1. Department of Biochemistry and Molecular Biology, Center for Apoptosis Research, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
2. These authors contributed equally to this work.

Correspondence to: Emad S. Alnemri¹ Correspondence and requests for materials should be addressed to E.S.A. (Email: E_Alnemri@lac.jci.tju.edu).

Host- and pathogen-associated cytoplasmic double-stranded DNA triggers the activation of a NALP3 (also known as cryopyrin and NLRP3)-independent inflammasome¹, which activates caspase-1 leading to maturation of pro-interleukin-1 and inflammation. The nature of the cytoplasmic-DNA-sensing inflammasome is currently unknown. Here we show that AIM2 (absent in melanoma 2), an interferon-inducible HIN-200 family member that contains an amino-terminal pyrin domain and a carboxy-terminal oligonucleotide/oligosaccharide-binding domain^{2, 3}, senses cytoplasmic DNA by means of its oligonucleotide/oligosaccharide-binding domain and interacts with ASC (apoptosis-associated speck-like protein containing a CARD) through its pyrin domain to activate caspase-1. The interaction of AIM2 with ASC also leads to the formation of the ASC pyroptosome⁴, which induces pyroptotic cell death in cells containing caspase-1. Knockdown of AIM2 by short interfering RNA reduced inflammasome/pyroptosome activation by cytoplasmic DNA in human and mouse macrophages, whereas stable expression of AIM2 in the non-responsive human embryonic kidney 293T cell line conferred responsiveness to cytoplasmic DNA. Our results show that cytoplasmic DNA triggers formation of the AIM2 inflammasome by inducing AIM2 oligomerization. This study identifies AIM2 as an important inflammasome component that senses potentially dangerous cytoplasmic DNA, leading to activation of the ASC pyroptosome and caspase-1.

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