Analysis of Brain-derived Neurotrophic Factor Signaling in Spinal Muscular Atrophy

脊髓性肌萎缩症中脑源性神经营养因子信号传导分析

• 批准号: 320351040
• 负责人: Privatdozentin Dr. Sibylle Jablonka
• 金额: --
• 依托单位: Institut für Klinische Neurobiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/320351040?language=en
• 关键词: Analysis; Brain; derived; Neurotrophic; Factor

Degeneration of anterior horn cells and denervation of muscles are the main clinical characteristics of spinal muscular atrophy (SMA) and well represented in SMA mouse models. Primary motoneurons from SMA type I mouse models exhibit altered axon elongation combined with reduced actin mRNA and protein levels in smaller growth cones. The differentiation defects correspond to impaired excitability at the nerve terminals due to reduced accumulation of N-type specific voltage-gated calcium channels (Cav2.2). These data raise the question whether the localization of e.g. growth factor receptors and their corresponding signaling pathways, which are important for differentiation and maturation of motoneurons, is affected in Smn-deficient motoneurons.In a first approach we could clearly show that the level of the Brain-derived Neurotrophic Factor (BDNF) receptor termed Tropomyosin-receptor-kinase B (TrkB) is reduced in growth cones of Smn-deficient motoneurons. Based on this observation we would like to investigate in detail how BDNF/TrkB signaling corresponds to affected actin cytoskeleton, excitability and neurotransmission in Smn-deficient motoneurons. The project shall be structured in three parts. In the first part we will focus on the time course of TrkB translocation at the growth cone in control and Smn-deficient motoneurons to understand how actin dynamics interfere with shifting TrkB to the cell surface in the presynaptic compartment of the neuromuscular endplate. As we know from our preliminary studies that the level of phospho-TrkB is significantly reduced in Smn-deficient growth cones, in the second part of our project we will try to figure out which signaling pathways downstream of TrkB (MAK kinase or Akt/mTOR pathway) support proper differentiation and maturation of presynapses in control motoneurons and which are affected in Smn-deficient motoneurons. It is in general an open question whether these pathways directly lead to altered release probability of synaptic vesicles or if newly synthesized proteins or rapid changes in the actin cytoskeleton are needed. Finally, the detailed analysis of affected BDNF/TrkB signaling in Smn-deficient motoneurons will be completed by experiments that focus on the intracellular rescue of actin transcript and proteins levels to understand whether defective BDNF/TrkB signaling, excitability disturbances and differentiation defects in Smn-deficient motoneurons can be compensated by proper formation of the actin cytoskeleton. Our expected results are thus important for a better understanding of the pathophysiology of SMA, in which presynaptic excitability, actin dynamics and neurotransmission are affected and thought to cause early events in the etiopathology.

脊髓性肌萎缩症（spinal muscular atrophy，SMA）的主要临床特征是前角细胞变性和肌肉失神经支配。来自SMA I型小鼠模型的初级运动神经元在较小的生长锥中表现出轴突伸长改变以及肌动蛋白mRNA和蛋白水平降低。分化缺陷对应于由于N型特异性电压门控钙通道（Cav2.2）的积累减少而导致的神经末梢兴奋性受损。这些数据提出了这样一个问题，即对于运动神经元的分化和成熟很重要的生长因子受体及其相应的信号传导途径的定位，在第一种方法中，我们可以清楚地表明，脑源性神经营养因子（BDNF）受体（称为原肌球蛋白受体激酶B（Trk B））的水平在Smn缺乏的运动神经元的生长锥中降低。运动神经元缺陷基于这一观察，我们想详细研究BDNF/TrkB信号如何对应于受影响的肌动蛋白细胞骨架，兴奋性和神经传递在Smn缺陷的运动神经元。该项目应分为三个部分。在第一部分中，我们将集中在控制和Smn缺陷的运动神经元的生长锥的TrkB易位的时间过程中，以了解肌动蛋白动力学如何干扰转移TrkB的神经肌肉终板的突触前区室的细胞表面。正如我们从我们的初步研究中所知道的，磷酸化TrkB的水平在Smn缺乏的生长锥中显著降低，在我们项目的第二部分中，我们将试图找出TrkB下游的哪些信号通路（MAK激酶或Akt/mTOR通路）支持对照运动神经元中突触前体的适当分化和成熟，以及哪些在Smn缺乏的运动神经元中受到影响。这是一个开放的问题，这些途径是否直接导致突触囊泡的释放概率改变，或者是否需要新合成的蛋白质或肌动蛋白细胞骨架的快速变化。最后，详细分析影响的BDNF/TrkB信号在Smn缺陷的运动神经元将完成的实验，专注于肌动蛋白转录和蛋白质水平的细胞内救援，以了解是否有缺陷的BDNF/TrkB信号，兴奋性障碍和分化缺陷的Smn缺陷的运动神经元可以通过适当形成的肌动蛋白细胞骨架补偿。因此，我们的预期结果是重要的，更好地了解SMA的病理生理，其中突触前兴奋性，肌动蛋白动力学和神经传递的影响，并认为导致早期事件的发病机制。