Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum
Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum
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DOI：
10.1016/j.neulet.2011.10.032
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发表时间：
2012-01
影响因子：
2.5
通讯作者：
Tina Unger;Stefanie Bette;Jiong Zhang;M. Theis;J. Engele
中科院分区：
文献类型：
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作者：
Tina Unger;Stefanie Bette;Jiong Zhang;M. Theis;J. Engele
胶质谷氨酸转运蛋白亚型GLT-1/EAAT-2和GLAST/EAAT-1清除大部分细胞外谷氨酸，并在各种急性和慢性脑疾病中严重失调。尽管之前已经发现了几种调节神经胶质谷氨酸转运蛋白表达的细胞外因子，但我们对控制神经胶质谷氨酸转运在健康和疾病中的调节网络的了解仍然不完整。在培养皮层星形胶质细胞的研究中，我们先前获得的证据表明，胶质谷氨酸转运蛋白的表达也受到间隙连接/连接蛋白的影响。为了评估间隙连接是否同样会控制神经胶质谷氨酸转运蛋白的体内表达，我们现在评估了它们在条件Cx43敲除小鼠大脑中的表达水平，Cx30总敲除，以及Cx43/Cx30双敲除。我们发现，无论是敲除Cx30、Cx43，还是两者都敲除，大脑皮层中GLT-1/EAAT-2蛋白水平的增加程度相似。相比之下，在Cx30/Cx43双敲除的大脑皮层中，GLAST/EAAT-1蛋白水平最高，这表明间隙连接对GLT-1/EAAT-2和GLAST/EAAT-1的表达有不同的影响。定量PCR分析进一步揭示了神经胶质谷氨酸转运蛋白表达的增加是由转录和翻译/翻译后过程引起的。此外，与Cx43fl/fl对照相比，Cx43/Cx30双敲除的海马中GLT-1/EAAT-2和GLAST/EAAT-1蛋白水平保持不变，表明间隙连接对胶质谷氨酸运输的脑区域特异性作用。由于星形细胞间隙连接偶联在各种形式的脑损伤中受到影响，我们的研究结果表明，间隙连接/连接蛋白是患病大脑皮层胶质谷氨酸转换的重要调节因子。
The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex.