title: Small molecule inhibitors induce conformational changes in the I domain and the I-like domain of lymphocyte function-associated antigen-1. Molecular insights into integrin inhibition.
abstract: The beta(2) integrin lymphocyte function-associated antigen-1 (LFA-1) is a conformationally flexible alpha/beta heterodimeric receptor, which is expressed on the surface of all leukocytes. LFA-1 mediates cell adhesion crucial for normal immune and inflammatory responses. Intracellular signals or cations are required to convert LFA-1 from a nonligand binding to a ligand binding state. Here we investigated the effect of small molecule inhibitors on LFA-1 by monitoring the binding of monoclonal antibodies mapped to different receptor domains. The inhibitors were found to not only induce epitope changes in the I domain of the alpha(L) chain but also in the I-like domain of the beta(2) chain depending on the individual chemical structure of the inhibitor and its binding site. For the first time, we provide strong evidence that the I-like domain represents a target for allosteric LFA-1 inhibition similar to the well established regulatory L-site on the I domain of LFA-1. Moreover, the antibody binding patterns observed in the presence of the various inhibitors establish a conformational interaction between the LFA-1 I domain and the I-like domain in the native receptor that is formed upon activation. Differentially targeting the binding sites of the inhibitors, the L-site and the I-like domain, may open new avenues for highly specific therapeutic intervention in diseases where integrins play a pathophysiological role.
authors.affiliation: Novartis Pharma AG, Preclinical Research, Basel CH-4002, Switzerland.
authors.forename: Karl
authors.initials: K
authors.lastname: Welzenbach
authors.forename: Ulrich
authors.initials: U
authors.lastname: Hommel
authors.forename: Gabriele
authors.initials: G
authors.lastname: Weitz-Schmidt
mesh_terms: D000495:Allosteric Site; D001665:Binding Sites; D019921:Biotinylation; D002448:Cell Adhesion; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005434:Flow Cytometry; D006801:Humans; D020128:Inhibitory Concentration 50; D016023:Integrins / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D019169:Jurkat Cells; D007962:Leukocytes / Q000378:metabolism; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry* / Q000378:metabolism; D016177:Macrophage-1 Antigen / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D000939:Epitopes; D016023:Integrins; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D018799:Intercellular Adhesion Molecule-1; D004492:Edetic Acid