Sirt3, a mitochondrial NAD(+)-dependent deacetylase, is regarded as a potential regulator in cellular metabolism. However, the role of Sirt3 in the regulation of mitochondrial F(o)F(1)ATPase and the linkage to mitochondrial diseases is unclear. In this study, we demonstrated a role of Sirt3 in the regulation of F(o)F(1)ATPase activity in human cells. Knockdown of Sirt3 in 143B cells by shRNA transfection caused increased acetylation levels of the α and OSCP subunits of F(o)F(1)ATPase. We showed that Sirt3 physically interacted with the OSCP and led to its subsequent deacetylation. By incubation of mitochondria with the purified Sirt3 protein, Sirt3 could regulate F(o)F(1)ATPase activity through its deacetylase activity. Moreover, suppression of Sirt3 reduced the F(o)F(1)ATPase activity, consequently decreased the intracellular ATP level, diminished the capacity of mitochondrial respiration, and compromised metabolic adaptability of 143B cells to the use of galactose as the energy source. In human cells harboring ≅85% of mtDNA with 4977bp deletion, we showed that oxidative stress induced a reduction of Sirt3 expression, and an increased acetylation of the OSCP subunit of F(o)F(1)ATPase. Importantly, the expression of Sirt3 was also decreased in the skin fibroblasts from patients with CPEO syndrome. We further demonstrated that oxidative stress induced by 5-10μM of menadione impaired the Sirt3-mediated deacetylation and activation on F(o)F(1)ATPase activity through decreasing the protein level of Sirt3. Our findings suggest that increased intracellular ROS levels might modulate the expression of Sirt3 which deacetylates and activates F(o)F(1)ATPase in human cells with mitochondrial dysfunction caused by a pathogenic mtDNA mutation.
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