O75143

Atg13(Autophagy related 13) is an autophagy factor and a target of the TOR kinase signaling pathway. Atg13 is essential for autophagosome formation and mitophagy. Atg13 is originally identified in yeast as a constitutively expressed protein that was genetically linked to Atg1, a protein kinase required for autophagy. Overexpression of Atg1 suppresses the defects in autophagy observed in Atg13 mutants. Autophagy requires a direct association between Atg1 and Atg13, and is inhibited by TOR-dependent phosphorylation of Atg13 under high-nutrient conditions. Similarly, mammalian Atg13 forms a complex with the Atg1 homologues ULK1/2, along with FIP200, which localizes to autophagic isolation membranes and regulates autophagosome biogenesis. mTOR phosphorylates both Atg13 and ULK1, suppressing ULK1 kinase activity and autophagy.