MOLECULAR BASIS OF ANTIDIABETOGENIC HORMONE ACTION

胰升糖素样肽-1(GLP-1)是一种有效的降血糖药物 刺激胰岛分泌胰岛素的激素-- 细胞，正在进行临床研究，用于治疗 非胰岛素依赖型糖尿病(NIDDM)这项提议旨在 资助一种新发现的细胞内钙离子的研究 大鼠原代培养中GLP-1激活的信号系统 胰岛β细胞。初步研究表明， GLP-1刺激细胞内[Ca~(2+)]i大幅升高 和持续组件，并通过激活 依赖cAMP的第二信使系统。这一点值得注意，因为一个 CAMP介导的[Ca~(2+)]i升高是一种强有力的刺激 胰岛素的分泌。这项建议的第一个具体目标是 确定对GLP-1的反应是否测量到瞬时的[Ca2+]i升高 作为蛋白质结果的钙离子储存动员的结果 激酶A介导的兰尼定受体(RyR)的磷酸化 细胞内钙离子释放通道。第二个具体目标是 确定[Ca~(2+)]i的持续升高是否源于Ca~(2+)的内流， 如果是，要确定是什么类型的离子通道(S)负责。 本文认为钙离子的内流是钙离子开放的结果。 生成内向膜的NS非选择性阳离子通道 当前的ICAMP。令人惊讶的是，这些渠道的开放不仅是为了回应 对GLP-1，但也对口服降糖磺脲类药物有反应 作为治疗NIDDM的处方格列本脲。因此，a 第三个具体目标是确定磺脲类化合物的这种作用是否 由高亲和力的磺酰脲受体(SUR)介导 CA-NS通道跨膜电导调节剂。要实现这些目标 具体目标、[Ca2+]i和膜电流的测量 用Fura-2荧光分光光度法从大鼠β细胞中获得 结合膜片钳电生理学。我们的近期目标是 阐明GLP-1影响的信号转导途径 β细胞内钙离子动态平衡。我们的长期目标是 为了确定这个钙信号系统的激活是否解释了 GLP-1治疗NIDDM的疗效观察

Glucagon-like peptide-1 (GLP-1) is a potent blood glucose-lowering hormone that stimulates the secretion of insulin from pancreatic beta- cells and which is under clinical investigation for use in treatment of non-insulin-dependent diabetes mellitus (NIDDM). This proposal seeks funding to support studies of a newly discovered intracellular Ca2+ signaling system that is activated by GLP-1 in primary culture of rat pancratic beta-cells. Preliminary studies are presented demonstrating that GLP-1 stimulates a large rise of [Ca2+]i that consists of transient and sustained components, and which is triggered by activation of a cAMP-dependent second messenger system. This is noteworthy because a cAMP-mediated rise of [Ca2+]i is known to be a powerful stimulus for secretion of insulin. A first Specific Aim of this proposal is to determine if the transient rise of [Ca2+]i measured in response to GLP-1 results from mobilization of Ca2+ stores as a consequence of protein kinase A-mediated phosphorylation of ryanodine receptor (RYR) intracellular Ca2+ release channels. A second Specific Aim is to determine if the sustained rise of [Ca2+]i results from influx of Ca2+, and if so, to determine what type(s) of ion channels are responsible. Here it is proposed that influx of Ca2+ results from the opening of Ca- NS nonselective cation channels that generate the inward membrane current IcAMP. Surprisingly, these channels open not only in response to GLP-1, but also in response to oral hypoglycemic sulfonylureas such as glyburide that are prescribed for treatment of NIDDM. Therefore, a third Specific Aim is to determine if this action of sulfonylureas is mediated by a high affinity sulfonylurea receptor (SUR) acting as a transmembrane conductance regulator of CA-NS channels. To achieve these Specific Aims, measurements of [Ca2+]i and membrane current will be obtained from rat beta-cells using fura-2 spectrofluorimetry in combination with patch clamp electrophysiology. Our immediate goal is to delineate the signal transduction pathways by which GLP-1 influence intracellular Ca2+ homeostasis in the beta-cell. Our long term goal is to determine if activation of this Ca2+ signaling system explains the therapeutic efficacy of GLP-1 for treatment of NIDDM.