title: ATG4B (Autophagin-1) phosphorylation modulates autophagy.
abstract: Autophagy is a catabolic cellular mechanism for entrapping cellular macromolecules and organelles in intracellular vesicles and degrading their contents by fusion with lysosomes. Important roles for autophagy have been elucidated for cell survival during nutrient insufficiency, eradication of intracellular pathogens, and counteracting aging through clearance of senescent proteins and mitochondria. Autophagic vesicles become decorated with LC3, a protein that mediates their fusion with lysosomes. LC3 is a substrate of the cysteine protease ATG4B (Autophagin-1), where cleavage generates a C-terminal glycine required for LC3 conjugation to lipids in autophagosomes. ATG4B both cleaves pro-LC3 and also hydrolyzes lipids from cleaved LC3. We show here that phosphorylation of ATG4B at Ser-383 and Ser-392 increases its hydrolyase activity as measured using LC3 as a substrate. Reconstituting atg4b(-/-) cells with phosphorylation-deficient ATG4B showed a role of ATG4B phosphorylation in LC3 delipidation and autophagic flux, thus demonstrating that the cellular activity of ATG4B is modulated by phosphorylation. Proteolytic conversion of pro-LC3 to LC3-I was not significantly impacted by ATG4B phosphorylation in cells. Phosphorylation-deficient ATG4B also showed reduced interactions with the lipid-conjugated LC3 but not unconjugated LC3. Taken together, these findings demonstrate a role for Ser-383 and Ser-392 phosphorylation of ATG4B in control of autophagy.
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037, Department of Radiation Oncology, Stanford University, Palo Alto, California 94305.
authors.forename: Zhifen
authors.initials: Z
authors.lastname: Yang
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037.
authors.forename: Rachel P
authors.initials: RP
authors.lastname: Wilkie-Grantham
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037.
authors.forename: Teruki
authors.initials: T
authors.lastname: Yanagi
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037, Department of Medical Education and Research; Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan 813, and.
authors.forename: Chih-Wen
authors.initials: CW
authors.lastname: Shu
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037, smatsuzawa@sbpdiscovery.org.
authors.forename: Shu-Ichi
authors.initials: S
authors.lastname: Matsuzawa
authors.affiliation: From the Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, California 92037, Roche, Pharmaceutical Research & Early Development, Roche Innovation Center-Basel, Basel, Switzerland CH4014 John_C.Reed@roche.com.
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
mesh_terms: D000818:Animals; D001343:Autophagy / Q000502:physiology*; D000071183:Autophagy-Related Proteins; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D054878:Lipoylation / Q000502:physiology*; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D059748:Proteolysis
chemical_list: D000071183:Autophagy-Related Proteins; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; C582881:Atg4b protein, mouse; D003546:Cysteine Endopeptidases
keywords: autophagy; phosphorylation; protease; protein kinase; protein-protein interaction