MECHANISMS OF PEPSINOGEN SECRETION FROM CHIEF CELLS

这个项目的长期目标是阐明细胞 胃蛋白酶原分泌的机制。为此， 首席调查员已经开发出了准备一份近 分散的分泌主细胞的同质群体 胃蛋白酶原对各种刺激的反应。这些细胞已经被 用来确定cAMP的变化调节了 促胰液素、血管活性肠肽、前列腺素和 霍乱毒素，而细胞钙浓度的变化起作用 在调节氨基甲胆碱、缩胆囊素和 钙离子载体。尽管早在几年前就知道了 胃蛋白酶原分泌的增强作用发生在 涉及cAMP变化的行动与以下代理相结合 这些作用涉及细胞内钙离子的变化，即细胞机制 调节这一现象的原因尚不清楚。然而，在 首席调查员发现，前一段时间的资金 其作用是通过细胞内钙离子的变化来调节的 可以通过一种途径增强cAMP介导酶的分泌 钙/钙调蛋白依赖的腺苷酸环化酶激活 系统。在其他组织中，类似的影响似乎是由 蛋白激酶C介导的蛋白组份的磷酸化 腺苷环化酶。因此，在本申请中，我们 建议检验以下假设：在主细胞中，蛋白质 由促分泌剂诱导的刺激细胞内的 钙/肌醇磷脂信使系统，具有钙-钙调蛋白- 对腺苷环化酶系统的依赖作用，导致 细胞内cAMP水平升高，从而导致 增强胃蛋白酶原分泌。这一假设将是 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，并通过调节体内和外- 细胞内钙浓度决定这些因素的作用 第二信使相互作用中的细胞介体 系统。我们还将确定是否将首席执行官的磷酸化 细胞蛋白质，如腺苷环化酶系统的组成部分， 当细胞被激活的促分泌剂刺激时发生 蛋白激酶C。我们实验室的这个新方向将 需要与系内教职员工协商。谁是生物化学系的 同意对这一项目给予支持。这些实验 将增加我们对所谓的“串音”之间的理解 主细胞中的第二信使系统。此外，新的 从这些研究中获得的信息应该会增加我们的 对分泌细胞中的信号转导有一般的了解。

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.