Mitophagy: The life-or-death dichotomy includes yeast

The degradation and recycling of mitochondria is an important household chore in eukaryotic cells. It is thought that mitochondrial autophagy, or mitophagy, is the major route by which mitochondria are degraded. In this view, the cell would selectively induce mitophagy to expunge malfunctioning mitochondria, thus ridding the cell of troublesome sources of reactive oxygen species, apoptosis-inducing factors, or unnecessary metabolic burden. This standard view of mitophagy, in addition to some experimental reports, points to a pro-survival role of mitophagy. However, there is also a significant amount of evidence that suggests a pro-death role of this process, some of it coming from studies in yeast. Aup1 is a protein phosphatase homolog that shows a genetic interaction with the Atg1 protein kinase, localizes to mitochondria, and is required for mitophagy under stationary phase conditions in lactate medium. In contrast with previous yeast studies on mitophagy, deletion of AUP1 results in decreased viability under mitophagy-inducing conditions, suggesting a pro-survival role under physiologically relevant conditions. Thus, the Janus-faced nature of mitophagy is conserved between yeast and mammalian systems.