Atg13 HORMA domain recruits Atg9 vesicles during autophagosome formation.
During autophagosome formation, autophagosome-related (Atg) proteins are recruited hierarchically to organize the preautophagosomal structure (PAS). Atg13, which plays a central role in the initial step of PAS formation, consists of two structural regions, the N-terminal HORMA (from Hop1, Rev7, and Mad2) domain and the C-terminal disordered region. The C-terminal disordered region of Atg13, which contains the binding sites for Atg1 and Atg17, is essential for the initiation step in which the Atg1 complex is formed to serve as a scaffold for the PAS. The N-terminal HORMA domain of Atg13 is also essential for autophagy, but its molecular function has not been established. In this study, we searched for interaction partners of the Atg13 HORMA domain and found that it binds Atg9, a multispanning membrane protein that exists on specific cytoplasmic vesicles (Atg9 vesicles). After the Atg1 complex is formed, Atg9 vesicles are recruited to the PAS and become part of the autophagosomal membrane. HORMA domain mutants, which are unable to interact with Atg9, impaired the PAS localization of Atg9 vesicles and exhibited severe defects in starvation-induced autophagy. Thus, Atg9 vesicles are recruited to the PAS via the interaction with the Atg13 HORMA domain. Based on these findings, we propose that the two distinct regions of Atg13 play crucial roles in distinct steps of autophagosome formation: In the first step, Atg13 forms a scaffold for the PAS via its C-terminal disordered region, and subsequently it recruits Atg9 vesicles via its N-terminal HORMA domain.
Frontier Research Center and Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan; and.
Sho W
SW
Suzuki
Frontier Research Center and yamamoto-hayashi@iri.titech.ac.jp yohsumi@iri.titech.ac.jp.
Hayashi
H
Yamamoto
Frontier Research Center and.
Yu
Y
Oikawa
Frontier Research Center and.
Chika
C
Kondo-Kakuta
Advanced Medical Research Center, Yokohama City University, Yokohama 236-0004, Japan.
Yayoi
Y
Kimura
Advanced Medical Research Center, Yokohama City University, Yokohama 236-0004, Japan.
Hisashi
H
Hirano
Frontier Research Center and yamamoto-hayashi@iri.titech.ac.jp yohsumi@iri.titech.ac.jp.
Yoshinori
Y
Ohsumi
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000378:metabolism*; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D010588:Phagosomes / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism
C413216:ATG13 protein, S cerevisiae; C434065:ATG9 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins
Atg13; Atg9; HORMA domain; autophagy