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Cdc20 proteolysis requires p38 MAPK signaling and Cdh1-independent APC/C ubiquitination during spindle assembly
1Molecular Carcinogenesis Laboratory, Department of Life Sciences, Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan.
Abstract:
Cdc20, an activator of the anaphase promoting complex/cyclosome (APC/C) ubiquitin ligase, initiates the destruction of key mitotic regulators to facilitate mitosis, while it is negatively regulated by the spindle assembly checkpoint (SAC) to prevent premature anaphase entry. Activation of the p38 mitogen-activated protein kinase could contribute to mitotic arrest, but the underlying mechanism is unknown. Here we report a novel pathway in which the p38 signaling triggers Cdc20 destruction under SAC elicited by cadmium, a human carcinogen. We found that the cadmium-induced prometaphase arrest was linked to decreased Cdc20 and accumulated cyclin A protein levels in human cells, whereas the activity of cyclin B1-Cdk1 was unaffected. The Cdc20 half-life was markedly shortened along with its ubiquitination and degradation via 26S proteasome in cadmium-treated asynchronous or G(2)-enriched cells. Depletion of APC3 markedly suppressed the cadmium-induced Cdc20 ubiquitination and proteolysis, while depletion of Cdh1, another activator of APC/C, did not. Intriguingly, blockage of p38 activity restored the Cdc20 levels for continuing mitosis under cadmium, while inhibition of JNK activity had no effect. The cadmium-induced Cdc20 proteolysis was also suppressed during transient depletion of p38alpha or stable expression a dominant negative form of p38. Inhibition of p38 abolished the induction of Mad2-Cdc20-APC3 complex by cadmium. Moreover, forced expression of MKK6-p38 signaling could promote Cdc20 degradation in a Cdh1-independent APC/C pathway. In summary, accelerated ubiquitination and proteolysis of Cdc20 is essential for prometaphase arrest that is mediated via the p38 signaling during SAC activation.
Insights
Cadmium exposure triggers cell cycle arrest by promoting Cdc20 destruction through p38 signaling, a novel pathway identified in human cells. This mechanism involves accelerated ubiquitination and proteasomal degradation of Cdc20, preventing premature anaphase entry.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cdc20 is a key activator of the anaphase promoting complex/cyclosome (APC/C) ubiquitin ligase, crucial for mitotic progression.
- The spindle assembly checkpoint (SAC) normally inhibits APC/C activity to prevent errors during mitosis.
- The role of p38 mitogen-activated protein kinase (MAPK) in cadmium-induced mitotic arrest and its underlying mechanisms remain unclear.
Purpose of the Study:
- To elucidate the novel pathway by which p38 signaling mediates Cdc20 destruction under SAC activation induced by cadmium.
- To investigate the role of p38 signaling in cadmium-induced prometaphase arrest and its impact on key cell cycle regulators.
Main Methods:
- Analysis of Cdc20 protein levels, ubiquitination, and degradation in cadmium-treated human cells.
- Investigation of the involvement of p38 MAPK, APC/C components (APC3, Cdh1), and other signaling pathways (JNK).
- Utilized techniques such as protein depletion, dominant-negative protein expression, and signaling pathway activation/inhibition.
Main Results:
- Cadmium exposure induced prometaphase arrest, decreased Cdc20 levels, and increased cyclin A, while cyclin B1-Cdk1 activity remained unaffected.
- Cdc20 half-life was reduced due to enhanced ubiquitination and 26S proteasome-mediated degradation, dependent on APC3 but not Cdh1.
- Inhibition of p38 signaling restored Cdc20 levels and mitosis, suppressed cadmium-induced Cdc20 proteolysis, and abolished Mad2-Cdc20-APC3 complex formation.
Conclusions:
- Accelerated ubiquitination and proteolysis of Cdc20, mediated by p38 signaling, are essential for cadmium-induced prometaphase arrest during SAC activation.
- This study reveals a novel mechanism linking p38 MAPK activation to Cdc20 degradation via an APC/C pathway independent of Cdh1.
- The findings highlight a critical role for p38-mediated Cdc20 regulation in cellular response to genotoxic stress from carcinogens like cadmium.
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