Titin-actin interaction in mouse myocardium:: Passive tension modulation and its regulation by calcium/S100A1
Titin-actin interaction in mouse myocardium:: Passive tension modulation and its regulation by calcium/S100A1
复制标题
DOI：
10.1016/s0006-3495(01)75876-6
复制
发表时间：
2001-10-01
影响因子：
3.4
通讯作者：
Granzier, H
中科院分区：
文献类型：
--
作者：
Yamasaki, R;Berri, M;Granzier, H
横纹肌的被动张力主要来自巨型蛋白肌联的延伸。然而，一些研究表明，在心肌中，肌动蛋白和肌动蛋白之间的相互作用也可能导致被动张力。我们表达了代表心脏 N2B 肌联蛋白可延伸区域的子结构域（串联 ig 片段、N2B 剪接元件和 PEVK 结构域）的重组片段，并测定了它们与 F-肌动蛋白的结合。 PEVK 片段结合 F-肌动蛋白，但未检测到其他片段的结合。与骨骼肌 PEVK 片段的比较表明，只有心脏 PEVK 在生理离子强度下结合肌动蛋白。使用体外运动和单肌细胞力学研究了 PEVK-肌动蛋白相互作用的重要性。当 F-肌动蛋白在运动测定中相对于肌联蛋白滑动时，PEVK 结构域和 F-肌动蛋白之间的动态相互作用阻碍了丝的滑动。肌细胞结果表明，类似的相互作用对被动紧张产生了重大影响。我们还研究了钙对 PEVK-肌动蛋白相互作用的影响。虽然单独使用钙没有效果，但心肌中高浓度的可溶性钙结合蛋白 S100A1 会以钙依赖性方式抑制 PEVK 与肌动蛋白的相互作用。凝胶叠加分析表明，S100A1 在体外以钙依赖性方式结合 PEVK 区域，并且在沿着 titin 可原位延伸区域的几个位点观察到 S100A1 结合，包括 PEVK 结构域。体外运动结果表明，S100A1-PEVK 相互作用减少了 F-肌动蛋白相对于 PEVK 结构域滑动时产生的力，我们推测 S100A1 可能提供一种机制，使细丝从肌联蛋白中释放出来，并在主动收缩之前减少基于肌联蛋白的张力。
Passive tension in striated muscles derives primarily from the extension of the giant protein titin. However, several studies have suggested that, in cardiac muscle, interactions between titin and actin might also contribute to passive tension. We expressed recombinant fragments representing the subdomains of the extensible region of cardiac N2B titin (tandem-ig segments, the N2B splice element, and the PEVK domain), and assayed them for binding to F-actin. The PEVK fragment bound F-actin, but no binding was detected for the other fragments. Comparison with a skeletal muscle PEVK fragment revealed that only the cardiac PEVK binds actin at physiological ionic strengths. The significance of PEVK-actin interaction was investigated using in vitro motility and single-myocyte mechanics. As F-actin slid relative to titin in the motility assay, a dynamic interaction between the PEVK domain and F-actin retarded filament sliding. Myocyte results suggest that a similar interaction makes a significant contribution to the passive tension. We also investigated the effect of calcium on PEVK-actin interaction. Although calcium alone had no effect, S100A1, a soluble calcium-binding protein found at high concentrations in the myocardium, inhibited PEVK-actin interaction in a calcium-dependent manner. Gel overlay analysis revealed that S100A1 bound the PEVK region in vitro in a calcium-dependent manner, and S100A1 binding was observed at several sites along titin's extensible region in situ, including the PEVK domain. In vitro motility results indicate that S100A1-PEVK interaction reduces the force that arises as F-actin slides relative to the PEVK domain, and we speculate that S100A1 may provide a mechanism to free the thin filament from titin and reduce titin-based tension before active contraction.