PHYSIOLOGICAL REGULATION OF GASTRIN GENE EXPRESSION

胃泌素基因表达的生理调节

• 批准号: 3463583
• 负责人: STEPHEN BRAND
• 金额: $ 10.52万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-08-01 至 1993-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3463583
• 关键词: DNA; G protein; acetylcholine; autoradiography; calcium flux; cyclic AMP; diacylglycerols; epidermal growth factor; gastric acid; gastric mucosa; gastrins; gel electrophoresis; gene expression; genetic enhancer element; hormone regulation /control mechanism; membrane channels; messenger RNA; nucleic acid hybridization; nucleic acid sequence; peptide hormone biosynthesis; peptides; reporter genes; somatostatin; tissue /cell culture; transcription factor

Gastrin secreted from antral G cells is the major hormonal regulator of gastric acid secretion. The secretion of gastrin is regulated by stimuli in the gastric lumen acting on the G cell's apical surface and by neurotransmitters released from mucosal nerves acting on the basal surface. Gastric secretions contain many potent regulatory peptides such as Epidermal Growth Factor (EGF). Preliminary studies have shown that EGF stimulates gastrin gene transcription. Mucosal nerves release Acetylcholine (ACH) and Gastrin Releasing Peptide (GRP) which directly stimulate G cells. Gastrin secretion from G cells is also under negative feedback inhibition from gastric acid, this being mediated by the paracrine action of the inhibitory peptide Somatostatin. The proposed studies evaluate the effects of these G cell stimuli (EGF, GRP and ACH) on gastrin gene transcription in gastrin expressing cell lines that have been identified in preliminary studies. The intracellular mechanism through which these extracellular stimuli regulate gastrin gene transcription will also be examined. Preliminary studies indicate that changes in intracellular calcium regulate gastrin gene expression whereas the other second messengers of hormone action, cAMP and Diacylglycerol, had no effect. The role of extracellular calcium flux through voltage sensitive membrane channels in regulating gastrin gene expression will be assessed. To further elucidate the intracellular events regulating gastrin gene transcription, cell lines derived from another gastrin expressing tissue (the pituitary) will also be studied. GH4 cells expressing an integrated gastrin reporter gene will be stimulated with EGF, GRP and ACH to compare effects on gastrin gene transcription with those of other genes such as prolactin. Preliminary studies also show that somatostatin directly inhibits gastrin gene transcription. The intracellular mechanism through which somatostatin inhibits gastrin gene expression will be studied, especially the role of membrane hyperpolarization induced by Gi protein and the consequent decrease in intracellular calcium. The cis acting sequences in the gastrin gene which confer responsiveness to these stimuli will be defined by transient expression assays of deletion mutants. Once identified, the gastrin response element(s) will be examined for transcriptional enhancer properties.

胃窦G细胞分泌的胃泌素是主要的激素 胃酸分泌调节剂。 胃泌素的分泌量是 受胃腔内作用于 G 细胞的刺激调节 顶端表面和粘膜释放的神经递质 神经作用于基底面。 胃分泌物含有 许多有效的调节肽，例如表皮生长因子 （表皮生长因子）。 初步研究表明EGF可刺激 胃泌素基因转录。 粘膜神经释放乙酰胆碱 (ACH) 和胃泌素释放肽 (GRP) 直接 刺激G细胞。 G细胞的胃泌素分泌也减少 胃酸的负反馈抑制，这是 由抑制肽的旁分泌作用介导 生长抑素。 拟议的研究评估了这些 G 细胞刺激的效果 （EGF、GRP 和 ACH）对胃泌素中胃泌素基因转录的影响 初步鉴定的表达细胞系 研究。 这些细胞内的机制 细胞外刺激调节胃泌素基因转录也会 被检查。 初步研究表明，变化 细胞内钙调节胃泌素基因表达，而 其他激素作用的第二信使，cAMP 和 二酰基甘油，没有效果。 细胞外钙的作用 通过电压敏感膜通道的通量调节 将评估胃泌素基因表达。 为了进一步阐明 调节胃泌素基因转录的细胞内事件，细胞 源自另一种胃泌素表达组织（垂体）的细胞系 也将被研究。 表达整合胃泌素的 GH4 细胞 报告基因将受到 EGF、GRP 和 ACH 的刺激 比较对胃泌素基因转录的影响与其他基因的影响 催乳素等基因。 初步研究还表明 生长抑素直接抑制胃泌素基因转录。 这 生长抑素抑制的细胞内机制 将研究胃泌素基因表达，特别是 Gi蛋白诱导的膜超极化 细胞内钙随之减少。 胃泌素基因中的顺式作用序列赋予 对这些刺激的反应将由瞬态定义 缺失突变体的表达测定。 一旦确定， 将检查胃泌素反应元件的转录情况 增强剂特性。