A1 Functions at the Mitochondria to Delay Endothelial Apoptosis in Response to Tumor Necrosis Factor

• Published in: The Journal of biological chemistry 2000-06, Vol.275 (24), p.18099-18107
• Main Authors: Duriez, Patrick J., Wong, Fred, Dorovini-Zis, Katerina, Shahidi, Réza, Karsan, Aly
• Format: Article
• Language: English
• Subjects: AA1 gene; Apoptosis; benzyloxycarbonyl-VAD-formylmethyl ketone; Bid protein; Caspase 3; Caspase 8; Caspase 9; Caspases - metabolism; Cells, Cultured; Cycloheximide - pharmacology; Cytochrome c Group - metabolism; Dactinomycin - pharmacology; DNA Replication; DNA-Binding Proteins - physiology; Endothelium - cytology; Homeodomain Proteins; Humans; Microcirculation; Microscopy, Immunoelectron; Minor Histocompatibility Antigens; Mitochondria - drug effects; Mitochondria - metabolism; NF-kappa B - drug effects; NF-kappa B - metabolism; poly(ADP-ribose) polymerase; Poly(ADP-ribose) Polymerases - metabolism; Protein Synthesis Inhibitors - pharmacology; Proto-Oncogene Proteins c-bcl-2 - genetics; Replication Protein C; Repressor Proteins; Saccharomyces cerevisiae Proteins; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M908925199

Tumor necrosis factor (TNF) does not cause endothelial apoptosis unless the expression of cytoprotective genes is blocked. We have previously demonstrated that one of the TNF-inducible cytoprotective genes is the Bcl-2 family member, A1. A1 is induced by the action of the transcription factor, NFκB, in response to inflammatory mediators. In this report we demonstrate that, as with other cell types, inhibition of NFκB initiates microvascular endothelial apoptosis in response to TNF. A1 is able to inhibit this apoptosis over 24 h. We demonstrate that A1 is localized to and functions at the mitochondria. Whereas A1 is able to inhibit mitochondrial depolarization, loss of cytochrome c,cleavage of caspase 9, BID, and poly(ADP-ribose) polymerase, it does not block caspase 8 or caspase 3 cleavage. In contrast, A1 is not able to prevent endothelial apoptosis by TNF over 72 h, when NFκB signaling is blocked. On the other hand, the caspase inhibitor, benzyloxycarbonyl-VAD-formylmethyl ketone, completely blocks TNF-induced endothelial apoptosis over 72 h. Our findings indicate that A1 is able to maintain temporary survival of endothelial cells in response to TNF by maintaining mitochondrial viability and function. However, a mitochondria-independent caspase pathway eventually results in endothelial death despite mitochondrial protection by A1.