CHLORIDE CHANNELS AND GASTRIC ACID SECRETION

胃溃疡疾病的治疗控制取决于控制盐酸分泌的干预措施。本研究的长远目标是明确参与调节盐酸分泌的分子和机制。HCl的分泌涉及胃H/K atp酶和一个转运系统，该转运系统由K提供H/K atp酶，由C1提供等量的C1用于HCl的生产。本研究拟验证的工作假设是，受刺激的家兔胃壁细胞的顶膜包含C1和K通道，这两个通道与调节胃HCl分泌密切相关，并且是必不可少的。本实验室克隆了C1通道C1C-2G，它是一个整流器，受Ca2+或Mg2+、CaMKII以及PKA、电压和细胞外ph控制。K通道似乎是一个内整流的K通道，受PKA和细胞外ph调节。二价阳离子也可能起作用。获得了候选K通道克隆RBHIK1，并将其与天然通道的特性进行比较和对比。生理上相关的K和C1的向外运动由本质上相同的效应器调节，并对电和化学环境的变化作出类似的反应。计划中的研究旨在了解细胞内离子在促进整流中的相互作用，蛋白激酶、电压和pH在促进CIC-2G向外移动C1和原生和克隆的内向整流K通道向外移动K中的作用。功能研究将辅以相关的结构研究，使用含有阳离子结合位点、磷酸化位点和pH传感器位点突变的通道cdna。适用于CI和K通道的具体目标是研究：1)阳离子在通道整改中的作用；2)蛋白激酶在C1和K通道功能中的作用；3)质子在C1和K通道功能中的作用；4)胃壁细胞通道在非分泌（休息）和分泌（刺激）状态下的位置。前3个目标将使用功能和相关结构方法进行研究。目标4将使用基于通道序列知识的结构探针来完成。这些研究努力解决有关调控HCl分泌的分子和机制的基本问题。

Therapeutic control of gastric ulcer disease depends upon interventions which control HCl secretion. The broad, long term objectives of this proposal are to define the molecules and mechanisms involved in regulated HCl secretion. HCl secretion involves the gastric H/K ATPase and a transport system for K to supply the H/K ATPase and for C1 to provide equivalents of C1 for HCl production. The working hypothesis to be tested in this proposal is that the apical membrane of the stimulated rabbit gastric parietal cell contains both C1 and K channels which are intimately associated with and essential for regulated gastric HCl secretion. The C1 channel, C1C-2G was cloned in this laboratory, and it is a rectifier which is controlled by Ca2+ or Mg2+, CaMKII as well as PKA, voltage, and extracellular pH. The K channel appears to be an inwardly rectifying K channel which is regulated by PKA and extracellular pH. Divalent cations may also play a role. A candidate K channel clone, RBHIK1, has been obtained and its properties will be compared and contrasted with those of the native channel. The physiologically relevant outward movement of both K and C1 are regulated by essentially the same effectors and respond similarly to changes in the electrical and chemical environments. The planned studies are directed toward understanding the interactions between intracellular ions in promoting rectification, the effects of protein kinases, voltage, and pH in promotion of outward movements of C1 by CIC-2G and of K by the native and cloned inwardly rectifying K channel. Functional studies will be complemented by correlated structural studies using channel cDNAs containing mutations of the cation binding sites, phosphorylation sites, and pH sensor sites. The Specific Aims which apply to both the CI and K channels are to study: 1) the role of cations in rectification of the channels; 2) the role of protein kinases in C1 and K channel function; 3) the role of protons in C1 and K channel function; and 4) the location of the channels in the gastric parietal cell in the non-secreting (resting) and secreting (stimulated) states. The first 3 aims will be studied using functional as well as correlated structural approaches. Aim 4 will be accomplished using structural probes based on knowledge of the sequence of the channels. These studies strive to address the fundamental questions regarding the molecules and mechanisms involved in regulated HCl secretion.