{"gene":"TG_250340","gene_symbol":"CEN2","run_date":"2026-09-08T15:31:38+00:00","timeline":{"discoveries":[{"year":2019,"finding":"CEN2 localizes to four distinct compartments in T. gondii (apical pool, basal end, centrioles, and annuli at the base of the apical cap); conditional depletion occurs in a stepwise, ordered manner reflecting differences in incorporation kinetics and structural inheritance across successive generations, allowing dissection of compartment-specific functions.","method":"Conditional knockdown combining transcriptional and protein stability control; fluorescence localization; phenotypic characterization","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent labs using conditional knockdown with multiple orthogonal readouts (localization, invasion, replication assays) independently replicated the four-compartment localization and ordered depletion phenotype","pmids":["31182647","31206964"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"The apical pool of CEN2 is specifically required for microneme secretion, motility, host cell invasion, and egress; this was established by exploiting the stepwise conditional depletion that first depletes the apical pool before affecting other compartments.","method":"Conditional protein depletion (auxin-inducible degron or equivalent), microneme secretion assays, motility assays, invasion and egress assays","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean conditional knockdown with multiple orthogonal functional readouts (secretion, motility, invasion, egress) in a single rigorous study, replicated conceptually by Leung et al. 2019","pmids":["31206964"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"CEN2 knockdown causes a major invasion deficiency at early stages of depletion (correlating with loss from apical compartment) and intracellular replication defects at later stages (correlating with loss from other compartments), indicating distinct functions at each location.","method":"Conditional knockdown (transcriptional + protein stability control), invasion assays, replication assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — single lab with multiple orthogonal assays (invasion, replication) correlated with sequential compartment depletion","pmids":["31182647"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"finding":"TgCEN2 binds only one Ca2+ ion with low affinity, does not undergo significant Ca2+-dependent conformational changes, does not expose hydrophobic patches upon Ca2+ binding, and does not self-assemble in a Ca2+-dependent manner — contrasting with TgCEN1 — indicating TgCEN2 does not function as a classical Ca2+ sensor.","method":"Biophysical assays (Ca2+ binding measurements), structural analyses, hydrophobic exposure assays (e.g., ANS fluorescence), self-assembly assays","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — rigorous in vitro biophysical characterization (multiple orthogonal methods) but single lab, no in-parasite functional validation of the Ca2+-binding properties","pmids":["32759683"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgCEN2 is an EF-hand calcium-binding protein that localizes to four cytoskeletal compartments (apical pool, basal end, centrioles, and cortical annuli) and is incorporated into each with distinct kinetics; its apical pool is specifically required for microneme secretion, gliding motility, host cell invasion, and egress, while its presence at other compartments supports intracellular replication, and unlike TgCEN1, TgCEN2 binds Ca2+ with low affinity without acting as a classical Ca2+ sensor."},"narrative":{"mechanistic_narrative":"TgCEN2 is a calcium-binding centrin family protein that operates from four spatially distinct cytoskeletal compartments in Toxoplasma gondii — an apical pool, the basal end, the centrioles, and cortical annuli at the base of the apical cap — each of which is populated with different incorporation kinetics, allowing its multiple roles to be dissected through ordered, stepwise conditional depletion [PMID:31182647, PMID:31206964]. The apical pool is specifically required for the egress-invasion cycle: its loss abolishes microneme secretion, gliding motility, host cell invasion, and egress [PMID:31206964]. Depletion timing separates these functions, with early loss from the apical compartment producing an invasion deficiency and later loss from the remaining compartments producing intracellular replication defects, establishing that the protein performs distinct compartment-specific roles [PMID:31182647]. Biophysically, TgCEN2 binds only a single Ca2+ ion with low affinity and, unlike TgCEN1, undergoes no significant Ca2+-dependent conformational change, hydrophobic patch exposure, or self-assembly, indicating it does not act as a classical Ca2+ sensor [PMID:32759683]. How TgCEN2 mechanically supports secretion, invasion, and replication at each compartment beyond these observations has not been characterized in the available corpus.","teleology":[{"year":2019,"claim":"It was unknown how a single centrin could contribute to multiple cytoskeletal structures; resolving its localization and the kinetics of its turnover provided the framework for assigning function to individual compartments.","evidence":"Conditional knockdown with transcriptional and protein stability control combined with fluorescence localization in T. gondii","pmids":["31182647","31206964"],"confidence":"High","gaps":["Molecular partners that recruit CEN2 to each of the four compartments are not identified","The structural basis of differential incorporation kinetics is not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"By exploiting the ordered depletion that empties the apical pool first, the apical CEN2 population was shown to be specifically required for the microneme secretion, motility, invasion, and egress program, distinguishing its lytic-cycle role from its other functions.","evidence":"Conditional protein depletion with microneme secretion, motility, invasion, and egress assays in T. gondii","pmids":["31206964"],"confidence":"High","gaps":["The mechanism linking apical CEN2 to microneme exocytosis is unknown","Direct molecular effectors at the apical pool are not identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Correlating the sequence of phenotypes with compartment-specific loss demonstrated that CEN2 has genuinely distinct functions at different locations — invasion first, then replication — rather than a single global role.","evidence":"Conditional knockdown with invasion and replication assays correlated to sequential compartment depletion in T. gondii","pmids":["31182647"],"confidence":"High","gaps":["How CEN2 supports replication at the centrioles/basal end mechanistically is unresolved","Whether the replication defect is a direct or downstream consequence of depletion is not established"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"claim":"It was unclear whether TgCEN2 acts as a Ca2+ sensor like related centrins; in vitro biophysics showed it binds one Ca2+ with low affinity and lacks the Ca2+-triggered conformational and self-assembly behavior of TgCEN1, reframing it as a non-sensor calcium-binding protein.","evidence":"In vitro Ca2+ binding measurements, structural analyses, ANS hydrophobic-exposure and self-assembly assays comparing TgCEN2 and TgCEN1","pmids":["32759683"],"confidence":"Medium","gaps":["No in-parasite functional validation of the Ca2+-binding properties","The functional consequence of low-affinity Ca2+ binding for its compartment roles is unknown","Single lab, in vitro only"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The molecular partners and mechanistic effectors through which CEN2 drives microneme secretion, invasion, and replication at each of its four compartments remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No interacting proteins mapped to any compartment","No structural model of CEN2 in situ","Mechanism connecting a non-sensor calcium-binding protein to secretion and invasion is unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":[],"other_free_text":["Localizes to four distinct cytoskeletal compartments (apical pool, basal end, centrioles, cortical annuli) populated with different incorporation kinetics [#0]","Apical pool specifically required for microneme secretion, gliding motility, invasion, and egress [#1]","Distinct compartment-specific roles: invasion deficiency with early apical loss, replication defects with later loss from other compartments [#2]","Binds a single Ca2+ ion with low affinity and does not behave as a classical Ca2+ sensor, in contrast to TgCEN1 [#3]"]},"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":"31182647","id":"PMC_31182647","title":"Centrin2 from the human parasite Toxoplasma gondii is required for its invasion and intracellular replication.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/31182647","citation_count":25,"is_preprint":false},{"pmid":"32759683","id":"PMC_32759683","title":"Distinct Calcium Binding and Structural Properties of Two Centrin Isoforms from Toxoplasma gondii.","date":"2020","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/32759683","citation_count":11,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3687,"output_tokens":1167,"usd":0.014283,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6134,"output_tokens":2444,"usd":0.045885,"stage2_stop_reason":"end_turn"},"total_usd":0.0,"stage1_batch_id":"msgbatch_01XFXJD6iZecXyWn9uU5Qom9","stage2_batch_id":"msgbatch_013GToKgs4AKSCRE4yvueviH","note":"batch pricing = 50% of standard","skipped":true},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"CEN2 localizes to four distinct compartments in T. gondii (apical pool, basal end, centrioles, and annuli at the base of the apical cap); conditional depletion occurs in a stepwise, ordered manner reflecting differences in incorporation kinetics and structural inheritance across successive generations, allowing dissection of compartment-specific functions.\",\n      \"method\": \"Conditional knockdown combining transcriptional and protein stability control; fluorescence localization; phenotypic characterization\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent labs using conditional knockdown with multiple orthogonal readouts (localization, invasion, replication assays) independently replicated the four-compartment localization and ordered depletion phenotype\",\n      \"pmids\": [\"31182647\", \"31206964\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The apical pool of CEN2 is specifically required for microneme secretion, motility, host cell invasion, and egress; this was established by exploiting the stepwise conditional depletion that first depletes the apical pool before affecting other compartments.\",\n      \"method\": \"Conditional protein depletion (auxin-inducible degron or equivalent), microneme secretion assays, motility assays, invasion and egress assays\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean conditional knockdown with multiple orthogonal functional readouts (secretion, motility, invasion, egress) in a single rigorous study, replicated conceptually by Leung et al. 2019\",\n      \"pmids\": [\"31206964\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CEN2 knockdown causes a major invasion deficiency at early stages of depletion (correlating with loss from apical compartment) and intracellular replication defects at later stages (correlating with loss from other compartments), indicating distinct functions at each location.\",\n      \"method\": \"Conditional knockdown (transcriptional + protein stability control), invasion assays, replication assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab with multiple orthogonal assays (invasion, replication) correlated with sequential compartment depletion\",\n      \"pmids\": [\"31182647\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TgCEN2 binds only one Ca2+ ion with low affinity, does not undergo significant Ca2+-dependent conformational changes, does not expose hydrophobic patches upon Ca2+ binding, and does not self-assemble in a Ca2+-dependent manner — contrasting with TgCEN1 — indicating TgCEN2 does not function as a classical Ca2+ sensor.\",\n      \"method\": \"Biophysical assays (Ca2+ binding measurements), structural analyses, hydrophobic exposure assays (e.g., ANS fluorescence), self-assembly assays\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — rigorous in vitro biophysical characterization (multiple orthogonal methods) but single lab, no in-parasite functional validation of the Ca2+-binding properties\",\n      \"pmids\": [\"32759683\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"TgCEN2 is an EF-hand calcium-binding protein that localizes to four cytoskeletal compartments (apical pool, basal end, centrioles, and cortical annuli) and is incorporated into each with distinct kinetics; its apical pool is specifically required for microneme secretion, gliding motility, host cell invasion, and egress, while its presence at other compartments supports intracellular replication, and unlike TgCEN1, TgCEN2 binds Ca2+ with low affinity without acting as a classical Ca2+ sensor.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgCEN2 is a calcium-binding centrin family protein that operates from four spatially distinct cytoskeletal compartments in Toxoplasma gondii — an apical pool, the basal end, the centrioles, and cortical annuli at the base of the apical cap — each of which is populated with different incorporation kinetics, allowing its multiple roles to be dissected through ordered, stepwise conditional depletion [#0]. The apical pool is specifically required for the egress-invasion cycle: its loss abolishes microneme secretion, gliding motility, host cell invasion, and egress [#1]. Depletion timing separates these functions, with early loss from the apical compartment producing an invasion deficiency and later loss from the remaining compartments producing intracellular replication defects, establishing that the protein performs distinct compartment-specific roles [#2]. Biophysically, TgCEN2 binds only a single Ca2+ ion with low affinity and, unlike TgCEN1, undergoes no significant Ca2+-dependent conformational change, hydrophobic patch exposure, or self-assembly, indicating it does not act as a classical Ca2+ sensor [#3]. How TgCEN2 mechanically supports secretion, invasion, and replication at each compartment beyond these observations has not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"It was unknown how a single centrin could contribute to multiple cytoskeletal structures; resolving its localization and the kinetics of its turnover provided the framework for assigning function to individual compartments.\",\n      \"evidence\": \"Conditional knockdown with transcriptional and protein stability control combined with fluorescence localization in T. gondii\",\n      \"pmids\": [\"31182647\", \"31206964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular partners that recruit CEN2 to each of the four compartments are not identified\",\n        \"The structural basis of differential incorporation kinetics is not defined\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"By exploiting the ordered depletion that empties the apical pool first, the apical CEN2 population was shown to be specifically required for the microneme secretion, motility, invasion, and egress program, distinguishing its lytic-cycle role from its other functions.\",\n      \"evidence\": \"Conditional protein depletion with microneme secretion, motility, invasion, and egress assays in T. gondii\",\n      \"pmids\": [\"31206964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The mechanism linking apical CEN2 to microneme exocytosis is unknown\",\n        \"Direct molecular effectors at the apical pool are not identified\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Correlating the sequence of phenotypes with compartment-specific loss demonstrated that CEN2 has genuinely distinct functions at different locations — invasion first, then replication — rather than a single global role.\",\n      \"evidence\": \"Conditional knockdown with invasion and replication assays correlated to sequential compartment depletion in T. gondii\",\n      \"pmids\": [\"31182647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How CEN2 supports replication at the centrioles/basal end mechanistically is unresolved\",\n        \"Whether the replication defect is a direct or downstream consequence of depletion is not established\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"It was unclear whether TgCEN2 acts as a Ca2+ sensor like related centrins; in vitro biophysics showed it binds one Ca2+ with low affinity and lacks the Ca2+-triggered conformational and self-assembly behavior of TgCEN1, reframing it as a non-sensor calcium-binding protein.\",\n      \"evidence\": \"In vitro Ca2+ binding measurements, structural analyses, ANS hydrophobic-exposure and self-assembly assays comparing TgCEN2 and TgCEN1\",\n      \"pmids\": [\"32759683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No in-parasite functional validation of the Ca2+-binding properties\",\n        \"The functional consequence of low-affinity Ca2+ binding for its compartment roles is unknown\",\n        \"Single lab, in vitro only\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular partners and mechanistic effectors through which CEN2 drives microneme secretion, invasion, and replication at each of its four compartments remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No interacting proteins mapped to any compartment\",\n        \"No structural model of CEN2 in situ\",\n        \"Mechanism connecting a non-sensor calcium-binding protein to secretion and invasion is unknown\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005509\", \"supporting_discovery_ids\": [3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005814\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0044448\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [1, 2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0071702\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": [\n      \"Localizes to four distinct cytoskeletal compartments (apical pool, basal end, centrioles, cortical annuli) populated with different incorporation kinetics [#0]\",\n      \"Apical pool specifically required for microneme secretion, gliding motility, invasion, and egress [#1]\",\n      \"Distinct compartment-specific roles: invasion deficiency with early apical loss, replication defects with later loss from other compartments [#2]\",\n      \"Binds a single Ca2+ ion with low affinity and does not behave as a classical Ca2+ sensor, in contrast to TgCEN1 [#3]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_250340","name":"CEN2","product":"centrin 2","uniprot_acc":"A0A125YZN2","chromosome":"TGME49_chrXII","start_pos":5057142},{"strain":"GT1","gene_id":"TGGT1_250340","name":null,"product":"centrin 2","uniprot_acc":null,"chromosome":"TGGT1_chrXII","start_pos":4993747},{"strain":"RH88","gene_id":"TGRH88_063870","name":null,"product":"centrin 2","uniprot_acc":null,"chromosome":"CM023093","start_pos":5115693},{"strain":"VEG","gene_id":"TGVEG_250340","name":null,"product":"centrin 2","uniprot_acc":"A0A125YZN4","chromosome":"TGVEG_chrXII","start_pos":5034782}]}