Department of Veterinary Anatomy, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan.
Basic Res Cardiol. 2011 Nov;106(6):1057-68. doi: 10.1007/s00395-011-0219-3. Epub 2011 Sep 3.
Eph receptors and ephrin ligands are membrane-bound cell-cell communication molecules with important roles not only in development but also in the physiology of many adult organs. However, their cellular localization and functions in the myocardium are virtually unknown and therefore, we have investigated the expression of EphB receptors and ephrin-B ligands in the rodent heart ventricles and their functions in the rodent cardiomyocytes of primary culture. Examinations by RT-PCR, immunohistochemistry and in situ hybridization revealed that the EphB receptors are preferentially expressed in cardiomyocytes and ephrin-B ligands in the vasculature in adult mouse heart ventricles. Interestingly, we found that inducing high levels of EphB receptor activation in primary cultures of rodent cardiomyocytes by stimulation with ephrin-B1-Fc desynchronized the contraction of adjacent clusters of cardiomyocytes that had contracted synchronously before the treatment. Co-immunoprecipitation experiments revealed that EphB4 physically associates with connexin43, a major component of gap junctions in the myocardium, and that EphB activation inhibits gap junctional intracellular communication between cardiomyocytes. The present findings suggest that ephrin-B-EphB signaling can modulate the electrical coupling of cardiomyocytes through effects on gap junctions.
Eph 受体和 Ephrin 配体是膜结合的细胞间通讯分子，它们不仅在发育过程中具有重要作用，而且在许多成年器官的生理学中也具有重要作用。然而，它们在心肌中的细胞定位和功能实际上是未知的，因此，我们研究了 EphB 受体和 Ephrin-B 配体在啮齿动物心室中的表达及其在原代培养的啮齿动物心肌细胞中的功能。通过 RT-PCR、免疫组织化学和原位杂交的检查表明，EphB 受体在成年小鼠心脏心室中的心肌细胞中优先表达，而 Ephrin-B 配体在血管中表达。有趣的是，我们发现，通过 Ephrin-B1-Fc 刺激诱导原代培养的啮齿动物心肌细胞中 EphB 受体的高水平激活，会使先前同步收缩的相邻心肌细胞簇的收缩失去同步。共免疫沉淀实验表明，EphB4 与间隙连接蛋白 43（心肌中间隙连接的主要成分）物理结合，而 EphB 激活抑制了心肌细胞之间的间隙连接细胞内通讯。本研究结果表明，Ephrin-B-EphB 信号可以通过对缝隙连接的作用来调节心肌细胞的电耦联。
