Molecular Organization and Function of Paranodal Axo-Glial Junctions

描述（由申请人提供）：髓鞘轴突旁神经胶质连接的分子组织和功能髓鞘轴突旁神经区包含一个特殊的区域，由髓鞘环和轴鞘之间形成的分离连接组成。这些轴胶质分离连接（AGSJs）一直是大量研究的对象。它们的主要分子成分是：接触蛋白相关蛋白（CASPR）、接触蛋白（CONT）和神经束蛋白的155kDa胶质异构体（NF155）。小鼠CASPR基因消融可导致AGSJs的破坏、副神经节轴突细胞骨架的破坏和浦肯野轴突的变性。CONT和NF缺失小鼠也不能形成AGSJs。在进一步的研究中，我们创建了髓鞘胶质特异性NF155突变小鼠，其不能在偏执区聚集CASPR，也不能形成agsj。此外，我们已经确定了一个含有PDZ结构域的细胞骨架蛋白，该蛋白与CASPR的细胞质区域相互作用，并定位于偏执体。尽管对agsj的了解越来越详细，但关于它们的组织及其在维持轴突健康和神经元功能中的重要作用仍然存在根本性的问题。在本提案中，我们建议使用遗传学，细胞生物学，分子和生化方法相结合，以小鼠为遗传模型系统来定义AGSJs与轴突/胶质细胞骨架之间的分子关系。我们的具体目标是：1)确定胶质细胞NF155在agsj的组织和维持中的作用。2)确定NF155与胶质细胞骨架在AGSJs形成和/或稳定中的结构/功能关系。3)确定在AGSJs组织中，副神经节轴鞘和轴突细胞骨架成分的CASPR之间的结构/功能关系。总的来说，拟议的研究应提供新的和基本的信息，这些信息将直接关系到agsj的组织及其在偏执中发挥作用的机制。在未来，这些研究将推进我们对髓磷脂相关病理（如多发性硬化症（MS））中agsj如何受损的理解。我们的发现也将为MS伴随的副神经轴突-神经胶质界面的功能缺陷提供见解，并有助于设计药物干预来保护轴突和髓鞘形成的神经胶质细胞之间的微妙关系。神经节旁轴索神经胶质连接的分子组织和功能

DESCRIPTION (provided by applicant): Molecular Organization and Function of Paranodal Axo-Glial Junctions The paranodal region of myelinated axons contains a specialized domain consisting of septate junctions formed between myelin loops and the axolemma. These axo-glial septate junctions (AGSJs) have been the object of considerable investigation. Their major molecular constituents are: Contactin-associated protein (CASPR), Contactin (CONT) and a 155kDa glial-isoform of Neurofascin (NF155). Genetic ablation of CASPR in mice results in the disruption of AGSJs, disorganization of the paranodal axonal cytoskeleton, and degeneration of the Purkinje axons. CONT and NF null mice also fail to form AGSJs. In further studies, we have created myelinating glial-specific NF155 mutant mice, which fail to cluster CASPR at the paranodes and also fail to form AGSJs. In addition, we have identified a PDZ domain-containing cytoskeletal protein that interacts with the cytoplasmic region of CASPR and localizes at the paranodes. Despite increasingly detailed knowledge of the AGSJs, there remain fundamental questions concerning their organization and their essential role in maintaining axonal health and neuronal function. In this proposal, we propose to use a combination of genetic, cell biological, molecular and biochemical methods to define the molecular relationship between AGSJs and axonal/glial cytoskeleton using mouse as a genetic model system. Our specific aims are: 1) Determine the role of glial NF155 in the organization and maintenance of the AGSJs. 2) Determine the structure/function relationship between NF155 and the glial cytoskeleton in the formation and/or stabilization of the AGSJs. 3) Determine the structure/function relationship between CASPR at the paranodal axolemma and axonal cytoskeletal components in the organization of the AGSJs. Collectively, the proposed studies should provide new and fundamental information that will bear directly on the organization of AGSJs and the mechanisms by which they function at the paranodes. In the future, these studies will advance our understanding of how AGSJs are compromised in myelin-related pathologies, like Multiple Sclerosis (MS). Our findings will also provide insights into the functional deficits that accompany MS at the paranodal axon-glial interface and help design pharmaceutical interventions to preserve the delicate relationship between the axons and the myelin-forming glial cells. Molecular Organization and Function of Paranodal Axo-Glial Junctions The studies described in this application relate to the molecular mechanisms that govern the establishment and organization of distinct axonal domains in the myelinated nerve fibers. This unique structure allows the saltatory propagation of the nerve impulses in the myelinated axons. Better understanding of these mechanisms may help to design future therapeutic strategies to myelin-related diseases or demyelination disorders like for example multiple sclerosis (MS) where remyelination is required and the axonal domain structure must be preserved.