Homophilic and heterophilic cadherin bond rupture forces in homo- or hetero-cellular systems measured by AFM based SCFS

Cadherins enable intercellular adherens junctions to withstand tensile forces in tissues, e.g. generated by intracellular actomyosin contraction. Single molecule force spectroscopy experiments in in-vitro experiments can reveal the cadherin-cadherin extracellular region binding dynamics such as bond formation and strength. However, characterization of cadherin homophilic and heterophilic binding in their native conformational and functional state in living cells has rarely been done. Here, we used Atomic Force Microscopy (AFM) based Single cell force Spectroscopy (SCFS) to measure rupture forces of homophilic and heterophilic bond formation of N-, OB- and E-cadherins in living fibroblast and epithelial cells in homo- and hetero-cellular arrangements, i.e. between same type of cells and between cells of different type. In addition, we used indirect immunofluorescence labelling to study and correlate the expression of these cadherins in intercellular adherens junctions. We showed that N/N and E/E cadherin homophilic bindings are stronger than N/OB, E/N and E/OB heterophilic bindings. Disassembly of intracellular actin filaments reduces the cadherin bond rupture forces suggesting a contribution of actin filaments in cadherin extracellular binding. Inactivation of myosin did not affect the cadherin rupture force in both homo- and hetero-cellular arrangements. Whereas, myosin inactivation particularly strengthened the N/OB heterophilic bond and reinforced the other cadherins homophilic bonds.