Institute of Carcinogenesis, N.N. Blokhin National Medical Research Center of Oncology, 115478 Moscow, Russia.
Cells. 2020 Feb 29;9(3):578. doi: 10.3390/cells9030578.
Epithelial-mesenchymal transition (EMT) plays an important role in development and also in initiation of metastasis during cancer. Disruption of cell-cell contacts during EMT allowing cells to detach from and migrate away from their neighbors remains poorly understood. Using immunofluorescent staining and live-cell imaging, we analyzed early events during EMT induced by epidermal growth factor (EGF) in IAR-20 normal epithelial cells. Control cells demonstrated stable adherens junctions (AJs) and robust contact paralysis, whereas addition of EGF caused rapid dynamic changes at the cell-cell boundaries: fragmentation of the circumferential actin bundle, assembly of actin network in lamellipodia, and retrograde flow. Simultaneously, an actin-binding protein EPLIN was phosphorylated, which may have decreased the stability of the circumferential actin bundle. Addition of EGF caused gradual replacement of linear E-cadherin-based AJs with dynamic and unstable punctate AJs, which, unlike linear AJs, colocalized with the mechanosensitive protein zyxin, confirming generation of centripetal force at the sites of cell-cell contacts during EMT. Our data show that early EMT promotes heightened dynamics at the cell-cell boundaries-replacement of stable AJs and actin structures with dynamic ones-which results in overall weakening of cell-cell adhesion, thus priming the cells for front-rear polarization and eventual migration.
上皮-间充质转化 (EMT) 在发育过程中起着重要作用,也在癌症转移的起始过程中起着重要作用。EMT 过程中细胞-细胞接触的破坏允许细胞从其相邻细胞上脱离并迁移,其机制仍知之甚少。本研究使用免疫荧光染色和活细胞成像,分析了表皮生长因子 (EGF) 在 IAR-20 正常上皮细胞中诱导 EMT 过程中的早期事件。对照组细胞表现出稳定的黏着连接 (AJ) 和强大的接触麻痹,而 EGF 的添加导致细胞-细胞边界的快速动态变化:环行肌动蛋白束的碎片化、片状伪足中的肌动蛋白网络组装和逆行流动。同时,肌动蛋白结合蛋白 EPLIN 被磷酸化,这可能降低了环行肌动蛋白束的稳定性。EGF 的添加导致基于线性 E-钙黏蛋白的 AJ 逐渐被动态和不稳定的点状 AJ 取代,与线性 AJ 不同,点状 AJ 与机械敏感蛋白 zyxin 共定位,这证实了 EMT 过程中在细胞-细胞接触部位产生了向心的力。我们的数据表明,早期 EMT 促进了细胞-细胞边界处的动态性增加——用动态的 AJ 和肌动蛋白结构取代稳定的 AJ 和肌动蛋白结构——这导致细胞-细胞黏附的整体减弱,从而为细胞的前后极化和最终迁移做好准备。