Another Route To Protein Disposal

In the primary pathway for discarding proteins, cells tag targeted proteins with ubiquitin and deliver them to the proteasome, the cell’s garbage disposal. But there’s another protein disposal pathway that doesn’t involve ubiquitin and that uses only the central core of the proteasome, a portion called the 20S proteasome. Biologists previously thought this second pathway was a passive, unregulated process. Michal Sharon and coworkers of Israel’s Weizmann Institute of Science now report that the process is regulated at least in part by a Parkinson’s disease-related protein called DJ-1, which is in tissues throughout the human body (Nat. Commun. 2015, DOI: 10.1038/ncomms7609). The researchers found that DJ-1 both inhibits and indirectly activates protein degradation. It inhibits protein degradation by directly binding to the 20S proteasome. But during oxidative stress, DJ-1 activates a protein called Nrf2, which is itself an activator of the 20S proteasome. Sharon and coworkers are now studying where DJ-1 binds the proteasome to figure out the mechanism by which it exerts its effects.