title: Analysis of acetylation stoichiometry suggests that SIRT3 repairs nonenzymatic acetylation lesions.
abstract: Acetylation is frequently detected on mitochondrial enzymes, and the sirtuin deacetylase SIRT3 is thought to regulate metabolism by deacetylating mitochondrial proteins. However, the stoichiometry of acetylation has not been studied and is important for understanding whether SIRT3 regulates or suppresses acetylation. Using quantitative mass spectrometry, we measured acetylation stoichiometry in mouse liver tissue and found that SIRT3 suppressed acetylation to a very low stoichiometry at its target sites. By examining acetylation changes in the liver, heart, brain, and brown adipose tissue of fasted mice, we found that SIRT3-targeted sites were mostly unaffected by fasting, a dietary manipulation that is thought to regulate metabolism through SIRT3-dependent deacetylation. Globally increased mitochondrial acetylation in fasted liver tissue, higher stoichiometry at mitochondrial acetylation sites, and greater sensitivity of SIRT3-targeted sites to chemical acetylation in vitro and fasting-induced acetylation in vivo, suggest a nonenzymatic mechanism of acetylation. Our data indicate that most mitochondrial acetylation occurs as a low-level nonenzymatic protein lesion and that SIRT3 functions as a protein repair factor that removes acetylation lesions from lysine residues.
authors.affiliation: The NNF Center for Protein Research, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark briantate.weinert@cpr.ku.dk chuna.choudhary@cpr.ku.dk.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Weinert
authors.affiliation: Division of Gastroenterology and Hepatology, Medical University Graz, Graz, Austria.
authors.forename: Tarek
authors.initials: T
authors.lastname: Moustafa
authors.affiliation: The NNF Center for Protein Research, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark.
authors.forename: Vytautas
authors.initials: V
authors.lastname: Iesmantavicius
authors.affiliation: Institute of Molecular Biosciences, University of Graz, Graz, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Zechner
authors.affiliation: The NNF Center for Protein Research, Faculty of Health Sciences University of Copenhagen, Copenhagen, Denmark briantate.weinert@cpr.ku.dk chuna.choudhary@cpr.ku.dk.
authors.forename: Chunaram
authors.initials: C
authors.lastname: Choudhary
mesh_terms: D000107:Acetylation; D000818:Animals; D005215:Fasting; D006367:HeLa Cells; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000201:enzymology; D009928:Organ Specificity; D011499:Protein Processing, Post-Translational; D056566:Sirtuin 3 / Q000502:physiology*
chemical_list: C525046:Sirt3 protein, mouse; D056566:Sirtuin 3
keywords: SIRT3; acetylation; mass spectrometry; proteomics; stoichiometry