title: Minimal interleukin 6 (IL-6) receptor stalk composition for IL-6 receptor shedding and IL-6 classic signaling.
abstract: Signaling of the pleiotropic cytokine Interleukin-6 (IL-6) is coordinated by membrane-bound and soluble forms of the IL-6 receptor (IL-6R) in processes called classic and trans-signaling, respectively. The soluble IL-6R is mainly generated by ADAM10- and ADAM17-mediated ectodomain shedding. Little is known about the role of the 52-amino acid-residue-long IL-6R stalk region in shedding and signal transduction. Therefore, we generated and analyzed IL-6R stalk region deletion variants for cleavability and biological activity. Deletion of 10 amino acids of the stalk region surrounding the ADAM17 cleavage site substantially blocked IL-6R proteolysis by ADAM17 but only slightly affected proteolysis by ADAM10. Interestingly, additional deletion of the remaining five juxtamembrane-located amino acids also abrogated ADAM10-mediated IL-6R shedding. Larger deletions within the stalk region, that do not necessarily include the ADAM17 cleavage site, also reduced ADAM10 and ADAM17-mediated IL-6R shedding, questioning the importance of cleavage site recognition. Furthermore, we show that a 22-amino acid-long stalk region is minimally required for IL-6 classic signaling. The gp130 cytokine binding sites are separated from the plasma membrane by ~96 Å. 22 amino acid residues, however, span maximally 83.6 Å (3.8 Å/amino acid), indicating that the three juxtamembrane fibronectin domains of gp130 are not necessarily elongated but somehow flexed to allow IL-6 classic signaling. Our findings underline a dual role of the IL-6R stalk region in IL-6 signaling. In IL-6 trans-signaling, it regulates proper proteolysis by ADAM10 and ADAM17. In IL-6 classic-signaling, it acts as a spacer to ensure IL-6·IL-6R·gp130 signal complex formation.
authors.affiliation: Institute of Biochemistry and Molecular Biology II, Medical Faculty, Heinrich-Heine University, 40225 Düsseldorf, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Baran
authors.forename: Rebecca
authors.initials: R
authors.lastname: Nitz
authors.forename: Joachim
authors.initials: J
authors.lastname: Grötzinger
authors.forename: Jürgen
authors.initials: J
authors.lastname: Scheller
authors.forename: Christoph
authors.initials: C
authors.lastname: Garbers
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000072197:ADAM10 Protein; D000072198:ADAM17 Protein; D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D050822:Cytokine Receptor gp130 / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D019947:Receptors, Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology*
chemical_list: C508600:IL6 protein, human; C508603:IL6R protein, human; C494199:IL6ST protein, human; C494200:Il6st protein, mouse; D015850:Interleukin-6; D008565:Membrane Proteins; D019947:Receptors, Interleukin-6; D050822:Cytokine Receptor gp130; D053829:Amyloid Precursor Protein Secretases; D051722:ADAM Proteins; D000072197:ADAM10 Protein; C491236:ADAM10 protein, human; C491234:Adam10 protein, mouse; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse
keywords: ADAM ADAMTS; ADAM10; ADAM17; IL-6 Signal Transduction; Interleukin; Interleukin-6; Interleukin-6 Receptor; Proteolytic Enzymes; Receptor Structure-Function; Signal Transduction
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