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首页> 外文期刊>Cell and Tissue Research >Agrin defines polarized distribution of orthogonal arrays of particles in astrocytes
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Agrin defines polarized distribution of orthogonal arrays of particles in astrocytes

机译：Agrin定义星形胶质细胞中颗粒正交阵列的极化分布

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Accumulating evidence indicates that agrin, a heparan sulphate proteoglycan of the extracellular matrix, plays a role in the organization and maintenance of the blood-brain barrier. This evidence is based on the differential effects of agrin isoforms on the expression and distribution of the water channel protein, aquaporin-4 (AQP4), on the swelling capacity of cultured astrocytes of neonatal mice and on freeze-fracture data revealing an agrin-dependent clustering of orthogonal arrays of particles (OAPs), the structural equivalent of AQP4. Here, we show that the OAP density in agrin-null mice is dramatically decreased in comparison with wild-types, by using quantitative freeze-fracture analysis of astrocytic membranes. In contrast, anti-AQP4 immunohistochemistry has revealed that the immunoreactivity of the superficial astrocytic endfeet of the agrin-null mouse is comparable with that in wild-type mice. Moreover, in vitro, wild-type and agrin-null astrocytes cultured from mouse embryos at embryonic day 19.5 differ neither in AQP4 immunoreactivity, nor in OAP density in freeze-fracture replicas. Analyses of brain tissue samples and cultured astrocytes by reverse transcription with the polymerase chain reaction have not demonstrated any difference in the level of AQP4 mRNA between wild-type astrocytes and astrocytes from agrin-null mice. Furthermore, we have been unable to detect any difference in the swelling capacity between wild-type and agrin-null astrocytes. These results clearly demonstrate, for the first time, that agrin plays a pivotal role for the clustering of OAPs in the endfoot membranes of astrocytes, whereas the mere presence of AQP4 is not sufficient for OAP clustering.
机译：越来越多的证据表明，凝集素是一种细胞外基质的硫酸乙酰肝素蛋白聚糖，在血脑屏障的组织和维持中发挥着作用。该证据是基于凝集素同工型对水通道蛋白aquaporin-4（AQP4）的表达和分布，新生小鼠培养的星形胶质细胞的溶胀能力以及冻裂数据显示的依赖于凝集素的差异性影响。粒子正交阵列（OAP）的聚类，其结构等同于AQP4。在这里，我们表明，通过使用星形细胞膜的定量冷冻断裂分析，与野生型相比，无凝集素的小鼠的OAP密度显着降低。相比之下，抗AQP4免疫组织化学表明，凝集素无效小鼠的表层星形细胞末端的免疫反应性与野生型小鼠相当。此外，在胚胎第19.5天从小鼠胚胎培养的体外，野生型和无凝集素的星形胶质细胞在AQP4免疫反应性和冷冻断裂复制物中的OAP密度方面均无差异。用聚合酶链反应通过逆转录对脑组织样品和培养的星形胶质细胞进行分析，结果表明野生型星形胶质细胞和无凝集素的小鼠星形胶质细胞之间的AQP4 mRNA水平没有任何差异。此外，我们还没有发现野生型和无凝集素的星形胶质细胞之间的溶胀能力的任何差异。这些结果首次清楚地表明，凝集素对于星形胶质细胞的足底膜中OAP的聚集起着关键作用，而仅AQP4的存在不足以实现OAP的聚集。

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