Figure 2. Model for a role of ubiquitination in mutual regulation of apoptosis and autophagy.

Autophagy can target ubiquitinated misfolded proteins, caspases, and other cargo (such as damaged mitochondria and invading bacteria) for degradation, probably through p62 and NBR1. Apoptosis and autophagy are counter-regulated in multiple steps, such as at p53, the Beclin 1/Bcl-2 interaction, the cleavage of Beclin 1 into the C-terminal region by caspases, and the autophagic degradation of caspases. Ubiquitination can promote degradation of both p53 and Beclin 1 and thus, controls the mutual regulation of apoptosis and autophagy.