Signaling pathways controlling myelination

描述（由申请人提供）：目前的研究集中在控制髓鞘形成的信号通路上。在少突胶质细胞中过度表达组成型活性Akt（蛋白激酶B）的转基因小鼠产生增加量的髓鞘。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调节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。待检验的假设是Akt信号直接调节少突胶质细胞分化和髓鞘形成。这将通过研究这些小鼠中发生的信号通路和基因表达变化来初步研究。因此，第一个目标将集中在调节CMS髓鞘形成的Akt下游的信号传导通路上。初步研究将调查一系列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MAP激酶通路。因此，我们也将研究这一途径，重点是Erk1/2信号转导。这一目标的主要焦点是调节髓鞘形成过多表型的mRNA和蛋白质。我们将研究这是否完全由无法停止髓鞘形成控制，或者是否对分化也有影响。因此，我们将研究Akt过表达是否以及如何影响少突胶质细胞分化，以及影响长期髓鞘形成过程。我们将研究Akt信号如何驱动CMS髓鞘形成，通过已知的少突胶质细胞谱系和分化标志物的表达进行评估，特别关注调节髓鞘形成的转录因子。控制髓鞘形成或少突胶质细胞分化的推定的主要Akt底物将通过在培养的少突胶质细胞中过表达或敲低这些蛋白质的表达来确认。该提案的第二个目的集中在Akt表达升高和髓鞘形成增加对发育中的神经元的影响上。研究集中在视神经轴突的发育，调查形态成熟和组织的节点郎维。我们的初步数据表明，少突胶质细胞过度表达Akt和发展中的轴突之间的强相互作用。将使用从PLP-Akt-DD小鼠获得的细胞在培养物中研究少突胶质细胞和神经元的相互作用。这些研究的重要性在于，确定调节髓鞘形成的关键Akt底物可能会导致治疗方法，以增强多发性硬化症的髓鞘再生。

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.