University of Oulu

Rajamäki K, Keskitalo S, Seppänen M, et al. Haploinsufficiency of A20 impairs protein–protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation. RMD Open 2018;4:e000740. doi: 10.1136/rmdopen-2018-000740

Haploinsufficiency of A20 impairs protein–protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation

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Author: Rajamäki, Kristiina1; Keskitalo, Salla2; Seppänen, Mikko3;
Organizations: 1Clinicum, Faculty of Medicine, University of Helsinki
2Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki
3Immunodeficiency Unit, Inflammation Center and Rare Diseases Center, Children's Hospital, Helsinki University and Helsinki University Hospital
4Department of Clinical Genetics, PEDEGO Research Unit, Medical Research Center, Oulu University Hospital and University of Oulu
5Department of Pediatrics, PEDEGO Research Unit, Medical Research Center, Oulu University Hospital and University of Oulu
6Institute for Molecular Medicine Finland, Helsinki Institute of Life Science (HiLIFE), University of Helsinki
7Department of Infection Control, Lapland Central Hospital
8Research Unit of Biomedicine, University of Oulu
9Respiratory Diseases, Research Unit of Internal Medicine, University of Oulu
10Medical Research Center Oulu, Oulu University Hospital
11Department of Radiology, Oulu University Hospital
12Department of Ophthalmology, PEDEGO Research Unit, Medical Research Center, Oulu University Hospital and University of Oulu
13Department of Medicine and Rehabilitation, Helsinki University Hospital and Helsinki University
14Research Unit of Internal Medicine, University of Oulu and Oulu University Hospital
15Department of Rheumatology, Inflammation Center, Helsinki University and Helsinki University Hospital
16Research Institute, Invalid Foundation
17Orton Orthopaedic Hospital
18Proteomics Unit, Institute of Biotechnology, University of Helsinki
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.4 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe201902064181
Language: English
Published: BMJ, 2018
Publish Date: 2019-02-06
Description:

Abstract

Objectives: TNFAIP3 encodes A20 that negatively regulates nuclear factor kappa light chain enhancer of activated B cells (NF-κB), the major transcription factor coordinating inflammatory gene expression. TNFAIP3 polymorphisms have been linked with a spectrum of inflammatory and autoimmune diseases and, recently, loss-of-function mutations in A20 were found to cause a novel inflammatory disease ‘haploinsufficiency of A20’ (HA20). Here we describe a family with HA20 caused by a novel TNFAIP3 loss-of-function mutation and elucidate the upstream molecular mechanisms linking HA20 to dysregulation of NF-κB and the related inflammasome pathway.

Methods: NF-κB activation was studied in a mutation-expressing cell line using luciferase reporter assay. Physical and close-proximity protein–protein interactions of wild-type and TNFAIP3 p.(Lys91*) mutant A20 were analysed using mass spectrometry. NF-κB -dependent transcription, cytokine secretion and inflammasome activation were compared in immune cells of the HA20 patients and control subjects.

Results: The protein–protein interactome of p.(Lys91*) mutant A20 was severely impaired, including interactions with proteins regulating NF-κB activation, DNA repair responses and the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The p.(Lys91*) mutant A20 failed to suppress NF-κB signalling, which led to increased NF-κB -dependent proinflammatory cytokine transcription. Functional experiments in the HA20 patients’ immune cells uncovered a novel caspase-8-dependent mechanism of NLRP3 inflammasome hyperresponsiveness that mediated the excessive secretion of interleukin-1β and interleukin-18.

Conclusions: The current findings significantly deepen our understanding of the molecular mechanisms underlying HA20 and other diseases associated with reduced A20 expression or function, paving the way for future therapeutic targeting of the pathway.

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Series: RMD open
ISSN: 2056-5933
ISSN-E: 2056-5933
ISSN-L: 2056-5933
Volume: 4
Issue: 2
Article number: e000740
DOI: 10.1136/rmdopen-2018-000740
OADOI: https://oadoi.org/10.1136/rmdopen-2018-000740
Type of Publication: A1 Journal article – refereed
Field of Science: 3121 Internal medicine
3111 Biomedicine
Subjects:
Funding: The study was supported by Finska läkaresällskapet (KKe, Dn), the Canadian Institutes of Health Research (tHc 135230; KKe), the Stockmann foundation (KKe) and the Paulo foundation (Kr).
Copyright information: © Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ. This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
  https://creativecommons.org/licenses/by-nc/4.0/