The Effect of Human bcl-2 and bcl-X Genes on Dengue Virus-Induced Apoptosis in Cultured Cells

Abstract

Infection of dengue viruses (DENs) can cause human dengue fever, hemorrhagic fever, or shock syndrome. Although DEN-induced apoptosis has been implicated in pathogenesis of the DEN-related diseases, the underlying mechanism remains largely unexplored. In this study, we investigated the effect of ectopic expression of human bcl-2 and bcl-X genes on DEN-induced apoptosis in cultured cells. We employed a human isolate of DEN serotype 2 (DEN-2), PL046, which not only caused cell-cycle arrest in the G1 phase but also induced apoptosis in infected baby hamster kidney (BHK-21) cells, murine neuroblastoma N18 cells, and human neuronal NT-2 cells. Our results reveal that overexpression of bcl-2 in fibroblast-like BHK-21 cells, although not inhibiting virus yields, delayed the process of DEN-induced apoptosis, thereby permitting surviving cells to become persistently infected. In contrast, stable bcl-2 expression in neuronal N18 cells failed to block DEN-induced apoptosis. On the other hand, Bcl-X(L), expressed predominantly in the nervous system, appeared to delay DEN's killing effect in neuronal N18 cells but not in fibroblast-like BHK-21 cells. In addition, inducible expression bcl-X(s), despite its proapoptotic property in other reported system, was found to merely accelerate cell death in DEN-infected N18 but not in infected BHK-21 cells. Thus, through studying the effect of human bcl-2-related genes, our results suggest that DEN infection may trigger target cells to undergo morphologically similar but biochemically distinct apoptotic pathways in a cell-specific manner.

The Interferon Stimulator Mitochondrial Antiviral Signaling Protein Facilitates Cell Death by Disrupting the Mitochondrial Membrane Potential and by Activating Caspases

“…To investigate the role of MAVS in viral infection, we determined the protein expression pattern of MAVS in mock-and DEN-2-infected N18 cells, a mouse neuroblastoma cell line that is susceptible to DEN-2 infection and has been used for studies of DEN-2 (35,45). In addition to the band for full-length MAVS, another major protein band of smaller molecular size was noted, and its abundance increased further during DEN-2 infection (Fig.…”

“…For the cleavage of isotope-labeled MAVS, Flag-tagged MAVS and its mutants were transcribed and translated in vitro by using TNT rabbit reticulocyte lysate (Promega) supplemented with [ 35 S]methionine (PerkinElmer), and the Flag-tagged proteins were purified by binding to Flag-Sepharose beads (Sigma-Aldrich). Ten microliters of 35 S-labeled Flag-tagged protein-binding beads was incubated with 1 U of recombinant active caspase-3 in reaction buffer as described above. After 1 h of incubation at 37°C, the reaction products were eluted in sample buffer, resolved by SDS-PAGE, and analyzed by autoradiography.…”

Endothelial Cell Sensitization by Death Receptor Fractions of an Anti–Dengue Nonstructural Protein 1 Antibody Induced Plasma Leakage, Coagulopathy, and Mortality in Mice

“…Rather than autoantibody-induced cell death, several studies have focused on the apoptosis that is directly induced by DENV infections (52)(53)(54). Studies have demonstrated that DENV infections elicit proapoptotic responses involving the suppression of Bcl-2 and Bcl-x L as well as the induction of Bax (40)(41)(42). The induction of TRAIL has been reported in human endothelial-like ECV304 cells following DENV infection (55).…”

“…Additionally, Bcl-2 family members, Bax and Bcl-x L , which previous studies have shown to be involved in the DENV-mediated regulation of cell death (40)(41)(42)(43), were analyzed for comparison. RT-PCR analysis revealed that the mRNA expression levels of the proapoptotic TRAIL-R1 (DR4) and Bax were upregulated after subcytotoxic DENV challenge (Supplemental Fig.…”

Targeting plasma membrane GRP78 for cancer growth inhibition

“…Once internalized, the apoptotic induction elicited by dengue virus has been well-characterized. [25][26][27] It would be interesting to determine if antibody-mediated GRP78 ligation mimics viral binding and infection. Thereby, GRP78 would still provide a protective function, but in this case the protective function would be to the surrounding cells and the organism as a whole.…”