1 mutations as causal for SHORT syndrome established a human disease of reduced PI3K-AKT-mTOR signaling.","evidence":"Whole-exome/Sanger sequencing across families with downstream S6 phosphorylation assay in patient lymphoblastoid cells","pmids":["23810382"],"confidence":"Medium","gaps":["Single downstream marker (S6) assayed","Mechanism narrowed to IRS1 association only in later work"]},{"year":2014,"claim":"Showing that immunodeficiency-causing splice mutations delete inhibitory iSH2/p110-binding residues established APDS2 as a gain-of-function disease via failed p110delta restraint.","evidence":"Patient T-cell studies, mutant overexpression, complex analysis, and PI3Kdelta-inhibitor rescue","pmids":["25488983","25133428"],"confidence":"High","gaps":["Isoform-specific quantitative activation defined later by HDX-MS","Variability across mutations not fully resolved"]},{"year":2014,"claim":"Multiple 2014 reports revealed unexpected nuclear/scaffolding roles for p85alpha and its truncation mutants in immune and oncogenic signaling beyond PI3K.","evidence":"Co-IP, nuclear fractionation, and signaling assays for p85alpha-OPN-i/Bcl-6, BRD7 competition for p85, and nuclear JNK/ERK scaffolding by R348*/L370fs mutants","pmids":["25436971","24657164","25284480"],"confidence":"High","gaps":["How nuclear translocation is regulated for wild-type vs mutant p85alpha incomplete","Generality of scaffolding roles across cell types unknown"]},{"year":2015,"claim":"Structural and biophysical characterization of the reversible p85alpha homodimer and its selective binding to unphosphorylated PTEN defined the mechanism protecting PTEN from WWP2-mediated degradation.","evidence":"AUC, FFS, SAXS, cross-linking, biochemical pulldown, in vitro PTEN phosphatase and degradation assays with domain mutants","pmids":["26475863","26222500"],"confidence":"High","gaps":["In vivo concentration-dependence of dimer-monomer switch not measured","Crosstalk between p110 binding and PTEN binding only partly resolved"]},{"year":2017,"claim":"Quantitative biochemistry resolved that APDS2-type iSH2 deletions hyperactivate p110delta far more than p110alpha by simultaneously disrupting nSH2/iSH2/cSH2 inhibitory contacts.","evidence":"Reconstituted kinase assays with HDX-MS comparing p110alpha vs p110delta activation; idelalisib sensitivity","pmids":["28167755"],"confidence":"High","gaps":["Cellular consequences of isoform-selective activation not modeled here","Other p85 contact regions not exhaustively mapped"]},{"year":2017,"claim":"Demonstrating TRAF6-mediated K63 ubiquitination of p85alpha at Lys513/519 revealed a ubiquitin-dependent, kinase-independent route to TGF-beta receptor coupling and motility.","evidence":"PLA, Co-IP, site-specific ubiquitination mutagenesis, migration assays, and tumor tissue analysis","pmids":["28676490"],"confidence":"High","gaps":["Deubiquitinase counterpart not identified","Generality beyond TGF-beta context unknown"]},{"year":2019,"claim":"Biochemical dissection of additional cancer mutations distinguished iSH2 truncations that broadly de-repress p110alpha from cSH2 mutations that reduce RTK responsiveness.","evidence":"Reconstituted kinase assays with HDX-MS on Q572* and R649W mutants","pmids":["31831213"],"confidence":"High","gaps":["Cellular and clinical correlates of each mutant not established","Crosstalk with PTEN-binding function not tested"]},{"year":2023,"claim":"Identifying NLRP6/RBX1-driven K256 ubiquitination and OPTN-mediated autophagic degradation of p85alpha defined a turnover mechanism whose loss destabilizes PTEN and activates PI3K/AKT.","evidence":"Co-IP, K256 site-specific ubiquitination mutagenesis, autophagy flux, OPTN interaction, PTEN stability, and tumor xenograft","pmids":["37770465"],"confidence":"High","gaps":["Physiological signals triggering this degradation unclear","Interplay with TRAF6 ubiquitination not addressed"]},{"year":null,"claim":"How the multiple p85alpha functions—p110 inhibition, PTEN stabilization, GAP activity, nuclear scaffolding, and ubiquitin/phosphorylation control—are coordinated within a single cell and dynamically partitioned between catalytic and non-catalytic pools remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No integrated model of how dimer-monomer equilibrium routes p85alpha among p110, PTEN, and nuclear partners","Quantitative cellular stoichiometry of competing complexes unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[9,17,21,22]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[7,14,15,25,36]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[5]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[10,17]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[8,15,16]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[8,14,15,16]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,19]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,9,21,24]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,30,42,12,21]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,3]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[8,41]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,11,21,22]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[39]}],"complexes":["class IA PI3K (p85alpha-p110alpha/p110delta)","p85alpha homodimer"],"partners":["PIK3CA","PIK3CD","PTEN","IRS1","XBP1","TRAF6","BRD7","RBX1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P27986","full_name":"Phosphatidylinositol 3-kinase regulatory subunit alpha","aliases":["Phosphatidylinositol 3-kinase 85 kDa regulatory subunit alpha","PI3-kinase subunit p85-alpha","PtdIns-3-kinase regulatory subunit p85-alpha"],"length_aa":724,"mass_kda":83.6,"function":"Binds to activated (phosphorylated) protein-Tyr kinases, through its SH2 domain, and acts as an adapter, mediating the association of the p110 catalytic unit to the plasma membrane. Necessary for the insulin-stimulated increase in glucose uptake and glycogen synthesis in insulin-sensitive tissues. Plays an important role in signaling in response to FGFR1, FGFR2, FGFR3, FGFR4, KITLG/SCF, KIT, PDGFRA and PDGFRB. Likewise, plays a role in ITGB2 signaling (PubMed:17626883, PubMed:19805105, PubMed:7518429). Modulates the cellular response to ER stress by promoting nuclear translocation of XBP1 isoform 2 in a ER stress- and/or insulin-dependent manner during metabolic overloading in the liver and hence plays a role in glucose tolerance improvement (PubMed:20348923)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P27986/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PIK3R1","classification":"Not Classified","n_dependent_lines":45,"n_total_lines":1208,"dependency_fraction":0.037251655629139076},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000145675","cell_line_id":"CID000596","localizations":[{"compartment":"membrane","grade":3},{"compartment":"cytoplasmic","grade":2},{"compartment":"vesicles","grade":2}],"interactors":[{"gene":"PIK3CB","stoichiometry":10.0},{"gene":"PIK3CD","stoichiometry":4.0},{"gene":"WDR6","stoichiometry":4.0},{"gene":"IRS4","stoichiometry":4.0},{"gene":"PIK3R2","stoichiometry":4.0},{"gene":"NISCH","stoichiometry":0.2},{"gene":"PIK3R3","stoichiometry":0.2},{"gene":"PPP5C","stoichiometry":0.2},{"gene":"PIK3CA","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000596","total_profiled":1310},"omim":[{"mim_id":"619393","title":"KELCH REPEAT- AND BTB DOMAIN-CONTAINING PROTEIN 2; KBTBD2","url":"https://www.omim.org/entry/619393"},{"mim_id":"618489","title":"BROMODOMAIN-CONTAINING PROTEIN 7; BRD7","url":"https://www.omim.org/entry/618489"},{"mim_id":"616005","title":"IMMUNODEFICIENCY 36 WITH LYMPHOPROLIFERATION; IMD36","url":"https://www.omim.org/entry/616005"},{"mim_id":"615513","title":"IMMUNODEFICIENCY 14A WITH LYMPHOPROLIFERATION, AUTOSOMAL DOMINANT; IMD14A","url":"https://www.omim.org/entry/615513"},{"mim_id":"615214","title":"AGAMMAGLOBULINEMIA 7, AUTOSOMAL RECESSIVE; AGM7","url":"https://www.omim.org/entry/615214"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PIK3R1"},"hgnc":{"alias_symbol":["GRB1","p85-ALPHA","p85","p85alpha"],"prev_symbol":[]},"alphafold":{"accession":"P27986","domains":[{"cath_id":"2.30.30.40","chopping":"2-81","consensus_level":"high","plddt":88.4202,"start":2,"end":81},{"cath_id":"1.10.555.10","chopping":"117-296","consensus_level":"high","plddt":87.4271,"start":117,"end":296},{"cath_id":"3.30.505.10","chopping":"329-429","consensus_level":"high","plddt":88.6965,"start":329,"end":429},{"cath_id":"1.10.287.1490","chopping":"441-586","consensus_level":"high","plddt":92.1144,"start":441,"end":586},{"cath_id":"3.30.505.10","chopping":"616-716","consensus_level":"high","plddt":87.436,"start":616,"end":716}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P27986","model_url":"https://alphafold.ebi.ac.uk/files/AF-P27986-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P27986-F1-predicted_aligned_error_v6.png","plddt_mean":83.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PIK3R1","jax_strain_url":"https://www.jax.org/strain/search?query=PIK3R1"},"sequence":{"accession":"P27986","fasta_url":"https://rest.uniprot.org/uniprotkb/P27986.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P27986/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P27986"}},"corpus_meta":[{"pmid":"9888855","id":"PMC_9888855","title":"Impaired 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\"method\": \"RAG2-deficient blastocyst complementation system with p85alpha-p55alpha-p50alpha knockout mice\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with specific cellular phenotype, replicated across lymphocyte populations with defined functional readouts\",\n      \"pmids\": [\"9888855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Pik3r1-/- mice show increased insulin sensitivity and hypoglycemia due to increased glucose transport in skeletal muscle and adipocytes; the isoform switch from p85alpha to p50alpha in knockout mice is associated with increased PtdIns(3,4,5)P3 generation and facilitated Glut4 translocation from low-density microsomes to the plasma membrane.\",\n      \"method\": \"Targeted gene disruption in mice; insulin-stimulated PI3K activity assay; PtdIns(3,4,5)P3 measurement; subcellular fractionation of Glut4\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple orthogonal biochemical readouts (PI3K activity, PIP3 levels, Glut4 fractionation), defined metabolic phenotype\",\n      \"pmids\": [\"9988280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Somatic deletions in the inter-SH2 region of PIK3R1 proximal to the Ser608 autoregulatory site (e.g., a 23-amino-acid deletion) result in constitutive PI3K activation, establishing PIK3R1 as an oncogene in colon and ovarian tumors.\",\n      \"method\": \"SSCP/heteroduplex mutation analysis of primary tumors; expression of mutant p85alpha protein in cells with PI3K activity assay\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct functional assay of mutant protein activation, supported by primary tumor mutation data\",\n      \"pmids\": [\"11606375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Heterozygous disruption of Pik3r1 reduces free p85alpha levels, restores the molecular balance between p85, p110, and IRS proteins, maintains normal PI3K activation while increasing insulin-stimulated Akt activity, and improves glucose tolerance and insulin sensitivity; this protects insulin-resistant mice from developing diabetes.\",\n      \"method\": \"Heterozygous Pik3r1 knockout in normal and insulin-resistant mice; PI3K activity assay; Akt phosphorylation; glucose tolerance tests\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic model with multiple orthogonal biochemical and metabolic readouts across multiple mouse models\",\n      \"pmids\": [\"11781359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"p85alpha-/- brown adipocyte cells show 70% reduction in p85 protein with parallel reduction of p110, 50% decrease in PI3K activity, and 30% decrease in Akt activity leading to decreased insulin-induced glucose uptake; p85alpha (but not p85beta) is required for insulin-stimulated JNK activation via cdc42 and MKK4, demonstrating a PI3K-independent signaling function.\",\n      \"method\": \"Gene-disrupted brown adipocyte cell lines; PI3K activity assay; Akt phosphorylation; glucose uptake; JNK activity; reconstitution with p85 mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal assays in defined KO cell lines, reconstitution experiments with domain mutants\",\n      \"pmids\": [\"14504291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"p85alpha possesses GTPase-activating protein (GAP) activity toward Rab5, Rab4, Cdc42, and Rac1 (with little activity toward Rab11), mediated by its BH domain; purified recombinant p85alpha directly binds Rab5; cells expressing BH domain mutants of p85 show reduced PDGFR degradation rates and sustained MAPK and Akt pathway activation.\",\n      \"method\": \"In vitro GAP assay with purified recombinant proteins; direct binding assay; BH domain mutant expression in cells; PDGFR degradation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted in vitro enzymatic assay with purified proteins, mutagenesis with functional cellular readout\",\n      \"pmids\": [\"15377662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"p85alpha-/- macrophages show 50% reduction in proliferation in response to M-CSF and GM-CSF, reduced migration and adhesion on fibronectin and VCAM-1, and defective phagocytosis; these are associated with reduced Akt and Rac activation (but not Erk activation), demonstrating a specific role for p85alpha in actin- and growth-based macrophage functions.\",\n      \"method\": \"Bone marrow-derived macrophages from p85alpha-/- mice; proliferation assays; wound-healing and chemotaxis assays; phagocytosis assay; Akt/Rac/Erk phosphorylation\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with multiple orthogonal functional and biochemical readouts in primary cells\",\n      \"pmids\": [\"15769893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The p85alpha gene generates three regulatory subunit isoforms (p85alpha, p55alpha, p50alpha) via alternative splicing; p50alpha forms heterodimers with p110 but uniquely with both wortmannin-sensitive and wortmannin-insensitive forms, exhibits markedly higher capacity for PI3K activation by insulin, and has higher affinity for tyrosine-phosphorylated IRS-1 than p85alpha or p55alpha.\",\n      \"method\": \"Expression cloning using 32P-labeled IRS-1; Northern blotting; co-immunoprecipitation; PI3K activity assay; wortmannin labeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical characterization across multiple methods (binding, activity, isoform-specific antibodies), replicated in multiple tissues\",\n      \"pmids\": [\"9065454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"p85alpha and p85beta form heterodimers that are disrupted by insulin treatment; the resulting p85 monomers interact with and increase nuclear translocation of the spliced form of XBP-1 (XBP-1s), promoting resolution of ER stress; this interaction is lost in ob/ob mice and restored by p85 overexpression in liver.\",\n      \"method\": \"Co-immunoprecipitation; nuclear fractionation; p85alpha/p85beta overexpression in ob/ob mice liver; XBP-1s nuclear localization assay\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, nuclear fractionation with functional consequence, in vivo rescue experiment\",\n      \"pmids\": [\"20348926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PIK3R1 mutations in the nSH2 and iSH2 domains (e.g., delH450-E451, delK459, delY463-L466, delR574-T576, N564D) bind p110alpha and increase pAKT(Ser473) levels, demonstrating gain-of-function PI3K activation; truncation mutations (R348X, K511VfsX2) do not bind p110alpha and show no change in pAKT.\",\n      \"method\": \"Stable expression of mutant p85alpha in U2OS cells; co-immunoprecipitation of p110alpha; Western blot of phospho-AKT(Ser473)\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional assay of multiple mutants with co-IP and signaling readout, clear structure-function relationship established\",\n      \"pmids\": [\"21478295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Multiple PIK3R1 and PIK3R2 mutations demonstrate gain-of-function PI3K pathway activation; p85alpha dimers bind and stabilize PTEN, and disruption of this interaction by mutations leads to PTEN destabilization and pathway activation, revealing a novel regulatory mechanism.\",\n      \"method\": \"Functional characterization of mutant proteins; co-immunoprecipitation of p85alpha dimers with PTEN; PI3K pathway signaling assays\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP of p85alpha dimer-PTEN complex, functional signaling assays, multiple mutations tested\",\n      \"pmids\": [\"21984976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Heterozygous mutations in PIK3R1 (including c.1906_1907insC and c.1945C>T p.Arg649Trp) cause SHORT syndrome; functional studies in lymphoblastoid cells with the PIK3R1 frameshift mutation show decreased phosphorylation of the downstream S6 target, indicating downregulation of PI3K-AKT-mTOR pathway signaling.\",\n      \"method\": \"Whole-exome sequencing; Sanger sequencing; functional phosphorylation assay in patient-derived lymphoblastoid cells\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — patient-derived cells with downstream phosphorylation readout, replicated in multiple families but limited to single downstream marker\",\n      \"pmids\": [\"23810382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A heterozygous splice site mutation in PIK3R1 (causing deletion of residues 434-475 in the inter-SH2 domain) activates PI3K signaling in T cells due to qualitative and quantitative binding changes in the p85alpha-p110delta complex and failure of the C-terminal region to properly inhibit p110delta catalytic activity.\",\n      \"method\": \"Patient cell studies; T cell overexpression of mutant p85alpha; PI3K signaling assays; p85alpha-p110delta complex analysis\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic dissection of p85-p110 interaction with functional signaling readout in patient and healthy cells\",\n      \"pmids\": [\"25488983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Two heterozygous PIK3R1 splice site mutations causing deletion of exon 10 (part of the p110-binding domain) produce a shortened p85alpha protein that causes elevated AKT phosphorylation in patient T cell blasts, consistent with loss of p85alpha-mediated inhibition of p110 activity.\",\n      \"method\": \"Whole-exome sequencing; Western blot of phospho-AKT in patient T cell blasts; PI3Kδ inhibitor rescue experiment\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived cells with AKT phosphorylation readout and pharmacological rescue, single lab\",\n      \"pmids\": [\"25133428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ICOS activation in CD4+ T cells promotes interaction of p85alpha with intracellular osteopontin (OPN-i), followed by OPN-i nuclear translocation, interaction with Bcl-6, and protection of Bcl-6 from ubiquitin-dependent proteasomal degradation, sustaining TFH and TFR cell differentiation.\",\n      \"method\": \"Co-immunoprecipitation; nuclear fractionation; Bcl-6 stability assay; genetic loss-of-function studies in TFH/TFR cells\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP of p85alpha-OPN-i complex, nuclear localization, protein stability assay with defined functional consequence\",\n      \"pmids\": [\"25436971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BRD7 binds to the iSH2 domain of p85alpha and facilitates nuclear translocation of p85alpha; BRD7-dependent depletion of p85 from the cytosol impairs p85/p110 complex formation, decreasing p110 protein levels and PI3K pathway signaling; BRD7 and p110 compete for p85 binding.\",\n      \"method\": \"Co-immunoprecipitation; nuclear fractionation; RNAi knockdown; Akt phosphorylation assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifying interaction surface, nuclear fractionation showing localization change, competition assay, RNAi with signaling readout\",\n      \"pmids\": [\"24657164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Naturally occurring PIK3R1 truncation mutations PIK3R1(R348*) and PIK3R1(L370fs) localize to the nucleus (unlike wild-type p85alpha) and unexpectedly increase JNK and ERK phosphorylation; these mutant proteins scaffold multiple JNK pathway components in the nucleus to facilitate nuclear JNK pathway activation.\",\n      \"method\": \"Expression of mutant PIK3R1 in cancer cells; nuclear localization studies; JNK/ERK phosphorylation assays; in vitro and in vivo MEK/JNK inhibitor response\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — subcellular localization experiments directly tied to functional signaling consequence, in vitro and in vivo drug response validation\",\n      \"pmids\": [\"25284480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p110alpha-free p85alpha homodimerizes via two intermolecular interactions (SH3:proline-rich region and BH:BH) to selectively bind unphosphorylated activated PTEN; homodimeric p85alpha protects PTEN from E3 ligase WWP2-mediated proteasomal degradation and enhances PTEN lipid phosphatase activity and membrane association; cancer-derived oncogenic p85alpha mutations disrupt homodimerization or the PTEN interaction surface.\",\n      \"method\": \"Biochemical pulldown; co-immunoprecipitation; in vitro PTEN lipid phosphatase assay; proteasomal degradation assay; domain mutant analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution of PTEN-p85alpha interaction, enzymatic activity assay, proteasomal degradation assay, multiple orthogonal methods\",\n      \"pmids\": [\"26222500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"p85alpha dimerizes via intermolecular SH3 domain-proline-rich motif interactions and BH-BH domain interactions both in vitro and in vivo; competition experiments show these are intermolecular interactions; binding of SH2 domain ligands does not affect the dimeric state.\",\n      \"method\": \"Deletion and point mutants; native PAGE for apparent molecular mass; competition experiments; in vitro and in vivo dimerization assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domain mutants tested in vitro and in vivo, competition experiments with defined interaction surfaces\",\n      \"pmids\": [\"10212202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Crystal structure of p110alpha/p85alpha reveals that oncogenic mutations predominantly occur at interfaces between p110 domains and between p110 and p85 domains; these mutations disrupt stabilizing interactions at the p110alpha-p85alpha interface; the iSH2 domain of p85alpha mediates membrane interaction.\",\n      \"method\": \"X-ray crystallography; structural analysis of oncogenic mutation positions\",\n      \"journal\": \"Cell cycle\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with structural analysis of mutation positions, but functional validation is limited within the abstract\",\n      \"pmids\": [\"18418043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRAF6 polyubiquitylates p85alpha on Lys513 and Lys519 in the iSH2 domain (Lys63-linked) in response to TGF-beta, promoting formation of a complex between TGF-beta type I receptor (TbetaRI) and p85alpha, leading to PI3K and AKT activation and cell motility; this activation is independent of TbetaRI kinase activity.\",\n      \"method\": \"In situ proximity ligation assay; co-immunoprecipitation; ubiquitination assay; mutagenesis of Lys513/Lys519; cell migration assay; prostate cancer tissue analysis\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — site-specific mutagenesis identifying ubiquitination sites, Co-IP of receptor-p85alpha complex, functional migration assay, tissue validation\",\n      \"pmids\": [\"28676490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"APDS2 mutation in p85alpha (deletion 434-475) leads to >300-fold basal activation of p110delta but only ~2-fold activation of p110alpha when associated with mutated p85alpha; the mutation disrupts inhibitory interactions from the nSH2, iSH2, and cSH2 domains of p85; all APDS mutations are inhibited by idelalisib.\",\n      \"method\": \"Biochemical kinase assays; hydrogen-deuterium exchange mass spectrometry; comparison of p110alpha vs p110delta activation by mutant p85alpha\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assay with HDX-MS structural analysis, quantitative comparison across isoforms\",\n      \"pmids\": [\"28167755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The oncogenic PIK3R1 Q572* truncation in the iSH2 domain disrupts all p85-inhibitory inputs and hyper-activates p110alpha more than p110delta; the R649W mutation in the cSH2 domain of PIK3R1 decreases sensitivity to activation by receptor tyrosine kinases.\",\n      \"method\": \"Biochemical kinase assays; hydrogen-deuterium exchange mass spectrometry\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay combined with HDX-MS structural analysis, isoform-specific mechanistic distinction\",\n      \"pmids\": [\"31831213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"p85alpha undergoes rapidly reversible concentration-dependent monomer-dimer assembly in vitro and in vivo; dimerization involves both SH3-PR1 and cSH2-cSH2 intermolecular interactions; the structural architecture of the p85alpha homodimer was determined by integrative methods including SAXS and chemical cross-linking.\",\n      \"method\": \"Analytical ultracentrifugation; fluorescence fluctuation spectroscopy (in vivo); SAXS; chemical cross-linking; integrative structure determination\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple biophysical methods with structural determination, in vitro and in vivo validation of dimerization\",\n      \"pmids\": [\"26475863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Activated Galpha(q) directly binds p110alpha/p85alpha PI3K (not p110gamma) in a GTP-dependent manner with approximately 7-fold stronger affinity than GDP-bound Galpha(q); Galpha(q) competes with Ras for binding to p110alpha/p85alpha by binding to the p85-binding domain of p110alpha (not the Ras-binding domain), inhibiting Ras activation of the PI3K/Akt pathway.\",\n      \"method\": \"Purified protein fluorescence spectroscopy; co-precipitation with deletion mutants; constitutively active Galpha(q)Q209L expression; PI3K/Akt signaling assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro binding assay with purified proteins, affinity measurement, domain mapping by deletion mutants, functional cellular assay\",\n      \"pmids\": [\"16268778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The N-terminal SH2, C-terminal SH2, and SH3 domains of p85alpha are required for interaction with the BCR/ABL protein network; a triple domain mutant of p85alpha (p85mut) disrupts binding to BCR/ABL and other fusion tyrosine kinases while retaining p110alpha binding, reducing PI3K and Akt activation and inhibiting BCR/ABL-dependent leukemogenic transformation.\",\n      \"method\": \"Point mutations in SH2 and SH3 domains; co-immunoprecipitation; PI3K activity assay; Akt phosphorylation; hematopoietic transformation assay; SCID mouse model\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-specific mutagenesis with co-IP, enzymatic activity, and in vivo leukemogenesis validation\",\n      \"pmids\": [\"16135792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"p85alpha (but not p85beta) is required for JNK activation in states of insulin resistance (high-fat diet-induced obesity, JNK1 overexpression); p85alpha activates JNK via cdc42 and MKK4, independently of its role as a PI3K heterodimer component and only in response to insulin and ER stress-inducing stimuli; both an intact N terminus and functional SH2 domains are required.\",\n      \"method\": \"p85alpha-/- and p85beta-/- cell lines; JNK activity assay; p85alpha domain mutant reconstitution; cdc42/MKK4 epistasis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO, domain mutant reconstitution, epistasis analysis identifying pathway components\",\n      \"pmids\": [\"17283057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"p85alpha (regulatory) and p110beta (catalytic) isoforms, but not p110alpha, are specifically required for androgen-stimulated androgen receptor transactivation and cell proliferation in prostate cancer cells; p110beta lipid kinase activity (not protein kinase activity) is required; p110beta is indispensable for androgen-induced AR-DNA interaction.\",\n      \"method\": \"siRNA knockdown of p85alpha/p110alpha/p110beta; AR transactivation assay; chromatin immunoprecipitation; tumor xenograft\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific siRNA knockdown with ChIP readout, kinase-dead mutant analysis, but PI3K-independent role of p85alpha not directly demonstrated\",\n      \"pmids\": [\"18372911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"p85alpha deficiency in osteoclasts results in impaired growth, differentiation, adhesion, and migration via integrin alphavbeta3, with reduced Akt and Erk1/2 activation; full-length p85alpha (but not SH3-domain-deleted version) is required for osteoclast maturation; p85alpha regulates expression of MITF, TRAP, cathepsin K, and beta3 integrin.\",\n      \"method\": \"p85alpha-/- osteoclast progenitors; in vivo bone histomorphometry; in vitro differentiation/adhesion/migration assays; microarray; reconstitution with SH3-deleted mutant\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with multiple cellular assays, in vivo bone phenotype, reconstitution with domain mutant identifying functional requirement for SH3 domain\",\n      \"pmids\": [\"18809581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"IREM-1 (CD300f) recruits p85alpha of PI3K (via tyrosine residues Y236 and Y263) and SHP-1 upon immunoprecipitation; PI3K recruitment through these residues (when Y205 and Y249 ITIM sites are mutated) drives degranulation in RBL cells, demonstrating dual inhibitory/activating signaling capacity of IREM-1 depending on p85alpha recruitment.\",\n      \"method\": \"Immunoprecipitation in transfected cells and U937 cells; IREM-1 tyrosine mutants; RBL cell degranulation assay; PI3K inhibitor treatment\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP in transfected and endogenous cells, functional degranulation assay with site-specific mutants\",\n      \"pmids\": [\"17202342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"p85alpha deficiency impairs NK cell lineage commitment (reducing NK cellularity in bone marrow and liver), Ly49 subset specification, NKG2D and NK1.1 receptor-mediated cytokine/chemokine generation, and NK-mediated cytotoxicity against tumor cells.\",\n      \"method\": \"p85alpha-/- mice; flow cytometric analysis of NK subset specification; NK cytotoxicity assays; cytokine measurement\",\n      \"journal\": \"Genes and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with multiple cellular phenotype readouts in primary NK cells, single lab\",\n      \"pmids\": [\"18548087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"p85alpha deficiency specifically impairs Kit ligand/SCF-induced (but not FcepsilonRI-initiated) mast cell secretory granule exocytosis, proliferation, and Akt phosphorylation, demonstrating receptor-specific usage of different PI3K family members in a single cell type.\",\n      \"method\": \"p85alpha-/- mast cells; Kit and FcepsilonRI cross-linking; exocytosis and proliferation assays; Akt phosphorylation; PI3K inhibitor (LY294002)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with receptor-specific functional dissection, pharmacological validation\",\n      \"pmids\": [\"10681597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PIK3R1 loss in ovarian cancer cells activates AKT through enhanced p110alpha kinase activity, decreased PTEN levels, and p110-independent JAK2/STAT3 signaling through deregulated Gab2 phosphorylation; PIK3R1 loss relieves negative inhibition on AKT and promotes assembly of JAK2/STAT3 signalosome.\",\n      \"method\": \"PIK3R1 knockdown in ovarian cancer cells; phosphoproteomics; Gab2 phosphorylation analysis; JAK2/STAT3 signaling assays; combination inhibitor treatment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic knockdown with phosphoproteomic analysis identifying Gab2 as mediator, multiple orthogonal signaling readouts\",\n      \"pmids\": [\"30755611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Both p85alpha and p85beta isoforms associate with p110 and PI3K activity in T cells; upon TCR/CD3 or PKC stimulation, the p110 complexed to p85alpha becomes rapidly phosphorylated on serine, while p85beta undergoes rapid increase in threonine phosphorylation, revealing differential regulation of the two PI3K isoforms.\",\n      \"method\": \"Phosphopeptide pulldown; isoform-specific monoclonal antibodies; T cell activation assays; phosphorylation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific antibodies with differential phosphorylation readout, single lab\",\n      \"pmids\": [\"8388374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"p85alpha deficiency in osteoclast progenitors (using p85alpha-/- mice) demonstrates that genetic disruption of p85alpha but not p85beta normalizes KITD814V oncogenic KIT-induced ligand-independent hyperproliferation and promiscuous cytokine responses in HSC/Ps and mast cell progenitors.\",\n      \"method\": \"Genetic disruption of p85alpha vs p85beta in KITD814V-expressing hematopoietic cells; proliferation assays; Rac inhibitor and rapamycin treatment\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific genetic disruption with functional proliferation readout, pharmacological validation\",\n      \"pmids\": [\"17483298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"C-terminal PIK3R1 mutations (SHORT syndrome) show severely reduced insulin-stimulated association of mutant but not WT p85alpha with IRS1; mutant p85alpha overexpression in 3T3-L1 preadipocytes attenuates insulin-induced AKT phosphorylation and adipocyte differentiation.\",\n      \"method\": \"Patient-derived cells (p.Tyr657X mutation); co-immunoprecipitation of p85alpha-IRS1; mutant p85alpha overexpression in 3T3-L1 cells; AKT phosphorylation; adipocyte differentiation assay\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP in patient-derived cells and reconstitution in 3T3-L1 cells, single lab\",\n      \"pmids\": [\"27766312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CBL mutations drive PI3K/AKT signaling via increased LYN activation and interaction with mutant CBL, leading to enhanced CBL phosphorylation, PIK3R1 recruitment, and downstream PI3K/AKT signaling; LYN inhibition (genetic or dasatinib) reduces CBL-PIK3R1 interaction and PI3K/AKT signaling.\",\n      \"method\": \"Global mass spectrometry phosphoproteomics; CBL interactome by MS; functional signaling assays; genetic ablation and dasatinib inhibition of LYN; in vitro and in vivo antiproliferative assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-defined interactome, genetic and pharmacological dissection of pathway, in vivo validation\",\n      \"pmids\": [\"33512474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PKA phosphorylates p85alpha on Ser83 adjacent to the N-terminal SH3 domain in vivo and in vitro; Ser83 phosphorylation is crucial for synergistic RARα/p85alpha binding induced by cAMP/RA co-treatment, and controls MCF7 cell proliferation, RA-induced inhibition of proliferation, migration, and RA-induced reduction of motility.\",\n      \"method\": \"PKA phosphorylation assay in vivo and in vitro; Ser83Ala and Ser83Asp p85alpha mutants; co-immunoprecipitation of RARα/p85alpha; cell growth and migration assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro phosphorylation assay with site-directed mutagenesis and functional cellular readout, single lab\",\n      \"pmids\": [\"22366926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"p85alpha promotes nucleolin (NCL) transcription via c-Jun activation; NCL binds EGFR mRNA and increases its stability; p85alpha thereby upregulates EGFR protein expression and promotes malignant cellular transformation in a PI3K-independent manner.\",\n      \"method\": \"p85alpha knockdown and knockout cells; EGFR mRNA stability assay; NCL overexpression rescue; c-Jun activation analysis\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD/KO with rescue experiment identifying NCL as intermediary, mRNA stability assay, single lab\",\n      \"pmids\": [\"26918608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NLRP6 binds p85alpha and recruits E3 ligase RBX1 to ubiquitinate p85alpha on Lys256; this ubiquitination is recognized by autophagy cargo receptor OPTN, causing selective autophagic degradation of p85alpha, subsequent reduction of PTEN stability, and activation of the PI3K/AKT pathway.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay with site-specific mutagenesis (K256); autophagy flux assay; OPTN interaction; PTEN stability assay; tumor xenograft\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — site-specific ubiquitination with mutagenesis, autophagy receptor identification, PTEN stability consequence, in vivo validation\",\n      \"pmids\": [\"37770465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PAK4 specifically interacts with p85alpha (the regulatory subunit of PI3K), and PAK4-deficient pancreatic cancer cells exhibit reduced AKT phosphorylation downstream of HGF signaling, implicating PAK4 in PI3K pathway activation via p85alpha interaction.\",\n      \"method\": \"Co-immunoprecipitation of PAK4 and p85alpha; PAK4 knockdown; AKT phosphorylation assay; HGF stimulation\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP identifying interaction, functional KD with signaling readout, single lab\",\n      \"pmids\": [\"28205613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"p85alpha deficiency in beta-cells markedly delays onset and severity of ER stress-induced diabetic phenotype in Akita+/- mice by decreasing activation of ER stress-dependent apoptotic pathways and preserving beta-cell mass; this is linked to p85alpha's role in promoting nuclear localization of XBP-1.\",\n      \"method\": \"p85alpha-deficient Akita+/- mice; beta-cell mass quantification; ER stress pathway assays; XBP-1 nuclear localization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with defined cellular phenotype (beta-cell apoptosis), mechanistic link to XBP-1 nuclear localization\",\n      \"pmids\": [\"24395790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"p85alpha deficiency in thymocytes impairs pre-TCR-controlled beta-selection (DN to DP transition) without affecting positive or negative selection; inhibition of p110delta blocks DN-to-DP transition in fetal thymic organ culture; PTEN deficiency (amplifying PI3K signals) accelerates this transition.\",\n      \"method\": \"p85alpha-/- Rag-2-/- mice with anti-CD3epsilon injection; p110delta inhibitor (IC87114) in fetal thymic organ culture; PTEN-/- thymic organ culture; flow cytometry of thymocyte subsets\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with pharmacological and epistatic validation across multiple experimental systems\",\n      \"pmids\": [\"17237381\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIK3R1 (p85alpha) is the predominant regulatory subunit of class IA PI3K that binds, stabilizes, and inhibits the p110 catalytic subunit via its nSH2, iSH2, and cSH2 domains; it also functions as an adaptor linking phosphotyrosine-containing receptors/IRS proteins to p110 activation, forms homodimers that bind and protect PTEN from proteasomal degradation, acts as a GAP for Rab5/Rab4 to regulate receptor trafficking, facilitates nuclear translocation of XBP-1s to resolve ER stress, participates in PI3K-independent JNK activation via cdc42/MKK4, can be ubiquitinated (by TRAF6 on Lys513/519 or by RBX1 on Lys256) to modulate its activity and stability, and undergoes PKA-mediated phosphorylation on Ser83 to integrate cAMP signaling; loss-of-function mutations cause immunodeficiency (APDS2) and SHORT syndrome via impaired p110 inhibition or disrupted IRS1 association, while gain-of-function mutations in the iSH2/nSH2 domains constitutively activate PI3K in cancer.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PIK3R1 encodes p85alpha, the predominant regulatory subunit of class IA PI3K, which binds the p110 catalytic subunit to stabilize and constitutively inhibit it while coupling its activation to phosphotyrosine-containing receptors and adaptors such as IRS proteins [#7, #9, #21]. The inhibitory function is mediated by the nSH2, iSH2, and cSH2 domains contacting p110; disruption of these contacts by deletions or truncations in the iSH2/nSH2 region releases p110 from inhibition and drives constitutive lipid-kinase activity [#2, #9, #21, #22]. The gene is functionally pleiotropic: full-length p85alpha forms homodimers through SH3-proline-rich and BH-BH (and cSH2-cSH2) intermolecular contacts, and these p110-free dimers bind, stabilize, and enhance the activity of PTEN, so that loss of p85alpha or its dimerization destabilizes PTEN and de-represses PI3K/AKT signaling [#10, #17, #18, #23]. Beyond its canonical lipid-kinase scaffold role, p85alpha carries BH-domain GAP activity toward Rab5/Rab4 and Cdc42/Rac1 that controls receptor (PDGFR) trafficking and degradation [#5], drives PI3K-independent JNK activation via Cdc42/MKK4 in insulin resistance and ER stress [#4, #26], and promotes nuclear translocation of XBP-1s to resolve ER stress [#8, #41]. Genetically, p85alpha is required for B-cell development, thymocyte beta-selection, NK and macrophage function, mast-cell and osteoclast signaling, and for insulin-stimulated GLUT4-mediated glucose uptake, where its dosage tunes metabolic sensitivity [#0, #1, #3, #6, #28, #42]. Heterozygous loss-of-function splice/truncation mutations cause the immunodeficiency APDS2 (via failed inhibition of p110delta) and SHORT syndrome (via disrupted IRS1 association and reduced PI3K-AKT-mTOR signaling), while iSH2/nSH2 gain-of-function mutations constitutively activate PI3K in cancer [#11, #12, #21, #22, #35]. Its activity is further modulated by post-translational modification, including TRAF6-mediated K63 ubiquitination on Lys513/519 promoting TGF-beta receptor coupling, RBX1/NLRP6-driven K256 ubiquitination targeting it for autophagic degradation, and PKA phosphorylation on Ser83 integrating cAMP signaling [#20, #37, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing that PIK3R1 generates multiple regulatory isoforms with distinct receptor-coupling properties answered how a single gene tunes PI3K responsiveness to insulin.\",\n      \"evidence\": \"Expression cloning with 32P-IRS-1, co-IP, and PI3K activity assays defining p85alpha/p55alpha/p50alpha isoforms\",\n      \"pmids\": [\"9065454\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific physiological roles of each isoform not resolved\", \"Structural basis of differential IRS-1 affinity not defined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Genetic ablation in mice defined the in vivo cellular requirements for p85alpha, separating an essential role in B-cell development from dispensability in T-cell development.\",\n      \"evidence\": \"RAG2 blastocyst complementation with p85alpha/p55alpha/p50alpha knockout mice and lymphocyte functional readouts\",\n      \"pmids\": [\"9888855\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular signal downstream of receptors not mapped\", \"Does not address adaptor vs catalytic-scaffold contribution\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrating that p85alpha dosage controls insulin sensitivity revealed the regulatory subunit as a rate-limiting tuner of metabolic PI3K signaling rather than merely a permissive scaffold.\",\n      \"evidence\": \"Targeted knockout mice with insulin-stimulated PI3K activity, PIP3 measurement, and GLUT4 fractionation; later confirmed by heterozygous models\",\n      \"pmids\": [\"9988280\", \"11781359\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of isoform switch (p85alpha to p50alpha) not fully defined\", \"Liver vs muscle vs adipose contributions partly separable\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Mapping the p85alpha homodimerization interfaces established that the protein self-associates independently of SH2 ligand binding, anticipating a p110-free pool.\",\n      \"evidence\": \"Deletion/point mutants, native PAGE, and competition experiments in vitro and in vivo\",\n      \"pmids\": [\"10212202\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of dimerization not yet known at this stage\", \"Stoichiometry in cells not quantified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Finding constitutively activating iSH2 deletions in tumors reclassified PIK3R1 as an oncogene, not solely a negative regulator.\",\n      \"evidence\": \"Mutation analysis of primary colon/ovarian tumors plus PI3K activity assay of mutant protein\",\n      \"pmids\": [\"11606375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise structural mechanism of activation deferred to later HDX-MS work\", \"Frequency across cancer types not established here\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showing p85alpha is required for insulin-stimulated JNK activation via Cdc42/MKK4 uncovered a PI3K-catalysis-independent signaling output of the regulatory subunit.\",\n      \"evidence\": \"p85alpha-/- brown adipocyte lines with reconstitution by domain mutants and JNK/Akt/glucose-uptake readouts\",\n      \"pmids\": [\"14504291\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical link between p85alpha and Cdc42 not reconstituted\", \"Physiological relevance addressed later in insulin resistance\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identifying BH-domain GAP activity toward Rab5/Rab4/Cdc42/Rac1 assigned p85alpha a direct role in receptor trafficking distinct from PI3K regulation.\",\n      \"evidence\": \"In vitro GAP assays with purified protein, direct Rab5 binding, and BH-mutant PDGFR degradation assays\",\n      \"pmids\": [\"15377662\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular GAP targets in vivo not exhaustively validated\", \"Regulation of the GAP activity unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defining Galpha(q) as a GTP-dependent binder of the p110alpha/p85alpha complex linked GPCR signaling to PI3K regulation via competition with Ras.\",\n      \"evidence\": \"Purified-protein fluorescence spectroscopy, deletion-mutant co-precipitation, and constitutively active Galpha(q) signaling assays\",\n      \"pmids\": [\"16268778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological GPCR contexts not established\", \"Net signaling outcome (inhibition vs activation) context-dependent\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Linking insulin-disrupted p85 monomers to XBP-1s nuclear translocation established a non-catalytic role in resolving ER stress.\",\n      \"evidence\": \"Reciprocal Co-IP, nuclear fractionation, and in vivo p85 overexpression rescue in ob/ob liver\",\n      \"pmids\": [\"20348926\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding region on XBP-1s not mapped\", \"Relationship to dimer-monomer equilibrium not quantified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Distinguishing gain-of-function SH2-domain mutations from loss-of-binding truncations clarified that PIK3R1 cancer mutations act by p110 retention with failed inhibition.\",\n      \"evidence\": \"Stable mutant expression in U2OS cells with p110alpha co-IP and phospho-AKT readout\",\n      \"pmids\": [\"21478295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative activation per mutant not measured biochemically here\", \"Isoform selectivity (p110alpha vs delta) addressed later\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Discovering that p85alpha dimers bind and stabilize PTEN defined a second tumor-suppressive axis lost in cancer mutations.\",\n      \"evidence\": \"Co-IP of p85alpha dimer-PTEN complex with functional signaling assays across multiple mutations\",\n      \"pmids\": [\"21984976\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PTEN protection deferred to later reconstitution\", \"In vivo contribution to tumor suppression not quantified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identifying heterozygous PIK3R1 mutations as causal for SHORT syndrome established a human disease of reduced PI3K-AKT-mTOR signaling.\",\n      \"evidence\": \"Whole-exome/Sanger sequencing across families with downstream S6 phosphorylation assay in patient lymphoblastoid cells\",\n      \"pmids\": [\"23810382\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single downstream marker (S6) assayed\", \"Mechanism narrowed to IRS1 association only in later work\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing that immunodeficiency-causing splice mutations delete inhibitory iSH2/p110-binding residues established APDS2 as a gain-of-function disease via failed p110delta restraint.\",\n      \"evidence\": \"Patient T-cell studies, mutant overexpression, complex analysis, and PI3Kdelta-inhibitor rescue\",\n      \"pmids\": [\"25488983\", \"25133428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Isoform-specific quantitative activation defined later by HDX-MS\", \"Variability across mutations not fully resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Multiple 2014 reports revealed unexpected nuclear/scaffolding roles for p85alpha and its truncation mutants in immune and oncogenic signaling beyond PI3K.\",\n      \"evidence\": \"Co-IP, nuclear fractionation, and signaling assays for p85alpha-OPN-i/Bcl-6, BRD7 competition for p85, and nuclear JNK/ERK scaffolding by R348*/L370fs mutants\",\n      \"pmids\": [\"25436971\", \"24657164\", \"25284480\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How nuclear translocation is regulated for wild-type vs mutant p85alpha incomplete\", \"Generality of scaffolding roles across cell types unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Structural and biophysical characterization of the reversible p85alpha homodimer and its selective binding to unphosphorylated PTEN defined the mechanism protecting PTEN from WWP2-mediated degradation.\",\n      \"evidence\": \"AUC, FFS, SAXS, cross-linking, biochemical pulldown, in vitro PTEN phosphatase and degradation assays with domain mutants\",\n      \"pmids\": [\"26475863\", \"26222500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo concentration-dependence of dimer-monomer switch not measured\", \"Crosstalk between p110 binding and PTEN binding only partly resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Quantitative biochemistry resolved that APDS2-type iSH2 deletions hyperactivate p110delta far more than p110alpha by simultaneously disrupting nSH2/iSH2/cSH2 inhibitory contacts.\",\n      \"evidence\": \"Reconstituted kinase assays with HDX-MS comparing p110alpha vs p110delta activation; idelalisib sensitivity\",\n      \"pmids\": [\"28167755\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular consequences of isoform-selective activation not modeled here\", \"Other p85 contact regions not exhaustively mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating TRAF6-mediated K63 ubiquitination of p85alpha at Lys513/519 revealed a ubiquitin-dependent, kinase-independent route to TGF-beta receptor coupling and motility.\",\n      \"evidence\": \"PLA, Co-IP, site-specific ubiquitination mutagenesis, migration assays, and tumor tissue analysis\",\n      \"pmids\": [\"28676490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Deubiquitinase counterpart not identified\", \"Generality beyond TGF-beta context unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Biochemical dissection of additional cancer mutations distinguished iSH2 truncations that broadly de-repress p110alpha from cSH2 mutations that reduce RTK responsiveness.\",\n      \"evidence\": \"Reconstituted kinase assays with HDX-MS on Q572* and R649W mutants\",\n      \"pmids\": [\"31831213\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular and clinical correlates of each mutant not established\", \"Crosstalk with PTEN-binding function not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying NLRP6/RBX1-driven K256 ubiquitination and OPTN-mediated autophagic degradation of p85alpha defined a turnover mechanism whose loss destabilizes PTEN and activates PI3K/AKT.\",\n      \"evidence\": \"Co-IP, K256 site-specific ubiquitination mutagenesis, autophagy flux, OPTN interaction, PTEN stability, and tumor xenograft\",\n      \"pmids\": [\"37770465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signals triggering this degradation unclear\", \"Interplay with TRAF6 ubiquitination not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple p85alpha functions—p110 inhibition, PTEN stabilization, GAP activity, nuclear scaffolding, and ubiquitin/phosphorylation control—are coordinated within a single cell and dynamically partitioned between catalytic and non-catalytic pools remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No integrated model of how dimer-monomer equilibrium routes p85alpha among p110, PTEN, and nuclear partners\", \"Quantitative cellular stoichiometry of competing complexes unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [9, 17, 21, 22]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [7, 14, 15, 25, 36]},\n      {\"term_id\": \"GO:0005154\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [10, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [8, 15, 16]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [8, 14, 15, 16]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 9, 21, 24]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 30, 42, 12, 21]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [8, 41]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 11, 21, 22]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [39]}\n    ],\n    \"complexes\": [\n      \"class IA PI3K (p85alpha-p110alpha/p110delta)\",\n      \"p85alpha homodimer\"\n    ],\n    \"partners\": [\n      \"PIK3CA\",\n      \"PIK3CD\",\n      \"PTEN\",\n      \"IRS1\",\n      \"XBP1\",\n      \"TRAF6\",\n      \"BRD7\",\n      \"RBX1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}