{"gene":"PITPNC1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2012,"finding":"PITPNC1 (RdgBβ) binds and transfers phosphatidic acid (PA) in addition to phosphatidylinositol (PI), but unlike Class I PITPs does not bind phosphatidylcholine. When purified from E. coli, PITPNC1 is preloaded with PA and phosphatidylglycerol. Incubation with permeabilized HL60 cells caused release of phosphatidylglycerol and incorporation of PA and PI. Activation of endogenous phospholipase D (or addition of bacterial PLD) increased PA binding at the expense of PI binding.","method":"In vitro lipid binding and transfer assays with purified recombinant PITPNC1; permeabilized cell incubation experiments; phospholipase D activation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of lipid binding and transfer with purified protein, multiple orthogonal biochemical methods in one study","pmids":["22822086"],"is_preprint":false},{"year":2016,"finding":"PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi. RAB1B localization enables recruitment of GOLPH3, which facilitates Golgi extension and enhanced vesicular release. This pathway drives secretion of pro-invasive and pro-angiogenic mediators HTRA1, MMP1, FAM3C, PDGFA, and ADAM10.","method":"Biochemical binding assays (PI4P binding), co-immunoprecipitation, cell-biological localization studies, loss-of-function and gain-of-function experiments with secretion and metastasis readouts","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (biochemical binding, Co-IP, cell biology, in vivo metastasis) in a single rigorous study with multiple downstream effectors validated","pmids":["26977884"],"is_preprint":false},{"year":2018,"finding":"PITPNC1 promotes anoikis resistance in gastric cancer cells through enhancement of fatty acid oxidation (FAO), upregulating CD36 and CPT1B expression. Adipocyte co-culture elevates PITPNC1 expression, which in turn facilitates omental metastasis via this FAO-dependent mechanism.","method":"siRNA knockdown and overexpression of PITPNC1; co-culture with adipocytes; in vitro anoikis assays; in vivo metastasis models; western blotting for CD36 and CPT1B","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic modulation with defined molecular readouts (CD36, CPT1B), in vivo validation, single lab","pmids":["30555557"],"is_preprint":false},{"year":2020,"finding":"PITPNC1 promotes radioresistance in rectal cancer by inhibiting reactive oxygen species (ROS) production. Knockdown of PITPNC1 increases ROS generation, and this effect is reversed by the ROS scavenger N-acetyl-L-cysteine (NAC), placing PITPNC1 upstream of ROS suppression.","method":"siRNA knockdown in SW620 and HCT116 cell lines; ROS measurement; NAC rescue experiments; apoptosis and proliferation assays under irradiation","journal":"Annals of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic modulation with pharmacological rescue (NAC), two cell lines, defined ROS mechanistic pathway placement","pmids":["32175419"],"is_preprint":false},{"year":2022,"finding":"PITPNC1 is required for thermogenesis in brown adipose tissue (BAT). Pitpnc1-/- mice develop hypothermia upon acute cold exposure. PITPNC1-deficient brown adipocytes show defective β-oxidation, abnormal thermogenesis-related mitochondrial metabolism, excessive phosphatidylcholine accumulation, and reduced phosphatidic acid, indicating that PITPNC1 maintains mitochondrial phospholipid homeostasis necessary for lipid mobilization and heat production.","method":"Pitpnc1 knockout mouse model; cold-exposure phenotyping (body temperature); metabolic and lipidomic analyses of brown adipocytes; mitochondrial function assays","journal":"Science China. Life sciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean knockout mouse with defined physiological phenotype, lipidomic and mitochondrial functional validation, multiple orthogonal methods","pmids":["36166181"],"is_preprint":false},{"year":2023,"finding":"PITPNC1 is transcriptionally regulated by KRAS through the MEK1/2 and JNK1/2 signaling pathways. PITPNC1 in turn controls mTOR localization via enhanced MYC protein stability to prevent autophagy, constituting a KRAS–PITPNC1–MYC–mTOR axis in lung and pancreatic cancer.","method":"Genetic modulation of KRAS; pharmacological inhibition of MEK1/2 and JNK1/2; PITPNC1 depletion in vitro and in vivo; RNA sequencing; subcellular localization assays for mTOR; MYC protein stability assays","journal":"Molecular cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pathway interventions (genetic and pharmacological), subcellular localization assay, in vivo validation, single lab","pmids":["37210549"],"is_preprint":false},{"year":2024,"finding":"PITPNC1 regulates CD155 surface expression on tumor cells through FASN (fatty acid synthase), thereby suppressing CD8+ T cell immune function and promoting radioresistance. Co-immunoprecipitation and immunofluorescence co-localization confirmed interaction between PITPNC1 and FASN. Silencing PITPNC1 inhibited FASN/CD155, enhanced CD8+ T cell killing, and reduced radioresistance in vivo.","method":"Immunoprecipitation; immunofluorescence co-localization; siRNA knockdown and lentiviral overexpression; co-culture of tumor cells with PBMCs/CD8+ T cells; in vivo tumor-bearing models; flow cytometry","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus co-localization plus genetic rescue in vitro and in vivo, single lab, multiple orthogonal methods","pmids":["38291470"],"is_preprint":false}],"current_model":"PITPNC1 is a Class II phosphatidylinositol transfer protein that binds and transfers phosphatidylinositol and phosphatidic acid (but not phosphatidylcholine); at the Golgi it binds PI4P to recruit RAB1B, which in turn recruits GOLPH3 to drive vesicular secretion of pro-tumorigenic factors; it is regulated by KRAS via MEK1/2 and JNK1/2, stabilizes MYC protein to control mTOR localization and suppress autophagy, promotes fatty-acid-oxidation-dependent anoikis resistance via CD36/CPT1B, suppresses ROS to confer radioresistance, regulates CD155 surface expression through FASN to dampen CD8+ T cell immunity, and maintains mitochondrial phospholipid homeostasis in brown adipose tissue to support thermogenesis."},"narrative":{"mechanistic_narrative":"PITPNC1 is a Class II phosphatidylinositol transfer protein whose lipid-shuttling activity is repurposed across secretory, metabolic, and immune-evasive programs in cancer and physiology [PMID:22822086, PMID:26977884]. Biochemically it binds and transfers phosphatidylinositol and phosphatidic acid but, unlike Class I PITPs, does not bind phosphatidylcholine, and its cargo preference shifts toward phosphatidic acid when phospholipase D is active [PMID:22822086]. At the Golgi, PITPNC1 binds the resident lipid PI4P and localizes RAB1B, which recruits GOLPH3 to drive Golgi extension and enhanced vesicular release of pro-invasive and pro-angiogenic mediators including HTRA1, MMP1, FAM3C, PDGFA, and ADAM10 [PMID:26977884]. PITPNC1 is a transcriptional target of KRAS acting through MEK1/2 and JNK1/2, and it in turn stabilizes MYC protein to control mTOR localization and suppress autophagy [PMID:37210549]. It supports tumor cell survival and metastasis through fatty-acid metabolism, enhancing fatty-acid oxidation via CD36 and CPT1B to confer anoikis resistance [PMID:30555557], suppressing reactive oxygen species to promote radioresistance [PMID:32175419], and interacting with FASN to regulate CD155 surface expression and thereby dampen CD8+ T cell killing [PMID:38291470]. Beyond cancer, PITPNC1 maintains mitochondrial phospholipid homeostasis in brown adipose tissue, where its loss causes defective β-oxidation and cold-induced hypothermia in knockout mice [PMID:36166181].","teleology":[{"year":2012,"claim":"Established the core biochemical identity of PITPNC1 by defining which lipids it binds and transfers, distinguishing it from Class I transfer proteins.","evidence":"In vitro lipid binding and transfer assays with purified recombinant protein, permeabilized cell incubations, and phospholipase D activation","pmids":["22822086"],"confidence":"High","gaps":["Structural basis of PA versus PI selectivity not resolved","Physiological consequence of lipid transfer not addressed in this study","No cellular localization context provided"]},{"year":2016,"claim":"Connected PITPNC1 lipid binding to a cellular function by showing it binds Golgi PI4P and assembles a RAB1B-GOLPH3 secretory module driving release of pro-metastatic factors.","evidence":"PI4P binding assays, co-immunoprecipitation, localization studies, and loss/gain-of-function with secretion and in vivo metastasis readouts","pmids":["26977884"],"confidence":"High","gaps":["How PA transfer activity relates to PI4P binding at the Golgi unclear","Selectivity of secreted cargo not mechanistically explained"]},{"year":2018,"claim":"Extended PITPNC1 function to fatty-acid metabolism, showing it drives anoikis resistance and omental metastasis via FAO upregulation.","evidence":"siRNA/overexpression, adipocyte co-culture, anoikis assays, in vivo metastasis models, and CD36/CPT1B western blotting","pmids":["30555557"],"confidence":"Medium","gaps":["Mechanism linking PITPNC1 to CD36/CPT1B transcription not defined","Single lab; not independently confirmed","Connection to its lipid-transfer activity untested"]},{"year":2020,"claim":"Placed PITPNC1 upstream of ROS suppression as a determinant of radioresistance in colorectal cancer.","evidence":"siRNA knockdown in two cell lines, ROS measurement, NAC rescue, and irradiation apoptosis/proliferation assays","pmids":["32175419"],"confidence":"Medium","gaps":["Molecular mechanism of ROS suppression unidentified","No in vivo validation in this study","Link to lipid metabolism or secretory function unexplored"]},{"year":2022,"claim":"Defined a physiological, non-cancer role: PITPNC1 maintains mitochondrial phospholipid homeostasis required for brown adipose thermogenesis.","evidence":"Pitpnc1 knockout mice with cold-exposure phenotyping, lipidomics, and mitochondrial functional assays","pmids":["36166181"],"confidence":"High","gaps":["Mechanism by which PITPNC1 regulates mitochondrial PC/PA balance not resolved","Whether direct lipid transfer to mitochondria occurs untested"]},{"year":2023,"claim":"Positioned PITPNC1 within a KRAS-driven signaling axis, identifying both its upstream regulators and a downstream MYC-mTOR-autophagy output.","evidence":"KRAS genetic modulation, MEK1/2 and JNK1/2 pharmacological inhibition, PITPNC1 depletion in vitro/in vivo, RNA-seq, mTOR localization and MYC stability assays","pmids":["37210549"],"confidence":"Medium","gaps":["Direct mechanism by which PITPNC1 stabilizes MYC not defined","Single lab; not independently confirmed","Relationship between lipid-transfer activity and MYC stabilization unknown"]},{"year":2024,"claim":"Linked PITPNC1 to tumor immune evasion by showing it interacts with FASN to regulate CD155 and suppress CD8+ T cell function.","evidence":"Co-IP, immunofluorescence co-localization, siRNA/overexpression, tumor cell-T cell co-culture, in vivo models, and flow cytometry","pmids":["38291470"],"confidence":"Medium","gaps":["Co-IP without reciprocal validation of PITPNC1-FASN interaction","How FASN activity drives CD155 surface expression not mechanistically resolved","Single lab; not independently confirmed"]},{"year":null,"claim":"How PITPNC1's biochemical lipid-transfer activity mechanistically unifies its diverse downstream roles in secretion, MYC stabilization, ROS suppression, and immune modulation remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No single mechanistic model connects lipid transfer to the metabolic and signaling phenotypes","Structural understanding of lipid-cargo regulation across contexts lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,1]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,4]}],"complexes":[],"partners":["RAB1B","GOLPH3","FASN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UKF7","full_name":"Cytoplasmic phosphatidylinositol transfer protein 1","aliases":["Mammalian rdgB homolog beta","M-rdgB beta","MrdgBbeta","Retinal degeneration B homolog beta","RdgBbeta"],"length_aa":332,"mass_kda":38.4,"function":"Catalyzes the transfer of phosphatidylinositol (PI) and phosphatidic acid (PA) between membranes (PubMed:10531358, PubMed:22822086). Binds PA derived from the phospholipase D signaling pathway and among the cellular PA species, preferably binds to the C16:0/16:1 and C16:1/18:1 PA species (PubMed:22822086) Catalyzes the transfer of phosphatidylinositol between membranes","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9UKF7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PITPNC1","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":[],"url":"https://opencell.sf.czbiohub.org/search/PITPNC1","total_profiled":1310},"omim":[{"mim_id":"611767","title":"MICRO RNA 126; MIR126","url":"https://www.omim.org/entry/611767"},{"mim_id":"605134","title":"PHOSPHATIDYLINOSITOL TRANSFER PROTEIN, CYTOPLASMIC, 1; PITPNC1","url":"https://www.omim.org/entry/605134"},{"mim_id":"604705","title":"MER TYROSINE KINASE PROTOONCOGENE; MERTK","url":"https://www.omim.org/entry/604705"},{"mim_id":"146731","title":"INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN 2; IGFBP2","url":"https://www.omim.org/entry/146731"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":24.4}],"url":"https://www.proteinatlas.org/search/PITPNC1"},"hgnc":{"alias_symbol":["RDGBB1","RDGBB","RDGB-BETA"],"prev_symbol":[]},"alphafold":{"accession":"Q9UKF7","domains":[{"cath_id":"3.30.530.20","chopping":"1-245","consensus_level":"medium","plddt":94.8655,"start":1,"end":245}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKF7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKF7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UKF7-F1-predicted_aligned_error_v6.png","plddt_mean":82.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PITPNC1","jax_strain_url":"https://www.jax.org/strain/search?query=PITPNC1"},"sequence":{"accession":"Q9UKF7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UKF7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UKF7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UKF7"}},"corpus_meta":[{"pmid":"26977884","id":"PMC_26977884","title":"PITPNC1 Recruits RAB1B to the Golgi Network to Drive Malignant Secretion.","date":"2016","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/26977884","citation_count":117,"is_preprint":false},{"pmid":"30555557","id":"PMC_30555557","title":"Adipocytes fuel gastric cancer omental metastasis via PITPNC1-mediated fatty acid metabolic reprogramming.","date":"2018","source":"Theranostics","url":"https://pubmed.ncbi.nlm.nih.gov/30555557","citation_count":98,"is_preprint":false},{"pmid":"22822086","id":"PMC_22822086","title":"Phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) binds and transfers phosphatidic acid.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22822086","citation_count":79,"is_preprint":false},{"pmid":"38291470","id":"PMC_38291470","title":"PITPNC1 Suppress CD8+ T cell immune function and promote radioresistance in rectal cancer by modulating FASN/CD155.","date":"2024","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38291470","citation_count":18,"is_preprint":false},{"pmid":"37210549","id":"PMC_37210549","title":"The phospholipid transporter PITPNC1 links KRAS to MYC to prevent autophagy in lung and pancreatic cancer.","date":"2023","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/37210549","citation_count":18,"is_preprint":false},{"pmid":"32175419","id":"PMC_32175419","title":"PITPNC1 fuels radioresistance of rectal cancer by inhibiting reactive oxygen species production.","date":"2020","source":"Annals of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32175419","citation_count":17,"is_preprint":false},{"pmid":"36166181","id":"PMC_36166181","title":"PITPNC1 promotes the thermogenesis of brown adipose tissue under acute cold exposure.","date":"2022","source":"Science China. Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36166181","citation_count":14,"is_preprint":false},{"pmid":"39406587","id":"PMC_39406587","title":"Expanding functions of the phosphatidylinositol/phosphatidate lipid transporter, PITPNC1 in physiology and in pathology.","date":"2024","source":"Advances in biological regulation","url":"https://pubmed.ncbi.nlm.nih.gov/39406587","citation_count":8,"is_preprint":false},{"pmid":"42186263","id":"PMC_42186263","title":"The Variant rs2706682 at PITPNC1, Which Enhances Vehicular Secretion, Associated With Systemic Lupus Erythematosus Susceptibility in Chinese Populations.","date":"2026","source":"International journal of immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/42186263","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6916,"output_tokens":2130,"usd":0.026349,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9138,"output_tokens":2798,"usd":0.05782,"stage2_stop_reason":"end_turn"},"total_usd":0.084169,"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\": 2012,\n      \"finding\": \"PITPNC1 (RdgBβ) binds and transfers phosphatidic acid (PA) in addition to phosphatidylinositol (PI), but unlike Class I PITPs does not bind phosphatidylcholine. When purified from E. coli, PITPNC1 is preloaded with PA and phosphatidylglycerol. Incubation with permeabilized HL60 cells caused release of phosphatidylglycerol and incorporation of PA and PI. Activation of endogenous phospholipase D (or addition of bacterial PLD) increased PA binding at the expense of PI binding.\",\n      \"method\": \"In vitro lipid binding and transfer assays with purified recombinant PITPNC1; permeabilized cell incubation experiments; phospholipase D activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of lipid binding and transfer with purified protein, multiple orthogonal biochemical methods in one study\",\n      \"pmids\": [\"22822086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PITPNC1 promotes malignant secretion by binding Golgi-resident PI4P and localizing RAB1B to the Golgi. RAB1B localization enables recruitment of GOLPH3, which facilitates Golgi extension and enhanced vesicular release. This pathway drives secretion of pro-invasive and pro-angiogenic mediators HTRA1, MMP1, FAM3C, PDGFA, and ADAM10.\",\n      \"method\": \"Biochemical binding assays (PI4P binding), co-immunoprecipitation, cell-biological localization studies, loss-of-function and gain-of-function experiments with secretion and metastasis readouts\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (biochemical binding, Co-IP, cell biology, in vivo metastasis) in a single rigorous study with multiple downstream effectors validated\",\n      \"pmids\": [\"26977884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PITPNC1 promotes anoikis resistance in gastric cancer cells through enhancement of fatty acid oxidation (FAO), upregulating CD36 and CPT1B expression. Adipocyte co-culture elevates PITPNC1 expression, which in turn facilitates omental metastasis via this FAO-dependent mechanism.\",\n      \"method\": \"siRNA knockdown and overexpression of PITPNC1; co-culture with adipocytes; in vitro anoikis assays; in vivo metastasis models; western blotting for CD36 and CPT1B\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic modulation with defined molecular readouts (CD36, CPT1B), in vivo validation, single lab\",\n      \"pmids\": [\"30555557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PITPNC1 promotes radioresistance in rectal cancer by inhibiting reactive oxygen species (ROS) production. Knockdown of PITPNC1 increases ROS generation, and this effect is reversed by the ROS scavenger N-acetyl-L-cysteine (NAC), placing PITPNC1 upstream of ROS suppression.\",\n      \"method\": \"siRNA knockdown in SW620 and HCT116 cell lines; ROS measurement; NAC rescue experiments; apoptosis and proliferation assays under irradiation\",\n      \"journal\": \"Annals of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic modulation with pharmacological rescue (NAC), two cell lines, defined ROS mechanistic pathway placement\",\n      \"pmids\": [\"32175419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PITPNC1 is required for thermogenesis in brown adipose tissue (BAT). Pitpnc1-/- mice develop hypothermia upon acute cold exposure. PITPNC1-deficient brown adipocytes show defective β-oxidation, abnormal thermogenesis-related mitochondrial metabolism, excessive phosphatidylcholine accumulation, and reduced phosphatidic acid, indicating that PITPNC1 maintains mitochondrial phospholipid homeostasis necessary for lipid mobilization and heat production.\",\n      \"method\": \"Pitpnc1 knockout mouse model; cold-exposure phenotyping (body temperature); metabolic and lipidomic analyses of brown adipocytes; mitochondrial function assays\",\n      \"journal\": \"Science China. Life sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockout mouse with defined physiological phenotype, lipidomic and mitochondrial functional validation, multiple orthogonal methods\",\n      \"pmids\": [\"36166181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PITPNC1 is transcriptionally regulated by KRAS through the MEK1/2 and JNK1/2 signaling pathways. PITPNC1 in turn controls mTOR localization via enhanced MYC protein stability to prevent autophagy, constituting a KRAS–PITPNC1–MYC–mTOR axis in lung and pancreatic cancer.\",\n      \"method\": \"Genetic modulation of KRAS; pharmacological inhibition of MEK1/2 and JNK1/2; PITPNC1 depletion in vitro and in vivo; RNA sequencing; subcellular localization assays for mTOR; MYC protein stability assays\",\n      \"journal\": \"Molecular cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pathway interventions (genetic and pharmacological), subcellular localization assay, in vivo validation, single lab\",\n      \"pmids\": [\"37210549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PITPNC1 regulates CD155 surface expression on tumor cells through FASN (fatty acid synthase), thereby suppressing CD8+ T cell immune function and promoting radioresistance. Co-immunoprecipitation and immunofluorescence co-localization confirmed interaction between PITPNC1 and FASN. Silencing PITPNC1 inhibited FASN/CD155, enhanced CD8+ T cell killing, and reduced radioresistance in vivo.\",\n      \"method\": \"Immunoprecipitation; immunofluorescence co-localization; siRNA knockdown and lentiviral overexpression; co-culture of tumor cells with PBMCs/CD8+ T cells; in vivo tumor-bearing models; flow cytometry\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus co-localization plus genetic rescue in vitro and in vivo, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"38291470\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PITPNC1 is a Class II phosphatidylinositol transfer protein that binds and transfers phosphatidylinositol and phosphatidic acid (but not phosphatidylcholine); at the Golgi it binds PI4P to recruit RAB1B, which in turn recruits GOLPH3 to drive vesicular secretion of pro-tumorigenic factors; it is regulated by KRAS via MEK1/2 and JNK1/2, stabilizes MYC protein to control mTOR localization and suppress autophagy, promotes fatty-acid-oxidation-dependent anoikis resistance via CD36/CPT1B, suppresses ROS to confer radioresistance, regulates CD155 surface expression through FASN to dampen CD8+ T cell immunity, and maintains mitochondrial phospholipid homeostasis in brown adipose tissue to support thermogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PITPNC1 is a Class II phosphatidylinositol transfer protein whose lipid-shuttling activity is repurposed across secretory, metabolic, and immune-evasive programs in cancer and physiology [#0, #1]. Biochemically it binds and transfers phosphatidylinositol and phosphatidic acid but, unlike Class I PITPs, does not bind phosphatidylcholine, and its cargo preference shifts toward phosphatidic acid when phospholipase D is active [#0]. At the Golgi, PITPNC1 binds the resident lipid PI4P and localizes RAB1B, which recruits GOLPH3 to drive Golgi extension and enhanced vesicular release of pro-invasive and pro-angiogenic mediators including HTRA1, MMP1, FAM3C, PDGFA, and ADAM10 [#1]. PITPNC1 is a transcriptional target of KRAS acting through MEK1/2 and JNK1/2, and it in turn stabilizes MYC protein to control mTOR localization and suppress autophagy [#5]. It supports tumor cell survival and metastasis through fatty-acid metabolism, enhancing fatty-acid oxidation via CD36 and CPT1B to confer anoikis resistance [#2], suppressing reactive oxygen species to promote radioresistance [#3], and interacting with FASN to regulate CD155 surface expression and thereby dampen CD8+ T cell killing [#6]. Beyond cancer, PITPNC1 maintains mitochondrial phospholipid homeostasis in brown adipose tissue, where its loss causes defective β-oxidation and cold-induced hypothermia in knockout mice [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established the core biochemical identity of PITPNC1 by defining which lipids it binds and transfers, distinguishing it from Class I transfer proteins.\",\n      \"evidence\": \"In vitro lipid binding and transfer assays with purified recombinant protein, permeabilized cell incubations, and phospholipase D activation\",\n      \"pmids\": [\"22822086\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of PA versus PI selectivity not resolved\",\n        \"Physiological consequence of lipid transfer not addressed in this study\",\n        \"No cellular localization context provided\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected PITPNC1 lipid binding to a cellular function by showing it binds Golgi PI4P and assembles a RAB1B-GOLPH3 secretory module driving release of pro-metastatic factors.\",\n      \"evidence\": \"PI4P binding assays, co-immunoprecipitation, localization studies, and loss/gain-of-function with secretion and in vivo metastasis readouts\",\n      \"pmids\": [\"26977884\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How PA transfer activity relates to PI4P binding at the Golgi unclear\",\n        \"Selectivity of secreted cargo not mechanistically explained\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended PITPNC1 function to fatty-acid metabolism, showing it drives anoikis resistance and omental metastasis via FAO upregulation.\",\n      \"evidence\": \"siRNA/overexpression, adipocyte co-culture, anoikis assays, in vivo metastasis models, and CD36/CPT1B western blotting\",\n      \"pmids\": [\"30555557\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism linking PITPNC1 to CD36/CPT1B transcription not defined\",\n        \"Single lab; not independently confirmed\",\n        \"Connection to its lipid-transfer activity untested\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Placed PITPNC1 upstream of ROS suppression as a determinant of radioresistance in colorectal cancer.\",\n      \"evidence\": \"siRNA knockdown in two cell lines, ROS measurement, NAC rescue, and irradiation apoptosis/proliferation assays\",\n      \"pmids\": [\"32175419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular mechanism of ROS suppression unidentified\",\n        \"No in vivo validation in this study\",\n        \"Link to lipid metabolism or secretory function unexplored\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a physiological, non-cancer role: PITPNC1 maintains mitochondrial phospholipid homeostasis required for brown adipose thermogenesis.\",\n      \"evidence\": \"Pitpnc1 knockout mice with cold-exposure phenotyping, lipidomics, and mitochondrial functional assays\",\n      \"pmids\": [\"36166181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which PITPNC1 regulates mitochondrial PC/PA balance not resolved\",\n        \"Whether direct lipid transfer to mitochondria occurs untested\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Positioned PITPNC1 within a KRAS-driven signaling axis, identifying both its upstream regulators and a downstream MYC-mTOR-autophagy output.\",\n      \"evidence\": \"KRAS genetic modulation, MEK1/2 and JNK1/2 pharmacological inhibition, PITPNC1 depletion in vitro/in vivo, RNA-seq, mTOR localization and MYC stability assays\",\n      \"pmids\": [\"37210549\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct mechanism by which PITPNC1 stabilizes MYC not defined\",\n        \"Single lab; not independently confirmed\",\n        \"Relationship between lipid-transfer activity and MYC stabilization unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked PITPNC1 to tumor immune evasion by showing it interacts with FASN to regulate CD155 and suppress CD8+ T cell function.\",\n      \"evidence\": \"Co-IP, immunofluorescence co-localization, siRNA/overexpression, tumor cell-T cell co-culture, in vivo models, and flow cytometry\",\n      \"pmids\": [\"38291470\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Co-IP without reciprocal validation of PITPNC1-FASN interaction\",\n        \"How FASN activity drives CD155 surface expression not mechanistically resolved\",\n        \"Single lab; not independently confirmed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PITPNC1's biochemical lipid-transfer activity mechanistically unifies its diverse downstream roles in secretion, MYC stabilization, ROS suppression, and immune modulation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No single mechanistic model connects lipid transfer to the metabolic and signaling phenotypes\",\n        \"Structural understanding of lipid-cargo regulation across contexts lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RAB1B\", \"GOLPH3\", \"FASN\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}