The DNA sensors AIM2 and IFI16 are SLE autoantigens that bind neutrophil extracellular traps

Abstract

Background:Nucleic acid binding proteins are frequently targeted as autoantigens in systemic lupus erythematosus (SLE) and other interferon (IFN)-linked rheumatic diseases. The AIM-like receptors (ALRs) are IFN-inducible innate sensors that form supramolecular assemblies along double-stranded (ds)DNA of various origins. Here, we investigate the ALR absent in melanoma 2 (AIM2) as a novel autoantigen in SLE, with similar properties to the established ALR autoantigen interferon-inducible protein 16 (IFI16). We examined neutrophil extracellular traps (NETs) as DNA scaffolds on which these antigens might interact in a pro-immune context.Methods:AIM2 autoantibodies were measured by immunoprecipitation in SLE and control subjects. Neutrophil extracellular traps were induced in control neutrophils and combined with purified ALR proteins in immunofluorescence and DNase protection assays. SLE renal tissues were examined for ALR-containing NETs by confocal microscopy.Results:AIM2 autoantibodies were detected in 41/131 (31.3%) SLE patients and 2/49 (4.1%) controls. Our SLE cohort revealed a frequent co-occurrence of anti-AIM2, anti-IFI16, and anti-DNA antibodies, and higher clinical measures of disease activity in patients positive for antibodies against these ALRs. We found that both ALRs bind NETs in vitro and in SLE renal tissues. We demonstrate that ALR binding causes NETs to resist degradation by DNase I, suggesting a mechanism whereby extracellular ALR-NET interactions may promote sustained IFN signaling.Conclusions:Our work suggests that extracellular ALRs bind NETs, leading to DNase resistant nucleoprotein fibers that are targeted as autoantigens in SLE.Funding:These studies were funded by NIH R01 DE12354 (AR), P30 AR070254, R01 GM 129342 (JS), K23AR075898 (CM), K08AR077100 (BA), the Jerome L. Greene Foundation and the Rheumatology Research Foundation. Dr. Antiochos and Dr. Mecoli are Jerome L. Greene Scholars. The Hopkins Lupus Cohort is supported by NIH grant R01 AR069572. Confocal imaging performed at the Johns Hopkins Microscopy Facility was supported by NIH Grant S10 OD016374.

Design Principles for Inflammasome Inhibition by Pyrin-Only-Proteins

“…For example, ASC is known to promote “solidification” of inflammasomes in a prion-like manner, allowing them to perpetuate even after cells undergo pyroptosis (Cai et al, 2014; Franklin et al, 2014; Shen et al, 2021). Moreover, AIM2 and IFI16 filaments also persist and are even stigmatized as autoantigens in debilitating autoimmune disorders such as systemic lupus erythematosus (SLE) and Sjögren’s Syndrome (Antiochos et al, 2018; Antiochos et al, 2022; Baer et al, 2016). Indeed, persisting inflammasome oligomers and their aberrant activities are implicated in a wide range of human diseases even including COVID-19 (Karki et al, 2017; Tartey & Kanneganti, 2020; Vora et al, 2021).…”

Neutrophil extracellular traps in systemic autoimmune and autoinflammatory diseases

“…Mice with genetic deletions of Dnase1 and/or Dnase1l3 have a lupus-like disease associated with defective neutrophil clearance, suggesting a putative link between nuclease activity and neutrophil dysregulation in this disease 89 , 92 , 93 . Furthermore, other factors affecting the clearance of NETs have been described, including nucleic acid oxidation during NET formation and complement C1q activation 45 , 77 , 94 – 96 . NET structures can be phagocytosed by macrophages, triggering the cGAS–STING pathway to induce type I interferon production 97 .…”

AIMing 2 treat atherosclerosis

“…Indeed, NETs induce IL-1β release from macrophages, a process that is connected to the aggravation of atherosclerosis in mice 5 . Mechanistic evidence indicates that AIM2 recognizes NET-DNA 6 . However, it is not clear how extracellular DNA is shuttled across the plasma membrane to be available for AIM2 sensing.…”