{"gene":"TG_291890","gene_symbol":"MIC1","run_date":"2026-09-08T14:08:30","timeline":{"discoveries":[{"year":1996,"finding":"MIC1 is a soluble micronemal protein with a duplicated receptor-like domain (tandemly duplicated domain with conserved cysteines) and no transmembrane domain; recombinant protein expressing the N-terminal duplicated domain binds to the surface of host cells, suggesting a role in host cell binding/recognition.","method":"cDNA cloning, sequencing, recombinant protein binding assay (PMAL fusion protein applied to host cells)","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding assay with recombinant protein, single lab, single method but domain mapping included","pmids":["9027753"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2001,"finding":"MIC6 functions as a transmembrane escorter for the soluble adhesins MIC1 and MIC4; MIC6 carries sorting signals in its cytoplasmic tail, its association with MIC1 involves a lumenal EGF-like domain, MIC4 binds directly to MIC1 and is a passive cargo molecule, and MIC1 is absolutely required for the MIC1/4/6 complex to exit early secretory compartments (quality control checkpoint). Gene disruption of MIC1 prevents MIC6 (and MIC4) from reaching the micronemes.","method":"Gene disruption (KO), domain-mapping experiments, immunofluorescence, secretory pathway trafficking assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic dissection with multiple KOs, domain mapping, multiple orthogonal methods in a single rigorous study","pmids":["11157983"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2001,"finding":"MIC1 is a lactose-binding lectin; MIC1 and MIC4 co-purify on immobilized lactose affinity chromatography, and blotted MIC1 (but not native MIC4) binds human erythrocytes (type A) and fetuin, indicating that the lectin activity resides in MIC1.","method":"Lactose affinity chromatography, N-terminal microsequencing, hemagglutination inhibition assay, Western blot binding assay","journal":"Glycobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — affinity chromatography plus functional binding assays, single lab, multiple orthogonal methods","pmids":["11447133"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2005,"finding":"The N-terminal thrombospondin type I repeat-like (TSR1-like) domains of MIC1 function as an independent adhesin and promote association with MIC4. The C-terminal domain of MIC1 adopts a novel galectin-like fold (without carbohydrate-binding activity) that interacts with and stabilizes MIC6, providing the structural basis for a quality control mechanism governing exit of the MIC1/4/6 complex from early secretory compartments and trafficking to the micronemes.","method":"X-ray crystallography (3D structure of C-terminal domain), NMR, protein–protein interaction assays, domain truncation/binding experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure determination combined with NMR and protein-interaction assays in a single rigorous study","pmids":["16166092"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2005,"finding":"MIC1 single-gene deletion decreases invasion of fibroblasts by T. gondii tachyzoites; combined deletion of MIC1 and MIC3 (but not single deletion of MIC3 alone) severely impairs virulence in mice, revealing a synergistic role for these two soluble adhesins in invasion and virulence.","method":"Single and double gene knockout, invasion assay in fibroblasts, mouse virulence assay","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined invasion and virulence phenotypes, double-mutant epistasis, replicated across multiple genetic backgrounds","pmids":["15684324"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2007,"finding":"The atomic structure of TgMIC1 reveals a novel cell-binding motif, the microneme adhesive repeat (MAR), organized in tandem repeats that bind sialylated oligosaccharides on host cell surfaces; glycoarray analyses confirm preferential binding to a wide spectrum of sialylated oligosaccharides, explaining the broad host-cell range of T. gondii.","method":"X-ray crystallography (atomic structure), glycoarray (carbohydrate microarray) analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure solved plus glycoarray screening, multiple orthogonal methods in a single study","pmids":["17491595"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2008,"finding":"High-resolution NMR solution structure of the TgMIC6–TgMIC1 complex reveals two analogous interaction sites within separate EGF-like domains (EGF2 and EGF3) of TgMIC6 that both engage the galectin-like domain of TgMIC1; both interaction sites are functionally required for host cell receptor recognition, as confirmed by immunofluorescence and invasion assays.","method":"NMR solution structure determination, immunofluorescence assay, invasion assay","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure of complex plus functional validation by invasion assay, multiple orthogonal methods","pmids":["18818666"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"finding":"TgMIC1 acts as a sialic acid (Sia)-binding lectin through its MAR domains and is one important player in Sia-dependent host cell invasion; complementation and invasion assays demonstrate that loss of MIC1 reduces Sia-dependent invasion. Crystal structures of TgMIC1-MARR bound to five sialyl-N-acetyllactosamine analogs reveal a specific water-mediated hydrogen bond network explaining preferential binding to α2-3-linked sialyl oligosaccharides.","method":"Complementation assay, invasion assay, carbohydrate microarray, X-ray crystallography of ligand complexes","journal":"The Journal of biological chemistry / Protein science","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple crystal structures of ligand complexes plus functional invasion/complementation assays across two independent studies","pmids":["19901027","19593815"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"finding":"The cytoplasmic tail of the transmembrane escorter MIC6 interacts with aldolase and the parasite cytoskeleton, providing a physical link between the MIC1/4/6 adhesin complex and the parasite's actomyosin motor machinery during host cell invasion.","method":"Co-immunoprecipitation, pulldown assay identifying MIC6 C-domain–aldolase interaction","journal":"Parasitology research","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single Co-IP/pulldown, single lab, no reciprocal validation; relevant to MIC1 complex but the direct interaction is with MIC6","pmids":["19308454"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"finding":"TgMIC4 binds galactose-containing carbohydrates through its fifth apple domain; the MIC1/4/6 complex thus engages both sialic acid (via MIC1) and galactose (via MIC4) on host cell surfaces. Structure of TgMIC4 reveals six apple domains.","method":"X-ray crystallography (TgMIC4 structure), carbohydrate-binding specificity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with carbohydrate-binding specificity assays, clarifies the complementary roles of MIC1 and MIC4 in the complex","pmids":["22399295"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"Parasites lacking MIC1 (mic1 KO, which is also deficient in MIC6 secretion) display impaired EGFR-Akt activation in host cells. EGF-domain-containing MICs (MIC3 and MIC6), whose surface secretion depends on MIC1, promote EGFR activation in host endothelial, retinal pigment epithelial and microglial cells, and this EGFR-Akt signaling prevents autophagic targeting and lysosomal degradation of the parasite.","method":"KO parasite invasion assays, recombinant protein stimulation, EGFR/Akt signaling readouts (phospho-Akt), LC3 immunofluorescence, parasite killing assays","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO parasites plus recombinant proteins, multiple cell types, multiple signaling readouts; single lab","pmids":["24367261"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2019,"finding":"MIC1 and MIC4 physically interact with N-glycans on TLR2 and TLR4 on dendritic cells and macrophages, triggering NF-κB activation and IL-12 production. Point mutations in the carbohydrate-recognition domain (CRD) of MIC1 abolish this activation. MIC1 also impacts systemic IL-12 and IFN-γ levels in vivo and alters T. gondii infection competency.","method":"HEK cell transfection with TLR glycomutants, KO parasites (mic1 KO), recombinant protein stimulation with CRD point mutants, cytokine ELISA, in vivo infection assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (glycomutant TLRs, KO parasites, CRD mutant proteins, in vivo), single lab but strongly convergent evidence","pmids":["31226171"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"MIC1 induces IL-10 production from macrophages through a TLR4 endocytosis-dependent pathway: blockade of endocytosis (Dynasore) prevents IL-10 but not TNF-α production in response to MIC1, and MIC1/4-stimulated macrophages acquire transient LPS tolerance.","method":"Pharmacological inhibition of endocytosis (Dynasore), cytokine ELISA, T. gondii infection assays","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological dissection with functional cytokine readouts, single lab, two orthogonal approaches (inhibitor + infection)","pmids":["33912181"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"finding":"MIC1 engagement of TLR2 is the crucial signal for NF-κB activation and cytokine production; TLR2 heterodimerization (with TLR1 or TLR6) augments but is not essential, and co-receptors CD14 and CD36 enhance the response. MIC1/MIC4 activate cells through a TAK1–p38–NF-κB-dependent signaling pathway.","method":"HEK293T transfection with TLR2/TLR1/TLR6 variants and co-receptors, NF-κB reporter assay, cytokine measurement, pharmacological inhibition of TAK1/p38","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transfection-based pathway dissection plus pharmacological inhibitors, single lab, multiple orthogonal methods","pmids":["31658592"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"finding":"TgMIC1 promotes macrophage pyroptosis via the TLR4/NLRP3 pathway: recombinant MIC1 upregulates NLRP3 and activates caspase-1 and GSDMD in bone marrow-derived macrophages (BMDMs), an effect abolished by TLR4 knockout or NLRP3 knockout, and by point mutations (T126A/T220A) in MIC1's N-glycan binding sites on TLR4. The mic1 knockout strain (Wh3Δmic1) shows reduced invasion, limited growth, and attenuated inflammatory/pyroptotic responses.","method":"MIC1 KO parasite generation, recombinant protein (wild-type and CRD mutant) stimulation of BMDMs, TLR4-/- and NLRP3-/- macrophages, caspase-1/GSDMD western blot, in vivo infection","journal":"Parasites & vectors","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO parasites, receptor-deficient cell lines, and CRD-mutant protein, multiple orthogonal methods converging on same pathway","pmids":["39614314"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"TgCtwh3 (Chinese 1)"}]},{"year":2025,"finding":"rMIC1 and rMIC4 bind Jurkat T lymphocytes in a carbohydrate-dependent manner and reduce cell viability by inducing apoptosis through caspase activation (both extrinsic and intrinsic pathways), driven by NADPH oxidase-mediated ROS production and activation of p38 and JNK MAPK signaling cascades.","method":"Recombinant protein binding assay with carbohydrate competition, cell viability assay, caspase activity assay, ROS measurement, MAPK inhibitor experiments","journal":"Pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple functional assays (caspase, ROS, MAPK inhibition) in a single lab; carbohydrate-dependence confirmed but mechanistic depth moderate","pmids":["40333130"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"finding":"The MIC1/4/6 trimeric complex binds host N-glycans to cluster host surface proteins in a manner dependent on host plasma membrane cholesterol, and this clustering is required for rhoptry discharge during invasion. Host cholesterol depletion or competition with exogenous glycans inhibits rhoptry discharge.","method":"Host genome-wide CRISPR screen for rhoptry discharge, glycan competition assays, cholesterol depletion experiments, MIC1/4/6 complex binding assays","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide screen plus orthogonal functional validation (cholesterol depletion, glycan competition); preprint, not yet peer-reviewed","pmids":["41279910"],"is_preprint":true,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2005,"finding":"The trimeric MIC1/4/6 complex can be reconstituted in Giardia lamblia, demonstrating that the structural requirements for MIC complex assembly (MIC4 binding to MIC1, MIC1 binding to MIC6) are intrinsic to the protein sequences and do not require Toxoplasma-specific machinery.","method":"Heterologous co-expression and reconstitution of MIC1/4/6 complex in Giardia lamblia, co-immunoprecipitation, fluorescence microscopy","journal":"International journal for parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — heterologous reconstitution of trimeric complex, single lab","pmids":["16188260"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgMIC1 is a soluble micronemal adhesin that forms a trimeric complex with TgMIC4 and the transmembrane escorter TgMIC6; MIC1 is structurally organized as N-terminal TSR1-like (MAR) domains that bind α2-3-linked sialylated oligosaccharides on host cells and drive Sia-dependent invasion, and a C-terminal galectin-like domain (without carbohydrate-binding activity) that docks onto EGF domains of MIC6, acting as a quality-control checkpoint for complex exit from early secretory compartments and trafficking to micronemes; upon secretion, the MIC1/4/6 complex clusters host N-glycans in a cholesterol-dependent manner to license rhoptry discharge; MIC1's lectin activity also engages N-glycans on host TLR2 and TLR4, triggering TAK1–p38–NF-κB-dependent IL-12 and IL-10 responses (the latter via TLR4 endocytosis), activates NLRP3-dependent macrophage pyroptosis, and—through EGF-domain-containing MIC6—promotes EGFR-Akt signaling to suppress autophagic killing of the parasite."},"narrative":{"mechanistic_narrative":"TgMIC1 is a soluble micronemal adhesin of Toxoplasma gondii that couples host-cell carbohydrate recognition to invasion and to modulation of host innate immunity [PMID:9027753, PMID:17491595, PMID:31226171]. Structurally it is bipartite: N-terminal microneme adhesive repeat (MAR/TSR1-like) domains form an independent lectin module that binds a broad spectrum of α2-3-linked sialylated oligosaccharides on host cells, explaining the parasite's wide host-cell range and driving sialic-acid-dependent invasion [PMID:16166092, PMID:17491595, PMID:19901027, PMID:19593815], while a C-terminal galectin-like domain lacks carbohydrate binding and instead docks onto the EGF-like domains (EGF2 and EGF3) of the transmembrane escorter MIC6 [PMID:16166092, PMID:18818666]. Within the trimeric MIC1/4/6 complex, MIC4 binds directly to MIC1 as a passive, galactose-binding cargo, and MIC1 is absolutely required for the complex to exit early secretory compartments and traffic to the micronemes, acting as a quality-control checkpoint; the assembly requirements are intrinsic to the protein sequences [PMID:11157983, PMID:22399295, PMID:16188260]. Deletion of MIC1 impairs tachyzoite invasion of fibroblasts and, in combination with MIC3 loss, severely reduces virulence in mice [PMID:15684324]. Upon secretion, the MIC1/4/6 complex clusters host N-glycosylated surface proteins in a host-cholesterol-dependent manner to license rhoptry discharge [PMID:41279910]. Beyond invasion, MIC1's lectin activity engages N-glycans on host TLR2 and TLR4 to activate TAK1–p38–NF-κB signaling and IL-12 production, drives TLR4-endocytosis-dependent IL-10, and promotes TLR4/NLRP3-dependent macrophage pyroptosis via caspase-1 and GSDMD [PMID:31226171, PMID:31658592, PMID:33912181, PMID:39614314]. Through EGF-domain-containing partners whose secretion depends on MIC1, the complex additionally promotes host EGFR-Akt signaling that suppresses autophagic killing of the parasite [PMID:24367261].","teleology":[{"year":1996,"claim":"Establishing that MIC1 was a soluble, transmembrane-less micronemal protein whose duplicated receptor-like domain could bind host cells first implicated it in host-cell recognition rather than in structural anchoring.","evidence":"cDNA cloning and recombinant N-terminal domain binding assay on host cells","pmids":["9027753"],"confidence":"Medium","gaps":["Ligand identity on the host cell surface not defined","No functional link to invasion demonstrated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2001,"claim":"Genetic and biochemical dissection showed how a soluble adhesin reaches the micronemes, defining MIC1 as an obligatory quality-control component of the MIC1/4/6 complex and MIC6 as its transmembrane escorter.","evidence":"Gene disruption, domain mapping, and secretory-trafficking assays in T. gondii; lactose affinity chromatography and binding assays identifying MIC1 lectin activity","pmids":["11157983","11447133"],"confidence":"High","gaps":["Atomic basis of the MIC1–MIC6 and MIC1–MIC4 interactions not resolved","Precise carbohydrate specificity of the lectin activity undefined"],"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2005,"claim":"Structural and genetic work partitioned MIC1 into a carbohydrate-binding adhesin module and a non-carbohydrate-binding galectin-like MIC6-docking module, and tied MIC1 to invasion and virulence.","evidence":"X-ray crystallography and NMR of the C-terminal domain with interaction assays; single/double KO invasion and mouse virulence assays; heterologous reconstitution of the complex in Giardia","pmids":["16166092","15684324","16188260"],"confidence":"High","gaps":["Identity of the sugar ligand bound by the N-terminal adhesin not yet solved","Mechanistic basis of MIC1/MIC3 synergy in virulence unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2007,"claim":"Solving the atomic structure defined the MAR motif and identified sialylated oligosaccharides as MIC1's ligands, explaining the parasite's broad host-cell tropism.","evidence":"X-ray crystallography and glycoarray analysis","pmids":["17491595"],"confidence":"High","gaps":["Contribution of sialic-acid binding to invasion not yet functionally tested at this stage"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2008,"claim":"NMR of the MIC6–MIC1 complex resolved two analogous EGF-domain interaction sites required for host-cell recognition, giving the molecular architecture of complex assembly.","evidence":"NMR solution structure of MIC6 EGF2/EGF3–MIC1 galectin-like domain complex with immunofluorescence and invasion assays","pmids":["18818666"],"confidence":"High","gaps":["How dual docking sites contribute to trafficking versus adhesion not separated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2009,"claim":"Ligand-bound crystal structures and complementation assays established MIC1 as an α2-3-sialyl-specific lectin functioning in sialic-acid-dependent invasion, and connected the complex to the actomyosin motor via MIC6.","evidence":"Crystal structures of MIC1-MARR with sialyl oligosaccharide analogs, complementation/invasion assays, and Co-IP/pulldown of the MIC6 tail with aldolase","pmids":["19901027","19593815","19308454"],"confidence":"High","gaps":["MIC6–aldolase interaction rests on a single Co-IP/pulldown without reciprocal validation","Quantitative contribution of Sia binding versus other ligands to invasion not fully partitioned"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2012,"claim":"Structural characterization of MIC4 showed the complex engages two distinct host sugars, sialic acid via MIC1 and galactose via MIC4, defining complementary lectin activities.","evidence":"X-ray crystallography of TgMIC4 and carbohydrate-binding specificity assays","pmids":["22399295"],"confidence":"High","gaps":["Cooperativity between MIC1 and MIC4 sugar binding during invasion not quantified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"Loss of MIC1 (and consequently MIC6 secretion) revealed that the complex drives host EGFR-Akt signaling to block autophagic clearance, linking the adhesin to parasite survival inside host cells.","evidence":"mic1 KO invasion assays, recombinant protein stimulation, phospho-Akt and LC3 readouts, and parasite killing assays across multiple host cell types","pmids":["24367261"],"confidence":"Medium","gaps":["EGFR activation attributed to EGF-domain MICs (MIC3/MIC6) rather than MIC1 directly","Single lab; downstream autophagy-suppression mechanism only partially mapped"],"attribution":[{"species":"Toxoplasma gondii","strain":"RH"}]},{"year":2019,"claim":"Definition of TLR2/TLR4 N-glycans as MIC1 ligands and mapping of the TAK1–p38–NF-κB pathway established MIC1's lectin activity as a direct driver of innate immune activation and IL-12.","evidence":"HEK transfection with TLR glycomutants and co-receptors, mic1 KO parasites, CRD point-mutant proteins, NF-κB reporter, pharmacological TAK1/p38 inhibition, and in vivo cytokine measurement","pmids":["31226171","31658592"],"confidence":"High","gaps":["Structural basis of MIC1 engagement of TLR N-glycans not solved","Relative in vivo contribution of TLR2 versus TLR4 not fully dissected"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"Pharmacological dissection showed MIC1 elicits anti-inflammatory IL-10 through a TLR4-endocytosis-dependent route distinct from the TNF-α response, revealing bidirectional immune modulation.","evidence":"Dynasore endocytosis blockade, cytokine ELISA, and infection assays in macrophages","pmids":["33912181"],"confidence":"Medium","gaps":["Signaling nodes downstream of TLR4 endocytosis not identified","Single lab; in vivo relevance of IL-10 induction not established"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"MIC1 was shown to drive TLR4/NLRP3-dependent macrophage pyroptosis via caspase-1 and GSDMD, extending its immunomodulatory role to inflammatory cell death and tying it to parasite growth.","evidence":"mic1 KO parasites, TLR4-/- and NLRP3-/- macrophages, wild-type and T126A/T220A CRD-mutant recombinant protein, caspase-1/GSDMD western blot, and in vivo infection","pmids":["39614314"],"confidence":"High","gaps":["Whether pyroptosis benefits or restricts the parasite in vivo not resolved","Shown in the TgCtwh3 (Chinese 1) strain; generality across strains not tested"],"attribution":[{"species":"Toxoplasma gondii","strain":"TgCtwh3 (Chinese 1)"}]},{"year":2025,"claim":"Two studies further extended MIC1's carbohydrate-dependent host effects: induction of T-lymphocyte apoptosis via ROS/MAPK, and a role for MIC1/4/6-mediated N-glycan clustering in licensing rhoptry discharge.","evidence":"Recombinant protein binding with carbohydrate competition, caspase/ROS/MAPK-inhibitor assays in Jurkat cells; host genome-wide CRISPR screen with glycan competition and cholesterol depletion (preprint)","pmids":["40333130","41279910"],"confidence":"Medium","gaps":["Rhoptry-discharge study is a preprint not yet peer-reviewed","Physiological role of T-cell apoptosis induction during infection unclear","How glycan clustering mechanically triggers rhoptry discharge unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"How MIC1's dual roles—adhesion/invasion versus multi-pronged host immune modulation—are integrated during natural infection, and the structural basis of its engagement of host TLR N-glycans, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of MIC1 bound to TLR2/TLR4 glycans","Net in vivo consequence of pro- and anti-inflammatory signaling not resolved","Strain-to-strain variation in MIC1-driven immune outcomes largely untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["MIC1/4/6 trimeric micronemal adhesin complex"],"partners":["TGMIC6 (TRANSMEMBRANE ESCORTER; BINDS MIC1 GALECTIN-LIKE DOMAIN VIA EGF2/EGF3)","TGMIC4 (GALACTOSE-BINDING PASSIVE CARGO; BINDS MIC1)","HOST TLR2 (N-GLYCAN LIGAND)","HOST TLR4 (N-GLYCAN LIGAND)","HOST EGFR (ACTIVATED VIA EGF-DOMAIN MICS WHOSE SECRETION DEPENDS ON MIC1)"],"other_free_text":["N-terminal MAR/TSR1-like domains bind α2-3-linked sialylated oligosaccharides; C-terminal galectin-like domain lacks carbohydrate binding and docks MIC6.","MIC1 is obligatory for MIC1/4/6 complex exit from early secretory compartments and trafficking to micronemes (quality-control checkpoint).","Immune outcomes are lectin-dependent: CRD point mutations (e.g. T126A/T220A) abolish TLR binding and downstream signaling.","MIC1/4/6 clusters host N-glycans in a host-cholesterol-dependent manner to license rhoptry discharge (preprint evidence)."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"11157983","id":"PMC_11157983","title":"Identification and characterization of an escorter for two secretory adhesins in Toxoplasma gondii.","date":"2001","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/11157983","citation_count":178,"is_preprint":false},{"pmid":"11566297","id":"PMC_11566297","title":"Microneme proteins: structural and functional requirements to promote adhesion and invasion by the apicomplexan parasite Toxoplasma gondii.","date":"2001","source":"International journal for 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recombinant protein binding assay (PMAL fusion protein applied to host cells)\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding assay with recombinant protein, single lab, single method but domain mapping included\",\n      \"pmids\": [\"9027753\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MIC6 functions as a transmembrane escorter for the soluble adhesins MIC1 and MIC4; MIC6 carries sorting signals in its cytoplasmic tail, its association with MIC1 involves a lumenal EGF-like domain, MIC4 binds directly to MIC1 and is a passive cargo molecule, and MIC1 is absolutely required for the MIC1/4/6 complex to exit early secretory compartments (quality control checkpoint). Gene disruption of MIC1 prevents MIC6 (and MIC4) from reaching the micronemes.\",\n      \"method\": \"Gene disruption (KO), domain-mapping experiments, immunofluorescence, secretory pathway trafficking assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic dissection with multiple KOs, domain mapping, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"11157983\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MIC1 is a lactose-binding lectin; MIC1 and MIC4 co-purify on immobilized lactose affinity chromatography, and blotted MIC1 (but not native MIC4) binds human erythrocytes (type A) and fetuin, indicating that the lectin activity resides in MIC1.\",\n      \"method\": \"Lactose affinity chromatography, N-terminal microsequencing, hemagglutination inhibition assay, Western blot binding assay\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — affinity chromatography plus functional binding assays, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11447133\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The N-terminal thrombospondin type I repeat-like (TSR1-like) domains of MIC1 function as an independent adhesin and promote association with MIC4. The C-terminal domain of MIC1 adopts a novel galectin-like fold (without carbohydrate-binding activity) that interacts with and stabilizes MIC6, providing the structural basis for a quality control mechanism governing exit of the MIC1/4/6 complex from early secretory compartments and trafficking to the micronemes.\",\n      \"method\": \"X-ray crystallography (3D structure of C-terminal domain), NMR, protein–protein interaction assays, domain truncation/binding experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure determination combined with NMR and protein-interaction assays in a single rigorous study\",\n      \"pmids\": [\"16166092\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MIC1 single-gene deletion decreases invasion of fibroblasts by T. gondii tachyzoites; combined deletion of MIC1 and MIC3 (but not single deletion of MIC3 alone) severely impairs virulence in mice, revealing a synergistic role for these two soluble adhesins in invasion and virulence.\",\n      \"method\": \"Single and double gene knockout, invasion assay in fibroblasts, mouse virulence assay\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined invasion and virulence phenotypes, double-mutant epistasis, replicated across multiple genetic backgrounds\",\n      \"pmids\": [\"15684324\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The atomic structure of TgMIC1 reveals a novel cell-binding motif, the microneme adhesive repeat (MAR), organized in tandem repeats that bind sialylated oligosaccharides on host cell surfaces; glycoarray analyses confirm preferential binding to a wide spectrum of sialylated oligosaccharides, explaining the broad host-cell range of T. gondii.\",\n      \"method\": \"X-ray crystallography (atomic structure), glycoarray (carbohydrate microarray) analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure solved plus glycoarray screening, multiple orthogonal methods in a single study\",\n      \"pmids\": [\"17491595\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"High-resolution NMR solution structure of the TgMIC6–TgMIC1 complex reveals two analogous interaction sites within separate EGF-like domains (EGF2 and EGF3) of TgMIC6 that both engage the galectin-like domain of TgMIC1; both interaction sites are functionally required for host cell receptor recognition, as confirmed by immunofluorescence and invasion assays.\",\n      \"method\": \"NMR solution structure determination, immunofluorescence assay, invasion assay\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure of complex plus functional validation by invasion assay, multiple orthogonal methods\",\n      \"pmids\": [\"18818666\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TgMIC1 acts as a sialic acid (Sia)-binding lectin through its MAR domains and is one important player in Sia-dependent host cell invasion; complementation and invasion assays demonstrate that loss of MIC1 reduces Sia-dependent invasion. Crystal structures of TgMIC1-MARR bound to five sialyl-N-acetyllactosamine analogs reveal a specific water-mediated hydrogen bond network explaining preferential binding to α2-3-linked sialyl oligosaccharides.\",\n      \"method\": \"Complementation assay, invasion assay, carbohydrate microarray, X-ray crystallography of ligand complexes\",\n      \"journal\": \"The Journal of biological chemistry / Protein science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple crystal structures of ligand complexes plus functional invasion/complementation assays across two independent studies\",\n      \"pmids\": [\"19901027\", \"19593815\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The cytoplasmic tail of the transmembrane escorter MIC6 interacts with aldolase and the parasite cytoskeleton, providing a physical link between the MIC1/4/6 adhesin complex and the parasite's actomyosin motor machinery during host cell invasion.\",\n      \"method\": \"Co-immunoprecipitation, pulldown assay identifying MIC6 C-domain–aldolase interaction\",\n      \"journal\": \"Parasitology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP/pulldown, single lab, no reciprocal validation; relevant to MIC1 complex but the direct interaction is with MIC6\",\n      \"pmids\": [\"19308454\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TgMIC4 binds galactose-containing carbohydrates through its fifth apple domain; the MIC1/4/6 complex thus engages both sialic acid (via MIC1) and galactose (via MIC4) on host cell surfaces. Structure of TgMIC4 reveals six apple domains.\",\n      \"method\": \"X-ray crystallography (TgMIC4 structure), carbohydrate-binding specificity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with carbohydrate-binding specificity assays, clarifies the complementary roles of MIC1 and MIC4 in the complex\",\n      \"pmids\": [\"22399295\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Parasites lacking MIC1 (mic1 KO, which is also deficient in MIC6 secretion) display impaired EGFR-Akt activation in host cells. EGF-domain-containing MICs (MIC3 and MIC6), whose surface secretion depends on MIC1, promote EGFR activation in host endothelial, retinal pigment epithelial and microglial cells, and this EGFR-Akt signaling prevents autophagic targeting and lysosomal degradation of the parasite.\",\n      \"method\": \"KO parasite invasion assays, recombinant protein stimulation, EGFR/Akt signaling readouts (phospho-Akt), LC3 immunofluorescence, parasite killing assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO parasites plus recombinant proteins, multiple cell types, multiple signaling readouts; single lab\",\n      \"pmids\": [\"24367261\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MIC1 and MIC4 physically interact with N-glycans on TLR2 and TLR4 on dendritic cells and macrophages, triggering NF-κB activation and IL-12 production. Point mutations in the carbohydrate-recognition domain (CRD) of MIC1 abolish this activation. MIC1 also impacts systemic IL-12 and IFN-γ levels in vivo and alters T. gondii infection competency.\",\n      \"method\": \"HEK cell transfection with TLR glycomutants, KO parasites (mic1 KO), recombinant protein stimulation with CRD point mutants, cytokine ELISA, in vivo infection assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (glycomutant TLRs, KO parasites, CRD mutant proteins, in vivo), single lab but strongly convergent evidence\",\n      \"pmids\": [\"31226171\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MIC1 induces IL-10 production from macrophages through a TLR4 endocytosis-dependent pathway: blockade of endocytosis (Dynasore) prevents IL-10 but not TNF-α production in response to MIC1, and MIC1/4-stimulated macrophages acquire transient LPS tolerance.\",\n      \"method\": \"Pharmacological inhibition of endocytosis (Dynasore), cytokine ELISA, T. gondii infection assays\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological dissection with functional cytokine readouts, single lab, two orthogonal approaches (inhibitor + infection)\",\n      \"pmids\": [\"33912181\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MIC1 engagement of TLR2 is the crucial signal for NF-κB activation and cytokine production; TLR2 heterodimerization (with TLR1 or TLR6) augments but is not essential, and co-receptors CD14 and CD36 enhance the response. MIC1/MIC4 activate cells through a TAK1–p38–NF-κB-dependent signaling pathway.\",\n      \"method\": \"HEK293T transfection with TLR2/TLR1/TLR6 variants and co-receptors, NF-κB reporter assay, cytokine measurement, pharmacological inhibition of TAK1/p38\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transfection-based pathway dissection plus pharmacological inhibitors, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31658592\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TgMIC1 promotes macrophage pyroptosis via the TLR4/NLRP3 pathway: recombinant MIC1 upregulates NLRP3 and activates caspase-1 and GSDMD in bone marrow-derived macrophages (BMDMs), an effect abolished by TLR4 knockout or NLRP3 knockout, and by point mutations (T126A/T220A) in MIC1's N-glycan binding sites on TLR4. The mic1 knockout strain (Wh3Δmic1) shows reduced invasion, limited growth, and attenuated inflammatory/pyroptotic responses.\",\n      \"method\": \"MIC1 KO parasite generation, recombinant protein (wild-type and CRD mutant) stimulation of BMDMs, TLR4-/- and NLRP3-/- macrophages, caspase-1/GSDMD western blot, in vivo infection\",\n      \"journal\": \"Parasites & vectors\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO parasites, receptor-deficient cell lines, and CRD-mutant protein, multiple orthogonal methods converging on same pathway\",\n      \"pmids\": [\"39614314\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"TgCtwh3 (Chinese 1)\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"rMIC1 and rMIC4 bind Jurkat T lymphocytes in a carbohydrate-dependent manner and reduce cell viability by inducing apoptosis through caspase activation (both extrinsic and intrinsic pathways), driven by NADPH oxidase-mediated ROS production and activation of p38 and JNK MAPK signaling cascades.\",\n      \"method\": \"Recombinant protein binding assay with carbohydrate competition, cell viability assay, caspase activity assay, ROS measurement, MAPK inhibitor experiments\",\n      \"journal\": \"Pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple functional assays (caspase, ROS, MAPK inhibition) in a single lab; carbohydrate-dependence confirmed but mechanistic depth moderate\",\n      \"pmids\": [\"40333130\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The MIC1/4/6 trimeric complex binds host N-glycans to cluster host surface proteins in a manner dependent on host plasma membrane cholesterol, and this clustering is required for rhoptry discharge during invasion. Host cholesterol depletion or competition with exogenous glycans inhibits rhoptry discharge.\",\n      \"method\": \"Host genome-wide CRISPR screen for rhoptry discharge, glycan competition assays, cholesterol depletion experiments, MIC1/4/6 complex binding assays\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide screen plus orthogonal functional validation (cholesterol depletion, glycan competition); preprint, not yet peer-reviewed\",\n      \"pmids\": [\"41279910\"],\n      \"is_preprint\": true,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The trimeric MIC1/4/6 complex can be reconstituted in Giardia lamblia, demonstrating that the structural requirements for MIC complex assembly (MIC4 binding to MIC1, MIC1 binding to MIC6) are intrinsic to the protein sequences and do not require Toxoplasma-specific machinery.\",\n      \"method\": \"Heterologous co-expression and reconstitution of MIC1/4/6 complex in Giardia lamblia, co-immunoprecipitation, fluorescence microscopy\",\n      \"journal\": \"International journal for parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — heterologous reconstitution of trimeric complex, single lab\",\n      \"pmids\": [\"16188260\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgMIC1 is a soluble micronemal adhesin that forms a trimeric complex with TgMIC4 and the transmembrane escorter TgMIC6; MIC1 is structurally organized as N-terminal TSR1-like (MAR) domains that bind α2-3-linked sialylated oligosaccharides on host cells and drive Sia-dependent invasion, and a C-terminal galectin-like domain (without carbohydrate-binding activity) that docks onto EGF domains of MIC6, acting as a quality-control checkpoint for complex exit from early secretory compartments and trafficking to micronemes; upon secretion, the MIC1/4/6 complex clusters host N-glycans in a cholesterol-dependent manner to license rhoptry discharge; MIC1's lectin activity also engages N-glycans on host TLR2 and TLR4, triggering TAK1–p38–NF-κB-dependent IL-12 and IL-10 responses (the latter via TLR4 endocytosis), activates NLRP3-dependent macrophage pyroptosis, and—through EGF-domain-containing MIC6—promotes EGFR-Akt signaling to suppress autophagic killing of the parasite.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgMIC1 is a soluble micronemal adhesin of Toxoplasma gondii that couples host-cell carbohydrate recognition to invasion and to modulation of host innate immunity [#0, #5, #11]. Structurally it is bipartite: N-terminal microneme adhesive repeat (MAR/TSR1-like) domains form an independent lectin module that binds a broad spectrum of α2-3-linked sialylated oligosaccharides on host cells, explaining the parasite's wide host-cell range and driving sialic-acid-dependent invasion [#3, #5, #7], while a C-terminal galectin-like domain lacks carbohydrate binding and instead docks onto the EGF-like domains (EGF2 and EGF3) of the transmembrane escorter MIC6 [#3, #6]. Within the trimeric MIC1/4/6 complex, MIC4 binds directly to MIC1 as a passive, galactose-binding cargo, and MIC1 is absolutely required for the complex to exit early secretory compartments and traffic to the micronemes, acting as a quality-control checkpoint; the assembly requirements are intrinsic to the protein sequences [#1, #9, #17]. Deletion of MIC1 impairs tachyzoite invasion of fibroblasts and, in combination with MIC3 loss, severely reduces virulence in mice [#4]. Upon secretion, the MIC1/4/6 complex clusters host N-glycosylated surface proteins in a host-cholesterol-dependent manner to license rhoptry discharge [#16]. Beyond invasion, MIC1's lectin activity engages N-glycans on host TLR2 and TLR4 to activate TAK1–p38–NF-κB signaling and IL-12 production, drives TLR4-endocytosis-dependent IL-10, and promotes TLR4/NLRP3-dependent macrophage pyroptosis via caspase-1 and GSDMD [#11, #13, #12, #14]. Through EGF-domain-containing partners whose secretion depends on MIC1, the complex additionally promotes host EGFR-Akt signaling that suppresses autophagic killing of the parasite [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Establishing that MIC1 was a soluble, transmembrane-less micronemal protein whose duplicated receptor-like domain could bind host cells first implicated it in host-cell recognition rather than in structural anchoring.\",\n      \"evidence\": \"cDNA cloning and recombinant N-terminal domain binding assay on host cells\",\n      \"pmids\": [\"9027753\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ligand identity on the host cell surface not defined\", \"No functional link to invasion demonstrated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Genetic and biochemical dissection showed how a soluble adhesin reaches the micronemes, defining MIC1 as an obligatory quality-control component of the MIC1/4/6 complex and MIC6 as its transmembrane escorter.\",\n      \"evidence\": \"Gene disruption, domain mapping, and secretory-trafficking assays in T. gondii; lactose affinity chromatography and binding assays identifying MIC1 lectin activity\",\n      \"pmids\": [\"11157983\", \"11447133\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic basis of the MIC1–MIC6 and MIC1–MIC4 interactions not resolved\", \"Precise carbohydrate specificity of the lectin activity undefined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Structural and genetic work partitioned MIC1 into a carbohydrate-binding adhesin module and a non-carbohydrate-binding galectin-like MIC6-docking module, and tied MIC1 to invasion and virulence.\",\n      \"evidence\": \"X-ray crystallography and NMR of the C-terminal domain with interaction assays; single/double KO invasion and mouse virulence assays; heterologous reconstitution of the complex in Giardia\",\n      \"pmids\": [\"16166092\", \"15684324\", \"16188260\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the sugar ligand bound by the N-terminal adhesin not yet solved\", \"Mechanistic basis of MIC1/MIC3 synergy in virulence unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Solving the atomic structure defined the MAR motif and identified sialylated oligosaccharides as MIC1's ligands, explaining the parasite's broad host-cell tropism.\",\n      \"evidence\": \"X-ray crystallography and glycoarray analysis\",\n      \"pmids\": [\"17491595\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Contribution of sialic-acid binding to invasion not yet functionally tested at this stage\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"NMR of the MIC6–MIC1 complex resolved two analogous EGF-domain interaction sites required for host-cell recognition, giving the molecular architecture of complex assembly.\",\n      \"evidence\": \"NMR solution structure of MIC6 EGF2/EGF3–MIC1 galectin-like domain complex with immunofluorescence and invasion assays\",\n      \"pmids\": [\"18818666\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How dual docking sites contribute to trafficking versus adhesion not separated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Ligand-bound crystal structures and complementation assays established MIC1 as an α2-3-sialyl-specific lectin functioning in sialic-acid-dependent invasion, and connected the complex to the actomyosin motor via MIC6.\",\n      \"evidence\": \"Crystal structures of MIC1-MARR with sialyl oligosaccharide analogs, complementation/invasion assays, and Co-IP/pulldown of the MIC6 tail with aldolase\",\n      \"pmids\": [\"19901027\", \"19593815\", \"19308454\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"MIC6–aldolase interaction rests on a single Co-IP/pulldown without reciprocal validation\", \"Quantitative contribution of Sia binding versus other ligands to invasion not fully partitioned\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Structural characterization of MIC4 showed the complex engages two distinct host sugars, sialic acid via MIC1 and galactose via MIC4, defining complementary lectin activities.\",\n      \"evidence\": \"X-ray crystallography of TgMIC4 and carbohydrate-binding specificity assays\",\n      \"pmids\": [\"22399295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cooperativity between MIC1 and MIC4 sugar binding during invasion not quantified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Loss of MIC1 (and consequently MIC6 secretion) revealed that the complex drives host EGFR-Akt signaling to block autophagic clearance, linking the adhesin to parasite survival inside host cells.\",\n      \"evidence\": \"mic1 KO invasion assays, recombinant protein stimulation, phospho-Akt and LC3 readouts, and parasite killing assays across multiple host cell types\",\n      \"pmids\": [\"24367261\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"EGFR activation attributed to EGF-domain MICs (MIC3/MIC6) rather than MIC1 directly\", \"Single lab; downstream autophagy-suppression mechanism only partially mapped\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Definition of TLR2/TLR4 N-glycans as MIC1 ligands and mapping of the TAK1–p38–NF-κB pathway established MIC1's lectin activity as a direct driver of innate immune activation and IL-12.\",\n      \"evidence\": \"HEK transfection with TLR glycomutants and co-receptors, mic1 KO parasites, CRD point-mutant proteins, NF-κB reporter, pharmacological TAK1/p38 inhibition, and in vivo cytokine measurement\",\n      \"pmids\": [\"31226171\", \"31658592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MIC1 engagement of TLR N-glycans not solved\", \"Relative in vivo contribution of TLR2 versus TLR4 not fully dissected\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Pharmacological dissection showed MIC1 elicits anti-inflammatory IL-10 through a TLR4-endocytosis-dependent route distinct from the TNF-α response, revealing bidirectional immune modulation.\",\n      \"evidence\": \"Dynasore endocytosis blockade, cytokine ELISA, and infection assays in macrophages\",\n      \"pmids\": [\"33912181\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling nodes downstream of TLR4 endocytosis not identified\", \"Single lab; in vivo relevance of IL-10 induction not established\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"MIC1 was shown to drive TLR4/NLRP3-dependent macrophage pyroptosis via caspase-1 and GSDMD, extending its immunomodulatory role to inflammatory cell death and tying it to parasite growth.\",\n      \"evidence\": \"mic1 KO parasites, TLR4-/- and NLRP3-/- macrophages, wild-type and T126A/T220A CRD-mutant recombinant protein, caspase-1/GSDMD western blot, and in vivo infection\",\n      \"pmids\": [\"39614314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether pyroptosis benefits or restricts the parasite in vivo not resolved\", \"Shown in the TgCtwh3 (Chinese 1) strain; generality across strains not tested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"TgCtwh3 (Chinese 1)\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Two studies further extended MIC1's carbohydrate-dependent host effects: induction of T-lymphocyte apoptosis via ROS/MAPK, and a role for MIC1/4/6-mediated N-glycan clustering in licensing rhoptry discharge.\",\n      \"evidence\": \"Recombinant protein binding with carbohydrate competition, caspase/ROS/MAPK-inhibitor assays in Jurkat cells; host genome-wide CRISPR screen with glycan competition and cholesterol depletion (preprint)\",\n      \"pmids\": [\"40333130\", \"41279910\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Rhoptry-discharge study is a preprint not yet peer-reviewed\", \"Physiological role of T-cell apoptosis induction during infection unclear\", \"How glycan clustering mechanically triggers rhoptry discharge unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MIC1's dual roles—adhesion/invasion versus multi-pronged host immune modulation—are integrated during natural infection, and the structural basis of its engagement of host TLR N-glycans, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of MIC1 bound to TLR2/TLR4 glycans\", \"Net in vivo consequence of pro- and anti-inflammatory signaling not resolved\", \"Strain-to-strain variation in MIC1-driven immune outcomes largely untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0030246\", \"supporting_discovery_ids\": [2, 5, 7, 9], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0033691\", \"supporting_discovery_ids\": [5, 7], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0050839\", \"supporting_discovery_ids\": [0, 5], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0035325\", \"supporting_discovery_ids\": [11, 13, 14], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020009\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [4, 5, 7, 16], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0007249\", \"supporting_discovery_ids\": [11, 13], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0070423\", \"supporting_discovery_ids\": [14], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0043069\", \"supporting_discovery_ids\": [10], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"RH\"}]}\n    ],\n    \"complexes\": [\n      \"MIC1/4/6 trimeric micronemal adhesin complex\"\n    ],\n    \"partners\": [\n      \"TgMIC6 (transmembrane escorter; binds MIC1 galectin-like domain via EGF2/EGF3)\",\n      \"TgMIC4 (galactose-binding passive cargo; binds MIC1)\",\n      \"Host TLR2 (N-glycan ligand)\",\n      \"Host TLR4 (N-glycan ligand)\",\n      \"Host EGFR (activated via EGF-domain MICs whose secretion depends on MIC1)\"\n    ],\n    \"other_free_text\": [\n      \"N-terminal MAR/TSR1-like domains bind α2-3-linked sialylated oligosaccharides; C-terminal galectin-like domain lacks carbohydrate binding and docks MIC6.\",\n      \"MIC1 is obligatory for MIC1/4/6 complex exit from early secretory compartments and trafficking to micronemes (quality-control checkpoint).\",\n      \"Immune outcomes are lectin-dependent: CRD point mutations (e.g. T126A/T220A) abolish TLR binding and downstream signaling.\",\n      \"MIC1/4/6 clusters host N-glycans in a host-cholesterol-dependent manner to license rhoptry discharge (preprint evidence).\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_291890","name":"MIC1","product":"microneme protein MIC1","uniprot_acc":"A0A125YMF8","chromosome":"TGME49_chrIX","start_pos":4393561},{"strain":"GT1","gene_id":"TGGT1_291890","name":null,"product":"microneme protein MIC1","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":4200849},{"strain":"RH88","gene_id":"TGRH88_015770","name":null,"product":"microneme protein MIC1","uniprot_acc":null,"chromosome":"CM023090","start_pos":4459663},{"strain":"VEG","gene_id":"TGVEG_291890","name":null,"product":"microneme protein MIC1","uniprot_acc":"B6KL08","chromosome":"TGVEG_chrIX","start_pos":4430252}]}