Mammalian Sir2 Homolog SIRT3 Regulates Global Mitochondrial Lysine Acetylation

Abstract

Homologs of the Saccharomyces cerevisiae Sir2 protein, sirtuins, promote longevity in many organisms. Studies of the sirtuin SIRT3 have so far been limited to cell culture systems. Here, we investigate the localization and function of SIRT3 in vivo. We show that endogenous mouse SIRT3 is a soluble mitochondrial protein. To address the function and relevance of SIRT3 in the regulation of energy metabolism, we generated and phenotypically characterized SIRT3 knockout mice. SIRT3-deficient animals exhibit striking mitochondrial protein hyperacetylation, suggesting that SIRT3 is a major mitochondrial deacetylase. In contrast, no mitochondrial hyperacetylation was detectable in mice lacking the two other mitochondrial sirtuins, SIRT4 and SIRT5. Surprisingly, despite this biochemical phenotype, SIRT3-deficient mice are metabolically unremarkable under basal conditions and show normal adaptive thermogenesis, a process previously suggested to involve SIRT3. Overall, our results extend the recent finding of lysine acetylation of mitochondrial proteins and demonstrate that SIRT3 has evolved to control reversible lysine acetylation in this organelle.

SUPPLEMENTAL MATERIAL

We are grateful to C. B. Newgard, J. R. Bain, O. R. Ilkayeva, R. D. Stevens, B. R. Wenner, and L. C. Naliboff (Metabolomics Laboratory, Sarah W. Stedman Nutrition & Metabolism Center, Duke University Medical Center, Durham, NC) for metabolite analysis. We thank N.-G. Larsson (Karolinska Institute, Stockholm, Sweden) for his generous gift of the TFAM antibody and members of the Alt and Verdin laboratories, B. J. North (Harvard Medical School), and B. B. Lowell (BIDMC, Harvard Medical School) for helpful discussions.

This work was supported by Ellison Medical Foundation Senior Scholar Awards (to F.W.A. and E.V.), by funds from the Sandler Foundation Program in Basic Sciences (to E.V.), and an NIH National Center for Research Resources facilities grant (1C06RR18928) to the J. David Gladstone Institutes. F.W.A. is an Investigator of the Howard Hughes Medical Institute. D.B.L. is supported by a K08 award from NIA/NIH. B.S. is the recipient of a UCSF Sandler Postdoctoral Research Fellowship Award. J.B. is supported by a grant from the Carlsberg Foundation. CEBI is supported by a grant from the Danish National Research Foundation.

F.W.A. and E.V. are members of the scientific advisory board of Sirtris Pharmaceuticals. L.G. is a founder and board member of Elixir Pharmaceuticals. G.Y., D.V., and A.M. are employees and shareholders of Regeneron Pharmaceuticals.

All animal experiments carried out herein were performed under established protocols per institutional guidelines.