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Published on: June 25, 2015
An anthrax lethal factor mutant that is defective at causing pyroptosis retains proapoptotic activity
Stephanie Ngai1, Sarah Batty, Kuo-Chieh Liao
1Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
The FEBS Journal
|November 20, 2009
Summary
Anthrax lethal factor (LF) mutant LF-K518E/E682G impairs Nlrp1b inflammasome activation and pyroptosis. This mutant retains the ability to downregulate the extracellular signal-related kinase (ERK) pathway, suggesting specific substrate defects.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Anthrax lethal toxin (LT) disrupts host immune responses by targeting cellular signaling pathways.
- Lethal factor (LF), a component of LT, cleaves mitogen-activated protein kinase kinases (MAPKKs), affecting signaling pathways like ERK, p38, and JNK.
- These disruptions contribute to Bacillus anthracis survival and proliferation within the host.
Purpose of the Study:
- To characterize a specific LF mutant, LF-K518E/E682G, for its effects on cellular processes and signaling pathways.
- To investigate the mutant's role in pyroptosis and Nlrp1b inflammasome activation.
- To determine the substrate specificity of the LF mutant.
Main Methods:
- Characterization of LF-K518E/E682G mutant in RAW 264.7 cells and a heterologous expression system.
- Assessment of pyroptosis induction and Nlrp1b inflammasome activation.
- Analysis of effects on ERK, p38, and c-Jun N-terminal kinase (JNK) signaling pathways.
- Evaluation of melanoma cell killing by the mutant.
Main Results:
- LF-K518E/E682G was defective in causing pyroptosis in RAW 264.7 cells and activating the Nlrp1b inflammasome.
- The mutant retained the ability to downregulate the ERK pathway but not the p38 or JNK pathways.
- LF-K518E/E682G efficiently killed melanoma cells, indicating retained cytotoxic function.
Conclusions:
- The LF-K518E/E682G mutant exhibits specific defects in cleaving substrates crucial for Nlrp1b inflammasome activation and pyroptosis.
- Despite these defects, the mutant retains partial signaling pathway modulation capabilities (ERK) and cytotoxic activity.
- These findings provide insights into LF substrate specificity and its role in anthrax pathogenesis.
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