{"gene":"TG_257530","gene_symbol":"ApiAT5","run_date":"2026-09-08T12:58:25","timeline":{"discoveries":[{"year":2019,"finding":"TgApiAT5-3 is a plasma membrane-localized amino acid transporter that functions as an exchanger for aromatic and large neutral amino acids, with particular importance for L-tyrosine scavenging and amino acid homeostasis in T. gondii tachyzoites.","method":"Functional characterization of ApiAT family transporters including heterologous expression, plasma membrane localization assays, and loss-of-function studies with intracellular growth phenotyping","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (heterologous expression, localization, loss-of-function with defined phenotype) in a single rigorous study","pmids":["30742695"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"ApiAT5-3 (TgApiAT5-3) is a tyrosine transporter of the major facilitator superfamily that is phosphorylated at serine 56 by TgCDPK3 upon induction of calcium signalling; this phosphorylation is beneficial but not essential for tyrosine import.","method":"Phosphoproteomic comparison of WT vs. ΔTgCDPK3 parasites; site-directed mutagenesis (S56A); conditional knockout; metabolomics; heterologous expression","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (phosphoproteomics, mutagenesis, metabolomics, heterologous expression) in a single rigorous study","pmids":["30402958"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"Conditional knockout of apiAT5-3 results in transcriptional upregulation of most ribosomal subunits (but no alternative transporters) and subsequent parasite death, demonstrating that ApiAT5-3 is essential for parasite survival.","method":"Conditional knockout of apiAT5-3 with transcriptomic analysis of resulting phenotype","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional knockout with defined lethal phenotype and transcriptomic follow-up, single lab","pmids":["30402958"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"TgApiAT5-3 is critical for parasite virulence, as demonstrated by loss-of-function studies showing its importance for intracellular growth of the tachyzoite stage.","method":"Loss-of-function genetic analysis with intracellular growth and virulence phenotyping","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined virulence phenotype, single lab, single study","pmids":["30742695"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgApiAT5-3 is an essential plasma membrane-localized major facilitator superfamily transporter in T. gondii tachyzoites that functions as an exchanger for aromatic and large neutral amino acids (primarily L-tyrosine), is phosphorylated at serine 56 by TgCDPK3 upon calcium signalling in a manner that is beneficial but not strictly required for transport activity, and is indispensable for parasite survival and virulence."},"narrative":{"mechanistic_narrative":"TgApiAT5-3 is a plasma membrane-localized major facilitator superfamily amino acid transporter that governs aromatic and large neutral amino acid homeostasis in Toxoplasma gondii tachyzoites, functioning as an exchanger with particular importance for L-tyrosine scavenging [PMID:30742695, PMID:30402958]. Its transport activity is modulated by calcium signalling: TgCDPK3 phosphorylates the transporter at serine 56, an event that is beneficial but not strictly required for tyrosine import [PMID:30402958]. Conditional loss of apiAT5-3 triggers transcriptional upregulation of ribosomal subunits without induction of compensatory transporters, followed by parasite death, establishing the transporter as essential for survival and for intracellular growth and virulence of the tachyzoite stage [PMID:30402958, PMID:30742695].","teleology":[{"year":2018,"claim":"Establishing that TgApiAT5-3 is a tyrosine transporter under kinase control connected amino acid uptake to calcium signalling in the parasite.","evidence":"phosphoproteomics of WT vs ΔTgCDPK3, S56A site-directed mutagenesis, conditional knockout, metabolomics, and heterologous expression in T. gondii","pmids":["30402958"],"confidence":"High","gaps":["Functional consequence of the S56 phosphorylation on transporter kinetics beyond a 'beneficial' effect is not resolved","Structural basis of substrate recognition and the exchange mechanism is undefined","Whether other kinases or signals regulate the transporter is unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"claim":"Conditional depletion showed the transporter is genuinely essential rather than redundant, with no compensatory transporter induction masking its loss.","evidence":"conditional knockout of apiAT5-3 with transcriptomic profiling in T. gondii","pmids":["30402958"],"confidence":"Medium","gaps":["Mechanistic link between transporter loss, ribosomal subunit upregulation, and cell death is not defined","Single-lab result"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Placing TgApiAT5-3 within the ApiAT transporter family defined it as a plasma membrane exchanger for aromatic and large neutral amino acids critical to amino acid homeostasis and virulence.","evidence":"heterologous expression, plasma membrane localization assays, and loss-of-function intracellular growth and virulence phenotyping in T. gondii","pmids":["30742695"],"confidence":"High","gaps":["Full substrate range and directionality of exchange beyond tyrosine not fully mapped","Contribution to virulence in vivo across life-cycle stages not characterized"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"How S56 phosphorylation mechanistically tunes transport, and how tyrosine deprivation is sensed to drive the lethal ribosomal response, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the transporter or its substrate-binding site","Mechanism coupling nutrient loss to ribosomal transcriptional response undefined","No data outside the tachyzoite stage"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["TGCDPK3 (PHOSPHORYLATES TGAPIAT5-3 AT SERINE 56)"],"other_free_text":["Functions as an exchanger for aromatic and large neutral amino acids, with a primary role in L-tyrosine scavenging.","Phosphorylated at serine 56 by TgCDPK3 upon calcium signalling; phosphorylation is beneficial but not essential for tyrosine import.","Essential for tachyzoite survival; conditional knockout causes ribosomal subunit transcriptional upregulation without compensatory transporter induction, followed by death.","Required for intracellular growth and virulence of the tachyzoite stage."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"30742695","id":"PMC_30742695","title":"The tyrosine transporter of Toxoplasma gondii is a member of the newly defined apicomplexan amino acid transporter (ApiAT) family.","date":"2019","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/30742695","citation_count":46,"is_preprint":false},{"pmid":"30402958","id":"PMC_30402958","title":"Characterisation of the Toxoplasma gondii tyrosine transporter and its phosphorylation by the calcium-dependent protein kinase 3.","date":"2018","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30402958","citation_count":16,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3370,"output_tokens":1074,"usd":0.01311,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5963,"output_tokens":1983,"usd":0.039695,"stage2_stop_reason":"end_turn"},"total_usd":0.052805,"stage1_batch_id":"msgbatch_01TEPNZ4MCzJ7xtsNwosiDRk","stage2_batch_id":"msgbatch_01FQShM7n1sfCr4pWTDShmki","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"TgApiAT5-3 is a plasma membrane-localized amino acid transporter that functions as an exchanger for aromatic and large neutral amino acids, with particular importance for L-tyrosine scavenging and amino acid homeostasis in T. gondii tachyzoites.\",\n      \"method\": \"Functional characterization of ApiAT family transporters including heterologous expression, plasma membrane localization assays, and loss-of-function studies with intracellular growth phenotyping\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (heterologous expression, localization, loss-of-function with defined phenotype) in a single rigorous study\",\n      \"pmids\": [\"30742695\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ApiAT5-3 (TgApiAT5-3) is a tyrosine transporter of the major facilitator superfamily that is phosphorylated at serine 56 by TgCDPK3 upon induction of calcium signalling; this phosphorylation is beneficial but not essential for tyrosine import.\",\n      \"method\": \"Phosphoproteomic comparison of WT vs. ΔTgCDPK3 parasites; site-directed mutagenesis (S56A); conditional knockout; metabolomics; heterologous expression\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (phosphoproteomics, mutagenesis, metabolomics, heterologous expression) in a single rigorous study\",\n      \"pmids\": [\"30402958\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Conditional knockout of apiAT5-3 results in transcriptional upregulation of most ribosomal subunits (but no alternative transporters) and subsequent parasite death, demonstrating that ApiAT5-3 is essential for parasite survival.\",\n      \"method\": \"Conditional knockout of apiAT5-3 with transcriptomic analysis of resulting phenotype\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional knockout with defined lethal phenotype and transcriptomic follow-up, single lab\",\n      \"pmids\": [\"30402958\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TgApiAT5-3 is critical for parasite virulence, as demonstrated by loss-of-function studies showing its importance for intracellular growth of the tachyzoite stage.\",\n      \"method\": \"Loss-of-function genetic analysis with intracellular growth and virulence phenotyping\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined virulence phenotype, single lab, single study\",\n      \"pmids\": [\"30742695\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"TgApiAT5-3 is an essential plasma membrane-localized major facilitator superfamily transporter in T. gondii tachyzoites that functions as an exchanger for aromatic and large neutral amino acids (primarily L-tyrosine), is phosphorylated at serine 56 by TgCDPK3 upon calcium signalling in a manner that is beneficial but not strictly required for transport activity, and is indispensable for parasite survival and virulence.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgApiAT5-3 is a plasma membrane-localized major facilitator superfamily amino acid transporter that governs aromatic and large neutral amino acid homeostasis in Toxoplasma gondii tachyzoites, functioning as an exchanger with particular importance for L-tyrosine scavenging [#0, #1]. Its transport activity is modulated by calcium signalling: TgCDPK3 phosphorylates the transporter at serine 56, an event that is beneficial but not strictly required for tyrosine import [#1]. Conditional loss of apiAT5-3 triggers transcriptional upregulation of ribosomal subunits without induction of compensatory transporters, followed by parasite death, establishing the transporter as essential for survival and for intracellular growth and virulence of the tachyzoite stage [#2, #3].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Establishing that TgApiAT5-3 is a tyrosine transporter under kinase control connected amino acid uptake to calcium signalling in the parasite.\",\n      \"evidence\": \"phosphoproteomics of WT vs \\u0394TgCDPK3, S56A site-directed mutagenesis, conditional knockout, metabolomics, and heterologous expression in T. gondii\",\n      \"pmids\": [\"30402958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Functional consequence of the S56 phosphorylation on transporter kinetics beyond a 'beneficial' effect is not resolved\",\n        \"Structural basis of substrate recognition and the exchange mechanism is undefined\",\n        \"Whether other kinases or signals regulate the transporter is unknown\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Conditional depletion showed the transporter is genuinely essential rather than redundant, with no compensatory transporter induction masking its loss.\",\n      \"evidence\": \"conditional knockout of apiAT5-3 with transcriptomic profiling in T. gondii\",\n      \"pmids\": [\"30402958\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanistic link between transporter loss, ribosomal subunit upregulation, and cell death is not defined\",\n        \"Single-lab result\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placing TgApiAT5-3 within the ApiAT transporter family defined it as a plasma membrane exchanger for aromatic and large neutral amino acids critical to amino acid homeostasis and virulence.\",\n      \"evidence\": \"heterologous expression, plasma membrane localization assays, and loss-of-function intracellular growth and virulence phenotyping in T. gondii\",\n      \"pmids\": [\"30742695\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Full substrate range and directionality of exchange beyond tyrosine not fully mapped\",\n        \"Contribution to virulence in vivo across life-cycle stages not characterized\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How S56 phosphorylation mechanistically tunes transport, and how tyrosine deprivation is sensed to drive the lethal ribosomal response, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model of the transporter or its substrate-binding site\",\n        \"Mechanism coupling nutrient loss to ribosomal transcriptional response undefined\",\n        \"No data outside the tachyzoite stage\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0015171\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0005302\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006865\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0006979\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TgCDPK3 (phosphorylates TgApiAT5-3 at serine 56)\"],\n    \"other_free_text\": [\n      \"Functions as an exchanger for aromatic and large neutral amino acids, with a primary role in L-tyrosine scavenging.\",\n      \"Phosphorylated at serine 56 by TgCDPK3 upon calcium signalling; phosphorylation is beneficial but not essential for tyrosine import.\",\n      \"Essential for tachyzoite survival; conditional knockout causes ribosomal subunit transcriptional upregulation without compensatory transporter induction, followed by death.\",\n      \"Required for intracellular growth and virulence of the tachyzoite stage.\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_257530","name":"ApiAT5","product":"apicomplexan amino acid transporter ApiAT5-3","uniprot_acc":"A0A125YHI0","chromosome":"TGME49_chrVIIb","start_pos":3990909},{"strain":"GT1","gene_id":"TGGT1_257530","name":null,"product":"transporter, major facilitator family protein","uniprot_acc":null,"chromosome":"TGGT1_chrVIIb","start_pos":3924727},{"strain":"RH88","gene_id":"TGRH88_072370","name":null,"product":"transporter, major facilitator family protein","uniprot_acc":null,"chromosome":"CM023089","start_pos":4026305},{"strain":"VEG","gene_id":"TGVEG_257530","name":null,"product":"transporter, major facilitator family protein","uniprot_acc":"B6KB03","chromosome":"TGVEG_chrVIIb","start_pos":4009563}]}