Functional significance of C-terminal mobile domain of cardiac troponin I.
Functional significance of C-terminal mobile domain of cardiac troponin I.
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DOI：
10.1016/j.abb.2017.09.017
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发表时间：
2017-11-15
影响因子：
3.9
通讯作者：
Dong WJ
中科院分区：
文献类型：
--
作者：
Bohlooli Ghashghaee N;Tanner BCW;Dong WJ
心肌收缩力的Ca 2+调节通过肌钙蛋白复合物介导，肌钙蛋白复合物包括三个亚基：cTnC、cTnI和cTnT。随着细胞内[Ca 2 +]的增加，cTnI减少其与肌动蛋白的结合相互作用，主要与cTnC相互作用，从而使收缩成为可能。这种调节转换的一部分涉及cTnI的移动的结构域（cTnI-MD），其在肌肉收缩性中的作用仍然是难以捉摸的。为了研究cTnI-MD的功能意义，我们设计了两个cTnI构建体，其中MD被不同程度地截短：cTnI（1-167）和cTnI（1-193）。这些截短被交换为皮肤大鼠乳头肌纤维中的内源性cTnI，并在短（1.9µm）和长（2.2µm）肌节长度（SL）下评估其对Ca 2+激活收缩和跨桥循环动力学的影响。我们的结果表明，cTnI（1-167）截短减少了SL诱导的收缩Ca 2+敏感性的增加，但没有减少SL依赖性的最大张力的增加，这表明细纤维和粗纤维对长度依赖性激活的贡献之间存在解偶联。与cTnI（WT）相比，两种截短型在两种SL均显示出更高的Ca 2+敏感性和更快的跨桥附着率。此外，cTnI（1-167）减慢MgADP释放速率并增强跨桥结合。我们的研究结果表明，cTnI-MD截断影响封闭状态的转换（S）和不稳定的封闭状态的位置原肌球蛋白。
Ca2+-regulation of cardiac contractility is mediated through the troponin complex, which comprises three subunits: cTnC, cTnI, and cTnT. As intracellular [Ca2+] increases, cTnI reduces its binding interactions with actin to primarily interact with cTnC, thereby enabling contraction. A portion of this regulatory switching involves the mobile domain of cTnI (cTnI-MD), the role of which in muscle contractility is still elusive. To study the functional significance of cTnI-MD, we engineered two cTnI constructs in which the MD was truncated to various extents: cTnI(1–167) and cTnI(1–193). These truncations were exchanged for endogenous cTnI in skinned rat papillary muscle fibers, and their influence on Ca2+-activated contraction and cross-bridge cycling kinetics was assessed at short (1.9µm) and long (2.2µm) sarcomere lengths (SLs). Our results show that the cTnI(1–167) truncation diminished the SL-induced increase in Ca2+-sensitivity of contraction, but not the SL-dependent increase in maximal tension, suggesting an uncoupling between the thin and thick filament contributions to length dependent activation. Compared to cTnI(WT), both truncations displayed greater Ca2+-sensitivity and faster cross-bridge attachment rates at both SLs. Furthermore, cTnI(1–167) slowed MgADP release rate and enhanced cross-bridge binding. Our findings imply that cTnI-MD truncations affect the blocked-to closed-state transition(s) and destabilize the closed-state position of tropomyosin.
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影响因子：
20.1
作者：
Foster, DB;Noguchi, T;Van Eyk, JE
通讯作者：
Van Eyk, JE
影响因子：
16.6
作者：
Fusi, L.;Brunello, E.;Yan, Z.;Irving, M.
通讯作者：
Irving, M.
影响因子：
3.4
作者：
Blumenschein, TMA;Stone, DB;Sykes, BD
通讯作者：
Sykes, BD
影响因子：
4.5
作者：
Fukuda, N;Wu, YM;Granzier, H
通讯作者：
Granzier, H
影响因子：
3.4
作者：
Brenner, B;Kraft, T;Chalovich, JM
通讯作者：
Chalovich, JM