Gap junctions formed by connexins 26 and 32 alone and in combination are differently affected by applied voltage.

作者：Luis Carlos Barrio, T Suchyna, Thaddeus A. Bargiello, L X Xu, R S Roginski, M V Bennett, B J Nicholson · 发表于：Proceedings of the National Academy of Sciences · 年份：1991 · DOI：10.1073/pnas.88.19.8410 · 被引用次数：341 · 研究领域：Connexins and lens biology、Ion channel regulation and function、Nicotinic Acetylcholine Receptors Study

Gap junctions are formed by a family of homologous proteins termed connexins. Their channels are dodecamers, and homomeric forms differ in their properties with respect to control by voltage and other gating stimuli. We report here the properties of coupling from expression of connexin complementary RNAs (cRNAs; sense to mRNA, antisense to cDNA) in Xenopus oocyte pairs in which endogenous coupling was blocked by injection of DNA oligonucleotides antisense to the mRNA of Cx38, the principal endogenous connexin. We found that a connexin recently sequenced from rat liver, Cx26, formed functional gap junctions whose conductance exhibited voltage dependence with unusual characteristics suggestive of two gating mechanisms. Junctional conductance (gj) was increased to a small degree by depolarization and decreased by hyperpolarization of either cell in a coupled pair, indicating dependence on the potential between the inside and outside of the cells (Vi-o). These changes were fast compared with the resolution of their measurement (ca. 10 ms). On a slower timescale, large transjunctional potentials (Vj) of either sign caused a more substantial decrease in conductance similar to that previously reported for several other gap junctions. Homotypic junctions formed of another connexin, Cx32, exhibited a similar slow dependence on Vj but no dependence on Vi-o. In contrast, heterotypic junctions between an oocyte expressing Cx26 and one expressing Cx32 were electrically asymmetric; they ex...