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Journal of Virology, March 2009, p. 2298-2309, Vol. 83, No. 5
0022-538X/09/$08.00+0     doi:10.1128/JVI.01245-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Severe Acute Respiratory Syndrome Coronavirus Triggers Apoptosis via Protein Kinase R but Is Resistant to Its Antiviral Activity{triangledown}

Verena Krähling,1 David A. Stein,2 Martin Spiegel,3,4 Friedemann Weber,4 and Elke Mühlberger1,5,6*

Department of Virology, Philipps University Marburg, Hans-Meerwein-Strasse 2, 35043 Marburg, Germany,1 Department of Microbiology, Oregon State University, Corvallis, Oregon,2 Institute of Virology, Georg August University Göttingen, Kreuzbergring 57, 37075 Göttingen, Germany,3 Department of Virology, Institute for Medical Microbiology and Hygiene, Hermann-Herder-Strasse 11, 79104 Freiburg, Germany,4 National Emerging Infectious Diseases Laboratories Institute,5 Department of Microbiology, Boston University School of Medicine, 72 East Concord Street, Boston, Massachusetts6

Received 16 June 2008/ Accepted 15 December 2008

In this study, infection of 293/ACE2 cells with severe acute respiratory syndrome coronavirus (SARS-CoV) activated several apoptosis-associated events, namely, cleavage of caspase-3, caspase-8, and poly(ADP-ribose) polymerase 1 (PARP), and chromatin condensation and the phosphorylation and hence inactivation of the eukaryotic translation initiation factor 2{alpha} (eIF2{alpha}). In addition, two of the three cellular eIF2{alpha} kinases known to be virus induced, protein kinase R (PKR) and PKR-like endoplasmic reticulum kinase (PERK), were activated by SARS-CoV. The third kinase, general control nonderepressible-2 kinase (GCN2), was not activated, but late in infection the level of GCN2 protein was significantly reduced. Reverse transcription-PCR analyses revealed that the reduction of GCN2 protein was not due to decreased transcription or stability of GCN2 mRNA. The specific reduction of PKR protein expression by antisense peptide-conjugated phosphorodiamidate morpholino oligomers strongly reduced cleavage of PARP in infected cells. Surprisingly, the knockdown of PKR neither enhanced SARS-CoV replication nor abrogated SARS-CoV-induced eIF2{alpha} phosphorylation. Pretreatment of cells with beta interferon prior to SARS-CoV infection led to a significant decrease in PERK activation, eIF2{alpha} phosphorylation, and SARS-CoV replication. The various effects of beta interferon treatment were found to function independently on the expression of PKR. Our results show that SARS-CoV infection activates PKR and PERK, leading to sustained eIF2{alpha} phosphorylation. However, virus replication was not impaired by these events, suggesting that SARS-CoV possesses a mechanism to overcome the inhibitory effects of phosphorylated eIF2{alpha} on viral mRNA translation. Furthermore, our data suggest that viral activation of PKR can lead to apoptosis via a pathway that is independent of eIF2{alpha} phosphorylation.

* Corresponding author. Mailing address: Department of Microbiology, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118. Phone: (617) 638-0336. Fax: (617) 638-4286. E-mail: muehlber{at}bu.edu

{triangledown} Published ahead of print on 24 December 2008.

Journal of Virology, March 2009, p. 2298-2309, Vol. 83, No. 5
0022-538X/09/$08.00+0     doi:10.1128/JVI.01245-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



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  • Schumann, M., Gantke, T., Muhlberger, E. (2009). Ebola Virus VP35 Antagonizes PKR Activity through Its C-Terminal Interferon Inhibitory Domain. J. Virol. 83: 8993-8997 [Abstract] [Full Text]  


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