Affinage · Toxoplasma gondii

AMA1

apical membrane antigen AMA1 · UniProt B6KAM0

Annotated
2026-09-08
68 papers in source corpus 28 papers cited in narrative 27 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TgAMA1 is a calcium-regulated type I transmembrane microneme protein of apicomplexan parasites that functions as the parasite-side adhesin at the moving junction (MJ), the ring-shaped structure through which the parasite penetrates its host cell (PMID:11083833, PMID:11087913, PMID:16244709). Following calcium-triggered microneme secretion, AMA1 relocates to the apical parasite surface, where its ectodomain binds the C-terminal region of the rhoptry neck protein RON2, which is itself inserted into the host cell membrane as part of a RON2/4/5/8 complex (PMID:16244709, PMID:19247437, PMID:21347354, PMID:21347343). High-resolution crystallography defines the interaction: RON2 docks into a central hydrophobic groove of the AMA1 ectodomain, framed by conserved Trp/Tyr residues and gated by the mobile DII loop, forming an extensively buried, mechanically stable interface that anchors the junction against the forces of invasion (PMID:20304917, PMID:21778402, PMID:25955165). Conditional depletion and genetic knockout studies place AMA1's function after initial attachment: it promotes tight apposition to the host cell and efficient internalization and contributes to rhoptry discharge, but junction assembly and penetration can proceed at reduced efficiency in its absence, in part through compensatory upregulation of AMA/RON paralogs — establishing AMA1 as a critical but non-obligatory adhesin rather than an essential invasin (PMID:16000372, PMID:22177563, PMID:24108241, PMID:24934579). AMA1 is subject to constitutive intramembrane cleavage within its transmembrane domain by the rhomboid proteases ROM4 and ROM5, and RON2 binding protects AMA1 from this cleavage while triggering outside-in dephosphorylation of Ser527 in its cytoplasmic tail; genetic evidence with cleavage-resistant and phosphomimetic alleles shows this regulated proteolysis and phosphorylation are tuned specifically to promote invasion (PMID:16102004, PMID:25846828, PMID:27624124, PMID:22523242). Palmitoylation regulates AMA1 retention and secretion from micronemes (PMID:26468752). The AMA1–RON2 system is conserved across apicomplexans and diversified into stage-specific paralog pairs — sporozoites use sporoAMA1/sporoRON2 and bradyzoites use AMA2/AMA4 — and AMA1–RON2 immunization confers protection against acute and chronic infection (PMID:16835460, PMID:21347343, PMID:23940612, PMID:36693095).

Mechanistic history

Synthesis pass · year-by-year structured walk · 24 steps
  1. 2000 High

    Establishing whether AMA1 is essential for invasion and where it acts defined it as an apically-delivered, invasion-critical microneme protein whose secretion is calcium-controlled.

    Evidence IFA/IEM localization, biochemical fractionation, failed knockout, and antiserum invasion inhibition in T. gondii tachyzoites, plus calcium-ionophore secretion assays

    PMID:11083833 PMID:11087913

    Open questions at the time
    • Molecular partner at the parasite surface not yet identified
    • Mechanistic step of invasion controlled by AMA1 unresolved
  2. 2005 High

    Conditional depletion pinpointed AMA1's action to after attachment — it is required for efficient invasion and rhoptry discharge but not microneme secretion or initial attachment.

    Evidence Regulatable-promoter conditional knockout with separate invasion, microneme, and rhoptry secretion assays in T. gondii RH

    PMID:16000372

    Open questions at the time
    • How AMA1 links to rhoptry discharge machinery unknown
    • Direct binding partner not yet defined
  3. 2005 High

    Identifying AMA1 in a complex with rhoptry neck (RON) proteins at the moving junction revealed the unexpected microneme–rhoptry collaboration that builds the invasion junction.

    Evidence Co-immunoprecipitation and immunoelectron microscopy localizing complex members to the MJ in T. gondii

    PMID:16244709

    Open questions at the time
    • Precise RON partner engaging AMA1 directly not defined
    • Membrane topology of the complex unresolved
  4. 2005 Medium

    Characterizing AMA1 shedding showed it is cleaved by a rhomboid-like protease within its transmembrane domain, and that intact protein persists on newly invaded parasites — distinguishing it mechanistically from PfAMA1.

    Evidence Pulse-chase labeling, protease inhibitor studies, and heterologous Drosophila rhomboid cleavage assay in T. gondii

    PMID:16102004

    Open questions at the time
    • Which endogenous rhomboid(s) cleave AMA1 not identified
    • Functional consequence of cleavage unresolved
  5. 2006 Medium

    Demonstrating PfAMA1–PfRON4 co-precipitation established that the AMA1–RON association is conserved across apicomplexan parasites.

    Evidence Co-immunoprecipitation of native proteins in Plasmodium falciparum

    PMID:16835460

    Open questions at the time
    • Direct vs. indirect nature of AMA1–RON4 contact unresolved
    • Structural basis not addressed
  6. 2009 High

    Resolving MJ topology showed RON2/4/5/8 are exported to the host membrane with RON4/5/8 on the cytoplasmic face while AMA1 sits in the parasite membrane, and that AMA1 pairs directly with RON2 independently of the other RONs.

    Evidence Metabolic labeling, immunoprecipitation, differential permeabilization, and antibody loading into host cells in T. gondii

    PMID:19247437

    Open questions at the time
    • Region of RON2 binding AMA1 not yet mapped
    • Structural interface undefined
  7. 2009 Medium

    Mapping the invasion-blocking mAb 4G2 epitope to the PfAMA1 hydrophobic groove (requiring Tyr251) showed that the RON-binding groove is the functional target of inhibitory antibodies.

    Evidence Antibody competition, site-directed mutagenesis of PfAMA1 Tyr251, and Co-IP in P. falciparum

    PMID:19165323

    Open questions at the time
    • Full atomic interface not resolved in this study
    • Single-residue analysis in one species
  8. 2010 High

    A genetic rescue with the released AMA1 cytoplasmic tail proposed that ROM4 cleavage of AMA1 triggers the switch from invasive to replicative mode — a model later revised.

    Evidence Conditional overexpression of dominant-negative TgROM4 rescued by AMA1 cytoplasmic-tail constructs, with replication assays (a 2025 erratum was subsequently issued)

    PMID:21205639 PMID:41379978

    Open questions at the time
    • Replication-switch interpretation contradicted by later invasion-specific data (#15)
    • Downstream signaling of the released tail undefined
  9. 2010 High

    The AMA1 ectodomain crystal structure defined a central hydrophobic groove framed by Trp353/Trp354/Tyr230 and gated by a short DII loop, giving an atomic candidate for the RON2 binding site.

    Evidence 2.0 Å X-ray crystal structure of full-length TgAMA1 ectodomain

    PMID:20304917

    Open questions at the time
    • Ligand-bound conformation not yet captured
    • Function of the DII loop untested
  10. 2010 High

    Knockout of ROM4 showed rhomboid processing of AMA1 and other adhesins establishes the apical-posterior surface gradient needed for apical orientation, gliding, and MJ formation.

    Evidence Tetracycline-regulatable ROM4 conditional knockout with adhesin surface IFA, invasion, and motility assays in T. gondii

    PMID:20421941

    Open questions at the time
    • Whether ROM4 is the sole AMA1 protease unresolved (later addressed by #22)
    • Coupling of surface gradient to junction formation mechanistically incomplete
  11. 2011 High

    Defining the AMA1-binding region of RON2 (D3/D4 segments) and showing D3 peptide blocks invasion without preventing rhoptry injection established RON2 as the molecular bridge tethering AMA1 to the host-cell-anchored MJ, downstream of effector delivery.

    Evidence Recombinant RON2 fragment pull-downs, MJ localization, invasion inhibition with D3-GST, and evacuole assays in T. gondii; complementary interaction and topology mapping plus invasion inhibition in T. gondii and P. falciparum

    PMID:21347354 PMID:21347343

    Open questions at the time
    • Atomic-resolution interface not yet solved in these studies
    • How the bridge withstands invasion forces unaddressed
  12. 2011 Medium

    AMA1 propeptide aliphatic residues were shown to be required for trafficking of AMA1 to the micronemes, defining the sorting determinant.

    Evidence Propeptide mutagenesis and GFP reporter trafficking assays in T. gondii

    PMID:21438967

    Open questions at the time
    • Receptor recognizing the propeptide signal not identified
    • AMA1 finding embedded in a broader MIC propeptide study
  13. 2011 High

    The AMA1–RON2 peptide co-crystal structure revealed a stepwise assembly producing an extensive buried interface, explaining how the junction resists the mechanical forces of penetration.

    Evidence 1.95 Å X-ray structure of TgAMA1 bound to a TgRON2 peptide

    PMID:21778402

    Open questions at the time
    • Dynamics of assembly in the membrane not captured
    • Contribution of the DII loop to selectivity not yet dissected
  14. 2011 High

    Genetic dissection showed AMA1 is dispensable for RON4 ring formation and functional junction assembly but enhances apposition and internalization frequency, and that RON4 can act without AMA1 in Plasmodium sporozoites — decoupling junction assembly from AMA1.

    Evidence Conditional knockdown/knockout of AMA1 and RON4 with invasion assays and RON4 ring IFA in T. gondii and P. berghei

    PMID:22177563

    Open questions at the time
    • What supports residual invasion without AMA1 not yet identified (later attributed to paralogs, #18)
    • Mechanism of the apposition enhancement unresolved
  15. 2012 High

    Cleavage-resistant AMA1 knock-in alleles revealed that intramembrane proteolysis of AMA1 promotes invasion specifically — refuting the earlier replication-switch model.

    Evidence TM-domain mutagenesis, heterologous cleavage assays, and knock-in complementation of a conditional knockout with growth/invasion readouts in T. gondii

    PMID:22523242

    Open questions at the time
    • Precise step of invasion enabled by cleavage not fully defined
    • Reconciliation with the released-tail signaling proposal incomplete
  16. 2013 High

    Deleting AMA1 across three zoite types in two species showed AMA1-null parasites are impaired in attachment but penetrate junctions normally, redefining AMA1 as a dispensable adhesin rather than an essential invasin.

    Evidence Genetic AMA1 deletion in Plasmodium sporozoites/merozoites and T. gondii RH tachyzoites, with assays separating attachment from penetration

    PMID:24108241

    Open questions at the time
    • Compensating molecules not identified in this study
    • Quantitative contribution of AMA1 to natural infection unresolved
  17. 2013 High

    Discovery of exclusively self-pairing sporozoite paralogs sporoAMA1/sporoRON2, with allosteric conformational change on binding and stage-specific peptide inhibition, revealed stage-specialized AMA1–RON2 modules governing invasion in a life-cycle-specific manner.

    Evidence IFA localization, interaction-specificity binding assays, crystallography of the sporoAMA1–sporoRON2 complex, and stage-specific invasion inhibition in T. gondii

    PMID:23940612

    Open questions at the time
    • Regulation of paralog expression across stages unresolved
    • In vivo requirement of the sporozoite module untested here
  18. 2014 High

    AMA1 gene disruption triggering compensatory AMA/RON paralog upregulation explained residual invasion in AMA1-null parasites and demonstrated molecular plasticity in MJ architecture while confirming AMA1–RON2 maintains junction integrity.

    Evidence Reverse genetics, conditional complementation, IFA, Western blot for paralog upregulation, and invasion assays in T. gondii

    PMID:24934579

    Open questions at the time
    • Trigger controlling paralog upregulation unknown
    • Whether paralogs form structurally identical junctions unresolved
  19. 2014 High

    Combining aldolase-binding mutants with an aldolase knockout established that the AMA1 cytoplasmic tail–aldolase interaction is dispensable for invasion — a negative result overturning the adhesin–motor linkage model for AMA1.

    Evidence In vitro tail–aldolase binding, mutagenesis, ALD conditional knockout, and gliding/invasion assays in T. gondii

    PMID:24550496

    Open questions at the time
    • The actual force-transducing partner of the AMA1 tail unidentified
    • Whether the tail engages the motor at all is unresolved
  20. 2015 High

    Structural and biophysical analysis showed the DII loop acts as a gatekeeper controlling groove access and RON2-ligand selectivity, since its deletion permits high-affinity binding of a normally weak Eimeria RON2 peptide.

    Evidence ITC with a RON2 peptide panel, DII-loop deletion mutagenesis, and crystallography of the TgAMA1ΔDIIloop–EtRON2 complex

    PMID:25955165

    Open questions at the time
    • Physiological signal that repositions the DII loop unknown
    • Selectivity role during natural cross-species interactions untested
  21. 2015 High

    Double-protease knockouts established that both ROM4 and ROM5 cleave AMA1, with ROM5 accounting for residual cleavage in the absence of ROM4, refining the identity of the responsible rhomboids.

    Evidence Cre and CRISPR-Cas9 knockouts of ROM4 and ROM5 with Western blot of AMA1 cleavage products and invasion/motility assays in T. gondii

    PMID:25846828

    Open questions at the time
    • Relative contribution of each rhomboid during live invasion unresolved
    • Regulation of cleavage timing not defined here
  22. 2015 Medium

    Identifying AMA1 palmitoylation and showing its blockade enhances release of AMA1 and other invasion proteins from micronemes established a lipid-modification switch controlling AMA1 retention/secretion.

    Evidence Acyl-RAC chemical proteomics, palmitoylation-site mutagenesis, and microneme secretion assays in T. gondii

    PMID:26468752

    Open questions at the time
    • Palmitoyltransferase acting on AMA1 not identified
    • Coupling of palmitoylation cycle to secretion signal unresolved
  23. 2016 High

    Showing that RON2 D3 binding protects AMA1 from rhomboid cleavage and drives dephosphorylation of tail Ser527, with a phosphomimetic S527D allele impairing invasion, established outside-in signaling through the AMA1–RON2 junction that couples ligand engagement to cleavage protection and tail phosphoregulation of invasion.

    Evidence Rhomboid cleavage assays ± D3 peptide, MS phosphorylation analysis, and allele-replacement genetics (phosphomimetic/phospho-null) with invasion assays in T. gondii

    PMID:27624124

    Open questions at the time
    • Kinase/phosphatase acting on Ser527 not identified
    • Downstream effectors of the dephosphorylation signal undefined
  24. 2023 High

    Mapping stage-specific MJ composition showed bradyzoites invade using paralogs AMA2/AMA4 (AMA4 driving early cyst burden) rather than AMA1, and that AMA1–RON2 immunization protects against acute and chronic infection, extending AMA1 biology to chronic-stage invasion and vaccine potential.

    Evidence Bradyzoite IFA, AMA4 knockout with cyst-burden quantification, and mouse vaccination/challenge with AMA1-RON2 in T. gondii

    PMID:36693095

    Open questions at the time
    • Regulatory basis of stage-specific paralog usage unknown
    • Structural interface of bradyzoite AMA paralogs unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • The identity of the cytoplasmic effectors that transduce AMA1 tail dephosphorylation and cleaved-tail signaling into invasion outcomes, and the regulatory logic governing stage-specific AMA/RON paralog deployment, remain open.
  • Ser527 kinase and phosphatase unidentified
  • Force-transducing partner of the AMA1 cytoplasmic tail unknown
  • Mechanism selecting AMA1 vs. paralogs across life-cycle stages undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
FRUCTOSE-1,6-BISPHOSPHATE ALDOLASE (ALD; BINDS CYTOPLASMIC TAIL IN VITRO BUT DISPENSABLE FOR INVASION)ROM4 (RHOMBOID PROTEASE; CLEAVES AMA1 TM DOMAIN)ROM5 (RHOMBOID PROTEASE; RESIDUAL AMA1 CLEAVAGE)RON2 (RON2 C-TERMINAL D3/D4 REGION; DIRECT LIGAND IN HYDROPHOBIC GROOVE)RON4RON5RON8
Complex memberships
AMA2/AMA4-based bradyzoite moving junctionMoving junction complex (AMA1 with RON2/RON4/RON5/RON8)TgAMA1–TgRON2 core adhesion pairsporoAMA1–sporoRON2 sporozoite-stage complex

Evidence

Reading pass · 27 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 TgAMA1 is a type I transmembrane protein that localizes to micronemes in intracellular tachyzoites; upon release of mature tachyzoites, it redistributes predominantly to the apical end of the parasite surface. A ~54 kDa N-terminal cleavage product is constitutively shed into the medium by extracellular parasites. Antiserum against recombinant TgAMA1 blocked invasion by ~40%, and viable TgAMA1 knockout could not be produced, indicating an essential role in invasion. Immunofluorescence assay, immunoelectron microscopy, Triton X-114 phase partitioning, iodonaphthalene azide labeling, knockout attempt, invasion inhibition assay with antiserum Infection and immunity High 11083833
2000 TgAMA1 secretion from micronemes is dramatically enhanced in response to treatments that elevate intracellular calcium levels, consistent with calcium-regulated microneme secretion. Calcium ionophore/ethanol stimulation assay with immunofluorescence and Western blot monitoring of TgAMA1 release Molecular and biochemical parasitology Medium 11087913
2005 Conditional depletion of TgAMA1 severely impairs host cell invasion without affecting microneme secretion or initial host cell attachment, but inhibits rhoptry secretion, suggesting TgAMA1 acts after initial attachment to regulate rhoptry discharge. Regulatable promoter conditional knockout, invasion assay, microneme secretion assay, rhoptry secretion assay Molecular biology of the cell High 16000372
2005 TgAMA1 associates with a trio of proteins at the moving junction (MJ); at least one of these partners derives from the rhoptry neck (RON proteins), revealing an unexpected collaboration between microneme-derived AMA1 and rhoptry neck proteins at the MJ. Co-immunoprecipitation, immunoelectron microscopy localizing complex members to the MJ PLoS pathogens High 16244709
2005 TgAMA1 is shed from the surface of extracellular tachyzoites via intramembrane cleavage within the luminal half of its transmembrane domain by a rhomboid-like protease, unlike PfAMA1 which is shed by juxtamembrane cleavage. Complete TgAMA1 shedding does not accompany invasion, as intact protein is detected on newly invaded tachyzoites. Pulse-chase metabolic labeling, inhibitor studies, comparison with Drosophila rhomboid-1 cleavage assay, Western blot of surface protein during invasion Molecular microbiology Medium 16102004
2006 PfAMA1 co-immunoprecipitates with the Plasmodium falciparum homologue of TgRON4, a rhoptry neck protein, demonstrating that the AMA1–RON4 association is conserved between Toxoplasma and Plasmodium. Co-immunoprecipitation of native parasite proteins Eukaryotic cell Medium 16835460
2009 The rhoptry neck proteins RON2, RON4, RON5, and RON8 form a complex that is exported to the host cell membrane during invasion, where RON4/5/8 associate with the cytoplasmic face, while AMA1 is inserted into the parasite membrane. RON2 and AMA1 can interact in the absence of other MJ members, and all MJ proteins undergo proteolytic maturation during trafficking to their organelles. Metabolic labeling, immunoprecipitation, differential permeabilization with digitonin/saponin, antibody loading into host cell, immunofluorescence PLoS pathogens High 19247437
2009 An invasion-inhibitory anti-PfAMA1 monoclonal antibody (mAb 4G2) cannot bind PfAMA1 when PfAMA1 is in complex with its RON partners; a single conserved residue Tyr251 in PfAMA1, located in the hydrophobic groove, is required for complex formation, suggesting mAb 4G2 inhibits invasion by blocking PfAMA1–RON interaction. Antibody competition assay, site-directed mutagenesis of PfAMA1 Tyr251, co-immunoprecipitation PLoS pathogens Medium 19165323
2010 Conditional overexpression of a catalytically inactive TgROM4 (rhomboid 4) caused a profound block in parasite replication that was completely rescued by expression of the cleaved cytoplasmic tail of TgAMA1 or PfAMA1, revealing that intramembrane cleavage of AMA1 by ROM4 and subsequent release of its cytoplasmic tail triggers the parasite's switch from an invasive to a replicative mode. Conditional overexpression of dominant-negative TgROM4, rescue with AMA1 cytoplasmic tail expression constructs, replication assay Science (New York, N.Y.) High 21205639 41379978
2010 The 2.0 Å X-ray crystal structure of full-length TgAMA1 ectodomain (domains I, II, III) reveals a central hydrophobic groove framed by conserved residues Trp353, Trp354, and Tyr230 from the DII loop, proposed as the RON2 binding site. The DII loop is 14 residues shorter than in Plasmodium AMA1 homologs and restricts access to the groove. X-ray crystallography at 2.0 Å resolution The Journal of biological chemistry High 20304917
2010 TgROM4 processes surface adhesins MIC2, AMA1, and MIC3; its suppression decreases MIC2 release into the supernatant, increases surface expression of adhesins, disrupts the normal apical-posterior gradient needed for efficient gliding motility, and severely impairs invasion. Parasites lacking TgROM4 bind host cells better but fail to apically orient and cannot generate a moving junction. Conditional knockout (tetracycline-regulatable), surface adhesin immunofluorescence, invasion assay, motility assay PLoS pathogens High 20421941
2011 The C-terminus of TgRON2 contains two short segments (D3 and D4) flanking a hydrophobic stretch that independently bind the ectodomain of TgAMA1. Pre-incubation with D3-GST fusion dramatically reduces invasion but does not prevent rhoptry bulb protein injection, demonstrating that TgRON2's C-terminal region forms the bridge between TgAMA1 and the host cell-associated MJ complex but is not required for rhoptry effector delivery. Immunofluorescence localization of TgRON2 to MJ, pull-down assays with recombinant RON2 fragments, invasion inhibition assay with D3-GST, evacuole assay PLoS pathogens High 21347354
2011 RON2 is inserted as an integral membrane protein in the host cell, and the region of RON2 that binds AMA1 was defined using multiple interaction assays. Recombinant RON2 protein inhibits invasion of both T. gondii and P. falciparum, demonstrating that the RON2–AMA1 interaction is critical for host cell entry by apicomplexan parasites. Multiple interaction assays with native and recombinant proteins (pull-down, ELISA-based binding), invasion inhibition with recombinant proteins, differential permeabilization to show RON2 membrane topology PLoS pathogens High 21347343
2011 The 1.95 Å crystal structure of TgAMA1 complexed with a TgRON2 peptide reveals a stepwise assembly mechanism producing an extensive buried surface area, providing structural explanation for how the MJ complex resists mechanical forces during invasion. X-ray crystallography at 1.95 Å resolution of TgAMA1–RON2 peptide complex Science (New York, N.Y.) High 21778402
2011 In T. gondii tachyzoites, AMA1 is dispensable for normal RON4 ring formation and functional tight junction assembly but enhances tachyzoite apposition to the host cell and increases internalization frequency. In P. berghei sporozoites, only RON4 (not AMA1) is required for hepatocyte invasion, demonstrating RON4 can act independently of AMA1. Conditional genetic knockdown/knockout of AMA1 and RON4 in T. gondii and P. berghei, invasion assays, immunofluorescence for RON4 ring formation Cell host & microbe High 22177563
2012 Intramembrane proteolysis of TgAMA1 facilitates host cell invasion: parasites expressing an uncleavable TgAMA1(AG/FF+GG/FF) mutant show a growth defect due to impaired invasion, not replication. This refutes the model in which intramembrane cleavage of TgAMA1 regulates replication and instead demonstrates its role is invasion-specific. Heterologous cleavage assay to characterize transmembrane domain determinants, mutagenesis of TgAMA1 TM domain, complementation of conditional knockout with cleavage-resistant alleles (transgenic and knock-in), growth/invasion assays Proceedings of the National Academy of Sciences of the United States of America High 22523242
2013 Plasmodium merozoites and Toxoplasma tachyzoites lacking AMA1 are impaired in host cell attachment but retain normal host cell penetration through the moving junction, indicating AMA1 is a dispensable adhesin rather than an essential invasin for junction-mediated entry. Genetic deletion of AMA1 in Plasmodium sporozoites, merozoites, and T. gondii tachyzoites; invasion assays distinguishing attachment from penetration Nature communications High 24108241
2013 Toxoplasma sporozoites express paralogues sporoAMA1 and sporoRON2 that localize to the apical region; they interact specifically and exclusively with each other (not with generic AMA1/RON2). Structural studies show sporoRON2 domain 3 binding to sporoAMA1 domains I/II causes major conformational changes allosterically in domain III. Pre-treatment of sporozoites with sporoRON2 domain 3 peptide blocks sporozoite invasion without affecting tachyzoites, and vice versa for generic RON2 domain 3. Localization by immunofluorescence, pull-down/binding assays for interaction specificity, X-ray crystallography of sporoAMA1–sporoRON2 complex, invasion inhibition assays PloS one High 23940612
2014 Disruption of the AMA1 gene in T. gondii results in upregulation of AMA1 and RON2 homologues (paralogs) that cooperate to support residual invasion, demonstrating molecular plasticity in MJ architecture. AMA1 interacts with RON2 to maintain MJ structural integrity and is required for parasite internalization. Reverse genetics (AMA1 gene disruption), conditional complementation, immunofluorescence, invasion assays, Western blot for paralog upregulation Nature communications High 24934579
2014 ALD (fructose-1,6-bisphosphate aldolase) binds the TgAMA1 cytoplasmic tail in vitro, but TgAMA1 cytoplasmic tail mutations that disrupt ALD binding in vitro show no correlation with host cell invasion in vivo. ALD knockout parasites show normal gliding and invasion in glucose-free medium, indicating ALD is not functionally essential for the adhesin-motor linkage and TgAMA1–aldolase interaction is dispensable for invasion. In vitro binding assay (cytoplasmic tail–aldolase), site-directed mutagenesis, ALD conditional depletion/knockout, invasion assay, gliding motility assay Proceedings of the National Academy of Sciences of the United States of America High 24550496
2015 TgAMA1 is palmitoylated; blocking AMA1 palmitoylation enhances the release of AMA1 and other invasion-related proteins from apical secretory organelles (micronemes), suggesting palmitoylation regulates AMA1 retention/secretion from micronemes. Chemical proteomics (acyl-RAC capture for palmitoylated proteins), palmitoylation site mutagenesis, microneme secretion assay Cell host & microbe Medium 26468752
2015 The DII loop of TgAMA1 acts as a structural gatekeeper governing ligand binding selectivity in the hydrophobic groove: deletion of the mobile DII loop portion (TgAMA1ΔDIIloop) allows high-affinity binding of an Eimeria tenella RON2 peptide (EtRON2) that normally binds with only weak affinity, while the crystal structure of TgAMA1ΔDIIloop–EtRON2 reveals spatially distinct anchor points in the AMA1 groove. Isothermal titration calorimetry with RON2 peptide panel, engineering of DII loop deletion mutant, X-ray crystallography of complex PloS one High 25955165
2015 ROM4 and ROM5 both contribute to intramembrane cleavage (MPP1 activity) of AMA1 in T. gondii: ROM4 KO reduces but does not abolish AMA1 cleavage, while ROM5 accounts for residual AMA1 cleavage in the absence of ROM4 and can also cleave other AMA family members. Cre-recombinase and CRISPR-Cas9 knockouts of ROM4 and ROM5, Western blot for AMA1 cleavage products, invasion and motility assays Molecular microbiology High 25846828
2016 Binding of TgRON2 D3 peptide to TgAMA1 protects TgAMA1 from rhomboid-mediated cleavage, thereby stabilizing the AMA1-host cell interaction at the moving junction. TgRON2 D3 binding also reduces phosphorylation of Ser527 on the TgAMA1 cytoplasmic tail; parasites expressing a phosphomimetic S527D TgAMA1 allele show an invasion defect, indicating outside-in signaling through the AMA1–RON2 interaction modulates invasion. Rhomboid cleavage assay with and without D3 peptide, phosphorylation analysis by mass spectrometry, transgenic complementation with phosphomimetic and phospho-null AMA1 alleles, invasion assays with hypercleavable AMA1 variants mBio High 27624124
2011 Conserved aliphatic residues (valine at position +3 of proM2AP, leucine at position +1 of proMIC5) in MIC propeptides are required for microneme targeting; the AMA1 propeptide contains valine/leucine near its N-terminus and mutagenesis of these residues impairs trafficking of AMA1 to micronemes. N-terminal deletion and mutagenesis of propeptide domains, GFP reporter trafficking assays, cross-species propeptide swap experiments Traffic (Copenhagen, Denmark) Medium 21438967
2010 TgAMA1 lacks targeting information within its C-terminal cytoplasmic domain for microneme trafficking; it can bind aldolase in vitro, and residues responsible for aldolase binding are essential for TgAMA1 function during invasion (at the time of this study, before the later genetic evidence refuted aldolase's functional role). C-terminal domain truncation/mutation, trafficking assays, aldolase binding assay in vitro, invasion complementation assay Molecular microbiology Low 20545864
2023 Bradyzoites invade host cells in an MJ-dependent fashion using AMA2 and AMA4 (paralogs of AMA1) rather than AMA1 itself. AMA4 plays a key role in cyst burden during chronic infection onset while being dispensable for the acute phase. AMA1-RON2 immunization provides strong protection against both acute and chronic infection. Immunofluorescence localization in bradyzoites, genetic knockout of AMA4, cyst burden quantification, mouse vaccination/challenge experiments Proceedings of the National Academy of Sciences of the United States of America High 36693095

Source papers

Stage 0 corpus · 68 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Identification of the moving junction complex of Toxoplasma gondii: a collaboration between distinct secretory organelles. PLoS pathogens 327 16244709
2011 The RON2-AMA1 interaction is a critical step in moving junction-dependent invasion by apicomplexan parasites. PLoS pathogens 268 21347343
2009 Export of a Toxoplasma gondii rhoptry neck protein complex at the host cell membrane to form the moving junction during invasion. PLoS pathogens 238 19247437
2011 The moving junction of apicomplexan parasites: a key structure for invasion. Cellular microbiology 227 21535344
2005 Conditional expression of Toxoplasma gondii apical membrane antigen-1 (TgAMA1) demonstrates that TgAMA1 plays a critical role in host cell invasion. Molecular biology of the cell 196 16000372
2011 Host cell invasion by apicomplexan parasites: insights from the co-structure of AMA1 with a RON2 peptide. Science (New York, N.Y.) 155 21778402
2012 Transcriptomic analysis of toxoplasma development reveals many novel functions and structures specific to sporozoites and oocysts. PloS one 140 22347997
2009 An inhibitory antibody blocks interactions between components of the malarial invasion machinery. PLoS pathogens 139 19165323
2000 Toxoplasma gondii homologue of plasmodium apical membrane antigen 1 is involved in invasion of host cells. Infection and immunity 134 11083833
2014 Plasticity and redundancy among AMA-RON pairs ensure host cell entry of Toxoplasma parasites. Nature communications 128 24934579
2006 Plasmodium falciparum AMA1 binds a rhoptry neck protein homologous to TgRON4, a component of the moving junction in Toxoplasma gondii. Eukaryotic cell 127 16835460
2013 Apical membrane antigen 1 mediates apicomplexan parasite attachment but is dispensable for host cell invasion. Nature communications 113 24108241
2011 The C-terminus of Toxoplasma RON2 provides the crucial link between AMA1 and the host-associated invasion complex. PLoS pathogens 105 21347354
2010 Rhomboid 4 (ROM4) affects the processing of surface adhesins and facilitates host cell invasion by Toxoplasma gondii. PLoS pathogens 101 20421941
2014 Toxoplasma aldolase is required for metabolism but dispensable for host-cell invasion. Proceedings of the National Academy of Sciences of the United States of America 100 24550496
2011 Independent roles of apical membrane antigen 1 and rhoptry neck proteins during host cell invasion by apicomplexa. Cell host & microbe 100 22177563
2011 Genetic mapping identifies novel highly protective antigens for an apicomplexan parasite. PLoS pathogens 96 21347348
2000 The Toxoplasma homolog of Plasmodium apical membrane antigen-1 (AMA-1) is a microneme protein secreted in response to elevated intracellular calcium levels. Molecular and biochemical parasitology 92 11087913
2014 The toxoplasma Acto-MyoA motor complex is important but not essential for gliding motility and host cell invasion. PloS one 91 24632839
2010 Intramembrane cleavage of AMA1 triggers Toxoplasma to switch from an invasive to a replicative mode. Science (New York, N.Y.) 82 21205639
2005 Distinct mechanisms govern proteolytic shedding of a key invasion protein in apicomplexan pathogens. Molecular microbiology 78 16102004
2011 Focus on the ringleader: the role of AMA1 in apicomplexan invasion and replication. Trends in parasitology 71 21659001
2015 Global Analysis of Palmitoylated Proteins in Toxoplasma gondii. Cell host & microbe 66 26468752
2010 Toxoplasma gondii transmembrane microneme proteins and their modular design. Molecular microbiology 60 20545864
2007 Toxoplasma gondii: DNA vaccination with genes encoding antigens MIC2, M2AP, AMA1 and BAG1 and evaluation of their immunogenic potential. Experimental parasitology 58 17379212
2006 Apical membrane antigen 1 is a cross-reactive antigen between Neospora caninum and Toxoplasma gondii, and the anti-NcAMA1 antibody inhibits host cell invasion by both parasites. Molecular and biochemical parasitology 58 17156863
2011 The moving junction protein RON8 facilitates firm attachment and host cell invasion in Toxoplasma gondii. PLoS pathogens 52 21423671
2014 RON5 is critical for organization and function of the Toxoplasma moving junction complex. PLoS pathogens 47 24651769
2013 Toxoplasma gondii sporozoites invade host cells using two novel paralogues of RON2 and AMA1. PloS one 46 23940612
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2008 Microneme rhomboid protease TgROM1 is required for efficient intracellular growth of Toxoplasma gondii. Eukaryotic cell 41 18310358
2015 Distinct contribution of Toxoplasma gondii rhomboid proteases 4 and 5 to micronemal protein protease 1 activity during invasion. Molecular microbiology 39 25846828
2018 Characterization of a multi-epitope peptide with selective MHC-binding capabilities encapsulated in PLGA nanoparticles as a novel vaccine candidate against Toxoplasma gondii infection. Vaccine 38 30181047
2008 Identification and characterization of the Plasmodium yoelii PyP140/RON4 protein, an orthologue of Toxoplasma gondii RON4, whose cysteine-rich domain does not protect against lethal parasite challenge infection. Infection and immunity 32 18710865
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2011 Forward targeting of Toxoplasma gondii proproteins to the micronemes involves conserved aliphatic amino acids. Traffic (Copenhagen, Denmark) 29 21438967
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2014 Insights and controversies into the role of the key apicomplexan invasion ligand, Apical Membrane Antigen 1. International journal for parasitology 28 25157917
2019 The first study on the usefulness of recombinant tetravalent chimeric proteins containing fragments of SAG2, GRA1, ROP1 and AMA1 antigens in the detection of specific anti-Toxoplasma gondii antibodies in mouse and human sera. PloS one 27 31170254
2017 Protection via a ROM4 DNA vaccine and peptide against Toxoplasma gondii in BALB/c mice. BMC infectious diseases 25 28077075
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2015 AMA1-deficient Toxoplasma gondii parasites transiently colonize mice and trigger an innate immune response that leads to long-lasting protective immunity. Infection and immunity 21 25847964
2012 Protective effect of a prime-boost strategy with plasmid DNA followed by recombinant adenovirus expressing TgAMA1 as vaccines against Toxoplasma gondii infection in mice. Parasitology international 21 22537971
2016 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. mBio 20 27624124
2020 Toxoplasma gondii Recombinant antigen AMA1: Diagnostic Utility of Protein Fragments for the Detection of IgG and IgM Antibodies. Pathogens (Basel, Switzerland) 18 31948063
2020 Virus-like particle vaccine displaying Toxoplasma gondii apical membrane antigen 1 induces protection against T. gondii ME49 infection in mice. Microbial pathogenesis 16 32097746
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2015 An Extended Surface Loop on Toxoplasma gondii Apical Membrane Antigen 1 (AMA1) Governs Ligand Binding Selectivity. PloS one 16 25955165
2013 Comparative characterization of microRNA profiles of different genotypes of Toxoplasma gondii. Parasitology 13 23714365
2019 Toxoplasma gondii Tetravalent Chimeric Proteins as Novel Antigens for Detection of Specific Immunoglobulin G in Sera of Small Ruminants. Animals : an open access journal from MDPI 11 31847285
2016 Multilevel Precision-Based Rational Design of Chemical Inhibitors Targeting the Hydrophobic Cleft of Toxoplasma gondii Apical Membrane Antigen 1 (AMA1). Genomics & informatics 11 27445648
2024 The Development of Toxoplasma gondii Recombinant Trivalent Chimeric Proteins as an Alternative to Toxoplasma Lysate Antigen (TLA) in Enzyme-Linked Immunosorbent Assay (ELISA) for the Detection of Immunoglobulin G (IgG) in Small Ruminants. International journal of molecular sciences 8 38673969
2022 Recombinant AMA1 Virus-like Particle Antigen for Serodiagnosis of Toxoplasma gondii Infection. Biomedicines 7 36359332
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2023 Screening of apical membrane antigen-1 (AMA1), dense granule protein-7 (GRA7) and rhoptry protein-16 (ROP16) antigens for a potential vaccine candidate against Toxoplasma gondii for chickens. Vaccine: X 5 37519774
2023 Establishment and application of an iELISA detection method for measuring apical membrane antigen 1 (AMA1) antibodies of Toxoplasma gondii in cats. BMC veterinary research 5 37924072
2022 Immunological evaluation of a novel multi-antigenic DNA vaccine encoding SAG1, SAG3, MIC4, GRA5, GRA7, AMA1and BAG1 against Toxoplasma gondii in BALB/c mice. Experimental parasitology 5 36403800
2018 Construction of an Adenovirus Vaccine Expressing the Cross-reactive Antigen AMA1 for Neospora caninum and Toxoplasma gondii and Its Immune Response in an Animal Model. Iranian journal of parasitology 5 30069207
2025 Vaccinia virus expressing MIC8 and AMA1 provides protection against Toxoplasma gondii ME49 infection. Parasites, hosts and diseases 3 41311041
2025 Recombinant vaccinia virus expressing MIC8, AMA1, or RON4 induce protection against Toxoplasma gondii ME49 strain infection. Acta tropica 3 40886931
2025 In Silico-Based Investigation of the Immunogenicity and Biochemical Attributes of Toxoplasma gondii Apical Membrane Antigen 1 (TgAMA1). Journal of parasitology research 3 40255910
2025 Efficacy of Heterologous Vaccination Using Virus-Like Particles and Vaccinia Virus Containing MIC8 and AMA1 Proteins of Toxoplasma gondii. Vaccines 2 40872947
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2026 Resveratrol modulates inflammatory gene expression in Toxoplasma gondii-infected microglia and shows structurally plausible interactions with parasite virulence proteins. Microbial pathogenesis 0 42142636
2025 Erratum for the Report "Intramembrane cleavage of AMA1 triggers Toxoplasma to switch from an invasive to a replicative mode" by J. M. Santos et al. Science (New York, N.Y.) 0 41379978
2025 Functionality of Toxoplasma gondii antibodies in a population of Beninese pregnant women exposed to malaria. Scientific reports 0 40102442