Roles of SLC26 Transporters in Urinary Oxalate Excretion and Kidney Disease

项目摘要本提案是为了继续一项长期的研究计划， 最初是针对研究离子交换剂介导的酸，碱和NaCl运输的近端 小管在这项工作的过程中，申请人克隆并表征了在细胞膜上表达的新型转运蛋白。 近曲小管细胞顶膜，SLC 26 A6。他们表明，SLC 26 A6能够介导Cl- 甲酸盐和Cl-草酸盐交换，并产生Slc 26 a6-null小鼠，以评估其在近端小管NaCl 运输然而，他们意外地观察到草酸钙尿石症的显著表型， 高尿酸血症他们发现高尿酸的原因是由于饮食中草酸盐的净吸收增加， SLC 26 A6介导的肠道草酸分泌缺陷。此外，其他人的工作表明， SLC 26 A1介导的草酸转运缺陷也可导致草酸钙尿石症。研究 因此，该项目被重新定向为关注SLC 26 A6和SLC 26 A1在草酸盐稳态中的作用， 高尿酸血症顶端转运蛋白SLC 26 A6和基底外侧转运蛋白SLC 26 A1各自在哺乳动物中表达。 参与草酸盐体内平衡的上皮组织：肠、肝和肾。此外，申请人 最近确定了SLC 26 A6介导的巨噬细胞中的草酸盐转运。本项目的总体目标 目的是阐明SLC 26 A6和SLC 26 A1在草酸盐稳态和肾脏疾病中的组织特异性作用。 在下一个项目期间，将努力实现以下具体目标： 1.确定SLC 26 A6和SLC 26 A1在草酸盐稳态中的组织特异性作用。生成鼠标线条 在肠、肝和肾中对编码SLC 26 A6和SLC 26 A1的基因进行组织特异性破坏， 并描述这些转运蛋白在防御高脂血症中的组织特异性作用 摄入或内源性产生的草酸盐负荷导致的高草酸尿症。 2.确定SLC 26 A6和SLC 26 A1在CKD中防御高脂血症的组织特异性作用。 描述SLC 26 A6和SLC 26 A1在一个人中防御高脂血症的组织特异性作用。 用马兜铃酸诱导的CKD模型，并评估是否导致过度的高血压 SLC 26 A6或SLC 26 A1的组织特异性缺失导致CKD的加速进展。 3.确定SLC 26 A6和SLC 26 A1在阿托伐他汀诱导的肿瘤坏死因子-α 1表达的发病机制中的组织特异性作用。 肾病表征SLC 26 A6在炎症细胞中介导草酸盐转运的作用， 评估特异性地在炎性细胞中缺失SLC 26 A6对尿酸盐诱导的肾病的影响， 并评估肾特异性SLC 26 A6和SLC 26 A1缺失对草酸盐肾病的影响。 这些研究将为草酸转运蛋白在调节肿瘤生长中的作用提供重要的新见解。 尿草酸排泄对草酸负荷的反应，在预防高血压和进行性 CKD中GFR的损失，以及在改善尿酸盐诱导的肾病中。

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.