Species Specificity of ADAM10 and ADAM17 Proteins in Interleukin-6 (IL-6) Trans-signaling and Novel Role of ADAM10 in Inducible IL-6 Receptor Shedding

Christoph Garbers,Nathalie Jänner,Athena Chalaris,Marcia L Moss,Doreen M Floss,Dörte Meyer,Friedrich Koch-Nolte,Stefan Rose-John,Jürgen Scheller

doi:10.1074/jbc.m111.229393

Abstract

Hypomorphic ADAM17(ex/ex) mice showed defects in mucosal regeneration due to inefficient enhanced GFR shedding. ADAM17 is the main sheddase of interleukin-6 receptor (IL-6R) to induce IL-6 trans-signaling. However, serum levels of soluble murine IL-6R were not reduced in ADAM17(ex/ex) mice, and murine ADAM17 was not the major sheddase of murine IL-6R. Shedding of murine IL-6R by murine ADAM17 was rescued in chimeric murine IL-6R proteins containing any extracellular domain but not the transmembrane and intracellular domain of human IL-6R. Apoptosis is a physiological stimulus of ADAM17-mediated shedding of human IL-6R. Even though apoptosis induced IL-6R shedding in mice, the responsible protease was identified as ADAM10. ADAM10 also was identified as protease responsible for ionomycin-induced shedding of murine and human IL-6R. However, in ADAM10-deficient murine embryonic fibroblasts, compensatory shedding of human IL-6R was mediated by ADAM17, but loss of ADAM10-mediated shedding of murine IL-6R was compensated by an as-yet-unidentified protease. Finally, we identified physiological purinergic P2X7 receptor stimulation as a novel inducer of murine and human IL-6R shedding solely mediated by ADAM10. In conclusion, we describe an unexpected species specificity of ADAM10 and ADAM17 and identified ADAM10 as novel inducible sheddase of IL-6R in mice and humans, which might have consequences for the interpretation of phenotypes from ADAM17- and ADAM10-deficient mice.

Highlights

Receptor (IL-6R)4 complex consists of the transmembrane proteins gp130 and interleukin-6 receptor (IL-6R)
Murine IL-6R Is Not a Major Substrate of Murine ADAM17— Serum level of soluble murine IL-6R was shown to be dependent on IL-6R shedding from immune (ϳ60%) and hepatic cells (ϳ30%) [26]
PMA induced only weak shedding of endogenous mIL-6R from murine CD3ϩ spleen cells of wild-type (79.3 Ϯ 2.5% versus 56.7 Ϯ 0.6%) mice, which was partially inhibited in ADAM17ex/ex mice (80.7 Ϯ 2.8% versus 72.4 Ϯ 2.7%), indicating that ADAM17 is a functional sheddase of mIL-6R, but ADAM17-induced shedding of IL-6R was much lower than expected (Fig. 1)

Summary

Introduction

Receptor (IL-6R)4 complex consists of the transmembrane proteins gp130 and IL-6R. a soluble form of IL-6R (sIL6R) acts as an agonist and forms complexes with IL-6. To identify structural prerequisites in hIL-6R, which are responsible for ADAM17-mediated shedding, we conducted gain-of-function PMA-induced shedding experiments with chimeric murine/human IL-6R proteins (Fig. 2).

Results

Conclusion