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Updated: Apr 11, 2026
Detection of Inflammasome Activation and Pyroptotic Cell Death in Murine Bone Marrow-derived Macrophages
Published on: May 21, 2018
MEX3B is a positive pan-inflammasome regulator
Abstract:
Inflammasomes lead to activation of inflammatory caspases, which induce pyroptosis and an inflammatory immune response to control microbial infections. Inflammasomes are tightly regulated to avoid lethal sepsis and chronic autoimmune conditions. However, posttranslational regulation of inflammatory caspases remains poorly defined. We constructed 375 individual ubiquitin ligase knockout lines by CRISPR-Cas9, performed an unbiased screening, and identified Muscle Excess 3B (MEX3B), an RNA-binding protein and ubiquitin ligase, as a positive regulator of the caspase-4 inflammasome. Genetic depletion of MEX3B inhibited not only the caspase-4 but also NLRP3 and NLRC4 inflammasomes, regarding caspase activation, pyroptosis, and secretion of inflammasome-dependent cytokines, in human cells and murine primary macrophages. This MEX3B function required its RNA-binding, but not ubiquitin ligase activity. These results suggest that MEX3B is a pan-inflammasome regulator and a potential therapeutic target for inflammation.
Insights
Muscle Excess 3B (MEX3B), an RNA-binding protein, regulates inflammasomes controlling immune responses. Depleting MEX3B inhibits inflammasome activation, pyroptosis, and cytokine release, suggesting it as a therapeutic target for inflammation.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Inflammasomes activate inflammatory caspases, driving pyroptosis and immune responses against microbes.
- Tight regulation of inflammasomes is crucial to prevent sepsis and autoimmune diseases.
- Posttranslational regulation of inflammatory caspases is not well understood.
Purpose of the Study:
- To identify novel regulators of inflammatory caspases and inflammasome activation.
- To investigate the role of ubiquitin ligases in inflammasome posttranslational regulation.
Main Methods:
- Generated 375 CRISPR-Cas9 ubiquitin ligase knockout lines for unbiased screening.
- Assessed inflammasome activation, pyroptosis, and cytokine secretion in human cells and murine macrophages.
- Investigated the functional requirement of MEX3B's RNA-binding and ubiquitin ligase activities.
Main Results:
- Identified Muscle Excess 3B (MEX3B), an RNA-binding protein and ubiquitin ligase, as a positive regulator of the caspase-4 inflammasome.
- Genetic depletion of MEX3B inhibited caspase-4, NLRP3, and NLRC4 inflammasomes.
- MEX3B's role in regulating inflammasomes required its RNA-binding activity, not its ubiquitin ligase activity.
Conclusions:
- MEX3B acts as a pan-inflammasome regulator, impacting caspase activation, pyroptosis, and cytokine secretion.
- MEX3B is a potential therapeutic target for treating inflammatory conditions.
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