Intracellular Signaling of Stretch Mediated Myocyte Growth

为了研究机械刺激诱导原癌基因表达的分子机制，我们在可变形的培养皿中培养新生大鼠心肌细胞，并通过拉伸贴壁细胞来施加体外机械载荷。心肌细胞拉伸增加了细胞总RNA含量和c-fos和骨骼α-肌动蛋白的mRNA水平，进而激活了蛋白质合成。CAT实验表明，c-fos基因的转录需要含有血清反应元件的序列。这种c-fos mRNA的积累在转录水平上被蛋白激酶C抑制剂抑制，并被蛋白激酶C的下调显著抑制。此外，心肌细胞拉伸增加了肌醇磷酸水平。这些发现表明，机械刺激可能直接诱导原癌基因的表达，可能是通过蛋白激酶C的激活。此外，我们还观察了心肌细胞拉伸对丝裂原活化蛋白(MAP)激酶的激活作用。这一结果提示，机械刺激诱导的核糖体蛋白质合成效率可能与MAP激活有关。

To examine the molecular mechanisms by which mechanical stimuli induce protooncogene expression, we cultured rat neonatal cardiocytes in deformable dishes and imposed an in vitro mechanical load by stretching the adherent cells. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos and skeletal alpha-actin followed by activation of protein synthesis. CAT assay indicated that sequences containing a serum response element were required for efficient transcription of c-fos gene by stretching. This accumulation of c-fos mRNA was suppressed by protein kinase C inhibitors at the transcriptional level and inhibited markedly by down-regulation of protein kinase C. Moreover, myocyte stretching increased inositol phosphate levels. These findings suggest that mechanical stimuli might directly induce protooncogene expression possibly via protein kinase C activation. Furthermore, we observed the activation of mitogen activated protein (MAP) kinase by myocytes stretching. This result suggest that MAP kinase activation might increase in efficiency of protein synthesis in ribosomes induced by mechanical stimuli.