Investigating Impact of Mutations R248C and S249C of FGFR3b on Bladder Cancer: A Computational Approach

Abstract

Genetic alterations in Fibroblast Growth Factor receptor 3 (FGFR3) have well-established contributions for various carcinomas and recently its role in Bladder Cancer has been increasingly reported. Upon activation, FGFR3 phosphorylates various downstream proteins, regulating multiple cellular responses like cell differentiation, proliferation, cell survival, and tumorigenesis. The isoform FGFR3b is most expressed in normal urothelial cells and its genetic aberrations contribute towards urothelial carcinoma. A recurrent theme of mutations is the substitution of an amino acid with Cysteine. Two common examples include the replacement of Arginine with Cysteine and that of Serine with Cysteine at positions 248 and 249 on exon 7 of FGFR3, respectively.

This study was designed to use in silico approach to investigate the impact of R248C and S249C mutations of FGFR3 on the structure and function of the protein along with the effects mutations may cause on the downstream pathways that lead to development of Bladder Cancer. After the sequence retrieval, the wildtype FGFR3b structure was modeled using computational tools, I-TASSER and Phyre2. This was followed by the introduction of mutations in the modeled structure on Dynamut. After structural assessment of the mutated proteins, an in-depth analysis of the interaction of each mutant was carried out with downstream adapter proteins, FRS2 and FRS3, using HADDOCK and PDBSum.

Based on the parameters of molecular flexibility, interatomic interactions, atomic fluctuations and deformation energies, the mutations R248C and S249C introduced into the wildtype structure of FGFR3b came out to be stabilizing (R248C < S249C). When the mutated heterodimers were docked against the downstream adapter proteins, the results indicated a greater stability and higher binding affinity with FRS2 (R248C < S249C) compared to wildtype receptor protein, therefore contributing to carcinogenesis. The results further predicted that the binding affinity between mutated (R248C and S249C) FGFR3b receptor and its downstream adapter FRS3 protein to be weak, but based on the results of the Van der Waal’s energy and insights into the ‘interacting residues’ between the two proteins of the complex, the interactions might be for longer duration, eventually having an oncogenic impact. In conclusion both heterodimer mutations R248C and S249C at exon 7 of FGFR3 are stabilizing and have tumorigenic potential either alone or in combination with other genetic factors, though further investigations are required to have a clear picture.