SULFATED OLIGOSACCHARIDES PROMOTE HEPATOCYTE GROWTH-FACTOR ASSOCIATION AND GOVERN ITS MITOGENIC ACTIVITY

Hepatocyte growth factor (HGF) is a potent mitogen, motogen, and morph ogen for various epithelial cell types. The pleiotropic effects of HGF are mediated by its binding to a specific high affinity receptor, c-M et. In addition, HGF binds to heparan sulfate proteoglycans on cell su rfaces and within the extracellular matrix. Incubation of HGF with 0.1 , 1.0, and 10 mu g/ml of heparin, heparan sulfate, or dextran sulfate resulted in a concentration-dependent increase in mitogenic potency in a primary rat hepatocyte bioassay, whereas sodium sulfate or fucoidan did not. Although co-incubation of HGF with sulfated compounds that e nhanced HGF-dependent mitogenesis did not alter the binding isotherm o f HGF for the c-Met receptor in a solid phase assay, an increase in au tophosphorylation of the c-Met receptor in intact A549 cells was obser ved upon their addition. A series of chemically sulfated malto oligosa ccharides varying in unit size and charge was tested in the bioassay i n order to provide additional insights into the nature of the HGF-hepa rin interaction. While sulfated di-, tri-, tetra-, and pentasaccharide s did not significantly potentiate HGF-dependent mitogenesis, larger o ligosaccharides such as the sulfated hexa-, hepta-, or a sulfated olig osaccharide mixture containing decasaccharides resulted in an approxim ate 2-, 4-, and 7-fold enhancement, respectively. We observed a correl ation between the sulfated oligosaccharide preparations that enhanced mitogenic potency and those that promoted HGF oligomerization in vitro , as measured by gel filtration and analytical ultracentrifugation. Th ese findings indicate that heparin-like molecules can stabilize HGF ol igomers, which may facilitate c-Met receptor dimerization and activati on.