Endoplasmic Reticulum PI(3)P Lipid Binding Targets Malaria Proteins to the Host Cell

Center for Rare and Neglected Diseases, University of Notre Dame, Notre Dame, IN 46556, USA.
Cell (Impact Factor: 32.24). 01/2012; 148(1-2):201-12. DOI: 10.1016/j.cell.2011.10.051
Source: PubMed


Hundreds of effector proteins of the human malaria parasite Plasmodium falciparum constitute a "secretome" carrying a host-targeting (HT) signal, which predicts their export from the intracellular pathogen into the surrounding erythrocyte. Cleavage of the HT signal by a parasite endoplasmic reticulum (ER) protease, plasmepsin V, is the proposed export mechanism. Here, we show that the HT signal facilitates export by recognition of the lipid phosphatidylinositol-3-phosphate (PI(3)P) in the ER, prior to and independent of protease action. Secretome HT signals, including those of major virulence determinants, bind PI(3)P with nanomolar affinity and amino acid specificities displayed by HT-mediated export. PI(3)P-enriched regions are detected within the parasite's ER and colocalize with endogenous HT signal on ER precursors, which also display high-affinity binding to PI(3)P. A related pathogenic oomycete's HT signal export is dependent on PI(3)P binding, without cleavage by plasmepsin V. Thus, PI(3)P in the ER functions in mechanisms of secretion and pathogenesis.

Download full-text


Available from: Kasturi Haldar, Dec 24, 2014
  • Source
    • "We investigated for host-cell targeting motifs RXLXE/D/Q (where X is a neutral or a hydrophobic amino acid residue) that were previously reported for their activity to export Plasmodium falciparum proteins from the intracellular parasites (Bhattacharjee et al., 2012) to the surrounding erythrocytes. We also searched for the presence of consensus sequences XBBXBX, XBBBXXBX and XBBBXXBBBXXBBX (where X is a neutral or hydrophobic amino acid residue and B is a basic amino acid residue ) which were implicated in hairpin binding (de Castro Cortes et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Orphan genes are protein coding genes that lack recognizable homologs in other organisms. These genes were reported to comprise a considerable fraction of coding regions in all sequenced genomes and thought to be allied with organism's lineage-specific traits. However, their evolutionary persistence and functional significance still remain elusive. Due to lack of homologs with the host genome and for their probable lineage-specific functional roles, orphan gene product of pathogenic protozoan might be considered as the possible therapeutic targets. L. major is an important parasitic protozoan of the genus Leishmania that is associated with the disease cutaneous leishmaniasis. Therefore, evolutionary and functional characterization of orphan genes in this organism may help in understanding the factors prevailing pathogen evolution and parasitic adaptation. In this study, we systematically identified orphan genes of L. major and employed several in-silico analyses for understanding their evolutionary and functional attributes. To trace the signatures of molecular evolution, we compared their evolutionary rate with non-orphan genes. In agreement with prior observations, here we noticed that orphan genes evolve at a higher rate as compared to non-orphan genes. Lower sequence conservation of orphan genes was previously attributed solely due to their younger gene age. However, here we observed that together with gene age, a number of genomic (like expression level, GC content, variation in codon usage) and proteomic factors (like protein length, intrinsic disorder content, hydropathicity) could independently modulate their evolutionary rate. We considered the interplay of all these factors and analyzed their relative contribution on protein evolutionary rate by regression analysis. On the functional level, we observed that orphan genes are associated with regulatory, growth factor and transport related processes. Moreover, these genes were found to be enriched with various types of interaction and trafficking motifs, implying their possible involvement in host-parasite interactions. Thus, our comprehensive analysis of L. major orphan genes provided evidence for their extensive roles in host-pathogen interactions and virulence. Copyright © 2015. Published by Elsevier B.V.
    Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 04/2015; 32. DOI:10.1016/j.meegid.2015.03.031 · 3.02 Impact Factor
  • Source
    • "It is not clear whether the early endosome, which in mammalian cells is decorated with the lipid PI3P and Rab5, exists as a discrete compartment in P. falciparum. PI3P has been localized to the food vacuole, the apicoplast and the luminal face of the ER [68], [69], none of which appears to represent a canonical early endosome. "
    [Show abstract] [Hide abstract]
    ABSTRACT: During the asexual intraerythrocytic stage, the malaria parasite Plasmodium falciparum must traffic newly-synthesized proteins to a broad array of destinations within and beyond the parasite's plasma membrane. In this study, we have localized two well-conserved protein components of eukaryotic endosomes, the retromer complex and the small GTPase Rab7, to define a previously-undescribed endosomal compartment in P. falciparum. Retromer and Rab7 co-localized to a small number of punctate structures within parasites. These structures, which we refer to as endosomes, lie in close proximity to the Golgi apparatus and, like the Golgi apparatus, are inherited by daughter merozoites. However, the endosome is clearly distinct from the Golgi apparatus as neither retromer nor Rab7 redistributed to the endoplasmic reticulum upon brefeldin A treatment. Nascent rhoptries (specialized secretory organelles required for invasion) developed adjacent to endosomes, an observation that suggests a role for the endosome in rhoptry biogenesis. A P. falciparum homolog of the sortilin family of protein sorting receptors (PfSortilin) was localized to the Golgi apparatus. Together, these results elaborate a putative Golgi-to-endosome protein sorting pathway in asexual blood stage parasites and suggest that one role of retromer is to mediate the retrograde transport of PfSortilin from the endosome to the Golgi apparatus.
    PLoS ONE 02/2014; 9(2):e89771. DOI:10.1371/journal.pone.0089771 · 3.23 Impact Factor
  • Source
    • "A recent systematic study in P. bergheiinfected erythrocytes identified 13 previously unrecognized PEXEL/HT proteins and PNEPs (Pasini et al., 2013), suggesting that other, and perhaps all, Plasmodium species export a large and diverse set of proteins to remodel the erythrocyte. The current data from asexual blood-stage parasites indicate that the PEXEL/HT-motif is cleaved by plasmepsin V in the parasite endoplasmic reticulum (Boddey et al., 2010; Russo et al., 2010), where the PEXEL/HTcontaining proteins are proposed to be recruited by binding to phosphatidylinositol 3-phosphate (PI3P) (Bhattacharjee et al., 2012). Identification of cleaved, N-acetylated peptides from PEXEL/HT proteins in stage I gametocytes indicates that this machinery is also active in the endoplasmic reticulum of gametocytes, an observation further supported by the fact that plasmepsin V is readily detectable in the proteomes of all asexual and sexual blood stages (Silvestrini et al., 2010). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Obligate intracellular pathogens actively remodel their host cells to boost propagation, survival, and persistence. Plasmodium falciparum, the causative agent of the most severe form of malaria, assembles a complex secretory system in erythrocytes. Export of parasite factors to the erythrocyte membrane is essential for parasite sequestration from the blood circulation and a major factor for clinical complications in falciparum malaria. Historic and recent molecular reports show that host cell remodeling is not exclusive to P. falciparum and that parasite-induced intra-erythrocytic membrane structures and protein export occur in several Plasmodia. Comparative analyses of P. falciparum asexual and sexual blood stages and imaging of liver stages from transgenic murine Plasmodium species show that protein export occurs in all intracellular phases from liver infection to sexual differentiation, indicating that mammalian Plasmodium species evolved efficient strategies to renovate erythrocytes and hepatocytes according to the specific needs of each life cycle phase. While the repertoire of identified exported proteins is remarkably expanded in asexual P. falciparum blood stages, the putative export machinery and known targeting signatures are shared across life cycle stages. A better understanding of the molecular mechanisms underlying Plasmodium protein export could assist in designing novel strategies to interrupt transmission between Anopheles mosquitoes and humans.
    Cellular Microbiology 12/2013; 16(3). DOI:10.1111/cmi.12251 · 4.92 Impact Factor
Show more