Cell Microbiol. 2009 Jul 13. [Epub ahead of print]
New roles for perforins and proteases in apicomplexan egress
Roiko MS, Carruthers VB.
Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109 U.S.A.
Summary Egress is a pivotal step in the lifecycle of intracellular pathogens initiating the transition from an expiring host cell to a fresh target cell. While much attention has been focused on understanding cell invasion by intracellular pathogens, recent work is providing a new appreciation of mechanisms and therapeutic potential of microbial egress. This review highlights recent insight into cell egress by apicomplexan parasites and emerging contributions of membranolytic and proteolytic secretory products, along with host proteases. New findings suggest that Toxoplasma gondii secretes a pore-forming protein, TgPLP1, during egress that facilitates parasite escape from the cell by perforating the parasitophorous membrane. Also, in a cascade of proteolytic events, Plasmodium falciparum late stage schizonts activate and secrete a subtilisin, PfSUB1, which processes enigmatic putative proteases called SERAs that contribute to merozoite egress. A new report also suggests that calcium-activated host proteases called calpains aid parasite exit, possibly by acting upon the host cytoskeleton. Together these discoveries reveal important new molecular players involved in the principal steps of egress by apicomplexans.
PMID: 19614666 [PubMed - as supplied by publisher]