MDPC-23细胞内Smad信号途径在转化生长因子β1调控Smad7基因转录中的作用

Role of Smad signaling in transcription of Smad7 gene mediated by TGF-β1 in odontoblast cell line MDPC-23

目的:研究成牙本质细胞系M DPC-23内Sm ad信号途径在转化生长因子β1(transform ing growth factor-β1,TGF-β1)调控Sm ad7基因转录调控中的作用,从基因转录水平探讨成牙本质细胞内TGF-β调控Sm ad7基因表达的分子机制。方法:培养M DPC-23细胞,通过瞬时共转染和报告基因检测方法观察Sm ad蛋白分子对Sm ad7启动子活性的影响,实验数据采用单因素方差分析。结果:当Sm ad7启动子(-408bp至+112bp)荧光素酶活性载体表达在M DPC-23细胞时,其基础启动子活性被TGF-β1显著诱导增加,而骨形成蛋白2(bone m orphogenetic protein-2,BM P-2)对其活性无明显影响。单独过表达Sm ad1、2、4、5对Sm ad7启动子活性无明显影响。Sm ad3过表达显著增强Sm ad7启动子活性,而Sm ad3与Sm ad4共转染进一步增强了Sm ad3的作用。过表达Sm ad3突变型载体或Sm ad3反义cDNA(AS-Sm ad3)均显著抑制TGF-β1对Sm ad7启动子活性的诱导作用。结论:在成牙本质细胞系M DPC-23内,TGF-β通过Sm ad3与Sm ad4协同调控Sm ad7基因转录。

PURPOSE: To investigate the role of Smad signaling in transcription of Smad7 gene mediated by TGF- β1 in odontoblast cell line MDPC-23, and to explore the molecular mechanism of Smad7 gene expression mediated by TGF-β1 at the transcriptional level. METHODS: Smad function and its role in transcription of Smad7 were investigated in cotransfection experiments using Smad7 promoter-luciferase reporter construct containing the sequence between -408 bp and +112 bp of mouse Smad7 gene. The data were analysed by one-way ANOVA. RESULTS: When the Smad7 promoter-luciferase reporter gene construct was expressed in MDPC-23 cells, its transcriptional activity was significantly induced by TGF-β1 treatment, whereas not by BMP-2 treatment. Overexpression of Smad1, 2, 4, or 5 had no effect on transcriptional activity of Smad7 promoter. Overexpression of Smad3 markedly promoted transcriptional activity of Smad7 promoter, whereas co-transfection of Smad3 and Smad4 doubled the effect of Smad3. Overexpression of Smad3 dominant negative mutant or Smad3 antisense cDNA (AS-Smad3) significantly inhibited transcriptional activity of Smad7 promoter induced by TGF-β1. CONCLUSION: TGF-β1 regulated transcription of Smad7 gene through association of Smad3 and Smad4 in MDPC-23 cells. Supported by National Natural Science Foundation (Grant No. 30200315).