CORE--ELECTROPHYSIOLOGY CORE

该核心的目的是为研究上皮钙通道（ECaC）和组分I、III和IV中的产电钠/二羧酸协同转运蛋白（NaDC-1）提供支持。ECaC通道存在于小肠顶膜和肾脏远曲小管（DCT），是跨细胞钙转运的“看门人”。ECaC是许多调节胃肠道和肾脏Ca 2+吸收的激素的主要靶点，如甲状旁腺激素、维生素D等（1）。Bindels博士（2）和Hediger博士的研究组（3，4）最近独立地分离了ECaC及其同种型的cDNA。我们还分离了兔ECaC 1的cDNA，并从Bindels博士（该核心的顾问）处获得了小鼠ECaC 2的cDNA。近端小管中的NaDC-1可重吸收过滤后的克雷布斯循环中间产物，并在调节尿柠檬酸盐浓度方面发挥重要作用（5）。低尿柠檬酸盐是肾结石形成的重要危险因素。在第一部分中，我们将检验吸收性高钙尿症（AH）相关的蛋白质产物的假设， AH相关腺苷酸环化酶（AHRAC）基因调节ECaC通道活性。在组分 III项目1，我们将研究细胞内与细胞外pH值在调节细胞周期中的作用。 产电NaDC-1（6）。在第三部分项目2中，我们将检验酸抑制ECaCl介导的DCT中的Ca 2+重吸收有助于高膳食蛋白摄入诱导的高钙尿症的假设，以及膜磷脂，磷脂酰肌醇4，5-二磷酸（PIP 2）调节ECaCl通道活性的假设。在第四部分中，我们将检验这样的假设，即雌激素缺乏导致钙结合蛋白-D28 k的下调（除了ECaC的下调之外）对肾钙是重要的。探讨钙结合蛋白-D28 k调控钙离子的分子机制 通过ECaC重吸收。

The purpose of this core is to provide support for studies on epithelial Ca 2+ channels (ECaC) and the electrogenic sodium/dicarboxylate co-transporter (NaDC-1) in components I, III, and IV. ECaC channels are present in the apical membrane of intestine and the distal convoluted tubule (DCT) of kidney and serve as gatekeepers for transcellular Ca 2+ transport in these sites. ECaC is a major target for many hormones that regulate gastrointestinal and kidney Ca 2+ absorption, such as parathyroid hormone, vitamin D, etc (1). cDNAs for ECaC and its isoforms have recently been isolated by Dr. Bindels' (2) and Dr. Hediger's groups (3, 4) independently. We have also isolated cDNA for rabbit ECaC1 and obtained cDNA for mouse ECaC2 from Dr. Bindels (consultant for this core) NaDC-1 in the proximal tubules reabsorbs filtered Krebs cycle intermediates and plays an important role in the regulation of urinary citrate concentrations (5). Low urinary citrate is an important risk factor for formation of kidney stone. In component I, we will test the hypothesis that protein product of an absorptive hypercalciuria (AH)-related gene, AH-related adenylate cyclase (AHRAC), regulates ECaC channel activity. In component III project 1, we will investigate the role of intracellular vs extracellular pH in the regulation of the electrogenic NaDC-1 (6). In component III project 2, we will test the hypothesis that acid inhibition of ECaCl-mediated Ca 2+ reabsorption in DCT contributes to the hypercalciuria induced by a high dietary protein intake and the hypothesis that membrane phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP2) regulates ECaC1 channel activity. In component IV, we will test the hypothesis that down-regulation of calbindin-D28k by estrogen lack (in addition to the downregulation of ECaC) is important for renal calcium. leak and examine the molecular mechanism by which calbindin- D28k regulates Ca 2+ reabsorption through ECaC.