Autophagy-related protein 8 (Atg8) family interacting motif in Atg3 mediates the Atg3-Atg8 interaction and is crucial for the cytoplasm-to-vacuole targeting pathway

J Biol Chem. 2010 Sep 17;285(38):29599-607. doi: 10.1074/jbc.M110.113670. Epub 2010 Jul 8.

Abstract

The autophagy-related protein 8 (Atg8) conjugation system is essential for the formation of double-membrane vesicles called autophagosomes during autophagy, a bulk degradation process conserved among most eukaryotes. It is also important in yeast for recognizing target vacuolar enzymes through the receptor protein Atg19 during the cytoplasm-to-vacuole targeting (Cvt) pathway, a selective type of autophagy. Atg3 is an E2-like enzyme that conjugates Atg8 with phosphatidylethanolamine. Here, we show that Atg3 directly interacts with Atg8 through the WEDL sequence, which is distinct from canonical interaction between E2 and ubiquitin-like modifiers. Moreover, NMR experiments suggest that the mode of interaction between Atg8 and Atg3 is quite similar to that between Atg8/LC3 and the Atg8 family interacting motif (AIM) conserved in autophagic receptors, such as Atg19 and p62. Thus, the WEDL sequence in Atg3 is a canonical AIM. In vitro analyses showed that Atg3 AIM is crucial for the transfer of Atg8 from the Atg8∼Atg3 thioester intermediate to phosphatidylethanolamine but not for the formation of the intermediate. Intriguingly, in vivo experiments showed that it is necessary for the Cvt pathway but not for starvation-induced autophagy. Atg3 AIM attenuated the inhibitory effect of Atg19 on Atg8 lipidation in vitro, suggesting that Atg3 AIM may be important for the lipidation of Atg19-bound Atg8 during the Cvt pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Autophagy-Related Protein 8 Family
  • Autophagy-Related Proteins
  • Cytoplasm / metabolism*
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Phosphatidylethanolamines / metabolism
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein Transport / genetics
  • Protein Transport / physiology
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Signal Transduction / genetics
  • Signal Transduction / physiology
  • Ubiquitin-Conjugating Enzymes / chemistry
  • Ubiquitin-Conjugating Enzymes / genetics
  • Ubiquitin-Conjugating Enzymes / metabolism
  • Vacuoles / metabolism*

Substances

  • ATG8 protein, S cerevisiae
  • Autophagy-Related Protein 8 Family
  • Autophagy-Related Proteins
  • Fungal Proteins
  • Microtubule-Associated Proteins
  • Phosphatidylethanolamines
  • Saccharomyces cerevisiae Proteins
  • phosphatidylethanolamine
  • Ubiquitin-Conjugating Enzymes
  • ATG3 protein, S cerevisiae