Related Experiment Videos
Requirement of BAX for efficient adenovirus-induced apoptosis
Elena Lomonosova1, T Subramanian, G Chinnadurai
1Institute for Molecular Virology, Saint Louis University School of Medicine, St. Louis, Missouri 63110, USA.
Abstract:
Infection of human epithelial cells with adenoviruses induces an apoptosis paradigm that is efficiently suppressed by the expression of viral E1B-19K protein, which is a functional homolog of the cellular antiapoptosis protein BCL-2. The mechanisms of adenovirus (Ad)-induced apoptosis appear to involve the cellular BCL-2 family proapoptotic proteins. Recent genetic studies with fibroblasts derived from mutant mouse embryos indicate that a class of the BCL-2 family proapoptotic proteins (designated BH-123 or multidomain proteins) such as BAX and BAK constitutes an essential component of the core apoptosis machinery in animal cells. We have examined the role of BAX in Ad-induced apoptosis in human epithelial cells using two colon cancer cell lines, HCT116Bax (Bax(+/-)) and HCT116BaxKO (Bax(-/-)) (L. Zhang, J. Yu, B. H. Park, K. W. Kinzler, and B. Vogelstein, Science 290:989-992, 2000). Infection of Bax(+/-) cells with an Ad type 2 mutant (dl250) defective in expression of the E1B-19K protein resulted in enhanced cytopathic effect, large plaques on cell monolayers, fragmentation of cellular DNA, and enhanced cell death. These mutant phenotypes were not efficiently expressed in Bax(-/-) cells, suggesting that BAX is essential for Ad-induced apoptosis. Infection of Bax(+/-) cells with dl250 induced increased levels of an N-terminally processed form of BAX. Cells infected with the 19K mutant also contained enhanced levels of truncated BAX in membrane-inserted form. Our results suggest that at least a part of the mechanism utilized by E1B-19K to suppress apoptosis during Ad infection may involve modulation of the activities of BAX.
Insights
Adenovirus infection triggers apoptosis, normally blocked by viral E1B-19K protein. This study shows BAX protein is essential for adenovirus-induced apoptosis in human cells, with E1B-19K modulating BAX activity.
Area of Science:
- Cell Biology
- Virology
- Molecular Biology
Background:
- Adenovirus infection induces apoptosis, a programmed cell death pathway.
- Viral E1B-19K protein, a homolog of BCL-2, suppresses adenovirus-induced apoptosis.
- BAX, a proapoptotic protein, is crucial for apoptosis in animal cells.
Purpose of the Study:
- To investigate the role of BAX in adenovirus-induced apoptosis in human epithelial cells.
- To understand how adenovirus E1B-19K protein modulates apoptosis through BAX.
Main Methods:
- Utilized HCT116 colon cancer cell lines with varying BAX expression (Bax(+/-) and Bax(-/-)).
- Infected cells with an adenovirus type 2 mutant (dl250) lacking E1B-19K expression.
- Analyzed cytopathic effects, DNA fragmentation, cell death, and BAX protein processing.
Main Results:
- Adenovirus dl250 infection caused enhanced cell death and DNA fragmentation in Bax(+/-) cells, but not Bax(-/-) cells.
- BAX appears essential for adenovirus-induced apoptosis.
- E1B-19K deficient adenovirus infection increased processed and membrane-inserted forms of BAX.
Conclusions:
- BAX is essential for adenovirus-induced apoptosis in human epithelial cells.
- Adenovirus E1B-19K protein likely suppresses apoptosis by modulating BAX activity.