Regulation of kinesin-5 during neuronal development: studies on dendrites

​中枢神经系统脊椎动物神经元通常具有一个长而细的轴突，具有均匀的正端-远端微管阵列和几个短而粗的锥形树突，具有混合极性微管阵列。轴突的主要目的是产生一个输出脉冲到一个可能遥远的目标，而树突的功能是收集和巩固传入的信息。运动蛋白-5是一种同四聚体运动蛋白，对有丝分裂纺锤体的形成至关重要，最近被证明在神经元中存在并起作用。也被称为Eg5或kif11， kinesin-5属于一组运动蛋白，通过影响微管相互之间的运输对细胞分裂至关重要。本研究假设了激酶5在终有丝分裂后神经元中的独特作用，旨在回答有关激酶5分布和活性调控的关键问题。在实验中，运动蛋白-5被耗尽或抑制的神经元显示出生长更快的轴突和异常细长的树突。因此，这一提议的首要假设是，驱动蛋白-5作为一个“刹车”来调节这些神经突的生长和发育。从机制上说，这个假设是通过限制微管通过其他分子马达进入轴突和树突的运输来减弱轴突和树突的生长。之前的工作是在轴突上完成的；这里的重点是树突。通过三个不同的具体目的来探索激酶5的调控：第一个目的是确定激酶5在树突微管阵列的发育和维持中的功能；第二项研究旨在确定酪蛋白-5磷酸化苏氨酸残基926的调控作用；第三个目的是确定驱动蛋白-5是否识别特定的微管翻译后修饰，以便在树突成熟时富集。在这三个目标中提出的研究利用尖端的细胞生物学分析，包括活细胞成像技术，定量免疫荧光和复杂的RNA干扰方法。分子马达通过调节微管极性模式强烈影响树突特征的假设可能对神经系统疾病的进展和潜在治疗具有深远的意义。

This proposal aims to determine function and regulation of a mitotic molecular motor protein called kinesin-5 in vertebrate neurons during their normal development. Central nervous system vertebrate neurons typically possess one long thin axon with a uniformly plus-end-distal microtubule array and several short thick tapering dendrites with mixed polarity microtubule array. While the axon¿s main purpose is to generate an outgoing impulse to a potentially faraway target, dendrites function to gather and consolidate incoming information. Kinesin-5, a homotetrameric motor protein known to be essential for the formation of the mitotic spindle, has recently been shown to be present and functional in neurons. Also called Eg5 or kif11, kinesin-5 belongs to a group of motor proteins that are crucial for cell division by influencing the transport of microtubules relative to one another. This proposal hypothesizes a unique role for kinesin-5 within the terminally post-mitotic neuron and aims to answer key questions on the regulation of kinesin-5¿s distribution and activity. A neuron where kinesin-5 is experimentally depleted or inhibited displays faster growing axons and abnormally long and thin dendrites. Therefore, the overarching hypothesis of this proposal is that kinesin-5 acts as a ¿brake¿ to modulate the growth and development of these neurites. Mechanistically, the hypothesis is that kinesin-5 attenuates the growth of axons and dendrites by limiting the transport of microtubules into them by other molecular motors. Previous work was done on axons; the emphasis here is on dendrites. Regulation of kinesin-5 is explored through three different specific aims ¿ the first aimed to determine kinesin-5 function in development and maintenance of the dendritic microtubule array; the second aimed to determine the regulatory role of kinesin-5 phosphorylation of threonine residue 926; and the third aimed to determine whether kinesin-5 recognizes specific microtubule post-translational modifications in order to become enriched in dendrites as they mature. Proposed studies in these three aims utilize cutting edge cell biological analyses including live-cell imaging techniques, quantitative immunofluorescence and sophisticated RNA interference approaches. The hypothesis that molecular motors strongly influence dendritic characteristics through regulation of microtubule polarity patterns may have profound implications for the progression and potential treatments of diseases of the nervous system.