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粘着斑形成的时间和空间调节在细胞迁移中发挥着重要作用。我们发现桩蛋白和 pi3OCas 的酪氨酸磷酸化是上皮间质转分化和细胞迁移过程中整合素激活的一个重要事件。 p130^<Cas>的酪氨酸磷酸化已被证明可促进细胞迁移。我们发现，在几种不同的实验细胞系统中，桩蛋白 cc 的酪氨酸磷酸化可减少趋触细胞迁移以及跨细胞侵袭活动，而 p130^<Cas> 的酪氨酸磷酸化则发挥与桩蛋白相反的作用。每个磷酸化无效突变体都充当每个表型的显性失活突变体。此外，我们发现桩蛋白 a 的过度表达降低了 NMuMG 细胞的细胞饱和密度，而 pi30^<Cas> 的过度表达则增加了细胞饱和密度。这些作用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显着改变，细胞也没有发生转化。添加表皮生长因子增加了桩蛋白α-过表达细胞的饱和密度，而在p130^<Cas>-过表达细胞中没有观察到进一步的增加。我们认为桩蛋白 a 和 p130^<Cas> 的酪氨酸磷酸化可能通过不同的信号传导途径对几种整合素介导的细胞事件发挥相反的作用。我们还发现桩蛋白与多个 ARFGAP 结合。 ARFGAP 是细胞内膜运输的调节因子。我们目前从酪氨酸磷酸化及其与 ARFGAP 的相互作用方面分析桩蛋白在细胞迁移活性调节中的作用。

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.