Sensing forces in cells using fluorescence FRET microscopy and optical tweezers

Forces inside cells play a fundamental role in cell behavior, for example in cancer cell migration. We focus on the vinculin protein which is involved in the stabilization of cell adhesion. Through fluorescence transfer (FRET), forces within vinculin can be measured with picoNewton sensitivity. We measure these internal forces while applying a calibrated external force with a laser-based optical tweezer via a microbead attached to the cell. Our most recent results using fibroblast cells show that the force applied with the optical tweezer induces the recruitment of vinculin and the formation of focal adhesions on the bead within a few minutes. Once the bead is attached to the cell, we record its trajectory and infer the force exerted by the cell. We correlate this force with the FRET efficiency of the force sensor.