Par1b/MARK2 Phosphorylates Kinesin-Like Motor Protein GAKIN/KIF13B To Regulate Axon Formation
Par1b/MARK2 Phosphorylates Kinesin-Like Motor Protein GAKIN/KIF13B To Regulate Axon Formation
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DOI：
10.1128/mcb.01181-09
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发表时间：
2010-03
影响因子：
5.3
通讯作者：
Yuta Yoshimura;T. Terabayashi;H. Miki
中科院分区：
文献类型：
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作者：
Yuta Yoshimura;T. Terabayashi;H. Miki
摘要在此，我们报道了Par1b/Mark2通过激动素超家族蛋白Gakin/KIF13B的磷酸化来调节轴突的形成。越来越多的证据表明，进化上保守的激酶Par1b在细胞极性调节中的重要性。利用培养的海马神经元，已经证明Par1b调节轴突的规格，但其潜在的机制仍不清楚。我们鉴定了Gakin/KIF13B是一个新的Par1b结合蛋白，揭示了Gakin/KIF13B是Par1b的生理底物，并且磷酸化位点在果蝇中是保守的。在海马神经元中，Gakin/KIF13B聚集在轴突末端的微管的远端，但不聚集在树突的末端。Gakin/KIF13B的过度表达本身可以诱导额外轴突的形成，而Par1b的共表达则以依赖于其激酶活性的方式抑制这种额外轴突的形成。相反，小干扰RNA(SiRNA)介导的Gakin/KIF13B基因敲除严重抑制了轴突的延伸，促进了无轴突表型的形成。通过共导入Gakin/KIF13B siRNA，抑制了Par1b siRNA引起的轴突外表型，从而将Gakin/KIF13B功能置于Par1b的下游。我们还发现Gakin/KIF13B通过Par1b磷酸化作用于磷脂酰肌醇3-激酶(PI3K)信号的下游。这些结果表明，Gakin/KIF13B是连接Par1b与轴突形成调控的关键中间体。
ABSTRACT Here we report that Par1b/MARK2 regulates axon formation via phosphorylation of a kinesin superfamily protein GAKIN/KIF13B. Accumulating evidence indicated the importance of the evolutionarily conserved kinase Par1b in the regulation of cell polarity. Using hippocampal neurons in culture, it has been shown that Par1b regulates axon specification, but the underlying mechanism remains uncharacterized. We identify GAKIN/KIF13B as a novel Par1b-binding protein and reveal that GAKIN/KIF13B is a physiological substrate for Par1b, and the phosphorylation sites are conserved from Drosophila. In hippocampal neurons, GAKIN/KIF13B accumulates at the distal part of the microtubules in the tips of axons, but not of dendrites. Overexpression of GAKIN/KIF13B by itself can induce the formation of extra axons, which is inhibited by the coexpression of Par1b in a manner dependent on its kinase activity. In contrast, small interfering RNA (siRNA)-mediated knockdown of GAKIN/KIF13B severely retards neurite extension and promotes the axonless phenotype. The extra axon phenotype caused by Par1b siRNA is suppressed by cointroduction of GAKIN/KIF13B siRNA, thus placing the GAKIN/KIF13B function downstream of Par1b. We also find that GAKIN/KIF13B acts downstream of the phosphatidylinositol 3-kinase (PI3K) signaling via Par1b phosphorylation. These results reveal that GAKIN/KIF13B is a key intermediate linking Par1b to the regulation of axon formation.