The role of the membrane confinement in the surface area regulation of cells.

We propose a new in vitro system to study the mechanics of surface area regulation in cells, which takes into an account the spatial confinement of the cell membrane. By coupling a lipid bilayer to the strain-controlled deformation of an elastic sheet, we show that upon straining the supported lipid bilayer expands its surface area by absorbing adherent lipid vesicles and upon compression decreases its area by expelling lipid tubes out of its plane. The processes are reversible and closely resemble in vivo observations on shrinking cells. Our results suggest that the mechanics of the area regulation in cells is controlled primarily by the membrane tension and the effects of the membrane confinement.