The malaria parasite spends part of its life cycle growing and dividing within red blood cells. Infection involves a well-orchestrated invasion process that is followed by growth and division within the so-called parasitophorous vacuole. The parasite progeny, the merozoites, need to escape both the parasitophorous vacuole membrane and the erythrocyte plasma membrane to free themselves. Possible mechanisms of release include the coordinated rupture of both membranes, fusion of the parasitophorous vacuole membrane with the plasma membrane (releasing the merozoites into the blood stream), or release of the parasitophorous vacuole containing the merozoites and subsequent vacuole rupture.
Glushakova et al. examined the fate of the host and vacuole membranes directly after labeling infected erythrocytes with fluorescent lipids. No erythrocyte ghosts were observed, suggesting that direct rupture of the erythrocyte membrane was unlikely; similarly, inhibition of membrane fusion did not block release. Instead, it appears that the erythrocytes suffer a two-stage release in which the infected erythrocyte membranes first fold and then rupture, releasing free merozoites and leaving behind plasma membrane and internal membrane fragments. How the parasite induces these changes to occur remains to be elucidated. -- SMH
Curr. Biol. 15, 1645 (2005).
