{"gene":"PIKFYVE","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":1999,"finding":"PIKfyve (p235) is a mammalian lipid kinase that synthesizes PtdIns5P and PtdIns(3,5)P2 in vitro, displaying striking specificity for PtdIns over PI substrates; deletion mutant analysis showed that regions beyond the predicted catalytic domain are critical for enzymatic activity.","method":"In vitro kinase assay with recombinant protein expressed in COS cells, HPLC analysis of lipid products, deletion mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro kinase activity with HPLC product identification, foundational paper","pmids":["10419465"],"is_preprint":false},{"year":2001,"finding":"PIKfyve enzymatic activity is required for mammalian cell morphology and endomembrane homeostasis; kinase-dead PIKfyve(K1831E) causes dominant vacuolation of endosomal origin, and disruption of the FYVE-domain localization signal abolishes this phenotype, indicating that active PIKfyve at late endocytic membranes is essential.","method":"Dominant-negative kinase-dead mutant expression, fluorescence microscopy, cell viability assays, rescue with wild-type PIKfyve","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — clean dominant-negative with defined phenotypic readout, rescued by wild-type, replicated across multiple cell types","pmids":["11285266"],"is_preprint":false},{"year":2001,"finding":"PIKfyve localizes to late endocytic membranes via its FYVE domain binding to PtdIns3P; the FYVE domain is absolutely required for endosomal membrane targeting, and wortmannin treatment dissociates PIKfyve from endosomes; an additional low-affinity PtdIns3P-binding site exists in the catalytic domain.","method":"PtdIns3P liposome binding assays, FYVE domain mutagenesis, wortmannin treatment, fluorescence microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding reconstitution with mutagenesis and cellular localization validation","pmids":["11706043"],"is_preprint":false},{"year":2002,"finding":"PIKfyve is responsible for PtdIns5P biosynthesis in cellular contexts; expression of PIKfyve(WT) increases intracellular PtdIns5P, while dominant-negative PIKfyve(K1831E) decreases it; PtdIns5P levels decrease under hypo-osmotic stress, linking PIKfyve to the osmotic response pathway.","method":"32P-labeling, HPLC head-group analysis, in vitro type II PIP kinase conversion assay, dominant-negative expression in multiple cell types","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — two independent approaches in multiple cell types, gain- and loss-of-function","pmids":["12270933"],"is_preprint":false},{"year":2003,"finding":"PIKfyve selectively regulates fluid-phase endocytosis and multivesicular body morphogenesis; kinase-dead PIKfyve impairs late uptake of horseradish peroxidase and disrupts MVB morphology (fewer internal vesicles), without affecting transferrin recycling, EGF receptor degradation, or cathepsin D sorting.","method":"Stable inducible cell lines, fluid-phase marker uptake, confocal microscopy with organelle markers, electron microscopy","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — clean inducible dominant-negative system with specific phenotypic readouts and EM confirmation","pmids":["14551253"],"is_preprint":false},{"year":2003,"finding":"PIKfyve physically interacts with the Rab9 effector p40 via its chaperonin domain; enzymatically active PIKfyve promotes membrane attachment of p40 and phosphorylates it on serine residues, facilitating late endosome-to-TGN transport.","method":"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, differential centrifugation, in vitro kinase assay, phosphoserine antibody","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP confirmed by yeast two-hybrid and GST pulldown, kinase activity demonstrated in vitro","pmids":["14530284"],"is_preprint":false},{"year":2004,"finding":"PKB/Akt phosphorylates PIKfyve on Ser318, stimulating its PtdIns3P 5-kinase activity; this phosphorylation occurs in intact cells in response to insulin in a PI3K-dependent manner; overexpression of PIKfyve[S318A] in adipocytes enhances insulin-stimulated IRAP/GLUT4 vesicle translocation.","method":"In vitro kinase assay, phospho-specific antibodies, 3T3-L1 adipocyte translocation assay, site-directed mutagenesis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 — in vitro phosphorylation by PKB demonstrated, confirmed in intact cells, functional consequence shown by mutation","pmids":["15546921"],"is_preprint":false},{"year":2004,"finding":"Human Vac14 (ArPIKfyve) is a positive regulator of PIKfyve enzymatic activity; it co-fractionates and co-localizes with PIKfyve, physically associates with it, and its siRNA-mediated knockdown reduces PIKfyve kinase activity and PtdIns(3,5)P2 production, causing endomembrane vacuolation.","method":"Co-immunoprecipitation, siRNA knockdown, in vitro kinase assay, 32P-labeling/HPLC, confocal microscopy","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — Co-IP plus in vitro activity assay plus siRNA knockdown with defined phenotypic and biochemical readouts","pmids":["15542851"],"is_preprint":false},{"year":2006,"finding":"PIKfyve is predominantly associated with early endosomal tubular and vesicular elements and regulates endosome-to-TGN retrograde transport; siRNA suppression of PIKfyve causes swollen endosomal structures and a clear defect in retrograde trafficking without affecting EGF receptor degradation or transferrin recycling.","method":"Live and fixed cell imaging, siRNA knockdown, receptor trafficking assays in HeLa cells","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — siRNA with specific functional readout (retrograde transport defect) and live imaging localization","pmids":["16954148"],"is_preprint":false},{"year":2007,"finding":"Sac3 (mammalian Fig4) forms a stable ternary complex with ArPIKfyve and PIKfyve; Sac3 preferentially hydrolyzes PtdIns(3,5)P2 in vitro; siRNA knockdown of Sac3 elevates PtdIns(3,5)P2 levels; reconstitution assays show Sac3 loss gains function in carrier vesicle formation while PIKfyve or ArPIKfyve depletion causes loss of function.","method":"Co-immunoprecipitation, co-fractionation, in vitro phosphatase assay, siRNA knockdown, 32P-labeling, in vitro vesicle formation reconstitution","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted ternary complex with in vitro phosphatase activity and in vitro vesicle formation assay","pmids":["17556371"],"is_preprint":false},{"year":2007,"finding":"PIKfyve mediates HB-EGF-stimulated EGFR nuclear trafficking and EGFR binding to the cyclin D1 promoter; PIKfyve was identified as part of EGFR immune complexes by mass spectrometry, and siRNA silencing of PIKfyve blocks EGFR nuclear translocation and cell cycle progression.","method":"Mass spectrometry of EGFR immune complexes, siRNA knockdown, nuclear fractionation, chromatin immunoprecipitation","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — MS identification plus siRNA with defined functional readout, single lab","pmids":["17909029"],"is_preprint":false},{"year":2008,"finding":"YM201636, a potent selective inhibitor of PIKfyve, blocks PtdIns(3,5)P2 production, causes accumulation of late endosomal compartments, and blocks retroviral budding; specificity confirmed by siRNA against PIKfyve and rescue with drug-resistant yeast Fab1 ortholog.","method":"Small-molecule inhibitor, siRNA knockdown, rescue with yeast Fab1, phosphoinositide measurements, cell biology assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — inhibitor specificity confirmed by orthogonal siRNA and yeast rescue, multiple functional readouts","pmids":["18188180"],"is_preprint":false},{"year":2008,"finding":"PIKfyve interacts with the kinesin adapter JLP via the PIKfyve cpn60_TCP1 domain; both proteins are required for microtubule-based endosome-to-TGN transport of furin but not microtubule-independent Tac-TGN38 delivery.","method":"Yeast two-hybrid, pulldown, co-immunoprecipitation, siRNA knockdown, cargo trafficking assay, microinjection of interacting peptides","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal binding methods plus functional specificity demonstrated with cargo-selective trafficking assay","pmids":["19056739"],"is_preprint":false},{"year":2009,"finding":"PIKfyve-containing PAS complex: Sac3 assembled within the PIKfyve-ArPIKfyve-Sac3 core retains active PtdIns(3,5)P2 phosphatase activity; the cpn60_TCP1 domain of PIKfyve mediates ArPIKfyve-Sac3 subcomplex binding; kinase and phosphatase activities do not affect complex stability.","method":"Truncation and point mutants of all three proteins in triple-transfected COS cells, vacuolation assay as functional readout, biochemical binding analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — systematic mutagenesis of contact sites with functional readout, confirms active phosphatase within complex","pmids":["19840946"],"is_preprint":false},{"year":2009,"finding":"PIKfyve regulates lysosomal targeting and degradation of voltage-gated Ca2+ channel CaV1.2; NMDA receptor activation recruits PIKfyve to CaV1.2 channels, increases PtdIns(3,5)P2, and promotes CaV1.2 targeting to lysosomes; PIKfyve knockdown prevents CaV1.2 degradation and increases neuronal susceptibility to excitotoxicity.","method":"Co-immunoprecipitation, siRNA knockdown, live imaging, neuronal excitotoxicity assays, PtdIns(3,5)P2 measurements","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — Co-IP showing physical interaction, siRNA with specific functional consequence (excitotoxicity), multiple orthogonal approaches","pmids":["19841139"],"is_preprint":false},{"year":2009,"finding":"PIKfyve stimulates EAAT2 glutamate transporter activity and increases its membrane abundance; the effect requires Ser318 in the SGK1 phosphorylation consensus of PIKfyve, as S318A mutant abolishes PIKfyve's stimulatory effect.","method":"Xenopus oocyte expression, electrophysiology, confocal microscopy, site-directed mutagenesis (S318A)","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — functional assay in oocytes with mutagenesis, single lab","pmids":["19910676"],"is_preprint":false},{"year":2010,"finding":"PIKfyve is required for macropinosome-to-late endosome/lysosome fusion; disruption of PIKfyve (by interfering mutant, siRNA, or pharmacological inhibition) inhibits intracellular replication of Salmonella by blocking SCV maturation and SPI2-T3SS engagement.","method":"Dominant-negative mutant, siRNA, pharmacological inhibition, 4D videomicroscopy, Salmonella infection assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — three independent methods (genetic, siRNA, pharmacological), specific functional pathway (macropinosome-LE fusion) identified by live imaging","pmids":["20300065"],"is_preprint":false},{"year":2012,"finding":"In vivo, Pikfyve generates all of the PI(3,5)P2 pool and is also responsible for nearly all PI5P production, with PI5P generated directly from PI(3,5)P2 likely via 3'-phosphatase activity; demonstrated using a Pikfyve hypomorph mouse and shRNA silencing of residual transcript.","method":"Mouse hypomorph (gene trap), shRNA silencing in fibroblasts, phosphoinositide mass measurement in tissues","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — in vivo mouse model plus shRNA, quantitative lipid measurements across multiple tissues","pmids":["23047693"],"is_preprint":false},{"year":2012,"finding":"PIKfyve-synthesized PtdIns5P mediates insulin-induced actin stress fiber disassembly, while PtdIns(3,5)P2 is responsible for cellular vacuolation; these two lipid products are functionally dissociable using differential dosing of YM201636.","method":"Differential-dose PIKfyve inhibitor (YM201636), HPLC phosphoinositide measurement, actin stress fiber imaging, GLUT4 translocation assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological dissection with quantitative lipid readouts and functional cellular assays, single lab","pmids":["22621786"],"is_preprint":false},{"year":2012,"finding":"PtdIns5P produced via PIKfyve and MTMR3 promotes cell migration; PIKfyve and MTMR3 constitute a phosphoinositide loop generating PtdIns5P via PtdIns(3,5)P2; exogenous PtdIns5P or bacterial PtdIns5P-producing enzyme directly stimulates migration.","method":"siRNA screen, migration assays in tissue culture and Drosophila in vivo model, exogenous PtdIns5P addition, bacterial enzyme","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches including in vivo Drosophila model, direct lipid addition, and genetic knockdown","pmids":["23154468"],"is_preprint":false},{"year":2013,"finding":"AKT phosphorylates and activates PIKfyve upon EGF stimulation, promoting vesicle trafficking of EGFR to lysosomes for degradation; in AKT-impaired cells EGFR accumulates in early endosomes with prolonged ERK/RSK signaling; similar regulation occurs for PDGFR.","method":"Kinase assay, phospho-specific antibodies, AKT inhibition, PIKfyve siRNA, receptor trafficking assays, dominant-negative approaches","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 — in vitro phosphorylation by AKT demonstrated, confirmed in cells, specific trafficking phenotype, replicated with two RTKs","pmids":["23757022"],"is_preprint":false},{"year":2013,"finding":"AMPK phosphorylates PIKfyve at Ser307, promoting its translocation to endosomal membranes and PtdIns(3,5)P2 synthesis; this is required for contraction/AMPK-stimulated glucose uptake in skeletal muscle.","method":"In vitro AMPK kinase assay, S307A mutant, subcellular fractionation, siRNA knockdown in myotubes, glucose uptake assay in muscle","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro phosphorylation demonstrated, S307A mutant loses translocation response, functional consequence in intact muscle","pmids":["23905686"],"is_preprint":false},{"year":2014,"finding":"PIKfyve inhibition blocks phagosome maturation in macrophages by delaying PtdIns3P removal and reducing acquisition of LAMP1 and cathepsin D on phagosomes, impairing degradative capacity without affecting acidification.","method":"PIKfyve pharmacological inhibitors, FcγR-mediated phagocytosis assay, live imaging, immunofluorescence with lysosomal markers, degradation assays","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 — multiple inhibitors, defined functional pathway (phagosome maturation), specific mechanistic steps identified","pmids":["25041080"],"is_preprint":false},{"year":2014,"finding":"PIKfyve is required for endolysosomal TLR-induced type I IFN production; PIKfyve inactivation induces expression of the transcriptional repressor ATF3, which binds the IFN promoter and blocks transcription; this is independent of receptor/ligand trafficking.","method":"PIKfyve pharmacological inhibition and genetic inactivation, ATF3 expression analysis, IFN promoter binding assay, chromatin IP","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological and genetic inactivation with mechanistic link to ATF3 promoter binding, single lab","pmids":["24600036"],"is_preprint":false},{"year":2015,"finding":"APP (amyloid precursor protein) directly binds Vac14 via its intracellular domain and associates with the PIKfyve complex (Vac14/PIKfyve/Fig4); APP binding drives formation of PI(3,5)P2-positive vesicles; APP family members are required for PIKfyve function; PIKfyve complex is required for APP trafficking.","method":"Proteo-liposome interactome assay, GST pulldown with purified Vac14, co-immunoprecipitation, C. elegans genetic epistasis, PI(3,5)P2 vesicle formation assay","journal":"Cellular and molecular life sciences","confidence":"High","confidence_rationale":"Tier 2 — direct binding to purified Vac14 plus in vivo C. elegans genetic epistasis and vesicle formation assay","pmids":["26216398"],"is_preprint":false},{"year":2016,"finding":"PIKfyve inhibition increases exosome secretion and induces secretory autophagy by impairing fusion of lysosomes with MVBs and autophagosomes; inhibition leads to more MVBs with more intraluminal vesicles and accumulation of autophagy proteins (LC3, p62, NBR1) in exosomal fractions.","method":"Apilimod treatment and siRNA, quantitative electron microscopy, mass spectrometry of exosomal fractions, density gradient fractionation, long-lived protein degradation assay","journal":"Cellular and molecular life sciences","confidence":"High","confidence_rationale":"Tier 2 — pharmacological and genetic approaches with quantitative EM and MS, multiple orthogonal readouts","pmids":["27438886"],"is_preprint":false},{"year":2016,"finding":"PIKfyve inhibition leads to lysosome enlargement primarily through lysosome coalescence (fusion over fission) rather than biosynthesis; PIKfyve inhibition activates TFEB/TFE3/MITF but this does not contribute to acute swelling; conditions reducing fusion curtail lysosome enlargement.","method":"Live imaging, organelle counting, fusion/fission dynamics analysis, TFEB/TFE3/MITF reporter assays, TFEB/TFE3 knockout","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — genetic deletion of TFEB plus live imaging of fusion dynamics, mechanistic model established","pmids":["29661845"],"is_preprint":false},{"year":2016,"finding":"PIKfyve regulates vacuole size and nutrient recovery during macropinocytosis, entosis, and phagocytosis through its downstream effector TRPML1 (cationic transporter); PIKfyve activity protects Ras-mutant cells from starvation-induced death.","method":"PIKfyve inhibitors, TRPML1 genetic manipulation, vacuole size measurement, nutrient recovery assay, starvation survival assay","journal":"Developmental cell","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological and genetic approaches, TRPML1 as downstream effector established, single lab","pmids":["27623384"],"is_preprint":false},{"year":2017,"finding":"Apilimod's cytotoxic activity is driven specifically by PIKfyve inhibition; a resistance mutation in the PIKfyve kinase domain confers apilimod resistance; a genome-wide CRISPR screen identified lysosomal genes and TFEB as determinants of apilimod sensitivity, supporting lysosome dysfunction as the major cytotoxic mechanism.","method":"Biochemical target validation, kinase domain resistance mutation, genome-wide CRISPR screen, siRNA knockdown","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — resistance mutation and genome-wide genetic screen, multiple orthogonal approaches","pmids":["28104689"],"is_preprint":false},{"year":2017,"finding":"PIKfyve is acylated by zDHHC9 and zDHHC21 acyltransferases; prion infection or UPR disturbs juxtavesicular acyltransferase topology causing PIKfyve deacylation, rapid degradation, and endolysosomal hypertrophy; overexpression of acyltransferases or PI(3,5)P2 supplementation suppresses prion-induced vacuolation.","method":"Acylation assay, zDHHC knockdown/overexpression, UPR induction, mouse/organotypic brain slice infection models, rescue with PI(3,5)P2","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 — acylation writer identified (zDHHC9/21), functional consequence of deacylation demonstrated, in vivo and cell models","pmids":["34291577"],"is_preprint":false},{"year":2017,"finding":"PIKfyve coordinates neutrophil immune response through activation of Rac GTPase; PIKfyve inhibition blocks chemotaxis, ROS production, and Rac activation, while phagosome-lysosome fusion block can be partially rescued by TRPML1 agonists or Ca2+ ionophores.","method":"Human and mouse neutrophils, PIKfyve inhibitors, Rac activation assay, chemotaxis assay, ROS measurement, phagosome maturation assay, Ca2+ ionophore rescue","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays in primary cells, TRPML1 pathway implicated, single lab","pmids":["28779020"],"is_preprint":false},{"year":2018,"finding":"PIKfyve promotes MHC class II antigen presentation by facilitating cathepsin S activity; PIKfyve inhibition delays phagosome-to-lysosome conversion and acidification, increases ROS, which reduces cathepsin S and B activity, impairing invariant chain processing and MHC class II presentation.","method":"PIKfyve inhibitors, cathepsin activity assay, phagosome maturation assay, novel bio-orthogonal antigen presentation assay, T cell activation assay","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway established (ROS→cathepsin→Ii processing→MHC II presentation), single lab with multiple assays","pmids":["30612035"],"is_preprint":false},{"year":2020,"finding":"The PIKfyve complex comprises five copies of Vac14 scaffolding protein and one copy each of PIKfyve kinase and Fig4 phosphatase; Fig4 is active as a lipid phosphatase within the complex while PIKfyve cannot access membrane-incorporated phosphoinositides due to steric constraints; PIKfyve autophosphorylation represses its lipid kinase activity and stimulates Fig4 phosphatase; Fig4 acts as a protein phosphatase on PIKfyve to stimulate its lipid kinase activity.","method":"Cryo-EM structure, structural-biochemical analysis, in vitro phosphatase and kinase assays, mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure with in vitro enzymatic validation and mutagenesis, complex stoichiometry established","pmids":["33098764"],"is_preprint":false},{"year":2020,"finding":"Pharmacological inhibition of PIKfyve with apilimod or vacuolin-1 blocks content release and infection by VSV-ZEBOV and SARS-CoV-2 by interfering with late endosomal trafficking required for viral entry.","method":"Chimeric VSV with ebolavirus/SARS-CoV-2 envelope proteins, live SARS-CoV-2 infection assay, apilimod and vacuolin-1 treatment, content release imaging","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — pharmacological inhibition confirmed with two inhibitor classes and live virus, specific step (endosomal content release) identified","pmids":["32764148"],"is_preprint":false},{"year":2021,"finding":"ULK1 activated by AMPK during glucose starvation phosphorylates PIKfyve on Ser1548, increasing PIKfyve activity and PI(5)P synthesis (without changing PI(3,5)P2 levels); this promotes PI(5)P-containing autophagosome formation and autophagy flux.","method":"In vitro kinase assay (ULK1 phosphorylating PIKfyve), phosphomimetic S1548D mutant, phosphoinositide measurements, autophagy flux assays in multiple cell lines","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1 — in vitro phosphorylation by ULK1, phosphomimetic mutant drives autophagy, quantitative lipid measurements","pmids":["34107300"],"is_preprint":false},{"year":2021,"finding":"PIKfyve inhibition activates an unconventional protein clearance mechanism involving exocytosis of aggregation-prone proteins, ameliorating ALS pathology in motor neurons from C9ORF72, TARDBP, FUS, and sporadic ALS models.","method":"Pharmacological PIKfyve inhibition, patient-derived iPSC motor neurons, ALS mouse models, exocytosis assays for aggregated proteins","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 2 — multiple ALS model systems, specific mechanism (exocytosis vs autophagy/UPS) identified, single lab","pmids":["36754049"],"is_preprint":false},{"year":2022,"finding":"PIKfyve inhibition selectively blocks mTORC1-mediated phosphorylation of TFEB at Ser-211 without impairing mTORC1 activity toward other substrates; PI(3,5)P2 depletion prevents mTORC1 access to TFEB; PP2A (not calcineurin) dephosphorylates TFEB Ser-211 when PIKfyve is inhibited, enabling TFEB nuclear localization.","method":"mTORC1 substrate phosphorylation profiling, PP2A and calcineurin inhibitors, TFEB nuclear localization assay, mTORC1-TFEB interaction assay","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic pathway established (PIKfyve→mTORC1-TFEB access→PP2A), single lab","pmids":["35020443"],"is_preprint":false},{"year":2022,"finding":"PIKfyve and its upstream PI3-kinase VPS34 coordinate a phosphoinositide cascade to regulate Retriever-mediated recycling of integrins from endosomes; PIKfyve inhibition displaces Retriever and CCC complexes from endosomes; endogenous PIKfyve co-localizes with SNX17, Retriever, WASH, and CCC on endosomes.","method":"Co-localization of endogenous proteins, PIKfyve inhibition, Retriever/CCC displacement assay, integrin recycling assay, VPS34 epistasis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis (VPS34-PIKfyve cascade), endogenous protein co-localization, cargo-specific recycling assay","pmids":["35040777"],"is_preprint":false},{"year":2023,"finding":"PIKfyve is recruited to phagosomes and macropinosomes and PI(3,5)P2 accumulates 3 min after engulfment; PIKfyve activation stimulates its own dissociation from the membrane; retention of PI(3,5)P2 differs between phagosomes and macropinosomes indicating pathway-specific regulation.","method":"Novel PI(3,5)P2 reporter (SnxA), live imaging in Dictyostelium and mammalian cells, PIKfyve recruitment vs. activity dissection","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — validated PI(3,5)P2 reporter in two model systems, live dynamics imaging, mechanistic insight on PIKfyve self-regulation","pmids":["37382666"],"is_preprint":false},{"year":2000,"finding":"PIKfyve protein and enzymatic activity are found in cytosol (~76%), low-density microsomal fraction (~20%), and plasma membrane (~4%) of 3T3-L1 adipocytes; PIKfyve associates with TGN/MVB markers rather than recycling endosomes; insulin recruits cytosolic PIKfyve to intracellular membranes with a concomitant increase in lipid kinase activity.","method":"Subcellular fractionation, immunoadsorption, density gradient sedimentation, fluorescence microscopy, immunokinase assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple fractionation approaches with functional enzyme assay, insulin-regulated redistribution established","pmids":["11112776"],"is_preprint":false},{"year":2001,"finding":"PIKfyve physically associates with class IA PI3-kinase (p85/p110) in 3T3-L1 adipocytes; insulin specifically activates class IA PI3-K within PIKfyve immune complexes independently of IRS protein tyrosine phosphorylation.","method":"Co-immunoprecipitation, in vitro PI3K kinase assay in immune complexes, wortmannin/Triton sensitivity, insulin stimulation","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP with functional kinase activity measurement, single lab","pmids":["11476939"],"is_preprint":false},{"year":2011,"finding":"NPM-ALK tyrosine kinase physically associates with PIKfyve, activates its lipid kinase activity through tyrosine kinase activity (complex formation is kinase-independent), and PIKfyve promotes NPM-ALK-mediated cell invasion and MMP9 surface localization/maturation.","method":"Co-immunoprecipitation, PIKfyve lipid kinase assay, siRNA, YM201636 inhibition, invasion assay, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus in vitro kinase activity measurement, functional invasion assay, single lab","pmids":["21737449"],"is_preprint":false},{"year":2015,"finding":"Class III PI3K (Vps34) is the main source of PtdIns3P for both PIKfyve enzymatic activity and membrane recruitment; Vps34 knockout in podocytes causes vacuolation through PIKfyve dysfunction, as PIKfyve overexpression rescues the vacuolation in PIKfyve-KO MEFs but not in Vps34-KO podocytes.","method":"Conditional Vps34 and Pikfyve knockout cells, HPLC phosphoinositide profiling, PtdIns3P biosensor, rescue experiments","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with quantitative lipid measurements, conditional KO cells with rescue experiments","pmids":["25619930"],"is_preprint":false},{"year":2015,"finding":"PIKfyve activity is required for TLR9 trafficking to the LAMP1+ endosomal compartment for type I IFN signaling; PIKfyve inhibition blocks AP-3 recruitment to TLR9 endosomes while leaving VAMP3+ endosome trafficking intact.","method":"PIKfyve inhibitor treatment, confocal microscopy with TLR9/CpG/compartment markers, FLT3L-bone marrow DCs, RAW264.7 cells","journal":"International immunology","confidence":"Medium","confidence_rationale":"Tier 2 — specific compartment-selective trafficking defect identified by imaging, single lab","pmids":["25170925"],"is_preprint":false},{"year":2019,"finding":"PIKfyve activity is required for efficient V-ATPase and hydrolase delivery to phagosomes in Dictyostelium; PIKfyve-null cells fail to acidify phagosomes and cannot kill bacteria, making them more susceptible to Legionella infection.","method":"PIKfyve gene disruption in Dictyostelium, phagosome acidification assay, protease delivery assay, bacterial killing assay, Legionella infection","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 — genetic null cells in model phagocyte with specific functional dissection (V-ATPase vs. protease delivery), confirmed ortholog","pmids":["30730983"],"is_preprint":false},{"year":2021,"finding":"PIKfyve inhibition reduces tau aggregate trafficking into lysosomes and reduces tau seeding in neurons; PIKfyve functions downstream of Rac1 in the endocytic mechanism by which tau aggregates are internalized and routed to lysosomes.","method":"PIKfyve pharmacological inhibition, siRNA, Rac1 genetic manipulation, fluorescence-based tau seeding assay in neurons","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis (Rac1-PIKfyve), pharmacological and genetic approaches, functional tau seeding readout, single lab","pmids":["33831417"],"is_preprint":false}],"current_model":"PIKfyve is an evolutionarily conserved lipid kinase that localizes to late endosomes/lysosomes via FYVE-domain binding to PtdIns3P (supplied by VPS34) and operates within a ternary complex with the scaffolding protein Vac14/ArPIKfyve and the lipid phosphatase Fig4/Sac3 (stoichiometry 5 Vac14 : 1 PIKfyve : 1 Fig4); within this complex PIKfyve phosphorylates PtdIns3P to generate PI(3,5)P2 and PtdIns to generate PI(5)P, its activity is stimulated by Vac14, repressed by PIKfyve autophosphorylation, and restored by Fig4's protein phosphatase activity on PIKfyve; PI(3,5)P2 and PI(5)P produced by PIKfyve govern endosomal fission, phagosome/lysosome maturation, GLUT4/integrin trafficking, TFEB transcriptional regulation via selective mTORC1-TFEB interaction and PP2A dephosphorylation, autophagy flux, and innate immune signaling, with its activity regulated by phosphorylation from PKB/AKT (Ser318), AMPK (Ser307), and ULK1 (Ser1548) in response to insulin, contraction, and glucose starvation respectively, and by acylation via zDHHC9/zDHHC21 that controls its stability."},"narrative":{"teleology":[{"year":1999,"claim":"The fundamental question of what lipid kinase activity PIKfyve possesses was resolved: it synthesizes both PtdIns5P and PtdIns(3,5)P2 in vitro with striking substrate specificity, establishing it as a dual-specificity phosphoinositide kinase.","evidence":"In vitro kinase assay with recombinant protein and HPLC product identification in COS cells","pmids":["10419465"],"confidence":"High","gaps":["No in vivo lipid measurements","Relative contribution of each product to cellular signaling unknown","Structural basis of substrate specificity unresolved"]},{"year":2001,"claim":"How PIKfyve reaches its site of action was established: the FYVE domain binds PtdIns3P on late endosomal membranes and is essential for membrane targeting, while kinase-dead PIKfyve causes dominant vacuolation demonstrating that active PIKfyve is required for endomembrane homeostasis.","evidence":"PtdIns3P liposome binding, FYVE domain mutagenesis, kinase-dead mutant expression with fluorescence microscopy and rescue in multiple cell types","pmids":["11285266","11706043"],"confidence":"High","gaps":["Whether additional membrane-targeting determinants beyond FYVE domain exist in vivo","Mechanism by which kinase loss leads to vacuolation not resolved"]},{"year":2003,"claim":"The cellular functions of PIKfyve were delineated: it selectively regulates fluid-phase endocytosis, MVB morphogenesis, and late endosome-to-TGN retrograde transport—but not transferrin recycling or EGF receptor degradation—establishing pathway specificity.","evidence":"Stable inducible kinase-dead lines, fluid-phase marker uptake, electron microscopy, yeast two-hybrid identification of Rab9 effector p40 interaction","pmids":["14551253","14530284"],"confidence":"High","gaps":["How PIKfyve achieves pathway specificity unclear","Relationship between p40 phosphorylation and retrograde transport not fully resolved"]},{"year":2004,"claim":"Signal-dependent regulation of PIKfyve was discovered: PKB/AKT phosphorylates Ser318 in response to insulin, stimulating kinase activity and modulating GLUT4 vesicle trafficking; simultaneously, Vac14/ArPIKfyve was identified as a required positive regulator and physical partner.","evidence":"In vitro PKB kinase assay, phospho-specific antibodies, S318A mutant in 3T3-L1 adipocytes; Co-IP, siRNA knockdown of Vac14 with in vitro kinase and HPLC readouts","pmids":["15546921","15542851"],"confidence":"High","gaps":["Whether other kinases phosphorylate Ser318 in non-insulin contexts","How Vac14 stimulates PIKfyve enzymatic activity mechanistically"]},{"year":2007,"claim":"The ternary PIKfyve–ArPIKfyve–Sac3 (PAS) complex was reconstituted, revealing that Sac3/Fig4 preferentially hydrolyzes PI(3,5)P2 and that balanced kinase/phosphatase activities within the complex control endosomal carrier vesicle formation.","evidence":"Co-IP, co-fractionation, in vitro phosphatase assay, siRNA, in vitro vesicle formation reconstitution","pmids":["17556371"],"confidence":"High","gaps":["Stoichiometry of the complex unknown at this stage","How Sac3 integrates into complex architecture unresolved"]},{"year":2009,"claim":"The cpn60/TCP1 domain of PIKfyve was identified as the key interaction module mediating both ArPIKfyve–Sac3 binding and the p40/JLP adapter interaction, and PIKfyve was shown to control lysosomal degradation of CaV1.2 channels in neurons, extending its substrates beyond canonical endosomal cargo.","evidence":"Systematic domain mutagenesis in triple-transfected cells; NMDA-dependent CaV1.2 co-IP, siRNA with excitotoxicity readout; JLP yeast two-hybrid and cargo-specific trafficking assays","pmids":["19840946","19841139","19056739"],"confidence":"High","gaps":["Whether cpn60_TCP1 domain interactions are mutually exclusive or simultaneous","How NMDA signaling activates PIKfyve"]},{"year":2012,"claim":"In vivo, PIKfyve was confirmed as the sole source of PI(3,5)P2 and the predominant source of PI5P (generated indirectly via 3-phosphatase action on PI(3,5)P2); functionally, PtdIns5P and PI(3,5)P2 were shown to be dissociable, with PI5P mediating actin remodeling and PI(3,5)P2 driving vacuolation.","evidence":"Pikfyve hypomorph mouse, shRNA, quantitative tissue phosphoinositide mass measurements; differential-dose YM201636 with HPLC and actin/GLUT4 assays","pmids":["23047693","22621786"],"confidence":"High","gaps":["Identity of the 3-phosphatase converting PI(3,5)P2 to PI5P in vivo","Tissue-specific regulation of each lipid product"]},{"year":2013,"claim":"Two additional upstream kinases—AKT (EGF-stimulated EGFR-to-lysosome routing) and AMPK (Ser307, contraction-stimulated glucose uptake)—were shown to directly phosphorylate and activate PIKfyve, establishing it as a signaling hub integrating growth factor and energy-sensing inputs.","evidence":"In vitro AKT/AMPK kinase assays, phosphomutants, receptor trafficking, glucose uptake in muscle","pmids":["23757022","23905686"],"confidence":"High","gaps":["Cross-talk between Ser307 and Ser318 phosphorylation events","Whether other metabolic kinases also regulate PIKfyve"]},{"year":2014,"claim":"PIKfyve was established as essential for phagosome maturation (PtdIns3P-to-PI(3,5)P2 conversion, LAMP1/cathepsin acquisition) and for endolysosomal TLR-induced type I IFN production (via ATF3 transcriptional repression), linking it to innate immunity.","evidence":"Multiple PIKfyve inhibitors in macrophage phagocytosis; pharmacological/genetic inactivation with ATF3/IFN promoter ChIP; TLR9/AP-3 trafficking assays","pmids":["25041080","24600036","25170925"],"confidence":"High","gaps":["How PI(3,5)P2 mechanistically promotes PtdIns3P removal on phagosomes","Whether ATF3 induction is a direct consequence of PI(3,5)P2 depletion or lysosome stress"]},{"year":2016,"claim":"The cellular consequences of PIKfyve loss were refined: lysosome enlargement results from coalescence (fusion over fission) rather than biosynthesis; PIKfyve inhibition increases exosome secretion via impaired MVB–lysosome fusion; the downstream effector TRPML1 was identified as a key mediator of vacuole resolution and nutrient recovery.","evidence":"Live fusion/fission dynamics imaging, TFEB/TFE3 knockout, quantitative EM and MS of exosomal fractions, TRPML1 genetic manipulation and starvation survival assays","pmids":["29661845","27438886","27623384"],"confidence":"High","gaps":["Whether TRPML1 is the sole PI(3,5)P2 effector for fission","How PI(3,5)P2 regulates the balance between exosomal release and degradation"]},{"year":2020,"claim":"Cryo-EM resolved the PAS complex architecture at 5 Vac14 : 1 PIKfyve : 1 Fig4 stoichiometry and revealed a self-regulatory circuit: PIKfyve autophosphorylation represses its kinase and stimulates Fig4 phosphatase, while Fig4 acts as a protein phosphatase on PIKfyve to restore kinase activity; sterically, PIKfyve cannot reach membrane-embedded substrates within the complex.","evidence":"Cryo-EM structure, in vitro phosphatase/kinase reconstitution, mutagenesis","pmids":["33098764"],"confidence":"High","gaps":["How the complex is remodeled to allow membrane access in vivo","How Vac14 pentamerization is regulated"]},{"year":2021,"claim":"A third upstream kinase, ULK1 (activated by AMPK during glucose starvation), was shown to phosphorylate PIKfyve Ser1548, selectively increasing PI5P (not PI(3,5)P2) synthesis and promoting PI5P-containing autophagosome formation, thereby linking PIKfyve to autophagy initiation.","evidence":"In vitro ULK1 kinase assay, S1548D phosphomimetic, quantitative phosphoinositide measurements, autophagy flux assays","pmids":["34107300"],"confidence":"High","gaps":["Structural basis for how Ser1548 phosphorylation shifts product specificity","Whether PI5P on autophagosomes recruits specific effectors"]},{"year":2021,"claim":"PIKfyve stability was shown to be controlled by palmitoylation by zDHHC9/zDHHC21; prion infection or UPR disrupts acyltransferase topology causing PIKfyve deacylation, degradation, and endolysosomal hypertrophy—a disease-relevant post-translational control mechanism.","evidence":"Acylation assays, zDHHC knockdown/overexpression, mouse and organotypic brain slice prion infection models, PI(3,5)P2 rescue","pmids":["34291577"],"confidence":"High","gaps":["Which palmitoylation site(s) on PIKfyve are critical","Whether deacylation is an active regulatory mechanism beyond disease contexts"]},{"year":2022,"claim":"The mechanism by which PIKfyve controls TFEB nuclear translocation was resolved: PI(3,5)P2 is required for mTORC1 to access TFEB (but not other substrates) at the lysosome, and PP2A (not calcineurin) dephosphorylates TFEB-Ser211 when PIKfyve is inhibited; separately, PIKfyve was shown to govern Retriever/CCC-mediated integrin recycling downstream of VPS34.","evidence":"mTORC1 substrate profiling, PP2A/calcineurin inhibitors, TFEB nuclear localization; endogenous co-localization, PIKfyve inhibition Retriever displacement, integrin recycling, VPS34 epistasis","pmids":["35020443","35040777"],"confidence":"Medium","gaps":["How PI(3,5)P2 physically mediates mTORC1–TFEB proximity","Whether PP2A regulation is TFEB-specific or extends to other TFE family members","How PIKfyve products recruit Retriever to endosomes"]},{"year":null,"claim":"Key unresolved questions include: (1) how the PIKfyve-Vac14-Fig4 complex is conformationally rearranged to allow PIKfyve access to membrane substrates in vivo; (2) the structural basis for phosphorylation-dependent switching between PI(3,5)P2 and PI5P product specificity; (3) the identity and regulation of the 3-phosphatase generating PI5P from PI(3,5)P2 in vivo; and (4) how tissue- and context-specific PIKfyve regulation is achieved.","evidence":"","pmids":[],"confidence":"High","gaps":["Membrane access mechanism for the intact PAS complex","Product specificity switching mechanism","In vivo 3-phosphatase identity","Tissue-specific regulatory mechanisms"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,3,6,17,34]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[5,32]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[1,2,8,39]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[14,22,26,44]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[39]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4,25,38]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[4,8,12,16,25,37]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,20,21]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[22,23,30,31,43,44]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[25,34]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3,17]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[37,39]}],"complexes":["PIKfyve-Vac14-Fig4 (PAS complex)"],"partners":["VAC14","FIG4","TRPML1","JLP","P40","VPS34"],"other_free_text":[]},"mechanistic_narrative":"PIKfyve is a phosphoinositide kinase that phosphorylates PtdIns3P to generate PI(3,5)P2 and PtdIns to generate PI(5)P, serving as the master regulator of endolysosomal membrane identity, fission/fusion balance, and cargo trafficking. It operates within a stoichiometrically defined ternary complex (5 Vac14 : 1 PIKfyve : 1 Fig4) in which Vac14 scaffolds and stimulates PIKfyve activity, PIKfyve autophosphorylation represses its own kinase while activating Fig4 phosphatase, and Fig4 acts as both a PI(3,5)P2 phosphatase and a protein phosphatase that dephosphorylates PIKfyve to restore kinase activity [PMID:10419465, PMID:33098764, PMID:17556371]. PIKfyve is recruited to endosomal membranes via FYVE-domain binding to VPS34-derived PtdIns3P, and its activity is modulated by PKB/AKT (Ser318), AMPK (Ser307), and ULK1 (Ser1548) phosphorylation in response to insulin, contraction, and glucose starvation, respectively, as well as by palmitoylation via zDHHC9/zDHHC21 that controls protein stability [PMID:11706043, PMID:15546921, PMID:23905686, PMID:34107300, PMID:34291577]. Through its lipid products, PIKfyve governs phagosome/lysosome maturation, MVB biogenesis, GLUT4 and integrin recycling, selective mTORC1–TFEB signaling, autophagy flux, exosome secretion, and innate immune responses including TLR trafficking and type I IFN production [PMID:14551253, PMID:25041080, PMID:35040777, PMID:35020443, PMID:34107300, PMID:27438886, PMID:24600036]."},"prefetch_data":{"uniprot":{"accession":"Q9Y2I7","full_name":"1-phosphatidylinositol 3-phosphate 5-kinase","aliases":["FYVE finger-containing phosphoinositide kinase","PIKfyve","Phosphatidylinositol 3-phosphate 5-kinase type III","PIPkin-III","Type III PIP kinase","Serine-protein kinase PIKFYVE"],"length_aa":2098,"mass_kda":237.1,"function":"Dual specificity kinase implicated in myriad essential cellular processes such as maintenance of endomembrane homeostasis, and endocytic-vacuolar pathway, lysosomal trafficking, nuclear transport, stress- or hormone-induced signaling and cell cycle progression (PubMed:23086417). The PI(3,5)P2 regulatory complex regulates both the synthesis and turnover of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2). Sole enzyme to catalyze the phosphorylation of phosphatidylinositol 3-phosphate on the fifth hydroxyl of the myo-inositol ring, to form (PtdIns(3,5)P2) (PubMed:17556371). Also catalyzes the phosphorylation of phosphatidylinositol on the fifth hydroxyl of the myo-inositol ring, to form phosphatidylinositol 5-phosphate (PtdIns(5)P) (PubMed:22621786). Has serine-protein kinase activity and is able to autophosphorylate and transphosphorylate. Autophosphorylation inhibits its own phosphatidylinositol 3-phosphate 5-kinase activity, stimulates FIG4 lipid phosphatase activity and down-regulates lipid product formation (PubMed:33098764). Involved in key endosome operations such as fission and fusion in the course of endosomal cargo transport (PubMed:22621786). Required for the maturation of early into late endosomes, phagosomes and lysosomes (PubMed:30612035). Regulates vacuole maturation and nutrient recovery following engulfment of macromolecules, initiates the redistribution of accumulated lysosomal contents back into the endosome network (PubMed:27623384). Critical regulator of the morphology, degradative activity, and protein turnover of the endolysosomal system in macrophages and platelets (By similarity). In neutrophils, critical to perform chemotaxis, generate ROS, and undertake phagosome fusion with lysosomes (PubMed:28779020). Plays a key role in the processing and presentation of antigens by major histocompatibility complex class II (MHC class II) mediated by CTSS (PubMed:30612035). Regulates melanosome biogenesis by controlling the delivery of proteins from the endosomal compartment to the melanosome (PubMed:29584722). Essential for systemic glucose homeostasis, mediates insulin-induced signals for endosome/actin remodeling in the course of GLUT4 translocation/glucose uptake activation (By similarity). Supports microtubule-based endosome-to-trans-Golgi network cargo transport, through association with SPAG9 and RABEPK (By similarity). Mediates EGFR trafficking to the nucleus (PubMed:17909029) (Microbial infection) Required for cell entry of coronaviruses SARS-CoV and SARS-CoV-2, as well as human coronavirus EMC (HCoV-EMC) by endocytosis","subcellular_location":"Endosome membrane; Early endosome membrane; Cytoplasmic vesicle, phagosome membrane; Late endosome membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y2I7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PIKFYVE","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000115020","cell_line_id":"CID000173","localizations":[{"compartment":"vesicles","grade":3},{"compartment":"cytoplasmic","grade":2}],"interactors":[{"gene":"FIG4","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"ESD","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000173","total_profiled":1310},"omim":[{"mim_id":"619871","title":"CORNEAL DYSTROPHY, PUNCTIFORM AND POLYCHROMATIC PRE-DESCEMET; PPPCD","url":"https://www.omim.org/entry/619871"},{"mim_id":"617054","title":"STRIATONIGRAL DEGENERATION, CHILDHOOD-ONSET; SNDC","url":"https://www.omim.org/entry/617054"},{"mim_id":"614235","title":"PDZ DOMAIN-CONTAINING PROTEIN 8; PDZD8","url":"https://www.omim.org/entry/614235"},{"mim_id":"609414","title":"PHOSPHOINOSITIDE KINASE, FYVE FINGER-CONTAINING; PIKFYVE","url":"https://www.omim.org/entry/609414"},{"mim_id":"609390","title":"FIG4 PHOSPHOINOSITIDE 5-PHOSPHATASE; FIG4","url":"https://www.omim.org/entry/609390"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PIKFYVE"},"hgnc":{"alias_symbol":["MGC40423","KIAA0981","PIP5K","p235","ZFYVE29","FAB1"],"prev_symbol":["PIP5K3"]},"alphafold":{"accession":"Q9Y2I7","domains":[{"cath_id":"3.30.40.10","chopping":"128-223","consensus_level":"high","plddt":76.948,"start":128,"end":223},{"cath_id":"1.10.10.10","chopping":"370-439","consensus_level":"high","plddt":85.8794,"start":370,"end":439},{"cath_id":"3.30.260.10","chopping":"591-683_832-882","consensus_level":"medium","plddt":90.4351,"start":591,"end":882},{"cath_id":"-","chopping":"1217-1383","consensus_level":"medium","plddt":90.3686,"start":1217,"end":1383},{"cath_id":"-","chopping":"1406-1433_1483-1507","consensus_level":"medium","plddt":88.0636,"start":1406,"end":1507},{"cath_id":"3.30.800.10","chopping":"1668-1692_1806-1940","consensus_level":"medium","plddt":88.8024,"start":1668,"end":1940},{"cath_id":"3.30.810.10","chopping":"1946-2098","consensus_level":"medium","plddt":83.3561,"start":1946,"end":2098}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2I7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2I7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2I7-F1-predicted_aligned_error_v6.png","plddt_mean":63.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PIKFYVE","jax_strain_url":"https://www.jax.org/strain/search?query=PIKFYVE"},"sequence":{"accession":"Q9Y2I7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y2I7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y2I7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2I7"}},"corpus_meta":[{"pmid":"19889969","id":"PMC_19889969","title":"PIP5K-driven PtdIns(4,5)P2 synthesis: regulation and cellular functions.","date":"2009","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/19889969","citation_count":271,"is_preprint":false},{"pmid":"18188180","id":"PMC_18188180","title":"A selective PIKfyve inhibitor blocks PtdIns(3,5)P(2) production and disrupts endomembrane transport and retroviral budding.","date":"2008","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/18188180","citation_count":250,"is_preprint":false},{"pmid":"2981831","id":"PMC_2981831","title":"Identification of two proteins (actin-binding protein and P235) that are hydrolyzed by endogenous Ca2+-dependent protease during platelet aggregation.","date":"1985","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/2981831","citation_count":230,"is_preprint":false},{"pmid":"10419465","id":"PMC_10419465","title":"PIKfyve, a mammalian ortholog of yeast Fab1p lipid kinase, synthesizes 5-phosphoinositides. Effect of insulin.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10419465","citation_count":222,"is_preprint":false},{"pmid":"16954148","id":"PMC_16954148","title":"The mammalian phosphatidylinositol 3-phosphate 5-kinase (PIKfyve) regulates endosome-to-TGN retrograde transport.","date":"2006","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/16954148","citation_count":220,"is_preprint":false},{"pmid":"27438886","id":"PMC_27438886","title":"PIKfyve inhibition increases exosome release and induces secretory autophagy.","date":"2016","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/27438886","citation_count":217,"is_preprint":false},{"pmid":"11285266","id":"PMC_11285266","title":"Mammalian cell morphology and endocytic membrane homeostasis require enzymatically active phosphoinositide 5-kinase PIKfyve.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11285266","citation_count":206,"is_preprint":false},{"pmid":"23047693","id":"PMC_23047693","title":"In vivo, Pikfyve generates PI(3,5)P2, which serves as both a signaling lipid and the major precursor for PI5P.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23047693","citation_count":195,"is_preprint":false},{"pmid":"32764148","id":"PMC_32764148","title":"Inhibition of PIKfyve kinase prevents infection by Zaire ebolavirus and SARS-CoV-2.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32764148","citation_count":166,"is_preprint":false},{"pmid":"28104689","id":"PMC_28104689","title":"Identification of apilimod as a first-in-class PIKfyve kinase inhibitor for treatment of B-cell non-Hodgkin lymphoma.","date":"2017","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/28104689","citation_count":165,"is_preprint":false},{"pmid":"19272020","id":"PMC_19272020","title":"Phosphatidylinositol 3,5-bisphosphate and Fab1p/PIKfyve underPPIn endo-lysosome function.","date":"2009","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/19272020","citation_count":161,"is_preprint":false},{"pmid":"17556371","id":"PMC_17556371","title":"Core protein machinery for mammalian phosphatidylinositol 3,5-bisphosphate synthesis and turnover that regulates the progression of endosomal transport. 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differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/26098172","citation_count":20,"is_preprint":false},{"pmid":"26125944","id":"PMC_26125944","title":"The Amyloid Precursor Protein Controls PIKfyve Function.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26125944","citation_count":20,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52535,"output_tokens":10912,"usd":0.160642},"stage2":{"model":"claude-opus-4-6","input_tokens":14887,"output_tokens":4501,"usd":0.28044},"total_usd":0.441082,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"PIKfyve (p235) is a mammalian lipid kinase that synthesizes PtdIns5P and PtdIns(3,5)P2 in vitro, displaying striking specificity for PtdIns over PI substrates; deletion mutant analysis showed that regions beyond the predicted catalytic domain are critical for enzymatic activity.\",\n      \"method\": \"In vitro kinase assay with recombinant protein expressed in COS cells, HPLC analysis of lipid products, deletion mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro kinase activity with HPLC product identification, foundational paper\",\n      \"pmids\": [\"10419465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PIKfyve enzymatic activity is required for mammalian cell morphology and endomembrane homeostasis; kinase-dead PIKfyve(K1831E) causes dominant vacuolation of endosomal origin, and disruption of the FYVE-domain localization signal abolishes this phenotype, indicating that active PIKfyve at late endocytic membranes is essential.\",\n      \"method\": \"Dominant-negative kinase-dead mutant expression, fluorescence microscopy, cell viability assays, rescue with wild-type PIKfyve\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean dominant-negative with defined phenotypic readout, rescued by wild-type, replicated across multiple cell types\",\n      \"pmids\": [\"11285266\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PIKfyve localizes to late endocytic membranes via its FYVE domain binding to PtdIns3P; the FYVE domain is absolutely required for endosomal membrane targeting, and wortmannin treatment dissociates PIKfyve from endosomes; an additional low-affinity PtdIns3P-binding site exists in the catalytic domain.\",\n      \"method\": \"PtdIns3P liposome binding assays, FYVE domain mutagenesis, wortmannin treatment, fluorescence microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding reconstitution with mutagenesis and cellular localization validation\",\n      \"pmids\": [\"11706043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PIKfyve is responsible for PtdIns5P biosynthesis in cellular contexts; expression of PIKfyve(WT) increases intracellular PtdIns5P, while dominant-negative PIKfyve(K1831E) decreases it; PtdIns5P levels decrease under hypo-osmotic stress, linking PIKfyve to the osmotic response pathway.\",\n      \"method\": \"32P-labeling, HPLC head-group analysis, in vitro type II PIP kinase conversion assay, dominant-negative expression in multiple cell types\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — two independent approaches in multiple cell types, gain- and loss-of-function\",\n      \"pmids\": [\"12270933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PIKfyve selectively regulates fluid-phase endocytosis and multivesicular body morphogenesis; kinase-dead PIKfyve impairs late uptake of horseradish peroxidase and disrupts MVB morphology (fewer internal vesicles), without affecting transferrin recycling, EGF receptor degradation, or cathepsin D sorting.\",\n      \"method\": \"Stable inducible cell lines, fluid-phase marker uptake, confocal microscopy with organelle markers, electron microscopy\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean inducible dominant-negative system with specific phenotypic readouts and EM confirmation\",\n      \"pmids\": [\"14551253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PIKfyve physically interacts with the Rab9 effector p40 via its chaperonin domain; enzymatically active PIKfyve promotes membrane attachment of p40 and phosphorylates it on serine residues, facilitating late endosome-to-TGN transport.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, differential centrifugation, in vitro kinase assay, phosphoserine antibody\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP confirmed by yeast two-hybrid and GST pulldown, kinase activity demonstrated in vitro\",\n      \"pmids\": [\"14530284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PKB/Akt phosphorylates PIKfyve on Ser318, stimulating its PtdIns3P 5-kinase activity; this phosphorylation occurs in intact cells in response to insulin in a PI3K-dependent manner; overexpression of PIKfyve[S318A] in adipocytes enhances insulin-stimulated IRAP/GLUT4 vesicle translocation.\",\n      \"method\": \"In vitro kinase assay, phospho-specific antibodies, 3T3-L1 adipocyte translocation assay, site-directed mutagenesis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro phosphorylation by PKB demonstrated, confirmed in intact cells, functional consequence shown by mutation\",\n      \"pmids\": [\"15546921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Human Vac14 (ArPIKfyve) is a positive regulator of PIKfyve enzymatic activity; it co-fractionates and co-localizes with PIKfyve, physically associates with it, and its siRNA-mediated knockdown reduces PIKfyve kinase activity and PtdIns(3,5)P2 production, causing endomembrane vacuolation.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, in vitro kinase assay, 32P-labeling/HPLC, confocal microscopy\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus in vitro activity assay plus siRNA knockdown with defined phenotypic and biochemical readouts\",\n      \"pmids\": [\"15542851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PIKfyve is predominantly associated with early endosomal tubular and vesicular elements and regulates endosome-to-TGN retrograde transport; siRNA suppression of PIKfyve causes swollen endosomal structures and a clear defect in retrograde trafficking without affecting EGF receptor degradation or transferrin recycling.\",\n      \"method\": \"Live and fixed cell imaging, siRNA knockdown, receptor trafficking assays in HeLa cells\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA with specific functional readout (retrograde transport defect) and live imaging localization\",\n      \"pmids\": [\"16954148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Sac3 (mammalian Fig4) forms a stable ternary complex with ArPIKfyve and PIKfyve; Sac3 preferentially hydrolyzes PtdIns(3,5)P2 in vitro; siRNA knockdown of Sac3 elevates PtdIns(3,5)P2 levels; reconstitution assays show Sac3 loss gains function in carrier vesicle formation while PIKfyve or ArPIKfyve depletion causes loss of function.\",\n      \"method\": \"Co-immunoprecipitation, co-fractionation, in vitro phosphatase assay, siRNA knockdown, 32P-labeling, in vitro vesicle formation reconstitution\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted ternary complex with in vitro phosphatase activity and in vitro vesicle formation assay\",\n      \"pmids\": [\"17556371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PIKfyve mediates HB-EGF-stimulated EGFR nuclear trafficking and EGFR binding to the cyclin D1 promoter; PIKfyve was identified as part of EGFR immune complexes by mass spectrometry, and siRNA silencing of PIKfyve blocks EGFR nuclear translocation and cell cycle progression.\",\n      \"method\": \"Mass spectrometry of EGFR immune complexes, siRNA knockdown, nuclear fractionation, chromatin immunoprecipitation\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS identification plus siRNA with defined functional readout, single lab\",\n      \"pmids\": [\"17909029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"YM201636, a potent selective inhibitor of PIKfyve, blocks PtdIns(3,5)P2 production, causes accumulation of late endosomal compartments, and blocks retroviral budding; specificity confirmed by siRNA against PIKfyve and rescue with drug-resistant yeast Fab1 ortholog.\",\n      \"method\": \"Small-molecule inhibitor, siRNA knockdown, rescue with yeast Fab1, phosphoinositide measurements, cell biology assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — inhibitor specificity confirmed by orthogonal siRNA and yeast rescue, multiple functional readouts\",\n      \"pmids\": [\"18188180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PIKfyve interacts with the kinesin adapter JLP via the PIKfyve cpn60_TCP1 domain; both proteins are required for microtubule-based endosome-to-TGN transport of furin but not microtubule-independent Tac-TGN38 delivery.\",\n      \"method\": \"Yeast two-hybrid, pulldown, co-immunoprecipitation, siRNA knockdown, cargo trafficking assay, microinjection of interacting peptides\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal binding methods plus functional specificity demonstrated with cargo-selective trafficking assay\",\n      \"pmids\": [\"19056739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PIKfyve-containing PAS complex: Sac3 assembled within the PIKfyve-ArPIKfyve-Sac3 core retains active PtdIns(3,5)P2 phosphatase activity; the cpn60_TCP1 domain of PIKfyve mediates ArPIKfyve-Sac3 subcomplex binding; kinase and phosphatase activities do not affect complex stability.\",\n      \"method\": \"Truncation and point mutants of all three proteins in triple-transfected COS cells, vacuolation assay as functional readout, biochemical binding analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis of contact sites with functional readout, confirms active phosphatase within complex\",\n      \"pmids\": [\"19840946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PIKfyve regulates lysosomal targeting and degradation of voltage-gated Ca2+ channel CaV1.2; NMDA receptor activation recruits PIKfyve to CaV1.2 channels, increases PtdIns(3,5)P2, and promotes CaV1.2 targeting to lysosomes; PIKfyve knockdown prevents CaV1.2 degradation and increases neuronal susceptibility to excitotoxicity.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, live imaging, neuronal excitotoxicity assays, PtdIns(3,5)P2 measurements\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP showing physical interaction, siRNA with specific functional consequence (excitotoxicity), multiple orthogonal approaches\",\n      \"pmids\": [\"19841139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PIKfyve stimulates EAAT2 glutamate transporter activity and increases its membrane abundance; the effect requires Ser318 in the SGK1 phosphorylation consensus of PIKfyve, as S318A mutant abolishes PIKfyve's stimulatory effect.\",\n      \"method\": \"Xenopus oocyte expression, electrophysiology, confocal microscopy, site-directed mutagenesis (S318A)\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional assay in oocytes with mutagenesis, single lab\",\n      \"pmids\": [\"19910676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIKfyve is required for macropinosome-to-late endosome/lysosome fusion; disruption of PIKfyve (by interfering mutant, siRNA, or pharmacological inhibition) inhibits intracellular replication of Salmonella by blocking SCV maturation and SPI2-T3SS engagement.\",\n      \"method\": \"Dominant-negative mutant, siRNA, pharmacological inhibition, 4D videomicroscopy, Salmonella infection assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — three independent methods (genetic, siRNA, pharmacological), specific functional pathway (macropinosome-LE fusion) identified by live imaging\",\n      \"pmids\": [\"20300065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In vivo, Pikfyve generates all of the PI(3,5)P2 pool and is also responsible for nearly all PI5P production, with PI5P generated directly from PI(3,5)P2 likely via 3'-phosphatase activity; demonstrated using a Pikfyve hypomorph mouse and shRNA silencing of residual transcript.\",\n      \"method\": \"Mouse hypomorph (gene trap), shRNA silencing in fibroblasts, phosphoinositide mass measurement in tissues\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo mouse model plus shRNA, quantitative lipid measurements across multiple tissues\",\n      \"pmids\": [\"23047693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PIKfyve-synthesized PtdIns5P mediates insulin-induced actin stress fiber disassembly, while PtdIns(3,5)P2 is responsible for cellular vacuolation; these two lipid products are functionally dissociable using differential dosing of YM201636.\",\n      \"method\": \"Differential-dose PIKfyve inhibitor (YM201636), HPLC phosphoinositide measurement, actin stress fiber imaging, GLUT4 translocation assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological dissection with quantitative lipid readouts and functional cellular assays, single lab\",\n      \"pmids\": [\"22621786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PtdIns5P produced via PIKfyve and MTMR3 promotes cell migration; PIKfyve and MTMR3 constitute a phosphoinositide loop generating PtdIns5P via PtdIns(3,5)P2; exogenous PtdIns5P or bacterial PtdIns5P-producing enzyme directly stimulates migration.\",\n      \"method\": \"siRNA screen, migration assays in tissue culture and Drosophila in vivo model, exogenous PtdIns5P addition, bacterial enzyme\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches including in vivo Drosophila model, direct lipid addition, and genetic knockdown\",\n      \"pmids\": [\"23154468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AKT phosphorylates and activates PIKfyve upon EGF stimulation, promoting vesicle trafficking of EGFR to lysosomes for degradation; in AKT-impaired cells EGFR accumulates in early endosomes with prolonged ERK/RSK signaling; similar regulation occurs for PDGFR.\",\n      \"method\": \"Kinase assay, phospho-specific antibodies, AKT inhibition, PIKfyve siRNA, receptor trafficking assays, dominant-negative approaches\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vitro phosphorylation by AKT demonstrated, confirmed in cells, specific trafficking phenotype, replicated with two RTKs\",\n      \"pmids\": [\"23757022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AMPK phosphorylates PIKfyve at Ser307, promoting its translocation to endosomal membranes and PtdIns(3,5)P2 synthesis; this is required for contraction/AMPK-stimulated glucose uptake in skeletal muscle.\",\n      \"method\": \"In vitro AMPK kinase assay, S307A mutant, subcellular fractionation, siRNA knockdown in myotubes, glucose uptake assay in muscle\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro phosphorylation demonstrated, S307A mutant loses translocation response, functional consequence in intact muscle\",\n      \"pmids\": [\"23905686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIKfyve inhibition blocks phagosome maturation in macrophages by delaying PtdIns3P removal and reducing acquisition of LAMP1 and cathepsin D on phagosomes, impairing degradative capacity without affecting acidification.\",\n      \"method\": \"PIKfyve pharmacological inhibitors, FcγR-mediated phagocytosis assay, live imaging, immunofluorescence with lysosomal markers, degradation assays\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitors, defined functional pathway (phagosome maturation), specific mechanistic steps identified\",\n      \"pmids\": [\"25041080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIKfyve is required for endolysosomal TLR-induced type I IFN production; PIKfyve inactivation induces expression of the transcriptional repressor ATF3, which binds the IFN promoter and blocks transcription; this is independent of receptor/ligand trafficking.\",\n      \"method\": \"PIKfyve pharmacological inhibition and genetic inactivation, ATF3 expression analysis, IFN promoter binding assay, chromatin IP\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic inactivation with mechanistic link to ATF3 promoter binding, single lab\",\n      \"pmids\": [\"24600036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"APP (amyloid precursor protein) directly binds Vac14 via its intracellular domain and associates with the PIKfyve complex (Vac14/PIKfyve/Fig4); APP binding drives formation of PI(3,5)P2-positive vesicles; APP family members are required for PIKfyve function; PIKfyve complex is required for APP trafficking.\",\n      \"method\": \"Proteo-liposome interactome assay, GST pulldown with purified Vac14, co-immunoprecipitation, C. elegans genetic epistasis, PI(3,5)P2 vesicle formation assay\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct binding to purified Vac14 plus in vivo C. elegans genetic epistasis and vesicle formation assay\",\n      \"pmids\": [\"26216398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIKfyve inhibition increases exosome secretion and induces secretory autophagy by impairing fusion of lysosomes with MVBs and autophagosomes; inhibition leads to more MVBs with more intraluminal vesicles and accumulation of autophagy proteins (LC3, p62, NBR1) in exosomal fractions.\",\n      \"method\": \"Apilimod treatment and siRNA, quantitative electron microscopy, mass spectrometry of exosomal fractions, density gradient fractionation, long-lived protein degradation assay\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic approaches with quantitative EM and MS, multiple orthogonal readouts\",\n      \"pmids\": [\"27438886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIKfyve inhibition leads to lysosome enlargement primarily through lysosome coalescence (fusion over fission) rather than biosynthesis; PIKfyve inhibition activates TFEB/TFE3/MITF but this does not contribute to acute swelling; conditions reducing fusion curtail lysosome enlargement.\",\n      \"method\": \"Live imaging, organelle counting, fusion/fission dynamics analysis, TFEB/TFE3/MITF reporter assays, TFEB/TFE3 knockout\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic deletion of TFEB plus live imaging of fusion dynamics, mechanistic model established\",\n      \"pmids\": [\"29661845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PIKfyve regulates vacuole size and nutrient recovery during macropinocytosis, entosis, and phagocytosis through its downstream effector TRPML1 (cationic transporter); PIKfyve activity protects Ras-mutant cells from starvation-induced death.\",\n      \"method\": \"PIKfyve inhibitors, TRPML1 genetic manipulation, vacuole size measurement, nutrient recovery assay, starvation survival assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic approaches, TRPML1 as downstream effector established, single lab\",\n      \"pmids\": [\"27623384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Apilimod's cytotoxic activity is driven specifically by PIKfyve inhibition; a resistance mutation in the PIKfyve kinase domain confers apilimod resistance; a genome-wide CRISPR screen identified lysosomal genes and TFEB as determinants of apilimod sensitivity, supporting lysosome dysfunction as the major cytotoxic mechanism.\",\n      \"method\": \"Biochemical target validation, kinase domain resistance mutation, genome-wide CRISPR screen, siRNA knockdown\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — resistance mutation and genome-wide genetic screen, multiple orthogonal approaches\",\n      \"pmids\": [\"28104689\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PIKfyve is acylated by zDHHC9 and zDHHC21 acyltransferases; prion infection or UPR disturbs juxtavesicular acyltransferase topology causing PIKfyve deacylation, rapid degradation, and endolysosomal hypertrophy; overexpression of acyltransferases or PI(3,5)P2 supplementation suppresses prion-induced vacuolation.\",\n      \"method\": \"Acylation assay, zDHHC knockdown/overexpression, UPR induction, mouse/organotypic brain slice infection models, rescue with PI(3,5)P2\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — acylation writer identified (zDHHC9/21), functional consequence of deacylation demonstrated, in vivo and cell models\",\n      \"pmids\": [\"34291577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PIKfyve coordinates neutrophil immune response through activation of Rac GTPase; PIKfyve inhibition blocks chemotaxis, ROS production, and Rac activation, while phagosome-lysosome fusion block can be partially rescued by TRPML1 agonists or Ca2+ ionophores.\",\n      \"method\": \"Human and mouse neutrophils, PIKfyve inhibitors, Rac activation assay, chemotaxis assay, ROS measurement, phagosome maturation assay, Ca2+ ionophore rescue\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays in primary cells, TRPML1 pathway implicated, single lab\",\n      \"pmids\": [\"28779020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PIKfyve promotes MHC class II antigen presentation by facilitating cathepsin S activity; PIKfyve inhibition delays phagosome-to-lysosome conversion and acidification, increases ROS, which reduces cathepsin S and B activity, impairing invariant chain processing and MHC class II presentation.\",\n      \"method\": \"PIKfyve inhibitors, cathepsin activity assay, phagosome maturation assay, novel bio-orthogonal antigen presentation assay, T cell activation assay\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway established (ROS→cathepsin→Ii processing→MHC II presentation), single lab with multiple assays\",\n      \"pmids\": [\"30612035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The PIKfyve complex comprises five copies of Vac14 scaffolding protein and one copy each of PIKfyve kinase and Fig4 phosphatase; Fig4 is active as a lipid phosphatase within the complex while PIKfyve cannot access membrane-incorporated phosphoinositides due to steric constraints; PIKfyve autophosphorylation represses its lipid kinase activity and stimulates Fig4 phosphatase; Fig4 acts as a protein phosphatase on PIKfyve to stimulate its lipid kinase activity.\",\n      \"method\": \"Cryo-EM structure, structural-biochemical analysis, in vitro phosphatase and kinase assays, mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with in vitro enzymatic validation and mutagenesis, complex stoichiometry established\",\n      \"pmids\": [\"33098764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Pharmacological inhibition of PIKfyve with apilimod or vacuolin-1 blocks content release and infection by VSV-ZEBOV and SARS-CoV-2 by interfering with late endosomal trafficking required for viral entry.\",\n      \"method\": \"Chimeric VSV with ebolavirus/SARS-CoV-2 envelope proteins, live SARS-CoV-2 infection assay, apilimod and vacuolin-1 treatment, content release imaging\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological inhibition confirmed with two inhibitor classes and live virus, specific step (endosomal content release) identified\",\n      \"pmids\": [\"32764148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ULK1 activated by AMPK during glucose starvation phosphorylates PIKfyve on Ser1548, increasing PIKfyve activity and PI(5)P synthesis (without changing PI(3,5)P2 levels); this promotes PI(5)P-containing autophagosome formation and autophagy flux.\",\n      \"method\": \"In vitro kinase assay (ULK1 phosphorylating PIKfyve), phosphomimetic S1548D mutant, phosphoinositide measurements, autophagy flux assays in multiple cell lines\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro phosphorylation by ULK1, phosphomimetic mutant drives autophagy, quantitative lipid measurements\",\n      \"pmids\": [\"34107300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PIKfyve inhibition activates an unconventional protein clearance mechanism involving exocytosis of aggregation-prone proteins, ameliorating ALS pathology in motor neurons from C9ORF72, TARDBP, FUS, and sporadic ALS models.\",\n      \"method\": \"Pharmacological PIKfyve inhibition, patient-derived iPSC motor neurons, ALS mouse models, exocytosis assays for aggregated proteins\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple ALS model systems, specific mechanism (exocytosis vs autophagy/UPS) identified, single lab\",\n      \"pmids\": [\"36754049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PIKfyve inhibition selectively blocks mTORC1-mediated phosphorylation of TFEB at Ser-211 without impairing mTORC1 activity toward other substrates; PI(3,5)P2 depletion prevents mTORC1 access to TFEB; PP2A (not calcineurin) dephosphorylates TFEB Ser-211 when PIKfyve is inhibited, enabling TFEB nuclear localization.\",\n      \"method\": \"mTORC1 substrate phosphorylation profiling, PP2A and calcineurin inhibitors, TFEB nuclear localization assay, mTORC1-TFEB interaction assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic pathway established (PIKfyve→mTORC1-TFEB access→PP2A), single lab\",\n      \"pmids\": [\"35020443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PIKfyve and its upstream PI3-kinase VPS34 coordinate a phosphoinositide cascade to regulate Retriever-mediated recycling of integrins from endosomes; PIKfyve inhibition displaces Retriever and CCC complexes from endosomes; endogenous PIKfyve co-localizes with SNX17, Retriever, WASH, and CCC on endosomes.\",\n      \"method\": \"Co-localization of endogenous proteins, PIKfyve inhibition, Retriever/CCC displacement assay, integrin recycling assay, VPS34 epistasis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (VPS34-PIKfyve cascade), endogenous protein co-localization, cargo-specific recycling assay\",\n      \"pmids\": [\"35040777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PIKfyve is recruited to phagosomes and macropinosomes and PI(3,5)P2 accumulates 3 min after engulfment; PIKfyve activation stimulates its own dissociation from the membrane; retention of PI(3,5)P2 differs between phagosomes and macropinosomes indicating pathway-specific regulation.\",\n      \"method\": \"Novel PI(3,5)P2 reporter (SnxA), live imaging in Dictyostelium and mammalian cells, PIKfyve recruitment vs. activity dissection\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — validated PI(3,5)P2 reporter in two model systems, live dynamics imaging, mechanistic insight on PIKfyve self-regulation\",\n      \"pmids\": [\"37382666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PIKfyve protein and enzymatic activity are found in cytosol (~76%), low-density microsomal fraction (~20%), and plasma membrane (~4%) of 3T3-L1 adipocytes; PIKfyve associates with TGN/MVB markers rather than recycling endosomes; insulin recruits cytosolic PIKfyve to intracellular membranes with a concomitant increase in lipid kinase activity.\",\n      \"method\": \"Subcellular fractionation, immunoadsorption, density gradient sedimentation, fluorescence microscopy, immunokinase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple fractionation approaches with functional enzyme assay, insulin-regulated redistribution established\",\n      \"pmids\": [\"11112776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PIKfyve physically associates with class IA PI3-kinase (p85/p110) in 3T3-L1 adipocytes; insulin specifically activates class IA PI3-K within PIKfyve immune complexes independently of IRS protein tyrosine phosphorylation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro PI3K kinase assay in immune complexes, wortmannin/Triton sensitivity, insulin stimulation\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with functional kinase activity measurement, single lab\",\n      \"pmids\": [\"11476939\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NPM-ALK tyrosine kinase physically associates with PIKfyve, activates its lipid kinase activity through tyrosine kinase activity (complex formation is kinase-independent), and PIKfyve promotes NPM-ALK-mediated cell invasion and MMP9 surface localization/maturation.\",\n      \"method\": \"Co-immunoprecipitation, PIKfyve lipid kinase assay, siRNA, YM201636 inhibition, invasion assay, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus in vitro kinase activity measurement, functional invasion assay, single lab\",\n      \"pmids\": [\"21737449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Class III PI3K (Vps34) is the main source of PtdIns3P for both PIKfyve enzymatic activity and membrane recruitment; Vps34 knockout in podocytes causes vacuolation through PIKfyve dysfunction, as PIKfyve overexpression rescues the vacuolation in PIKfyve-KO MEFs but not in Vps34-KO podocytes.\",\n      \"method\": \"Conditional Vps34 and Pikfyve knockout cells, HPLC phosphoinositide profiling, PtdIns3P biosensor, rescue experiments\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with quantitative lipid measurements, conditional KO cells with rescue experiments\",\n      \"pmids\": [\"25619930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIKfyve activity is required for TLR9 trafficking to the LAMP1+ endosomal compartment for type I IFN signaling; PIKfyve inhibition blocks AP-3 recruitment to TLR9 endosomes while leaving VAMP3+ endosome trafficking intact.\",\n      \"method\": \"PIKfyve inhibitor treatment, confocal microscopy with TLR9/CpG/compartment markers, FLT3L-bone marrow DCs, RAW264.7 cells\",\n      \"journal\": \"International immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — specific compartment-selective trafficking defect identified by imaging, single lab\",\n      \"pmids\": [\"25170925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIKfyve activity is required for efficient V-ATPase and hydrolase delivery to phagosomes in Dictyostelium; PIKfyve-null cells fail to acidify phagosomes and cannot kill bacteria, making them more susceptible to Legionella infection.\",\n      \"method\": \"PIKfyve gene disruption in Dictyostelium, phagosome acidification assay, protease delivery assay, bacterial killing assay, Legionella infection\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic null cells in model phagocyte with specific functional dissection (V-ATPase vs. protease delivery), confirmed ortholog\",\n      \"pmids\": [\"30730983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PIKfyve inhibition reduces tau aggregate trafficking into lysosomes and reduces tau seeding in neurons; PIKfyve functions downstream of Rac1 in the endocytic mechanism by which tau aggregates are internalized and routed to lysosomes.\",\n      \"method\": \"PIKfyve pharmacological inhibition, siRNA, Rac1 genetic manipulation, fluorescence-based tau seeding assay in neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (Rac1-PIKfyve), pharmacological and genetic approaches, functional tau seeding readout, single lab\",\n      \"pmids\": [\"33831417\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIKfyve is an evolutionarily conserved lipid kinase that localizes to late endosomes/lysosomes via FYVE-domain binding to PtdIns3P (supplied by VPS34) and operates within a ternary complex with the scaffolding protein Vac14/ArPIKfyve and the lipid phosphatase Fig4/Sac3 (stoichiometry 5 Vac14 : 1 PIKfyve : 1 Fig4); within this complex PIKfyve phosphorylates PtdIns3P to generate PI(3,5)P2 and PtdIns to generate PI(5)P, its activity is stimulated by Vac14, repressed by PIKfyve autophosphorylation, and restored by Fig4's protein phosphatase activity on PIKfyve; PI(3,5)P2 and PI(5)P produced by PIKfyve govern endosomal fission, phagosome/lysosome maturation, GLUT4/integrin trafficking, TFEB transcriptional regulation via selective mTORC1-TFEB interaction and PP2A dephosphorylation, autophagy flux, and innate immune signaling, with its activity regulated by phosphorylation from PKB/AKT (Ser318), AMPK (Ser307), and ULK1 (Ser1548) in response to insulin, contraction, and glucose starvation respectively, and by acylation via zDHHC9/zDHHC21 that controls its stability.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PIKfyve is a phosphoinositide kinase that phosphorylates PtdIns3P to generate PI(3,5)P2 and PtdIns to generate PI(5)P, serving as the master regulator of endolysosomal membrane identity, fission/fusion balance, and cargo trafficking. It operates within a stoichiometrically defined ternary complex (5 Vac14 : 1 PIKfyve : 1 Fig4) in which Vac14 scaffolds and stimulates PIKfyve activity, PIKfyve autophosphorylation represses its own kinase while activating Fig4 phosphatase, and Fig4 acts as both a PI(3,5)P2 phosphatase and a protein phosphatase that dephosphorylates PIKfyve to restore kinase activity [PMID:10419465, PMID:33098764, PMID:17556371]. PIKfyve is recruited to endosomal membranes via FYVE-domain binding to VPS34-derived PtdIns3P, and its activity is modulated by PKB/AKT (Ser318), AMPK (Ser307), and ULK1 (Ser1548) phosphorylation in response to insulin, contraction, and glucose starvation, respectively, as well as by palmitoylation via zDHHC9/zDHHC21 that controls protein stability [PMID:11706043, PMID:15546921, PMID:23905686, PMID:34107300, PMID:34291577]. Through its lipid products, PIKfyve governs phagosome/lysosome maturation, MVB biogenesis, GLUT4 and integrin recycling, selective mTORC1–TFEB signaling, autophagy flux, exosome secretion, and innate immune responses including TLR trafficking and type I IFN production [PMID:14551253, PMID:25041080, PMID:35040777, PMID:35020443, PMID:34107300, PMID:27438886, PMID:24600036].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"The fundamental question of what lipid kinase activity PIKfyve possesses was resolved: it synthesizes both PtdIns5P and PtdIns(3,5)P2 in vitro with striking substrate specificity, establishing it as a dual-specificity phosphoinositide kinase.\",\n      \"evidence\": \"In vitro kinase assay with recombinant protein and HPLC product identification in COS cells\",\n      \"pmids\": [\"10419465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo lipid measurements\", \"Relative contribution of each product to cellular signaling unknown\", \"Structural basis of substrate specificity unresolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"How PIKfyve reaches its site of action was established: the FYVE domain binds PtdIns3P on late endosomal membranes and is essential for membrane targeting, while kinase-dead PIKfyve causes dominant vacuolation demonstrating that active PIKfyve is required for endomembrane homeostasis.\",\n      \"evidence\": \"PtdIns3P liposome binding, FYVE domain mutagenesis, kinase-dead mutant expression with fluorescence microscopy and rescue in multiple cell types\",\n      \"pmids\": [\"11285266\", \"11706043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether additional membrane-targeting determinants beyond FYVE domain exist in vivo\", \"Mechanism by which kinase loss leads to vacuolation not resolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"The cellular functions of PIKfyve were delineated: it selectively regulates fluid-phase endocytosis, MVB morphogenesis, and late endosome-to-TGN retrograde transport—but not transferrin recycling or EGF receptor degradation—establishing pathway specificity.\",\n      \"evidence\": \"Stable inducible kinase-dead lines, fluid-phase marker uptake, electron microscopy, yeast two-hybrid identification of Rab9 effector p40 interaction\",\n      \"pmids\": [\"14551253\", \"14530284\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PIKfyve achieves pathway specificity unclear\", \"Relationship between p40 phosphorylation and retrograde transport not fully resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Signal-dependent regulation of PIKfyve was discovered: PKB/AKT phosphorylates Ser318 in response to insulin, stimulating kinase activity and modulating GLUT4 vesicle trafficking; simultaneously, Vac14/ArPIKfyve was identified as a required positive regulator and physical partner.\",\n      \"evidence\": \"In vitro PKB kinase assay, phospho-specific antibodies, S318A mutant in 3T3-L1 adipocytes; Co-IP, siRNA knockdown of Vac14 with in vitro kinase and HPLC readouts\",\n      \"pmids\": [\"15546921\", \"15542851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other kinases phosphorylate Ser318 in non-insulin contexts\", \"How Vac14 stimulates PIKfyve enzymatic activity mechanistically\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The ternary PIKfyve–ArPIKfyve–Sac3 (PAS) complex was reconstituted, revealing that Sac3/Fig4 preferentially hydrolyzes PI(3,5)P2 and that balanced kinase/phosphatase activities within the complex control endosomal carrier vesicle formation.\",\n      \"evidence\": \"Co-IP, co-fractionation, in vitro phosphatase assay, siRNA, in vitro vesicle formation reconstitution\",\n      \"pmids\": [\"17556371\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the complex unknown at this stage\", \"How Sac3 integrates into complex architecture unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The cpn60/TCP1 domain of PIKfyve was identified as the key interaction module mediating both ArPIKfyve–Sac3 binding and the p40/JLP adapter interaction, and PIKfyve was shown to control lysosomal degradation of CaV1.2 channels in neurons, extending its substrates beyond canonical endosomal cargo.\",\n      \"evidence\": \"Systematic domain mutagenesis in triple-transfected cells; NMDA-dependent CaV1.2 co-IP, siRNA with excitotoxicity readout; JLP yeast two-hybrid and cargo-specific trafficking assays\",\n      \"pmids\": [\"19840946\", \"19841139\", \"19056739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether cpn60_TCP1 domain interactions are mutually exclusive or simultaneous\", \"How NMDA signaling activates PIKfyve\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"In vivo, PIKfyve was confirmed as the sole source of PI(3,5)P2 and the predominant source of PI5P (generated indirectly via 3-phosphatase action on PI(3,5)P2); functionally, PtdIns5P and PI(3,5)P2 were shown to be dissociable, with PI5P mediating actin remodeling and PI(3,5)P2 driving vacuolation.\",\n      \"evidence\": \"Pikfyve hypomorph mouse, shRNA, quantitative tissue phosphoinositide mass measurements; differential-dose YM201636 with HPLC and actin/GLUT4 assays\",\n      \"pmids\": [\"23047693\", \"22621786\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the 3-phosphatase converting PI(3,5)P2 to PI5P in vivo\", \"Tissue-specific regulation of each lipid product\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Two additional upstream kinases—AKT (EGF-stimulated EGFR-to-lysosome routing) and AMPK (Ser307, contraction-stimulated glucose uptake)—were shown to directly phosphorylate and activate PIKfyve, establishing it as a signaling hub integrating growth factor and energy-sensing inputs.\",\n      \"evidence\": \"In vitro AKT/AMPK kinase assays, phosphomutants, receptor trafficking, glucose uptake in muscle\",\n      \"pmids\": [\"23757022\", \"23905686\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cross-talk between Ser307 and Ser318 phosphorylation events\", \"Whether other metabolic kinases also regulate PIKfyve\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"PIKfyve was established as essential for phagosome maturation (PtdIns3P-to-PI(3,5)P2 conversion, LAMP1/cathepsin acquisition) and for endolysosomal TLR-induced type I IFN production (via ATF3 transcriptional repression), linking it to innate immunity.\",\n      \"evidence\": \"Multiple PIKfyve inhibitors in macrophage phagocytosis; pharmacological/genetic inactivation with ATF3/IFN promoter ChIP; TLR9/AP-3 trafficking assays\",\n      \"pmids\": [\"25041080\", \"24600036\", \"25170925\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PI(3,5)P2 mechanistically promotes PtdIns3P removal on phagosomes\", \"Whether ATF3 induction is a direct consequence of PI(3,5)P2 depletion or lysosome stress\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The cellular consequences of PIKfyve loss were refined: lysosome enlargement results from coalescence (fusion over fission) rather than biosynthesis; PIKfyve inhibition increases exosome secretion via impaired MVB–lysosome fusion; the downstream effector TRPML1 was identified as a key mediator of vacuole resolution and nutrient recovery.\",\n      \"evidence\": \"Live fusion/fission dynamics imaging, TFEB/TFE3 knockout, quantitative EM and MS of exosomal fractions, TRPML1 genetic manipulation and starvation survival assays\",\n      \"pmids\": [\"29661845\", \"27438886\", \"27623384\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TRPML1 is the sole PI(3,5)P2 effector for fission\", \"How PI(3,5)P2 regulates the balance between exosomal release and degradation\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Cryo-EM resolved the PAS complex architecture at 5 Vac14 : 1 PIKfyve : 1 Fig4 stoichiometry and revealed a self-regulatory circuit: PIKfyve autophosphorylation represses its kinase and stimulates Fig4 phosphatase, while Fig4 acts as a protein phosphatase on PIKfyve to restore kinase activity; sterically, PIKfyve cannot reach membrane-embedded substrates within the complex.\",\n      \"evidence\": \"Cryo-EM structure, in vitro phosphatase/kinase reconstitution, mutagenesis\",\n      \"pmids\": [\"33098764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the complex is remodeled to allow membrane access in vivo\", \"How Vac14 pentamerization is regulated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A third upstream kinase, ULK1 (activated by AMPK during glucose starvation), was shown to phosphorylate PIKfyve Ser1548, selectively increasing PI5P (not PI(3,5)P2) synthesis and promoting PI5P-containing autophagosome formation, thereby linking PIKfyve to autophagy initiation.\",\n      \"evidence\": \"In vitro ULK1 kinase assay, S1548D phosphomimetic, quantitative phosphoinositide measurements, autophagy flux assays\",\n      \"pmids\": [\"34107300\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for how Ser1548 phosphorylation shifts product specificity\", \"Whether PI5P on autophagosomes recruits specific effectors\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"PIKfyve stability was shown to be controlled by palmitoylation by zDHHC9/zDHHC21; prion infection or UPR disrupts acyltransferase topology causing PIKfyve deacylation, degradation, and endolysosomal hypertrophy—a disease-relevant post-translational control mechanism.\",\n      \"evidence\": \"Acylation assays, zDHHC knockdown/overexpression, mouse and organotypic brain slice prion infection models, PI(3,5)P2 rescue\",\n      \"pmids\": [\"34291577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which palmitoylation site(s) on PIKfyve are critical\", \"Whether deacylation is an active regulatory mechanism beyond disease contexts\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The mechanism by which PIKfyve controls TFEB nuclear translocation was resolved: PI(3,5)P2 is required for mTORC1 to access TFEB (but not other substrates) at the lysosome, and PP2A (not calcineurin) dephosphorylates TFEB-Ser211 when PIKfyve is inhibited; separately, PIKfyve was shown to govern Retriever/CCC-mediated integrin recycling downstream of VPS34.\",\n      \"evidence\": \"mTORC1 substrate profiling, PP2A/calcineurin inhibitors, TFEB nuclear localization; endogenous co-localization, PIKfyve inhibition Retriever displacement, integrin recycling, VPS34 epistasis\",\n      \"pmids\": [\"35020443\", \"35040777\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How PI(3,5)P2 physically mediates mTORC1–TFEB proximity\", \"Whether PP2A regulation is TFEB-specific or extends to other TFE family members\", \"How PIKfyve products recruit Retriever to endosomes\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: (1) how the PIKfyve-Vac14-Fig4 complex is conformationally rearranged to allow PIKfyve access to membrane substrates in vivo; (2) the structural basis for phosphorylation-dependent switching between PI(3,5)P2 and PI5P product specificity; (3) the identity and regulation of the 3-phosphatase generating PI5P from PI(3,5)P2 in vivo; and (4) how tissue- and context-specific PIKfyve regulation is achieved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Membrane access mechanism for the intact PAS complex\", \"Product specificity switching mechanism\", \"In vivo 3-phosphatase identity\", \"Tissue-specific regulatory mechanisms\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 3, 6, 17, 34]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [5, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1, 2, 8, 39]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [14, 22, 26, 44]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [39]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4, 25, 38]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [4, 8, 12, 16, 25, 37]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 20, 21]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [22, 23, 30, 31, 43, 44]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [25, 34]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3, 17]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [37, 39]}\n    ],\n    \"complexes\": [\n      \"PIKfyve-Vac14-Fig4 (PAS complex)\"\n    ],\n    \"partners\": [\n      \"VAC14\",\n      \"FIG4\",\n      \"TRPML1\",\n      \"JLP\",\n      \"p40\",\n      \"VPS34\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}