Molecular Organization and Function of Paranodal Axo-Glial Junctions

描述(申请人提供)：结旁轴突连接的分子组织和功能有髓轴突的旁结节区包含一个特殊的区域，由髓鞘环和轴膜之间形成的分隔连接组成。这些轴突-胶质细胞间隔连接(AGSJ)已成为大量研究的对象。它们的主要分子组成是：联系蛋白相关蛋白(CASPR)、联系蛋白(CONT)和155 kDa神经筋蛋白的胶质细胞亚型(NF155)。小鼠CASPR的遗传消融导致AGSJ的破坏，结旁轴突细胞骨架的破坏和浦肯野轴突的退化。CONT和NF零小鼠也不能形成AGSJ。在进一步的研究中，我们创造了髓鞘胶质特异性NF155突变小鼠，它们无法在副阳极处聚集CASPR，也无法形成AGSJ。此外，我们还鉴定了一种含有PDZ结构域的细胞骨架蛋白，它与CASPR的细胞质区域相互作用，并定位于副节点。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问题。在这个方案中，我们建议使用遗传学、细胞生物学、分子和生化方法相结合的方法来确定AGSJs与轴突/神经胶质细胞骨架之间的分子关系，并以小鼠为遗传模型系统。我们的具体目标是：1)确定神经胶质细胞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AGSJ形成和/或稳定过程中的结构/功能关系。3)确定结旁轴膜CASPR与AGSJ组织中轴突细胞骨架成分之间的结构/功能关系。总体而言，拟议的研究应提供新的基本信息，这些信息将直接关系到科技咨询小组的组织及其在偏执型机构中发挥作用的机制。在未来，这些研究将促进我们对AGSJ在髓鞘相关病理中如何受损的理解，如多发性硬化症(MS)。我们的发现还将提供对结旁结旁轴突-神经胶质界面伴随多发性硬化的功能缺陷的见解，并有助于设计药物干预措施，以保护轴突和形成髓鞘的神经胶质细胞之间的微妙关系。结旁轴突-神经胶质连接的分子组成和功能 本申请中描述的研究涉及支配有髓神经纤维中不同轴突域的建立和组织的分子机制。这种独特的结构允许神经冲动在有髓轴突中的跳跃传播。更好地了解这些机制可能有助于设计未来治疗髓鞘相关疾病或脱髓鞘疾病的策略，例如多发性硬化症(MS)，在这些疾病中，需要重新髓鞘形成，必须保留轴突域结构。

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.