Identification of residues important both for primary receptor binding and specificity in fibroblast growth factor-7.
Fibroblast growth factors (FGFs) mediate a multitude of physiological and pathological processes by activating a family of tyrosine kinase receptors (FGFRs). Each FGFR binds to a unique subset of FGFs and ligand binding specificity is essential in regulating FGF activity. FGF-7 recognizes one FGFR isoform known as the FGFR2 IIIb isoform or keratinocyte growth factor receptor (KGFR), whereas FGF-2 binds well to FGFR1, FGFR2, and FGFR4 but interacts poorly with KGFR. Previously, mutations in FGF-2 identified a set of residues that are important for high affinity receptor binding, known as the primary receptor-binding site. FGF-7 contains this primary site as well as a region that restricts interaction with FGFR1. The sequences that confer on FGF-7 its specific binding to KGFR have not been identified. By utilizing domain swapping and site-directed mutagenesis we have found that the loop connecting the beta4-beta5 strands of FGF-7 contributes to high affinity receptor binding and is critical for KGFR recognition. Replacement of this loop with the homologous loop from FGF-2 dramatically reduced both the affinity of FGF-7 for KGFR and its biological potency but did not result in the ability to bind FGFR1. Point mutations in residues comprising this loop of FGF-7 reduced both binding affinity and biological potency. The reciprocal loop replacement mutant (FGF2-L4/7) retained FGF-2 like affinity for FGFR1 and for KGFR. Our results show that topologically similar regions in these two FGFs have different roles in regulating receptor binding specificity and suggest that specificity may require the concerted action of distinct regions of an FGF.
Sher
I
I
Department of Biology and Department of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Lang
T
T
Lubinsky-Mink
S
S
Kuhn
J
J
Adir
N
N
Chatterjee
S
S
Schomburg
D
D
Ron
D
D
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002942:Circular Dichroism; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D016220:Fibroblast Growth Factor 1; D051526:Fibroblast Growth Factor 10; D016222:Fibroblast Growth Factor 2 / Q000737:chemistry / Q000378:metabolism; D051518:Fibroblast Growth Factor 3; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors / Q000737:chemistry / Q000378:metabolism; D006133:Growth Substances / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D008024:Ligands; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011485:Protein Binding; D020033:Protein Isoforms; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013696:Temperature
D016895:Culture Media, Serum-Free; C496444:FGF3 protein, human; C496453:FGF7 protein, human; C489197:Fgf3 protein, mouse; C496454:Fgf7 protein, mouse; D051526:Fibroblast Growth Factor 10; D051518:Fibroblast Growth Factor 3; D006133:Growth Substances; D008024:Ligands; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D017468:Receptors, Fibroblast Growth Factor; D017978:Receptors, Growth Factor; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor