Integrin receptor specificity for human red cell ICAM-4 ligand.
Résumé
The red cell intercellular adhesion molecule-4 (ICAM-4) binds to different members of the integrin receptor families. To better define the ICAM-4 integrin receptor specificity, cell transfectants individually expressing various integrins were used to demonstrate that {alpha}L{beta}2, {alpha}M{beta}2, and {alpha}IIb{beta}3 (activated) bind specifically and dose dependently to the recombinant ICAM-4-Fc protein. We also show that cell surface ICAM-4 interacts with the cell surface {alpha}V{beta}3 integrin. In addition, using a {alpha}4{beta}1 cell transfectant and {beta}2 integrin-deficient LAD cells, we show here that ICAM-4 failed to interact with {alpha}4{beta}1 even after {alpha}4{beta}1 activation by phorbol ester or with the monoclonal antibody TS2/16 (+ Mn2+). ICAM-4 amino acids that are critical for {alpha}IIb{beta}3 and {alpha}V{beta}3 interaction were identified by domain deletion analysis, site-directed mutagenesis and synthetic peptide inhibition. Our results provide evidence that the {beta}3 integrin binding sites encompass the first and second Ig-like domains of ICAM-4. However, while the {alpha}IIb{beta}3 contact site comprises the ABED face of domain D1 with an extension in the C'-E loop of domain D2, the {alpha}V{beta}3 contact site comprises residues on both faces of D1 and in the C'-E loop of D2. These data, together with our previous results, demonstrate that different integrins bind to different but partly overlapping sites on ICAM-4, and that ICAM-4 may accommodate multiple integrin receptors present on leukocytes, platelets and endothelial cells.