Department of Cell Biology and Molecular Medicine, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey.
Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Newark, New Jersey.
Am J Physiol Heart Circ Physiol. 2022 Nov 1;323(5):H983-H995. doi: 10.1152/ajpheart.00179.2022. Epub 2022 Oct 7.
Dilated cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD), an inherited degenerative disease of the cardiac and skeletal muscle caused by absence of the protein dystrophin. We showed one hallmark of DMD cardiomyopathy is the dysregulation of cardiac gap junction channel protein connexin-43 (Cx43). Proper Cx43 localization and function at the cardiac intercalated disc (ID) is regulated by post-translational phosphorylation of Cx43-carboxy-terminus residues S325/S328/S330 (pS-Cx43). Concurrently, Cx43 traffics along microtubules (MTs) for targeted delivery to the ID. In DMD hearts, absence of dystrophin results in a hyperdensified and disorganized MT cytoskeleton, yet the link with pS-Cx43 remains unaddressed. To gain insight into the relationship between MTs and pS-Cx43, DMD mice (mdx) and pS-Cx43-deficient (mdxS3A) mice were treated with an inhibitor of MT polymerization, colchicine (Colch). Colch treatment protected mdx, not mdxS3A mice, against Cx43 remodeling, improved MT directionality, and enhanced pS-Cx43/tubulin interaction. Likewise, severe arrhythmias were prevented in isoproterenol-stressed mdx, not mdxS3A mice. Furthermore, MT directionality was improved in pS-Cx43-mimicking mdx (mdxS3E). Mdxutr and mdxutrS3A mice, lacking one copy of dystrophin homolog utrophin, displayed enhanced cardiac fibrosis and reduced lifespan compared with mdxutrS3E; and Colch treatment corrected cardiac fibrosis in mdxutr but not mdxutrS3A. Collectively, the data suggest that improved MT directionality reduces Cx43 remodeling and that pS-Cx43 is necessary and sufficient to regulate MT organization, which plays crucial role in correcting cardiac dysfunction in DMD mice. Thus, identification of novel organizational mechanisms acting on pS-Cx43-MT will help develop novel cardioprotective therapies for DMD cardiomyopathy. We found that colchicine administration to Cx43-phospho-deficient dystrophic mice fails to protect against Cx43 remodeling. Conversely, Cx43-phospho-mimic dystrophic mice display a normalized MT network. We envision a bidirectional regulation whereby correction of the dystrophic MTs leads to correction of Cx43 remodeling, which in turn leads to further correction of the MTs. Our findings suggest a link between phospho-Cx43 and MTs that provides strong foundations for novel therapeutics in DMD cardiomyopathy.
扩张型心肌病是杜氏肌营养不良症（DMD）的主要死亡原因，DMD 是一种遗传性进行性肌肉疾病，由缺失蛋白 dystrophin 引起。我们发现 DMD 心肌病的一个标志是心脏缝隙连接通道蛋白连接蛋白 43（Cx43）的失调。Cx43 在心脏闰盘（ID）的正确定位和功能是由 Cx43 羧基末端残基 S325/S328/S330（pS-Cx43）的翻译后磷酸化调节的。同时，Cx43 沿着微管（MTs）运输，以靶向递送到 ID。在 DMD 心脏中，缺失 dystrophin 会导致 MT 细胞骨架过度密集和紊乱，但与 pS-Cx43 的联系仍未得到解决。为了深入了解 MTs 和 pS-Cx43 之间的关系，用 MT 聚合抑制剂秋水仙碱（Colch）处理 DMD 小鼠（mdx）和 pS-Cx43 缺陷（mdxS3A）小鼠。Colch 处理可保护 mdx，而不是 mdxS3A 小鼠，防止 Cx43 重塑，改善 MT 方向性，并增强 pS-Cx43/微管相互作用。同样，异丙肾上腺素应激的 mdx 小鼠而非 mdxS3A 小鼠可预防严重心律失常。此外，pS-Cx43 模拟 mdx（mdxS3E）可改善 MT 方向性。与 mdxutrS3E 相比，缺乏一个 dystrophin 同源物 utrophin 的 mdxutr 和 mdxutrS3A 小鼠表现出增强的心脏纤维化和寿命缩短；Colch 处理可纠正 mdxutr 中的心脏纤维化，但不能纠正 mdxutrS3A。总之，数据表明，改善 MT 方向性可减少 Cx43 重塑，而 pS-Cx43 是调节 MT 组织所必需的，这在纠正 DMD 小鼠心脏功能障碍方面起着至关重要的作用。因此，鉴定作用于 pS-Cx43-MT 的新型组织机制将有助于为 DMD 心肌病开发新的心脏保护疗法。我们发现，向 Cx43 磷酸缺陷型 DMD 小鼠给予秋水仙碱治疗不能防止 Cx43 重塑。相反，Cx43 磷酸模拟型 DMD 小鼠显示出正常的 MT 网络。我们设想一种双向调节，即纠正 DMD 的 MTs 导致 Cx43 重塑的纠正，而 Cx43 重塑的纠正又导致 MTs 的进一步纠正。我们的研究结果表明，磷酸化 Cx43 和 MTs 之间存在联系，为 DMD 心肌病的新型治疗方法提供了坚实的基础。
