Interaction between myosin heavy chain and troponin isoforms modulate cardiac myofiber contractile dynamics
Interaction between myosin heavy chain and troponin isoforms modulate cardiac myofiber contractile dynamics
复制标题
DOI：
10.1152/ajpregu.00157.2007
复制
发表时间：
2007-10-01
影响因子：
2.8
通讯作者：
Campbell, Kenneth B.
中科院分区：
文献类型：
--
作者：
Chandra, Murali;Tschirgi, Matthew L.;Campbell, Kenneth B.
种属特异性肌球蛋白重链（MHC）和肌钙蛋白（Tn）亚型的协调表达可能带来动态互补，以使肌肉收缩速度与种属特异性心率相匹配。收缩系统的功能和动态力长度的测量进行了从小鼠和大鼠心脏的肌纤维和重组同源肌钙蛋白或orthoglycan肌钙蛋白重建后的肌纤维。小鼠纤维的长度介导的跨桥（XB）募集（B）和张力重建（k（tr））的速率常数明显快于大鼠纤维。小鼠的张力成本（ATP酶/张力）和长度介导的XB变形的速率常数（c）均高于大鼠。因此，小鼠纤维在所有动态和功能方面都比大鼠纤维快。小鼠肌钙蛋白显著增加大鼠纤维中的B和k（tr）;相反，大鼠肌钙蛋白显著降低小鼠纤维中的B和k（tr）。因此，长度介导的招聘轴承XB发生更迅速地在小鼠Tn的存在下比在大鼠Tn的存在下，表明XB招聘的速度由Tn调节。Tn和MHC之间存在显著的相互作用，因此Tn或MHC的变化影响XB募集的速度。我们的数据表明，心肌收缩的动力学是不同的，在小鼠和大鼠心脏，因为在MHC和Tn序列的异质性。在肌丝水平，互补调节收缩蛋白的协调表达产生功能性动态表型，其允许心血管系统在不同心率下有效地发挥功能。
Coordinated express of species-specific myosin heavy chain (MHC) and troponin (Tn) isoforms may bring about a dynamic complementarity to match muscle contraction speed with species-specific heart rates. Contractile system function and dynamic force-length measurements were made in muscle fibers from mouse and rat hearts and in muscle fibers after reconstitution with either recombinant homologous Tn or orthologous Tn. The rate constants of length-mediated cross-bridge (XB) recruitment (b) and tension redevelopment (k(tr)) of mouse fibers were significantly faster than those of rat fibers. Both the tension cost (ATPase/tension) and rate constant of length-mediated XB distortion (c) were higher in the mouse than in the rat. Thus the mouse fiber was faster in all dynamic and functional aspects than the rat fiber. Mouse Tn significantly increased b and k(tr) in rat fibers; conversely, rat Tn significantly decreased b and k(tr) in mouse fibers. Thus the length-mediated recruitment of force-bearing XB occurs much more rapidly in the presence of mouse Tn than in the presence of rat Tn, demonstrating that the speed of XB recruitment is regulated by Tn. There was a significant interaction between Tn and MHC such that changes in either Tn or MHC affected the speed of XB recruitment. Our data demonstrate that the dynamics of myocardial contraction are different in the mouse and rat hearts because of sequence heterogeneity in MHC and Tn. At the myofilament level, coordinated expression of complementary regulatory contractile proteins produces a functional dynamic phenotype that allows the cardiovascular systems to function effectively at different heart rates.