The proteasome subunit RPN10 functions as a specific receptor for degradation of the 26S proteasome by macroautophagy in Arabidopsis.

The ubiquitin-proteasome system (UPS) and macroautophagy/autophagy are 2 main degradative routes, which are important for cellular homeostasis. In a study conducted by Marshall et al., the authors demonstrated that the UPS and autophagy converge in Arabidopsis (see the punctum in issue #11-10). In particular, they found that the 26S proteasome is degraded by autophagy, either nonselectively (induced by nitrogen starvation) or selectively (induced by proteasome inhibition). The selective phenotype is mediated through the proteasome subunit RPN10, which can bind both ubiquitin and ATG8. This newly identified autophagic degradation of the proteasome is termed "proteaphagy," and the process reveals an interesting relationship between these degradative systems.