Mechanisms of CNS node of Ranvier formation

描述（由申请人提供）：哺乳动物神经系统中动作电位的快速有效传播需要髓鞘形成和电压门控离子通道在髓鞘间隙（称为朗氏结）处的高密度聚集。尽管许多脱髓鞘疾病和损伤引起淋巴结破坏和神经系统功能障碍，但负责朗维尔中枢神经系统（CNS）淋巴结处离子通道聚集的机制仍然未知。我们提出三种不同的细胞和分子相互作用有助于CNS节点的形成和维持：1）轴突细胞粘附分子与独特的CNS结细胞外基质之间的相互作用，2）轴突与结旁连接处的髓鞘化胶质细胞之间的相互作用建立了膜蛋白扩散屏障以限制结蛋白的侧向移动，和3）结膜蛋白和结细胞骨架支架之间的相互作用维持离子通道的高密度簇。因此，在中枢神经系统中可能存在多种重叠机制，以促进离子通道在郎维叶结处的聚集。在这个项目中，我们将采取细胞生物学和遗传学的方法来确定中枢神经系统朗维尔结形成的机制。我们将集中在中枢神经系统节点的形成所必需的外在的，胶质源性的相互作用。在第一个目标中，我们将阐明结细胞粘附分子和CNS结ECM蛋白之间的分子相互作用。我们将确定可溶性ECM蛋白是否足以诱导纯化的神经元培养物中的结蛋白的聚集。在第二个目标中，我们将进行遗传分析的单，双，和三重敲除小鼠缺乏细胞外基质分子，结旁连接，和/或细胞骨架的相互作用，以揭示存在，并要求，每个重叠的机制。 公共卫生相关性：朗氏结或其分子组成的破坏是脱髓鞘的结果之一，并导致许多疾病和损伤的病理生理学，包括多发性硬化和脊髓损伤。因此，任何旨在治疗这些疾病或逆转其破坏性作用的治疗努力都需要详细了解朗维尔结形成和维持的机制。节点一直是人们关注的焦点，不仅因为它们在健康和疾病中的重要功能，而且因为它们的组装代表了神经元和神经胶质细胞之间必须发生的精心设计的相互作用的最佳例子之一。

DESCRIPTION (provided by applicant): Rapid and efficient propagation of action potentials in the mammalian nervous system requires both myelination and the high-density clustering of voltage-gated ion channels at gaps in the myelin sheath called nodes of Ranvier. Although many demyelinating diseases and injuries cause disruption of nodes and nervous system dysfunction, the mechanisms that are responsible for ion channel clustering at central nervous system (CNS) nodes of Ranvier remain unknown. We propose that three distinct cellular and molecular interactions contribute to CNS node formation and maintenance: 1) interactions between axonal cell adhesion molecules and a unique CNS nodal extracellular matrix, 2) interactions between axons and myelinating glia at paranodal junctions set up a membrane protein diffusion barrier to restrict the lateral mobility of nodal proteins, and 3) interactions between nodal membrane proteins and nodal cytoskeletal scaffolds maintain high density clusters of ion channels. Thus, multiple, overlapping mechanisms may exist in the CNS to facilitate ion channel clustering at nodes of Ranvier. In this project we will undertake both cell biological and genetic methods to determine the mechanisms underlying CNS node of Ranvier formation. We will focus on the extrinsic, glial-derived interactions that are necessary for CNS node formation. In the first aim we will elucidate the molecular interactions between nodal cell adhesion molecules and CNS nodal ECM proteins. We will determine if soluble ECM proteins are sufficient to induce clustering of nodal proteins in purified neuronal cultures. In the second aim we will perform genetic analyses of single, double, and triple knockout mice lacking extracellular matrix molecules, paranodal junctions, and/or cytoskeletal interactions to uncover the existence of, and requirement for, each overlapping mechanism. PUBLIC HEALTH RELEVANCE: Disruption of nodes of Ranvier or their molecular composition is one consequence of demyelination and contributes to the pathophysiology of many diseases and injuries including multiple sclerosis and spinal cord injury. Thus, any therapeutic effort aimed at treating these diseases or reversing their devastating effects will require a detailed understanding of the mechanisms responsible for node of Ranvier formation and maintenance. Nodes have been the focus of much interest not only because of their functional importance in both health and disease, but also because their assembly represents one of the best examples of the elaborate reciprocal interactions that must occur between neurons and glial cells.