Function of ATP-sensitive Potassium Channels

描述（由申请人提供）：我们的长期目标是了解 通过离子和激素协调调节胰岛素分泌 途径。为了帮助理解离子路径，我们克隆并表达了 高亲和力磺脲类受体，SUR 1，β细胞调节亚基 SUR 1/klR6.2KATP通道。SUR 1和KIR6.2突变导致隐性形式 婴儿期持续性高胰岛素血症性低血糖，HI，特征为： 尽管有严重的低血糖，胰岛素分泌仍然过量。巧合的是， (Sur 1 KO）小鼠血糖正常，尽管它们具有相同的电生理学特征。 在HI β细胞中观察到的表型我们最近对SurIKO小鼠的研究确定了两种 “代偿”反应：1）它们保持“基础”葡萄糖依赖性， 胰岛素释放的Ca 2+依赖性调节，尽管释放改变 动力学，和2）出乎意料地，Sur 1 KO胰岛显示对肠促胰岛素没有反应， GLP- 1和GIP。这种缺陷是继发于对升高的 cAMP，并用于破坏肠胰岛轴，有效地去除 对Sur 1 KO动物胰岛素分泌的有效刺激。我们已经表明 肠促胰岛素通过以下途径增强葡萄糖诱导的胰岛素分泌 PKA非依赖性途径。我们的结果表明，SUR 1与非PKA相互作用 依赖性途径，我们假设涉及cAMP-GEF或Epac家族， 鸟嘌呤-核苷酸交换因子，该途径的缺失破坏cAMP 感应我们将通过直接测量和描述 SURI -Epac相互作用。我们将确定受影响的cAMP效应子通路 通过比较几种激酶级联和Rab 3A/Rim通路的激活， 已知的胞吐作用的重要性，在对照与Sur 1 KO胰岛。我们将测试 假设HI和HI之间葡萄糖稳态的显著差异 新生儿与Sur 1 KO小鼠的差异是后者完全缺乏SURI的结果， 制备在Sur 1 KO背景下表达突变型SUR 1的转基因小鼠。这些 研究将提供对磺脲类药物受体功能的深入了解， cAMP如何增强分泌，更深入地了解胰岛素 分泌受到调节，肠胰岛轴在其中的重要性 调节，并可能提出新的治疗策略HI和目标， 新药的设计

DESCRIPTION (provided by applicant): Our long-term objective is to understand the regulation of insulin secretion via coordination of ionic and hormonal pathways. To help understand the ionic path, we cloned and expressed the high-affinity sulfonylurea receptor, SUR1, the regulatory subunit of Beta-cell SUR1/klR6.2 KATP channels. Mutations in SUR1 and KIR6.2 cause a recessive form of persistent hyperinsulinemic hypoglycemia of infancy, HI, characterized by excess insulin secretion despite severe hypoglycemia. Paradoxically, Sun null (Sur 1 KO) mice are normoglycemic, although they share the electrophysiologic phenotype seen in HI Beta-cells Our recent work on SurIKO mice identify two 'compensatory' responses: 1) they retain a 'basal' glucose-dependent, Ca2+-dependent regulation of insulin release, albeit with altered release kinetics, and 2) unexpectedly Sur 1KO islets show no response to the incretins, GLP- 1 and GIP. This defect is secondary to an impaired response to elevated cAMP and serves to disrupt the enteroinsular axis, effectively removing a potent stimulus for insulin secretion in the Sur1 KO animals. We have shown that potentiation of glucose-induced insulin secretion by incretins occurs via a PKA independent pathway. Our results imply SUR1 interacts with non-PKA dependent pathway which we hypothesize involves the cAMP-GEF or Epac family of guanine-nucleotide exchange factors and that loss of this pathway disrupts cAMP sensing. We will test this hypothesis by directly measuring and characterizing SURI -Epac interactions. We will identify the affected cAMP effector pathway(s) by comparing activation of several kinase cascades and the Rab3A/Rim path, of known importance for exocytosis, in control vs Sur1KO islets. We will test the hypothesis that the dramatic difference in glucose homeostasis between HI neonates vs Sur1KO mice is the result of the latter completely lacking SURI by making transgenic mice expressing mutant SUR1 on the Sur1KO background. These studies will provide insight into sulfonylurea receptor function, understanding of how cAMP potentiates secretion, a deeper understanding of how insulin secretion is regulated and the importance of the enteroinsular axis in this regulation, and may suggest novel therapeutic strategies for HI and targets for the design of novel drugs.