Abstract
Integrins are fundamental to the control of protrusion and motility in adherent cells. However, the mechanisms by which specific members of this receptor family cooperate in signaling to cytoskeletal and adhesion dynamics are poorly understood. Here, we show that the loss of beta3 integrin in fibroblasts results in enhanced focal adhesion turnover and migration speed but impaired directional motility on both 2D and 3D matrices. These motility defects are coupled with an increased rate of actin-based protrusion. Analysis of downstream signaling events reveals that loss of beta3 integrin results in a loss of protein kinase A-dependent phosphorylation of the actin regulatory protein vasodilator-stimulated phosphoprotein (VASP). Dephosphorylated VASP in beta3-null cells is preferentially associated with Rap1-GTP-interacting adaptor molecule (RIAM) both in vitro and in vivo, which leads to enhanced formation of a VASP-RIAM complex at focal adhesions and subsequent increased binding of talin to beta1 integrin. These data demonstrate a novel mechanism by which alphavbeta3 integrin acts to locally suppress beta1 integrin activation and regulate protrusion, adhesion dynamics, and persistent migration.