CDB15:0000798 ICAM4 — ITGAM
Experimentally validated in Human, Mixed species; Orthology-inferred in Human, Mouse, Rat, Frog, Zebrafish, Macaque, Pig, Dog, Cow, Chimp, Horse, Marmoset, Sheep
Title
Journal:; Year Published:
Abstract
Binding sites of leukocyte beta 2 integrins (LFA-1, Mac-1) on the human ICAM-4/LW blood group protein.
The Journal of biological chemistry, 2000; PubMed, Homo sapiens ICAM4 — Homo sapiens ITGAM
ABSTRACT: The red cell ICAM-4/LW blood group glycoprotein, which belongs to the family of intercellular adhesion molecules (ICAMs), has been reported to interact with CD11a/CD18 (LFA-1) and CD11b/CD18 (Mac-1) beta(2) integrins. To better define the basis of the ICAM-4/beta(2) integrin interaction, we have generated wild-type, domain-deleted and mutated recombinant chimeric ICAM-4-Fc proteins and analyzed their interaction in a cellular adhesion assay with LFA-1 and Mac-1 L-cell stable transfectants. We found that monoclonal antibodies against CD11a, CD11b, CD18, or LW(ab) block adhesion of transfectant L-cells to immobilized ICAM-4-Fc protein and that the ICAM-4/beta(2) integrin interaction was highly sensitive to the presence of the divalent cations Ca(2+) and Mg(2+). Deletion of individual Ig-domains D1 or D2 of the extracellular part of ICAM-4 showed that LFA-1 binds to the first Ig-like domain, whereas the Mac-1 binding site encompassed both the first and the second Ig-like domains. Based on the crystal structure of ICAM-2, we propose a model for the Ig-like domains D1 and D2 of ICAM-4. Accordingly, by site-directed mutagenesis of 22 amino acid positions spread out on all faces of the ICAM-4 molecule, we identified four exposed residues, Leu(80), Trp(93), and Arg(97) on the CFG face and Trp(77) on the E-F loop of domain D1 that may contact LFA-1 as part of the binding site. However, the single and double mutants R52E and T91Q on the CFG face of domain D1, which correspond to the key residues Glu(34) and Gln(73) for ICAM-1 binding to LFA-1, had no effect on LFA-1 binding. In contrast, all mutants on the CFG face of domain D1 and residues Glu(151) and Thr(154) in the C'-E loop of the domain D2 seem to play a dominant role in Mac-1 binding. These data suggest that the binding site for LFA-1 on ICAM-4 overlaps but is distinct from the Mac-1 binding site.
Integrin receptor specificity for human red cell ICAM-4 ligand. Critical residues for alphaIIbeta3 binding.
European journal of biochemistry, 2004; PubMed, Mus Musculus Icam4 — Homo sapiens ITGAM
ABSTRACT: 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 alphaLbeta2, alphaMbeta2, and alphaIIbbeta3 (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 alphaVbeta3 integrin. In addition, using a alpha4beta1 cell transfectant and beta2 integrin-deficient LAD cells, we show here that ICAM-4 failed to interact with alpha4beta1 even after alpha4beta1 activation by phorbol ester or with the monoclonal antibody TS2/16 (+ Mn2+). ICAM-4 amino acids that are critical for alphaIIbbeta3 and alphaVbeta3 interaction were identified by domain deletion analysis, site-directed mutagenesis and synthetic peptide inhibition. Our results provide evidence that the beta3 integrin binding sites encompass the first and second Ig-like domains of ICAM-4. However, while the alphaIIbbeta3 contact site comprises the ABED face of domain D1 with an extension in the C'-E loop of domain D2, the alphaVbeta3 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.