Mitochondria are degraded though autophagy, which is called mitophagy. In yeast, this process relies on specific proteins from the core autophagy machinery: autophagy-related gene 8 (Atg8) interacts with Atg32 and anchors, through its phosphatidylethanolamine (PE) tail, to the membranous phagophores from which the autophagosome vesicle evolves. Anchoring leads to recruitment of mitochondria to the phagophore and, eventually, vesicular degradation. Thus, Atg8-PE is a central factor for autophagy, but it remains unclear how the various cellular PE signalling pathways contribute to this. Nadine Camougrand and colleagues (Vigié et al., 2019) have now investigated the role of different cellular PE pools through analysis of PE synthesis mutants. The authors found that whereas autophagy induction is not affected upon the absence of one PE synthesis pathway, yeast mitophagy triggered by nitrogen starvation requires the phosphatidylserine decarboxylase Psd1. In addition, this failure of mitophagy after loss of Psd1 might be caused by the absence of Atg8 from the mitochondrial surface. Conversely, the decarboxylase Psd2 is necessary for mitophagy in the stationary phase of growth, and to a lesser extent contributes to nitrogen starvation-induced mitophagy. This work establishes that different cellular conditions exploit different PE signalling pathways to modulate mitophagy in yeast.
