Molecular Mechanisms of L1-dependnet axon growth (intracellular L2-trafficking and signaling pathways)

L1 依赖性轴突生长的分子机制（细胞内 L2 运输和信号传导途径）

基本信息

批准号：
13680857
负责人：
KAMIGUCHI Hiroyuki
金额：
$ 2.18万
依托单位：
The Institute of Physical and Chemical Research
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

In the developing nervous system, central and peripheral axon tracts are formed by axons that have elongated from the neuronal soma and reached their appropriate targets. Various cell adhesion molecules (CAMs) expressed on the growing axon and its tip (the growth Cone) interact with environmental cues, regulate growth cone motility, and navigate the axon along the correct path. In this research project, we have analyzed the functions of the immunoglobulin superfamily CAM Li and its interacting protein, ankyrin_B, and obtained the following results : 1.Ankyrin_B functions as a molecular clutch that connects retrograde F-actin flow with the L1 cytoplasmic domain (L1CD), thereby transmitting traction force that drives neurite initiation. 2.After moving into the central domain of growth cones by coupling with retrograde F-actin flow, L1 is endocytosed via the AP-2 and clathrin-mediated pathway followed by recycling to the plasma membrane of the growth cone leading edge. This type of intracellular L1 trafficking is required to create and maintain a gradient of L1-mediated adhesion (strong adhesion at the front and weak adhesion at the rear) in growth cones. It is also required for anterograde migration of the growth cones. 3.L1 interaction with AP-2 is regulated by phosphorylation/dephosphorylation of Tyr^<1176> in the L1CD. Clathrin-mediated endocytosis of L1 is triggered by the tyrosine dephosphorylation. 4.This tyrosine can be phosphorylated by the non-receptor tyrosine kinase Src that is localized to lipid rafts, specialized membrane microdomains enriched in cholesterol and sphingolipids. 5.Lipid rafts in the growth cone peripheral domain are critical for L1-based axon growth. These results help to understand the molecular mechanisms of axon growth.

在发展中的神经系统中，中央和周围轴突是由从神经元体内拉长并达到其适当靶标的轴突形成的。在生长的轴突及其尖端（生长锥）上表达的各种细胞粘附分子（CAM）与环境线索相互作用，调节生长锥运动，并沿正确的路径导航轴突。在该研究项目中，我们分析了免疫球蛋白超家族CAM LI及其相互作用的蛋白Ankyrin_B的功能，并获得了以下结果：1。Ankyrin_b是将逆行F-actin流动与L1细胞质结构量连接的分子离合器（ L1CD），从而传递驱动神经突引发的牵引力。 2.在通过与逆行F-肌动蛋白流相连进入生长锥的中心结构域后，L1通过AP-2内吞和网格蛋白介导的途径，然后回收到生长锥领先边缘的质膜。需要这种类型的细胞内L1运输才能在生长锥中创建和维持L1介导的粘附梯度（前部的粘附力和后部较弱的粘附）。生长锥的顺行迁移也是必需的。 3.L1与AP-2的相互作用受L1CD中Tyr^<1176>的磷酸化/去磷酸化调节。网格蛋白介导的L1内吞作用是由酪氨酸去磷酸化引发的。 4.这种酪氨酸可以被局部含在脂质筏的非受体酪氨酸激酶SRC磷酸化，该酪氨酸激酶SRC富含胆固醇和鞘脂。 5.生长锥外围结构域中的唇木筏对于基于L1的轴突生长至关重要。这些结果有助于了解轴突生长的分子机制。