Connexin 43: a new player in Duchenne muscular dystrophy associated cardiomyopathy

总结 杜氏肌营养不良症（DMD）是一种进行性肌肉疾病，严重的心脏并发症。 扩张性心肌病是一种严重的疾病，在18岁以上的DMD患者中100%明显。超过 40%的DMD患者死于心力衰竭。然而，营养不良的研究 心肌病仍然相当有限。罪魁祸首-肌营养不良蛋白的丢失-是一种肌膜下蛋白， 保护骨骼肌和心肌免受机械性损伤，并调节许多 下游细胞通路。虽然最近的策略，以恢复抗肌萎缩蛋白水平保持希望，医疗 科学界也在寻找肌营养不良蛋白下游的替代治疗靶点。我们 发现关键证据表明连接蛋白43（Cx43）在DMD心肌病中的有害作用。我们展示 在mdx和mdx：utrophin敲除小鼠的心脏中，以及在 DMD患者的心脏我们还表明，选择性药理学抑制Cx43功能或遗传 Cx43的减少导致应激mdx小鼠中心律失常的挽救和过早死亡的预防， 以及防止长期心肌病的发展。我们确定mdx中的Cx43是 在丝氨酸残基的特定三联体中低磷酸化（S325/328/330）。磷酸化的减少， 相同的三联体在各种心脏病理中促进Cx43重塑，导致不期望的开放。 Cx43半通道，药物敏感性和不可逆的长期后果。我们认为 DMD中Cx43的心脏重塑有助于细胞Ca 2+超载和氧化应激，导致 心律失常、纤维化，并因此导致心力衰竭的发展。我们相信磷酸三重态 S325/328/330是Cx43重构的驱动力。在本提案中，我们将首先确定 Cx43突变体的表达可保护mdx小鼠在功能性和功能性心脏病中免于发展心脏病理学， 组织学水平（Aim 1）以及细胞水平（Aim 2）。为了解决这个问题，将Cx43敲入小鼠 与mdx小鼠杂交，以掺入携带谷氨酸而不是丝氨酸的Cx43磷酸突变 在磷酸三联体中，从而模拟永久磷酸化。在目标3中，我们将研究分子 负责营养不良心脏中Cx43半通道增强开放的机制。我们尤其 会检查过量的活性氧是否会打开半通道严格设盲的功能、组织学和 将进行生化分析。

SUMMARY Duchenne muscular dystrophy (DMD) is a progressive muscle disease with severe cardiac complications. Dilated cardiomyopathy is a serious condition apparent in 100% of DMD patients over 18 years of age. Over 40% (and increasing) of DMD patients are dying from heart failure. However, studies of dystrophic cardiomyopathy remain quite limited. The culprit – loss of dystrophin – is a subsarcolemmal protein that protects skeletal and cardiac muscle from mechanically induced damage and regulates a number of downstream cellular pathways. While recent strategies to restore dystrophin levels keep hopes up, the medical and scientific communities are also seeking alternative therapeutic targets downstream of dystrophin. We found key evidence suggesting a detrimental role for connexin-43 (Cx43) in DMD-cardiomyopathy. We showed that Cx43 is upregulated and remodeled in the heart of mdxand mdx:utrophin knockout mice, as well as in the heart of DMD patients. We also showed that selective pharmacological inhibition of Cx43 function or genetic reduction of Cx43 leads to a rescue of arrhythmias and prevention of premature death in stressed mdx mice, as well as protection from the development of long-term cardiomyopathy. We determined that Cx43 in mdx is hypophosphorylated in a specific triplet of serine residues (S325/328/330). Reduction of phosphorylation in this same triplet promotes Cx43 remodeling in a variety of cardiac pathologies, leading to undesired opening of Cx43 hemichannels, arrhythmic susceptibility and irreversible long-term consequences. We believe that cardiac remodeling of Cx43 in DMD contributes to cellular Ca2+ overload and oxidative stress, leading to arrhythmias, fibrosis and consequently, to the development of heart failure. We believe that the phospho-triplet S325/328/330 is the driving force for Cx43 remodeling. In this proposal we will first determine whether expression of a mutant form of Cx43 protects mdx mice from developing cardiac pathology on functional and histological (Aim 1) as well as on cellular (Aim 2) levels. To address this question, Cx43 knockin mice will be crossed with mdx mice, to incorporate the Cx43 phospho-mutation harboring glutamic acids instead of serines in the phospho-triplet thus mimicking permanent phosphorylation. In Aim 3 we will investigate molecular mechanisms responsible for enhanced opening of Cx43 hemichannels in dystrophic hearts. In particular, we will examine if excessive ROS opens the hemichannels. Rigorous blinded functional, histological and biochemical analysis will be conducted.