Kawai-Kowase Keiko, Sato Hiroko, Oyama Yuko, Kanai Hiroyoshi, Sato Mahito, Doi Hiroshi, Kurabayashi Masahiko
Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-Maebashi, Gunma, Japan.
Arterioscler Thromb Vasc Biol. 2004 Aug;24(8):1384-90. doi: 10.1161/01.ATV.0000136548.17816.07. Epub 2004 Jun 24.
Transforming growth factor-beta1 (TGFbeta1) and fibroblast growth factor (FGF) families play a pivotal role during vascular development and in the pathogenesis of vascular disease. However, the interaction of intracellular signaling evoked by each of these growth factors is not well understood. The present study was undertaken to examine the molecular mechanisms that mediate the effects of TGFbeta1 and basic FGF (bFGF) on smooth muscle cell (SMC) gene expression.
TGFbeta1 induction of SMC gene expression, including smooth muscle protein 22-alpha (SM22alpha) and smooth muscle alpha-actin, was examined in the pluripotent 10T1/2 cells. Marked increase in these mRNA levels by TGFbeta1 was inhibited by c-Src-tyrosine kinase inhibitors and protein synthesis inhibitor cycloheximide. Functional studies with deletion and site-directed mutation analysis of the SM22alpha promoter demonstrated that TGFbeta1 activated the SM22alpha promoter through a CC(A/T-rich)6GG (CArG) box, which serves as a serum response factor (SRF)-binding site. TGFbeta1 increased SRF expression through an increase in transcription of the SRF gene. In the presence of bFGF, TGFbeta1 induction of SMC marker gene expression was significantly attenuated. Transient transfection assays showed that bFGF significantly suppressed induction of the SM22alpha promoter-driven luciferase activity by TGFbeta1, whereas bFGF had no effects on the TGFbeta1-mediated increase in SRF expression and SRF:DNA binding activity. Mitogen-activated protein kinase kinase-1 (MEK1) inhibitor PD98059 abrogated the bFGF-mediated suppression of TGFbeta1-induced SMC gene expression.
Our data suggest that bFGF-induced MEK/extracellular signal-regulated kinase signaling plays an antagonistic role in TGFbeta1-induced SMC gene expression through suppression of the SRF function. These data indicate that opposing effects of bFGF and TGFbeta1 on SMC gene expression control the phenotypic plasticity of SMCs.
转化生长因子-β1（TGFβ1）和成纤维细胞生长因子（FGF）家族在血管发育及血管疾病发病机制中起关键作用。然而，这些生长因子各自引发的细胞内信号相互作用尚未完全明确。本研究旨在探讨介导TGFβ1和碱性成纤维细胞生长因子（bFGF）对平滑肌细胞（SMC）基因表达影响的分子机制。
在多能性的10T1/2细胞中检测TGFβ1对SMC基因表达的诱导作用，包括平滑肌蛋白22-α（SM22α）和平滑肌α-肌动蛋白。TGFβ1引起的这些mRNA水平显著升高受到c-Src酪氨酸激酶抑制剂和蛋白质合成抑制剂环己酰亚胺的抑制。对SM22α启动子进行缺失和定点突变分析的功能研究表明，TGFβ1通过CC（A/T丰富）6GG（CArG）框激活SM22α启动子，该框作为血清反应因子（SRF）结合位点。TGFβ1通过增加SRF基因的转录来提高SRF表达。在bFGF存在的情况下，TGFβ1对SMC标记基因表达的诱导作用显著减弱。瞬时转染实验表明，bFGF显著抑制TGFβ1对SM22α启动子驱动的荧光素酶活性的诱导，而bFGF对TGFβ1介导的SRF表达增加和SRF:DNA结合活性无影响。丝裂原活化蛋白激酶激酶-1（MEK1）抑制剂PD98059消除了bFGF介导的对TGFβ1诱导的SMC基因表达的抑制作用。
我们的数据表明，bFGF诱导的MEK/细胞外信号调节激酶信号通过抑制SRF功能在TGFβ1诱导的SMC基因表达中起拮抗作用。这些数据表明，bFGF和TGFβ1对SMC基因表达的相反作用控制着SMC的表型可塑性。
