mTOR inhibits autophagy by controlling ULK1 ubiquitylation, self-association and function through AMBRA1 and TRAF6

F Nazio, F Strappazzon, M Antonioli, P Bielli… - Nature cell …, 2013 - nature.com
F Nazio, F Strappazzon, M Antonioli, P Bielli, V Cianfanelli, M Bordi, C Gretzmeier, J Dengjel
Nature cell biology, 2013nature.com
Autophagy is important in the basal or stress-induced clearance of bulk cytosol, damaged
organelles, pathogens and selected proteins by specific vesicles, the autophagosomes.
Following mTOR (mammalian target of rapamycin) inhibition, autophagosome formation is
primed by the ULK1 and the beclin-1–Vps34–AMBRA1 complexes, which are linked
together by a scaffold platform, the exocyst. Although several regulative steps have been
described along this pathway, few targets of mTOR are known, and the cross-talk between …
Abstract
Autophagy is important in the basal or stress-induced clearance of bulk cytosol, damaged organelles, pathogens and selected proteins by specific vesicles, the autophagosomes. Following mTOR (mammalian target of rapamycin) inhibition, autophagosome formation is primed by the ULK1 and the beclin-1–Vps34–AMBRA1 complexes, which are linked together by a scaffold platform, the exocyst. Although several regulative steps have been described along this pathway, few targets of mTOR are known, and the cross-talk between ULK1 and beclin 1 complexes is still not fully understood. We show that under non-autophagic conditions, mTOR inhibits AMBRA1 by phosphorylation, whereas on autophagy induction, AMBRA1 is dephosphorylated. In this condition, AMBRA1, interacting with the E3-ligase TRAF6, supports ULK1 ubiquitylation by LYS-63-linked chains, and its subsequent stabilization, self-association and function. As ULK1 has been shown to activate AMBRA1 by phosphorylation, the proposed pathway may act as a positive regulation loop, which may be targeted in human disorders linked to impaired autophagy.
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