title: Kinetics comparisons of mammalian Atg4 homologues indicate selective preferences toward diverse Atg8 substrates.
abstract: The Atg4 cysteine proteases are required for processing Atg8 for the latter to be conjugated to phosphatidylethanolamine on autophagosomal membranes, a key step in autophagosome biogenesis. Notably, whereas there are only one atg4 and one atg8 gene in the yeast, the mammals have four Atg4 homologues and six Atg8 homologues. The Atg8 homologues seem to play different roles in autophagosome biogenesis, and previous studies had indicated that they could be differentially processed by Atg4 homologues. The present study provided the first detailed kinetics analysis of all four Atg4 homologues against four representative Atg8 homologues. The data indicated that Atg4B possessed the broadest spectrum against all substrates, followed by Atg4A, whereas Atg4C and Atg4D had minimal activities as did the catalytic mutant of Atg4B (C74S). On the other hand, GATE-16 seemed to be the overall best substrate for Atg4 proteases. The kinetics parameters of Atg4B were also affected by its structure and that of the substrates, indicating a process of induced fit. The determination of the kinetics parameters of the various Atg4-Atg8 pairs provides a base for the understanding of the potential selective impact of the reaction on autophagosome biogenesis.
authors.affiliation: Department of Pathology and Laboratory Medicine, Indiana University School of Medicine Indianapolis, Indiana 46202, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Hou
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wang
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Chen
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Shao
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Yin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D002384:Catalysis; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008322:Mammals; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D013379:Substrate Specificity
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; C498698:GABARAPL2 protein, human; D008840:Microfilament Proteins; C474025:ATG4A protein, human; C507524:ATG4B protein, human; C543490:ATG4D protein, human; D003546:Cysteine Endopeptidases