Sirt3-Mediated Deacetylation of Evolutionarily Conserved Lysine 122 Regulates MnSOD Activity in Response to Stress

Abstract

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. Re-introduction 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 micro-vacuolization in their hepatocytes.

Caspase-2 deficiency accelerates chemically induced liver cancer in mice

“…Sirt3 has several substrates involved in oxidative stress response such as MnSOD. 34 Consistent with the lack of increased Sirt3 activity as observed in WT, SOD activity was lower in DEN-injected Casp2 −/− mice, which is likely to contribute to higher oxidative damage in this group. Further, higher serum ALT levels and ALP levels indicate increased liver injury in this group of mice.…”

The Protein Deacetylase SIRT3 Prevents Oxidative Stress-induced Keratinocyte Differentiation

“…Keratinocytes-SIRT3 acts through several targets to both reduce superoxide production and enhance the oxidative stress response and detoxification mechanisms (8,(11)(12)(13)(14)(15)(16)(17). Consistent with the repression of mitochondrial oxidative stress by SIRT3, mitochondrial superoxide levels decreased in SIRT3-overexpressing keratinocytes (Fig.…”

“…Decreased availability of the sirtuin co-substrate NAD ϩ may lead to decreased SIRT3 activity in keratinocytes during differentiation. Given the well established role of SIRT3 as a regulator of mitochondrial oxidative stress (8,(11)(12)(13)(14)(15)(16)(17)(18), mitochondrial superoxide levels increased in both primary and immortalized keratinocytes with differentiation. We identified SIRT3 as a key regulator of this phenotype; constitutive SIRT3 deficiency resulted in increased mitochondrial superoxide levels, whereas constitutive SIRT3 expression reduced mitochondrial ROS.…”

“…It binds and deacetylates several mitochondrial proteins that promote mitochondrial oxidative metabolism, such as electron transport chain subunits and fatty acid oxidation enzymes (9,10). SIRT3 also dampens mitochondrial oxidative stress via deacetylation and subsequent activation of SOD2 and isocitrate dehydrogenase (8,(11)(12)(13)(14)(15)(16)(17)(18).…”

An acetylome peptide microarray reveals specificities and deacetylation substrates for all human sirtuin isoforms

“…3a; Supplementary Data 1 and 7), such as aconitase 2 (Lys50) and mitochondrial malate dehydrogenase (MDH; Lys239,335). Further identified targets likely contribute to the Sirt3 function in stress response 29,31 , such as the mitochondrial heat shock proteins mtHsp60 (Lys473, -469 and -156) and mtHsp75 (Lys332). For Sirt5, the best mitochondrial substrates are from the metabolic enzymes medium-chain acyl-CoA dehydrogenase (Lys212, 279, 301) and hydroxymethylglutaryl-CoA synthase 2 (Lys437), and from heat shock proteins mtHsp70 (Lys234) and mtHsp60 (Lys462, -130, -82 and 125).…”