AMPA Receptor Expression and Selective Neuronal Death

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS），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。证据表明ALS涉及AMPA受体介导的谷氨酸兴奋性毒性，我们的工作已经开始阐明这一机制对运动神经元选择性的基础。我们发现，培养的脊髓运动神经元对兴奋性毒性的易感性与AMPA受体对Ca2具有特别高的渗透性或特别弱的脱敏程度无关，而是与AMPA受体在非常高的表面密度下的表达有关。这种特性，高密度功能性AMPA受体的表达，似乎足以解释脊髓运动神经元的体外选择性易感性。更一般地说，作为整个项目主题的假设是，ALS中的运动神经元选择性易感性可能在很大程度上可以通过其谷氨酸受体表达的独特特征来解释。

DESCRIPTION (provided by applicant): 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 examine whether disease-related acquired alterations in AMPA receptor expression might affect vulnerability to excitotoxicity. In particular, the effects of chronic exposure to sub-lethal concentrations of NO on the editing of mRNA for G1uR2 will be examined. Specific aim 3 will determine whether upper motor neurons, which form the corticospinal tract, also exhibit a pattern of AMPA receptor expression that explains their selective vulnerability. These experiments will help to define a very clear mechanism for motor neuron degeneration in ALS putting molecular targets for therapy into sharp focus.