The mitochondrial phosphatidylserine decarboxylase Psd1 is involved in nitrogen starvation-induced mitophagy in yeast

Abstract

Mitophagy, the selective degradation of mitochondria by autophagy, is a central process that is essential for the maintenance of cell homeostasis. It is implicated in the clearance of superfluous or damaged mitochondria and requires specific proteins and regulators to perform. In yeast, Atg32, an outer mitochondrial membrane protein, interacts with the ubiquitin-like Atg8 protein, promoting the recruitment of mitochondria to the phagophore and their sequestration within autophagosomes. Atg8 is anchored to the phagophore and autophagosome membranes thanks to a phosphatidylethanolamine tail. In Saccharomyces cerevisiae, several phosphatidylethanolamine synthesis pathways have been characterized, but their contribution to autophagy and mitophagy are unknown. Through different approaches, we show that Psd1, the mitochondrial phosphatidylserine decarboxylase, is involved in mitophagy induction only after nitrogen starvation, whereas Psd2, which is located in vacuole, Golgi and endosome membranes, is required preferentially for mitophagy induction in the stationary phase of growth but also to a lesser extent for nitrogen starvation-induced mitophagy. Our results suggest that the mitophagy defect observed in Δpsd1 yeast cells after nitrogen starvation may be due to a failure of Atg8 recruitment to mitochondria.