CIHR Group in Matrix Dynamics, University of Toronto, Toronto, Ontario M5S 3E2, Canada.
J Biol Chem. 2010 Mar 19;285(12):9273-81. doi: 10.1074/jbc.M109.075218. Epub 2010 Jan 13.
The development of fibrosis promotes the differentiation of myofibroblasts, pro-fibrotic cells, which contribute to tissue dysfunction. Myofibroblast differentiation is dependent on actin assembly, which in response to force, is mediated by various actin-binding proteins including the mammalian Diaphanous-related formins (mDia). We examined the role of mDia in the mechano-sensing pathway that leads to force-induced expression of alpha-smooth muscle actin (SMA), a marker and critical determinant of myofibroblast differentiation. In cells treated with siRNA to knockdown mDia and then subjected to tensile force using collagen-coated magnetite beads attached to beta1 integrins, actin assembly was inhibited at bead contact sites. Force-induced nuclear translocation of MRTF-A, a transcriptional co-activator of SMA, was reduced 50% by mDia knockdown. The expression of the transcriptional co-activator of SMA, serum response factor, was reduced by 50% after siRNA knockdown of mDia or by 100% in cells transfected with catalytically inactive mDia. Force-induced activation of the SMA promoter and SMA expression were blocked by knockdown of siRNA of mDia. In anchored collagen gel assays to measure myofibroblast-mediated contraction, knockdown of mDia reduced contraction by 50%. We conclude that mDia plays an important role in the development of force-induced transcriptional activation of SMA and myofibroblast differentiation.
纤维化的发展促进了肌成纤维细胞的分化，即促纤维化细胞，这有助于组织功能障碍。肌成纤维细胞的分化依赖于肌动蛋白的组装，而肌动蛋白的组装在受到力的作用时，是由各种肌动蛋白结合蛋白介导的，包括哺乳动物的 Diaphanous 相关formin（mDia）。我们研究了 mDia 在机械感应途径中的作用，该途径导致力诱导的α-平滑肌肌动蛋白（SMA）表达，SMA 是肌成纤维细胞分化的标志物和关键决定因素。在用 mDia 的 siRNA 处理的细胞中，然后用附着在β1 整合素上的胶原包被的磁铁珠施加张力，在珠接触部位抑制肌动蛋白组装。mDia 敲低可使力诱导的 SMA 转录共激活因子 MRTF-A 的核易位减少 50%。用 mDia 的 siRNA 敲低或用无催化活性的 mDia 转染的细胞中 SMA 的转录共激活因子血清反应因子的表达减少了 50%。mDia 的 siRNA 敲低可阻断力诱导的 SMA 启动子激活和 SMA 表达。在用于测量肌成纤维细胞介导的收缩的锚定胶原凝胶测定中，mDia 的敲低使收缩减少了 50%。我们得出结论，mDia 在力诱导的 SMA 转录激活和肌成纤维细胞分化的发展中发挥重要作用。
