TY - JOUR T1 - Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration JF - bioRxiv DO - 10.1101/071936 SP - 071936 AU - Pontus Nordenfelt AU - Travis I. Moore AU - Shalin B. Mehta AU - Joseph Mathew Kalappurakkal AU - Vinay Swaminathan AU - Nobuyasu Koga AU - Talley J. Lambert AU - David Baker AU - Jennifer C. Waters AU - Rudolf Oldenbourg AU - Tomomi Tani AU - Satyajit Mayor AU - Clare M. Waterman AU - Timothy A. Springer Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/01/19/071936.abstract N2 - Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin head, known from crystal structures, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid head of the full integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin, and measure orientation with fluorescence polarization microscopy. Dependent on coupling to the cytoskeleton, integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. We have developed a method that places atomic, ~Å structures of cell surface receptors in the context of functional, cellular length-scale, ~μm measurements and shows that rotation and tilt of cell surface receptors relative to the membrane plane can be restrained by interactions with other cellular components. ER -