Almad Akshata A, Doreswamy Arpitha, Gross Sarah K, Richard Jean-Philippe, Huo Yuqing, Haughey Norman, Maragakis Nicholas J
Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland.
Glia. 2016 Jul;64(7):1154-69. doi: 10.1002/glia.22989. Epub 2016 Apr 16.
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motor neurons in the CNS. Astrocytes play a critical role in disease progression of ALS. Astrocytes are interconnected through a family of gap junction proteins known as connexins (Cx). Cx43 is a major astrocyte connexin conducting crucial homeostatic functions in the CNS. Under pathological conditions, connexin expression and functions are altered. Here we report that an abnormal increase in Cx43 expression serves as one of the mechanisms for astrocyte-mediated toxicity in ALS. We observed a progressive increase in Cx43 expression in the SOD1(G93A) mouse model of ALS during the disease course. Notably, this increase in Cx43 was also detected in the motor cortex and spinal cord of ALS patients. Astrocytes isolated from SOD1(G93A) mice as well as human induced pluripotent stem cell (iPSC)-derived astrocytes showed an increase in Cx43 protein, which was found to be an endogenous phenomenon independent of neuronal co-culture. Increased Cx43 expression led to important functional consequences when tested in SOD1(G93A) astrocytes when compared to control astrocytes over-expressing wild-type SOD1 (SOD1(WT) ). We observed SOD1(G93A) astrocytes exhibited enhanced gap junction coupling, increased hemichannel-mediated activity, and elevated intracellular calcium levels. Finally, we tested the impact of increased expression of Cx43 on MN survival and observed that use of both a pan Cx43 blocker and Cx43 hemichannel blocker conferred neuroprotection to MNs cultured with SOD1(G93A) astrocytes. These novel findings show a previously unrecognized role of Cx43 in ALS-related motor neuron loss. GLIA 2016;64:1154-1169.
肌萎缩侧索硬化症（ALS）是一种神经退行性疾病，其特征是中枢神经系统（CNS）中的运动神经元逐渐丧失。星形胶质细胞在ALS的疾病进展中起关键作用。星形胶质细胞通过称为连接蛋白（Cx）的间隙连接蛋白家族相互连接。Cx43是一种主要的星形胶质细胞连接蛋白，在中枢神经系统中执行关键的稳态功能。在病理条件下，连接蛋白的表达和功能会发生改变。在此，我们报告Cx43表达的异常增加是ALS中星形胶质细胞介导的毒性机制之一。我们观察到在ALS的SOD1（G93A）小鼠模型的病程中，Cx43表达逐渐增加。值得注意的是，在ALS患者的运动皮层和脊髓中也检测到了Cx43的这种增加。从SOD1（G93A）小鼠以及人诱导多能干细胞（iPSC）衍生的星形胶质细胞中分离出的星形胶质细胞显示Cx43蛋白增加，这被发现是一种独立于神经元共培养的内源性现象。与过表达野生型SOD1（SOD1（WT））的对照星形胶质细胞相比，在SOD1（G93A）星形胶质细胞中测试时，Cx43表达增加导致了重要的功能后果。我们观察到SOD1（G93A）星形胶质细胞表现出增强的间隙连接耦合、增加的半通道介导的活性以及升高的细胞内钙水平。最后，我们测试了Cx43表达增加对运动神经元存活的影响，并观察到使用泛Cx43阻滞剂和Cx43半通道阻滞剂均能为与SOD（G93A）星形胶质细胞共培养的运动神经元提供神经保护。这些新发现表明Cx43在ALS相关的运动神经元丧失中具有先前未被认识到的作用。《胶质细胞》2016年；64:1154 - 1169。
