Affinity and Stoichiometry of E-cadherin/EGFR Complexes-relevance to Proliferation and Force Transduction

Abstract

This study investigated the molecular mechanism of E-cadherin association with the epidermal growth factor receptor (EGFR) at cell surfaces. Cross talk between EGFR and the adhesion protein, epithelial E-cadherin is well known to regulate contact inhibited proliferation in epithelia. In addition, E-cadherin-mediated force transduction signaling involves EGF-dependent, EGFR activation. Despite biochemical evidence that E-cadherin and EGFR form hetero complexes, we do not know which protein domains mediate the association, the receptor binding affinity, or the complex stoichiometry. Moreover, the mechanism by which E-cadherin suppresses EGFR signaling is also unresolved. Here we used Full-Spectral-Imaging FRET (FSI-FRET) measurements to quantify the hetero complex stoichiometry and the binding affinity between E-cadherin and EGFR, at the plasma membranes of live cells. Domain deletions mapped the cadherin regions that mediate receptor binding. Co-immunoprecipitation studies qualitatively support the FSI-FRET results. FSI-FRET and co-IP measurements show that soluble EGF regulates the hetero complex formation. Additional measurements show that mechanically perturbing E-cadherin receptors also disrupts the complex. These findings suggest a mechanism by which E-cadherin may suppress EGFR signaling. They also suggest how increased tension on intercellular adhesions could override contact inhibited proliferation, to potentiate tissue growth. Our results are not only relevant to epithelia, but may have broader implications in other tissues, such as in the vascular endothelium, where VE-cadherin and VEGFR2/3 coordinately regulate endothelial proliferation and fluid shear alignment.