title: Self-interaction is critical for Atg9 transport and function at the phagophore assembly site during autophagy.
abstract: Autophagy is the degradation of a cell's own components within lysosomes (or the analogous yeast vacuole), and its malfunction contributes to a variety of human diseases. Atg9 is the sole integral membrane protein required in formation of the initial sequestering compartment, the phagophore, and is proposed to play a key role in membrane transport; the phagophore presumably expands by vesicular addition to form a complete autophagosome. It is not clear through what mechanism Atg9 functions at the phagophore assembly site (PAS). Here we report that Atg9 molecules self-associate independently of other known autophagy proteins in both nutrient-rich and starvation conditions. Mutational analyses reveal that self-interaction is critical for anterograde transport of Atg9 to the PAS. The ability of Atg9 to self-interact is required for both selective and nonselective autophagy at the step of phagophore expansion at the PAS. Our results support a model in which Atg9 multimerization facilitates membrane flow to the PAS for phagophore formation.
authors.affiliation: Life Sciences Institute and Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Congcong
authors.initials: C
authors.lastname: He
authors.forename: Misuzu
authors.initials: M
authors.lastname: Baba
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Klionsky
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000502:physiology*; D000071183:Autophagy-Related Proteins; D004252:DNA Mutational Analysis; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D010588:Phagosomes / Q000378:metabolism*; D017354:Point Mutation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C441008:ATG18 protein, S cerevisiae; C434065:ATG9 protein, S cerevisiae; D000071183:Autophagy-Related Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000626:Aminopeptidases; C019689:APE1 protein, S cerevisiae