Gramsch B, Gabriel H D, Wiemann M, Grümmer R, Winterhager E, Bingmann D, Schirrmacher K
Department of Physiology, University of Essen, Essen, D-45122, Germany.
Exp Cell Res. 2001 Apr 1;264(2):397-407. doi: 10.1006/excr.2000.5145.
Bone cells form a functional syncytium as they are coupled by gap junctions composed mainly of connexin 43 (Cx43). To further understand the role of Cx43 in bone cell growth and differentiation, we stably transfected Cx45-expressing UMR 106-01 cells with Cx43 using an expression vector containing rat Cx43 cDNA. Three stably transfected clones were analyzed, all of which showed altered expression of Cx43 and/or Cx45 as was obvious from immunocytochemistry and Northern blotting. Double whole-cell patch clamping revealed single-channel conductances of 20 (Cx45) and 60 pS (Cx43). The overexpression of Cx43 led to an increase in dye coupling concomitant with elevated gap-junctional conductance. The phenotype of the transfected clones was characterized by an increased proliferation (4- to 7-fold) compared to controls. Moreover, a transfectant clone with 10- to 12-fold enhanced Cx43 expression showed a significantly increased calcium content of the extracellular matrix and enlarged mineralization nodules, while alkaline phosphatase was moderately increased. We conclude that enhanced gap-junctional coupling via Cx43 significantly promotes proliferation and differentiation of UMR cells.
骨细胞通过主要由连接蛋白43（Cx43）组成的缝隙连接相互连接，形成一个功能合胞体。为了进一步了解Cx43在骨细胞生长和分化中的作用，我们使用含有大鼠Cx43 cDNA的表达载体，将表达Cx45的UMR 106-01细胞稳定转染Cx43。对三个稳定转染的克隆进行了分析，从免疫细胞化学和Northern印迹法可以明显看出，所有克隆的Cx43和/或Cx45表达均发生了改变。双细胞全细胞膜片钳记录显示，Cx45的单通道电导为20 pS，Cx43为60 pS。Cx43的过表达导致染料偶联增加，同时缝隙连接电导升高。与对照相比，转染克隆的表型特征为增殖增加（4至7倍）。此外，一个Cx43表达增强10至12倍的转染克隆显示，细胞外基质中的钙含量显著增加，矿化结节增大，而碱性磷酸酶略有增加。我们得出结论，通过Cx43增强的缝隙连接偶联显著促进了UMR细胞的增殖和分化。
