{"gene":"TG_209820","gene_symbol":"STX1","run_date":"2026-09-08T11:06:21","timeline":{"discoveries":[{"year":2023,"finding":"An unconventional SNARE complex comprising TgStx1, TgStx20, and TgStx21 mediates vesicular fusion at the plasma membrane and is essential for exocytosis of surface proteins and vesicular fusion at the apical annuli in T. gondii — distinct from the canonical Stx1/SNAP25 mechanism used in mammalian cells.","method":"Conditional knockout / loss-of-function analysis with phenotypic readout (exocytosis of surface proteins, vesicular fusion at apical annuli); SNARE complex characterization","journal":"PLoS Pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular phenotype and complex identification, single lab, single study","pmids":["36972314"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"finding":"SNARE proteins, including TgStx1, localize specifically to apical annuli in the plasma membrane, and these sites are the location of dense granule vesicle fusion and exocytosis after invasion; perturbation of secretion at apical annuli strongly impairs parasite growth.","method":"Direct localization by imaging (integral membrane protein localization to apical annular sites); functional perturbation with growth and secretion phenotype readout","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional consequence (secretion perturbation and growth impairment), single lab, multiple readouts","pmids":["38270431"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"In Toxoplasma gondii, TgStx1 forms an unconventional SNARE complex with TgStx20 and TgStx21 that localizes specifically to apical annuli in the plasma membrane and mediates vesicular fusion and exocytosis of surface proteins and dense granule cargo at these sites after invasion, playing an essential role in parasite growth."},"narrative":{"mechanistic_narrative":"In Toxoplasma gondii, TgStx1 is a syntaxin-family SNARE that drives vesicular fusion and exocytosis at the parasite plasma membrane through an unconventional SNARE complex assembled with TgStx20 and TgStx21, mechanistically distinct from the canonical mammalian Stx1/SNAP25 machinery [PMID:36972314]. Conditional loss of this complex abolishes exocytosis of surface proteins and vesicular fusion, establishing it as essential for parasite growth [PMID:36972314]. TgStx1 and its partner SNAREs localize specifically to the apical annuli of the plasma membrane, which are the sites of dense granule vesicle fusion and cargo exocytosis after invasion; disrupting secretion at these sites strongly impairs parasite growth [PMID:38270431]. Beyond this apical-annuli SNARE-mediated fusion role, no further mechanistic detail for TgStx1 has been characterized in the available corpus.","teleology":[{"year":2023,"claim":"It was unknown how T. gondii mediates vesicular fusion at the plasma membrane; this established that an unconventional SNARE complex of TgStx1/TgStx20/TgStx21 performs this fusion and is essential for surface-protein exocytosis, distinguishing the parasite mechanism from the canonical mammalian Stx1/SNAP25 pathway.","evidence":"Conditional knockout / loss-of-function with exocytosis and vesicular-fusion readouts plus SNARE complex characterization in T. gondii","pmids":["36972314"],"confidence":"Medium","gaps":["No structural model of the TgStx1/TgStx20/TgStx21 complex or the assembly determinants","Cargo repertoire beyond surface proteins not fully defined","Regulation of complex assembly/disassembly unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"It was unknown where in the parasite this SNARE machinery acts; this localized TgStx1 and partner SNAREs to the apical annuli and identified these as the sites of dense granule vesicle fusion and post-invasion exocytosis, linking the fusion machinery to a defined subcellular platform required for growth.","evidence":"Direct imaging of integral membrane protein localization to apical annular sites with functional secretion-perturbation and growth readouts in T. gondii","pmids":["38270431"],"confidence":"Medium","gaps":["Mechanism targeting TgStx1 specifically to apical annuli is unknown","How dense granule vesicles are delivered to these sites is not established","Temporal control of fusion relative to invasion not resolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"How the TgStx1 SNARE complex is assembled, regulated, and targeted to apical annuli, and the full range of cargo it delivers, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural or biochemical reconstitution of the unconventional SNARE complex","Targeting and regulatory factors for apical annuli localization unidentified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Unconventional SNARE complex: TgStx1 + TgStx20 + TgStx21"],"partners":["TGSTX20","TGSTX21"],"other_free_text":["Localizes to apical annuli of the plasma membrane, the sites of dense granule vesicle fusion and post-invasion exocytosis [#1]","Essential for parasite growth; perturbation of apical annuli secretion strongly impairs growth [#0, #1]","Mechanistically distinct from canonical mammalian Stx1/SNAP25 fusion [#0]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"34340555","id":"PMC_34340555","title":"The Dissection of SNAREs Reveals Key Factors for Vesicular Trafficking to the Endosome-like Compartment and Apicoplast via the Secretory System in Toxoplasma gondii.","date":"2021","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/34340555","citation_count":20,"is_preprint":false},{"pmid":"36972314","id":"PMC_36972314","title":"An unconventional SNARE complex mediates exocytosis at the plasma membrane and vesicular fusion at the apical annuli in Toxoplasma gondii.","date":"2023","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/36972314","citation_count":11,"is_preprint":false},{"pmid":"38270431","id":"PMC_38270431","title":"Apical annuli are specialised sites of post-invasion secretion of dense granules in Toxoplasma.","date":"2024","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/38270431","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4030,"output_tokens":606,"usd":0.01059,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5311,"output_tokens":1836,"usd":0.036228,"stage2_stop_reason":"end_turn"},"total_usd":0.046818,"stage1_batch_id":"msgbatch_01WokvBYTB6JLnYrpD4rXnyV","stage2_batch_id":"msgbatch_01M7hsQDvz6AqVC9DLVjQzzc","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2023,\n      \"finding\": \"An unconventional SNARE complex comprising TgStx1, TgStx20, and TgStx21 mediates vesicular fusion at the plasma membrane and is essential for exocytosis of surface proteins and vesicular fusion at the apical annuli in T. gondii — distinct from the canonical Stx1/SNAP25 mechanism used in mammalian cells.\",\n      \"method\": \"Conditional knockout / loss-of-function analysis with phenotypic readout (exocytosis of surface proteins, vesicular fusion at apical annuli); SNARE complex characterization\",\n      \"journal\": \"PLoS Pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular phenotype and complex identification, single lab, single study\",\n      \"pmids\": [\"36972314\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SNARE proteins, including TgStx1, localize specifically to apical annuli in the plasma membrane, and these sites are the location of dense granule vesicle fusion and exocytosis after invasion; perturbation of secretion at apical annuli strongly impairs parasite growth.\",\n      \"method\": \"Direct localization by imaging (integral membrane protein localization to apical annular sites); functional perturbation with growth and secretion phenotype readout\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional consequence (secretion perturbation and growth impairment), single lab, multiple readouts\",\n      \"pmids\": [\"38270431\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"In Toxoplasma gondii, TgStx1 forms an unconventional SNARE complex with TgStx20 and TgStx21 that localizes specifically to apical annuli in the plasma membrane and mediates vesicular fusion and exocytosis of surface proteins and dense granule cargo at these sites after invasion, playing an essential role in parasite growth.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"In Toxoplasma gondii, TgStx1 is a syntaxin-family SNARE that drives vesicular fusion and exocytosis at the parasite plasma membrane through an unconventional SNARE complex assembled with TgStx20 and TgStx21, mechanistically distinct from the canonical mammalian Stx1/SNAP25 machinery [#0]. Conditional loss of this complex abolishes exocytosis of surface proteins and vesicular fusion, establishing it as essential for parasite growth [#0]. TgStx1 and its partner SNAREs localize specifically to the apical annuli of the plasma membrane, which are the sites of dense granule vesicle fusion and cargo exocytosis after invasion; disrupting secretion at these sites strongly impairs parasite growth [#1]. Beyond this apical-annuli SNARE-mediated fusion role, no further mechanistic detail for TgStx1 has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2023,\n      \"claim\": \"It was unknown how T. gondii mediates vesicular fusion at the plasma membrane; this established that an unconventional SNARE complex of TgStx1/TgStx20/TgStx21 performs this fusion and is essential for surface-protein exocytosis, distinguishing the parasite mechanism from the canonical mammalian Stx1/SNAP25 pathway.\",\n      \"evidence\": \"Conditional knockout / loss-of-function with exocytosis and vesicular-fusion readouts plus SNARE complex characterization in T. gondii\",\n      \"pmids\": [\"36972314\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"single lab, single study\",\n      \"gaps\": [\n        \"No structural model of the TgStx1/TgStx20/TgStx21 complex or the assembly determinants\",\n        \"Cargo repertoire beyond surface proteins not fully defined\",\n        \"Regulation of complex assembly/disassembly unresolved\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"It was unknown where in the parasite this SNARE machinery acts; this localized TgStx1 and partner SNAREs to the apical annuli and identified these as the sites of dense granule vesicle fusion and post-invasion exocytosis, linking the fusion machinery to a defined subcellular platform required for growth.\",\n      \"evidence\": \"Direct imaging of integral membrane protein localization to apical annular sites with functional secretion-perturbation and growth readouts in T. gondii\",\n      \"pmids\": [\"38270431\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"direct localization with functional consequence, single lab\",\n      \"gaps\": [\n        \"Mechanism targeting TgStx1 specifically to apical annuli is unknown\",\n        \"How dense granule vesicles are delivered to these sites is not established\",\n        \"Temporal control of fusion relative to invasion not resolved\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the TgStx1 SNARE complex is assembled, regulated, and targeted to apical annuli, and the full range of cargo it delivers, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural or biochemical reconstitution of the unconventional SNARE complex\",\n        \"Targeting and regulatory factors for apical annuli localization unidentified\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0000149\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006887\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0006906\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\n      \"Unconventional SNARE complex: TgStx1 + TgStx20 + TgStx21\"\n    ],\n    \"partners\": [\n      \"TgStx20\",\n      \"TgStx21\"\n    ],\n    \"other_free_text\": [\n      \"Localizes to apical annuli of the plasma membrane, the sites of dense granule vesicle fusion and post-invasion exocytosis [#1]\",\n      \"Essential for parasite growth; perturbation of apical annuli secretion strongly impairs growth [#0, #1]\",\n      \"Mechanistically distinct from canonical mammalian Stx1/SNAP25 fusion [#0]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_209820","name":"STX1","product":"syntaxin 1","uniprot_acc":"S8F8N8","chromosome":"TGME49_chrIb","start_pos":1466391},{"strain":"GT1","gene_id":"TGGT1_209820","name":null,"product":"syntaxin protein","uniprot_acc":null,"chromosome":"TGGT1_chrIb","start_pos":1486705},{"strain":"RH88","gene_id":"TGRH88_021360","name":null,"product":"syntaxin protein","uniprot_acc":null,"chromosome":"CM023082","start_pos":541284},{"strain":"VEG","gene_id":"TGVEG_209820","name":null,"product":"syntaxin protein","uniprot_acc":"B9QKP5","chromosome":"TGVEG_chrIb","start_pos":1468455}]}