{"gene":"TG_267730","gene_symbol":"","run_date":"2026-09-08T14:08:29","timeline":{"discoveries":[{"year":2018,"finding":"Disruption of the putative GDP-fucose transporter gene (NST2) in T. gondii results in loss of O-fucosylation on MIC2 thrombospondin type I repeats (TSRs), markedly reduced cellular levels of MIC2, mislocalization of MIC2 to earlier secretory compartments (in 10–15% of vacuoles), and defects in host cell attachment and invasion comparable to Δmic2 phenotype, establishing NST2 as the Golgi GDP-fucose transporter required for POFUT2-dependent O-fucosylation of TSR-containing proteins.","method":"Gene knockout (Δnst2), mass spectrometry glycan analysis, anti-GlcFuc antibody detection, immunofluorescence microscopy, host cell invasion/attachment assays in human foreskin fibroblasts","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout with multiple orthogonal readouts (MS glycan loss, antibody detection, localization, functional invasion assay), corroborated by parallel Δpofut2 results","pmids":["30538131"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"The putative GDP-fucose transporter NST2 in Toxoplasma gondii transports GDP-fucose into the secretory pathway (Golgi), where it serves as the sugar-nucleotide donor for POFUT2-mediated O-fucosylation of thrombospondin type I repeats on MIC2; loss of NST2 abolishes MIC2 O-fucosylation, destabilizes MIC2, causes its mislocalization away from micronemes, and impairs host cell attachment and invasion."},"narrative":{"mechanistic_narrative":"The putative GDP-fucose transporter NST2 in Toxoplasma gondii supplies the sugar-nucleotide donor required for O-fucosylation of thrombospondin type I repeats (TSRs) within the secretory pathway [PMID:30538131]. Disruption of NST2 abolishes O-fucosylation on the TSRs of the micronemal adhesin MIC2, markedly reduces cellular MIC2 levels, and mislocalizes MIC2 to earlier secretory compartments, identifying NST2 as the Golgi GDP-fucose transporter that feeds POFUT2-dependent O-fucosylation of TSR-containing proteins [PMID:30538131]. Loss of NST2 impairs host cell attachment and invasion to an extent comparable to the Δmic2 phenotype, linking this glycosylation pathway to parasite infectivity [PMID:30538131]. Beyond [PMID:30538131], no further mechanistic detail has been characterized in the available corpus.","teleology":[{"year":2018,"claim":"Whether a dedicated Golgi GDP-fucose transporter supports TSR O-fucosylation in T. gondii was unknown; knockout of NST2 established that this transporter is required to deliver GDP-fucose for POFUT2-dependent modification of MIC2, coupling glycosylation to adhesin stability and invasion.","evidence":"Gene knockout (Δnst2) with mass spectrometry glycan analysis, anti-GlcFuc antibody detection, immunofluorescence, and host cell invasion/attachment assays in human foreskin fibroblasts","pmids":["30538131"],"confidence":"High","gaps":["Direct biochemical demonstration of GDP-fucose transport activity by NST2 (e.g. reconstituted transport assay) is not shown","The full set of TSR-containing substrates beyond MIC2 dependent on NST2 is not defined","Structural basis of substrate recognition and Golgi targeting of NST2 is uncharacterized"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"Whether NST2 directly transports GDP-fucose across the Golgi membrane and the complete substrate repertoire and structural mechanism remain to be established.","evidence":"","pmids":[],"confidence":"High","gaps":["No in vitro transport reconstitution establishing direct GDP-fucose transport","No structural model of the transporter","Substrate scope beyond MIC2 undefined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["POFUT2 (FUNCTIONALLY LINKED O-FUCOSYLTRANSFERASE)","MIC2 (TSR-CONTAINING SUBSTRATE GLYCOPROTEIN)"],"other_free_text":["Loss of NST2 destabilizes MIC2 and mislocalizes it away from micronemes to earlier secretory compartments, impairing host cell attachment and invasion comparable to Δmic2 [#0]."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"30538131","id":"PMC_30538131","title":"O-Fucosylation of thrombospondin-like repeats is required for processing of microneme protein 2 and for efficient host cell invasion by Toxoplasma gondii tachyzoites.","date":"2018","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30538131","citation_count":23,"is_preprint":false},{"pmid":"33158988","id":"PMC_33158988","title":"The nucleocytosolic O-fucosyltransferase SPINDLY affects protein expression and virulence in Toxoplasma gondii.","date":"2020","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33158988","citation_count":13,"is_preprint":false},{"pmid":"36250576","id":"PMC_36250576","title":"Spindly is a nucleocytosolic O-fucosyltransferase in Dictyostelium and related proteins are widespread in protists and bacteria.","date":"2023","source":"Glycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/36250576","citation_count":6,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4232,"output_tokens":506,"usd":0.010143,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5163,"output_tokens":1381,"usd":0.03017,"stage2_stop_reason":"end_turn"},"total_usd":0.040313,"stage1_batch_id":"msgbatch_015xmQKDRqnTh9anE4m7LiD6","stage2_batch_id":"msgbatch_01JLpkFTVhoQBNgqHCKFrVVU","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"Disruption of the putative GDP-fucose transporter gene (NST2) in T. gondii results in loss of O-fucosylation on MIC2 thrombospondin type I repeats (TSRs), markedly reduced cellular levels of MIC2, mislocalization of MIC2 to earlier secretory compartments (in 10–15% of vacuoles), and defects in host cell attachment and invasion comparable to Δmic2 phenotype, establishing NST2 as the Golgi GDP-fucose transporter required for POFUT2-dependent O-fucosylation of TSR-containing proteins.\",\n      \"method\": \"Gene knockout (Δnst2), mass spectrometry glycan analysis, anti-GlcFuc antibody detection, immunofluorescence microscopy, host cell invasion/attachment assays in human foreskin fibroblasts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout with multiple orthogonal readouts (MS glycan loss, antibody detection, localization, functional invasion assay), corroborated by parallel Δpofut2 results\",\n      \"pmids\": [\"30538131\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"The putative GDP-fucose transporter NST2 in Toxoplasma gondii transports GDP-fucose into the secretory pathway (Golgi), where it serves as the sugar-nucleotide donor for POFUT2-mediated O-fucosylation of thrombospondin type I repeats on MIC2; loss of NST2 abolishes MIC2 O-fucosylation, destabilizes MIC2, causes its mislocalization away from micronemes, and impairs host cell attachment and invasion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"The putative GDP-fucose transporter NST2 in Toxoplasma gondii supplies the sugar-nucleotide donor required for O-fucosylation of thrombospondin type I repeats (TSRs) within the secretory pathway [#0]. Disruption of NST2 abolishes O-fucosylation on the TSRs of the micronemal adhesin MIC2, markedly reduces cellular MIC2 levels, and mislocalizes MIC2 to earlier secretory compartments, identifying NST2 as the Golgi GDP-fucose transporter that feeds POFUT2-dependent O-fucosylation of TSR-containing proteins [#0]. Loss of NST2 impairs host cell attachment and invasion to an extent comparable to the Δmic2 phenotype, linking this glycosylation pathway to parasite infectivity [#0]. Beyond [#0], no further mechanistic detail has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Whether a dedicated Golgi GDP-fucose transporter supports TSR O-fucosylation in T. gondii was unknown; knockout of NST2 established that this transporter is required to deliver GDP-fucose for POFUT2-dependent modification of MIC2, coupling glycosylation to adhesin stability and invasion.\",\n      \"evidence\": \"Gene knockout (Δnst2) with mass spectrometry glycan analysis, anti-GlcFuc antibody detection, immunofluorescence, and host cell invasion/attachment assays in human foreskin fibroblasts\",\n      \"pmids\": [\"30538131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct biochemical demonstration of GDP-fucose transport activity by NST2 (e.g. reconstituted transport assay) is not shown\",\n        \"The full set of TSR-containing substrates beyond MIC2 dependent on NST2 is not defined\",\n        \"Structural basis of substrate recognition and Golgi targeting of NST2 is uncharacterized\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether NST2 directly transports GDP-fucose across the Golgi membrane and the complete substrate repertoire and structural mechanism remain to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No in vitro transport reconstitution establishing direct GDP-fucose transport\",\n        \"No structural model of the transporter\",\n        \"Substrate scope beyond MIC2 undefined\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005457\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0000139\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0036066\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"POFUT2 (functionally linked O-fucosyltransferase)\", \"MIC2 (TSR-containing substrate glycoprotein)\"],\n    \"other_free_text\": [\n      \"Loss of NST2 destabilizes MIC2 and mislocalizes it away from micronemes to earlier secretory compartments, impairing host cell attachment and invasion comparable to Δmic2 [#0].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":{"gene":"TG_267730","tier":"COVERAGE","verdict":"Coverage note","subtype":"corpus_unverifiable","uniprot_band":"empty","rules_fired":"R1","issue":"R1: record has no curated symbol, so its corpus cannot name it (named in 1/20); grounding untestable — coverage note, not a collision"},"strains":[{"strain":"ME49","gene_id":"TGME49_267730","name":null,"product":"GDP-fucose transporter NST2","uniprot_acc":"S8F229","chromosome":"TGME49_chrIX","start_pos":398540},{"strain":"GT1","gene_id":"TGGT1_267730","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":233923},{"strain":"RH88","gene_id":"TGRH88_010370","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023090","start_pos":449203},{"strain":"VEG","gene_id":"TGVEG_267730","name":null,"product":"putative GDP-fucose transporter","uniprot_acc":"B9QP49","chromosome":"TGVEG_chrIX","start_pos":425848}]}