Effects of agrin on the expression and distribution of the water channel protein aquaporin-4 and volume regulation in cultured astrocytes
Effects of agrin on the expression and distribution of the water channel protein aquaporin-4 and volume regulation in cultured astrocytes
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DOI：
10.1111/j.1460-9568.2007.05850.x
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发表时间：
2007-10-01
影响因子：
3.4
通讯作者：
Wolburg, Hartwig
中科院分区：
文献类型：
--
作者：
Noell, Susan;Fallier-Becker, Petra;Wolburg, Hartwig
Agrin是一种细胞外基质的硫酸肝素蛋白多糖，以组织神经肌肉连接处的突触后分化而闻名。越来越多的证据也表明，agrin在中枢神经系统发育中的作用，包括血脑屏障的形成和维持。本研究描述了agin对新生小鼠水通道蛋白水通道蛋白4 （AQP4）的表达和分布以及培养的星形胶质细胞肿胀能力的影响。星形胶质细胞在含有聚dl -鸟氨酸的底物上培养，抗aqp4免疫反应性均匀且弥漫性分布。然而，如果星形胶质细胞在agin条件培养基中培养，我们观察到aqp4特异性膜相关染色的强度增加。冷冻断裂研究显示，当外源agrin存在于星形胶质细胞培养中时，出现正交颗粒阵列的聚类，代表AQP4的结构等效。神经元和非神经元的agrin亚型（分别为agrin A0B0和agrin A4B8）能够诱导膜相关的AQP4染色。神经蛋白A4B8培养的星形胶质细胞的水输送能力和膜内颗粒正交排列密度增加，而内皮和脑膜a4b0培养的星形胶质细胞则没有增加。RT-PCR结果显示，agin A4B8增加了AQP4 M23剪接变体的表达水平，降低了AQP4 M1剪接变体的表达水平。对血脑屏障包括病理条件下水肿形成的调节和维持的意义进行了讨论。
Agrin is a heparan sulfate proteoglycan of the extracellular matrix and is known for organizing the postsynaptic differentiation of the neuromuscular junction. Increasing evidence also suggests roles for agrin in the developing CNS, including the formation and maintenance of the blood-brain barrier. Here we describe effects of agrin on the expression and distribution of the water channel protein aquaporin-4 (AQP4) and on the swelling capacity of cultured astrocytes of newborn mice. If astrocytes were cultured on a substrate containing poly DL-ornithine, anti-AQP4 immunoreactivity was evenly and diffusely distributed. If, however, astrocytes were cultured in the presence of agrin-conditioned medium, we observed an increase in the intensity of AQP4-specific membrane-associated staining. Freeze-fracture studies revealed a clustering of orthogonal arrays of particles, representing a structural equivalent of AQP4, when exogenous agrin was present in the astrocyte cultures. Neuronal and non-neuronal agrin isoforms (agrin A0B0 and agrin A4B8, respectively) were able to induce membrane-associated AQP4 staining. Water transport capacity as well as the density of orthogonal arrays of intramembranous particles was increased in astrocytes cultured with the neuronal agrin isoform A4B8, but not with the endothelial and meningeal isoform A0B0. RT-PCR demonstrated that agrin A4B8 increased the level of the M23 splice variant of AQP4 and decreased the level of the M1 splice variant of AQP4. Implications for the regulation and maintenance of the blood-brain barrier including oedema formation under pathological conditions are discussed.