Slack J K, Catling A D, Eblen S T, Weber M J, Parsons J T
Department of Microbiology, Health Sciences Center, University of Virginia, Charlottesville, Virginia 22908, USA.
J Biol Chem. 1999 Sep 17;274(38):27177-84. doi: 10.1074/jbc.274.38.27177.
Epidermal growth factor stimulates migration of a number of cell types, yet the signaling pathways that regulate epidermal growth factor-stimulated migration are poorly defined. In this report, we employ a transient transfection migration assay to assess the role of components of the Ras-mitogen-activated protein (MAP) kinase signaling pathway in epidermal growth factor-stimulated chemotaxis of rat embryo fibroblasts. Expression of dominant negative Ras blocks epidermal growth factor-mediated chemotaxis, while constitutively active Ras has no effect on chemokinesis or chemotaxis. PD98059 and U0126, inhibitors of MAP kinase kinase (MEK) activity, decreased epidermal growth factor-stimulated migration, while kinase-defective MEK1, an inhibitor of MAP kinase activation, enhanced migration. To understand the paradoxical effects of these molecules on epidermal growth factor-induced migration, we examined the role of c-Raf on migration. Expression of either wild type c-Raf or the catalytic domain of c-Raf effectively inhibited epidermal growth factor-stimulated cell migration. We suggest that, whereas Ras activity is necessary to promote epidermal growth factor-stimulated migration, sustained activation of c-Raf may be important in down-regulating migratory signaling pathways triggered by epidermal growth factor receptor activation. Further, activation of c-Raf upon inhibition of the MEK-MAP kinase pathway may contribute to the inhibition of cell migration observed with pharmacological MEK inhibitors.
表皮生长因子可刺激多种细胞类型的迁移，然而，调节表皮生长因子刺激迁移的信号通路却尚未明确。在本报告中，我们采用瞬时转染迁移试验来评估Ras-丝裂原活化蛋白（MAP）激酶信号通路的组分在表皮生长因子刺激大鼠胚胎成纤维细胞趋化作用中的作用。显性负性Ras的表达可阻断表皮生长因子介导的趋化作用，而组成型激活的Ras对细胞运动或趋化作用无影响。MAP激酶激酶（MEK）活性抑制剂PD98059和U0126可降低表皮生长因子刺激的迁移，而MAP激酶激活抑制剂激酶缺陷型MEK1则增强迁移。为了解这些分子对表皮生长因子诱导迁移的矛盾作用，我们研究了c-Raf在迁移中的作用。野生型c-Raf或c-Raf催化结构域的表达均有效抑制表皮生长因子刺激的细胞迁移。我们认为，虽然Ras活性对于促进表皮生长因子刺激的迁移是必需的，但c-Raf的持续激活可能在下调由表皮生长因子受体激活触发的迁移信号通路中起重要作用。此外，MEK-MAP激酶途径受抑制时c-Raf的激活可能导致用MEK药理抑制剂观察到的细胞迁移抑制。
