{"gene":"TG_300100","gene_symbol":"RON2","run_date":"2026-09-11T11:01:00","timeline":{"discoveries":[{"year":2005,"finding":"RON2 (together with RON4 and RON5) was identified as a rhoptry neck protein that associates with the microneme protein AMA1 at the moving junction during host cell invasion, forming a complex derived from two distinct secretory organelles (micronemes and rhoptry necks).","method":"Co-immunoprecipitation, mass spectrometry, immunofluorescence localization during invasion","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP with MS identification, localization at MJ confirmed, replicated across multiple subsequent studies","pmids":["16244709"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"finding":"RON2 and AMA1 can interact directly in the absence of other MJ complex members (RON4, RON5, RON8), as shown by metabolic labelling and immunoprecipitation. Additionally, RON2 is targeted to the host cell membrane upon secretion, where RON4/5/8 associate with the cytoplasmic face of the host cell membrane.","method":"Metabolic labelling, immunoprecipitation, differential permeabilization, antibody loading into host cell","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods in single study, replicated by subsequent work","pmids":["19247437"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"finding":"RON8 was identified as an additional member of the RON2/4/5 complex at the moving junction. All RON proteins (RON2, RON4, RON5, RON8) are present at the MJ during invasion and undergo proteolytic maturation during trafficking to the rhoptries.","method":"Biochemical fractionation, Co-immunoprecipitation, immunofluorescence during invasion","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods, replicated","pmids":["19247437"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2011,"finding":"RON2 is inserted as an integral membrane protein in the host cell membrane and directly binds AMA1 through a specific region near its C-terminus. This RON2-AMA1 interaction is critical for invasion by both T. gondii and P. falciparum, demonstrated by invasion inhibition assays using recombinant proteins.","method":"Interaction assays with native and recombinant proteins, invasion inhibition assays, membrane topology analysis","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple interaction assays, functional invasion inhibition, demonstrated in two species","pmids":["21347343"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"The C-terminus of TgRON2 contains two short segments (D3 and D4) flanking a hydrophobic stretch that independently associate with the ectodomain of TgAMA1. Pre-incubation with D3 peptide (fused to GST) dramatically reduces invasion but does not prevent injection of rhoptry bulb proteins, demonstrating that the RON2 C-terminus forms the crucial bridge between AMA1 and the rest of the MJ complex.","method":"Deletion mapping, GST-fusion pulldown, invasion inhibition assay, rhoptry injection assay","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain mapping with functional validation, multiple orthogonal assays in single lab","pmids":["21347354"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2011,"finding":"Crystal structure of TgAMA1 complexed with a RON2 peptide was determined at 1.95 Å resolution, revealing that RON2 binds the hydrophobic groove of AMA1 through a stepwise assembly mechanism creating extensive buried surface area, enabling resistance to mechanical forces during invasion.","method":"X-ray crystallography at 1.95 Å resolution","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure, functionally validated in prior invasion inhibition studies","pmids":["21778402"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"finding":"RON5 plays a key role in organization of the MJ RON complex: conditional knockdown of RON5 causes complete degradation of RON2 and mistargeting of RON4 within the secretory pathway, demonstrating that RON5 is required for RON2 stability. Loss of RON5 also abolishes host cell invasion and prevents evacuole formation, but does not impact egress.","method":"Conditional knockdown (tetracycline-regulatable), immunofluorescence, invasion assay, evacuole assay, egress assay","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic knockdown with defined mechanistic consequences for RON2 stability, multiple phenotypic readouts","pmids":["24651769"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"finding":"AMA1 interacts with RON2 to maintain MJ structural integrity in T. gondii and is required for parasite internalization. Disruption of the AMA1 gene results in upregulation of AMA1 and RON2 homologues (paralogues) that cooperate to support residual invasion, demonstrating plasticity in MJ composition.","method":"Reverse genetics (gene disruption), conditional complementation, invasion assays, immunofluorescence","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reverse genetics with multiple orthogonal assays, reveals AMA1-RON2 functional interaction and molecular plasticity","pmids":["24934579"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"finding":"When Toxoplasma lacks toxofilin and cannot locally remodel cortical actin, the RON2-containing moving junction fails to anchor to the host cell cortex and travels retrogradely, demonstrating that junction anchoring requires host cortex remodeling for efficient invasion. RON2 molecules are eventually posteriorly capped and cleaved/released in failed invasion events.","method":"Live imaging of fluorescently-tagged RON2, kinematic analysis of >1000 invasion events, toxofilin mutant parasites","journal":"BMC biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging with functional mutant, single lab, kinematic measurements","pmids":["25551479"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2015,"finding":"The AMA1 DII loop governs ligand binding selectivity for RON2; removing the mobile portion of the DII loop (TgAMA1ΔDIIloop) dramatically increases binding affinity for non-cognate RON2 peptides (e.g., EtRON2). Crystal structure of TgAMA1ΔDIIloop with EtRON2 identified spatially distinct anchor points in the AMA1 groove, supporting a model where the DII loop acts as a structural gatekeeper.","method":"Site-directed mutagenesis, isothermal titration calorimetry, X-ray crystallography","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with ITC binding measurements and mutagenesis, single lab","pmids":["25955165"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2015,"finding":"TgAMA4 (a sporozoite-expressed AMA paralogue) forms a high-affinity functional complex with its coevolved partner TgRON2L1. Crystal structures of TgAMA4 in apo and TgRON2L1-bound forms revealed an unexpected architecture lacking both a deep surface groove and a key surface loop present in AMA1-RON2 complexes, defining a distinct assembly mechanism.","method":"Co-crystallization, X-ray crystallography (apo and bound forms), alanine scanning mutagenesis, binding affinity measurements","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures with mutagenesis validation, single lab, novel mechanistic insight","pmids":["26712012"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"Binding of TgRON2 domain 3 (D3) peptide to TgAMA1 protects AMA1 from rhomboid protease-mediated cleavage of its transmembrane domain, stabilizing AMA1 at the moving junction. Parasites expressing a hypercleavable AMA1 invade less efficiently. Additionally, TgAMA1-TgRON2 interaction leads to dephosphorylation of S527 on the AMA1 cytoplasmic tail, and a phosphomimetic S527D allele causes invasion defects, revealing outside-in signaling through the MJ.","method":"Peptide treatment assays, cleavage assays, phosphomimetic/phosphoablative AMA1 mutants, invasion efficiency assays","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal assays (cleavage, phosphorylation, invasion), mutagenesis, single lab","pmids":["27624124"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"finding":"RON2, RON4, and RON5 cooperate to actively recruit host cell proteins CIN85, CD2AP, and ESCRT-I components ALIX and TSG101 to the moving junction during invasion. Parasite mutants unable to recruit these host proteins show inefficient invasion in culture and attenuated virulence in mice, demonstrating that the RON complex subverts conserved host machinery.","method":"Co-immunoprecipitation, interaction mapping, parasite mutagenesis, invasion assays, mouse virulence model","journal":"Nature microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods, interaction mapping, functional mutants, in vivo validation","pmids":["28848228"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"Sporozoites express paralogue sporoRON2 (RON2L2) that localizes to the apical region and interacts specifically and exclusively with sporoAMA1 (not with generic AMA1), while generic RON2 interacts only with generic AMA1. Pretreatment with domain 3 of sporoRON2 inhibits sporozoite but not tachyzoite invasion, and vice versa for generic RON2 D3, demonstrating stage-specific AMA-RON pairings.","method":"Co-immunoprecipitation, structural studies of interacting domains, invasion inhibition assays with stage-specific parasites","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple binding and functional assays with reciprocal specificity controls, single lab","pmids":["23940612"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2023,"finding":"Bradyzoites invade host cells in an MJ-dependent fashion but use paralogue proteins AMA2 and AMA4 (with AMA4 partnering RON2L1) rather than canonical AMA1-RON2. AMA1-RON2 complex immunization induces strong protection against both acute and chronic infection, while AMA4-RON2L1 more selectively targets chronic infection.","method":"Reverse genetics (gene knockout), invasion assays, immunization/challenge experiments in mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic knockouts with defined phenotypes, functional immunization validation, single lab","pmids":["36693095"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"finding":"RON4L1 is an additional member of the MJ complex that is targeted to the cytosolic face of the host membrane upon secretion. Critically, RON4L1 trafficking to the MJ is not affected by the absence of RON2, RON4, and RON5, suggesting the co-existence of independent MJ complexes in tachyzoites.","method":"Immunofluorescence, gene knockout (RON4L1 KO), invasion and virulence assays, triple RON2/4/5-independent localization experiments","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO and localization studies in multiple genetic backgrounds, single lab","pmids":["29263399"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"finding":"RON2-depleted parasites generate a transient host cell membrane conductance increase (invasion pore) prior to invasion but fail to invade, demonstrating that RON2 is not essential for generation of the conductance pathway/pore but is required for productive invasion. Without RON2, the quantal conductance mean differs significantly (0.19 nS vs 0.26 nS for wild-type), implicating RON2 in modulating pore characteristics.","method":"Electrophysiological recordings at sub-200 µs resolution, RON2-depleted parasites, time-series quantal conductance analysis","journal":"bioRxiv (preprint) / EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiological measurement with RON2-depleted parasites, novel method, single lab","pmids":["39416144","40973829"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2024,"finding":"The transcription factor TgAP2XII-9 directly targets RON2 (along with RON4 and RON8) gene loci as shown by CUT&Tag, and its deficiency leads to significant downregulation of rhoptry neck proteins including RON2, resulting in invasion and egress defects, establishing RON2 as a transcriptional target of AP2XII-9 during S/M phase.","method":"CUT&Tag chromatin profiling, conditional knockdown, invasion and egress assays","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CUT&Tag with functional validation, single lab","pmids":["39207100"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgRON2 is a rhoptry neck protein that is secreted and inserted as an integral membrane protein into the host cell membrane during invasion, where its C-terminal domain (particularly D3 and D4 segments) directly binds the hydrophobic groove of the microneme protein AMA1 on the parasite surface to form the core of the moving junction (MJ); the RON2/4/5/8 complex is stabilized by RON5 (which is required for RON2 stability), recruits host proteins CIN85, CD2AP, ALIX, and TSG101 to the MJ, and the RON2-AMA1 interaction protects AMA1 from rhomboid-mediated shedding while triggering dephosphorylation of the AMA1 cytoplasmic tail, collectively enabling the mechanical force required for host cell penetration; stage-specific paralogues (sporoRON2/RON2L1/RON2L2) pair exclusively with cognate AMA paralogues for sporozoite and bradyzoite invasion, revealing a conserved but plastic AMA-RON pairing strategy across the Toxoplasma life cycle."},"narrative":{"mechanistic_narrative":"RON2 is a rhoptry neck protein of Toxoplasma gondii that forms the parasite-derived core of the moving junction (MJ), the ring-shaped adhesion structure that drives host cell invasion [PMID:16244709]. Upon secretion, RON2 is inserted as an integral membrane protein into the host cell membrane, where its C-terminus is displayed to the parasite surface while its partner proteins RON4/5/8 associate with the cytoplasmic face of the host membrane [PMID:19247437, PMID:21347343]. The RON2 C-terminus binds directly to the microneme protein AMA1 on the parasite surface, bridging AMA1 to the rest of the MJ complex; two short segments (D3 and D4) flanking a hydrophobic stretch dock into the hydrophobic groove of the AMA1 ectodomain through a stepwise, high-buried-surface assembly that resists the mechanical forces of penetration, and this interaction is required for invasion in both T. gondii and P. falciparum [PMID:21347343, PMID:21347354, PMID:21778402]. Within the MJ complex, RON5 is required for RON2 stability—its loss triggers complete RON2 degradation and abolishes invasion [PMID:24651769]—and the RON2/4/5 module actively recruits host CIN85, CD2AP, and the ESCRT-I components ALIX and TSG101 to the junction to support efficient invasion and virulence [PMID:28848228]. The RON2-AMA1 interaction also protects AMA1 from rhomboid-mediated shedding and drives dephosphorylation of the AMA1 cytoplasmic tail, constituting an outside-in signal that promotes productive entry [PMID:27624124]. The AMA-RON pairing is stage-specific and structurally plastic: sporozoites and bradyzoites deploy cognate paralogue pairs (sporoRON2/RON2L1 with sporoAMA1/AMA4) that bind exclusively to their partners and use distinct groove architectures, revealing a conserved but adaptable invasion strategy across the life cycle [PMID:26712012, PMID:23940612, PMID:36693095]. RON2 expression is a direct transcriptional target of AP2XII-9 during the S/M phase [PMID:39207100]. RON2-depleted parasites can generate a transient host cell membrane conductance increase prior to invasion but fail to invade productively, demonstrating that RON2 is not essential for generation of the conductance pathway but is required for productive invasion [PMID:39416144, PMID:40973829].","teleology":[{"year":2005,"claim":"Establishing that rhoptry neck proteins physically join the microneme protein AMA1 at the moving junction answered how two distinct secretory organelles cooperate to build the invasion machinery.","evidence":"Co-IP, mass spectrometry, and immunofluorescence localization of RON2/RON4 during invasion in T. gondii","pmids":["16244709"],"confidence":"High","gaps":["Did not define which RON provides the direct AMA1 contact","Membrane topology of the complex unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"claim":"Showing that RON2 inserts into the host membrane while RON4/5/8 coat its cytoplasmic face, and that RON2 binds AMA1 without other complex members, resolved the physical architecture and the direct AMA1 partner.","evidence":"Metabolic labelling, IP, differential permeabilization, and antibody loading into host cells; RON8 identified as an additional complex member in T. gondii","pmids":["19247437"],"confidence":"High","gaps":["Region of RON2 mediating AMA1 binding not mapped","Mechanism of RON2 membrane insertion unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2011,"claim":"Mapping the AMA1-binding region to the RON2 C-terminus (D3/D4) and solving the AMA1-RON2 co-structure explained how the junction resists mechanical force and that this bridge is essential for invasion across apicomplexa.","evidence":"Deletion mapping, GST-fusion pulldowns, invasion/rhoptry-injection inhibition assays, and a 1.95 Å AMA1-RON2 crystal structure in T. gondii and P. falciparum","pmids":["21347343","21347354","21778402"],"confidence":"High","gaps":["How D3/D4 binding is coupled to downstream RON4/5/8 function not defined","Contribution of the hydrophobic stretch to membrane insertion vs binding unclear"],"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Discovering that sporozoites use a dedicated sporoRON2/sporoAMA1 pair with reciprocal binding specificity revealed that AMA-RON pairings are stage-specific rather than universal.","evidence":"Co-IP, interaction-domain studies, and stage-specific reciprocal invasion-inhibition assays in T. gondii","pmids":["23940612"],"confidence":"High","gaps":["Structural basis of paralogue specificity not yet defined","In vivo role during natural sporozoite infection untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"claim":"Defining RON5 as essential for RON2 stability and showing paralogue upregulation upon AMA1 loss established both the assembly hierarchy of the complex and the plasticity of MJ composition.","evidence":"Conditional RON5 knockdown with invasion/evacuole/egress readouts; AMA1 gene disruption with conditional complementation in T. gondii","pmids":["24651769","24934579"],"confidence":"High","gaps":["Molecular basis of RON5-dependent RON2 stabilization unknown","Functional capacity of compensating paralogues only partially characterized"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2014,"claim":"Live imaging linked productive junction anchoring to host cortical actin remodeling, showing that a RON2-containing junction must be tethered to the host cortex for invasion to succeed.","evidence":"Live imaging of fluorescent RON2 and kinematic analysis of >1000 invasion events in toxofilin-mutant T. gondii","pmids":["25551479"],"confidence":"Medium","gaps":["Direct RON2 contribution to anchoring vs bystander role unresolved","Molecular link between RON complex and host cortex not identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2015,"claim":"Structural and thermodynamic dissection of the AMA1 DII loop and of the divergent AMA4-RON2L1 complex explained how binding selectivity is enforced and how paralogue pairs achieve distinct assembly architectures.","evidence":"Site-directed mutagenesis, ITC, and X-ray crystallography of TgAMA1ΔDIIloop-EtRON2 and apo/bound TgAMA4-RON2L1 in T. gondii","pmids":["25955165","26712012"],"confidence":"High","gaps":["How gatekeeping is regulated during natural invasion unclear","Whether groove-less architectures generalize to other paralogues untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"claim":"Showing that RON2 D3 binding shields AMA1 from rhomboid cleavage and triggers cytoplasmic-tail dephosphorylation established the junction as a site of outside-in signaling that stabilizes AMA1 for productive entry.","evidence":"Peptide/cleavage assays and phosphomimetic/phosphoablative AMA1 (S527) mutants with invasion readouts in T. gondii","pmids":["27624124"],"confidence":"High","gaps":["Kinase/phosphatase acting on the AMA1 tail not identified","Downstream effectors of the dephosphorylation signal unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2017,"claim":"Demonstrating recruitment of host CIN85, CD2AP, ALIX, and TSG101 by RON2/4/5, and the existence of a RON2/4/5-independent RON4L1 complex, revealed that the junction subverts conserved host machinery and that multiple MJ complexes may coexist.","evidence":"Co-IP, interaction mapping, parasite mutants, invasion assays, and mouse virulence; RON4L1 knockout and RON2/4/5-independent localization in T. gondii","pmids":["28848228","29263399"],"confidence":"Medium","gaps":["Functional role of recruited host ESCRT components in membrane biology at the MJ not fully defined","Relationship between parallel RON complexes and single vs multiple junctions unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2023,"claim":"Genetic dissection of bradyzoite invasion showed that chronic-stage parasites substitute AMA2/AMA4-RON2L1 for the canonical AMA1-RON2 pair, and that these pairs have distinct vaccine potential.","evidence":"Gene knockouts, invasion assays, and immunization/challenge experiments in mice with T. gondii","pmids":["36693095"],"confidence":"High","gaps":["Regulatory switch controlling stage-specific paralogue expression unknown","Structural detail of the bradyzoite complexes incomplete"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"Electrophysiology of RON2-depleted parasites separated pore formation from productive invasion, showing RON2 is dispensable for the invasion-associated conductance but required for entry and for setting pore properties.","evidence":"Sub-200 µs electrophysiological recordings and quantal conductance analysis of RON2-depleted RH parasites","pmids":["39416144","40973829"],"confidence":"Medium","gaps":["Molecular identity of the conductance pathway/pore unknown","How RON2 modulates quantal conductance mechanistically unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2024,"claim":"Identifying AP2XII-9 as a direct transcriptional regulator of RON2 placed the gene within a cell-cycle-linked program controlling rhoptry neck protein expression.","evidence":"CUT&Tag chromatin profiling and conditional AP2XII-9 knockdown with invasion/egress assays in T. gondii","pmids":["39207100"],"confidence":"Medium","gaps":["Full transcriptional network co-regulating RON2 not mapped","Direct vs indirect effects on RON2 protein levels not fully separated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Moving junction complex RON2/RON4/RON5/RON8","RON2-AMA1 complex","sporoRON2(RON2L2)-sporoAMA1 complex","RON2L1-AMA4 complex","RON4L1-containing MJ complex (RON2/4/5-independent)"],"partners":["AMA1 (MICRONEME PROTEIN, DIRECT BINDING PARTNER)","RON4","RON5 (REQUIRED FOR RON2 STABILITY)","RON8","SPOROAMA1","AMA4","HOST CIN85","HOST CD2AP","HOST ALIX","HOST TSG101 (ESCRT-I)","AP2XII-9 (TRANSCRIPTIONAL REGULATOR)"],"other_free_text":["RON2 C-terminal D3 and D4 segments flank a hydrophobic stretch and dock into the AMA1 hydrophobic groove via stepwise assembly with extensive buried surface area.","RON2-AMA1 binding protects AMA1 from rhomboid-mediated transmembrane cleavage and triggers dephosphorylation of AMA1 cytoplasmic tail residue S527 (outside-in signaling).","RON2 is dispensable for the transient invasion-associated host membrane conductance pore but required for productive invasion and modulates quantal conductance (RH strain).","AMA-RON pairings are stage-specific and structurally plastic across tachyzoite, sporozoite, and bradyzoite stages.","AMA1-RON2 immunization protects against acute and chronic infection; AMA4-RON2L1 more selectively targets chronic infection."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"16244709","id":"PMC_16244709","title":"Identification of the moving junction complex of Toxoplasma gondii: a collaboration between distinct secretory organelles.","date":"2005","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/16244709","citation_count":327,"is_preprint":false},{"pmid":"21347343","id":"PMC_21347343","title":"The RON2-AMA1 interaction is a critical step in moving junction-dependent invasion by apicomplexan parasites.","date":"2011","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/21347343","citation_count":268,"is_preprint":false},{"pmid":"19247437","id":"PMC_19247437","title":"Export of a Toxoplasma gondii rhoptry neck protein complex at the host cell membrane to form the moving junction during invasion.","date":"2009","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/19247437","citation_count":238,"is_preprint":false},{"pmid":"21535344","id":"PMC_21535344","title":"The moving junction of apicomplexan parasites: a key structure for invasion.","date":"2011","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/21535344","citation_count":227,"is_preprint":false},{"pmid":"16309467","id":"PMC_16309467","title":"The rhoptry neck protein RON4 re-localizes at the moving junction during Toxoplasma gondii invasion.","date":"2005","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/16309467","citation_count":172,"is_preprint":false},{"pmid":"21778402","id":"PMC_21778402","title":"Host cell invasion by apicomplexan parasites: insights from the co-structure of AMA1 with a RON2 peptide.","date":"2011","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/21778402","citation_count":155,"is_preprint":false},{"pmid":"22347997","id":"PMC_22347997","title":"Transcriptomic analysis of toxoplasma development reveals many novel functions and structures specific to sporozoites and oocysts.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22347997","citation_count":140,"is_preprint":false},{"pmid":"24934579","id":"PMC_24934579","title":"Plasticity and redundancy among AMA-RON pairs ensure host cell entry of Toxoplasma parasites.","date":"2014","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/24934579","citation_count":128,"is_preprint":false},{"pmid":"21347354","id":"PMC_21347354","title":"The C-terminus of Toxoplasma RON2 provides the crucial link between AMA1 and the host-associated invasion complex.","date":"2011","source":"PLoS 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sporozoites invade host cells using two novel paralogues of RON2 and AMA1.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23940612","citation_count":46,"is_preprint":false},{"pmid":"25551479","id":"PMC_25551479","title":"The toxoplasma-host cell junction is anchored to the cell cortex to sustain parasite invasive force.","date":"2014","source":"BMC biology","url":"https://pubmed.ncbi.nlm.nih.gov/25551479","citation_count":32,"is_preprint":false},{"pmid":"26712012","id":"PMC_26712012","title":"Dissecting the interface between apicomplexan parasite and host cell: Insights from a divergent AMA-RON2 pair.","date":"2015","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/26712012","citation_count":29,"is_preprint":false},{"pmid":"25582167","id":"PMC_25582167","title":"Protective immunity induced by peptides of AMA1, RON2 and RON4 containing T-and B-cell epitopes via an intranasal route against toxoplasmosis in mice.","date":"2015","source":"Parasites & vectors","url":"https://pubmed.ncbi.nlm.nih.gov/25582167","citation_count":28,"is_preprint":false},{"pmid":"36693095","id":"PMC_36693095","title":"Invasion of Toxoplasma gondii bradyzoites: Molecular dissection of the moving junction proteins and effective vaccination targets.","date":"2023","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/36693095","citation_count":24,"is_preprint":false},{"pmid":"27624124","id":"PMC_27624124","title":"Not a Simple Tether: Binding of Toxoplasma gondii AMA1 to RON2 during Invasion Protects AMA1 from Rhomboid-Mediated Cleavage and Leads to Dephosphorylation of Its Cytosolic Tail.","date":"2016","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/27624124","citation_count":20,"is_preprint":false},{"pmid":"22427839","id":"PMC_22427839","title":"Identification of a new rhoptry neck complex RON9/RON10 in the Apicomplexa parasite Toxoplasma gondii.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22427839","citation_count":18,"is_preprint":false},{"pmid":"25955165","id":"PMC_25955165","title":"An Extended Surface Loop on Toxoplasma gondii Apical Membrane Antigen 1 (AMA1) Governs Ligand Binding Selectivity.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25955165","citation_count":16,"is_preprint":false},{"pmid":"29263399","id":"PMC_29263399","title":"RON4L1 is a new member of the moving junction complex in Toxoplasma gondii.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29263399","citation_count":16,"is_preprint":false},{"pmid":"27445648","id":"PMC_27445648","title":"Multilevel Precision-Based Rational Design of Chemical Inhibitors Targeting the Hydrophobic Cleft of Toxoplasma gondii Apical Membrane Antigen 1 (AMA1).","date":"2016","source":"Genomics & informatics","url":"https://pubmed.ncbi.nlm.nih.gov/27445648","citation_count":11,"is_preprint":false},{"pmid":"39207100","id":"PMC_39207100","title":"Cell cycle-regulated transcription factor AP2XII-9 is a key activator for asexual division and apicoplast inheritance in Toxoplasma gondii tachyzoite.","date":"2024","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/39207100","citation_count":8,"is_preprint":false},{"pmid":"36512904","id":"PMC_36512904","title":"Proteomic characterization of Toxoplasma gondii ME49 derived strains resistant to the artemisinin derivatives artemiside and artemisone implies potential mode of action independent of ROS formation.","date":"2022","source":"International journal for parasitology. Drugs and drug resistance","url":"https://pubmed.ncbi.nlm.nih.gov/36512904","citation_count":7,"is_preprint":false},{"pmid":"28662729","id":"PMC_28662729","title":"The moving junction protein RON4, although not critical, facilitates host cell invasion and stabilizes MJ members.","date":"2017","source":"Parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/28662729","citation_count":6,"is_preprint":false},{"pmid":"30326220","id":"PMC_30326220","title":"Deciphering ophthalmic adaptive inhibitors targeting RON4 of Toxoplasma gondii: An integrative in silico approach.","date":"2018","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30326220","citation_count":5,"is_preprint":false},{"pmid":"40973829","id":"PMC_40973829","title":"The invasion pore induced by Toxoplasma gondii.","date":"2025","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/40973829","citation_count":2,"is_preprint":false},{"pmid":"39416144","id":"PMC_39416144","title":"The invasion pore induced by Toxoplasma gondii.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/39416144","citation_count":1,"is_preprint":false},{"pmid":"40881926","id":"PMC_40881926","title":"In silico evaluation of Toxoplasma gondii rhoptry neck proteins (TgRONs) for potential immunogenic epitopes.","date":"2025","source":"EXCLI journal","url":"https://pubmed.ncbi.nlm.nih.gov/40881926","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16858,"output_tokens":5024,"usd":0.062967,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11762,"output_tokens":5442,"usd":0.09743,"stage2_stop_reason":"end_turn"},"total_usd":0.169557,"stage1_batch_id":"msgbatch_01S6GjoYQm8LTPUsdhASdqag","stage2_batch_id":"msgbatch_01VX63RTMdBJqsG6gQMqoCjz","note":"batch pricing = 50% of standard","corrective_rerun":"2026-09-10 wrong-gene rerun (round-4 rules)","corrective_reason":"summary amended","hand_review_patch":"2026-09-11 AK hand-review verdicts (handoff/tools_2026-09-11/patch)","hand_review_verdict":"edit"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"RON2 (together with RON4 and RON5) was identified as a rhoptry neck protein that associates with the microneme protein AMA1 at the moving junction during host cell invasion, forming a complex derived from two distinct secretory organelles (micronemes and rhoptry necks).\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunofluorescence localization during invasion\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP with MS identification, localization at MJ confirmed, replicated across multiple subsequent studies\",\n      \"pmids\": [\"16244709\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"RON4 (a rhoptry neck protein) re-localizes to the moving junction during Toxoplasma gondii invasion, as identified by a monoclonal antibody and mass spectrometry, establishing rhoptry neck proteins as structural components of the moving junction.\",\n      \"method\": \"Monoclonal antibody generation, affinity purification, mass spectrometry, immunofluorescence\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization at MJ during invasion, independently replicated\",\n      \"pmids\": [\"16309467\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RON2 and AMA1 can interact directly in the absence of other MJ complex members (RON4, RON5, RON8), as shown by metabolic labelling and immunoprecipitation. Additionally, RON2 is targeted to the host cell membrane upon secretion, where RON4/5/8 associate with the cytoplasmic face of the host cell membrane.\",\n      \"method\": \"Metabolic labelling, immunoprecipitation, differential permeabilization, antibody loading into host cell\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods in single study, replicated by subsequent work\",\n      \"pmids\": [\"19247437\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RON8 was identified as an additional member of the RON2/4/5 complex at the moving junction. All RON proteins (RON2, RON4, RON5, RON8) are present at the MJ during invasion and undergo proteolytic maturation during trafficking to the rhoptries.\",\n      \"method\": \"Biochemical fractionation, Co-immunoprecipitation, immunofluorescence during invasion\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods, replicated\",\n      \"pmids\": [\"19247437\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RON2 is inserted as an integral membrane protein in the host cell membrane and directly binds AMA1 through a specific region near its C-terminus. This RON2-AMA1 interaction is critical for invasion by both T. gondii and P. falciparum, demonstrated by invasion inhibition assays using recombinant proteins.\",\n      \"method\": \"Interaction assays with native and recombinant proteins, invasion inhibition assays, membrane topology analysis\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple interaction assays, functional invasion inhibition, demonstrated in two species\",\n      \"pmids\": [\"21347343\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The C-terminus of TgRON2 contains two short segments (D3 and D4) flanking a hydrophobic stretch that independently associate with the ectodomain of TgAMA1. Pre-incubation with D3 peptide (fused to GST) dramatically reduces invasion but does not prevent injection of rhoptry bulb proteins, demonstrating that the RON2 C-terminus forms the crucial bridge between AMA1 and the rest of the MJ complex.\",\n      \"method\": \"Deletion mapping, GST-fusion pulldown, invasion inhibition assay, rhoptry injection assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mapping with functional validation, multiple orthogonal assays in single lab\",\n      \"pmids\": [\"21347354\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of TgAMA1 complexed with a RON2 peptide was determined at 1.95 Å resolution, revealing that RON2 binds the hydrophobic groove of AMA1 through a stepwise assembly mechanism creating extensive buried surface area, enabling resistance to mechanical forces during invasion.\",\n      \"method\": \"X-ray crystallography at 1.95 Å resolution\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure, functionally validated in prior invasion inhibition studies\",\n      \"pmids\": [\"21778402\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RON5 plays a key role in organization of the MJ RON complex: conditional knockdown of RON5 causes complete degradation of RON2 and mistargeting of RON4 within the secretory pathway, demonstrating that RON5 is required for RON2 stability. Loss of RON5 also abolishes host cell invasion and prevents evacuole formation, but does not impact egress.\",\n      \"method\": \"Conditional knockdown (tetracycline-regulatable), immunofluorescence, invasion assay, evacuole assay, egress assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic knockdown with defined mechanistic consequences for RON2 stability, multiple phenotypic readouts\",\n      \"pmids\": [\"24651769\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"AMA1 interacts with RON2 to maintain MJ structural integrity in T. gondii and is required for parasite internalization. Disruption of the AMA1 gene results in upregulation of AMA1 and RON2 homologues (paralogues) that cooperate to support residual invasion, demonstrating plasticity in MJ composition.\",\n      \"method\": \"Reverse genetics (gene disruption), conditional complementation, invasion assays, immunofluorescence\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reverse genetics with multiple orthogonal assays, reveals AMA1-RON2 functional interaction and molecular plasticity\",\n      \"pmids\": [\"24934579\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"When Toxoplasma lacks toxofilin and cannot locally remodel cortical actin, the RON2-containing moving junction fails to anchor to the host cell cortex and travels retrogradely, demonstrating that junction anchoring requires host cortex remodeling for efficient invasion. RON2 molecules are eventually posteriorly capped and cleaved/released in failed invasion events.\",\n      \"method\": \"Live imaging of fluorescently-tagged RON2, kinematic analysis of >1000 invasion events, toxofilin mutant parasites\",\n      \"journal\": \"BMC biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging with functional mutant, single lab, kinematic measurements\",\n      \"pmids\": [\"25551479\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The AMA1 DII loop governs ligand binding selectivity for RON2; removing the mobile portion of the DII loop (TgAMA1ΔDIIloop) dramatically increases binding affinity for non-cognate RON2 peptides (e.g., EtRON2). Crystal structure of TgAMA1ΔDIIloop with EtRON2 identified spatially distinct anchor points in the AMA1 groove, supporting a model where the DII loop acts as a structural gatekeeper.\",\n      \"method\": \"Site-directed mutagenesis, isothermal titration calorimetry, X-ray crystallography\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with ITC binding measurements and mutagenesis, single lab\",\n      \"pmids\": [\"25955165\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TgAMA4 (a sporozoite-expressed AMA paralogue) forms a high-affinity functional complex with its coevolved partner TgRON2L1. Crystal structures of TgAMA4 in apo and TgRON2L1-bound forms revealed an unexpected architecture lacking both a deep surface groove and a key surface loop present in AMA1-RON2 complexes, defining a distinct assembly mechanism.\",\n      \"method\": \"Co-crystallization, X-ray crystallography (apo and bound forms), alanine scanning mutagenesis, binding affinity measurements\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures with mutagenesis validation, single lab, novel mechanistic insight\",\n      \"pmids\": [\"26712012\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Binding of TgRON2 domain 3 (D3) peptide to TgAMA1 protects AMA1 from rhomboid protease-mediated cleavage of its transmembrane domain, stabilizing AMA1 at the moving junction. Parasites expressing a hypercleavable AMA1 invade less efficiently. Additionally, TgAMA1-TgRON2 interaction leads to dephosphorylation of S527 on the AMA1 cytoplasmic tail, and a phosphomimetic S527D allele causes invasion defects, revealing outside-in signaling through the MJ.\",\n      \"method\": \"Peptide treatment assays, cleavage assays, phosphomimetic/phosphoablative AMA1 mutants, invasion efficiency assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal assays (cleavage, phosphorylation, invasion), mutagenesis, single lab\",\n      \"pmids\": [\"27624124\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RON2, RON4, and RON5 cooperate to actively recruit host cell proteins CIN85, CD2AP, and ESCRT-I components ALIX and TSG101 to the moving junction during invasion. Parasite mutants unable to recruit these host proteins show inefficient invasion in culture and attenuated virulence in mice, demonstrating that the RON complex subverts conserved host machinery.\",\n      \"method\": \"Co-immunoprecipitation, interaction mapping, parasite mutagenesis, invasion assays, mouse virulence model\",\n      \"journal\": \"Nature microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods, interaction mapping, functional mutants, in vivo validation\",\n      \"pmids\": [\"28848228\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Sporozoites express paralogue sporoRON2 (RON2L2) that localizes to the apical region and interacts specifically and exclusively with sporoAMA1 (not with generic AMA1), while generic RON2 interacts only with generic AMA1. Pretreatment with domain 3 of sporoRON2 inhibits sporozoite but not tachyzoite invasion, and vice versa for generic RON2 D3, demonstrating stage-specific AMA-RON pairings.\",\n      \"method\": \"Co-immunoprecipitation, structural studies of interacting domains, invasion inhibition assays with stage-specific parasites\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple binding and functional assays with reciprocal specificity controls, single lab\",\n      \"pmids\": [\"23940612\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Bradyzoites invade host cells in an MJ-dependent fashion but use paralogue proteins AMA2 and AMA4 (with AMA4 partnering RON2L1) rather than canonical AMA1-RON2. AMA1-RON2 complex immunization induces strong protection against both acute and chronic infection, while AMA4-RON2L1 more selectively targets chronic infection.\",\n      \"method\": \"Reverse genetics (gene knockout), invasion assays, immunization/challenge experiments in mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockouts with defined phenotypes, functional immunization validation, single lab\",\n      \"pmids\": [\"36693095\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RON4L1 is an additional member of the MJ complex that is targeted to the cytosolic face of the host membrane upon secretion. Critically, RON4L1 trafficking to the MJ is not affected by the absence of RON2, RON4, and RON5, suggesting the co-existence of independent MJ complexes in tachyzoites.\",\n      \"method\": \"Immunofluorescence, gene knockout (RON4L1 KO), invasion and virulence assays, triple RON2/4/5-independent localization experiments\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO and localization studies in multiple genetic backgrounds, single lab\",\n      \"pmids\": [\"29263399\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RON2-depleted parasites generate a transient host cell membrane conductance increase (invasion pore) prior to invasion but fail to invade, demonstrating that RON2 is not essential for generation of the conductance pathway/pore but is required for productive invasion. Without RON2, the quantal conductance mean differs significantly (0.19 nS vs 0.26 nS for wild-type), implicating RON2 in modulating pore characteristics.\",\n      \"method\": \"Electrophysiological recordings at sub-200 µs resolution, RON2-depleted parasites, time-series quantal conductance analysis\",\n      \"journal\": \"bioRxiv (preprint) / EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiological measurement with RON2-depleted parasites, novel method, single lab\",\n      \"pmids\": [\"39416144\", \"40973829\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The transcription factor TgAP2XII-9 directly targets RON2 (along with RON4 and RON8) gene loci as shown by CUT&Tag, and its deficiency leads to significant downregulation of rhoptry neck proteins including RON2, resulting in invasion and egress defects, establishing RON2 as a transcriptional target of AP2XII-9 during S/M phase.\",\n      \"method\": \"CUT&Tag chromatin profiling, conditional knockdown, invasion and egress assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CUT&Tag with functional validation, single lab\",\n      \"pmids\": [\"39207100\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgRON2 is a rhoptry neck protein that is secreted and inserted as an integral membrane protein into the host cell membrane during invasion, where its C-terminal domain (particularly D3 and D4 segments) directly binds the hydrophobic groove of the microneme protein AMA1 on the parasite surface to form the core of the moving junction (MJ); the RON2/4/5/8 complex is stabilized by RON5 (which is required for RON2 stability), recruits host proteins CIN85, CD2AP, ALIX, and TSG101 to the MJ, and the RON2-AMA1 interaction protects AMA1 from rhomboid-mediated shedding while triggering dephosphorylation of the AMA1 cytoplasmic tail, collectively enabling the mechanical force required for host cell penetration; stage-specific paralogues (sporoRON2/RON2L1/RON2L2) pair exclusively with cognate AMA paralogues for sporozoite and bradyzoite invasion, revealing a conserved but plastic AMA-RON pairing strategy across the Toxoplasma life cycle.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RON2 is a rhoptry neck protein of Toxoplasma gondii that forms the parasite-derived core of the moving junction (MJ), the ring-shaped adhesion structure that drives host cell invasion [#0, #1]. Upon secretion, RON2 is inserted as an integral membrane protein into the host cell membrane, where its C-terminus is displayed to the parasite surface while its partner proteins RON4/5/8 associate with the cytoplasmic face of the host membrane [#2, #4]. The RON2 C-terminus binds directly to the microneme protein AMA1 on the parasite surface, bridging AMA1 to the rest of the MJ complex; two short segments (D3 and D4) flanking a hydrophobic stretch dock into the hydrophobic groove of the AMA1 ectodomain through a stepwise, high-buried-surface assembly that resists the mechanical forces of penetration, and this interaction is required for invasion in both T. gondii and P. falciparum [#4, #5, #6]. Within the MJ complex, RON5 is required for RON2 stability—its loss triggers complete RON2 degradation and abolishes invasion [#7]—and the RON2/4/5 module actively recruits host CIN85, CD2AP, and the ESCRT-I components ALIX and TSG101 to the junction to support efficient invasion and virulence [#13]. The RON2-AMA1 interaction also protects AMA1 from rhomboid-mediated shedding and drives dephosphorylation of the AMA1 cytoplasmic tail, constituting an outside-in signal that promotes productive entry [#12]. The AMA-RON pairing is stage-specific and structurally plastic: sporozoites and bradyzoites deploy cognate paralogue pairs (sporoRON2/RON2L1 with sporoAMA1/AMA4) that bind exclusively to their partners and use distinct groove architectures, revealing a conserved but adaptable invasion strategy across the life cycle [#11, #14, #15]. RON2 expression is a direct transcriptional target of AP2XII-9 during the S/M phase [#18].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing that rhoptry neck proteins physically join the microneme protein AMA1 at the moving junction answered how two distinct secretory organelles cooperate to build the invasion machinery.\",\n      \"evidence\": \"Co-IP, mass spectrometry, and immunofluorescence localization of RON2/RON4 during invasion in T. gondii\",\n      \"pmids\": [\"16244709\", \"16309467\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which RON provides the direct AMA1 contact\", \"Membrane topology of the complex unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showing that RON2 inserts into the host membrane while RON4/5/8 coat its cytoplasmic face, and that RON2 binds AMA1 without other complex members, resolved the physical architecture and the direct AMA1 partner.\",\n      \"evidence\": \"Metabolic labelling, IP, differential permeabilization, and antibody loading into host cells; RON8 identified as an additional complex member in T. gondii\",\n      \"pmids\": [\"19247437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Region of RON2 mediating AMA1 binding not mapped\", \"Mechanism of RON2 membrane insertion unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mapping the AMA1-binding region to the RON2 C-terminus (D3/D4) and solving the AMA1-RON2 co-structure explained how the junction resists mechanical force and that this bridge is essential for invasion across apicomplexa.\",\n      \"evidence\": \"Deletion mapping, GST-fusion pulldowns, invasion/rhoptry-injection inhibition assays, and a 1.95 Å AMA1-RON2 crystal structure in T. gondii and P. falciparum\",\n      \"pmids\": [\"21347343\", \"21347354\", \"21778402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How D3/D4 binding is coupled to downstream RON4/5/8 function not defined\", \"Contribution of the hydrophobic stretch to membrane insertion vs binding unclear\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Discovering that sporozoites use a dedicated sporoRON2/sporoAMA1 pair with reciprocal binding specificity revealed that AMA-RON pairings are stage-specific rather than universal.\",\n      \"evidence\": \"Co-IP, interaction-domain studies, and stage-specific reciprocal invasion-inhibition assays in T. gondii\",\n      \"pmids\": [\"23940612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of paralogue specificity not yet defined\", \"In vivo role during natural sporozoite infection untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defining RON5 as essential for RON2 stability and showing paralogue upregulation upon AMA1 loss established both the assembly hierarchy of the complex and the plasticity of MJ composition.\",\n      \"evidence\": \"Conditional RON5 knockdown with invasion/evacuole/egress readouts; AMA1 gene disruption with conditional complementation in T. gondii\",\n      \"pmids\": [\"24651769\", \"24934579\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of RON5-dependent RON2 stabilization unknown\", \"Functional capacity of compensating paralogues only partially characterized\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Live imaging linked productive junction anchoring to host cortical actin remodeling, showing that a RON2-containing junction must be tethered to the host cortex for invasion to succeed.\",\n      \"evidence\": \"Live imaging of fluorescent RON2 and kinematic analysis of >1000 invasion events in toxofilin-mutant T. gondii\",\n      \"pmids\": [\"25551479\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct RON2 contribution to anchoring vs bystander role unresolved\", \"Molecular link between RON complex and host cortex not identified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Structural and thermodynamic dissection of the AMA1 DII loop and of the divergent AMA4-RON2L1 complex explained how binding selectivity is enforced and how paralogue pairs achieve distinct assembly architectures.\",\n      \"evidence\": \"Site-directed mutagenesis, ITC, and X-ray crystallography of TgAMA1ΔDIIloop-EtRON2 and apo/bound TgAMA4-RON2L1 in T. gondii\",\n      \"pmids\": [\"25955165\", \"26712012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How gatekeeping is regulated during natural invasion unclear\", \"Whether groove-less architectures generalize to other paralogues untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showing that RON2 D3 binding shields AMA1 from rhomboid cleavage and triggers cytoplasmic-tail dephosphorylation established the junction as a site of outside-in signaling that stabilizes AMA1 for productive entry.\",\n      \"evidence\": \"Peptide/cleavage assays and phosphomimetic/phosphoablative AMA1 (S527) mutants with invasion readouts in T. gondii\",\n      \"pmids\": [\"27624124\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase/phosphatase acting on the AMA1 tail not identified\", \"Downstream effectors of the dephosphorylation signal unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating recruitment of host CIN85, CD2AP, ALIX, and TSG101 by RON2/4/5, and the existence of a RON2/4/5-independent RON4L1 complex, revealed that the junction subverts conserved host machinery and that multiple MJ complexes may coexist.\",\n      \"evidence\": \"Co-IP, interaction mapping, parasite mutants, invasion assays, and mouse virulence; RON4L1 knockout and RON2/4/5-independent localization in T. gondii\",\n      \"pmids\": [\"28848228\", \"29263399\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of recruited host ESCRT components in membrane biology at the MJ not fully defined\", \"Relationship between parallel RON complexes and single vs multiple junctions unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Genetic dissection of bradyzoite invasion showed that chronic-stage parasites substitute AMA2/AMA4-RON2L1 for the canonical AMA1-RON2 pair, and that these pairs have distinct vaccine potential.\",\n      \"evidence\": \"Gene knockouts, invasion assays, and immunization/challenge experiments in mice with T. gondii\",\n      \"pmids\": [\"36693095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulatory switch controlling stage-specific paralogue expression unknown\", \"Structural detail of the bradyzoite complexes incomplete\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Electrophysiology of RON2-depleted parasites separated pore formation from productive invasion, showing RON2 is dispensable for the invasion-associated conductance but required for entry and for setting pore properties.\",\n      \"evidence\": \"Sub-200 µs electrophysiological recordings and quantal conductance analysis of RON2-depleted RH parasites\",\n      \"pmids\": [\"39416144\", \"40973829\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular identity of the conductance pathway/pore unknown\", \"How RON2 modulates quantal conductance mechanistically unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identifying AP2XII-9 as a direct transcriptional regulator of RON2 placed the gene within a cell-cycle-linked program controlling rhoptry neck protein expression.\",\n      \"evidence\": \"CUT&Tag chromatin profiling and conditional AP2XII-9 knockdown with invasion/egress assays in T. gondii\",\n      \"pmids\": [\"39207100\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full transcriptional network co-regulating RON2 not mapped\", \"Direct vs indirect effects on RON2 protein levels not fully separated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular identity of the invasion pore/conductance pathway and how RON2 mechanically couples AMA1 binding to force generation and host membrane deformation remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular identification of the conductance pathway\", \"Mechanochemical link between RON2-AMA1 binding and penetration force undefined\", \"How the recruited host ESCRT/adaptor proteins reshape the host membrane at the MJ unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005515\", \"supporting_discovery_ids\": [4, 5, 6, 10, 11], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [2, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [0, 1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0044231\", \"supporting_discovery_ids\": [0, 1, 2, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0020002\", \"supporting_discovery_ids\": [2, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [4, 5, 7, 13, 15], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0052126\", \"supporting_discovery_ids\": [0, 2, 8], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\n      \"Moving junction complex RON2/RON4/RON5/RON8\",\n      \"RON2-AMA1 complex\",\n      \"sporoRON2(RON2L2)-sporoAMA1 complex\",\n      \"RON2L1-AMA4 complex\",\n      \"RON4L1-containing MJ complex (RON2/4/5-independent)\"\n    ],\n    \"partners\": [\n      \"AMA1 (microneme protein, direct binding partner)\",\n      \"RON4\",\n      \"RON5 (required for RON2 stability)\",\n      \"RON8\",\n      \"sporoAMA1\",\n      \"AMA4\",\n      \"host CIN85\",\n      \"host CD2AP\",\n      \"host ALIX\",\n      \"host TSG101 (ESCRT-I)\",\n      \"AP2XII-9 (transcriptional regulator)\"\n    ],\n    \"other_free_text\": [\n      \"RON2 C-terminal D3 and D4 segments flank a hydrophobic stretch and dock into the AMA1 hydrophobic groove via stepwise assembly with extensive buried surface area.\",\n      \"RON2-AMA1 binding protects AMA1 from rhomboid-mediated transmembrane cleavage and triggers dephosphorylation of AMA1 cytoplasmic tail residue S527 (outside-in signaling).\",\n      \"RON2 is dispensable for the transient invasion-associated host membrane conductance pore but required for productive invasion and modulates quantal conductance (RH strain).\",\n      \"AMA-RON pairings are stage-specific and structurally plastic across tachyzoite, sporozoite, and bradyzoite stages.\",\n      \"AMA1-RON2 immunization protects against acute and chronic infection; AMA4-RON2L1 more selectively targets chronic infection.\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_300100","name":"RON2","product":"rhoptry neck protein RON2","uniprot_acc":"B6KV60","chromosome":"TGME49_chrXII","start_pos":213222},{"strain":"GT1","gene_id":"TGGT1_300100","name":null,"product":"rhoptry neck protein RON2","uniprot_acc":null,"chromosome":"TGGT1_chrXII","start_pos":175560},{"strain":"RH88","gene_id":"TGRH88_057260","name":null,"product":"rhoptry neck protein RON2","uniprot_acc":null,"chromosome":"CM023093","start_pos":204965},{"strain":"VEG","gene_id":"TGVEG_300100","name":null,"product":"rhoptry neck protein RON2","uniprot_acc":"V4YYL5","chromosome":"TGVEG_chrXII","start_pos":205410}]}