Potentiation of tumor necrosis factor-alpha-induced cell death by rottlerin through a cytochrome-C-independent pathway.
The protein kinase C (PKC) signal transduction pathway negatively regulates receptor-initiated cell death. In HeLa cells, tumor necrosis factor-alpha (TNF)-mediated cell death involved mitochondria and was blocked by the overexpression of Bcl-2. The PKC-specific inhibitor bisindolylmaleimide and the PKCdelta inhibitor rottlerin enhanced TNF-induced cell death. We have investigated if potentiation of TNF-induced cell death by rottlerin involved amplification of the mitochondrial pathway. TNF induced cleavage of the proapoptotic protein Bid and release of mitochondrial cytochrome c. Rottlerin enhanced activation of caspase-8 and cleavage of Bid. It also enhanced activation of caspase-9 but it did not increase cytochrome c in the cytosol. It, however, increased release of mitochondrial apoptosis-inducing factor (AIF) to the cytosol. Overexpression of Bcl-2 prevented release of both cytochrome c and AIF to the cytosol. Prolonged exposure (> or =6 h) of HeLa cells to rottlerin and TNF decreased the level of cytochrome c but not of AIF in the cytosol. These results suggest that rottlerin activates a cytochrome-c-independent cell death pathway to potentiate cell death by TNF.
Basu
Alakananda
A
Dept of Molecular Biology and Immunology, University of North Texas Health Science Center, 5300 Camp Bowie Boulevard, Fort Worth, TX 76107, USA. abasu@hsc.unt.edu
Johnson
Daniel E
DE
Woolard
Matthew D
MD
D000098:Acetophenones / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001578:Benzopyrans / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D003574:Cytochrome c Group / Q000187:drug effects* / Q000378:metabolism; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006367:HeLa Cells; D006801:Humans; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology
D000098:Acetophenones; D001578:Benzopyrans; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D014409:Tumor Necrosis Factor-alpha; C085746:rottlerin; D011493:Protein Kinase C