N-linked glycosylation is essential for the stability but not the signaling function of the interleukin-6 signal transducer glycoprotein 130.
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.
Waetzig
Georg H
GH
CONARIS Research Institute AG, 24118 Kiel, Germany. g.waetzig@conaris.de
Chalaris
Athena
A
Rosenstiel
Philip
P
Suthaus
Jan
J
Holland
Christin
C
Karl
Nadja
N
Vallés Uriarte
Lorena
L
Till
Andreas
A
Scheller
Jürgen
J
Grötzinger
Joachim
J
Schreiber
Stefan
S
Rose-John
Stefan
S
Seegert
Dirk
D
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D050822:Cytokine Receptor gp130 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D055550:Protein Stability; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction
D006023:Glycoproteins; D007074:Immunoglobulin G; D015850:Interleukin-6; D008024:Ligands; D011993:Recombinant Fusion Proteins; D050796:STAT3 Transcription Factor; C480482:glycoprotein 130, human; D050822:Cytokine Receptor gp130; D009584:Nitrogen; D010100:Oxygen