Regulation of Metal Ion Homeostasis by Channel Kinases

描述(申请人提供)：本项目的目标是通过研究通道蛋白激酶的结构和功能，揭示脊椎动物中金属离子稳态，特别是镁离子稳态的调节机制。通道激酶，也被称为“Chanzymes”(通道加酶)，是最近发现的双功能分子，由一个离子通道与一个蛋白激酶融合而成。最近的研究表明，通道蛋白TRPM6和TRPM7在脊椎动物体内金属离子动态平衡的调节中起着关键作用。具体地说，通道酶有几个主要功能：1)作为镁通道，它们代表着镁稳态的关键调节因素，并可能提供哺乳动物细胞中主要的镁摄取机制；2)作为痕量金属离子通道，通道酶可能为痕量金属离子(如锰和锌)进入细胞提供主要的离子通道机制。在项目1(Andrea Fleig，Pi)中，我们将对TRPM7和TRPM6离子通道进行生物物理、分子和功能分析。我们将研究为二价金属离子提供选择性的通道渗透的分子决定因素。在项目2(Alexey Ryazanov，4PI)中，我们将研究TRPM7和TRPM6激酶的生理功能和激活机制。我们将确定这些激酶识别的序列基序，并确定它们的生理底物。在项目3(Andrew Scharenberg，PI)中，我们将研究TRPM7在调节镁稳态中的作用。我们将确定TRPM7介导镁依赖的细胞和生物体生长调节的信号通路。在项目4(John Stokes，Pi)中，我们将使用基因敲除小鼠模型分析TRPM6和TRPM7在镁稳态调节中的作用。我们将确定镁平衡如何影响TRPM6或TRPM7缺陷小鼠的肾功能。我们还将开发具有条件和器官特异性TRPM6和TRPM7基因敲除的小鼠。这些项目将得到一个行政核心(核心A)和一个动物和分析核心(核心B)的支持。这项工作具有高度的医学意义，因为通道激酶可能在缺血和中风等情况下发挥作用，而且通道激酶的突变正在导致与金属离子失衡相关的疾病。

DESCRIPTION (provided by applicant): The goal of this program is to uncover the mechanism of the regulation of metal ion homeostasis, particularly magnesium homeostasis in vertebrates through the investigation of the structure and function of channel kinases. Channel kinases, also know as "chanzymes" (channels plus enzymes) are recently discovered bifunctional molecules that consist of an ion channel fused to a protein kinase. Recent evidence suggests that channel kinases TRPM6 and TRPM7 play a key role in the regulation of metal ion homeostasis in vertebrates. Specifically, channel kinases have several major functions: 1) As magnesium channels they represent key regulators of magnesium homeostasis and may provide the major magnesium uptake mechanism in mammalian cells; 2) As trace metal ion channels, channel kinases may provide a major ion channel mechanism for cellular entry of trace metal ions such as manganese and zinc. In Project 1 (Andrea Fleig, PI), we will perform biophysical, molecular, and functional analysis of the TRPM7 and TRPM6 ion channels. We will investigate molecular determinants of channel permeation that provide selectivity for divalent metal ions. In Project 2 (Alexey Ryazanov, 4PI), we will investigate the physiological function and mechanism of activation of TRPM7 and TRPM6 kinases. We will determine sequence motifs recognized by these kinases and identify their physiological substrates. In Project 3 (Andrew Scharenberg, PI) we will investigate the role of TRPM7 in the regulation of magnesium homeostasis. We will identify signaling pathways through which TRPM7 mediates magnesium-dependent regulation of cell and organism growth. In Project 4 (John Stokes, PI), we will analyze the role of TRPM6 and TRPM7 in the regulation of magnesium homeostasis using knockout mouse models. We will determine how magnesium balance affects kidney function in mice deficient in TRPM6 or TRPM7. We will also develop mice with conditional and organ-specific knockouts of TRPM6 and TRPM7. These projects will be supported by an Administrative Core (Core A), and an Animal and Analytical Core (Core B). This work has a high degree of medical relevance considering that channel kinases are likely to play a role in such conditions as ischemia and stroke, and since mutations in channel kinases are causing diseases associated with metal ion imbalance.