{"gene":"TG_215775","gene_symbol":"ROP8","run_date":"2026-09-08T11:06:29","timeline":{"discoveries":[{"year":2009,"finding":"X-ray crystal structures of ROP8 (and ROP2) revealed a typical bilobate kinase fold with a novel N-terminal extension that stabilizes the N-lobe; ROP8 is catalytically inactive (pseudokinase), and ROP18 (active kinase) phosphorylates ROP8 in vitro.","method":"X-ray crystallography, in vitro kinase assay, mutagenesis, mass spectrometry","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure solved, in vitro kinase assay with mass spectrometry confirmation, mutagenesis of key residues, multiple orthogonal methods in one study","pmids":["19197235"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"finding":"ROP8 (and ROP2) exist in a complex with ROP18 and GRA7, as shown by co-immunoprecipitation; ROP18 and GRA7 act together in the same pathway to target immunity-related GTPases (IRGs), with ROP8 acting as a pseudokinase scaffold in this complex.","method":"Co-immunoprecipitation, genetic epistasis (double mutant gra7/rop18), IFN-γ-activated macrophage survival assay, in vitro GTPase binding assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP establishing complex, supported by genetic epistasis with double mutant, direct in vitro binding assay, multiple orthogonal methods","pmids":["24390541"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":1997,"finding":"ROP8 localizes to the rhoptries of Toxoplasma gondii, as demonstrated by expression of the novel open reading frame in Neospora caninum transfectants and immunoblot analysis with antibodies to T. gondii rhoptry protein families; the protein product was processed as a ~52 kDa rhoptry-targeted protein.","method":"Transfection into Neospora caninum, immunoblot with rhoptry-specific antibodies, subcellular localization","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment by expression in heterologous system with immunoblot; replicated indirectly by later structural studies","pmids":["9364966"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Neospora caninum","strain":""}]},{"year":2010,"finding":"Knockout of the entire ROP2 locus (ROP2a, ROP2b, and ROP8) showed that these proteins are NOT required for recruitment of host mitochondria to the parasitophorous vacuole membrane; mitochondrial association was indistinguishable from parental strain.","method":"Genetic knockout (deletion of ROP2a/ROP2b/ROP8 locus), fluorescence microscopy of host mitochondrial recruitment","journal":"International journal for parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic knockout with direct microscopic readout; negative result, single lab","pmids":["20637758"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"Structural comparison of ROP8 with other rhoptry kinase (ROPK) family members identified ROPK-specific conserved features: a conserved insert in the kinase hinge region and a disulfide bridge in the kinase substrate-binding lobe, as well as an N-terminal extension (NTE) shared across a sub-clade, informing the distinction between active and degenerate (pseudokinase) members.","method":"Comparative structural analysis using solved structures of ROP2, ROP5, ROP8; sequence conservation mapping; evolutionary analysis","journal":"BMC evolutionary biology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — structural analysis using existing crystal structures, computational comparative analysis, single study with no functional mutagenesis of these specific features","pmids":["23742205"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"A mutation in ROP8 (identified by whole-genome sequencing of drug-resistant clones) conferred partial resistance to the benzoquinone acyl hydrazone compound KG8, implicating ROP8 in sensitivity to this experimental therapeutic; however, ROP1 mutation was the primary resistance determinant.","method":"Chemical mutagenesis, in vitro selection, whole-genome sequencing of resistant clones","journal":"Antimicrobial agents and chemotherapy","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single mutation identified by sequencing, not functionally validated for ROP8 specifically; ROP8 mutation was a minor contributor","pmids":["33361291"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2026,"finding":"Thiazolidin-4-one derivatives interact directly with recombinant ROP8 protein (shown by DARTS assay) and inhibit parasitophorous vacuole formation in T. gondii, suggesting ROP8 is a druggable target involved in PV formation.","method":"DARTS (drug affinity responsive target stability) assay, confocal microscopy of parasitophorous vacuole formation","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct protein-drug interaction demonstrated by DARTS with functional PV formation readout by confocal microscopy, single lab, single study","pmids":["41727434"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"finding":"Long-read sequencing of independently maintained T. gondii ME49 isolates revealed copy number variation in the ROP8-ROP2A locus, with a 13 kb expansion increasing ROP2A-ROP8 gene copy number from three to six copies, demonstrating intra-strain genomic plasticity at this virulence locus.","method":"Oxford Nanopore long-read sequencing, de novo genome assembly, pangenomic genotyping, structural variant calling","journal":"BMC genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — rigorous genomic sequencing and assembly with structural variant detection, but functional consequences of copy number variation not experimentally tested, single study","pmids":["41339799"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"ME49"}]}],"current_model":"ROP8 is a catalytically inactive pseudokinase (pseudokinase confirmed by crystal structure) secreted from rhoptry organelles into the parasitophorous vacuole membrane; it participates in a complex with the active kinase ROP18 and effector GRA7 that targets host immunity-related GTPases (IRGs) to promote parasite survival in activated macrophages, while being dispensable for host mitochondrial recruitment to the PV; its N-terminal extension and conserved kinase-fold features are regulated by ROP18-mediated phosphorylation, and direct drug binding to ROP8 can inhibit PV formation."},"narrative":{"mechanistic_narrative":"ROP8 is a rhoptry-secreted pseudokinase of Toxoplasma gondii that acts as a scaffolding component of the parasite's effector machinery targeting host immunity-related GTPases (IRGs) [PMID:24390541]. Crystal structures show ROP8 adopts a bilobate protein-kinase fold stabilized by a distinctive N-terminal extension, but it lacks catalytic activity and is instead a substrate phosphorylated in vitro by the active rhoptry kinase ROP18 [PMID:19197235]. Within IFN-γ-activated macrophages, ROP8 assembles in a complex with ROP18 and the dense-granule effector GRA7 that acts on IRGs to promote parasite survival [PMID:24390541], although deletion of the ROP2/ROP8 locus does not impair recruitment of host mitochondria to the parasitophorous vacuole membrane [PMID:20637758]. ROP8 localizes to the rhoptry organelles and is processed to a mature ~52 kDa protein [PMID:9364966]. It has been identified as a directly druggable target: thiazolidin-4-one derivatives bind recombinant ROP8 and inhibit parasitophorous vacuole formation [PMID:41727434].","teleology":[{"year":1997,"claim":"Establishing where the ROP8 gene product resides was the first step in assigning it to the parasite's invasion/secretion apparatus, showing it is a rhoptry-targeted protein.","evidence":"Heterologous expression in Neospora caninum transfectants and immunoblot with rhoptry-specific antibodies revealing a processed ~52 kDa product","pmids":["9364966"],"confidence":"Medium","gaps":["Function within the rhoptry unresolved at this stage","No enzymatic or interaction data"],"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Neospora caninum","strain":""}]},{"year":2009,"claim":"Solving the crystal structure resolved whether ROP8 is an active kinase, establishing it as a catalytically inactive pseudokinase that itself serves as a phosphorylation substrate.","evidence":"X-ray crystallography, in vitro kinase assay with mass spectrometry, and mutagenesis showing ROP18 phosphorylates ROP8 and defining the stabilizing N-terminal extension","pmids":["19197235"],"confidence":"High","gaps":["Functional consequence of ROP18-mediated phosphorylation of ROP8 in vivo not defined","No cellular role assigned"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2010,"claim":"Genetic ablation tested whether the ROP2/ROP8 locus drives host mitochondrial recruitment to the PV, ruling out this proposed role.","evidence":"Knockout of the ROP2a/ROP2b/ROP8 locus with fluorescence microscopy of host mitochondrial association, indistinguishable from parental strain","pmids":["20637758"],"confidence":"Medium","gaps":["Does not isolate ROP8-specific contribution from ROP2a/ROP2b","Negative result from a single lab"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"Comparative structural analysis defined the family features distinguishing active from degenerate rhoptry kinases, placing ROP8 among the pseudokinase members.","evidence":"Comparative analysis of solved ROP2/ROP5/ROP8 structures with sequence-conservation and evolutionary mapping, identifying a hinge insert, substrate-lobe disulfide, and shared N-terminal extension","pmids":["23742205"],"confidence":"Medium","gaps":["No functional mutagenesis of the identified conserved features","Purely computational/structural inference"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"claim":"Co-IP and genetic epistasis assigned ROP8 a role in a multiprotein effector complex, framing it as a pseudokinase scaffold acting with ROP18 and GRA7 against host IRGs.","evidence":"Reciprocal co-immunoprecipitation, gra7/rop18 double-mutant epistasis, IFN-γ-activated macrophage survival assay, and in vitro GTPase binding","pmids":["24390541"],"confidence":"High","gaps":["ROP8-specific contribution to the complex not separated from ROP18/GRA7 by targeted deletion","Mechanism by which ROP8 scaffolds the complex not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"Drug-resistance profiling probed whether ROP8 influences chemotherapeutic sensitivity, implicating it as a minor determinant of resistance to the compound KG8.","evidence":"Chemical mutagenesis, in vitro selection, and whole-genome sequencing of resistant clones identifying a ROP8 mutation alongside the primary ROP1 determinant","pmids":["33361291"],"confidence":"Low","gaps":["ROP8 mutation not functionally validated for the resistance phenotype","ROP8 was a minor contributor relative to ROP1"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"claim":"Long-read genomics revealed intra-strain genomic plasticity at the ROP8 locus, showing copy-number expansion at this virulence locus.","evidence":"Oxford Nanopore long-read sequencing and de novo assembly of ME49 isolates detecting a 13 kb expansion increasing ROP2A-ROP8 copies from three to six","pmids":["41339799"],"confidence":"Medium","gaps":["Functional consequences of copy-number variation not tested","Impact on ROP8 expression or virulence unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":"ME49"}]},{"year":2026,"claim":"Target-engagement assays established ROP8 as a directly druggable protein whose engagement blocks parasitophorous vacuole formation.","evidence":"DARTS assay showing direct binding of thiazolidin-4-one derivatives to recombinant ROP8, with confocal microscopy of impaired PV formation","pmids":["41727434"],"confidence":"Medium","gaps":["Whether the PV-formation defect is caused specifically by ROP8 engagement rather than off-target effects not established","Mechanistic link between ROP8 and PV formation not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"How ROP8's pseudokinase scaffolding activity and its ROP18-mediated phosphorylation mechanistically contribute to IRG targeting and PV formation remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No ROP8-specific knockout phenotype for IRG targeting","Functional role of ROP18 phosphorylation of ROP8 in vivo undefined","Molecular basis of ROP8's contribution to PV formation unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["ROP8-ROP18-GRA7 effector complex targeting host immunity-related GTPases [#1]"],"partners":["ROP18 (ACTIVE RHOPTRY KINASE; PHOSPHORYLATES ROP8) [#0, #1]","GRA7 (DENSE-GRANULE EFFECTOR) [#1]","IMMUNITY-RELATED GTPASES (IRGS; COMPLEX TARGET) [#1]"],"other_free_text":["Catalytically inactive pseudokinase with a bilobate kinase fold stabilized by a novel N-terminal extension [#0]","Processed to a mature ~52 kDa rhoptry-targeted protein [#2]","Dispensable for host mitochondrial recruitment to the PV membrane (ROP2/ROP8 locus deletion) [#3]","Directly druggable: thiazolidin-4-one derivatives bind ROP8 and inhibit PV formation [#6]; a ROP8 mutation is a minor determinant of KG8 resistance [#5]","ROP2A-ROP8 locus exhibits copy-number variation (three-to-six copy expansion) in ME49 isolates [#7]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"24390541","id":"PMC_24390541","title":"Toxoplasma GRA7 effector increases turnover of immunity-related GTPases and contributes to acute virulence in the mouse.","date":"2014","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/24390541","citation_count":104,"is_preprint":false},{"pmid":"31954995","id":"PMC_31954995","title":"Vaccination with a novel multi-epitope ROP8 DNA vaccine against acute Toxoplasma gondii infection induces strong B and T cell responses in mice.","date":"2020","source":"Comparative immunology, microbiology and infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/31954995","citation_count":70,"is_preprint":false},{"pmid":"23742205","id":"PMC_23742205","title":"Structural and evolutionary adaptation of rhoptry kinases and pseudokinases, a family of coccidian virulence factors.","date":"2013","source":"BMC evolutionary biology","url":"https://pubmed.ncbi.nlm.nih.gov/23742205","citation_count":69,"is_preprint":false},{"pmid":"19197235","id":"PMC_19197235","title":"Novel structural and regulatory features of rhoptry secretory kinases in Toxoplasma gondii.","date":"2009","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/19197235","citation_count":57,"is_preprint":false},{"pmid":"29705360","id":"PMC_29705360","title":"Bioinformatics analysis of ROP8 protein to improve vaccine design against Toxoplasma gondii.","date":"2018","source":"Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/29705360","citation_count":49,"is_preprint":false},{"pmid":"9364966","id":"PMC_9364966","title":"The expression of Toxoplasma proteins in Neospora caninum and the identification of a gene encoding a novel rhoptry protein.","date":"1997","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/9364966","citation_count":42,"is_preprint":false},{"pmid":"23509124","id":"PMC_23509124","title":"Protective immune response in BALB/c mice induced by DNA vaccine of the ROP8 gene of Toxoplasma gondii.","date":"2013","source":"The American journal of tropical medicine and hygiene","url":"https://pubmed.ncbi.nlm.nih.gov/23509124","citation_count":31,"is_preprint":false},{"pmid":"20637758","id":"PMC_20637758","title":"Association of host mitochondria with the parasitophorous vacuole during Toxoplasma infection is not dependent on rhoptry proteins ROP2/8.","date":"2010","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/20637758","citation_count":31,"is_preprint":false},{"pmid":"33548480","id":"PMC_33548480","title":"Protective efficacy by a novel multi-epitope vaccine, including MIC3, ROP8, and SAG1, against acute Toxoplasma gondii infection in BALB/c mice.","date":"2021","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/33548480","citation_count":21,"is_preprint":false},{"pmid":"31078709","id":"PMC_31078709","title":"In silico analysis and expression of a novel chimeric antigen as a vaccine candidate against Toxoplasma gondii.","date":"2019","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/31078709","citation_count":21,"is_preprint":false},{"pmid":"24986686","id":"PMC_24986686","title":"Sero-diagnostic evaluation of Toxoplasma gondii recombinant Rhoptry antigen 8 expressed in E. coli.","date":"2014","source":"Parasites & vectors","url":"https://pubmed.ncbi.nlm.nih.gov/24986686","citation_count":20,"is_preprint":false},{"pmid":"32768514","id":"PMC_32768514","title":"Enhancing immune responses by a novel multi-epitope ROP8 DNA vaccine plus interleukin-12 plasmid as a genetic adjuvant against acute Toxoplasma gondii infection in BALB/c mice.","date":"2020","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/32768514","citation_count":15,"is_preprint":false},{"pmid":"33713726","id":"PMC_33713726","title":"Designing and developing of high-resolution melting technique for separating different types of Toxoplasma gondii by analysis of B1 and ROP8 gene regions.","date":"2021","source":"Journal of microbiological methods","url":"https://pubmed.ncbi.nlm.nih.gov/33713726","citation_count":5,"is_preprint":false},{"pmid":"35082886","id":"PMC_35082886","title":"Phylogenetic Analysis and Genetics Polymorphisms Evaluation of ROP8 and B1 Genes of Toxoplasma gondii in Livestock and Poultry Hosts of Yazd, Qom and Golestan Provinces of Iran.","date":"2021","source":"Iranian journal of parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/35082886","citation_count":4,"is_preprint":false},{"pmid":"26436382","id":"PMC_26436382","title":"Sequence variation in ROP8 gene among Toxoplasma gondii isolates from different hosts and geographical localities.","date":"2015","source":"Genetics and molecular research : GMR","url":"https://pubmed.ncbi.nlm.nih.gov/26436382","citation_count":4,"is_preprint":false},{"pmid":"36162598","id":"PMC_36162598","title":"Protective immunity induced with a DNA vaccine encoding B- and T-cells multi-epitope SAG1, ROP16, MIC4, GRA12, M2AP, and multi-epitope ROP8 against acute and chronic toxoplasmosis in BALB/c mice.","date":"2022","source":"Experimental parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/36162598","citation_count":2,"is_preprint":false},{"pmid":"38372452","id":"PMC_38372452","title":"Comparison of the immune response and protection against the experimental Toxoplasma gondii infection elicited by immunization with the recombinant proteins BAG1, ROP8, and BAG1-ROP8.","date":"2024","source":"Parasite immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38372452","citation_count":1,"is_preprint":false},{"pmid":"41727434","id":"PMC_41727434","title":"Recombinant ROP8 antigen: diagnostics, immunogenicity, and therapeutic targeting in toxoplasmosis.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41727434","citation_count":0,"is_preprint":false},{"pmid":"33361291","id":"PMC_33361291","title":"In Vitro Selection Implicates ROP1 as a Resistance Gene for an Experimental Therapeutic Benzoquinone Acyl Hydrazone in Toxoplasma gondii.","date":"2021","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/33361291","citation_count":0,"is_preprint":false},{"pmid":"41339799","id":"PMC_41339799","title":"Intra-strain genetic heterogeneity in Toxoplasma gondii ME49: Oxford Nanopore long-read sequencing reveals copy number variation in the ROP8-ROP2A locus.","date":"2025","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/41339799","citation_count":0,"is_preprint":false},{"pmid":"26541043","id":"PMC_26541043","title":"[Research Advance on Toxoplasma gondii Rhoptry Protein 2 Family as Candidate Vaccine Molecules].","date":"2015","source":"Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi = Chinese journal of parasitology & parasitic diseases","url":"https://pubmed.ncbi.nlm.nih.gov/26541043","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13004,"output_tokens":2167,"usd":0.035758,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7642,"output_tokens":3623,"usd":0.064393,"stage2_stop_reason":"end_turn"},"total_usd":0.100151,"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\": 2009,\n      \"finding\": \"X-ray crystal structures of ROP8 (and ROP2) revealed a typical bilobate kinase fold with a novel N-terminal extension that stabilizes the N-lobe; ROP8 is catalytically inactive (pseudokinase), and ROP18 (active kinase) phosphorylates ROP8 in vitro.\",\n      \"method\": \"X-ray crystallography, in vitro kinase assay, mutagenesis, mass spectrometry\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure solved, in vitro kinase assay with mass spectrometry confirmation, mutagenesis of key residues, multiple orthogonal methods in one study\",\n      \"pmids\": [\"19197235\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ROP8 (and ROP2) exist in a complex with ROP18 and GRA7, as shown by co-immunoprecipitation; ROP18 and GRA7 act together in the same pathway to target immunity-related GTPases (IRGs), with ROP8 acting as a pseudokinase scaffold in this complex.\",\n      \"method\": \"Co-immunoprecipitation, genetic epistasis (double mutant gra7/rop18), IFN-γ-activated macrophage survival assay, in vitro GTPase binding assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP establishing complex, supported by genetic epistasis with double mutant, direct in vitro binding assay, multiple orthogonal methods\",\n      \"pmids\": [\"24390541\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"ROP8 localizes to the rhoptries of Toxoplasma gondii, as demonstrated by expression of the novel open reading frame in Neospora caninum transfectants and immunoblot analysis with antibodies to T. gondii rhoptry protein families; the protein product was processed as a ~52 kDa rhoptry-targeted protein.\",\n      \"method\": \"Transfection into Neospora caninum, immunoblot with rhoptry-specific antibodies, subcellular localization\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment by expression in heterologous system with immunoblot; replicated indirectly by later structural studies\",\n      \"pmids\": [\"9364966\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Neospora caninum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Knockout of the entire ROP2 locus (ROP2a, ROP2b, and ROP8) showed that these proteins are NOT required for recruitment of host mitochondria to the parasitophorous vacuole membrane; mitochondrial association was indistinguishable from parental strain.\",\n      \"method\": \"Genetic knockout (deletion of ROP2a/ROP2b/ROP8 locus), fluorescence microscopy of host mitochondrial recruitment\",\n      \"journal\": \"International journal for parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic knockout with direct microscopic readout; negative result, single lab\",\n      \"pmids\": [\"20637758\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Structural comparison of ROP8 with other rhoptry kinase (ROPK) family members identified ROPK-specific conserved features: a conserved insert in the kinase hinge region and a disulfide bridge in the kinase substrate-binding lobe, as well as an N-terminal extension (NTE) shared across a sub-clade, informing the distinction between active and degenerate (pseudokinase) members.\",\n      \"method\": \"Comparative structural analysis using solved structures of ROP2, ROP5, ROP8; sequence conservation mapping; evolutionary analysis\",\n      \"journal\": \"BMC evolutionary biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structural analysis using existing crystal structures, computational comparative analysis, single study with no functional mutagenesis of these specific features\",\n      \"pmids\": [\"23742205\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A mutation in ROP8 (identified by whole-genome sequencing of drug-resistant clones) conferred partial resistance to the benzoquinone acyl hydrazone compound KG8, implicating ROP8 in sensitivity to this experimental therapeutic; however, ROP1 mutation was the primary resistance determinant.\",\n      \"method\": \"Chemical mutagenesis, in vitro selection, whole-genome sequencing of resistant clones\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single mutation identified by sequencing, not functionally validated for ROP8 specifically; ROP8 mutation was a minor contributor\",\n      \"pmids\": [\"33361291\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Thiazolidin-4-one derivatives interact directly with recombinant ROP8 protein (shown by DARTS assay) and inhibit parasitophorous vacuole formation in T. gondii, suggesting ROP8 is a druggable target involved in PV formation.\",\n      \"method\": \"DARTS (drug affinity responsive target stability) assay, confocal microscopy of parasitophorous vacuole formation\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct protein-drug interaction demonstrated by DARTS with functional PV formation readout by confocal microscopy, single lab, single study\",\n      \"pmids\": [\"41727434\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Long-read sequencing of independently maintained T. gondii ME49 isolates revealed copy number variation in the ROP8-ROP2A locus, with a 13 kb expansion increasing ROP2A-ROP8 gene copy number from three to six copies, demonstrating intra-strain genomic plasticity at this virulence locus.\",\n      \"method\": \"Oxford Nanopore long-read sequencing, de novo genome assembly, pangenomic genotyping, structural variant calling\",\n      \"journal\": \"BMC genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — rigorous genomic sequencing and assembly with structural variant detection, but functional consequences of copy number variation not experimentally tested, single study\",\n      \"pmids\": [\"41339799\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"ME49\"}]\n    }\n  ],\n  \"current_model\": \"ROP8 is a catalytically inactive pseudokinase (pseudokinase confirmed by crystal structure) secreted from rhoptry organelles into the parasitophorous vacuole membrane; it participates in a complex with the active kinase ROP18 and effector GRA7 that targets host immunity-related GTPases (IRGs) to promote parasite survival in activated macrophages, while being dispensable for host mitochondrial recruitment to the PV; its N-terminal extension and conserved kinase-fold features are regulated by ROP18-mediated phosphorylation, and direct drug binding to ROP8 can inhibit PV formation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ROP8 is a rhoptry-secreted pseudokinase of Toxoplasma gondii that acts as a scaffolding component of the parasite's effector machinery targeting host immunity-related GTPases (IRGs) [#1]. Crystal structures show ROP8 adopts a bilobate protein-kinase fold stabilized by a distinctive N-terminal extension, but it lacks catalytic activity and is instead a substrate phosphorylated in vitro by the active rhoptry kinase ROP18 [#0]. Within IFN-\\u03b3-activated macrophages, ROP8 assembles in a complex with ROP18 and the dense-granule effector GRA7 that acts on IRGs to promote parasite survival [#1], although deletion of the ROP2/ROP8 locus does not impair recruitment of host mitochondria to the parasitophorous vacuole membrane [#3]. ROP8 localizes to the rhoptry organelles and is processed to a mature ~52 kDa protein [#2]. It has been identified as a directly druggable target: thiazolidin-4-one derivatives bind recombinant ROP8 and inhibit parasitophorous vacuole formation [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing where the ROP8 gene product resides was the first step in assigning it to the parasite's invasion/secretion apparatus, showing it is a rhoptry-targeted protein.\",\n      \"evidence\": \"Heterologous expression in Neospora caninum transfectants and immunoblot with rhoptry-specific antibodies revealing a processed ~52 kDa product\",\n      \"pmids\": [\"9364966\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Function within the rhoptry unresolved at this stage\", \"No enzymatic or interaction data\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Neospora caninum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Solving the crystal structure resolved whether ROP8 is an active kinase, establishing it as a catalytically inactive pseudokinase that itself serves as a phosphorylation substrate.\",\n      \"evidence\": \"X-ray crystallography, in vitro kinase assay with mass spectrometry, and mutagenesis showing ROP18 phosphorylates ROP8 and defining the stabilizing N-terminal extension\",\n      \"pmids\": [\"19197235\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of ROP18-mediated phosphorylation of ROP8 in vivo not defined\", \"No cellular role assigned\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Genetic ablation tested whether the ROP2/ROP8 locus drives host mitochondrial recruitment to the PV, ruling out this proposed role.\",\n      \"evidence\": \"Knockout of the ROP2a/ROP2b/ROP8 locus with fluorescence microscopy of host mitochondrial association, indistinguishable from parental strain\",\n      \"pmids\": [\"20637758\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not isolate ROP8-specific contribution from ROP2a/ROP2b\", \"Negative result from a single lab\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Comparative structural analysis defined the family features distinguishing active from degenerate rhoptry kinases, placing ROP8 among the pseudokinase members.\",\n      \"evidence\": \"Comparative analysis of solved ROP2/ROP5/ROP8 structures with sequence-conservation and evolutionary mapping, identifying a hinge insert, substrate-lobe disulfide, and shared N-terminal extension\",\n      \"pmids\": [\"23742205\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional mutagenesis of the identified conserved features\", \"Purely computational/structural inference\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Co-IP and genetic epistasis assigned ROP8 a role in a multiprotein effector complex, framing it as a pseudokinase scaffold acting with ROP18 and GRA7 against host IRGs.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, gra7/rop18 double-mutant epistasis, IFN-\\u03b3-activated macrophage survival assay, and in vitro GTPase binding\",\n      \"pmids\": [\"24390541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"ROP8-specific contribution to the complex not separated from ROP18/GRA7 by targeted deletion\", \"Mechanism by which ROP8 scaffolds the complex not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Drug-resistance profiling probed whether ROP8 influences chemotherapeutic sensitivity, implicating it as a minor determinant of resistance to the compound KG8.\",\n      \"evidence\": \"Chemical mutagenesis, in vitro selection, and whole-genome sequencing of resistant clones identifying a ROP8 mutation alongside the primary ROP1 determinant\",\n      \"pmids\": [\"33361291\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"ROP8 mutation not functionally validated for the resistance phenotype\", \"ROP8 was a minor contributor relative to ROP1\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Long-read genomics revealed intra-strain genomic plasticity at the ROP8 locus, showing copy-number expansion at this virulence locus.\",\n      \"evidence\": \"Oxford Nanopore long-read sequencing and de novo assembly of ME49 isolates detecting a 13 kb expansion increasing ROP2A-ROP8 copies from three to six\",\n      \"pmids\": [\"41339799\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of copy-number variation not tested\", \"Impact on ROP8 expression or virulence unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"ME49\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Target-engagement assays established ROP8 as a directly druggable protein whose engagement blocks parasitophorous vacuole formation.\",\n      \"evidence\": \"DARTS assay showing direct binding of thiazolidin-4-one derivatives to recombinant ROP8, with confocal microscopy of impaired PV formation\",\n      \"pmids\": [\"41727434\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the PV-formation defect is caused specifically by ROP8 engagement rather than off-target effects not established\", \"Mechanistic link between ROP8 and PV formation not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ROP8's pseudokinase scaffolding activity and its ROP18-mediated phosphorylation mechanistically contribute to IRG targeting and PV formation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No ROP8-specific knockout phenotype for IRG targeting\", \"Functional role of ROP18 phosphorylation of ROP8 in vivo undefined\", \"Molecular basis of ROP8's contribution to PV formation unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004672\", \"supporting_discovery_ids\": [0, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0019210\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0035838\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [1, 6], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0052150\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0051673\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\"ROP8-ROP18-GRA7 effector complex targeting host immunity-related GTPases [#1]\"],\n    \"partners\": [\"ROP18 (active rhoptry kinase; phosphorylates ROP8) [#0, #1]\", \"GRA7 (dense-granule effector) [#1]\", \"immunity-related GTPases (IRGs; complex target) [#1]\"],\n    \"other_free_text\": [\n      \"Catalytically inactive pseudokinase with a bilobate kinase fold stabilized by a novel N-terminal extension [#0]\",\n      \"Processed to a mature ~52 kDa rhoptry-targeted protein [#2]\",\n      \"Dispensable for host mitochondrial recruitment to the PV membrane (ROP2/ROP8 locus deletion) [#3]\",\n      \"Directly druggable: thiazolidin-4-one derivatives bind ROP8 and inhibit PV formation [#6]; a ROP8 mutation is a minor determinant of KG8 resistance [#5]\",\n      \"ROP2A-ROP8 locus exhibits copy-number variation (three-to-six copy expansion) in ME49 isolates [#7]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_215775","name":"ROP8","product":"rhoptry protein ROP8","uniprot_acc":"A0A125YFK9","chromosome":"TGME49_chrX","start_pos":7152523},{"strain":"GT1","gene_id":"TGGT1_215775","name":null,"product":"rhoptry protein ROP8","uniprot_acc":null,"chromosome":"TGGT1_chrX","start_pos":7045451},{"strain":"RH88","gene_id":"TGRH88_038870","name":null,"product":"rhoptry protein ROP8","uniprot_acc":null,"chromosome":"CM023091","start_pos":381137},{"strain":"VEG","gene_id":"TGVEG_215775","name":null,"product":"rhoptry protein ROP8","uniprot_acc":"B9QMZ2","chromosome":"TGVEG_chrX","start_pos":7085638}]}