Lipidation of the LC3/GABARAP family of autophagy proteins relies on a membrane-curvature-sensing domain in Atg3

Nat Cell Biol. 2014 May;16(5):415-24. doi: 10.1038/ncb2940. Epub 2014 Apr 20.

Abstract

The components supporting autophagosome growth on the cup-like isolation membrane are likely to be different from those found on closed and maturing autophagosomes. The highly curved rim of the cup may serve as a functionally required surface for transiently associated components of the early acting autophagic machinery. Here we demonstrate that the E2-like enzyme, Atg3, facilitates LC3/GABARAP lipidation only on membranes exhibiting local lipid-packing defects. This activity requires an amino-terminal amphipathic helix similar to motifs found on proteins targeting highly curved intracellular membranes. By tuning the hydrophobicity of this motif, we can promote or inhibit lipidation in vitro and in rescue experiments in Atg3-knockout cells, implying a physiologic role for this stress detection. The need for extensive lipid-packing defects suggests that Atg3 is designed to work at highly curved membranes, perhaps including the limiting edge of the growing phagophore.

Publication types

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

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Motifs
  • Animals
  • Autophagy-Related Protein 7
  • Autophagy-Related Protein 8 Family
  • Autophagy-Related Proteins
  • Cell Membrane / enzymology*
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Liposomes
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Knockout
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Mutation
  • Phosphatidylethanolamines / metabolism
  • Rats
  • Signal Transduction*
  • Stress, Physiological
  • Transfection
  • Ubiquitin-Activating Enzymes / genetics
  • Ubiquitin-Activating Enzymes / metabolism
  • Ubiquitin-Conjugating Enzymes / deficiency
  • Ubiquitin-Conjugating Enzymes / genetics
  • Ubiquitin-Conjugating Enzymes / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Autophagy-Related Protein 8 Family
  • Autophagy-Related Proteins
  • Cytoskeletal Proteins
  • GABARAP protein, mouse
  • GABARAPL1 protein, human
  • GABARAPL2 protein, human
  • LC3 protein, rat
  • Liposomes
  • MAP1LC3 protein, mouse
  • Membrane Proteins
  • Microfilament Proteins
  • Microtubule-Associated Proteins
  • Phosphatidylethanolamines
  • phosphatidylethanolamine
  • Ubiquitin-Conjugating Enzymes
  • Atg7 protein, human
  • Autophagy-Related Protein 7
  • Ubiquitin-Activating Enzymes
  • Atg3 protein, mouse