title: Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain.
abstract: Type I interferons serve as the first line of defense against pathogen invasion. Binding of IFNs to its receptors, IFNAR1 and IFNAR2, is leading to activation of the IFN response. To determine whether structural perturbations observed during binding are propagated to the cytoplasmic domain, multiple mutations were introduced into the transmembrane helix and its surroundings. Insertion of one to five alanine residues near either the N or C terminus of the transmembrane domain (TMD) likely promotes a rotation of 100° and a translation of 1.5 Å per added residue. Surprisingly, the added alanines had little effect on the binding affinity of IFN to the cell surface receptors, STAT phosphorylation, or gene induction. Similarly, substitution of the juxtamembrane residues of the TMD with alanines, or replacement of the TMD of IFNAR1 with that of IFNAR2, did not affect IFN binding or activity. Finally, only the addition of 10 serine residues (but not 2 or 4) between the extracellular domain of IFNAR1 and the TMD had some effect on signaling. Bioinformatic analysis shows a correlation between high sequence conservation of TMDs of cytokine receptors and the ability to transmit structural signals. Sequence conservation near the TMD of IFNAR1 is low, suggesting limited functional importance for this region. Our results suggest that IFN binding to the extracellular domains of IFNAR1 and IFNAR2 promotes proximity between the intracellular domains and that differential signaling is a function of duration of activation and affinity of binding rather than specific conformational changes transmitted from the outside to the inside of the cell.
authors.affiliation: From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Nanaocha
authors.initials: N
authors.lastname: Sharma
authors.affiliation: From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Geeta
authors.initials: G
authors.lastname: Longjam
authors.affiliation: From the Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel gideon.schreiber@weizmann.ac.il.
authors.forename: Gideon
authors.initials: G
authors.lastname: Schreiber
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D019295:Computational Biology; D017124:Conserved Sequence; D055786:Gene Knockout Techniques; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D016254:Mutagenesis, Insertional; D050505:Mutant Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D053633:Receptor, Interferon alpha-beta / Q000819:agonists* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C554158:IFNA2 protein, human; C507964:IFNAR1 protein, human; C508033:IFNAR2 protein, human; D016898:Interferon-alpha; D050505:Mutant Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D053633:Receptor, Interferon alpha-beta
keywords: cell signaling; cytokine receptor; interferon; mutagenesis; protein-protein interaction; transmembrane domain