The Plasmodium falciparum Vps4 homolog mediates multivesicular body formation

Abstract

Members of the apicomplexan family of parasites contain morphologically unique secretory organelles termed rhoptries that are essential for host cell invasion. Rhoptries contain internal membranes, and thus resemble multivesicular bodies. To determine whether multivesicular body endosomal intermediates are formed in Apicomplexa, we used the Plasmodium falciparum homolog of the class E gene, Vps4, as a probe. Endogenous P. falciparum Vps4 (PfVps4) localized to the cytoplasm of P. falciparum trophozoites, and transgenic PfVps4 localized to the cytosol in P. falciparum, in the related parasite Toxoplasma gondii and in COS cells. When mutated to block ATP hydrolysis, transiently expressed PfVps4 localized instead to large vesicular structures in P. falciparum. The same construct, and another mutant blocked in ATP binding, generated large cholesterol-enriched multivesicular bodies in both COS cells and T. gondii. Mutant PfVps4 structures in T. gondii co-localized with markers for early endosomes. These results demonstrate a conservation of Vps4 function across wide phylogenetic boundaries, and indicate that endosomal multivesicular bodies form in both P. falciparum and T. gondii.

Phosphatidylinositol 3-Phosphate, an Essential Lipid in Plasmodium, Localizes to the Food Vacuole Membrane and the Apicoplast

“…In other organisms, PI(3,5)P 2 is localized mainly on multivesicular bodies (MVBs) and is implicated in the maintenance of endosome and lysosome/vacuole morphology and in endosome-to-Golgi complex and MVB-to-vacuole trafficking (18,47). In apicomplexan parasites, MVB-like structures have so far been observed only upon disturbance of endocytic pathways by chemical or mutational manipulations (65), suggesting that endosomal trafficking in Plasmodium might be different from the classical scheme described for yeast and mammals.…”

Host Cholesterol Synthesis Contributes to Growth of Intracellular Toxoplasma gondii in Macrophages

“…Previous studies have shown that T. gondii exploits host LDLR-mediated endocytosis for cholesterol acquisition from endo-lysosomes [5,20,27]. This dependence on exogenous sources of cholesterol suggests the parasite has developed mechanisms for acquiring, transporting and sorting this lipid.…”

Chloroquine-resistant isoforms of the Plasmodium falciparum chloroquine resistance transporter acidify lysosomal pH in HEK293 cells more than chloroquine-sensitive isoforms

“…Co-expression of a dominant negative tetraspanin mutant, CD63-AEVM [39], did not alter PfCRT targeting to the lysosome (not shown). We noted that the P. falciparum genome sequence [40] contains homologues of human vacuolar protein sorting protein VPS4 [41,42] and human sorting nexin 4 (SNX4) [43]. Co-expression of dominant negative mutants of either of these proteins did not perturb PfCRT sorting to the lysosome.…”