A novel link between autophagy and the ubiquitin-proteasome system.

Autophagy and the ubiquitin-proteasome system (UPS) are the major routes for intracellular protein degradation. These two pathways were previously thought to be largely distinct. Here we summarize our recent work that demonstrates that long-term autophagy inhibition slows the clearance of short-lived UPS-specific substrates, like p53. This is caused by the accumulation of p62 after autophagy inhibition. These data suggest that the ramifications of a block in autophagy may be much wider than what was previously thought. Rather than simply decreasing clearance of autophagic substrates, while UPS flux is undisturbed, the cell will have to contend with a decrease in clearance by both major routes.