The role of focal adhesion kinase in CNS myelination

描述(由申请人提供)：髓鞘的形成是发育过程中的关键步骤，允许在哺乳动物中枢神经系统(CNS)有限的空间内发生有效的传导速度。在这个过程中，少突胶质细胞(OLG)，即CMS的髓鞘细胞，发出许多与轴突相关的突起，并最终包裹它们。OLG质膜与细胞外基质(ECM)之间的相互作用对于OLG突起成熟为髓鞘至关重要。因此，本研究的长期目标是研究OLG-ECM相互作用在突起生长和髓鞘形成过程中的作用。蛋白粘着斑激酶(FAK)在质膜-ECM相互作用中起核心作用。此外，FAK蛋白和磷酸化水平在髓鞘形成过程中也会发生变化。为了进一步研究FAK在髓鞘形成中的作用，我们通过使用在蛋白脂蛋白(PLP)启动子(PLP/CreERT)控制下表达他莫昔芬诱导的Cre蛋白的转基因小鼠(PLP/CreERT)和含有FAK的同源重组FAK等位基因的小鼠(其中FAK的第二个激动域两侧是loxP位点)，产生了条件性FAK基因敲除小鼠。该系统允许在OLG在与轴突相互作用并开始髓鞘形成之前发出进程的时间点进行OLG特异性FAK基因敲除。根据我们的初步观察和粘着斑组分对正常的OLG突起生长的作用，我们假设FAK，特别是它在酪氨酸925残基的磷酸化状态调节OLG突起的生长/重塑和髓鞘形成。特别是，我们的研究将确定FAK在1)体内OLG髓鞘形成和髓鞘形态中的作用，以及2)OLG体外生长/重塑过程中的作用。在病理条件下，如多发性硬化症(MS)患者中看到的髓鞘形成不当，会导致永久性残疾。不幸的是，在这种情况下修复髓鞘是有限的，目前还没有根治性的治疗方法。因此，更好地了解调控OGL过程生长/重塑和髓鞘形成的分子机制将有助于确定在此类病理条件下刺激重新髓鞘形成的可能治疗靶点。

DESCRIPTION (provided by applicant): The formation of the myelin sheath is a crucial step during development allowing for efficient conduction velocities to occur in the limited space of the mammalian central nervous system (CNS). During this event, oligodendrocytes (OLGs), the myelinating cells of the CMS, send out numerous processes that associate with axonal segments and ultimately enwrap them. For the maturation of OLG processes into myelin sheaths, interactions between the OLG plasma membrane and the extracellular matrix (ECM) are of vital importance. Therefore, the long term goal of this study is to investigate the role of OLG-ECM interactions during process outgrowth and myelination. The protein focal adhesion kinase (FAK) plays a central role in plasma membrane-ECM interactions. In addition, FAK protein and phosphorylation levels are altered during myelination. To further investigate the role of FAK for myelination we generated conditional FAK knockout mice, by using transgenic mice that express a tamoxifen-inducible Cre protein under the control of the proteolipid protein (PLP) promoter (PLP/CreERT) and mice that harbor homologous recombined FAK alleles in which the second kinase domain of FAK is flanked by loxP sites (FAKflox/flox). This system allows for an OLG-specific FAK knockout at a time point when OLGs are sending out processes before interacting with axons and beginning myelination. Based on our preliminary observations and the role of focal adhesion constituents for proper OLG process outgrowth, we hypothesize that FAK and in particular its phosphorylation state at the tyrosine 925 residue regulates OLG process outgrowth/remodeling and myelination. In particular our investigations proposed here will determine the role of FAK in 1) OLG myelination and myelin morphology in vivo and 2) OLG process outgrowth/remodeling in vitro. Improper myelination in pathological conditions, such as is seen in Multiple Sclerosis (MS) patients, results in persistent disabilities. Unfortunately repair of the myelin sheath under these conditions is limited and no curative treatment is currently available. Thus, a better understanding of the molecular mechanisms regulating OGL process outgrowth/remodeling and myelination will aid in identifying possible therapeutic targets to stimulate remyelination in such pathological conditions.