{"gene":"IP6K1","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":2016,"finding":"IP6K1 catalytic activity is required for cytoplasmic dynein-driven vesicle transport; IP7 pyrophosphorylates Ser51 of dynein intermediate chain (IC), promoting IC interaction with p150(Glued) subunit of dynactin, and IC recruitment to membranes. Cells lacking IP6K1 show defects in endosomal sorting, vesicle movement, and Golgi maintenance that are reversed by catalytically active but not inactive IP6K1.","method":"KO cell lines, catalytically inactive mutant rescue, in vitro pyrophosphorylation assay, Co-IP, membrane fractionation, live imaging of vesicle movement","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including in vitro pyrophosphorylation, Co-IP, KO rescue with active vs. inactive mutant, and functional transport assays","pmids":["27474409"],"is_preprint":false},{"year":2016,"finding":"IP6K1 promotes cell migration and actin cytoskeleton remodeling via FAK and Paxillin activation; IP6K1-null MEFs show defects in adhesion-dependent signaling, cell spreading, and migration that are reversed by catalytically active but not inactive IP6K1, indicating 5-IP7 synthesis drives cell locomotion.","method":"KO MEFs, catalytically inactive mutant rescue, immunoblot for FAK/Paxillin phosphorylation, migration and invasion assays, gene expression analysis","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined phenotype, active vs. inactive rescue, multiple pathway readouts","pmids":["27140681"],"is_preprint":false},{"year":2016,"finding":"IP6K1 regulates adipocyte energy metabolism by suppressing AMPK-mediated thermogenesis; adipocyte-specific deletion of Ip6k1 enhances AMPK activation, UCP1/PGC1α expression, and thermogenic energy expenditure. IP6 and IP6K1 differentially regulate upstream kinase-mediated AMPK stimulatory phosphorylation in vitro.","method":"Adipocyte-specific KO mice, in vitro kinase assays, immunoblot, UCP1/PGC1α expression, AMPK depletion epistasis, energy expenditure measurement","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 — tissue-specific KO with defined thermogenic phenotype, in vitro kinase assays, AMPK epistasis experiment","pmids":["27701146"],"is_preprint":false},{"year":2016,"finding":"IP6K1 preferentially binds phosphatidic acid (PA), and this binding is required for IP6K1 nuclear localization and transcriptional repression of myo-inositol-3-phosphate synthase (MIPS/Isyna1), thereby negatively regulating inositol synthesis in mammalian cells.","method":"Ip6k1 ablation in MEFs, PA-binding assay, subcellular fractionation/nuclear localization, DNA methylation analysis, qRT-PCR for Isyna1 expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — KO with defined molecular phenotype, direct PA-binding experiment, nuclear localization tied to transcriptional repression","pmids":["26953345"],"is_preprint":false},{"year":2022,"finding":"Phosphatidic acid (PA) synthesized at the plasma membrane by phospholipase D (PLD) induces nuclear translocation of IP6K1 and represses MIPS expression. AMPK activates PLD-mediated PA synthesis, linking glucose deprivation or mood-stabilizing drugs (valproate, lithium) to IP6K1 nuclear translocation and MIPS repression.","method":"Pharmacological PLD stimulation, direct PA supplementation, AMPK activation by glucose deprivation/drugs, nuclear translocation imaging, MIPS immunoblot, organelle-specific PA manipulation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal pharmacological approaches, localization directly tied to functional transcriptional outcome, ER vs plasma membrane PA specificity determined","pmids":["35963434"],"is_preprint":false},{"year":2019,"finding":"IP6K1 and IP6K2 together control inositol pyrophosphate (IP7/IP8) metabolism; IP6K1/2-knockout HCT116 cells lack IP7/IP8, have elevated intracellular ATP and free phosphate, and show reduced phosphate import and export. Inositol pyrophosphates regulate phosphate export via binding to the SPX domain of the phosphate exporter XPR1.","method":"CRISPR KO of IP6K1/2, PAGE and HPLC inositol phosphate analysis, nucleotide analysis, Malachite green phosphate assay, [32Pi] pulse labeling, XPR1 SPX-domain binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal biochemical methods, direct SPX-domain binding assay, clean double-KO system","pmids":["31186349"],"is_preprint":false},{"year":2018,"finding":"Platelet IP6K1-mediated inorganic polyphosphate (polyP) production is essential for infection-induced neutrophil-platelet aggregate (NPA) formation; IP6K1 inhibition reduces serum polyP levels, which regulates NPAs via the bradykinin pathway and bradykinin-mediated neutrophil activation, thereby reducing pulmonary neutrophil accumulation.","method":"Ip6k1 KO mice, pharmacological IP6K1 inhibition (TNP), platelet polyP measurement, NPA flow cytometry, bradykinin pathway analysis, polyphosphate rescue experiment, bacterial pneumonia model","journal":"Science translational medicine","confidence":"High","confidence_rationale":"Tier 2 — genetic KO plus pharmacological inhibition, polyP rescue experiment, pathway epistasis with bradykinin, multiple orthogonal readouts","pmids":["29618559"],"is_preprint":false},{"year":2017,"finding":"IP6K1 is a component of the chromatoid body in round spermatids and is required for its formation; Ip6k1-null spermatids lack chromatoid bodies and show premature translational derepression of TNP2 and PRM2, resulting in abnormal chromatin remodeling, failure of spermatid differentiation, and azoospermia.","method":"Ip6k1 KO mice, immunofluorescence/localization of IP6K1 to chromatoid body, immunoblot for TNP2/PRM2/histones, spermatogenesis phenotype analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — KO with specific mechanistic phenotype (translational derepression), direct localization to chromatoid body, multiple molecular readouts","pmids":["28743739"],"is_preprint":false},{"year":2021,"finding":"IP6K1 upregulates processing body (P-body) formation independently of its catalytic activity by binding to ribosomes and interacting with the mRNA decapping complex (EDC4, DCP1A/B, DCP2, DDX6); IP6K1 augments DDX6-4E-T interaction and binding to eIF4E on the 5' mRNA cap, tipping the balance toward translational repression. IP6K1-depleted cells show reduced microRNA-mediated translational suppression and increased stability of DCP2-regulated transcripts.","method":"IP6K1 KD/KO, Co-IP of decapping complex components, ribosome fractionation, P-body quantification, mRNA stability assays, catalytically inactive mutant analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IPs, catalytic activity-independent function established by mutant, multiple functional readouts (P-body number, miRNA suppression, mRNA stability)","pmids":["34841428"],"is_preprint":false},{"year":2021,"finding":"IP6K1 interacts with O-GlcNAcase in human NASH liver tissue and its deletion reduces protein O-GlcNAcylation in mouse liver, linking IP6K1 to regulation of protein O-GlcNAc modification in hepatic metabolism.","method":"Co-immunoprecipitation, mass spectrometry, immunoblot for O-GlcNAcylation in KO vs WT mouse livers and human NASH samples","journal":"Molecular metabolism","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP/MS identification with functional correlate (O-GlcNAcylation changes), not yet fully reconstituted mechanistically","pmids":["34757046"],"is_preprint":false},{"year":2017,"finding":"IP6K1 deletion in MSCs results in higher MDM2 and lower p53 protein levels, leading to reduced intrinsic mitochondrial ROS, enhanced osteogenesis and hematopoiesis-supporting activity, and reduced adipogenic differentiation.","method":"Ip6k1 KO mice, MSC isolation, immunoblot for MDM2/p53, mitochondrial ROS measurement, osteogenic/adipogenic differentiation assays","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined molecular pathway (MDM2-p53-ROS axis) and multiple cellular readouts, single lab","pmids":["28577302"],"is_preprint":false},{"year":2024,"finding":"IP6K1 forms a complex with AP3B1 and CK2α; IP6K1 interacts with multiple proteins that undergo 5-InsP7-mediated pyrophosphorylation (NOLC1, TCOF, UBF1, AP3B1), and disrupting IP6K1 binding to AP3B1 lowers its in vivo pyrophosphorylation, suggesting IP6K1 acts as a scaffold to coordinate CK2-mediated pre-phosphorylation and subsequent pyrophosphorylation of substrates.","method":"Mass spectrometry interactome, Co-IP of IP6K1-AP3B1-CK2α complex, in vivo pyrophosphorylation assay with IP6K1-binding mutant","journal":"Bioscience reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — MS interactome confirmed by Co-IP and functional pyrophosphorylation assay, single lab","pmids":["39230924"],"is_preprint":false},{"year":2024,"finding":"IP6K1 and its product 5PP-InsP5 bind apoA-I and recruit UBE4A to induce apoA-I ubiquitination and degradation; depleting 5PP-InsP5 by IP6K1 deletion or inhibition disrupts UBE4A-apoA-I interaction, preventing apoA-I degradation and elevating circulating apoA-I, thereby reducing atherosclerosis.","method":"Co-immunoprecipitation, chemical biology 5PP-InsP5 binding assays, hepatocyte-specific IP6K1 KO mice, apoA-I KO epistasis, Oil Red O/H&E plaque assessment","journal":"Metabolism: clinical and experimental","confidence":"High","confidence_rationale":"Tier 2 — direct protein-protein interaction by Co-IP, 5PP-InsP5 binding assay, epistasis with apoA-I KO, hepatocyte-specific KO with atherosclerotic phenotype","pmids":["39643078"],"is_preprint":false},{"year":2025,"finding":"IP6K1 mediates hyperglycemia-induced endothelial senescence by stabilizing LKB1 (disrupting Hsp/Hsc70 and CHIP-mediated LKB1 degradation), which shifts LKB1 signaling from AMPK activation to p53 pathway activation, resulting in p53-dependent senescence; endothelial-specific IP6K1 KO attenuates and overexpression exacerbates this phenotype.","method":"Co-IP (LKB1-IP6K1, LKB1-Hsp70, LKB1-CHIP, LKB1-p53), endothelial cell-specific KO and overexpression mice, immunoblot for AMPK/p53/senescence markers","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 — multiple Co-IPs establishing mechanism, tissue-specific KO and OE with concordant phenotype, single lab","pmids":["39792359"],"is_preprint":false},{"year":2010,"finding":"Recombinant mouse IP6K1 purified from E. coli catalyzes the synthesis of InsP7 (5-IP7) from IP6 in vitro and can pyrophosphorylate protein serine residues in a kinase-independent manner using this product.","method":"Recombinant protein purification from E. coli, in vitro kinase assay, radiolabeled [32P]-InsP7 production, in vitro protein pyrophosphorylation","journal":"Methods in molecular biology (Clifton, N.J.)","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro reconstitution of enzymatic activity with purified recombinant protein","pmids":["20645182"],"is_preprint":false},{"year":2024,"finding":"Renal IP6K1 and IP6K2 together are required for normal expression and function of Na+/Pi cotransporters NaPi-IIa and NaPi-IIc; renal tubular-specific double KO mice show reduced phosphate uptake into proximal brush border membranes, hypophosphatemia, reduced FGF23, and increased bone resorption despite hypophosphatemia.","method":"Renal tubular-specific Ip6k1/2 DKO mice, in vitro opossum kidney cell KO, phosphate transport assays, brush border membrane vesicle uptake, FGF23 ELISA, immunoblot for cotransporters","journal":"Journal of the American Society of Nephrology : JASN","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO confirmed in vitro and in vivo with direct phosphate transport measurements and molecular expression data","pmids":["38317282"],"is_preprint":false},{"year":2024,"finding":"IP6K1 KO neurons display lower action potential frequency and deepened afterhyperpolarization, consistent with increased Na+/K+-ATPase (NKA) activity resulting from IP6K1-regulated NKA stability (via PI3K p85α autoinhibitory domain pathway).","method":"Electrophysiology of IP6K1 KO neurons, action potential frequency and afterhyperpolarization measurement","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined electrophysiological phenotype, mechanism referenced from prior work on NKA-PI3K p85α pathway, single lab","pmids":["38350944"],"is_preprint":false},{"year":2025,"finding":"IP6K1 regulates mitochondrial polyphosphate (polyP) levels through 5-InsP7 synthesis; IP6K1 KO mice and cells show significantly reduced mitochondrial polyP, impaired mitochondrial respiration, and reduced membrane potential. Catalytically active but not inactive IP6K1 restores polyP synthesis and membrane potential, while both active and inactive forms rescue mitochondrial respiration, indicating dual catalytic-dependent and independent mechanisms.","method":"DAPI fluorescence-based polyP assay, mitochondrial fractionation, mitochondrial respiration (Seahorse), membrane potential measurement, KO cells/mice, active vs. inactive IP6K1 rescue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods, active vs. inactive rescue distinguishes catalytic and non-catalytic functions; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.06.17.659843"],"is_preprint":true},{"year":2025,"finding":"IP6K1 interacts with the proteoglycan SDC4 and supports secretory granule biogenesis in gastric chief cells independently of its catalytic activity; IP6K1 KO AGS cells and Ip6k1-/- mice lack pepsinogen C (PGC) and gastric lipase F (LIPF) granules, and PGC granule formation is restored by reintroduction of either active or inactive IP6K1.","method":"Ip6k1 KO mice, CRISPR/Cas9 KO in AGS cells, Co-IP of IP6K1-SDC4, immunofluorescence of granules, active vs. inactive IP6K1 rescue","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — KO phenotype in vivo and in vitro, Co-IP of binding partner SDC4, active vs. inactive rescue establishing catalytic independence; preprint","pmids":["bio_10.1101_2025.09.17.676719"],"is_preprint":true},{"year":2025,"finding":"IP6K1 is a substrate of the Cys-Arg/N-degron pathway under hypoxia; loss of IP6K1 impairs glucose uptake, glycolytic ATP production, mitochondrial morphology, and metabolic adaptation under hypoxic conditions.","method":"Proteomics/global N-terminal Cys-degron profiling, mutagenesis, IP6K1 KO cells under hypoxia, glucose uptake and ATP production assays, mitochondrial morphology imaging","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 — IP6K1 identified as N-degron substrate by proteomics, functional consequences of KO described but upstream degradation mechanism for IP6K1 specifically not fully validated; preprint","pmids":["bio_10.1101_2025.01.20.633921"],"is_preprint":true}],"current_model":"IP6K1 is a conserved inositol hexakisphosphate kinase that converts IP6 to 5-IP7 (InsP7), which regulates diverse cellular processes including dynein-driven vesicle transport (via Ser51 pyrophosphorylation of dynein IC), AMPK-mediated thermogenesis and energy metabolism, cell migration via FAK/Paxillin signaling, phosphate homeostasis through XPR1 and renal NaPi cotransporters, inositol synthesis via PA-dependent nuclear translocation and MIPS repression, mRNA translational control via P-body assembly, and apoA-I stability via UBE4A recruitment; additionally, IP6K1 exerts catalytic activity-independent scaffold functions in secretory granule biogenesis and mRNA cap remodeling."},"narrative":{"teleology":[{"year":2010,"claim":"Establishing that IP6K1 directly converts IP6 to 5-IP7 and can pyrophosphorylate protein serines resolved the fundamental enzymatic activity and opened investigation into protein-level signaling by inositol pyrophosphates.","evidence":"Recombinant mouse IP6K1 purified from E. coli, in vitro kinase assay with radiolabeled substrates","pmids":["20645182"],"confidence":"High","gaps":["Endogenous substrate selectivity for protein pyrophosphorylation not defined","Structural basis for 5-position specificity not resolved"]},{"year":2016,"claim":"Demonstration that IP6K1-generated 5-IP7 pyrophosphorylates dynein IC-Ser51 to promote dynactin binding and membrane recruitment revealed the first specific in vivo protein substrate and linked IP6K1 to cytoplasmic dynein-driven vesicle transport and Golgi maintenance.","evidence":"IP6K1 KO cells, catalytically active vs. inactive mutant rescue, in vitro pyrophosphorylation, Co-IP, live vesicle imaging","pmids":["27474409"],"confidence":"High","gaps":["Whether other dynein-associated cargoes are similarly regulated is unknown","Quantitative contribution of pyrophosphorylation vs. canonical phosphorylation at Ser51 not resolved"]},{"year":2016,"claim":"Parallel work showed IP6K1 catalytic activity drives FAK/Paxillin phosphorylation, cell spreading, and migration, broadening the kinase's role to adhesion-dependent signaling and actin remodeling.","evidence":"IP6K1 KO MEFs, active vs. inactive rescue, migration/invasion assays, FAK/Paxillin immunoblot","pmids":["27140681"],"confidence":"High","gaps":["Whether 5-IP7 acts directly on FAK or through an intermediate is not resolved","Relevance to in vivo tumor invasion not tested"]},{"year":2016,"claim":"Adipocyte-specific IP6K1 deletion showed the kinase suppresses AMPK-mediated thermogenesis and UCP1 expression, establishing IP6K1 as a metabolic regulator of energy expenditure and a potential anti-obesity target.","evidence":"Adipocyte-specific KO mice, AMPK epistasis, in vitro kinase assays, energy expenditure calorimetry","pmids":["27701146"],"confidence":"High","gaps":["Direct molecular mechanism connecting 5-IP7 to AMPK inhibition not fully delineated","Whether IP6K1 acts on AMPK directly or upstream kinases in vivo remains unclear"]},{"year":2016,"claim":"Discovery that IP6K1 binds phosphatidic acid and translocates to the nucleus to repress MIPS/Isyna1 transcription revealed a lipid-sensing mechanism coupling IP6K1 to inositol biosynthesis regulation.","evidence":"IP6K1 KO MEFs, PA-binding assay, nuclear fractionation, qRT-PCR for Isyna1","pmids":["26953345"],"confidence":"High","gaps":["How IP6K1 mediates transcriptional repression of MIPS at the chromatin level is unresolved","PA-binding domain on IP6K1 not mapped"]},{"year":2017,"claim":"Localization of IP6K1 to the chromatoid body and demonstration that its loss abolishes chromatoid body formation and derepresses TNP2/PRM2 translation established IP6K1 as essential for post-transcriptional control during spermiogenesis.","evidence":"Ip6k1 KO mice, immunofluorescence of chromatoid body markers, immunoblot for TNP2/PRM2","pmids":["28743739"],"confidence":"High","gaps":["Whether this function requires catalytic activity or scaffolding is not determined","Direct RNA or RNP targets of IP6K1 in chromatoid body not identified"]},{"year":2018,"claim":"IP6K1 was shown to be required for platelet inorganic polyphosphate production that drives neutrophil-platelet aggregate formation via the bradykinin pathway, extending IP6K1 function to innate immunity and thromboinflammation.","evidence":"Ip6k1 KO mice, pharmacological IP6K1 inhibition, polyP rescue, NPA flow cytometry, bacterial pneumonia model","pmids":["29618559"],"confidence":"High","gaps":["Mechanism by which IP6K1 controls mitochondrial/platelet polyP synthesis is undefined","Contribution of IP6K1 vs. IP6K2 to platelet polyP not separated"]},{"year":2019,"claim":"Double KO of IP6K1/2 eliminated IP7/IP8, elevated intracellular ATP and phosphate, and impaired phosphate export via XPR1 SPX-domain binding, unifying inositol pyrophosphate signaling with cellular phosphate homeostasis.","evidence":"CRISPR IP6K1/2 DKO in HCT116, PAGE/HPLC inositol phosphate profiling, 32Pi flux, XPR1 SPX-domain binding assay","pmids":["31186349"],"confidence":"High","gaps":["Individual contributions of IP6K1 vs. IP6K2 to phosphate export not fully dissected","In vivo tissue-specific phosphate phenotype of single IP6K1 KO not addressed here"]},{"year":2021,"claim":"IP6K1 was found to scaffold the mRNA decapping complex and promote P-body assembly independently of catalytic activity, establishing a kinase-independent role in translational repression and mRNA turnover.","evidence":"IP6K1 KD/KO, reciprocal Co-IPs of decapping complex, ribosome fractionation, P-body quantification, catalytically inactive mutant rescue","pmids":["34841428"],"confidence":"High","gaps":["Structural basis for IP6K1-decapping complex interaction unknown","Whether P-body scaffolding and chromatoid body functions share a common mechanism is untested"]},{"year":2022,"claim":"The upstream signal for IP6K1 nuclear translocation was traced to PLD-generated PA at the plasma membrane, regulated by AMPK, linking metabolic stress and mood-stabilizing drugs to MIPS repression and inositol depletion.","evidence":"Pharmacological PLD stimulation, AMPK activation by glucose deprivation/valproate/lithium, organelle-specific PA manipulation, nuclear translocation imaging","pmids":["35963434"],"confidence":"High","gaps":["Whether PA-dependent nuclear import uses a classical NLS or alternative mechanism is unresolved","Contribution of IP6K1 nuclear translocation to mood-stabilizer therapeutic efficacy not established"]},{"year":2024,"claim":"IP6K1 forms a ternary complex with AP3B1 and CK2α, acting as a scaffold to coordinate CK2-mediated pre-phosphorylation and subsequent 5-IP7-dependent pyrophosphorylation of substrates, revealing a general mechanism for substrate targeting.","evidence":"Mass spectrometry interactome, Co-IP of IP6K1-AP3B1-CK2α, in vivo pyrophosphorylation assay with IP6K1-binding mutant of AP3B1","pmids":["39230924"],"confidence":"Medium","gaps":["Whether this scaffolding mechanism applies broadly to all pyrophosphorylation substrates is untested","Structural details of the ternary complex are unknown","Single-lab finding"]},{"year":2024,"claim":"Renal tubular double KO of IP6K1/2 demonstrated that inositol pyrophosphates are required for NaPi-IIa/IIc cotransporter expression and renal phosphate reabsorption, establishing an in vivo tissue-specific phosphate homeostasis role.","evidence":"Renal tubular-specific Ip6k1/2 DKO mice, brush border membrane vesicle phosphate uptake, FGF23 measurement, cotransporter immunoblot","pmids":["38317282"],"confidence":"High","gaps":["Individual contribution of IP6K1 vs. IP6K2 in renal phosphate handling not resolved","Mechanism by which 5-IP7 regulates cotransporter expression is undefined"]},{"year":2024,"claim":"IP6K1-generated 5-IP7 binds apoA-I and recruits UBE4A for ubiquitination, establishing a direct mechanism linking IP6K1 to apoA-I degradation and atherosclerosis susceptibility.","evidence":"Co-IP, 5-IP7 chemical binding assays, hepatocyte-specific IP6K1 KO mice, apoA-I KO epistasis, atherosclerotic plaque analysis","pmids":["39643078"],"confidence":"High","gaps":["Structural basis of 5-IP7-apoA-I interaction not determined","Whether IP6K1 similarly regulates other apolipoproteins is unknown"]},{"year":2025,"claim":"IP6K1 was shown to stabilize LKB1 by disrupting Hsp/Hsc70-CHIP-mediated degradation, redirecting LKB1 signaling from AMPK to p53 to drive hyperglycemia-induced endothelial senescence.","evidence":"Multiple Co-IPs, endothelial-specific IP6K1 KO and overexpression mice, immunoblot for AMPK/p53/senescence markers","pmids":["39792359"],"confidence":"Medium","gaps":["Whether this mechanism requires 5-IP7 or is catalysis-independent is not addressed","Relevance to diabetic vascular disease in humans not validated","Single-lab finding"]},{"year":null,"claim":"Key unresolved questions include: the structural basis for IP6K1's dual catalytic and scaffolding functions; how substrate selectivity for protein pyrophosphorylation is achieved in vivo; the mechanism linking IP6K1 to mitochondrial polyphosphate synthesis; and whether kinase-dependent vs. kinase-independent functions segregate by subcellular compartment or tissue.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal structure of full-length IP6K1 with substrates","No systematic delineation of catalytic vs. non-catalytic functions across tissues","Mechanism of mitochondrial polyP regulation by IP6K1 is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,2,5,14]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[3,4]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[8,11,18]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,13]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3,4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,8]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[17]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,13]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,3,5,12]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[7,8]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[6]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[11,12]}],"complexes":["mRNA decapping complex","IP6K1-AP3B1-CK2α complex","chromatoid body"],"partners":["DIC (DYNEIN INTERMEDIATE CHAIN)","EDC4","DDX6","DCP2","AP3B1","CSNK2A1","SDC4","UBE4A"],"other_free_text":[]},"mechanistic_narrative":"IP6K1 is a conserved inositol hexakisphosphate kinase that synthesizes 5-IP7 (5-PP-InsP5) from IP6 and exerts both catalytic and scaffolding functions across diverse cellular processes including vesicle transport, energy metabolism, phosphate homeostasis, mRNA translational control, and secretory granule biogenesis. The 5-IP7 product pyrophosphorylates serine residues on substrates such as dynein intermediate chain to promote dynactin binding and dynein-driven vesicle transport, activates FAK/Paxillin signaling for cell migration, and recruits UBE4A to apoA-I for ubiquitin-mediated degradation [PMID:27474409, PMID:27140681, PMID:39643078]. IP6K1 suppresses AMPK-mediated thermogenesis in adipocytes, regulates phosphate export via XPR1 SPX-domain engagement by inositol pyrophosphates, and controls renal Na+/Pi cotransporter expression [PMID:27701146, PMID:31186349, PMID:38317282]. Independent of catalytic activity, IP6K1 scaffolds the mRNA decapping complex (EDC4, DCP1A/B, DCP2, DDX6) to promote P-body assembly and translational repression, coordinates CK2-mediated pre-phosphorylation of pyrophosphorylation substrates via an AP3B1–CK2α complex, and supports secretory granule biogenesis in gastric chief cells [PMID:34841428, PMID:39230924]."},"prefetch_data":{"uniprot":{"accession":"Q92551","full_name":"Inositol hexakisphosphate kinase 1","aliases":["Inositol hexaphosphate kinase 1"],"length_aa":441,"mass_kda":50.2,"function":"Converts inositol hexakisphosphate (InsP6) to diphosphoinositol pentakisphosphate (InsP7/PP-InsP5). Converts 1,3,4,5,6-pentakisphosphate (InsP5) to PP-InsP4","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q92551/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IP6K1","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SEC61B","stoichiometry":0.2},{"gene":"VCP","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/IP6K1","total_profiled":1310},"omim":[{"mim_id":"621025","title":"RAB3A-INTERACTING PROTEIN-LIKE 1; RAB3IL1","url":"https://www.omim.org/entry/621025"},{"mim_id":"606992","title":"INOSITOL HEXAPHOSPHATE KINASE 2; IP6K2","url":"https://www.omim.org/entry/606992"},{"mim_id":"606991","title":"INOSITOL HEXAPHOSPHATE KINASE 1; IP6K1","url":"https://www.omim.org/entry/606991"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoli fibrillar center","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/IP6K1"},"hgnc":{"alias_symbol":["KIAA0263"],"prev_symbol":["IHPK1"]},"alphafold":{"accession":"Q92551","domains":[{"cath_id":"3.30.470.160","chopping":"23-98_159-344_389-438","consensus_level":"medium","plddt":89.3963,"start":23,"end":438}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92551","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92551-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92551-F1-predicted_aligned_error_v6.png","plddt_mean":74.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IP6K1","jax_strain_url":"https://www.jax.org/strain/search?query=IP6K1"},"sequence":{"accession":"Q92551","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92551.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92551/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92551"}},"corpus_meta":[{"pmid":"31186349","id":"PMC_31186349","title":"The 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Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/38399478","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.17.676719","title":"IP6K1 interacts with the syndecan SDC4 to support secretory granule biogenesis in gastric chief cells","date":"2025-09-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.17.676719","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.17.659843","title":"Mammalian mitochondrial polyphosphate is regulated by the 5-InsP<sub>7</sub>synthase IP6K1","date":"2025-06-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.17.659843","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.01.20.633921","title":"Global Profiling of N-terminal Cysteine-Dependent Degradation Mechanisms","date":"2025-01-22","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.20.633921","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17077,"output_tokens":5351,"usd":0.065748},"stage2":{"model":"claude-opus-4-6","input_tokens":8867,"output_tokens":3946,"usd":0.214477},"total_usd":0.280225,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"IP6K1 catalytic activity is required for cytoplasmic dynein-driven vesicle transport; IP7 pyrophosphorylates Ser51 of dynein intermediate chain (IC), promoting IC interaction with p150(Glued) subunit of dynactin, and IC recruitment to membranes. Cells lacking IP6K1 show defects in endosomal sorting, vesicle movement, and Golgi maintenance that are reversed by catalytically active but not inactive IP6K1.\",\n      \"method\": \"KO cell lines, catalytically inactive mutant rescue, in vitro pyrophosphorylation assay, Co-IP, membrane fractionation, live imaging of vesicle movement\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including in vitro pyrophosphorylation, Co-IP, KO rescue with active vs. inactive mutant, and functional transport assays\",\n      \"pmids\": [\"27474409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"IP6K1 promotes cell migration and actin cytoskeleton remodeling via FAK and Paxillin activation; IP6K1-null MEFs show defects in adhesion-dependent signaling, cell spreading, and migration that are reversed by catalytically active but not inactive IP6K1, indicating 5-IP7 synthesis drives cell locomotion.\",\n      \"method\": \"KO MEFs, catalytically inactive mutant rescue, immunoblot for FAK/Paxillin phosphorylation, migration and invasion assays, gene expression analysis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined phenotype, active vs. inactive rescue, multiple pathway readouts\",\n      \"pmids\": [\"27140681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"IP6K1 regulates adipocyte energy metabolism by suppressing AMPK-mediated thermogenesis; adipocyte-specific deletion of Ip6k1 enhances AMPK activation, UCP1/PGC1α expression, and thermogenic energy expenditure. IP6 and IP6K1 differentially regulate upstream kinase-mediated AMPK stimulatory phosphorylation in vitro.\",\n      \"method\": \"Adipocyte-specific KO mice, in vitro kinase assays, immunoblot, UCP1/PGC1α expression, AMPK depletion epistasis, energy expenditure measurement\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — tissue-specific KO with defined thermogenic phenotype, in vitro kinase assays, AMPK epistasis experiment\",\n      \"pmids\": [\"27701146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"IP6K1 preferentially binds phosphatidic acid (PA), and this binding is required for IP6K1 nuclear localization and transcriptional repression of myo-inositol-3-phosphate synthase (MIPS/Isyna1), thereby negatively regulating inositol synthesis in mammalian cells.\",\n      \"method\": \"Ip6k1 ablation in MEFs, PA-binding assay, subcellular fractionation/nuclear localization, DNA methylation analysis, qRT-PCR for Isyna1 expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined molecular phenotype, direct PA-binding experiment, nuclear localization tied to transcriptional repression\",\n      \"pmids\": [\"26953345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Phosphatidic acid (PA) synthesized at the plasma membrane by phospholipase D (PLD) induces nuclear translocation of IP6K1 and represses MIPS expression. AMPK activates PLD-mediated PA synthesis, linking glucose deprivation or mood-stabilizing drugs (valproate, lithium) to IP6K1 nuclear translocation and MIPS repression.\",\n      \"method\": \"Pharmacological PLD stimulation, direct PA supplementation, AMPK activation by glucose deprivation/drugs, nuclear translocation imaging, MIPS immunoblot, organelle-specific PA manipulation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal pharmacological approaches, localization directly tied to functional transcriptional outcome, ER vs plasma membrane PA specificity determined\",\n      \"pmids\": [\"35963434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IP6K1 and IP6K2 together control inositol pyrophosphate (IP7/IP8) metabolism; IP6K1/2-knockout HCT116 cells lack IP7/IP8, have elevated intracellular ATP and free phosphate, and show reduced phosphate import and export. Inositol pyrophosphates regulate phosphate export via binding to the SPX domain of the phosphate exporter XPR1.\",\n      \"method\": \"CRISPR KO of IP6K1/2, PAGE and HPLC inositol phosphate analysis, nucleotide analysis, Malachite green phosphate assay, [32Pi] pulse labeling, XPR1 SPX-domain binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal biochemical methods, direct SPX-domain binding assay, clean double-KO system\",\n      \"pmids\": [\"31186349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Platelet IP6K1-mediated inorganic polyphosphate (polyP) production is essential for infection-induced neutrophil-platelet aggregate (NPA) formation; IP6K1 inhibition reduces serum polyP levels, which regulates NPAs via the bradykinin pathway and bradykinin-mediated neutrophil activation, thereby reducing pulmonary neutrophil accumulation.\",\n      \"method\": \"Ip6k1 KO mice, pharmacological IP6K1 inhibition (TNP), platelet polyP measurement, NPA flow cytometry, bradykinin pathway analysis, polyphosphate rescue experiment, bacterial pneumonia model\",\n      \"journal\": \"Science translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO plus pharmacological inhibition, polyP rescue experiment, pathway epistasis with bradykinin, multiple orthogonal readouts\",\n      \"pmids\": [\"29618559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"IP6K1 is a component of the chromatoid body in round spermatids and is required for its formation; Ip6k1-null spermatids lack chromatoid bodies and show premature translational derepression of TNP2 and PRM2, resulting in abnormal chromatin remodeling, failure of spermatid differentiation, and azoospermia.\",\n      \"method\": \"Ip6k1 KO mice, immunofluorescence/localization of IP6K1 to chromatoid body, immunoblot for TNP2/PRM2/histones, spermatogenesis phenotype analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO with specific mechanistic phenotype (translational derepression), direct localization to chromatoid body, multiple molecular readouts\",\n      \"pmids\": [\"28743739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IP6K1 upregulates processing body (P-body) formation independently of its catalytic activity by binding to ribosomes and interacting with the mRNA decapping complex (EDC4, DCP1A/B, DCP2, DDX6); IP6K1 augments DDX6-4E-T interaction and binding to eIF4E on the 5' mRNA cap, tipping the balance toward translational repression. IP6K1-depleted cells show reduced microRNA-mediated translational suppression and increased stability of DCP2-regulated transcripts.\",\n      \"method\": \"IP6K1 KD/KO, Co-IP of decapping complex components, ribosome fractionation, P-body quantification, mRNA stability assays, catalytically inactive mutant analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IPs, catalytic activity-independent function established by mutant, multiple functional readouts (P-body number, miRNA suppression, mRNA stability)\",\n      \"pmids\": [\"34841428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IP6K1 interacts with O-GlcNAcase in human NASH liver tissue and its deletion reduces protein O-GlcNAcylation in mouse liver, linking IP6K1 to regulation of protein O-GlcNAc modification in hepatic metabolism.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunoblot for O-GlcNAcylation in KO vs WT mouse livers and human NASH samples\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP/MS identification with functional correlate (O-GlcNAcylation changes), not yet fully reconstituted mechanistically\",\n      \"pmids\": [\"34757046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"IP6K1 deletion in MSCs results in higher MDM2 and lower p53 protein levels, leading to reduced intrinsic mitochondrial ROS, enhanced osteogenesis and hematopoiesis-supporting activity, and reduced adipogenic differentiation.\",\n      \"method\": \"Ip6k1 KO mice, MSC isolation, immunoblot for MDM2/p53, mitochondrial ROS measurement, osteogenic/adipogenic differentiation assays\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined molecular pathway (MDM2-p53-ROS axis) and multiple cellular readouts, single lab\",\n      \"pmids\": [\"28577302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IP6K1 forms a complex with AP3B1 and CK2α; IP6K1 interacts with multiple proteins that undergo 5-InsP7-mediated pyrophosphorylation (NOLC1, TCOF, UBF1, AP3B1), and disrupting IP6K1 binding to AP3B1 lowers its in vivo pyrophosphorylation, suggesting IP6K1 acts as a scaffold to coordinate CK2-mediated pre-phosphorylation and subsequent pyrophosphorylation of substrates.\",\n      \"method\": \"Mass spectrometry interactome, Co-IP of IP6K1-AP3B1-CK2α complex, in vivo pyrophosphorylation assay with IP6K1-binding mutant\",\n      \"journal\": \"Bioscience reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — MS interactome confirmed by Co-IP and functional pyrophosphorylation assay, single lab\",\n      \"pmids\": [\"39230924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IP6K1 and its product 5PP-InsP5 bind apoA-I and recruit UBE4A to induce apoA-I ubiquitination and degradation; depleting 5PP-InsP5 by IP6K1 deletion or inhibition disrupts UBE4A-apoA-I interaction, preventing apoA-I degradation and elevating circulating apoA-I, thereby reducing atherosclerosis.\",\n      \"method\": \"Co-immunoprecipitation, chemical biology 5PP-InsP5 binding assays, hepatocyte-specific IP6K1 KO mice, apoA-I KO epistasis, Oil Red O/H&E plaque assessment\",\n      \"journal\": \"Metabolism: clinical and experimental\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct protein-protein interaction by Co-IP, 5PP-InsP5 binding assay, epistasis with apoA-I KO, hepatocyte-specific KO with atherosclerotic phenotype\",\n      \"pmids\": [\"39643078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IP6K1 mediates hyperglycemia-induced endothelial senescence by stabilizing LKB1 (disrupting Hsp/Hsc70 and CHIP-mediated LKB1 degradation), which shifts LKB1 signaling from AMPK activation to p53 pathway activation, resulting in p53-dependent senescence; endothelial-specific IP6K1 KO attenuates and overexpression exacerbates this phenotype.\",\n      \"method\": \"Co-IP (LKB1-IP6K1, LKB1-Hsp70, LKB1-CHIP, LKB1-p53), endothelial cell-specific KO and overexpression mice, immunoblot for AMPK/p53/senescence markers\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple Co-IPs establishing mechanism, tissue-specific KO and OE with concordant phenotype, single lab\",\n      \"pmids\": [\"39792359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Recombinant mouse IP6K1 purified from E. coli catalyzes the synthesis of InsP7 (5-IP7) from IP6 in vitro and can pyrophosphorylate protein serine residues in a kinase-independent manner using this product.\",\n      \"method\": \"Recombinant protein purification from E. coli, in vitro kinase assay, radiolabeled [32P]-InsP7 production, in vitro protein pyrophosphorylation\",\n      \"journal\": \"Methods in molecular biology (Clifton, N.J.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro reconstitution of enzymatic activity with purified recombinant protein\",\n      \"pmids\": [\"20645182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Renal IP6K1 and IP6K2 together are required for normal expression and function of Na+/Pi cotransporters NaPi-IIa and NaPi-IIc; renal tubular-specific double KO mice show reduced phosphate uptake into proximal brush border membranes, hypophosphatemia, reduced FGF23, and increased bone resorption despite hypophosphatemia.\",\n      \"method\": \"Renal tubular-specific Ip6k1/2 DKO mice, in vitro opossum kidney cell KO, phosphate transport assays, brush border membrane vesicle uptake, FGF23 ELISA, immunoblot for cotransporters\",\n      \"journal\": \"Journal of the American Society of Nephrology : JASN\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO confirmed in vitro and in vivo with direct phosphate transport measurements and molecular expression data\",\n      \"pmids\": [\"38317282\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IP6K1 KO neurons display lower action potential frequency and deepened afterhyperpolarization, consistent with increased Na+/K+-ATPase (NKA) activity resulting from IP6K1-regulated NKA stability (via PI3K p85α autoinhibitory domain pathway).\",\n      \"method\": \"Electrophysiology of IP6K1 KO neurons, action potential frequency and afterhyperpolarization measurement\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined electrophysiological phenotype, mechanism referenced from prior work on NKA-PI3K p85α pathway, single lab\",\n      \"pmids\": [\"38350944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IP6K1 regulates mitochondrial polyphosphate (polyP) levels through 5-InsP7 synthesis; IP6K1 KO mice and cells show significantly reduced mitochondrial polyP, impaired mitochondrial respiration, and reduced membrane potential. Catalytically active but not inactive IP6K1 restores polyP synthesis and membrane potential, while both active and inactive forms rescue mitochondrial respiration, indicating dual catalytic-dependent and independent mechanisms.\",\n      \"method\": \"DAPI fluorescence-based polyP assay, mitochondrial fractionation, mitochondrial respiration (Seahorse), membrane potential measurement, KO cells/mice, active vs. inactive IP6K1 rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, active vs. inactive rescue distinguishes catalytic and non-catalytic functions; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.06.17.659843\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IP6K1 interacts with the proteoglycan SDC4 and supports secretory granule biogenesis in gastric chief cells independently of its catalytic activity; IP6K1 KO AGS cells and Ip6k1-/- mice lack pepsinogen C (PGC) and gastric lipase F (LIPF) granules, and PGC granule formation is restored by reintroduction of either active or inactive IP6K1.\",\n      \"method\": \"Ip6k1 KO mice, CRISPR/Cas9 KO in AGS cells, Co-IP of IP6K1-SDC4, immunofluorescence of granules, active vs. inactive IP6K1 rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO phenotype in vivo and in vitro, Co-IP of binding partner SDC4, active vs. inactive rescue establishing catalytic independence; preprint\",\n      \"pmids\": [\"bio_10.1101_2025.09.17.676719\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IP6K1 is a substrate of the Cys-Arg/N-degron pathway under hypoxia; loss of IP6K1 impairs glucose uptake, glycolytic ATP production, mitochondrial morphology, and metabolic adaptation under hypoxic conditions.\",\n      \"method\": \"Proteomics/global N-terminal Cys-degron profiling, mutagenesis, IP6K1 KO cells under hypoxia, glucose uptake and ATP production assays, mitochondrial morphology imaging\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — IP6K1 identified as N-degron substrate by proteomics, functional consequences of KO described but upstream degradation mechanism for IP6K1 specifically not fully validated; preprint\",\n      \"pmids\": [\"bio_10.1101_2025.01.20.633921\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"IP6K1 is a conserved inositol hexakisphosphate kinase that converts IP6 to 5-IP7 (InsP7), which regulates diverse cellular processes including dynein-driven vesicle transport (via Ser51 pyrophosphorylation of dynein IC), AMPK-mediated thermogenesis and energy metabolism, cell migration via FAK/Paxillin signaling, phosphate homeostasis through XPR1 and renal NaPi cotransporters, inositol synthesis via PA-dependent nuclear translocation and MIPS repression, mRNA translational control via P-body assembly, and apoA-I stability via UBE4A recruitment; additionally, IP6K1 exerts catalytic activity-independent scaffold functions in secretory granule biogenesis and mRNA cap remodeling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"IP6K1 is a conserved inositol hexakisphosphate kinase that synthesizes 5-IP7 (5-PP-InsP5) from IP6 and exerts both catalytic and scaffolding functions across diverse cellular processes including vesicle transport, energy metabolism, phosphate homeostasis, mRNA translational control, and secretory granule biogenesis. The 5-IP7 product pyrophosphorylates serine residues on substrates such as dynein intermediate chain to promote dynactin binding and dynein-driven vesicle transport, activates FAK/Paxillin signaling for cell migration, and recruits UBE4A to apoA-I for ubiquitin-mediated degradation [PMID:27474409, PMID:27140681, PMID:39643078]. IP6K1 suppresses AMPK-mediated thermogenesis in adipocytes, regulates phosphate export via XPR1 SPX-domain engagement by inositol pyrophosphates, and controls renal Na+/Pi cotransporter expression [PMID:27701146, PMID:31186349, PMID:38317282]. Independent of catalytic activity, IP6K1 scaffolds the mRNA decapping complex (EDC4, DCP1A/B, DCP2, DDX6) to promote P-body assembly and translational repression, coordinates CK2-mediated pre-phosphorylation of pyrophosphorylation substrates via an AP3B1–CK2α complex, and supports secretory granule biogenesis in gastric chief cells [PMID:34841428, PMID:39230924].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Establishing that IP6K1 directly converts IP6 to 5-IP7 and can pyrophosphorylate protein serines resolved the fundamental enzymatic activity and opened investigation into protein-level signaling by inositol pyrophosphates.\",\n      \"evidence\": \"Recombinant mouse IP6K1 purified from E. coli, in vitro kinase assay with radiolabeled substrates\",\n      \"pmids\": [\"20645182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous substrate selectivity for protein pyrophosphorylation not defined\", \"Structural basis for 5-position specificity not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstration that IP6K1-generated 5-IP7 pyrophosphorylates dynein IC-Ser51 to promote dynactin binding and membrane recruitment revealed the first specific in vivo protein substrate and linked IP6K1 to cytoplasmic dynein-driven vesicle transport and Golgi maintenance.\",\n      \"evidence\": \"IP6K1 KO cells, catalytically active vs. inactive mutant rescue, in vitro pyrophosphorylation, Co-IP, live vesicle imaging\",\n      \"pmids\": [\"27474409\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other dynein-associated cargoes are similarly regulated is unknown\", \"Quantitative contribution of pyrophosphorylation vs. canonical phosphorylation at Ser51 not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Parallel work showed IP6K1 catalytic activity drives FAK/Paxillin phosphorylation, cell spreading, and migration, broadening the kinase's role to adhesion-dependent signaling and actin remodeling.\",\n      \"evidence\": \"IP6K1 KO MEFs, active vs. inactive rescue, migration/invasion assays, FAK/Paxillin immunoblot\",\n      \"pmids\": [\"27140681\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether 5-IP7 acts directly on FAK or through an intermediate is not resolved\", \"Relevance to in vivo tumor invasion not tested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Adipocyte-specific IP6K1 deletion showed the kinase suppresses AMPK-mediated thermogenesis and UCP1 expression, establishing IP6K1 as a metabolic regulator of energy expenditure and a potential anti-obesity target.\",\n      \"evidence\": \"Adipocyte-specific KO mice, AMPK epistasis, in vitro kinase assays, energy expenditure calorimetry\",\n      \"pmids\": [\"27701146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular mechanism connecting 5-IP7 to AMPK inhibition not fully delineated\", \"Whether IP6K1 acts on AMPK directly or upstream kinases in vivo remains unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery that IP6K1 binds phosphatidic acid and translocates to the nucleus to repress MIPS/Isyna1 transcription revealed a lipid-sensing mechanism coupling IP6K1 to inositol biosynthesis regulation.\",\n      \"evidence\": \"IP6K1 KO MEFs, PA-binding assay, nuclear fractionation, qRT-PCR for Isyna1\",\n      \"pmids\": [\"26953345\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How IP6K1 mediates transcriptional repression of MIPS at the chromatin level is unresolved\", \"PA-binding domain on IP6K1 not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Localization of IP6K1 to the chromatoid body and demonstration that its loss abolishes chromatoid body formation and derepresses TNP2/PRM2 translation established IP6K1 as essential for post-transcriptional control during spermiogenesis.\",\n      \"evidence\": \"Ip6k1 KO mice, immunofluorescence of chromatoid body markers, immunoblot for TNP2/PRM2\",\n      \"pmids\": [\"28743739\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this function requires catalytic activity or scaffolding is not determined\", \"Direct RNA or RNP targets of IP6K1 in chromatoid body not identified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"IP6K1 was shown to be required for platelet inorganic polyphosphate production that drives neutrophil-platelet aggregate formation via the bradykinin pathway, extending IP6K1 function to innate immunity and thromboinflammation.\",\n      \"evidence\": \"Ip6k1 KO mice, pharmacological IP6K1 inhibition, polyP rescue, NPA flow cytometry, bacterial pneumonia model\",\n      \"pmids\": [\"29618559\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which IP6K1 controls mitochondrial/platelet polyP synthesis is undefined\", \"Contribution of IP6K1 vs. IP6K2 to platelet polyP not separated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Double KO of IP6K1/2 eliminated IP7/IP8, elevated intracellular ATP and phosphate, and impaired phosphate export via XPR1 SPX-domain binding, unifying inositol pyrophosphate signaling with cellular phosphate homeostasis.\",\n      \"evidence\": \"CRISPR IP6K1/2 DKO in HCT116, PAGE/HPLC inositol phosphate profiling, 32Pi flux, XPR1 SPX-domain binding assay\",\n      \"pmids\": [\"31186349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contributions of IP6K1 vs. IP6K2 to phosphate export not fully dissected\", \"In vivo tissue-specific phosphate phenotype of single IP6K1 KO not addressed here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"IP6K1 was found to scaffold the mRNA decapping complex and promote P-body assembly independently of catalytic activity, establishing a kinase-independent role in translational repression and mRNA turnover.\",\n      \"evidence\": \"IP6K1 KD/KO, reciprocal Co-IPs of decapping complex, ribosome fractionation, P-body quantification, catalytically inactive mutant rescue\",\n      \"pmids\": [\"34841428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for IP6K1-decapping complex interaction unknown\", \"Whether P-body scaffolding and chromatoid body functions share a common mechanism is untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The upstream signal for IP6K1 nuclear translocation was traced to PLD-generated PA at the plasma membrane, regulated by AMPK, linking metabolic stress and mood-stabilizing drugs to MIPS repression and inositol depletion.\",\n      \"evidence\": \"Pharmacological PLD stimulation, AMPK activation by glucose deprivation/valproate/lithium, organelle-specific PA manipulation, nuclear translocation imaging\",\n      \"pmids\": [\"35963434\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PA-dependent nuclear import uses a classical NLS or alternative mechanism is unresolved\", \"Contribution of IP6K1 nuclear translocation to mood-stabilizer therapeutic efficacy not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"IP6K1 forms a ternary complex with AP3B1 and CK2α, acting as a scaffold to coordinate CK2-mediated pre-phosphorylation and subsequent 5-IP7-dependent pyrophosphorylation of substrates, revealing a general mechanism for substrate targeting.\",\n      \"evidence\": \"Mass spectrometry interactome, Co-IP of IP6K1-AP3B1-CK2α, in vivo pyrophosphorylation assay with IP6K1-binding mutant of AP3B1\",\n      \"pmids\": [\"39230924\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether this scaffolding mechanism applies broadly to all pyrophosphorylation substrates is untested\", \"Structural details of the ternary complex are unknown\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Renal tubular double KO of IP6K1/2 demonstrated that inositol pyrophosphates are required for NaPi-IIa/IIc cotransporter expression and renal phosphate reabsorption, establishing an in vivo tissue-specific phosphate homeostasis role.\",\n      \"evidence\": \"Renal tubular-specific Ip6k1/2 DKO mice, brush border membrane vesicle phosphate uptake, FGF23 measurement, cotransporter immunoblot\",\n      \"pmids\": [\"38317282\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contribution of IP6K1 vs. IP6K2 in renal phosphate handling not resolved\", \"Mechanism by which 5-IP7 regulates cotransporter expression is undefined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"IP6K1-generated 5-IP7 binds apoA-I and recruits UBE4A for ubiquitination, establishing a direct mechanism linking IP6K1 to apoA-I degradation and atherosclerosis susceptibility.\",\n      \"evidence\": \"Co-IP, 5-IP7 chemical binding assays, hepatocyte-specific IP6K1 KO mice, apoA-I KO epistasis, atherosclerotic plaque analysis\",\n      \"pmids\": [\"39643078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of 5-IP7-apoA-I interaction not determined\", \"Whether IP6K1 similarly regulates other apolipoproteins is unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"IP6K1 was shown to stabilize LKB1 by disrupting Hsp/Hsc70-CHIP-mediated degradation, redirecting LKB1 signaling from AMPK to p53 to drive hyperglycemia-induced endothelial senescence.\",\n      \"evidence\": \"Multiple Co-IPs, endothelial-specific IP6K1 KO and overexpression mice, immunoblot for AMPK/p53/senescence markers\",\n      \"pmids\": [\"39792359\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether this mechanism requires 5-IP7 or is catalysis-independent is not addressed\", \"Relevance to diabetic vascular disease in humans not validated\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for IP6K1's dual catalytic and scaffolding functions; how substrate selectivity for protein pyrophosphorylation is achieved in vivo; the mechanism linking IP6K1 to mitochondrial polyphosphate synthesis; and whether kinase-dependent vs. kinase-independent functions segregate by subcellular compartment or tissue.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure of full-length IP6K1 with substrates\", \"No systematic delineation of catalytic vs. non-catalytic functions across tissues\", \"Mechanism of mitochondrial polyP regulation by IP6K1 is unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 5, 14]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [8, 11, 18]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 13]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 3, 5, 12]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [7, 8]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [11, 12]}\n    ],\n    \"complexes\": [\n      \"mRNA decapping complex\",\n      \"IP6K1-AP3B1-CK2α complex\",\n      \"chromatoid body\"\n    ],\n    \"partners\": [\n      \"DIC (dynein intermediate chain)\",\n      \"EDC4\",\n      \"DDX6\",\n      \"DCP2\",\n      \"AP3B1\",\n      \"CSNK2A1\",\n      \"SDC4\",\n      \"UBE4A\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}