Molecular Basis of Antidiabetogenic Hormone Action

实验治疗中的一个新兴主题涉及使用胰高血糖素样肽-1-（7-36）- 酰胺（GLP-1）及其合成肽类似物（“肠促胰岛素模拟物”）来降低血糖水平 在2型糖尿病患者中。GLP-1的这一作用至少部分是由于其能够刺激细胞增殖， 胰岛β细胞分泌胰岛素。鉴于既定的 GLP-1对糖尿病治疗的重要性，我们的实验室有兴趣定义信号 β细胞GLP-1受体（GLP-1-R）的转导特性。为此，我们集中精力， 新发现的信号机制，使用第二信使cAMP激活cAMP- 被命名为Epad和Epac 2的受调节的鸟嘌呤核苷酸交换因子（交换蛋白 直接由环AMP激活）。我们的研究使我们假设GLP-1，一种cAMP升高因子， 激素，刺激Ca 2+依赖性胰岛素分泌，这种促胰岛素作用不受 蛋白激酶A（PKA），以及Epac。为了验证我们的假设， Epac在GLP-1-R介导的信号转导中的作用，本项目的具体目的是：1）确定 GLP-1使用Epad和/或Epac 2通过Ca 2+诱导的Ca 2+转运过程来动员细胞内Ca 2+。 起源于内质网（ER）且可能涉及IP 3受体或 Ryanodine受体，2）评估Rap家族GTPases在ER Ca 2+过程中发挥的作用。 动员，特别强调Rap 1作为连接激活的中间体的潜在作用， Epac对磷脂酶C-β的刺激，以及3）确定一种新的信号传导的性质 β细胞生长因子和受体酪氨酸激酶利用Ras GTP酶 将Epac 2募集到质膜，在质膜Epac 2与其推定的效应分子的相互作用 磺酰脲受体-1（SUR 1）。这条调查路线的相关性是显而易见的。 我们希望建立一种新的血液类型的“抗糖尿病”特性的分子基础。 激活GLP-1-R并刺激胰腺胰岛素分泌的降糖药。

An emerging theme in experimental therapeutics concerns the use of glucagon-like peptide-1-(7-36)- amide (GLP-1) and its synthetic peptide analogs (the "incretin mimetics") to lower levels of blood glucose in Type 2 diabetic subjects. This action of GLP-1 results, at least in part, from its ability to stimulate the secretion of insulin from pancreatic beta cells located in the islets of Langerhans. Given the established importance of GLP-1 for the treatment of diabetes, our laboratory is interested in defining the signal transduction properties of the beta cell GLP-1 receptor (GLP-1-R). To this end, we have focused on a newly-discovered signaling mechanism that uses the second messenger cAMP to activate cAMP- regulated guanine nucleotide exchange factors designated as Epad and Epac2 (the Exchange Proteins directly Activated by Cyclic AMP). Our studies lead us to Hypothesize that GLP-1, a cAMP-elevating hormone, stimulates Ca2+-dependent insulin secretion, and that this insulinotropic action is mediated not simply by protein kinase A (PKA), but also by Epac. To test our Hypothesis concerning the putative role of Epac in GLP-1-R-mediated signal transduction, the Specific Aims of this project are to: 1) determine if GLP-1 uses Epad and/or Epac2 to mobilize intracellular Ca2+ via a process of Ca2+-induced Ca2+ release (CICR) that originates at the endoplasmic reticulum (ER) and which may involve IP3 receptors or ryanodine receptors, 2) assess what role Rap family GTPases play in the process of ER Ca2"1" mobilization, with special emphasis on the potential role of Rap1 as an intermediary linking activation of Epac to the stimulation of phospholipase C-epsilon, and 3) determine the nature of a novel signaling mechanism by which beta cell growth factors and receptor tyrosine kinases utilize the Ras GTPases to recruit Epac2 to the plasma membrane where an interaction of Epac2 with its putative effector molecule the sulfonylurea receptor-1 (SUR1) occurs. The Relevance of this line of investigation is fully apparent. We wish to establish the molecular basis for "antidiabetogenic" properties of a new class of blood glucose-lowering agents that activate the GLP-1-R and which stimulate pancreatic insulin secretion.