Bid is involved in Chinese giant salamander iridovirus-induced apoptosis and is involved in virus replication in an amphibian cell line (2023)


Bid (BH3-interacting domain death agonist), a BH3-only protein of the B-cell lymphoma (BCL-2) family, has a pro-apoptotic function linking the extrinsic and intrinsic apoptotic pathways (Rigo et al., 2019). Following death receptor signaling, cytoplasmic resident Bid is cleaved by activated caspase-8 to produce a truncated form of Bid known as tBid (Li et al., 1998). tBid translocates into mitochondria and triggers cytochrome releaseCand activation of downstream caspases culminating in cell apoptosis (Wei et al., 2000). Bid has been shown to indirectly activate BAX/BAK effector proteins, neutralizing anti-apoptotic BCL-2 proteins, thus allowing BAX/BAK unhindered, spontaneous activation in the environment of the mitochondrial outer membrane, leading to the initiation of apoptosis (Huang et al., 2019 .) Bid contains a conserved BH3 domain that is required for interaction with Bcl-2 family proteins and for pro-death activity (Yin, 2006).

Bid has been reported to play a functional role in apoptosis induced by viral infection in mammals. Hepatitis C virus (HCV) core protein modulates apoptosis by enhancing Bid cleavage and activating the mitochondrial signaling pathway (Chou et al., 2005). A modified Bid containing a specific cleavage site recognized by the NS3/NS4A serine protease reduces HCV infection in mice and lowers serum HCV titers (Hsu et al., 2003). Hepatitis B virus (HBV) infection causes subsequent overexpression of death-associated receptors, which increases Bid cleavage ( Lin and Zhang, 2017 ). In epithelial cells, HEK293 Bid was required for reovirus-induced apoptosis and virus replication (Danthi et al., 2010a). Bid cleavage also occurred during influenza A virus-induced apoptosis (Yeganeh et al., 2018). The Orf virus-encoded ORFV119 protein can induce Bid expression and activation to achieve cell death (Li et al., 2018). In carp and rare minnows, Bid-deficient fish reduce carp reovirus (GCRV)-induced apoptosis (He et al., 2017). However, the function of Bida during viral infection in amphibians still remains unclear.

Chinese giant salamander iridovirus (GSIV) belongs to the large dsDNA virus family Iridoviridae, which exhibits icosahedral symmetry with a diameter of approximately 120–200 nm (Geng et al., 2011). It is the main pathogen of the Chinese giant salamander and causes severe diseases in this endangered species (Ma et al., 2014). For now, there is no effective way to prevent and treat this disease, which is the biggest threat to the survival of this species. In our previous study, GSIV infection induced typical apoptotic cell death via extrinsic and intrinsic pathways (Li et al., 2019). Moreover, Bid mRNA expression was significantly increased during the late infection process. Further studies are needed to determine the functional role of AdBid in GSIV-induced apoptosis.

This study investigated the sequence characterization and expression patterns of the Bid gene and its function in GSIV-induced apoptotic cell death using a Chinese giant salamander cell line (GSM cells). The results showed that Bid can enhance GSIV-induced apoptosis and contribute to virus replication. Together, our findings suggest that Bid promotes GSIV-induced apoptosis in the Chinese giant salamander, providing new insight into a potential regulatory mechanism during iridovirus infection.

Excerpts of Sections

Animals, cells and viruses

All animal handling procedures and experiments were approved by the Animal Care and Use Committee of the Yangtze River Fisheries Research Institute of the Chinese Academy of Fisheries Sciences. Chinese giant salamanders with an average weight of 200 g were obtained from the breeding of the Yangtze River Fisheries Research Institute. Before the experiment, the animals were kept in plastic aquariums at 20-22°C and fed diced fathead minnow meat daily for two weeks. The giant salamander cell line (GSM) was

AdBid sequence analysis

AdBid consists of 191 amino acid residues with a calculated molecular weight of 21.3 kDa and a theoretical isoelectric point (pI) of 4.93 (Figure 1A). Like other Bids, AdBid has a BH3 interaction domain (BID) (residues 2–185) (Figure 1B). Sequence alignments showed that AdBid shares 24%, 24%, 27%, 27%, 28%, 30%, 34%, 37%, 50% and 52% of total sequence identity with Bid homologues from fish and amphibian species includingRhincodon typus,Danish Rerio,Poeciliopsis fertile,


The Bcl-2 (B-cell lymphoma-2) superfamily is a class of proteins primarily involved in the intrinsic pathway of apoptosis, sharing conserved sequences (~20 residues) known as Bcl-2 (BH) domains or homology motifs (designated BH1, BH2, BH3 and BH4 corresponding to α-helical segments) (Sato et al., 1994; Adams and Cory, 1998). Bid, a BH3-interacting domain death agonist, is a proapoptotic member of the BH3-only Bcl-2 superfamily and as such has intracellular targeting capabilities

Thank you

The work was supported by grants fromLife Sciences Foundation of Hubei Provincefrom the chin (2020CFB347) iCentral scientific institution of public interest Foundation for fundamental research,CAFS(2020XT0401).

Quoted (4)

  • Amphibian invitromes: past, present and future contributions to our understanding of amphibian resilience

    2023, Developmental and comparative immunology

    Around the world, many amphibian populations are in decline, and infectious diseases are the main cause. Given the enormous threat that infectious diseases pose to amphibian populations, there is a need to understand the host-pathogen-environment interactions that govern amphibian susceptibility to disease and mortality. However, the use of animals in research raises an ethical dilemma, which is complicated by althe rate at which many amphibian populations decline. Therefore,in vitroresearch systems such as cell lines are valuable tools for advancing our understanding of the amphibian immune system. In this review, we compile a list of established amphibian cell lines (amphibian invitromes) to date, highlighting how research using amphibian cell lines has increased our understanding of the amphibian immune system, ranavirus defense, andBatrachochytrium dendrobatidisreplication in host cells and represent our view of how the future use of amphibian cell lines could advance the field of amphibian immunology.

  • Establishment and characterization of a cell line from the brain of Japanese flounder (Paralichthys olivaceus) and its application in the study of viral infections

    2023, Aquaculture

    Excerpt from the quote:

    It is the main pathogen affecting the Chinese giant salamander and leading to severe disease in this endangered species (Ma et al., 2014). Only a limited number of susceptible cell lines have been reported for both viruses (Ariel et al., 2009; Li et al., 2014; Li et al., 2021). Therefore, the JFB cell line we created here provides a new in vitro model for BIV and GSIV studies, especially for virus propagation and preparation of virus vaccines and study of virus-host cell interactions.

    Fish cell lines are an important tool in many biological studies. Here, we generated a new Japanese flounder (JFB) cell line from the brain tissue of Japanese flounder (Paralichthys olivaceus), which was successfully cultured for more than 120 passages and consisted mainly of fibroblast-like cells. Sequencing of the actin gene confirmed that JFB cells were derived from Japanese flounder, and JFB was also identified as a neural stem cell line based on nestin gene mRNA expression. JFB cells could grow at temperatures from 17 to 29°C, with an optimum temperature of 23°C. Karyotype analysis showed that the number of chromosome modifications is 48, which indicates a normal diploid number of chromosomes. The transfection efficiency of pEGFP-N1 in JFB cells was up to 30%. JFB cells were susceptible to Hirame rhabdovirus (HIRRV), Lymphocystis virus virus (LCDV), Bohle virus (BIV) and Chinese giant salamander iridovirus (GSIV), as shown by varying degrees of cytopathic effects. Viral infection or poly(I:C) stimulation increased the expression of many genes associated with the immune system, includingIL-1β,IL8,MXandTNF. These results indicated that the newly established JFB cell line is an ideal tool for studying gene manipulation, host-virus interaction and potential vaccine development.

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© 2020 Elsevier Ltd. All rights reserved.

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