PHOSPHOINOSITIDE HYDROLYSIS AND BETA CELL SECRETION

磷酸肌醇水解和 β 细胞分泌

• 批准号: 2141650
• 负责人: WALTER S. ZAWALICH
• 金额: $ 20.88万
• 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 1998-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2141650
• 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.

胰岛β细胞对胰岛素分泌的调节是一种 多方面、复杂和协调的进程。除了葡萄糖， β细胞依赖于荷尔蒙、神经递质的呈现。 和其他燃料来调整胰岛素的分泌模式和反应 胰岛素需求。它未能正确分析传入的 信息并适当地将其与胰岛素分泌结果相结合 在葡萄糖稳态失稳的情况下，在最糟糕的情况下，II型非- 胰岛素依赖型糖尿病(NIDDM)转导系统 这使得β细胞不仅能够预测胰岛素的需求，而且 对不同激动剂的刺激有递增的反应 荷尔蒙的输出一直是密集调查的对象。上一首 研究表明，磷脂酰肌醇(PI)循环中的信息流 在决定β细胞如何 对不同的激动剂有反应。我们的工作假设是β细胞 PI水解物参与了胰岛素分泌的两相模式 在燃料或神经体液刺激的胰岛中观察到，b)在扩增的 由两种神经体液激动剂引发的胰岛的分泌反应 如乙酰胆碱或缩胆囊素和燃料激动剂，如葡萄糖 或琥珀酸单甲酯，以及c)在抑制过程中， 脱敏或第三相释放，其特征是对 胰岛长期暴露于几种激动剂，包括高血糖 (葡萄糖毒性)、琥珀酸单甲酯、乙酰胆碱或缩胆囊素。 磷脂酶C、蛋白激酶C的激活，在 后一种酶，即它对蛋白质底物进行磷酸化的能力 在这些回复中承担重要的角色。新隔离的小岛，没有 将采用外分泌污染。他们表现出强烈的胰岛素 对燃料或神经体液刺激的分泌反应可与 在活体内观察到的或与灌流的胰腺制剂一起观察的。他们 可以用单抗进行更详细的生化分析 或针对磷脂酶C蛋白同工酶的多克隆抗体 激酶C及其已建立的几种蛋白质底物，以及 二酰甘油激活酶。此外，与在体内的发现类似， β细胞对刺激的敏感性可以增强或可逆 通过适当的操作和这些贡献抑制 可以评估酶对观察到的反应的反应。我们的目标是 阐明近端和远端事件对磷脂酰肌醇水解的贡献 在调节胰岛β细胞的胰岛素分泌方面。自.以来 β细胞无法正确感知葡萄糖的可逆性失败 II型糖尿病的特征，将特别强调 确定这一转导途径对无序的贡献 从胰岛中观察到的分泌物，在 胞外葡萄糖浓度。最重要的是来自临床的 从长远来看，我们将创造条件，约束 制定第三阶段放行或(如果已建立)操作 通过恢复正常的Beta来促进或加速其逆转 细胞对化疗的敏感性。