Role of SMN in Neuronal Apoptosis

描述（由申请人提供）：脊髓性肌萎缩症患者 (SMA)SMN1（运动神经元存活）基因突变导致 脊髓运动神经元的丧失。SMA是两种最常见的遗传性疾病之一， 儿童死亡的原因。SMA疾病中的运动神经元缺陷是 这显然是由于不适当的细胞死亡，而不是由于 神经发生然而，SMN突变导致 该神经元亚群过早死亡是未知的。我们开发了 用于评估凋亡调节因子功能的辛德毕斯病毒载体系统 在培养的神经元和小鼠的中枢神经系统（CNS）中。Sindbis 病毒具有强烈的亲神经性，专门针对大脑神经元 和包括脊髓运动神经元的脊髓。使用这个模型，我们有 显示SMN保护原代神经元（但不是各种细胞系）免受 辛德毕斯病毒诱导的细胞凋亡。SMN还可保护小鼠免受后 肢体瘫痪和死亡。然而，SMN的患者突变体不仅不能 保护，而不是加速培养和小鼠神经元的凋亡 导致瘫痪和早期死亡率增加。此外，瞬态 这些突变SMN蛋白在分化的神经元样细胞中的表达 在没有病毒感染的情况下也触发凋亡性细胞死亡。我们将 现在探索SMN调节神经细胞的分子机制 死亡之路在第一个目标中，我们试图了解SMNA7通常如何 会杀死神经元我们将确定SMN d7诱导的 神经元死亡需要半胱天冬酶或细胞死亡的其他组分 机械.将使用半胱天冬酶探索指定途径的因果关系 抑制剂，转基因和敲除小鼠品系。SMN似乎被切割 在神经元损伤期间。在第二个目的中，研究了这种裂解事件在 细胞死亡、相关蛋白酶和稳定SMN切割的功能 碎片将被追踪。此外，一组新的抗体， 将开发区分SMN的切割和野生型形式，以探索 蛋白水解在SMN功能中的作用。最后，我们将通过以下方式来实现这些机制： 全长SMN增强神经元存活，特别强调 脊髓运动神经元

DESCRIPTION (provided by applicant): Patients with Spinal Muscular Atrophy (SMA) have mutations in the SMN1 (survival motor neuron) gene leading to the loss of spinal cord motor neurons. SMA is one of the two most common genetic causes of mortality in children. The motor neuron deficiency in SMA disease is apparently due to inappropriate cell death rather than a defect in neurogenesis. However, the molecular mechanisms by which SMN mutations lead to the premature death of this neuron subset are not known. We have developed the Sindbis virus vector system for assessing the functions of apoptosis regulators in cultured neurons and in the central nervous system (CNS) of mice. Sindbis virus is potently neuronotropic, specifically targeting neurons of the brain and spinal cord including spinal cord motor neurons. Using this model we have shown that SMN protects primary neurons (but not a variety of cell lines) from apoptotic cell death induced by Sindbis virus. SMN also protects mice from hind limb paralysis and death. However, patient mutants of SMN not only fail to protect, but rather accelerate apoptosis of neurons in culture and in mice leading to increased paralysis and early mortality. In addition, transient expression of these mutant SMN proteins in differentiated neuron-like cells also triggers apoptotic cell death in the absence of a virus infection. We will now explore the molecular mechanisms by which SMN modulates the neuronal cell death pathway. In the first aim, we seek to understand how SMNA7, commonly found in SMA patients, kills neurons. We will determine if SMN d7-induced neuronal death requires caspases or other components of the cell death machinery. The causality of assigned pathways will be explored using caspase inhibitors, transgenic and knockout mouse lines. SMN appears to be cleaved during neuronal injury. In the second aim, the role of this cleavage event in cell death, the proteases involved and the function of stable SMN cleavage fragments will be pursued. In addition, a panel of new antibodies that can distinguish cleaved and wild type forms of SMN will be developed to explore the role of proteolysis in SMN function. Finally, we will pursue the mechanisms by which full length SMN enhances neuronal survival with specific emphasis on spinal cord motor neurons.