Identification of critical residues in bovine IFNAR-1 responsible for interferon binding.
Interferons have antiviral, antigrowth and immunomodulatory effects. The human type I interferons, IFN-alpha, IFN-beta, and IFN-omega, induce somewhat different cellular effects but act through a common receptor complex, IFNAR, composed of subunits IFNAR-1 and IFNAR-2. Human IFNAR-2 binds all type I IFNs but with lower affinity and different specificity than the IFNAR complex. Human IFNAR-1 has low intrinsic binding of human IFNs but strongly affects the affinity and differential ligand specificity of the IFNAR complex. Understanding IFNAR-1 interactions with the interferons is critical to elucidating the differential ligand specificity and activation by type I IFNs. However, studies of ligand interactions with human IFNAR-1 are compromised by its low affinity. The homologous bovine IFNAR-1 serendipitously binds human IFN-alphas with nanomolar affinity. Exploiting its strong binding of human IFN-alpha2, we have identified residues important for ligand binding. Mutagenesis of any of five aromatic residues of bovine IFNAR-1 caused strong decreases in ligand binding, whereas mutagenesis of proximal neutral or charged residues had smaller effects. These residues were mapped onto a homology model of IFNAR-1 to identify the ligand-binding face of IFNAR-1, which is consistent with previous structure/function studies of human IFNAR-1. The topology of IFNAR-1/IFN interactions appears novel when compared with previously studied cytokine receptors.
Department of Molecular Genetics & Microbiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
E C
EC
Cutrone
J A
JA
Langer
D000409:Alanine; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000911:Antibodies, Monoclonal; D001665:Binding Sites; D001666:Binding Sites, Antibody; D019556:COS Cells; D002417:Cattle; D002522:Chlorocebus aethiops; D006801:Humans; D007370:Interferon Type I / Q000378:metabolism*; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000378:metabolism; D016899:Interferon-beta / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008565:Membrane Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry; D010766:Phosphorylation; D011487:Protein Conformation; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D000911:Antibodies, Monoclonal; C507964:IFNAR1 protein, human; D007370:Interferon Type I; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D008024:Ligands; D008565:Membrane Proteins; D010446:Peptide Fragments; D017471:Receptors, Interferon; D011994:Recombinant Proteins; C063743:interferon omega 1; D053633:Receptor, Interferon alpha-beta; D016899:Interferon-beta; D000409:Alanine