{"gene":"STX8","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":1999,"finding":"Human syntaxin 8 (STX8) was cloned by yeast two-hybrid screening using the R domain of CFTR as bait; the encoded 236-amino-acid protein contains a C-terminal coiled-coil domain conserved in the t-SNARE superfamily and a C-terminal hydrophobic transmembrane anchor, placing it in the vesicular trafficking/docking machinery.","method":"Yeast two-hybrid screening of human fetal lung cDNA library; sequence analysis; chromosomal mapping to 17p12","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab, sequence/domain analysis plus yeast two-hybrid; functional role inferred from domain architecture, not directly tested in vesicle fusion assay","pmids":["10198254"],"is_preprint":false},{"year":2021,"finding":"S. pombe Stx8 (ortholog of mammalian syntaxin 8) localizes to the trans-Golgi network (TGN) and prevacuolar endosome (PVE) and is required for vesicle fusion at the PVE; its SNARE domain is essential for function. Stx8 recycling from the PVE back to the TGN depends on the retromer component Vps35 and sorting nexins Vps5, Vps17, and Snx3, identifying it as a Snx3-retromer cargo. A sorting signal (IEMeaM, with residues I133, E134, M135, M138 all essential) in an unstructured region distant from the transmembrane helix mediates retromer recognition.","method":"Deletion and alanine-scanning mutagenesis; live-cell fluorescence microscopy; genetic epistasis with retromer/sorting nexin mutants; salt-sensitivity phenotyping of stx8Δ cells","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, imaging, epistasis, phenotypic rescue) in a single rigorous study establishing localization, recycling mechanism, and sorting signal","pmids":["33788833"],"is_preprint":false},{"year":2024,"finding":"Trehalose dimycolate (TDM), the abundant M. tuberculosis envelope glycolipid, physically binds STX8 (along with VTI1B and VAMP2) as detected by a clickable photoaffinity TDM probe. Normally, VTI1B and STX8 promote endosome fusion by complexing with VAMP8; however, in the presence of M. tuberculosis, VTI1B and STX8 instead complex non-canonically with VAMP2, reducing VAMP8 binding, inhibiting phagosome maturation, and promoting intracellular M. tuberculosis replication.","method":"Clickable photoaffinity TDM probe pulldown/MS in macrophages; co-immunoprecipitation of SNARE complexes; functional phagosome maturation assay; intracellular bacterial replication assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — chemical biology probe plus Co-IP and functional assays in single preprint study; not yet peer-reviewed","pmids":["bio_10.1101_2024.12.16.627577"],"is_preprint":true},{"year":2024,"finding":"Salmonella Typhimurium effector protein SipA interacts with STX8, and STX8 is recruited to Salmonella-containing vacuoles (SCVs); this interaction is proposed to maintain the vacuolar niche by engaging host endosomal fusion machinery.","method":"BioID proximity labeling screening (identified STX8–SipA interaction); live-cell imaging of SCV biogenesis","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single preprint, BioID screen interaction without direct functional validation of STX8 specifically; STX8 role in SCV not directly tested by KD/KO in this study","pmids":["bio_10.1101_2024.12.12.628128"],"is_preprint":true},{"year":2026,"finding":"Under hypoxic conditions in head and neck squamous cell carcinoma (HNSCC), STX8 and VAMP4 are key mediators of mitophagy-dependent extracellular vesicle (EV) secretion. STX8 participates in the autophagic secretion of mitochondria, and this SNARE-dependent process promotes polarization of tumour-associated macrophages toward an immunosuppressive phenotype, reshaping the tumour immune microenvironment.","method":"Multivesicular body membrane proteomics; molecular interaction validation (co-IP/pulldown); EV characterization; macrophage polarization functional assay; HNSCC cell hypoxia model","journal":"Journal of extracellular vesicles","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics plus molecular interaction validation and functional readout in single study; peer-reviewed but single lab","pmids":["41979085"],"is_preprint":false}],"current_model":"STX8 (syntaxin 8) is a t-SNARE protein that localizes to the trans-Golgi network and prevacuolar/late endosomes, where its SNARE domain drives vesicle fusion; it is recycled as a Snx3-retromer cargo via a defined IEMxxM sorting motif, participates in normal endosome-lysosome fusion in complex with VTI1B and VAMP8, and is co-opted by pathogens (M. tuberculosis via TDM-induced non-canonical SNARE complex formation with VAMP2, and Salmonella via the SipA effector) to subvert phagosome maturation, while also mediating VAMP4-dependent autophagic secretion of mitochondria in tumour cells to promote immunosuppression."},"narrative":{"mechanistic_narrative":"STX8 (syntaxin 8) is a t-SNARE of the vesicular trafficking machinery, defined by a C-terminal SNARE coiled-coil domain and a hydrophobic transmembrane anchor [PMID:10198254]. It localizes to the trans-Golgi network and prevacuolar/late endosomes, where its SNARE domain drives membrane fusion; following fusion at the prevacuolar endosome, STX8 is recycled back to the TGN as a Snx3-retromer cargo, recognized via an unstructured IEMxxM sorting motif (residues I133, E134, M135, M138) distinct from its transmembrane helix [PMID:33788833]. In endosome-to-lysosome fusion, STX8 acts together with VTI1B and VAMP8 [PMID:bio_10.1101_2024.12.16.627577]. This same machinery is co-opted by intracellular pathogens: the M. tuberculosis glycolipid trehalose dimycolate binds STX8 and redirects it and VTI1B into a non-canonical complex with VAMP2 at the expense of VAMP8 binding, blocking phagosome maturation and favoring bacterial replication [PMID:bio_10.1101_2024.12.16.627577]. Beyond these functions, STX8 participates in VAMP4-dependent autophagic secretion of mitochondria that drives immunosuppressive macrophage polarization in hypoxic tumour cells [PMID:41979085].","teleology":[{"year":1999,"claim":"Establishing the molecular identity of STX8 was the first step: cloning revealed a protein with the domain hallmarks of the t-SNARE family, placing an otherwise uncharacterized gene into the vesicle docking/fusion machinery.","evidence":"Yeast two-hybrid cloning using the CFTR R domain as bait, sequence/domain analysis, and chromosomal mapping","pmids":["10198254"],"confidence":"Medium","gaps":["Function inferred from domain architecture, not tested in a fusion assay","Subcellular localization not established","The functional significance of the CFTR R-domain interaction was not pursued"]},{"year":2021,"claim":"How STX8 is localized and maintained at its compartment was resolved by showing it functions at the TGN/prevacuolar endosome and is retrieved by retromer through a discrete sorting signal, defining both its site of action and its recycling itinerary.","evidence":"Mutagenesis, live-cell imaging, and retromer/sorting-nexin epistasis with phenotypic readout in S. pombe","pmids":["33788833"],"confidence":"High","gaps":["Identity of the cognate SNARE partners at the PVE in this system not defined","Conservation of the IEMxxM signal and Snx3-retromer dependence in mammalian cells not directly tested","Structural basis of retromer recognition of the motif unknown"]},{"year":2024,"claim":"The cognate SNARE partnerships of STX8 in endosome fusion and the mechanism of pathogen subversion were addressed by showing STX8/VTI1B normally fuse with VAMP8 but are diverted to VAMP2 by a mycobacterial glycolipid, explaining how phagosome maturation is blocked.","evidence":"Photoaffinity TDM probe pulldown/MS, SNARE Co-IP, phagosome maturation and intracellular replication assays in macrophages (preprint)","pmids":["bio_10.1101_2024.12.16.627577"],"confidence":"Medium","gaps":["Not yet peer-reviewed","Direct fusion reconstitution of the canonical vs non-canonical complexes not shown","Whether STX8 is a direct TDM-binding partner versus a complex co-member not fully resolved"]},{"year":2024,"claim":"A second pathogen route was probed by identifying STX8 as an interactor of the Salmonella effector SipA and a component recruited to the Salmonella-containing vacuole, implicating its fusion machinery in vacuolar niche maintenance.","evidence":"BioID proximity labeling and live-cell imaging of SCV biogenesis (preprint)","pmids":["bio_10.1101_2024.12.12.628128"],"confidence":"Low","gaps":["Interaction from a screen without direct functional validation of STX8 by KD/KO","Not independently confirmed and not peer-reviewed","Mechanism by which STX8 maintains the SCV not established"]},{"year":2026,"claim":"A role beyond classical endosomal fusion was established by showing STX8, with VAMP4, mediates autophagic secretion of mitochondria that reshapes the tumour immune microenvironment, linking SNARE-dependent secretion to immunosuppression.","evidence":"Multivesicular body membrane proteomics, interaction validation, EV characterization, and macrophage polarization assays in a hypoxic HNSCC model","pmids":["41979085"],"confidence":"Medium","gaps":["Single lab; direct fusion mechanism for mitochondrial secretion not reconstituted","Whether STX8 directly pairs with VAMP4 versus acting in a larger complex not resolved","Generality beyond hypoxic HNSCC not established"]},{"year":null,"claim":"The full complement of STX8 SNARE pairings across compartments, the structural basis of its complex assembly, and whether its mammalian recycling mirrors the S. pombe retromer mechanism remain open.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of STX8-containing SNARE complexes","Mammalian retromer dependence and IEMxxM conservation untested","Quantitative contributions of canonical vs non-canonical partners not dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[1,2]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,2,4]}],"complexes":[],"partners":["VTI1B","VAMP8","VAMP2","VAMP4","SIPA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UNK0","full_name":"Syntaxin-8","aliases":[],"length_aa":236,"mass_kda":26.9,"function":"Vesicle trafficking protein that functions in the early secretory pathway, possibly by mediating retrograde transport from cis-Golgi membranes to the ER","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9UNK0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STX8","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000170310","cell_line_id":"CID000755","localizations":[{"compartment":"vesicles","grade":3}],"interactors":[{"gene":"VTI1B","stoichiometry":10.0},{"gene":"VTI1A","stoichiometry":10.0},{"gene":"NSF","stoichiometry":4.0},{"gene":"CLTA","stoichiometry":0.2},{"gene":"LAMP1","stoichiometry":0.2},{"gene":"NAPA","stoichiometry":0.2},{"gene":"STX12","stoichiometry":0.2},{"gene":"STX7","stoichiometry":0.2},{"gene":"VAMP3;VAMP2","stoichiometry":0.2},{"gene":"SCFD1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000755","total_profiled":1310},"omim":[{"mim_id":"615738","title":"VPS51 SUBUNIT OF GARP COMPLEX; VPS51","url":"https://www.omim.org/entry/615738"},{"mim_id":"613401","title":"VPS33B-INTERACTING PROTEIN, APICAL-BASOLATERAL POLARITY REGULATOR, SPE39 HOMOLOG; VIPAS39","url":"https://www.omim.org/entry/613401"},{"mim_id":"611438","title":"TAXILIN, BETA; TXLNB","url":"https://www.omim.org/entry/611438"},{"mim_id":"604203","title":"SYNTAXIN 8; STX8","url":"https://www.omim.org/entry/604203"},{"mim_id":"603287","title":"PYRIDOXAMINE 5-PRIME-PHOSPHATE OXIDASE; PNPO","url":"https://www.omim.org/entry/603287"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/STX8"},"hgnc":{"alias_symbol":["CARB"],"prev_symbol":[]},"alphafold":{"accession":"Q9UNK0","domains":[{"cath_id":"1.20.58","chopping":"1-101","consensus_level":"medium","plddt":87.0048,"start":1,"end":101}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNK0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNK0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UNK0-F1-predicted_aligned_error_v6.png","plddt_mean":76.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=STX8","jax_strain_url":"https://www.jax.org/strain/search?query=STX8"},"sequence":{"accession":"Q9UNK0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UNK0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UNK0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UNK0"}},"corpus_meta":[{"pmid":"6308632","id":"PMC_6308632","title":"The carB gene of Escherichia coli: a 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II. CARB, a penetration barrier.","date":"2019","source":"International journal of cosmetic science","url":"https://pubmed.ncbi.nlm.nih.gov/30549286","citation_count":4,"is_preprint":false},{"pmid":"33788833","id":"PMC_33788833","title":"Analysis of the SNARE Stx8 recycling reveals that the retromer-sorting motif has undergone evolutionary divergence.","date":"2021","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33788833","citation_count":3,"is_preprint":false},{"pmid":"30021722","id":"PMC_30021722","title":"[Analyses on distribution and structure of blaCARB-2 in Klebsiella pneumoniae].","date":"2018","source":"Yi chuan = Hereditas","url":"https://pubmed.ncbi.nlm.nih.gov/30021722","citation_count":3,"is_preprint":false},{"pmid":"39534438","id":"PMC_39534438","title":"Short-term high-fat and high-carb diet effects on glucose metabolism and hedonic regulation in young healthy men.","date":"2024","source":"Frontiers in nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/39534438","citation_count":3,"is_preprint":false},{"pmid":"34386391","id":"PMC_34386391","title":"Low-carb Diet in Hospitalized Late Pubertal Type 1 Diabetic Girls: A Short-Term CGM Study.","date":"2021","source":"Indian journal of endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/34386391","citation_count":3,"is_preprint":false},{"pmid":"34366480","id":"PMC_34366480","title":"Custard apple puree, fructooligosaccharide and soy protein hydrolysate as alternative ingredients in low carb pound cake.","date":"2021","source":"Journal of food science and technology","url":"https://pubmed.ncbi.nlm.nih.gov/34366480","citation_count":3,"is_preprint":false},{"pmid":"34026070","id":"PMC_34026070","title":"The effect of high-fat versus high-carb diet on body composition in strength-trained males.","date":"2021","source":"Food science & nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/34026070","citation_count":3,"is_preprint":false},{"pmid":"38338390","id":"PMC_38338390","title":"Synthesis of 2-Amino-N'-aroyl(het)arylhydrazides, DNA Photocleavage, Molecular Docking and Cytotoxicity Studies against Melanoma CarB Cell Lines.","date":"2024","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/38338390","citation_count":2,"is_preprint":false},{"pmid":"11984418","id":"PMC_11984418","title":"Should you recommend a low-carb, high-protein diet?","date":"2002","source":"The Nurse practitioner","url":"https://pubmed.ncbi.nlm.nih.gov/11984418","citation_count":2,"is_preprint":false},{"pmid":"21589461","id":"PMC_21589461","title":"4-(4-Pyrid-yl)pyridinium 3-amino-5-carb-oxy-2,4,6-triiodo-benzoate-5-amino-2,4,6-triiodo-isophthalic acid (1/1).","date":"2010","source":"Acta crystallographica. 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Section E, Structure reports online","url":"https://pubmed.ncbi.nlm.nih.gov/22346877","citation_count":1,"is_preprint":false},{"pmid":"33527469","id":"PMC_33527469","title":"A highly resistant structure between the cuticle and the cortex of human hair III: Characterzation of the structure CARB.","date":"2021","source":"International journal of cosmetic science","url":"https://pubmed.ncbi.nlm.nih.gov/33527469","citation_count":1,"is_preprint":false},{"pmid":"25484705","id":"PMC_25484705","title":"Crystal structure of 9-(4-bromo-but-yl)-9H-fluorene-9-carb-oxy-lic acid.","date":"2014","source":"Acta crystallographica. Section E, Structure reports online","url":"https://pubmed.ncbi.nlm.nih.gov/25484705","citation_count":1,"is_preprint":false},{"pmid":"40071035","id":"PMC_40071035","title":"Crystal structure, Hirshfeld surface analysis, DFT and mol-ecular docking studies of 4'-(benz-yloxy)-[1,1'-biphen-yl]-3-carb-oxy-lic acid.","date":"2025","source":"Acta crystallographica. Section E, Crystallographic communications","url":"https://pubmed.ncbi.nlm.nih.gov/40071035","citation_count":1,"is_preprint":false},{"pmid":"41196107","id":"PMC_41196107","title":"Deciphering the Role of VIM, STX8, and MIF in Pneumoconiosis Susceptibility: A Mendelian Randomization Analysis of the Lung-Gut Axis and Multi-Omics Insights from European and East Asian Populations.","date":"2025","source":"Biomedical and environmental sciences : BES","url":"https://pubmed.ncbi.nlm.nih.gov/41196107","citation_count":0,"is_preprint":false},{"pmid":"41979085","id":"PMC_41979085","title":"VAMP4/STX8 Mediate the Autophagic Secretion of Mitochondria and Promote TAMs Polarization in HNSCC.","date":"2026","source":"Journal of extracellular vesicles","url":"https://pubmed.ncbi.nlm.nih.gov/41979085","citation_count":0,"is_preprint":false},{"pmid":"33231159","id":"PMC_33231159","title":"Current Evidence Regarding Low-carb Diets for The Metabolic Control of Type-2 Diabetes.","date":"2021","source":"Current diabetes reviews","url":"https://pubmed.ncbi.nlm.nih.gov/33231159","citation_count":0,"is_preprint":false},{"pmid":"32459903","id":"PMC_32459903","title":"[The content of essential and toxic microelements in the organs of mice of various lines receiving a high-carb high-fat diet and supplemented with quercetin].","date":"2020","source":"Voprosy pitaniia","url":"https://pubmed.ncbi.nlm.nih.gov/32459903","citation_count":0,"is_preprint":false},{"pmid":"22922262","id":"PMC_22922262","title":"The attachment disorders of muscle: failure to carb-load.","date":"2012","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/22922262","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.12.16.627577","title":"Trehalose dimycolate inhibits phagosome maturation and promotes intracellular  <i>M. tuberculosis</i>  growth via noncanonical SNARE interaction","date":"2024-12-16","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.16.627577","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.12.628128","title":"<i>Salmonella</i>  Typhimurium Manipulates Syntaxin 7 to Navigate Endo-Lysosomal Trafficking in Host Cells","date":"2024-12-12","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.12.628128","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.10.25329355","title":"Remission of type 2 diabetes can be achieved in short and long-lasting type 2 diabetes: results of a randomized controlled trial in individuals with overweight and obesity","date":"2025-06-11","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.10.25329355","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.11.25323777","title":"<i>In Silico</i>Metagenomic Analysis of Antibiotic Resistance Genes in South American Wastewater Treatment Plants: A Baseline for Environmental Surveillance","date":"2025-03-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.11.25323777","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.02.12.636430","title":"A metagenomic approach to One Health surveillance of antimicrobial resistance in a UK veterinary centre","date":"2025-02-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.12.636430","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.20.677523","title":"A natural history of AMR in  <i>Klebsiella pneumoniae</i>  : Global diversity, predictors, and predictions of evolutionary pathways","date":"2025-09-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.20.677523","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":39939,"output_tokens":2005,"usd":0.074946,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8365,"output_tokens":2382,"usd":0.050688,"stage2_stop_reason":"end_turn"},"total_usd":0.125634,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking through the corpus, I need to identify papers about the human STX8 (syntaxin 8) gene and its orthologs, excluding the many \"CARB\" alias collisions (beta-lactamases, carbamoyl-phosphate synthetase, dietary studies, carotenoid biosynthesis genes, etc.).\n\nRelevant papers about STX8/syntaxin 8:\n- PMID:10198254 — cloning of human STX8\n- PMID:33788833 — S. pombe Stx8 (ortholog), retromer recycling\n- PMID:41979085 — VAMP4/STX8 in autophagic secretion of mitochondria\n- bio_10.1101_2024.12.16.627577 — TDM/STX8 SNARE interactions\n- bio_10.1101_2024.12.12.628128 — Salmonella/STX8 interaction\n- PMID:10781590 — CARB gene (CIP-1-associated regulator of cyclin B) — this is a different human gene, not STX8. The alias \"CARB\" for STX8 refers to something else; checking: HGNC lists STX8 with alias CARB. But PMID:10781590 describes \"CARB\" as a p21-binding protein associated with cyclin B and centrosome. This appears to be a different protein than syntaxin 8. I'll treat this as a collision.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"Human syntaxin 8 (STX8) was cloned by yeast two-hybrid screening using the R domain of CFTR as bait; the encoded 236-amino-acid protein contains a C-terminal coiled-coil domain conserved in the t-SNARE superfamily and a C-terminal hydrophobic transmembrane anchor, placing it in the vesicular trafficking/docking machinery.\",\n      \"method\": \"Yeast two-hybrid screening of human fetal lung cDNA library; sequence analysis; chromosomal mapping to 17p12\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab, sequence/domain analysis plus yeast two-hybrid; functional role inferred from domain architecture, not directly tested in vesicle fusion assay\",\n      \"pmids\": [\"10198254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"S. pombe Stx8 (ortholog of mammalian syntaxin 8) localizes to the trans-Golgi network (TGN) and prevacuolar endosome (PVE) and is required for vesicle fusion at the PVE; its SNARE domain is essential for function. Stx8 recycling from the PVE back to the TGN depends on the retromer component Vps35 and sorting nexins Vps5, Vps17, and Snx3, identifying it as a Snx3-retromer cargo. A sorting signal (IEMeaM, with residues I133, E134, M135, M138 all essential) in an unstructured region distant from the transmembrane helix mediates retromer recognition.\",\n      \"method\": \"Deletion and alanine-scanning mutagenesis; live-cell fluorescence microscopy; genetic epistasis with retromer/sorting nexin mutants; salt-sensitivity phenotyping of stx8Δ cells\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, imaging, epistasis, phenotypic rescue) in a single rigorous study establishing localization, recycling mechanism, and sorting signal\",\n      \"pmids\": [\"33788833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Trehalose dimycolate (TDM), the abundant M. tuberculosis envelope glycolipid, physically binds STX8 (along with VTI1B and VAMP2) as detected by a clickable photoaffinity TDM probe. Normally, VTI1B and STX8 promote endosome fusion by complexing with VAMP8; however, in the presence of M. tuberculosis, VTI1B and STX8 instead complex non-canonically with VAMP2, reducing VAMP8 binding, inhibiting phagosome maturation, and promoting intracellular M. tuberculosis replication.\",\n      \"method\": \"Clickable photoaffinity TDM probe pulldown/MS in macrophages; co-immunoprecipitation of SNARE complexes; functional phagosome maturation assay; intracellular bacterial replication assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chemical biology probe plus Co-IP and functional assays in single preprint study; not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.12.16.627577\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Salmonella Typhimurium effector protein SipA interacts with STX8, and STX8 is recruited to Salmonella-containing vacuoles (SCVs); this interaction is proposed to maintain the vacuolar niche by engaging host endosomal fusion machinery.\",\n      \"method\": \"BioID proximity labeling screening (identified STX8–SipA interaction); live-cell imaging of SCV biogenesis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single preprint, BioID screen interaction without direct functional validation of STX8 specifically; STX8 role in SCV not directly tested by KD/KO in this study\",\n      \"pmids\": [\"bio_10.1101_2024.12.12.628128\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Under hypoxic conditions in head and neck squamous cell carcinoma (HNSCC), STX8 and VAMP4 are key mediators of mitophagy-dependent extracellular vesicle (EV) secretion. STX8 participates in the autophagic secretion of mitochondria, and this SNARE-dependent process promotes polarization of tumour-associated macrophages toward an immunosuppressive phenotype, reshaping the tumour immune microenvironment.\",\n      \"method\": \"Multivesicular body membrane proteomics; molecular interaction validation (co-IP/pulldown); EV characterization; macrophage polarization functional assay; HNSCC cell hypoxia model\",\n      \"journal\": \"Journal of extracellular vesicles\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics plus molecular interaction validation and functional readout in single study; peer-reviewed but single lab\",\n      \"pmids\": [\"41979085\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"STX8 (syntaxin 8) is a t-SNARE protein that localizes to the trans-Golgi network and prevacuolar/late endosomes, where its SNARE domain drives vesicle fusion; it is recycled as a Snx3-retromer cargo via a defined IEMxxM sorting motif, participates in normal endosome-lysosome fusion in complex with VTI1B and VAMP8, and is co-opted by pathogens (M. tuberculosis via TDM-induced non-canonical SNARE complex formation with VAMP2, and Salmonella via the SipA effector) to subvert phagosome maturation, while also mediating VAMP4-dependent autophagic secretion of mitochondria in tumour cells to promote immunosuppression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STX8 (syntaxin 8) is a t-SNARE of the vesicular trafficking machinery, defined by a C-terminal SNARE coiled-coil domain and a hydrophobic transmembrane anchor [#0]. It localizes to the trans-Golgi network and prevacuolar/late endosomes, where its SNARE domain drives membrane fusion; following fusion at the prevacuolar endosome, STX8 is recycled back to the TGN as a Snx3-retromer cargo, recognized via an unstructured IEMxxM sorting motif (residues I133, E134, M135, M138) distinct from its transmembrane helix [#1]. In endosome-to-lysosome fusion, STX8 acts together with VTI1B and VAMP8 [#2]. This same machinery is co-opted by intracellular pathogens: the M. tuberculosis glycolipid trehalose dimycolate binds STX8 and redirects it and VTI1B into a non-canonical complex with VAMP2 at the expense of VAMP8 binding, blocking phagosome maturation and favoring bacterial replication [#2]. Beyond these functions, STX8 participates in VAMP4-dependent autophagic secretion of mitochondria that drives immunosuppressive macrophage polarization in hypoxic tumour cells [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing the molecular identity of STX8 was the first step: cloning revealed a protein with the domain hallmarks of the t-SNARE family, placing an otherwise uncharacterized gene into the vesicle docking/fusion machinery.\",\n      \"evidence\": \"Yeast two-hybrid cloning using the CFTR R domain as bait, sequence/domain analysis, and chromosomal mapping\",\n      \"pmids\": [\"10198254\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Function inferred from domain architecture, not tested in a fusion assay\",\n        \"Subcellular localization not established\",\n        \"The functional significance of the CFTR R-domain interaction was not pursued\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"How STX8 is localized and maintained at its compartment was resolved by showing it functions at the TGN/prevacuolar endosome and is retrieved by retromer through a discrete sorting signal, defining both its site of action and its recycling itinerary.\",\n      \"evidence\": \"Mutagenesis, live-cell imaging, and retromer/sorting-nexin epistasis with phenotypic readout in S. pombe\",\n      \"pmids\": [\"33788833\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of the cognate SNARE partners at the PVE in this system not defined\",\n        \"Conservation of the IEMxxM signal and Snx3-retromer dependence in mammalian cells not directly tested\",\n        \"Structural basis of retromer recognition of the motif unknown\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The cognate SNARE partnerships of STX8 in endosome fusion and the mechanism of pathogen subversion were addressed by showing STX8/VTI1B normally fuse with VAMP8 but are diverted to VAMP2 by a mycobacterial glycolipid, explaining how phagosome maturation is blocked.\",\n      \"evidence\": \"Photoaffinity TDM probe pulldown/MS, SNARE Co-IP, phagosome maturation and intracellular replication assays in macrophages (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.12.16.627577\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Not yet peer-reviewed\",\n        \"Direct fusion reconstitution of the canonical vs non-canonical complexes not shown\",\n        \"Whether STX8 is a direct TDM-binding partner versus a complex co-member not fully resolved\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A second pathogen route was probed by identifying STX8 as an interactor of the Salmonella effector SipA and a component recruited to the Salmonella-containing vacuole, implicating its fusion machinery in vacuolar niche maintenance.\",\n      \"evidence\": \"BioID proximity labeling and live-cell imaging of SCV biogenesis (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.12.12.628128\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Interaction from a screen without direct functional validation of STX8 by KD/KO\",\n        \"Not independently confirmed and not peer-reviewed\",\n        \"Mechanism by which STX8 maintains the SCV not established\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"A role beyond classical endosomal fusion was established by showing STX8, with VAMP4, mediates autophagic secretion of mitochondria that reshapes the tumour immune microenvironment, linking SNARE-dependent secretion to immunosuppression.\",\n      \"evidence\": \"Multivesicular body membrane proteomics, interaction validation, EV characterization, and macrophage polarization assays in a hypoxic HNSCC model\",\n      \"pmids\": [\"41979085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab; direct fusion mechanism for mitochondrial secretion not reconstituted\",\n        \"Whether STX8 directly pairs with VAMP4 versus acting in a larger complex not resolved\",\n        \"Generality beyond hypoxic HNSCC not established\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The full complement of STX8 SNARE pairings across compartments, the structural basis of its complex assembly, and whether its mammalian recycling mirrors the S. pombe retromer mechanism remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural model of STX8-containing SNARE complexes\",\n        \"Mammalian retromer dependence and IEMxxM conservation untested\",\n        \"Quantitative contributions of canonical vs non-canonical partners not dissected\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 2, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"VTI1B\", \"VAMP8\", \"VAMP2\", \"VAMP4\", \"SipA\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":3,"faith_pct":100.0}}