title: Structure-function study of the extracellular domain of the human type I interferon receptor (IFNAR)-1 subunit.
abstract: Despite accumulating information about the different effector molecules and signaling cascades that are invoked on interferon-alpha (IFN-alpha) binding to the type 1 IFN receptor, little is known about the specifics of the binding interactions between the ligand and the receptor complex. The IFN-alpha/beta receptor (IFNAR)-2 subunit of the IFN receptor is considered the primary binding chain of the receptor, yet it is clear that both receptor subunits, IFNAR-1 and IFNAR-2, cooperate in the high-affinity binding of IFN to the receptor complex. Earlier results from our laboratory suggested that an association of IFNAR-1 with membrane Galalpha1-4Gal-containing glycolipids facilitates receptor-mediated signaling. The data implicated amino acid residues in the SD100 domain of IFNAR-1 in the glycosphingolipid (GSL) modification of the type 1 IFN receptor. Interestingly, the human and murine counterparts of IFNAR-1 exhibit remarkable species specificity despite their considerable amino acid sequence identity. Certainly, those amino acid residues that effect GSL modification of IFNAR-1 are conserved between species, yet specific regions of IFNAR-1 that confer species specificity have not been defined. To delineate further the role of the IFNAR-1 SD100A domain in receptor function, a chimeric cDNA was assembled, in which the SD100A domain of the murine IFNAR-1 chain was replaced with the human sequence. This construct was expressed in IFNAR-1-/- mouse embryonic fibroblasts, and stable transfectants were established. Transfectants are fully sensitive to murine IFN-alpha4 treatment with respect to the induction of IFN-stimulated gene factor 3 (ISGF3) and sis-inducing factor (SIF) signal transducer and activator of transcription factor (Stat) complexes, exhibiting comparable levels of Stat activation to those observed in IFNAR-1-/- cells reconstituted with intact MuIFNAR-1. Similar results were obtained with IFN-induced antiviral and growth inhibitory responses. Viewed together, these data suggest that the SD100A domain of IFNAR-1 does not contribute to species-specific IFN binding.
authors.affiliation: Department of Immunology, University of Toronto, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Kumaran
authors.forename: O R
authors.initials: OR
authors.lastname: Colamonici
authors.forename: E N
authors.initials: EN
authors.lastname: Fish
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism; D008565:Membrane Proteins; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014162:Transfection
chemical_list: D017931:DNA Primers; C507964:IFNAR1 protein, human; C508034:Ifnar2 protein, mouse; D016898:Interferon-alpha; D008565:Membrane Proteins; D017471:Receptors, Interferon; D011993:Recombinant Fusion Proteins; D053633:Receptor, Interferon alpha-beta