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Journal of Virology, July 2009, p. 6546-6553, Vol. 83, No. 13
0022-538X/09/$08.00+0     doi:10.1128/JVI.00353-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Theiler's Murine Encephalomyelitis Virus Leader Protein Is the Only Nonstructural Protein Tested That Induces Apoptosis When Transfected into Mammalian Cells ^,

Jilao Fan,^1, Kyung-No Son,^1,2, Sevim Yildiz Arslan,² Zhiguo Liang,¹ and Howard L. Lipton^1,2*

Departments of Neurology & Rehabilitation Medicine,¹ Microbiology-Immunology, University of Illinois at Chicago, Chicago, Illinois 60612-7344²

Received 17 February 2009/ Accepted 21 April 2009

Theiler's murine encephalomyelitis virus (TMEV) induces two distinct cell death programs, necrosis and apoptosis. The apoptotic pathway is of particular interest because TMEV persists in the central nervous system of mice, largely in infiltrating macrophages, which undergo apoptosis. Infection of murine macrophages in culture induces apoptosis that is Bax dependent through the intrinsic or mitochondrial pathway, restricting infectious-virus yields and raising the possibility that apoptosis represents a mechanism to attenuate TMEV yet promote macrophage-to-macrophage spread during persistent infection. To help define the cellular stressors and upstream signaling events leading to apoptosis during TMEV infection, we screened baby hamster kidney (BHK-21) cells transfected to express individual nonstructural genes (except 3B) of the low-neurovirulence BeAn virus strain for cell death. Only expression of the leader protein led to apoptosis, as assessed by fluorescence-activated cell sorting analysis of propidium iodide- and annexin V-stained transfected cells, immunoblot analysis of poly(ADP-ribose) polymerase and caspase cleavages, electron microscopy, and inhibition of apoptosis by the pancaspase inhibitor qVD-OPh. After transfection, Bak and not Bax expression increased, suggesting that the apical pathway leading to activation of these Bcl-2 multi-BH-domain proapoptotic proteins differs in BeAn virus infection versus L transfection. Mutation to remove the CHCC Zn finger motif from L, a motif required by L to mediate inhibition of nucleocytoplasmic trafficking, significantly reduced L-protein-induced apoptosis in both BHK-21 and M1-D macrophages.

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* Corresponding author. Mailing address: Department of Microbiology and Immunology, MC 790, University of Illinois at Chicago, 835 South Wolcott, Chicago, IL 60612-7344. Phone: (312) 996-5754. Fax: (312) 355-3581. E-mail: hlipton{at}uic.edu

Published ahead of print on 29 April 2009.

Supplemental material for this article may be found at http://jvi.asm.org/.

These authors contributed equally to the study.

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Journal of Virology, July 2009, p. 6546-6553, Vol. 83, No. 13
0022-538X/09/$08.00+0     doi:10.1128/JVI.00353-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Son, K.-N., Pugazhenthi, S., Lipton, H. L. (2009). Activation of Tumor Suppressor Protein p53 Is Required for Theiler's Murine Encephalomyelitis Virus-Induced Apoptosis in M1-D Macrophages. J. Virol. 83: 10770-10777 [Abstract] [Full Text]