Function of ATP-sensitive Potassium Channels

描述(申请人提供)：我们的长期目标是了解 通过离子和激素的协调调节胰岛素的分泌 小路。为了帮助理解离子路径，我们克隆并表达了 高亲和力磺脲受体--β细胞调节亚基SUR1 SUR1/KLR6.2 KATP通道。SUR1和KIR6.2基因突变导致隐性形式 婴儿期持续性高胰岛素低血糖，HI的特征是 尽管有严重的低血糖，但胰岛素分泌过多。矛盾的是，Sun Null (Sur 1 KO)小鼠血糖正常，尽管它们有相同的电生理 HI Beta细胞的表型我们最近在Suriko小鼠身上的工作发现了两种 “代偿”反应：1)它们保持对葡萄糖的“基础”依赖， 依赖于钙离子的胰岛素释放调节，尽管有变化的释放 动力学，以及2)出乎意料的Sur 1KO胰岛对胰岛素没有反应， GLP-1和GIP。这种缺陷是由于对升高的反应受损所致。 CAMP，并用于扰乱肠岛轴，有效地移除 对苏黎世KO动物胰岛素分泌的有效刺激。我们已经展示了 胰岛素对葡萄糖诱导的胰岛素分泌的增强是通过 一条PKA非依赖途径。我们的结果提示SUR1与非PKA相互作用 我们假设的依赖通路涉及cAMP-egf或EPAC家族 鸟嘌呤核苷酸交换因子和这一途径的缺失扰乱cAMP 感官。我们将通过直接测量和表征来检验这一假设 Suri-EPAC相互作用。我们将确定受影响的cAMP效应通路(S) 通过比较几个激酶级联和Rab3A/Rim通路的激活， 已知胞吐的重要性，在对照和Sur1KO胰岛。我们将测试 假设HI和HI之间在血糖稳态方面的显著差异 新生儿VS Sur1KO小鼠是后者完全缺乏Suri-by的结果 以Sur1KO为背景制备表达突变SUR1的转基因小鼠。这些 研究将提供对磺酰脲受体功能的洞察，了解 CAMP如何促进分泌，对胰岛素如何 分泌是受调节的，而肠岛轴在这方面的重要性 调节，并可能为HI提出新的治疗策略和靶点 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.