Sirtuin 3, a New Target of PGC-1α, Plays an Important Role in the Suppression of ROS and Mitochondrial Biogenesis

Background: Sirtuin 3 (SIRT3) is one of the seven mammalian sirtuins, which are homologs of the yeast Sir2 gene. SIRT3 is the only sirtuin with a reported association with the human life span. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1 alpha) plays important roles in adaptive thermogenesis, gluconeogenesis, mitochondrial biogenesis and respiration. PGC-1 alpha induces several key reactive oxygen species (ROS)-detoxifying enzymes, but the molecular mechanism underlying this is not well understood. Results: Here we show that PGC-1 alpha strongly stimulated mouse Sirt3 gene expression in muscle cells and hepatocytes. Knockdown of PGC-1 alpha led to decreased Sirt3 gene expression. PGC-1 alpha activated the mouse SIRT3 promoter, which was mediated by an estrogen-related receptor (ERR) binding element (ERRE) (-407/-399) mapped to the promoter region. Chromatin immunoprecipitation and electrophoretic mobility shift assays confirmed that ERR alpha bound to the identified ERRE and PGC-1 alpha co-localized with ERR alpha in the mSirt3 promoter. Knockdown of ERR alpha reduced the induction of Sirt3 by PGC-1 alpha in C2C12 myotubes. Furthermore, Sirt3 was essential for PGC-1 alpha-dependent induction of ROS-detoxifying enzymes and several components of the respiratory chain, including glutathione peroxidase-1, superoxide dismutase 2, ATP synthase 5c, and cytochrome c. Overexpression of SIRT3 or PGC-1 alpha in C2C12 myotubes decreased basal ROS level. In contrast, knockdown of mSIRT3 increased basal ROS level and blocked the inhibitory effect of PGC-1 alpha on cellular ROS production. Finally, SIRT3 stimulated mitochondrial biogenesis, and SIRT3 knockdown decreased the stimulatory effect of PGC-1 alpha on mitochondrial biogenesis in C2C12 myotubes. Conclusion: Our results indicate that Sirt3 functions as a downstream target gene of PGC-1 alpha and mediates the PGC-1 alpha effects on cellular ROS production and mitochondrial biogenesis. Thus, SIRT3 integrates cellular energy metabolism and ROS generation. The elucidation of the molecular mechanisms of SIRT3 regulation and its physiological functions may provide a novel target for treating ROS-related disease.