Hsp90·Cdc37 Complexes with Protein Kinases Form Cooperatively with Multiple Distinct Interaction Sites

Area of Science:

• Molecular Chaperones
• Protein Kinase Regulation
• Structural Biology

Background:

• Protein kinases are key clients of heat shock protein 90 (Hsp90).
• The cochaperone cell division cycle 37 (Cdc37) recruits kinases to Hsp90.
• Hsp90-Cdc37 interaction involves Hsp90's middle domain and Cdc37's N-terminal region.

Purpose of the Study:

• To map the binding site between Caenorhabditis elegans Cdc37 (CeCdc37) and the Hsp90 middle domain.
• To identify key amino acids involved in the CeCdc37-Hsp90 interaction.
• To investigate the conservation of kinase binding to Cdc37 across species.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to map binding interfaces.
• Biochemical analysis to define relevant amino acids for CeCdc37-Hsp90 interaction.
• Comparative analysis of kinase binding to Cdc37 in mammals and nematodes.

Main Results:

• The Hsp90 middle domain binds to the N-terminal region of CeCdc37.
• Specific amino acids critical for the CeCdc37-Hsp90 interaction were identified.
• Kinase binding to Cdc37, particularly B-Raf, is conserved between mammals and nematodes.
• Cdc37's C-terminal region is important for kinase binding, while the N-terminal region affects nucleotide binding.
• A cooperative ternary complex of Cdc37, kinase, and Hsp90 is formed.
• While conserved, the interaction of mitogen-activated protein kinase Erk2 with the Cdc37·Hsp90 complex shows slight variations in domain contributions.

Conclusions:

• Distinct interfaces mediate CeCdc37 and Hsp90 interactions.
• Kinase binding mechanisms to the Hsp90 chaperone machinery show conserved and variable features across different kinases.
• Understanding these interactions provides insights into Hsp90-dependent kinase regulation.