Abstract
The molecular chaperone Hsp90 and its cochaperone Cdc37 are both essential proteins critical for the folding of hundreds of client proteins, including protein kinases involved in cancer progression, making it a therapeutic target. However, how do Hsp90 and its co-chaperone Cdc37 influence the stability and abundance of their client proteins on a proteome-wide scale? In our first study, we took advantage of yeast genetics and employed Data-Independent Acquisition Mass Spectrometry (DIA-MS) to study nine temperature-sensitive Hsp90 mutants that disrupt distinct phases of its folding cycle. We found the mutations have differing effects on client proteins. These included transcription factors like Msn2/Msn4, Gcn2, and Hsf1, as well as downstream processes such as rRNA processing, translation, and DNA repair. In our current study we used the same quantitative proteomics approach to study a temperature sensitive mutation in Cdc37 under control and heat shock conditions. Based on prior studies that showed up to 2/3 of protein kinases are dependent on Cdc37, we expected that most of the affected proteins would be kinases. However, only one kinase was strongly affected. For example, Tpk3 kinase was impacted in both studies, while Mck1, a mitogen-activated kinase, was affected only in Hsp90 mutants. Additionally, we identified a variety of non-kinase proteins affected by Cdc37 mutation. For example, Oye3, an oxidoreductase linked to oxidative stress, was reduced in both studies. These findings suggest that Cdc37 supports a broader range of non-kinase clients, emphasizing the need for further exploration of its regulatory roles. We aim to elucidate the functional impact of mutant Hsp90 and Cdc37 on the putative clients identified here to expand our understanding of the Hsp90-Cdc37 system and its implications for cellular regulation beyond kinases and transcription factors.