Myofilament calcium sensitivity does not affect cross-bridge activation-relaxation kinetics
Myofilament calcium sensitivity does not affect cross-bridge activation-relaxation kinetics
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DOI：
10.1152/ajpregu.00630.2006
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发表时间：
2007-03-01
影响因子：
2.8
通讯作者：
Poggesi, Corrado
中科院分区：
文献类型：
--
作者：
de Tombe, Pieter P.;Belus, Alexandra;Poggesi, Corrado
肌丝钙敏感性不影响跨桥激活-松弛动力学。Am J Physiol Regul Integr Comp Physiol 292：R1129-R1136，2007。首次出版于2006年11月2日; doi：10.1152/ajpregu。00630.2006.-我们采用单肌原纤维技术，以测试是否存在的缓慢骨骼肌钙蛋白-I（ssTnI）是足以诱导增加肌丝钙敏感性（EC 50）和是否调制EC 50影响力的发展动态。使用通过快速溶液转换激活的兔腰大肌肌原纤维进行研究，其中Tn部分被重组心脏Tn（cTnT）或由重组cTn-T（cTnT）和cTn-C（cTnC）组成的Tn以及重组ssTnI（ssTnI-嵌合体Tn）取代。在刚性溶液（0.5mg/ml Tn; 20 ℃; 2小时）中进行Tn交换，并通过SDS-PAGE确认。cTnI交换诱导EC 50降低; ssTnI-嵌合体Tn交换诱导EC 50进一步降低（以μ M计：内源性Tn，1.35 +/- 0.08; cTnI，1.04 +/- 0.13; ssTnI-嵌合体Tn，0.47 +/- 0.03）。100 μ M苄普地尔也降低了EC 50（对照：2.04 +/- 0.03 μ M;苄普地尔1.35 +/- 0.03 μ M）。任何组之间的最大张力均无差异。尽管EC 50显着变化，但在任何条件下动态激活-松弛参数均不受影响。我们的研究结果表明：1）将ssTnI掺入骨骼肌快肌节足以诱导肌丝Ca 2+敏感性增加，2）肌动蛋白-肌球蛋白相互作用的动力学与EC 50无关。这一结果表明，固有的跨桥循环速率不改变的动态细丝激活。
Myofilament calcium sensitivity does not affect cross-bridge activation-relaxation kinetics. Am J Physiol Regul Integr Comp Physiol 292:R1129-R1136, 2007. First published November 2, 2006; doi:10.1152/ajpregu. 00630.2006.-We employed single myofibril techniques to test whether the presence of slow skeletal troponin-I (ssTnI) is sufficient to induce increased myofilament calcium sensitivity (EC50) and whether modulation of EC50 affects the dynamics of force development. Studies were performed using rabbit psoas myofibrils activated by rapid solution switch and in which Tn was partially replaced for either recombinant cardiac Tn(cTn) or Tn composed of recombinant cTn-T (cTnT) and cTn-C (cTnC), and recombinant ssTnI (ssTnI-chimera Tn). Tn exchange was performed in rigor solution (0.5 mg/ml Tn; 20 C; 2 h) and confirmed by SDS-PAGE. cTnI exchange induced a decrease in EC50; ssTnI-chimera Tn exchange induced a further decrease in EC50 (in mu M: endogenous Tn, 1.35 +/- 0.08; cTnI, 1.04 +/- 0.13; ssTnI-chimera Tn, 0.47 +/- 0.03). EC50 was also decreased by application of 100 mu M bepridil (control: 2.04 +/- 0.03 mu M; bepridil 1.35 +/- 0.03 mu M). Maximum tension was not different between any groups. Despite marked alterations in EC50, none of the dynamic activation- relaxation parameters were affected under any condition. Our results show that 1) incorporation of ssTnI into the fast skeletal sarcomere is sufficient to induce increased myofilament Ca2+ sensitivity, and 2) the dynamics of actin-myosin interaction do not correlate with EC50. This result suggests that intrinsic cross-bridge cycling rate is not altered by the dynamics of thin-filament activation.