ATP-Sensitive Potassium Channels and Insulin Secretion

描述（由申请人提供）：胰岛细胞的atp敏感钾（KATP）通道通过将葡萄糖代谢与膜兴奋性耦合在葡萄糖刺激的胰岛素分泌中起关键作用。细胞KATP通道由磺酰脲受体SUR1和向内整流钾通道Kir6.2组成。SUR1和Kir6.2基因的功能缺失突变是先天性高胰岛素血症的主要原因。相反，功能获得通道突变导致相反的疾病新生儿糖尿病。我们研究的长期目标是了解细胞KATP通道的调节，这种调节在疾病中是如何受到干扰的，以及我们如何操纵通道调节来对抗胰岛素分泌紊乱。迄今为止，这项赠款支持的工作已经确定了在疾病背景下渠道生物发生和贩运的重要性。在这个更新应用中，我们建议研究如何通过生理信号调节细胞膜上的KATP通道密度来控制胰岛素的分泌。这是基于我们的初步发现，已知瘦素作为脂糖轴反馈调节的一部分抑制胰岛素分泌，显着增加了细胞中KATP通道的表面表达。本应用的主要目的是验证瘦素通过触发信号级联增加KATP传导和抑制胰岛素分泌来促进KATP通道运输到细胞表面的假设。此外，我们建议继续努力开发能够克服突变KATP通道运输缺陷的药物，作为先天性高胰岛素血症的新治疗策略。为此，我们已经获得了几种有希望增强通道表面表达的小分子的初步结果。因此，本应用的第二个主要目标是验证在先天性高胰岛素症中发现的运输受损的KATP突变体的表面表达和功能可以通过小分子伴侣恢复细胞功能来恢复。我们将结合生化、成像和电生理学方法来检验上述假设。在Aim 1中，我们将阐明瘦素增加细胞表面KATP通道表达的信号传导和细胞机制。在目标2中，我们将鉴定和表征新的药物伴侣，以拯救COS细胞、啮齿动物和人类胰岛细胞中贩运受损的KATP通道。这项研究具有创新性，因为它使用我们实验室为这些通道开发的独特工具和知识，测试了细胞中KATP通道运输的生理和药理学调节的新概念。从人类健康和基础科学的角度来看，这项研究都很重要。它将确定能够纠正由疾病突变引起的通道运输缺陷的新化合物，从而使其具有很高的转化潜力。此外，它将揭示新的生理信号机制，可能被用来控制KATP通道表面表达，从而在胰岛素分泌性疾病患者中实现葡萄糖-分泌偶联。

DESCRIPTION (provided by applicant): ATP-sensitive potassium (KATP) channels of islet ¿-cells play a key role in glucose-stimulated insulin secretion by coupling glucose metabolism to membrane excitability. The ¿-cell KATP channel is formed by the sulfonylurea receptor SUR1 and the inward rectifier potassium channel Kir6.2. Loss-of-function mutations in SUR1 and Kir6.2 are the primary cause of congenital hyperinsulinism. In contrast, gain-of-function channel mutations cause the opposite disease neonatal diabetes. The long-term goal of our research is to understand regulation of ¿-cell KATP channels, how this regulation is perturbed in disease and how we may manipulate channel regulation to combat insulin secretion disorders. Work supported by this grant to date has established the importance of channel biogenesis and trafficking in the context of disease. In this renewal application, we propose to study how KATP channel density in the ¿-cell membrane is regulated by physiological signals to control insulin secretion. This is based on our preliminary finding that leptin, which is known to inhibit insulin secretion as part of the adipoinsular axis feedback regulation, markedly increases surface expression of KATP channels in ¿-cells. A major goal of this application is to test the hypothesis that leptin promotes KATP channel trafficking to the cell surface by triggering a signaling cascade to increase KATP conductance and inhibit insulin secretion. In addition, we propose to continue our efforts on developing pharmacological agents that can overcome the trafficking defects of mutant KATP channels as a novel therapeutic strategy for congenital hyperinsulinism. To this end, we have obtained preliminary results on several promising small molecules that enhance channel surface expression. Thus, a second major goal of this application is to test the hypothesis that surface expression and function of trafficking-impaired KATP mutants identified in congenital hyperinsulinism can be restored by small molecule chaperones to recover ¿-cell function. We will combine biochemical, imaging and electrophysiology approaches to test the above hypotheses. In Aim 1, we will elucidate the signaling and cellular mechanisms by which leptin increases surface expression of ¿-cell KATP channels. In Aim 2, we will identify and characterize novel pharmacological chaperones that rescue trafficking-impaired KATP channels in COS cells and rodent and human islets/¿-cells. The research is innovative because it tests novel concepts in physiological and pharmacological regulation of KATP channel trafficking in ¿-cells using unique tools and knowledge developed by our lab for these channels. The research is significant from both human health and basic science standpoints. It will identify new chemical compounds that can correct channel trafficking defects caused by disease mutations, thus giving it high translational potential. Moreover, it will reveal novel physiological signaling mechanisms that may be exploited to control KATP channel surface expression, thereby glucose-secretion coupling in patients with insulin secretion disease.