Bovine ephemeral fever virus-induced apoptosis requires virus gene expression and activation of Fas and mitochondrial signaling pathway.
Although induction of apoptosis by bovine ephemeral fever virus (BEFV) in several cell lines has been previously demonstrated by our laboratory, less information is available on the process of BEFV-induced apoptosis in terms of cellular pathways and specific proteins involved. In order to determine the step in viral life cycle at which apoptosis of infected cells is triggered, chemical and physical agents were used to block viral infection. Treatment of BHK-21 infected cells with ammonium chloride (NH4Cl) or cells infected with UV-inactivated BEFV was seen to abrogate virus apoptosis induction, suggesting that virus uncoating and gene expression are required for the induction of apoptosis. Using soluble death receptors Fc:Fas chimera to block Fas signaling, BEFV-induced apoptosis was inhibited in cells. BEFV infection of BHK-21 cells results in the Fas-dependent activation of caspase 8 and cleavage of Bid. This initiated the dissipation of the membrane potential and the release of cytochrome c but not AIF or Smac/DIABLO from mitochondrial into cytoplasm leading to activation of caspase 9. Combined activation of the death receptor and mitochondrial pathways results in activation of the downstream effecter caspase 3 leading to cleavage of PARP. Fas-mediated BEFV-induced apoptosis could be suppressed by the overexpression of Bcl-2 or by treatment with caspase inhibitors and soluble death receptors Fc:Fas chimera. Taken together, this study provided first evidence demonstrating that BEFV-induced apoptosis requires viral gene expression and occurs through the activation of Fas and mitochondrion-mediated caspase-dependent pathways.
Lin
Chi-Hung
CH
Department of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
Shih
Wen-Ling
WL
Lin
Feng-Lang
FL
Hsieh
Yao-Ching
YC
Kuo
Yur-Ren
YR
Liao
Ming-Huei
MH
Liu
Hung-Jen
HJ
Liu
Hung-Jeng
HJ
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation; D018115:Ephemeral Fever Virus, Bovine / Q000502:physiology* / Q000528:radiation effects; D015967:Gene Expression Regulation, Viral; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*; D053218:Receptors, Death Domain / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014466:Ultraviolet Rays; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
D051023:BH3 Interacting Domain Death Agonist Protein; D061945:Caspase Inhibitors; D053218:Receptors, Death Domain; D014764:Viral Proteins; D019014:fas Receptor; D045304:Cytochromes c; D020169:Caspases