Imaging of the subsurface structures of "unroofed" Plasmodium falciparum-infected erythrocytes

Intraerythrocytic stages of Plasmodium falciparum parasites modify the membranes of their host erythrocytes with numerous expressed proteins. They also install new membranous structures in the erythrocyte cytoplasm, including Maurer's clefts (MC) and a tubulovesicular network. These structures support molecular trafficking processes that are necessary for the growth and multiplication of P. falciparum intraerythrocytic stages. To study the morphology and organization of these modifications, we prepared samples of P. falciparum-infected erythrocytes by 'unroofing' techniques and examined them by transmission electron microscopy. Images of the 'unroofed' parasitized erythrocytes feature cytoskeleton alterations and the presence of new membranous structures generated by P. falciparum, including small vesicles and MC connected by extensions to the inner erythrocyte membrane. Non-parasitized erythrocytes showed no evidence of these structures or extensions. In further experiments, we observed a relative absence of MC and extensions after treatment of parasitized erythrocytes with aluminum tetrafluoride (AlF₄(-)), an inhibitor of vesicle trafficking. The morphology and physical location of MC, extensions and small vesicles in unroofed specimens are consistent with the role of these structures in the trafficking of P. falciparum proteins to the surface of parasitized erythrocytes.