{"gene":"TG_208730","gene_symbol":"MCP4","run_date":"2026-09-08T11:06:19","timeline":{"discoveries":[{"year":2013,"finding":"MCP4 physically associates with bradyzoite pseudokinase 1 (BPK1) in the cyst wall, as identified by immunoprecipitation of BPK1 from in vitro bradyzoite cultures; MCP4 is thus a binding partner of BPK1 within the cyst wall complex.","method":"Immunoprecipitation from in vitro bradyzoite cultures followed by protein identification","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP experiment identifying MCP4 as a BPK1-associated protein; no reciprocal pull-down or orthogonal validation reported in abstract","pmids":["23291621"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"MCP4 is a component of the Toxoplasma gondii cyst wall, as confirmed by its identification in a purified cyst wall preparation enriched by Percoll gradient centrifugation and CST1 immunoprecipitation, analyzed by LC-MS/MS.","method":"Subcellular fractionation (Percoll gradient enrichment), immunoprecipitation with CST1 antibody, liquid chromatography-tandem mass spectrometry (LC-MS/MS)","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomic identification in enriched cyst wall fraction using two orthogonal purification steps; localization not independently validated for MCP4 specifically in this study","pmids":["31040239"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"MCP4 expression is transcriptionally repressed in tachyzoites by the ApiAP2 factor AP2IV-4; deletion of AP2IV-4 resulted in ectopic expression of MCP4 (a bradyzoite-specific cyst wall component) during the tachyzoite stage, placing AP2IV-4 upstream of MCP4 in the transcriptional regulatory hierarchy controlling bradyzoite differentiation.","method":"Genetic deletion (AP2IV-4 knockout) with immunological detection of MCP4 expression in replicating tachyzoites; murine animal model validation","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with specific phenotypic readout (ectopic MCP4 expression), single lab, validated in vivo","pmids":["29718996"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"MCP4 is a bradyzoite-specific cyst wall protein whose expression is transcriptionally repressed in tachyzoites by the ApiAP2 factor AP2IV-4, physically associates with BPK1 (and co-purifies with MAG1, GRA2, GRA3, GRA5, GRA8, and GRA9) within the cyst wall, and localizes to this structure as confirmed by proteomic characterization of purified cyst wall fractions."},"narrative":{"mechanistic_narrative":"MCP4 is a bradyzoite-specific cyst wall protein of Toxoplasma gondii that contributes to the protein architecture of the tissue cyst wall during chronic-stage differentiation [PMID:31040239]. It physically associates with the bradyzoite pseudokinase BPK1 within the cyst wall complex, marking it as a member of this wall-associated assembly [PMID:23291621]. Its stage-restricted expression is enforced transcriptionally: the ApiAP2 factor AP2IV-4 represses MCP4 in tachyzoites, and loss of AP2IV-4 causes ectopic MCP4 expression in replicating tachyzoites, placing AP2IV-4 upstream of MCP4 in the regulatory hierarchy governing bradyzoite differentiation [PMID:29718996]. Beyond its cyst wall localization, its BPK1 association, and its AP2IV-4-dependent repression, no biochemical activity or structural function for MCP4 has been characterized in the available corpus.","teleology":[{"year":2013,"claim":"To define the molecular composition of the bradyzoite cyst wall complex, MCP4 was identified as a physical partner of the pseudokinase BPK1, establishing it as a member of a wall-associated protein assembly rather than a free-standing factor.","evidence":"Immunoprecipitation of BPK1 from in vitro bradyzoite cultures with protein identification","pmids":["23291621"],"confidence":"Medium","gaps":["Single Co-IP without reciprocal pull-down or orthogonal validation of the MCP4-BPK1 interaction","The functional consequence of the MCP4-BPK1 association is undefined","Whether the interaction is direct or bridged by other cyst wall components is unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"claim":"To understand how MCP4's bradyzoite-restricted expression is controlled, the ApiAP2 factor AP2IV-4 was shown to repress MCP4 in tachyzoites, placing a specific transcriptional regulator upstream of this cyst wall component in the differentiation program.","evidence":"AP2IV-4 genetic knockout with immunological detection of ectopic MCP4 in tachyzoites, validated in a murine model","pmids":["29718996"],"confidence":"Medium","gaps":["Whether AP2IV-4 binds the MCP4 locus directly or acts indirectly is not resolved","The activating factors that drive MCP4 expression in bona fide bradyzoites are not identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"To confirm MCP4's subcellular assignment, proteomic analysis of a purified cyst wall fraction independently placed MCP4 in the cyst wall, corroborating its role as a structural constituent of this compartment.","evidence":"Percoll gradient enrichment and CST1 immunoprecipitation of the cyst wall followed by LC-MS/MS","pmids":["31040239"],"confidence":"Medium","gaps":["Localization not independently validated for MCP4 specifically (e.g. by tagging or microscopy) in this study","The contribution of MCP4 to cyst wall integrity or persistence is untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The biochemical activity and structural function of MCP4 within the cyst wall, and the mechanism by which it engages BPK1 and other wall components, remain unknown.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No loss-of-function phenotype for MCP4 itself has been reported","No structural model or biochemical activity is defined","Whether MCP4 is required for cyst wall formation or bradyzoite persistence is untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Cyst wall protein complex (BPK1-associated)"],"partners":["BPK1"],"other_free_text":["Bradyzoite-specific cyst wall protein whose tachyzoite-stage expression is repressed by the ApiAP2 transcription factor AP2IV-4","Co-purifies with cyst wall fractions enriched via CST1 immunoprecipitation"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"29718996","id":"PMC_29718996","title":"Transcriptional repression by ApiAP2 factors is central to chronic toxoplasmosis.","date":"2018","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/29718996","citation_count":77,"is_preprint":false},{"pmid":"31040239","id":"PMC_31040239","title":"Enrichment and Proteomic Characterization of the Cyst Wall from In Vitro Toxoplasma gondii Cysts.","date":"2019","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/31040239","citation_count":65,"is_preprint":false},{"pmid":"23291621","id":"PMC_23291621","title":"Bradyzoite pseudokinase 1 is crucial for efficient oral infectivity of the Toxoplasma gondii tissue cyst.","date":"2013","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/23291621","citation_count":41,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4033,"output_tokens":914,"usd":0.012904,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5763,"output_tokens":1856,"usd":0.037608,"stage2_stop_reason":"end_turn"},"total_usd":0.050512,"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\": 2013,\n      \"finding\": \"MCP4 physically associates with bradyzoite pseudokinase 1 (BPK1) in the cyst wall, as identified by immunoprecipitation of BPK1 from in vitro bradyzoite cultures; MCP4 is thus a binding partner of BPK1 within the cyst wall complex.\",\n      \"method\": \"Immunoprecipitation from in vitro bradyzoite cultures followed by protein identification\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP experiment identifying MCP4 as a BPK1-associated protein; no reciprocal pull-down or orthogonal validation reported in abstract\",\n      \"pmids\": [\"23291621\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MCP4 is a component of the Toxoplasma gondii cyst wall, as confirmed by its identification in a purified cyst wall preparation enriched by Percoll gradient centrifugation and CST1 immunoprecipitation, analyzed by LC-MS/MS.\",\n      \"method\": \"Subcellular fractionation (Percoll gradient enrichment), immunoprecipitation with CST1 antibody, liquid chromatography-tandem mass spectrometry (LC-MS/MS)\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomic identification in enriched cyst wall fraction using two orthogonal purification steps; localization not independently validated for MCP4 specifically in this study\",\n      \"pmids\": [\"31040239\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MCP4 expression is transcriptionally repressed in tachyzoites by the ApiAP2 factor AP2IV-4; deletion of AP2IV-4 resulted in ectopic expression of MCP4 (a bradyzoite-specific cyst wall component) during the tachyzoite stage, placing AP2IV-4 upstream of MCP4 in the transcriptional regulatory hierarchy controlling bradyzoite differentiation.\",\n      \"method\": \"Genetic deletion (AP2IV-4 knockout) with immunological detection of MCP4 expression in replicating tachyzoites; murine animal model validation\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with specific phenotypic readout (ectopic MCP4 expression), single lab, validated in vivo\",\n      \"pmids\": [\"29718996\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"MCP4 is a bradyzoite-specific cyst wall protein whose expression is transcriptionally repressed in tachyzoites by the ApiAP2 factor AP2IV-4, physically associates with BPK1 (and co-purifies with MAG1, GRA2, GRA3, GRA5, GRA8, and GRA9) within the cyst wall, and localizes to this structure as confirmed by proteomic characterization of purified cyst wall fractions.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MCP4 is a bradyzoite-specific cyst wall protein of Toxoplasma gondii that contributes to the protein architecture of the tissue cyst wall during chronic-stage differentiation [#1]. It physically associates with the bradyzoite pseudokinase BPK1 within the cyst wall complex, marking it as a member of this wall-associated assembly [#0]. Its stage-restricted expression is enforced transcriptionally: the ApiAP2 factor AP2IV-4 represses MCP4 in tachyzoites, and loss of AP2IV-4 causes ectopic MCP4 expression in replicating tachyzoites, placing AP2IV-4 upstream of MCP4 in the regulatory hierarchy governing bradyzoite differentiation [#2]. Beyond its cyst wall localization, its BPK1 association, and its AP2IV-4-dependent repression, no biochemical activity or structural function for MCP4 has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"To define the molecular composition of the bradyzoite cyst wall complex, MCP4 was identified as a physical partner of the pseudokinase BPK1, establishing it as a member of a wall-associated protein assembly rather than a free-standing factor.\",\n      \"evidence\": \"Immunoprecipitation of BPK1 from in vitro bradyzoite cultures with protein identification\",\n      \"pmids\": [\"23291621\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single Co-IP without reciprocal pull-down or orthogonal validation of the MCP4-BPK1 interaction\",\n        \"The functional consequence of the MCP4-BPK1 association is undefined\",\n        \"Whether the interaction is direct or bridged by other cyst wall components is unknown\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"To understand how MCP4's bradyzoite-restricted expression is controlled, the ApiAP2 factor AP2IV-4 was shown to repress MCP4 in tachyzoites, placing a specific transcriptional regulator upstream of this cyst wall component in the differentiation program.\",\n      \"evidence\": \"AP2IV-4 genetic knockout with immunological detection of ectopic MCP4 in tachyzoites, validated in a murine model\",\n      \"pmids\": [\"29718996\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether AP2IV-4 binds the MCP4 locus directly or acts indirectly is not resolved\",\n        \"The activating factors that drive MCP4 expression in bona fide bradyzoites are not identified\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"To confirm MCP4's subcellular assignment, proteomic analysis of a purified cyst wall fraction independently placed MCP4 in the cyst wall, corroborating its role as a structural constituent of this compartment.\",\n      \"evidence\": \"Percoll gradient enrichment and CST1 immunoprecipitation of the cyst wall followed by LC-MS/MS\",\n      \"pmids\": [\"31040239\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Localization not independently validated for MCP4 specifically (e.g. by tagging or microscopy) in this study\",\n        \"The contribution of MCP4 to cyst wall integrity or persistence is untested\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical activity and structural function of MCP4 within the cyst wall, and the mechanism by which it engages BPK1 and other wall components, remain unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No loss-of-function phenotype for MCP4 itself has been reported\",\n        \"No structural model or biochemical activity is defined\",\n        \"Whether MCP4 is required for cyst wall formation or bradyzoite persistence is untested\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"cyst wall\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"bradyzoite differentiation\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\"Cyst wall protein complex (BPK1-associated)\"],\n    \"partners\": [\"BPK1\"],\n    \"other_free_text\": [\n      \"Bradyzoite-specific cyst wall protein whose tachyzoite-stage expression is repressed by the ApiAP2 transcription factor AP2IV-4\",\n      \"Co-purifies with cyst wall fractions enriched via CST1 immunoprecipitation\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_208730","name":"MCP4","product":"microneme adhesive repeat protein MCP4","uniprot_acc":"S8GKM2","chromosome":"TGME49_chrIb","start_pos":832243},{"strain":"GT1","gene_id":"TGGT1_208730","name":null,"product":"putative microneme protein","uniprot_acc":null,"chromosome":"TGGT1_chrIb","start_pos":849268},{"strain":"RH88","gene_id":"TGRH88_022280","name":null,"product":"putative microneme protein","uniprot_acc":null,"chromosome":"CM023082","start_pos":1174125},{"strain":"VEG","gene_id":"TGVEG_208730","name":null,"product":"putative microneme protein","uniprot_acc":"A0A125YX25","chromosome":"TGVEG_chrIb","start_pos":832332}]}