Plasmodium falciparum: protein localization along a novel, lipid-rich tubovesicular membrane network in infected erythrocytes.

Erythrocytes infected with Plasmodium falciparum contain a novel network of tubovesicular membranes which can be prominently labeled by fluorescent sphingolipids and have been implicated in trafficking pathways in infected red cells. We have developed a method to simultaneously image lipids of the tubovesicular membrane network and exported parasite proteins by high-resolution confocal microscopy. Our results indicate that Exp1 (a 23-kDa protein marker of the parasitophorous vacuolar membrane and intraerythrocytic loops) concentrates in membrane domains on the periphery of the parasite and in the tubovesicular membrane network. In contrast, a 45-kDa protein localized to the Maurer's clefts is distributed in punctate domains along lipid labeled tubovesicular membranes, frequently along the periphery of the network juxtaposed to the red cell membrane. These results strongly suggest that the lipid-rich tubovesicular membranes are a complex network containing domains of parasite proteins.