HspB8 interacts with BAG3 in a "native-like" conformation forming a complex that displays chaperone-like activity

Area of Science:

• Biochemistry
• Biophysics
• Molecular Biology

Background:

• The Heat Shock Protein B8 (HspB8)-Binding Immunoglobulin Protein 3 (BAG3) complex is vital for cellular protein quality control.
• Understanding the self-assembly and complex formation mechanisms of HspB8 and BAG3 is crucial for elucidating their function.

Purpose of the Study:

• To investigate the auto-assembly tendencies of HspB8 and BAG3.
• To characterize the formation and stability of the HspB8-BAG3 complex.
• To assess the chaperone-like activity of HspB8, BAG3, and their complex on protein aggregation.

Main Methods:

• Solubility assays
• Thioflavin T assays
• Fourier transform infrared spectroscopy (FTIR)
• Atomic force microscopy (AFM)
• Surface plasmon resonance (SPR)

Main Results:

• HspB8 self-assembles into oligomers with a native-like conformation at high concentrations, while BAG3 exhibits poor aggregation.
• HspB8 and BAG3 form a stable complex in a native-like conformation.
• SPR analysis confirmed HspB8 as an obligate partner for BAG3 in vivo.
• The HspB8-BAG3 complex demonstrated enhanced activity in binding and inhibiting the aggregation of the Josephin domain compared to HspB8 alone.

Conclusions:

• HspB8 and BAG3 form a stable, functional complex with significant chaperone-like activity.
• This stable assembly contributes to the physiological role of the HspB8-BAG3 complex in maintaining protein homeostasis.
• The findings provide mechanistic insights into the protein quality control functions mediated by this complex.