Syntrophin-dependent expression and localization of Aquaporin-4 water channel protein
Syntrophin-dependent expression and localization of Aquaporin-4 water channel protein
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DOI：
10.1073/pnas.241508198
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发表时间：
2001-11-20
影响因子：
11.1
通讯作者：
Adams, ME
中科院分区：
文献类型：
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作者：
Neely, JD;Amiry-Moghaddam, M;Adams, ME
水通道蛋白-4（AQP 4）水通道有助于血管周围星形胶质细胞终足中的脑水稳态，在那里它是集中的。我们推测，AQP 4是通过AQP 4 C末端与突触营养蛋白（肌营养不良蛋白复合物的一种组分）的PSD 95-Discs large-ZO 1（PDZ）结构域结合而被拴系在该位点。脑的化学交联和免疫共沉淀证实AQP 4与复合物相关，包括肌营养不良蛋白、β-肌营养不良蛋白聚糖和突触营养蛋白。在缺乏α-突触营养蛋白（α-Syn（-/-））的小鼠的脑和骨骼肌中研究了AQP 4的表达。在α-Syn（-/-）小鼠脑中，AQP 4表达的总水平似乎正常，但极化的亚细胞定位被逆转。高分辨率免疫金分析显示，a-Syn（-/-）小鼠小脑和大脑皮层中邻近血管的星形胶质细胞终足膜中AQP 4表达显著降低，但面对神经元的膜中AQP 4表达水平高于正常水平。相比之下，a-Syn（-/-）小鼠的骨骼肌中几乎不存在AQP 4。在AQP 4 C末端的PDZ结合共有序列（Ser-Ser-瓦尔）的缺失类似地降低了转染细胞系中的表达，并且脉冲追踪标记证明了增加的降解速率。这些结果表明，AQP 4在脑中的血管周围定位需要α-Syn，并且AQP 4在膜中的稳定性通过C-末端PDZ结合基序增加。
The Aquaporin-4 (AQP4) water channel contributes to brain water homeostasis in perivascular astrocyte endfeet where it is concentrated. We postulated that AQP4 is tethered at this site by binding of the AQP4 C terminus to the PSD95-Discs large-ZO1 (PDZ) domain of syntrophin, a component of the dystrophin protein complex. Chemical cross-linking and coimmunoprecipitations from brain demonstrated AQP4 in association with the complex, including dystrophin, beta -dystroglycan, and syntrophin. AQP4 expression was studied in brain and skeletal muscle of mice lacking alpha -syntrophin (alpha -Syn(-/-)). The total level of AQP4 expression appears normal in brains of alpha -Syn(-/-) mice, but the polarized subcellular localization is reversed. High-resolution immunogold analyses revealed that AQP4 expression is markedly reduced in astrocyte endfeet membranes adjacent to blood vessels in cerebellum and cerebral cortex of alpha -Syn(-/-) mice, but is present at higher than normal levels in membranes facing neuropil. In contrast, AQP4 is virtually absent from skeletal muscle in alpha -Syn(-/-) mice. Deletion of the PDZ-binding consensus (Ser-Ser-Val) at the AQP4 C terminus similarly reduced expression in transfected cell lines, and pulse-chase labeling demonstrated an increased degradation rate. These results demonstrate that perivascular localization of AQP4 in brain requires alpha -Syn, and stability of AQP4 in the membrane is increased by the C-terminal PDZ-binding motif.