{"gene":"TG_278660","gene_symbol":"ATP4","run_date":"2026-09-08T14:08:30","timeline":{"discoveries":[{"year":2019,"finding":"TgATP4 localizes to the plasma membrane of Toxoplasma gondii, as determined by direct experimental characterization.","method":"Subcellular fractionation / localization experiments (genetic and physiological approaches)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence, single lab, multiple orthogonal approaches described","pmids":["30723156"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"TgATP4 functions as a Na+ efflux pump required for cytosolic Na+ regulation; knockdown of TgATP4 rendered parasites unable to regulate their cytosolic Na+ concentration but had no effect on resting pH or Ca2+ levels.","method":"Genetic knockdown combined with ion concentration physiological measurements (cytosolic Na+ monitoring)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean knockdown with defined ionic phenotype, multiple orthogonal physiological readouts (Na+, pH, Ca2+) in a single rigorous study","pmids":["30723156"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"PfATP4 inhibitors (including cipargamin) caused an increase in cytosolic Na+ and cytosolic alkalinization in wild-type parasites but not in TgATP4 knockdown parasites, demonstrating that TgATP4 is the molecular target of these compounds in Toxoplasma.","method":"Pharmacological inhibition combined with genetic knockdown and physiological ion/pH measurements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — epistatic pharmacological-genetic experiment with multiple orthogonal readouts (Na+ and pH) in a single rigorous study","pmids":["30723156"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"Knockdown or disruption of TgATP4 caused a growth defect attributable specifically to reduced viability of extracellular parasites, and TgATP4-disrupted parasites showed reduced virulence in mice.","method":"Genetic knockdown/disruption with growth and in vivo virulence assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function with defined cellular and in vivo phenotype, single lab","pmids":["30723156"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"Phylogenetic analysis established that ATP4 proteins form a clade of P-type ATPases restricted to apicomplexans and their closest relatives, representing a conserved Na+ regulatory mechanism across apicomplexan parasites.","method":"Phylogenetic analysis combined with functional genetic and physiological characterization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phylogenetic classification supported by functional experiments, single lab","pmids":["30723156"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgATP4 is an apicomplexan-restricted P-type ATPase localized to the plasma membrane of Toxoplasma gondii that functions as a Na+ efflux pump (exchanging Na+ for H+), essential for cytosolic Na+ homeostasis; its loss impairs extracellular parasite viability, reduces in vivo virulence, and renders parasites insensitive to PfATP4-class antimalarial compounds that otherwise elevate cytosolic Na+ and alkalinize the cytosol."},"narrative":{"mechanistic_narrative":"ATP4 (TgATP4) is a plasma membrane P-type ATPase of Toxoplasma gondii that functions as a Na+ efflux pump essential for cytosolic Na+ homeostasis [PMID:30723156]. Genetic knockdown abolishes the parasite's ability to regulate cytosolic Na+ without affecting resting pH or Ca2+, defining a selective role in sodium regulation [PMID:30723156]. TgATP4 is the molecular target of PfATP4-class antimalarial compounds, including cipargamin, which elevate cytosolic Na+ and alkalinize the cytosol in wild-type but not TgATP4-knockdown parasites [PMID:30723156]. Loss of TgATP4 reduces the viability of extracellular parasites and attenuates virulence in mice [PMID:30723156]. Phylogenetically, ATP4 proteins form an apicomplexan-restricted clade representing a conserved Na+ regulatory mechanism across these parasites [PMID:30723156]. Beyond these findings, no further mechanistic or structural detail has been characterized in the available corpus.","teleology":[{"year":2019,"claim":"Establishing where TgATP4 acts was prerequisite to assigning its transport function; localization placed it at the plasma membrane, the interface for ion exchange with the extracellular environment.","evidence":"Subcellular fractionation and localization experiments in T. gondii","pmids":["30723156"],"confidence":"Medium","gaps":["Topology and membrane insertion determinants not resolved","No structural model of the transporter"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Whether TgATP4 regulates a specific ion was unknown; knockdown showed it is required for cytosolic Na+ regulation but dispensable for pH and Ca2+ homeostasis, defining it as a selective Na+ efflux pump.","evidence":"Genetic knockdown with cytosolic Na+, pH, and Ca2+ physiological measurements in T. gondii","pmids":["30723156"],"confidence":"High","gaps":["Direct demonstration of Na+/H+ exchange stoichiometry not shown","Transport activity not reconstituted in vitro"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"The molecular target of PfATP4-class antimalarials in Toxoplasma was untested; epistatic pharmacology-genetics established TgATP4 as the target, since the compounds' ionic effects require the protein.","evidence":"Pharmacological inhibition (cipargamin) combined with knockdown and ion/pH measurements in T. gondii","pmids":["30723156"],"confidence":"High","gaps":["Drug-binding site on TgATP4 not mapped","Resistance mutations not characterized"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"The physiological importance of Na+ regulation was addressed by loss-of-function; disruption reduced extracellular parasite viability and virulence in mice, linking Na+ homeostasis to fitness and pathogenesis.","evidence":"Genetic knockdown/disruption with growth assays and in vivo mouse virulence assays","pmids":["30723156"],"confidence":"Medium","gaps":["Mechanism linking extracellular Na+ dysregulation to loss of viability unresolved","Stage-specific requirements not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Whether ATP4 function is conserved beyond Toxoplasma was addressed phylogenetically; ATP4 proteins form an apicomplexan-restricted P-type ATPase clade, indicating a conserved parasite Na+ regulatory mechanism.","evidence":"Phylogenetic analysis alongside functional genetic and physiological characterization","pmids":["30723156"],"confidence":"Medium","gaps":["Functional conservation across other apicomplexans not directly tested here","Evolutionary origin of the clade not resolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The catalytic and structural basis of Na+/H+ exchange by TgATP4 and the precise drug-binding determinants remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No in vitro reconstitution of transport activity","No structure or drug-binding site mapping","Ion exchange stoichiometry undetermined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":[],"other_free_text":["Molecular target of PfATP4-class antimalarial compounds including cipargamin in T. gondii [#2]","Required for extracellular parasite viability and in vivo virulence in mice [#3]","Member of an apicomplexan-restricted P-type ATPase clade [#4]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"30723156","id":"PMC_30723156","title":"Characterization of the ATP4 ion pump in Toxoplasma gondii.","date":"2019","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30723156","citation_count":19,"is_preprint":false},{"pmid":"33023071","id":"PMC_33023071","title":"The Functioning of Na+-ATPases from Protozoan Parasites: Are These Pumps Targets for Antiparasitic Drugs?","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33023071","citation_count":16,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3415,"output_tokens":1165,"usd":0.01386,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6208,"output_tokens":2243,"usd":0.043557,"stage2_stop_reason":"end_turn"},"total_usd":0.057417,"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\": 2019,\n      \"finding\": \"TgATP4 localizes to the plasma membrane of Toxoplasma gondii, as determined by direct experimental characterization.\",\n      \"method\": \"Subcellular fractionation / localization experiments (genetic and physiological approaches)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence, single lab, multiple orthogonal approaches described\",\n      \"pmids\": [\"30723156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TgATP4 functions as a Na+ efflux pump required for cytosolic Na+ regulation; knockdown of TgATP4 rendered parasites unable to regulate their cytosolic Na+ concentration but had no effect on resting pH or Ca2+ levels.\",\n      \"method\": \"Genetic knockdown combined with ion concentration physiological measurements (cytosolic Na+ monitoring)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockdown with defined ionic phenotype, multiple orthogonal physiological readouts (Na+, pH, Ca2+) in a single rigorous study\",\n      \"pmids\": [\"30723156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PfATP4 inhibitors (including cipargamin) caused an increase in cytosolic Na+ and cytosolic alkalinization in wild-type parasites but not in TgATP4 knockdown parasites, demonstrating that TgATP4 is the molecular target of these compounds in Toxoplasma.\",\n      \"method\": \"Pharmacological inhibition combined with genetic knockdown and physiological ion/pH measurements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistatic pharmacological-genetic experiment with multiple orthogonal readouts (Na+ and pH) in a single rigorous study\",\n      \"pmids\": [\"30723156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Knockdown or disruption of TgATP4 caused a growth defect attributable specifically to reduced viability of extracellular parasites, and TgATP4-disrupted parasites showed reduced virulence in mice.\",\n      \"method\": \"Genetic knockdown/disruption with growth and in vivo virulence assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function with defined cellular and in vivo phenotype, single lab\",\n      \"pmids\": [\"30723156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Phylogenetic analysis established that ATP4 proteins form a clade of P-type ATPases restricted to apicomplexans and their closest relatives, representing a conserved Na+ regulatory mechanism across apicomplexan parasites.\",\n      \"method\": \"Phylogenetic analysis combined with functional genetic and physiological characterization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phylogenetic classification supported by functional experiments, single lab\",\n      \"pmids\": [\"30723156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgATP4 is an apicomplexan-restricted P-type ATPase localized to the plasma membrane of Toxoplasma gondii that functions as a Na+ efflux pump (exchanging Na+ for H+), essential for cytosolic Na+ homeostasis; its loss impairs extracellular parasite viability, reduces in vivo virulence, and renders parasites insensitive to PfATP4-class antimalarial compounds that otherwise elevate cytosolic Na+ and alkalinize the cytosol.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATP4 (TgATP4) is a plasma membrane P-type ATPase of Toxoplasma gondii that functions as a Na+ efflux pump essential for cytosolic Na+ homeostasis [#0, #1]. Genetic knockdown abolishes the parasite's ability to regulate cytosolic Na+ without affecting resting pH or Ca2+, defining a selective role in sodium regulation [#1]. TgATP4 is the molecular target of PfATP4-class antimalarial compounds, including cipargamin, which elevate cytosolic Na+ and alkalinize the cytosol in wild-type but not TgATP4-knockdown parasites [#2]. Loss of TgATP4 reduces the viability of extracellular parasites and attenuates virulence in mice [#3]. Phylogenetically, ATP4 proteins form an apicomplexan-restricted clade representing a conserved Na+ regulatory mechanism across these parasites [#4]. Beyond these findings, no further mechanistic or structural detail has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing where TgATP4 acts was prerequisite to assigning its transport function; localization placed it at the plasma membrane, the interface for ion exchange with the extracellular environment.\",\n      \"evidence\": \"Subcellular fractionation and localization experiments in T. gondii\",\n      \"pmids\": [\"30723156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Topology and membrane insertion determinants not resolved\", \"No structural model of the transporter\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Whether TgATP4 regulates a specific ion was unknown; knockdown showed it is required for cytosolic Na+ regulation but dispensable for pH and Ca2+ homeostasis, defining it as a selective Na+ efflux pump.\",\n      \"evidence\": \"Genetic knockdown with cytosolic Na+, pH, and Ca2+ physiological measurements in T. gondii\",\n      \"pmids\": [\"30723156\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration of Na+/H+ exchange stoichiometry not shown\", \"Transport activity not reconstituted in vitro\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The molecular target of PfATP4-class antimalarials in Toxoplasma was untested; epistatic pharmacology-genetics established TgATP4 as the target, since the compounds' ionic effects require the protein.\",\n      \"evidence\": \"Pharmacological inhibition (cipargamin) combined with knockdown and ion/pH measurements in T. gondii\",\n      \"pmids\": [\"30723156\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Drug-binding site on TgATP4 not mapped\", \"Resistance mutations not characterized\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The physiological importance of Na+ regulation was addressed by loss-of-function; disruption reduced extracellular parasite viability and virulence in mice, linking Na+ homeostasis to fitness and pathogenesis.\",\n      \"evidence\": \"Genetic knockdown/disruption with growth assays and in vivo mouse virulence assays\",\n      \"pmids\": [\"30723156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking extracellular Na+ dysregulation to loss of viability unresolved\", \"Stage-specific requirements not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Whether ATP4 function is conserved beyond Toxoplasma was addressed phylogenetically; ATP4 proteins form an apicomplexan-restricted P-type ATPase clade, indicating a conserved parasite Na+ regulatory mechanism.\",\n      \"evidence\": \"Phylogenetic analysis alongside functional genetic and physiological characterization\",\n      \"pmids\": [\"30723156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional conservation across other apicomplexans not directly tested here\", \"Evolutionary origin of the clade not resolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The catalytic and structural basis of Na+/H+ exchange by TgATP4 and the precise drug-binding determinants remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of transport activity\", \"No structure or drug-binding site mapping\", \"Ion exchange stoichiometry undetermined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008554\", \"supporting_discovery_ids\": [1, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0005391\", \"supporting_discovery_ids\": [1, 4], \"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:0006883\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": [\n      \"Molecular target of PfATP4-class antimalarial compounds including cipargamin in T. gondii [#2]\",\n      \"Required for extracellular parasite viability and in vivo virulence in mice [#3]\",\n      \"Member of an apicomplexan-restricted P-type ATPase clade [#4]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_278660","name":"ATP4","product":"P-type ATPase4","uniprot_acc":"S8EPT0","chromosome":"TGME49_chrXII","start_pos":5948520},{"strain":"GT1","gene_id":"TGGT1_278660","name":null,"product":"putative P-type ATPase4","uniprot_acc":null,"chromosome":"TGGT1_chrXII","start_pos":5863040},{"strain":"RH88","gene_id":"TGRH88_065220","name":null,"product":"putative P-type ATPase4","uniprot_acc":null,"chromosome":"CM023093","start_pos":6026376},{"strain":"VEG","gene_id":"TGVEG_278660","name":null,"product":"putative P-type ATPase4","uniprot_acc":"B9QMJ0","chromosome":"TGVEG_chrXII","start_pos":5954616}]}