Dokument

Summary:
In order to grow and survive the human malaria parasite Plasmodium falciparum synthesizes and exports hundreds of proteins in order to modify the infected red blood cell. In previous studies, our group found that two members of parasite encoded type II Hsp40s (PEF55, PFA660) associate with highly mobile structure in the infected host cell, which are referred to as J-dots. Furthermore, an exported parasite chaperone, PfHsp70x was identified which also associated with these structures. To understand the role of J-dots in host cell modification, we aimed to purify J-dots and identify the proteome of these parasite-induced intra-erythrocytic structures. This would allow us to further construct a protein-protein interactions network of the P. falciparum infect red blood cell. In this study, multiple proteomics methods were used to profile PFE55-PfHsp70x chaperone/co-chaperone protein complexes (J-dots). By using differential centrifugation as well as immunoblotting of BN-PAGE and 2D BN/SDS PAGE, PFE55 and PfHsp70x were visualized in the same complex with a high molecular weight >223KDa. Furthermore, two exported proteins, PfPHISTc and PfGEXP18 were identified by co-immunoprecipitation (co-IP) and LC-MS/MS to interact with PFE55 and PfHsp70x, and subsequently to localize to J-dots In addition, further protein complexes containing PFE55 and PfHsp70x were found not only in the parasite infected erythrocyte cytosol but also in the parasitophorous vacuole. Surprisingly, PfHsp70x was also found associated with a protein translocon at the parasitophorous vacuole, termed PTEX. Proteomic analysis of the co-IP also suggested an interaction between human Hsp70 and PFE55. Taken together, our data indicates PfHsp70x-PFE55 chaperones/co-chaperone complexes are involved in exported protein trafficking from the parasitophorous vacuole into the erythrocyte cytosol. Potentially, these complexes could be aiding in protein folding and unfolding during passage through the PTEX translocon. Moreover, the fact that many exported proteins were found associated with PfHsp70x, further highlights the role of PfHsp70x in coordinating exported protein trafficking.

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