Mitochondrial metabolism is dependent on coenzyme A (CoA) to support metabolic processes like fatty acid oxidation, ketogenesis, and gluconeogenesis. Accumulation of CoA results in increased fatty acid oxidation, which drives gluconeogenesis in diabetes. Abnormally high CoA levels in skeletal muscle blunt mitochondrial ATP synthesis by decreasing the activity of complex I of the electron transport chain. Despite this evidence linking increased CoA to metabolic dysregulation, the mechanisms regulating CoA levels within the mitochondria are currently unknown. Nudt8 is an uncharacterized member of the Nudix hydrolase superfamily. This protein has been annotated as a potential CoA-degrading enzyme due to its high sequence homology to Nudt7, a previously characterized CoA diphosphohydrolase that resides in the peroxisomes. Our preliminary data show that Nudt8 specifically degrades free CoA and CoA thioesters. Additionally, Nudt8 localizes to the mitochondria and is expressed in highly oxidative tissues such as the heart, kidney, liver, brown adipose tissue, and muscle. The CoA-degrading activity of Nudt8, coupled with its localization to the mitochondria, suggests a role for this enzyme in the regulation of mitochondrial CoA levels and thus, metabolism. The proposed research will utilize adeno-associated virus to achieve over-expression of Nudt8 in the liver, followed by analysis of its effects on mitochondrial CoA pool size and composition, and on the mitochondrial metabolism of fatty acids and glucose. Additionally, mechanisms regulating Nudt8 expression and activity will be elucidated. The proposed research will be completed with the support of the excellent research facilities available to the applicant and in collaboration with other investigators within and outside the Department of Biochemistry at West Virginia University. The highly collaborative environment, combined with a personalized training plan, will allow the applicant to acquire skills in a broad range of techniques and to develop critical thinking skills, both of which are essential for a trainee to develop into a successful scientist. The applicant will participate in rigorous course work and oral presentations; these practices will provide an extensive knowledge base in metabolism and enhance the ability of the applicant to communicate his scientific ideas. Overall, the proposed combination of research and training plans will produce a well-rounded scientist as well as valuable insight into the regulation of the mitochondrial CoA pool and potential of targeting Nudt8 to correct the dysregulated mitochondrial metabolism that underlies a variety of metabolic diseases.
Accumulation coenzyme A within the mitochondria results in sustained fatty acid oxidation and contributes to the hyperglycemic phenotype of diabetes. This study will characterize the role of a novel CoA-degrading enzyme, Nudt8, in the regulation of the mitochondrial CoA pool and mitochondrial metabolism. This research will establish the potential to target Nudt8 to correct dysregulated mitochondrial metabolism, which is a hallmark for a variety of metabolic disorders.
