PHOSPHOINOSITIDE HYDROLYSIS AND BETA CELL SECRETION

磷酸肌醇水解和 β 细胞分泌

• 批准号: 2414796
• 负责人: WALTER S. ZAWALICH
• 金额: $ 29.75万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-05-01 至 1999-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2414796
• 关键词: Chordata; biological signal transduction; cholecystokinin; hormone regulation /control mechanism; hydrolysis; insulin; noninsulin dependent diabetes mellitus; pancreatic islet function; phosphatidylinositols; phospholipase C; phosphorylation; protein kinase C; secretion; succinates

The regulation of insulin secretion from pancreatic beta cells is a multifaceted, complex and coordinated process. In addition to glucose, the beta cell relies on the presentation of hormones, neurotransmitters and other fuels to adjust insulin secretory patterns and responses to insulin requirements. Its failure to properly analyze incoming information and to appropriately couple this to insulin secretion results in a failure of glucose homeostasis and, in the worst case, Type II non- insulin dependent diabetes mellitus (NIDDM). The transduction systems that allow the beta cell not only to anticipate insulin requirements but to respond to stimulation by various agonists with graded increments of hormone output have been the subject of intense investigation. Previous studies suggest that information flow in the phosphoinositide (PI) cycle occupies a particularly unique role in determining how the beta cell responds to different agonists. Our working hypothesis is that beta cell PI hydrolysis participates a) in the biphasic pattern of insulin secretion observed in fuel - or neurohumoral-stimulated islets, b) in the amplified secretory response noted with islets primed by both neurohumoral agonists such as acetylcholine or cholecystokinin and fuel agonists such as glucose or monomethylsuccinate, and c) in the process of suppression, desensitization or third phase release which characterizes the response of islets chronically exposed to several agonists including high glucose (glucose toxicity), monomethylsuccinate, acetylcholine or cholecystokinin. The activation of phospholipase C, protein kinase C and, in the case of the latter enzyme, its ability to phosphorylate its protein substrates assume importance in these responses. Freshly isolated islets, free from exocrine contamination will be employed. They display vigorous insulin secretory responses to fuel or neurohumoral stimulation comparable to those observed in vivo or with the perfused pancreas preparation. They can be subjected to further detailed biochemical analysis using monoclonal or polyclonal antibodies directed at isozymes of phospholpase C, protein kinase C, and several of its established protein substrates, and diacylglycerol kinase. Furthermore, and similar to findings made in vivo, beta cell sensitivity to stimulation can be either augmented or reversibly suppressed with the appropriate manipulation and the contribution of these enzymes to the responses observed can be assessed. Our goal is to elucidate the contribution of events proximal and distal to PI hydrolysis in the regulation of insulin secretion from pancreatic beta cells. Since a reversible failure of beta cells to appropriately sense glucose characterizes Type II diabetes, particular emphasis will be placed on establishing the contribution of this transduction pathway to disordered secretion observed from islets exposed to modest increments in the extracellular glucose concentration. Most important from a clinical perspective, we will establish the conditions which restrain the development of third phase release or, if established, manipulations which facilitate or accelerate its reversal with the restoration of normal beta cell chemosensitivity.

胰腺β细胞分泌胰岛素的调节是一个重要的机制。 这是一个多方面、复杂和协调的过程。 除了葡萄糖， β细胞依赖于激素和神经递质 和其他燃料来调节胰岛素分泌模式和对胰岛素分泌的反应。 胰岛素需求。 它未能正确分析传入 信息并将其适当地与胰岛素分泌结果相结合 在葡萄糖稳态失败，在最坏的情况下，II型非- 胰岛素依赖型糖尿病（NIDDM）。 转导系统 它不仅能让β细胞预测胰岛素的需求， 对各种激动剂的刺激作出反应， 激素分泌一直是深入研究的主题。 先前 研究表明，磷脂酰肌醇（PI）循环中的信息流 在决定β细胞 对不同的激动剂有反应 我们的假设是β细胞 PI水解参与a）胰岛素分泌的双相模式 在燃料或神经体液刺激的胰岛中观察到，B）在扩增的 用两种神经体液激动剂引发的胰岛观察到分泌反应 如乙酰胆碱或胆囊收缩素和燃料激动剂如葡萄糖 或琥珀酸单甲酯，和c）在抑制过程中， 脱敏或第三相释放，其特征在于 胰岛长期暴露于几种激动剂，包括高糖 （葡萄糖毒性）、琥珀酸单甲酯、乙酰胆碱或胆囊收缩素。 磷脂酶C、蛋白激酶C的激活，以及在 后一种酶磷酸化其蛋白质底物的能力 在这些反应中发挥重要作用。 新鲜分离的胰岛，不含 将采用外分泌污染。 它们的胰岛素分泌旺盛 对燃料或神经体液刺激的分泌反应与 在体内或用灌注的胰腺制备物观察到的那些。 他们 可以使用单克隆抗体进行进一步详细的生物化学分析， 或针对磷脂酶C、蛋白质 激酶C及其几种已建立的蛋白质底物，以及 二酰基甘油激酶 此外，与体内研究结果相似， β细胞对刺激的敏感性可以增强或可逆地 通过适当的操纵和这些因素的作用， 可以评估酶对观察到的应答的影响。 我们的目标是 阐明PI水解近端和远端事件的作用 在调节胰腺β细胞分泌胰岛素中的作用。 以来 β细胞无法正确感知葡萄糖的可逆性故障 II型糖尿病的特点，将特别强调 建立这种转导途径对紊乱的 从暴露于适度增量的胰岛中观察到的分泌 细胞外葡萄糖浓度 最重要的是从临床 从这个角度来看，我们将建立约束的条件， 开发第三阶段释放或（如果已确定） 促进或加速其逆转与恢复正常β 细胞化学敏感性