Role of paxillin isoforms and their tyrosine phosphorylation in cell migration.

基于肌动蛋白的细胞骨架组织和局灶黏附形成的时空调控在细胞迁移中起着至关重要的作用。我们发现paxillin和pi3OCas的酪氨酸磷酸化是在上皮-间质转分化和细胞迁移过程中整合素激活的重要事件。酪氨酸磷酸化p130^<Cas>已被证明促进细胞迁移。我们发现paxillin cc的酪氨酸磷酸化在几种不同的实验细胞系统中可减少触致细胞迁移和跨细胞侵袭活动，而p130^<Cas>的酪氨酸磷酸化则与paxillina的作用相反。每个磷酸化零突变体在每种表型中都表现为显性阴性。此外，我们发现过表达paxillin a降低了NMuMG细胞的细胞饱和密度，而过表达pi30^< cas>增加了细胞饱和密度。这些影响似乎也依赖于酪氨酸磷酸化事件。生长期的细胞生长速率和形态没有明显改变，细胞也没有转化。表皮生长因子的加入增加了paxillin α-过表达细胞的饱和密度，而p130^<Cas>-过表达细胞的饱和密度未见进一步增加。我们认为paxillin a和p130^<Cas>的酪氨酸磷酸化可能通过不同的信号通路对整合素介导的一些细胞事件产生相反的影响。我们还发现paxillin与几个arfgap结合。ARFGAPs是细胞膜内运输的调节因子。我们目前从其酪氨酸磷酸化及其与ARFGAPs的相互作用方面分析了paxillin在调节细胞迁移活性中的作用。

Temporal and spatial regulation of actin-based cytoskeletal organization and focal adhesion formation play an essential role in cell migration. We found that tyrosine phosphorylation of paxillin and pi3OCas was a prominent event upon integrin activation during epithelial-mesenchymal transdifferentiation and cell migration. Tyrosine phosphorylation of p130^<Cas> has been demonstrated to facilitate cell migration. We showed that tyrosine phosphorylation of paxillin cc acts to reduce haptotactic cell migration as well as transcellular invasive activities in several different experimental cell systems, whereas tyrosine phosphorylation of p130^<Cas> exerts opposing effects to those of paxillina. Each of the phosphorylation-null mutant acted as dominant-negatives for each phenotype. Moreover, we found that overexpression of paxillin a reduced the cell saturation density of NMuMG cells while overexpression of pi30^<Cas> increased it. These effects also seemed to be dependent on the tyrosine phosphorylation events. Cell growth rates and morphologies at growing phases were not significantly altered, nor were cells transformed. Addition of epidermal growth factor increased saturation density of the paxillin α-overexpressing cells, while no further increment was observed in p130^<Cas>-overexpressing cells. We propose that tyrosine phosphorylation of paxillin a and p130^<Cas> exert opposing effects on several integrin-mediated cellular events, possibly through different signaling pathways. We also found that paxillin binds to several ARFGAPs. ARFGAPs are regulators of intracellular membrane trafficking. We currently analysing role of paxillin from aspects of its tyrosine phosphorylation and its interaction with ARFGAPs, in regulation of cell migratory activity.