{"gene":"PF3D7_0423800","run_date":"2026-09-07T10:55:51","timeline":{"discoveries":[{"year":2012,"finding":"CyRPA is expressed in late schizonts, localizes at the apex of merozoites by immunofluorescence, and CyRPA-specific monoclonal antibodies substantially inhibit parasite growth in vitro and in vivo in a P. falciparum NOD-scid IL2Rγ(null) mouse model engrafted with human erythrocytes, establishing a role for CyRPA in erythrocyte invasion.","method":"Immunofluorescence microscopy; in vitro growth inhibition assay; passive immunization in humanized mouse model","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional consequence; in vitro and in vivo inhibition by specific mAbs, single lab with multiple methods","pmids":["22593616"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"CyRPA is a GPI-anchored protein that localizes in the micronemes and forms a multiprotein complex with PfRH5 and PfRipr on the merozoite surface; co-immunoprecipitation with antibodies against each of the three proteins detected the intact complex; CyRPA is essential for erythrocyte invasion; CyRPA does not bind erythrocytes directly, indicating its invasion-inhibitory antibodies likely act by blocking PfRH5-PfRipr/CyRPA interactions; antibodies against CyRPA and PfRH5 showed synergistic invasion inhibition.","method":"GPI-anchor verification; immunofluorescence/co-localization; co-immunoprecipitation; conditional knockdown; in vitro growth inhibition 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, GPI-anchor biochemistry, localization, conditional knockdown with invasion phenotype, multiple orthogonal methods in one study","pmids":["25583518"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Conditional loss of CyRPA function blocks merozoite invasion of erythrocytes; super-resolution microscopy showed CyRPA colocalizes with PfRipr and PfRH5 at the junction between merozoites and erythrocytes during invasion; the PfRH5/PfRipr/CyRPA complex is required for triggering Ca2+ release from the host erythrocyte and establishing the tight junction.","method":"Conditional expression system (loss-of-function); super-resolution microscopy; Ca2+ release assay","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with specific invasion phenotype, super-resolution localization at functional junction, Ca2+ assay, multiple orthogonal methods","pmids":["27374406"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"Crystal structure of CyRPA reveals a six-bladed β-propeller fold similar to the sialidase fold, but CyRPA has no sialidase activity and fulfills a purely non-enzymatic structural function; crystal structure of CyRPA in complex with an invasion-inhibitory antibody Fab fragment identifies the protective antibody epitope.","method":"X-ray crystallography (CyRPA alone and CyRPA-Fab complex); sialidase activity assay (negative result for enzymatic activity)","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of free protein and antibody complex, enzymatic activity directly tested and ruled out, two independent crystal structures in one study","pmids":["28195038"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"CyRPA directly interacts with PfRH5; an invasion-inhibitory monoclonal antibody to CyRPA blocks CyRPA binding to PfRH5 and prevents complex formation; crystal structures of CyRPA alone and in complex with an antibody Fab fragment identify the PfRH5-interacting region of CyRPA (a functionally conserved epitope).","method":"X-ray crystallography; binding assay (CyRPA-PfRH5 interaction); monoclonal antibody blocking assay; in vitro growth inhibition assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus direct binding assay plus mAb blocking mechanism, multiple orthogonal methods in one rigorous study","pmids":["28195530"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Cryo-EM structure of the Rh5-CyRPA-Ripr complex at subnanometre resolution shows CyRPA is a critical mediator of complex assembly; blades 4–6 of the CyRPA β-propeller are contact sites for both Rh5 and Ripr; the limited contacts between Rh5-CyRPA and CyRPA-Ripr are consistent with dissociation of Rh5 and Ripr from CyRPA during membrane insertion; the full Rh5-CyRPA-Ripr complex binds the erythrocyte cell line JK-1 significantly better than Rh5 alone, and this enhanced binding involves insertion of Rh5 and Ripr into host membranes.","method":"Cryo-electron microscopy structure determination; erythrocyte binding assay; comparison with crystal structure of Rh5-basigin","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with subnanometre resolution plus functional binding assay, identifies specific CyRPA blade contacts","pmids":["30542156"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Antibodies specific for CyRPA prevent trimeric complex (Rh5/Ripr/CyRPA) formation, establishing that the inhibitory mechanism of anti-CyRPA antibodies acts at the level of complex assembly.","method":"Antibody blocking assay of complex formation; in vitro growth inhibition assay","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct complex-formation blocking assay, single lab, two methods (complex assay + GIA)","pmids":["30965383"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"In P. knowlesi, CyRPA (PkCyRPA) is essential for successful erythrocyte invasion in vitro, but unlike in P. falciparum, PkCyRPA does not form a complex with PkRIPR or with an RH5-like molecule; PkCyRPA appears to function independently of other parasite binding partners in P. knowlesi.","method":"Conditional knockdown (loss-of-function) in P. knowlesi; co-immunoprecipitation (negative result for PkCyRPA-PkRIPR complex)","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with invasion phenotype plus reciprocal Co-IP establishing absence of complex; single lab, two orthogonal methods","pmids":["31185066"],"is_preprint":false,"attribution":[{"species":"Plasmodium knowlesi","strain":""}]},{"year":2022,"finding":"CyRPA (as part of the PCRCR pentameric complex with PfPTRAMP, PfCSS, PfRH5, and PfRipr) is essential for erythrocyte invasion; the PCRCR complex functions to anchor contact between merozoite and erythrocyte membranes during strong parasite deformations; CyRPA is a component of this pentameric complex.","method":"Conditional knockout of PfPTRAMP and PfCSS; invasion-inhibitory nanobodies; lattice light-sheet microscopy; complex biochemistry","journal":"Nature microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KOs and nanobody inhibition establish the pentameric PCRCR complex and its function, CyRPA's role attributed as a complex member; single study but multiple rigorous methods","pmids":["36396942"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"The aspartic protease plasmepsin X (PMX) processes the PCRCR complex in micronemes by removing the N-terminal prodomain of PfRH5, which activates PCRCR function and unmasks the complex to bind basigin on the erythrocyte membrane; CyRPA is a component of this complex that is regulated by PMX processing.","method":"Conditional knockdown of PMX; biochemical processing assay; erythrocyte binding assay","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional knockdown with invasion phenotype and direct biochemical processing assay; CyRPA's specific role within PCRCR not tested separately from complex","pmids":["37072430"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"Cryo-EM structure of the PfRCR complex (PfRH5, PfCyRPA, PfRIPR) shows that PfCyRPA presents PfRH5 and forms part of the structured core; the elongated tail of PfRIPR is flexibly linked to the PfCyRPA-PfRH5 core; CyRPA-binding antibodies neutralize invasion through a steric mechanism (shown by modelling and erythrocyte-binding assay); a rigid, disulfide-locked PfRH5 can mediate efficient erythrocyte invasion (contradicting membrane-opening hypothesis).","method":"Cryo-electron microscopy structure determination; erythrocyte-binding assay; structural modelling","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure of full RCR complex with functional binding assay identifying steric inhibition mechanism; rigorous single study with multiple methods","pmids":["38123677"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Growth-inhibitory antibodies against CyRPA bind epitopes on a single face of CyRPA; pairs of non-competing inhibitory antibodies show strongly synergistic growth-inhibitory activity by forming lateral heterotypic interactions that slow antibody dissociation from CyRPA.","method":"Structural studies (antibody-CyRPA complexes); surface plasmon resonance (antibody dissociation kinetics); in vitro growth inhibition assay with antibody combinations","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal/structural studies plus SPR kinetics plus GIA, multiple orthogonal methods revealing mechanism of synergy, single rigorous study","pmids":["35177602"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"CyRPA functions as a lectin that binds glycans terminating with α2-6-linked N-acetylneuraminic acid (Neu5Ac) on the erythrocyte surface; CyRPA has a >50-fold binding preference for human α2-6-linked Neu5Ac over non-human α2-6-linked N-glycolylneuraminic acid; lectin-binding sites were identified by molecular modelling and validated by mutagenesis; transgenic parasites expressing CyRPA with single amino acid exchange mutants in the lectin sites showed impaired invasion, demonstrating the functional importance of lectin activity.","method":"Glycan-binding assay; molecular modelling; site-directed mutagenesis; transgenic parasite lines with endogenous CyRPA point mutants; in vitro growth inhibition with small molecules and lectin-site-specific antibodies","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — lectin activity assay plus mutagenesis validated in endogenous transgenic parasite lines plus functional invasion assay; multiple orthogonal methods in one rigorous study","pmids":["38573856"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"Anti-CyRPA monoclonal antibodies block invasion and additionally inactivate extracellular merozoites by triggering a developmental pathway normally seen only after successful invasion; combining anti-CyRPA and anti-PfRH5 mAbs enhances the degree of invasion inhibition observed by live-cell imaging.","method":"Live-cell imaging with monoclonal antibodies; in vitro growth inhibition assay","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging with mAbs establishing timing and stage of inhibition plus secondary inactivation phenotype; single lab, two orthogonal methods","pmids":["37713419"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"Structure-guided design of a CyRPA epitope mimic (PfCyRPA-EM) comprising blades 1 and 2 of the six-bladed β-propeller (the face exposed in the PCRCR complex and containing the epitopes of the most potent growth-inhibitory antibodies) elicits antibodies with superior growth-inhibitory activity at lower concentrations than full-length CyRPA in a preclinical model, establishing that blades 1 and 2 harbour the critical protective epitopes.","method":"Structure-guided protein engineering; immunization in preclinical model; in vitro growth inhibition assay","journal":"EMBO molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — structure-guided design with functional readout in preclinical model; single lab, structure plus immunogenicity assay","pmids":["41772083"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"Sites 154 and 209 of PfCyRPA — previously reported as sufficient to switch glycan-binding preference between human (Neu5Ac) and ape glycans — are identical in P. falciparum and its gorilla precursor P. praefalciparum, and no other differences were found near the CyRPA glycan-binding sites; thus the gorilla precursor appears pre-adapted to bind human sialoglycans, and these two sites do not explain P. falciparum adaptation to humans.","method":"Comparative genome sequence analysis of P. falciparum, P. praefalciparum, and P. reichenowi","journal":"Genome biology and evolution","confidence":"Low","confidence_rationale":"Tier 4 / Weak — purely computational/sequence comparison, no direct experimental manipulation of CyRPA in this study","pmids":["39865504"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium praefalciparum","strain":""}]}],"current_model":"PfCyRPA (PF3D7_0423800) is a GPI-anchored, six-bladed β-propeller protein localized in merozoite micronemes that functions as a central scaffold of the essential PfRH5–PfCyRPA–PfRIPR (RCR) tripartite complex — itself part of the larger pentameric PCRCR complex — where CyRPA mediates complex assembly by contacting PfRH5 via blades 4–6 and PfRIPR, has no enzymatic activity, binds human erythrocyte sialoglycans (α2-6-linked Neu5Ac) via a lectin site on its β-propeller that is essential for invasion, is activated in micronemes by plasmepsin X processing of PfRH5, and is required for the Ca2+-release step and tight-junction formation during erythrocyte invasion; growth-inhibitory antibodies predominantly target a single face of CyRPA (blades 1–2) and act by blocking CyRPA–PfRH5 complex formation or by steric occlusion."},"narrative":{"mechanistic_narrative":"CyRPA (PF3D7_0423800) is a GPI-anchored, apically localized micronemal protein of the P. falciparum merozoite that is essential for erythrocyte invasion, acting as the central structural scaffold of the PfRH5–PfRIPR–CyRPA (RCR) tripartite complex and the larger PCRCR pentameric complex [PMID:25583518, PMID:27374406, PMID:36396942]. Structurally it is a six-bladed β-propeller resembling a sialidase fold but is enzymatically inert, fulfilling a purely non-enzymatic role [PMID:28195038]. CyRPA mediates assembly of the invasion complex: it binds PfRH5 directly and contacts both PfRH5 and PfRIPR through blades 4–6 of the propeller, presenting PfRH5 within the structured core while the PfRIPR tail extends flexibly, and the assembled complex binds erythrocytes far more efficiently than PfRH5 alone [PMID:28195530, PMID:30542156, PMID:38123677]. During invasion CyRPA colocalizes with PfRH5 and PfRIPR at the merozoite–erythrocyte tight junction, where the complex triggers host Ca2+ release and anchors membrane contact; complex function is activated by plasmepsin X processing of PfRH5's prodomain in micronemes [PMID:27374406, PMID:36396942, PMID:37072430]. Independently of its scaffolding role, CyRPA acts as a lectin that binds erythrocyte glycans terminating in human α2-6-linked Neu5Ac, with point mutations in the lectin site impairing invasion [PMID:38573856]. CyRPA is a leading blood-stage vaccine target: growth-inhibitory antibodies cluster on one face of the propeller (blades 1–2), neutralizing invasion by blocking complex formation or through steric occlusion, and act synergistically both in pairs and in combination with anti-PfRH5 antibodies [PMID:28195530, PMID:30965383, PMID:38123677, PMID:35177602]. Notably, the CyRPA ortholog in P. knowlesi is likewise essential for invasion but functions independently, without forming a complex with a PfRIPR or PfRH5 counterpart [PMID:31185066].","teleology":[{"year":2012,"claim":"Established that CyRPA is an invasion-relevant antigen by showing apical expression in schizonts/merozoites and that specific antibodies block parasite growth in vitro and in humanized mice.","evidence":"Immunofluorescence, in vitro growth inhibition, and passive immunization in a humanized mouse model","pmids":["22593616"],"confidence":"Medium","gaps":["No molecular partners or mechanism of invasion contribution identified","Whether CyRPA acts alone or in a complex not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"Resolved how CyRPA contributes to invasion by showing it is a GPI-anchored micronemal protein that assembles with PfRH5 and PfRIPR into an essential complex, and does not bind erythrocytes directly — explaining that its inhibitory antibodies act by blocking complex interactions.","evidence":"GPI-anchor biochemistry, reciprocal co-immunoprecipitation, conditional knockdown, and growth inhibition assays","pmids":["25583518"],"confidence":"High","gaps":["Structural basis of the interactions unknown","Direct erythrocyte-binding role (later revised by lectin activity) not yet examined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Placed the complex at the point of entry by showing CyRPA colocalizes with PfRH5/PfRIPR at the tight junction and is required to trigger host Ca2+ release, defining the functional step it controls during invasion.","evidence":"Conditional loss-of-function, super-resolution microscopy, and Ca2+ release assay","pmids":["27374406"],"confidence":"High","gaps":["Molecular trigger of Ca2+ release not defined","CyRPA's specific contribution versus the whole complex not isolated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"Defined CyRPA's molecular nature and the antibody target by solving its six-bladed β-propeller structure, ruling out sialidase activity, mapping the PfRH5-interacting region, and showing an inhibitory antibody blocks CyRPA–PfRH5 binding and complex formation.","evidence":"X-ray crystallography of free CyRPA and CyRPA–Fab complexes, sialidase activity assay (negative), direct PfRH5-binding and antibody-blocking assays","pmids":["28195038","28195530"],"confidence":"High","gaps":["Architecture of the full trimeric complex not resolved","Role of remaining propeller faces unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Revealed the architecture of the assembled RCR complex, showing CyRPA uses blades 4–6 to bridge PfRH5 and PfRIPR and that the complex enhances erythrocyte binding over PfRH5 alone, defining CyRPA as the assembly hub.","evidence":"Subnanometre cryo-EM structure of the Rh5–CyRPA–Ripr complex plus erythrocyte binding assay","pmids":["30542156"],"confidence":"High","gaps":["Dynamics of proposed complex dissociation during membrane insertion not directly observed","Precise contribution of each blade contact to invasion untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Confirmed the antibody neutralization mechanism by directly demonstrating that anti-CyRPA antibodies prevent trimeric complex formation.","evidence":"Antibody blocking of complex assembly plus growth inhibition assay","pmids":["30965383"],"confidence":"Medium","gaps":["Does not distinguish assembly blockade from steric mechanisms","Epitope face not mapped in this study"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Tested conservation of CyRPA function across species, showing P. knowlesi CyRPA is essential for invasion but functions without forming a PfRIPR/PfRH5-like complex, indicating the complex-dependent mechanism is not universal.","evidence":"Conditional knockdown in P. knowlesi and co-immunoprecipitation (negative for complex)","pmids":["31185066"],"confidence":"Medium","gaps":["Mechanism by which PkCyRPA acts independently unknown","PkCyRPA binding partners not identified"],"attribution":[{"species":"Plasmodium knowlesi","strain":""}]},{"year":2022,"claim":"Extended the complex to a pentameric PCRCR assembly (PfPTRAMP, PfCSS, PfRH5, PfRIPR, CyRPA) that anchors merozoite–erythrocyte membrane contact during deformation, and defined the CyRPA epitope face driving synergistic antibody neutralization.","evidence":"Conditional knockouts, invasion-inhibitory nanobodies, lattice light-sheet microscopy, complex biochemistry (PCRCR); structural studies, SPR kinetics and combination GIA (antibody synergy)","pmids":["36396942","35177602"],"confidence":"Medium","gaps":["CyRPA's specific role within PCRCR not separated from the whole complex","In vivo relevance of antibody synergy not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"Clarified regulation and mechanism by showing plasmepsin X processing of PfRH5 activates the PCRCR complex to bind basigin, resolving the full RCR structure with CyRPA presenting PfRH5, and demonstrating anti-CyRPA antibodies inhibit both by steric occlusion and by prematurely inactivating extracellular merozoites.","evidence":"Conditional PMX knockdown and processing/binding assays; cryo-EM of the full PfRCR complex with modelling; live-cell imaging with mAbs","pmids":["37072430","38123677","37713419"],"confidence":"High","gaps":["How processing propagates to CyRPA function not directly tested","Mechanism of premature merozoite inactivation unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Revised the view that CyRPA does not engage erythrocytes by identifying it as a lectin binding human α2-6-linked Neu5Ac, with lectin-site point mutations impairing invasion, assigning CyRPA a direct receptor-recognition function.","evidence":"Glycan-binding assays, molecular modelling, site-directed mutagenesis in endogenous transgenic parasites, and functional invasion/GIA assays","pmids":["38573856"],"confidence":"High","gaps":["Reconciliation with earlier finding that CyRPA does not bind erythrocytes directly not fully resolved","How lectin binding integrates with complex assembly during invasion unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"Advanced CyRPA as a vaccine immunogen by showing a structure-guided blades 1–2 epitope mimic elicits superior growth-inhibitory antibodies, confirming these blades harbour the critical protective epitopes.","evidence":"Structure-guided protein engineering, preclinical immunization, and growth inhibition assay","pmids":["41772083"],"confidence":"Medium","gaps":["Efficacy in humans not established","Durability and breadth of the antibody response not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Examined the evolutionary origin of CyRPA's human glycan specificity, finding that lectin-site residues 154 and 209 are identical between P. falciparum and its gorilla precursor P. praefalciparum, so these sites do not explain adaptation to human erythrocytes.","evidence":"Comparative genome sequence analysis across P. falciparum, P. praefalciparum, and P. reichenowi","pmids":["39865504"],"confidence":"Low","gaps":["Purely computational; no experimental test of glycan preference for the precursor CyRPA","Actual determinants of host adaptation remain unidentified"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium praefalciparum","strain":""}]},{"year":null,"claim":"How CyRPA's lectin-mediated sialoglycan binding is mechanistically integrated with its scaffolding of the RCR/PCRCR complex, PfRH5 presentation, and the triggering of host Ca2+ release during tight-junction formation remains to be defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Temporal and spatial coordination of lectin binding versus complex assembly unknown","Molecular link from complex engagement to erythrocyte Ca2+ release undefined","CyRPA's autonomous contribution within the pentameric PCRCR not experimentally isolated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PfRH5–CyRPA–PfRIPR (RCR) tripartite complex","PCRCR pentameric complex (PfPTRAMP, PfCSS, PfRH5, PfRIPR, CyRPA)"],"partners":["PFRH5","PFRIPR","PFPTRAMP (VIA PCRCR COMPLEX)","PFCSS (VIA PCRCR COMPLEX)","PLASMEPSIN X (REGULATES COMPLEX VIA PFRH5 PROCESSING)","ERYTHROCYTE Α2-6-LINKED NEU5AC SIALOGLYCANS (LIGAND)"],"other_free_text":["Six-bladed β-propeller with a sialidase-like fold but no sialidase/enzymatic activity; purely structural scaffold [#3].","Contacts PfRH5 and PfRIPR through propeller blades 4–6; blades 1–2 form the antibody-exposed face carrying the most potent growth-inhibitory epitopes [#5, #14].","Required for triggering host erythrocyte Ca2+ release and tight-junction formation during invasion [#2].","Growth-inhibitory antibodies neutralize by blocking complex assembly and by steric occlusion, and can act synergistically in pairs and with anti-PfRH5 antibodies [#6, #10, #11, #13].","In P. knowlesi the ortholog is essential for invasion but functions independently of a PfRIPR/PfRH5-like complex [#7]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"30028591","id":"PMC_30028591","title":"Engineering a Rugged Nanoscaffold To Enhance Plug-and-Display Vaccination.","date":"2018","source":"ACS nano","url":"https://pubmed.ncbi.nlm.nih.gov/30028591","citation_count":248,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27374406","id":"PMC_27374406","title":"Essential Role of the PfRh5/PfRipr/CyRPA Complex during Plasmodium falciparum Invasion of Erythrocytes.","date":"2016","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/27374406","citation_count":163,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA","cysteine-rich protective antigen"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25583518","id":"PMC_25583518","title":"Multiprotein complex between the GPI-anchored CyRPA with PfRH5 and PfRipr is crucial for Plasmodium falciparum erythrocyte invasion.","date":"2015","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/25583518","citation_count":144,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA","cysteine-rich protective antigen"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30542156","id":"PMC_30542156","title":"Structure of Plasmodium falciparum Rh5-CyRPA-Ripr invasion complex.","date":"2018","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/30542156","citation_count":84,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28949293","id":"PMC_28949293","title":"Identification of highly-protective combinations of Plasmodium vivax recombinant proteins for vaccine 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Section D, Structural biology","url":"https://pubmed.ncbi.nlm.nih.gov/40192714","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41332710","id":"PMC_41332710","title":"Evaluating the potential of cross-species neutralization of anti-PfCyRPA and anti-PfRIPR Monoclonal Antibodies.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41332710","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA","PfCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39816834","id":"PMC_39816834","title":"Reticulocyte Binding Protein Homologue 5 is a target of balancing selection in the Plasmodium falciparum population of Papua New Guinea.","date":"2023","source":"Frontiers in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/39816834","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38604871","id":"PMC_38604871","title":"A targetable receptor-binding site on PfCyRPA to aid in the fight against malaria.","date":"2024","source":"Trends in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/38604871","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA","PfCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41205844","id":"PMC_41205844","title":"Plasmodium vivax cysteine-rich protective antigen (PvCyRPA), an important element for vaccine strategies targeting P. vivax, interacts with human erythrocyte surface.","date":"2025","source":"Acta tropica","url":"https://pubmed.ncbi.nlm.nih.gov/41205844","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CyRPA","cysteine-rich protective antigen","PvCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"41772083","id":"PMC_41772083","title":"Structure-guided design of a PfCyRPA-based vaccine against blood-stage malaria.","date":"2026","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41772083","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40343341","id":"PMC_40343341","title":"PTRAMP, CSS and Ripr form a conserved complex required for merozoite invasion of Plasmodium species into erythrocytes.","date":"2025","source":"Research square","url":"https://pubmed.ncbi.nlm.nih.gov/40343341","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"36682939","id":"PMC_36682939","title":"A complex equation - adding to Plasmodium falciparum invasion.","date":"2023","source":"Trends in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/36682939","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfCyRPA"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":35850,"output_tokens":4754,"usd":0.08943,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11285,"output_tokens":5353,"usd":0.095125,"stage2_stop_reason":"end_turn"},"total_usd":0.184555,"stage1_batch_id":"msgbatch_01DbiymDmubkPpYvdbAu5a7V","stage2_batch_id":"msgbatch_012TbrWvMRH129T7PQ4SmvrJ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"CyRPA is expressed in late schizonts, localizes at the apex of merozoites by immunofluorescence, and CyRPA-specific monoclonal antibodies substantially inhibit parasite growth in vitro and in vivo in a P. falciparum NOD-scid IL2Rγ(null) mouse model engrafted with human erythrocytes, establishing a role for CyRPA in erythrocyte invasion.\",\n      \"method\": \"Immunofluorescence microscopy; in vitro growth inhibition assay; passive immunization in humanized mouse model\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional consequence; in vitro and in vivo inhibition by specific mAbs, single lab with multiple methods\",\n      \"pmids\": [\"22593616\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CyRPA is a GPI-anchored protein that localizes in the micronemes and forms a multiprotein complex with PfRH5 and PfRipr on the merozoite surface; co-immunoprecipitation with antibodies against each of the three proteins detected the intact complex; CyRPA is essential for erythrocyte invasion; CyRPA does not bind erythrocytes directly, indicating its invasion-inhibitory antibodies likely act by blocking PfRH5-PfRipr/CyRPA interactions; antibodies against CyRPA and PfRH5 showed synergistic invasion inhibition.\",\n      \"method\": \"GPI-anchor verification; immunofluorescence/co-localization; co-immunoprecipitation; conditional knockdown; in vitro growth inhibition 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, GPI-anchor biochemistry, localization, conditional knockdown with invasion phenotype, multiple orthogonal methods in one study\",\n      \"pmids\": [\"25583518\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Conditional loss of CyRPA function blocks merozoite invasion of erythrocytes; super-resolution microscopy showed CyRPA colocalizes with PfRipr and PfRH5 at the junction between merozoites and erythrocytes during invasion; the PfRH5/PfRipr/CyRPA complex is required for triggering Ca2+ release from the host erythrocyte and establishing the tight junction.\",\n      \"method\": \"Conditional expression system (loss-of-function); super-resolution microscopy; Ca2+ release assay\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with specific invasion phenotype, super-resolution localization at functional junction, Ca2+ assay, multiple orthogonal methods\",\n      \"pmids\": [\"27374406\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structure of CyRPA reveals a six-bladed β-propeller fold similar to the sialidase fold, but CyRPA has no sialidase activity and fulfills a purely non-enzymatic structural function; crystal structure of CyRPA in complex with an invasion-inhibitory antibody Fab fragment identifies the protective antibody epitope.\",\n      \"method\": \"X-ray crystallography (CyRPA alone and CyRPA-Fab complex); sialidase activity assay (negative result for enzymatic activity)\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of free protein and antibody complex, enzymatic activity directly tested and ruled out, two independent crystal structures in one study\",\n      \"pmids\": [\"28195038\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CyRPA directly interacts with PfRH5; an invasion-inhibitory monoclonal antibody to CyRPA blocks CyRPA binding to PfRH5 and prevents complex formation; crystal structures of CyRPA alone and in complex with an antibody Fab fragment identify the PfRH5-interacting region of CyRPA (a functionally conserved epitope).\",\n      \"method\": \"X-ray crystallography; binding assay (CyRPA-PfRH5 interaction); monoclonal antibody blocking assay; in vitro growth inhibition assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus direct binding assay plus mAb blocking mechanism, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"28195530\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-EM structure of the Rh5-CyRPA-Ripr complex at subnanometre resolution shows CyRPA is a critical mediator of complex assembly; blades 4–6 of the CyRPA β-propeller are contact sites for both Rh5 and Ripr; the limited contacts between Rh5-CyRPA and CyRPA-Ripr are consistent with dissociation of Rh5 and Ripr from CyRPA during membrane insertion; the full Rh5-CyRPA-Ripr complex binds the erythrocyte cell line JK-1 significantly better than Rh5 alone, and this enhanced binding involves insertion of Rh5 and Ripr into host membranes.\",\n      \"method\": \"Cryo-electron microscopy structure determination; erythrocyte binding assay; comparison with crystal structure of Rh5-basigin\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with subnanometre resolution plus functional binding assay, identifies specific CyRPA blade contacts\",\n      \"pmids\": [\"30542156\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Antibodies specific for CyRPA prevent trimeric complex (Rh5/Ripr/CyRPA) formation, establishing that the inhibitory mechanism of anti-CyRPA antibodies acts at the level of complex assembly.\",\n      \"method\": \"Antibody blocking assay of complex formation; in vitro growth inhibition assay\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct complex-formation blocking assay, single lab, two methods (complex assay + GIA)\",\n      \"pmids\": [\"30965383\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In P. knowlesi, CyRPA (PkCyRPA) is essential for successful erythrocyte invasion in vitro, but unlike in P. falciparum, PkCyRPA does not form a complex with PkRIPR or with an RH5-like molecule; PkCyRPA appears to function independently of other parasite binding partners in P. knowlesi.\",\n      \"method\": \"Conditional knockdown (loss-of-function) in P. knowlesi; co-immunoprecipitation (negative result for PkCyRPA-PkRIPR complex)\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with invasion phenotype plus reciprocal Co-IP establishing absence of complex; single lab, two orthogonal methods\",\n      \"pmids\": [\"31185066\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CyRPA (as part of the PCRCR pentameric complex with PfPTRAMP, PfCSS, PfRH5, and PfRipr) is essential for erythrocyte invasion; the PCRCR complex functions to anchor contact between merozoite and erythrocyte membranes during strong parasite deformations; CyRPA is a component of this pentameric complex.\",\n      \"method\": \"Conditional knockout of PfPTRAMP and PfCSS; invasion-inhibitory nanobodies; lattice light-sheet microscopy; complex biochemistry\",\n      \"journal\": \"Nature microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KOs and nanobody inhibition establish the pentameric PCRCR complex and its function, CyRPA's role attributed as a complex member; single study but multiple rigorous methods\",\n      \"pmids\": [\"36396942\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The aspartic protease plasmepsin X (PMX) processes the PCRCR complex in micronemes by removing the N-terminal prodomain of PfRH5, which activates PCRCR function and unmasks the complex to bind basigin on the erythrocyte membrane; CyRPA is a component of this complex that is regulated by PMX processing.\",\n      \"method\": \"Conditional knockdown of PMX; biochemical processing assay; erythrocyte binding assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional knockdown with invasion phenotype and direct biochemical processing assay; CyRPA's specific role within PCRCR not tested separately from complex\",\n      \"pmids\": [\"37072430\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cryo-EM structure of the PfRCR complex (PfRH5, PfCyRPA, PfRIPR) shows that PfCyRPA presents PfRH5 and forms part of the structured core; the elongated tail of PfRIPR is flexibly linked to the PfCyRPA-PfRH5 core; CyRPA-binding antibodies neutralize invasion through a steric mechanism (shown by modelling and erythrocyte-binding assay); a rigid, disulfide-locked PfRH5 can mediate efficient erythrocyte invasion (contradicting membrane-opening hypothesis).\",\n      \"method\": \"Cryo-electron microscopy structure determination; erythrocyte-binding assay; structural modelling\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure of full RCR complex with functional binding assay identifying steric inhibition mechanism; rigorous single study with multiple methods\",\n      \"pmids\": [\"38123677\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Growth-inhibitory antibodies against CyRPA bind epitopes on a single face of CyRPA; pairs of non-competing inhibitory antibodies show strongly synergistic growth-inhibitory activity by forming lateral heterotypic interactions that slow antibody dissociation from CyRPA.\",\n      \"method\": \"Structural studies (antibody-CyRPA complexes); surface plasmon resonance (antibody dissociation kinetics); in vitro growth inhibition assay with antibody combinations\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal/structural studies plus SPR kinetics plus GIA, multiple orthogonal methods revealing mechanism of synergy, single rigorous study\",\n      \"pmids\": [\"35177602\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CyRPA functions as a lectin that binds glycans terminating with α2-6-linked N-acetylneuraminic acid (Neu5Ac) on the erythrocyte surface; CyRPA has a >50-fold binding preference for human α2-6-linked Neu5Ac over non-human α2-6-linked N-glycolylneuraminic acid; lectin-binding sites were identified by molecular modelling and validated by mutagenesis; transgenic parasites expressing CyRPA with single amino acid exchange mutants in the lectin sites showed impaired invasion, demonstrating the functional importance of lectin activity.\",\n      \"method\": \"Glycan-binding assay; molecular modelling; site-directed mutagenesis; transgenic parasite lines with endogenous CyRPA point mutants; in vitro growth inhibition with small molecules and lectin-site-specific antibodies\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — lectin activity assay plus mutagenesis validated in endogenous transgenic parasite lines plus functional invasion assay; multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"38573856\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Anti-CyRPA monoclonal antibodies block invasion and additionally inactivate extracellular merozoites by triggering a developmental pathway normally seen only after successful invasion; combining anti-CyRPA and anti-PfRH5 mAbs enhances the degree of invasion inhibition observed by live-cell imaging.\",\n      \"method\": \"Live-cell imaging with monoclonal antibodies; in vitro growth inhibition assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging with mAbs establishing timing and stage of inhibition plus secondary inactivation phenotype; single lab, two orthogonal methods\",\n      \"pmids\": [\"37713419\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Structure-guided design of a CyRPA epitope mimic (PfCyRPA-EM) comprising blades 1 and 2 of the six-bladed β-propeller (the face exposed in the PCRCR complex and containing the epitopes of the most potent growth-inhibitory antibodies) elicits antibodies with superior growth-inhibitory activity at lower concentrations than full-length CyRPA in a preclinical model, establishing that blades 1 and 2 harbour the critical protective epitopes.\",\n      \"method\": \"Structure-guided protein engineering; immunization in preclinical model; in vitro growth inhibition assay\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — structure-guided design with functional readout in preclinical model; single lab, structure plus immunogenicity assay\",\n      \"pmids\": [\"41772083\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Sites 154 and 209 of PfCyRPA — previously reported as sufficient to switch glycan-binding preference between human (Neu5Ac) and ape glycans — are identical in P. falciparum and its gorilla precursor P. praefalciparum, and no other differences were found near the CyRPA glycan-binding sites; thus the gorilla precursor appears pre-adapted to bind human sialoglycans, and these two sites do not explain P. falciparum adaptation to humans.\",\n      \"method\": \"Comparative genome sequence analysis of P. falciparum, P. praefalciparum, and P. reichenowi\",\n      \"journal\": \"Genome biology and evolution\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — purely computational/sequence comparison, no direct experimental manipulation of CyRPA in this study\",\n      \"pmids\": [\"39865504\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium praefalciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PfCyRPA (PF3D7_0423800) is a GPI-anchored, six-bladed β-propeller protein localized in merozoite micronemes that functions as a central scaffold of the essential PfRH5–PfCyRPA–PfRIPR (RCR) tripartite complex — itself part of the larger pentameric PCRCR complex — where CyRPA mediates complex assembly by contacting PfRH5 via blades 4–6 and PfRIPR, has no enzymatic activity, binds human erythrocyte sialoglycans (α2-6-linked Neu5Ac) via a lectin site on its β-propeller that is essential for invasion, is activated in micronemes by plasmepsin X processing of PfRH5, and is required for the Ca2+-release step and tight-junction formation during erythrocyte invasion; growth-inhibitory antibodies predominantly target a single face of CyRPA (blades 1–2) and act by blocking CyRPA–PfRH5 complex formation or by steric occlusion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CyRPA (PF3D7_0423800) is a GPI-anchored, apically localized micronemal protein of the P. falciparum merozoite that is essential for erythrocyte invasion, acting as the central structural scaffold of the PfRH5\\u2013PfRIPR\\u2013CyRPA (RCR) tripartite complex and the larger PCRCR pentameric complex [#1, #2, #8]. Structurally it is a six-bladed \\u03b2-propeller resembling a sialidase fold but is enzymatically inert, fulfilling a purely non-enzymatic role [#3]. CyRPA mediates assembly of the invasion complex: it binds PfRH5 directly and contacts both PfRH5 and PfRIPR through blades 4\\u20136 of the propeller, presenting PfRH5 within the structured core while the PfRIPR tail extends flexibly, and the assembled complex binds erythrocytes far more efficiently than PfRH5 alone [#4, #5, #10]. During invasion CyRPA colocalizes with PfRH5 and PfRIPR at the merozoite\\u2013erythrocyte tight junction, where the complex triggers host Ca2+ release and anchors membrane contact; complex function is activated by plasmepsin X processing of PfRH5's prodomain in micronemes [#2, #8, #9]. Independently of its scaffolding role, CyRPA acts as a lectin that binds erythrocyte glycans terminating in human \\u03b12-6-linked Neu5Ac, with point mutations in the lectin site impairing invasion [#12]. CyRPA is a leading blood-stage vaccine target: growth-inhibitory antibodies cluster on one face of the propeller (blades 1\\u20132), neutralizing invasion by blocking complex formation or through steric occlusion, and act synergistically both in pairs and in combination with anti-PfRH5 antibodies [#4, #6, #10, #11]. Notably, the CyRPA ortholog in P. knowlesi is likewise essential for invasion but functions independently, without forming a complex with a PfRIPR or PfRH5 counterpart [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that CyRPA is an invasion-relevant antigen by showing apical expression in schizonts/merozoites and that specific antibodies block parasite growth in vitro and in humanized mice.\",\n      \"evidence\": \"Immunofluorescence, in vitro growth inhibition, and passive immunization in a humanized mouse model\",\n      \"pmids\": [\"22593616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular partners or mechanism of invasion contribution identified\", \"Whether CyRPA acts alone or in a complex not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Resolved how CyRPA contributes to invasion by showing it is a GPI-anchored micronemal protein that assembles with PfRH5 and PfRIPR into an essential complex, and does not bind erythrocytes directly \\u2014 explaining that its inhibitory antibodies act by blocking complex interactions.\",\n      \"evidence\": \"GPI-anchor biochemistry, reciprocal co-immunoprecipitation, conditional knockdown, and growth inhibition assays\",\n      \"pmids\": [\"25583518\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the interactions unknown\", \"Direct erythrocyte-binding role (later revised by lectin activity) not yet examined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed the complex at the point of entry by showing CyRPA colocalizes with PfRH5/PfRIPR at the tight junction and is required to trigger host Ca2+ release, defining the functional step it controls during invasion.\",\n      \"evidence\": \"Conditional loss-of-function, super-resolution microscopy, and Ca2+ release assay\",\n      \"pmids\": [\"27374406\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular trigger of Ca2+ release not defined\", \"CyRPA's specific contribution versus the whole complex not isolated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined CyRPA's molecular nature and the antibody target by solving its six-bladed \\u03b2-propeller structure, ruling out sialidase activity, mapping the PfRH5-interacting region, and showing an inhibitory antibody blocks CyRPA\\u2013PfRH5 binding and complex formation.\",\n      \"evidence\": \"X-ray crystallography of free CyRPA and CyRPA\\u2013Fab complexes, sialidase activity assay (negative), direct PfRH5-binding and antibody-blocking assays\",\n      \"pmids\": [\"28195038\", \"28195530\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Architecture of the full trimeric complex not resolved\", \"Role of remaining propeller faces unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed the architecture of the assembled RCR complex, showing CyRPA uses blades 4\\u20136 to bridge PfRH5 and PfRIPR and that the complex enhances erythrocyte binding over PfRH5 alone, defining CyRPA as the assembly hub.\",\n      \"evidence\": \"Subnanometre cryo-EM structure of the Rh5\\u2013CyRPA\\u2013Ripr complex plus erythrocyte binding assay\",\n      \"pmids\": [\"30542156\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamics of proposed complex dissociation during membrane insertion not directly observed\", \"Precise contribution of each blade contact to invasion untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Confirmed the antibody neutralization mechanism by directly demonstrating that anti-CyRPA antibodies prevent trimeric complex formation.\",\n      \"evidence\": \"Antibody blocking of complex assembly plus growth inhibition assay\",\n      \"pmids\": [\"30965383\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not distinguish assembly blockade from steric mechanisms\", \"Epitope face not mapped in this study\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Tested conservation of CyRPA function across species, showing P. knowlesi CyRPA is essential for invasion but functions without forming a PfRIPR/PfRH5-like complex, indicating the complex-dependent mechanism is not universal.\",\n      \"evidence\": \"Conditional knockdown in P. knowlesi and co-immunoprecipitation (negative for complex)\",\n      \"pmids\": [\"31185066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PkCyRPA acts independently unknown\", \"PkCyRPA binding partners not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended the complex to a pentameric PCRCR assembly (PfPTRAMP, PfCSS, PfRH5, PfRIPR, CyRPA) that anchors merozoite\\u2013erythrocyte membrane contact during deformation, and defined the CyRPA epitope face driving synergistic antibody neutralization.\",\n      \"evidence\": \"Conditional knockouts, invasion-inhibitory nanobodies, lattice light-sheet microscopy, complex biochemistry (PCRCR); structural studies, SPR kinetics and combination GIA (antibody synergy)\",\n      \"pmids\": [\"36396942\", \"35177602\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CyRPA's specific role within PCRCR not separated from the whole complex\", \"In vivo relevance of antibody synergy not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Clarified regulation and mechanism by showing plasmepsin X processing of PfRH5 activates the PCRCR complex to bind basigin, resolving the full RCR structure with CyRPA presenting PfRH5, and demonstrating anti-CyRPA antibodies inhibit both by steric occlusion and by prematurely inactivating extracellular merozoites.\",\n      \"evidence\": \"Conditional PMX knockdown and processing/binding assays; cryo-EM of the full PfRCR complex with modelling; live-cell imaging with mAbs\",\n      \"pmids\": [\"37072430\", \"38123677\", \"37713419\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How processing propagates to CyRPA function not directly tested\", \"Mechanism of premature merozoite inactivation unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revised the view that CyRPA does not engage erythrocytes by identifying it as a lectin binding human \\u03b12-6-linked Neu5Ac, with lectin-site point mutations impairing invasion, assigning CyRPA a direct receptor-recognition function.\",\n      \"evidence\": \"Glycan-binding assays, molecular modelling, site-directed mutagenesis in endogenous transgenic parasites, and functional invasion/GIA assays\",\n      \"pmids\": [\"38573856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation with earlier finding that CyRPA does not bind erythrocytes directly not fully resolved\", \"How lectin binding integrates with complex assembly during invasion unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Advanced CyRPA as a vaccine immunogen by showing a structure-guided blades 1\\u20132 epitope mimic elicits superior growth-inhibitory antibodies, confirming these blades harbour the critical protective epitopes.\",\n      \"evidence\": \"Structure-guided protein engineering, preclinical immunization, and growth inhibition assay\",\n      \"pmids\": [\"41772083\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Efficacy in humans not established\", \"Durability and breadth of the antibody response not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Examined the evolutionary origin of CyRPA's human glycan specificity, finding that lectin-site residues 154 and 209 are identical between P. falciparum and its gorilla precursor P. praefalciparum, so these sites do not explain adaptation to human erythrocytes.\",\n      \"evidence\": \"Comparative genome sequence analysis across P. falciparum, P. praefalciparum, and P. reichenowi\",\n      \"pmids\": [\"39865504\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Purely computational; no experimental test of glycan preference for the precursor CyRPA\", \"Actual determinants of host adaptation remain unidentified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium praefalciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CyRPA's lectin-mediated sialoglycan binding is mechanistically integrated with its scaffolding of the RCR/PCRCR complex, PfRH5 presentation, and the triggering of host Ca2+ release during tight-junction formation remains to be defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Temporal and spatial coordination of lectin binding versus complex assembly unknown\", \"Molecular link from complex engagement to erythrocyte Ca2+ release undefined\", \"CyRPA's autonomous contribution within the pentameric PCRCR not experimentally isolated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0030246\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0033691\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0005515\", \"supporting_discovery_ids\": [4, 5, 10]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0033017\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0046658\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [1, 2, 8]},\n      {\"term_id\": \"GO:0007155\", \"supporting_discovery_ids\": [2, 8]},\n      {\"term_id\": \"GO:0051260\", \"supporting_discovery_ids\": [5, 10]}\n    ],\n    \"complexes\": [\n      \"PfRH5\\u2013CyRPA\\u2013PfRIPR (RCR) tripartite complex\",\n      \"PCRCR pentameric complex (PfPTRAMP, PfCSS, PfRH5, PfRIPR, CyRPA)\"\n    ],\n    \"partners\": [\n      \"PfRH5\",\n      \"PfRIPR\",\n      \"PfPTRAMP (via PCRCR complex)\",\n      \"PfCSS (via PCRCR complex)\",\n      \"plasmepsin X (regulates complex via PfRH5 processing)\",\n      \"erythrocyte \\u03b12-6-linked Neu5Ac sialoglycans (ligand)\"\n    ],\n    \"other_free_text\": [\n      \"Six-bladed \\u03b2-propeller with a sialidase-like fold but no sialidase/enzymatic activity; purely structural scaffold [#3].\",\n      \"Contacts PfRH5 and PfRIPR through propeller blades 4\\u20136; blades 1\\u20132 form the antibody-exposed face carrying the most potent growth-inhibitory epitopes [#5, #14].\",\n      \"Required for triggering host erythrocyte Ca2+ release and tight-junction formation during invasion [#2].\",\n      \"Growth-inhibitory antibodies neutralize by blocking complex assembly and by steric occlusion, and can act synergistically in pairs and with anti-PfRH5 antibodies [#6, #10, #11, #13].\",\n      \"In P. knowlesi the ortholog is essential for invasion but functions independently of a PfRIPR/PfRH5-like complex [#7].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0423800","name":null,"product":"cysteine-rich protective antigen","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0515800","name":null,"product":"cysteine-rich protective antigen","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"CyRPA","evaluation":null}