Hsp90 Co-chaperones as Drug Targets in Cancer: Current Perspectives

Hsp90 is a molecular chaperone that regulates the function of numerous oncogenic transcription factors and signalling intermediates in the cell. Inhibition of Hsp90 is sufficient to induce the proteosomal degradation of many of these proteins, and as such, the Hsp90 chaperone has been regarded as a promising drug target. The appropriate functioning of the Hsp90 chaperone is dependent on its ATPase activity and interactions with a cohort of non-substrate accessory proteins known as co-chaperones. Co-chaperones associate with Hsp90 at all stages of the chaperone cycle and regulate a range of Hsp90 functions, including ATP hydrolysis and client protein binding and release. Given the ability of co-chaperones to organise the function of the Hsp90 molecular machine, these proteins are now regarded as potential drug targets. Herein the role of selected Hsp90 co-chaperones Hop, Cdc37, p23 and Aha1 as possible drug targets is discussed with a focus on cancer.