Bcl-xL Reduces Chinese Giant Salamander Iridovirus-Induced Mitochondrial Apoptosis by Interacting with Bak and Inhibiting the p53 Pathway

Abstract

Chinese giant salamander iridovirus (GSIV) infection could lead to mitochondrial apoptosis in this animal, a process that involves B-cell lymphoma-2 (BCL-2) superfamily molecules. The mRNA expression level of Bcl-xL, a crucial antiapoptotic molecule in the BCL-2 family, was reduced in early infection and increased in late infection. However, the molecular mechanism remains unknown. In this study, the function and regulatory mechanisms of Chinese giant salamander (Andrias davidianus) Bcl-xL (AdBcl-xL) during GSIV infection were investigated. Western blotting assays revealed that the level of Bcl-xL protein was downregulated markedly as the infection progressed. Plasmids expressing AdBcl-xL or AdBcl-xL short interfering RNAs were separately constructed and transfected into Chinese giant salamander muscle cells. Confocal microscopy showed that overexpressed AdBcl-xL was translocated to the mitochondria after infection with GSIV. Additionally, flow cytometry analysis demonstrated that apoptotic progress was reduced in both AdBcl-xL-overexpressing cells compared with those in the control, while apoptotic progress was enhanced in cells silenced for AdBcl-xL. A lower number of copies of virus major capsid protein genes and a reduced protein synthesis were confirmed in AdBcl-xL-overexpressing cells. Moreover, AdBcl-xL could bind directly to the proapoptotic molecule AdBak with or without GSIV infection. In addition, the p53 level was inhibited and the mRNA expression levels of crucial regulatory molecules in the p53 pathway were regulated in AdBcl-xL-overexpressing cells during GSIV infection. These results suggest that AdBcl-xL plays negative roles in GSIV-induced mitochondrial apoptosis and virus replication by binding to AdBak and inhibiting p53 activation.

Molecular characterization and expression analysis of B-cell lymphoma-2 in Trachinotus ovatus and its role in apoptotic process

“…Previous studies have reported that p53 signaling is a crucial pathway that participates in the regulation of the apoptotic signaling cascade, which has been shown to be a direct transcriptional activator of Bax/Bak ( 9 ). ( 65 ) revealed that the protein level of p53 increased during Chinese giant salamander iridovirus (GSIV)-induced apoptosis in Andrias davidianus and that the anti-apoptotic molecule AdBcl-xL inhibited the anti-apoptotic effect of p53. Therefore, our results suggest that the anti-apoptotic activity of TroBcl2 may be related to inhibition of p53 activation.…”

Infectious Spleen and Kidney Necrosis Virus (ISKNV) Triggers Mitochondria-Mediated Dynamic Interaction Signals via an Imbalance of Bax/Bak over Bcl-2/Bcl-xL in Fish Cells

“…On the other hand, Chinese giant salamander iridovirus (GSIV) infection inhibits the expression of AdBcl-xL [ 53 ], and overexpression suppresses virus replication. Furthermore, AdBcl-xL inhibits the mitochondrial apoptotic cell death induced by GSIV by binding to Bak, which reduces caspase-3 and caspase-9 activation.…”

Mastering Death: The Roles of Viral Bcl-2 in dsDNA Viruses

“…He et al (2019) postulate that the mitochondrial localization of TFV vBcl-2 suggests a role in the direct inhibition of intrinsic apoptosis [ 66 ]. Chinese giant salamander ( Andrias davidianus ) iridovirus (GSIV) has been shown to regulate apoptosis in vitro, with GSIV promoting both intrinsic and extrinsic pathways of apoptosis in infected cells [ 67 ], with further in vitro studies by Li et al (2021) showing that the Chinese giant salamander Bcl-x L was capable of limiting GSIV infection when overexpressed in cultured giant salamander muscle cells [ 68 ].…”