Signaling pathways controlling myelination

描述（由申请人提供）：目前的研究重点是控制髓鞘形成的信号通路。在少突胶质细胞中过度表达构成性活性Akt（蛋白激酶B）的转基因小鼠产生的髓磷脂数量增加。此外，对这些小鼠的神经元也有影响。目前的研究主要集中在确定Akt调控髓鞘形成的信号通路，以及Akt在少突胶质细胞中的表达对神经元的影响。待验证的假设是Akt信号直接调控少突胶质细胞分化和髓鞘形成。这将首先通过研究这些小鼠的信号通路和基因表达变化来进行调查。因此，第一个目标将集中在Akt下游调控CMS髓鞘形成的信号通路上。初步研究将研究一系列Akt磷酸化底物的激活/失活状态，包括转录因子、mTOR和其他已知的Akt底物。我们的研究表明，Akt在这些小鼠中的过表达诱导了MAP激酶通路。因此，我们也将研究这一途径，重点关注Erk1/2信号。这一目标的主要焦点是mrna和蛋白质调节多髓鞘表型。我们将调查这是否完全由无法停止髓鞘形成控制，或者是否也有对分化的影响。因此，除了影响长期髓鞘形成过程外，我们还将研究Akt过表达是否以及如何影响少突胶质细胞分化。我们将通过已知少突胶质细胞谱系和分化标记的表达来评估Akt信号如何驱动CMS髓鞘形成，并对调节髓鞘形成的转录因子特别感兴趣。通过在培养的少突胶质细胞中过表达或敲低这些蛋白的表达，将证实控制髓鞘形成或少突胶质细胞分化的主要Akt底物。该提案的第二个目的是关注Akt表达升高和髓鞘形成增加对发育中的神经元的影响。研究重点是视神经轴突发育，探讨Ranvier淋巴结的形态成熟和组织。我们的初步数据表明，过表达Akt的少突胶质细胞与发育中的轴突之间存在强烈的相互作用。少突胶质细胞和神经元的相互作用将在培养中研究，使用从PLP-Akt-DD小鼠获得的细胞。这些研究的重要性在于，确定调控髓鞘形成的关键Akt底物可能导致增强多发性硬化症髓鞘形成的治疗方法。

DESCRIPTION (provided by applicant): The current studies focus on the signaling pathways controlling myelination. Transgenic mice that overexpress constitutively active Akt (protein kinase B) in oligodendrocytes produce increased amounts of myelin. Furthermore, there are effects on the neurons in these mice. The current studies focus on identifying the signaling pathways by which Akt regulates myelination, and the impact of Akt expression in oligodendrocytes on neurons. The hypothesis to be tested is that Akt signaling directly regulates oligodendrocyte differentiation and myelination. This will be investigated initially by studying the signaling pathways and gene expression changes that occur in these mice. Thus, the first aim will focus on the signaling pathways downstream of Akt that regulate CMS myelination. Initial studies will investigate the activation/inactivation state of a series of Akt phospho-substrates, including transcription factors, mTOR and other known Akt substrates. Our studies demonstrate that Akt overexpression in these mice induces the MAP kinase pathway. We will therefore investigate this pathway as well, focusing on Erk1/2 signaling. The main focus of this aim is on mRNAs and proteins that regulate the hypermyelination phenotype. We will investigate whether this is exclusively controlled by an inability to stop myelinating, or if there is also an impact on differentiation. Thus, we will study whether and how Akt overexpression impacts oligodendrocyte differentiation, in addition to impacting the long-term myelination process. We will investigate how Akt signaling drives CMS myelination as assessed by expression of known oligodendrocyte lineage and differentiation markers, with particular interest in the transcription factors regulating myelination. Putative major Akt substrates controlling myelination or oligodendrocyte differentiation will be confirmed by over- expressing or knocking down expression of these proteins in cultured oligodendrocytes. The second aim of the proposal focuses on the effect of elevated Akt expression and increased myelination on developing neurons. Studies focus on axonal development in optic nerve, investigating morphological maturation and organization of nodes of Ranvier. Our preliminary data demonstrate strong interactions between oligodendrocytes overexpressing Akt and developing axons. Interactions of oligodendrocytes and neurons will be studied in culture, using cells obtained from PLP-Akt-DD mice. The importance of these studies is that identifying the crucial Akt substrate(s) that regulates myelination may lead to therapeutic approaches to enhance remyelination in multiple sclerosis.