Studies of Motoneuorn Death-Insight into SMAs and ALS

描述(由申请人提供)：神经元死亡是发育中的和病理性的中枢神经系统(CNS)的一个显著特征。在过去的十年里，这位研究人员和其他许多人的工作提供了有价值的信息，概述了神经元死亡的几个关键特征。以鸡脊髓运动神经元为模型系统，我们采用了两种方法来确定营养支持不足导致运动神经元死亡的生化和分子机制。在第一种方法中，我们调查了被确认在非神经元死亡中起作用的因素是否也与运动神经元死亡有关。为此，我们确定了促凋亡分子Bax从细胞质中的位置到细胞膜(线粒体和细胞核)的易位，这与细胞死亡的承诺一致。在这一事件之后，细胞色素c从线粒体中释放出来，特定的caspase被激活。在第二种方法中，我们进行了消减杂交筛选，以特定地识别当运动神经元致力于细胞死亡时差异表达的信息。通过这种方法，我们发现淀粉样前体蛋白(APP)在失去营养支持的运动神经元中的表达比提供营养支持的健康运动神经元增加。令人惊讶的是，我们发现APP是caspase的底物，这种相互作用实际上可能促进神经元对死亡的承诺。在这个竞争性的续订应用中，实验的目标有两个。 首先，我们在前一个时期发现的许多事件都与细胞死亡的执行阶段有关。我们将扩展我们的研究，以确定那些将侮辱(例如，失去营养支持)与细胞对死亡级联的明显承诺联系在一起的事件。 在第二个目标中，实验计划通过探索外源性和内源性HSPs、泛素和蛋白酶体通路在缺乏营养支持的情况下促进死亡的作用来检查神经元对营养因子剥夺的压力的反应。 这些实验的结果将提供有关运动神经元如何对环境中的不利变化做出反应的信息。这些类型的数据可能为为什么在肌萎缩侧索硬化症(ALS)和脊髓性肌萎缩症(SMA)中这种神经元群体容易受到破坏提供新的见解。

DESCRIPTION (provided by applicant): Neuronal death is a prominent feature of the developing and pathological central nervous system (CNS). During the past decade work from this investigator and many others has provided valuable information outlining several of the key features of neuronal death. Using chick spinal motoneurons as our model system, we have taken two approaches to identify biochemical and molecular mechanisms underlying motoneuron death resulting from insufficient trophic support. In the first approach, we have investigated if factors identified to have a role in nonneuronal deaths are also involved in motoneuron death. To this end, we identified a translocation of the pro-apoptotic molecule Bax from location in cytoplasm to organelle membrane (mitochondria and nuclear) coincident with the cells commitment to death. Following this event, cytochrome c is released from mitochondria and specific caspases are activated. In the second approach, we performed a subtractive hybridization screen to specifically identify messages that are differentially expressed when motoneurons are committed to cell death. With this approach we found that the amyloid precursor protein (APP) has increased expression in motoneurons deprived of trophic support as compared to healthy counterparts supplied with support. Surprisingly, we identified that APP is a substrate of for caspases and that this interaction may actually promote the neurons commitment to death. The goals of the experiments in this competing renewal application are two fold. First, many of the events that we have identified during the previous period are associated with the execution phase of cell death. We will extend our studies to identify those events that link insult (e.g., loss of trophic support) with the cell's apparent commitment to the death cascade. In the second aim, experiments are plan to examine how neurons respond to the stress of trophic factor deprivation by exploring the roles of exogenous and endogenous Hsps, ubiquitin and the proteasome pathways have in promoting death in the absence of trophic support. Results of these experiments will provide information regarding how motoneurons respond to adverse changes in their environment. These type of data may provide novel insight as to why this neuronal population is susceptible to destruction in amyotrophic lateral Sclerosis (ALS) and the spinal muscular atrophies (SMAs).