Spatio-temporal analysis of cell response to a rigidity gradient: a quantitative study by multiple optical tweezers
Résumé
We investigate the dynamic response of single cells to weak and local rigidities, applied at controlled adhesion sites. Using multiple latex beads functionalized with fibronectin and trapped each in its own optical trap, we study in real time the reaction of single 3T3 fibroblast cells to asymmetrical tensions in the tens of pN.microm(-1) range. We show that the cell feels a rigidity gradient even in this low range of tension, and develops with time an adapted change in the force exerted on each adhesion site. The rate at which the force increases is proportional to the trap stiffness. Actomyosin recruitment is regulated in space and time along the rigidity gradient, resulting in a linear relationship between the amount of recruited actin and the force developed independently on the trap stiffness. This time-regulated actomyosin behavior sustains a constant and rigidity-independent velocity of the beads inside the traps. Altogether, our results show that strengthening of extracellular matrix-cytoskeleton linkages along a rigidity gradient is regulated by controlling the adhesion area and actomyosin recruitment, so as to maintain a constant deformation of the extracellular matrix.
