Autophagy proteins play cytoprotective and cytocidal roles in leucine starvation-induced cell death in Saccharomyces cerevisiae

Autophagy is essential for prolonging yeast survival during nutrient deprivation; however, this report shows that some autophagy proteins may also be accelerating population death in those conditions. While leucine starvation caused YCA1-mediated apoptosis characterized by increased annexin V staining, nitrogen deprivation triggered necrotic death characterized by increased propidium iodide uptake. Although a Delta atg8 strain died faster than its parental strain during nitrogen starvation, this mutant died slower than its parent during leucine starvation. Conversely, a Delta atg11 strain died slower than its parent during nitrogen starvation, but faster during leucine starvation. Curiously, although GFP-Atg8 complemented the Delta atg8 mutation, this protein made ATG8 cells more sensitive to nitrogen starvation, and less sensitive to leucine starvation. These results were difficult to explain if autophagy only extended life but could be an indication that a second form of autophagy could concurrently facilitate either apoptotic or necrotic cell death.