Rab-coupling protein coordinates recycling of α5β1 integrin and EGFR1 to promote cell migration in 3D microenvironments

Here we show that blocking the adhesive function of alpha v beta 3 integrin with soluble RGD ligands, such as osteopontin or cilengitide, promoted association of Rab-coupling protein (RCP) with alpha 5 beta 1 integrin and drove RCP-dependent recycling of alpha 5 beta 1 to the plasma membrane and its mobilization to dynamic ruffling protrusions at the cell front. These RCP-driven changes in alpha 5 beta 1 trafficking led to acquisition of rapid/random movement on two-dimensional substrates and to a marked increase in fibronectin-dependent migration of tumor cells into three-dimensional matrices. Recycling of alpha 5 beta 1 integrin did not affect its regulation or ability to form adhesive bonds with substrate fibronectin. Instead, alpha 5 beta 1 controlled the association of EGFR1 with RCP to promote the coordinate recycling of these two receptors. This modified signaling downstream of EGFR1 to increase its autophosphorylation and activation of the proinvasive kinase PKB/Akt. We conclude that RCP provides a scaffold that promotes the physical association and coordinate trafficking of alpha 5 beta 1 and EGFR1 and that this drives migration of tumor cells into three-dimensional matrices.