Sustained activation of extracellular signal-regulated kinase stimulated by hepatocyte growth factor leads to integrin α2 expression that is involved in cell scattering

We have previously shown that hepatocyte growth factor (HGF) selectively increases the expression of integrin alpha (2) in Madin-Darby canine kidney (MDCK) cells. In this study, we have further investigated the signal transduction pathways responsible for the event and its role in HGF-induced cell scattering. We found that the level of integrin alpha (2)beta (1) expression induced by HGF correlated with the extent of cell scattering and that a functional blocking antibody against integrin alpha (2) at the concentration of 25 mug/ml partially (40%) inhibited the HGF-induced cell scattering, However, in the presence of the specific phosphatidylinositol 3-kinase inhibitor LY294002 or the selective Src family kinase inhibitor PP1, although cells retained their response to HGF for increasing integrin alpha (2) expression, they failed to scatter, indicating that increased expression of integrin alpha (2) alone is not sufficient for cell scattering. Moreover, epidermal growth factor, which induced a transient (1 h) activation of extracellular signal-regulated kinase (ERK) in MDCK cells, only slightly increased integrin alpha (2) expression and failed to trigger cell scattering. Conversely, HGF induced a sustained (at least 12 h) activation of ERK in the cells, Expression of constitutively active ERK kinase (MEK) in MDCK cells led to increased expression of integrin alpha (2) even in the absence of HGF stimulation. In contrast, expression of ERK phosphatase or dominant negative MEK inhibited HGF-induced integrin alpha (2) expression. Taken together, our results suggest that the increased expression of integrin alpha (2)beta (1) by HGF is at least partially required for cell scattering and that the duration of MEK/ERK activation is likely to be a crucial determinant for cells to activate integrin alpha (2) expression and cell scattering.