Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, and Department of Surgery, University of Toronto, Toronto, ON M5B 1W8, Canada Department of Immunology, Juntendo University School of Medicine, Tokyo 113-8421, Japan Division of Pediatric Pulmonology, Case Western Reserve University, Cleveland, OH 44106 Laboratory of Tissue Repair and Regeneration, Matrix Dynamics Group, Faculty of Dentistry, University of Toronto, Toronto, ON M5S 3E2, Canada.
Mol Biol Cell. 2013 Nov;24(21):3326-36. doi: 10.1091/mbc.E13-04-0220. Epub 2013 Sep 4.
Induction of epithelial-myofibroblast transition (EMyT), a robust fibrogenic phenotype change hallmarked by α-smooth muscle actin (SMA) expression, requires transforming growth factor-β1 (TGFβ) and the absence/uncoupling of intracellular contacts. This suggests that an "injured" epithelium may be topically susceptible to TGFβ. To explore this concept, we use an epithelial wound model in which intact and contact-deprived regions of the same monolayer can be analyzed simultaneously. We show that TGFβ elicits dramatically different responses at these two loci. SMA expression and initially enhanced nuclear Smad3 accumulation followed by Smad3 mRNA and protein down-regulation occur exclusively at the wound. Mechanistically, three transcriptional coactivators whose localization is regulated by cell contact integrity are critical for these local effects. These are myocardin-related transcription factor (MRTF), the driver of the SMA promoter; β-catenin, which counteracts the known inhibitory effect of Smad3 on MRTF and maintains MRTF protein stability and mRNA expression in the wound; and TAZ, a Hippo effector and Smad3 retention factor. Remarkably, active TAZ stimulates the SMA and suppresses the Smad3 promoter, whereas TAZ silencing prevents wound-restricted expression of SMA and loss of Smad3. Such locus-specific reprogramming might play key roles in wound healing and the susceptibility of the injured epithelium to fibrogenesis.
上皮细胞-肌成纤维细胞转化(EMyT)的诱导是一种强大的纤维生成表型变化,其特征是α-平滑肌肌动蛋白(SMA)的表达,这需要转化生长因子-β1(TGFβ)和细胞内接触的缺失/解耦联。这表明“受伤”的上皮细胞可能容易受到 TGFβ 的影响。为了探索这一概念,我们使用上皮细胞伤口模型,其中可以同时分析同一单层中完整和无接触的区域。我们表明,TGFβ 在这两个部位引起了截然不同的反应。SMA 表达和最初增强的核 Smad3 积累,随后 Smad3 mRNA 和蛋白下调,仅发生在伤口处。从机制上讲,三个转录共激活因子的定位受细胞接触完整性的调节,对于这些局部效应至关重要。这些是肌球蛋白相关转录因子(MRTF),它是 SMA 启动子的驱动子;β-连环蛋白,它抵消了 Smad3 对 MRTF 的已知抑制作用,并维持了伤口中 MRTF 蛋白的稳定性和 mRNA 表达;以及 TAZ,Hippo 效应物和 Smad3 保留因子。值得注意的是,活性 TAZ 刺激 SMA 并抑制 Smad3 启动子,而 TAZ 沉默可防止 SMA 在伤口部位的受限表达和 Smad3 的丢失。这种特定部位的重编程可能在伤口愈合和受伤上皮细胞对纤维化的易感性中发挥关键作用。
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