Cottrell G Trevor, Wu Yan, Burt Janis M
Department of Physiology, Arizona Health Sciences Center, University of Arizona, Tucson, Arizona 85724, USA.
Am J Physiol Cell Physiol. 2002 Jun;282(6):C1469-82. doi: 10.1152/ajpcell.00484.2001.
In cells that coexpress connexin (Cx)40 and Cx43, the ratio of expression can vary depending on the cellular environment. We examined the effect of changing Cx40:Cx43 expression ratio on functional gap junction properties. Rin cells transfected with Cx40 or Cx43 (Rin40, Rin43) were cocultured with 6B5n, A7r5, A7r540C1, or A7r540C3 cells for electrophysiological and dye coupling analysis. Cx40:Cx43 expression ratio in 6B5n, A7r5, A7r540C1, and A7r540C3 cells was ~1:1, 3:1, 5:1, and 10:1, respectively. When Rin43 cells were paired with coexpressing cells, there was an increasing asymmetry of voltage-dependent gating and a shift toward smaller conductance events as Cx40:Cx43 ratio increased in the coexpressing cell. These observations could not be predicted by linear combinations of Cx40 and Cx43 properties in proportion to the expressed ratios of the two Cxs. When Rin40 cells were paired with coexpressing cells, the net voltage gating and single-channel conductance behavior were similar to those of Rin40/Rin40 cell pairs. Dye permeability properties of cell monolayers demonstrated that as Cx40:Cx43 expression ratio increased in coexpressing cells the charge and size selectivity of dye transfer reflected that of Rin40 cells, as would be predicted. These data indicate that the electrophysiological properties of heteromeric/heterotypic channels are not directly related to the proportions of Cx constituents expressed in the cell; however, the dye permeability of these same channels can be predicted by the relative Cx contributions.
在共表达连接蛋白（Cx）40和Cx43的细胞中，表达比例会因细胞环境而异。我们研究了改变Cx40:Cx43表达比例对功能性缝隙连接特性的影响。将转染了Cx40或Cx43的Rin细胞（Rin40、Rin43）与6B5n、A7r5、A7r540C1或A7r540C3细胞共培养，用于电生理和染料偶联分析。6B5n、A7r5、A7r540C1和A7r540C3细胞中的Cx40:Cx43表达比例分别约为1:1、3:1、5:1和10:1。当Rin43细胞与共表达细胞配对时，随着共表达细胞中Cx40:Cx43比例增加，电压依赖性门控的不对称性增加，且向更小电导事件偏移。这些观察结果无法通过按照两种连接蛋白的表达比例对Cx40和Cx43特性进行线性组合来预测。当Rin40细胞与共表达细胞配对时，净电压门控和单通道电导行为与Rin40/Rin40细胞对相似。细胞单层的染料通透性特性表明，正如预期的那样，随着共表达细胞中Cx40:Cx43表达比例增加，染料转移的电荷和大小选择性反映了Rin40细胞的情况。这些数据表明，异聚体/异型通道的电生理特性与细胞中表达的连接蛋白成分比例没有直接关系；然而，这些相同通道的染料通透性可以通过连接蛋白的相对贡献来预测。
