The N-end rule ubiquitin ligase UBR2 mediates NLRP1B inflammasome activation by anthrax lethal toxin

Anthrax lethal toxin (LT) is known to induce NLRP1B inflammasome activation and pyroptotic cell death in macrophages from certain mouse strains in its metalloprotease activity-dependent manner, but the underlying mechanism is unknown. Here, we establish a simple but robust cell system bearing dual-f...

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Bibliographic Details
Published in:The EMBO journal 2019-07, Vol.38 (13), p.e101996
Main Authors: Xu, Hao, Shi, Jianjin, Gao, Hang, Liu, Ying, Yang, Zhenxiao, Shao, Feng, Dong, Na
Format: Article
Language:English
Subjects:
Animals
Antigens, Bacterial - adverse effects
Apoptosis Regulatory Proteins - chemistry
Apoptosis Regulatory Proteins - metabolism
Bacterial Toxins - adverse effects
Caspase 1 - metabolism
CRISPR-Cas Systems
Gene Knockout Techniques
HEK293 Cells
Humans
Inflammasomes - drug effects
Macrophages - drug effects
Macrophages - metabolism
Mice
Protein Domains
Proteolysis - drug effects
RAW 264.7 Cells
RNA, Small Interfering - pharmacology
Ubiquitin-Conjugating Enzymes - metabolism
Ubiquitin-Protein Ligases - chemistry
Ubiquitin-Protein Ligases - metabolism
Ubiquitination - drug effects
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Summary:Anthrax lethal toxin (LT) is known to induce NLRP1B inflammasome activation and pyroptotic cell death in macrophages from certain mouse strains in its metalloprotease activity-dependent manner, but the underlying mechanism is unknown. Here, we establish a simple but robust cell system bearing dual-fluorescence reporters for LT-induced ASC specks formation and pyroptotic lysis. A genome-wide siRNA screen and a CRISPR-Cas9 knockout screen were applied to this system for identifying genes involved in LT-induced inflammasome activation. UBR2, an E3 ubiquitin ligase of the N-end rule degradation pathway, was found to be required for LT-induced NLRP1B inflammasome activation. LT is known to cleave NLRP1B after Lys44. The cleaved NLRP1B, bearing an N-terminal leucine, was targeted by UBR2-mediated ubiquitination and degradation. UBR2 partnered with an E2 ubiquitin-conjugating enzyme UBE2O in this process. NLRP1B underwent constitutive autocleavage before the C-terminal CARD domain. UBR2-mediated degradation of LT-cleaved NLRP1B thus triggered release of the noncovalent-bound CARD domain for subsequent caspase-1 activation. Our study illustrates a unique mode of inflammasome activation in cytosolic defense against bacterial insults.
ISSN:0261-4189
1460-2075
DOI:10.15252/embj.2019101996