HORMONAL REGULATION OF PHOSPHOINOSITIDE METABOLISM

磷脂酰肌醇代谢的激素调节

• 批准号: 3235639
• 负责人: JOHN N FAIN
• 金额: $ 14.32万
• 依托单位: UNIVERSITY OF TENNESSEE HEALTH SCI CTR
• 依托单位国家: 美国
• 财政年份: 1985
• 资助国家: 美国
• 起止时间: 1985-09-01 至 1991-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3235639
• 关键词: adenosine diphosphate; adenosinetriphosphatase; affinity labeling; alpha adrenergic agent; alpha adrenergic receptor; aluminum; autoradiography; bacterial toxins; binding proteins; calcium transporting ATPase; cell free system; cholera toxin; enterotoxins; enzyme induction /repression; fluorine; gel electrophoresis; glycosylation; guanine nucleotides; guanosinetriphosphatases; high performance liquid chromatography; hormone receptor; hormone regulation /control mechanism; ion exchange chromatography; laboratory mouse; laboratory rabbit; laboratory rat; lipid metabolism; liver cells; liver metabolism; magnesium; membrane proteins; pertussis; phosphatidylinositols; phospholipase C; phospholipids; radiotracer; tissue /cell culture; vasopressins

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.

这些研究的目的是检查激素调节