title: Localization of the binding site on intercellular adhesion molecule-3 (ICAM-3) for lymphocyte function-associated antigen 1 (LFA-1).
abstract: Intercellular adhesion molecule 3 (ICAM-3; CD50) is the predominant counter-receptor on resting T cells and monocytes for the leukocyte integrin, lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18), and may play an important role in the initial stages of the T cell-dependent immune response. Deletion of individual immunoglobulin superfamily (IgSF) domains of ICAM-3 and ICAM-3 IgSF domain chimeras with CD21 showed there is a single LFA-1 binding site in ICAM-3 and that IgSF domain 1 is necessary and sufficient for LFA-1 binding. Epitope mapping and functional studies performed with 17 anti-ICAM-3 monoclonal antibodies demonstrated that only some monoclonal antibodies, with epitopes wholly within domain 1 of ICAM-3, were able to block binding of ICAM-3 bearing cells to purified LFA-1, in agreement with the data obtained from the domain deletion mutants and CD21 chimeras. Analysis of a panel of 45 point mutants of domain 1 of ICAM-3 identified five residues that may contact LFA-1 as part of the binding site, Asn23, Ser25, Glu37, Phe54, and Gln75. These five residues are predicted by molecular modeling, based on the structure of vascular cell adhesion molecule 1 (VCAM-1), to cluster in two distinct locations on domain 1 of ICAM-3 on the BED face (Asn23 and Ser25) and on the C strand or CD loop (E37), the E strand (F54), and the FG loop (Q75). The residues, Asn23 and Ser25, comprise a consensus N-linked glycosylation site.
authors.affiliation: Center for Blood Research and Harvard Medical School, Department of Pathology, Boston, Massachusetts 21150, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Klickstein
authors.forename: M R
authors.initials: MR
authors.lastname: York
authors.forename: A R
authors.initials: AR
authors.lastname: Fougerolles
authors.forename: T A
authors.initials: TA
authors.lastname: Springer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D001665:Binding Sites; D019556:COS Cells; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D018604:Epitope Mapping; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; D015815:Cell Adhesion Molecules; C483616:ICAM3 protein, human; D016169:Lymphocyte Function-Associated Antigen-1; D011994:Recombinant Proteins