PLoS Biology (Jan 2017)

Proteolytic Origin of the Soluble Human IL-6R In Vivo and a Decisive Role of N-Glycosylation.

  • Steffen Riethmueller,
  • Prasath Somasundaram,
  • Johanna C Ehlers,
  • Chien-Wen Hung,
  • Charlotte M Flynn,
  • Juliane Lokau,
  • Maria Agthe,
  • Stefan Düsterhöft,
  • Yijue Zhu,
  • Joachim Grötzinger,
  • Inken Lorenzen,
  • Tomas Koudelka,
  • Kosuke Yamamoto,
  • Ute Pickhinke,
  • Rielana Wichert,
  • Christoph Becker-Pauly,
  • Marisa Rädisch,
  • Alexander Albrecht,
  • Markus Hessefort,
  • Dominik Stahnke,
  • Carlo Unverzagt,
  • Stefan Rose-John,
  • Andreas Tholey,
  • Christoph Garbers

DOI
https://doi.org/10.1371/journal.pbio.2000080
Journal volume & issue
Vol. 15, no. 1
p. e2000080

Abstract

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Signaling of the cytokine interleukin-6 (IL-6) via its soluble IL-6 receptor (sIL-6R) is responsible for the proinflammatory properties of IL-6 and constitutes an attractive therapeutic target, but how the sIL-6R is generated in vivo remains largely unclear. Here, we use liquid chromatography-mass spectrometry to identify an sIL-6R form in human serum that originates from proteolytic cleavage, map its cleavage site between Pro-355 and Val-356, and determine the occupancy of all O- and N-glycosylation sites of the human sIL-6R. The metalloprotease a disintegrin and metalloproteinase 17 (ADAM17) uses this cleavage site in vitro, and mutation of Val-356 is sufficient to completely abrogate IL-6R proteolysis. N- and O-glycosylation were dispensable for signaling of the IL-6R, but proteolysis was orchestrated by an N- and O-glycosylated sequon near the cleavage site and an N-glycan exosite in domain D1. Proteolysis of an IL-6R completely devoid of glycans is significantly impaired. Thus, glycosylation is an important regulator for sIL-6R generation.