Reduced binding of FGF1 to mutant fibroblast growth factor receptor 3

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Activating mutations in fibroblast growth factor receptor 3 (FGFR3) are linked to severe developmental disorders like thanatophoric dysplasia type I (TD1) and achondroplasia (ACH).
• The D2-D3 linker region of FGFR3 is crucial for its function, and specific mutations within this region can lead to disease.
• FGFR3 mutations are also implicated in various cancers.

Purpose of the Study:

• To investigate the functional consequences of specific FGFR3 mutations, R242C and G374R, on the binding affinity to fibroblast growth factor 1 (FGF1).
• To elucidate the role of the FGFR3 D2-D3 linker region in ligand binding and receptor conformation.

Main Methods:

• Introduction of human orthologous mutations (R248C and G380R) into murine FGFR3, creating R242C and G374R mutants.
• Assessment of FGF1 (16 kDa and 18 kDa forms) binding to wild-type and mutant FGFR3 in cell-free and cellular systems.

Main Results:

• The FGFR3-R242C mutant showed a significant reduction in FGF1 binding, emphasizing the D2-D3 linker's importance for ligand affinity.
• The FGFR3-G374R mutant exhibited normal FGF1 binding in vitro but reduced binding in living cells, suggesting subtle conformational changes at the cell surface.

Conclusions:

• The D2-D3 linker region of FGFR3 plays a critical role in determining the binding affinity for FGF1.
• Minor conformational alterations in FGFR3, as seen in the G374R mutant, can lead to functionally relevant changes in ligand binding within a cellular context.