Fas ligand-induced apoptosis is regulated by nitric oxide through the inhibition of fas receptor clustering and the nitrosylation of protein kinase Cepsilon.
Apoptosis induced by the death-inducing ligand FasL (CD95L) is a major mechanism of cell death. Trophoblast cells express the Fas receptor yet survive in an environment that is rich in the ligand. We report that basal nitric oxide (NO) production is responsible for the resistance of trophoblasts to FasL-induced apoptosis. In this study we demonstrate that basal NO production resulted in the inhibition of receptor clustering following ligand binding. In addition NO also protected cells through the selective nitrosylation, and inhibition, of protein kinase Cepsilon (PKCepsilon) but not PKCalpha. In the absence of NO production PKCepsilon interacted with, and phosphorylated, the anti-apoptotic protein cFLIP. The interaction is predominantly with the short form of cFLIP and its phosphorylation reduces its recruitment to the death-inducing signaling complex (DISC) that is formed following binding of a death-inducing ligand to its receptor. Inhibition of cFLIP recruitment to the DISC leads to increased activation of caspase 8 and subsequently to apoptosis. Inhibition of PKCepsilon using siRNA significantly reversed the sensitivity to apoptosis induced by inhibition of NO synthesis suggesting that NO-mediated inhibition of PKCepsilon plays an important role in the regulation of Fas-induced apoptosis.
Dash
Philip R
PR
Division of Basic Medical Sciences, St George's, University of London, Cranmer Terrace, London, UK. p.dash@sgul.ac.uk
McCormick
James
J
Thomson
Mika J C B
MJ
Johnstone
Alan P
AP
Cartwright
Judith E
JE
Whitley
Guy Stj
GS
D017209:Apoptosis / Q000187:drug effects; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000378:metabolism; D053222:Fas Ligand Protein / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D047468:Immunoprecipitation; D008954:Models, Biological; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009603:Nitroso Compounds / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D019014:fas Receptor / Q000037:antagonists & inhibitors*
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D053418:Death Domain Receptor Signaling Adaptor Proteins; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D009603:Nitroso Compounds; D019014:fas Receptor; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D019331:NG-Nitroarginine Methyl Ester