The Second Apoptotic Inhibitor Encoded by Guinea Pig Cytomegalovirus
Congenital CMV infection (cCMV): When cytomegalovirus (CMV) infects to pregnant women, viruses are able to transmit to fetus through placenta. The cCMV occurs with a prevalence of about 1 per 300 birth. About 30% of infants with cCMV presents some symptoms including healing loss and developmental disorder. But, we have no effective treatment or vaccine to prevent cCMV.
Aim of this study: To prevent the progression of pathogens in our body, immune system induces several responses, including fever, antibody production, and cell death (apoptosis). Especially, CMV has many genes to overcome host immune responses. The inhibition of cell death by viral gene products leads to effective production of progeny viruses. In this research, we tried to elucidate the inhibitory mechanism of cell death using guinea pig CMV (GPCMV), which is a fine model of human CMV infection.
Achievements: Previously, we showed that gp38.1, a GPCMV gene product, is able to inhibit the function of BAX, a Bcl-2 family member to induce apoptosis (Noguchi et al., J. Gen .Virol. 2020). However, our results indicated that GPCMV has another gene to prevent apoptosis. In this study, we identified gp38.3-2 as the second anti-apoptotic gene of GPCMV to prevent the function of BAK (Satoh et al., J. Virol. 2022).
Staurosporine (STS) induced apoptosis was prevented by the expression of gp38.3, which we predicted as a candidate of anti-apoptotic gene (Fig.1A, B). Furthermore, the disruption of gp38.3-2, a short sequence in gp38.3 ORF, prevented the anti-apoptotic effect of gp38.2. Therefore, our results indicated that gp38.3-2 had anti-apoptotic activity.
We constructed a recombinant GPCMV which disrupted gp38.3-2 gene (Δ38.3-2). The cell death was ten times increased by the infection of Δ38.3-2 than its repair virus (r38.3-2) (Fig. 2A). In addition, the yield of progeny virus was ten times decreased in Δ38.3-2 infected cells (Fig. 2B). In addition, the deletion of gp38.3-2 reduced the infection of monocyte, which predicted as the vehicle for virus in vivo (Fig. 2C). However the deletion of gp38.3-2 did not presented any obvious difference in the recombinant virus infected animals.
According to the prediction of 3D structures, gp38.3-2 was surrounded by the 3 helixes of BAK (helix 3 - 5) to interact with BH3-BH1 motif (Fig. 3A). The interaction between gp38-3.2 and BAK was confirmed by the immunoprecipitation assay and immunofluorescent assay (Fig.3B).
- We identified gp38.3-2 as the second anti-apoptotic gene of GPCMV.
- Viral encoded anti-apoptotic genes would function in combination with each other because the virulence was not impaired by the disruption of single gene.
- The function of gp38.3-2 is able to use to prevent cell death.
Information of our article
Journal : Journal of Virology
Title : Characterization of the Second Apoptosis Inhibitor Encoded by Guinea Pig Cytomegalovirus
Authors : Keisuke Satoh, Keita Takahashi, Kazuma Noguchi, Yuhki Kobayashi, Ryuichi Majima, Yoshihiko Iwase, Keisuke Yamaguchi, Yukina Masuda, Tetsuo Koshizuka, Naoki Inoue
URL : https://pubmed.ncbi.nlm.nih.gov/36472439/