A reaction-diffusion model of basic fibroblast growth factor interactions with cell surface receptors

Area of Science:

• Biochemistry
• Cell Biology
• Mathematical Modeling

Background:

• Basic fibroblast growth factor (FGF-2) is a key angiogenic factor implicated in diseases like cancer and in normal tissue development.
• Despite extensive study, FGF-2 binding kinetics and signaling pathways remain incompletely understood.
• Heparan sulfate proteoglycans (HSPGs) and FGF-2 dimerization are critical but poorly defined aspects of FGF-2 signaling.

Purpose of the Study:

• To elucidate the role of low-affinity HSPGs in FGF-2 signaling.
• To identify the minimal signaling complex responsible for FGF-2 activity.
• To investigate the impact of FGF-2 ligand dimerization on its biological activity.

Main Methods:

• Development of a mathematical model simulating FGF-2 diffusion and ligand-receptor binding kinetics.
• Incorporation of unique features: internalized species degradation, dual ligand binding to FGFR, and FGF-2 dimerization.
• Scaling of all experimental reaction rates and diffusivity values to physiological temperature (37°C).

Main Results:

• FGF-2-induced cellular responses arise from a dynamic interplay of FGF-2/HSPG/FGFR triads and double triads.
• FGF-2-bound HSPGs (FGF-2/HSPG complexes) also contribute to the overall signaling milieu.
• Ligand dimerization was shown to potentially regulate FGF-2 activity by favoring the formation of more stable double triads over less stable triads.

Conclusions:

• The mathematical model provides novel insights into the complex mechanisms governing FGF-2 signaling.
• Heparan sulfate proteoglycans and FGF-2 dimerization are crucial regulators of FGF-2's angiogenic and mitogenic potential.
• Understanding these molecular interactions is vital for developing targeted therapies for FGF-2-related diseases.