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J. Exp. Med.,
Volume 188, Number 1, July 1, 1998 211-216
B-regulated X-chromosome-linked
iap Gene Expression Protects Endothelial Cells from Tumor
Necrosis Factor
-induced Apoptosis
By
From the Department of Vascular Biology and Thrombosis Research, Vienna International Research
and Cooperation Center/University of Vienna, A-1235 Vienna, Austria
By differential screening of tumor necrosis factor
(TNF-
) and lipopolysaccharide (LPS)-
activated endothelial cells (ECs), we have identified a cDNA clone that turned out to be a
member of the inhibitor of apoptosis (iap) gene family. iap genes function to protect cells from
undergoing apoptotic death in response to a variety of stimuli. These iap genes, hiap1, hiap2,
and xiap were found to be strongly upregulated upon treatment of ECs with the inflammatory
cytokines TNF-
, interleukin 1
, and LPS, reagents that lead to activation of the nuclear transcription factor
B (NF-
B). Indeed, overexpression of I
B
, an inhibitor of NF-
B, suppresses the induced expression of iap genes and sensitizes ECs to TNF-
-induced apoptosis.
Ectopic expression of one member of the human iap genes, human X-chromosome-linked iap
(xiap), using recombinant adenovirus overrules the I
B
effect and protects ECs from TNF-
-
induced apoptosis. We conclude that xiap represents one of the NF-
B-regulated genes that
counteracts the apoptotic signals caused by TNF-
and thereby prevents ECs from undergoing apoptosis during inflammation.
B
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