Sekirnjak C, Martone M E, Weiser M, Deerinck T, Bueno E, Rudy B, Ellisman M
Department of Neuroscience, University of California at San Diego, La Jolla 92092, USA.
Brain Res. 1997 Aug 22;766(1-2):173-87. doi: 10.1016/s0006-8993(97)00527-1.
Voltage-gated potassium channels constitute the largest group of heteromeric ion channels discovered to date. Over 20 genes have been isolated, encoding different channel subunit proteins which form functional tetrameric K+ channels. We have analyzed the subcellular localization of subunit Kv3.1b, a member of the Kv3 (Shaw-like) subfamily, in rat brain at the light and electron microscopic level, using immunocytochemical detection. Detailed localization was carried out in specific neurons of the neocortex, hippocampus and cerebellum. The identity of Kv3.1b-positive neurons was established using double labeling with markers for specific neuronal populations. In the neocortex, the Kv3.1b subunit was expressed in most parvalbumin-containing bipolar, basket or chandelier cells, and in some bipolar or double bouquet neurons containing calbindin. In the hippocampus, Kv3.1b was expressed in many parvalbumin-containing basket cells, as well as in calbindin-positive neurons in the stratum oriens, and in a small number of interneurons that did not stain for either parvalbumin or calbindin. Kv3.1b protein was not present in pyramidal cells in the neocortex and the hippocampus, but these cells were outlined by labeled presynaptic terminals from interneuron axons that surround the postsynaptic cell. In the cerebellar cortex, granule cells were the only population expressing the channel protein. Careful examination of individual granule cells revealed a non-uniform distribution of Kv3.1 staining on the somata: circular bands of labeling were present in the vicinity of the axon hillock. In cortical and hippocampal interneurons, as well as in cerebellar granule cells, the Kv3.1b subunit was present in somatic and unmyelinated axonal membranes and adjacent cytoplasm, as well as in the most proximal portion of dendritic processes, but not throughout most of the dendrite. Labeling was also seen in the terminals of labeled axons, but not at a higher concentration than in other parts of the axon. The distribution in the cells analyzed supports a role in action potential transmission by regulating action potential duration.
电压门控钾通道是迄今为止发现的最大的异源离子通道家族。已分离出20多个基因，它们编码不同的通道亚基蛋白，这些蛋白形成功能性的四聚体钾通道。我们运用免疫细胞化学检测方法，在大鼠脑的光镜和电镜水平上分析了Kv3（类Shaw）亚家族成员亚基Kv3.1b的亚细胞定位。在新皮层、海马体和小脑的特定神经元中进行了详细的定位。使用针对特定神经元群体的标记物进行双重标记，确定了Kv3.1b阳性神经元的身份。在新皮层中，Kv3.1b亚基在大多数含小白蛋白的双极细胞、篮状细胞或吊灯细胞中表达，也在一些含钙结合蛋白的双极细胞或双束神经元中表达。在海马体中，Kv3.1b在许多含小白蛋白的篮状细胞中表达，也在海马体原层中含钙结合蛋白的神经元以及少数既不表达小白蛋白也不表达钙结合蛋白的中间神经元中表达。新皮层和海马体的锥体细胞中不存在Kv3.1b蛋白，但这些细胞被围绕突触后细胞的中间神经元轴突的标记突触前终末勾勒出来。在小脑皮层中，颗粒细胞是唯一表达该通道蛋白的细胞群体。对单个颗粒细胞的仔细检查发现，Kv3.1染色在细胞体上分布不均匀：在轴丘附近存在环状标记带。在皮层和海马体的中间神经元以及小脑颗粒细胞中，Kv3.1b亚基存在于体细胞和无髓鞘轴突膜及相邻细胞质中，也存在于树突突起的最近端部分，但在树突的大部分区域不存在。在标记轴突的终末也可见标记，但浓度并不高于轴突的其他部位。在所分析的细胞中的分布支持其通过调节动作电位持续时间在动作电位传导中发挥作用。
