THE ROLE OF THE CYTOSKELETON IN PLASMODIUM-FALCIPARUM MEROZOITE BIOLOGY - AN ELECTRON-MICROSCOPIC VIEW

The biochemical, ultrastructural and experimental data concerning the organization and biological roles of the merozoite cytoskeleton are br iefly reviewed. Actin is known to be expressed in the asexual erythroc ytic stages, and has also been demonstrated in Plasmodium falciparum m erozoites biochemically and visualized by fluorescence microscopy afte r appropriate labelling. Experimental evidence indicates that actin-my osin-based motility is important in merozoite locomotion during red-ce ll invasion. Microtubules also occur in P. falciparum merozoites in th e form of a small longitudinal band of subpellicular microtubules, and experiments with anti-microtubule drugs indicate that microtubules ar e involved in some aspect of invasion. In the late-stage schizont, mic rotubules are also important in merozoite morphogenesis. The numbers a nd positions of the merozoite apices within the schizont are spatially related to the spindle poles of the final mitotic division, and extra nuclear microtubules are probably responsible for the trafficking of v esicles from a single Golgi cisterna to form the apical organelles. In addition to these cytoskeletal structures, numerous short cytoskeleta l filaments of unknown composition attach the merozoite plasma membran e to the underlying pellicular cisterna, and this process may drive th e budding of merozoites from the parent schizont.