Regulation of the Molecular Brake Region in FGFR2 Kinase

Abstract

Unregulated activity of tyrosine kinases (TKS) is responsible for numerous developmental musculoskeletal diseases and cancers. The regulatory mechanisms of tks and how they are affected by point mutations are still in need of elucidation. Fibroblast growth factor receptor (FGFR) kinase is a TK whose regulatory element, the “molecular brake,” is thought to prevent constitutive activation of the receptor, despite not being near the kinase's active site. germline mutations in this “molecular brake” region in FGFR cause musculoskeletal disorders such as craniosynostosis and dwarfism, while somatic mutations can lead to uninhibited cell growth, causing an array of cancers. furthermore, it is thought that the majority of pathogenic activating mutations in protein kinases are in “molecular brake”-like regions. However, the mechanism through which the “molecular brake” of FGFR kinase is disengaged, allowing for signal transduction, is still unknown. using path-based molecular dynamics (MD) simulations, we have shown that the inward motion of the kinase's activation loop upon tyrosine phosphorylation is correlated with disengagement of the “molecular brake.” results of the string method in collective variables, which finds the minimum free energy path connecting the loop-out and loop-in states, indicate found that inward motion of loop occurs within 1 frame of “molecular brake” disengagement. Furthermore, umbrella sampling shows that in loop-out conformations, the disengaged state of the “molecular brake” is less stable, while in loop-in conformations, the disengaged state becomes more stable. Our results suggest that the “molecular brake” is allosterically controlled by the activation loop motion. An understanding of the “molecular brake” disengagement mechanism will provide avenues for targeted therapies to counteract pathologic over-activation of fgfr kinase leading to uncontrolled signal transduction and uninhibited cell growth.