Prochnow N, Hoffmann S, Vroman R, Klooster J, Bunse S, Kamermans M, Dermietzel R, Zoidl G
Department of Neuroanatomy and Molecular Brain Research, Ruhr University, University Street 150, D-44780 Bochum, Germany.
Neuroscience. 2009 Sep 15;162(4):1039-54. doi: 10.1016/j.neuroscience.2009.04.064. Epub 2009 May 3.
In the retina, chemical and electrical synapses couple neurons into functional networks. New candidates encoding for electrical synapse proteins have recently emerged. In the present study, we determined the localization of the candidate protein pannexin1 (zfPanx1) in the zebrafish retina and studied the functional properties of zfPanx1 exogenously expressed in Neuroblastoma 2a (N2a) cells. zfPanx1 was identified on the surface of horizontal cell dendrites invaginating deeply into the cone pedicle near the glutamate release sites of the cones, providing in vivo evidence for hemichannel formation at that location. This strategic position of zfPanx1 in the photoreceptor synapse could potentially allow modulation of cone output. Using whole cell voltage clamp and excised patch recordings of transfected N2a cells, we demonstrated that zfPanx1 forms voltage-activated hemichannels with a large unitary conductance in vitro. These channels can open at physiological membrane potentials. Functional channels were not formed following mutation of a single amino acid within a conserved protein motif recently shown to be N-glycosylated in rodent Panx1. Together, these findings indicate that zfPanx1 displays properties similar to its mammalian homologues and can potentially play an important role in functions of the outer retina.
在视网膜中，化学突触和电突触将神经元连接成功能网络。最近出现了编码电突触蛋白的新候选蛋白。在本研究中，我们确定了候选蛋白泛素连接蛋白1（zfPanx1）在斑马鱼视网膜中的定位，并研究了在神经母细胞瘤2a（N2a）细胞中外源表达的zfPanx1的功能特性。zfPanx1在水平细胞树突表面被鉴定出来，这些树突深深侵入到靠近视锥细胞谷氨酸释放位点的视锥小足内，为该位置形成半通道提供了体内证据。zfPanx1在光感受器突触中的这一战略位置可能会对视锥细胞输出进行调节。通过对转染的N2a细胞进行全细胞电压钳制和膜片钳记录，我们证明zfPanx1在体外形成具有大单位电导的电压激活半通道。这些通道可以在生理膜电位下开放。在最近显示在啮齿动物Panx1中进行N-糖基化的保守蛋白基序内的单个氨基酸发生突变后，未形成功能性通道。总之，这些发现表明zfPanx1表现出与其哺乳动物同源物相似的特性，并且可能在外视网膜的功能中发挥重要作用。
