MOLECULAR ANALYSIS OF VOLTAGE DEPENDENCE OF HETEROTYPIC GAP-JUNCTIONS FORMED BY CONNEXINS 26 AND 32
MOLECULAR ANALYSIS OF VOLTAGE DEPENDENCE OF HETEROTYPIC GAP-JUNCTIONS FORMED BY CONNEXINS 26 AND 32
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DOI：
10.1016/s0006-3495(92)81804-0
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发表时间：
1992-04-01
影响因子：
3.4
通讯作者：
BARGIELLO, TA
中科院分区：
文献类型：
--
作者：
RUBIN, JB;VERSELIS, VK;BARGIELLO, TA
通过将表达由Cx 32形成的半通道的非洲爪蟾卵母细胞与表达由Cx 26形成的半通道的非洲爪蟾卵母细胞配对形成的异型间隙连接显示了新的跨接电压（V（j））依赖性，这不是由这些连接蛋白在同型构型中的行为预测的。观察到初始和稳态电流的整流。连接处Cx 26侧的相对阳性和阴性分别导致初始电导（g（j 0））增加和降低。只有Cx 26的相对阳性降低稳态电导（g（j-无穷大））。这种行为表明半通道之间的相互作用影响间隙连接门控。通过将Cx 32和Cx 26与嵌合连接蛋白配对来检查第一胞外环（E1）在这些相互作用中的作用，其中Cx 32 E1被Cx 26 E1替换（Cx 32 * 26 E1）。两个连接都以g（j 0）/V（j）关系进行整流，其陡度低于Cx 32/Cx 26。在Cx 32/Cx 32 * 26 E1连接处，任一极性V（j）的g（j-无穷大）均降低。Cx 26 E1中两个氨基酸的突变增加了g（j 0）/V（j）和g（j-infinity）/V（j）关系的陡度。这些数据表明，快速整流可以由失配的E1域引起，并且E1可能有助于快速和慢速V（j）依赖过程的电压感测机制。
Heterotypic gap junctions formed by pairing Xenopus oocytes expressing hemichannels formed of Cx32 with those expressing hemichannels formed of Cx26 displayed novel transjunctional voltage (V(j)) dependence not predicted by the behavior of these connexins in homotypic configurations. Rectification of initial and steady-state currents was observed. Relative positivity and negativity on the Cx26 side of the junction resulted in increased and decreased initial conductance (g(j0)), respectively. Only relative positivity on the Cx26 decreased steady-state conductance (g(j-infinity)). This behavior suggested that interactions between hemichannels influences gap junction gating. The role of the first extracellular loop (E1) in these interactions was examined by pairing Cx32 and Cx26 with a chimeric connexin in which Cx32 E1 was replaced with Cx26 E1 (Cx32*26E1). Both junctions rectified with g(j0)/V(j) relations that were less steep than that observed for Cx32/Cx26. Decreases in g(j-infinity) occurred for either polarity V(j) in the Cx32/Cx32*26E1 junction. Mutation of two amino acids in Cx26 E1 increased the steepness of both the g(j0)/V(j) and g(j-infinity)/V(j) relations. These data demonstrate that fast rectification can arise from mismatched E1 domains and that E1 may contribute to the voltage sensing mechanisms underlying both fast and slow V(j)-dependent processes.