Actomyosin motors and Mechanism of Myelin Formation

描述（由申请人提供）：髓鞘由神经胶质膜围绕轴突螺旋缠绕形成。负责这一过程的机制尚不清楚，但可能涉及神经胶质细胞细胞骨架的变化。 我们实验室最近的数据强烈表明，通过肌球蛋白轻链（MLC）的磷酸化调节肌动球蛋白组装是这个过程的一个重要方面。我们已经发现Rho相关激酶（ROCK）和肌球蛋白轻链激酶（MLCK），这两种参与MLC磷酸化的主要激酶，在髓鞘形成中具有非常不同的作用。在雪旺细胞-神经元共培养物中，ROCK的抑制导致非典型的雪旺细胞形态，其中细胞异常分支并沿着轴突的长度形成多个小的独立髓鞘段，每个髓鞘段具有相关的节点和副节点。这种组织部分类似于由少突胶质细胞形成的髓鞘。相比之下，MLCK的抑制似乎通过干扰髓鞘围绕轴突的螺旋缠绕来防止髓鞘形成。我们还发现MLC磷酸化在发育过程中髓鞘形成开始时被强烈但短暂地激活。在这项研究中，我们将测试的假设，ROCK和MLCK，调节MLC磷酸化的两个主要途径，因此肌动球蛋白活性，直接参与髓鞘形态的控制和其周围的轴突包裹。该项目的总体目标是提供新的见解的机制，调节髓鞘形态和形成的PNS和CNS。对髓鞘形成的分子机制的基本了解有助于开发新的治疗策略，以促进疾病的髓鞘再生，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.