The proteasome is a large multi-protein complex that degrades proteins. You can think of it as the cell’s “garbage disposal”: it is shaped like a tube, and proteins enter this tube before being chewed up (cleaved) and expelled out the other end. The proteasome has several key roles:
- Turning off cellular processes by degrading the proteins involved in those processes.
- Maintaining protein quality control by degrading superfluous, damaged, or misfolded proteins.
- Degrading microbial proteins into fragments that subsequently activate the immune system to defend against infection.
Researchers from the Weizmann Institute in Israel recently discovered a new function for the proteasome: the production of antimicrobial peptides, which are small proteins that fight bacterial infections. In the absence of the proteasome, disease-causing bacteria overwhelm both cells and mice. However, when the proteasome is present and “turbocharged” by the bacteria, the protein fragments it produces disrupt bacterial membranes and limit infection. Importantly, this antibacterial defense mechanism is cell-autonomous, meaning it occurs independently of the immune system.
