Targeting Pathways of Axonal Cell Adhesion Molecules

项目摘要/摘要 哺乳动物的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。 这项拟议工作的长期目标是理解神经结构在 分子水平。许多神经元突起的正常运作关键依赖于正确的 许多蛋白质在特定细胞位置的定位。通过极化来确保正确的定位 跨高尔基体网络的膜运输以及内吞和内吞分选。我的实验室研究 神经元如何完成极化的膜交通，以建立不同的区域，如轴突和 树枝状结构。 轴突和树突之间的功能差异要求许多分子 潜在的信号接收、整合和传播在空间上是分开的。各种黏附分子 同样需要正确本地化。轴突细胞黏附分子L1/NgCAM对正常大脑至关重要 发育；L1的突变会导致多形性神经发育缺陷，称为撞车综合征。在……里面 在之前的资助期间，我们开发了动力学、功能干扰和活体成像方法。 确定轴突细胞黏附分子L1/NgCAM如何运动到轴突。我们演示了 它是通过一种新的途径做到这一点的：通过体树突状内体进行跨细胞作用。其他货物，如 转铁蛋白(TFN)受体和AMPA受体也穿过体树突状内体，但不是 最终归类为轴突。这项拟议研究的目标是阐明亚细胞组织和 神经细胞极化膜运输的分子调控，尤其是内小体。我们会 确定哪些隔室和哪些调节器完成了对不同蛋白质进行分选的任务 体树突内涵体到轴突或树突。在前期工作中，我们已经确定了三个 蛋白质作为NgCAM运输的调节者，我们将阐明NEEP21、Synaxin13(Aim 1)和 Rme1/EHD1(Aim 2)在NgCAM和转铁蛋白分选中的应用。最后，我们会问，如果内体贩运 L1/NgCAM是构成的或受配体调节(目标3)。神经元膜运输的中枢性 大量与神经退行性变有遗传联系的贩运调节器突显了这一功能 条件。因此，揭示神经元内体的复杂性对许多方面都有广泛的意义 神经功能的变化。对照转铁蛋白Will探讨L1/NgCAM转运调节因子的作用 引导人们对极化内体系统的神经元特异性阐述有了新的见解。从L1开始 神经元损伤和中风后表达上调，理解L1运输到轴突 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.