title: Host erythrocyte environment influences the localization of exported protein 2, an essential component of the Plasmodium translocon.
abstract: Malaria parasites replicating inside red blood cells (RBCs) export a large subset of proteins into the erythrocyte cytoplasm to facilitate parasite growth and survival. PTEX, the parasite-encoded translocon, mediates protein transport across the parasitophorous vacuolar membrane (PVM) in Plasmodium falciparum-infected erythrocytes. Proteins exported into the erythrocyte cytoplasm have been localized to membranous structures, such as Maurer's clefts, small vesicles, and a tubovesicular network. Comparable studies of protein trafficking in Plasmodium vivax-infected reticulocytes are limited. With Plasmodium yoelii-infected reticulocytes, we identified exported protein 2 (Exp2) in a proteomic screen of proteins putatively transported across the PVM. Immunofluorescence studies showed that P. yoelii Exp2 (PyExp2) was primarily localized to the PVM. Unexpectedly, PyExp2 was also associated with distinct, membrane-bound vesicles in the reticulocyte cytoplasm. This is in contrast to P. falciparum in mature RBCs, where P. falciparum Exp2 (PfExp2) is exclusively localized to the PVM. Two P. yoelii-exported proteins, PY04481 (encoded by a pyst-a gene) and PY06203 (PypAg-1), partially colocalized with these PyExp2-positive vesicles. Further analysis revealed that with P. yoelii, Plasmodium berghei, and P. falciparum, cytoplasmic Exp2-positive vesicles were primarily observed in CD71(+) reticulocytes versus mature RBCs. In transgenic P. yoelii 17X parasites, the association of hemagglutinin-tagged PyExp2 with the PVM and cytoplasmic vesicles was retained, but the pyexp2 gene was refractory to deletion. These data suggest that the localization of Exp2 in mouse and human RBCs can be influenced by the host cell environment. Exp2 may function at multiple points in the pathway by which parasites traffic proteins into and through the reticulocyte cytoplasm.
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Elamaran
authors: E
authors: Meibalan
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Mary Ann
authors: MA
authors: Comunale
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Ana M
authors: AM
authors: Lopez
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Lawrence W
authors: LW
authors: Bergman
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Anand
authors: A
authors: Mehta
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA.
authors: Akhil B
authors: AB
authors: Vaidya
authors: Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA jburns@drexelmed.edu.
authors: James M
authors: JM
authors: Burns
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000378:metabolism; D004912:Erythrocytes / Q000469:parasitology*; D006790:Host-Parasite Interactions; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D016778:Malaria, Falciparum / Q000469:parasitology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010961:Plasmodium / Q000235:genetics*; D021381:Protein Transport; D040901:Proteomics; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins