Five FGF receptors with distinct expression patterns

The fibroblast growth factors (FGF) constitute a polypeptide family whose members can interact with cell surface receptors to modulate gene expression for cell proliferation and differentiation. Seven struc­turally related heparin binding FGFs are known. The first discovered members of the family were aFGF and bFGF, also called HBGF-1/ ECGF (heparin binding growth factor/endothelial cell growth factor) and HBGF-2, respectively. The tertiary fold of bFGF is similar to that of interleukin-1 [1–3]. Amino acid sequence analysis demonstrates 55% identity between aFGF and bFGF. Sequence homology and similar biological responses suggest that they are derived from a common ancestral gene. Both aFGF and bFGF also lack an N-terminal signal peptide sequence (Fig. 1) and thus their mechanism of secretion is unknown.