Biophysical properties of human β-cardiac myosin with converter mutations that cause hypertrophic cardiomyopathy.
Biophysical properties of human β-cardiac myosin with converter mutations that cause hypertrophic cardiomyopathy.
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DOI：
10.1126/sciadv.1601959
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发表时间：
2017-02
期刊：
影响因子：
13.6
通讯作者：
Spudich JA
中科院分区：
文献类型：
--
作者：
Kawana M;Sarkar SS;Sutton S;Ruppel KM;Spudich JA
转化器HCM突变只会导致肌球蛋白的生物物理学上的微小变化，这表明了一种可供选择的过度收缩机制。肥厚型心肌病(HCM)的发病率为1/500，是心律失常和心力衰竭的重要原因。在临床上，肥厚性心肌病的特点是引起过度收缩，治疗的目的是控制过度活跃的生理学。β-心肌肌球蛋白的突变约占肥厚性心肌病相关基因突变的40%，肌球蛋白的转换结构域是引起肥厚性心肌病突变的热点；然而，这些突变对肌球蛋白生物力学功能的潜在主要影响仍不清楚。我们假设这些突变会影响肌球蛋白的生物力学性质，例如增加肌球蛋白的内在力和/或占空比，从而增加肌节的整合力。使用重组人β-心肌肌球蛋白，我们表征了三个严重的hCM引起的转换域突变：R719W、R723G和G741R的分子效应。与我们的假设相反，R719W和R723G突变的肌球蛋白的内力比野生型降低，而G741R的内力没有变化。肌球蛋白R719W和R723G的肌动蛋白和调节细丝滑动速度快约15%，而G741R的速度没有变化。这三种突变蛋白的三磷酸腺苷酶活性和负荷依赖的速度变化曲线都与野生型非常相似。这些结果表明，携带这些转换结构域突变的人β-心肌肌球蛋白的净生物力学特性与野生型非常相似，甚至略有收缩不足，这促使我们考虑临床观察到的高收缩的另一种机制。未来的工作包括这些突变如何影响肌节内的蛋白质相互作用，从而增加参与力量产生的肌球蛋白头的可用性。
Converter HCM mutations cause only small changes in the biophysics of myosin, suggesting an alternative mechanism for hypercontractility. Hypertrophic cardiomyopathy (HCM) affects 1 in 500 individuals and is an important cause of arrhythmias and heart failure. Clinically, HCM is characterized as causing hypercontractility, and therapies are aimed toward controlling the hyperactive physiology. Mutations in the β-cardiac myosin comprise ~40% of genetic mutations associated with HCM, and the converter domain of myosin is a hotspot for HCM-causing mutations; however, the underlying primary effects of these mutations on myosin’s biomechanical function remain elusive. We hypothesize that these mutations affect the biomechanical properties of myosin, such as increasing its intrinsic force and/or its duty ratio and therefore the ensemble force of the sarcomere. Using recombinant human β-cardiac myosin, we characterize the molecular effects of three severe HCM-causing converter domain mutations: R719W, R723G, and G741R. Contrary to our hypothesis, the intrinsic forces of R719W and R723G mutant myosins are decreased compared to wild type and unchanged for G741R. Actin and regulated thin filament gliding velocities are ~15% faster for R719W and R723G myosins, whereas there is no change in velocity for G741R. Adenosine triphosphatase activities and the load-dependent velocity change profiles of all three mutant proteins are very similar to those of wild type. These results indicate that the net biomechanical properties of human β-cardiac myosin carrying these converter domain mutations are very similar to those of wild type or are even slightly hypocontractile, leading us to consider an alternative mechanism for the clinically observed hypercontractility. Future work includes how these mutations affect protein interactions within the sarcomere that increase the availability of myosin heads participating in force production.