title: LC3, GABARAP and GATE16 localize to autophagosomal membrane depending on form-II formation.
abstract: Rat LC3, a homologue of yeast Atg8 (Aut7/Apg8), localizes to autophagosomal membranes after post-translational modifications. The C-terminal fragment of LC3 is cleaved immediately following synthesis to yield a cytosolic form called LC3-I. A subpopulation of LC3-I is further converted to an autophagosome-associating form, LC3-II. Because yeast Atg8 is conjugated with phosphatidylethanolamine (PE) by a ubiquitin-like system, it has been hypothesized that LC3 is modified in a similar manner. Here, we show that [(14)C]-ethanolamine was preferentially incorporated into LC3-II, suggesting that LC3-II is a PE-conjugated form. LC3-II can be a substrate of mammalian Atg4B, a homologue of yeast Atg8-PE deconjugase, supporting the idea that LC3-II is LC3-PE. Moreover, two other mammalian homologues of yeast Atg8, gamma-aminobutyric-acid-type-A-receptor-associated protein (GABARAP) and Golgi-associated ATPase enhancer of 16 kDa (GATE16) also generate form II, which are recovered in membrane fractions. Generation of the form II correlates with autophagosome association of GABARAP and GATE16. These results suggest that all mammalian Atg8 homologues receive a common modification to associate with autophagosomal membrane as the form II.
authors.affiliation: Department of Cell Biology, National Institute for Basic Biology, Myodaiji 38, Okazaki 444-8585, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kabeya
authors.forename: Noboru
authors.initials: N
authors.lastname: Mizushima
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Satsuki
authors.initials: S
authors.lastname: Oshitani-Okamoto
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Yoshimori
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D000071190:Autophagy-Related Protein 8 Family; D002250:Carbon Radioisotopes; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D045744:Cell Line, Tumor; D019856:Ethanolamine / Q000378:metabolism; D005456:Fluorescent Dyes; D005998:Glycine / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D049408:Luminescent Agents; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008840:Microfilament Proteins; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D011233:Precipitin Tests; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development; D013234:Stem Cells / Q000166:cytology; D013347:Subcellular Fractions / Q000378:metabolism; D013379:Substrate Specificity; D018243:Teratocarcinoma
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000071190:Autophagy-Related Protein 8 Family; D002250:Carbon Radioisotopes; D002352:Carrier Proteins; D005456:Fluorescent Dyes; C116741:GABARAP protein, human; C498698:GABARAPL2 protein, human; C407740:Gabarapl2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D049408:Luminescent Agents; C477012:MAP1LC3A protein, human; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D019856:Ethanolamine; D005998:Glycine