Intramembrane proteolysis mediates shedding of a key adhesin during erythrocyte invasion by the malaria parasite

O’Donnell, Rachel; Hackett, Fiona; Howell, Steven; Treeck, Moritz; Struck, Nicole S.; Krnajski, Zita; Withers‐Martinez, Chrislaine; Gilberger, Tim‐Wolf; Blackman, Michael J.

doi:10.1083/jcb.200604136

Cited by 161 publications

(154 citation statements)

References 48 publications

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“…2 A and B, respectively). This is in contrast with a report that assigned PfROM1 to be exclusively in micronemes (13). The construct used in the previous P. falciparum study (13) lacked 76 aa encoded by the first two exons of PfROM1 that included the first transmembrane domain of PfROM1.…”

Section: Distinct Localization Pattern Of Pfrom1 Identifies the Mononcontrasting

confidence: 47%

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Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

Singh

Plassmeyer

Gaur

et al. 2007

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

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Compartmentalization of proteins into subcellular organelles in eukaryotic cells is a fundamental mechanism of regulating complex cellular functions. Many proteins of Plasmodium falciparum merozoites involved in invasion are compartmentalized into apical organelles. We have identified a new merozoite organelle that contains P. falciparum rhomboid-1 (PfROM1), a protease that cleaves the transmembrane regions of proteins involved in invasion. By immunoconfocal microscopy, PfROM1 was localized to a single, thread-like structure on one side of the merozoites that appears to be in close proximity to the subpellicular microtubules. PfROM1 was not found associated with micronemes, rhoptries, or dense granules, the three identified secretory organelles of invasion. Release of merozoites from schizonts resulted in the movement of PfROM1 from the lateral asymmetric localization to the merozoite apical pole and the posterior pole. We have named this single thread-like organelle in merozoites, the mononeme. malaria A picomplexa are named for a set of secretory organelles (rhoptries, micronemes, and dense granules) found at the apical end of these parasites, the end that invades cells in the vertebrate host (1). These organelles were first identified by their distinct morphological appearances in transmission electron microscopy (2-4). Many parasite proteins required for invasion of erythrocytes are segregated into the micronemes (5, 6). For example, Plasmodium falciparum apical membrane antigen 1 (AMA1) is held in the micronemes in merozoites inside of erythrocytes. Release from the erythrocyte triggers the movement of AMA1 to the cell surface where it functions in invasion (7,8). Similarly, rhoptries sequester a different set of proteins and their contents are released onto the erythrocyte surface (4, 9), presumably to break the local cytoskeleton and to initiate formation of the parasitophorous vacuole. Taken together, these observations provide evidence for compartmentalization of parasite proteins into distinct organelles with related functions in invasion. Presumably, such compartmentalization provides a mechanism for orchestrating the timing of delivery or activity of the proteins during the complex process of invasion.Apicomplexan rhomboid proteases have been implicated to play an important role in host cell invasion (10, 11). PfROM1 substrates have been identified in P. falciparum by using a mammalian cell-based proteolytic assay (12) that identified various micronemal proteins as potential substrates including AMA1. Because AMA1 has been implicated as essential for invasion, separation of PfROM1 from this substrate within the parasite may be important to prevent premature cleavage. Studies defining the spatiotemporal distribution of PfROM1 in P. falciparum merozoites are, therefore, likely to contribute to a clearer understanding of its role in erythrocyte invasion. Expression of hemagglutinin (HA)-tagged P. falciparum rhomboid-1 (PfROM1) localizes it to a new subcellular compartment distinct from other known meroz...

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Section: Distinct Localization Pattern Of Pfrom1 Identifies the Mononcontrasting

confidence: 47%

“…PfROM1 was also thought to be located in micronemes (13), based on data localizing a PfROM1 construct that was missing two 5Ј exons which encode one of the transmembrane domains of PfROM1 (SI Figs. 7, 8, and 10).…”

Section: Discussionmentioning

confidence: 99%

Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

Singh

Plassmeyer

Gaur

et al. 2007

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

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“…Surface labeling of COS-7 cells was carried out using unfixed preparations as previously described (55). Slides were mounted in Citifluor (Citifluor Ltd., Canterbury, UK).…”

Section: Methodsmentioning

confidence: 99%

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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102

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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“…Toxoplasma encodes six rhomboids (10), two of which have been functionally dissected: ROM1 is expressed in the micronemes but does not play a crucial role in invasion (11,12); ROM4 localizes to the plasma membrane (13,14) and cleaves MIC2, AMA1, and MIC8 (15). Plasmodium falciparum ROM4 sheds the micronemal erythrocyte-binding protein EBA175 (16) and possibly other adhesins (17). After invasion, the parasite initiates replication within a parasitophorous vacuole.…”

Section: H Ost Cell Invasion By Toxoplasma Andmentioning

confidence: 99%

Intramembrane Cleavage of AMA1 Triggers Toxoplasma to Switch from an Invasive to a Replicative Mode

Santos

Ferguson

Blackman

et al. 2011

Science

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Intramembrane proteolysis mediates shedding of a key adhesin during erythrocyte invasion by the malaria parasite

Cited by 161 publications

References 48 publications

Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease

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

Intramembrane Cleavage of AMA1 Triggers Toxoplasma to Switch from an Invasive to a Replicative Mode

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