Sassoè-Pognetto M, Kirsch J, Grünert U, Greferath U, Fritschy J M, Möhler H, Betz H, Wässle H
Max-Planck-Institut für Hirnforschung, Frankfurt, Germany.
J Comp Neurol. 1995 Jun 19;357(1):1-14. doi: 10.1002/cne.903570102.
Gephyrin is a protein that copurifies with the glycine receptor (GlyR) and is required for the clustering of GlyRs at postsynaptic sites. Previously, it was thought that antibody mAb 7a, directed against gephyrin, was a specific marker for GlyR. However, there is evidence that gephyrin can also be found at nonglycinergic synapses. Here, immunocytochemistry was applied to show this directly for the rat retina. Both gephyrin and different subunits of the gamma-aminobutyric acid (GABA)A receptor were localized to discrete puncta in the inner plexiform layer, and these puncta were shown by electron microscopy to represent synaptic sites. Double immunocytochemistry revealed that GABAA receptors and GlyRs are not colocalized. However, gephyrin and different subunits of GABAA receptors were found to occur at the same synapses. The amount of colocalization varied with the GABAA receptor subunit composition and was most extensive for the alpha 2 subunit, less for the alpha 3 subunit, and minimal for the alpha 1 subunit. The gephyrin present at GABAergic synapses of the retina might also be involved with clustering of receptors at the postsynaptic sites. Hence, localization of gephyrin can no longer be considered as a unique marker of glycinergic synapses.
桥连蛋白是一种与甘氨酸受体（GlyR）共纯化的蛋白质，是GlyR在突触后位点聚集所必需的。以前，人们认为针对桥连蛋白的单克隆抗体mAb 7a是GlyR的特异性标志物。然而，有证据表明桥连蛋白也可以在非甘氨酸能突触中发现。在此，应用免疫细胞化学方法直接在大鼠视网膜中证实了这一点。桥连蛋白和γ-氨基丁酸（GABA）A受体的不同亚基都定位于内网状层中的离散小点，并且通过电子显微镜显示这些小点代表突触位点。双重免疫细胞化学显示GABAA受体和GlyR并非共定位。然而，发现桥连蛋白和GABAA受体的不同亚基存在于相同的突触中。共定位的数量随GABAA受体亚基组成而变化，对于α2亚基最为广泛，对于α3亚基较少，对于α1亚基最少。视网膜GABA能突触处存在的桥连蛋白也可能与受体在突触后位点的聚集有关。因此，桥连蛋白的定位不能再被视为甘氨酸能突触的独特标志物。
