ACTIVATION OF THE 41 43 KDA MITOGEN-ACTIVATED PROTEIN-KINASE SIGNALING PATHWAY IS REQUIRED FOR HEPATOCYTE GROWTH FACTOR-INDUCED CELL SCATTERING/

Hepatocyte growth factor (HGF) markedly induced the spreading, dissoci ation and scattering of Madin-Darby canine kidney epithelial cells (MD CK) and human stomach adenocarcinoma cells (TMK1). Scattering of MDCK and TMK1 cells was induced by 12-O-tetradecanoyl-phorbol-13-acetate (P MA) and epidermal growth factor (EGF), respectively. In all these agen t-stimulated cells, rapid activation of Raf-l, MAP kinase/ERK kinase ( MEK), 41/43 kDa MAP kinases and p90(rsk) was commonly observed. In con trast, PMA neither induced the scattering nor activation of all these kinases in TMK1 cells. Pretreatment of MDCK and TMK1 cells with 2-(2-a mino-3-methoxyphenyl) choromone (AMPC), a specific inhibitor of MEK, s electively inhibited the HGF-, PMA- and EGF-stimulated activities of M EM, 41/43 kDa MAP kinases and p90(rsk) in a dose dependent manner. AMP C-pretreatment, however, did not affect HGF-, PMA- or EGF-induced acti vation of Raf-l, nor HGF-induced activation of phosphatidylinositol 3- kinase in these cells. Importantly, HGF-, PMA- and EGF-induced scatter ing of MDCK and TMK1 cells was inhibited at doses of AMPC similar to t hose that gave comparable levels of inhibition of the activities of ME R, 41/43 kDa MAP kinases and p90(rsk), These results suggest that acti vation of the 41/43 kDa MAP kinase signaling pathway is required for t he motility response of MDCK and TMK1 cells induced by agents such as HGF, PMA and EGF.