Autoinhibitory regulation of S100A8/S100A9 alarmin activity locally restricts sterile inflammation
Thomas Vogl, … , Thomas Pap, Johannes Roth
Thomas Vogl, … , Thomas Pap, Johannes Roth
Published April 3, 2018
Citation Information: J Clin Invest. 2018;128(5):1852-1866. https://doi.org/10.1172/JCI89867.
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Research Article Autoimmunity Inflammation

Autoinhibitory regulation of S100A8/S100A9 alarmin activity locally restricts sterile inflammation

Abstract

Autoimmune diseases, such as psoriasis and arthritis, show a patchy distribution of inflammation despite systemic dysregulation of adaptive immunity. Thus, additional tissue-derived signals, such as danger-associated molecular patterns (DAMPs), are indispensable for manifestation of local inflammation. S100A8/S100A9 complexes are the most abundant DAMPs in many autoimmune diseases. However, regulatory mechanisms locally restricting DAMP activities are barely understood. We now unravel for the first time, to our knowledge, a mechanism of autoinhibition in mice and humans restricting S100-DAMP activity to local sites of inflammation. Combining protease degradation, pull-down assays, mass spectrometry, and targeted mutations, we identified specific peptide sequences within the second calcium-binding EF-hands triggering TLR4/MD2-dependent inflammation. These binding sites are free when S100A8/S100A9 heterodimers are released at sites of inflammation. Subsequently, S100A8/S100A9 activities are locally restricted by calcium-induced (S100A8/S100A9)2 tetramer formation hiding the TLR4/MD2-binding site within the tetramer interphase, thus preventing undesirable systemic effects. Loss of this autoinhibitory mechanism in vivo results in TNF-α–driven fatal inflammation, as shown by lack of tetramer formation in crossing S100A9–/– mice with 2 independent TNF-α–transgene mouse strains. Since S100A8/S100A9 is the most abundant DAMP in many inflammatory diseases, specifically blocking the TLR4-binding site of active S100 dimers may represent a promising approach for local suppression of inflammatory diseases, avoiding systemic side effects.

Authors

Thomas Vogl, Athanasios Stratis, Viktor Wixler, Tom Völler, Sumita Thurainayagam, Selina K. Jorch, Stefanie Zenker, Alena Dreiling, Deblina Chakraborty, Mareike Fröhling, Peter Paruzel, Corinna Wehmeyer, Sven Hermann, Olympia Papantonopoulou, Christiane Geyer, Karin Loser, Michael Schäfers, Stephan Ludwig, Monika Stoll, Tomas Leanderson, Joachim L. Schultze, Simone König, Thomas Pap, Johannes Roth

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Figure 2

Phenotype of TTP–/– S100A9–/– mice.

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Phenotype of TTP–/– S100A9–/– mice. (A) Disease progression of TTP–/– S1...
(A) Disease progression of TTP–/– S100A9–/– mice versus controls (10 mice per group) is shown by the adapted PASI scores from P1–P9. *P < 0.05; **P < 0.01; ***P < 0.001, Mann-Whitney U test. (B) Photographs and skin sections of TTP–/– S100A9–/–, TTP–/–, S100A9–/–, and WT mice at day 9 after birth. Sections were stained with H&E or by immunohistochemistry for S100A8 or immunofluorescence for the indicated epidermal differentiation markers or invading T cells (CD3), granulocytes (Gr1), and macrophages (F4/80) (fluorescence, green signal) and Ki67 (fluorescence, red signal). Blue and red counterstaining shows nuclei. Scale bars: 200 μm (H&E); 50 μm (immunostaining). (C) Epidermis thickness was determined for at least 3 sections per mouse and for each section at 3 different sites and at least 5 mice for each group. (D and E) Expression of IFN-γ, IL-6, IL-17, IL-22, IL-23, and IL-36 in the skin of TTP–/– S100A9–/– mice at day 9 after birth compared with TTP–/– and S100A9–/– mice. The mRNA levels in the skin were measured by qRT-PCR (D) and quantified at the protein level by FACS-based analysis (E) of 3 independent experiments. Data represent mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001, 1-way ANOVA (C–E).