Pratt Stephen J, Epple Holly, Ward Michael, Feng Yunfeng, Braga Vania M, Longmore Gregory D
Department of Medicine, Washington University, St. Louis, MO 63130, USA.
J Cell Biol. 2005 Feb 28;168(5):813-24. doi: 10.1083/jcb.200406083. Epub 2005 Feb 22.
Cell migration requires extension of lamellipodia that are stabilized by formation of adhesive complexes at the leading edge. Both processes are regulated by signaling proteins recruited to nascent adhesive sites that lead to activation of Rho GTPases. The Ajuba/Zyxin family of LIM proteins are components of cellular adhesive complexes. We show that cells from Ajuba null mice are inhibited in their migration, without associated abnormality in adhesion to extracellular matrix proteins, cell spreading, or integrin activation. Lamellipodia production, or function, is defective and there is a selective reduction in the level and tyrosine phosphorylation of FAK, p130Cas, Crk, and Dock180 at nascent focal complexes. In response to migratory cues Rac activation is blunted in Ajuba null cells, as detected biochemically and by FRET analysis. Ajuba associates with the focal adhesion-targeting domain of p130Cas, and rescue experiments suggest that Ajuba acts upstream of p130Cas to localize p130Cas to nascent adhesive sites in migrating cells thereby leading to the activation of Rac.
细胞迁移需要片状伪足的延伸，而片状伪足通过在前缘形成黏附复合物得以稳定。这两个过程均受招募至新生黏附位点的信号蛋白调控，这些信号蛋白会导致Rho GTP酶的激活。Ajuba/LIM蛋白家族是细胞黏附复合物的组成部分。我们发现，来自Ajuba基因敲除小鼠的细胞迁移受到抑制，而其与细胞外基质蛋白的黏附、细胞铺展或整合素激活均无相关异常。片状伪足的产生或功能存在缺陷，并且在新生黏着斑复合物处，FAK、p130Cas、Crk和Dock180的水平及酪氨酸磷酸化水平均有选择性降低。生化检测和荧光共振能量转移分析表明，在迁移信号的作用下，Ajuba基因敲除细胞中的Rac激活减弱。Ajuba与p130Cas的黏着斑靶向结构域相关联，拯救实验表明，Ajuba在p130Cas上游起作用，将p130Cas定位至迁移细胞中的新生黏附位点，从而导致Rac的激活。
