AMPHIBIAN FGF-1 IS STRUCTURALLY AND FUNCTIONALLY SIMILAR TO BUT ANTIGENICALLY DISTINGUISHABLE FROM ITS MAMMALIAN COUNTERPART

Recent studies have shown that fibroblast growth factors (FGF) play an important role in the diverse cellular mechanisms involved with verte brate development, One system which has received a great deal of atten tion is the developing limb in part because of the extensive epithelia l-mesenchymal interactions that take place during this process, Becaus e it closely parallels the developmental process of the limb and is a model for wound repair, the phenomenom of amphibian limb regeneration has been used to investigate the role of FGF in these processes, We ha ve recently reported on the cloning and functional characterization of an FGF receptor (FGFR) isolated from amphibian regenerative tissue, I n this report, we describe the isolation and characterization of an FG F-1 molecule from the newt, Notophthalmus viridescens. Amino acid sequ ence comparisons indicate that the newt FGF-1 exhibits between 79 to 8 3% identity with FGF-1 from mammalian and avian species, The full leng th cDNA of the newt FGF-1 was cloned into a prokaryotic expression vec tor and purified from E. coli. Although the newt FGF-I shares a high d egree of primary amino acid sequence similarity with other FGF-1 molec ules, the recombinant protein was not detected in a Western blot analy sis using a polyclonal antibody directed against mammalian FGF-1, Desp ite the antigenic divergence, the newt FGF-1 was capable of binding to NIH/3T3 and Chinese hamster ovary cells overexpressing mammalian and amphibian FGFRs with dissociation constants comparable to those report ed for mammalian FGF-1. Newt FGF-1 could also be cross-linked to recep tors on the surface of NIH/3T3 cells, In addition, it elicits a mitoge nic response in NIH/3T3 cells indistinguishable from human recombinant FGF-1.