Nutrient-dependent mTORC1 association with the ULK1-Atg13-FIP200 complex required for autophagy

Mol Biol Cell. 2009 Apr;20(7):1981-91. doi: 10.1091/mbc.e08-12-1248. Epub 2009 Feb 11.

Abstract

Autophagy is an intracellular degradation system, by which cytoplasmic contents are degraded in lysosomes. Autophagy is dynamically induced by nutrient depletion to provide necessary amino acids within cells, thus helping them adapt to starvation. Although it has been suggested that mTOR is a major negative regulator of autophagy, how it controls autophagy has not yet been determined. Here, we report a novel mammalian autophagy factor, Atg13, which forms a stable approximately 3-MDa protein complex with ULK1 and FIP200. Atg13 localizes on the autophagic isolation membrane and is essential for autophagosome formation. In contrast to yeast counterparts, formation of the ULK1-Atg13-FIP200 complex is not altered by nutrient conditions. Importantly, mTORC1 is incorporated into the ULK1-Atg13-FIP200 complex through ULK1 in a nutrient-dependent manner and mTOR phosphorylates ULK1 and Atg13. ULK1 is dephosphorylated by rapamycin treatment or starvation. These data suggest that mTORC1 suppresses autophagy through direct regulation of the approximately 3-MDa ULK1-Atg13-FIP200 complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acids / deficiency
  • Amino Acids / pharmacology*
  • Animals
  • Autophagy / drug effects*
  • Autophagy-Related Protein-1 Homolog
  • Autophagy-Related Proteins
  • Cell Line
  • Cell Membrane / drug effects
  • Cell Membrane / enzymology
  • Cell Membrane / ultrastructure
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Molecular Weight
  • Multiprotein Complexes
  • Phosphorylation / drug effects
  • Protein Binding / drug effects
  • Protein Kinases / metabolism
  • Protein Transport / drug effects
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proteins
  • TOR Serine-Threonine Kinases
  • Transcription Factors / metabolism*

Substances

  • ATG13 protein, human
  • Adaptor Proteins, Signal Transducing
  • Amino Acids
  • Autophagy-Related Proteins
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • Proteins
  • Rb1cc1 protein, mouse
  • Transcription Factors
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Autophagy-Related Protein-1 Homolog
  • Mechanistic Target of Rapamycin Complex 1
  • Protein-Serine-Threonine Kinases
  • Ulk1 protein, mouse