Semliki forest virus-induced endoplasmic reticulum stress accelerates apoptotic death of mammalian cells.
The alphavirus Semliki Forest virus (SFV) and its derived vectors induce apoptosis in mammalian cells. Here, we show that apoptosis is associated with the loss of mitochondrial membrane potential followed by the activation of caspase-3, caspase-8, and caspase-9. Cell death can be partially suppressed by treatment with the pan-caspase inhibitor zVAD-fmk. To determine the role of SFV structural proteins in cell death, the temporal course of cell death was compared in cells infected with SFV and cells infected with SFV virus replicon particles (VRPs) lacking some or all of the virus structural genes. In the absence of virus structural proteins, cell death was delayed. The endoplasmic reticulum (ER) stress response, as determined by the splicing of X-box binding protein 1 (XBP1) transcripts and the activation of caspase-12, was activated in virus-infected cells but not in VRP (SFV lacking structural genes)-infected cells. The C/EBP-homologous protein (CHOP) was upregulated by both virus and VRP infections. The virus envelope proteins but not the virus capsid protein triggered ER stress. These results demonstrate that in NIH 3T3 cells, SFV envelope glycoproteins trigger the unfolded protein response of the ER and accelerate apoptotic cell death initiated by virus replicase activity.
Barry
Gerald
G
Roslin Institute, College of Medicine & Veterinary Medicine, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, United Kingdom.
Fragkoudis
Rennos
R
Ferguson
Mhairi C
MC
Lulla
Aleksei
A
Merits
Andres
A
Kohl
Alain
A
Fazakerley
John K
JK
D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D020782:Matrix Metalloproteinases / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D012672:Semliki forest virus / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D056811:Unfolded Protein Response / Q000502:physiology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D014764:Viral Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D051742:Transcription Factor CHOP; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020782:Matrix Metalloproteinases