Insulin induces a transcriptional activation of epiregulin, HB-EGF and amphiregulin, by a PI3K-dependent mechanism: Identification of a specific insulin-responsive promoter element
Insulin induces a transcriptional activation of epiregulin, HB-EGF and amphiregulin, by a PI3K-dependent mechanism: Identification of a specific insulin-responsive promoter element
复制标题
DOI：
10.1016/j.bbrc.2007.01.047
复制
发表时间：
2007-03-23
影响因子：
3.1
通讯作者：
Sorensen, Boe S.
中科院分区：
文献类型：
--
作者：
Ornskov, Dorthe;Nexo, Ebba;Sorensen, Boe S.
以前我们已经表明，RT 4膀胱癌细胞的胰岛素刺激导致增殖增加，这需要HER I活化，并且伴随EGF配体肝素结合EGF样生长因子（HB-EGF）、双调蛋白（AR）和表皮调节蛋白（EPI）的mRNA表达增加[D. Ornskov，E. Nexo，B.S. Sorensen，Insulin-induced proliferation of bladder cancer cells is mediated through activation of the epidermal growth factor system，FEBS J. 273（2006）5479-5489]。在本论文中，我们研究了导致这种胰岛素诱导表达的分子机制。我们用放线菌素D抑制转录后监测mRNA的衰减，并证明胰岛素介导的增加不是由mRNA稳定性增强引起的。在未处理的细胞中，HB-EGF mRNA是最不稳定的，而AR和EPI mRNA衰减较慢的动力学。然而，HB-EGF和EPI的启动子分析表明，胰岛素刺激转录。对EPI启动子的研究确定胰岛素反应元件位于-564至-365 bp区域。该区域含有转录因子SP1、AP 1和NF-κ B的潜在结合位点。有趣的是，所有三种转录因子都可以被PI 3 K激活。我们证明，胰岛素诱导的HB-EGF，AR和EPI mRNA的表达是完全阻止由特定的PI 3 K抑制剂渥曼青霉素，这表明PI 3 K的参与。(c)2007年爱思唯尔公司All rights reserved.
Previously we have shown that insulin-stimulation of RT4 bladder cancer cells leads to increased proliferation, which require HER I activation, and is accompanied by increased mRNA expression of the EGF-ligands heparin-binding EGF-like growth factor (HB-EGF), amphiregulin (AR), and epiregulin (EPI) [D. Ornskov, E. Nexo, B.S. Sorensen, Insulin-induced proliferation of bladder cancer cells is mediated through activation of the epidermal growth factor system, FEBS J. 273 (2006) 5479-5489]. In the present paper, we have investigated the molecular mechanism leading to this insulin-induced expression. We monitored the decay of mRNA after inhibiting transcription with Actinomycin D and demonstrated that the insulin-mediated increase was not caused by enhanced mRNA stability. In untreated cells, HB-EGF mRNA was the least stable, whereas AR and EPI mRNA decayed with slower kinetics. However, promoter analysis of HB-EGF and EPI demonstrated that insulin stimulated transcription. Studies on the EPI promoter identified the insulin-responsive element to be located in the region -564 to -365 bp. This region contains potential binding sites for the transcription factors SP1, AP1, and NF-KB. Interestingly, all three transcription factors can be activated by PI3K. We demonstrate that the insulin-induced expression of HB-EGF, AR, and EPI mRNA is completely prevented by the specific PI3K inhibitor Wortmannin, suggesting an involvement of the PI3K. (c) 2007 Elsevier Inc. All rights reserved.