Integrity of cell-cell contacts is a critical regulator of TGF-β1-induced epithelial-to-myofibroblast transition -: Role for β-catenin
Integrity of cell-cell contacts is a critical regulator of TGF-β1-induced epithelial-to-myofibroblast transition -: Role for β-catenin
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DOI：
10.1016/s0002-9440(10)63247-6
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发表时间：
2004-12-01
影响因子：
6
通讯作者：
Kapus, A
中科院分区：
文献类型：
--
作者：
Masszi, A;Fan, L;Kapus, A
肾小管上皮损伤和 TGF-β1 诱导上皮细胞转化为表达 α-平滑肌肌动蛋白 (SMA) 的肌成纤维细胞是肾纤维化的关键特征。由于损伤会损害细胞间连接并促进纤维化，我们假设细胞接触是 TGF-β1 触发的上皮间质转化 (EMT) 的关键调节因子。在这里，我们表明，TGF-β1 无法在完整的汇合单层中诱导 EMT，但损伤诱导的上皮完整性丧失的三种不同模型（亚汇合、受伤和 Ca2+ 去除造成的接触分解）恢复了其 EMT 诱导作用。这表现为 E-钙粘蛋白的损失、纤连蛋白的产生和 SMA 表达的增加。单独使用 TGF-β1 或接触拆卸只能适度刺激汇合层中的 SNU 启动子，但一起使用时表现出很强的协同作用。由于 β-连环蛋白是完整粘附连接的组成部分，但当从不稳定的接触中释放出来时，可能充当转录共激活剂，因此我们研究了它在 TGF-β1 引发的 EMT 中的作用。单独的接触分解会诱导 E-钙粘蛋白和 β-连环蛋白的降解，但 TGF-β1 选择性地拯救 β-连环蛋白并刺激 β-连环蛋白驱动的报告基因 TopFLASH。此外，游离β-连环蛋白与N-钙粘蛋白胞质尾部的螯合抑制了TGF-β1加接触分解诱导的SMA启动子激活和蛋白表达。这些结果表明，β-连环蛋白依赖性二次打击机制，其中初始上皮损伤和 TGF-β1 都是 EMT 所必需的。
Injury of the tubular epithelium and TGF-beta1-induced conversion of epithelial cells to a-smooth muscle actin (SMA)-expressing myofibroblasts are key features of kidney fibrosis. Since injury damages intercellular junctions and promotes fibrosis, we hypothesized that cell contacts are critical regulators of TGF-beta1-triggered epithelial-to-mesenchymal transition (EMT). Here we show that TGF-beta1 was unable to induce EMT in intact confluent monolayers, but three different models of injury-induced loss of epithelial integrity (subconfluence, wounding, and contact disassembly by Ca2+-removal) restored its EMT-inducing effect. This manifested in loss of E-cadherin, increased fibronectin production and SMA expression. TGF-beta1 or contact disassembly alone only modestly stimulated the SNU promoter in confluent layers, but together exhibited strong synergy. Since beta-catenin is a component of intact adherens junctions, but when liberated from destabilized contacts may act as a transcriptional co-activator, we investigated its role in TGF-beta1-provoked EMT. Contact disassembly alone induced degradation of E-cadherin and beta-catenin, but TGF-beta1 selectively rescued beta-catenin and stimulated the beta-catenin-driven reporter TopFLASH. Moreover, chelation of free beta-catenin with the N-cadherin cytoplasmic tail suppressed the TGF-beta1 plus contact disassembly-induced SMA promoter activation and protein expression. These results suggest a beta-catenin-dependent two-hit mechanism in which both an initial epithelial injury and TGF-beta1 are required for EMT.