Membrane tension increase by cell stretching. (A) Schematic representation of the experimental setup used to stretch the cells. (B) Membrane and actin during cell stretching. Arrows, lamellipodial protrusion before stretch; arrowheads, collapse of the lamellipodial protrusion during stretch and formation of arc-shape structures at the cell edge; asterisks, lamellipodium reappearance when stretch is released. (C) Actin and paxillin during cell stretching. Arrows, lamellipodial protrusion before stretch; cross, paxillin focal adhesions at the back of the lamellipodium; arrowheads, collapse of the lamellipodial protrusion during stretch and formation of arc-shape structures at the cell edge; asterisks, lamellipodium reappearance when stretch is released. (D) Actin and paxillin during cell stretching in a BBI-treated cell. Asterisks, lamellipodium reappearance when stretch is released. (E) Membrane and actin during relaxation of prestretched PDMS substrate. Arrows, lamellipodial protrusion before relaxation; arrowheads, ruffling of the lamellipodial protrusion immediately after relaxation; asterisks, lamellipodium reappearance after relaxation. (F) Actin and paxillin during relaxation of prestretched PDMS substrate. Arrows, lamellipodial protrusion before relaxation; cross, paxillin focal adhesions at the back of the lamellipodium; arrowheads, ruffling of the lamellipodial protrusion immediately after relaxation; asterisks, lamellipodium reappearance after relaxation. All procedures were repeated for at least five different cells in each condition, and all showed behaviors similar to those represented in the figure. Bars, 10 µm.