N-linked glycosylation is essential for the stability but not the signaling function of the interleukin-6 signal transducer glycoprotein 130

J Biol Chem. 2010 Jan 15;285(3):1781-9. doi: 10.1074/jbc.M109.075952. Epub 2009 Nov 13.

Abstract

N-Linked glycosylation is an important determinant of protein structure and function. The interleukin-6 signal transducer glycoprotein 130 (gp130) is a common co-receptor for cytokines of the interleukin (IL)-6 family and is N-glycosylated at 9 of 11 potential sites. Whereas N-glycosylation of the extracellular domains D1-D3 of gp130 has been shown to be dispensable for binding of the gp130 ligand IL-6 and its cognate receptor in vitro, the role of the N-linked glycans on domains D4 and D6 is still unclear. We have mutated the asparagines of all nine functional N-glycosylation sites of gp130 to glutamine and systematically analyzed the consequences of deleted N-glycosylation (dNG) in both cellular gp130 and in a soluble gp130-IgG1-Fc fusion protein (sgp130Fc). Our results show that sgp130Fc-dNG is inherently unstable and degrades rapidly under conditions that do not harm wild-type sgp130Fc. Consistently, the bulk of cellular gp130-dNG is not transported to the plasma membrane but is degraded in the proteasome. However, the small quantities of gp130-dNG, which do reach the cell surface, are still able to activate the key gp130 signaling target signal transducer and activator of transcription-3 (STAT3) upon binding of the agonistic complex of IL-6 and soluble IL-6 receptor. In conclusion, N-linked glycosylation is required for the stability but not the signal-transducing function of gp130.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cricetinae
  • Cricetulus
  • Cytokine Receptor gp130 / chemistry*
  • Cytokine Receptor gp130 / genetics
  • Cytokine Receptor gp130 / metabolism*
  • Glycoproteins / chemistry*
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • Glycosylation
  • Humans
  • Immunoglobulin G / metabolism
  • Interleukin-6 / metabolism*
  • Ligands
  • Mice
  • Nitrogen / metabolism*
  • Oxygen / metabolism
  • Protein Stability
  • Protein Transport
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • STAT3 Transcription Factor / metabolism
  • Sequence Deletion
  • Signal Transduction*

Substances

  • Glycoproteins
  • Immunoglobulin G
  • Interleukin-6
  • Ligands
  • Recombinant Fusion Proteins
  • STAT3 Transcription Factor
  • glycoprotein 130, human
  • Cytokine Receptor gp130
  • Nitrogen
  • Oxygen