Analysis of mutations in fibroblast growth factor (FGF) and a pathogenic mutation in FGF receptor (FGFR) provides direct evidence for the symmetric two-end model for FGFR dimerization.
Two competing models for fibroblast growth factor (FGF) receptor (FGFR) dimerization have recently emerged based on ternary FGF-FGFR-heparin crystal structures. In the symmetric two-end model, heparin promotes dimerization of two FGF-FGFR complexes by stabilizing bivalent interactions of the ligand and receptor through primary and secondary sites and by stabilizing direct receptor-receptor contacts. In the asymmetric model, there are no protein-protein contacts between the two FGF-FGFR complexes, which are bridged solely by heparin. To identify the correct mode of FGFR dimerization, we abolished interactions at the secondary ligand-receptor interaction site, which are observed only in the symmetric two-end model, using site-directed mutagenesis. Cellular studies and real-time binding assays, as well as matrix-assisted laser desorption ionization-time of flight analysis, demonstrate that loss of secondary ligand-receptor interactions results in diminished FGFR activation due to decreased dimerization without affecting FGF-FGFR binding. Additionally, structural and biochemical analysis of an activating FGFR2 mutation resulting in Pfeiffer syndrome confirms the physiological significance of receptor-receptor contacts in the symmetric two-end model and provides a novel mechanism for FGFR gain of function in human skeletal disorders. Taken together, the data validate the symmetric two-end model of FGFR dimerization and argue against the asymmetric model of FGFR dimerization.
Ibrahimi
Omar A
OA
Department of Pharmacology, New York University School of Medicine, New York, NY 10016, USA.
Yeh
Brian K
BK
Eliseenkova
Anna V
AV
Zhang
Fuming
F
Olsen
Shaun K
SK
Igarashi
Makoto
M
Aaronson
Stuart A
SA
Linhardt
Robert J
RJ
Mohammadi
Moosa
M
D000818:Animals; D002478:Cells, Cultured; D019281:Dimerization; D051526:Fibroblast Growth Factor 10; D005346:Fibroblast Growth Factors / Q000235:genetics* / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D020349:Surface Plasmon Resonance
D051526:Fibroblast Growth Factor 10; D017468:Receptors, Fibroblast Growth Factor; D005346:Fibroblast Growth Factors; D006493:Heparin; D051497:Receptor, Fibroblast Growth Factor, Type 2