Lash J A, Critser E S, Pressler M L
Krannert Institute of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis 46202.
J Biol Chem. 1990 Aug 5;265(22):13113-7.
Gap junctional proteins (connexins) form aqueous channels that enable direct cell-cell transfer of ions and small molecules. The distribution and conductance of gap junction channels in cardiac muscle determine the pattern and synchrony of cellular activation. However, the capacity for smooth muscle to restrict contractile events temporally and spatially suggests that cell-cell coupling or its regulation may be decidedly different in this tissue. We isolated a cDNA from vascular smooth muscle which encodes a connexin (Mr 43,187) structurally homologous to cardiac connexin43. Vascular smooth muscle connexin43 mRNA was expressed prominently in smooth muscle tissues, cultured vascular myocytes, and arterial endothelial cells. A model for functional expression of connexins was developed in two-cell B6D2 mouse embryos. Microinjection of in vitro transcribed vascular smooth muscle connexin43 mRNA was shown to be sufficient to induce intercellular coupling in previously uncoupled blastomeres. Through the construction of two deletion mutants of connexin43, we also show that the formation of cell-to-cell connections does not depend upon a predicted cytoplasmic region within 98 residues of the carboxyl terminus. Finally, the identification of connexin43 in smooth muscle and endothelial cells provides supporting evidence for the existence of heterocellular coupling between cells of the vascular intima.
间隙连接蛋白（连接蛋白）形成水性通道，使离子和小分子能够在细胞间直接转移。心肌中间隙连接通道的分布和电导决定了细胞激活的模式和同步性。然而，平滑肌在时间和空间上限制收缩事件的能力表明，这种组织中的细胞间偶联或其调节可能明显不同。我们从血管平滑肌中分离出一种互补DNA（cDNA），它编码一种与心肌连接蛋白43结构同源的连接蛋白（分子量43,187）。血管平滑肌连接蛋白43信使核糖核酸（mRNA）在平滑肌组织、培养的血管平滑肌细胞和动脉内皮细胞中显著表达。在双细胞B6D2小鼠胚胎中建立了连接蛋白功能表达模型。体外转录的血管平滑肌连接蛋白43 mRNA显微注射显示足以在先前未偶联的卵裂球中诱导细胞间偶联。通过构建连接蛋白43的两个缺失突变体，我们还表明细胞间连接的形成不依赖于羧基末端98个残基内预测的细胞质区域。最后，在平滑肌和内皮细胞中鉴定出连接蛋白43，为血管内膜细胞间存在异细胞偶联提供了支持证据。
