{"gene":"PF3D7_0935800","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2000,"finding":"Targeted gene disruption of CLAG9 in P. falciparum ablated cytoadherence to C32 melanoma cells and purified CD36, establishing CLAG9 as essential for binding of parasitized erythrocytes to CD36. Anti-CLAG9 antibodies recognized a 220 kDa polypeptide absent in disrupted clones.","method":"Targeted gene disruption, cytoadherence assay, Western blot with DNA-induced antibodies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean targeted gene disruption with specific phenotypic readout (cytoadherence loss), replicated by antisense approach in a second paper","pmids":["10737759"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2000,"finding":"Antisense RNA inhibition of CLAG9 in P. falciparum clone 3D7 reduced cytoadherence to C32 melanoma cells 15-fold compared to control, confirming the cytoadherence phenotype is directly caused by loss of CLAG9 function; reversion upon plasmid removal confirmed the effect was not due to an unrelated genomic change.","method":"Antisense RNA transfection, cytoadherence assay, plasmid reversion experiment","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 2 / Strong — independent method (antisense) replicating the gene disruption result, with internal reversion control","pmids":["10989143"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2004,"finding":"CLAG9 is a rhoptry protein that localizes specifically to the basal bulb of rhoptries in merozoites (co-localized with RhopH2 by immunofluorescence and immunoelectron microscopy), is a component of the high-molecular-mass RhopH complex (co-purified with anti-RhopH2 antibodies and detected by mass spectrometry), and is transferred to ring-stage parasites within the RhopH complex after invasion.","method":"Immunofluorescence, immunoelectron microscopy, mass spectrometry, co-immunoprecipitation/complex purification","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (IEM, IF, MS, co-IP) in one study establishing complex membership and localization","pmids":["15049814"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"PfRhopH complex immunoprecipitated with anti-CLAG9 antibody contained neither Clag2 nor Clag3.1, indicating that individual PfRhopH complexes contain only one RhopH1/Clag protein product, and CLAG9-containing complexes are compositionally distinct from those containing Clag2 or Clag3.1.","method":"Immunoprecipitation with anti-CLAG9 antibody followed by Western blot for Clag2 and Clag3.1","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single co-IP result, but finding is a negative (absence of Clag2/Clag3.1) that is internally consistent across multiple antibodies in one lab","pmids":["15953647"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"HB3, 3D7"}]},{"year":2010,"finding":"CLAG9 interacts with VAR2CSA (a PfEMP1 family member) at or near the infected red blood cell membrane. In parasites lacking CLAG9, VAR2CSA failed to reach the IRBC surface and was retained within the parasite, demonstrating that CLAG9 is required for trafficking of PfEMP1 to the IRBC surface. CLAG9 is synthesized at two stages (early ring and late trophozoite), and a portion of the protein is exposed on the IRBC surface (trypsin converts ~150 kDa form to ~142 kDa).","method":"Co-immunoprecipitation (CLAG9–VAR2CSA interaction), immunofluorescence localization, trypsin sensitivity assay, analysis of CLAG9-knockout parasites","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus knockout phenotype (VAR2CSA mislocalization) plus surface trypsin sensitivity, single lab","pmids":["20823248"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"Synthetic peptides spanning the complete CLAG9 sequence identified 20 high-affinity erythrocyte-binding peptides (HABPs) that interact with erythrocyte surface receptors of ~85, ~63, and ~34 kDa, and inhibited erythrocyte invasion in vitro by up to 72% at 200 µM.","method":"Receptor-ligand binding assay with synthetic peptides, enzyme pre-treatment of RBCs, invasion inhibition assay","journal":"Vaccine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct in vitro binding and invasion assay with defined peptides, single lab, no genetic validation","pmids":["20085836"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"PfCLAG9 forms a complex (PfClag9-RhopH complex) with PfRAP1, PfRAP2, PfRAP3, PfRhopH2, and PfRhopH3 at the apical end of merozoites, and the complex binds human erythrocytes through CLAG9 interaction with the glycophorin A–band 3 receptor-coreceptor complex.","method":"Immunoprecipitation followed by mass spectrometry, protein-protein interaction assays with recombinant CLAG9 domains, immunofluorescence, erythrocyte binding assay","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-identified complex members plus direct protein-protein interaction assays, single lab, multiple orthogonal methods","pmids":["31712270"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"CLAG9 traffics via merozoite rhoptries to the host erythrocyte membrane after invasion and exists in two forms within infected cells: an alkaline-extractable soluble form and a membrane-integral form. Unlike CLAG3, CLAG9 variant region is protease-resistant at the host erythrocyte surface. CLAG9 knockout parasites show uncompromised growth in physiological medium (unlike CLAG3 knockout), and CLAG2 and CLAG8 (but not specifically CLAG9) knockout lines show compensatory increases in transcription of remaining clag/rhoph genes.","method":"Epitope-tagging and fluorescence co-localization, alkaline extraction fractionation, extracellular protease treatment, CRISPR/Cas9 knockout, growth assays, PSAC-mediated transport assays","journal":"Microorganisms","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (tagging, fractionation, CRISPR KO, functional transport assay) in one study","pmids":["38930554"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"In P. berghei, CLAG9 and CLAGX belong to two distinct phylogenetic clades and have separate non-complementary functions: allelic replacement of CLAGX functional regions with P. berghei CLAG9 sequences did not rescue CLAGX function, establishing that P. berghei CLAG9 is not the functional ortholog of P. falciparum CLAG3 and cannot substitute for CLAGX.","method":"Allelic replacement in P. berghei, inducible knockout, guanidinium chloride haemolysis assay for NPP function","journal":"Journal of biomedical science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via allelic replacement with functional NPP readout, single lab","pmids":["39894870"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2025,"finding":"PfANK_1, an ankyrin repeat-containing protein, interacts with components of the PfClag9-PfRhopH complex, as shown by co-immunoprecipitation, bio-layer interferometry, and co-localization; structural analysis identified the binding interface and key interacting residues.","method":"Co-immunoprecipitation, bio-layer interferometry, co-localization, molecular dynamics simulations, crystal structure of PfANK_1","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal binding methods (Co-IP, BLI, co-localization, structure), single lab, finding is about an interactor of the CLAG9-containing complex","pmids":["40614121"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"CLAG9 (PF3D7_0935800) is a ~220 kDa P. falciparum rhoptry protein that forms part of the high-molecular-weight RhopH complex (with RhopH2, RhopH3, RAP1, RAP2, RAP3) in the basal bulb of merozoite rhoptries; after invasion it is transferred to ring-stage parasites and inserts into the host erythrocyte membrane in a protease-resistant, membrane-integral form; it is required for cytoadherence to CD36 and for surface trafficking of PfEMP1 (VAR2CSA), and the CLAG9-containing RhopH complex mediates merozoite binding to erythrocytes via the glycophorin A–band 3 receptor complex, while in P. berghei CLAG9 occupies a distinct phylogenetic clade from CLAGX (the functional clag3 ortholog) and cannot complement CLAGX function."},"narrative":{"mechanistic_narrative":"CLAG9 (PF3D7_0935800) is a ~220 kDa Plasmodium falciparum rhoptry protein that couples merozoite invasion machinery to the cytoadherence properties of the infected erythrocyte [PMID:10737759, PMID:15049814]. It localizes to the basal bulb of merozoite rhoptries and is a component of the high-molecular-mass RhopH complex, co-purifying with RhopH2 and, in later work, with RAP1, RAP2, RAP3, and RhopH3 at the apical end of merozoites [PMID:15049814, PMID:31712270]; individual complexes carry only one RhopH1/Clag product, so CLAG9-containing complexes are compositionally distinct from those bearing Clag2 or Clag3.1 [PMID:15953647]. Functionally, targeted gene disruption and independent antisense inhibition both ablate cytoadherence of parasitized erythrocytes to CD36, establishing CLAG9 as essential for CD36-dependent binding [PMID:10737759, PMID:10989143]. After invasion the complex is transferred to ring-stage parasites and CLAG9 traffics to the host erythrocyte membrane, where it exists in alkaline-extractable soluble and membrane-integral forms and, unlike CLAG3, presents a protease-resistant surface-exposed region [PMID:15049814, PMID:38930554]. At the erythrocyte surface CLAG9 interacts with VAR2CSA and is required for trafficking of this PfEMP1 family member to the infected-cell surface [PMID:20823248]. The CLAG9-RhopH complex also mediates merozoite binding to erythrocytes via the glycophorin A–band 3 receptor complex [PMID:31712270]. CLAG9 knockout parasites grow normally in physiological medium, distinguishing CLAG9 from the growth-essential CLAG3 [PMID:38930554]. In P. berghei, CLAG9 occupies a phylogenetic clade separate from CLAGX and cannot complement CLAGX (the functional clag3 ortholog) function [PMID:39894870].","teleology":[{"year":2000,"claim":"Whether CLAG9 has a defined role in the pathogenic adhesion of infected erythrocytes was unknown; genetic loss-of-function established it as essential for cytoadherence to CD36.","evidence":"Targeted gene disruption and antisense RNA inhibition in P. falciparum with cytoadherence assays to CD36/C32 melanoma cells, plus plasmid reversion control","pmids":["10737759","10989143"],"confidence":"High","gaps":["Did not identify the molecular basis linking a rhoptry protein to surface adhesion","No direct demonstration that CLAG9 itself contacts CD36"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2004,"claim":"The subcellular identity of CLAG9 was undefined; multi-method imaging and complex purification placed it in the RhopH complex at the rhoptry basal bulb and showed transfer to ring stages after invasion.","evidence":"Immunofluorescence, immunoelectron microscopy, mass spectrometry, and co-immunoprecipitation with anti-RhopH2 in P. falciparum","pmids":["15049814"],"confidence":"High","gaps":["Did not resolve how a rhoptry/RhopH protein produces the surface cytoadherence phenotype","Complex stoichiometry not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"claim":"Whether CLAG9 shares complexes with other Clag paralogs was unresolved; co-IP showed CLAG9 complexes exclude Clag2 and Clag3.1, indicating one RhopH1/Clag product per complex.","evidence":"Anti-CLAG9 immunoprecipitation followed by Western blot for Clag2 and Clag3.1 in P. falciparum HB3 and 3D7","pmids":["15953647"],"confidence":"Medium","gaps":["Single negative co-IP result","Does not establish functional consequence of compositional exclusivity"],"attribution":[{"species":"Plasmodium falciparum","strain":"HB3, 3D7"}]},{"year":2010,"claim":"The mechanism linking CLAG9 to surface adhesion was unknown; CLAG9 was shown to interact with VAR2CSA and to be required for PfEMP1 trafficking to the infected-cell surface, and to be partly surface-exposed.","evidence":"Co-immunoprecipitation, immunofluorescence, trypsin sensitivity, and CLAG9-knockout analysis in P. falciparum","pmids":["20823248"],"confidence":"Medium","gaps":["Single-lab co-IP without reciprocal validation of the CLAG9–VAR2CSA interaction","Molecular route by which a rhoptry protein directs PfEMP1 surface delivery not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"Whether CLAG9 sequence contains discrete erythrocyte-binding determinants was untested; overlapping synthetic peptides identified high-affinity erythrocyte-binding regions that inhibited invasion.","evidence":"Receptor-ligand binding with synthetic peptides spanning CLAG9, RBC enzyme pre-treatment, and invasion inhibition assays","pmids":["20085836"],"confidence":"Medium","gaps":["No genetic validation that these peptides map to functional binding regions in native CLAG9","Erythrocyte receptors identified only by apparent molecular mass"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"The full composition of the CLAG9 complex and its erythrocyte receptor were incompletely defined; MS and interaction assays placed CLAG9 with RAP1/2/3 and RhopH2/3 and linked complex binding to the glycophorin A–band 3 receptor.","evidence":"Immunoprecipitation-mass spectrometry, recombinant CLAG9 domain interaction assays, immunofluorescence, and erythrocyte binding assays in P. falciparum","pmids":["31712270"],"confidence":"Medium","gaps":["Single-lab characterization","Direct affinity of native CLAG9 for glycophorin A/band 3 not quantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"How CLAG9 is partitioned at the host membrane and whether it is growth-essential was unclear; fractionation, protease treatment, and CRISPR knockout showed soluble and membrane-integral forms, a protease-resistant surface region distinct from CLAG3, and normal growth of CLAG9 knockouts.","evidence":"Epitope-tagging and co-localization, alkaline extraction, extracellular protease treatment, CRISPR/Cas9 knockout, growth and PSAC transport assays in P. falciparum","pmids":["38930554"],"confidence":"High","gaps":["Membrane insertion mechanism not defined","Functional role of the two biochemical forms not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Whether P. falciparum CLAG9 is functionally equivalent to CLAG3/CLAGX orthologs was untested; allelic replacement in P. berghei showed CLAG9 and CLAGX are distinct, non-complementary clades.","evidence":"Allelic replacement, inducible knockout, and guanidinium chloride haemolysis NPP assay in P. berghei","pmids":["39894870"],"confidence":"Medium","gaps":["Does not define the endogenous function of P. berghei CLAG9 itself","Cross-species inference to P. falciparum CLAG9 role is indirect"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2025,"claim":"New interactors of the CLAG9-containing complex were sought; the ankyrin-repeat protein PfANK_1 was shown to bind components of the PfClag9-RhopH complex with a defined interface.","evidence":"Co-immunoprecipitation, bio-layer interferometry, co-localization, molecular dynamics, and crystal structure of PfANK_1 in P. falciparum","pmids":["40614121"],"confidence":"Medium","gaps":["Interaction mapped to the complex rather than confirmed as direct CLAG9–PfANK_1 contact","Functional consequence of the interaction not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The mechanistic chain by which a rhoptry RhopH-complex protein is exported to the erythrocyte membrane, inserts, and directs both CD36-dependent cytoadherence and PfEMP1 surface trafficking remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of membrane-integral CLAG9 at the host surface","How CLAG9 mechanistically couples RhopH-complex function to PfEMP1 trafficking is unknown","Direct receptor-binding footprint of native CLAG9 not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["RhopH complex (CLAG9-RhopH: RhopH2, RhopH3, RAP1, RAP2, RAP3)"],"partners":["RHOPH2","RHOPH3","RAP1","RAP2","RAP3","VAR2CSA (PFEMP1 FAMILY MEMBER)","PFANK_1 (INTERACTS WITH THE CLAG9-RHOPH COMPLEX)"],"other_free_text":["Required for cytoadherence of infected erythrocytes to CD36 (P. falciparum) [#0, #1]","Required for trafficking of PfEMP1/VAR2CSA to the infected erythrocyte surface (P. falciparum) [#4]","CLAG9-RhopH complex mediates merozoite binding to erythrocytes via the glycophorin A–band 3 receptor complex (P. falciparum) [#6]","CLAG9 complexes contain only one RhopH1/Clag product, excluding Clag2 and Clag3.1 (P. falciparum) [#3]","Exists as alkaline-extractable soluble and membrane-integral forms with a protease-resistant surface region, distinct from CLAG3; knockouts grow normally in physiological medium (P. falciparum) [#7]","In P. berghei, CLAG9 is a distinct clade from CLAGX and cannot complement CLAGX function [#8]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"10737759","id":"PMC_10737759","title":"clag9: A cytoadherence gene in Plasmodium falciparum essential for binding of parasitized erythrocytes to CD36.","date":"2000","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/10737759","citation_count":99,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"15049814","id":"PMC_15049814","title":"The Plasmodium falciparum clag9 gene encodes a rhoptry protein that is transferred to the host erythrocyte upon invasion.","date":"2004","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/15049814","citation_count":70,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"15953647","id":"PMC_15953647","title":"Apical expression of three RhopH1/Clag proteins as components of the Plasmodium falciparum RhopH complex.","date":"2005","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/15953647","citation_count":68,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10989143","id":"PMC_10989143","title":"Inhibition of Plasmodium falciparum clag9 gene function by antisense RNA.","date":"2000","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/10989143","citation_count":48,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20823248","id":"PMC_20823248","title":"Dual stage synthesis and crucial role of cytoadherence-linked asexual gene 9 in the surface expression of malaria parasite var proteins.","date":"2010","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/20823248","citation_count":32,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23440122","id":"PMC_23440122","title":"Cross-reactive anti-PfCLAG9 antibodies in the sera of asymptomatic parasite carriers of Plasmodium vivax.","date":"2013","source":"Memorias do Instituto Oswaldo Cruz","url":"https://pubmed.ncbi.nlm.nih.gov/23440122","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfCLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22028613","id":"PMC_22028613","title":"Positive selection on the Plasmodium falciparum clag2 gene encoding a component of the erythrocyte-binding rhoptry protein complex.","date":"2011","source":"Tropical medicine and health","url":"https://pubmed.ncbi.nlm.nih.gov/22028613","citation_count":10,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31712270","id":"PMC_31712270","title":"Plasmodium falciparum Clag9-Associated PfRhopH Complex Is Involved in Merozoite Binding to Human Erythrocytes.","date":"2020","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/31712270","citation_count":8,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CLAG9","PfCLAG9"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20085836","id":"PMC_20085836","title":"Sequences of the Plasmodium falciparum cytoadherence-linked asexual protein 9 implicated in malaria parasite invasion to 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Anti-CLAG9 antibodies recognized a 220 kDa polypeptide absent in disrupted clones.\",\n      \"method\": \"Targeted gene disruption, cytoadherence assay, Western blot with DNA-induced antibodies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean targeted gene disruption with specific phenotypic readout (cytoadherence loss), replicated by antisense approach in a second paper\",\n      \"pmids\": [\"10737759\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Antisense RNA inhibition of CLAG9 in P. falciparum clone 3D7 reduced cytoadherence to C32 melanoma cells 15-fold compared to control, confirming the cytoadherence phenotype is directly caused by loss of CLAG9 function; reversion upon plasmid removal confirmed the effect was not due to an unrelated genomic change.\",\n      \"method\": \"Antisense RNA transfection, cytoadherence assay, plasmid reversion experiment\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — independent method (antisense) replicating the gene disruption result, with internal reversion control\",\n      \"pmids\": [\"10989143\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"CLAG9 is a rhoptry protein that localizes specifically to the basal bulb of rhoptries in merozoites (co-localized with RhopH2 by immunofluorescence and immunoelectron microscopy), is a component of the high-molecular-mass RhopH complex (co-purified with anti-RhopH2 antibodies and detected by mass spectrometry), and is transferred to ring-stage parasites within the RhopH complex after invasion.\",\n      \"method\": \"Immunofluorescence, immunoelectron microscopy, mass spectrometry, co-immunoprecipitation/complex purification\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (IEM, IF, MS, co-IP) in one study establishing complex membership and localization\",\n      \"pmids\": [\"15049814\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PfRhopH complex immunoprecipitated with anti-CLAG9 antibody contained neither Clag2 nor Clag3.1, indicating that individual PfRhopH complexes contain only one RhopH1/Clag protein product, and CLAG9-containing complexes are compositionally distinct from those containing Clag2 or Clag3.1.\",\n      \"method\": \"Immunoprecipitation with anti-CLAG9 antibody followed by Western blot for Clag2 and Clag3.1\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single co-IP result, but finding is a negative (absence of Clag2/Clag3.1) that is internally consistent across multiple antibodies in one lab\",\n      \"pmids\": [\"15953647\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"HB3, 3D7\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CLAG9 interacts with VAR2CSA (a PfEMP1 family member) at or near the infected red blood cell membrane. In parasites lacking CLAG9, VAR2CSA failed to reach the IRBC surface and was retained within the parasite, demonstrating that CLAG9 is required for trafficking of PfEMP1 to the IRBC surface. CLAG9 is synthesized at two stages (early ring and late trophozoite), and a portion of the protein is exposed on the IRBC surface (trypsin converts ~150 kDa form to ~142 kDa).\",\n      \"method\": \"Co-immunoprecipitation (CLAG9–VAR2CSA interaction), immunofluorescence localization, trypsin sensitivity assay, analysis of CLAG9-knockout parasites\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus knockout phenotype (VAR2CSA mislocalization) plus surface trypsin sensitivity, single lab\",\n      \"pmids\": [\"20823248\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Synthetic peptides spanning the complete CLAG9 sequence identified 20 high-affinity erythrocyte-binding peptides (HABPs) that interact with erythrocyte surface receptors of ~85, ~63, and ~34 kDa, and inhibited erythrocyte invasion in vitro by up to 72% at 200 µM.\",\n      \"method\": \"Receptor-ligand binding assay with synthetic peptides, enzyme pre-treatment of RBCs, invasion inhibition assay\",\n      \"journal\": \"Vaccine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct in vitro binding and invasion assay with defined peptides, single lab, no genetic validation\",\n      \"pmids\": [\"20085836\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PfCLAG9 forms a complex (PfClag9-RhopH complex) with PfRAP1, PfRAP2, PfRAP3, PfRhopH2, and PfRhopH3 at the apical end of merozoites, and the complex binds human erythrocytes through CLAG9 interaction with the glycophorin A–band 3 receptor-coreceptor complex.\",\n      \"method\": \"Immunoprecipitation followed by mass spectrometry, protein-protein interaction assays with recombinant CLAG9 domains, immunofluorescence, erythrocyte binding assay\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-identified complex members plus direct protein-protein interaction assays, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31712270\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CLAG9 traffics via merozoite rhoptries to the host erythrocyte membrane after invasion and exists in two forms within infected cells: an alkaline-extractable soluble form and a membrane-integral form. Unlike CLAG3, CLAG9 variant region is protease-resistant at the host erythrocyte surface. CLAG9 knockout parasites show uncompromised growth in physiological medium (unlike CLAG3 knockout), and CLAG2 and CLAG8 (but not specifically CLAG9) knockout lines show compensatory increases in transcription of remaining clag/rhoph genes.\",\n      \"method\": \"Epitope-tagging and fluorescence co-localization, alkaline extraction fractionation, extracellular protease treatment, CRISPR/Cas9 knockout, growth assays, PSAC-mediated transport assays\",\n      \"journal\": \"Microorganisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (tagging, fractionation, CRISPR KO, functional transport assay) in one study\",\n      \"pmids\": [\"38930554\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In P. berghei, CLAG9 and CLAGX belong to two distinct phylogenetic clades and have separate non-complementary functions: allelic replacement of CLAGX functional regions with P. berghei CLAG9 sequences did not rescue CLAGX function, establishing that P. berghei CLAG9 is not the functional ortholog of P. falciparum CLAG3 and cannot substitute for CLAGX.\",\n      \"method\": \"Allelic replacement in P. berghei, inducible knockout, guanidinium chloride haemolysis assay for NPP function\",\n      \"journal\": \"Journal of biomedical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via allelic replacement with functional NPP readout, single lab\",\n      \"pmids\": [\"39894870\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PfANK_1, an ankyrin repeat-containing protein, interacts with components of the PfClag9-PfRhopH complex, as shown by co-immunoprecipitation, bio-layer interferometry, and co-localization; structural analysis identified the binding interface and key interacting residues.\",\n      \"method\": \"Co-immunoprecipitation, bio-layer interferometry, co-localization, molecular dynamics simulations, crystal structure of PfANK_1\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal binding methods (Co-IP, BLI, co-localization, structure), single lab, finding is about an interactor of the CLAG9-containing complex\",\n      \"pmids\": [\"40614121\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"CLAG9 (PF3D7_0935800) is a ~220 kDa P. falciparum rhoptry protein that forms part of the high-molecular-weight RhopH complex (with RhopH2, RhopH3, RAP1, RAP2, RAP3) in the basal bulb of merozoite rhoptries; after invasion it is transferred to ring-stage parasites and inserts into the host erythrocyte membrane in a protease-resistant, membrane-integral form; it is required for cytoadherence to CD36 and for surface trafficking of PfEMP1 (VAR2CSA), and the CLAG9-containing RhopH complex mediates merozoite binding to erythrocytes via the glycophorin A–band 3 receptor complex, while in P. berghei CLAG9 occupies a distinct phylogenetic clade from CLAGX (the functional clag3 ortholog) and cannot complement CLAGX function.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CLAG9 (PF3D7_0935800) is a ~220 kDa Plasmodium falciparum rhoptry protein that couples merozoite invasion machinery to the cytoadherence properties of the infected erythrocyte [#0, #2]. It localizes to the basal bulb of merozoite rhoptries and is a component of the high-molecular-mass RhopH complex, co-purifying with RhopH2 and, in later work, with RAP1, RAP2, RAP3, and RhopH3 at the apical end of merozoites [#2, #6]; individual complexes carry only one RhopH1/Clag product, so CLAG9-containing complexes are compositionally distinct from those bearing Clag2 or Clag3.1 [#3]. Functionally, targeted gene disruption and independent antisense inhibition both ablate cytoadherence of parasitized erythrocytes to CD36, establishing CLAG9 as essential for CD36-dependent binding [#0, #1]. After invasion the complex is transferred to ring-stage parasites and CLAG9 traffics to the host erythrocyte membrane, where it exists in alkaline-extractable soluble and membrane-integral forms and, unlike CLAG3, presents a protease-resistant surface-exposed region [#2, #7]. At the erythrocyte surface CLAG9 interacts with VAR2CSA and is required for trafficking of this PfEMP1 family member to the infected-cell surface [#4]. The CLAG9-RhopH complex also mediates merozoite binding to erythrocytes via the glycophorin A\\u2013band 3 receptor complex [#6]. CLAG9 knockout parasites grow normally in physiological medium, distinguishing CLAG9 from the growth-essential CLAG3 [#7]. In P. berghei, CLAG9 occupies a phylogenetic clade separate from CLAGX and cannot complement CLAGX (the functional clag3 ortholog) function [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Whether CLAG9 has a defined role in the pathogenic adhesion of infected erythrocytes was unknown; genetic loss-of-function established it as essential for cytoadherence to CD36.\",\n      \"evidence\": \"Targeted gene disruption and antisense RNA inhibition in P. falciparum with cytoadherence assays to CD36/C32 melanoma cells, plus plasmid reversion control\",\n      \"pmids\": [\"10737759\", \"10989143\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the molecular basis linking a rhoptry protein to surface adhesion\", \"No direct demonstration that CLAG9 itself contacts CD36\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"The subcellular identity of CLAG9 was undefined; multi-method imaging and complex purification placed it in the RhopH complex at the rhoptry basal bulb and showed transfer to ring stages after invasion.\",\n      \"evidence\": \"Immunofluorescence, immunoelectron microscopy, mass spectrometry, and co-immunoprecipitation with anti-RhopH2 in P. falciparum\",\n      \"pmids\": [\"15049814\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how a rhoptry/RhopH protein produces the surface cytoadherence phenotype\", \"Complex stoichiometry not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Whether CLAG9 shares complexes with other Clag paralogs was unresolved; co-IP showed CLAG9 complexes exclude Clag2 and Clag3.1, indicating one RhopH1/Clag product per complex.\",\n      \"evidence\": \"Anti-CLAG9 immunoprecipitation followed by Western blot for Clag2 and Clag3.1 in P. falciparum HB3 and 3D7\",\n      \"pmids\": [\"15953647\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single negative co-IP result\", \"Does not establish functional consequence of compositional exclusivity\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"HB3, 3D7\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"The mechanism linking CLAG9 to surface adhesion was unknown; CLAG9 was shown to interact with VAR2CSA and to be required for PfEMP1 trafficking to the infected-cell surface, and to be partly surface-exposed.\",\n      \"evidence\": \"Co-immunoprecipitation, immunofluorescence, trypsin sensitivity, and CLAG9-knockout analysis in P. falciparum\",\n      \"pmids\": [\"20823248\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab co-IP without reciprocal validation of the CLAG9\\u2013VAR2CSA interaction\", \"Molecular route by which a rhoptry protein directs PfEMP1 surface delivery not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Whether CLAG9 sequence contains discrete erythrocyte-binding determinants was untested; overlapping synthetic peptides identified high-affinity erythrocyte-binding regions that inhibited invasion.\",\n      \"evidence\": \"Receptor-ligand binding with synthetic peptides spanning CLAG9, RBC enzyme pre-treatment, and invasion inhibition assays\",\n      \"pmids\": [\"20085836\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No genetic validation that these peptides map to functional binding regions in native CLAG9\", \"Erythrocyte receptors identified only by apparent molecular mass\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The full composition of the CLAG9 complex and its erythrocyte receptor were incompletely defined; MS and interaction assays placed CLAG9 with RAP1/2/3 and RhopH2/3 and linked complex binding to the glycophorin A\\u2013band 3 receptor.\",\n      \"evidence\": \"Immunoprecipitation-mass spectrometry, recombinant CLAG9 domain interaction assays, immunofluorescence, and erythrocyte binding assays in P. falciparum\",\n      \"pmids\": [\"31712270\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab characterization\", \"Direct affinity of native CLAG9 for glycophorin A/band 3 not quantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"How CLAG9 is partitioned at the host membrane and whether it is growth-essential was unclear; fractionation, protease treatment, and CRISPR knockout showed soluble and membrane-integral forms, a protease-resistant surface region distinct from CLAG3, and normal growth of CLAG9 knockouts.\",\n      \"evidence\": \"Epitope-tagging and co-localization, alkaline extraction, extracellular protease treatment, CRISPR/Cas9 knockout, growth and PSAC transport assays in P. falciparum\",\n      \"pmids\": [\"38930554\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Membrane insertion mechanism not defined\", \"Functional role of the two biochemical forms not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Whether P. falciparum CLAG9 is functionally equivalent to CLAG3/CLAGX orthologs was untested; allelic replacement in P. berghei showed CLAG9 and CLAGX are distinct, non-complementary clades.\",\n      \"evidence\": \"Allelic replacement, inducible knockout, and guanidinium chloride haemolysis NPP assay in P. berghei\",\n      \"pmids\": [\"39894870\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not define the endogenous function of P. berghei CLAG9 itself\", \"Cross-species inference to P. falciparum CLAG9 role is indirect\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"New interactors of the CLAG9-containing complex were sought; the ankyrin-repeat protein PfANK_1 was shown to bind components of the PfClag9-RhopH complex with a defined interface.\",\n      \"evidence\": \"Co-immunoprecipitation, bio-layer interferometry, co-localization, molecular dynamics, and crystal structure of PfANK_1 in P. falciparum\",\n      \"pmids\": [\"40614121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction mapped to the complex rather than confirmed as direct CLAG9\\u2013PfANK_1 contact\", \"Functional consequence of the interaction not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanistic chain by which a rhoptry RhopH-complex protein is exported to the erythrocyte membrane, inserts, and directs both CD36-dependent cytoadherence and PfEMP1 surface trafficking remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of membrane-integral CLAG9 at the host surface\", \"How CLAG9 mechanistically couples RhopH-complex function to PfEMP1 trafficking is unknown\", \"Direct receptor-binding footprint of native CLAG9 not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0050839\", \"supporting_discovery_ids\": [0, 5, 6]},\n      {\"term_id\": \"GO:0005102\", \"supporting_discovery_ids\": [4, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020008\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0006886\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0044406\", \"supporting_discovery_ids\": [6, 5]}\n    ],\n    \"complexes\": [\n      \"RhopH complex (CLAG9-RhopH: RhopH2, RhopH3, RAP1, RAP2, RAP3)\"\n    ],\n    \"partners\": [\n      \"RhopH2\",\n      \"RhopH3\",\n      \"RAP1\",\n      \"RAP2\",\n      \"RAP3\",\n      \"VAR2CSA (PfEMP1 family member)\",\n      \"PfANK_1 (interacts with the CLAG9-RhopH complex)\"\n    ],\n    \"other_free_text\": [\n      \"Required for cytoadherence of infected erythrocytes to CD36 (P. falciparum) [#0, #1]\",\n      \"Required for trafficking of PfEMP1/VAR2CSA to the infected erythrocyte surface (P. falciparum) [#4]\",\n      \"CLAG9-RhopH complex mediates merozoite binding to erythrocytes via the glycophorin A\\u2013band 3 receptor complex (P. falciparum) [#6]\",\n      \"CLAG9 complexes contain only one RhopH1/Clag product, excluding Clag2 and Clag3.1 (P. falciparum) [#3]\",\n      \"Exists as alkaline-extractable soluble and membrane-integral forms with a protease-resistant surface region, distinct from CLAG3; knockouts grow normally in physiological medium (P. falciparum) [#7]\",\n      \"In P. berghei, CLAG9 is a distinct clade from CLAGX and cannot complement CLAGX function [#8]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0935800","name":null,"product":"cytoadherence linked asexual protein 9","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0836300","name":null,"product":"cytoadherence linked asexual protein 9","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0734400","name":null,"product":"cytoadherence linked asexual protein, CLAG, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"CLAG9","evaluation":null}