CHLORIDE CHANNELS AND GASTRIC ACID SECRETION

胃溃疡疾病的治疗控制依赖于干预措施 控制HCl的分泌。这一广泛而长期的目标 建议是定义参与调控的分子和机制 胃酸分泌。 而ATP燃料Mg 2+依赖，K+- 依赖和H+转运胃H/K ATP酶（EC 1.2.1.26），HCl H/K ATP酶的产生也需要K+和Cl-从 细胞质穿过顶膜到达分泌小管。K+是一个 H/K ATP酶和Cl-的底物提供了HCl的Cl-当量 生产跨胃壁细胞顶膜的离子转运 受cAMP依赖性蛋白激酶控制。这些渠道的功能 在pH 3或更低的苛刻但生理相关的条件下 冲洗通道的胞质外表面。酸和电压 激活的Cl-通道已被表征、克隆和表达， 在过去的3年中，酸稳定性K+通道也得到了表征 融资期。这些渠道已被证明是目标，本身， cAMP依赖性蛋白激酶。 体外激活HCl蓄积， 还证实了分离的胃囊泡。的目标 目前的建议是进一步阐明这些新的作用， 发现胃壁细胞分泌的Cl-和K+通道 膜调节HCl分泌。 拟议的研究是必要的 了解生理相关机制的控制盐酸 分泌物作为主要的工作假设，离子的活性 壁细胞分泌膜的通道代表了一个主要的 调节哺乳动物HCl分泌的靶点。的重点 本申请旨在理解这些离子 通道在调节HCl分泌中起作用。具体目标是 因此，l）比较和对比电生理特性 通道与宏观措施的K+和Cl-通量和H+ 积累 2)确定酸的调节机制， 来自天然和重组来源的电压调节Cl-通道。 还将研究新发现的K+通道的调节3） 确定独特的监管方面的结构基础， 氯通道。4)确定Cl-通道的定位位点， 胃粘膜内的细胞，以及Cl-通道的分布 在非分泌和分泌状态的壁细胞内; 5） 检查胃Cl-通道由一个 C1 C-2基因的可变剪接转录本。 这些研究提供 重要的分子和机制与生理细胞和 盐酸分泌的整个动物研究，并可能提供一个范例， 了解细胞和分子机制， 由上皮细胞调节分泌。

Therapeutic control of gastric ulcer disease relies upon interventions which control HCl secretion. The broad, long term objectives of this proposal are to define the molecules and mechanisms involved in regulation of gastric HCl secretion. Whereas ATP fuels the Mg2+-dependent, K+- dependent and H+-transporting gastric H/K ATPase (EC 1.2.1.26), HCl production by the H/K ATPase also requires K+ and Cl- passage from the cytosol across the apical membrane to the secretory canaliculus. K+ is a substrate for the H/K ATPase and Cl- provides equivalents of Cl- for HCl production. Ion transport across the gastric parietal cell apical membrane is under control by cAMP dependent protein kinase. These channels function under the harsh, but physiologically relevant condition of pH 3 or lower bathing the extracytosolic face of the channel. An acid and voltage activated Cl- channel has been characterized, cloned and expressed, and an acid stable K+ channel has also been characterized during the past 3 year funding period. The channels have been shown to be targets, per se, of cAMP dependent protein kinase. In vitro activation of HCl accumulation by isolated gastric vesicles has also been demonstrated. The goals of the present proposal are to further elucidate the role of these newly discovered Cl- and K+ channels of the gastric parietal cell secretory membrane in regulated HCl secretion. The proposed studies are essential to understanding the physiologically relevant mechanisms of control of HCl secretion. As the major working hypothesis, the activity of the ion channels of the secretory membrane of the parietal cell represent a major target of the regulation of HCl secretion in mammals. The focus of the present application is directed toward understanding how these ion channels function in regulated HCl secretion. The specific aims are therefore to l) Compare and contrast the electrophysiological properties of the channels with macroscopic measures of K+ and Cl- flux and H+ accumulation. 2) Determine the mechanisms of regulation of the acid and voltage regulated Cl- channel from native and recombinant sources. Regulation of the newly identified K+ channel will also be studied 3) Determine the structural basis for the unique regulatory aspects of the Cl- channel. 4) Determine the sites of localization of the Cl- channel to cells within the gastric mucosa, and the distribution of the Cl- channels within the parietal cell in the non-secreting and secreting state and; 5) Examine the hypothesis that the gastric Cl- channel is encoded by an alternatively spliced transcript of the C1C-2 gene. These studies provide important molecular and mechanistic links with physiological cellular and whole animal studies of HCl secretion and may provide a paradigm for understanding the cellular and molecular mechanisms which underlie regulated secretion by epithelia.