New Export Pathway in Plasmodium falciparum-Infected Erythrocytes: Role of the Parasite Group II Chaperonin, PfTRiC

Abstract

The malaria parasite type II chaperonin PfTRiC is exported to the host erythrocyte cytoplasm and translocates unfolded parasite proteins from the parasitophorous vacuole to the membrane of Maurer's clefts. Since some of these exported proteins have the PEXEL export signature, the PfTRiC cargos likely use the PTEX translocon to pass through the parasitophorous vacuole membrane. Detection of PfTRiC in the parasitophorous vacuole lumen suggests a role for this chaperonin in the export of parasite proteins through different compartments. The export of numerous proteins to the plasma membrane of its host erythrocyte is essential for the virulence and survival of the malaria parasite Plasmodium falciparum. The Maurer's clefts, membrane structures transposed by the parasite in the cytoplasm of its host erythrocyte, play the role of a marshal platform for such exported parasite proteins. We identify here the export pathway of three resident proteins of the Maurer's clefts membrane: the proteins are exported as soluble forms in the red cell cytoplasm to the Maurer's clefts membrane in association with the parasite group II chaperonin (PfTRIC), a chaperone complex known to bind and address a large spectrum of unfolded proteins to their final location. We have also located the domain of interaction with PfTRiC within the amino-terminal domain of one of these Maurer's cleft proteins, PfSBP1. Because several Maurer's cleft membrane proteins with different export motifs seem to follow the same route, we propose a general role for PfTRiC in the trafficking of malarial parasite proteins to the host erythrocyte.