ULK1 complex

The ULK1 complex is a tetrameric serine/threonine kinase assembly comprising ULK1 (Unc-51-like autophagy-activating kinase 1), scaffold FIP200, and regulatory subunits ATG13 and ATG101. It is the primary initiator of autophagosome formation in mammals: upon activation, ULK1 phosphorylates ATG14, stimulates the class III PI3-kinase complex, and triggers phagophore nucleation. Two master regulators integrate opposing nutrient signals: mTORC1 phosphorylates ULK1 at Ser757 under nutrient sufficiency, disrupting its AMPK interaction and suppressing autophagy; AMPK, activated by energy deficit (elevated AMP/ATP), phosphorylates ULK1 at Ser317 and Ser777, stimulating the complex (Kim et al., 2011; Egan et al., 2011). With age, Ser555 phosphorylation declines in human and murine skeletal muscle, correlating with impaired mitophagy, mitochondrial ROS accumulation, and contractile weakness. In cognitively unimpaired adults (COGNORM, n=75), serum ULK1 falls with age; in Alzheimer patients (NorCog Cohort, n=316), reduced ULK1 associated with deficient autophagic flux and tauopathy. ULK1 overexpression in AD mouse models restored autophagy, lowered amyloid-beta and acetylated tau, and delayed cognitive decline (Pan et al., 2026). No ULK1 agonist has entered clinical trials.