Liposome Adhesion Generates Contractile Traction Stresses

Abstract

Mechanical forces generated by cells mediate shape changes that occur during essential life processes including polarization, division and spreading. While the cell cytoskeleton is recognized for its myriad contributions to force generation, the mechanisms by which the cell membrane may also generate forces are often overlooked. Therefore, we explore the potential that membrane generates mechanical tension on cellular length scales by measuring the traction stresses generated during liposome adhesion and spreading on compliant substrates. We find that giant liposomes devoid of a cytoskeleton generate contractile traction stresses on par with those exerted by living cells. These stresses result from the equilibration of internal, hydrostatic pressures elevated by the membrane tension built by strong adhesion to the substrate. These results highlight the active role of membranes in the generation of mechanical stresses on cellular length scales. Furthermore, it uncovers that the modulation of hydrostatic pressure via membrane tension and adhesion can be channeled to perform mechanical work on the environment, providing a more comprehensive description of cell contractility and force generation.