Hirano Arlene A, Brandstätter Johann H, Brecha Nicholas C
Department of Neurobiology & Medicine, Geffen School of Medicine at University of California at Los Angeles, 90095, USA.
J Comp Neurol. 2005 Jul 18;488(1):70-81. doi: 10.1002/cne.20577.
The mechanism underlying transmitter release from retinal horizontal cells is poorly understood. We investigated the possibility of vesicular transmitter release from mammalian horizontal cells by examining the expression of synaptic proteins that participate in vesicular transmitter release at chemical synapses. Using immunocytochemistry, we evaluated the cellular and subcellular distribution of complexin I/II, syntaxin-1, and synapsin I in rabbit retina. Strong labeling for complexin I/II, proteins that regulate a late step in vesicular transmitter release, was found in both synaptic layers of the retina, and in somata of A- and B-type horizontal cells, of gamma-aminobutyric acid (GABA)- and glycinergic amacrine cells, and of ganglion cells. Immunoelectron microscopy demonstrated the presence of complexin I/II in horizontal cell processes postsynaptic to rod and cone ribbon synapses. Syntaxin-1, a core protein of the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) complex known to bind to complexin, and synapsin I, a synaptic vesicle-associated protein involved in the Ca(2+)-dependent recruitment of synaptic vesicles for transmitter release, were also present in the horizontal cells and their processes at photoreceptor synapses. Photoreceptors and bipolar cells did not express any of these proteins at their axon terminals. The presence of complexin I/II, syntaxin-1, and synapsin I in rabbit horizontal cell processes and tips suggests that a vesicular mechanism may underlie transmitter release from mammalian horizontal cells.
视网膜水平细胞释放神经递质的潜在机制目前还知之甚少。我们通过检测参与化学突触中囊泡性神经递质释放的突触蛋白的表达，来研究哺乳动物水平细胞中囊泡性神经递质释放的可能性。利用免疫细胞化学技术，我们评估了复合蛋白I/II、 syntaxin-1和突触素I在兔视网膜中的细胞和亚细胞分布。在视网膜的两个突触层、A 型和 B 型水平细胞的胞体、γ-氨基丁酸（GABA）能和甘氨酸能无长突细胞以及神经节细胞中，发现了对复合蛋白I/II的强标记，复合蛋白I/II是调节囊泡性神经递质释放后期步骤的蛋白质。免疫电子显微镜显示，在与视杆和视锥带状突触形成突触后的水平细胞突起中存在复合蛋白I/II。Syntaxin-1是可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）复合体的核心蛋白，已知其可与复合蛋白结合，突触素I是一种与突触小泡相关的蛋白，参与Ca(2+)依赖性募集突触小泡以释放神经递质，它们也存在于水平细胞及其在光感受器突触处的突起中。光感受器和双极细胞在其轴突终末不表达这些蛋白中的任何一种。兔水平细胞突起和末梢中存在复合蛋白I/II、 syntaxin-1和突触素I，这表明囊泡机制可能是哺乳动物水平细胞释放神经递质的基础。
