Sustained activation of extracellular signal-regulated kinase stimulated by hepatocyte growth factor leads to integrin alpha(2) expression that is involved in cell scattering

We have previously shown that hepatocyte growth factor (HGF) selectively in creases the expression of integrin alpha (2) in Madin-Darby canine kidney ( MDCK) cells. In this study, we have further investigated the signal transdu ction pathways responsible for the event and its role in HGF-induced cell s cattering. 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 fu nctional blocking antibody against integrin alpha (2) at the concentration of 25 mug/ml partially (40%) inhibited the HGF-induced cell scattering, How ever, in the presence of the specific phosphatidylinositol 3-kinase inhibit or LY294002 or the selective Src family kinase inhibitor PP1, although cell s retained their response to HGF for increasing integrin alpha (2) expressi on, they failed to scatter, indicating that increased expression of integri n alpha (2) alone is not sufficient for cell scattering. Moreover, epiderma l growth factor, which induced a transient (1 h) activation of extracellula r signal-regulated kinase (ERK) in MDCK cells, only slightly increased inte grin alpha (2) expression and failed to trigger cell scattering. Conversely , HGF induced a sustained (at least 12 h) activation of ERK in the cells, E xpression of constitutively active ERK kinase (MEK) in MDCK cells led to in creased expression of integrin alpha (2) even in the absence of HGF stimula tion. In contrast, expression of ERK phosphatase or dominant negative MEK i nhibited HGF-induced integrin alpha (2) expression. Taken together, our res ults suggest that the increased expression of integrin alpha (2)beta (1) by HGF is at least partially required for cell scattering and that the durati on of MEK/ERK activation is likely to be a crucial determinant for cells to activate integrin alpha (2) expression and cell scattering.