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Published on: May 21, 2020
UCP4 is a target effector of the NF-κB c-Rel prosurvival pathway against oxidative stress
Jessica Wing-Man Ho1, Philip Wing-Lok Ho, Hui-Fang Liu
1Division of Neurology, University Department of Medicine, University of Hong Kong, Hong Kong, People's Republic of China.
Abstract:
Mitochondrial uncoupling protein-4 (UCP4) enhances neuronal survival in 1-methyl-4-phenylpyridinium (MPP(+)) toxicity by suppressing oxidative stress and preserving intracellular ATP and mitochondrial membrane potential (MMP). NF-κB regulates neuronal viability via its complexes, p65 mediating cell death and c-Rel promoting cell survival. We reported previously that NF-κB mediates UCP4 neuroprotection against MPP(+) toxicity. Here, we investigated its link with the NF-κB c-Rel prosurvival pathway in alleviating mitochondrial dysfunction and oxidative stress. We overexpressed a c-Rel-encoding plasmid in SH-SY5Y cells and showed that c-Rel overexpression induced NF-κB activity without affecting p65 level. Overexpression of c-Rel increased UCP4 promoter activity and protein expression. Electrophoretic mobility shift assay showed that H(2)O(2) increased NF-κB binding to the UCP4 promoter and that NF-κB complexes were composed of p50/p50 and p50/c-Rel dimers. Under H(2)O(2)-induced oxidative stress, UCP4 knockdown significantly increased superoxide levels, decreased reduced glutathione (GSH) levels, and increased oxidized glutathione levels, compared to controls. UCP4 expression induced by c-Rel overexpression significantly decreased superoxide levels and preserved GSH levels and MMP under similar stress. These protective effects of c-Rel overexpression in H(2)O(2)-induced oxidative stress were significantly reduced after UCP4 knockdown, indicating that UCP4 is a target effector gene of the NF-κB c-Rel prosurvival pathway to mitigate the effects of oxidative stress.
Insights
Mitochondrial uncoupling protein-4 (UCP4) protects neurons by activating the NF-κB c-Rel pathway, reducing oxidative stress and preserving mitochondrial function. This pathway targets UCP4 to mitigate neuronal damage.
Area of Science:
- Neuroscience
- Mitochondrial Biology
- Cellular Signaling
Background:
- Mitochondrial uncoupling protein-4 (UCP4) is crucial for neuronal survival against oxidative stress.
- Nuclear factor-kappa B (NF-κB) signaling, involving p65 (cell death) and c-Rel (cell survival), regulates neuronal viability.
- Previous work established NF-κB's role in UCP4-mediated neuroprotection against MPP(+) toxicity.
Purpose of the Study:
- To investigate the specific role of the NF-κB c-Rel prosurvival pathway in UCP4-mediated neuroprotection.
- To elucidate the molecular mechanisms by which c-Rel influences UCP4 expression and function under oxidative stress.
- To determine if UCP4 acts as a downstream effector of the c-Rel prosurvival pathway.
Main Methods:
- Overexpression of c-Rel in SH-SY5Y neuroblastoma cells.
- Assessing NF-κB activity and UCP4 promoter activity using luciferase assays.
- Electrophoretic mobility shift assays (EMSA) to analyze NF-κB binding to the UCP4 promoter.
- UCP4 knockdown experiments to evaluate its necessity for c-Rel's protective effects.
- Measurement of oxidative stress markers (superoxide, GSH/GSSG ratio) and mitochondrial membrane potential (MMP).
Main Results:
- c-Rel overexpression enhanced NF-κB activity and significantly increased UCP4 promoter activity and protein expression.
- EMSA confirmed NF-κB binding to the UCP4 promoter, with p50/p50 and p50/c-Rel dimers involved.
- Under H(2)O(2)-induced oxidative stress, UCP4 knockdown exacerbated oxidative damage and MMP loss.
- c-Rel overexpression mitigated oxidative stress and preserved MMP, effects abolished by UCP4 knockdown.
- These findings indicate UCP4 is a key effector of c-Rel-mediated neuroprotection.
Conclusions:
- The NF-κB c-Rel prosurvival pathway directly upregulates UCP4 expression.
- UCP4 acts as a critical downstream effector of c-Rel, mediating neuroprotection against oxidative stress.
- Targeting the c-Rel/UCP4 axis represents a potential therapeutic strategy for neurodegenerative diseases involving mitochondrial dysfunction and oxidative stress.
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