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Mind Bomb Regulates Cell Death during TNF Signaling by Suppressing RIPK1's Cytotoxic Potential
Rebecca Feltham1, Kunzah Jamal2, Tencho Tenev2
1The Breast Cancer Now Toby Robins Research Centre, Institute of Cancer Research, Fulham Road, London SW3 6JB, UK; Walter and Elisa Hall Institute, 1G Royal Parade, Parkville, Victoria 3052, Australia.
Abstract:
Tumor necrosis factor (TNF) is an inflammatory cytokine that can signal cell survival or cell death. The mechanisms that switch between these distinct outcomes remain poorly defined. Here, we show that the E3 ubiquitin ligase Mind Bomb-2 (MIB2) regulates TNF-induced cell death by inactivating RIPK1 via inhibitory ubiquitylation. Although depletion of MIB2 has little effect on NF-κB activation, it sensitizes cells to RIPK1- and caspase-8-dependent cell death. We find that MIB2 represses the cytotoxic potential of RIPK1 by ubiquitylating lysine residues in the C-terminal portion of RIPK1. Our data suggest that ubiquitin conjugation of RIPK1 interferes with RIPK1 oligomerization and RIPK1-FADD association. Disruption of MIB2-mediated ubiquitylation, either by mutation of MIB2's E3 activity or RIPK1's ubiquitin-acceptor lysines, sensitizes cells to RIPK1-mediated cell death. Together, our findings demonstrate that Mind Bomb E3 ubiquitin ligases can function as additional checkpoint of cytokine-induced cell death, selectively protecting cells from the cytotoxic effects of TNF.
Insights
Mind Bomb-2 (MIB2) regulates tumor necrosis factor (TNF)-induced cell death by inactivating RIPK1 through inhibitory ubiquitylation. MIB2 acts as a checkpoint, protecting cells from TNF
Area of Science:
- Molecular Biology
- Cell Death Pathways
- Ubiquitin Signaling
Background:
- Tumor necrosis factor (TNF) is a cytokine that can induce either cell survival or cell death.
- The precise mechanisms controlling TNF's dual signaling outcomes are not fully understood.
- Understanding these mechanisms is crucial for developing targeted therapies for diseases involving TNF signaling.
Purpose of the Study:
- To elucidate the role of the E3 ubiquitin ligase Mind Bomb-2 (MIB2) in regulating TNF-induced cell death.
- To investigate how MIB2 modulates the activity of Receptor-Interacting Protein Kinase 1 (RIPK1) in response to TNF.
- To identify the molecular mechanisms by which MIB2 influences cell fate decisions upon TNF stimulation.
Main Methods:
- Depletion of MIB2 using genetic or molecular techniques.
- Analysis of NF-κB activation and RIPK1/caspase-8-dependent cell death.
- Biochemical assays to detect RIPK1 ubiquitylation at specific lysine residues and assess RIPK1 oligomerization and RIPK1-FADD association.
Main Results:
- MIB2 depletion sensitizes cells to TNF-induced cell death, particularly RIPK1- and caspase-8-dependent death, without significantly affecting NF-κB activation.
- MIB2 inactivates RIPK1 by catalyzing inhibitory ubiquitylation at C-terminal lysine residues.
- Ubiquitination of RIPK1 by MIB2 interferes with RIPK1 oligomerization and its association with FADD, thereby repressing cytotoxic signaling.
Conclusions:
- Mind Bomb-2 (MIB2) acts as a critical negative regulator of TNF-induced cytotoxicity.
- MIB2 protects cells from RIPK1-mediated cell death through inhibitory ubiquitylation of RIPK1.
- MIB2 functions as an essential checkpoint in cytokine-induced cell death pathways, highlighting its therapeutic potential.