Cdk5 regulation of the GRAB-mediated Rab8-Rab11 cascade in axon outgrowth.
Cdk5 regulation of the GRAB-mediated Rab8-Rab11 cascade in axon outgrowth.
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DOI：
10.1523/jneurosci.2197-16.2017
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发表时间：
2016
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影响因子：
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通讯作者：
Kotaro Furusawa;A. Asada;Pamela J. Urrutia;C. González-Billault;M. Fukuda;S. Hisanaga
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文献类型：
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作者：
Kotaro Furusawa;A. Asada;Pamela J. Urrutia;C. González-Billault;M. Fukuda;S. Hisanaga
神经元通过轴突和树突相互交流。然而，对轴突和树突形成所涉及的分子机制的全面表征仍然不完整。神经突的生长需要提供膜成分以进行表面扩张。建议轴突生长的两种膜来源，高尔基体秘书囊泡和内吞回收内体。在非神经元细胞中，分泌囊泡从高尔基体的运输由 Rab 小 GTPases 的成员 Rab8 调节，而内体的回收则由 Rab 的另一个成员 Rab11 调节。然而，这些囊泡在生长的轴突中是否协调或独立运输尚不清楚。在此，我们发现 GRAB（Rab8 的鸟嘌呤核苷酸交换因子）是轴突生长的新型调节剂。 GRAB 的敲低抑制了培养的小鼠大脑皮层神经元的轴突生长。 GRAB 介导 Rab11A 和 Rab8A 之间的相互作用，并且该活性受到 Cdk5-p35 Ser169 和 Ser180 磷酸化的调节。不可磷酸化的GRAB突变体S169/180A比磷酸化模拟GRAB突变体S169/180D更大程度地促进轴突生长。 GRAB 的磷酸化抑制了其鸟嘌呤核苷酸交换因子活性及其将 Rab8A 募集到 Rab11A 阳性内体的能力。 GRAB 及其 Cdk5 磷酸化的体内功能在小鼠胚胎大脑中发育神经元的迁移和过程形成中得到了体现。这些结果表明，GRAB 通过以 Cdk5 依赖性方式激活 Rab8A 并将其募集到 Rab11A 阳性内体来调节轴突生长。意义陈述虽然轴突的生长需要膜供应来进行表面扩张，但调节轴突生长中膜运输的分子机制仍不清楚。在这里，我们证明 GRAB（Rab8 的鸟嘌呤核苷酸交换因子）是轴突生长的新型调节剂。 GRAB 通过介导神经元中 Rab11 和 Rab8 之间的相互作用来促进轴突膜运输。 GRAB 的活性受 Cdk5 磷酸化的调节。我们描述了 GRAB 及其 Cdk5 磷酸化在胚胎大脑神经元迁移和过程形成过程中的体内作用。因此，轴突生长的膜供应由 Cdk5 通过 Rab11-GRAB-Rab8 级联调节。
Neurons communicate with each other through their axons and dendrites. However, a full characterization of the molecular mechanisms involved in axon and dendrite formation is still incomplete. Neurite outgrowth requires the supply of membrane components for surface expansion. Two membrane sources for axon outgrowth are suggested, Golgi secretary vesicles and endocytic recycling endosomes. In non-neuronal cells, trafficking of secretary vesicles from Golgi is regulated by Rab8, a member of Rab small GTPases, and that of recycling endosomes is by Rab11, another member of Rabs. However, whether these vesicles are coordinately or independently transported in growing axons is unknown. Herein, we find that GRAB, a guanine nucleotide exchange factor for Rab8, is a novel regulator of axon outgrowth. Knockdown of GRAB suppressed axon outgrowth of cultured mouse brain cortical neurons. GRAB mediates the interaction between Rab11A and Rab8A and this activity is regulated by phosphorylation at Ser169 and Ser180 by Cdk5-p35. The non-phosphorylatable GRAB mutant S169/180A promoted axonal outgrowth to a greater extent than did the phospho-mimic GRAB mutant S169/180D. Phosphorylation of GRAB suppressed its guanine nucleotide exchange factor activity and its ability to recruit Rab8A to Rab11A-positive endosomes. In vivo function of GRAB and its Cdk5-phophorylation was shown in migration and process formation of developing neurons in embryonic mouse brains. These results indicate that GRAB regulates axonal outgrowth via activation and recruitment of Rab8A to Rab11A-positive endosomes in a Cdk5-dependent manner. SIGNIFICANCE STATEMENT While axon outgrowth requires membrane supply for surface expansion, the molecular mechanisms regulating the membrane transport in growing axons remains unclear. Here, we demonstrate that GRAB, a guanine nucleotide exchange factor for Rab8, is a novel regulator of axon outgrowth. GRAB promotes the axonal membrane transport by mediating the interaction between Rab11 and Rab8 in neurons. The activity of GRAB is regulated by phosphorylation with Cdk5. We describe an in vivo role for GRAB and its Cdk5 phosphorylation during neuronal migration and process formation in embryonic brains. Thus the membrane supply for axonal outgrowth is regulated by Cdk5 through the Rab11-GRAB-Rab8 cascade.