| Cadherins and integrin receptors form crucial extracellular adhesive connections with, respectively, adjacent cells and the extracellular matrix, and transduce mechanical signals across cell membranes. The role of adhesive complexes in diseases, cardiomyopathies, atherosclerosis, cancer, stem cell fate and morphogenesis has shed light on the importance of these adhesive complexes in human physiology.;Results presented in this thesis identified biochemical processes and signal transduction pathways in cadherin-based mechanotransduction. In this thesis, I investigated the role of E-cadherin in mechanotransduction, using modified Magnetic Twisting Cytometry (MTC) and Traction Force Microscopy (TFM) coupled with fluorescence imaging. A major focus of Chapter 2 is the role of a cadherin-associated protein alpha-catenin in force transduction. MTC and TFM studies using alpha-catenin knockdown cells and knockdown cells rescued with alpha-catenin mutants demonstrated unambiguously that alpha-catenin enhances cadherin-mediated traction generation and force sensing. Additionally, I identified the minimal extracellular cadherin domain required for cell-cell adhesion and "outside-in" activation of traction generation and cell spreading.;Studies in Chapter 3, which combined MTC and TFM, identified a new E-cadherin mechanotransduction mechanism, in addition to the mechanism supported by alpha-catenin. This new mechanism is not confined to cadherin junctions alone, but triggers signals that globally alter cell mechanics and perturb distal focal adhesions. Using specific fluorescent reporters and chemical inhibitors, we defined key events in the specific signaling pathway that links E-cadherin force transduction to global changes in cell contractility. These findings expand the current E-Cadherin mechanotransduction model, beyond cell-cell junctions, and elucidate an additional mechanism that integrates integrins with E-cadherin based mechanotransduction. This finding will enhance the understanding and treatment of mechanotransduction based diseases and the development of in vitro tissue engineering principles. |
