title: Characterization of ICAM-4 binding to the I domains of the CD11a/CD18 and CD11b/CD18 leukocyte integrins.
abstract: Intercellular adhesion molecule-4 (ICAM-4, LW blood group antigen), a member of the immunoglobulin superfamily expressed on red cells, has been reported to bind to CD11a/CD18 and CD11b/CD18 leukocyte integrins. The location of the ICAM-4 binding sites on CD11a/CD18 and CD11b/CD18 are not known. CD11/CD18 integrin I domains have been found to act as major binding sites for physiological ligands and a negatively charged glutamic acid in ICAMs is considered important for binding. ICAM-4 lacks such a residue, which is replaced by an arginine. However, we demonstrate here that ICAM-4 in red cells and transfected fibroblasts interacts specifically with the I domains of CD11a/CD18 and CD11b/CD18 integrins. The binding was inhibited by anti-I domain and anti-ICAM-4 antibodies and it was dependent on divalent cations. Interestingly, ICAM-4 negative red cells were still able to bind to the CD11b/CD18 I domain but the binding of these cells to the CD11a/CD18 I domain was clearly reduced. Using a solid phase assay, we were able to show that isolated I domains directly and specifically bind to purified recombinant ICAM-4 in a cation dependent manner. Competition experiments indicated that the binding sites in ICAM-4 for the CD11a and CD11b I domains are different. However, the ICAM-4 binding region in both I domains seems to overlap with the regions recognized by the ICAM-1 and ICAM-2. Thus we have established that the I domains contain an ICAM-4 binding region in CD11a/CD18 and CD11b/CD18 leukocyte integrins.
authors.affiliation: Department of Biosciences, Division of Biochemistry, University of Helsinki, Finland.
authors.forename: Eveliina
authors.initials: E
authors.lastname: Ihanus
authors.forename: Liisa
authors.initials: L
authors.lastname: Uotila
authors.forename: Anne
authors.initials: A
authors.lastname: Toivanen
authors.forename: Michael
authors.initials: M
authors.lastname: Stefanidakis
authors.forename: Pascal
authors.initials: P
authors.lastname: Bailly
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Cartron
authors.forename: Carl G
authors.initials: CG
authors.lastname: Gahmberg
mesh_terms: D000818:Animals; D001665:Binding Sites; D001666:Binding Sites, Antibody; D040881:CD11a Antigen / Q000737:chemistry* / Q000235:genetics; D039481:CD11b Antigen / Q000737:chemistry* / Q000235:genetics; D018821:CD18 Antigens / Q000737:chemistry*; D019556:COS Cells; D002448:Cell Adhesion / Q000276:immunology; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000276:immunology; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D007962:Leukocytes / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry; D014162:Transfection
chemical_list: D040881:CD11a Antigen; D039481:CD11b Antigen; D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; C095100:ICAM4 protein, human; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase