The deubiquitinase OTUB1 augments NF-\u03baB-dependent immune responses in dendritic cells in infection and inflammation by stabilizing UBC13

Floriana Mulas,Antonio Barragan,Xu Wang,Anna Brunn,Ulrich Kalinke,Dirk Schlüter,Shanshan Song,Berend Isermann,Gopala Nishanth,Michael Naumann,Wenjing Yi,Pia-Katharina Larsen,Martina Deckert

doi:10.1038/s41423-020-0362-6

Abstract

Dendritic cells (DCs) are indispensable for defense against pathogens but may also contribute to immunopathology. Activation of DCs upon the sensing of pathogens by Toll-like receptors (TLRs) is largely mediated by pattern recognition receptor/nuclear factor-κB (NF-κB) signaling and depends on the appropriate ubiquitination of the respective signaling molecules. However, the ubiquitinating and deubiquitinating enzymes involved and their interactions are only incompletely understood. Here, we reveal that the deubiquitinase OTU domain, ubiquitin aldehyde binding 1 (OTUB1) is upregulated in DCs upon murine Toxoplasmagondii infection and lipopolysaccharide challenge. Stimulation of DCs with the TLR11/12 ligand T. gondii profilin and the TLR4 ligand lipopolysaccharide induced an increase in NF-κB activation in OTUB1-competent cells, resulting in elevated interleukin-6 (IL-6), IL-12, and tumor necrosis factor (TNF) production, which was also observed upon the specific stimulation of TLR2, TLR3, TLR7, and TLR9. Mechanistically, OTUB1 promoted NF-κB activity in DCs by K48-linked deubiquitination and stabilization of the E2-conjugating enzyme UBC13, resulting in increased K63-linked ubiquitination of IRAK1 (IL-1 receptor-associated kinase 1) and TRAF6 (TNF receptor-associated factor 6). Consequently, DC-specific deletion of OTUB1 impaired the production of cytokines, in particular IL-12, by DCs over the first 2 days of T. gondii infection, resulting in the diminished production of protective interferon-γ (IFN-γ) by natural killer cells, impaired control of parasite replication, and, finally, death from chronic T.encephalitis, all of which could be prevented by low-dose IL-12 treatment in the first 3 days of infection. In contrast, impaired OTUB1-deficient DC activation and cytokine production by OTUB1-deficient DCs protected mice from lipopolysaccharide-induced immunopathology. Collectively, these findings identify OTUB1 as a potent novel regulator of DCs during infectious and inflammatory diseases.

Highlights

Dendritic cells (DCs) are key sentinel cells and professional antigenpresenting cells (APCs) of the immune system.[1]
OTUB1 is upregulated in DCs during T. gondii infection and LPS challenge Since OTUB1 has been reported to interact with molecules critical for activation of the immune system and DCs are key immune cells that protect the host from various infectious diseases, including toxoplasmosis,[25,26] and contribute to immunopathology in sepsis,[21,27,28,29] we asked whether DC-specific OTUB1 is regulated during murine toxoplasmosis and LPS-induced sepsis
The OTUB1 protein was constitutively expressed in splenic CD11c+ cells, which comprise all major populations of DCs,[1] but its levels were significantly increased during T. gondii infection and LPS challenge (Fig. 1a, b)

Summary

Introduction

Dendritic cells (DCs) are key sentinel cells and professional antigenpresenting cells (APCs) of the immune system.[1]. The detection of pathogens by DCs is primarily mediated by pattern recognition receptors (PRRs), which are essential for DC activation and subsequent immune responses. Among PRRs are the Toll-like receptors (TLRs), which consist of 10 human and 12 murine members. TLR11 and TLR12, which are expressed in only mice, sense very few pathogen-associated molecular pattern molecules (PAMPs), including Toxoplasma (T.) gondii profilin (TgPFN), which activates the MyD88/nuclear factorκB (NF-κB) pathway, leading to protective interleukin-12 (IL-12) production by CD8+ cDC1s within a few hours after infection.[3,4,5] In contrast, TLR4 is expressed by many cell types in mice and humans, including cDC1s, cDC2s, and pDCs, and induces activation of the NF-κB and mitogen-activated protein kinase (MAPK) pathways upon engagement by Gram-negative bacterial lipopolysaccharides (LPS). Exaggerated stimulation of TLR4 by LPS may lead to severe immunopathology, as observed in sepsis.[6]

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Results

Conclusion