A New Target for Kidney Stone Prevention: Calcium-Sensitive Transport of Citrate

预防肾结石的新目标：柠檬酸盐的钙敏感转运

• 批准号: 8730145
• 负责人: Kathleen S Hering-Smith
• 金额: $ 30.1万
• 依托单位: TULANE UNIVERSITY OF LOUISIANA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8730145
• 关键词: Accounting; Acidosis; Affinity; Anatomy; Animals; Apical; Calcium; Calculi; Cell Line; Cells; Citrates; Data; Development; Didelphidae; Disease; Excretory function; Genes; Goals; Health Care Costs; Human; In Vitro; Intestinal Absorption; Intestines; Investigation; Ions; Kidney; Kidney Calculi; Knockout Mice; Knowledge; Lead; Magnesium; Medical; Methods; Molecular; Morbidity - disease rate; Mus; Nephrolithiasis; Outcome; Phenotype; Physiological; Physiological Processes; Prevention; Prevention strategy; Process; Proximal Kidney Tubules; Publishing; Regulation; Relative (related person); Research; Residual state; Role; Side; Succinates; Surface; Testing; Transport Process; Urine; Work; absorption; apical membrane; base; citrate carrier; cost; dicarboxylate-binding protein; extracellular; hypercalciuria; improved; in vivo; inhibitor/antagonist; kidney cell; novel; prevent; treatment strategy; tricarboxylate; urinary

DESCRIPTION (provided by applicant): Kidney stones are a common & serious illness. Urinary citrate is the most important inhibitor of calcium stones by keeping calcium soluble. The regulation of citrate transport in the kidney has received inadequate investigation & remains poorly understood. A single transporter NaDC1 has been assumed to be responsible for intestinal & renal citrate reabsorption. However we have recently identified a novel calcium-sensitive citrate transport process. The overall objective of this application is to determine the mechanisms & regulation of kidney proximal tubule apical citrate transport via a novel apical calcium-sensitive transporter, & the relative roles of NaDC1 & NaDC3. Our central hypothesis is that the novel citrate reabsorptive process functions to limit citrate transport in the proximal tubule when calcium is increased. Elucidation of previously unidentified citrate transporters can potentially lead to new treatments to increase urinary citrate. Aims are: 1) Define the novel calcium-sensitive citrate transporter & its role in the proximal tubule. Our working hypothesis, based on data in three proximal tubule cell lines, is that in addition to NaDC1, a novel calcium- sensitive dicarboxylate transporter is present on the apical side of the proximal tubule. We will use knockdown of NaDC1 in these cell lines to demonstrate this. Also we will determine citrate transport rates & the extracellular calcium-sensitivity for the remaining citrate transport process found in proximal tubule cells grown from dissected proximal tubule segments from knockout mice. 2) Determine the role of NaDC3 in proximal tubule reabsorption of citrate. Based on our surprising preliminary data, we will determine if NaDC3 is expressed on the apical membrane & accounts for calcium- sensitive citrate reabsorption. We will determine the localization of NaDC3 in the proximal tubule & determine the calcium sensitivity on the apical surface. We will also determine the role of basolateral NaDC3. 3) Determine the role of NaDC1 in renal reabsorption & intestinal absorption of citrate. Our working hypothesis is that NaDC1 is not the exclusive mechanism of citrate transport in the kidney & intestine. Other apical mechanisms may both be important in conditions such as acidosis & hypercalciuria. We will use NaDC1 knockout mice & compare renal citrate reabsorption in the -/- to +/+ mice both under baseline & conditions of acidosis & hypercalciuria. We will also determine intestinal citrate absorption in NaDC1 knockout mice.. These studies will establish new paradigms in understanding citrate reabsorption in both the kidney proximal tubule & the intestine, & how these paradigms are impacted in acidosis & hypercalciuria. These outcomes are expected to have an important impact since understanding the regulation of citrate transport in the proximal tubule will dramatically improve strategies in the prevention of calcium stones.

描述（由申请人提供）： 肾结石是一种常见且严重的疾病。尿柠檬酸盐通过保持钙的可溶性而成为钙结石最重要的抑制剂。肾脏中柠檬酸盐转运的调节尚未得到充分的研究并且仍然知之甚少。单一转运蛋白 NaDC1 被认为负责肠道和肾脏的柠檬酸盐重吸收。然而，我们最近发现了一种新型的钙敏感柠檬酸盐转运过程。本申请的总体目标是确定肾近曲小管顶端柠檬酸盐通过新型顶端钙敏感转运蛋白转运的机制和调节，以及 NaDC1 和 NaDC3 的相对作用。我们的中心假设是，当钙增加时，新的柠檬酸盐重吸收过程起到限制近曲小管中柠檬酸盐转运的作用。阐明以前未识别的柠檬酸盐转运蛋白可能会导致增加尿柠檬酸盐的新疗法。目标是：1) 定义新型钙敏感性柠檬酸转运蛋白及其在近曲小管中的作用。基于三种近曲小管细胞系的数据，我们的工作假设是，除了 NaDC1 之外，近曲小管的顶端侧还存在一种新型钙敏感性二羧酸转运蛋白。我们将在这些细胞系中使用 NaDC1 的敲低来证明这一点。我们还将确定柠檬酸盐转运速率和剩余柠檬酸盐转运过程的细胞外钙敏感性 发现于从基因敲除小鼠解剖的近端小管片段中生长的近端小管细胞中。 2)确定NaDC3在近曲小管柠檬酸盐重吸收中的作用。根据我们令人惊讶的初步数据，我们将确定 NaDC3 是否在顶膜上表达并解释钙敏感的柠檬酸盐重吸收。我们将确定 NaDC3 在近端小管中的定位并确定心尖表面的钙敏感性。我们还将确定基底外侧 NaDC3 的作用。 3)确定NaDC1在肾脏重吸收和肠道吸收柠檬酸盐中的作用。我们的工作假设是 NaDC1 并不是肾脏和肠道中柠檬酸盐转运的唯一机制。其他顶端机制在酸中毒和高钙尿等病症中可能都很重要。我们将使用 NaDC1 敲除小鼠并比较 -/- 与 +/+ 小鼠在基线以及酸中毒和高钙尿条件下的肾脏柠檬酸盐重吸收。我们还将确定 NaDC1 敲除小鼠肠道柠檬酸盐的吸收。这些研究将建立新的范例，以了解肾近曲小管和肠道中的柠檬酸盐重吸收，以及这些范例如何影响酸中毒和高钙尿症。这些结果预计将产生重要影响，因为了解近曲小管中柠檬酸盐转运的调节将极大地改善预防钙结石的策略。