Elfgang C, Eckert R, Lichtenberg-Fraté H, Butterweck A, Traub O, Klein R A, Hülser D F, Willecke K
Institut für Genetik, Abt. Molekulargenetik, Universität Bonn, Germany.
J Cell Biol. 1995 May;129(3):805-17. doi: 10.1083/jcb.129.3.805.
DNAs coding for seven murine connexins (Cx) (Cx26, Cx31, Cx32, Cx37, Cx40, Cx43, and Cx45) are functionally expressed in human HeLa cells that were deficient in gap junctional communication. We compare the permeabilities of gap junctions comprised of different connexins to iontophoretically injected tracer molecules. Our results show that Lucifer yellow can pass through all connexin channels analyzed. On the other hand, propidium iodide and ethidium bromide penetrate very poorly or not at all through Cx31 and Cx32 channels, respectively, but pass through channels of other connexins. 4,6 Diamidino-2-phenylindole (DAPI) dihydrochloride shows less transfer among Cx31 or Cx43 transfectants. Neurobiotin is weakly transferred among Cx31 transfectants. Total junctional conductance in Cx31 or Cx45 transfected cells is only about half as high as in other connexin transfectants analyzed and does not correlate exactly with any of the tracer permeabilities. Permeability through different connexin channels appears to be dependent on the molecular structure of each tracer, i.e. size, charge and possibly rigidity. This supports the hypothesis that different connexin channels show different permeabilities to second messenger molecules as well as metabolites and may fulfill in this way their specific role in growth control and differentiation of cell types. In addition, we have investigated the function of heterotypic gap junctions after co-cultivation of two different connexin transfectants, one of which had been prelabeled with fluorescent dextran beads. Analysis of Lucifer yellow transfer reveals that HeLa cells expressing Cx31 (beta-type connexin) do not communicate with any other connexin transfectant tested but only with themselves. Two other beta-type connexin transfectants, HeLa-Cx26 and -Cx32, do not transmit Lucifer yellow to any of the alpha-type connexins analyzed. Among alpha-type connexins, Cx40 does not communicate with Cx43. Thus, connexins differ in their ability to form functional heterotypic gap junctions among mammalian cells.
编码七种小鼠连接蛋白（Cx）（Cx26、Cx31、Cx32、Cx37、Cx40、Cx43和Cx45）的DNA在缺乏间隙连接通讯的人HeLa细胞中实现了功能表达。我们比较了由不同连接蛋白组成的间隙连接对离子电渗注入示踪分子的通透性。我们的结果表明，荧光黄可以穿过所有分析的连接蛋白通道。另一方面，碘化丙啶和溴化乙锭分别很难或根本不能穿过Cx31和Cx32通道，但能穿过其他连接蛋白的通道。4,6-二脒基-2-苯基吲哚（DAPI）二盐酸盐在Cx31或Cx43转染细胞中的转移较少。神经生物素在Cx31转染细胞中的转移较弱。Cx31或Cx45转染细胞中的总连接电导仅约为其他分析的连接蛋白转染细胞的一半，并且与任何示踪分子的通透性并不完全相关。通过不同连接蛋白通道的通透性似乎取决于每个示踪分子的分子结构，即大小、电荷以及可能的刚性。这支持了以下假设：不同的连接蛋白通道对第二信使分子以及代谢物具有不同的通透性，并可能以此方式在细胞类型的生长控制和分化中发挥其特定作用。此外，我们在共培养两种不同的连接蛋白转染细胞后研究了异型间隙连接的功能，其中一种已用荧光葡聚糖珠预标记。对荧光黄转移的分析表明，表达Cx31（β型连接蛋白）的HeLa细胞不与任何其他测试的连接蛋白转染细胞通讯，而只与自身通讯。另外两种β型连接蛋白转染细胞，HeLa-Cx26和-Cx32，不将荧光黄传递给任何分析的α型连接蛋白。在α型连接蛋白中，Cx40不与Cx43通讯。因此，连接蛋白在形成哺乳动物细胞间功能性异型间隙连接的能力上存在差异。
