Replication of a cytopathic strain of bovine viral diarrhea virus activates PERK and induces endoplasmic reticulum stress-mediated apoptosis of MDBK cells.
Endoplasmic reticulum (ER) stress signaling is an adaptive cellular response to the loss of ER Ca(2+) homeostasis and/or the accumulation of misfolded, unassembled, or aggregated proteins in the ER lumen. ER stress-activated signaling pathways regulate protein synthesis initiation and can also trigger apoptosis through the ER-associated caspase 12. Viruses that utilize the host cell ER as an integral part of their life cycle would be predicted to cause some level of ER stress. Bovine viral diarrhea virus (BVDV) is a positive-stranded RNA virus of the Flaviviridae family. BVDV and related flaviviruses use the host ER as the primary site of envelope glycoprotein biogenesis, genomic replication, and particle assembly. We are using a cytopathic strain of BVDV (cpBVDV) that causes cellular apoptosis as a model system to determine how virus-induced ER stress contributes to pathogenesis. We show that, in a natural infection of MDBK cells, cpBVDV activates the ER transmembrane kinase PERK (PKR-like ER kinase) and causes hyperphosphorylation of the translation initiation factor eIF2 alpha, consistent with the induction of an ER stress response. Additionally, we show that initiation of cellular apoptosis correlates with downregulation of the antiapoptotic Bcl-2 protein, induced expression of caspase 12, and a decrease in intracellular glutathione levels. Defining the molecular stress pathways leading to cpBVDV-induced apoptosis provides the basis to study how other ER-tropic viruses, such as hepatitis C and B viruses, modulate the host cell ER stress response during the course of persistent infection.
Department of Biochemistry and Molecular Pharmacology, The Jefferson Center for Biomedical Research, Thomas Jefferson University, Doylestown, Pennsylvania 18901, USA.
Robert
R
Jordan
Lijuan
L
Wang
Thomas M
TM
Graczyk
Timothy M
TM
Block
Patrick R
PR
Romano
D000818:Animals; D017209:Apoptosis; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis; D002352:Carrier Proteins / Q000096:biosynthesis; D053454:Caspase 12; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D001908:Diarrhea Viruses, Bovine Viral / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005978:Glutathione / Q000032:analysis; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones / Q000096:biosynthesis; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000096:biosynthesis; D014779:Virus Replication; D019892:eIF-2 Kinase / Q000378:metabolism*
D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; D053454:Caspase 12; D020169:Caspases; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; D005978:Glutathione; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D019253:Proto-Oncogene Proteins c-bcl-2; D051742:Transcription Factor CHOP; D014157:Transcription Factors; D019892:eIF-2 Kinase