Beyer E C, Davis L M, Saffitz J E, Veenstra R D
Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Braz J Med Biol Res. 1995 Apr;28(4):415-25.
Gap junctions contain channels which allow the exchange of ions and small molecules between adjacent cells. In the heart, these channels are crucial for normal intercellular current flow and the propagation of action potentials throughout the myocardium. Molecular cloning studies have demonstrated that these channels are formed by members of a family of related proteins called connexins each containing conserved and unique regions. There are several consequences of this multiplicity of connexins. Multiple connexins are expressed in differing, but sometimes overlapping, distributions within cardiovascular and other tissues. Connexin40, connexin43, and connexin45 are all found in cardiac myocytes, but their abundance differs in specialized cardiac regions with disparate conductive properties. Individual connexins form channels with differing voltage-dependence, conductance, and permeability properties, as demonstrated by functional expression of the cloned sequences. Connexins differ in their modification by phosphorylation, which may contribute to physiological regulation of intercellular communication. Expression of multiple connexins may lead to the formation of multiple channel types in a single tissue or cell and potentially allows mixing to form heterotypic and/or heteromeric channels. Thus, multiple connexins may contribute to the differences in intercellular resistance in cardiac regions with differing conductive properties and possibly may allow differences in the signalling molecules that pass between cells.
间隙连接包含允许离子和小分子在相邻细胞之间交换的通道。在心脏中，这些通道对于正常的细胞间电流流动以及动作电位在整个心肌中的传播至关重要。分子克隆研究表明，这些通道由一类相关蛋白质家族的成员形成，称为连接蛋白，每个连接蛋白都包含保守和独特的区域。连接蛋白的这种多样性有几个后果。多种连接蛋白在心血管和其他组织中以不同但有时重叠的分布表达。连接蛋白40、连接蛋白43和连接蛋白45都存在于心肌细胞中，但它们在具有不同传导特性的特殊心脏区域中的丰度不同。如克隆序列的功能表达所示，单个连接蛋白形成具有不同电压依赖性、电导和通透性特性的通道。连接蛋白在磷酸化修饰方面存在差异，这可能有助于细胞间通讯的生理调节。多种连接蛋白的表达可能导致在单个组织或细胞中形成多种通道类型，并可能允许混合形成异型和/或异聚体通道。因此，多种连接蛋白可能导致具有不同传导特性的心脏区域中细胞间电阻的差异，并且可能允许在细胞之间传递的信号分子存在差异。
