Allosteric Modulation of Cadherin Affinity

Abstract

We report direct evidence for the allosteric regulation of cadherin adhesion by conformational changes and inside-out signaling. Cadherins are essential proteins that mediate intercellular cohesion in all tissues, and circumstantial evidence suggested that cadherins, like integrins are allosterically regulated by inside-out signaling. Recent findings with conformationally-specific antibodies provided biochemical evidence that cadherin adhesion is allosterically modulated by conformational changes propagating through the cadherin cytoplasmic domain and in the phosphorylation state of a cytoplasmic binding protein, p120 catenin. Here we present direct evidence, using micropipette manipulation, that antibody-induced conformational changes alter the intrinsic affinity of membrane-bound cadherins. Micropipette manipulation measurements quantified the two-dimensional affinity and dissociation rate between cell surface cadherins. We used Colo205 cells, which express a full complement of surface E-cadherin, but do not aggregate unless treated with a kinase inhibitor or activating antibodies. Kinetic measurements between Colo205 cells and cadherin-displaying red blood cells showed that the activating monoclonal antibodies, as well as the kinase inhibitor staurosporine, substantially increased the intrinsic affinity of membrane bound cadherins. Neutral antibodies, which bind cadherin but do not alter Colo205 aggregation, had no effect on cell-cell binding. This important finding demonstrates conformational coupling between cadherin binding activity, cytoplasmic domain conformations, and intracellular signaling.