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Activation of the apoptotic Fas antigen-encoding gene upon influenza virus infection involving spontaneously produced
T Takizawa1, R Fukuda, T Miyawaki
1Department of Biochemistry, Aichi Human Service Center, Japan.
Abstract:
We previously demonstrated that influenza virus infection induces apoptosis in culture cells. Here, we examined the activation of the Fas antigen gene that encodes an apoptosis-mediating membrane protein in the virus-infected cells. The virus elicited a transient but marked increase in Fas antigen mRNA 3 to 4 hr after infection, followed by the expression of the antigen on the cell surface. Poly(I)-poly(C), a synthetic double-stranded RNA, similarly activated Fas antigen gene expression, and poly(I)-poly(C)-treated cells are highly susceptible to the cell killing effect of IgM isotype of anti-Fas monoclonal antibody. On the other hand, the IgG isotype of anti-Fas monoclonal antibody, which has an inhibitory effect on Fas Ag-mediated cell death, suppressed the virus-induced cell death. Prior exposure of the cells to anti-interferon-beta antibody decreased the degree of cell death as well as the amount of Fas mRNA. The autophosphorylation activity of double-stranded RNA-activated protein kinase was also decreased in the antibody-treated cells. Moreover, a protein kinase inhibitor, 2-aminopurine, blocked the Fas Ag gene activation by poly(I)-poly(C). These results suggested that the activation of Fas Ag gene in the early phase of infection is an important event for apoptosis, and that it is regulated by the double-stranded RNA/interferon system involving protein phosphorylation.
Insights
Influenza virus infection triggers apoptosis by activating the Fas antigen gene. This process involves the double-stranded RNA/interferon system and protein phosphorylation, crucial for early infection cell death.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Influenza virus infection is known to induce apoptosis in cultured cells.
- The Fas antigen is a membrane protein that mediates apoptosis.
Purpose of the Study:
- To investigate the activation of the Fas antigen gene in virus-infected cells.
- To elucidate the regulatory mechanisms of Fas antigen gene activation during influenza infection.
Main Methods:
- Measuring Fas antigen mRNA levels post-infection.
- Assessing Fas antigen expression on the cell surface.
- Utilizing Poly(I)-poly(C) as a synthetic double-stranded RNA stimulus.
- Employing anti-Fas monoclonal antibodies (IgM and IgG isotypes).
- Using anti-interferon-beta antibody and a protein kinase inhibitor (2-aminopurine).
Main Results:
- Influenza virus infection caused a transient increase in Fas antigen mRNA and subsequent cell surface expression.
- Poly(I)-poly(C) also activated Fas antigen gene expression, increasing susceptibility to IgM anti-Fas antibody-mediated cell death.
- IgG anti-Fas antibody suppressed virus-induced cell death.
- Interferon-beta antibody treatment reduced cell death and Fas mRNA levels, along with double-stranded RNA-activated protein kinase activity.
- 2-aminopurine inhibited Poly(I)-poly(C)-induced Fas antigen gene activation.
Conclusions:
- Fas antigen gene activation is a key event in early influenza infection-induced apoptosis.
- The double-stranded RNA/interferon system, involving protein phosphorylation, regulates this Fas antigen gene activation.