Phosphorylation of the regulatory light chains of myosin affects Ca2+ sensitivity of skeletal muscle contraction
Phosphorylation of the regulatory light chains of myosin affects Ca2+ sensitivity of skeletal muscle contraction
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DOI：
10.1152/japplphysiol.00858.2001
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发表时间：
2002-04-01
影响因子：
3.3
通讯作者：
Potter, JD
中科院分区：
文献类型：
--
作者：
Szczesna, D;Zhao, JJ;Potter, JD
肌球蛋白调节轻链(RLC)的磷酸化在平滑肌收缩中的作用已得到证实，但在横纹肌(骨骼肌和心肌)中其作用仍存在争议。我们研究了重组肌球蛋白和皮肤骨骼肌纤维中RLC磷酸化的影响，其中测量了钙敏感性和稳态力发展的动力学。与未磷酸化的RLC相比，经磷酸化的RLC重组的骨骼肌肌球蛋白对细丝调节的ATPase活性产生了更高的钙敏感性(产生半最大激活的钙浓度的对数变化=类似于0.25)。去皮的骨骼肌纤维对钙离子的力敏感性也是如此，随着磷酸化的RLC重建纤维，这种敏感性会增加。此外，我们还表明，内源性RLC的磷酸化水平是力量发育对钙的敏感性的关键决定因素。研究RLC磷酸化对笼中钙离子DM-Nitphen的力激活动力学的影响，结果表明，力的发展速率略有增加，但统计学意义不大。然而，当未磷酸化的RLC重组纤维随后被外源肌球蛋白轻链激酶磷酸化时，观察到初始稳态力的69%到84%。综上所述，我们的结果表明，尽管结合到肌钙蛋白-原肌球蛋白复合体上的钙离子是骨骼肌收缩的主要调节因子，但RLC在这一过程中起着重要的调节作用。
The role of phosphorylation of the myosin regulatory light chains (RLC) is well established in smooth muscle contraction, but in striated (skeletal and cardiac) muscle its role is still controversial. We have studied the effects of RLC phosphorylation in reconstituted myosin and in skinned skeletal muscle fibers where Ca2+ sensitivity and the kinetics of steady-state force development were measured. Skeletal muscle myosin reconstituted with phosphorylated RLC produced a much higher Ca2+ sensitivity of thin filament-regulated ATPase activity than nonphosphorylated RLC (change in -log of the Ca2+ concentration producing half-maximal activation = similar to0.25). The same was true for the Ca2+ sensitivity of force in skinned skeletal muscle fibers, which increased on reconstitution of the fibers with the phosphorylated RLC. In addition, we have shown that the level of endogenous RLC phosphorylation is a crucial determinant of the Ca2+ sensitivity of force development. Studies of the effects of RLC phosphorylation on the kinetics of force activation with the caged Ca2+, DM-nitrophen, showed a slight increase in the rates of force development with low statistical significance. However, an increase from 69 to 84% of the initial steady-state force was observed when nonphosphorylated RLC-reconstituted fibers were subsequently phosphorylated with exogenous myosin light chain kinase. In conclusion, our results suggest that, although Ca2+ binding to the troponin-tropomyosin complex is the primary regulator of skeletal muscle contraction, RLC play an important modulatory role in this process.