MOLECULAR STUDIES OF GAP JUNCTION REMODELING

研究表明，缝隙连接细胞间通讯的失调，或缝隙连接重构，是导致室性心律失常的基础。利用犬脑梗塞模型，本项目的研究表明，缝隙连接结构位置的改变和缝隙连接的电生理特性的变化与折返回路中的阻断功能线有关。在人类缺血性心肌病以及我们对患有室性心动过速和心脏性猝死的转基因小鼠的研究中，也观察到了类似的缝隙连接重构。然而，肌病心脏表现出大量的结构和功能扰动，因此，很难独立于其他促成因素来研究这种独特的心律失常。这项研究的目的是了解缝隙连接重塑的分子机制，并确定异常的细胞间偶联对心律失常底物形成的具体贡献。因此，申请人已经开始阐明控制缝隙连接表达和重塑的机制，并发现Wnt信号级联通过双重转录和翻译后机制通过β-catenin发挥作用，是控制缝隙连接蛋白43表达的重要调控途径。此外，他们还准备了几种条件基因靶向的小鼠模型，以阐明重塑在致心律失常底物形成中的作用。他们的目标是利用基因靶向和嵌合小鼠，在连接重塑、传导异常和心律失常发生方面进行研究；2)确定β-连环素介导的信号在正常和重塑心肌细胞和心脏中Cx43表达的调节中的作用及其与其他信号通路的关系；3)确定缝隙连接折返性兴奋的负责机制似乎与缝隙连接分布的变化有关。阐明缝隙连接重构的调控机制及其在致心律失常底物中的作用，对于寻找致死性心律失常的新的药物治疗方法具有重要意义。

Description (Adapted from Applicant's Abstract) Several lines of investigation suggest that dysregulation of gap junction intercellular communication, or gap junctional remodeling, contributes to the substrate for ventricular arrhythmias. Using the canine infarct model, investigations in this Program have shown that changes in the structural location of gap junctions and the electrophysiological properties of gap junctions are associated with functional lines of block in reentrant circuits. Similar gap junctional remodeling has also been observed in human ischemic cardiomyopathy and in our studies of genetically modified mice with ventricular tachycardia and sudden cardiac death. Myopathic hearts, however, show a multitude of structural and functional perturbations, thus, the unique arrhythmias has been difficult to study in isolation from other contributory factors. The goal of the studies described in this proposal is to understand the molecular mechanisms of gap junctional remodeling and to determine the specific contribution of dysregulated intercellular coupling to the formation of the arrhythmogenic substrate. The applicant has, therefore, begun to elucidate mechanisms controlling gap junctional expression and remodeling and discovered that the Wnt signaling cascade, acting through beta-catenin via duel transcriptional and post-translational mechanisms, is an important regulatory pathway controlling connexin43 expression. Furthermore, they have prepared several conditions gene-targeted murine models to elucidate the role of remodeling in formation of the arrhythmogenic substrate. Their goals in junctional remodeling, conduction abnormalities and arrhythmogenesis, using gene-targeted and chimeric mice; 2) to determine the role of beta-catenin mediated signaling and its relationship with other signaling pathways in the regulation of Cx43 expression in normal and remodeled cardiomyocytes and hearts; 3) to determine the mechanisms responsible for gap junctional reentrant excitation appears to be related to changes in gap junction distribution. Elucidation of the mechanisms regulating gap junctional remodeling and its role in the arrhythmogenic substrate have significant implications for novel pharmacotherapy of lethal cardiac arrhythmias.