Structure-function analysis of human IL-6 receptor: dissociation of amino acid residues required for IL-6-binding and for IL-6 signal transduction through gp130

EMBO J. 1993 Apr;12(4):1705-12.

Abstract

Here, we report the analysis of the structure-function relationship of the extracellular region of human interleukin 6 receptor (IL-6R). Upon binding of IL-6, IL-6R becomes associated extracellularly with a non-IL-6-binding but signal transducing molecule, gp130, and the IL-6 signal is generated. In this region, the cytokine receptor family domain, but not the immunoglobulin-like domain, was responsible both for IL-6 binding and for signal transduction through gp130. Because a soluble, extracellular portion of IL-6R (sIL-6R) could bind IL-6 and mediate IL-6 functions through gp130, amino acid substitutions were introduced into sIL-6R by site-directed mutagenesis. The results, together with the previously proposed tertiary structure model, suggested that the amino acid residues critical for IL-6 binding have a tendency to be distributed to the hinge region between the two 'barrel'-like fibronectin type III modules and to the same side of these two 'barrels'. Amino acid residues, of which substitutions barely affected the IL-6-binding but did abolish the IL-6 signalling capability of sIL-6R, were identified and found to be located mainly in the membrane proximal half of the second barrel. sIL-6R mutants carrying such substitutions lacked the capacity to associate with gp130 in the presence of IL-6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigens, CD*
  • Cell Line
  • Chlorocebus aethiops
  • Cytokine Receptor gp130
  • Glycoproteins / physiology*
  • Humans
  • In Vitro Techniques
  • Interleukin-6 / physiology*
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Binding
  • Protein Structure, Tertiary
  • Receptors, Immunologic / chemistry*
  • Receptors, Immunologic / metabolism
  • Receptors, Interleukin-6
  • Signal Transduction
  • Structure-Activity Relationship
  • Transfection

Substances

  • Antigens, CD
  • Glycoproteins
  • IL6ST protein, human
  • Il6st protein, mouse
  • Interleukin-6
  • Membrane Glycoproteins
  • Receptors, Immunologic
  • Receptors, Interleukin-6
  • Cytokine Receptor gp130