Cardiac myosin binding protein-C phosphorylation accelerates β-cardiac myosin detachment rate in mouse myocardium
Cardiac myosin binding protein-C phosphorylation accelerates β-cardiac myosin detachment rate in mouse myocardium
复制标题
心肌肌球蛋白结合蛋白-C 磷酸化加速小鼠心肌中β-心肌肌球蛋白脱离率
DOI：
10.1152/ajpheart.00673.2020
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发表时间：
2021
影响因子：
4.8
通讯作者：
Palmer, Bradley M.
中科院分区：
文献类型：
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作者：
Tanner, Bertrand C.;Previs, Michael J.;Wang, Yuan;Robbins, Jeffrey;Palmer, Bradley M.
心肌肌球蛋白结合蛋白-C（cMyBP-C）是一种影响肌节硬度并通过其磷酸化调节心肌收缩-舒张的粗丝蛋白。已显示cMyBP-C的磷酸化和cMyBP-C的消融增加了完整肌节中肌动蛋白-肌球蛋白跨桥循环中MgADP的释放速率。cMyBP-C对Pi依赖性肌球蛋白动力学的影响尚未得到研究。我们研究了cMyBP-C及其磷酸化对来自缺乏cMyBP-C的非转基因和纯合转基因小鼠的携带β-心肌肌球蛋白同种型的去膜乳头肌条中肌球蛋白动力学的影响。我们使用快速拉伸和随机长度扰动分析来表征肌球蛋白脱离和力发展的速率超过0 - 12 mM Pi，并在最大（pCa 4.8）和接近一半的最大（pCa 5.75）Ca 2+激活。蛋白激酶A（PKA）处理应用于一半的条以探测cMyBP-C磷酸化对肌球蛋白动力学的Pi敏感性的影响。增加Pi增加肌球蛋白跨桥脱离率与无cMyBP-C的肌肉相似，尽管这些比率在无cMyBP-C的肌肉中更高。当cMyBP-C存在于所有Pi上时，用PKA处理心肌条加速了脱离率，但当cMyBP-C不存在时则没有。在所有肌肉中，力量发展的速率随着Pi的增加而增加。然而，当cMyBP-C存在与不存在时，速率力发展的Pi敏感性降低，表明cMyBP-C抑制动力冲程的Pi依赖性逆转或稳定跨桥连接以提高完成动力冲程的概率。这些结果支持cMyBP-C在减缓肌球蛋白脱离速率中的功能作用，可能是通过与肌球蛋白的直接相互作用或通过cMyBP-C依赖的粗肌丝和肌丝晶格的刚度改变应变依赖性肌球蛋白脱离。PKA治疗降低了cMyBP-C减缓肌球蛋白脱离的作用，从而有效地加速了β-肌球蛋白在完整肌丝晶格中的脱离。NEW & NOTEWORTHY长度扰动分析用于证明β-心肌肌球蛋白在完整肌丝晶格中的脱离和募集的特征速率被Pi、cMyBP-C的磷酸化和cMyBP-C的缺失加速。结果表明，cMyBP-C通常减缓肌球蛋白脱离，包括PI依赖性脱离，并且这种抑制在磷酸化或不存在cMyBP-C的情况下释放。
Cardiac myosin binding protein-C (cMyBP-C) is a thick filament protein that influences sarcomere stiffness and modulates cardiac contraction-relaxation through its phosphorylation. Phosphorylation of cMyBP-C and ablation of cMyBP-C have been shown to increase the rate of MgADP release in the acto-myosin cross-bridge cycle in the intact sarcomere. The influence of cMyBP-C on Pi-dependent myosin kinetics has not yet been examined. We investigated the effect of cMyBP-C, and its phosphorylation, on myosin kinetics in demembranated papillary muscle strips bearing the β-cardiac myosin isoform from nontransgenic and homozygous transgenic mice lacking cMyBP-C. We used quick stretch and stochastic length-perturbation analysis to characterize rates of myosin detachment and force development over 0–12 mM Pi and at maximal (pCa 4.8) and near-half maximal (pCa 5.75) Ca2+activation. Protein kinase A (PKA) treatment was applied to half the strips to probe the effect of cMyBP-C phosphorylation on Pi sensitivity of myosin kinetics. Increasing Pi increased myosin cross-bridge detachment rate similarly for muscles with and without cMyBP-C, although these rates were higher in muscle without cMyBP-C. Treating myocardial strips with PKA accelerated detachment rate when cMyBP-C was present over all Pi, but not when cMyBP-C was absent. The rate of force development increased with Pi in all muscles. However, Pi sensitivity of the rate force development was reduced when cMyBP-C was present versus absent, suggesting that cMyBP-C inhibits Pi-dependent reversal of the power stroke or stabilizes cross-bridge attachment to enhance the probability of completing the power stroke. These results support a functional role for cMyBP-C in slowing myosin detachment rate, possibly through a direct interaction with myosin or by altering strain-dependent myosin detachment via cMyBP-C-dependent stiffness of the thick filament and myofilament lattice. PKA treatment reduces the role for cMyBP-C to slow myosin detachment and thus effectively accelerates β-myosin detachment in the intact myofilament lattice.NEW & NOTEWORTHYLength perturbation analysis was used to demonstrate that β-cardiac myosin characteristic rates of detachment and recruitment in the intact myofilament lattice are accelerated by Pi, phosphorylation of cMyBP-C, and the absence of cMyBP-C. The results suggest that cMyBP-C normally slows myosin detachment, including Pi-dependent detachment, and that this inhibition is released with phosphorylation or absence of cMyBP-C.