Plasmodium falciparum Antigen 332 Is a Resident Peripheral Membrane Protein of Maurer's Clefts

Sandra Nilsson,Qijun Chen,Mats Wahlgren,Davide Angeletti,Kirsten Moll,Tobias Spielmann

doi:10.1371/journal.pone.0046980

Sandra Nilsson, Qijun Chen + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0046980

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Abstract

During the intraerythrocytic development of Plasmodium falciparum, the malaria parasite remodels the host cell cytosol by inducing membranous structures termed Maurer's clefts and inserting parasite proteins into the red blood cell cytoskeleton and plasma membrane. Pf332 is the largest known asexual malaria antigen that is exported into the red blood cell cytosol where it associates with Maurer's clefts. In the current work, we have utilized a set of different biochemical assays to analyze the solubility of the endogenous Pf332 molecule during its trafficking from the endoplasmic reticulum within the parasite to the host cell cytosol. Solubilization studies demonstrate that Pf332 is synthesized and trafficked within the parasite as a peripheral membrane protein, which after export into the host cell cytosol associates with the cytoplasmic side of Maurer's clefts in a peripheral manner. By immunofluorescence microscopy and flow cytometry, we show that Pf332 persists in close association with Maurer's clefts throughout trophozoite maturation and schizogony, and does not become exposed at the host cell surface. Our data also indicate that Pf332 interacts with the host cell cytoskeleton, but only in very mature parasite stages. Thus, the present study describes Pf332 as a resident peripheral membrane protein of Maurer's clefts and suggests that the antigen participates in host cytoskeleton modifications at completion of the intraerythrocytic developmental cycle.

Highlights

Plasmodium falciparum parasites cause the most severe form of malaria with over 225 million clinical cases leading to approximately 800 000 deaths every year [1]
These host cell modifications are mediated by a subset of parasite-derived proteins that are exported across the parasitophorous vacuole (PV) membrane (PVM) into the red blood cells (RBC) cytosol where they interact with the host cell cytoskeleton or are exposed at the RBC surface [4,5]
The Pf332 protein can first be detected within the parasite at 20–24 h post invasion (p.i.), after which it translocates across the PVM into the host cell cytosol [30,31]

Summary

Introduction

Plasmodium falciparum parasites cause the most severe form of malaria with over 225 million clinical cases leading to approximately 800 000 deaths every year [1]. These host cell modifications are mediated by a subset of parasite-derived proteins that are exported across the PV membrane (PVM) into the RBC cytosol where they interact with the host cell cytoskeleton or are exposed at the RBC surface [4,5]. Cytoskeleton binding proteins such as knob-associated histidinerich protein (KAHRP) [6,7], P. falciparum erythrocyte membrane protein 3 (PfEMP3) [8], mature parasite-infected erythrocyte surface antigen (MESA) [9,10], and ring parasite-infected erythrocyte surface antigen (RESA) [11,12] are known to be responsible for the increased rigidity of pRBC, whereas the virulence and surface associated P. falciparum erythrocyte membrane protein 1 (PfEMP1) is a known mediator of the adhesive phenotype [13,14,15]. Gaining more insight into host cell modifications exerted by P. falciparum is essential for increasing our understanding of malaria pathogenesis, and may lead to novel intervention strategies for controlling malaria

Results

Discussion

Experimental Procedures