Insulin secretion by the pancreatic a-cell is a complex and highly regulated process. Disruption of this process can lead to inadequate insulin secretion that fails to meet the physiological demands of the body, leading to the development of insulin-dependent and non-insulin dependent diabetes mellitus. Of the various pathways involved in insulin secretion, the heterotrimeric G protein plays a vital role in regulating insulin secretion. The long-term objective of this work is to elucidate the signal transduction pathways mediated by heterotrimeric G proteins in the regulation of insulin secretion. Three different gene specific knockout mouse lines, namely Goalpha (total), Goalpha1, and Goalpha2 have been generated by the PI. Preliminary investigations have demonstrated that Goalpha2 knockout mice handled a glucose load more efficiently than their wild type counterparts. In addition, a glucose-induced insulin secretion was greater in Goalpha2 knockout mice. Thus, it appears that Go2 plays a critical inhibitory role in insulin over-secretion, and a disruption in its normal homeostasis can cause diseases. Based on these preliminary studies, our hypothesis is that Go2 G protein is a key mediator in the modulation of insulin secretion by the pancreatic beta cells. To test this hypothesis, the following specific aims will be pursued: 1] Determine whether the dynamic insulin secretion and the sensitivity of beta-cells to glucose stimulation are regulated by Go2 protein. 2] Define the intracellular pathway(s) linking the activation of Go2 G-protein to inhibit insulin secretion using electrophysiology, cell biology and biochemical approaches. 3] Determine whether over activation of inhibitory pathway will suppress insulin secretion using tissue specific transgenic animal approach. The results of these experiments will unequivocally prove the role of Go2 G protein in insulin secretion, thereby setting the stage for designing future interventional strategies in managing diabetes.
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