title: Atg9 vesicles recruit vesicle-tethering proteins Trs85 and Ypt1 to the autophagosome formation site.
abstract: Atg9 is a transmembrane protein that is essential for autophagy. In the budding yeast Saccharomyces cerevisiae, it has recently been revealed that Atg9 exists on cytoplasmic small vesicles termed Atg9 vesicles. To identify the components of Atg9 vesicles, we purified the Atg9 vesicles and subjected them to mass spectrometry. We found that their protein composition was distinct from other organellar membranes and that Atg9 and Atg27 in particular are major components of Atg9 vesicles. In addition to these two components, Trs85, a specific subunit of the transport protein particle III (TRAPPIII) complex, and the Rab GTPase Ypt1 were also identified. Trs85 directly interacts with Atg9, and the Trs85-containing TRAPPIII complex facilitates the association of Ypt1 onto Atg9 vesicles. We also showed that Trs85 and Ypt1 are localized to the preautophagosomal structure in an Atg9-dependent manner. Our data suggest that Atg9 vesicles recruit the TRAPPIII complex and Ypt1 to the preautophagosomal structure. The vesicle-tethering machinery consequently acts in the process of autophagosome formation.
authors.affiliation: Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Kakuta
authors.forename: Hayashi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Lumi
authors.initials: L
authors.lastname: Negishi
authors.forename: Chika
authors.initials: C
authors.lastname: Kondo-Kakuta
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hayashi
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
mesh_terms: D001343:Autophagy; D000071183:Autophagy-Related Proteins; D022162:Cytoplasmic Vesicles / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C434065:ATG9 protein, S cerevisiae; D000071183:Autophagy-Related Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C579080:TRS85 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C060755:YPT1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins