Project 4: Mechanisms of Mg2+ Homeostatis: Mouse Models

镁对每个哺乳动物细胞都至关重要。它是蛋白质的重要辅因子 合成、核酸合成和稳定性、能量利用和膜兴奋性。尽管 尽管镁具有重要的生物学意义，但对镁的体内平衡是如何调节的知之甚少。过去几年 研究人员已经发现了三种基因，当它们发生突变时，就形成了家族性疾病的遗传基础。 导致低镁血症其中一个基因，TRPM 6，是由美国大学的研究发现的。 爱荷华州，与来自德国马尔堡的一个小组同时出版，并独立于该小组。失去这位 基因产物导致继发性低钙血症的低镁血症综合征。TRPM 6基因 当产物与至少一种其它蛋白质TRPM 7相互作用时，其似乎形成Mg通道。主要 TRPM 6在结肠和肾远曲小管表达的位置支持以下观点： 这些蛋白质在镁的吸收和排泄中起主要作用。作为一个项目4在一个程序来阐明 TRPM 6和TRPM 7在镁稳态中的作用，我们假设这两种蛋白相互作用， 增强肠和肾远曲小管细胞对镁的吸收。我们还假设， 两种蛋白质的α激酶结构域在调节吸收细胞中的Mg转运中起关键作用。我们 还提出镁缺乏和α激酶结构域在调节细胞中起重要作用， 与信道传输功能不直接相关的功能。拟议的研究将启动一项详细的 评估这些基因产物如何在TRPM 6和TRPM 7被破坏的小鼠模型中发挥作用 基因.拟议的实验将测试与该基因如何在Mg中发挥作用有关的特定假设 消耗，它的功能障碍和低镁血症一般如何产生低钾血症，以及TRPM 6 基因产物影响小鼠的发育。具体目的是：1）确定Mg如何平衡 影响正常小鼠和TRPM 6和TRPM 7基因受损小鼠的节段性肾单位功能; 2)开发具有条件失活的TRPM 6和TRPM 7基因的小鼠模型。

Magnesium is of critical importance to every mammalian cell. It is an important cofactor for protein synthesis, nucleic acid synthesis and stability, energy utilization, and membrane excitability. Despite its biological importance, relatively little is known about how Mg homeostasis is regulated. In the past few years investigators have uncovered three genes that, when mutated, form the genetic basis for familial disorders leading to hypomagnesemia. One of those genes, TRPM6, was uncovered by work done at the University of Iowa and published simultaneous with, and independent of, a group from Marburg, Germany. Loss of this gene product leads to the syndrome of hypomagnesemia with secondary hypocalcemia. This TRPM6 gene product appears to form a Mg channel when it interacts with at least one other protein, TRPM7. The major locations where TRPM6 is expressed, the colon and renal distal convoluted tubule, support the notion that these proteins play a major role in absorption and excretion of Mg. As a Project 4 in a Program to elucidate the role of TRPM6 and TRPM7 in Mg homeostasis, we hypothesize that these two proteins interact to enhance Mg absorption by intestine and renal distal convoluted tubule cells. We also hypothesize that the alpha kinase domains of both proteins serve a critical role in regulating Mg transport in absorptive cells. We also propose that Mg deficiency and the alpha kinase domains play important roles in regulating cell functions not directly related to channel transport function. The proposed studies will initiate a detailed assessment of how these gene products function in mouse models with a disrupted TRPM6 and TRPM7 genes. The proposed experiments will test specific hypotheses related to how this gene functions in Mg depletion, how its dysfunction and hypomagnesemia in general produce hypokalemia, and how the TRPM6 gene product influences development of the mouse. The specific aims are: 1) Determine how Mg balance affects the segmental nephron function in normal mice and mice with disrupted TRPM6 and TRPM7 genes; 2) Develop mouse models with a conditionally inactivated TRPM6 and TRPM7 genes.