E-Cadherin-mediated adhesion in the absence of the cytoskeletal machinery*

E-Cadherin-mediated cell-cell adhesion plays a crucial role in biomechanics. We develop a biomimetic emulsion[1] to probe the physical basis of cadherin adhesion and characterize the role of lateral cis interactions in cadherin recruitment. Calcium activates droplet adhesion in Brownian as well as athermal droplets packed under gravity. To achieve a cohesive tissue, we show that compression is necessary to zip up interfaces. Cadherin adhesions in these transparent 3D emulsions, give an equation of state relating the area as a function of the cadherin density. While the MT exhibits a linear relationship, the WT diverges at a lower density, in agreement with the crystal lattice density[2].The free energy of binding on 2D interfaces is on the order of 15kT per molecule. The cadherin density ratio inside and outside adhesions reveals that cis interactions play an important role in recruiting the proteins more efficiently than the MT. Both WT and MT proteins self-assemble into solid adhesions, as shown by their lack of Fluorescence Recovery after Photobleaching (FRAP). These results suggest that active processes inside the cell work to avoid the spontaneous zipping of interfaces by extracellular cadherin proteins.
Pontani et al. Biophys. J. (2016)
Harrison et al. Structure (2011)