Dissecting the Cdc37 cochaperone code: Functional roles in chaperone-mediated stress adaptation

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Cdc37 is a crucial co-chaperone that links protein kinases to the Hsp90 chaperone machinery.
• Phosphorylation at Serine 14 (S14) and Serine 17 (S17) are known regulators of Cdc37 activity.
• The comprehensive impact of phosphorylation across the entire Cdc37 protein remains largely unexplored.

Purpose of the Study:

• To systematically investigate the functional consequences of phosphorylation at all potential sites across the Cdc37 protein.
• To identify novel phosphorylation sites regulating Cdc37 function under various cellular conditions.
• To establish a resource for understanding the role of Cdc37 post-translational modifications in cellular proteostasis and disease.

Main Methods:

• Creation of a comprehensive "Cdc37 code collection" comprising 46 yeast strains, each expressing a single phospho-site mutant of Cdc37.
• Extensive phenotypic profiling of these mutant strains across a broad spectrum of environmental and chemical stressors.
• Comparative analysis of stress response phenotypes to identify unique and overlapping regulatory roles of different phosphorylation sites.

Main Results:

• Canonical phosphorylation sites (S14, S17) are confirmed as essential for stress tolerance.
• 34 novel phospho-mutants exhibited distinct and stress-specific phenotypes, indicating diverse regulatory roles.
• Minimal overlap in stress responses among the novel mutants suggests modular and context-dependent regulation of Cdc37 function.
• Site-specific phosphorylation intricately modulates Cdc37's capacity to maintain proteostasis under diverse cellular challenges.

Conclusions:

• Cdc37 function is extensively modulated by site-specific phosphorylation, impacting its role in maintaining proteostasis.
• The study identifies numerous novel regulatory phosphorylation sites on Cdc37, expanding our understanding of its post-translational regulation.
• These findings provide a valuable resource for future research into the chaperone-kinase network and its dysregulation in disease states.