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Apg8 is a ubiquitin-like protein involved in autophagy in yeast. Apg8 is covalently but transiently attached to membrane lipids through the actions of activating, conjugating, and processing/deconjugating enzymes. The mammalian Apg8 homologues GATE-16, GARARAP, and MAP1-LC3 have been implicated in intra-Golgi transport, receptor sorting, and autophagy, respectively. All are served by a single set of activating and conjugating enzymes. Here we identify a novel mammalian Apg8 homologue, which we name Apg8L, and describe the synthesis of electrophilic probes based on the GATE-16, GARARAP, MAP1-LC3, and Apg8L proteins. These probes not only form specific adducts in crude cell lysates, but also allow identification of the cellular proteases specific for the C termini of these Apg8 homologues. We find a single protease, Apg4B/autophagin-1, capable of acting on GATE-16, GABARAP, MAP1-LC3, and Apg8L. The Apg4B/autophagin-1 protease thus serves as a processing/deconjugating enzyme for these four highly divergent mammalian Apg8 homologues.

Original publication

DOI

10.1074/jbc.M308762200

Type

Journal article

Journal

J Biol Chem

Publication Date

19/12/2003

Volume

278

Pages

51841 - 51850

Keywords

Animals, Autophagy, Carrier Proteins, Cysteine Endopeptidases, Cytoskeletal Proteins, Exopeptidases, Membrane Proteins, Mice, Microtubule-Associated Proteins, Molecular Probes, Protein Processing, Post-Translational, Saccharomyces cerevisiae Proteins, Sequence Alignment, Sequence Homology, Ubiquitins