{"gene":"STXBP3","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2021,"finding":"Damaging heterozygous or biallelic variants in STXBP3 interfere with intron splicing or protein stability, leading to reduced STXBP3 protein expression. Knockdown of STXBP3 in CaCo2 epithelial cells resulted in defects in cell polarity, establishing a role for STXBP3 in intracellular vesicular trafficking and epithelial cell polarity.","method":"Whole exome sequencing, Sanger sequencing, Western blot (protein stability), siRNA knockdown in CaCo2 cells with cell polarity readout","journal":"Journal of Crohn's & colitis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function knockdown with defined cellular phenotype (polarity defect) plus protein stability analysis; single lab, two orthogonal methods","pmids":["33891011"],"is_preprint":false},{"year":2008,"finding":"STXBP3 functions as a vesicle docking inhibitor in enterochromaffin (EC) cells; antisense knockdown of STXBP3 significantly reduced serotonin (5-HT) secretion, indicating STXBP3 regulates secretory vesicle docking/exocytosis in EC cells.","method":"Antisense knockdown of STXBP3 in neoplastic EC cells (KRJ-I) with 5-HT secretion assay","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, loss-of-function with defined secretory phenotype, but single method and limited mechanistic detail in abstract","pmids":["18556422"],"is_preprint":false},{"year":2019,"finding":"STXBP3 (MUNC18-3), unlike MUNC18-1, lacks a hydrophobic residue at the position corresponding to V263 in β-sheet 10 and therefore fails to restore a normal submembrane F-actin network in Munc18-1-KO chromaffin cells. Introduction of a hydrophobic residue at the corresponding position in STXBP3 rescued normal F-actin network organization, demonstrating that this residue governs F-actin regulation independently of syntaxin1 targeting.","method":"Mutagenesis of STXBP3, expression in Munc18-1-KO mouse chromaffin cells, F-actin network imaging","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — active-site/domain mutagenesis with functional rescue readout; single lab but two orthogonal methods (mutagenesis + imaging)","pmids":["31719162"],"is_preprint":false},{"year":2025,"finding":"In a genome-wide CRISPR activation screen, STXBP3 was identified as a SNARE-associated protein that collaborates with MARCKSL1 in regulating extracellular vesicle secretion at the plasma membrane, implicating STXBP3 in SNARE-mediated membrane fusion events relevant to EV biogenesis.","method":"Genome-wide CRISPR activation screen for CD63 surface levels, followed by genomic activation/ablation and proteomic approaches","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — identified as collaborator in a screen-based study; mechanistic role of STXBP3 itself not directly dissected; single preprint, indirect evidence","pmids":["bio_10.1101_2025.07.24.665424"],"is_preprint":true}],"current_model":"STXBP3 (Munc18c/UNC-18C) is a syntaxin-binding protein that regulates intracellular vesicular trafficking and exocytosis: it acts as a vesicle docking regulator in secretory cells (including enterochromaffin and adipocytes controlling GLUT4 trafficking), is required for normal epithelial cell polarity, and—unlike its paralog MUNC18-1—lacks the hydrophobic β-sheet 10 residue needed to regulate the submembrane F-actin network, a function that can be conferred by mutagenesis at that position."},"narrative":{"mechanistic_narrative":"STXBP3 (Munc18c/MUNC18-3) is a syntaxin-binding protein that regulates intracellular vesicular trafficking and regulated exocytosis [PMID:18556422]. In secretory enterochromaffin cells it controls vesicle docking and serotonin release, with loss of STXBP3 reducing 5-HT secretion [PMID:18556422], and in epithelial cells it is required for normal cell polarity, where reduced STXBP3 expression produces polarity defects [PMID:33891011]. Although structurally related to MUNC18-1, STXBP3 lacks the hydrophobic β-sheet 10 residue corresponding to V263 and therefore cannot restore the submembrane F-actin network in Munc18-1-KO chromaffin cells; introducing a hydrophobic residue at that position confers F-actin regulatory activity, establishing that this residue governs F-actin organization independently of syntaxin1 targeting [PMID:31719162].","teleology":[{"year":2008,"claim":"Established that STXBP3 acts in regulated secretion by controlling secretory vesicle docking/exocytosis, defining its functional role in a secretory cell type.","evidence":"Antisense knockdown in neoplastic enterochromaffin cells (KRJ-I) with serotonin secretion assay","pmids":["18556422"],"confidence":"Medium","gaps":["Single method without reciprocal/biochemical validation of the docking step","Direct syntaxin partner in EC cells not identified","No structural basis for the docking activity established"]},{"year":2019,"claim":"Resolved why STXBP3 diverges functionally from MUNC18-1, mapping F-actin regulatory capacity to a single β-sheet 10 hydrophobic residue distinct from syntaxin targeting.","evidence":"Mutagenesis of STXBP3 expressed in Munc18-1-KO mouse chromaffin cells with F-actin network imaging","pmids":["31719162"],"confidence":"Medium","gaps":["Physiological relevance of STXBP3 lacking native F-actin activity not addressed","Molecular mechanism linking the residue to F-actin remodeling not dissected","Endogenous role of this residue in STXBP3-expressing cell types unknown"]},{"year":2021,"claim":"Linked STXBP3 loss-of-function to epithelial cell polarity, extending its trafficking role beyond regulated secretion and connecting it to human disease variants.","evidence":"Whole exome/Sanger sequencing of variants, Western blot for protein stability, and siRNA knockdown in CaCo2 cells with cell polarity readout","pmids":["33891011"],"confidence":"Medium","gaps":["Molecular pathway connecting STXBP3 to polarity machinery not defined","Causality of variants in patient phenotype not established by rescue","Trafficking cargo affected in epithelial cells not identified"]},{"year":2025,"claim":"Implicated STXBP3 in SNARE-mediated membrane fusion underlying extracellular vesicle secretion, broadening its trafficking remit to EV biogenesis.","evidence":"Genome-wide CRISPR activation screen for CD63 surface levels with genomic activation/ablation and proteomics (preprint)","pmids":["bio_10.1101_2025.07.24.665424"],"confidence":"Low","gaps":["Mechanistic role of STXBP3 itself not directly dissected; identified as a screen collaborator","Single preprint, not peer-reviewed or independently confirmed","Direct interaction with MARCKSL1 or the SNARE machinery not validated biochemically"]},{"year":null,"claim":"How STXBP3 selects specific syntaxin partners and coordinates docking across distinct cell types (secretory, epithelial, EV-secreting) remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No defined syntaxin/SNARE binding partner identified in the timeline","No structural model of STXBP3-SNARE complexes","Unified mechanism reconciling secretion, polarity, and EV roles not established"]}],"mechanism_profile":{"molecular_activity":[],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00186","full_name":"Syntaxin-binding protein 3","aliases":["Platelet Sec1 protein","PSP","Protein unc-18 homolog 3","Unc18-3","Protein unc-18 homolog C","Unc-18C"],"length_aa":592,"mass_kda":67.8,"function":"Together with STX4 and VAMP2, may play a role in insulin-dependent movement of GLUT4 and in docking/fusion of intracellular GLUT4-containing vesicles with the cell surface in adipocytes","subcellular_location":"Cytoplasm, cytosol; Cell membrane","url":"https://www.uniprot.org/uniprotkb/O00186/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STXBP3","classification":"Not Classified","n_dependent_lines":341,"n_total_lines":1208,"dependency_fraction":0.28228476821192056},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SLC16A1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/STXBP3","total_profiled":1310},"omim":[{"mim_id":"608339","title":"SYNTAXIN-BINDING PROTEIN 3; STXBP3","url":"https://www.omim.org/entry/608339"},{"mim_id":"186591","title":"SYNTAXIN 4; STX4","url":"https://www.omim.org/entry/186591"},{"mim_id":"138190","title":"SOLUTE CARRIER FAMILY 2 (FACILITATED GLUCOSE TRANSPORTER), MEMBER 4; SLC2A4","url":"https://www.omim.org/entry/138190"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/STXBP3"},"hgnc":{"alias_symbol":["UNC-18C"],"prev_symbol":[]},"alphafold":{"accession":"O00186","domains":[{"cath_id":"3.40.50.2060","chopping":"6-139","consensus_level":"high","plddt":92.7405,"start":6,"end":139},{"cath_id":"3.40.50.1910","chopping":"143-244_477-505_519-579","consensus_level":"high","plddt":91.7921,"start":143,"end":579},{"cath_id":"3.90.830.10","chopping":"248-446","consensus_level":"medium","plddt":91.4187,"start":248,"end":446}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00186","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00186-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00186-F1-predicted_aligned_error_v6.png","plddt_mean":89.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=STXBP3","jax_strain_url":"https://www.jax.org/strain/search?query=STXBP3"},"sequence":{"accession":"O00186","fasta_url":"https://rest.uniprot.org/uniprotkb/O00186.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00186/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00186"}},"corpus_meta":[{"pmid":"18556422","id":"PMC_18556422","title":"Luminal regulation of normal and neoplastic human EC cell serotonin release is mediated by bile salts, amines, tastants, and olfactants.","date":"2008","source":"American journal of physiology. Gastrointestinal and liver physiology","url":"https://pubmed.ncbi.nlm.nih.gov/18556422","citation_count":192,"is_preprint":false},{"pmid":"22482075","id":"PMC_22482075","title":"Analyzing microarray data of Alzheimer's using cluster analysis to identify the biomarker genes.","date":"2012","source":"International journal of Alzheimer's disease","url":"https://pubmed.ncbi.nlm.nih.gov/22482075","citation_count":46,"is_preprint":false},{"pmid":"21897333","id":"PMC_21897333","title":"Genes linked to energy metabolism and immunoregulatory mechanisms are associated with subcutaneous adipose tissue distribution in HIV-infected men.","date":"2011","source":"Pharmacogenetics and genomics","url":"https://pubmed.ncbi.nlm.nih.gov/21897333","citation_count":17,"is_preprint":false},{"pmid":"35205299","id":"PMC_35205299","title":"Genomic Diversity Profiling and Breed-Specific Evolutionary Signatures of Selection in Arunachali Yak.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/35205299","citation_count":17,"is_preprint":false},{"pmid":"23478142","id":"PMC_23478142","title":"Lipoprotein lipase in chronic lymphocytic leukaemia - strong biomarker with lack of functional significance.","date":"2013","source":"Leukemia research","url":"https://pubmed.ncbi.nlm.nih.gov/23478142","citation_count":15,"is_preprint":false},{"pmid":"32292414","id":"PMC_32292414","title":"Genome-Wide Association Study and Fine Mapping Reveals Candidate Genes for Birth Weight of Yorkshire and Landrace Pigs.","date":"2020","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32292414","citation_count":14,"is_preprint":false},{"pmid":"33891011","id":"PMC_33891011","title":"Variants in STXBP3 are Associated with Very Early Onset Inflammatory Bowel Disease, Bilateral Sensorineural Hearing Loss and Immune Dysregulation.","date":"2021","source":"Journal of Crohn's & colitis","url":"https://pubmed.ncbi.nlm.nih.gov/33891011","citation_count":11,"is_preprint":false},{"pmid":"25028245","id":"PMC_25028245","title":"Munc18c: a controversial regulator of peripheral insulin action.","date":"2014","source":"Trends in endocrinology and metabolism: TEM","url":"https://pubmed.ncbi.nlm.nih.gov/25028245","citation_count":11,"is_preprint":false},{"pmid":"31719162","id":"PMC_31719162","title":"MUNC18-1 regulates the submembrane F-actin network, independently of syntaxin1 targeting, via hydrophobicity in β-sheet 10.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/31719162","citation_count":6,"is_preprint":false},{"pmid":"18597059","id":"PMC_18597059","title":"Genes that code for T cell signaling proteins establish transcriptional regulatory networks during thymus ontogeny.","date":"2008","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18597059","citation_count":6,"is_preprint":false},{"pmid":"38062110","id":"PMC_38062110","title":"Integrated omics analysis of coronary artery calcifications and myocardial infarction: the Framingham Heart Study.","date":"2023","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38062110","citation_count":4,"is_preprint":false},{"pmid":"36532048","id":"PMC_36532048","title":"STXBP3 and GOT2 predict immunological activity in acute allograft rejection.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36532048","citation_count":3,"is_preprint":false},{"pmid":"40764951","id":"PMC_40764951","title":"Multi-omics insights into functional alterations of the liver in growth-retarded offspring: transcriptomic, epigenetic and metabolomic profiles.","date":"2025","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/40764951","citation_count":3,"is_preprint":false},{"pmid":"40748624","id":"PMC_40748624","title":"Identify new pseudogene RPL7P1-oriented network as a drug target against infections pre-existing diabetes.","date":"2025","source":"Integrative biology : quantitative biosciences from nano to macro","url":"https://pubmed.ncbi.nlm.nih.gov/40748624","citation_count":1,"is_preprint":false},{"pmid":"40790764","id":"PMC_40790764","title":"The mitochondrial hub gene UCHL1 May serve as a potential biomarker for diagnosing diabetic cardiomyopathy: a comprehensive integration of biological pathways.","date":"2025","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/40790764","citation_count":0,"is_preprint":false},{"pmid":"42072699","id":"PMC_42072699","title":"Remodeling of the circRNA Landscape in Myocardial Infarction Integrates Nuclear Regulation, DNA Damage Response, and Cardiomyocyte Structural Pathways.","date":"2026","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/42072699","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.24.665424","title":"CRISPR activation screen uncovers MARCKSL1 as a gauge for extracellular vesicle secretion","date":"2025-07-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.24.665424","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11276,"output_tokens":1197,"usd":0.025892,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7735,"output_tokens":1792,"usd":0.041737,"stage2_stop_reason":"end_turn"},"total_usd":0.067629,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"Damaging heterozygous or biallelic variants in STXBP3 interfere with intron splicing or protein stability, leading to reduced STXBP3 protein expression. Knockdown of STXBP3 in CaCo2 epithelial cells resulted in defects in cell polarity, establishing a role for STXBP3 in intracellular vesicular trafficking and epithelial cell polarity.\",\n      \"method\": \"Whole exome sequencing, Sanger sequencing, Western blot (protein stability), siRNA knockdown in CaCo2 cells with cell polarity readout\",\n      \"journal\": \"Journal of Crohn's & colitis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function knockdown with defined cellular phenotype (polarity defect) plus protein stability analysis; single lab, two orthogonal methods\",\n      \"pmids\": [\"33891011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"STXBP3 functions as a vesicle docking inhibitor in enterochromaffin (EC) cells; antisense knockdown of STXBP3 significantly reduced serotonin (5-HT) secretion, indicating STXBP3 regulates secretory vesicle docking/exocytosis in EC cells.\",\n      \"method\": \"Antisense knockdown of STXBP3 in neoplastic EC cells (KRJ-I) with 5-HT secretion assay\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, loss-of-function with defined secretory phenotype, but single method and limited mechanistic detail in abstract\",\n      \"pmids\": [\"18556422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"STXBP3 (MUNC18-3), unlike MUNC18-1, lacks a hydrophobic residue at the position corresponding to V263 in β-sheet 10 and therefore fails to restore a normal submembrane F-actin network in Munc18-1-KO chromaffin cells. Introduction of a hydrophobic residue at the corresponding position in STXBP3 rescued normal F-actin network organization, demonstrating that this residue governs F-actin regulation independently of syntaxin1 targeting.\",\n      \"method\": \"Mutagenesis of STXBP3, expression in Munc18-1-KO mouse chromaffin cells, F-actin network imaging\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site/domain mutagenesis with functional rescue readout; single lab but two orthogonal methods (mutagenesis + imaging)\",\n      \"pmids\": [\"31719162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a genome-wide CRISPR activation screen, STXBP3 was identified as a SNARE-associated protein that collaborates with MARCKSL1 in regulating extracellular vesicle secretion at the plasma membrane, implicating STXBP3 in SNARE-mediated membrane fusion events relevant to EV biogenesis.\",\n      \"method\": \"Genome-wide CRISPR activation screen for CD63 surface levels, followed by genomic activation/ablation and proteomic approaches\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — identified as collaborator in a screen-based study; mechanistic role of STXBP3 itself not directly dissected; single preprint, indirect evidence\",\n      \"pmids\": [\"bio_10.1101_2025.07.24.665424\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"STXBP3 (Munc18c/UNC-18C) is a syntaxin-binding protein that regulates intracellular vesicular trafficking and exocytosis: it acts as a vesicle docking regulator in secretory cells (including enterochromaffin and adipocytes controlling GLUT4 trafficking), is required for normal epithelial cell polarity, and—unlike its paralog MUNC18-1—lacks the hydrophobic β-sheet 10 residue needed to regulate the submembrane F-actin network, a function that can be conferred by mutagenesis at that position.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STXBP3 (Munc18c/MUNC18-3) is a syntaxin-binding protein that regulates intracellular vesicular trafficking and regulated exocytosis [#1]. In secretory enterochromaffin cells it controls vesicle docking and serotonin release, with loss of STXBP3 reducing 5-HT secretion [#1], and in epithelial cells it is required for normal cell polarity, where reduced STXBP3 expression produces polarity defects [#0]. Although structurally related to MUNC18-1, STXBP3 lacks the hydrophobic β-sheet 10 residue corresponding to V263 and therefore cannot restore the submembrane F-actin network in Munc18-1-KO chromaffin cells; introducing a hydrophobic residue at that position confers F-actin regulatory activity, establishing that this residue governs F-actin organization independently of syntaxin1 targeting [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that STXBP3 acts in regulated secretion by controlling secretory vesicle docking/exocytosis, defining its functional role in a secretory cell type.\",\n      \"evidence\": \"Antisense knockdown in neoplastic enterochromaffin cells (KRJ-I) with serotonin secretion assay\",\n      \"pmids\": [\"18556422\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\n        \"Single method without reciprocal/biochemical validation of the docking step\",\n        \"Direct syntaxin partner in EC cells not identified\",\n        \"No structural basis for the docking activity established\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved why STXBP3 diverges functionally from MUNC18-1, mapping F-actin regulatory capacity to a single β-sheet 10 hydrophobic residue distinct from syntaxin targeting.\",\n      \"evidence\": \"Mutagenesis of STXBP3 expressed in Munc18-1-KO mouse chromaffin cells with F-actin network imaging\",\n      \"pmids\": [\"31719162\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\n        \"Physiological relevance of STXBP3 lacking native F-actin activity not addressed\",\n        \"Molecular mechanism linking the residue to F-actin remodeling not dissected\",\n        \"Endogenous role of this residue in STXBP3-expressing cell types unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked STXBP3 loss-of-function to epithelial cell polarity, extending its trafficking role beyond regulated secretion and connecting it to human disease variants.\",\n      \"evidence\": \"Whole exome/Sanger sequencing of variants, Western blot for protein stability, and siRNA knockdown in CaCo2 cells with cell polarity readout\",\n      \"pmids\": [\"33891011\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\n        \"Molecular pathway connecting STXBP3 to polarity machinery not defined\",\n        \"Causality of variants in patient phenotype not established by rescue\",\n        \"Trafficking cargo affected in epithelial cells not identified\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated STXBP3 in SNARE-mediated membrane fusion underlying extracellular vesicle secretion, broadening its trafficking remit to EV biogenesis.\",\n      \"evidence\": \"Genome-wide CRISPR activation screen for CD63 surface levels with genomic activation/ablation and proteomics (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.07.24.665424\"],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\n        \"Mechanistic role of STXBP3 itself not directly dissected; identified as a screen collaborator\",\n        \"Single preprint, not peer-reviewed or independently confirmed\",\n        \"Direct interaction with MARCKSL1 or the SNARE machinery not validated biochemically\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How STXBP3 selects specific syntaxin partners and coordinates docking across distinct cell types (secretory, epithelial, EV-secreting) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\n        \"No defined syntaxin/SNARE binding partner identified in the timeline\",\n        \"No structural model of STXBP3-SNARE complexes\",\n        \"Unified mechanism reconciling secretion, polarity, and EV roles not established\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":3,"faith_pct":100.0}}