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Involvement of p27(kip1) in ceramide-mediated apoptosis in HL-60 cells
1Department of Life Science, College of Natural Sciences, Chung-Ang University, Seoul, South Korea.
Abstract:
Ceramide acts as a mediator of apoptosis in various cell lines, but little is known regarding the molecular mechanism linked to the cell cycle. In the present study, we examined the expression of p27(kip1) and its relationship to apoptosis induced by ceramide. We demonstrated that treatment of HL-60 cells with C6-ceramide resulted in G1 phase elevation followed by apoptotic cleavage associated with increase in the level of cdk inhibitor p27(kip1). Ceramide inhibited the kinase activities of cdk2 and cdk4 within 24 h of treatment. Ceramide-induced inhibition of cdk2 and cdk4 kinase activities was accompanied by increase of p27(kip1) in the cdks complexes. In addition, we have shown that both the cell death and expression of p27(kip1) protein induced by ceramide were significantly decreased in HL-60 cells overexpressing bcl-2. Furthermore, ceramide induced a significant increase in Bax protein expression coincided with increase in p27(kip1) protein level. These findings indicate that p27(kip1) may play important roles in mediating ceramide-induced apoptosis and its expression can be regulated by Bax and Bcl-2.
Insights
Ceramide induces apoptosis by affecting the cell cycle, increasing the expression of the CDK inhibitor p27(kip1). Bcl-2 overexpression reduces ceramide-induced cell death and p27(kip1) levels, suggesting p27(kip1) plays a key role in ceramide-mediated apoptosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Ceramide is known to mediate apoptosis, but its precise role in cell cycle regulation during this process is unclear.
- Understanding the molecular mechanisms linking ceramide-induced apoptosis to the cell cycle is crucial for cancer research.
Purpose of the Study:
- To investigate the role of p27(kip1) in ceramide-induced apoptosis.
- To explore the relationship between ceramide, cell cycle arrest, and apoptosis in HL-60 cells.
Main Methods:
- Treatment of HL-60 cells with C6-ceramide.
- Analysis of cell cycle progression (G1 phase elevation).
- Measurement of cyclin-dependent kinase (cdk) inhibitor p27(kip1) levels and its association with cdks.
- Assessment of Bax and Bcl-2 protein expression.
- Evaluation of ceramide-induced apoptosis in cells overexpressing Bcl-2.
Main Results:
- C6-ceramide treatment led to G1 phase arrest and apoptosis, accompanied by increased p27(kip1) levels.
- Ceramide inhibited cdk2 and cdk4 kinase activities by increasing p27(kip1) within their complexes.
- Bcl-2 overexpression significantly reduced ceramide-induced cell death and p27(kip1) expression.
- Ceramide increased Bax protein expression concurrently with p27(kip1) levels.
Conclusions:
- p27(kip1) is implicated in mediating ceramide-induced apoptosis.
- The expression of p27(kip1) during ceramide-induced apoptosis is influenced by the balance of Bax and Bcl-2 proteins.