Oxidative Stress and the Mitochondrial Proteome in Diabetic Neuropathy

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Diabetic peripheral neuropathy (DPN) is a common complication in diabetic individuals that results from a progressive degeneration of neurons and Schwann cells (SCs). Although much attention has focused on neuronal loss in DPN, SCs also undergo substantial degeneration and are critical for re-establishing axon- glial interaction necessary for regeneration. Analysis of the inter-related metabolic insults induced by hyper- glycemia have identified that increased production of superoxide anion may be a focal event that contributes to mitochondria! dysfunction and apoptosis of SCs. On the other hand, insulin-like growth factor-1 (IGF-1) decreases mitochondrial dysfunction and apoptosis of SCs. To date, the role of oxidative stress and IGF-1 in regulating mitochondrial function in SCs have focused only on a small subset of proteins that contribute to apoptosis. However, it is unclear that SCs undergo extensive apoptosis in DPN. We hypothesize that the opposing effects of superoxide production and IGF-1 signaling in SCs may be more critical in balancing changes in both the expression and post-translational modification of mitochondrial proteins that affect aspects of organellar homeostasis central to regulating SC regeneration. Since a significant gap exists with regard to the broad effect of glucose-induced superoxide production and IGF-1 signaling in maintaining the mitochondrial proteome, our specific aims are to: 1) Identify the role of glucose-induced superoxide production in altering the mitochondrial proteome of SCs using pharmacological, molecular and quantitative proteomic approaches. 2) Identify the role of glucose-induced superoxide production in enhancing the level of tyrosine nitration in the mitochondrial proteome. 3) Identify the sufficiency/necessity of phosphatidyl- inositol 3 kinase in attenuating glucose-induced superoxide production by IGF-1. Collectively, our studies will identify mitochondrial proteins that are susceptible to glucose-induced oxidative stress and improve our understanding of how growth factor signaling may improve mitochondrial function in diabetic nerve.