Fishman G I, Spray D C, Leinwand L A
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461.
J Cell Biol. 1990 Aug;111(2):589-98. doi: 10.1083/jcb.111.2.589.
Gap junctions permit the passage of ions and chemical mediators from cell to cell. To identify the molecular genetic basis for this coupling in the human heart, we have isolated clones from a human fetal cardiac cDNA library which encode the full-length human cardiac gap junction (HCGJ) mRNA. The predicted amino acid sequence is homologous to the rat cardiac gap junction protein, connexin43 (Beyer, E. D., D. Paul, and D. A. Goodenough. 1987. J. Cell Biol. 105:2621-2629), differing by 9 of 382 amino acids. HCGJ mRNA is detected as early as fetal week 15 and persists in adult human cardiac samples. Genomic DNA analysis suggests the presence of two highly homologous HCGJ loci, only one of which is functional. Stable transfection of the HCGJ cDNA into SKHep1 cells, a human hepatoma line which is communication deficient, leads to the formation of functional channels. Junctional conductance in pairs of transfectants containing 10 copies of the HCGJ sequence is high (approximately 20 nS). Single channel currents are detectable in this expression system and correspond to conductances of approximately 60 pS. These first measurements of the HCGJ channel are similar to the junctional conductance recorded between pairs of rat or guinea pig cardiocytes.
缝隙连接允许离子和化学介质在细胞间通过。为了确定人类心脏中这种偶联的分子遗传学基础，我们从人胎儿心脏cDNA文库中分离出了编码全长人心脏缝隙连接（HCGJ）mRNA的克隆。预测的氨基酸序列与大鼠心脏缝隙连接蛋白连接蛋白43同源（Beyer, E. D., D. Paul, and D. A. Goodenough. 1987. J. Cell Biol. 105:2621 - 2629），在382个氨基酸中有9个不同。HCGJ mRNA早在胎儿第15周就可检测到，并在成人心脏样本中持续存在。基因组DNA分析表明存在两个高度同源的HCGJ基因座，其中只有一个是有功能的。将HCGJ cDNA稳定转染到SKHep1细胞（一种缺乏细胞间通讯的人肝癌细胞系）中，会导致功能性通道的形成。含有10个拷贝HCGJ序列的转染细胞对之间的连接电导很高（约20 nS）。在这个表达系统中可检测到单通道电流，其电导约为60 pS。这些对HCGJ通道的首次测量结果与在大鼠或豚鼠心肌细胞对之间记录的连接电导相似。
