Phosphatidylinositol 3-kinase/Akt signaling controls endothelial cell sensitivity to Fas-mediated apoptosis via regulation of FLICE-inhibitory protein (FLIP).
Fas is constitutively expressed on endothelial cells, but in contrast to smooth muscle and other cell types, endothelial cells are highly resistant to Fas-mediated apoptosis. In this study, we examined the role of the serine/threonine kinase Akt/PKB in controlling the sensitivity of endothelial cells to Fas-mediated apoptosis. Serum deprivation inhibited expression of the caspase-8 inhibitor FLICE-inhibitory protein (FLIP), which functions downstream from Fas. FLIP expression levels were restored when serum-depleted cells were treated with vascular endothelial growth factor. Treatment with the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitors wortmannin or LY294002 or infection of the adenoviral construct expressing dominant-negative Akt (Adeno-dnAkt) also inhibited the expression of FLIP in endothelial cells, whereas the MEK inhibitor PD98059 had no effect. Conversely, adenovirus-mediated transfection of a constitutively-active Akt gene abolished the wortmannin- and LY294002-mediated downregulation of FLIP. Suppression of PI 3-kinase signaling sensitized endothelial cells to Fas-mediated apoptosis. Under conditions of suppressed PI 3-kinase signaling, restoration of FLIP expression reversed the induced sensitivity of endothelial cells to Fas-mediated apoptosis. These data suggest that inhibition of Fas-mediated apoptosis, via promotion of FLIP expression, is a mechanism through which Akt signaling can promote endothelial cell survival.
Suhara
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T
Division of Cardiovascular Research, St. Elizabeth's Medical Center, Boston,MA 02135, USA. kwalsh@world.std.com
Mano
T
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Oliveira
B E
BE
Walsh
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K
D000730:Androstadienes / Q000494:pharmacology; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation; D016228:Endothelial Growth Factors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008222:Lymphokines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D013752:Tetracycline / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D000077191:Wortmannin; D019014:fas Receptor / Q000276:immunology / Q000502:physiology*
D000730:Androstadienes; D000906:Antibodies; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D008222:Lymphokines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D013752:Tetracycline; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D000077191:Wortmannin; D019014:fas Receptor; C506386:CFLAR protein, human; C494918:AKT1 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human