title: Accelerated degradation of FADD and procaspase 8 in cells expressing human papilloma virus 16 E6 impairs TRAIL-mediated apoptosis.
abstract: Viruses have developed sophisticated strategies to evade host defenses and facilitate the production and spread of progeny. In this study, we show that transfection of the human papillomavirus (HPV) 16 E6 oncogene into HCT116 cells provides protection from tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. Additionally, we demonstrate that the protection provided by E6 is dose-dependent because higher levels of E6 provide greater protection. The mechanism underlying this protection involves a rapid reduction in the protein levels of both Fas-associated death domain (FADD) and procaspase 8, which results in suppression of the activation of caspases 8, 3 and 2. Interestingly, E6 does not interfere with the mitochondrial apoptotic pathway even though HCT116 cells have been classified as type II cells with regard to TRAIL signaling. These findings demonstrate that E6 has a more generalized effect on signaling by death ligands than was previously thought and support the notion that E6 can utilize p53-independent mechanisms to modulate cell survival.
authors.affiliation: Department of Biochemistry and Microbiology, Center for Molecular Biology and Gene Therapy, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
authors.forename: T O
authors.initials: TO
authors.lastname: Garnett
authors.forename: M
authors.initials: M
authors.lastname: Filippova
authors.forename: P J
authors.initials: PJ
authors.lastname: Duerksen-Hughes
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism*; D045325:HCT116 Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014162:Transfection
chemical_list: C068651:E6 protein, Human papillomavirus type 16; D053200:Fas-Associated Death Domain Protein; D009856:Oncogene Proteins, Viral; D011498:Protein Precursors; D012097:Repressor Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; D053181:Caspase 8