ADAM disintegrin-like domain recognition by the lymphocyte integrins α4β1 and α4β7

The ADAM (a disintegrin and metalloprotease) family of proteins possess both proteolytic and adhesive domains. We have established previously that the disintegrin domain of ADAM28, an ADAM expressed by human lymphocytes, is recognized by the integrin alpha 4 beta 1. The present study characterizes the integrin binding properties of the disintegrin-like domains of human ADAM7, ADAM28 and ADAM33 with the integrins alpha 4 beta 1, alpha 4 beta 7 and alpha 9 beta 1. Cell-adhesion assays demonstrated that, similar to ADAM28, the ADAM7 disintegrin domain supported alpha 4 beta 1 dependent Jurkat cell adhesion, whereas the ADAM33 disintegrin domain did not. The lymphocyte integrin alpha 4 beta 7 was also found to recognize both disintegrin domains of ADAM7 and ADAM28, but not of ADAM33. This is the first demonstration that mammalian disintegrins are capable of interacting with alpha 4 beta 7. All three disintegrin domains supported alpha 9 beta 1-dependent cell adhesion. Recognition by both alpha 4 beta 1 and alpha 4 beta 7 of ADAM7 and ADAM28 was activation-dependent, requiring either the presence of Mn2+ or an activating monoclonal antibody for cell attachment. Charge-to-alanine mutagenesis experiments revealed that the same residues within an individual ADAM disintegrin domain function in recognizing multiple integrins. However, the residues within a specific region of each ADAM disintegrin-like domain required for integrin binding were distinct. These results establish that ADAM7 and ADAM28 are recognized by the leucocyte integrins1 alpha 4 beta 1, alpha 4 beta 7 and alpha 9 beta 1. ADAM33 exclusively supported only alpha 9 beta 1-dependent adhesion.