IONIC CHANNELS IN MAMMALIAN MYELINATED NERVES

先前对哺乳动物有髓神经中K通道的电生理学和药理学分析已经确定，K通道的失调是脱髓鞘疾病中主要传导缺陷的基础。然而，无论是涉及的K通道基因的分子特异性，也不知道其适当的膜定位的分子机制。长期目标是填补这一知识空白。目前的目标是专注于Kv1.1，一种快速延迟整流器，在结旁连接处特异性表达，并与髓鞘基因共同调节。我们将利用我们实验室产生的Kv1.1无效突变小鼠来探索与我们理解脱髓鞘疾病中异常功能相关的关于此K通道的三个重要问题。这是第一次，具有正常形态但在髓鞘下面遗传缺失K通道亚型的有髓鞘神经可用于功能分析。在目标1中，我们将使用Kv1.1无效突变体来探索Kv1.1在稳定有髓纤维中的过渡区和分支点中所发挥的新作用。在目标2中，我们将利用我们的Kv1.1无效突变体来检查Kv1.1是否是负责传导阻滞或促进脱髓鞘轴突存活的关键钾通道。在目标3中，我们将使用我们的Kv1.1无效突变体作为无效背景，可以引入转基因来测试通道聚类的两个假设。与此相关的是，Kv β亚基的作用，它与Kv1.1共定位，并被认为是促进有效的表面表达，将在Kv β突变小鼠（也在我们的实验室产生）进行检查。

Previous electrophysiological and pharmacological analysis of K channels in mammalian myelinated nerves have established that dysregulation of K channels underlie major conduction deficits in demyelinating diseases. However, neither the molecular specificity of the K channel genes involved nor the molecular mechanism for their proper membrane localization are known. The long-term goal is to fill in this knowledge gap. The immediate goal is to focus on Kv1.1, a fast delayed rectifier that is expressed specifically at the paranodal junction and is co-regulated with myelin genes. We will utilize a Kv1.1 null mutant mouse generated in our laboratory to explore three important questions concerning this K channel that are relevant to our understanding of abnormal functions in demyelinating diseases. For the first time, myelinated nerves with normal morphology but with a K channel subtype genetically deleted underneath the myelin is available for functional analysis. In Aim 1, we will use the Kv1.1 null mutant to explore a novel role played by Kv1.1 in stabilizing transition zones and branch points in myelinated fibers. In Aim 2, we will utilize our Kv1.1 null mutant to examine whether Kv1.1 is the key potassium channel responsible for conduction block, or for promoting survival of, demyelinated axons. In Aim 3, we will use our Kv1.1 null mutant as a null background against which transgenes can be introduced to test two hypotheses of channel clustering. Relatedly, the role of Kvbeta subunits, which colocalize with Kv1.1 and are thought to promote efficient surface expression, will be examined in Kvbeta mutant mice (also generated in our laboratory).