Polarized epithelial cell migration depends on rear end stress fiber tension

• Galiya Sakaeva
• Dmytro Kotsur
• Kritika Sahni
• Georg Dreissen
• Julian Mattes
• Bernd Hoffmann
• Rudolf Merkel

Actin stress fibers (SFs) play a central role in cell adhesion and migration. Recently laser ablation has become a popular tool to understand mechanical properties of actin SFs and to measure forces generated by single or multiple actin SFs in non-locomoting cells, but still less is known about the role of individual actin SFs in migrating cells. Here we perform laser nanosurgery combined with live-cell microscopy and traction force microscopy (TFM) to investigate contribution of the actin ventral SF at the rear end to cell shape, migration and force transmission in migrating keratinocytes (NHEK). We show that severing of this highly contractile SF results in fast replacement of the severed SF by new actin fiber containing myosin II, alpha-actinin and zyxin. This event is followed by subsequent protrusion of lamellipodium at the cell rear end. These processes lead to global cell shape alterations including loss of polarity and temporal halt of migration. Additionally TFM demonstrates that disruption of the actin ventral SF induces immediate relaxation of the underlying prestressed substrate and significant force adaptation on the long term after the laser ablation. Altogether, these data show the importance of the ventral SF at the cell tail for cell polarity, migration and force generation.