Characterization of fibroblast growth factor-6 expressed by Chinese hamster ovary cells as a glycosylated mitogen for human vascular endothelial cells

The gene for fibroblast growth factor (FGF)-6/hst-2 was originally identifi ed by its close homology with the FGF-4/hst-1 gene. Aside from its ability to transform cultured fibroblasts, the characteristics of FGF-6 protein hav e only been studied using a simple preparation from E. coli, In the present study, we expressed FGF-6 cDNA in CHO cells and characterized the resultan t protein. We found that CHO cells secreted several forms of the FGF-6 poly peptide, and that there were multiple N-terminal modifications. The longest form (18-kDa) contained the sequence, SerProAlaGlyAlaArg, as its N-terminu s, which was consistent with the signal peptide cleavage site predicted fro m its primary structure. The core polypeptide was primarily modified by het erogeneous N-glycans that were sialylated to a small degree; among them, bi antennary structures were found to predominate. Moreover, possible O-glycos ylation was also detected. N-glycosylated FGF-6 potently induced DNA synthe sis and proliferation of human vascular endothelial cells, whereas in the a bsence of N-glycosylation, FGF-6 mitogenicity was substantially diminished. The results clearly indicate that FGF-6 expressed by mammalian cells is a glycosylated mitogen for vascular endothelial cells and further suggests th at N-glycosylation plays a key role in determining the mitogenicity of FGF- 6.