Entfaltung ist essentiell für die Translokation löslicher Proteine über die Membran der parasitophoren Vakuole im Plasmodium falciparum-infizierten Erythrozyten

Upon invasion of mature erythrocytes, the human malaria parasite Plasmodium falciparum resides in a parasitophorous vacuole and traffics a large number of proteins to its host cell. How exactly these proteins gain access to the red blood cell is poorly understood. To investigate the effect of protein folding on the transport of model substrate proteins to the host cell, a murine DHFR-fusion protein system was established and used in this work. Using this system it could be shown that soluble proteins must pass into the erythrocyte cytoplasm in an unfolded state. The transport of reporter constructs containing the mDHFR was, upon addition of DHFR-stabilizing agents, blocked within the lumen of the PV. This transport block was dose dependent and reversible. These findings strongly suggest that soluble parasite proteins destined for transport to the host red blood cell must translocate across the parasitophorous vacuolar membrane in an unfolded configuration. These data are suggestive of a rate-limiting PCC-mediated step in the transport of parasite-encoded proteins to the erythrocyte cytosol, and additionally imply an important role for molecular chaperones in keeping parasite proteins in a ‘translocation competent’ state prior to membrane passage.