Mechanisms of CNS node of Ranvier formation.

 描述(申请人提供)：兰维尔结节上的离子通道聚集是有髓轴突的基本特征。结节Na+通道簇具有几个重要的功能优势，包括减少能量和空间需求，以及增加动作电位传导速度。我们最近发现，多个重叠的机制参与了Ranvier形成的CNS节点的形成。这些机制包括内在机制(神经元机制)和外在机制(神经胶质机制)。外在机制包括轴突细胞黏附分子和胶质细胞来源的细胞外基质分子之间的相互作用，以及轴突连接依赖的扩散屏障限制膜蛋白到结节。内在机制取决于细胞骨架和支架蛋白。结节Na+通道聚集机制的冗余性使遗传小鼠模型成为发现中枢神经系统结节如何形成的唯一容易处理的方法。尽管取得了这些进展，但这些机制如何工作的分子细节仍然知之甚少，甚至存在争议。在这里，我们将使用新开发的遗传小鼠模型来阐明兰维尔结节形成和维持的分子机制。我们建议确定NF186和节点ECM在Ranvier组装和维护节点中的作用。我们建议确定血影蛋白如何将结节Na+通道蛋白复合体与潜在的肌动蛋白细胞骨架联系起来。最后，我们建议确定偏阳极作为侧向扩散障碍的作用。这里提出的实验继续和扩展了我们之前的研究，这些研究发现了Ranvier形成的CNS节点的多个重叠机制。

 DESCRIPTION (provided by applicant): Ion channel clustering at nodes of Ranvier is an essential feature of myelinated axons. Nodal Na+ channel clusters confer several important functional advantages including decreased energy and space requirements, and increased action potential conduction velocity. We recently showed that multiple, overlapping mechanisms contribute to CNS node of Ranvier formation. These mechanisms include both intrinsic (neuronal) and extrinsic (glial mechanisms). Extrinsic mechanisms include interactions between axonal cell adhesion molecules and glia-derived extracellular matrix molecules, as well as an axoglial junction-dependent diffusion barrier that restricts membrane proteins to nodes. Intrinsic mechanisms depend on cytoskeletal and scaffolding proteins. The redundancy of nodal Na+ channel clustering mechanisms makes genetic mouse models the only tractable approach to discover how CNS nodes are formed. Despite these advances, the molecular details for how these mechanisms work remain poorly understood and are even controversial. Here, we will use newly developed genetic mouse models to elucidate the molecular mechanisms responsible for node of Ranvier formation and maintenance. We propose to determine the roles of NF186 and the nodal ECM in node of Ranvier assembly and maintenance. We propose to determine how spectrins function to link the nodal Na+ channel protein complex to the underlying actin cytoskeleton. And finally, we propose to determine how paranodes function as lateral diffusion barriers. The experiments proposed here continue and extend our previous studies that identified multiple, overlapping mechanisms for CNS node of Ranvier formation.