Targeting Pathways of Axonal Cell Adhesion Molecules

项目总结/摘要 哺乳动物神经元进化为具有高度复杂的结构，这是神经元功能的基础。 这项工作的长期目标是了解神经元结构的详细阐述， 分子水平。许多神经元过程的正常运作至关重要地依赖于正确的 许多蛋白质在特定细胞位置的定位。通过极化确保正确定位 来自transGolgi网络的膜运输以及通过内吞作用和内体分选。我的实验室研究 神经元如何完成极化膜交通，以建立不同的领域，如轴突和 树突 轴突和树突在功能上的差异要求许多分子 潜在的信号接收、积分和传播可以在空间上分离。各种粘附分子 同样需要正确定位。轴突细胞粘附分子L1/NgCAM对正常脑至关重要 L1突变导致多形神经发育缺陷，称为CRASH综合征。在 在上一个资助期，我们开发了培养的动态，功能干扰和实时成像方法。 神经元，以确定轴突细胞粘附分子L1/NgCAM如何行进到轴突。我们证明 它是通过一种新的途径：通过体树突内体的转胞吞作用。其他货物，如 转铁蛋白（Tfn）受体和AMPA受体，也穿过体树突内体，但不是 最终被分类为轴突。这项研究的目的是阐明亚细胞组织， 神经元中极化膜转运的分子调节，特别关注内体。我们将 确定哪些隔室和哪些调节器完成从细胞中分选不同蛋白质的任务， 体树突内体与轴突或树突的连接。在初步工作中，我们已经确定了三个 蛋白作为NgCAM运输的调节剂，我们将阐明NEEP 21，syntaxin 13（Aim 1）和 Rme 1/EHD 1（Aim 2）在NgCAM和转铁蛋白分选中的作用。最后，我们会问， L1/NgCAM是组成型的或受配体调节（Aim 3）。神经细胞膜运输的中心性 功能是强调了大量的贩运调节基因与神经退行性疾病 条件因此，揭示神经元内体的复杂性对许多方面具有广泛的意义 神经元功能。与转铁蛋白相比，探索L1/NgCAM运输调节剂的作用将 导致新的见解神经元特异性的阐述极化内体系统。由于L1 表达在神经元损伤和中风后上调，理解L1向轴突的运输， 对损伤后再生过程的影响。

Project Summary/Abstract Mammalian neurons evolved to have a highly complex architecture that underlies neuronal function. The long-term goal of the proposed work is to understand the elaboration of neuronal architecture on a molecular level. Proper functioning of many neuronal processes is crucially dependent on the correct localization of many proteins at specific cellular locations. Correct localization is ensured by polarized membrane traffic from the trans Golgi network and by endocyctosis and endosomal sorting. My lab studies how neurons accomplish polarized membrane traffic in order to establish distinct domains, such as axons and dendrites. The difference in functions between axons and dendrites requires that many of the molecules underlying signal reception, integration, and propagation be spatially segregated. Various adhesion molecules similarly need to be localized correctly. The axonal cell adhesion molecule L1/NgCAM is crucial to normal brain development; mutations in L1 lead to pleiomorphic neurodevelopmental defects, called CRASH syndrome. In the previous funding period, we developed kinetic, function-interfering, and live-imaging approaches in cultured neurons to determine how the axonal cell adhesion molecule L1/NgCAM travels to the axon. We demonstrated that it does so via a novel route: transcytosis via somatodendritic endosomes. Other cargos, such as transferrin (Tfn) receptors and AMPA receptors, also traverse somatodendritic endosomes, but are not ultimately sorted to axons. The goal of the proposed research is to elucidate the subcellular organization and molecular regulation of polarized membrane transport in neurons, focusing in particular on endosomes. We will determine which compartments and which regulators accomplish the task of sorting different proteins from somatodendritic endosomes to either axons or dendrites. In preliminary work, we already identified three proteins as regulators of NgCAM trafficking, and we will elucidate the roles of NEEP21, syntaxin13 (Aim 1) and Rme1/EHD1 (Aim 2) in the sorting of NgCAM and transferrin. Lastly, we will ask if endosomal trafficking of L1/NgCAM is constitutive or regulated by ligands (Aim 3). The centrality of membrane traffic for neuronal function is underscored by the large number of trafficking regulators genetically linked to neurodegenerative conditions. Uncovering the complexities of neuronal endosomes thus has wide implications for many aspects of neuronal functioning. Probing the role of regulators for L1/NgCAM trafficking in comparison to transferrin will lead to new insights into the neuronal-specific elaboration of a polarized endosomal system. Since L1 expression is upregulated after neuronal injury and after stroke, understanding L1 trafficking to axons has implications for regenerative processes after injury.