The Role of Mitochondrial Protein Acetylation in Left Ventricular Function

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 DESCRIPTION (provided by applicant): I want to understand the role that mitochondrial protein acetylation plays in the mechanism of heart failure. Heart failure carries a significant disease burden in the United States, with more than half of those with heart failure dying within 5 years of diagnosis. Many prevalent cardiovascular diseases, such as ischemic, hypertensive and diabetic cardiomyopathy, progress relentlessly to heart failure. The mechanisms underlying heart failure are not well understood and require further investigation. Mitochondrial protein acetylation is emerging as an important post-translational modification in cardiovascular diseases, such as that of diabetic and ischemic cardiomyopathy. Sirtuin 3 (SIRT3) is the sirtuin primarily responsible for regulating the acetylation state of proteins in the mitochondria. SIRT3 i a highly conserved NAD+ dependent mitochondrial deacetylase. Its targets include key metabolic enzymes, such as those involved in fatty acid metabolism (long chain acyl CoA dehydrogenase, or LCAD), oxidative phosphorylation (ATP synthase), and glucose metabolism (pyruvate dehydrogenase, or PDH), among others. We have recently shown that SIRT3 is inactivated in a model of congenital hypertrophic cardiomyopathy and heart failure, Friedreich's Ataxia (FRDA) cardiomyopathy. The result is marked hyperacetylation of mitochondrial proteins. We have new evidence that hyperacetylation in these hearts progresses concurrently with worsening heart function. FRDA is an autosomal recessive disease of childhood onset that results in relentlessly progressive neurogenic and cardiogenic dysfunction. Heart failure is the most common cause of death in FRDA. I believe that mitochondrial protein hyperacetylation damages cardiac energy homeostasis by inhibiting activity of key enzymes involved in heart metabolism, and that dysregulated mitochondrial protein acetylation contributes to this heart failure. My project proposes to test this hypothesis by manipulating mitochondrial protein acetylation and measuring cardiac cellular and physiologic function in a mouse model of FRDA, which serves as a model of hypertrophic cardiomyopathy and heart failure. I will manipulate acetylation by increasing SIRT3 activity in FXN-ablated hearts by two mechanisms: Aim I will test the hypothesis that increasing SIRT3 expression will improve heart function in the FRDA model of hypertrophic cardiomyopathy and heart failure. I will use genetic overexpression of SIRT3 in mouse models of FRDA. Aim II will test the hypothesis that increasing NAD+ levels in mitochondria will stimulate SIRT3 activity and improve heart function in the FRDA model of hypertrophic cardiomyopathy and heart failure. I will increase the level of NAD+ in these FRDA mice using a NAD+ precursor. All mice and reagents are in hand. At the end of my two-year proposal, I hope to understand the relationship between protein acetylation and the heart disease of FRDA, and possibly identify SIRT3 as a therapeutic target. My findings in the long term may further our understanding of heart failure and acetylation in other metabolic cardiovascular disease, such as diabetes, metabolic syndrome, and ischemic cardiomyopathy.