Distinct effects of Atg3 and Atg10 on Autophagosome Formation in Yeast

Autophagosome formation involves two E2 enzymes: Atg3, which conjugates Atg8 to the lipid phosphatidylethanolamine, and Atg10, which conjugates Atg12 to Atg5. Although both are required for autophagy, it is unclear exactly what roles these pathways play in the process of autophagosome formation. We used baker's yeast expressing mutant versions of both Atg3 and Atg10 that reduce, but do not eliminate, their activity to better understand their effects on Atg8 lipidation, autophagic flux, and the size and number of autophagosomes formed during nitrogen starvation. We found that while Atg3 primarily affects Atg8 lipidation and autophagosome size, Atg10 has less of an effect on Atg8 lipidation and primarily controls autophagosome number. This demonstrates that these two enzymes have distinct mechanistic roles in autophagosome formation, and implies an as-of-yet undiscovered function for the Atg12-Atg5 conjugate.