Controlling Cell Geometry Affects the Spatial Distribution of Load Across Vinculin

The shape of adherent cells is known to be a key determinant of cellular processes such as proliferation, apoptosis, and differentiation. Manipulation of cell shape affects stem cell differentiation, gene expression, and the response of cells to mechanical stimulation. Shape sensing is at least partially due to mechanically-sensitive signaling within focal adhesions (FAs). Therefore, we evaluate the dependence of cellular force generation on cellular geometry by measuring loads across the FA protein vinculin using an engineered Förster Resonance Energy Transfer-based biosensor. To control cellular geometry, vinculin deficient mouse embryonic fibroblasts stably expressing the vinculin sensor were confined to specific shapes of the same area using photopatterning techniques. It was observed that the tension across vinculin increases at the edges of the cells. However, vinculin supporting compressive loads was found in the center of cells, with an increase in compression observed with increasing aspect ratio. This phenomena is consistent with observations of compressive forces directly under the nucleus and supported by our observation of increased nuclear deformation and enhanced apical actin organization, though this is the first time compressive loads across vinculin have been shown to maintain FA assembly. This suggests a new paradigm for mechanosensitivity in adhesion mechanobiology, where the compressive and tensile loads across particular proteins must be considered.