Solanas Guiomar, Porta-de-la-Riva Montserrat, Agustí Cristina, Casagolda David, Sánchez-Aguilera Francisco, Larriba María Jesús, Pons Ferran, Peiró Sandra, Escrivà Maria, Muñoz Alberto, Duñach Mireia, de Herreros Antonio García, Baulida Josep
Unitat de Biofísica-CEB, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain.
J Cell Sci. 2008 Jul 1;121(Pt 13):2224-34. doi: 10.1242/jcs.021667.
E-cadherin and its transcriptional repressor Snail1 (Snai1) are two factors that control epithelial phenotype. Expression of Snail1 promotes the conversion of epithelial cells to mesenchymal cells, and occurs concomitantly with the downregulation of E-cadherin and the upregulation of expression of mesenchymal genes such as those encoding fibronectin and LEF1. We studied the molecular mechanism controlling the expression of these genes in mesenchymal cells. Forced expression of E-cadherin strongly downregulated fibronectin and LEF1 RNA levels, indicating that E-cadherin-sensitive factors are involved in the transcription of these genes. E-cadherin overexpression decreased the transcriptional activity of the fibronectin promoter and reduced the interaction of beta-catenin and NF-kappaB with this promoter. Similar to beta-catenin, NF-kappaB was found, by co-immunoprecipitation and pull-down assays, to be associated with E-cadherin and other cell-adhesion components. Interaction of the NF-kappaB p65 subunit with E-cadherin or beta-catenin was reduced when adherens junctions were disrupted by K-ras overexpression or by E-cadherin depletion using siRNA. These conditions did not affect the association of p65 with the NF-kappaB inhibitor IkappaBalpha. The functional significance of these results was stressed by the stimulation of NF-kappaB transcriptional activity, both basal and TNF-alpha-stimulated, induced by an E-cadherin siRNA. Therefore, these results demonstrate that E-cadherin not only controls the transcriptional activity of beta-catenin but also that of NF-kappaB. They indicate too that binding of this latter factor to the adherens junctional complex prevents the transcription of mesenchymal genes.
E-钙黏蛋白及其转录抑制因子Snail1（Snai1）是控制上皮表型的两个因子。Snail1的表达促进上皮细胞向间充质细胞的转化，同时伴随着E-钙黏蛋白的下调以及间充质基因（如编码纤连蛋白和LEF1的基因）表达的上调。我们研究了控制这些基因在间充质细胞中表达的分子机制。E-钙黏蛋白的强制表达强烈下调了纤连蛋白和LEF1的RNA水平，表明E-钙黏蛋白敏感因子参与了这些基因的转录。E-钙黏蛋白的过表达降低了纤连蛋白启动子的转录活性，并减少了β-连环蛋白和核因子κB与该启动子的相互作用。通过免疫共沉淀和下拉实验发现，与β-连环蛋白类似，核因子κB与E-钙黏蛋白及其他细胞黏附成分相关。当通过K-ras过表达或使用小干扰RNA耗尽E-钙黏蛋白破坏黏着连接时，核因子κB p65亚基与E-钙黏蛋白或β-连环蛋白的相互作用减少。这些条件并不影响p65与核因子κB抑制剂IκBα的结合。E-钙黏蛋白小干扰RNA诱导的基础和肿瘤坏死因子α刺激的核因子κB转录活性增强，强调了这些结果的功能意义。因此，这些结果表明E-钙黏蛋白不仅控制β-连环蛋白的转录活性，还控制核因子κB的转录活性。它们还表明，后者与黏着连接复合物的结合可阻止间充质基因的转录。
