Mechanisms of CNS node of Ranvier formation

项目摘要 哺乳动物神经细胞动作电位的快速有效传播 系统需要髓鞘形成和电压门控离子的高密度聚集 通道的间隙中的髓鞘称为节点的兰维尔。尽管许多 脱髓鞘疾病和损伤导致淋巴结和神经系统的破坏 功能障碍，负责离子通道聚集在中央的机制 神经系统（CNS）的朗维尔节点仍然未知。我们建议， 不同的细胞和分子相互作用有助于CNS结的形成， 维持：1）轴突细胞粘附分子和一个独特的 CNS结细胞外基质，2）轴突和髓鞘化胶质细胞之间的相互作用， 结旁连接形成了一个膜蛋白扩散屏障，限制了细胞的横向扩散， 节蛋白的流动性，以及3）节膜蛋白和 结状细胞骨架支架保持离子通道的高密度簇。因此，在本发明中， 中枢神经系统中可能存在多种重叠的机制， 聚集在Ranvier节点上。在这个项目中，我们将进行细胞生物学和 遗传学方法来确定中枢神经系统朗维尔结的机制 阵我们将集中在外在的，胶质细胞衍生的相互作用，这是必要的， CNS结形成。在第一个目标中，我们将阐明分子相互作用 结细胞粘附分子和CNS结ECM蛋白之间的关系。我们将 确定可溶性ECM蛋白是否足以诱导结蛋白的聚集， 纯化的神经元培养物。在第二个目标中，我们将对单个， 缺乏细胞外基质分子的双重和三重基因敲除小鼠，结旁 连接和/或细胞骨架相互作用，以揭示存在和要求 对于每个重叠机制。

PROJECT SUMMARY 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.