Identification of Amino Acids in the CD11a I-domain Important for Binding of the Leukocyte Function-associated Antigen-1 (LFA-1) to Intercellular Adhesion Molecule-1 (ICAM-1)

• Published in: The Journal of biological chemistry Vol. 270; no. 21; pp. 12635 - 12640
• Main Authors: Edwards, Caroline P., Champe, Mark, Gonzalez, Tania, Wessinger, Mary Ellen, Spencer, Steven A., Presta, Leonard G., Berman, Phillip W., Bodary, Sarah C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.05.1995; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Cell Adhesion - genetics; Cell Adhesion - physiology; Chlorides - pharmacology; DNA Mutational Analysis; Epitopes; Humans; Intercellular Adhesion Molecule-1 - metabolism; Ligands; Lymphocyte Function-Associated Antigen-1 - genetics; Lymphocyte Function-Associated Antigen-1 - immunology; Lymphocyte Function-Associated Antigen-1 - metabolism; Magnesium Chloride - pharmacology; Manganese Compounds - pharmacology; Mice; Point Mutation; Protein Binding - drug effects; Recombinant Fusion Proteins - metabolism; Species Specificity; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.270.21.12635

Leukocyte function-associated antigen-1 (LFA-1) is a cell surface adhesion receptor for intercellular adhesion molecule-1, −2, and −3 (ICAM-1, −2, −3). Using human/murine chimeras of the I-domain of the LFA-1 α subunit (CD11a), we recently identified the epitopes recognized by eight monoclonal antibodies against CD11a that inhibit LFA-1 binding to ICAM-1. In this report, we determined that replacement of the entire human I-domain with the entire murine I-domain in CD11a completely abrogated LFA-1 binding to human ICAM-1 without affecting the gross conformation or heterodimer formation of LFA-1, as assayed by antibody binding. In order to assess which residues of the I-domain are responsible for binding to ICAM-1, we tested the ability of a panel of human/murine I-domain chimeras to bind to human ICAM-1. When complexed with CD18, all CD11a chimeras bound ICAM-1 at levels comparable to wild-type CD11a/CD18, indicating that the residues in these chimeras which differ in human and murine I-domains may not play a critical role in LFA-1 binding to ICAM-1. A series of point mutations of residues that are conserved between murine and human CD11a I-domains, as well as between CD11b and CD11c, were also generated. Substitution of alanine for proline at position 192 in the human CD11a I-domain abrogated adhesion of LFA-1 to ICAM-1. Antibody binding data suggested that this was due to conformational changes within the I-domain. Mutation of the aspartic acids at positions 137 and 239 to either alanine or lysine completely destroyed ICAM-1 binding. The conformation of LFA-1 alanine mutants was not significantly altered. This suggests that these aspartic acids are required for binding of human LFA-1 to human ICAM-1.