Ion channel regulation of pancreatic islet cell function

项目总结/摘要 据估计，四分之一的退伍军人患有糖尿病，在退伍军人群体中，这主要是2型糖尿病。 糖尿病这种情况会导致心脏病、中风、视网膜病、肾病和神经病， 是我们退伍军人发病率和死亡率高的原因。因此，了解生物学 糖尿病，发现调节b细胞功能的新分子，开发创新的治疗方法 这些方法将对我们老年退伍军人的健康产生重大影响。2型糖尿病是 其特征在于胰岛素敏感性的丧失，并且最终，胰岛素分泌的相对丧失， 胰腺B细胞胰腺b细胞的胰岛素分泌是由Ca 2+通过电压门控的 Ca 2+通道（VGCC）触发胰岛素囊泡与b细胞质膜融合。 我们最近报道了SWELL 1（LRRC 8a），一个富含亮氨酸重复序列的蛋白， 家族，是β细胞中ICl、SWELL所必需的。SWELL 1介导的IC 1，SWELL在由 葡萄糖输入，并且这产生有助于VGCC激活的去极化电流，从而调节 胰岛素分泌和全身性炎症。事实上，SWELL 1缺陷β细胞的小鼠表现出葡萄糖代谢受损， 刺激胰岛素分泌和葡萄糖耐受不良。此外，我们发现，ICl，SWELL在两种小鼠中均降低， 2型糖尿病（T2 D）背景下的SWELL 1信号传导减少表明SWELL 1信号传导减少与糖尿病相关。 患有2型糖尿病的B细胞功能受损本提案的目的是通过以下方式界定这些机制： 在基础条件下和在类型2的设置中，SWELL 1信号传导调节b细胞功能 糖尿病我们的中心假设是SWELL 1调节葡萄糖刺激的胰岛素分泌， PI 3 K-AKT-mTOR信号在b细胞中维持系统性高血压，并损害SWELL 1 信号传导导致2型糖尿病中的B细胞衰竭。这项建议的贡献是重大的 因为它探索了创新的概念，SWELL 1利用双信令域（信道与 LRRD）调节健康和T2 D中的B细胞功能。重要的是，该提案还将界定 在b细胞SWELL 1和T2 D之间，并测试减少的SWELL 1信号传导可能驱动受损的b细胞 T2 D功能我们提出以下两个目标： 目标#1：描述SWELL 1介导的兴奋-分泌偶联调节机制。 目的#2：剖析SWELL 1宏观复合物调节AKT-mTOR的分子机制 B细胞中的信号。 这项提议的贡献是创新的，因为它描绘了一种新的SWELL 1信号通路， 将葡萄糖介导的b细胞肿胀与b细胞去极化和胰岛素释放（b细胞肿胀的一种形式）联系起来， 活化或“溶胀-分泌”偶联。这一提议将增强我们对b细胞生物学的理解， 2型糖尿病患者的B细胞衰竭的新的治疗方法。 !

Project Summary/Abstract It is estimated that 1 in 4 Veterans suffer from diabetes, and, in the Veteran population, this is largely Type 2 diabetes. This condition drives heart disease, stroke, retinopathy, nephropathy and neuropathy, all of which are a cause of significant morbidity and mortality among our Veterans. As such, understanding the biology of diabetes, discovering novel molecules that regulate b-cell function and developing innovative therapeutic approaches will have a significant impact on the health of our aging veteran population. Type 2 diabetes is characterized by both a loss of insulin sensitivity and, ultimately, a relative loss of insulin-secretion from the pancreatic b-cell. Insulin secretion from the pancreatic b-cell is triggered by Ca2+ influx through voltage-gated Ca2+ channels (VGCC) to trigger insulin vesicle fusion with the b-cell plasma membrane. We recently reported that SWELL1 (LRRC8a), a member of the Leucine Rich Repeat Containing protein family, is required for ICl,SWELL in β-cells. SWELL1-mediated ICl,SWELL activates upon b-cell swelling induced by glucose import, and this generates a depolarizing current contributing to VGCC activation, thereby regulating insulin secretion and systemic glycemia. Indeed, mice with SWELL1-deficient β-cells exhibit impaired glucose- stimulated insulin secretion and glucose intolerance. Moreover, we find that ICl,SWELL is reduced in both mouse and humans in the context of Type 2 diabetes (T2D) indicating that reduced SWELL1 signaling is associated with impaired b-cell function in T2D. The objective of the current proposal is to delineate the mechanisms by which SWELL1 signaling regulates b-cell function, under basal conditions, and in the setting of Type 2 diabetes. Our central hypothesis is that SWELL1 regulates both glucose-stimulated insulin secretion and PI3K-AKT-mTOR signaling in b-cells to maintain systemic glycaemia, and that impaired SWELL1 signaling contributes to b-cell failure in Type 2 diabetes. The contribution of this proposal is significant because it explores the innovative concept the SWELL1 utilizes dual signaling domains (channel versus LRRD) to regulate b-cell function in health and T2D. Importantly, this proposal will also define the relationship between b-cell SWELL1 and T2D and test the notion that reduced SWELL1 signaling may drive impaired b-cell function in T2D. We propose the following two AIMs: AIM#1: Delineate the mechanism(s) of SWELL1-mediated regulation of excitation-secretion coupling. AIM#2: Dissect the molecular mechanisms of SWELL1 macro-complex regulation of AKT-mTOR signaling in b-cells. The contribution of this proposal is innovative because it delineates a novel SWELL1 signaling pathway that connects glucose-mediated b-cell swelling to b-cell depolarization and insulin-release - a form of b-cell swell- activation or “swell-secretion” coupling. This proposal will enhance our understanding of b-cell biology and help direct novel therapeutic approaches to b-cell failure in Type 2 diabetes. !