Rapamycin allosterically inhibits the proteasome

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Rapamycin is a known inhibitor of the mammalian target of rapamycin (mTOR) kinase, exhibiting immunosuppressive and proapoptotic effects.
• The proteasome is a critical intracellular protease complex responsible for protein degradation via the ubiquitin-proteasome pathway.

Purpose of the Study:

• To investigate the effects of rapamycin on proteasome function in vitro.
• To explore the potential of rapamycin and its analogs as modulators of proteasome activity.

Main Methods:

• In vitro assays measuring proteinase and peptidase activities of the 20S proteasome core.
• Analysis of the binding interactions between rapamycin, proteasome activators (19S cap, PA200), and the 20S proteasome core.
• Conformational dynamics studies of the proteasomal gate upon rapamycin treatment.

Main Results:

• Rapamycin inhibits proteinase and peptidase activities of the 20S proteasome core at low micromolar concentrations.
• Rapamycin interferes with the binding of the 19S cap and PA200 activator to the 20S proteasome core.
• Rapamycin alters the conformational dynamics of the proteasomal gate, impacting substrate entry.

Conclusions:

• Rapamycin and its analogs, including seco-rapamycin, target the proteasome by binding to its α face, allosterically affecting its function.
• These findings suggest a dual mechanism of action for rapamycin, impacting both mTOR and proteasome pathways.
• The study provides a basis for designing novel allosteric drugs targeting the proteasome for therapeutic purposes.