title: Apg13p and Vac8p are part of a complex of phosphoproteins that are required for cytoplasm to vacuole targeting.
abstract: We have been studying protein components that function in the cytoplasm to vacuole targeting (Cvt) pathway and the overlapping process of macroautophagy. The Vac8 and Apg13 proteins are required for the import of aminopeptidase I (API) through the Cvt pathway. We have identified a protein-protein interaction between Vac8p and Apg13p by both two-hybrid and co-immunoprecipitation analysis. Subcellular fractionation of API indicates that Vac8p and Apg13p are involved in the vesicle formation step of the Cvt pathway. Kinetic analysis of the Cvt pathway and autophagy indicates that, although Vac8p is essential for Cvt transport, it is less important for autophagy. In vivo phosphorylation experiments demonstrate that both Vac8p and Apg13p are phosphorylated proteins, and Apg13p phosphorylation is regulated by changing nutrient conditions. Although Apg13p interacts with the serine/threonine kinase Apg1p, this protein is not required for phosphorylation of either Vac8p or Apg13p. Subcellular fractionation experiments indicate that Apg13p and a fraction of Apg1p are membrane-associated. Vac8p and Apg13p may be part of a larger protein complex that includes Apg1p and additional interacting proteins. Together, these components may form a protein complex that regulates the conversion between Cvt transport and autophagy in response to changing nutrient conditions.
authors.affiliation: Section of Microbiology, University of California, Davis 95616, USA.
authors.forename: S V
authors.initials: SV
authors.lastname: Scott
authors.forename: D C
authors.initials: DC
authors.lastname: Nice
authors.forename: J J
authors.initials: JJ
authors.lastname: Nau
authors.forename: L S
authors.initials: LS
authors.lastname: Weisman
authors.forename: Y
authors.initials: Y
authors.lastname: Kamada
authors.forename: I
authors.initials: I
authors.lastname: Keizer-Gunnink
authors.forename: T
authors.initials: T
authors.lastname: Funakoshi
authors.forename: M
authors.initials: M
authors.lastname: Veenhuis
authors.forename: Y
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: D J
authors.initials: DJ
authors.lastname: Klionsky
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000626:Aminopeptidases / Q000378:metabolism; D000071183:Autophagy-Related Proteins; D001692:Biological Transport; D003593:Cytoplasm / Q000378:metabolism*; D015723:Gene Library; D007700:Kinetics; D008074:Lipoproteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D008854:Microscopy, Electron; D008954:Models, Biological; D010750:Phosphoproteins / Q000378:metabolism* / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D020798:Two-Hybrid System Techniques; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins
chemical_list: C413216:ATG13 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D029701:Saccharomyces cerevisiae Proteins; C111373:VAC8 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D017346:Protein Serine-Threonine Kinases; D000626:Aminopeptidases; C019689:APE1 protein, S cerevisiae