SUMMARY

Cell adhesion to extracellular matrices (ECM) is essential to numerous physiological processes including cell migration, embryonic development, and proper inflammatory responses. Abnormalities in adhesion can lead to pathological conditions such as cancer metastasis and impaired wound-healing. Focal adhesions (FAs) serve as structural links and signal transduction elements between the cell and its extracellular environment. A FA adhesion protein of particular importance is vinculin, a ubiquitously expressed actin-binding protein that is found both at sites of cell-cell and cell-matrix junctions. Vinculin binds to talin and together forms a ternary complex with β1-integrin. This β1-integrin-talin-vinculin complex plays a central role in the regulation of FA assembly and cell spreading and migration. Nevertheless, the specific contribution to adhesive force generation of the β1-integrin-talin-vinculin complex remains poorly understood. The objective of this project was to analyze the role of vinculin in the cell adhesion strengthening process. Our central hypothesis was that vinculin modulates adhesion strength via regulating the size and/or composition of the integrin-talin-F-actin complex. Using a unique combination of biochemical reagents and engineering techniques along with quantitative and sensitive adhesion strength measurements, we demonstrate that vinculin modulates adhesion strength in two distinct ways: integrin binding and focal adhesion assembly. Importantly, we show that both the head and tail domain of the protein modulate adhesion strength, and that their physical linkage is required for maximum adhesion strength.