title: Interleukin-6 (IL-6) antagonism by soluble IL-6 receptor alpha mutated in the predicted gp130-binding interface.
abstract: Interleukin-6 (IL-6) triggers the formation of a high affinity receptor complex constituted by the ligand-binding subunit IL-6 receptor alpha (IL-6R alpha) and the signal-transducing beta chain gp130. Since the cytoplasmic region of IL-6R alpha is not required for signal transduction, soluble forms of IL-6R alpha (sIL-6R alpha) show agonistic properties because they are still able to originate IL-6.sIL-6R alpha complexes, which in turn associate with gp130. A three-dimensional model of the human IL-6.IL-6R alpha.gp130 complex has been constructed and verified by site-directed mutagenesis of regions in shIL-6R alpha (where "h" is human) anticipated to contact hgp130, with the final goal of generating receptor variants with antagonistic properties. In good agreement with our structural model, substitutions at Asn-230, His-280, and Asp-281 selectively impaired the capability of shIL-6R alpha to associate with hgp130 both in vitro and on the cell surface, without affecting its affinity for hIL-6. Moreover, the multiple substitution mutant A228D/N230D/H280S/D281V expressed as a soluble protein partially antagonized hIL-6 bioactivity on hepatoma cells.
authors.affiliation: Department of Genetics, Istituto di Ricerche di Biologia Molecolare P. Angeletti, Rome, Italy.
authors.forename: A L
authors.initials: AL
authors.lastname: Salvati
authors.forename: A
authors.initials: A
authors.lastname: Lahm
authors.forename: G
authors.initials: G
authors.lastname: Paonessa
authors.forename: G
authors.initials: G
authors.lastname: Ciliberto
authors.forename: C
authors.initials: C
authors.lastname: Toniatti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D003198:Computer Simulation; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D046911:Macromolecular Substances; D008545:Melanoma / Q000473:pathology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017924:Nucleopolyhedroviruses; D011487:Protein Conformation; D018123:Receptors, Interleukin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019947:Receptors, Interleukin-6; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D012995:Solubility; D018411:Spodoptera; D014407:Tumor Cells, Cultured; D000093242:Interleukin-6 Inhibitors
chemical_list: D046911:Macromolecular Substances; D018123:Receptors, Interleukin; D019947:Receptors, Interleukin-6; D011993:Recombinant Fusion Proteins; D000093242:Interleukin-6 Inhibitors