Abstract
Bile acids induce hepatocyte injury by enhancing death receptor-mediated apoptosis. In this study, bile acid effects on TRAIL-mediated apoptosis were examined to gain insight into bile acid potentiation of death receptor signaling. TRAIL-induced apoptosis of HuH-7 cells, stably transfected with a bile acid transporter, was enhanced by bile acids. Caspase 8 and 10 activation, bid cleavage, cytosolic cytochrome c, and caspase 3 activation by TRAIL were all increased by the bile acid glycochenodeoxycholate (GCDCA). GCDCA (100 microm) did not alter expression of TRAIL-R1/DR4, TRAIL-R2/DR5, procaspase 8, cFLIP-L, cFLIP-s, Bax, Bcl-xL, or Bax. However, both caspase 8 and caspase 10 recruitment and processing within the TRAIL death-inducing signaling complex (DISC) were greater in GCDCA-treated cells whereas recruitment of cFLIP long and short was reduced. GCDCA stimulated phosphorylation of both cFLIP isoforms, which was associated with decreased binding to GST-FADD. The protein kinase C antagonist chelerythrine prevented bile acid-stimulated cFLIP-L and -s phosphorylation, restored cFLIP binding to GST-FADD, and attenuated bile acid potentiation of TRAIL-induced apoptosis. These results provide new insights into the mechanisms of bile acid cytotoxicity and the proapoptotic effects of cFLIP phosphorylation in TRAIL signaling.
Publication types
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Adaptor Proteins, Signal Transducing*
-
Apoptosis / physiology*
-
Apoptosis Regulatory Proteins
-
Biological Transport / physiology
-
CASP8 and FADD-Like Apoptosis Regulating Protein
-
Carrier Proteins / genetics
-
Carrier Proteins / metabolism*
-
Caspase 10
-
Caspase 8
-
Caspase 9
-
Caspase Inhibitors
-
Caspases / metabolism
-
Cell Fractionation
-
Enzyme Activation
-
Enzyme Inhibitors / metabolism*
-
Fas-Associated Death Domain Protein
-
Glycochenodeoxycholic Acid / metabolism*
-
Humans
-
Hydroxysteroid Dehydrogenases*
-
Intracellular Signaling Peptides and Proteins*
-
Membrane Glycoproteins / genetics
-
Membrane Glycoproteins / metabolism*
-
Microscopy, Fluorescence
-
Phosphorylation
-
Protein Binding
-
Protein Isoforms
-
Protein Kinase C / metabolism
-
Proto-Oncogene Proteins / metabolism
-
Proto-Oncogene Proteins c-bcl-2 / metabolism
-
Recombinant Fusion Proteins / metabolism
-
Signal Transduction / physiology
-
TNF-Related Apoptosis-Inducing Ligand
-
Tumor Cells, Cultured
-
Tumor Necrosis Factor-alpha / genetics
-
Tumor Necrosis Factor-alpha / metabolism*
-
bcl-2-Associated X Protein
Substances
-
Adaptor Proteins, Signal Transducing
-
Apoptosis Regulatory Proteins
-
BAX protein, human
-
CASP8 and FADD-Like Apoptosis Regulating Protein
-
CFLAR protein, human
-
Carrier Proteins
-
Caspase Inhibitors
-
Enzyme Inhibitors
-
FADD protein, human
-
Fas-Associated Death Domain Protein
-
Intracellular Signaling Peptides and Proteins
-
Membrane Glycoproteins
-
Protein Isoforms
-
Proto-Oncogene Proteins
-
Proto-Oncogene Proteins c-bcl-2
-
Recombinant Fusion Proteins
-
TNF-Related Apoptosis-Inducing Ligand
-
TNFSF10 protein, human
-
Tumor Necrosis Factor-alpha
-
bcl-2-Associated X Protein
-
bile acid binding proteins
-
Glycochenodeoxycholic Acid
-
Hydroxysteroid Dehydrogenases
-
AKR1C2 protein, human
-
Protein Kinase C
-
CASP8 protein, human
-
CASP9 protein, human
-
Caspase 10
-
Caspase 8
-
Caspase 9
-
Caspases
-
CASP10 protein, human