cDNA cloning and expression of a human FGF receptor which binds acidic and basic FGF

We have isolated and characterized a cDNA clone, phFGFR, encoding a human fibroblast growth factor (FGF) receptor. phFGFR contains an open reading frame which encodes an 820 amino acid polypeptide with three immunoglobulin-like domains in the extracellular part and an intracellular split tyrosine kinase domain. Transient expression in COS-1 cells and immunoprecipitation using an antiserum raised against a C-terminal peptide, gave rise to two components, representing mature (130 kDa) and precursor (115 kDa) forms of the phFGFR encoded polypeptide, which was denoted hFGFR-1. Crosslinking of iodinated acidic FGF (aFGF) and basic FGF (bFGF) to transiently expressing COS-1 cells revealed a major band of 95 kDa, which was competed for by both aFGF and bFGF. From Scatchard analyses, the Kd:s for binding of aFGF and bFGF to hFGFR-1 were estimated to 25 pM and 41 pM, respectively. Thus, phFGFR encodes a human FGF receptor with high affinity for both aFGF and bFGF.