title: Post-Golgi Sec proteins are required for autophagy in Saccharomyces cerevisiae.
abstract: In eukaryotic cells, autophagy mediates the degradation of cytosolic contents in response to environmental change. Genetic analyses in fungi have identified over 30 autophagy-related (ATG) genes and provide substantial insight into the molecular mechanism of this process. However, one essential issue that has not been resolved is the origin of the lipids that form the autophagosome, the sequestering vesicle that is critical for autophagy. Here, we report that two post-Golgi proteins, Sec2 and Sec4, are required for autophagy. Sec4 is a Rab family GTPase, and Sec2 is its guanine nucleotide exchange factor. In sec2 and sec4 conditional mutant yeast, the anterograde movement of Atg9, a proposed membrane carrier, is impaired during starvation conditions. Similarly, in the sec2 mutant, Atg8 is inefficiently recruited to the phagophore assembly site, which is involved in autophagosome biogenesis, resulting in the generation of fewer autophagosomes. We propose that following autophagy induction the function of Sec2 and Sec4 are diverted to direct membrane flow to autophagosome formation.
authors.affiliation: Life Sciences Institute and Departments of Molecular, Cellular and Developmental Biology, and Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Jiefei
authors.initials: J
authors.lastname: Geng
authors.forename: Usha
authors.initials: U
authors.lastname: Nair
authors.forename: Kyoko
authors.initials: K
authors.lastname: Yasumura-Yorimitsu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Klionsky
mesh_terms: D001343:Autophagy / Q000502:physiology*; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D006056:Golgi Apparatus / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010588:Phagosomes / Q000378:metabolism; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C113757:ATG8 protein, S cerevisiae; C434065:ATG9 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; C064456:SEC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins
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