Nematode CDC-37 and DNJ-13 form complexes and can interact with HSP-90

Area of Science:

• Molecular biology
• Protein biochemistry
• Cellular homeostasis

Background:

• Molecular chaperones Hsc70 and Hsp90 regulate protein folding and proteostasis.
• Eukaryotic chaperones utilize cofactors to define client proteins and regulate ATPase activity.
• Hsp40 proteins (J-domain proteins) and Hsp90-cofactors are key components of chaperone machinery.

Purpose of the Study:

• To investigate the interaction between Hsp40 family proteins and Hsp90-cofactors.
• To characterize the specific binding of nematode DNJ-13 to the Hsp90-cofactor CDC-37.
• To elucidate the functional consequences of this interaction on chaperone complex assembly and activity.

Main Methods:

• Analytical ultracentrifugation (AUC) to determine binding affinity and stoichiometry.
• Cross-linking coupled with mass spectrometry (XL-MS) to identify interaction interfaces.
• Biochemical assays to assess the effect of DNJ-13 on CDC-37/HSP-90 complex formation and nucleotide dependence.

Main Results:

• Nematode Hsp40 protein DNJ-13 directly binds to Hsp90-cofactor CDC-37 with low micromolar affinity.
• The interaction involves the J-domain of DNJ-13 and both N- and C-terminal regions of CDC-37.
• DNJ-13 enhances the formation of the CDC-37/HSP-90 complex and modulates its nucleotide-dependent behavior.
• DNJ-12, another Hsp40 protein, does not exhibit similar binding to CDC-37, indicating specificity.

Conclusions:

• A direct link exists between Hsp40 proteins and Hsp90-cofactors, mediated by proteins like DNJ-13 and CDC-37.
• This interaction contributes to the intricate regulation of client protein processing by the Hsc70 and Hsp90 chaperone systems.
• The findings suggest a coordinated mechanism involving different chaperone families for maintaining proteostasis.