HORMONAL REGULATION OF PHOSPHOINOSITIDE METABOLISM

这些研究的目的是检查荷尔蒙的调节 肌醇磷脂在大鼠肝细胞和其他组织中的代谢 细胞。在肝脏中，α-1儿茶酚胺和加压素被激活 继发于细胞内糖原磷酸化酶的升高 钙和二酰甘油。钙的升高是次要的 1，4，5三磷酸肌醇的形成 磷脂酶C诱导的磷脂酰肌醇4，5- 二磷酸(PIP2)和二酰基甘油一样。现在很明显， 磷脂酶C的活性受鸟嘌呤核苷酸的调节。 这个项目的重点是鸟嘌呤核苷酸在 激素诱导的磷脂酰肌醇4，5- 双磷酸盐。我们的长期目标是分离膜 结合的磷脂酶C负责分解 磷脂酰肌醇。对鸟嘌呤核苷酸的需求 提示一种鸟嘌呤核苷酸结合蛋白，暂定 称为NP，可能参与激素-受体的偶联 磷脂酶C的复合体活性将是 使用氚PIP2进行了检查。我们将尝试将NP标记为 GTP类似物，并找到一种毒素，将其ADP-核糖化，与 分离这种假定的鸟嘌呤核苷酸的最终目的是 结合蛋白。将继续对监管进行调查，由 刺激多磷肌醇分解的激动剂，高 亲和力GTP酶在肝细胞和其他细胞类型中的活性。我们 打算建立鸟嘌呤核苷酸结合的身份 涉及蛋白质。加压素对肝细胞的抑制作用 (Ca~(2+)~(2+))~(2+))ATPase活性将在 如果有的话，试图阐明这一效应与 肌醇磷脂分解。这个项目主要是一个 使用生化技术进行新陈代谢研究。这个 研究是在实验动物身上进行的，应该提供 对各种新陈代谢疾病和 尤其是糖尿病。

The aim of these studies is to examine the hormonal regulation of phosphoinositide metabolism in rat hepatocytes and other cells. In liver, alpha-1 catecholamines and vasopressin activate glycogen phosphorylase secondary to an elevation of intracellular calcium and diacylglycerol. The rise in calcium is secondary to formation of inositol 1,4,5 trisphosphate derived from phospholipase C-induced breakdown of phosphatidylinositol 4,5- bisphosphate (PIP2) as is diacylglycerol. It is now clear that phospholipase C activity is regulated by guanine nucleotides. This project focuses on the role of guanine nucleotides in hormone induced breakdown of phosphatidyl-inositol 4,5- bisphosphate. Our long-term goal is isolation of the membrane bound phospholipase C responsible for breakdown of phosphoinositides. The requirement for guanine nucleotides suggests that a guanine nucleotide binding protein, tentatively called Np, may be involved in coupling of hormone-receptor complexes to phospholipase C. Phospholipase C activity will be examined using tritiated PIP2. We will attempt to label Np with GTP analogues and find a toxin that will ADP-ribosylate it, with the eventual aim of isolating this putative guanine nucleotide binding protein. Investigations will continue on the regulation by agonists that stimulate polyphosphoinositide breakdown, of high affinity GTPase activity in hepatocytes and other cell types. We intend to establish the identity of the guanine nucleotide binding protein involved. The inhibition by vasopressin of hepatocyte (Ca2+ Mg2+) ATPase activity will be further investigated in an attempt to elucidate the link, if any, between this effect and phosphoinositide breakdown. This project is primarily a metabolic investigation using biochemical techniques. The studies are done in experimental animals and should provide significant insights into various diseases of metabolism and especially diabetes.