Recombinant human soluble FGFR-4 was fused with the Fc part of human IgG1 and is a
disulfide-linked heterodimeric protein.
Fibroblast growth factors (FGFs) comprise a family of at least eighteen structurally
related proteins that are involved in a multitude of physiological and pathological cellular
processes, including cell growth, differentiation, angiogenesis, wound healing and
tumorgenesis. The biological activities of the FGFs are mediated by a family of type I
transmembrane tyrosine kinases which undergo dimerization and autophosphorylation
after ligand binding.
Four distinct genes encoding closely related FGF receptors, FGF R1 - 4, are known. All
four genes for FGF Rs encode proteins with an N-terminal signal peptide, three
immunoglobulin (Ig)-like domains, an acid-box region containing a run of acidic residues
between the IgI and IgII domains, a transmembrane domain and the split tyrosine-kinase
domain. Multiple forms of FGF R1 - 3 are generated by alternative splicing of the
mRNAs. A frequent splicing event involving FGF R1 and 2 results in receptors containing
all three Ig domains, referred to as the a isoform, or only IgII and IgIII, referred to as the b
isoform. Only the a isoform has been identified for FGF R3 and FGF R4. Additional
splicing events for FGF R1 - 3, involving the C-terminal half of the IgIII domain encoded
by two mutually exclusive alternative exons, generate FGF receptors with alternative IgIII
domains (IIIb and IIIc). A IIIa isoform which is a secreted FGF binding protein containing
only the N-terminal half of the IgIII domain plus some intron sequences has also been
reported for FGF R1. Mutations in FGF R1 - 3 have been found in patients with birth
defects involving craniosynostosis.
