CALCIUM RECEPTOR SIGNALING OF P450 ARACHIDONIC ACID METABOLITES

在本计划项目的项目#3中要探索的假设是 细胞色素P450(P450)花生四烯酸(AA)代谢产物提供 胞外钙/多价阳离子的主要信号系统- 感知哺乳动物肾脏中的G蛋白偶联受体(CaSR)。遗传 对人类和实验动物的生理学研究表明 CaSR不仅对细胞外钙依赖 甲状旁腺激素对甲状旁腺的调节作用 肾脏对二价矿物质的正常处理。CASR用来表示 哺乳动物肾单位的许多上皮节，尤其是在 形成初始近端小管的细胞的尿面 Henle环上升段的血-间质表面 被称为粗升肢(TAL)。因为盐分的运输过程在 近端小管和TAL均参与调节的二价体 矿物质离子排泄，激活这些肾单位节段的CaSR是 有望调节尿液中钙和镁的流失。调变 CASR在这些节段的转运过程也改变了肾脏 排出盐和水的过程，有助于确保钙 镁可以排出，降低患肾结石的可能性。 形成或发生肾钙质沉着。具体地说，钙激活细胞 TAL中的CaSR起着内源性“环”利尿剂的作用，而这 机制可能解释膳食钙摄入量的有益效果 在实验动物和人类中发现的血压。使用组合 分子、生物化学和生理方法，我们将：a) 鉴定参与水稻CaSR信号转导的特异性P450基因(S) 肾小管上皮细胞；b)定义特定的P450 omega/omega-1 激活CaSR产生的AA代谢物；c)识别 CaSR-P450信号通路的酶成分；以及d)定义 CaSR作用对盐分运移过程的生理影响结果： 这些研究应该明确CASR在肾脏调节中的作用。 二价矿物质动态平衡和盐水平衡。

The hypothesis to be explored in Project #3 of this Program Project is that cytochrome P450 (P450) arachidonic acid (AA) metabolites provide a major signaling system for the extracellular calcium/polyvalent cation- sensing G protein-coupled receptor (CaSR) in the mammalian kidney. Genetic and physiological studies in man and laboratory animals have demonstrated that the CaSR is crucial not only for the extracellular calcium-dependent regulation of parathyroid hormone form parathyroid glands, but also for normal divalent mineral handling by the kidney. The CaSR is expressed in many epithelial segments of the mammalian kidney nephron, particularly at the urinary face of cells forming the initial proximal tubule and at the blood-interstitial face of the ascending segment of the loop of Henle called the thick ascending limb (TAL). Since salt transport processes in both the proximal tubule and TAL are involved in regulated divalent mineral ion excretion, activation of the CaSR in these nephron segments is expected to modulate calcium and magnesium loss in the urine. Modulation of transport processes by the CaSR in these segments also alter the kidney excretion of salt and water, processes that help to ensure that calcium and magnesium can be excreted with a reduced likelihood for kidney stone formation or nephrocalcinosis. Specifically, calcium activation of the CaSR in the TAL functions as in endogenous "loop" diuretic, and this mechanism may account for the beneficial effect of dietary calcium intake on blood pressure seen in laboratory animals and man. Using a combination of molecular, biochemical and physiological approaches, we will: a) identify the specific P450 gene(s) involved in CaSR signaling in the kidney tubule epithelial cells; b) define the specific P450 omega/omega-1 AA metabolites generated by activation of the CaSR; c) identify the enzymatic components of the CaSR-P450 signaling pathway; and d) define the physiological effects of CaSR action on salt transport process. Results of these studies should define roles for the CaSR in the renal regulation of divalent mineral homeostasis and salt and water balance.