RESUMO
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 Sirt3â»/â» livers at 3 months of age. Livers of Sirt3â»/â» mice exhibit decreased MnSOD activity, but not immunoreactive protein, relative to wild-type livers. Reintroduction of wild-type but not deacetylation null Sirt3 into Sirt3â»/â» MEFs deacetylated lysine and restored MnSOD activity. Site-directed mutagenesis of MnSOD lysine 122 to an arginine, mimicking deacetylation (lenti-MnSOD(K122-R)), increased MnSOD activity when expressed in MnSODâ»/â» MEFs, suggesting acetylation directly regulates function. Furthermore, infection of Sirt3â»/â» MEFs with lenti-MnSOD(K122-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 Sirt3â»/â» livers, and these irradiated livers displayed significant IR-induced cell damage and microvacuolization in their hepatocytes.
Assuntos
Sequência Conservada , Evolução Molecular , Lisina/metabolismo , Estresse Oxidativo , Sirtuína 3/metabolismo , Superóxido Dismutase/metabolismo , Acetilação , Animais , Arginina/metabolismo , Linhagem Celular , Camundongos , Mutagênese Sítio-Dirigida , Sirtuína 3/deficiência , Sirtuína 3/genéticaRESUMO
Oxidative damage to proteins is one of the major pathogenic mechanisms in many chronic diseases. Therefore, inhibition of this oxidative damage can be an important part of therapeutic strategies. Pyridoxamine (PM), a prospective drug for treatment of diabetic nephropathy, has been previously shown to inhibit several oxidative and glycoxidative pathways, thus protecting amino acid side chains of the proteins from oxidative damage. Here, we demonstrated that PM can also protect protein backbone from fragmentation induced via different oxidative mechanisms including autoxidation of glucose. This protection was due to hydroxyl radical scavenging by PM and may contribute to PM therapeutic effects shown in clinical trials.