Genetic deletion of the mitochondrial deacetylase sirtuin-3 (Sirt3) results in increased mitochondrial superoxide, a tumor-permissive environment, and mammary tumor development. MnSOD contains a nutrient- and ionizing radiation (IR)-dependent reversible acetyl-lysine that is hyperacetylated in Sirt3-/- livers at 3 months of age. Livers of Sirt3-/- mice exhibit decreased MnSOD activity, but not immunoreactive protein, relative to wild-type livers. Reintroduction of wild-type but not deacetylation null Sirt3 into Sirt3-/- MEFs deacetylated lysine and restored MnSOD activity. Site-directed mutagenesis of MnSOD lysine 122 to an arginine, mimicking deacetylation (lenti-MnSODK122-R), increased MnSOD activity when expressed in MnSOD-/- MEFs, suggesting acetylation directly regulates function. Furthermore, infection of Sirt3-/- MEFs with lenti-MnSODK122-R inhibited in vitro immortalization by an oncogene (Ras), inhibited IR-induced genomic instability, and decreased mitochondrial superoxide. Finally, IR was unable to induce MnSOD deacetylation or activity in Sirt3-/- livers, and these irradiated livers displayed significant IR-induced cell damage and microvacuolization in their hepatocytes.
Bibliographical noteFunding Information:
D.G. is supported by 1R01CA152601-01 from the NCI, BC093803 from the DOD, and SPORE P50CA98131. D.R.S., A.K.O., and M.C.C. are supported by grants from the NIH and DOE (R01CA133114, T32CA078586, P30CA086862, and DE-SC0000830). J.D.P. is supported by F30AG030839. We thank Melissa Stauffer of Scientific Editing Solutions for editorial assistance.