Drosophila CLIP-190 and mammalian CLIP-170 display reduced microtubule plus end association in the nervous system.
Drosophila CLIP-190 and mammalian CLIP-170 display reduced microtubule plus end association in the nervous system.
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果蝇夹190和哺乳动物夹170在神经系统中显示降低的微管和末端关联。
DOI：
10.1091/mbc.e14-06-1083
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发表时间：
2015-04-15
影响因子：
3.3
通讯作者：
Prokop A
中科院分区：
文献类型：
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作者：
Beaven R;Dzhindzhev NS;Qu Y;Hahn I;Dajas-Bailador F;Ohkura H;Prokop A
通常，夹子通过结合它们的正端来促进微管的生长。然而，在神经元中，小鼠CLIP-170和Fly CLIP-190是弱末端结合蛋白，而是在生长锥体中心形成肌动蛋白/肌球蛋白VI依赖的斑块。Clip-190的总缺失，即使与其他四个正端结合蛋白一起，也没有显示出在神经元MT调节中的作用。轴突的作用就像电缆，用电线连接神经系统。极微管束(MT)形成它们的脊椎，并驱动它们的生长。此外，末端跟踪蛋白(+TIPS)调节MT的生长动力学和正端的方向性。然而，目前关于+TIP功能的知识大多来自于体外和非神经元细胞的工作，可能不一定适用于轴突MTS的非常不同的背景。例如，+TIPS的CLIP家族在非神经细胞中是已知的MT聚合启动子。然而，我们在这里表明，无论是果蝇CLIP-190还是哺乳动物CLIP-170都不是神经元中显著的MT+末端追踪器，我们认为这是由于含有CAP-Gly结构域的N-末端的低正端亲和力和通过C-末端的分子内抑制。相反，CLIP-190和CLIP-170都在生长锥体中形成依赖于肌动蛋白的F-肌动蛋白斑块，通过卷曲的卷曲结构域与肌球蛋白VI的结合而介导。由于我们在体内和培养中的功能丧失分析未能揭示CLIP-190的轴突作用，即使在与其他四个+TIP的双突变组合中，我们认为CLIP-190和-170不是必要的轴突延伸调节因子。我们的发现表明，已知的非神经细胞的+TIP功能不一定适用于轴突中非常独特的MT网络的调节。
Usually, CLIPs promote microtubule growth by binding their plus ends. However, in neurons, mouse CLIP-170 and fly CLIP-190 are weak end binders, instead forming actin/myosin VI–dependent patches in the center of growth cones. Total CLIP-190 loss, even together with four other plus end binders, reveals no role in neuronal MT regulation. Axons act like cables, electrically wiring the nervous system. Polar bundles of microtubules (MTs) form their backbones and drive their growth. Plus end–tracking proteins (+TIPs) regulate MT growth dynamics and directionality at their plus ends. However, current knowledge about +TIP functions, mostly derived from work in vitro and in nonneuronal cells, may not necessarily apply to the very different context of axonal MTs. For example, the CLIP family of +TIPs are known MT polymerization promoters in nonneuronal cells. However, we show here that neither Drosophila CLIP-190 nor mammalian CLIP-170 is a prominent MT plus end tracker in neurons, which we propose is due to low plus end affinity of the CAP-Gly domain–containing N-terminus and intramolecular inhibition through the C-terminus. Instead, both CLIP-190 and CLIP-170 form F-actin–dependent patches in growth cones, mediated by binding of the coiled-coil domain to myosin-VI. Because our loss-of-function analyses in vivo and in culture failed to reveal axonal roles for CLIP-190, even in double-mutant combinations with four other +TIPs, we propose that CLIP-190 and -170 are not essential axon extension regulators. Our findings demonstrate that +TIP functions known from nonneuronal cells do not necessarily apply to the regulation of the very distinct MT networks in axons.