Molecular Mechanisms for Growth Factor Action of Gastrin

虽然特征是刺激胃酸分泌，肽激素胃泌素也发挥生长促进作用， 正常和恶性胃肠道组织。虽然许多研究已经阐明了负责的机制， 促胃液素对胃酸分泌的刺激作用，介导促胃液素的生长因子作用的分子事件已经被 只有部分特征。胃泌素通过激活胰腺癌细胞的促增殖作用 ERK和早期反应基因c-fos的表达。此外，我们最近观察到胃泌素是一种有效的细胞凋亡抑制剂， 凋亡因此，我们推测，胃泌素的生理功能之一是刺激细胞生长， 生存本申请的总体目标将是剖析介导生长促进的分子机制， 以胰腺癌细胞和胃壁细胞为模型，研究胃泌素的抗凋亡作用。在第一个具体目标中，我们将 探讨胃泌素对早期反应基因c-fos表达的影响。在这些实验中，我们将采用 荧光素酶报告基因构建体包含c-fos基因启动子中存在的几个DNA调控元件。在 特别地，我们将研究ERK和p38激酶在c-fos转录调节中的功能。另外的实验 将集中于小GTP结合蛋白Ras、Rac和Cdc 42在胃泌素向c-fos的信号传导中的作用，以及在调节 AR 4 - 2 J细胞的生长。在这些实验中，我们将采用腺病毒介导的基因转移法， 将Ras、Rac和Cdc 4 - 2的突变体导入AR 4 - 2 J细胞中，以实现这些GTP酶的高水平表达。在第二 具体的目的，我们将研究信号转导途径负责胃泌素的抗凋亡作用，在这两个 AR 4 - 2 J细胞和胃壁细胞。这些研究将集中在调节胃泌素的分子机制上 诱导蛋白激酶AKT，已知其在多种系统中促进细胞存活。AKT激酶在细胞凋亡中的作用 胃泌素的抗凋亡作用将通过腺病毒介导的AKT显性负突变体的基因转移来评估。通过 通过这些研究，我们希望不仅在生理学、细胞和分子生物学领域，而且在 作为临床医学的竞技场，我们相信我们的研究可能有助于选择性胃泌素激动剂应用的理论基础 和拮抗剂作为治疗人类疾病的治疗剂。

Although characterized as a stimulant of gastric acid secretion, the peptide hormone gastrin also exerts growth-promotingeffects on normal and malignantgastrointestinal tissues. While numerous studies have elucidated the mechanisms that are responsible for the stimulatory effect of gastrin on gastric acid secretion,the molecular events that mediate the growth factor action of gastrin have been only partially characterized. Gastrin stimulatesthe growth of rat pancreatic adenocarcinoma cells (AR4-2J) through activationof the ERKs and of the early response gene c-fos. In addition,we have recently observed that gastrin is a potent inhibitor ofcellular apoptosis. Accordingly, we speculate that one of the physiological functions of gastrin is to stimulate both cellular growth and survival. The overall goal of this applicationwill be to dissect the molecular mechanisms that mediate the growth promoting and anti-apoptotic effects of gastrin using pancreatic cancer cells and gastric parietal cells, as our models. In the first specific aim, we will investigate the effect of gastrin on the expression of the early response genes c-fos. For these experiments we will take advantageof luciferase reporter gene constructs comprisingseveral DNA-regulatory elements present in the promoters of the c-fos gene. In particular, we will study the function of the ERKs and of p38 kinase in the regulation of c-fos transcription. Additional experiments will be focused on the role of the small GTP-bindingproteins Ras, Rac, and Cdc 42 in gastrin signalingto c-fos and in the regulation of AR4-2J cell growth. For these experiments we will take advantageof adenoviral mediated gene transfer of dominantnegative mutants of Ras, Rac, and Cdc 42 into the AR4-2J cells, in order to achieve high levels of expression of these GTP-ases. In the second specific aim, we will investigatethe signal transductionpathwaysresponsible for the anti-apoptotic effect of gastrin in both the AR4-2J cells and in the gastric parietal cells. These studies will be focused on the molecular mechanism that regulate gastrin induction of the protein kinase AKT which is known to promote cell survivalin multiple systems. The role of AKT kinase in the anti-apoptotic effect of gastrin will beassessed by adenoviral mediated gene transfer of dominant negative mutantsof AKT. Through these studies, we hope to shed new knowledgenot only in the areas of physiology and cellular and molecular biology, but also in the arena of clinical medicine as, we believe that our studies may contributeto the rationale for application of selective gastrin agonists and antagonistsas therapeutic agents in treatmentof human diseases.