Increased Protein Stability of FGF1 Can Compensate for Its Reduced Affinity for Heparin

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...

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Bibliographic Details
Published in:The Journal of biological chemistry 2009-09, Vol.284 (37), p.25388-25403
Main Authors: Zakrzewska, Malgorzata, Wiedlocha, Antoni, Szlachcic, Anna, Krowarsch, Daniel, Otlewski, Jacek, Olsnes, Sjur
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Cell Proliferation
Fibroblast Growth Factor 1 - chemistry
Heparin - chemistry
Humans
Mechanisms of Signal Transduction
Mice
Mutagenesis, Site-Directed
NIH 3T3 Cells
Protein Binding
Protein Conformation
Protein Stability
Receptors, Fibroblast Growth Factor - chemistry
Signal Transduction
Thermodynamics
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Summary: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.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M109.001289