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

肾脏近端小管和胃肠道中的顶端氯/碱交换器与NHE 3平行工作，并且对于氯吸收和流体稳态是必需的。然而，很少有人知道这种交换器的分子身份和主要功能模式。SLC26A6，也称为PAT1或CFEX，是一个大的，高度保守的离子转运蛋白家族（命名为SLC26A）的成员，其中许多介导阴离子交换。SLC26A6可介导Cl~-/HCO_3~-、Cl~-/甲酸盐和Cl~-/草酸盐交换，是近端小管顶端Cl~-/碱交换的理想候选者。我们的实验表明，SLC26A6介导Cl-/HCO3-交换，位于近端小管、小肠和胃壁细胞小管囊泡的顶膜上，并被NH4+上调，NH4+是一种天然的C1-/HCO3-交换途径。 在肾脏近端小管和小肠中发生化学物质。我们进一步证明了在大鼠和小鼠离体微灌注近端小管和胃壁细胞tubulovesicles中存在顶端CI/HCO3交换。我们假设SLC26A6是肾脏近端小管和十二指肠中的主要顶端阴离子交换器，在生理条件下主要作为Cl-/HCO3-交换器起作用，并且负责大部分氯化物吸收。在胃中，PAT 1可能是必不可少的中和的管腔酸度的H-K-ATP酶的囊泡在休息状态。当前的目的 本发明的目的是确定顶端Cl-/IHCO3-交换器和PAT 1（SLC 26 A6）在肾近端小管和胃肠道中的氯（和液体）吸收中的作用。为此，我们建议：1。在离体微灌注近端小管中表征顶端Cl/HCO3-交换器，并确定其在模拟近端小管环境的溶液存在下在氯离子重吸收中的作用，2。使用SLC26A6（PAT1）敲除小鼠确定SLC26A6在肾近端小管中的顶端Cltbase交换和cr重吸收中的作用。检测肾脏近曲小管SLC26A6（PAT1）和顶端Cl-/HCO3-交换器的急性和慢性调节。确定SLC26A6在胃和肠功能中的作用， 包括使用SLC26A6缺失小鼠的Cl吸收和针对十二指肠中的酸损伤和胃中的酸分泌的保护。深入了解生理状态下肾脏近曲小管和上消化道中PAT 1和顶端Cl-/HCO 3-交换的功能和分子特性以及对PAT 1缺陷小鼠的检查，将显著增强我们对顶端Cl-/碱交换和上皮组织中Cr吸收的理解。他们应该进一步促进未来的调查，这种转运蛋白的作用，在影响电解质和酸碱平衡的病理生理状态。

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.