Komuro I, Katoh Y, Kaida T, Shibazaki Y, Kurabayashi M, Hoh E, Takaku F, Yazaki Y
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
J Biol Chem. 1991 Jan 15;266(2):1265-8.
To examine the molecular mechanisms by which mechanical stimuli induce cardiac hypertrophy and specific gene 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. Nuclear run-off transcription assay revealed that this increase in c-fos mRNA level by stretching at least partially reflects changes in the transcriptional status. The transfected chloramphenicol acetyltransferase gene linked to upstream sequences of the fos gene indicated that sequences containing a serum response element were required for efficient transcription by stretching and that sequences containing a cAMP/calcium response element might not be involved in the c-fos response to myocyte stretching. The accumulation of c-fos mRNA by stretching 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, and activation of protein kinase C by phorbol esters stimulated the expression of c-fos and skeletal alpha-actin genes. These findings suggest that mechanical stimuli (myocyte stretching) might directly induce cardiac hypertrophy and specific gene expression possibly via protein kinase C activation.
为了研究机械刺激诱导心肌肥大和特定基因表达的分子机制，我们将大鼠新生心肌细胞培养在可变形培养皿中，并通过拉伸贴壁细胞施加体外机械负荷。心肌细胞拉伸增加了总细胞RNA含量以及c-fos和骨骼肌α-肌动蛋白的mRNA水平。核转录分析表明，拉伸导致的c-fos mRNA水平升高至少部分反映了转录状态的变化。与fos基因上游序列相连的转染氯霉素乙酰转移酶基因表明，含有血清反应元件的序列是拉伸有效转录所必需的，而含有cAMP/钙反应元件的序列可能不参与心肌细胞拉伸对c-fos的反应。拉伸导致的c-fos mRNA积累在转录水平上被蛋白激酶C抑制剂抑制，并且通过下调蛋白激酶C而明显受到抑制。此外，心肌细胞拉伸增加了肌醇磷酸水平，佛波酯对蛋白激酶C的激活刺激了c-fos和骨骼肌α-肌动蛋白基因的表达。这些发现表明，机械刺激（心肌细胞拉伸）可能通过蛋白激酶C激活直接诱导心肌肥大和特定基因表达。
