Reciprocal regulation of the Fibroblast Growth Factor Receptor 2 (FGFR2) and the Transient Receptor Potential Ankyrin 1 (TRPA1) through their direct interaction

Tyrosine Kinase Receptors (RTKs) regulate fundamental cellular processes including cell proliferation, survival and invasion and thus, dysregulation of their activation is implicated in human malignancies. The canonical mechanism of activation is initiated by receptor activation through ligand-induced dimerization, and autophosphorylation of key tyrosine residues along the C-terminal cytoplasmic domain. It has been demonstrated in the past that FGFR2, an RTK, can dimerise in the absence of ligand resulting in signal activation or inhibition depending on the equilibrium of C-terminal-binding proteins i.e. GRB2 and PLCγ1. This study provided the first indication of a novel direct interaction between FGFR2 and a non-selective cation channel, TRPA1, through the C-terminal domain of FGFR2 and the Ankyrin repeat domain of TRPA1. The interaction was studied by protein interaction techniques in an overexpression system. The FGFR2-TRPA1 complex was also detected in a human lung adenocarcinoma cell line suggesting a possible implication in cancer.
The regulatory effect of TRPA1 on FGFR2 was also investigated. In basal conditions, the interaction with TRPA1 exhibits an inhibitory effect on FGFR2 autophosphorylation which results in downstream PLCγ1 pathway inhibition. Co-immunoprecipitation experiments revealed a decrease in PLCγ1 binding to FGFR2 in the presence of TRPA1 explaining the reduction in the PLCγ1 pathway activation. Upon stimulating conditions, TRPA1-mediated receptor inhibition is raised, as shown by increase in p-FGFR2 however, binding of PLCγ1 to the C-terminal of FGFR2 is still impeded. Finally, a model of TRPA1-mediated regulation of the FGFR2 signalling was proposed in which TRPA1 prevents aberrant basal stimulation of the receptor while maintaining PLCγ1 pathway inhibition even in the presence of ligand. These findings provided the first evidence of direct interaction between an RTK and a TRP channel as well as proposed a novel regulatory mechanism of FGFR2 signalling that can facilitate in the development of therapeutic strategies for FGFR2-related diseases.