Hofer A, Dermietzel R
Institute of Anatomy, Technical University, Dresden, Germany.
Glia. 1998 Sep;24(1):141-54. doi: 10.1002/(sici)1098-1136(199809)24:1<141::aid-glia13>3.0.co;2-r.
Astrocytes constitute a metabolically and electrically coupled syncytium which is essential for the regulation of ionic homeostasis of the interstitial brain fluid and for coordinating responses to neuronal activities. The structural avenues that couple individual astrocytes are provided by gap junctions which consist of transmembraneous channels that bridge the extracellular space. Each gap junction channel is composed of two hemichannels (connexons) that dock to each other via their extracellular loops. Here we report on the characterization of external loop antibodies that visualize hemichannels in specific plasma membranes of vital astrocytes. Hemichannels were found to be concentrated on cytoplasmic processes and filopodia of subconfluent cells. Specificity of hemichannel-binding was evaluated by blockage of Lucifer Yellow (LY) dye-transfer and Ca2+ transmission, as well as LY uptake under calcium-deficient conditions. Our data indicate that hemichannels are accessible from the extracytoplasmic side either for direct visualization or functional manipulation. The availability of such a probe will allow in vivo experiments which require selective and/or temporal blocking of gap junctions in animal models.
星形胶质细胞构成了一个代谢和电耦合的合体细胞，这对于调节脑间质液的离子稳态以及协调对神经元活动的反应至关重要。连接单个星形胶质细胞的结构通道由缝隙连接提供，缝隙连接由跨膜通道组成，这些通道跨越细胞外空间。每个缝隙连接通道由两个半通道（连接子）组成，它们通过细胞外环相互对接。在这里，我们报告了外部环抗体的特性，这些抗体可在活的星形胶质细胞的特定质膜中可视化半通道。发现半通道集中在亚汇合细胞的细胞质突起和丝状伪足上。通过阻断荧光黄（LY）染料转移和Ca2+传递以及在缺钙条件下的LY摄取来评估半通道结合的特异性。我们的数据表明，半通道可从细胞质外侧进入，用于直接可视化或功能操作。这种探针的可用性将允许在动物模型中进行需要选择性和/或暂时阻断缝隙连接的体内实验。
