{"gene":"TG_206490","gene_symbol":"MCA1","run_date":"2026-09-08T11:06:16","timeline":{"discoveries":[{"year":2016,"finding":"TgMCA1 undergoes autoproteolytic processing, is dispersed throughout the cytoplasm under normal conditions, and relocalizes to the nucleus when parasites are exposed to extracellular buffer, suggesting nuclear execution of its function.","method":"Western blot (autoproteolytic processing), indirect immunofluorescence assay (localization)","journal":"Frontiers in microbiology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — two orthogonal methods (WB + IFA) in a single study establishing localization and processing, but no structural or in vitro reconstitution data","pmids":["26834715"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"TgMCA1 contributes to apoptosis-like cell death in T. gondii: knockout parasites show significantly fewer TUNEL-positive cells after extracellular buffer treatment, while overexpression increases TUNEL-positive cells and reduces intracellular parasite growth.","method":"TUNEL assay on TgMCA1 knockout and overexpression strains treated with extracellular buffer","journal":"Frontiers in microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function and gain-of-function with defined phenotypic readout (TUNEL), single lab","pmids":["26834715"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"Deletion of MCA1 alone does not affect parasite propagation in vitro or virulence in vivo, indicating MCA1 is functionally redundant for replication and pathogenesis.","method":"In vitro growth assay and in vivo virulence assessment of TgMCA1 knockout strain","journal":"Frontiers in microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout with two orthogonal phenotypic readouts (in vitro growth, in vivo virulence), single lab; this is a negative result for growth/virulence","pmids":["26834715"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"MCA1 and MCA2 localize to the cytoplasm with punctuated aggregation and partially co-localize with the inner membrane complex (IMC) of T. gondii.","method":"Indirect immunofluorescence assay on transgenic strains","journal":"Parasites & vectors","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with fluorescence microscopy, single lab, no functional consequence directly linked to IMC localization alone","pmids":["34384491"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2021,"finding":"Combined deletion of MCA1 and MCA2 (double knockout) impairs endodyogeny, causing multiple nuclei and abnormal IMC1 expression; IMC1 in the double-knockout strain becomes detergent-soluble, indicating that MCA1 and MCA2 are required for IMC1 maturation (insolubilization).","method":"MCA1/MCA2 double-knockout strain analysis: proliferation assay, microscopy for endodyogeny defects, detergent-solubility assay for IMC1","journal":"Parasites & vectors","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (double KO) with multiple orthogonal phenotypic and biochemical readouts (proliferation, microscopy, detergent fractionation), single lab","pmids":["34384491"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2021,"finding":"MCA1 single knockout shows normal growth rate, confirming functional redundancy with MCA2 for parasite replication; only the combined deletion reduces proliferation.","method":"In vitro growth assay comparing single and double knockout strains to parental RHΔku80","journal":"Parasites & vectors","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic comparison of single vs. double KO with clear phenotypic readout; single lab; the single-KO result is a replicated negative finding","pmids":["34384491"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]}],"current_model":"TgMCA1 is a cysteine protease that undergoes autoproteolytic processing, localizes to the cytoplasm and partially to the inner membrane complex (IMC), relocalizes to the nucleus during extracellular stress, and contributes to apoptosis-like cell death; it is functionally redundant with MCA2 for normal replication, but together MCA1 and MCA2 are required for IMC1 maturation (insolubilization) and proper endodyogeny, as shown by the proliferation defects, multiple-nuclei phenotype, and detergent-soluble IMC1 in the MCA1/MCA2 double-knockout strain."},"narrative":{"mechanistic_narrative":"TgMCA1 is a Toxoplasma gondii cysteine protease (metacaspase) that undergoes autoproteolytic processing and contributes to apoptosis-like cell death and to the biogenesis of the inner membrane complex (IMC) during endodyogeny [PMID:26834715, PMID:34384491]. Under normal conditions the protein is dispersed throughout the cytoplasm with punctate aggregation and partially co-localizes with the IMC, but relocalizes to the nucleus when parasites are exposed to extracellular buffer, consistent with a nuclear execution step in stress-induced cell death [PMID:26834715, PMID:34384491]. Functionally, TgMCA1 drives apoptosis-like death: its knockout reduces, and its overexpression increases, TUNEL-positive parasites after extracellular buffer treatment [PMID:26834715]. TgMCA1 is redundant with MCA2 for replication and virulence — single deletion has no effect on growth or pathogenesis — but the two proteases together are required for normal endodyogeny and for IMC1 maturation, since their combined loss produces proliferation defects, multiple nuclei, and detergent-soluble (unprocessed/immature) IMC1 [PMID:26834715, PMID:34384491]. The direct proteolytic substrates of TgMCA1 and the molecular basis of its IMC1-maturation role have not been characterized in the available corpus.","teleology":[{"year":2016,"claim":"Establishing whether TgMCA1 is a functional protease and how its localization is regulated addressed how a metacaspase might execute a stress response in T. gondii.","evidence":"Western blot for autoproteolytic processing and indirect immunofluorescence for localization in T. gondii","pmids":["26834715"],"confidence":"Medium","gaps":["No in vitro reconstitution or structural data on the protease activity","The trigger and machinery driving nuclear relocalization are unidentified","No direct substrate identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"Genetic loss- and gain-of-function tests answered whether TgMCA1 actively promotes cell death versus merely correlating with it, linking the protease to an apoptosis-like death program.","evidence":"TUNEL assay on TgMCA1 knockout and overexpression strains after extracellular buffer treatment","pmids":["26834715"],"confidence":"Medium","gaps":["The downstream death effectors and cleaved targets are unknown","Physiological relevance of buffer-induced death is unclear","Single lab, single phenotypic readout"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"Deleting MCA1 alone tested its requirement for the parasite lytic cycle and revealed functional redundancy rather than an essential role in replication or virulence.","evidence":"In vitro growth assay and in vivo virulence assessment of the TgMCA1 knockout","pmids":["26834715"],"confidence":"Medium","gaps":["Redundant partner not yet identified in this study","Negative result does not exclude subtle fitness roles"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"Mapping MCA1/MCA2 to the IMC and testing double-deletion epistasis identified a non-death role: joint requirement for endodyogeny and IMC1 maturation.","evidence":"IFA localization plus MCA1/MCA2 double-knockout proliferation, endodyogeny microscopy, and IMC1 detergent-solubility assay in RHΔku80","pmids":["34384491"],"confidence":"Medium","gaps":["Whether MCA1 cleaves IMC1 directly is not shown","Molecular mechanism of IMC1 insolubilization is unresolved","Individual contribution of MCA1 vs MCA2 to IMC maturation not separated"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":null,"claim":"The direct proteolytic substrates of TgMCA1 and the biochemical mechanism by which it and MCA2 drive IMC1 maturation remain unknown.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No substrate identified for TgMCA1","No structural model of the protease","Signal linking extracellular stress to nuclear relocalization uncharacterized"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["MCA2"],"other_free_text":["Undergoes autoproteolytic processing [#0]","Partially co-localizes with the inner membrane complex (IMC) [#3]","Relocalizes from cytoplasm to nucleus upon extracellular buffer stress [#0]","Functionally redundant with MCA2 for replication and virulence; jointly required for endodyogeny and IMC1 maturation (insolubilization) [#2, #4, #5]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"26834715","id":"PMC_26834715","title":"The Apoptotic Role of Metacaspase in Toxoplasma gondii.","date":"2016","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/26834715","citation_count":32,"is_preprint":false},{"pmid":"34384491","id":"PMC_34384491","title":"Requirement of Toxoplasma gondii metacaspases for IMC1 maturation, endodyogeny and virulence in mice.","date":"2021","source":"Parasites & vectors","url":"https://pubmed.ncbi.nlm.nih.gov/34384491","citation_count":5,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3652,"output_tokens":1531,"usd":0.01696,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6661,"output_tokens":2233,"usd":0.044565,"stage2_stop_reason":"end_turn"},"total_usd":0.061525,"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\": 2016,\n      \"finding\": \"TgMCA1 undergoes autoproteolytic processing, is dispersed throughout the cytoplasm under normal conditions, and relocalizes to the nucleus when parasites are exposed to extracellular buffer, suggesting nuclear execution of its function.\",\n      \"method\": \"Western blot (autoproteolytic processing), indirect immunofluorescence assay (localization)\",\n      \"journal\": \"Frontiers in microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — two orthogonal methods (WB + IFA) in a single study establishing localization and processing, but no structural or in vitro reconstitution data\",\n      \"pmids\": [\"26834715\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TgMCA1 contributes to apoptosis-like cell death in T. gondii: knockout parasites show significantly fewer TUNEL-positive cells after extracellular buffer treatment, while overexpression increases TUNEL-positive cells and reduces intracellular parasite growth.\",\n      \"method\": \"TUNEL assay on TgMCA1 knockout and overexpression strains treated with extracellular buffer\",\n      \"journal\": \"Frontiers in microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function and gain-of-function with defined phenotypic readout (TUNEL), single lab\",\n      \"pmids\": [\"26834715\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deletion of MCA1 alone does not affect parasite propagation in vitro or virulence in vivo, indicating MCA1 is functionally redundant for replication and pathogenesis.\",\n      \"method\": \"In vitro growth assay and in vivo virulence assessment of TgMCA1 knockout strain\",\n      \"journal\": \"Frontiers in microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout with two orthogonal phenotypic readouts (in vitro growth, in vivo virulence), single lab; this is a negative result for growth/virulence\",\n      \"pmids\": [\"26834715\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MCA1 and MCA2 localize to the cytoplasm with punctuated aggregation and partially co-localize with the inner membrane complex (IMC) of T. gondii.\",\n      \"method\": \"Indirect immunofluorescence assay on transgenic strains\",\n      \"journal\": \"Parasites & vectors\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with fluorescence microscopy, single lab, no functional consequence directly linked to IMC localization alone\",\n      \"pmids\": [\"34384491\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Combined deletion of MCA1 and MCA2 (double knockout) impairs endodyogeny, causing multiple nuclei and abnormal IMC1 expression; IMC1 in the double-knockout strain becomes detergent-soluble, indicating that MCA1 and MCA2 are required for IMC1 maturation (insolubilization).\",\n      \"method\": \"MCA1/MCA2 double-knockout strain analysis: proliferation assay, microscopy for endodyogeny defects, detergent-solubility assay for IMC1\",\n      \"journal\": \"Parasites & vectors\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (double KO) with multiple orthogonal phenotypic and biochemical readouts (proliferation, microscopy, detergent fractionation), single lab\",\n      \"pmids\": [\"34384491\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MCA1 single knockout shows normal growth rate, confirming functional redundancy with MCA2 for parasite replication; only the combined deletion reduces proliferation.\",\n      \"method\": \"In vitro growth assay comparing single and double knockout strains to parental RHΔku80\",\n      \"journal\": \"Parasites & vectors\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic comparison of single vs. double KO with clear phenotypic readout; single lab; the single-KO result is a replicated negative finding\",\n      \"pmids\": [\"34384491\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    }\n  ],\n  \"current_model\": \"TgMCA1 is a cysteine protease that undergoes autoproteolytic processing, localizes to the cytoplasm and partially to the inner membrane complex (IMC), relocalizes to the nucleus during extracellular stress, and contributes to apoptosis-like cell death; it is functionally redundant with MCA2 for normal replication, but together MCA1 and MCA2 are required for IMC1 maturation (insolubilization) and proper endodyogeny, as shown by the proliferation defects, multiple-nuclei phenotype, and detergent-soluble IMC1 in the MCA1/MCA2 double-knockout strain.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TgMCA1 is a Toxoplasma gondii cysteine protease (metacaspase) that undergoes autoproteolytic processing and contributes to apoptosis-like cell death and to the biogenesis of the inner membrane complex (IMC) during endodyogeny [#0, #1, #4]. Under normal conditions the protein is dispersed throughout the cytoplasm with punctate aggregation and partially co-localizes with the IMC, but relocalizes to the nucleus when parasites are exposed to extracellular buffer, consistent with a nuclear execution step in stress-induced cell death [#0, #3]. Functionally, TgMCA1 drives apoptosis-like death: its knockout reduces, and its overexpression increases, TUNEL-positive parasites after extracellular buffer treatment [#1]. TgMCA1 is redundant with MCA2 for replication and virulence — single deletion has no effect on growth or pathogenesis — but the two proteases together are required for normal endodyogeny and for IMC1 maturation, since their combined loss produces proliferation defects, multiple nuclei, and detergent-soluble (unprocessed/immature) IMC1 [#2, #4, #5]. The direct proteolytic substrates of TgMCA1 and the molecular basis of its IMC1-maturation role have not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing whether TgMCA1 is a functional protease and how its localization is regulated addressed how a metacaspase might execute a stress response in T. gondii.\",\n      \"evidence\": \"Western blot for autoproteolytic processing and indirect immunofluorescence for localization in T. gondii\",\n      \"pmids\": [\"26834715\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No in vitro reconstitution or structural data on the protease activity\",\n        \"The trigger and machinery driving nuclear relocalization are unidentified\",\n        \"No direct substrate identified\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Genetic loss- and gain-of-function tests answered whether TgMCA1 actively promotes cell death versus merely correlating with it, linking the protease to an apoptosis-like death program.\",\n      \"evidence\": \"TUNEL assay on TgMCA1 knockout and overexpression strains after extracellular buffer treatment\",\n      \"pmids\": [\"26834715\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The downstream death effectors and cleaved targets are unknown\",\n        \"Physiological relevance of buffer-induced death is unclear\",\n        \"Single lab, single phenotypic readout\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Deleting MCA1 alone tested its requirement for the parasite lytic cycle and revealed functional redundancy rather than an essential role in replication or virulence.\",\n      \"evidence\": \"In vitro growth assay and in vivo virulence assessment of the TgMCA1 knockout\",\n      \"pmids\": [\"26834715\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Redundant partner not yet identified in this study\",\n        \"Negative result does not exclude subtle fitness roles\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Mapping MCA1/MCA2 to the IMC and testing double-deletion epistasis identified a non-death role: joint requirement for endodyogeny and IMC1 maturation.\",\n      \"evidence\": \"IFA localization plus MCA1/MCA2 double-knockout proliferation, endodyogeny microscopy, and IMC1 detergent-solubility assay in RH\\u0394ku80\",\n      \"pmids\": [\"34384491\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MCA1 cleaves IMC1 directly is not shown\",\n        \"Molecular mechanism of IMC1 insolubilization is unresolved\",\n        \"Individual contribution of MCA1 vs MCA2 to IMC maturation not separated\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct proteolytic substrates of TgMCA1 and the biochemical mechanism by which it and MCA2 drive IMC1 maturation remain unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No substrate identified for TgMCA1\",\n        \"No structural model of the protease\",\n        \"Signal linking extracellular stress to nuclear relocalization uncharacterized\"\n      ],\n      \"attribution\": []\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004197\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [0, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006915\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MCA2\"],\n    \"other_free_text\": [\n      \"Undergoes autoproteolytic processing [#0]\",\n      \"Partially co-localizes with the inner membrane complex (IMC) [#3]\",\n      \"Relocalizes from cytoplasm to nucleus upon extracellular buffer stress [#0]\",\n      \"Functionally redundant with MCA2 for replication and virulence; jointly required for endodyogeny and IMC1 maturation (insolubilization) [#2, #4, #5]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_206490","name":"MCA1","product":"metacaspase MCA1","uniprot_acc":"S8F2G8","chromosome":"TGME49_chrVIIa","start_pos":932262},{"strain":"GT1","gene_id":"TGGT1_206490","name":null,"product":"ICE family protease (caspase) p20 domain-containing protein","uniprot_acc":null,"chromosome":"TGGT1_chrVIIa","start_pos":908830},{"strain":"RH88","gene_id":"TGRH88_033520","name":null,"product":"ICE family protease (caspase) p20 domain-containing protein","uniprot_acc":null,"chromosome":"CM023088","start_pos":1011138},{"strain":"VEG","gene_id":"TGVEG_206490","name":null,"product":"ICE family protease (caspase) p20 domain-containing protein","uniprot_acc":"V4ZDI2","chromosome":"TGVEG_chrVIIa","start_pos":990141}]}