The αvβ3 Integrin Regulates α5β1-mediated Cell Migration toward Fibronectin

This study examines the interactions of α v β 3 and α 5 β 1 in the regulation of cell migration. Human embryonic kidney (HEK) 293 cells that express α 5 β 1 endogenously were transfected with α v β 3 and β 3 mutants, and their attachment and migration to fibronectin (Fn) and vitronectin (Vn) were measured. An α v β 3 blocking antibody and the α v β 3 ligand cyclic G-Pen-GRGDSPC-A inhibited α 5 β 1 -mediated migration toward Fn, but not attachment to Fn. This function was α v β 3 -specific since α v β 5 transfection and α v β 5 blocking antibody did not produce this effect. Mutations introduced into the β 3 integrin subunit to dissect this phenomenon revealed the following. Disruption of the ligand binding domain by the Glanzmann thrombasthenia mutation β 3 -D119Y constitutively abolished migration toward both Vn and Fn, and attachment to Vn but not to Fn. Insertion of the Glanzmann mutation β 3 -S752P into the cytoplasmic domain or its truncation (β 3 -Δ717) abolished binding to Vn but not to Fn. Inhibition of migration toward Fn was inhibited in these cells by α v β 3 blocking antibody. α v β 3 -mediated inhibition was, however, abolished by truncation of the transmembrane domain (β 3 -Δ693). These findings demonstrate α v β 3 regulation of α 5 β 1 -mediated cell migration and suggest that the β 3 transmembrane domain is essential for this function.