title: Bile acids stimulate cFLIP phosphorylation enhancing TRAIL-mediated apoptosis.
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.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Medical School, Clinic, and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: Hajime
authors.initials: H
authors.lastname: Higuchi
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Yoon
authors.forename: Annette
authors.initials: A
authors.lastname: Grambihler
authors.forename: Nathan
authors.initials: N
authors.lastname: Werneburg
authors.forename: Steven F
authors.initials: SF
authors.lastname: Bronk
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001692:Biological Transport / Q000502:physiology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053455:Caspase 10; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002458:Cell Fractionation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism*; D053200:Fas-Associated Death Domain Protein; D005999:Glycochenodeoxycholic Acid / Q000378:metabolism*; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; D053455:Caspase 10; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases; D004791:Enzyme Inhibitors; D053200:Fas-Associated Death Domain Protein; D005999:Glycochenodeoxycholic Acid; D006913:Hydroxysteroid Dehydrogenases; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D011493:Protein Kinase C; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; C494826:BAX protein, human; C506386:CFLAR protein, human; C505533:FADD protein, human; C505653:TNFSF10 protein, human; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); C505530:CASP8 protein, human; C506433:CASP9 protein, human; C506438:CASP10 protein, human