Abstract 19675: Cardiac Mitochondrial Proteins are Hyperacetylated in a Mouse Model of Friedreich's Ataxia
Background: Friedreich's Ataxia (FRDA) is the most common inherited ataxia and is caused by a GAA triplet intronic repeat expansion of the FRDA gene encoding the mitochondrial iron-binding protein frataxin. Although FRDA patients suffer spinocerebellar degeneration, the primary cause of mortality is cardiomyopathy. Mitochondrial iron-overload and elevated ROS are known to contribute to the disease pathology, but detailed molecular mechanisms remain unknown.
Methods and Results: Cardiac mitochondria from 24-29 day-old WT and frataxin conditional knockout NSE-CRE Δ/L3 mice were isolated by differential centrifugation for Western Blot and redox ratio analysis as defined by [NAD]/ [NADH]. Multiple Western Blot markers were used to confirm the purity of the mitochondrial fraction. Western Blots were normalized to VDAC and redox experiments were normalized to total mitochondrial protein. Significance was determined using Student's t-test. Conditional frataxin knockout mouse hearts exhibit global hyperacetylation of mitochondrial proteins with characteristic deficiencies of respiratory complexes I and II. Mitochondrial levels of NAD-dependent deacetylase SIRT3, which is responsible for global mitochondrial deacetylation, were unchanged. Conditional KO cardiac mitochondria display significant (p<.01) increases in total [NAD] (WT: 1426±626 pmol NAD/mg protein, KO: 6750±1177 pmol NAD/mg protein) and [NAD]/ [NADH] (WT: 0.73± 0.43, KO: 5.91±1.59) as compared to control animals.
Conclusions: FRDA mouse models demonstrate hyperacetylation of cardiac mitochondrial proteins despite maintenance of mitochondrial SIRT3 and an increase in [NAD]/ [NADH]. Hyperacetylation of mitochondrial proteins is known to impair energy homeostasis and could contribute to the pathophysiology of Friedreich's Ataxia.
- © 2010 by American Heart Association, Inc.