SMALL GTP-BINDING PROTEINS IN PLASMODIUM-FALCIPARUM

During its erythrocytic life cycle Plasmodium falciparum exchanges com pounds with host cells through phagocytosis and exocytosis. In eucaryo tic cells, small GTP-binding proteins of the Ras superfamily appear to be involved in different steps of membrane trafficking and in intrace llular signals. In this paper, we investigate the Rab4, Rab6 and Ras-r elated proteins in P falciparum infected red cells. We report that P f alciparum Rab and Ras-related proteins could be distinguished from the ir counterparts by iso-electrofocusing and immunoblotting. The localiz ation of P falciparum Rab4 and Rab6 was studied by immunogold electron microscopy on ultrathin frozen sections of infected red blood cells. Rab4 parasite-related protein was found associated with the membranes of early endosome-like structures near the parasite plasma membrane. R ab6-related protein was associated with the Golgi/trans Golgi network, as already suggested by immunofluorescence microscopy studies and Ras -related protein was cytoplasmic and plasma membrane-associated. These results are in accordance with their mammalian counterparts and suppo rt the implication of Rab-related proteins in vesicular trafficking in Plasmodium.