High-affinity binding sites for related fibroblast growth factor ligands reside within different receptor immunoglobulin-like domains.
Growth factors of the fibroblast growth factor (FGF) family bind receptors whose external domains are organized in a series of immunoglobulin-like loops. We engineered expression constructs in which cDNAs encoding individual immunoglobulin-like domains of the keratinocyte growth factor (KGF/FGF-7) receptor were fused to the mouse immunoglobulin heavy chain Fc domain (HFc). Each chimera was efficiently secreted from NIH 3T3 transfectants and migrated at the predicted molecular mass after SDS/PAGE. Scatchard analysis revealed that the chimera containing immunoglobulin-like domains 2 (D2) and 3 (D3) bound KGF and acidic FGF at high affinities comparable to the native receptor. However, individual immunoglobulin-like domain chimeras demonstrated marked specificity in their ligand interactions. D2-HFc bound acidic FGF at high affinity, whereas it did not detectably interact with KGF. Conversely, D3-HFc bound KGF at high affinity but exhibited no detectable interaction with acidic FGF. Their selective ligand binding properties were confirmed by the specific neutralization of acidic FGF or KGF mitogenic activity using D2 or D3 HFc, respectively. All of these findings establish that the major binding sites for related FGF ligands are localized to distinct receptor immunoglobulin-like domains.
Cheon
H G
HG
Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD 20892.
LaRochelle
W J
WJ
Bottaro
D P
DP
Burgess
W H
WH
Aaronson
S A
SA
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002417:Cattle; D018076:DNA, Complementary / Q000235:genetics; D051526:Fibroblast Growth Factor 10; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D015202:Protein Engineering; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D018076:DNA, Complementary; C496453:FGF7 protein, human; C496454:Fgf7 protein, mouse; D051526:Fibroblast Growth Factor 10; D006133:Growth Substances; D007136:Immunoglobulins; D008024:Ligands; D017468:Receptors, Fibroblast Growth Factor; D017978:Receptors, Growth Factor; D011993:Recombinant Fusion Proteins; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor