MOLECULAR STUDIES OF GAP JUNCTION REMODELING

几项研究表明，间隙连接细胞间通讯的失调或间隙连接重构是室性心律失常的基础。利用犬梗死模型，本项目的研究表明，缝隙连接的结构位置和缝隙连接的电生理特性的变化与可重入回路的功能阻滞线有关。在人类缺血性心肌病和我们对室性心动过速和心源性猝死的转基因小鼠的研究中也观察到类似的间隙连接重构。然而，肌病心脏表现出大量的结构和功能紊乱，因此，这种独特的心律失常很难与其他因素分离开来进行研究。本研究的目的是了解间隙连接重塑的分子机制，并确定细胞间偶联失调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β -catenin双重转录和翻译后机制起作用，是控制connexin43表达的重要调控途径。此外，他们还制备了几种条件基因靶向小鼠模型来阐明重塑在心律失常底物形成中的作用。他们的目标在连接重塑，传导异常和心律失常，使用基因靶向和嵌合小鼠；2)确定β -连环蛋白介导的信号通路及其与其他信号通路在正常和重构心肌细胞及心脏中Cx43表达调控中的作用；3)确定缝隙结重入激励的机制似乎与缝隙结分布的变化有关。阐明缝隙连接重构的调节机制及其在致心律失常底物中的作用，对致命性心律失常的新药物治疗具有重要意义。

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.