{"gene":"ITPKA","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2015,"finding":"Full-length ITPKA induces formation of dense, branched actin networks rather than simple linear bundles. The N-terminal actin-binding domain (ABD) forms homodimers that bind F-actin while the monomeric C-terminal catalytic domain inserts between adjacent actin filaments, preventing thick bundle formation. When embedded in this actin network, InsP3 kinase activity is doubled, and the product Ins(1,3,4,5)P4 inhibits spontaneous actin polymerization, suggesting a local negative-feedback regulation.","method":"In vitro F-actin incubation assay, STED microscopy, InsP3 kinase activity measurement, domain-deletion analysis","journal":"Cytoskeleton (Hoboken, N.J.)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein, STED imaging, enzymatic assay, and domain-level mechanistic dissection in a single study","pmids":["25620569"],"is_preprint":false},{"year":2015,"finding":"Over-expression of Itpka (and Itpkb) inhibits NGF-induced neurite outgrowth in PC12 cells through both its F-actin binding activity and its Ins(1,4,5)P3 3-kinase catalytic activity; over-expression of the isolated N-terminal F-actin binding domain alone (lacking catalytic activity) was as effective as full-length enzyme, and kinase-dead mutants caused an intermediate reduction in neurite length, demonstrating independent contributions of both activities.","method":"Over-expression of GFP-tagged wild-type, kinase-dead mutant, and N-terminal domain constructs in PC12 cells with quantitative neurite outgrowth assay; comparison with Itpkc and IPMK isoforms","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean gain-of-function and domain-dissection experiments in a defined cell model with multiple constructs; single lab","pmids":["25892505"],"is_preprint":false},{"year":2023,"finding":"Under basal conditions, the actin-bundling activity of ITPKA (not its Ins(1,4,5)P3-kinase activity) is the primary driver of ITPKA-promoted migration and invasion in lung cancer H1299 cells. A dominant-negative actin-binding mutant ITPKAL34P blocked filopodial actin dynamics, wound-healing migration, and invasive protrusion into collagen I. The Ins(1,4,5)P3-kinase activity provides only a modest (13%) additional migratory boost upon ATP stimulation, reversed by the inhibitor GNF362.","method":"Over-expression of dominant-negative ITPKAL34P and catalytic-inactive ITPKA mutants; wound-healing migration assay; collagen I invasion assay; live-cell actin dynamics imaging; pharmacological inhibition with GNF362","journal":"Bioscience reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mutant constructs and pharmacological inhibitor used in parallel with defined phenotypic readouts; single lab","pmids":["36688944"],"is_preprint":false},{"year":2018,"finding":"ITPKA (IP3K-A) binds to microtubule end-binding protein EB3; this interaction is regulated by PKA-dependent phosphorylation of ITPKA at Ser119. The ITPKA–EB3 complex dynamically dissociates and reassociates during chemically induced LTP, linking ITPKA to microtubule cytoskeleton remodeling during synaptic plasticity.","method":"Co-immunoprecipitation, PKA phosphorylation assay, Ser119 phospho-mutant analysis, chemically induced LTP paradigm","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP with phospho-mutant validation; single lab, single study","pmids":["30466786"],"is_preprint":false},{"year":2020,"finding":"ITPKA interacts with Drebrin 1 (DBN1) in lung adenocarcinoma cells and this interaction contributes to ITPKA-promoted EMT and metastatic phenotypes; ITPKA transcription in LUAD is activated by the transcription factor TFAP2A.","method":"Co-immunoprecipitation (ITPKA–DBN1 interaction); chromatin immunoprecipitation / reporter assay for TFAP2A-driven ITPKA transcription; in vitro cell migration/invasion assays with knockdown","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP for protein interaction and functional assays for transcriptional regulation; single lab but two orthogonal mechanistic readouts","pmids":["32015686"],"is_preprint":false},{"year":2021,"finding":"ITPKA interacts with MDM2 and stabilizes p53 protein, thereby promoting cellular senescence in ovarian cancer cells. Overexpression of ITPKA induced senescence and inhibited anchorage-independent growth, while knockdown had opposite effects. ITPKA expression is negatively regulated by miR-203.","method":"Co-immunoprecipitation (ITPKA–MDM2), p53 protein stability assay, overexpression/knockdown with senescence and growth assays, miR-203 functional experiments","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus functional rescue experiments; single lab, single study","pmids":["33879633"],"is_preprint":false},{"year":2024,"finding":"ITPKA interacts with PYCR1 and phosphorylates PYCR1 at serine 29. This phosphorylation blocks Stub1 E3-ligase-mediated ubiquitination of PYCR1, stabilizing PYCR1 protein levels and promoting glioma cell proliferation and invasion.","method":"Co-immunoprecipitation, in vitro kinase assay with phospho-site mapping (Ser29), ubiquitination assay with Stub1, in vivo tumorigenicity assay","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP, kinase assay, and ubiquitination assay provide orthogonal evidence; single lab, single study","pmids":["39170313"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of the ITPKA–F-actin complex revealed a novel short linear F-actin binding motif (SFM) within ITPKA. Mutagenesis identified essential amino acids of the SFM required for F-actin binding and affinity modulation (binding affinity 13–89 µM range across SFM-containing proteins).","method":"Cryo-EM structure determination of ITPKA–F-actin complex; computational SLiMFold pipeline; mutagenesis of SFM residues with binding affinity measurements","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — cryo-EM structure with mutagenesis validation; single preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.04.16.649135"],"is_preprint":true},{"year":2025,"finding":"Morpholino-mediated depletion of Itpka in Xenopus laevis embryos causes defects in head, brain, and eye development, rescued by co-injection of Xenopus itpka RNA, demonstrating a required role for Itpka in anterior neural development.","method":"Morpholino oligonucleotide knockdown in Xenopus laevis; RNA rescue experiment; analysis of marker gene expression","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with RNA rescue in an in vivo vertebrate model; single study, single lab","pmids":["40703653"],"is_preprint":false}],"current_model":"ITPKA is a bifunctional neuronal/oncogenic kinase that (1) phosphorylates Ins(1,4,5)P3 to Ins(1,3,4,5)P4 via its C-terminal catalytic domain and (2) remodels the actin cytoskeleton through a short linear F-actin binding motif in its N-terminal domain, with cryo-EM revealing the structural basis of F-actin engagement; actin-bundling activity predominantly drives cancer cell migration and invasion under basal conditions while kinase activity provides an auxiliary boost upon ATP stimulation; ITPKA also functions as a kinase for non-canonical substrates (phosphorylating PYCR1-Ser29 to block its ubiquitination) and as a scaffold (binding EB3 in a PKA-Ser119-phosphorylation-dependent manner and binding MDM2 to stabilize p53); its transcription is activated by TFAP2A and suppressed by miR-203, and it plays an essential role in anterior neural development in vertebrates."},"narrative":{"mechanistic_narrative":"ITPKA is a bifunctional protein that couples inositol phosphate signaling to actin cytoskeleton remodeling, with roles spanning neuronal morphogenesis, vertebrate neural development, and cancer cell motility [PMID:25620569, PMID:36688944]. Its C-terminal catalytic domain phosphorylates Ins(1,4,5)P3, while an N-terminal actin-binding domain forms homodimers that engage F-actin; in the full-length enzyme these activities are reciprocally coupled, with embedding in an actin network doubling kinase activity and the product Ins(1,3,4,5)P4 feeding back to inhibit spontaneous actin polymerization [PMID:25620569]. A cryo-EM structure of the ITPKA–F-actin complex defined a short linear F-actin binding motif and the residues required for filament engagement [PMID:bio_10.1101_2025.04.16.649135]. The actin-bundling activity, rather than the kinase activity, is the primary driver of migration and invasion in lung cancer cells, with kinase activity contributing only a modest ATP-stimulated boost [PMID:36688944], while in neurons both activities independently restrain NGF-induced neurite outgrowth [PMID:25892505]. Beyond its canonical lipid substrate, ITPKA phosphorylates PYCR1 at Ser29 to block its Stub1-mediated ubiquitination and promote glioma growth [PMID:39170313], and it acts as a scaffold by binding the microtubule end-binding protein EB3 in a PKA-Ser119-phosphorylation-dependent manner during synaptic plasticity [PMID:30466786] and by binding MDM2 to stabilize p53 and drive senescence [PMID:33879633]. ITPKA is required for anterior neural development in Xenopus [PMID:40703653], its transcription is activated by TFAP2A [PMID:32015686] and repressed by miR-203 [PMID:33879633].","teleology":[{"year":2015,"claim":"Established the structural and functional coupling between ITPKA's two activities, answering whether actin engagement and kinase catalysis influence one another.","evidence":"In vitro F-actin reconstitution, STED microscopy, InsP3 kinase assay, and domain-deletion analysis of full-length ITPKA","pmids":["25620569"],"confidence":"High","gaps":["Did not resolve atomic-level contacts of the actin-binding motif","In vitro reconstitution may not capture cellular regulation"]},{"year":2015,"claim":"Demonstrated that both the F-actin binding and kinase activities of ITPKA independently regulate a cellular morphogenetic process (neurite outgrowth).","evidence":"Over-expression of wild-type, kinase-dead, and isolated N-terminal domain constructs with quantitative neurite outgrowth assays in PC12 cells","pmids":["25892505"],"confidence":"Medium","gaps":["Gain-of-function overexpression rather than endogenous loss-of-function","Single cell model and single lab"]},{"year":2018,"claim":"Identified ITPKA as a scaffold for microtubule end-binding protein EB3 under phosphoregulatory control, extending its cytoskeletal role to microtubules during synaptic plasticity.","evidence":"Co-immunoprecipitation, PKA phosphorylation assay, and Ser119 phospho-mutant analysis in a chemically induced LTP paradigm","pmids":["30466786"],"confidence":"Medium","gaps":["Single Co-IP without reciprocal structural validation","Functional consequence of EB3 binding for plasticity not directly demonstrated"]},{"year":2020,"claim":"Linked ITPKA to EMT/metastasis through DBN1 interaction and identified TFAP2A as a transcriptional activator, clarifying upstream regulation and a downstream effector partner.","evidence":"Co-IP for ITPKA–DBN1, ChIP/reporter assay for TFAP2A, and migration/invasion assays with knockdown in lung adenocarcinoma cells","pmids":["32015686"],"confidence":"Medium","gaps":["Direct binding interface with DBN1 not mapped","Single lab"]},{"year":2021,"claim":"Revealed a non-cytoskeletal tumor-suppressive arm in which ITPKA binds MDM2 to stabilize p53 and drive senescence, and identified miR-203 as a negative regulator.","evidence":"Co-IP (ITPKA–MDM2), p53 stability assay, overexpression/knockdown senescence and growth assays, and miR-203 functional experiments in ovarian cancer cells","pmids":["33879633"],"confidence":"Medium","gaps":["Mechanism of how ITPKA binding affects MDM2 activity not resolved","Context-dependent (apparently opposite to pro-invasive roles elsewhere)"]},{"year":2024,"claim":"Expanded ITPKA's catalytic repertoire to a protein substrate, showing it phosphorylates PYCR1-Ser29 to block ubiquitination, coupling kinase activity to protein stability in glioma.","evidence":"Co-IP, in vitro kinase assay with Ser29 phospho-site mapping, Stub1 ubiquitination assay, and in vivo tumorigenicity assay","pmids":["39170313"],"confidence":"Medium","gaps":["Whether PYCR1 is a direct versus indirect substrate in cells not fully resolved","Single lab, single study"]},{"year":2025,"claim":"Provided the structural basis of F-actin engagement by defining a short linear F-actin binding motif and its essential residues.","evidence":"Cryo-EM of the ITPKA–F-actin complex, SLiMFold computational pipeline, and SFM mutagenesis with binding affinity measurements (preprint)","pmids":["bio_10.1101_2025.04.16.649135"],"confidence":"Medium","gaps":["Not yet peer-reviewed","Functional consequences of the SFM mutations in cells not established"]},{"year":2025,"claim":"Established a required in vivo developmental role for ITPKA in vertebrate anterior neural patterning.","evidence":"Morpholino knockdown of Itpka in Xenopus laevis with RNA rescue and marker gene analysis","pmids":["40703653"],"confidence":"Medium","gaps":["Did not dissect which ITPKA activity (kinase vs actin) drives the phenotype","Morpholino off-target effects not fully excluded beyond rescue"]},{"year":null,"claim":"It remains unresolved how the kinase, actin-bundling, and scaffolding activities of ITPKA are differentially deployed across neurons, development, and distinct tumor contexts where they appear to have opposing outcomes.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model integrating tumor-suppressive (p53) and pro-invasive (actin/PYCR1) roles","Endogenous regulation of activity switching unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[6]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,2,7]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,5]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,2,7]}],"pathway":[],"complexes":[],"partners":["EB3","DBN1","MDM2","PYCR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P23677","full_name":"Inositol-trisphosphate 3-kinase A","aliases":["Inositol 1,4,5-trisphosphate 3-kinase A","IP3 3-kinase A","IP3K A","InsP 3-kinase A"],"length_aa":461,"mass_kda":51.0,"function":"Catalyzes the phosphorylation of 1D-myo-inositol 1,4,5-trisphosphate (InsP3) into 1D-myo-inositol 1,3,4,5-tetrakisphosphate and participates to the regulation of calcium homeostasis","subcellular_location":"Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/P23677/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ITPKA","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ITPKA","total_profiled":1310},"omim":[{"mim_id":"606992","title":"INOSITOL HEXAPHOSPHATE KINASE 2; IP6K2","url":"https://www.omim.org/entry/606992"},{"mim_id":"606476","title":"INOSITOL 1,4,5-TRISPHOSPHATE 3-KINASE C; ITPKC","url":"https://www.omim.org/entry/606476"},{"mim_id":"147522","title":"INOSITOL 1,4,5-TRISPHOSPHATE 3-KINASE B; ITPKB","url":"https://www.omim.org/entry/147522"},{"mim_id":"147521","title":"INOSITOL 1,4,5-TRISPHOSPHATE 3-KINASE A; ITPKA","url":"https://www.omim.org/entry/147521"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":57.3},{"tissue":"intestine","ntpm":17.0}],"url":"https://www.proteinatlas.org/search/ITPKA"},"hgnc":{"alias_symbol":["IP3KA","IP3-3KA"],"prev_symbol":[]},"alphafold":{"accession":"P23677","domains":[{"cath_id":"3.30.470.160","chopping":"197-267_329-459","consensus_level":"medium","plddt":95.8996,"start":197,"end":459},{"cath_id":"-","chopping":"276-327","consensus_level":"medium","plddt":92.0892,"start":276,"end":327}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P23677","model_url":"https://alphafold.ebi.ac.uk/files/AF-P23677-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P23677-F1-predicted_aligned_error_v6.png","plddt_mean":71.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ITPKA","jax_strain_url":"https://www.jax.org/strain/search?query=ITPKA"},"sequence":{"accession":"P23677","fasta_url":"https://rest.uniprot.org/uniprotkb/P23677.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P23677/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P23677"}},"corpus_meta":[{"pmid":"32015686","id":"PMC_32015686","title":"TFAP2A Induced ITPKA Serves as an Oncogene and Interacts with DBN1 in Lung Adenocarcinoma.","date":"2020","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32015686","citation_count":35,"is_preprint":false},{"pmid":"28377279","id":"PMC_28377279","title":"Inositol-1,4,5-trisphosphate 3-kinase-A (ITPKA) is frequently over-expressed and functions as an oncogene in several tumor types.","date":"2017","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/28377279","citation_count":28,"is_preprint":false},{"pmid":"25620569","id":"PMC_25620569","title":"The catalytic domain of inositol-1,4,5-trisphosphate 3-kinase-a contributes to ITPKA-induced modulation of F-actin.","date":"2015","source":"Cytoskeleton (Hoboken, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/25620569","citation_count":13,"is_preprint":false},{"pmid":"25892505","id":"PMC_25892505","title":"Regulation of NGF-driven neurite outgrowth by Ins(1,4,5)P3 kinase is specifically associated with the two isoenzymes Itpka and Itpkb in a model of PC12 cells.","date":"2015","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/25892505","citation_count":8,"is_preprint":false},{"pmid":"36558932","id":"PMC_36558932","title":"A Class I HDAC Inhibitor BG45 Alleviates Cognitive Impairment through the CaMKII/ITPKA/Ca2+ Signaling Pathway.","date":"2022","source":"Pharmaceuticals (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36558932","citation_count":7,"is_preprint":false},{"pmid":"33879633","id":"PMC_33879633","title":"ITPKA induces cell senescence, inhibits ovarian cancer tumorigenesis and can be downregulated by miR-203.","date":"2021","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/33879633","citation_count":6,"is_preprint":false},{"pmid":"36688944","id":"PMC_36688944","title":"The actin bundling activity of ITPKA mainly accounts for its migration-promoting effect in lung cancer cells.","date":"2023","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/36688944","citation_count":3,"is_preprint":false},{"pmid":"39170313","id":"PMC_39170313","title":"ITPKA phosphorylates PYCR1 and promotes the progression of glioma.","date":"2024","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/39170313","citation_count":2,"is_preprint":false},{"pmid":"30466786","id":"PMC_30466786","title":"PKA-dependent phosphorylation of IP3K-A at Ser119 regulates a binding affinity with EB3.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/30466786","citation_count":1,"is_preprint":false},{"pmid":"37664985","id":"PMC_37664985","title":"Commentary on: The actin bundling activity of ITPKA mainly accounts for its migration-promoting effect in lung cancer cells.","date":"2023","source":"Bioscience 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motif","date":"2025-04-16","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.16.649135","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8396,"output_tokens":2569,"usd":0.031862,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9725,"output_tokens":2904,"usd":0.060612,"stage2_stop_reason":"end_turn"},"total_usd":0.092474,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"Full-length ITPKA induces formation of dense, branched actin networks rather than simple linear bundles. The N-terminal actin-binding domain (ABD) forms homodimers that bind F-actin while the monomeric C-terminal catalytic domain inserts between adjacent actin filaments, preventing thick bundle formation. When embedded in this actin network, InsP3 kinase activity is doubled, and the product Ins(1,3,4,5)P4 inhibits spontaneous actin polymerization, suggesting a local negative-feedback regulation.\",\n      \"method\": \"In vitro F-actin incubation assay, STED microscopy, InsP3 kinase activity measurement, domain-deletion analysis\",\n      \"journal\": \"Cytoskeleton (Hoboken, N.J.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein, STED imaging, enzymatic assay, and domain-level mechanistic dissection in a single study\",\n      \"pmids\": [\"25620569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Over-expression of Itpka (and Itpkb) inhibits NGF-induced neurite outgrowth in PC12 cells through both its F-actin binding activity and its Ins(1,4,5)P3 3-kinase catalytic activity; over-expression of the isolated N-terminal F-actin binding domain alone (lacking catalytic activity) was as effective as full-length enzyme, and kinase-dead mutants caused an intermediate reduction in neurite length, demonstrating independent contributions of both activities.\",\n      \"method\": \"Over-expression of GFP-tagged wild-type, kinase-dead mutant, and N-terminal domain constructs in PC12 cells with quantitative neurite outgrowth assay; comparison with Itpkc and IPMK isoforms\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean gain-of-function and domain-dissection experiments in a defined cell model with multiple constructs; single lab\",\n      \"pmids\": [\"25892505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Under basal conditions, the actin-bundling activity of ITPKA (not its Ins(1,4,5)P3-kinase activity) is the primary driver of ITPKA-promoted migration and invasion in lung cancer H1299 cells. A dominant-negative actin-binding mutant ITPKAL34P blocked filopodial actin dynamics, wound-healing migration, and invasive protrusion into collagen I. The Ins(1,4,5)P3-kinase activity provides only a modest (13%) additional migratory boost upon ATP stimulation, reversed by the inhibitor GNF362.\",\n      \"method\": \"Over-expression of dominant-negative ITPKAL34P and catalytic-inactive ITPKA mutants; wound-healing migration assay; collagen I invasion assay; live-cell actin dynamics imaging; pharmacological inhibition with GNF362\",\n      \"journal\": \"Bioscience reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mutant constructs and pharmacological inhibitor used in parallel with defined phenotypic readouts; single lab\",\n      \"pmids\": [\"36688944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ITPKA (IP3K-A) binds to microtubule end-binding protein EB3; this interaction is regulated by PKA-dependent phosphorylation of ITPKA at Ser119. The ITPKA–EB3 complex dynamically dissociates and reassociates during chemically induced LTP, linking ITPKA to microtubule cytoskeleton remodeling during synaptic plasticity.\",\n      \"method\": \"Co-immunoprecipitation, PKA phosphorylation assay, Ser119 phospho-mutant analysis, chemically induced LTP paradigm\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP with phospho-mutant validation; single lab, single study\",\n      \"pmids\": [\"30466786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ITPKA interacts with Drebrin 1 (DBN1) in lung adenocarcinoma cells and this interaction contributes to ITPKA-promoted EMT and metastatic phenotypes; ITPKA transcription in LUAD is activated by the transcription factor TFAP2A.\",\n      \"method\": \"Co-immunoprecipitation (ITPKA–DBN1 interaction); chromatin immunoprecipitation / reporter assay for TFAP2A-driven ITPKA transcription; in vitro cell migration/invasion assays with knockdown\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP for protein interaction and functional assays for transcriptional regulation; single lab but two orthogonal mechanistic readouts\",\n      \"pmids\": [\"32015686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ITPKA interacts with MDM2 and stabilizes p53 protein, thereby promoting cellular senescence in ovarian cancer cells. Overexpression of ITPKA induced senescence and inhibited anchorage-independent growth, while knockdown had opposite effects. ITPKA expression is negatively regulated by miR-203.\",\n      \"method\": \"Co-immunoprecipitation (ITPKA–MDM2), p53 protein stability assay, overexpression/knockdown with senescence and growth assays, miR-203 functional experiments\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus functional rescue experiments; single lab, single study\",\n      \"pmids\": [\"33879633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITPKA interacts with PYCR1 and phosphorylates PYCR1 at serine 29. This phosphorylation blocks Stub1 E3-ligase-mediated ubiquitination of PYCR1, stabilizing PYCR1 protein levels and promoting glioma cell proliferation and invasion.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay with phospho-site mapping (Ser29), ubiquitination assay with Stub1, in vivo tumorigenicity assay\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP, kinase assay, and ubiquitination assay provide orthogonal evidence; single lab, single study\",\n      \"pmids\": [\"39170313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of the ITPKA–F-actin complex revealed a novel short linear F-actin binding motif (SFM) within ITPKA. Mutagenesis identified essential amino acids of the SFM required for F-actin binding and affinity modulation (binding affinity 13–89 µM range across SFM-containing proteins).\",\n      \"method\": \"Cryo-EM structure determination of ITPKA–F-actin complex; computational SLiMFold pipeline; mutagenesis of SFM residues with binding affinity measurements\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — cryo-EM structure with mutagenesis validation; single preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.04.16.649135\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Morpholino-mediated depletion of Itpka in Xenopus laevis embryos causes defects in head, brain, and eye development, rescued by co-injection of Xenopus itpka RNA, demonstrating a required role for Itpka in anterior neural development.\",\n      \"method\": \"Morpholino oligonucleotide knockdown in Xenopus laevis; RNA rescue experiment; analysis of marker gene expression\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with RNA rescue in an in vivo vertebrate model; single study, single lab\",\n      \"pmids\": [\"40703653\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ITPKA is a bifunctional neuronal/oncogenic kinase that (1) phosphorylates Ins(1,4,5)P3 to Ins(1,3,4,5)P4 via its C-terminal catalytic domain and (2) remodels the actin cytoskeleton through a short linear F-actin binding motif in its N-terminal domain, with cryo-EM revealing the structural basis of F-actin engagement; actin-bundling activity predominantly drives cancer cell migration and invasion under basal conditions while kinase activity provides an auxiliary boost upon ATP stimulation; ITPKA also functions as a kinase for non-canonical substrates (phosphorylating PYCR1-Ser29 to block its ubiquitination) and as a scaffold (binding EB3 in a PKA-Ser119-phosphorylation-dependent manner and binding MDM2 to stabilize p53); its transcription is activated by TFAP2A and suppressed by miR-203, and it plays an essential role in anterior neural development in vertebrates.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ITPKA is a bifunctional protein that couples inositol phosphate signaling to actin cytoskeleton remodeling, with roles spanning neuronal morphogenesis, vertebrate neural development, and cancer cell motility [#0, #2]. Its C-terminal catalytic domain phosphorylates Ins(1,4,5)P3, while an N-terminal actin-binding domain forms homodimers that engage F-actin; in the full-length enzyme these activities are reciprocally coupled, with embedding in an actin network doubling kinase activity and the product Ins(1,3,4,5)P4 feeding back to inhibit spontaneous actin polymerization [#0]. A cryo-EM structure of the ITPKA–F-actin complex defined a short linear F-actin binding motif and the residues required for filament engagement [#7]. The actin-bundling activity, rather than the kinase activity, is the primary driver of migration and invasion in lung cancer cells, with kinase activity contributing only a modest ATP-stimulated boost [#2], while in neurons both activities independently restrain NGF-induced neurite outgrowth [#1]. Beyond its canonical lipid substrate, ITPKA phosphorylates PYCR1 at Ser29 to block its Stub1-mediated ubiquitination and promote glioma growth [#6], and it acts as a scaffold by binding the microtubule end-binding protein EB3 in a PKA-Ser119-phosphorylation-dependent manner during synaptic plasticity [#3] and by binding MDM2 to stabilize p53 and drive senescence [#5]. ITPKA is required for anterior neural development in Xenopus [#8], its transcription is activated by TFAP2A [#4] and repressed by miR-203 [#5].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established the structural and functional coupling between ITPKA's two activities, answering whether actin engagement and kinase catalysis influence one another.\",\n      \"evidence\": \"In vitro F-actin reconstitution, STED microscopy, InsP3 kinase assay, and domain-deletion analysis of full-length ITPKA\",\n      \"pmids\": [\"25620569\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve atomic-level contacts of the actin-binding motif\", \"In vitro reconstitution may not capture cellular regulation\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated that both the F-actin binding and kinase activities of ITPKA independently regulate a cellular morphogenetic process (neurite outgrowth).\",\n      \"evidence\": \"Over-expression of wild-type, kinase-dead, and isolated N-terminal domain constructs with quantitative neurite outgrowth assays in PC12 cells\",\n      \"pmids\": [\"25892505\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Gain-of-function overexpression rather than endogenous loss-of-function\", \"Single cell model and single lab\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified ITPKA as a scaffold for microtubule end-binding protein EB3 under phosphoregulatory control, extending its cytoskeletal role to microtubules during synaptic plasticity.\",\n      \"evidence\": \"Co-immunoprecipitation, PKA phosphorylation assay, and Ser119 phospho-mutant analysis in a chemically induced LTP paradigm\",\n      \"pmids\": [\"30466786\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP without reciprocal structural validation\", \"Functional consequence of EB3 binding for plasticity not directly demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Linked ITPKA to EMT/metastasis through DBN1 interaction and identified TFAP2A as a transcriptional activator, clarifying upstream regulation and a downstream effector partner.\",\n      \"evidence\": \"Co-IP for ITPKA–DBN1, ChIP/reporter assay for TFAP2A, and migration/invasion assays with knockdown in lung adenocarcinoma cells\",\n      \"pmids\": [\"32015686\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding interface with DBN1 not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a non-cytoskeletal tumor-suppressive arm in which ITPKA binds MDM2 to stabilize p53 and drive senescence, and identified miR-203 as a negative regulator.\",\n      \"evidence\": \"Co-IP (ITPKA–MDM2), p53 stability assay, overexpression/knockdown senescence and growth assays, and miR-203 functional experiments in ovarian cancer cells\",\n      \"pmids\": [\"33879633\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of how ITPKA binding affects MDM2 activity not resolved\", \"Context-dependent (apparently opposite to pro-invasive roles elsewhere)\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Expanded ITPKA's catalytic repertoire to a protein substrate, showing it phosphorylates PYCR1-Ser29 to block ubiquitination, coupling kinase activity to protein stability in glioma.\",\n      \"evidence\": \"Co-IP, in vitro kinase assay with Ser29 phospho-site mapping, Stub1 ubiquitination assay, and in vivo tumorigenicity assay\",\n      \"pmids\": [\"39170313\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PYCR1 is a direct versus indirect substrate in cells not fully resolved\", \"Single lab, single study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the structural basis of F-actin engagement by defining a short linear F-actin binding motif and its essential residues.\",\n      \"evidence\": \"Cryo-EM of the ITPKA–F-actin complex, SLiMFold computational pipeline, and SFM mutagenesis with binding affinity measurements (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.04.16.649135\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Not yet peer-reviewed\", \"Functional consequences of the SFM mutations in cells not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established a required in vivo developmental role for ITPKA in vertebrate anterior neural patterning.\",\n      \"evidence\": \"Morpholino knockdown of Itpka in Xenopus laevis with RNA rescue and marker gene analysis\",\n      \"pmids\": [\"40703653\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not dissect which ITPKA activity (kinase vs actin) drives the phenotype\", \"Morpholino off-target effects not fully excluded beyond rescue\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the kinase, actin-bundling, and scaffolding activities of ITPKA are differentially deployed across neurons, development, and distinct tumor contexts where they appear to have opposing outcomes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model integrating tumor-suppressive (p53) and pro-invasive (actin/PYCR1) roles\", \"Endogenous regulation of activity switching unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 2, 7]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [],\n    \"partners\": [\"EB3\", \"DBN1\", \"MDM2\", \"PYCR1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}