CYCLIC AMP-DEPENDENT MEDIATION OF PARIETAL CELL FUNCTION

消化性溃疡疾病的表现是最常见的几种 医疗投诉。然而，虽然有效的药物疗法 以H2-组胺受体为靶标的基因在过去十年中得到了进化， 负责酸分泌的细胞内机制仍然难以捉摸。 CAMP作为组胺刺激的胃酸分泌介质的作用 壁细胞是公认的。然而，这些机制实际上 负责将cAMP信号转化为生理信号 对分泌物的反应仍然知之甚少。我们最近发现 II型调节亚基的一个亚类去磷酸化 CAMP依赖的蛋白激酶可能是血管紧张素转换酶的关键步骤 顶层细胞中的cAMP信号。我们的工作假设是 CAMP可能通过蛋白激酶和cAMP的协同激活发挥作用 磷酸酶活性。这一假设所固有的信念是 CAMP依赖的蛋白激酶激活II调节亚单位(RII) CAMP依赖蛋白激酶作为cAMP感受器蛋白。这项提议将 追求五条主线：第一，蛋白质的作用 磷酸酶和激酶活性在组胺刺激中的作用 RII的原位磷酸化将在以下情况下进行评估 蛋白磷酸酶抑制剂(冈田酸)和cAMP依赖性 蛋白激酶抑制剂(H-8)。第二，RII在中国的不同亚型 壁细胞的膜结合和胞质隔间将是 以及影响这些蛋白质的蛋白激酶系统将 被描绘出来。第三，不同类型的RII的存在 亚细胞隔间将使用亚细胞建立 分级和免疫细胞化学。第四，RII蛋白磷酸酶 膜组分中的活性将被分离并表征为 组胺行动的协调中心。第五，由于夏令营对 壁细胞的功能似乎部分是通过活动来调节的。 除cAMP依赖的蛋白激酶外，RII与其他 细胞蛋白质，特别是与细胞骨架的成分 将会被调查。第六，由于壁细胞的分泌是 在cAMP依赖和cAMP非依赖机制的刺激下， 组胺能和胆碱能刺激的共同特征是 调查以确定蛋白磷酸酶活性是否可能 代表一个共同的调解人。这些调查应该能澄清一些 壁细胞分泌酸的基本机制 是受控制的。扩展我们对细胞内的理解 负责酸分泌的过程可能会导致新的方法 治疗消化性溃疡和其他分泌性疾病。

The manifestations of peptic ulcer disease constitute some of the commonest medical complaints. However, while potent pharmacological therapies targeted at the H2-histamine receptor have evolved over the past decade, the intracellular mechanisms responsible for acid secretion remain elusive. The role of cAMP as a mediator of histamine stimulated acid secretion from parietal cells is well recognized. Nevertheless, the mechanisms actually responsible for the translation of the cAMP signal into the physiological response of secretion remain poorly understood. We have recently found that the dephosphorylation of a subclass of Type II regulatory subunit of cAMP-dependent protein kinase may be a critical step in the processing of the cAMP signal in the parietal cell. It is our working hypothesis that cAMP may act through a coordinated activation of both kinase and phosphatase activities. Inherent in this hypothesis is the belief that cAMP-dependent protein kinase activation II regulatory subunit (RII) of cAMP-dependent protein kinase as a cAMP sensor protein. This proposal will pursue five major lines of investigation: First, the role of protein phosphatase and kinase activities in mediating the histamine stimulation on the phosphorylation of RII in situ will be evaluated in the presence of both a protein phosphatase inhibitor (okadaic acid) and a cAMP-dependent protein kinase inhibitor (H-8). Second, distinct isotypes of RII in membrane-bound and cytosolic compartments of parietal cells will be characterized and the protein kinase systems affecting these proteins will be delineated. Third, the presence of isotypes of RII in distinct subcellular compartments will be established using subcellular fractionation and immunocytochemistry. Fourth, RII protein phosphatase activities in membrane fractions will be isolated and characterized as focal points for histamine action. Fifth, since the effects of cAMP on parietal cell function appear to be in part mediated through activities other than cAMP-dependent protein kinase, the association of RII with other cellular proteins and, in particular, with components of the cytoskeleton will be investigated. Sixth, since secretion by parietal cells is stimulated by both cAMP-dependent and cAMP-independent mechanisms, the common features of histaminergic and cholinergic stimulation will be investigated to determine whether protein phosphatase activities might represent a common mediator. These investigations should elucidate some of the basic mechanisms by which the secretion of acid from the parietal cell is controlled. Expansion of our understanding of the intracellular processes responsible for acid secretion may lead to new methods for the treatment of peptic ulcer disease and other secretory disorders.