ULK-Atg13-FIP200 complexes mediate mTOR signaling to the autophagy machinery

Mol Biol Cell. 2009 Apr;20(7):1992-2003. doi: 10.1091/mbc.e08-12-1249. Epub 2009 Feb 18.

Abstract

Autophagy, the starvation-induced degradation of bulky cytosolic components, is up-regulated in mammalian cells when nutrient supplies are limited. Although mammalian target of rapamycin (mTOR) is known as the key regulator of autophagy induction, the mechanism by which mTOR regulates autophagy has remained elusive. Here, we identify that mTOR phosphorylates a mammalian homologue of Atg13 and the mammalian Atg1 homologues ULK1 and ULK2. The mammalian Atg13 binds both ULK1 and ULK2 and mediates the interaction of the ULK proteins with FIP200. The binding of Atg13 stabilizes and activates ULK and facilitates the phosphorylation of FIP200 by ULK, whereas knockdown of Atg13 inhibits autophagosome formation. Inhibition of mTOR by rapamycin or leucine deprivation, the conditions that induce autophagy, leads to dephosphorylation of ULK1, ULK2, and Atg13 and activates ULK to phosphorylate FIP200. These findings demonstrate that the ULK-Atg13-FIP200 complexes are direct targets of mTOR and important regulators of autophagy in response to mTOR signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Autophagy*
  • Autophagy-Related Protein-1 Homolog
  • Autophagy-Related Proteins
  • Cell Line
  • Humans
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Mice
  • Phagosomes / metabolism
  • Phosphorylation
  • Protein Binding
  • Protein Kinases / metabolism*
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism*
  • Protein-Tyrosine Kinases / metabolism*
  • Signal Transduction*
  • TOR Serine-Threonine Kinases

Substances

  • ATG13 protein, human
  • Adaptor Proteins, Signal Transducing
  • Autophagy-Related Proteins
  • Intracellular Signaling Peptides and Proteins
  • RB1CC1 protein, human
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Protein-Tyrosine Kinases
  • Autophagy-Related Protein-1 Homolog
  • Protein-Serine-Threonine Kinases
  • ULK1 protein, human
  • Ulk1 protein, mouse
  • Ulk2 protein, human