The Plasmodium falciparum Vps4 homolog mediates multivesicular body formation

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 R falciparum and T gondii.