Department of Neurobiology, University of Oldenburg, D-26111 Oldenburg, Germany.
J Comp Neurol. 2013 Apr 1;521(5):1119-35. doi: 10.1002/cne.23223.
Pannexin1 (Panx1) belongs to a class of vertebrate proteins that exhibits sequence homology to innexins, the invertebrate gap junction proteins, and which also shares topological similarities with vertebrate gap junction proteins, the connexins. Unlike gap junctional channels, Panx1 forms single-membrane channels, whose functional role in neuronal circuits is still unsettled. We therefore investigated the subcellular distribution of Panx1 in the mouse retina of wildtype and Panx1-null mice by reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and electron microscopy. Use of Panx1-deficient mice served as a model to assess the physiological role of Panx1 by electroretinographic recordings and also to ensure the specificity of the anti-Panx1 antibody labeling. Expression of Panx1 was found in type 3a OFF bipolar cells and in dendrites and axonal processes of horizontal cells. Panx1 was also found in horizontal cell dendrites representing the lateral elements of the triad synapse at cone and rod terminals. In vivo electroretinography of Panx1 knockout mice indicated an increased a- and b-wave compared to Panx1 wildtype mice under scotopic conditions. The effect on the b-wave was confirmed by in vitro electroretinograms from the inner retina. These results suggest that Panx1 channels serve as sinks for extracellular current flow making them possible candidates for the mediation of feedback from horizontal cells to photoreceptors.
Pannexin1 (Panx1) 属于脊椎动物蛋白的一类，与昆虫的间隙连接蛋白 innexin 具有序列同源性，并且与脊椎动物的间隙连接蛋白 connexin 具有拓扑相似性。与间隙连接通道不同，Panx1 形成单分子膜通道，其在神经元回路中的功能作用仍未确定。因此，我们通过逆转录聚合酶链反应 (RT-PCR)、免疫组织化学和电子显微镜检查，研究了野生型和 Panx1 缺失型小鼠视网膜中 Panx1 的亚细胞分布。使用 Panx1 缺失型小鼠作为模型，通过视网膜电图记录评估 Panx1 的生理作用，并确保抗 Panx1 抗体标记的特异性。在 3a OFF 双极细胞和水平细胞的树突和轴突中发现了 Panx1 的表达。Panx1 也存在于水平细胞树突中，代表锥体和杆状末端三突触的横向元件。Panx1 敲除小鼠的体内视网膜电图表明，在暗适应条件下，与 Panx1 野生型小鼠相比，a-和 b-波增加。来自视网膜内层的体外视网膜电图证实了 b-波的影响。这些结果表明，Panx1 通道充当细胞外电流的汇流，使它们成为水平细胞向光感受器反馈的可能候选者。
