Shedding of Endogenous Interleukin-6 Receptor (IL-6R) Is Governed by A Disintegrin and Metalloproteinase (ADAM) Proteases while a Full-length IL-6R Isoform Localizes to Circulating Microvesicles

• Published in: The Journal of biological chemistry Vol. 290; no. 43; pp. 26059 - 26071
• Main Authors: Schumacher, Neele, Meyer, Dörte, Mauermann, Andre, von der Heyde, Jan, Wolf, Janina, Schwarz, Jeanette, Knittler, Katharina, Murphy, Gillian, Michalek, Matthias, Garbers, Christoph, Bartsch, Jörg W., Guo, Songbo, Schacher, Beate, Eickholz, Peter, Chalaris, Athena, Rose-John, Stefan, Rabe, Björn
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23.10.2015; American Society for Biochemistry and Molecular Biology
• Subjects: ADAM; ADAM Proteins - metabolism; ADAM10; ADAM10 Protein; ADAM17; ADAM17 Protein; Amyloid Precursor Protein Secretases - metabolism; Animals; Cell Line; exosomes; Humans; interleukin 6 (IL-6); interleukin 6 receptor (IL6R); Lipopolysaccharides - pharmacology; Membrane Proteins - metabolism; Mice; microvesicles; Molecular Bases of Disease; Monocytes - drug effects; Monocytes - metabolism; protease; Protein Isoforms - metabolism; Proteolysis; Receptors, Interleukin-6 - genetics; Receptors, Interleukin-6 - metabolism; RNA Splicing; shedding; Tetradecanoylphorbol Acetate - pharmacology; interleukin 6 receptor (IL6R); protease; ADAM; ADAM17; exosomes; interleukin 6 (IL-6); ADAM10; shedding; microvesicles
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.649509

Generation of the soluble interleukin-6 receptor (sIL-6R) is a prerequisite for pathogenic IL-6 trans-signaling, which constitutes a distinct signaling pathway of the pleiotropic cytokine interleukin-6 (IL-6). Although in vitro experiments using ectopically overexpressed IL-6R and candidate proteases revealed major roles for the metalloproteinases ADAM10 and ADAM17 in IL-6R shedding, the identity of the protease(s) cleaving IL-6R in more physiological settings, or even in vivo, remains unknown. By taking advantage of specific pharmacological inhibitors and primary cells from ADAM-deficient mice we established that endogenous IL-6R of both human and murine origin is shed by ADAM17 in an induced manner, whereas constitutive release of endogenous IL-6R is largely mediated by ADAM10. Although circulating IL-6R levels are altered in various diseases, the origin of blood-borne IL-6R is still poorly understood. It has been shown previously that ADAM17 hypomorphic mice exhibit unaltered levels of serum sIL-6R. Here, by quantification of serum sIL-6R in protease-deficient mice as well as human patients we also excluded ADAM10, ADAM8, neutrophil elastase, cathepsin G, and proteinase 3 from contributing to circulating sIL-6R. Furthermore, we ruled out alternative splicing of the IL-6R mRNA as a potential source of circulating sIL-6R in the mouse. Instead, we found full-length IL-6R on circulating microvesicles, establishing microvesicle release as a novel mechanism for sIL-6R generation. Background: A soluble form of IL-6 receptor mediates pathogenic IL-6 trans-signaling. Results: ADAM10 and ADAM17 release IL-6 receptor from both human and murine monocytes/macrophages, whereas in the blood IL-6 receptor is also present on microvesicles. Conclusion: Shedding of endogenous IL-6 receptor is similar in humans and mice. Significance: Microvesicle release represents a novel mode of soluble IL-6 receptor generation with potential clinical implications.