PDF(Pubmed)
Abstract：
Skeletal muscle actin (ACTA1) mutations are a prevalent cause of skeletal myopathies consistent with ACTA1\'s high expression in skeletal muscle. Rare de novo mutations in ACTA1 associated with combined cardiac and skeletal myopathies have been reported, but ACTA1 represents only ~20% of the total actin pool in cardiomyocytes, making its role in cardiomyopathy controversial. Here we demonstrate how a mutation in an actin isoform expressed at low levels in cardiomyocytes can cause cardiomyopathy by focusing on a unique ACTA1 mutation, R256H. We previously identified this mutation in multiple family members with dilated cardiomyopathy (DCM), who had reduced systolic function without clinical skeletal myopathy. Using a battery of multiscale biophysical tools, we show that R256H has potent functional effects on ACTA1 function at the molecular scale and in human cardiomyocytes. Importantly, we demonstrate that R256H acts in a dominant manner, where the incorporation of small amounts of mutant protein into thin filaments is sufficient to disrupt molecular contractility, and that this effect is dependent on the presence of troponin and tropomyosin. To understand the structural basis of this change in regulation, we resolved a structure of R256H filaments using Cryo-EM, and we see alterations in actin\'s structure that have the potential to disrupt interactions with tropomyosin. Finally, we show that ACTA1R256H/+ human induced pluripotent stem cell cardiomyocytes demonstrate reduced contractility and sarcomeric disorganization. Taken together, we demonstrate that R256H has multiple effects on ACTA1 function that are sufficient to cause reduced contractility and establish a likely causative relationship between ACTA1 R256H and clinical cardiomyopathy.
摘要：
骨骼肌肌动蛋白（ACTA1）突变是骨骼肌病的普遍原因，与ACTA1在骨骼肌中的高表达一致。已经报道了与合并的心脏和骨骼肌病相关的ACTA1中罕见的从头突变，但ACTA1只占心肌细胞总肌动蛋白池的20%，使其在心肌病中的作用引起争议。在这里，我们展示了在心肌细胞中低水平表达的肌动蛋白亚型的突变如何通过关注独特的ACTA1突变来引起心肌病。R256H.我们先前在患有扩张型心肌病（DCM）的多个家族成员中发现了这种突变，收缩功能降低，没有临床骨骼肌病。使用一系列多尺度生物物理工具，我们显示R256H在分子尺度和人心肌细胞中对ACTA1功能具有有效的功能作用。重要的是,我们证明了R256H以占主导地位的方式起作用，在细丝中掺入少量的突变蛋白足以破坏分子的收缩性，这种作用取决于肌钙蛋白和原肌球蛋白的存在。为了理解这种监管变化的结构基础，我们使用Cryo-EM解析了R256H细丝的结构，我们看到肌动蛋白结构的改变有可能破坏与原肌球蛋白的相互作用。最后,我们显示ACTA1R256H/+人诱导多能干细胞心肌细胞表现出收缩性降低和肌节解体。一起来看,我们证明R256H对ACTA1功能有多种作用,足以导致收缩力降低,并在ACTA1R256H与临床心肌病之间建立了可能的因果关系.
■众所周知，骨骼肌肌动蛋白突变会导致骨骼肌病，但是它们在心肌病中的作用一直存在争议，因为骨骼肌肌动蛋白在心脏中仅以适度的水平表达。这里,我们证明了骨骼肌肌动蛋白突变在原子和分子尺度上强烈导致肌动蛋白功能的多种缺陷，它以占主导地位的方式运作，导致心肌细胞收缩缺陷。我们的结果确定了骨骼肌肌动蛋白突变如何导致心肌细胞功能障碍，并为未来研究骨骼肌肌动蛋白在心肌病中的作用奠定了基础。
■众所周知，骨骼肌肌动蛋白突变会导致骨骼肌病，但是它们在心肌病中的作用一直存在争议，因为骨骼肌肌动蛋白在心脏中仅以适度的水平表达。这里,我们证明了骨骼肌肌动蛋白突变在原子和分子尺度上强烈导致肌动蛋白功能的多种缺陷，它以占主导地位的方式运作，导致心肌细胞收缩缺陷。我们的结果确定了骨骼肌肌动蛋白突变如何导致心肌细胞功能障碍，并为未来研究骨骼肌肌动蛋白在心肌病中的作用奠定了基础。
