Mechanisms of CNS node of Ranvier formation

描述(申请人提供)：动作电位在哺乳动物神经系统中的快速和有效传播需要髓鞘形成和高密度的电压门控离子通道在称为兰维尔结节的髓鞘缝隙处。虽然许多脱髓鞘疾病和损伤会导致节点中断和神经系统功能障碍，但导致兰维尔中枢神经系统(CNS)节点离子通道聚集的机制仍不清楚。我们认为，三种不同的细胞和分子相互作用有助于CNS结节的形成和维持：1)轴突细胞黏附分子与独特的CNS结节细胞外基质之间的相互作用；2)轴突与结旁交界处的髓鞘胶质细胞之间的相互作用建立膜蛋白扩散屏障以限制结节蛋白的横向移动；3)结节膜蛋白与结节细胞骨架支架之间的相互作用维持着高密度的离子通道簇。因此，在CNS中可能存在多个重叠的机制，以促进在Ranvier的节点处的离子通道聚集。在这个项目中，我们将采用细胞生物学和遗传学方法来确定Ranvier形成的CNS节点的潜在机制。我们将专注于中枢神经系统结节形成所必需的外在的、神经胶质来源的相互作用。在第一个目标中，我们将阐明结节细胞黏附分子与中枢神经系统结节细胞外基质蛋白之间的分子相互作用。我们将确定可溶性的ECM蛋白是否足以在纯化的神经元培养中诱导结节蛋白的聚集。在第二个目标中，我们将对缺乏细胞外基质分子、结旁连接和/或细胞骨架相互作用的单、双和三基因敲除小鼠进行遗传分析，以揭示每种重叠机制的存在和要求。 公共卫生相关性：兰维尔结节或其分子组成的破坏是脱髓鞘的后果之一，并有助于许多疾病和损伤的病理生理学，包括多发性硬化症和脊髓损伤。因此，任何旨在治疗这些疾病或逆转其破坏性影响的治疗努力都需要对兰维尔结节形成和维持的机制有详细的了解。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功能重要性，还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复杂的相互作用的最好例子之一。

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.