MECHANISMS OF PEPSINOGEN SECRETION FROM CHIEF CELLS

该项目的长期目标是阐明细胞 胃蛋白酶原分泌的机制。 为此所述 主要研究者已经开发出了一种方法， 一群分散的主细胞， 胃蛋白酶原对各种刺激的反应。 这些细胞已经 用于确定cAMP的变化介导了 促胰液素、血管活性肠肽、胰高血糖素，和 霍乱毒素，而细胞钙浓度的变化发挥作用， 在介导卡巴胆碱、胆囊收缩素和 钙离子载体。 虽然几年前人们就知道 胃蛋白酶原分泌的增强作用发生在 涉及cAMP变化的作用与 作用包括细胞钙离子的变化， 介导这种现象的是未知的。 但在 前一段时间的资金，首席研究员发现， 其作用由细胞钙变化介导的药物 可以通过增强cAMP介导的酶分泌， 腺苷酸环化酶的钙/钙调素依赖性激活 系统 在其他组织中，类似的影响似乎是由 蛋白激酶C介导的磷酸化的组分 腺苷酸环化酶 因此，在本申请中，我们 我建议测试以下假设：在主要细胞，蛋白质 激酶C，由促分泌素诱导的刺激激活， 钙/磷酸肌醇信使系统，具有钙-钙调素- 对腺苷酸环化酶系统的依赖性作用， cAMP的细胞水平增加，从而引起 胃蛋白酶原分泌的增强。 这一假设将是 通过使用各种钙调蛋白抑制剂和激活剂进行测试， 蛋白激酶C的抑制剂，并通过调节细胞内和细胞外 细胞钙浓度，以确定这些作用 第二信使与第三信使相互作用中的细胞介质 系统. 我们还将确定是否磷酸化的首席 细胞蛋白，如腺苷酸环化酶系统的组分， 当细胞受到促分泌素刺激时， 蛋白激酶C 我们实验室的这个新方向将 需要咨询系里的教员。生物化学家， 同意支持这个项目。 这些实验 将增加我们对所谓的“串扰”的理解， 主细胞中的第二信使系统。 而且新 从这些研究中获得的信息应该会增加我们的 总体了解分泌细胞中的信号传导。

The long-range goals of this project are to elucidate the cellular mechanisms of pepsinogen secretion. For this purpose, the Principal Investigator has developed methods for preparing a nearly homogeneous population of dispersed chief cells that secrete pepsinogen in response to various stimuli. These cells have been used to determine that changes in cAMP mediate the actions of secretin, vasoactive intestinal peptide, prostaglandins, and cholera toxin, whereas changes in cell calcium concentration play a role in mediating the actions of carbachol, cholecystokinin, and calcium ionophores. Although it has been known for several years that potentiation of pepsinogen secretion occurs when agents whose actions involve changes in cAMP are combined with agents whose actions involve changes in cell calcium, the cellular mechanisms mediating this phenomonon were unknown. However, during the previous period of funding, the Principal Investigator discovered that agents whose actions are mediated by changes in cell calcium can potentiate cAMP-mediated enzyme secretion by means of a calcium/calmodulin-dependent activation of the adenylate cyclase system. In other tissues, similar effects appear to be caused by a protein kinase C-mediated phosphorylation of components of adenylate cyclase. Therefore, in the present application, we propose to test the following hypothesis: In chief cells, protein kinase C, activated by secretagogue-induced stimulation of the calcium/phosphoinositide messenger system, has calcium-calmodulin- dependent actions on the adenylate cyclase system that result in augmentation of cellular levels of cAMP, thereby causing potentiation of pepsinogen secretion. This hypothesis will be tested by using various inhibitors of calmodulin and activators and inhibitors of protein kinase C, and by modulating intra- and extra- cellular calcium concentration to determine the role of these cellular mediators in the interaction between second messenger systems. We will also determine whether phosphorylation of chief cell proteins, such as components of the adenylate cyclase system, occurs when cells are stimulated by secretagogues that activate protein kinase C. This new direction for our laboratory will require consultation with faculty in the Dept. of Biochemistry who agree to lend their support to this project. These experiments will increase our understanding of so-called "cross-talk" between second messenger systems in chief cells. Moreover, the new information gained from these studies should increase our understanding of signal transduction in secretory cells in general.