A small peptide promotes EphA2 kinase-dependent signaling by stabilizing EphA2 dimers

Background: The EphA2 receptor tyrosine kinase is known to promote cancer cell malignancy in the absence of activation by ephrin ligands. This behavior depends on high EphA2 phosphorylation on Ser897 and low tyrosine phosphorylation, resulting in increased cell migration and invasiveness. We have previously shown that EphA2 forms dimers in the absence of ephrin ligand binding, and that dimerization of unliganded EphA2 can decrease EphA2 Ser897 phosphorylation. We have also identified a small peptide called YSA, which binds EphA2 and competes with the naturally occurring ephrin ligands. Methods: Here, we investigate the effect of YSA on EphA2 dimer stability and EphA2 function using quantitative FRET techniques, Western blotting, and cell motility assays. Results: We find that the YSA peptide stabilizes the EphA2 dimer, increases EphA2 Tyr phosphorylation, and decreases both Ser897 phosphorylation and cell migration. Conclusions: The experiments demonstrate that the small peptide ligand YSA reduces EphA2 Ser897 protumorigenic signaling by stabilizing the EphA2 dimer. General significance: This work is a proof-of-principle demonstration that EphA2 homointeractions in the plasma membrane can be pharmacologically modulated to decrease the pro-tumorigenic signaling of the receptor. (C) 2016 Elsevier B.V. All rights reserved.