Chemical genetic analysis of Apg1 reveals a non-kinase role in the induction of autophagy.
Macroautophagy is a catabolic membrane trafficking phenomenon that is observed in all eukaryotic cells in response to various stimuli, such as nitrogen starvation and challenge with specific hormones. In the yeast Saccharomyces cerevisiae, the induction of autophagy involves a direct signal transduction mechanism that affects membrane dynamics. In this system, the induction process modifies a constitutive trafficking pathway called the cytoplasm-to-vacuole targeting (Cvt) pathway, which transports the vacuolar hydrolase aminopeptidase I, from the formation of small Cvt vesicles to the formation of autophagosomes. Apg1 is one of the proteins required for the direct signal transduction cascade that modifies membrane dynamics. Although Apg1 is required for both the Cvt pathway and autophagy, we find that Apg1 kinase activity is required only for Cvt trafficking of aminopeptidase I but not for import via autophagy. In addition, the data support a novel role for Apg1 in nucleation of autophagosomes that is distinct from its catalytic kinase activity and imply a qualitative difference in the mechanism of autophagosome and Cvt vesicle formation.
Abeliovich
Hagai
H
University of Michigan, Department of Molecular, Cellular and Developmental Biology, Ann Arbor 48109, USA.
Zhang
Chao
C
Dunn
William A
WA
Shokat
Kevan M
KM
Klionsky
Daniel J
DJ
D000626:Aminopeptidases / Q000378:metabolism; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D003062:Codon; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D049452:Green Fluorescent Proteins; D007074:Immunoglobulin G / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D016366:Open Reading Frames; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011487:Protein Conformation; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics*; D012685:Sepharose / Q000737:chemistry; D020123:Sirolimus / Q000494:pharmacology; D013997:Time Factors; D020798:Two-Hybrid System Techniques; D014617:Vacuoles / Q000378:metabolism
D000071183:Autophagy-Related Proteins; D003062:Codon; D007074:Immunoglobulin G; D008164:Luminescent Proteins; D010710:Phosphates; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D012685:Sepharose; D011494:Protein Kinases; C477823:ATG1 protein, S cerevisiae; D000626:Aminopeptidases; D009584:Nitrogen; D020123:Sirolimus