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

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Rajamäki , K , Keskitalo , S , Seppänen , M , Kuismin , O , Vähäsalo , P , Trotta , L , Väänänen , A , Glumoff , V , Keskitalo , P , Kaarteenaho , R , Jartti , A , Hautala , N , Jackson , P , Nordström , D C , Saarela , J , Hautala , T , Eklund , K K & Varjosalo , M 2018 , ' Haploinsufficiency of A20 impairs protein–protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation ' , RMD open , vol. 4 , no. 2 , e000740 . https://doi.org/10.1136/rmdopen-2018-000740

Title: Haploinsufficiency of A20 impairs protein–protein interactome and leads into caspase-8-dependent enhancement of NLRP3 inflammasome activation
Author: Rajamäki, Kristiina; Keskitalo, Salla; Seppänen, Mikko; Kuismin, Outi; Vähäsalo, Paula; Trotta, Luca; Väänänen, Antti; Glumoff, Virpi; Keskitalo, Paula; Kaarteenaho, Riitta; Jartti, Airi; Hautala, Nina; Jackson, Päivi; Nordström, Dan C; Saarela, Janna; Hautala, Timo; Eklund, Kari K; Varjosalo, Markku
Contributor: University of Helsinki, Clinicum
University of Helsinki, Institute of Biotechnology
University of Helsinki, Children's Hospital
University of Helsinki, Genomics of Neurological and Neuropsychiatric Disorders
University of Helsinki, Institute for Molecular Medicine Finland
University of Helsinki, Department of Medicine
University of Helsinki, Janna Saarela / Principal Investigator
University of Helsinki, Department of Medicine
University of Helsinki, Molecular Systems Biology
Date: 2018-10-01
Language: eng
Belongs to series: RMD open
ISSN: 2056-5933
URI: http://hdl.handle.net/10138/298825
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.
Subject: 1182 Biochemistry, cell and molecular biology
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