Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.
J Cell Sci. 2012 Oct 15;125(Pt 20):4853-64. doi: 10.1242/jcs.108910. Epub 2012 Aug 1.
Hepatocyte growth factor/scatter factor (HGF) is unique by inducing epithelial cell scattering, a cellular event pivotal to HGF-mediated invasive-growth response essential for embryonic development and metastasis. Krüppel-like factor 4 (KLF4) is a multifunctional zinc-finger transcription factor involved in cell proliferation, differentiation and self-renewal. We herein present the first evidence for the functional connection between KLF4 and HGF-induced cell scattering. In particular, we found that KLF4 was upregulated by HGF in two independent epithelial cell types, HepG2 and MDCK, whereas KLF4 knockdown inhibited HGF-induced E-cadherin suppression and cell scattering. Moreover, enforced nuclear KLF4 expression alone was sufficient to upregulate KLF4, downregulate E-cadherin and trigger scattering. Chromatin immunoprecipitation (ChIP) analysis further revealed that KLF4 induced suppression of E-cadherin transcription by directly binding to the E-cadherin promoter. Additionally, we proved that HGF-induced upregulation of KLF4 transcription and cell scattering require activation of the MEK/ERK signaling pathway and the induction of early growth response 1 (EGR-1). At the mechanistic level, ChIP analysis validated a direct binding of EGR-1 to the KLF4 promoter to induce KLF4 transcription; in turn, EGR-1-induced KLF4 binds to its own promoter, thus creating a positive feedback mechanism to sustain KLF4 expression and the resultant cell scattering. We conclude that KLF4 upregulation by HGF represents a novel mechanism mediating HGF-induced cell scattering and perhaps other associated events such as cell migration and invasion.
肝细胞生长因子/分散因子（HGF）通过诱导上皮细胞分散而独具特色，这是一种对 HGF 介导的侵袭性生长反应至关重要的细胞事件，对胚胎发育和转移至关重要。Krüppel 样因子 4（KLF4）是一种多功能锌指转录因子，参与细胞增殖、分化和自我更新。我们在此首次证明了 KLF4 与 HGF 诱导的细胞分散之间的功能联系。特别是，我们发现 HGF 在两种独立的上皮细胞类型 HepG2 和 MDCK 中上调 KLF4，而 KLF4 敲低抑制了 HGF 诱导的 E-钙粘蛋白抑制和细胞分散。此外，强制核 KLF4 表达本身足以上调 KLF4、下调 E-钙粘蛋白并引发分散。染色质免疫沉淀（ChIP）分析进一步表明，KLF4 通过直接结合 E-钙粘蛋白启动子诱导 E-钙粘蛋白转录的抑制。此外，我们证明 HGF 诱导的 KLF4 转录上调和细胞分散需要激活 MEK/ERK 信号通路和早期生长反应 1（EGR-1）的诱导。在机制水平上，ChIP 分析验证了 EGR-1 与 KLF4 启动子的直接结合以诱导 KLF4 转录；反过来，EGR-1 诱导的 KLF4 结合其自身的启动子，从而建立一个正反馈机制来维持 KLF4 表达和由此产生的细胞分散。我们得出结论，HGF 上调 KLF4 代表了一种介导 HGF 诱导的细胞分散的新机制，也许还有其他相关事件，如细胞迁移和侵袭。
