Gao Feng, Li Fang, Miao Yanying, Dong Ling-Dan, Zhang Sheng-Hai, Wu Jihong, Sun Xing-Huai, Wang Zhongfeng
Department of Ophthalmology at Eye and ENT hospital, Fudan University, Shanghai 200031, China; Institutes of Brain Science, Fudan University, Shanghai 200031, China; State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200031, China; Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University, Shanghai 200031, China.
Institutes of Brain Science, Fudan University, Shanghai 200031, China; Institute of Neurobiology, Fudan University, Shanghai 200031, China; State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200031, China.
Neurosci Lett. 2015 Feb 19;588:12-7. doi: 10.1016/j.neulet.2014.12.048. Epub 2014 Dec 27.
Müller cell gliosis is a general response in a variety of pathological alternations of the retina, which is characterized by the upregulated expression of glial fibrillary acidic protein (GFAP) and the downregulation of membrane K(+) conductance. We have demonstrated that downregulation of Kir K(+) currents in Müller cells in an experimental glaucoma model is due to activation of group I metabotropic glutamate receptor (mGluR I) by glutamate, which contributes to Müller cell gliosis. Here, whether and how activation of mGluR I modulate membrane Kir4.1 protein internalization and Kir4.1 mRNA expression were investigated in purified cultured rat retinal Müller cells using immunocytochemistry, Western blot and real-time PCR techniques. DHPG (10μM, a selective mGluR I agonist) treatment induced Müller cell gliosis, as evidenced by enhanced GFAP expression. Although total Kir4.1 proteins extracted from the DHPG-treated cells kept unchanged, Kir4.1 proteins in the cell membrane compartment were significantly decreased, which was prior to the change of GFAP in time course. In addition, DHPG (10 and 100μM) treatment induced a transient decrease in Kir4.1 mRNA expression in the cells. All these results suggest that activation of mGluR I by DHPG may decrease the number of functional Kir4.1 channels in purified cultured rat retinal Müller cells through modulating Kir4.1 protein and mRNA, thus contributing to Müller cell gliosis.
穆勒细胞胶质增生是视网膜多种病理改变中的一种普遍反应，其特征是胶质纤维酸性蛋白（GFAP）表达上调以及膜钾离子电导下调。我们已经证明，在实验性青光眼模型中，穆勒细胞中内向整流钾电流（Kir）的下调是由于谷氨酸激活了I组代谢型谷氨酸受体（mGluR I），这促进了穆勒细胞胶质增生。在此，我们使用免疫细胞化学、蛋白质免疫印迹和实时聚合酶链反应技术，在纯化培养的大鼠视网膜穆勒细胞中研究了mGluR I的激活是否以及如何调节膜Kir4.1蛋白的内化和Kir4.1信使核糖核酸（mRNA）的表达。二氢吡啶（DHPG，10微摩尔，一种选择性mGluR I激动剂）处理诱导了穆勒细胞胶质增生，GFAP表达增强证明了这一点。虽然从经DHPG处理的细胞中提取的总Kir4.1蛋白保持不变，但细胞膜区室中的Kir4.1蛋白显著减少，这在时间进程上先于GFAP的变化。此外，DHPG（10和100微摩尔）处理诱导细胞中Kir4.1 mRNA表达短暂下降。所有这些结果表明，DHPG激活mGluR I可能通过调节Kir4.1蛋白和mRNA来减少纯化培养的大鼠视网膜穆勒细胞中功能性Kir4.1通道的数量，从而促进穆勒细胞胶质增生。
