UNIQUE CONDUCTANCE, GATING, AND SELECTIVE PERMEABILITY PROPERTIES OF GAP JUNCTION CHANNELS FORMED BY CONNEXIN40
UNIQUE CONDUCTANCE, GATING, AND SELECTIVE PERMEABILITY PROPERTIES OF GAP JUNCTION CHANNELS FORMED BY CONNEXIN40
复制标题
DOI：
10.1161/01.res.77.4.813
复制
发表时间：
1995-10-01
影响因子：
20.1
通讯作者：
VEENSTRA, RD
中科院分区：
文献类型：
--
作者：
BEBLO, DA;WANG, HZ;VEENSTRA, RD
Connexin40在特殊的心脏传导（结和His-Purkinje）组织和心房中选择性表达，但这种间隙连接蛋白形成的通道特性尚未被研究。采用双全细胞电压-阻尼技术研究了转染Cx40的小鼠神经母细胞瘤（N2A）细胞间大鼠连接蛋白40 （Cx40）缝隙连接通道的电导、门控和选择性通透性。宏观稳态结电导门控依赖于跨结电压，玻尔兹曼半失活电压为+/- 50 mV，剩余电压不敏感归一化结电导为最大值的35%，门控电荷价为3。在120 mmol/L谷氨酸钾存在下，大鼠Cx40缝隙连接通道的斜率电导为158 +/- 2 pS （n=4）。四对电池中的两对偶尔也观察到低电导状态，等于主开路电导的21%至48%。发现多通道打开概率是异构的。通过离子取代和染料转移实验，测定了阴离子荧光素衍生物在大鼠Cx40通道中的相对氯钾电导和染料渗透性。大鼠Cx40通道在120 mmol/L KCI下的最大电导为180 +/- 18 pS (n=3)，相对于钾，可检测到氯离子的通透性为0.29，表明阳离子比阴离子有一定的选择性。Ck40缝隙连接对2',7'-二氯荧光素（diCl-F）和极性更高的b -羧基荧光素染料具有渗透性；然而，diCl-F染料转移并没有随着结电导的增加而增加。
Connexin40 is selectively expressed in specialized cardiac conduction (nodal and His-Purkinje) tissues and the atrium, yet the channel properties formed by this gap junction protein have not been investigated. The conductance, gating, and selective permeability of rat connexin40 (Cx40) gap junction channels between pairs of Cx40-transfected mouse neuroblastoma (N2A) cells in culture were studied by using dual whole-cell voltage-damp techniques. The macroscopic steady state junctional conductance gating was dependent on transjunctional voltage with a Boltzmann half-inactivation voltage of +/- 50 mV, a residual voltage-insensitive normalized junctional conductance of 35% of maximum, and a gating charge valence of 3. In the presence of 120 mmol/L potassium glutamate, the slope conductance of single rat Cx40 gap junction channels measured 158 +/- 2 pS (n=4). Lower conductance states equal to 21% to 48% of the main open-state conductance were also occasionally observed in two of the four cell pairs. Multichannel open probabilities were found to be heterogeneous. Ion substitution and dye transfer experiments were performed to determine the relative chloride/potassium conductance and dye permeability of anionic fluorescein derivatives in rat Cx40 channels. The rat Cx40 channel had a maximum conductance of 180 +/- 18 pS (n=3) in 120 mmol/L KCI and a detectable chloride permeability of 0.29 relative to potassium, indicating some selectivity for cations over anions. Ck40 gap junctions were permeable to 2',7'-dichlorofluorescein (diCl-F) and also to the more polar B-carboxyfluorescein dye; however, diCl-F dye transfer was not observed to increase with increasing junctional conductance.