{"gene":"PIP4K2B","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1997,"finding":"PIP4K2B (PIP5KIIbeta) directly binds the juxtamembrane region of the p55 TNF receptor (TNFR1) but not the p75 TNF receptor, Fas antigen, or p75 neurotrophin receptor. In vitro experiments with recombinant fusion proteins confirmed the specific interaction. TNF-alpha treatment of HeLa cells resulted in increased PIP5K activity, linking p55 TNFR signaling to phosphatidylinositol turnover via PIP4K2B.","method":"Yeast two-hybrid screen, in vitro pulldown with recombinant fusion proteins, cellular PIP5K activity assay after TNF-alpha treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal in vitro binding confirmed with recombinant proteins plus cellular activity assay, single lab, two orthogonal methods","pmids":["9038203"],"is_preprint":false},{"year":2013,"finding":"PIP4K2B is synthetically lethal with TP53 loss in vivo: mice homozygous for deletion of both TP53 and PIP4K2B were not viable. Knockdown of PI5P4Kα and β in p53-deficient breast cancer cells impaired growth and elevated reactive oxygen species leading to senescence. PIP4K2A−/−, PIP4K2B+/−, TP53−/− mice showed dramatically reduced tumor formation compared to TP53−/− littermates, establishing PIP4K2B as essential for growth of p53-null tumors.","method":"shRNA knockdown in breast cancer cell lines, xenograft assays, genetic mouse models (germline knockout), ROS measurement","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vitro and in vivo genetic methods, replicated across cell and mouse models in a single rigorous study","pmids":["24209622"],"is_preprint":false},{"year":2015,"finding":"PIP4K2B localizes predominantly to the nucleus and regulates nuclear PI5P levels and expression of myogenic genes during myoblast differentiation. A targeted screen identified the PHD finger of TAF3 (a TATA box binding protein-associated factor) as a nuclear PI interactor, and PI binding by TAF3 modulates its association with H3K4me3 in vitro and with chromatin in vivo. TAF3 mutant analysis demonstrated that TAF3 transduces PIP4K2B-mediated alterations in PI into changes in specific gene transcription.","method":"shRNA knockdown of PIP4K2B, lipid-binding screen, chromatin immunoprecipitation, TAF3 PHD finger mutagenesis, in vitro PI-binding assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (lipid screen, mutagenesis, ChIP, in vitro binding) in a single rigorous study establishing mechanistic pathway","pmids":["25866244"],"is_preprint":false},{"year":2015,"finding":"PIP4K2B isoform localizes predominantly to the nucleus among the three PIP4K isoforms, consistent with its role in regulating nuclear phosphoinositide levels.","method":"Subcellular fractionation and localization studies (reviewed/summarized in the context of PIP4K isoform biology)","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization described across multiple studies cited in review, but this abstract is a review summarizing prior experimental findings","pmids":["25728392"],"is_preprint":false},{"year":2017,"finding":"MANF triggers hypothalamic insulin resistance by enhancing the ER localization and activity of PIP4K2B. Increased hypothalamic MANF protein levels caused hyperphagia and enhanced PIP4K2B ER activity, while decreased MANF caused hypophagia, placing PIP4K2B downstream of MANF in hypothalamic insulin signaling.","method":"In vivo manipulation of hypothalamic MANF levels (overexpression and knockdown), measurement of PIP4K2B ER localization and activity, food intake and body weight phenotyping","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis established in vivo with direct measurement of PIP4K2B localization and activity, single lab","pmids":["28924165"],"is_preprint":false},{"year":2018,"finding":"Deletion of both Pip4k2a and Pip4k2b in mouse liver causes accumulation of lipid droplets and autophagic vesicles during fasting due to a defect in autophagosome clearance (impaired autophagic flux). Similar defects occur in nutrient-starved Pip4k2a−/−Pip4k2b−/− MEFs and in C. elegans lacking the PI5P4K ortholog, establishing that this PI5P→PI(4,5)P2 synthesis pathway is required for autophagy-mediated nutrient recycling.","method":"Liver-specific and MEF double knockout mouse models, electron microscopy of autophagic vesicles, lipid droplet staining, autophagy flux assays, C. elegans genetic model","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genetic models (mouse liver KO, MEF KO, C. elegans), multiple functional readouts, independently replicated across organisms","pmids":["29727621"],"is_preprint":false},{"year":2019,"finding":"PIP4K2B (together with PIP4K2A and PIP4K2C) suppresses PI(4,5)P2 synthesis and insulin-dependent PI3K signaling through a catalytic-independent mechanism. Loss of all three PIP4Ks paradoxically increased PI(4,5)P2 and insulin-stimulated PI(3,4,5)P3. Reintroduction of either wild-type or kinase-dead PIP4K mutants restored PI(4,5)P2 levels, indicating the mechanism is non-catalytic. PIP4Ks suppress PIP5K activity through a direct binding interaction mediated by the N-terminal VMLΦPDD motif of PIP4K.","method":"CRISPR/Cas9 triple knockout of PIP4K2A/2B/2C, phosphoinositide mass spectrometry, reintroduction of wild-type vs. kinase-dead mutants, direct PIP4K–PIP5K binding assay, N-terminal motif mutagenesis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — kinase-dead mutagenesis distinguishing catalytic vs. non-catalytic function, direct binding interaction mapped, phosphoinositide measurements, multiple orthogonal methods in single rigorous study","pmids":["31091439"],"is_preprint":false},{"year":2013,"finding":"Knockdown of PIP4K2B in normal (MCF10A) and tumor (MCF7) breast epithelial cells decreased transcription and expression of E-cadherin (CDH1) and enhanced TGF-β-induced epithelial-to-mesenchymal transition (EMT), linking PIP4K2B activity to E-cadherin regulation and EMT suppression.","method":"shRNA-mediated knockdown of PIP4K2B in breast epithelial cell lines, qRT-PCR and western blot for CDH1, TGF-β-induced EMT assay","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined molecular and cellular readouts, single lab, two orthogonal endpoints (transcription and EMT phenotype)","pmids":["24127122"],"is_preprint":false},{"year":2014,"finding":"PIP4K2B has enzymatic activity that can be pharmacologically inhibited: a small-molecule inhibitor (SAR088) identified by high-throughput screening showed potency and selectivity against PIP4K2B in enzymatic and cellular assays, and lowered blood glucose in obese hyperglycemic rats in vivo, validating PIP4K2B kinase activity as relevant to insulin/glucose regulation.","method":"High-throughput enzymatic screening, in vitro kinase assay, cellular assay, in vivo dosing in Zucker diabetic fatty rats","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct enzymatic inhibition confirmed in vitro and in vivo, single lab","pmids":["24845568"],"is_preprint":false},{"year":2020,"finding":"In mouse brain, PI5P4Kβ (encoded by PIP4K2B) is expressed early in development and localizes to neuronal populations, especially hippocampus and cortex, co-localizing with the neuronal marker NeuN. Ultrastructural analysis showed PI5P4Kβ is present in axon terminals and dendritic spines adjacent to the synaptic membrane.","method":"Immunofluorescence with antibodies validated by genetic deletion of pip4k2b, dual-label immunofluorescence, electron microscopy/immunoperoxidase in mouse and primate/human brain","journal":"The Journal of comparative neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — antibody specificity validated by KO animals, multiple imaging modalities; localization without demonstrated functional consequence","pmids":["32449185"],"is_preprint":false},{"year":2023,"finding":"PIP4K2B is mechanoresponsive: its protein level decreases in cells growing on soft substrates. Direct silencing or pharmacological inhibition of PIP4K2B reduces the epigenetic regulator UHRF1, alters nuclear polarity, nuclear envelope tension, and chromatin compaction, causes YAP cytoplasmic retention and impaired transcriptional activity, and leads to defects in cell spreading and motility.","method":"Soft vs. stiff substrate cell culture, siRNA/shRNA knockdown, pharmacological inhibition, nuclear mechanics measurements, UHRF1 protein quantification, YAP localization imaging, migration/spreading assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetic KD, pharmacological inhibition, nuclear mechanics, imaging of YAP), functional pathway placement from substrate stiffness through PIP4K2B→UHRF1→chromatin→YAP axis","pmids":["36918565"],"is_preprint":false},{"year":2024,"finding":"PIP4K2B is a downstream target of the histone methyltransferase NSD1 in HNSCC. NSD1 positively regulates PIP4K2B gene transcription through an H3K36me2-dependent mechanism. PIP4K2B depletion in HNSCC downregulates the mTOR pathway and reduces cell growth in vitro, with context-dependent effects (rescuable by PIP4K2B overexpression in laryngeal but not tongue/hypopharynx cells).","method":"RPPA analysis, NSD1 knockdown with PIP4K2B measurement, chromatin studies for H3K36me2, PIP4K2B shRNA knockdown, mTOR pathway western blot, rescue overexpression experiment","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct regulatory mechanism identified (NSD1→H3K36me2→PIP4K2B transcription) with functional rescue, single lab","pmids":["38539515"],"is_preprint":false},{"year":2026,"finding":"Crystal structure of PIP4K2A in complex with a dual α/β inhibitor (422A) reveals a water-mediated interaction in the specificity pocket. Comparative structural analysis with PIP4K2B indicates that deeper penetration into the specificity pocket enhances PIP4K2A binding but is less well tolerated in PIP4K2B due to local steric constraints, explaining why most inhibitors have lower potency toward PIP4K2B.","method":"X-ray crystallography of PIP4K2A–inhibitor complex, comparative structural analysis with PIP4K2B","journal":"Acta crystallographica. Section D, Structural biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — crystal structure provides high-quality data for PIP4K2A; structural inference about PIP4K2B isoform differences is comparative/modeled, not a PIP4K2B crystal structure per se","pmids":["42117906"],"is_preprint":false}],"current_model":"PIP4K2B is a predominantly nuclear phosphatidylinositol-5-phosphate 4-kinase that phosphorylates PI5P to generate PI(4,5)P2, and acts as a mechanoresponsive, stress-regulated enzyme that (1) directly binds and is activated by the p55 TNF receptor, (2) suppresses PIP5K activity and PI(4,5)P2/PI(3,4,5)P3 synthesis through a catalytic-independent interaction via its N-terminal VMLΦPDD motif, (3) regulates nuclear PI5P levels to modulate TAF3-dependent gene transcription and myoblast differentiation, (4) controls autophagosome clearance and lipid homeostasis, (5) maintains E-cadherin expression and suppresses EMT, (6) responds to mechanical softness by decreasing protein levels, triggering UHRF1 reduction, chromatin remodeling, and YAP inactivation, (7) is transcriptionally regulated by NSD1 via H3K36me2, and (8) is synthetically lethal with TP53 loss, making it essential for p53-null tumor growth."},"narrative":{"mechanistic_narrative":"PIP4K2B is a predominantly nuclear phosphatidylinositol-5-phosphate 4-kinase that converts PI5P to PI(4,5)P2 and couples phosphoinositide metabolism to stress responses, gene transcription, autophagy, and mechanosensing [PMID:25728392, PMID:31091439, PMID:24845568]. It regulates nuclear PI5P pools that are read out by the PHD finger of the transcription factor TAF3, whose PI-modulated association with H3K4me3-marked chromatin transduces PIP4K2B activity into changes in myogenic gene expression [PMID:25866244]. Beyond its catalytic role, PIP4K2B exerts a non-catalytic function: it directly binds and suppresses PIP5K, thereby restraining PI(4,5)P2 and insulin-stimulated PI(3,4,5)P3 synthesis, an activity preserved by kinase-dead enzyme and mapped to its N-terminal VMLΦPDD motif [PMID:31091439]. Together with PIP4K2A, it is required for autophagosome clearance and lipid homeostasis during nutrient deprivation across mouse and C. elegans models [PMID:29727621]. PIP4K2B acts as a mechanoresponsive node whose protein levels fall on soft substrates, lowering the epigenetic regulator UHRF1, remodeling chromatin and nuclear mechanics, and driving YAP cytoplasmic retention [PMID:36918565]; its transcription is positively controlled by NSD1 through an H3K36me2-dependent mechanism in head and neck cancer [PMID:38539515]. PIP4K2B sustains E-cadherin expression and suppresses TGF-β-induced EMT [PMID:24127122], and is synthetically lethal with TP53 loss, rendering it essential for the growth of p53-null tumors [PMID:24209622].","teleology":[{"year":1997,"claim":"Established the first protein partner and an upstream signaling input for PIP4K2B by linking it to inflammatory receptor signaling, answering how PI turnover might be triggered at the membrane.","evidence":"Yeast two-hybrid screen and in vitro pulldown with recombinant fusion proteins, plus cellular PIP5K activity assay after TNF-alpha in HeLa cells","pmids":["9038203"],"confidence":"Medium","gaps":["Reciprocal validation in cells and the structural basis of the TNFR1 juxtamembrane interaction not resolved","Whether the measured PIP5K activity increase reflects PIP4K2B catalysis directly is not distinguished","Downstream consequences of TNFR1-PIP4K2B coupling not defined"]},{"year":2013,"claim":"Defined a therapeutically actionable genetic dependency by showing PIP4K2B is synthetically lethal with TP53 loss and required for p53-null tumor growth.","evidence":"shRNA knockdown in breast cancer lines, xenografts, germline mouse knockouts, and ROS measurement","pmids":["24209622"],"confidence":"High","gaps":["Molecular mechanism connecting PIP4K2B loss to ROS elevation and senescence not fully resolved","Relative contributions of catalytic versus non-catalytic functions to the dependency unclear"]},{"year":2013,"claim":"Connected PIP4K2B to epithelial identity by showing it maintains E-cadherin transcription and suppresses EMT, framing a tumor-suppressive role distinct from its growth dependency.","evidence":"shRNA knockdown in MCF10A and MCF7 cells, qRT-PCR/western for CDH1, TGF-β-induced EMT assay","pmids":["24127122"],"confidence":"Medium","gaps":["Mechanism linking PIP4K2B to CDH1 transcription not defined","Whether the effect is catalytic or signaling-dependent untested"]},{"year":2014,"claim":"Validated PIP4K2B kinase activity as a druggable and physiologically relevant target through a selective inhibitor with metabolic effects in vivo.","evidence":"High-throughput enzymatic screen, in vitro kinase and cellular assays, and dosing in Zucker diabetic fatty rats","pmids":["24845568"],"confidence":"Medium","gaps":["In vivo glucose-lowering not mechanistically tied to a specific PIP4K2B substrate pool","Off-target and isoform selectivity in vivo not fully resolved"]},{"year":2015,"claim":"Identified the nuclear effector mechanism by which PIP4K2B-controlled PI5P is read into transcription, via TAF3 PHD-finger PI binding and chromatin association.","evidence":"shRNA knockdown, lipid-binding screen, TAF3 PHD mutagenesis, ChIP, and in vitro PI-binding assays during myoblast differentiation","pmids":["25866244","25728392"],"confidence":"High","gaps":["How PIP4K2B activity quantitatively sets nuclear PI5P at specific loci not mapped","Generality of the TAF3 readout beyond myogenic genes unknown"]},{"year":2017,"claim":"Placed PIP4K2B downstream of MANF in hypothalamic insulin signaling, linking its ER localization and activity to feeding behavior and insulin resistance.","evidence":"In vivo hypothalamic MANF overexpression and knockdown with measurement of PIP4K2B ER localization/activity and feeding phenotypes","pmids":["28924165"],"confidence":"Medium","gaps":["Direct biochemical link between MANF and PIP4K2B not established","ER versus nuclear pool contributions to the phenotype not separated"]},{"year":2018,"claim":"Demonstrated a conserved metabolic function in autophagy, showing the PI5P→PI(4,5)P2 pathway is required for autophagosome clearance and lipid homeostasis during nutrient stress.","evidence":"Liver-specific and MEF double Pip4k2a/2b knockouts, electron microscopy, lipid droplet staining, autophagy flux assays, and a C. elegans ortholog model","pmids":["29727621"],"confidence":"High","gaps":["Isoform-specific contribution of PIP4K2B versus PIP4K2A not separated","Step in autophagosome maturation/clearance controlled by the lipid product not pinpointed"]},{"year":2019,"claim":"Resolved a paradoxical regulatory role by showing PIP4K2B suppresses PI(4,5)P2 and PI3K signaling non-catalytically through direct binding to PIP5K via its N-terminal VMLΦPDD motif.","evidence":"CRISPR triple knockout, phosphoinositide mass spectrometry, wild-type versus kinase-dead rescue, direct binding assay, and N-terminal motif mutagenesis","pmids":["31091439"],"confidence":"High","gaps":["Structural basis of the PIP4K-PIP5K binding interaction not solved","Balance between catalytic and non-catalytic outputs in different cell contexts unclear"]},{"year":2020,"claim":"Mapped PIP4K2B expression to developing neurons and synaptic compartments, suggesting a neuronal role not yet functionally tested.","evidence":"KO-validated immunofluorescence, dual-label imaging, and immuno-EM in mouse and primate/human brain","pmids":["32449185"],"confidence":"Medium","gaps":["No demonstrated functional consequence of synaptic PIP4K2B localization","Substrate and signaling role at axon terminals/dendritic spines undefined"]},{"year":2023,"claim":"Identified PIP4K2B as a mechanoresponsive regulator linking substrate stiffness to chromatin state and YAP activity through a PIP4K2B→UHRF1→chromatin→YAP axis.","evidence":"Soft/stiff substrate culture, knockdown and pharmacological inhibition, nuclear mechanics measurements, UHRF1 quantification, YAP imaging, and migration assays","pmids":["36918565"],"confidence":"High","gaps":["Mechanism by which substrate softness lowers PIP4K2B protein not defined","Whether catalytic activity or scaffolding drives UHRF1 reduction unresolved"]},{"year":2024,"claim":"Established upstream transcriptional control of PIP4K2B by NSD1 via H3K36me2 and tied PIP4K2B to mTOR signaling and growth in head and neck cancer.","evidence":"RPPA, NSD1 knockdown, H3K36me2 chromatin studies, PIP4K2B shRNA, mTOR western blot, and rescue overexpression","pmids":["38539515"],"confidence":"Medium","gaps":["Direct NSD1 occupancy at the PIP4K2B locus not fully characterized","Basis of context-dependent rescue between tumor subsites unexplained"]},{"year":2026,"claim":"Provided a structural rationale for isoform-selective inhibition, explaining why most inhibitors are less potent against PIP4K2B than PIP4K2A.","evidence":"X-ray crystallography of a PIP4K2A-inhibitor complex with comparative structural analysis of PIP4K2B","pmids":["42117906"],"confidence":"Medium","gaps":["No PIP4K2B crystal structure with inhibitor; isoform inference is comparative/modeled","Specificity-pocket conclusions not experimentally validated for PIP4K2B"]},{"year":null,"claim":"How PIP4K2B's catalytic (PI5P→PI(4,5)P2) and non-catalytic (PIP5K suppression) activities are partitioned across nuclear, ER, autophagic, and synaptic compartments to produce distinct physiological outputs remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model assigning each phenotype to a specific lipid pool or compartment","Structure of full-length PIP4K2B and its PIP5K complex not solved","Regulation of PIP4K2B protein stability by mechanical and metabolic cues mechanistically undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[6,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[5,8]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[5]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[2,11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,10]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,11]}],"complexes":[],"partners":["TNFRSF1A","PIP5K","TAF3","NSD1","MANF","UHRF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P78356","full_name":"Phosphatidylinositol 5-phosphate 4-kinase type-2 beta","aliases":["1-phosphatidylinositol 5-phosphate 4-kinase 2-beta","Diphosphoinositide kinase 2-beta","Phosphatidylinositol 5-phosphate 4-kinase type II beta","PI(5)P 4-kinase type II beta","PIP4KII-beta","PtdIns(5)P-4-kinase isoform 2-beta"],"length_aa":416,"mass_kda":47.4,"function":"Participates in the biosynthesis of phosphatidylinositol 4,5-bisphosphate (PubMed:26774281, PubMed:9038203). Preferentially utilizes GTP, rather than ATP, for PI(5)P phosphorylation and its activity reflects changes in direct proportion to the physiological GTP concentration (PubMed:26774281). Its GTP-sensing activity is critical for metabolic adaptation (PubMed:26774281). PIP4Ks negatively regulate insulin signaling through a catalytic-independent mechanism. They interact with PIP5Ks and suppress PIP5K-mediated PtdIns(4,5)P2 synthesis and insulin-dependent conversion to PtdIns(3,4,5)P3 (PubMed:31091439)","subcellular_location":"Endoplasmic reticulum membrane; Cell membrane; Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P78356/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PIP4K2B","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000276293","cell_line_id":"CID000156","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"membrane","grade":3},{"compartment":"nucleoplasm","grade":1},{"compartment":"vesicles","grade":1}],"interactors":[{"gene":"PIP5K2B","stoichiometry":10.0},{"gene":"PIP4K2A","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000156","total_profiled":1310},"omim":[{"mim_id":"617104","title":"PHOSPHATIDYLINOSITOL 5-PHOSPHATE 4-KINASE, TYPE II, GAMMA; PIP4K2C","url":"https://www.omim.org/entry/617104"},{"mim_id":"603261","title":"PHOSPHATIDYLINOSITOL 5-PHOSPHATE 4-KINASE, TYPE II, BETA; PIP4K2B","url":"https://www.omim.org/entry/603261"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PIP4K2B"},"hgnc":{"alias_symbol":["PIP5KIIB","PIP5KIIbeta"],"prev_symbol":["PIP5K2B"]},"alphafold":{"accession":"P78356","domains":[{"cath_id":"3.30.800.10","chopping":"36-203","consensus_level":"medium","plddt":92.901,"start":36,"end":203},{"cath_id":"3.30.810.10","chopping":"205-296_342-416","consensus_level":"medium","plddt":91.2746,"start":205,"end":416}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P78356","model_url":"https://alphafold.ebi.ac.uk/files/AF-P78356-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P78356-F1-predicted_aligned_error_v6.png","plddt_mean":84.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PIP4K2B","jax_strain_url":"https://www.jax.org/strain/search?query=PIP4K2B"},"sequence":{"accession":"P78356","fasta_url":"https://rest.uniprot.org/uniprotkb/P78356.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P78356/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P78356"}},"corpus_meta":[{"pmid":"11980659","id":"PMC_11980659","title":"Targets 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Molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41695382","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18646,"output_tokens":3820,"usd":0.056619,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11690,"output_tokens":4403,"usd":0.084263,"stage2_stop_reason":"end_turn"},"total_usd":0.140882,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"PIP4K2B (PIP5KIIbeta) directly binds the juxtamembrane region of the p55 TNF receptor (TNFR1) but not the p75 TNF receptor, Fas antigen, or p75 neurotrophin receptor. In vitro experiments with recombinant fusion proteins confirmed the specific interaction. TNF-alpha treatment of HeLa cells resulted in increased PIP5K activity, linking p55 TNFR signaling to phosphatidylinositol turnover via PIP4K2B.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro pulldown with recombinant fusion proteins, cellular PIP5K activity assay after TNF-alpha treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal in vitro binding confirmed with recombinant proteins plus cellular activity assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"9038203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIP4K2B is synthetically lethal with TP53 loss in vivo: mice homozygous for deletion of both TP53 and PIP4K2B were not viable. Knockdown of PI5P4Kα and β in p53-deficient breast cancer cells impaired growth and elevated reactive oxygen species leading to senescence. PIP4K2A−/−, PIP4K2B+/−, TP53−/− mice showed dramatically reduced tumor formation compared to TP53−/− littermates, establishing PIP4K2B as essential for growth of p53-null tumors.\",\n      \"method\": \"shRNA knockdown in breast cancer cell lines, xenograft assays, genetic mouse models (germline knockout), ROS measurement\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vitro and in vivo genetic methods, replicated across cell and mouse models in a single rigorous study\",\n      \"pmids\": [\"24209622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIP4K2B localizes predominantly to the nucleus and regulates nuclear PI5P levels and expression of myogenic genes during myoblast differentiation. A targeted screen identified the PHD finger of TAF3 (a TATA box binding protein-associated factor) as a nuclear PI interactor, and PI binding by TAF3 modulates its association with H3K4me3 in vitro and with chromatin in vivo. TAF3 mutant analysis demonstrated that TAF3 transduces PIP4K2B-mediated alterations in PI into changes in specific gene transcription.\",\n      \"method\": \"shRNA knockdown of PIP4K2B, lipid-binding screen, chromatin immunoprecipitation, TAF3 PHD finger mutagenesis, in vitro PI-binding assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (lipid screen, mutagenesis, ChIP, in vitro binding) in a single rigorous study establishing mechanistic pathway\",\n      \"pmids\": [\"25866244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIP4K2B isoform localizes predominantly to the nucleus among the three PIP4K isoforms, consistent with its role in regulating nuclear phosphoinositide levels.\",\n      \"method\": \"Subcellular fractionation and localization studies (reviewed/summarized in the context of PIP4K isoform biology)\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization described across multiple studies cited in review, but this abstract is a review summarizing prior experimental findings\",\n      \"pmids\": [\"25728392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MANF triggers hypothalamic insulin resistance by enhancing the ER localization and activity of PIP4K2B. Increased hypothalamic MANF protein levels caused hyperphagia and enhanced PIP4K2B ER activity, while decreased MANF caused hypophagia, placing PIP4K2B downstream of MANF in hypothalamic insulin signaling.\",\n      \"method\": \"In vivo manipulation of hypothalamic MANF levels (overexpression and knockdown), measurement of PIP4K2B ER localization and activity, food intake and body weight phenotyping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis established in vivo with direct measurement of PIP4K2B localization and activity, single lab\",\n      \"pmids\": [\"28924165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Deletion of both Pip4k2a and Pip4k2b in mouse liver causes accumulation of lipid droplets and autophagic vesicles during fasting due to a defect in autophagosome clearance (impaired autophagic flux). Similar defects occur in nutrient-starved Pip4k2a−/−Pip4k2b−/− MEFs and in C. elegans lacking the PI5P4K ortholog, establishing that this PI5P→PI(4,5)P2 synthesis pathway is required for autophagy-mediated nutrient recycling.\",\n      \"method\": \"Liver-specific and MEF double knockout mouse models, electron microscopy of autophagic vesicles, lipid droplet staining, autophagy flux assays, C. elegans genetic model\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genetic models (mouse liver KO, MEF KO, C. elegans), multiple functional readouts, independently replicated across organisms\",\n      \"pmids\": [\"29727621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PIP4K2B (together with PIP4K2A and PIP4K2C) suppresses PI(4,5)P2 synthesis and insulin-dependent PI3K signaling through a catalytic-independent mechanism. Loss of all three PIP4Ks paradoxically increased PI(4,5)P2 and insulin-stimulated PI(3,4,5)P3. Reintroduction of either wild-type or kinase-dead PIP4K mutants restored PI(4,5)P2 levels, indicating the mechanism is non-catalytic. PIP4Ks suppress PIP5K activity through a direct binding interaction mediated by the N-terminal VMLΦPDD motif of PIP4K.\",\n      \"method\": \"CRISPR/Cas9 triple knockout of PIP4K2A/2B/2C, phosphoinositide mass spectrometry, reintroduction of wild-type vs. kinase-dead mutants, direct PIP4K–PIP5K binding assay, N-terminal motif mutagenesis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — kinase-dead mutagenesis distinguishing catalytic vs. non-catalytic function, direct binding interaction mapped, phosphoinositide measurements, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"31091439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Knockdown of PIP4K2B in normal (MCF10A) and tumor (MCF7) breast epithelial cells decreased transcription and expression of E-cadherin (CDH1) and enhanced TGF-β-induced epithelial-to-mesenchymal transition (EMT), linking PIP4K2B activity to E-cadherin regulation and EMT suppression.\",\n      \"method\": \"shRNA-mediated knockdown of PIP4K2B in breast epithelial cell lines, qRT-PCR and western blot for CDH1, TGF-β-induced EMT assay\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined molecular and cellular readouts, single lab, two orthogonal endpoints (transcription and EMT phenotype)\",\n      \"pmids\": [\"24127122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PIP4K2B has enzymatic activity that can be pharmacologically inhibited: a small-molecule inhibitor (SAR088) identified by high-throughput screening showed potency and selectivity against PIP4K2B in enzymatic and cellular assays, and lowered blood glucose in obese hyperglycemic rats in vivo, validating PIP4K2B kinase activity as relevant to insulin/glucose regulation.\",\n      \"method\": \"High-throughput enzymatic screening, in vitro kinase assay, cellular assay, in vivo dosing in Zucker diabetic fatty rats\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct enzymatic inhibition confirmed in vitro and in vivo, single lab\",\n      \"pmids\": [\"24845568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In mouse brain, PI5P4Kβ (encoded by PIP4K2B) is expressed early in development and localizes to neuronal populations, especially hippocampus and cortex, co-localizing with the neuronal marker NeuN. Ultrastructural analysis showed PI5P4Kβ is present in axon terminals and dendritic spines adjacent to the synaptic membrane.\",\n      \"method\": \"Immunofluorescence with antibodies validated by genetic deletion of pip4k2b, dual-label immunofluorescence, electron microscopy/immunoperoxidase in mouse and primate/human brain\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — antibody specificity validated by KO animals, multiple imaging modalities; localization without demonstrated functional consequence\",\n      \"pmids\": [\"32449185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PIP4K2B is mechanoresponsive: its protein level decreases in cells growing on soft substrates. Direct silencing or pharmacological inhibition of PIP4K2B reduces the epigenetic regulator UHRF1, alters nuclear polarity, nuclear envelope tension, and chromatin compaction, causes YAP cytoplasmic retention and impaired transcriptional activity, and leads to defects in cell spreading and motility.\",\n      \"method\": \"Soft vs. stiff substrate cell culture, siRNA/shRNA knockdown, pharmacological inhibition, nuclear mechanics measurements, UHRF1 protein quantification, YAP localization imaging, migration/spreading assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetic KD, pharmacological inhibition, nuclear mechanics, imaging of YAP), functional pathway placement from substrate stiffness through PIP4K2B→UHRF1→chromatin→YAP axis\",\n      \"pmids\": [\"36918565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PIP4K2B is a downstream target of the histone methyltransferase NSD1 in HNSCC. NSD1 positively regulates PIP4K2B gene transcription through an H3K36me2-dependent mechanism. PIP4K2B depletion in HNSCC downregulates the mTOR pathway and reduces cell growth in vitro, with context-dependent effects (rescuable by PIP4K2B overexpression in laryngeal but not tongue/hypopharynx cells).\",\n      \"method\": \"RPPA analysis, NSD1 knockdown with PIP4K2B measurement, chromatin studies for H3K36me2, PIP4K2B shRNA knockdown, mTOR pathway western blot, rescue overexpression experiment\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct regulatory mechanism identified (NSD1→H3K36me2→PIP4K2B transcription) with functional rescue, single lab\",\n      \"pmids\": [\"38539515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Crystal structure of PIP4K2A in complex with a dual α/β inhibitor (422A) reveals a water-mediated interaction in the specificity pocket. Comparative structural analysis with PIP4K2B indicates that deeper penetration into the specificity pocket enhances PIP4K2A binding but is less well tolerated in PIP4K2B due to local steric constraints, explaining why most inhibitors have lower potency toward PIP4K2B.\",\n      \"method\": \"X-ray crystallography of PIP4K2A–inhibitor complex, comparative structural analysis with PIP4K2B\",\n      \"journal\": \"Acta crystallographica. Section D, Structural biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — crystal structure provides high-quality data for PIP4K2A; structural inference about PIP4K2B isoform differences is comparative/modeled, not a PIP4K2B crystal structure per se\",\n      \"pmids\": [\"42117906\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PIP4K2B is a predominantly nuclear phosphatidylinositol-5-phosphate 4-kinase that phosphorylates PI5P to generate PI(4,5)P2, and acts as a mechanoresponsive, stress-regulated enzyme that (1) directly binds and is activated by the p55 TNF receptor, (2) suppresses PIP5K activity and PI(4,5)P2/PI(3,4,5)P3 synthesis through a catalytic-independent interaction via its N-terminal VMLΦPDD motif, (3) regulates nuclear PI5P levels to modulate TAF3-dependent gene transcription and myoblast differentiation, (4) controls autophagosome clearance and lipid homeostasis, (5) maintains E-cadherin expression and suppresses EMT, (6) responds to mechanical softness by decreasing protein levels, triggering UHRF1 reduction, chromatin remodeling, and YAP inactivation, (7) is transcriptionally regulated by NSD1 via H3K36me2, and (8) is synthetically lethal with TP53 loss, making it essential for p53-null tumor growth.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PIP4K2B is a predominantly nuclear phosphatidylinositol-5-phosphate 4-kinase that converts PI5P to PI(4,5)P2 and couples phosphoinositide metabolism to stress responses, gene transcription, autophagy, and mechanosensing [#3, #6, #8]. It regulates nuclear PI5P pools that are read out by the PHD finger of the transcription factor TAF3, whose PI-modulated association with H3K4me3-marked chromatin transduces PIP4K2B activity into changes in myogenic gene expression [#2]. Beyond its catalytic role, PIP4K2B exerts a non-catalytic function: it directly binds and suppresses PIP5K, thereby restraining PI(4,5)P2 and insulin-stimulated PI(3,4,5)P3 synthesis, an activity preserved by kinase-dead enzyme and mapped to its N-terminal VMLΦPDD motif [#6]. Together with PIP4K2A, it is required for autophagosome clearance and lipid homeostasis during nutrient deprivation across mouse and C. elegans models [#5]. PIP4K2B acts as a mechanoresponsive node whose protein levels fall on soft substrates, lowering the epigenetic regulator UHRF1, remodeling chromatin and nuclear mechanics, and driving YAP cytoplasmic retention [#10]; its transcription is positively controlled by NSD1 through an H3K36me2-dependent mechanism in head and neck cancer [#11]. PIP4K2B sustains E-cadherin expression and suppresses TGF-β-induced EMT [#7], and is synthetically lethal with TP53 loss, rendering it essential for the growth of p53-null tumors [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established the first protein partner and an upstream signaling input for PIP4K2B by linking it to inflammatory receptor signaling, answering how PI turnover might be triggered at the membrane.\",\n      \"evidence\": \"Yeast two-hybrid screen and in vitro pulldown with recombinant fusion proteins, plus cellular PIP5K activity assay after TNF-alpha in HeLa cells\",\n      \"pmids\": [\"9038203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Reciprocal validation in cells and the structural basis of the TNFR1 juxtamembrane interaction not resolved\",\n        \"Whether the measured PIP5K activity increase reflects PIP4K2B catalysis directly is not distinguished\",\n        \"Downstream consequences of TNFR1-PIP4K2B coupling not defined\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined a therapeutically actionable genetic dependency by showing PIP4K2B is synthetically lethal with TP53 loss and required for p53-null tumor growth.\",\n      \"evidence\": \"shRNA knockdown in breast cancer lines, xenografts, germline mouse knockouts, and ROS measurement\",\n      \"pmids\": [\"24209622\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism connecting PIP4K2B loss to ROS elevation and senescence not fully resolved\",\n        \"Relative contributions of catalytic versus non-catalytic functions to the dependency unclear\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected PIP4K2B to epithelial identity by showing it maintains E-cadherin transcription and suppresses EMT, framing a tumor-suppressive role distinct from its growth dependency.\",\n      \"evidence\": \"shRNA knockdown in MCF10A and MCF7 cells, qRT-PCR/western for CDH1, TGF-β-induced EMT assay\",\n      \"pmids\": [\"24127122\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism linking PIP4K2B to CDH1 transcription not defined\",\n        \"Whether the effect is catalytic or signaling-dependent untested\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Validated PIP4K2B kinase activity as a druggable and physiologically relevant target through a selective inhibitor with metabolic effects in vivo.\",\n      \"evidence\": \"High-throughput enzymatic screen, in vitro kinase and cellular assays, and dosing in Zucker diabetic fatty rats\",\n      \"pmids\": [\"24845568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"In vivo glucose-lowering not mechanistically tied to a specific PIP4K2B substrate pool\",\n        \"Off-target and isoform selectivity in vivo not fully resolved\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified the nuclear effector mechanism by which PIP4K2B-controlled PI5P is read into transcription, via TAF3 PHD-finger PI binding and chromatin association.\",\n      \"evidence\": \"shRNA knockdown, lipid-binding screen, TAF3 PHD mutagenesis, ChIP, and in vitro PI-binding assays during myoblast differentiation\",\n      \"pmids\": [\"25866244\", \"25728392\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How PIP4K2B activity quantitatively sets nuclear PI5P at specific loci not mapped\",\n        \"Generality of the TAF3 readout beyond myogenic genes unknown\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed PIP4K2B downstream of MANF in hypothalamic insulin signaling, linking its ER localization and activity to feeding behavior and insulin resistance.\",\n      \"evidence\": \"In vivo hypothalamic MANF overexpression and knockdown with measurement of PIP4K2B ER localization/activity and feeding phenotypes\",\n      \"pmids\": [\"28924165\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical link between MANF and PIP4K2B not established\",\n        \"ER versus nuclear pool contributions to the phenotype not separated\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated a conserved metabolic function in autophagy, showing the PI5P→PI(4,5)P2 pathway is required for autophagosome clearance and lipid homeostasis during nutrient stress.\",\n      \"evidence\": \"Liver-specific and MEF double Pip4k2a/2b knockouts, electron microscopy, lipid droplet staining, autophagy flux assays, and a C. elegans ortholog model\",\n      \"pmids\": [\"29727621\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Isoform-specific contribution of PIP4K2B versus PIP4K2A not separated\",\n        \"Step in autophagosome maturation/clearance controlled by the lipid product not pinpointed\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved a paradoxical regulatory role by showing PIP4K2B suppresses PI(4,5)P2 and PI3K signaling non-catalytically through direct binding to PIP5K via its N-terminal VMLΦPDD motif.\",\n      \"evidence\": \"CRISPR triple knockout, phosphoinositide mass spectrometry, wild-type versus kinase-dead rescue, direct binding assay, and N-terminal motif mutagenesis\",\n      \"pmids\": [\"31091439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the PIP4K-PIP5K binding interaction not solved\",\n        \"Balance between catalytic and non-catalytic outputs in different cell contexts unclear\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped PIP4K2B expression to developing neurons and synaptic compartments, suggesting a neuronal role not yet functionally tested.\",\n      \"evidence\": \"KO-validated immunofluorescence, dual-label imaging, and immuno-EM in mouse and primate/human brain\",\n      \"pmids\": [\"32449185\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No demonstrated functional consequence of synaptic PIP4K2B localization\",\n        \"Substrate and signaling role at axon terminals/dendritic spines undefined\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified PIP4K2B as a mechanoresponsive regulator linking substrate stiffness to chromatin state and YAP activity through a PIP4K2B→UHRF1→chromatin→YAP axis.\",\n      \"evidence\": \"Soft/stiff substrate culture, knockdown and pharmacological inhibition, nuclear mechanics measurements, UHRF1 quantification, YAP imaging, and migration assays\",\n      \"pmids\": [\"36918565\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which substrate softness lowers PIP4K2B protein not defined\",\n        \"Whether catalytic activity or scaffolding drives UHRF1 reduction unresolved\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established upstream transcriptional control of PIP4K2B by NSD1 via H3K36me2 and tied PIP4K2B to mTOR signaling and growth in head and neck cancer.\",\n      \"evidence\": \"RPPA, NSD1 knockdown, H3K36me2 chromatin studies, PIP4K2B shRNA, mTOR western blot, and rescue overexpression\",\n      \"pmids\": [\"38539515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct NSD1 occupancy at the PIP4K2B locus not fully characterized\",\n        \"Basis of context-dependent rescue between tumor subsites unexplained\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Provided a structural rationale for isoform-selective inhibition, explaining why most inhibitors are less potent against PIP4K2B than PIP4K2A.\",\n      \"evidence\": \"X-ray crystallography of a PIP4K2A-inhibitor complex with comparative structural analysis of PIP4K2B\",\n      \"pmids\": [\"42117906\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No PIP4K2B crystal structure with inhibitor; isoform inference is comparative/modeled\",\n        \"Specificity-pocket conclusions not experimentally validated for PIP4K2B\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PIP4K2B's catalytic (PI5P→PI(4,5)P2) and non-catalytic (PIP5K suppression) activities are partitioned across nuclear, ER, autophagic, and synaptic compartments to produce distinct physiological outputs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No unified model assigning each phenotype to a specific lipid pool or compartment\",\n        \"Structure of full-length PIP4K2B and its PIP5K complex not solved\",\n        \"Regulation of PIP4K2B protein stability by mechanical and metabolic cues mechanistically undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016301\", \"supporting_discovery_ids\": [2, 6, 8]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [5, 8]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [2, 11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 10]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 11]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TNFRSF1A\", \"PIP5K\", \"TAF3\", \"NSD1\", \"MANF\", \"UHRF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}