The role of parasite heat shock proteins in protein trafficking and host cell remodeling

Malaria parasites are principally intracellular pathogens of erythrocytes and hepatocytes. For the parasites to grow rapidly and to avoid host immunity they must extensively modify their host cells by exporting hundreds of proteins into them. These exported proteins specifically help permeabilise the host cell so additional nutrients can be obtained and to avoid splenic clearance, the exported proteins modify the erythrocyte surface to promote cytoadherance within the microvasculature. Since erythrocytes lack many of the protein trafficking systems present in normal cells, parasites export their own. Many exported proteins help transport, traffic and refold other exported proteins into functional complexes once they reach their final destinations in the host. Exported trafficking systems and their cargoes are best understood in the most deadly human malaria pathogen Plasmodium falciparum, because it can be cultured in the laboratory. Trafficking and refolding require protein chaperone ATPases and we will present the latest data on exported chaperones. In particular, we will discuss the role of HSP101 in the protein translocon that provides a portal for protein export into the host compartment. Plasmodium species also export a few Hsp40s that probably function co-operatively with host Hsp70s. P. falciparum is however unique in that it exports also many additional Hsp40s as well as its own Hsp70-x and the roles of these will also be discussed.