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BCL-XL binds and antagonizes RASSF6 tumor suppressor to suppress p53 expression
Xiaoyin Xu1,2, Hiroaki Iwasa1, Shakhawoat Hossain1,3
1Department of Medical Biochemistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Abstract:
RASSF6, a member of the tumor suppressor Ras-association domain family proteins, induces apoptosis in the caspase-dependent and caspase-independent manners. RASSF6 interacts with MDM2 and stabilizes p53. BCL-XL is a prosurvival member of BCL-2 family proteins. BCL-XL directly inhibits proapoptotic BAX and BAK. BCL-XL also traps tBID, a proapoptotic activator BH3-only protein, and sequesters p53. In addition, BCL-XL regulates the mitochondrial membrane permeability via voltage-dependent anion channel. In these manners, BCL-XL plays an antiapoptotic role. We report the interaction of BCL-XL with RASSF6. BCL-XL inhibits the interaction between RASSF6 and MDM2 and suppresses p53 expression. Consequently, BCL-XL antagonizes RASSF6-mediated apoptosis. Thus, the inhibition of RASSF6-mediated apoptosis also underlies the prosurvival role of BCL-XL.
Insights
The anti-apoptotic protein BCL-XL inhibits the tumor suppressor RASSF6, preventing RASSF6-mediated apoptosis by blocking its interaction with MDM2 and subsequent p53 stabilization. This reveals a novel prosurvival mechanism for BCL-XL.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- RASSF6 is a tumor suppressor protein that induces apoptosis and interacts with MDM2 to stabilize p53.
- BCL-XL is a prosurvival protein that inhibits apoptosis through various mechanisms, including direct inhibition of BAX and BAK, trapping tBID, and sequestering p53.
Purpose of the Study:
- To investigate the interaction between BCL-XL and RASSF6.
- To elucidate the functional consequences of this interaction on RASSF6-mediated apoptosis and p53 expression.
Main Methods:
- Co-immunoprecipitation assays to detect protein-protein interactions.
- Western blotting to assess protein levels (p53, RASSF6, MDM2).
- Apoptosis assays to quantify cell death.
Main Results:
- BCL-XL directly interacts with RASSF6.
- BCL-XL inhibits the interaction between RASSF6 and MDM2.
- BCL-XL suppresses RASSF6-induced p53 expression.
- BCL-XL antagonizes RASSF6-mediated apoptosis.
Conclusions:
- BCL-XL directly inhibits RASSF6 function by preventing its interaction with MDM2.
- This inhibition leads to suppressed p53 expression and antagonism of RASSF6-induced apoptosis.
- The findings highlight a novel prosurvival role for BCL-XL in antagonizing tumor suppressor activity.
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