ULK1/Atg1 is a serine/threonine protein kinase essential for autophagy. In mammals, ULK1 usually forms a large complex with Atg13 and FIP200, which are highly phosphorylated by the serine/threonine protein kinase known as mammalian target of rapamycin (mTOR), leading to its inactivation. Under starvation conditions, mTOR dissociates from the ULK1-Atg13-FIP200 complex, resulting in reduced phosphorylation of ULK1 and Atg13. This triggers localization of the ULK1-Atg13-FIP200 complex in the isolation membrane and recovery of ULK1 kinase activity, thereby promoting autophagy.
■ Western blotting