Mishima Wataru, Suzuki Atsushi, Yamaji Satoshi, Yoshimi Ryusuke, Ueda Atsuhisa, Kaneko Takeshi, Tanaka Junko, Miwa Yoshihiro, Ohno Shigeo, Ishigatsubo Yoshiaki
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura Kanazawa-ku, Yokohama 236-0004 Japan.
Genes Cells. 2004 Mar;9(3):193-204. doi: 10.1111/j.1356-9597.2004.00717.x.
Rho GTPases, Cdc42 and Rac1, play pivotal roles in cell migration by efficiently integrating cell-substrate adhesion and actin polymerization. Although it has been suggested that integrins stimulate these Rho GTPases via some of integrin binding proteins such as focal adhesion kinase (FAK) and paxillin, the precise molecular mechanism is largely unknown. In this study, we showed that the over-expression of RP1 corresponding to the first CH domain (CH1) of affixin, an integrin-linked kinase (ILK)-binding protein, induced a significant actin reorganization in MDCK cells by activating Cdc42/Rac1. Affixin full length and RP1 co-immunoprecipitated with alphaPIX, a Cdc42/Rac1-specific guanine nucleotide exchanging factor (GEF), and they co-localized at the tips of lamellipodia in motile cells. The involvement of alphaPIX in the RP1-induced Cdc42 activation was demonstrated by the significant dominant negative effect of a point mutant of alphaPIX, alphaPIX (L383R, L384S), lacking GEF activity. Our data strongly support that ILK and affixin provide a novel signalling pathway that links integrin signalling to Cdc42/Rac1 activation.
Rho GTP酶、Cdc42和Rac1通过有效整合细胞-基质黏附与肌动蛋白聚合作用，在细胞迁移中发挥关键作用。尽管有人提出整合素通过一些整合素结合蛋白（如黏着斑激酶（FAK）和桩蛋白）刺激这些Rho GTP酶，但其精确的分子机制仍 largely未知。在本研究中，我们发现对应于附着蛋白（一种整合素连接激酶（ILK）结合蛋白）第一个CH结构域（CH1）的RP1过表达，通过激活Cdc42/Rac1在MDCK细胞中诱导了显著的肌动蛋白重组。附着蛋白全长和RP1与αPIX（一种Cdc42/Rac1特异性鸟嘌呤核苷酸交换因子（GEF））共免疫沉淀，并且它们在运动细胞的片状伪足尖端共定位。缺乏GEF活性的αPIX点突变体αPIX（L383R，L384S）的显著显性负效应证明了αPIX参与RP1诱导的Cdc42激活。我们的数据有力支持ILK和附着蛋白提供了一条将整合素信号传导与Cdc42/Rac1激活联系起来的新信号通路。
