Rothstein J D, Van Kammen M, Levey A I, Martin L J, Kuncl R W
Department of Neurology, Johns Hopkins University, Baltimore, MD, USA.
Ann Neurol. 1995 Jul;38(1):73-84. doi: 10.1002/ana.410380114.
The pathogenesis of sporadic amyotrophic lateral sclerosis (ALS) is unknown, but defects in synaptosomal high-affinity glutamate transport have been observed. In experimental models, chronic loss of glutamate transport can produce a loss of motor neurons and, therefore, could contribute to the disease. With the recent cloning of three glutamate transporters, i.e., EAAC1, GLT-1, and GLAST, it has become possible to determine if the loss of glutamate transport in ALS is subtype specific. We developed C-terminal, antioligopeptide antibodies that were specific for each glutamate transporter. EAAC1 is selective for neurons, while GLT-1 and GLAST are selective for astroglia. Tissue from various brain regions of ALS patients and controls were examined by immunoblot or immunocytochemical methods for each transporter subtype. All tissue was matched for age and postmortem delay. GLT-1 immunoreactive protein was severely decreased in ALS, both in motor cortex (71% decrease compared with control) and in spinal cord. In approximately a quarter of the ALS motor cortex specimens, the loss of GLT-1 protein (90% decrease from control) was dramatic. By contrast, there was only a modest loss (20% decrease from control) of immunoreactive protein EAAC1 in ALS motor cortex, and there was no appreciable change in GLAST. The minor loss of EAAC1 could be secondary to loss of cortical motor neurons. As a comparison, glial fibrillary acidic protein, which is selectively localized to astroglia, was not changed in ALS motor cortex. Because there is no loss of astroglia in ALS, the dramatic abnormalities in GLT-1 could reflect a primary defect in GLT-1 protein, a secondary loss due to down regulation, or other toxic processes.
散发性肌萎缩侧索硬化症（ALS）的发病机制尚不清楚，但已观察到突触体高亲和力谷氨酸转运存在缺陷。在实验模型中，谷氨酸转运的长期丧失可导致运动神经元丧失，因此可能与该疾病有关。随着最近三种谷氨酸转运体即EAAC1、GLT-1和GLAST的克隆成功，确定ALS中谷氨酸转运丧失是否具有亚型特异性成为可能。我们开发了对每种谷氨酸转运体具有特异性的C末端抗寡肽抗体。EAAC1对神经元具有选择性，而GLT-1和GLAST对星形胶质细胞具有选择性。通过免疫印迹或免疫细胞化学方法对ALS患者和对照的不同脑区组织进行每种转运体亚型的检测。所有组织在年龄和死后延迟方面进行匹配。在ALS患者中，运动皮层（与对照相比减少71%）和脊髓中的GLT-1免疫反应性蛋白均严重减少。在大约四分之一的ALS运动皮层标本中，GLT-1蛋白的丧失（比对照减少90%）非常显著。相比之下，ALS运动皮层中免疫反应性蛋白EAAC1仅有适度丧失（比对照减少20%），而GLAST没有明显变化。EAAC1的轻微丧失可能继发于皮层运动神经元的丧失。作为比较，选择性定位于星形胶质细胞的胶质纤维酸性蛋白在ALS运动皮层中没有变化。由于ALS中星形胶质细胞没有丧失，GLT-1的显著异常可能反映GLT-1蛋白的原发性缺陷、下调导致的继发性丧失或其他毒性过程。
