title: Increased protein stability of FGF1 can compensate for its reduced affinity for heparin.
abstract: Human FGF1 (fibroblast growth factor 1) is a powerful signaling molecule with a short half-life in vivo and a denaturation temperature close to physiological. Binding to heparin increases the stability of FGF1 and is believed to be important in the formation of FGF1.fibroblast growth factor receptor (FGFR) active complex. In order to reveal the function of heparin in FGF1.FGFR complex formation and signaling, we constructed several FGF1 variants with reduced affinity for heparin and with diverse stability. We determined their biophysical properties and biological activities as well as their ability to translocate across cellular membranes. Our study showed that increased thermodynamic stability of FGF1 nicely compensates for decreased binding of heparin in FGFR activation, induction of DNA synthesis, and cell proliferation. By stepwise introduction of stabilizing mutations into the K118E (K132E) FGF1 variant that shows reduced affinity for heparin and is inactive in stimulation of DNA synthesis, we were able to restore the full mitogenic activity of this mutant. Our results indicate that the main role of heparin in FGF-induced signaling is to protect this naturally unstable protein against heat and/or proteolytic degradation and that heparin is not essential for a direct FGF1-FGFR interaction and receptor activation.
authors: Centre for Cancer Biomedicine, University of Oslo, and Department of Biochemistry, Institute for Cancer Research, Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway.
authors: Malgorzata
authors: M
authors: Zakrzewska
authors: Antoni
authors: A
authors: Wiedlocha
authors: Anna
authors: A
authors: Szlachcic
authors: Daniel
authors: D
authors: Krowarsch
authors: Jacek
authors: J
authors: Otlewski
authors: Sjur
authors: S
authors: Olsnes
mesh_terms: D000818:Animals; D001665:Binding Sites; D049109:Cell Proliferation; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry*; D006493:Heparin / Q000737:chemistry*; D006801:Humans; D051379:Mice; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D011485:Protein Binding; D011487:Protein Conformation; D055550:Protein Stability; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry*; D015398:Signal Transduction; D013816:Thermodynamics
chemical_list: D017468:Receptors, Fibroblast Growth Factor; D016220:Fibroblast Growth Factor 1; D006493:Heparin