Structural comparison of apical membrane antigen 1 orthologues and paralogues in apicomplexan parasites

Chesne-Seck, Marie-Laure; Pizarro, J.C.; Normand, B. Vulliez-Le; Collins, Christine R.; Blackman, Michael J.; Faber, Bart W.; Remarque, Edmond J.; Kocken, Clemens H. M.; Thomas, Alan W.; Bentley, G.A.

doi:10.1016/j.molbiopara.2005.07.007

Cited by 86 publications

(92 citation statements)

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“…In contrast, the second AMA clade consists of AMA4 from Toxoplasma and its orthologs in Eimeria and Neospora. Intriguingly, although the functionally important Plasmodium MAEBLs (18-20) have been described with different relationships to AMA1 (13,22), our analysis indicates that MAEBL is most closely related to AMA4 (Fig. 1, Left).…”

Section: Resultsmentioning

confidence: 56%

“…Intriguingly, recent studies have shown that the AMA1-RON2 complex is an attractive target for therapeutic intervention (9)(10)(11)(12). The importance of the AMA1-RON2 pairing is also reflected in the observation that many apicomplexan parasites encode functional paralogs that are generally expressed in a stage-specific manner (13)(14)(15). We recently showed that, in addition to AMA1 and RON2, T. gondii harbors three additional AMA paralogs and two additional RON2 paralogs (14,15): TgAMA2 forms a functional invasion complex with TgRON2 (15), TgAMA3 (also annotated as SporoAMA1) selectively coordinates TgRON2 L2 (14), and TgAMA4 binds TgRON2 L1 (15).…”

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confidence: 99%

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Dissecting the interface between apicomplexan parasite and host cell: Insights from a divergent AMA–RON2 pair

Parker

Penarete-Vargas

Hamilton

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Plasmodium falciparum and Toxoplasma gondii are widely studied parasites in phylum Apicomplexa and the etiological agents of severe human malaria and toxoplasmosis, respectively. These intracellular pathogens have evolved a sophisticated invasion strategy that relies on delivery of proteins into the host cell, where parasite-derived rhoptry neck protein 2 (RON2) family members localize to the host outer membrane and serve as ligands for apical membrane antigen (AMA) family surface proteins displayed on the parasite. Recently, we showed that T. gondii harbors a novel AMA designated as TgAMA4 that shows extreme sequence divergence from all characterized AMA family members. Here we show that sporozoite-expressed TgAMA4 clusters in a distinct phylogenetic clade with Plasmodium merozoite apical erythrocyte-binding ligand (MAEBL) proteins and forms a high-affinity, functional complex with its coevolved partner, TgRON2 L1 . High-resolution crystal structures of TgAMA4 in the apo and TgRON2 L1 -bound forms complemented with alanine scanning mutagenesis data reveal an unexpected architecture and assembly mechanism relative to previously characterized AMA-RON2 complexes. Principally, TgAMA4 lacks both a deep surface groove and a key surface loop that have been established to govern RON2 ligand binding selectivity in other AMAs. Our study reveals a previously underappreciated level of molecular diversity at the parasite-host-cell interface and offers intriguing insight into the adaptation strategies underlying sporozoite invasion. Moreover, our data offer the potential for improved design of neutralizing therapeutics targeting a broad range of AMA-RON2 pairs and apicomplexan invasive stages.Apicomplexa | Toxoplasma gondii | invasion | moving junction | X-ray crystallography P hylum Apicomplexa comprises >5,000 parasitic protozoan species, many of which cause devastating diseases on a global scale. Two of the most prevalent species are Toxoplasma gondii and Plasmodium falciparum, the causative agents of toxoplasmosis and severe human malaria, respectively (1, 2). The obligate intracellular apicomplexan parasites lead complex and diverse lifestyles that require invasion of many different cell types. Despite this diversity of target host cells, most apicomplexans maintain a generally conserved mechanism for active invasion (3). The parasite initially glides over the surface of a host cell and then reorients to place its apical end in close contact to the hostcell membrane. After this initial attachment, a circumferential ring of adhesion (termed the moving or tight junction) is formed, through which the parasite actively propels itself while concurrently depressing the host-cell membrane to create a nascent protective vacuole (4).Formation of the moving junction relies on a pair of highly conserved parasite proteins: rhoptry neck protein 2 (RON2) and apical membrane antigen 1 (AMA1). Initially, parasites discharge RON2 into the host cell membrane where an extracellular portion (domain 3; D3) serves as a ligand for AMA1 displa...

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Section: Resultsmentioning

confidence: 56%

mentioning

confidence: 99%

Dissecting the interface between apicomplexan parasite and host cell: Insights from a divergent AMA–RON2 pair

Parker

Penarete-Vargas

Hamilton

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The domain II loop lies against the non-polymorphic face of the molecule (45). Although two residues of this loop (Lys 357 and Phe 367 ) form part of a hydrophobic trough in domain I that is surrounded by polymorphic residues, the epitope recognized by 4G2 lies some distance from these polymorphic residues.…”

Section: Discussionmentioning

confidence: 99%

“…PfAMA1 exhibits significant polymorphism, and polymorphic residues have been identified at 52 different positions within the ectodomain (45). In most cases these are dimorphic, being represented by one or the other of two alternative residues, but more extensive diversity is evident at a number of positions.…”

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Fine Mapping of an Epitope Recognized by an Invasion-inhibitory Monoclonal Antibody on the Malaria Vaccine Candidate Apical Membrane Antigen 1

Collins¹,

Withers‐Martinez²,

Bentley

et al. 2007

Journal of Biological Chemistry

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103

115

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Antibodies that inhibit red blood cell invasion by the Plasmodium merozoite block the erythrocytic cycle responsible for clinical malaria. The invasion-inhibitory monoclonal antibody (mAb) 4G2 recognizes a conserved epitope in the ectodomain of the essential Plasmodium falciparum microneme protein and vaccine candidate, apical membrane antigen 1 (PfAMA1). Here we demonstrate that purified Fab fragments of 4G2 inhibit invasion markedly more efficiently than the intact mAb, suggesting that the invasion-inhibitory activity of this mAb is not due solely to steric effects and that the epitope lies within a functionally critical region of the molecule. We have taken advantage of a synthetic gene encoding a modified form of PfAMA1, and existing x-ray crystal structure data, to fully characterize this epitope. We first validate the gene by demonstrating that it fully complements the function of the authentic gene in P. falciparum. We then use it to identify a group of residues within the previously described domain II loop of PfAMA1 that are critical for recognition by mAb 4G2 and demonstrate that the epitope lies exclusively within this loop with no contributions from residues in other domains of the molecule. This is the first complete characterization of a conserved invasion-inhibitory epitope on PfAMA1. Our results will aid in the design of subunit vaccines designed to generate a broadly effective, focused anti-PfAMA1 protective immune response and may help elucidate the function of PfAMA1.Over half of the world's population is exposed to malaria (1). Until recently, the disease was controlled in or eradicated from a number of areas. However, the emergence of insecticide-resistant mosquito vectors and multidrug-resistant forms of the causative agent has contributed to resurgences of the disease, which in some cases have resulted in near catastrophic epidemics. As a result malaria remains a global problem, affecting many of the poorest nations and representing a serious threat to travelers. The development and implementation of effective new drugs and a vaccine is of paramount importance.Clinical malaria results from replication of protozoan parasites of the genus Plasmodium in circulating erythrocytes. Like most apicomplexan pathogens, the malaria merozoite invades its host cell in a multistep process initiated by reversible binding to receptors on the erythrocyte surface, followed by high affinity attachment via the apical end of the merozoite, and finally entry into a parasitophorous vacuole. Invasion is facilitated by the discharge of apical secretory organelles called micronemes and rhoptries. The type I integral membrane microneme protein apical membrane antigen 1 (AMA1) 2 is widely regarded as a leading candidate for inclusion in a malaria vaccine (2-5). Identified initially in the simian malaria species Plasmodium knowlesi as a target of a monoclonal antibody (mAb) that prevented erythrocyte invasion (6), homologues of AMA1 have been identified in all species of Plasmodium (6 -13) and in all other apicomplexa...

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Solution NMR characterization of apical membrane antigen 1 and small molecule interactions as a basis for designing new antimalarials

Krishnarjuna

Lim

Devine

et al. 2016

J of Molecular Recognition

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Plasmodium falciparum apical membrane antigen 1 (PfAMA1) plays an important role in the invasion by merozoites of human red blood cells during a malaria infection. A key region of PfAMA1 is a conserved hydrophobic cleft formed by 12 hydrophobic residues. As anti-apical membrane antigen 1 antibodies and other inhibitory molecules that target this hydrophobic cleft are able to block the invasion process, PfAMA1 is an attractive target for the development of strain-transcending antimalarial agents. As solution nuclear magnetic resonance spectroscopy is a valuable technique for the rapid characterization of protein-ligand interactions, we have determined the sequence-specific backbone assignments for PfAMA1 from two P. falciparum strains, FVO and 3D7. Both selective labelling and unlabelling strategies were used to complement triple-resonance experiments in order to facilitate the assignment process. We have then used these assignments for mapping the binding sites for small molecules, including benzimidazoles, pyrazoles and 2-aminothiazoles, which were selected on the basis of their affinities measured from surface plasmon resonance binding experiments. Among the compounds tested, benzimidazoles showed binding to a similar region on both FVO and 3D7 PfAMA1, suggesting that these compounds are promising scaffolds for the development of novel PfAMA1 inhibitors. Copyright © 2016 John Wiley & Sons, Ltd.

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Structural comparison of apical membrane antigen 1 orthologues and paralogues in apicomplexan parasites

Cited by 86 publications

References 49 publications

Dissecting the interface between apicomplexan parasite and host cell: Insights from a divergent AMA–RON2 pair

Dissecting the interface between apicomplexan parasite and host cell: Insights from a divergent AMA–RON2 pair

Fine Mapping of an Epitope Recognized by an Invasion-inhibitory Monoclonal Antibody on the Malaria Vaccine Candidate Apical Membrane Antigen 1

Solution NMR characterization of apical membrane antigen 1 and small molecule interactions as a basis for designing new antimalarials

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