AMPA Receptor Expression and Selective Neuronal Death

描述（由申请人提供）：肌萎缩侧索硬化症（ALS）是一种致命的进行性神经退行性疾病，运动神经元选择性死亡，原因尚不完全清楚。这种显著的选择性脆弱性为这种毁灭性疾病的机制提供了重要线索。有证据表明，ALS涉及AMPA受体介导的谷氨酸兴奋毒性，我们的工作已经开始阐明这种机制的运动神经元的选择性的基础。我们发现，培养的脊髓运动神经元的兴奋性毒性的脆弱性不相关的AMPA受体的表达具有特别高的渗透性Ca2+或特别弱的脱敏程度，而是与AMPA受体的表达在一个非常高的表面密度。高密度的AMPA受体表达的这种特性似乎足以解释脊髓运动神经元在体外的选择性脆弱性。更一般地说，作为整个项目的一个主题的假设是，ALS中运动神经元的选择性脆弱性可能在很大程度上是由其谷氨酸受体表达的独特特征来解释的。 本提案将延长初步供资期的工作，以解决与这一假设有关的三个重要问题。具体目标1将使用应用于来自成熟大鼠的急性脊髓切片中的运动神经元的膜片钳和分子技术，定义脊髓组织环境中的成熟运动神经元表达的AMPA受体的生理和分子特征。 具体目标2将确定形成皮质脊髓束的上运动神经元是否也表现出谷氨酸受体表达的模式，这解释了它们的选择性脆弱性，无论是AMPA受体还是NMDA受体主要介导这些细胞中的损伤。

DESCRIPTION (provided by applicant): In amyotrophic lateral sclerosis (ALS), a fatal progressive neurodegenerative disorder, motor neurons selectively die, for reasons that are incompletely understood. This remarkable selective vulnerability provides an important clue to the mechanism of this devastating disease. Evidence suggests that ALS involves glutamate excitotoxicity mediated by AMPA receptors, and our work has begun to elucidate the basis for the selectivity for motor neurons of this mechanism. We showed that vulnerability to excitotoxicity of cultured spinal motor neurons correlates not with their expression of AMPA receptors having a particularly high permeability to Ca2+ or a particularly weak degree of desensitization, but rather with expression of AMPA receptors at a very high surface density. This property, expression of a high density of functional AMPA receptors, appears to be sufficient to explain the in vitro selective vulnerability of spinal motor neurons. More generally, the hypothesis serving as a theme of the entire project is that motor neuron selective vulnerability in ALS may be largely explained by the unique features of their glutamate receptor expression. The present proposal will extend the work of the initial funding period to address three important issues relating to this hypothesis. Specific aim 1 will define the physiological and molecular characteristics of AMPA receptors expressed by mature motor neurons in the tissue environment of the spinal cord, using patch-clamp and molecular techniques applied to motor neurons in acute spinal cord slices from mature rats. Specific aim 2 will determine whether upper motor neurons, which form the corticospinal tract, also exhibit a pattern of glutamate receptor expression that explains their selective vulnerability, whether it be AMPA receptors or NMDA receptors that primarily mediate injury in these cells.