Activation of the 41/43 kDa mitogen-activated protein kinase signaling pathway is required for hepatocyte growth factor-induced cell scattering

Abstract

Hepatocyte growth factor (HGF) markedly induced the spreading, dissociation and scattering of Madin ± Darby canine kidney epithelial cells (MDCK) and human stomach adenocarcinoma cells (TMK1). Scattering of MDCK and TMK1 cells was induced by 12-Otetradecanoyl-phorbol-13-acetate (PMA) and epidermal growth factor (EGF), respectively. In all these agentstimulated cells, rapid activation of Raf-1, MAP kinase/ ERK kinase (MEK), 41/43 kDa MAP kinases and p90 rsk was commonly observed. In contrast, PMA neither induced the scattering nor activation of all these kinases in TMK1 cells. Pretreatment of MDCK and TMK1 cells with 2-(2-amino-3-methoxyphenyl) choromone (AMPC), a speci®c inhibitor of MEK, selectively inhibited the HGF-, PMA-and EGF-stimulated activities of MEK, 41/43 kDa MAP kinases and p90 rsk in a dose dependent manner. AMPC-pretreatment, however, did not aect HGF-, PMA-or EGF-induced activation of Raf-1, nor HGF-induced activation of phosphatidylinositol 3-kinase in these cells. Importantly, HGF-, PMA-and EGFinduced scattering of MDCK and TMK1 cells was inhibited at doses of AMPC similar to those that gave comparable levels of inhibition of the activities of MEK, 41/43 kDa MAP kinases and p90 rsk . These results suggest that activation of the 41/43 kDa MAP kinase signaling pathway is required for the motility response of MDCK and TMK1 cells induced by agents such as HGF, PMA and EGF.

Constitutive activation of the 41-/43-kDa mitogen-activated protein kinase signaling pathway in human tumors

“…The activation of 41-/43-kDa MAP kinases was accompanied by the activation of Raf-1 in the majority of tumor cells and was completely associated with the activation of MEK and of p90 rsk in all the tumor cell lines examined. We also determined the activities of Raf-1 and p90 rsk by an in vitro kinase assay of the (Tanimura et al, 1998), and obtained essentially the same results as those shown in Figure 3 (data not shown). Furthermore, the constitutive activation of MAP kinases was always associated with the constitutive activation of MEK in all the primary tumor samples analysed (Figure 2).…”

Rap1 Regulates E-cadherin-mediated Cell-Cell Adhesion

“…The mechanism by which Rap1 induces this epithelial reversion is not clear. Oncogenic Ras induces a fibroblastic phenotype at least in part by the disruption of adherens junctions (AJs), a process that is mediated by mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK) (33,34). Rap1 was first identified as a suppressor of the Ras-transformed phenotype of fibroblasts (2).…”

Suppression of Adriamycin-induced Apoptosis by Sustained Activation of the Phosphatidylinositol-3′-OH kinase-Akt Pathway

“…PI3-K Activity Assay-PI3-K activity was examined according to the method of Tanimura et al (39). Briefly, MKN74 cells were seeded at a density of 9.…”

“…The EGF receptor also has tyrosine kinase activity, and its autophosphorylated tyrosine residues are associated with signaling molecules such as phospholipase C␥, Shc, and Gab1 (32)(33)(34)(35)(36). Although receptors for both HGF/SF and EGF seem to be able to activate common signaling pathways, such as PI3-K and Ras-mitogen-activated protein (MAP) kinase pathways (37)(38)(39)(40)(41)(42), the set of pathways activated in response to HGF/SF or EGF depends on the individual systems used for experiments.…”