Dessy C, Kim I, Sougnez C L, Laporte R, Morgan K G
Signal Transduction Group, Boston Biomedical Research Institute, Boston MA 02114, USA.
Am J Physiol. 1998 Oct;275(4):C1081-6. doi: 10.1152/ajpcell.1998.275.4.C1081.
The purpose of this study was to investigate the potential role of mitogen-activated protein (MAP) kinase in smooth muscle contraction by monitoring MAP kinase activation, caldesmon phosphorylation, and contractile force during agonist stimulation. Isometric tension in response to KCl and phenylephrine (PE) was measured from strips of ferret aorta. MAP kinase activation was monitored by Western blot using a phosphospecific p44/p42 MAP kinase antibody. Caldesmon phosphorylation was assessed using specific phosphocaldesmon antibodies. We report here that treatment of smooth muscle strips with PD-098059, a specific inhibitor of MAP kinase kinase, did not detectably modify the KCl-evoked contraction but significantly inhibited the contraction to PE in the absence of extracellular Ca2+. In this experimental condition, where the contraction occurs in the absence of increases in 20-kDa myosin light chain phosphorylation, PD-098059 also inhibited significantly MAP kinase and caldesmon phosphorylation. Collectively, these results demonstrate a direct cause-and-effect relationship between MAP kinase activation and Ca2+-independent smooth muscle contraction and support the concept of caldesmon phosphorylation as the missing link between both events.
本研究的目的是通过监测激动剂刺激过程中的丝裂原活化蛋白（MAP）激酶激活、钙调蛋白磷酸化和收缩力，来研究MAP激酶在平滑肌收缩中的潜在作用。从雪貂主动脉条测量对氯化钾（KCl）和去氧肾上腺素（PE）的等长张力。使用磷酸特异性p44/p42 MAP激酶抗体通过蛋白质印迹法监测MAP激酶激活。使用特异性磷酸钙调蛋白抗体评估钙调蛋白磷酸化。我们在此报告，用MAP激酶激酶的特异性抑制剂PD-098059处理平滑肌条，未显著改变KCl诱发的收缩，但在无细胞外Ca2+的情况下显著抑制了对PE的收缩。在这种实验条件下，收缩在20 kDa肌球蛋白轻链磷酸化未增加的情况下发生，PD-098059也显著抑制了MAP激酶和钙调蛋白磷酸化。总体而言，这些结果证明了MAP激酶激活与Ca2+非依赖性平滑肌收缩之间存在直接的因果关系，并支持钙调蛋白磷酸化是这两个事件之间缺失环节的概念。
