Roles of SLC26 Transporters in Urinary Oxalate Excretion and Kidney Disease

本提案是为了继续一项长期研究方案，该方案曾 最初致力于研究离子交换器在近端介导酸碱和氯化钠的运输 小管。在这项工作中，申请者克隆并鉴定了一种表达在 近端小管细胞顶膜，SLC26A6。结果表明，SLC26A6具有介导氯离子的能力。 甲酸和氯-草酸交换，并建立Slc26a6缺失的小鼠以评估其在近端小管氯化钠中的作用 运输。然而，他们出人意料地观察到了一种惊人的草酸钙尿石症表型，原因是 高草酸尿症。他们发现，高草酸尿症的原因是膳食中草酸的净吸收增加。 与SLC26A6介导的肠道草酸分泌缺陷有关。此外，其他人的工作表明， SLC26A1介导的草酸转运缺陷也可能导致草酸钙尿石症。这项研究 因此，计划被重新定向，将重点放在SLC26A6和SLC26A1在草酸动态平衡和 高草酸尿症。顶端转运蛋白SLC26A6和基底侧转运蛋白SLC26A1分别在 参与草酸动态平衡的上皮组织：肠、肝和肾。此外，申请者 最近发现了SLC26A6介导的巨噬细胞草酸转运。这个项目的总体目标是 旨在揭示SLC26A6和SLC26A1在草酸动态平衡和肾脏疾病中的组织特异性作用。 在下一个项目期间，将实现以下具体目标： 1.确定SLC26A6和SLC26A1在草酸动态平衡中的组织特异性作用。生成鼠标线 通过对肠道、肝脏和肾脏中编码SLC26A6和SLC26A1的基因进行组织特异性破坏， 并表征了这些转运蛋白在预防高草酸血症和 由摄入或内源性产生的草酸负荷引起的高草酸尿。 2.确定SLC26A6和SLC26A1在防治慢性肾脏病高草酸血症中的组织特异性作用。 SLC26A6和SLC26A1在小鼠抗高草酸血症中的组织特异性作用 马兜铃酸诱导慢性肾功能不全动物模型的建立 SLC26A6或SLC26A1的组织特异性缺失会加速CKD的进展。 3.确定SLC26A6和SLC26A1在草酸诱导的动物发病机制中的组织特异性作用。 肾病。描述SLC26A6在介导炎症细胞草酸转运中的作用， 评估在炎症细胞中特异性缺失SLC26A6对草酸肾病的影响。 并评估肾脏特异性缺失SLC26A6和SLC26A1对草酸肾病的影响。 拟议中的研究将为了解草酸转运体在 尿草酸排泄对草酸负荷的反应，在预防高草酸血症和进展性疾病中的作用 慢性肾脏病中GFR的丢失，以及草酸诱导的肾病的改善。

Project Summary The present proposal is for continuation of a longstanding research program that had originally been directed at studying the ion exchangers mediating acid-base and NaCl transport in the proximal tubule. In the course of this work the applicants cloned and characterized a novel transporter expressed on the apical membrane of proximal tubule cells, SLC26A6. They showed that SLC26A6 is capable of mediating Cl- formate and Cl-oxalate exchange, and generated Slc26a6-null mice to evaluate its role in proximal tubule NaCl transport. However, they unexpectedly observed a striking phenotype of calcium oxalate urolithiasis due to hyperoxaluria. They found that the cause of the hyperoxaluria is increased net absorption of dietary oxalate due to a defect in SLC26A6-mediated oxalate secretion in the intestine. In addition, work by others indicated that a defect in SLC26A1-mediated oxalate transport could also result in calcium oxalate urolithiasis. The research program was therefore re-directed to focus on the roles of SLC26A6 and SLC26A1 in oxalate homeostasis and hyperoxaluria. The apical transporter SLC26A6 and basolateral transporter SLC26A1 are each expressed in the epithelial tissues participating in oxalate homeostasis: intestine, liver and kidney. Moreover, the applicants have recently identified SLC26A6-mediated oxalate transport in macrophages. The overall goal of this project is to unravel the tissue-specific roles of SLC26A6 and SLC26A1 in oxalate homeostasis and kidney disease. During the next project period, the following specific aims will be pursued: 1. Determine tissue-specific roles of SLC26A6 and SLC26A1 in oxalate homeostasis. Generate mouse lines with tissue-specific disruption of the genes encoding SLC26A6 and SLC26A1 in intestine, liver and kidney, and characterize the tissue-specific roles of these transporters in defending against hyperoxalemia and hyperoxaluria resulting from ingested or endogenously produced oxalate loads. 2. Determine tissue-specific roles of SLC26A6 and SLC26A1 in defending against hyperoxalemia in CKD. Characterize tissue-specific roles of SLC26A6 and SLC26A1 in defending against hyperoxalemia in a model of CKD induced with aristolochic acid, and evaluate whether exaggerated hyperoxalemia resulting from tissue-specific deletion of SLC26A6 or SLC26A1 leads to accelerated progression of CKD. 3. Determine tissue-specific roles of SLC26A6 and SLC26A1 in the pathogenesis of oxalate-induced nephropathy. Characterize the role of SLC26A6 in mediating oxalate transport in inflammatory cells, assess the impact of deleting SLC26A6 specifically in inflammatory cells on oxalate-induced nephropathy, and assess the impact of kidney-specific deletion of SLC26A6 and SLC26A1 on oxalate nephropathy. The proposed studies will provide important new insights into the roles of oxalate transporters in governing urinary oxalate excretion in response to oxalate loading, in defending against hyperoxalemia and progressive loss of GFR in CKD, and in modifying oxalate-induced nephropathy.