title: 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.
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.
authors.affiliation: Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Nobuo N
authors.initials: NN
authors.lastname: Noda
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakatogawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kumeta
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: Fuyuhiko
authors.initials: F
authors.lastname: Inagaki
mesh_terms: D020816:Amino Acid Motifs; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D003593:Cytoplasm / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
chemical_list: C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D005656:Fungal Proteins; D008869:Microtubule-Associated Proteins; D010714:Phosphatidylethanolamines; D029701:Saccharomyces cerevisiae Proteins; C483858:phosphatidylethanolamine; D044763:Ubiquitin-Conjugating Enzymes; C104235:ATG3 protein, S cerevisiae