The "linker" region (amino acids 38-47) of the disintegrin elegantin is a novel inhibitory domain of integrin α5β 1-dependent cell adhesion on fibronectin: Evidence for the negative regulation of fibronectin synergy site biological activity

Disintegrins are a family of potent inhibitors of cell-cell and cell-matrix adhesion. In this study we have identified a region of the disintegrin elegantin, termed the "linker domain" (amino acids 38-47), with inhibitory activity toward α5β1-mediated cell adhesion on fibronectin (Fn). Using a chimeric structure-function approach in which sequences of the functionally distinct disintegrin kistrin were introduced into the elegantin template at targeted sites, a loss of inhibitory function toward α5β1-mediated adhesion on Fn was observed when the elegantin linker domain was substituted. Subsequent analysis comparing the inhibitory efficacies of the panel of elegantin-kistrin chimeras toward CHO α5 cell adhesion on recombinant Fn III 6-10 fragments showed that the loss of inhibitory activity associated with the disruption of the elegantin linker domain was dependent upon the presence of a functional Fn III9 synergy site within the Fn III 6-10 substrate. This suggested that the elegantin linker domain inhibits primarily the activity of the Fn synergy domain in promoting α5β1 integrin-mediated cell adhesion. Construction of a cyclic peptide corresponding to the entire region of the elegantin linker domain showed that this domain has intrinsic α5β1 inhibitory activity comparable with the activity of the RGDS peptide. These data demonstrate a novel biological function for a disintegrin domain that antagonizes integrin-mediated cell adhesion.