R-Ras controls axon branching through afadin in cortical neurons.
R-Ras controls axon branching through afadin in cortical neurons.
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DOI：
10.1091/mbc.e12-02-0103
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发表时间：
2012-07
影响因子：
3.3
通讯作者：
Oinuma I
中科院分区：
文献类型：
--
作者：
Iwasawa N;Negishi M;Oinuma I
R-RAS下游的一条信号通路被确定为控制皮质神经元中的轴突分支。除了已知的R-RAS作为PI3K信号通路激活剂的作用外，还发现了一种新的细胞骨架调节系统，通过调节肌动蛋白结合蛋白afadin来诱导轴突分支。轴突生长、引导和分支的调节对于构建正确的神经网络是必不可少的。R-RAS是一个RAS家族的小GTP酶，在轴突的形成和引导中起着重要的作用。在轴突形成过程中，R-RAS激活一系列磷脂酰肌醇3-激酶信号，诱导微管组装启动子-崩溃素反应介体蛋白-2的激活。然而，连接R-RAS和肌动蛋白细胞骨架调节轴突形态的信号分子仍然不清楚。在这里，我们确定afadin，一种含有RAS关联(RA)结构域的肌动蛋白结合蛋白，是R-RAS通过F-肌动蛋白重组诱导轴突分支的效应器。我们观察到，在轴突发育阶段，皮层神经元中的内源性Afadin与R-RAS的相互作用。异位表达的afadin增加了轴突分支的数量，这一作用需要RA结构域和羧基末端的F-肌动蛋白结合域。RNA干扰敲除实验表明，内源性afadin的敲除既抑制了培养的皮质神经元的基础轴突分支，也抑制了R-RAS介导的轴突分支。亚细胞定位分析表明，活化的R-RAS诱导的afadin及其RA结构域的易位是导致afadin定位于细胞膜并诱导Neuro2a细胞轴突发育的原因。总体而言，我们的发现证明了R-RAS下游控制轴突分支的一条新的信号通路。
A signaling pathway downstream of R-Ras is identified that controls axon branching in cortical neurons. Besides the well-known role of R-Ras as an activator of the PI3K signaling pathway, a novel system of cytoskeletal regulation is found by which R-Ras induces axon branching through regulation of the actin-binding protein afadin. Regulation of axon growth, guidance, and branching is essential for constructing a correct neuronal network. R-Ras, a Ras-family small GTPase, has essential roles in axon formation and guidance. During axon formation, R-Ras activates a series of phosphatidylinositol 3-kinase signaling, inducing activation of a microtubule-assembly promoter—collapsin response mediator protein-2. However, signaling molecules linking R-Ras to actin cytoskeleton–regulating axonal morphology remain obscure. Here we identify afadin, an actin-binding protein harboring Ras association (RA) domains, as an effector of R-Ras inducing axon branching through F-actin reorganization. We observe endogenous interaction of afadin with R-Ras in cortical neurons during the stage of axonal development. Ectopic expression of afadin increases axon branch number, and the RA domains and the carboxyl-terminal F-actin binding domain are required for this action. RNA interference knockdown experiments reveal that knockdown of endogenous afadin suppressed both basal and R-Ras–mediated axon branching in cultured cortical neurons. Subcellular localization analysis shows that active R-Ras–induced translocation of afadin and its RA domains is responsible for afadin localizing to the membrane and inducing neurite development in Neuro2a cells. Overall, our findings demonstrate a novel signaling pathway downstream of R-Ras that controls axon branching.