Heparin Modulates the Mitogenic Activity of Fibroblast Growth Factor by Inducing Dimerization of its Receptor. A 3D View by Using NMR

• Published in: Chembiochem : a European journal of chemical biology Vol. 14; no. 14; pp. 1732 - 1744
• Main Authors: Nieto, Lidia, Canales, Ángeles, Fernández, Israel S., Santillana, Elena, González-Corrochano, Rocío, Redondo-Horcajo, Mariano, Cañada, F. Javier, Nieto, Pedro, Martín-Lomas, Manuel, Giménez-Gallego, Guillermo, Jiménez-Barbero, Jesús
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23.09.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Binding Sites; Cell Line; Dimerization; fibroblast growth factor; fibroblast growth factor receptor; Fibroblast Growth Factors - chemistry; Fibroblast Growth Factors - genetics; Fibroblast Growth Factors - metabolism; Heparan sulfate; heparin; Heparin - metabolism; Heparitin Sulfate - metabolism; Humans; Molecular Dynamics Simulation; molecular recognition; Molecular weight; NMR spectroscopy; Nuclear Magnetic Resonance, Biomolecular; Protein Structure, Tertiary; Receptor, Fibroblast Growth Factor, Type 2 - chemistry; Receptor, Fibroblast Growth Factor, Type 2 - genetics; Receptor, Fibroblast Growth Factor, Type 2 - metabolism; Recombinant Proteins - biosynthesis; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Ultracentrifugation; heparin; molecular recognition; fibroblast growth factor; NMR spectroscopy; fibroblast growth factor receptor
• ISSN: 1439-4227; 1439-7633
• DOI: 10.1002/cbic.201300313

In vitro mitogenesis assays have shown that sulfated glycosaminoglycans (GAGs; heparin and heparan sulfate) cause an enhancement of the mitogenic activity of fibroblast growth factors (FGFs). Herein, we report that the simultaneous presence of FGF and the GAG is not an essential requisite for this event to take place. Indeed, preincubation with heparin (just before FGF addition) of cells lacking heparan sulfate produced an enhancing effect equivalent to that observed when the GAG and the protein are simultaneously added. A first structural characterization of this effect by analytical ultracentrifugation of a soluble preparation of the heparin‐binding domain of fibroblast growth factor receptor 2 (FGFR2) and a low molecular weight (3 kDa) heparin showed that the GAG induces dimerization of FGFR2. To derive a high resolution structural picture of this molecular recognition process, the interactions of a soluble heparin‐binding domain of FGFR2 with two different homogeneous, synthetic, and mitogenically active sulfated GAGs were analyzed by NMR spectroscopy. These studies, assisted by docking protocols and molecular dynamics simulations, have demonstrated that the interactions of these GAGs with the soluble heparin‐binding domain of FGFR induces formation of an FGFR dimer; its architecture is equivalent to that in one of the two distinct crystallographic structures of FGFR in complex with both heparin and FGF1. This preformation of the FGFR dimer (with similar topology to that of the signaling complex) should favor incorporation of the FGF component to form the final assemblage of the signaling complex, without major entropy penalty. This cascade of events is probably at the heart of the observed activating effect of heparin in FGF‐driven mitogenesis. Held together with a hairpin: A structural explanation of the modulation of FGF‐driven mitogenesis by heparin and heparan sulfate is given. Full enhancement occurs when heparin is previously incubated with the receptors, which then dimerize and adopt the relative conformation present in the complete signaling complex.