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Proc Natl Acad Sci U S A. 2017 Feb 7;114(6):E961-E969. doi: 10.1073/pnas.1613305114. Epub 2017 Jan 17.

Active MLKL triggers the NLRP3 inflammasome in a cell-intrinsic manner.

Author information

1
Cell Signalling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.
2
Department of Medical Biology, University of Melbourne, Parkville, VIC 3010, Australia.
3
Institute for Molecular Bioscience and Centre for Inflammation and Disease Research, The University of Queensland, St. Lucia, QLD 4072, Australia.
4
Inflammation Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.
5
Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109.
6
Systems Biology & Personalised Medicine Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.
7
Department of Medical Biology, University of Melbourne, Parkville, VIC 3010, Australia; lawlor@wehi.edu.au lindqvist@wehi.edu.au vince@wehi.edu.au.
8
Cell Signalling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia; lawlor@wehi.edu.au lindqvist@wehi.edu.au vince@wehi.edu.au.

Abstract

Necroptosis is a physiological cell suicide mechanism initiated by receptor-interacting protein kinase-3 (RIPK3) phosphorylation of mixed-lineage kinase domain-like protein (MLKL), which results in disruption of the plasma membrane. Necroptotic cell lysis, and resultant release of proinflammatory mediators, is thought to cause inflammation in necroptotic disease models. However, we previously showed that MLKL signaling can also promote inflammation by activating the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome to recruit the adaptor protein apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC) and trigger caspase-1 processing of the proinflammatory cytokine IL-1β. Here, we provide evidence that MLKL-induced activation of NLRP3 requires (i) the death effector four-helical bundle of MLKL, (ii) oligomerization and association of MLKL with cellular membranes, and (iii) a reduction in intracellular potassium concentration. Although genetic or pharmacological targeting of NLRP3 or caspase-1 prevented MLKL-induced IL-1β secretion, they did not prevent necroptotic cell death. Gasdermin D (GSDMD), the pore-forming caspase-1 substrate required for efficient NLRP3-triggered pyroptosis and IL-1β release, was not essential for MLKL-dependent death or IL-1β secretion. Imaging of MLKL-dependent ASC speck formation demonstrated that necroptotic stimuli activate NLRP3 cell-intrinsically, indicating that MLKL-induced NLRP3 inflammasome formation and IL-1β cleavage occur before cell lysis. Furthermore, we show that necroptotic activation of NLRP3, but not necroptotic cell death alone, is necessary for the activation of NF-κB in healthy bystander cells. Collectively, these results demonstrate the potential importance of NLRP3 inflammasome activity as a driving force for inflammation in MLKL-dependent diseases.

KEYWORDS:

Gasdermin D; MLKL; NLRP3; interleukin-1β; necroptosis

PMID:
28096356
PMCID:
PMC5307433
DOI:
10.1073/pnas.1613305114
[Indexed for MEDLINE]
Free PMC Article

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