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Published on: November 2, 2018
IKK-β/NF-κB p65 mediates p27(Kip1) protein degradation in arsenite response
Wei Guo1, Jinyi Liu2, Jinlong Jian2
1Nelson Institute of Environmental Medicine, New York University School of Medicine, 57 Old Forge Road, Tuxedo, NY 10987, United States; Pathology Department, Wuhan University, 185 Donghu Rd., Wuhan, Hubei 430071, China.
Abstract:
p27(Kip1) is a potent inhibitor of the cyclin-dependent kinases that drive G1 to S phase transition. Since deregulation of p27(Kip1) is found in many malignancies and is associated with the poor prognosis, elucidation of the molecular bases for regulation of p27(Kip1) expression is of great significance, not only in providing insight into the understanding of biological p27(Kip1), but also in the development of new cancer therapeutic tactics. We here explored the inhibitory regulation of IKKβ on p27(Kip1) expression following arsenite exposure. We found that although the basal level of p27(Kip1) expression in the IKKβ(-/-) cells is much lower than that in the IKKβ(+/+) cells, the deletion of IKKβ in the MEFs led to a marked increase in p27(Kip1) protein induction due to arsenite exposure in comparison to that in the IKKβ(+/+) cells. The IKKβ regulatory effect on p27(Kip1) expression was also verified in the IKKβ(-/-) and IKKβ(-/-) cells with IKKβ reconstitutional expression, IKKβ(-/-) (IKKβ). Further studies indicated that IKKβ-mediated p27(Kip1) downregulation occurred at protein degradation level via p65-dependent and p50-independent manner. Moreover, the results obtained from the comparison of arsenite-induced GSK3β activation among transfectants of WT, IKKβ(-/-) and IKKβ(-/-) (IKKβ), and the utilization of GSKβ shRNA, demonstrated that IKKβ regulation of p27 protein degradation was mediated by GSK3β following arsenite exposure.
Insights
Inhibitor of cyclin-dependent kinases, p27(Kip1), is crucial in cancer. This study reveals Inhibitor of kappa B kinase subunit beta (IKKβ) regulates p27(Kip1) protein degradation via GSK3β, offering new cancer therapy insights.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- Cancer Biology
Background:
- p27(Kip1) is a key cell cycle inhibitor, crucial for G1 to S phase transition.
- Deregulation of p27(Kip1) is linked to numerous malignancies and poor prognosis.
- Understanding p27(Kip1) regulation is vital for cancer therapeutic development.
Purpose of the Study:
- To investigate the inhibitory regulation of Inhibitor of kappa B kinase subunit beta (IKKβ) on p27(Kip1) expression.
- To elucidate the molecular mechanisms underlying IKKβ-mediated regulation of p27(Kip1) following arsenite exposure.
Main Methods:
- Utilized wild-type (IKKβ(+/+)) and knockout (IKKβ(-/-)) mouse embryonic fibroblasts (MEFs).
- Performed p27(Kip1) expression analysis following arsenite exposure in IKKβ(+/+) and IKKβ(-/-) cells.
- Investigated IKKβ's role in p27(Kip1) protein degradation pathways, including p65 and GSK3β involvement.
- Employed shRNA to confirm GSK3β's role in IKKβ-mediated p27(Kip1) regulation.
Main Results:
- Deletion of IKKβ in MEFs resulted in significantly increased p27(Kip1) protein induction upon arsenite exposure compared to wild-type cells.
- IKKβ-mediated downregulation of p27(Kip1) occurs at the protein degradation level.
- This degradation is dependent on p65 but independent of p50.
- IKKβ regulates p27(Kip1) protein degradation through the activation of GSK3β following arsenite exposure.
Conclusions:
- IKKβ plays an inhibitory role in p27(Kip1) expression by promoting its protein degradation.
- GSK3β is a key mediator in the IKKβ-regulated degradation of p27(Kip1) after arsenite exposure.
- These findings provide novel insights into the molecular regulation of p27(Kip1) and suggest potential therapeutic targets for cancers with p27(Kip1) deregulation.
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