Diabetic neuropathies and their associated neurological complications represent one of the least tractable problems encountered in the clinics during long term management of the disease. Although the consequences and costs are clear, the underlying pathogenic mechanisms remain obscure. One proposed mechanism is alteration of axonal transport processes. Evidence that changes in axonal transport do occur in diabetic nerves exists, but the data do not establish whether this plays a primary or secondary role in development of diabetic neuropathy and the biochemical basis for these changes has been unclear. Recent studies in our laboratory have identified a series of kinase activities that inhibit or modulate fast axonal transport. Unexpectedly, several of these kinase activities are known to be altered in diabetic tissues, including protein kinase C and glycogen synthase kinase 3b. Preliminary data suggest that misregulation of kinase and phosphatase activities in nervous tissue associated with inappropriate levels of insulin may affect kinesin-based motility and targeting of specific neuronal proteins. This may provide a critical link between metabolic changes in diabetic patients and the mechanisms of fast axonal transport. In this application, we propose to analyze kinesin phosphorylation in normal and diabetic nerves in a rat model of type 1 diabetes. These experiments will determine the extent to which kinesin is altered in diabetic nerve and facilitate identification of kinase/phosphatase pathways involved. As specific phosphorylation patterns relevant to diabetes are identified, we will characterize biochemical and biophysical effects of kinesin phosphorylation at sites altered in diabetes. These studies will determine how kinesin phosphorylation may affect kinesin motor activities. Finally, we will evaluate changes in kinesin function in diabetic nerves. These experiments will determine the extent to which diabetes induced alterations in phosphorylation affect metabolic turnover of kinesin, interaction of kinesin with other motor proteins and kinesin based motility of membrane bounded organelles. Studies of the effects that insulin levels and diabetes may have on kinesin-based transport processes have the potential to identify promising protective strategies that will minimize or eliminate diabetic neuropathies in clinically controlled diabetics.
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