de Lanerolle P, Condit J R, Tanenbaum M, Adelstein R S
Nature. 1982 Aug 26;298(5877):871-2. doi: 10.1038/298871a0.
Myosin phosphorylation plays an important part in excitation--contraction coupling in smooth muscle. Phosphorylation by a Ca2+, calmodulin-dependent kinase stimulates the actin-activated Mg2+-ATPase activity of smooth muscle myosin, suggesting that myosin phosphorylation regulates smooth muscle contraction. This hypothesis is supported by evidence that myosin is phosphorylated during contraction and dephosphorylated during relaxation of intact smooth muscles stimulated with a single agonist concentration. However, there is little information regarding the response to stimulation with various agonist concentrations. As the dose-response relationships for phosphorylation and tension should be similar if myosin phosphorylation does, in fact, regulate smooth muscle contraction, we studied myosin phosphorylation in tracheal smooth muscle stimulated with a broad range of concentrations of the cholinergic agonist, methacholine. The results of these experiments are consistent with the hypothesis that myosin phosphorylation regulates smooth muscle contraction but they indicate a relatively complex relationship between myosin phosphorylation and the generation of isometric tension.
肌球蛋白磷酸化在平滑肌的兴奋 - 收缩偶联中起重要作用。由钙调蛋白依赖性激酶进行的磷酸化刺激平滑肌肌球蛋白的肌动蛋白激活的镁离子 - ATP酶活性，这表明肌球蛋白磷酸化调节平滑肌收缩。完整平滑肌在用单一激动剂浓度刺激时，收缩过程中肌球蛋白被磷酸化，舒张过程中去磷酸化，这一证据支持了该假说。然而，关于不同激动剂浓度刺激的反应信息很少。如果肌球蛋白磷酸化确实调节平滑肌收缩，那么磷酸化与张力的剂量 - 反应关系应该相似，因此我们研究了用广泛浓度的胆碱能激动剂乙酰甲胆碱刺激气管平滑肌时的肌球蛋白磷酸化情况。这些实验结果与肌球蛋白磷酸化调节平滑肌收缩的假说一致，但它们表明肌球蛋白磷酸化与等长张力产生之间存在相对复杂的关系。
