Transcriptional profiling of Vero E6 cells over-expressing SARS-CoV S2 subunit: Insights on viral regulation of apoptosis and proliferation

Abstract

We have previously demonstrated that over-expression of spike protein (S) of severe acute respiratory syndrome coronavirus (SARS-CoV) or its C-terminal subunit (S2) is sufficient to induce apoptosis in vitro. To further investigate the possible roles of S2 in SARS-CoV-induced apoptosis and pathogenesis of SARS, we characterized the host expression profiles induced upon S2 over-expression in Vero E6 cells by oligonucleotide microarray analysis. Possible activation of mitochondrial apoptotic pathway in S2 expressing cells was suggested, as evidenced by the up-regulation of cytochrome c and down-regulation of the Bcl-2 family anti-apoptotic members. Inhibition of Bcl-2-related anti-apoptotic pathway was further supported by the diminution of S2-induced apoptosis in Vero E6 cells over-expressing Bcl-xL. In addition, modulation of CCN E2 and CDKN 1A implied the possible control of cell cycle arrest at G1/S phase. This study is expected to extend our understanding on the pathogenesis of SARS at a molecular level.

Immunogenicity of an adenoviral-based Middle East Respiratory Syndrome coronavirus vaccine in BALB/c mice

“…A truncated RBD of MERS-CoV S protein was recently reported to potently inhibit viral infection and induce strong neutralizing antibody responses [45,46]. SARS-CoV S and S2, but neither S1 nor other structural proteins, can induce apoptosis in Vero E6 cells [47,48] and no histopathological changes were observed in various tissues of rats immunized with a recombinant adenovirus containing a truncated S1 fragment of the SARS-CoV [49]. In contrast, vaccination with recombinant modified MVA expressing SARS-CoV S protein is associated with enhanced hepatitis after challenge with SARS-CoV [50,51] and SARS-CoV has been shown to infect hepatocytes and cause hepatitis in some human cases [51][52][53], raising concerns about the safety of a vaccine that contains the full-length SARS-CoV S protein.…”

Coronavirus-induced ER stress response and its involvement in regulation of coronavirus–host interactions

“…Transcription induction of ER protein chaperones, such as the immunoglobulin heavy chain-binding protein (BiP, also known as glucose regulated protein 78, or GRP78) or glucose-regulated protein 94 (GRP94), is generally accepted as an indicator of ER stress (Samali et al, 2010). In global transcriptome studies, induction of BiP and GRP94, as well as other genes related to ER stress, has been detected in cells infected with SARS-CoV or in cells over-expressing the SARS-CoV spike protein (Tang et al, 2005;Yeung et al, 2008). Consistent with these findings, activation of luciferase reporters under the control of BiP or GRP94 promoters has been observed in cells infected with SARS-CoV (Chan et al, 2006).…”

Modulation of Host Cell Death by SARS Coronavirus Proteins

“…Here, expressions of several genes involved in the extrinsic apoptotic pathway were downregulated, whereas the upregulation of CYCS and of Mdm-2 involved in the regulation of p53 degradation provides a hint to an activation of the intrinsic apoptotic pathway. The antiapoptotic proteins Mcl-1, Bcl-xL and Bcl-2 were downregulated by S2 over-expression (Yeung et al 2008), in line with a downregulation of Bcl-2 in SARS-CoV infected Vero E6 cells (Ren et al 2005). However, in contrast to infected cells (Mizutani et al 2004b), components of the MAPK pathway were also downregulated (Yeung et al 2008).…”

“…The antiapoptotic proteins Mcl-1, Bcl-xL and Bcl-2 were downregulated by S2 over-expression (Yeung et al 2008), in line with a downregulation of Bcl-2 in SARS-CoV infected Vero E6 cells (Ren et al 2005). However, in contrast to infected cells (Mizutani et al 2004b), components of the MAPK pathway were also downregulated (Yeung et al 2008). Since S expression triggers ER stress response , prolonged ER stress in S expressing cells might finally lead to apoptotic cell death.…”

“…Induction of apoptosis by S appears to be unique for SARS-CoV S since neither MHV (An et al 1999) nor infectious bronchitis virus (IBV) (Liu et al 2001) S proteins induced apoptosis. In a follow-up study, microarray analysis of S2-transduced Vero E6 cells was performed (Yeung et al 2008). Here, expressions of several genes involved in the extrinsic apoptotic pathway were downregulated, whereas the upregulation of CYCS and of Mdm-2 involved in the regulation of p53 degradation provides a hint to an activation of the intrinsic apoptotic pathway.…”