Affiliation:
1. Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University, Philadelphia, Pennsylvania, USA
Abstract
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 (
Py
Exp2) was primarily localized to the PVM. Unexpectedly,
Py
Exp2 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 (
Pf
Exp2) is exclusively localized to the PVM. Two
P. yoelii
-exported proteins, PY04481 (encoded by a
pyst-a
gene) and PY06203 (
Py
pAg-1), partially colocalized with these
Py
Exp2-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
Py
Exp2 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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
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