Simian varicella virus induces apoptosis in monkey kidney cells by the intrinsic pathway and involves downregulation of bcl-2 expression.
Simian varicella virus (SVV) causes varicella in primates, becomes latent in ganglionic neurons, and reactivates to produce zoster. SVV produces a cytopathic effect in monkey kidney cells in tissue culture. To study the mechanism by which SVV-infected cells die, we examined markers of apoptosis 24 to 64 h postinfection (hpi). Western blot analysis of virus-infected cell lysates revealed a significant increase in the levels of the cleaved active form of caspase-3, accompanied by a parallel increase in caspase-3 activity at 40 to 64 hpi. Caspase-9, a marker for the intrinsic pathway, was activated significantly in SVV-infected cells at all time points, whereas trace levels of the active form of caspase-8, an extrinsic pathway marker, was detected only at 64 hpi. Bcl-2 expression at the mRNA and protein levels was decreased by 50 to 70% throughout the course of virus infection. Release of cytochrome c, an activator of caspase-9, from mitochondria into the cytoplasm was increased by 200% at 64 hpi. Analysis of Vero cells infected with SVV expressing green fluorescent protein (SVV-GFP) at 64 hpi revealed colocalization of the active forms of caspase-3 and caspase-9 and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining with GFP. A significant decrease in the bcl-2 mRNA levels along with an abundance of mRNA specific for SVV genes 63, 40, and 21 was seen in the fraction of Vero cells that were infected with SVV-GFP. Together, these findings indicate that SVV induces apoptosis in cultured Vero cells through the intrinsic pathway in which Bcl-2 is downregulated.
Pugazhenthi
Subbiah
S
Departments of Medicine, University of Colorado Denver School of Medicine, Aurora, 80045, USA.
Gilden
Donald H
DH
Nair
Sreekala
S
McAdoo
Anne
A
Wellish
Mary
M
Brazeau
Elizabeth
E
Mahalingam
Ravi
R
D000818:Animals; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002644:Chickenpox / Q000473:pathology; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000235:genetics; D000882:Haplorhini; D007668:Kidney / Q000473:pathology / Q000821:virology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis; D013997:Time Factors; D018140:Varicellovirus / Q000472:pathogenicity*; D014709:Vero Cells
D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D020169:Caspases