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Location: Children's Nutrition Research Center

Title: Regulation of succinate dehydrogenase activity by SIRT3 in mammalian mitochondria

item Cimen, Huseyin
item Han, Min-joon
item Yang, Yongjie
item Tong, Qiang
item Koc, Hasan
item Koc, Emine

Submitted to: Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2009
Publication Date: 1/19/2010
Citation: Cimen, H., Han, M., Yang, Y., Tong, Q., Koc, H., Koc, E.C. 2010. Regulation of succinate dehydrogenase activity by SIRT3 in mammalian mitochondria. Biochemistry. 49(2):304-311.

Interpretive Summary: SIRT3 protein is a deacetylases, an enzyme that removes acetyl modification from target proteins. The function of SIRT3 in a cell is not clear. In this study, we found that SIRT3 could regulate a key metabolic enzyme, succinate dehydrogenase, through binding and modifying one of its subunits (SdhA). We observed that stimulation of SIRT3 expression in cells led to a decrease of SdhA acetyl modification with increased succinate dehydrogenase enzymatic activity. In addition, we treated cells with SIRT3 inhibitors to block SIRT3 removal of acetyl modification from SdhA, which led to suppression of succinate dehydrogenase enzymatic activity. Our findings constitute the first evidence of the regulation of succinate dehydrogenase activity by the reversible modification of the SdhA protein by SIRT3 deacetylase.

Technical Abstract: A member of the sirtuin family of NAD (+) dependent deacetylases, SIRT3, is identified as one of the major mitochondrial deacetylases, located in mammalian mitochondria responsible for deacetylation of several metabolic enzymes and components of oxidative phosphorylation. Regulation of protein deacetylation by SIRT3 is important for mitochondrial metabolism, cell survival, and longevity. In this study, we identified one of the Complex II subunits, succinate dehydrogenase flavoprotein (SdhA) subunit, as a novel SIRT3 substrate in SIRT3 knockout mice. Several acetylated Lys residues were mapped by tandem mass spectrometry, and we determined the role of acetylation in Complex II activity in SIRT3 knockout mice. In agreement with SIRT3-dependent activation of Complex I, we observed that deacetylation of the SdhA subunit increased the Complex II activity in wild-type mice. In addition, we treated K562 cell lines with nicotinamide and kaempferol to inhibit deacetylase activity of SIRT3 and stimulate SIRT3 expression, respectively. Stimulation of SIRT3 expression decreased the level of acetylation of the SdhA subunit and increased Complex II activity in kaempherol-treated cells compared to control and nicotinamide-treated cells. Evaluation of acetylated residues in the SdhA crystal structure from porcine and chicken suggests that acetylation of the hydrophilic surface of SdhA may control the entry of the substrate into the active site of the protein and regulate the enzyme.