Assembly of the Node of Ranvier

描述（由申请方提供）：在轴突起始段（AIS）产生动作电位，并通过Ranvier结处的跳跃传导传播。这些结构域在电压门控Na+通道中高度富集，其与β亚基、神经元细胞粘附分子（特别是神经成束蛋白（NF）186）和细胞骨架蛋白锚蛋白G和piv血影蛋白形成多聚体复合物。我们最近已经证明NF 186靶向PNS节点是通过其细胞外相互作用介导的，它通过其胞质结构域募集锚蛋白G在节点形成中具有重要作用，而锚蛋白G反过来又是钠通道积累所需的。相反，锚蛋白在初始片段的积累，这也是结构域组织的关键是内在指定的，独立于NF 186。这些研究提出了一些关键问题。目标节点的蛋白质来源是什么？它们如何到达该站点？结的组成部分，一旦组装，稳定地表达在节点或他们不断营业额，如果是这样，这种营业额增强脱髓鞘？最后，CNS节点是否像PNS节点一样组装（即由细胞外信号指导）或更类似于初始片段（即通过与锚蛋白G的相互作用从内向外指导）？在本提案中，我们解决了这些问题，并通过以下方式进一步表征节点组装的机制：i）确定蛋白质如何运输到PNS节点，包括它们是从细胞表面池募集还是经由定向囊泡运输，和iii）检查CNS节点对共培养物中NF 186依赖性信号和转基因小鼠中靶向信号的依赖性。这些研究应该提供重要的轴神经胶质细胞的相互作用，调节组装和维护节点的朗维尔新的见解。他们也将是一个重要的基础，阐明病理变化的节点，导致脱髓鞘。

DESCRIPTION (provided by applicant): Action potentials are generated at the axon initial segment (AIS) and are propagated via saltatory conduction at nodes of Ranvier. These domains are highly enriched in voltage gated Na+ channels, which form a multimeric complex with beta subunits, neuronal cell adhesion molecules, notably neurofascin (NF) 186, and the cytoskeletal proteins ankyrin G and piv spectrin. We have recently demonstrated that targeting of NF186 to PNS nodes is mediated via its extracellular interactions, that it has an essential role in node formation by recruiting ankyrin G via its cytoplasmic domain, and that ankyrin G in turn, is required for the accumulation of sodium channels. In contrast, ankyrin accumulation at initial segments, which is also critical for domain organization is intrinsically specified, independent of NF186. These studies raise a number of key questions. What is the source of proteins targeted to the node and how do they traffic to this site? Are nodal components, once assembled, stably expressed at the node or do they continuously turnover and, if so, is this turnover enhanced by demyelination? Finally, do CNS nodes assemble like PNS nodes (i.e. directed by extracellular signals) or more akin to initial segments (i.e. directed from the inside-out via interactions with ankyrin G)? In this proposal, we address these questions and further characterize mechanisms of node assembly by: i) determining how proteins traffic to PNS nodes, including whether they are recruited from cell surface pools or via directed vesicular transport, ii) live image nodes to examine dynamic changes that occur during development and with demyelination, and iii) examine the dependence of CNS nodes on NF186- dependent signals in cocultures and targeting signals in transgenic mice. These studies should provide important new insights into the axo-glial interactions that regulate the assembly and maintenance of nodes of Ranvier. They will also be an important foundation for elucidating pathogenetic changes at nodes that result from demyelination.