Structural Basis of Katp Channel Gating

ATP敏感钾(KAIP)通道在细胞代谢和细胞兴奋性之间起着关键作用 控制不同的生理过程，包括激素分泌，血管张力的控制，以及 缺血时心肌和神经元活动的调节。这个项目的长期目标是 是为了了解KATP通道门控的结构基础。为了实现这一目标，我们的研究重点是 胰岛亚型的KATP通道，是由四个组成的异构体复合体 内向整流钾通道Kir6.2亚基和四个调节性磺脲受体1亚基。在……里面 胰岛p细胞、KATP通道作为葡萄糖感受器调节胰岛素的分泌。两个基因中的任何一个的突变 导致通道功能丧失的Kir6.2或SUR1是先天性高胰岛素血症的主要原因，a 尽管血糖水平较低，但胰岛素持续分泌的疾病。另一方面， 导致通道活性增强的Kir6.2基因突变最近被证明会导致新生儿 糖尿病。几种生理分子，包括细胞内的ATP、MgADP和膜 磷脂酰肌醇，特别是PI-4，5-P2(PIP2)调节KATP通道的活动。但是，结构性的 对这些分子控制通道活性至关重要的通道蛋白的特征不是 清楚地明白了。本应用程序的目标是深入了解KATP的结构-功能关系 通过研究疾病中发现的突变如何影响经络，使用正向遗传学方法 功能。在第一个目标中，我们将确定由九个新发现的Kir6.2突变引起的通道缺陷 使用COS细胞治疗先天性高胰岛素血症，解决通道生物发生/表达的两个缺陷 和门控。然后我们将评估这些突变如何影响p细胞的生理，以及它们如何应对 通过在大鼠胰腺P细胞系中表达突变Kir6.2进行潜在的分子或药物治疗 INS-1.在第二个目标中，我们将对最近在新生儿中发现的Kir6.2突变进行类似的研究 糖尿病。在第三个目标中，我们将确定Kir6.2胞质结构域中的亚基之间的相互作用 对门控和Kir6.2亚基之间的物理关联很重要，这是基于我们之前的发现 Kir6.2亚基间离子对的破坏会损害正常的通道门控。我们将专注于潜力 由在先天性高胰岛素血症或其他疾病中发现的突变残基介导的相互作用 新生儿糖尿病。所提出的研究不仅将使我们更好地理解结构-功能 KATP通道的相互关系及其引起胰岛素分泌性疾病的分子基础 突变。这种知识可能有助于确定药物开发的新结构位点，并对 为这些疾病设计有效的治疗策略。

ATP-sensitive potassium (KAip) channels play a key role in coupling cell metabolism to cell excitability and govern diverse physiological processes including hormone secretion, control of vascular tone, and modulation of the activity of cardiac muscle and neurons during ischemia. The long-term goal of this project is to understand the structural basis of KATP channel gating. Towards this goal, our research has focused on the pancreatic subtype of KATP channels, which are heteromultimeric complexes each composed of four inwardly rectifying potassium channel Kir6.2 subunits and four regulatory sulfonylurea receptor 1 subunits. In pancreatic p-cells, KATP channels serve as glucose sensors to regulate insulin secretion. Mutations in either Kir6.2 or SUR1 that lead to loss of channel function are the major cause of congenital hyperinsulinism, a disease characterized by persistent insulin secretion despite low plasma glucose level. On the other hand, mutations in Kir6.2 that lead to gain of channel activity have recently been shown to cause neonatal diabetes. Several physiological molecules, including intracellular ATP, MgADP, and membrane phosphoinositides, especially PI-4,5-P2 (PIP2), regulate the activity of KATP channels. However, structural features of the channel proteins that are critical for control of channel activity by these molecules are not clearly understood. The goal of this application is to gain insight to the structure-function relationship of KATP channels using a forward genetics approach by studying how mutations identified in disease affect channel function. In the first aim, we will determine channel defects caused by nine novel Kir6.2 mutations identified in congenital hyperinsulinism using COS cells, addressing both defects in channel biogenesis/expression and gating. We will then evaluate how these mutations impact on p-cell physiology and how they respond to potential molecular or pharmacological treatments, by expressing mutant Kir6.2 in a rat pancreatic p-cell line INS-1. In the second aim, we will perform similar studies on Kir6.2 mutations recently identified in neonatal diabetes. In the third aim, we will identify intersubunit interactions in the cytoplasmic domain of Kir6.2 that are important for gating and for physical association between Kir6.2 subunits, based on our previous finding that disruption of an intersubunit ion pair in Kir6.2 impairs normal channel gating. We will focus on potential interactions that are mediated by residues that have been found mutated in congenital hyperinsulinism or neonatal diabetes. The proposed study will better our understanding of not only the structure-function relationships of KATP channels but also the molecular basis of insulin secretion diseases caused by channel mutations. Such knowledge may help identify novel structural sites for drug development and is essential for designing effective therapeutic strategies for these diseases.