首页> 美国卫生研究院文献>American Journal of Physiology - Lung Cellular and Molecular Physiology >EGF antagonizes TGF-β-induced tropoelastin expression in lung fibroblasts via stabilization of Smad corepressor TGIF
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EGF antagonizes TGF-β-induced tropoelastin expression in lung fibroblasts via stabilization of Smad corepressor TGIF

机译:EGF通过稳定Smad核心抑制剂TGIF拮抗TGF-β诱导的肺成纤维细胞原弹性蛋白表达

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摘要

We previously reported that neutrophil elastase (NE) downregulates transforming growth factor-β (TGF-β)-maintained tropoelastin mRNA levels in lung fibroblasts through transactivation of the epidermal growth factor (EGF) receptor (EGFR)/Mek/Erk pathway, which is dependent on the NE-initiated release of soluble EGFR ligands. In the present study, we investigated the mechanism by which EGF downregulates tropoelastin expression. We found that EGF downregulates tropoelastin expression through inhibition of TGF-β signaling. We show that EGF does not prevent the TGF-β-induced nuclear accumulation of Smad2/3; rather, EGF stabilizes the short-lived Smad transcriptional corepressor TG-interacting factor (TGIF) via EGFR/Mek/Erk-mediated phosphorylation of TGIF. Elevation of TGIF levels, either by TGIF overexpression or prevention of TGIF degradation, is sufficient to inhibit TGF-β-induced tropoelastin expression. Moreover, TGIF is essential for EGF-mediated downregulation of tropoelastin expression, inasmuch as small interfering RNA knockdown of TGIF blocked EGF-induced downregulation of tropoelastin. Finally, we demonstrated that NE treatment, which releases EGF-like growth factors, causes stabilization of TGIF through the EGFR/Mek/Erk pathway. These results suggest that EGFR/Mek/Erk signaling specifically antagonizes the proelastogenic action of TGF-β in lung fibroblasts by stabilizing the Smad transcriptional corepressor TGIF.
机译:我们先前曾报道,中性粒细胞弹性蛋白酶(NE)通过表皮生长因子(EGF)受体(EGFR)/ Mek / Erk途径的反式激活下调了肺成纤维细胞中转化生长因子-β(TGF-β)维持的原弹性蛋白mRNA水平。取决于NE启动的可溶性EGFR配体释放。在本研究中,我们研究了EGF下调原弹性蛋白表达的机制。我们发现EGF通过抑制TGF-β信号传导而下调原弹性蛋白的表达。我们表明,EGF不能阻止TGF-β诱导Smad2 / 3的核蓄积;相反,EGF通过EGFR / Mek / Erk介导的TGIF磷酸化来稳定短命的Smad转录共加压因子TG相互作用因子(TGIF)。通过TGIF过表达或防止TGIF降解,TGIF水平的升高足以抑制TGF-β诱导的原弹性蛋白表达。此外,TGIF对于EGF介导的原弹性蛋白表达下调是必不可少的,因为TGIF的小干扰RNA敲低可阻断EGF诱导的原弹性蛋白的下调。最后,我们证明了NE处理会释放出类似EGF的生长因子,从而通过EGFR / Mek / Erk途径引起TGIF的稳定。这些结果表明,EGFR / Mek / Erk信号传导通过稳定Smad转录共加压因子TGIF来特异性拮抗TGF-β在肺成纤维细胞中的促弹性生成作用。

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