Functional characterization of R2TP-Hsp90 complex in different organisms

Abstract

The maintenance of protein homeostasis is critical for cellular survival, and molecular chaperones are essential for this process. One of the more important proteins involved in this process is Hsp90, which also has key roles in a plethora of cellular functions. Dr. Walid A. Houry's group at University of Toronto (Canada) identified 627 putative Hsp90 interacting proteins and discovered the R2TP complex in yeast. R2TP consists of the highly conserved in eukaryotes called Rvb1 and Rvb2 helicases which bind tightly Pih1 and Tah1, the Hsp90 cofactors. Notably, many studies have revealed that a large range of carcinomas exhibit increased expression of Rvb1 and Rvb2 proteins. Furthermore, yeast Pih1, known as PIH1D1 in humans, interacts with various components in the cell and Tah1 contains tetratricopeptide repeat (TPR) motifs, which interact with the MEEVD motif on Hsp90 C-terminus that is known to mediate the interaction of Hsp90 with its co-chaperones. In this sense, Dr. Carlos Ramos's group at Unicamp (Brazil) has been studying orthologs of the R2TP complex from Leishmania major, an obligate intracellular protozoan parasite which causes a human disease named cutaneous leishmaniasis. Therefore, the R2TP complex appears to play a critical role in the rapid multiplication of these parasites and our group speculates that the R2TP complex is also important for the parasite Leishmania major as in yeast and humans. Despite the advances in studies of the R2TP-Hsp90 complex in different biological processes, the understanding of its cellular roles and specifically mechanism of function is still poorly understood. Therefore, this project will undertake a collaborative effort of both groups aiming at elucidating the molecular basis of R2TP activity in different organisms. Considering the above, this project aims to further investigate R2TP complex by (1) characterizing the ATPase and helicase activity of Rvb1/2 and (2) use the yeast and mammalian cells system to understand the molecular basis of R2TP complex. The knowledge gained with this study will improve the experimental effort in understand the protozoan ortholog. Lastly, given the techniques and approaches wich a phD student will use, this project will provide a unique opportunity to expand her scientific horizons to 'think outside the box' and tackle a problem from different angles. (AU)