Interaction of mitochondrial fusion and transmembrane potential in diabetic cardiovascular damage



 DESCRIPTION (provided by applicant): This proposal explores the interaction of mitochondrial fusion dynamics and transmembrane potential (∆ψm) as an underlying mechanism and translational target in diabetic cardiovascular damage. Type 2 diabetes mellitus is a rapidly-increasing public health concern, causing decreased cardiac efficiency as the leading cause of mortality among Type 2 diabetics. A range of clinical and experimental data suggests that the cytokine-mediated inflammation that drives diabetic pathology directly damages mitochondria, the organellar network responsible for cellular bioenergetics. Crucially, however, it is unknown what level of mitochondrial damage can be sustained in highly-oxidative cardiac cells before pathology ensues. Our previous studies of mitochondrial structure/function in neuromuscular disease, utilizing cell-based imaging and functional assays, provide a ready approach to address this gap in knowledge. To maintain bioenergetic homeostasis, mitochondria balance their organization between a united, reticular network (OPA1-mediated fusion) and a fragmented population of individual organelles (DRP1-mediated fission). The ∆ψm across the mitochondrial inner membrane is required for mitochondrial fusion, linking organellar function and structural dynamics. Strikingly, our preliminary data indicate that a sharply-defined threshold of 50% of ∆ψm is required for mitochondrial fusion. This threshold is independent of mitochondrial fission activity, and appears to be mediated by OMA1, a stress-response protease that has been shown to cleave the mitochondrial OPA1 fusion protein in response to low ∆ψm. Accordingly, we hypothesize that this threshold is an intrinsic property of human mitochondria mediated by expression of OPA1, and is damaged by cytokines, committing cardiac cells to apoptosis. The proposed aims mechanistically explore this threshold and the impacts of cytokine-mediated damage on ∆ψm and fusion dynamics, with major potential for a novel translational approach protecting cardiac mitochondria against cytokine-mediated damage. These aims an excellent fit with the outlined priorites for the SCORE SC3 mechanism, as the proposal will extend knowledge of mitochondrial homeostasis into the context of a leading public health problem, and will build biomedical research and enhance student research access at a leading Hispanic-serving institution that has not been a major recipient of NIH support.