The cell dissociation and motility triggered by scatter factor/hepatocyte growth factor are mediated through the cytoplasmic domain of the c-Met receptor

Abstract

Scatter factor (SF), which dissociates epithelial cell colonies into individual cells and stimulates the migration of epithelial cells, is identical to hepatocyte growth factor (HGF), a mitogen for melanocytes, endothelial cells and epithelial cells, including hepatocytes. It was previously shown by cDNA transfection that the mitogenic effect of SF/HGF is mediated by activation of the tyrosine phosphorylation of the c-Met receptor (the c-met proto-oncogene product). In this study, we constructed a cDNA encoding a chimeric receptor composed of the extracellular domain of the epidermal growth factor (EGF) receptor and the transmembrane and cytoplasmic domains of the c-Met receptor. We transfected the cDNA into the B16-F1 mouse melanoma cell line to investigate whether the cell dissociation and motility were mediated through this chimeric receptor following ligand stimulation. The chimeric receptor cDNA was expressed in the transfected cells and the protein product was transported to the cell surface in the correct transmembrane orientation. EGF treatment of the chimeric receptor-expressing cells markedly enhanced tyrosine phosphorylation of the chimeric receptor and led to scattered morphology and enhanced motility. This scattered morphology was inhibited by a tyrosine kinase inhibitor. Based on these results, we concluded that the cell dissociation and motility triggered by SF/HGF were mediated through the cytoplasmic domain of the c-Met receptor by activation of its tyrosine kinase. Thus, it is likely that the different biological effects of SF/HGF are mediated by different intracellular signal cascades.