Pathological retrograde signaling in ALS

描述(申请人提供)：脑源性神经营养因子(BDNF)激活TrkB受体支持纯运动神经元在体外存活，并在一些体内损伤范例中拯救运动神经元。此外，在BDNF存在的情况下生长的运动神经元将导致对有毒侮辱的脆弱状态。例如，当运动神经元在包括BDNF在内的营养因子的鸡尾酒中生长时，TrkB拮抗剂(从基因或药物上)可以保护神经元免受与肌萎缩侧索硬化症相关的兴奋毒性和蛋白毒性侮辱。BDNF-TrkB信号的这种不利特性的机制尚不完全清楚，但已知的是依赖于从头蛋白质的合成。TrkB表达于轴突、树突和胞体的质膜上。利用Campenot隔室培养系统，我们发现Trk在轴树突域(而不是胞体)激活，使运动神经元容易受到毒害。由于轴突和树突在细胞和分子生物学水平上有很大的不同，因此确定脆弱性信号来自哪个隔室是至关重要的。在特定的目标#1中，我们将产生嵌合的TrkB蛋白，将其表达靶向轴突或树突结构域。接下来，我们将确定TrkB的激活在哪个区段导致易感受性突变的SOD毒性。轴-树突结构域中的mRNAs至少部分不同于细胞体中的mRNAs。微阵列分析为我们提供了候选分子，可能是BDNF作用的分子机制的基础。在特定的目标#2中，我们将操纵表达强的候选分子，并确定它们是否取消了BDNF使运动神经元容易受到伤害的能力。这些高风险-高收益的实验将为运动神经元病的发病机制提供新的见解。 公共卫生相关性：肌萎缩侧索硬化症(ALS)是一种神经退行性疾病，运动神经元死亡，个体逐渐变得虚弱。在啮齿动物模型系统中，一种名为TrkB的细胞表面受体的激活可以使运动神经元容易受到与ALS相关的侮辱。在这项提案中，我们将确定TrkB在运动神经元表面(例如，轴突和树突)的激活使它们容易受到伤害。接下来，我们将研究在TrkB激活后经历新合成的轴突或树突中候选分子的重要性。这些研究将为肌萎缩侧索硬化症中运动神经元死亡的原因带来机械性的洞察。

DESCRIPTION (provided by applicant): The activation of the receptor TrkB by brain derived neurotrophic factor (BDNF) supports the survival of pure motor neurons in vitro and rescues motor neurons in some in vivo lesion paradigms. In addition, growing motor neurons in the presence of BDNF will induce a state of vulnerability to toxic insults. For example, when motor neurons are grown in a cocktail of trophic factors including BDNF, TrkB antagonism (genetically or pharmacologically) protects against excitotoxic and proteotoxic insults relevant to ALS. The mechanism of this adverse property of BDNF-TrkB signaling is incompletely understood but is known to depend on de novo protein synthesis. TrkB is displayed on the plasma membrane of axons, dendrites and the cell soma. Using Campenot compartment culture system, we find that activation of Trk in the axo- dendritic domain (not the cell soma) renders motor neurons vulnerable to toxic insult. Since axons and dendrites differ dramatically at the cell and molecular biological level it is essential to determine from which compartment the vulnerability signal originates. In Specific aim #1, we will generate chimeric TrkB proteins that target its expression to either the axonal or the dendritic domain. Next we will determine in which compartment TrkB activation leads to vulernability mutant SOD toxicity. The repertoire of mRNAs in the axo-dendritic domain is at least partially distinct from those present in the cell body. A microarray analysis provides us with candidate molecules that might underlie the molecular mechanism of the effect of BDNF. In Specific aim #2, we will manipulate the expression strong candidate molecules and determine if they abrogate the capacity of BDNF to render motor neurons vulnerable to insult. These high-risk-high gain experiments will provide novel insight into the pathogenesis of motor neuron disease. PUBLIC HEALTH RELEVANCE: Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease in which motor neurons die and individuals become progressively weak. In rodent model systems, activation of a cell surface receptor called TrkB can make motor neurons vulnerable to insults relevant to ALS. In this proposal we will determine where on the surface of a motor neuron (e.g., axons versus dendrites) activation of TrkB renders them vulnerable to insult. Next we will study the importance of candidate molecules in axons or dendrites that undergo new synthesis upon activation of TrkB. These studies will bring mechanistic insight into why motor neurons die in ALS.