SIRT3 Deacetylates and Activates OPA1 To Regulate Mitochondrial Dynamics during Stress

Abstract

Mitochondrial morphology is regulated by the balance between two counteracting mitochondrial processes of fusion and fission. There is significant evidence suggesting a stringent association between morphology and bioenergetics of mitochondria. Morphological alterations in mitochondria are linked to several pathological disorders, including cardiovascular diseases. The consequences of stress-induced acetylation of mitochondrial proteins on the organelle morphology remain largely unexplored. Here we report that OPA1, a mitochondrial fusion protein, was hyperacetylated in hearts under pathological stress and this posttranslational modification reduced the GTPase activity of the protein. The mitochondrial deacetylase SIRT3 was capable of deacetylating OPA1 and elevating its GTPase activity. Mass spectrometry and mutagenesis analyses indicated that in SIRT3-deficient cells OPA1 was acetylated at lysine 926 and 931 residues. Overexpression of a deacetylation-mimetic version of OPA1 recovered the mitochondrial functions of OPA1-null cells, thus demonstrating the functional significance of K926/931 acetylation in regulating OPA1 activity. Moreover, SIRT3-dependent activation of OPA1 contributed to the preservation of mitochondrial networking and protection of cardiomyocytes from doxorubicin-mediated cell death. In summary, these data indicated that SIRT3 promotes mitochondrial function not only by regulating activity of metabolic enzymes, as previously reported, but also by regulating mitochondrial dynamics by targeting OPA1.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.01483-13.

ACKNOWLEDGMENTS

This study was supported by the NIH-RO1 grants HL83423, HL117041, and HL111455 to M.P.G.

We thank F. W. Alt and Christopher Rhodes for providing SIRT3KO and db/db mice, respectively. We are thankful to Marcia Haigis for providing SIRT3 WT and KO immortalized MEFs. We express gratitude to Paul Schumacker, Daniel Linseman, and Eric Verdin for providing the DNA vectors mentioned in Materials and Methods. We also thank Vytas Bindokas, Christine Labno, Shirley Bond, and Yimei Chen for the technical help in microscopy work.