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J Biol Chem. 2004 Jan 9;279(2):1513-25. Epub 2003 Oct 8.

The Akt-regulated forkhead transcription factor FOXO3a controls endothelial cell viability through modulation of the caspase-8 inhibitor FLIP.

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1
Molecular Cardiology/Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA.

Abstract

FLICE-inhibitory protein (FLIP) is a homolog of caspase-8 that lacks catalytic activity and has been shown to be important in protecting endothelial cells from apoptosis. The serine/threonine kinase Akt/PKB was recently reported to promote FLIP expression in endothelial and tumor cells. Here we examined the role of the forkhead transcription factor FOXO3a, a downstream target of Akt, in controlling FLIP regulation in endothelial cells. FOXO3a nuclear translocation was regulated by Akt in human umbilical vein endothelial cells. Transduction of a nonphosphorylatable, constitutively active mutant of FOXO3a (TM-FOXO3a) led to the down-regulation of FLIP levels. Transduction with TM-FOXO3a also increased caspase-8 activity and promoted apoptosis in endothelial cells. Conversely, transduction of a dominant-negative mutant of FOXO3a up-regulated FLIP levels and protected endothelial cells from apoptosis under serum deprivation conditions. Restoration of intracellular FLIP blocked caspase-8 activation and inhibited apoptosis in TM-FOXO3a-transduced cells. These data suggest that FOXO3a is a downstream target of Akt in endothelial cells that can promote apoptosis via FLIP down-regulation and activation of the extrinsic apoptotic pathway.

PMID:
14551207
DOI:
10.1074/jbc.M304736200
[Indexed for MEDLINE]
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