{"gene":"PAFAH1B3","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2001,"finding":"The PAFAH1B3 protein interacts with LIS1 as part of the heterotrimeric PAF-AH1B complex; a truncated PAFAH1B3 (first 136 amino acids) encoded by a PAFAH1B3-CLK2 fusion gene lost its ability to interact with LIS1, demonstrating that the C-terminal portion of PAFAH1B3 is required for LIS1 binding.","method":"Molecular characterization of chromosomal translocation breakpoints; expression analysis of fusion protein; interaction assay showing loss of LIS1 binding by truncated PAFAH1B3","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction and loss-of-function experiment with defined molecular truncation, single lab but mechanistically clear","pmids":["11285245"],"is_preprint":false},{"year":2014,"finding":"PAFAH1B3 inactivation in breast cancer cells alters the levels of signaling lipids (consistent with its role as a PAF acetylhydrolase), and metabolomic profiling showed that PAFAH1B3 loss enhances tumor-suppressing signaling lipids, placing PAFAH1B3 as a critical metabolic node whose enzymatic activity drives cancer pathogenicity.","method":"Metabolic mapping/metabolomic profiling; loss-of-function (PAFAH1B3 inactivation) with metabolomic readout in breast cancer cell lines","journal":"Chemistry & biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — metabolomic profiling combined with loss-of-function, single lab, two orthogonal methods (metabolomics + cell-based functional assays)","pmids":["24954006"],"is_preprint":false},{"year":2018,"finding":"PAFAH1B3 regulates intracellular levels of platelet-activating factor (PAF); loss of Pafah1b3 sensitizes BCR-ABL1 BCP-ALL leukemia cells to TKI dasatinib in vivo, and this sensitization is partially reversed by antagonism of the PAF receptor (PAFR), indicating that PAFAH1B3-controlled PAF/PAFR signaling mediates leukemia cell survival in the microenvironment.","method":"In vivo and in vitro RNAi screens; Pafah1b3 KO vs. overexpressing cell lines; PAFR antagonist rescue experiment in mouse model of BCR-ABL1 BCP-ALL","journal":"Blood advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo RNAi screen with mechanistic rescue by PAFR antagonist, single lab but multiple approaches (KO, OE, pharmacological rescue)","pmids":["29853524"],"is_preprint":false},{"year":2018,"finding":"PAFAH1B3 localizes to the meiotic spindle structure at metaphase I and II in bovine, murine, and human oocytes; inhibition of PAFAH1B3 enzymatic activity (by the selective inhibitor P11 or by antibody microinjection) caused arrest at metaphase I with defective spindle morphology and failure of first polar body extrusion, demonstrating a functional role for PAFAH1B3 catalytic activity in meiotic spindle formation.","method":"Immunolocalization across species (bovine, murine, human oocytes); microtubule manipulation (nocodazole, taxol, cryopreservation); selective enzymatic inhibitor (P11); antibody microinjection; assessment of spindle morphology and polar body extrusion","journal":"Reproduction, fertility, and development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (localization, pharmacological inhibition, antibody microinjection) replicated across three species with clear functional readout","pmids":["30008286"],"is_preprint":false},{"year":2024,"finding":"KLF9 directly binds to the promoter of PAFAH1B3 and inhibits its transcriptional activity, thereby negatively regulating PAFAH1B3 expression in pancreatic cancer cells; overexpression of PAFAH1B3 partially rescues the suppression of proliferation, invasion, and migration induced by KLF9 overexpression, placing PAFAH1B3 downstream of KLF9 in this pathway.","method":"Chromatin immunoprecipitation (ChIP); dual-luciferase reporter assay; rescue/epistasis experiment with KLF9 and PAFAH1B3 co-overexpression; western blotting; in vitro and in vivo functional assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and dual-luciferase reporter directly establish transcriptional regulation, with epistasis rescue experiment, single lab","pmids":["38649699"],"is_preprint":false},{"year":2024,"finding":"PAFAH1B3 binds to SMAD7, disrupting SMAD7's interaction with TGF-β receptor 1 (TβR1), which reduces TβR1 ubiquitination and degradation, thereby sustaining TGF-β signaling and driving hepatic stellate cell activation and liver fibrosis; pharmacological inhibition of PAFAH1B3 by 3-IN-P11 attenuated fibrosis in mice.","method":"Co-immunoprecipitation (PAFAH1B3 binding to SMAD7); assessment of TβR1 ubiquitination and degradation; Pafah1b3 knockout mouse model (CCl4-induced fibrosis); pharmacological inhibition with 3-IN-P11; western blotting of TGF-β signaling components","journal":"Journal of pharmaceutical analysis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifies binding partner, KO model with pharmacological validation, single lab but multiple orthogonal methods","pmids":["39906692"],"is_preprint":false},{"year":2026,"finding":"PAFAH1B3 coordinates with the transcription factor E2F8 to promote VEGFA transcription in gastric cancer cells; VEGFA overexpression rescues the proliferation and migration defects caused by PAFAH1B3 knockdown, placing VEGFA as a downstream effector in the PAFAH1B3/E2F8/VEGFA pathway.","method":"Transcriptomic profiling of PAFAH1B3 knockdown cells; VEGFA rescue experiment; functional assays (proliferation, migration, apoptosis); xenograft animal models","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transcriptomic profiling plus epistasis rescue experiment and in vivo validation, single lab","pmids":["42140448"],"is_preprint":false},{"year":2021,"finding":"PAFAH1B3 knockdown in osteosarcoma cells inhibited proliferation and promoted apoptosis; ChIP assay indicated that the proliferative effect of PAFAH1B3 is linked to regulation of EIF4EBP1, MYC, PTGS2, and RPS6KB1 expression.","method":"Loss-of-function (siRNA knockdown); tumor xenograft growth assay; ChIP assay; in vitro proliferation and apoptosis assays","journal":"Frontiers in oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — ChIP data links PAFAH1B3 to downstream gene regulation but the mechanism is only partially characterized, single lab, limited orthogonal validation","pmids":["34136395"],"is_preprint":false}],"current_model":"PAFAH1B3 is a catalytic subunit of the heterotrimeric PAF acetylhydrolase 1B complex that hydrolyzes platelet-activating factor (PAF); it interacts with the LIS1 regulatory subunit via its C-terminal domain, localizes to the meiotic spindle where its enzymatic activity is required for spindle formation and meiotic progression, regulates intracellular PAF levels to modulate PAF/PAFR-dependent cell survival signaling, and in multiple cancer contexts promotes cell proliferation and invasion through downstream effectors including VEGFA (via E2F8), EMT-related pathways, and TGF-β signaling (by binding SMAD7 and preventing TβR1 degradation), with its transcription negatively regulated by KLF9."},"narrative":{"mechanistic_narrative":"PAFAH1B3 is a catalytic subunit of the heterotrimeric platelet-activating factor acetylhydrolase 1B complex that hydrolyzes signaling lipids and, through this enzymatic activity, controls intracellular levels of platelet-activating factor (PAF) [PMID:24954006, PMID:29853524]. It assembles into the PAF-AH1B complex via a C-terminal region required for binding the LIS1 regulatory subunit [PMID:11285245]. PAFAH1B3 catalytic activity is functionally essential during oocyte meiosis: the protein localizes to the meiotic spindle at metaphase I and II, and selective enzymatic inhibition or antibody microinjection arrests cells at metaphase I with defective spindle morphology and failed first polar body extrusion [PMID:30008286]. Through its control of PAF/PAFR signaling, PAFAH1B3 supports cell survival, and its loss sensitizes BCR-ABL1 leukemia cells to dasatinib in a PAFR-dependent manner [PMID:29853524]. In multiple cancer and fibrotic contexts PAFAH1B3 drives proliferation, migration, and invasion: it cooperates with E2F8 to promote VEGFA transcription in gastric cancer [PMID:42140448], and it binds SMAD7 to block SMAD7–TβR1 association, reducing TβR1 ubiquitination and sustaining TGF-β signaling to promote hepatic stellate cell activation and liver fibrosis [PMID:39906692]. PAFAH1B3 expression is negatively regulated by KLF9, which binds its promoter and represses transcription [PMID:38649699].","teleology":[{"year":2001,"claim":"Established how PAFAH1B3 is incorporated into the PAF-AH1B complex by mapping the LIS1-binding determinant to its C-terminal region.","evidence":"Characterization of a PAFAH1B3-CLK2 fusion translocation and interaction assays showing a 136-aa N-terminal truncation lost LIS1 binding","pmids":["11285245"],"confidence":"Medium","gaps":["Structural basis of the C-terminal LIS1 interface not resolved","Functional consequence of the fusion protein not established","Catalytic activity of the truncated protein not assessed"]},{"year":2014,"claim":"Linked PAFAH1B3 enzymatic activity to cancer metabolism by showing its loss elevates tumor-suppressing signaling lipids.","evidence":"Metabolomic profiling combined with PAFAH1B3 loss-of-function in breast cancer cell lines","pmids":["24954006"],"confidence":"Medium","gaps":["Specific lipid substrates not definitively assigned","Downstream signaling consequences of altered lipids not mapped","Single-lab cell-line evidence"]},{"year":2018,"claim":"Connected PAFAH1B3 lipid-hydrolase activity to a survival pathway by showing it controls intracellular PAF and that its loss sensitizes leukemia cells to TKI via PAF/PAFR signaling.","evidence":"In vivo/in vitro RNAi screens, KO and overexpression cell lines, and PAFR antagonist rescue in a BCR-ABL1 BCP-ALL mouse model","pmids":["29853524"],"confidence":"Medium","gaps":["Only partial reversal by PAFR antagonism indicates additional effectors","Mechanism linking PAF levels to TKI sensitivity not fully resolved"]},{"year":2018,"claim":"Demonstrated a catalysis-dependent cellular role for PAFAH1B3 in meiosis by localizing it to the meiotic spindle and showing enzymatic inhibition arrests metaphase I.","evidence":"Cross-species immunolocalization (bovine, murine, human oocytes) with selective inhibitor P11 and antibody microinjection scoring spindle morphology and polar body extrusion","pmids":["30008286"],"confidence":"High","gaps":["Lipid substrate(s) acted on at the spindle not identified","Molecular link between PAF hydrolysis and microtubule organization unknown"]},{"year":2021,"claim":"Began to map proliferative downstream effectors of PAFAH1B3 in osteosarcoma.","evidence":"siRNA knockdown, xenograft growth, ChIP, and proliferation/apoptosis assays linking PAFAH1B3 to EIF4EBP1, MYC, PTGS2, and RPS6KB1","pmids":["34136395"],"confidence":"Low","gaps":["Mechanism only partially characterized with limited orthogonal validation","Direct vs. indirect regulation of the named genes not distinguished","No biochemical link to PAFAH1B3 enzymatic activity"]},{"year":2024,"claim":"Identified an upstream transcriptional repressor by showing KLF9 directly binds the PAFAH1B3 promoter to suppress its expression.","evidence":"ChIP, dual-luciferase reporter, and KLF9/PAFAH1B3 co-overexpression rescue in pancreatic cancer cells with in vitro and in vivo assays","pmids":["38649699"],"confidence":"Medium","gaps":["Only partial rescue indicates additional KLF9 targets","Regulation in non-pancreatic contexts not tested"]},{"year":2024,"claim":"Defined a non-canonical scaffold function whereby PAFAH1B3 sustains TGF-β signaling by sequestering SMAD7 to stabilize TβR1.","evidence":"Co-IP of PAFAH1B3 with SMAD7, TβR1 ubiquitination/degradation assays, Pafah1b3 KO CCl4 fibrosis model, and pharmacological inhibition with 3-IN-P11","pmids":["39906692"],"confidence":"Medium","gaps":["Whether SMAD7 binding requires catalytic activity is unclear","Reciprocal validation and structural detail of the SMAD7 interface lacking"]},{"year":2026,"claim":"Placed VEGFA downstream of PAFAH1B3 via cooperation with E2F8 to drive gastric cancer proliferation and migration.","evidence":"Transcriptomic profiling of knockdown cells, VEGFA rescue experiment, functional assays, and xenograft models","pmids":["42140448"],"confidence":"Medium","gaps":["Direct physical interaction between PAFAH1B3 and E2F8 not established","Link to lipid-hydrolase activity not defined"]},{"year":null,"claim":"How PAFAH1B3's lipid-hydrolase activity mechanistically connects its diverse roles — meiotic spindle assembly, PAF/PAFR survival signaling, and its scaffold/transcriptional effects in cancer and fibrosis — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Whether catalytic vs. scaffold functions are separable is untested","No structural model of the active site or partner interfaces","Direct lipid substrate identities across contexts not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1,2,3]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[5]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,5]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[3]}],"complexes":["PAF acetylhydrolase 1B (PAF-AH1B)"],"partners":["PAFAH1B1/LIS1","SMAD7","E2F8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q15102","full_name":"Platelet-activating factor acetylhydrolase IB subunit alpha1","aliases":["PAF acetylhydrolase 29 kDa subunit","PAF-AH 29 kDa subunit","PAF-AH subunit gamma","PAFAH subunit gamma"],"length_aa":231,"mass_kda":25.7,"function":"Alpha1 catalytic subunit of the cytosolic type I platelet-activating factor (PAF) acetylhydrolase (PAF-AH (I)) heterotetrameric enzyme that catalyzes the hydrolyze of the acetyl group at the sn-2 position of PAF and its analogs and modulates the action of PAF. The activity and substrate specificity of PAF-AH (I) are affected by its subunit composition. Both alpha1/alpha1 homodimer (PAFAH1B3/PAFAH1B3 homodimer) and alpha1/alpha2 heterodimer(PAFAH1B3/PAFAH1B2 heterodimer) hydrolyze 1-O-alkyl-2-acetyl-sn-glycero-3-phosphoric acid (AAGPA) more efficiently than PAF, but they have little hydrolytic activity towards 1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylethanolamine (AAGPE). Plays an important role during the development of brain","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q15102/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PAFAH1B3","classification":"Not Classified","n_dependent_lines":23,"n_total_lines":1208,"dependency_fraction":0.01903973509933775},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PAFAH1B3","total_profiled":1310},"omim":[{"mim_id":"612082","title":"CAPICUA TRANSCRIPTIONAL REPRESSOR; CIC","url":"https://www.omim.org/entry/612082"},{"mim_id":"608223","title":"ASPIRIN RESISTANCE","url":"https://www.omim.org/entry/608223"},{"mim_id":"603074","title":"PLATELET-ACTIVATING FACTOR ACETYLHYDROLASE, ISOFORM 1B, GAMMA SUBUNIT; PAFAH1B3","url":"https://www.omim.org/entry/603074"},{"mim_id":"602989","title":"CDC-LIKE KINASE 2; CLK2","url":"https://www.omim.org/entry/602989"},{"mim_id":"602508","title":"PLATELET-ACTIVATING FACTOR ACETYLHYDROLASE, ISOFORM 1B, BETA SUBUNIT; PAFAH1B2","url":"https://www.omim.org/entry/602508"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Intermediate filaments","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PAFAH1B3"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q15102","domains":[{"cath_id":"3.40.50.1110","chopping":"7-219","consensus_level":"high","plddt":97.8714,"start":7,"end":219}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15102","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15102-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15102-F1-predicted_aligned_error_v6.png","plddt_mean":94.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PAFAH1B3","jax_strain_url":"https://www.jax.org/strain/search?query=PAFAH1B3"},"sequence":{"accession":"Q15102","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15102.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15102/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15102"}},"corpus_meta":[{"pmid":"11285245","id":"PMC_11285245","title":"Functional hemizygosity of PAFAH1B3 due to a PAFAH1B3-CLK2 fusion gene in a female with mental retardation, ataxia and atrophy of the brain.","date":"2001","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11285245","citation_count":48,"is_preprint":false},{"pmid":"24954006","id":"PMC_24954006","title":"Metabolic profiling reveals PAFAH1B3 as a critical driver of breast cancer pathogenicity.","date":"2014","source":"Chemistry & biology","url":"https://pubmed.ncbi.nlm.nih.gov/24954006","citation_count":45,"is_preprint":false},{"pmid":"34136395","id":"PMC_34136395","title":"Aberrant Expression of PAFAH1B3 Affects Proliferation and Apoptosis in Osteosarcoma.","date":"2021","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34136395","citation_count":12,"is_preprint":false},{"pmid":"29853524","id":"PMC_29853524","title":"In vivo RNAi screening identifies Pafah1b3 as a target for combination therapy with TKIs in BCR-ABL1 BCP-ALL.","date":"2018","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/29853524","citation_count":12,"is_preprint":false},{"pmid":"30008286","id":"PMC_30008286","title":"Platelet-activating factor acetylhydrolase 1B3 (PAFAH1B3) is required for the formation of the meiotic spindle during in vitro oocyte maturation.","date":"2018","source":"Reproduction, fertility, and development","url":"https://pubmed.ncbi.nlm.nih.gov/30008286","citation_count":8,"is_preprint":false},{"pmid":"37102492","id":"PMC_37102492","title":"PAFAH1B3 Regulates Papillary Thyroid Carcinoma Cell Proliferation and Metastasis by Affecting the EMT.","date":"2024","source":"Current medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37102492","citation_count":7,"is_preprint":false},{"pmid":"39553628","id":"PMC_39553628","title":"Comparative proteomic analysis between tumor tissues and intratumoral exosomes from lung adenocarcinoma patients identifies PAFAH1B3 as an exosomal protein key for initiating metastasis in lung adenocarcinoma.","date":"2024","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/39553628","citation_count":4,"is_preprint":false},{"pmid":"38649699","id":"PMC_38649699","title":"PAFAH1B3 is a KLF9 target gene that promotes proliferation and metastasis in pancreatic cancer.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38649699","citation_count":3,"is_preprint":false},{"pmid":"39906692","id":"PMC_39906692","title":"Unveiling the role of Pafah1b3 in liver fibrosis: A novel mechanism revealed.","date":"2024","source":"Journal of pharmaceutical analysis","url":"https://pubmed.ncbi.nlm.nih.gov/39906692","citation_count":1,"is_preprint":false},{"pmid":"41009369","id":"PMC_41009369","title":"PAFAH1B3 Exists in Linear Chromosomal and Extrachromosomal Circular DNA and Promotes HCC Progression via EMT.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41009369","citation_count":0,"is_preprint":false},{"pmid":"42140448","id":"PMC_42140448","title":"PAFAH1B3 promotes gastric cancer progression by enhancing E2F8-mediated transcriptional activation of VEGFA expression.","date":"2026","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/42140448","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7553,"output_tokens":2368,"usd":0.02909,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9497,"output_tokens":3004,"usd":0.061292,"stage2_stop_reason":"end_turn"},"total_usd":0.090382,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"The PAFAH1B3 protein interacts with LIS1 as part of the heterotrimeric PAF-AH1B complex; a truncated PAFAH1B3 (first 136 amino acids) encoded by a PAFAH1B3-CLK2 fusion gene lost its ability to interact with LIS1, demonstrating that the C-terminal portion of PAFAH1B3 is required for LIS1 binding.\",\n      \"method\": \"Molecular characterization of chromosomal translocation breakpoints; expression analysis of fusion protein; interaction assay showing loss of LIS1 binding by truncated PAFAH1B3\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction and loss-of-function experiment with defined molecular truncation, single lab but mechanistically clear\",\n      \"pmids\": [\"11285245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PAFAH1B3 inactivation in breast cancer cells alters the levels of signaling lipids (consistent with its role as a PAF acetylhydrolase), and metabolomic profiling showed that PAFAH1B3 loss enhances tumor-suppressing signaling lipids, placing PAFAH1B3 as a critical metabolic node whose enzymatic activity drives cancer pathogenicity.\",\n      \"method\": \"Metabolic mapping/metabolomic profiling; loss-of-function (PAFAH1B3 inactivation) with metabolomic readout in breast cancer cell lines\",\n      \"journal\": \"Chemistry & biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — metabolomic profiling combined with loss-of-function, single lab, two orthogonal methods (metabolomics + cell-based functional assays)\",\n      \"pmids\": [\"24954006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PAFAH1B3 regulates intracellular levels of platelet-activating factor (PAF); loss of Pafah1b3 sensitizes BCR-ABL1 BCP-ALL leukemia cells to TKI dasatinib in vivo, and this sensitization is partially reversed by antagonism of the PAF receptor (PAFR), indicating that PAFAH1B3-controlled PAF/PAFR signaling mediates leukemia cell survival in the microenvironment.\",\n      \"method\": \"In vivo and in vitro RNAi screens; Pafah1b3 KO vs. overexpressing cell lines; PAFR antagonist rescue experiment in mouse model of BCR-ABL1 BCP-ALL\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo RNAi screen with mechanistic rescue by PAFR antagonist, single lab but multiple approaches (KO, OE, pharmacological rescue)\",\n      \"pmids\": [\"29853524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PAFAH1B3 localizes to the meiotic spindle structure at metaphase I and II in bovine, murine, and human oocytes; inhibition of PAFAH1B3 enzymatic activity (by the selective inhibitor P11 or by antibody microinjection) caused arrest at metaphase I with defective spindle morphology and failure of first polar body extrusion, demonstrating a functional role for PAFAH1B3 catalytic activity in meiotic spindle formation.\",\n      \"method\": \"Immunolocalization across species (bovine, murine, human oocytes); microtubule manipulation (nocodazole, taxol, cryopreservation); selective enzymatic inhibitor (P11); antibody microinjection; assessment of spindle morphology and polar body extrusion\",\n      \"journal\": \"Reproduction, fertility, and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (localization, pharmacological inhibition, antibody microinjection) replicated across three species with clear functional readout\",\n      \"pmids\": [\"30008286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KLF9 directly binds to the promoter of PAFAH1B3 and inhibits its transcriptional activity, thereby negatively regulating PAFAH1B3 expression in pancreatic cancer cells; overexpression of PAFAH1B3 partially rescues the suppression of proliferation, invasion, and migration induced by KLF9 overexpression, placing PAFAH1B3 downstream of KLF9 in this pathway.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP); dual-luciferase reporter assay; rescue/epistasis experiment with KLF9 and PAFAH1B3 co-overexpression; western blotting; in vitro and in vivo functional assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and dual-luciferase reporter directly establish transcriptional regulation, with epistasis rescue experiment, single lab\",\n      \"pmids\": [\"38649699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PAFAH1B3 binds to SMAD7, disrupting SMAD7's interaction with TGF-β receptor 1 (TβR1), which reduces TβR1 ubiquitination and degradation, thereby sustaining TGF-β signaling and driving hepatic stellate cell activation and liver fibrosis; pharmacological inhibition of PAFAH1B3 by 3-IN-P11 attenuated fibrosis in mice.\",\n      \"method\": \"Co-immunoprecipitation (PAFAH1B3 binding to SMAD7); assessment of TβR1 ubiquitination and degradation; Pafah1b3 knockout mouse model (CCl4-induced fibrosis); pharmacological inhibition with 3-IN-P11; western blotting of TGF-β signaling components\",\n      \"journal\": \"Journal of pharmaceutical analysis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifies binding partner, KO model with pharmacological validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"39906692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"PAFAH1B3 coordinates with the transcription factor E2F8 to promote VEGFA transcription in gastric cancer cells; VEGFA overexpression rescues the proliferation and migration defects caused by PAFAH1B3 knockdown, placing VEGFA as a downstream effector in the PAFAH1B3/E2F8/VEGFA pathway.\",\n      \"method\": \"Transcriptomic profiling of PAFAH1B3 knockdown cells; VEGFA rescue experiment; functional assays (proliferation, migration, apoptosis); xenograft animal models\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transcriptomic profiling plus epistasis rescue experiment and in vivo validation, single lab\",\n      \"pmids\": [\"42140448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PAFAH1B3 knockdown in osteosarcoma cells inhibited proliferation and promoted apoptosis; ChIP assay indicated that the proliferative effect of PAFAH1B3 is linked to regulation of EIF4EBP1, MYC, PTGS2, and RPS6KB1 expression.\",\n      \"method\": \"Loss-of-function (siRNA knockdown); tumor xenograft growth assay; ChIP assay; in vitro proliferation and apoptosis assays\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — ChIP data links PAFAH1B3 to downstream gene regulation but the mechanism is only partially characterized, single lab, limited orthogonal validation\",\n      \"pmids\": [\"34136395\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PAFAH1B3 is a catalytic subunit of the heterotrimeric PAF acetylhydrolase 1B complex that hydrolyzes platelet-activating factor (PAF); it interacts with the LIS1 regulatory subunit via its C-terminal domain, localizes to the meiotic spindle where its enzymatic activity is required for spindle formation and meiotic progression, regulates intracellular PAF levels to modulate PAF/PAFR-dependent cell survival signaling, and in multiple cancer contexts promotes cell proliferation and invasion through downstream effectors including VEGFA (via E2F8), EMT-related pathways, and TGF-β signaling (by binding SMAD7 and preventing TβR1 degradation), with its transcription negatively regulated by KLF9.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PAFAH1B3 is a catalytic subunit of the heterotrimeric platelet-activating factor acetylhydrolase 1B complex that hydrolyzes signaling lipids and, through this enzymatic activity, controls intracellular levels of platelet-activating factor (PAF) [#1, #2]. It assembles into the PAF-AH1B complex via a C-terminal region required for binding the LIS1 regulatory subunit [#0]. PAFAH1B3 catalytic activity is functionally essential during oocyte meiosis: the protein localizes to the meiotic spindle at metaphase I and II, and selective enzymatic inhibition or antibody microinjection arrests cells at metaphase I with defective spindle morphology and failed first polar body extrusion [#3]. Through its control of PAF/PAFR signaling, PAFAH1B3 supports cell survival, and its loss sensitizes BCR-ABL1 leukemia cells to dasatinib in a PAFR-dependent manner [#2]. In multiple cancer and fibrotic contexts PAFAH1B3 drives proliferation, migration, and invasion: it cooperates with E2F8 to promote VEGFA transcription in gastric cancer [#6], and it binds SMAD7 to block SMAD7–TβR1 association, reducing TβR1 ubiquitination and sustaining TGF-β signaling to promote hepatic stellate cell activation and liver fibrosis [#5]. PAFAH1B3 expression is negatively regulated by KLF9, which binds its promoter and represses transcription [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established how PAFAH1B3 is incorporated into the PAF-AH1B complex by mapping the LIS1-binding determinant to its C-terminal region.\",\n      \"evidence\": \"Characterization of a PAFAH1B3-CLK2 fusion translocation and interaction assays showing a 136-aa N-terminal truncation lost LIS1 binding\",\n      \"pmids\": [\"11285245\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the C-terminal LIS1 interface not resolved\", \"Functional consequence of the fusion protein not established\", \"Catalytic activity of the truncated protein not assessed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked PAFAH1B3 enzymatic activity to cancer metabolism by showing its loss elevates tumor-suppressing signaling lipids.\",\n      \"evidence\": \"Metabolomic profiling combined with PAFAH1B3 loss-of-function in breast cancer cell lines\",\n      \"pmids\": [\"24954006\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific lipid substrates not definitively assigned\", \"Downstream signaling consequences of altered lipids not mapped\", \"Single-lab cell-line evidence\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected PAFAH1B3 lipid-hydrolase activity to a survival pathway by showing it controls intracellular PAF and that its loss sensitizes leukemia cells to TKI via PAF/PAFR signaling.\",\n      \"evidence\": \"In vivo/in vitro RNAi screens, KO and overexpression cell lines, and PAFR antagonist rescue in a BCR-ABL1 BCP-ALL mouse model\",\n      \"pmids\": [\"29853524\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only partial reversal by PAFR antagonism indicates additional effectors\", \"Mechanism linking PAF levels to TKI sensitivity not fully resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated a catalysis-dependent cellular role for PAFAH1B3 in meiosis by localizing it to the meiotic spindle and showing enzymatic inhibition arrests metaphase I.\",\n      \"evidence\": \"Cross-species immunolocalization (bovine, murine, human oocytes) with selective inhibitor P11 and antibody microinjection scoring spindle morphology and polar body extrusion\",\n      \"pmids\": [\"30008286\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Lipid substrate(s) acted on at the spindle not identified\", \"Molecular link between PAF hydrolysis and microtubule organization unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Began to map proliferative downstream effectors of PAFAH1B3 in osteosarcoma.\",\n      \"evidence\": \"siRNA knockdown, xenograft growth, ChIP, and proliferation/apoptosis assays linking PAFAH1B3 to EIF4EBP1, MYC, PTGS2, and RPS6KB1\",\n      \"pmids\": [\"34136395\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Mechanism only partially characterized with limited orthogonal validation\", \"Direct vs. indirect regulation of the named genes not distinguished\", \"No biochemical link to PAFAH1B3 enzymatic activity\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified an upstream transcriptional repressor by showing KLF9 directly binds the PAFAH1B3 promoter to suppress its expression.\",\n      \"evidence\": \"ChIP, dual-luciferase reporter, and KLF9/PAFAH1B3 co-overexpression rescue in pancreatic cancer cells with in vitro and in vivo assays\",\n      \"pmids\": [\"38649699\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only partial rescue indicates additional KLF9 targets\", \"Regulation in non-pancreatic contexts not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a non-canonical scaffold function whereby PAFAH1B3 sustains TGF-β signaling by sequestering SMAD7 to stabilize TβR1.\",\n      \"evidence\": \"Co-IP of PAFAH1B3 with SMAD7, TβR1 ubiquitination/degradation assays, Pafah1b3 KO CCl4 fibrosis model, and pharmacological inhibition with 3-IN-P11\",\n      \"pmids\": [\"39906692\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SMAD7 binding requires catalytic activity is unclear\", \"Reciprocal validation and structural detail of the SMAD7 interface lacking\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Placed VEGFA downstream of PAFAH1B3 via cooperation with E2F8 to drive gastric cancer proliferation and migration.\",\n      \"evidence\": \"Transcriptomic profiling of knockdown cells, VEGFA rescue experiment, functional assays, and xenograft models\",\n      \"pmids\": [\"42140448\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction between PAFAH1B3 and E2F8 not established\", \"Link to lipid-hydrolase activity not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PAFAH1B3's lipid-hydrolase activity mechanistically connects its diverse roles — meiotic spindle assembly, PAF/PAFR survival signaling, and its scaffold/transcriptional effects in cancer and fibrosis — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether catalytic vs. scaffold functions are separable is untested\", \"No structural model of the active site or partner interfaces\", \"Direct lipid substrate identities across contexts not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005819\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\"PAF acetylhydrolase 1B (PAF-AH1B)\"],\n    \"partners\": [\"PAFAH1B1/LIS1\", \"SMAD7\", \"E2F8\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}