Ramesh Narayanaswamy, Massaad Michel J, Kumar Lalit, Koduru Suresh, Sasahara Yoji, Anton Ines, Bhasin Manoj, Libermann Towia, Geha Raif
Mol Cell Biol. 2014 Jul;34(14):2600-10. doi: 10.1128/MCB.00017-14.
The actin cytoskeleton is essential for cell adhesion and migration, functions important for tumor invasion. In addition to binding N-WASP/WASP, WIP binds and stabilizes F-actin. WIP(-/-) fibroblasts were used to test the role of WIP in F-actin function. WIP(-/-) cells had defective focal adhesion (FA), stress fiber assembly, and adherence to substrates, functions that were restored by transduction of wild-type WIP. Protein and mRNA levels of several FA constituents regulated by the myocardin-related transcription factor (MRTF)–serum response factor (SRF) transcription factor complex were reduced in WIP(-/-) fibroblasts. The level of G-actin, which sequesters MRTF in the cytoplasm, was increased, and nuclear localization of MRTF-A and SRF was reduced, in WIP(-/-) fibroblasts. Transfection of an MRTF-A mutant that constitutively translocates to the nucleus or transfection of constitutively active SRF restored FA and stress fiber assembly. Fibroblasts from knock-in mice expressing a WIP mutant that fails to bind actin phenocopied WIP(-/-) fibroblasts. Thus, WIP is a novel regulator of FA assembly and cell adhesion.
肌动蛋白细胞骨架对于细胞黏附和迁移至关重要,而细胞黏附和迁移是肿瘤侵袭的重要功能。除了结合N-WASP/WASP外,WIP还能结合并稳定F-肌动蛋白。利用WIP(-/-)成纤维细胞来测试WIP在F-肌动蛋白功能中的作用。WIP(-/-)细胞的粘着斑(FA)、应力纤维组装以及对底物的粘附存在缺陷,而转导野生型WIP可恢复这些功能。在WIP(-/-)成纤维细胞中,由心肌素相关转录因子(MRTF)-血清反应因子(SRF)转录因子复合物调控的几种FA成分的蛋白质和mRNA水平降低。在WIP(-/-)成纤维细胞中,将MRTF隔离在细胞质中的G-肌动蛋白水平升高,MRTF-A和SRF的核定位降低。转染组成型易位至细胞核的MRTF-A突变体或转染组成型活性SRF可恢复FA和应力纤维组装。表达无法结合肌动蛋白的WIP突变体的敲入小鼠的成纤维细胞表现出与WIP(-/-)成纤维细胞相似的表型。因此,WIP是FA组装和细胞黏附的新型调节因子。