神经元轴突发育的膜转运机制研究

Neurons have a typical polarized structure, with the single axon sending out information and multiple dendrites receiving information. Besides the functional difference, axons and dendrites have a marked difference in their morphology, e.g., total length and area of the single axon greatly outnumber that of total dendrites of the same cell, which renders axons capable of projecting to and controlling remote targets. It is generally believed that asymmetric cytoskeleton regulation and polarized membrane insertion are involved in neuronal polarization and axonal growth. Indeed, previous studies have identified many molecules that regulate axon development through regulating cytoskeleton dynamics, directly or indirectly. However, mechanisms regarding polarized membrane addition remain largely unknown. Recently, we find that tumor suppressor Lgl1 and Rab10 play an important role in polarized membrane insertion during axon development and have identified Rab10 as a marker for plasmalemmal precursor vesicles (PPVs). Here, we will identify Rab10 effectors and determine their roles and mechanisms. Like other vesicles, PPVs should experience formation, transportation, and membrane fusion, whereas mechanisms are not known. Based on our previous studies, this proposal aims to investigate roles of motor proteins, e.g., Myosin and Kinesin, and membrane associated proteins, e.g., MARCKS, in the following consecutive steps of PPVs: formation, transportation, tethering, docking, and membrane fusion. At the same time, we will study functions of these molecules in axon development in various model systems.

神经元具有典型的极性结构--单根轴突负责传出信息,而具有复杂分支的多根树突负责接受信息。除了功能上的差异,轴突和树突形态上具有很大不同.轴突的长度和总面积大大超过树突的总和,这种特点使它投射到远端组织或脑区支配效应细胞。神经元的极化和轴突的生长需要细胞骨架成分的不对称性调控以及细胞膜前体向某个神经突起的极性插入。以前的研究鉴定了很多直接或者间接调节细胞骨架的分子,但关于细胞膜的极性增加机制却知之甚少。最近,我们发现抑癌蛋白Lgl1以及Rab10在细胞膜极性插入以及轴突发育中的作用,并发现Rab10是质膜前体囊泡(PPV)的标志分子。本项目将重点研究Rab10的效应因子及其作用机制。在前期工作基础上，本项目重点研究Myosin和Kinesin等马达蛋白，以及MARCKS等膜相关蛋白在PPV形成、转运、拴系、锚定以及膜融合过程中的作用；系统分析这些分子在神经元轴突发育中的作用。

神经元的极化和轴突的生长需要细胞膜前体向某个神经突起的极性插入。本项目重点研究调节脂膜前体囊泡(PPV)的形成、运输以及膜融合的分子机制，深入解析这些分子对轴突发育的影响。我们发现Myosin Vb在Rab10 PPV从TGN发生过程中起重要作用，Rab10/JIP-1/KLC复合物调节PPV沿轴突的顺向运输，MARCKS蛋白介导PPV的锚定和膜融合；系统分析了这些分子在神经元轴突发育中的作用。这些研究深入研究了PPV的调控机理，阐明了PPV在轴突生长中的作用。除此之外，我们分析了膜内吞分子Rab5在轴突导向中的作用，发现Rab5参与了轴突排斥因子Sema3A介导的生长锥塌缩和轴突的成束化。我们还发现细胞自噬在轴突再生中的作用。在该项目支持下，共发表研究论文8篇，综述1篇。