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Published on: May 21, 2018
Vibrio vulnificus MARTX cytotoxin triggers necroptosis-driven macrophage cell death
Horng-Ren Lo1, Chia-Ming Hsieh2, Chun-Ya Chen3
1Department of Medical Laboratory Science and Biotechnology, Fooyin University, Kaohsiung, Taiwan.
Background:
Vibrio vulnificus, a gram-negative bacterium, commonly infects humans via contaminated seafood or wounds and can cause severe sepsis. The multifunctional autoprocessing repeat-in-toxin (MARTX) is one of the most crucial virulence factors in V. vulnificus, associated with host pathogenesis. V. vulnificus MARTX induces serious cell damage, leading to subsequent cell death. However, the specific modalities of cell death are diverse and not fully understood.
Methods:
Murine macrophage cells were challenged with V. vulnificus wild-type and ΔrtxA1 strains. Necroptotic events were assessed through western blotting, cytokine production assays, and fluorescence-based analyses.
Results:
In this study, we showed that MARTX is essential for V. vulnificus-induced macrophage necroptosis as it activates receptor-interacting protein kinase 3 (RIPK3)/mixed-lineage kinase domain-like pseudokinase (MLKL) signaling. In contrast, the MARTX-deficient mutant (ΔrtxA1) substantially enhanced phagocytosis by macrophages and abolished necroptosis. We further found that MARTX elicited MLKL mobilization to membrane lipid rafts in response to necroptosis. Disruption of lipid rafts using cholesterol depletion/usurping agents significantly alleviated V. vulnificus-induced cell death.
Conclusions:
Our findings reveal that V. vulnificus MARTX induces macrophage cell death via the necroptosis pathway, dependent on adequate cholesterol levels and potentially involving other cell death mechanisms.
Insights
Vibrio vulnificus toxin (MARTX) triggers macrophage necroptosis, a programmed cell death pathway. This process requires cholesterol and involves RIPK3/MLKL signaling, offering new insights into bacterial pathogenesis.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Vibrio vulnificus is a dangerous pathogen causing sepsis.
- The MARTX toxin is a key virulence factor.
- Mechanisms of V. vulnificus-induced cell death are not fully understood.
Purpose of the Study:
- To investigate the role of MARTX in V. vulnificus-induced macrophage cell death.
- To elucidate the specific cell death pathway involved.
Main Methods:
- Murine macrophages were infected with V. vulnificus strains.
- Necroptosis was assessed using western blotting, cytokine assays, and fluorescence.
- Lipid rafts were disrupted to evaluate their role.
Main Results:
- MARTX is essential for V. vulnificus-induced necroptosis, activating RIPK3/MLKL signaling.
- MARTX deficiency increased phagocytosis and abolished necroptosis.
- MLKL localized to lipid rafts during necroptosis, and raft disruption reduced cell death.
Conclusions:
- V. vulnificus MARTX induces macrophage necroptosis via RIPK3/MLKL.
- Cholesterol levels are crucial for this cell death pathway.
- Other cell death mechanisms may also be involved.
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