Actomyosin motors and Mechanism of Myelin Formation

描述(申请人提供)：髓鞘由轴突周围的神经胶质膜螺旋包裹而成。负责这一过程的机制尚不清楚，但可能涉及胶质细胞细胞骨架的变化。我们实验室最近的数据有力地表明，通过肌球蛋白轻链(MLC)的磷酸化来调节肌球蛋白组装是这一过程的一个重要方面。我们发现Rho相关激酶(ROCK)和肌球蛋白轻链激酶(MLCK)是参与MLC磷酸化的两个主要激酶，在髓鞘形成过程中具有非常不同的作用。在雪旺细胞-神经元共培养中，抑制ROCK导致非典型的雪旺细胞形态，细胞沿着轴突的长度异常地分支并形成多个独立的小髓鞘片段，每个片段都有相关的结节和副节点。这种组织部分类似于少突胶质细胞形成的髓鞘。相比之下，抑制MLCK似乎通过干扰髓鞘围绕轴突的螺旋包裹而阻止了髓鞘的形成。我们还发现，在发育过程中，MLC的磷酸化是强健的，但是短暂的，在髓鞘形成开始时激活。在这项研究中，我们将检验这一假设，即ROCK和MLCK是调节MLC磷酸化从而调节肌动球蛋白活性的两个主要途径，它们直接参与控制髓鞘形态及其包裹轴突。这个项目的总体目标是为调节三叉神经节和中枢神经系统中髓鞘形态和形成的机制提供新的见解。对髓鞘形成的分子机制的基本了解应该有助于开发新的治疗策略，以促进疾病的重新髓鞘形成；例如多发性硬化症和外周脱髓鞘神经病。

DESCRIPTION (provided by applicant): The myelin sheath forms by the spiral wrapping of a glial membrane around an axon. The; mechanisms responsible for this process are unknown but are likely to involve changes in the glial cell cytoskeleton. Recent data from our laboratory strongly suggest that regulation of actomyosin assembly via phosphorylation of myosin light chain (MLC) is an important aspect of this process. We have found that Rho-associated kinase (ROCK) and myosin light chain kinase (MLCK), two of the major kinases involved in MLC phosphorylation, have very distinct roles on myelination. In Schwann cell-neuron cocultures, inhibition of ROCK results in atypical Schwann cell morphology, with cells that branch aberrantly and form multiple, small independent myelin segments along the length of axons, each with associated nodes and paranodes. This organization partially resembles myelin formed by oligodendrocytes. By contrast, inhibition of MLCK appears to prevent myelination by interfering with the spiral wrapping of the myelin sheath around the axon. We have also found that MLC phosphorylation is robustly, but transiently, activated at the onset of myelination during development. In this study we will test the hypothesis that ROCK and MLCK, two of the major pathways regulating MLC phosphorylation and hence actomyosin activity, are directly involved in the control of myelin morphology and its wrapping around the axon. The overall goal of this project is to provide novel insights into the mechanisms that regulate myelin morphology and formation in the PNS and CNS. A basic understanding of the molecular machinery of myelination should aid in the development of new therapeutic strategies to promote remyelination in diseases; such as multiple sclerosis and peripheral demyelinating neuropathies.