Role of axoglial CAMs in the organization of myelinated axons

轴胶质 CAM 在有髓轴突组织中的作用

• 批准号: 8416894
• 负责人: ELIOR PELES
• 金额: $ 16.72万
• 依托单位: WEIZMANN INSTITUTE OF SCIENCE
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-12-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8416894
• 关键词: Affect; Axon; Binding; Cell Adhesion Molecules; Cells; Cytoskeleton; Demyelinating Diseases; Demyelinations; Development; Disease; Exhibits; Fiber; Gene Targeting; Generations; Genes; Heparan Sulfate Proteoglycan; Human; Ion Channel; Lead; Mediating; Membrane; Molecular; Morphology; Movement; Multiple Sclerosis; Mus; Mutant Strains Mice; Myelin; Myelin Sheath; Nerve; Nerve Fibers; Nervous system structure; Neuroglia; Neurons; Nodal; Peripheral Nerves; Peripheral Nervous System; Phenotype; Physiological; Play; Positioning Attribute; Potassium Channel; Prevalence; Property; Proteins; Ranvier' s Nodes; Recruitment Activity; Research; Role; Route; Schwann Cells; Site; System; TAG-1 axonal glycoprotein; Testing; Transgenic Organisms; design; hereditary neuropathy; in vivo; mutant; public health relevance; research study; restoration; scaffold

DESCRIPTION (provided by applicant): The myelin sheath covers the axon in segments that are separated by the nodes of Ranvier. In the underlying axons Na+ channels are clustered at the nodes of Ranvier, separated by a specialized axoglial paranodal junction (PNJ) from K+ channels that are found at the nearby juxtaparanodal region (JXP). This organization is essential for the saltatory movement of the nerve impulses, and its disturbance results in pathophysiological changes often seen in demyelinating human disorders. In the peripheral nervous system (PNS), myelinating Schwann cells regulate this precise organization of the axonal membrane through unknown mechanisms. We have previously identified several cell adhesion molecules (CAMs), including gliomedin, Caspr, Caspr2, and Necl4, which mediate axoglial contact at specific sites along the longitudinal axis of the myelin unit. These CAMs play important roles in the organization of myelinated axons: gliomedin cluster Na+ channels at nodes, Caspr is involved in the generation of a membrane barrier at the PNJ that restricts the distribution of Na+ and K+ channels to the nodes and JXP, respectively, Caspr2 serves as a scaffold that maintains K+ channels at the JXP, and Necl proteins organize the internodal membrane. The objective of the proposed research is to study the molecular mechanisms underlying the function of these axoglial CAMs in the generation of functional domains along myelinated axons. First, complementation experiments will be carried out using myelinating Schwann cells/neuron cultures isolated from gldn-/- mice to determine how the channels clustering activity of gliomedin is being regulated. Secondly, a transgenic rescue approach will be taken to examine the hypothesis that the PNJ restricts the distribution of Na+ channels to the nodal gap by forming a membrane barrier, which depends on the presence of the axonal cytoskeleton. Third, a similar in vivo approach will be taken in order to examine the mode of interaction between Caspr2 and TAG-1 and to reveal the underlying mechanisms by which these molecules recruit and retain Kv1 channels at the JXP. Finally, we will study the role of Necl proteins in the organization of myelinated axons by analyzing the morphology and the molecular organization of peripheral nerves of mutant mice lacking Necl4, as well as mice lacking the cytoskeletal linker protein 4.1G, which colocalizes and associates with Necl4 in myelinating Schwann cells. Altogether, the proposed experiments will provide important information about the coordinated differentiation of axons and myelin-forming cells, which allow myelinated fibers to maximize their conduction velocity. Better understanding these mechanisms may thus lead to new routes to the restoration of function in demyelinated axons and may prove useful in the design of therapeutical strategies for demyelinating disorders.

描述（由申请人提供）：髓鞘覆盖轴突，由Ranvier淋巴结隔开。在下面的轴突中，Na+通道聚集在Ranvier节点上，由一个特殊的轴交旁结（PNJ）与附近旁结旁区（JXP）发现的K+通道分开。这种组织对于神经冲动的跳跃运动是必不可少的，它的紊乱会导致脱髓鞘疾病中常见的病理生理变化。在周围神经系统（PNS）中，髓鞘化雪旺细胞通过未知的机制调节轴突膜的这种精确组织。我们之前已经确定了几种细胞粘附分子（CAMs），包括胶质瘤蛋白、Caspr、Caspr2和Necl4，它们介导髓鞘单位纵向轴向特定位点的轴胶质接触。这些CAMs在有髓鞘轴突的组织中发挥重要作用：胶质聚质蛋白聚集Na+通道位于节点，Caspr参与PNJ膜屏障的生成，分别限制Na+和K+通道在节点和JXP的分布，Caspr2作为维持JXP的K+通道的支架，Necl蛋白组织结间膜。本研究的目的是研究这些轴胶质cam在沿有髓鞘轴突产生功能域的分子机制。首先，利用从gldn-/-小鼠分离的髓鞘雪旺细胞/神经元培养物进行互补实验，以确定gliomedin的通道聚集活性是如何被调节的。其次，将采用转基因拯救方法来检验PNJ通过形成膜屏障来限制Na+通道分布到节点间隙的假设，这取决于轴突细胞骨架的存在。第三，将采用类似的体内方法来检查Caspr2和TAG-1之间的相互作用模式，并揭示这些分子在JXP中招募和保留Kv1通道的潜在机制。最后，我们将通过分析缺乏Necl4的突变小鼠和缺乏细胞骨架连接蛋白4.1G的小鼠的外周神经的形态和分子组织来研究Necl蛋白在髓鞘化雪旺细胞中与Necl4共定位并相关的组织中的作用。总之，所提出的实验将提供轴突和髓鞘形成细胞的协调分化的重要信息，这使得髓鞘纤维最大化其传导速度。因此，更好地理解这些机制可能会导致脱髓鞘轴突功能恢复的新途径，并可能在脱髓鞘疾病的治疗策略设计中被证明是有用的。