{"gene":"TG_223000","gene_symbol":"DLC8a","run_date":"2026-09-06T08:22:39","timeline":{"discoveries":[{"year":2012,"finding":"TgDLC8a localizes specifically to the conoid at the apical end of T. gondii, a localization not shared by its orthologs in Eimeria, Plasmodium, or humans, establishing that conoid targeting is a unique feature of TgDLC8a.","method":"Subcellular localization by imaging/fractionation; comparative analysis with orthologs","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional comparative context, single lab, two orthogonal lines of evidence (localization + ortholog comparison)","pmids":["23233536"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"finding":"TgDLC8a forms a homodimer via β-strand swapping (each monomer's β strand interacts with the antiparallel β' strand of the opposing monomer), creating two identical binding grooves adapted for multitarget recognition — a structural arrangement distinct from the PfDLC8 homodimer.","method":"Crystal structure determination and structural comparison","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with mechanistic validation of dimerization interface and functional implications","pmids":["23233536"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"finding":"A phosphomimetic mutation S88E renders TgDLC8a monomeric and cytosolic in T. gondii, demonstrating that phosphorylation at S88 controls both the oligomeric state and subcellular localization of TgDLC8a.","method":"Site-directed mutagenesis (S88E phosphomimetic), localization imaging in T. gondii","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — active-site/PTM mutagenesis combined with in-parasite localization, single lab but two orthogonal readouts (dimerization state + localization shift)","pmids":["23233536"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"finding":"Overexpression of the monomeric phosphomimetic TgDLC8a-S88E inhibits parasite growth in human fibroblasts, establishing a functional requirement for the dimeric/conoid-localized form in parasite replication.","method":"Overexpression of S88E mutant; parasite growth assay in human fibroblasts","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function via dominant-negative overexpression with defined growth phenotype, single lab","pmids":["23233536"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"DLC8a localizes to the conoid, and its conditional depletion perturbs microneme exocytosis, demonstrating a role for DLC8a in microneme secretion.","method":"Conditional knockdown (auxin-inducible degron or similar), microneme secretion assays","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional depletion with direct secretion assay readout, combined with localization, single lab but multiple orthogonal phenotypic readouts","pmids":["31206964"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"Conditional depletion of DLC8a disrupts apical docking of rhoptry organelles, revealing a role for DLC8a in rhoptry positioning at the apical pole.","method":"Conditional knockdown, ultrastructural/imaging analysis of rhoptry docking","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional depletion with direct organelle localization readout, single lab, multiple phenotypic assays","pmids":["31206964"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"Depletion of DLC8a causes a severe defect in host cell invasion, consistent with its dual role in microneme secretion and rhoptry docking, placing DLC8a as acting at a different step in the exocytosis cascade than CEN2.","method":"Conditional knockdown, invasion assays, phenotypic comparison with CEN2 depletion (epistatic dissection)","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional loss-of-function with defined invasion phenotype and pathway placement via comparison with CEN2, single lab but multiple assays","pmids":["31206964"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgDLC8a is a conoid-localized dynein light chain that forms a β-strand-swapped homodimer (controlled by phosphorylation at S88, which when mimicked renders the protein monomeric and cytosolic), and is required for efficient microneme exocytosis and apical docking of rhoptries, thereby enabling host cell invasion by Toxoplasma gondii."},"narrative":{"mechanistic_narrative":"TgDLC8a is a dynein light chain of Toxoplasma gondii that localizes specifically to the conoid at the parasite's apical end and functions in the apical secretory machinery required for host cell invasion [PMID:23233536, PMID:31206964]. Unlike its orthologs in Eimeria, Plasmodium, or humans, conoid targeting is a unique feature of TgDLC8a [PMID:23233536]. The protein forms a homodimer through β-strand swapping, in which each monomer's β strand pairs with the antiparallel β' strand of the opposing monomer to create two identical binding grooves suited for multitarget recognition, a structural arrangement distinct from the PfDLC8 homodimer [PMID:23233536]. Phosphorylation at S88 controls this behavior: the phosphomimetic S88E mutation renders the protein monomeric and cytosolic, and its overexpression inhibits parasite growth, establishing that the dimeric, conoid-localized form is required for replication [PMID:23233536]. Conditional depletion of DLC8a perturbs microneme exocytosis and disrupts apical docking of rhoptry organelles, and this dual defect produces a severe block in host cell invasion, with DLC8a acting at a step in the exocytosis cascade distinct from CEN2 [PMID:31206964].","teleology":[{"year":2012,"claim":"Establishing where TgDLC8a acts, its conoid localization at the apical end distinguished it from orthologs and pointed to a role specific to the T. gondii invasion apparatus.","evidence":"Subcellular localization imaging/fractionation and comparative analysis against Eimeria, Plasmodium, and human orthologs","pmids":["23233536"],"confidence":"Medium","gaps":["Does not identify binding partners at the conoid","Mechanism of conoid targeting unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"claim":"The crystal structure resolved how TgDLC8a assembles, showing a β-strand-swapped homodimer with two identical grooves adapted for multitarget recognition and distinct from PfDLC8.","evidence":"Crystal structure determination and structural comparison","pmids":["23233536"],"confidence":"High","gaps":["Cargo/target ligands occupying the binding grooves not identified","In vivo relevance of multitarget recognition untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"claim":"Phosphorylation at S88 was shown to be a switch controlling oligomeric state and localization, and the dimeric conoid-bound form was shown to be required for replication.","evidence":"S88E phosphomimetic mutagenesis with in-parasite localization plus dominant-negative overexpression growth assay in human fibroblasts","pmids":["23233536"],"confidence":"High","gaps":["Kinase responsible for S88 phosphorylation not identified","Whether S88 phosphorylation is regulated during the lytic cycle unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Conditional depletion defined the cellular function, showing DLC8a is required for microneme exocytosis and apical rhoptry docking, and that loss produces a severe invasion defect at a step distinct from CEN2.","evidence":"Conditional knockdown with microneme secretion assays, rhoptry docking imaging, invasion assays, and epistatic comparison to CEN2","pmids":["31206964"],"confidence":"High","gaps":["Molecular link between DLC8a and the secretory/docking machinery not defined","Direct binding partners mediating these functions unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The direct cargo/partner ligands engaged by the two binding grooves, and the kinase that phosphorylates S88 to regulate dimer disassembly, remain unidentified.","evidence":"","pmids":[],"confidence":"High","gaps":["No identified binding partners at the conoid","S88 kinase unknown","Mechanistic connection between dimer state and secretion/docking undefined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["β-strand-swapped TgDLC8a homodimer"],"partners":[],"other_free_text":["Phosphomimetic S88E converts TgDLC8a to a monomeric, cytosolic form and acts as a dominant-negative inhibitor of parasite growth [#2, #3].","Required for microneme exocytosis and apical docking of rhoptries; acts at a step in the exocytosis cascade distinct from CEN2 [#4, #5, #6].","Conoid targeting is unique to the T. gondii ortholog relative to Eimeria, Plasmodium, and human DLC8 [#0]."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"31206964","id":"PMC_31206964","title":"The roles of Centrin 2 and Dynein Light Chain 8a in apical secretory organelles discharge of Toxoplasma gondii.","date":"2019","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/31206964","citation_count":27,"is_preprint":false},{"pmid":"23233536","id":"PMC_23233536","title":"Dynein light chain 8a of Toxoplasma gondii, a unique conoid-localized β-strand-swapped homodimer, is required for an efficient parasite growth.","date":"2012","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/23233536","citation_count":17,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3435,"output_tokens":1612,"usd":0.017243,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6824,"output_tokens":2297,"usd":0.045773,"stage2_stop_reason":"end_turn"},"total_usd":0.063016,"stage1_batch_id":"msgbatch_01WgHz6kceqm573AGLyz57at","stage2_batch_id":"msgbatch_01LK4wDYj5zYquahv7gi9893","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"TgDLC8a localizes specifically to the conoid at the apical end of T. gondii, a localization not shared by its orthologs in Eimeria, Plasmodium, or humans, establishing that conoid targeting is a unique feature of TgDLC8a.\",\n      \"method\": \"Subcellular localization by imaging/fractionation; comparative analysis with orthologs\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional comparative context, single lab, two orthogonal lines of evidence (localization + ortholog comparison)\",\n      \"pmids\": [\"23233536\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TgDLC8a forms a homodimer via β-strand swapping (each monomer's β strand interacts with the antiparallel β' strand of the opposing monomer), creating two identical binding grooves adapted for multitarget recognition — a structural arrangement distinct from the PfDLC8 homodimer.\",\n      \"method\": \"Crystal structure determination and structural comparison\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with mechanistic validation of dimerization interface and functional implications\",\n      \"pmids\": [\"23233536\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A phosphomimetic mutation S88E renders TgDLC8a monomeric and cytosolic in T. gondii, demonstrating that phosphorylation at S88 controls both the oligomeric state and subcellular localization of TgDLC8a.\",\n      \"method\": \"Site-directed mutagenesis (S88E phosphomimetic), localization imaging in T. gondii\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — active-site/PTM mutagenesis combined with in-parasite localization, single lab but two orthogonal readouts (dimerization state + localization shift)\",\n      \"pmids\": [\"23233536\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Overexpression of the monomeric phosphomimetic TgDLC8a-S88E inhibits parasite growth in human fibroblasts, establishing a functional requirement for the dimeric/conoid-localized form in parasite replication.\",\n      \"method\": \"Overexpression of S88E mutant; parasite growth assay in human fibroblasts\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function via dominant-negative overexpression with defined growth phenotype, single lab\",\n      \"pmids\": [\"23233536\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DLC8a localizes to the conoid, and its conditional depletion perturbs microneme exocytosis, demonstrating a role for DLC8a in microneme secretion.\",\n      \"method\": \"Conditional knockdown (auxin-inducible degron or similar), microneme secretion assays\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional depletion with direct secretion assay readout, combined with localization, single lab but multiple orthogonal phenotypic readouts\",\n      \"pmids\": [\"31206964\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Conditional depletion of DLC8a disrupts apical docking of rhoptry organelles, revealing a role for DLC8a in rhoptry positioning at the apical pole.\",\n      \"method\": \"Conditional knockdown, ultrastructural/imaging analysis of rhoptry docking\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional depletion with direct organelle localization readout, single lab, multiple phenotypic assays\",\n      \"pmids\": [\"31206964\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Depletion of DLC8a causes a severe defect in host cell invasion, consistent with its dual role in microneme secretion and rhoptry docking, placing DLC8a as acting at a different step in the exocytosis cascade than CEN2.\",\n      \"method\": \"Conditional knockdown, invasion assays, phenotypic comparison with CEN2 depletion (epistatic dissection)\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional loss-of-function with defined invasion phenotype and pathway placement via comparison with CEN2, single lab but multiple assays\",\n      \"pmids\": [\"31206964\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgDLC8a is a conoid-localized dynein light chain that forms a β-strand-swapped homodimer (controlled by phosphorylation at S88, which when mimicked renders the protein monomeric and cytosolic), and is required for efficient microneme exocytosis and apical docking of rhoptries, thereby enabling host cell invasion by Toxoplasma gondii.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgDLC8a is a dynein light chain of Toxoplasma gondii that localizes specifically to the conoid at the parasite's apical end and functions in the apical secretory machinery required for host cell invasion [#0, #4]. Unlike its orthologs in Eimeria, Plasmodium, or humans, conoid targeting is a unique feature of TgDLC8a [#0]. The protein forms a homodimer through β-strand swapping, in which each monomer's β strand pairs with the antiparallel β' strand of the opposing monomer to create two identical binding grooves suited for multitarget recognition, a structural arrangement distinct from the PfDLC8 homodimer [#1]. Phosphorylation at S88 controls this behavior: the phosphomimetic S88E mutation renders the protein monomeric and cytosolic, and its overexpression inhibits parasite growth, establishing that the dimeric, conoid-localized form is required for replication [#2, #3]. Conditional depletion of DLC8a perturbs microneme exocytosis and disrupts apical docking of rhoptry organelles, and this dual defect produces a severe block in host cell invasion, with DLC8a acting at a step in the exocytosis cascade distinct from CEN2 [#4, #5, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Establishing where TgDLC8a acts, its conoid localization at the apical end distinguished it from orthologs and pointed to a role specific to the T. gondii invasion apparatus.\",\n      \"evidence\": \"Subcellular localization imaging/fractionation and comparative analysis against Eimeria, Plasmodium, and human orthologs\",\n      \"pmids\": [\"23233536\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not identify binding partners at the conoid\", \"Mechanism of conoid targeting unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The crystal structure resolved how TgDLC8a assembles, showing a β-strand-swapped homodimer with two identical grooves adapted for multitarget recognition and distinct from PfDLC8.\",\n      \"evidence\": \"Crystal structure determination and structural comparison\",\n      \"pmids\": [\"23233536\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cargo/target ligands occupying the binding grooves not identified\", \"In vivo relevance of multitarget recognition untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Phosphorylation at S88 was shown to be a switch controlling oligomeric state and localization, and the dimeric conoid-bound form was shown to be required for replication.\",\n      \"evidence\": \"S88E phosphomimetic mutagenesis with in-parasite localization plus dominant-negative overexpression growth assay in human fibroblasts\",\n      \"pmids\": [\"23233536\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for S88 phosphorylation not identified\", \"Whether S88 phosphorylation is regulated during the lytic cycle unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Conditional depletion defined the cellular function, showing DLC8a is required for microneme exocytosis and apical rhoptry docking, and that loss produces a severe invasion defect at a step distinct from CEN2.\",\n      \"evidence\": \"Conditional knockdown with microneme secretion assays, rhoptry docking imaging, invasion assays, and epistatic comparison to CEN2\",\n      \"pmids\": [\"31206964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between DLC8a and the secretory/docking machinery not defined\", \"Direct binding partners mediating these functions unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct cargo/partner ligands engaged by the two binding grooves, and the kinase that phosphorylates S88 to regulate dimer disassembly, remain unidentified.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No identified binding partners at the conoid\", \"S88 kinase unknown\", \"Mechanistic connection between dimer state and secretion/docking undefined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0045504\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0042803\", \"supporting_discovery_ids\": [1, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [0, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0046718\", \"supporting_discovery_ids\": [6], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0017157\", \"supporting_discovery_ids\": [4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\"β-strand-swapped TgDLC8a homodimer\"],\n    \"partners\": [],\n    \"other_free_text\": [\n      \"Phosphomimetic S88E converts TgDLC8a to a monomeric, cytosolic form and acts as a dominant-negative inhibitor of parasite growth [#2, #3].\",\n      \"Required for microneme exocytosis and apical docking of rhoptries; acts at a step in the exocytosis cascade distinct from CEN2 [#4, #5, #6].\",\n      \"Conoid targeting is unique to the T. gondii ortholog relative to Eimeria, Plasmodium, and human DLC8 [#0].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_223000","name":"DLC8a","product":"dynein light chain DLC8a","uniprot_acc":"A0A125YL67","chromosome":"TGME49_chrII","start_pos":1367930},{"strain":"GT1","gene_id":"TGGT1_223000","name":null,"product":"dynein light chain DLC","uniprot_acc":null,"chromosome":"TGGT1_chrII","start_pos":1350278},{"strain":"RH88","gene_id":"TGRH88_001710","name":null,"product":"dynein light chain DLC","uniprot_acc":null,"chromosome":"CM023083","start_pos":1523958},{"strain":"VEG","gene_id":"TGVEG_223000","name":null,"product":"dynein light chain DLC","uniprot_acc":"B9QHI3","chromosome":"TGVEG_chrII","start_pos":1374071}]}