Apical CI/OH-/HCO3-exchanger in kidney and GI tract

肾脏和胃肠道的顶端 CI/OH-/HCO3-交换器

• 批准号: 6727910
• 负责人: MANOOCHER SOLEIMANI
• 金额: $ 36.58万
• 依托单位: UNIVERSITY OF CINCINNATI
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-06 至 2007-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6727910
• 关键词: antiport; apical membrane; bicarbonates; chloride ion; gastrointestinal system; genetically modified animals; immunocytochemistry; ion transport; kidney; laboratory mouse; membrane transport proteins; northern blottings; renal tubule; sodium chloride; western blottings

The apical chloride/base exchanger in kidney proximal tubule and gastrointestinal tract works in parallel with NHE3 and is essential for chloride absorption and fluid homeostasis. However, less is known about the molecular identity and the main functional mode of this exchanger. SLC26A6, also known as PAT1 or CFEX, is a member of a large, highly conserved family of ion transporters (designated as SLC26A) many of which mediate anion exchange. SLC26A6 can mediate CI'/HCO3-, Cl/formate and Cl-/oxalate exchanges, indicating that it is an ideal candidate for apical Cl/base exchange in proximal tubule. Our experiments demonstrate that SLC26A6 mediates CI-/HCO3- exchange, is located on the apical membrane of proximal tubule, small intestine and tubulovesicles of gastric parietal cells, and is upregulated by NH4+, a naturally occurring chemical in kidney proximal tubule and small intestine. We further demonstrate the presence of an apical CI/HCO3- exchange in rat and mouse isolated microperfused proximal tubules and in tubulovesicles of gastric parietal cells. We hypothesize that SLC26A6 is the main apical anion exchanger in kidney proximal tubule and duodenum, functions predominantly as a CI-/HCO3- exchanger under physiologic conditions and is responsible for the bulk of chloride absorption. In the stomach, PAT1 may be essential for neutralizing the luminal acidity of H-K-ATPase-containing vesicles during the resting state. The purpose of the current proposal is to ascertain the role of the apical CI-/IHCO3- exchanger and PAT1 (SLC26A6) in chloride (and fluid) absorption in kidney proximal tubule and gastrointestinal tract. Toward this end, we propose to: 1. Characterize the apical CI/HCO3- exchanger in isolated microperfused proximal tubule and ascertain its role in chloride reabsorption in the presence of solutions mimicking proximal tubule milieu, 2. Ascertain the role of SLC26A6 in apical Cltbase exchange and cr reabsorption in kidney proximal tubules using SLC26A6 (PAT1) null mice, 3. Examine the acute and chronic regulation of SLC26A6 (PAT1) and apical CI-/HCO3- exchanger in kidney proximal tubule, and 4. Determine the role of SLC26A6 in gastric and intestinal function, including CI absorption and protection against acid injury in the duodenum and acid secretion in the stomach, using SLC26A6 null mice. Insight into the functional and molecular properties of PAT1 and apical CI-/HCO3- exchange in kidney proximal tubule and upper gastrointestinal tract in physiologic states and examination of PAT1 deficient mice should significantly enhance our understanding regarding the apical CI-/base exchanger and cr absorption in epithelial tissues. They should further facilitate future investigations into the role of this transporter in pathophysiologic states affecting electrolyte and acid-base homeostasis.

肾近曲小管和胃肠道中的顶端氯/碱交换器与 NHE3 并行工作，对于氯吸收和体液稳态至关重要。然而，人们对这种交换剂的分子特性和主要功能模式知之甚少。 SLC26A6，也称为 PAT1 或 CFEX，是一个大型、高度保守的离子转运蛋白家族（称为 SLC26A）的成员，其中许多离子转运蛋白介导阴离子交换。 SLC26A6 可以介导 Cl'/HCO3-、Cl/甲酸盐和 Cl-/草酸盐交换，表明它是近曲小管顶端 Cl/碱基交换的理想候选者。我们的实验表明，SLC26A6 介导 CI-/HCO3- 交换，位于胃壁细胞的近端小管、小肠和管泡的顶膜上，并被 NH4+（天然的一种物质）上调。 肾近曲小管和小肠中发生的化学物质。我们进一步证明在大鼠和小鼠分离的微灌注近端小管和胃壁细胞的小管小泡中存在顶端 CI/HCO3-交换。我们假设 SLC26A6 是肾近端小管和十二指肠中主要的顶端阴离子交换剂，在生理条件下主要充当 CI-/HCO3- 交换剂，并负责大量氯离子的吸收。在胃中，PAT1 可能对于中和静息状态下含有 H-K-ATP 酶的囊泡的管腔酸度至关重要。当前的目的 该提案旨在确定顶端 CI-/IHCO3- 交换器和 PAT1 (SLC26A6) 在肾脏近端小管和胃肠道吸收氯离子（和液体）中的作用。为此，我们建议： 1. 表征分离的微灌注近端小管中的心尖 CI/HCO3-交换器，并确定其在模拟近端小管环境的溶液存在下氯离子重吸收中的作用，2. 确定 SLC26A6 在心尖 Cltbase 中的作用使用 SLC26A6 (PAT1) 缺失小鼠进行肾近端小管的交换和 cr 重吸收，3. 检查急性和慢性肾近曲小管中 SLC26A6 (PAT1) 和顶端 CI-/HCO3- 交换器的调节，以及 4. 确定 SLC26A6 在胃和肠功能中的作用， 包括使用 SLC26A6 缺失小鼠进行 CI 吸收、防止十二指肠酸损伤和胃酸分泌。深入了解生理状态下肾近端小管和上胃肠道中 PAT1 和顶端 CI-/HCO3- 交换的功能和分子特性以及对 PAT1 缺陷小鼠的检查，应显着增强我们对顶端 CI-/碱交换和 cr 吸收的理解在上皮组织中。他们应该进一步促进未来对该转运蛋白在影响电解质和酸碱稳态的病理生理状态中的作用的研究。