UC San Diego

General and selective autophagy are pathways eukaryotic cells can utilize to degrade damaged or superfluous cellular components, but they are also survival mechanisms during starvation. Therefore these degradation pathways can be activated by starvation conditions, typically carbon and/or nitrogen sources. We investigated the effects of nitrogen and carbon starvation on autophagy- related pathway; in particular we focused on peroxisome degradation (pexophagy) and the nutrient sensing pathways involved. Pexophagy in Saccharomyces cerevisiae requires the integration of two signals; one leading to activation, by phosphorylation, of the pexophagy receptor, Atg36, and a second to activate the core autophagy machinery. Atg36 phosphorylation depends on the presence of glucose, and the induction of core autophagy machinery depends on the inactivation of the Tor1 (Target of rapamycin) complex in the absence of nitrogen. The glucose signal has led us to the PKA (cAMP-dependent protein kinase A) signaling pathway which seems to be directly or indirectly implicated in the phosphorylation of Atg36. This discovery has led to a deeper understanding of the effects of carbon and nitrogen on pexophagy in yeast that may apply to other selective autophagy pathways