{"gene":"TG_318510","gene_symbol":"NSF","run_date":"2026-09-08T15:15:13","timeline":{"discoveries":[{"year":1999,"finding":"Dense granule secretion in T. gondii occurs constitutively in a calcium-independent manner, and is mediated by the NSF/SNAP/SNARE/Rab machinery: N-ethylmaleimide (an NSF inhibitor) and recombinant bovine Rab-GDI inhibited dense granule release, while recombinant hamster NSF and bovine alpha-SNAP augmented release in streptolysin O-permeabilized parasites. GTP (via GTPγS) but not cAMP stimulated secretion in an ATP-dependent manner, placing Rab GTPase activity upstream of fusion.","method":"Streptolysin O-permeabilized parasite secretion assays with recombinant mammalian NSF, alpha-SNAP, and Rab-GDI; pharmacological inhibition with N-ethylmaleimide; beta-lactamase reporter in stably transfected parasites; GTPγS and cAMP stimulation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — functional reconstitution with recombinant proteins in permeabilized parasite system, multiple orthogonal pharmacological and biochemical approaches in a single rigorous study","pmids":["9891012"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"Toxoplasma gondii NSF, together with SNAP, SNAREs, and Rab GTPases, drives constitutive, calcium-independent dense granule exocytosis, as demonstrated by the ability of recombinant NSF and alpha-SNAP to augment secretion and by inhibition with N-ethylmaleimide or Rab-GDI in a permeabilized parasite system."},"narrative":{"mechanistic_narrative":"In Toxoplasma gondii, NSF is a component of the vesicle-fusion machinery that drives constitutive, calcium-independent dense granule exocytosis [PMID:9891012]. In streptolysin O-permeabilized parasites, recombinant hamster NSF together with bovine alpha-SNAP augmented dense granule release, while N-ethylmaleimide (an NSF inhibitor) and recombinant Rab-GDI blocked it, placing NSF, SNAP, SNAREs, and Rab GTPases in a common secretory pathway [PMID:9891012]. Secretion was stimulated by GTPgammaS but not cAMP and required ATP, positioning Rab GTPase activity upstream of NSF/SNAP-mediated fusion [PMID:9891012]. Beyond this single reconstitution study, no further mechanistic detail on Toxoplasma NSF has been characterized in the available corpus.","teleology":[{"year":1999,"claim":"It was unknown whether T. gondii dense granule secretion used the conserved NSF/SNAP/SNARE/Rab fusion machinery and how it was regulated; reconstitution in permeabilized parasites established this machinery drives constitutive, calcium-independent release with Rab GTPase activity upstream of fusion.","evidence":"Streptolysin O-permeabilized parasite secretion assays with recombinant mammalian NSF, alpha-SNAP and Rab-GDI, N-ethylmaleimide inhibition, beta-lactamase reporter, and GTPgammaS/cAMP stimulation","pmids":["9891012"],"confidence":"High","gaps":["The endogenous T. gondii NSF protein was not cloned or characterized; recombinant mammalian orthologs were used as surrogates","The specific SNARE substrates and Rab GTPase(s) acting in this pathway were not identified","No structural or biochemical characterization of the parasite NSF itself"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The identity and biochemistry of the endogenous Toxoplasma NSF, its cognate SNAREs, and the Rab GTPase(s) coordinating dense granule fusion remain uncharacterized.","evidence":"","pmids":[],"confidence":"High","gaps":["No characterization of endogenous parasite NSF protein","No identified SNARE or Rab partners specific to dense granule exocytosis"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["ALPHA-SNAP (FUNCTIONAL COOPERATION IN PERMEABILIZED PARASITE SECRETION) [#0]","RAB GTPASE / RAB-GDI-SENSITIVE ACTIVITY UPSTREAM OF FUSION [#0]"],"other_free_text":["NSF activity inferred from N-ethylmaleimide-sensitive, ATP-dependent dense granule release; recombinant hamster NSF used to augment secretion in permeabilized T. gondii [#0]","Dense granule secretion is constitutive and calcium-independent, stimulated by GTPgammaS but not cAMP [#0]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"9891012","id":"PMC_9891012","title":"Constitutive calcium-independent release of Toxoplasma gondii dense granules occurs through the NSF/SNAP/SNARE/Rab machinery.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9891012","citation_count":50,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":2845,"output_tokens":510,"usd":0.008093,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5154,"output_tokens":1434,"usd":0.03081,"stage2_stop_reason":"end_turn"},"total_usd":0.038903,"stage1_batch_id":"msgbatch_01S6GjoYQm8LTPUsdhASdqag","stage2_batch_id":"msgbatch_01VX63RTMdBJqsG6gQMqoCjz","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"Dense granule secretion in T. gondii occurs constitutively in a calcium-independent manner, and is mediated by the NSF/SNAP/SNARE/Rab machinery: N-ethylmaleimide (an NSF inhibitor) and recombinant bovine Rab-GDI inhibited dense granule release, while recombinant hamster NSF and bovine alpha-SNAP augmented release in streptolysin O-permeabilized parasites. GTP (via GTPγS) but not cAMP stimulated secretion in an ATP-dependent manner, placing Rab GTPase activity upstream of fusion.\",\n      \"method\": \"Streptolysin O-permeabilized parasite secretion assays with recombinant mammalian NSF, alpha-SNAP, and Rab-GDI; pharmacological inhibition with N-ethylmaleimide; beta-lactamase reporter in stably transfected parasites; GTPγS and cAMP stimulation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — functional reconstitution with recombinant proteins in permeabilized parasite system, multiple orthogonal pharmacological and biochemical approaches in a single rigorous study\",\n      \"pmids\": [\"9891012\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"Toxoplasma gondii NSF, together with SNAP, SNAREs, and Rab GTPases, drives constitutive, calcium-independent dense granule exocytosis, as demonstrated by the ability of recombinant NSF and alpha-SNAP to augment secretion and by inhibition with N-ethylmaleimide or Rab-GDI in a permeabilized parasite system.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"In Toxoplasma gondii, NSF is a component of the vesicle-fusion machinery that drives constitutive, calcium-independent dense granule exocytosis [#0]. In streptolysin O-permeabilized parasites, recombinant hamster NSF together with bovine alpha-SNAP augmented dense granule release, while N-ethylmaleimide (an NSF inhibitor) and recombinant Rab-GDI blocked it, placing NSF, SNAP, SNAREs, and Rab GTPases in a common secretory pathway [#0]. Secretion was stimulated by GTPgammaS but not cAMP and required ATP, positioning Rab GTPase activity upstream of NSF/SNAP-mediated fusion [#0]. Beyond this single reconstitution study, no further mechanistic detail on Toxoplasma NSF has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"It was unknown whether T. gondii dense granule secretion used the conserved NSF/SNAP/SNARE/Rab fusion machinery and how it was regulated; reconstitution in permeabilized parasites established this machinery drives constitutive, calcium-independent release with Rab GTPase activity upstream of fusion.\",\n      \"evidence\": \"Streptolysin O-permeabilized parasite secretion assays with recombinant mammalian NSF, alpha-SNAP and Rab-GDI, N-ethylmaleimide inhibition, beta-lactamase reporter, and GTPgammaS/cAMP stimulation\",\n      \"pmids\": [\"9891012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The endogenous T. gondii NSF protein was not cloned or characterized; recombinant mammalian orthologs were used as surrogates\",\n        \"The specific SNARE substrates and Rab GTPase(s) acting in this pathway were not identified\",\n        \"No structural or biochemical characterization of the parasite NSF itself\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity and biochemistry of the endogenous Toxoplasma NSF, its cognate SNAREs, and the Rab GTPase(s) coordinating dense granule fusion remain uncharacterized.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No characterization of endogenous parasite NSF protein\",\n        \"No identified SNARE or Rab partners specific to dense granule exocytosis\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0031072\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006887\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0006906\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"alpha-SNAP (functional cooperation in permeabilized parasite secretion) [#0]\",\n      \"Rab GTPase / Rab-GDI-sensitive activity upstream of fusion [#0]\"\n    ],\n    \"other_free_text\": [\n      \"NSF activity inferred from N-ethylmaleimide-sensitive, ATP-dependent dense granule release; recombinant hamster NSF used to augment secretion in permeabilized T. gondii [#0]\",\n      \"Dense granule secretion is constitutive and calcium-independent, stimulated by GTPgammaS but not cAMP [#0]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_318510","name":"NSF","product":"N-ethylmaleimide-sensitive fusion protein, putative","uniprot_acc":"A0A125YPA6","chromosome":"TGME49_chrIV","start_pos":1262977},{"strain":"GT1","gene_id":"TGGT1_318510","name":null,"product":"putative N-ethylmaleimide-sensitive fusion protein","uniprot_acc":null,"chromosome":"TGGT1_chrIV","start_pos":1205264},{"strain":"RH88","gene_id":"TGRH88_008040","name":null,"product":"putative N-ethylmaleimide-sensitive fusion protein","uniprot_acc":null,"chromosome":"CM023085","start_pos":1285684},{"strain":"VEG","gene_id":"TGVEG_318510","name":null,"product":"putative N-ethylmaleimide-sensitive fusion protein","uniprot_acc":"B9PVD8","chromosome":"TGVEG_chrIV","start_pos":1273170}]}