Department of Pathology, Medical College, Nantong University, nantong, Jiangsu, 226011, P.R. China.
Neoplasma. 2011;58(1):65-73.
Until recently, Cip/Kip members were almost solely viewed as nuclear proteins with a principal function of inhibiting cyclin/cyclin dependent kinase (CDK) activity and hence, inhibiting cell cycle progression. P27(Kip1) (hereafter p27) belongs to the Cip/Kip family that binds and inhibits all the cyclin/CDK complexes, thus often referred as a universal CDK inhibitor. However, emerging studies now suggest that Cip/Kip proteins play additional roles outside of the nucleus. Indeed, previous reports have linked p27 to the regulation of actin dynamics and cell migration. In this study, we constructed a model of migration-activated glioma cells by using the migration-stimulating substrate, a kind of ECM, laminin in vitro. Our results present evidence that laminin drives glioma cell migration without altering cell proliferation. Further, actively migrating cells which expressioned high phosphorylation of p27 at Ser10, and induced its cytoplasmic localization. In this process, Jab1 and CRM1 were also involved. Thus phosphorylation of p27 at Ser10 is necessary for both cytoplasmic localization and induction of cell migration. These observations solidified a genetic role of p27 in cell migration and this was independent of cyclin/CDK inhibition. Eventually, we transiently transfected p27S10A into T98G glioma cells, found that overexpression of p27S10A inhibited cell migration but not cell proliferation. These data linked phosphorylation of p27 at Ser10 and cell motility. Therefore, the major phosphorylation site at Ser10 of p27 played a pivotal role in the migration of malignant glioma cells.
直到最近,Cip/Kip 成员几乎被认为是仅存在于细胞核内的蛋白,其主要功能是抑制细胞周期蛋白/细胞周期蛋白依赖性激酶(CDK)的活性,从而抑制细胞周期进程。P27(Kip1)(简称 p27)属于 Cip/Kip 家族,可与所有细胞周期蛋白/CDK 复合物结合并抑制其活性,因此常被称为通用 CDK 抑制剂。然而,目前的研究表明 Cip/Kip 蛋白在核外还具有其他功能。事实上,先前的研究将 p27 与肌动蛋白动态和细胞迁移的调节联系起来。在这项研究中,我们通过使用体外迁移刺激底物即细胞外基质中的层粘连蛋白构建了一个迁移激活的神经胶质瘤细胞模型。我们的结果表明,层粘连蛋白可驱动神经胶质瘤细胞迁移,而不改变细胞增殖。此外,表达高磷酸化 p27 的 Ser10 的活跃迁移细胞,并诱导其细胞质定位。在此过程中,Jab1 和 CRM1 也参与其中。因此,p27 的 Ser10 磷酸化对于细胞质定位和诱导细胞迁移都是必需的。这些观察结果证实了 p27 在细胞迁移中的遗传作用,这与细胞周期蛋白/CDK 抑制无关。最后,我们将 p27S10A 瞬时转染到 T98G 神经胶质瘤细胞中,发现过表达 p27S10A 可抑制细胞迁移,但不抑制细胞增殖。这些数据将 p27 的 Ser10 磷酸化与细胞运动联系起来。因此,p27 的 Ser10 主要磷酸化位点在恶性神经胶质瘤细胞的迁移中起关键作用。
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