EXCEED THE SPACE PROVIDED. The overall goal of this research program is to understand the role of K channels in the regulation of insulin secretion. Excitation-secretion coupling in insulin-secreting _-cells is a calcium-dependent process that involves a dynamic interplay between K and Ca 2 channels. Ca 2 channels mediate the action potential and K channels regulate the membrane potential (Vm). Following glucose stimulationthe ]3-cell depolarizes, activating voltage-dependent Ca 2 and K channels, j3-cells then display characteristic oscillations of electrical activity consisting of depolarized plateaus upon which are superimposed bursts of Ca 2 channel- mediated action potentials, interrupted by periodic intervals of K* channelmediated repolarization. Repolarization of Vm is critical in the regulation of insulin secretion, but knowledge of the specific K channels involved is incomplete, particularly in human islets. We have shown that the Kv2.x family (Kv2.1 and Kv2.2) of delayed rectifier voltage-dependent K (Kv) channels plays an essential role in t3-cell repolarization and insulin secretion. We propose to test the role of specific Kv2 isoforms and their modulators in 13-cell physiology.
The specific aims are divided into two areas: further studies in mouse islets, and studies in human islets.
(Aim 1) To test the hypothesis that Kv2.x channels regulate the Kv current of mouse _cells. Kv2.x channels will be specifically inhibited by expression of dominant-negative mutant Kv2.1 and Kv2.2 cDNAs in mouse islet cells in vitro, and the effects on V_ intracellular concentration, and insulin secretion will be determined. Kv2.x expression will be inhibited in transgenic mouse models usingl3-cell specific promoters, and islet function assessed in vitro and in vivo.
(Aim 2) To define the role of Kv channels in human l_-cell function. Kv channels and accessory subunits expressed in fluorescently-sorted human 13-cells will be identified. Their roles in i3-cell signaling will be characterized pharmacologically and further characterized by targeting expression of dominant-negative mutant Kv constructs using viral transduction. We anticipate that our studies will provide a better understanding of the underlying molecular mechanisms that regulate insulin secretion and will facilitate development of new therapeutic strategies to treat diabetes.. PERFORMANCE SITE ========================================Section End===========================================
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