Yamazaki T, Komuro I, Kudoh S, Zou Y, Shiojima I, Mizuno T, Takano H, Hiroi Y, Ueki K, Tobe K
Third Department of Medicine, University of Tokyo School of Medicine, Japan.
J Clin Invest. 1995 Jul;96(1):438-46. doi: 10.1172/JCI118054.
We have previously shown that stretching cardiac myocytes evokes activation of protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and 90-kD ribosomal S6 kinase (p90rsk). To clarify the signal transduction pathways from external mechanical stress to nuclear gene expression in stretch-induced cardiac hypertrophy, we have elucidated protein kinase cascade of phosphorylation by examining the time course of activation of MAP kinase kinase kinases (MAPKKKs), MAP kinase kinase (MAPKK), MAPKs, and p90rsk in neonatal rat cardiac myocytes. Mechanical stretch transiently increased the activity of MAPKKKs. An increase in MAPKKKs activity was first detected at 1 min and maximal activation was observed at 2 min after stretch. The activity of MAPKK was increased by stretch from 1-2 min, with a peak at 5 min after stretch. In addition, MAPKs and p90rsk were maximally activated at 8 min and at 10 approximately 30 min after stretch, respectively. Raf-1 kinase (Raf-1) and (MAPK/extracellular signal-regulated kinase) kinase kinase (MEKK), both of which have MAPKKK activity, were also activated by stretching cardiac myocytes for 2 min. The angiotensin II receptor antagonist partially suppressed activation of Raf-1 and MAPKs by stretch. The stretch-induced hypertrophic responses such as activation of Raf-1 and MAPKs and an increase in amino acid uptake was partially dependent on PKC, while a PKC inhibitor completely abolished MAPK activation by angiotensin II. These results suggest that mechanical stress activates the protein kinase cascade of phosphorylation in cardiac myocytes in the order of Raf-1 and MEKK, MAPKK, MAPKs and p90rsk, and that angiotensin II, which may be secreted from stretched myocytes, may be partly involved in stretch-induced hypertrophic responses by activating PKC.
我们先前已表明，拉伸心肌细胞可引发蛋白激酶C（PKC）、丝裂原活化蛋白激酶（MAPK）和90-kD核糖体S6激酶（p90rsk）的激活。为阐明拉伸诱导心肌肥大过程中从外部机械应力到核基因表达的信号转导途径，我们通过检测新生大鼠心肌细胞中MAP激酶激酶激酶（MAPKKK）、MAP激酶激酶（MAPKK）、MAPK和p90rsk的激活时间进程，阐明了磷酸化的蛋白激酶级联反应。机械拉伸短暂增加了MAPKKK的活性。拉伸后1分钟首次检测到MAPKKK活性增加，2分钟时观察到最大激活。拉伸1至2分钟后MAPKK的活性增加，拉伸后5分钟达到峰值。此外，MAPK和p90rsk分别在拉伸后8分钟和10至30分钟达到最大激活。具有MAPKKK活性的Raf-1激酶（Raf-1）和（MAPK/细胞外信号调节激酶）激酶激酶（MEKK），也通过拉伸心肌细胞2分钟而被激活。血管紧张素II受体拮抗剂部分抑制了拉伸对Raf-1和MAPK的激活。拉伸诱导的肥大反应，如Raf-1和MAPK的激活以及氨基酸摄取的增加，部分依赖于PKC，而PKC抑制剂完全消除了血管紧张素II对MAPK的激活。这些结果表明，机械应力按Raf-1和MEKK、MAPKK、MAPK和p90rsk的顺序激活心肌细胞中的磷酸化蛋白激酶级联反应，并且可能从拉伸的心肌细胞分泌的血管紧张素II可能通过激活PKC部分参与拉伸诱导的肥大反应。
