![]() ![]() Taken together, these results confirm that DNAJA1 is a hub for anticancer drug resistance and that DNAJA1 inhibition is a potent strategy to sensitize cancer cells to current and future therapeutics. Several hits were validated using a DNAJA1 inhibitor (116-9e) in castration-resistant prostate cancer cell (CRPC) and spheroid models. ![]() 41 compounds showed strong synergy with DNAJA1 loss, whereas 18 dramatically lost potency. To confirm this role, we screened the NIH Approved Oncology collection for chemical-genetic interactions with loss of DNAJA1 in cancer. We found DNAJA1 to be upregulated in a variety of cancers, suggesting a role in malignancy. Rather than targeting Hsp70 itself, here we have examined the feasibility of inhibiting the Hsp70 co-chaperone DNAJA1 as a novel anticancer strategy. Hsp70 is regulated by a suite of co-chaperone molecules that bring “clients” to the primary chaperone for efficient folding. However, attempts to develop anti-chaperone drugs targeting molecules such as Hsp70 have been hampered by toxicity issues. The Hsp90 closed conformation bound to ATP is associated with late cochaperones p23/Sba1 or Aha1 that control the ATPase activity and the release of client proteins.Heat shock protein 70 (Hsp70) is an important molecular chaperone that regulates oncoprotein stability and tumorigenesis. The open Hsp90 form is associated with early cochaperones Tah1-Pih1 or Hop/Sti1 that allow the loading of client proteins. It forms a molecular clamp which conformation is governed by the binding and hydrolysis of ATP. Hsp90 is a dimeric protein composed of three domains. Given the importance of the Hsp90 chaperon and of its clients in many diseases including cancer, the three-dimensional structures that we propose to solve should have a strong impact on the development of new therapeutic approaches and the rational design of novel Hsp90 inhibitors is one of our major goals. This project will provide a thorough understanding, at the atomic scale, of the mechanisms at work during the assembly of multi-protein complexes by Hsp90. For this purpose, we use a structural approach mixing protein crystallography with functional studies using the tools of the biochemistry, biophysics as well as molecular biology in the yeast model Saccharomyces cerevisiae. We are particularly interested in understanding the role of cochaperones in the mechanism of client proteins recognition and assembly, together with the molecular basis of the coupling between ATPase activity, associated conformational changes and clients activation. Our team seeks to elucidate the molecular mechanisms of this chaperone machinery at the origin of client proteins maturation. The regulation of this ATPase cycle involves a set of partner proteins called cochaperones, making the Hsp90 chaperone a highly complex system (figure). It is coupled with the nucleotide binding and hydrolysis and Hsp90 thus acts like a molecular clamp. The maturation of client proteins is an ATP-dependent phenomenon. While the study of the mechanism of action of many molecular chaperones as much progressed in recent years, that of Hsp90 remains poorly understood. Because the specific inhibition of the chaperone causes the degradation of these oncogenic clients by the proteasome, Hsp90 has attracted an unprecedented interest as a rational anticancer target with the potential to simultaneously abrogate the hallmark characteristics of cancer cells. Many of these clients control functions involved in malignant transformation such as cell proliferation, immortalization, angiogenesis or apoptosis. All these proteins depend on Hsp90 for their maturation or their assembly and are called Hsp90 client proteins. More recently, Hsp90 was involved in the assembly of numerous molecular machines such as RNA polymerases, ribonucleoproteins (RNPs) like the telomerase, or Phosphatidylinositol 3-kinase-related protein kinases (PIKKs) including mTOR. Among these chaperones, the Hsp90 protein was first found associated with cell signaling proteins such as steroid nuclear receptors and tyrosine kinases. Molecular chaperones are key players controlling the biogenesis of these macromolecular assemblies. Thus, they constitute a set of molecules whose social behavior is essential to the organization of living systems. They most often work within multiprotein complexes where their actions are regulated through networks of protein-protein interactions. Proteins are essential for the many processes that govern the life of a cell. ![]()
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