Genome-wide identification, characterization, and expression analysis of the transient receptor potential gene family in mandarin fish Siniperca chuatsi.

BACKGROUND: Temperature is a crucial environmental determinant for the vitality and development of teleost fish, yet the underlying mechanisms by which they sense temperature fluctuations remain largely unexplored. Transient receptor potential (TRP) proteins, renowned for their involvement in temperature sensing, have not been characterized in teleost fish, especially regarding their temperature-sensing capabilities. RESULTS: In this study, a genome-wide analysis was conducted, identifying a total of 28 TRP genes in the mandarin fish Siniperca chuatsi. These genes were categorized into the families of TRPA, TRPC, TRPP, TRPM, TRPML, and TRPV. Despite notable variations in conserved motifs across different subfamilies, TRP family members shared common structural features, including ankyrin repeats and the TRP domain. Tissue expression analysis showed that each of these TRP genes exhibited a unique expression pattern. Furthermore, examination of the tissue expression patterns of ten selected TRP genes following exposure to both high and low temperature stress indicated the expression of TRP genes were responsive to temperatures changes. Moreover, the expression profiles of TRP genes in response to mandarin fish virus infections showed significant upregulation for most genes after Siniperca chuatsi rhabdovirus, mandarin fish iridovirus and infectious spleen and kidney necrosis virus infection. CONCLUSIONS: This study characterized the TRP family genes in mandarin fish genome-wide, and explored their expression patterns in response to temperature stress and virus infections. Our work will enhance the overall understanding of fish TRP channels and their possible functions.

Interaction of Teleost Fish TRPV4 with DEAD Box RNA Helicase 1 Regulates Iridovirus Replication.

Viral diseases are a significant risk to the aquaculture industry. Transient receptor potential vanilloid 4 (TRPV4) has been reported to be involved in regulating viral activity in mammals, but its regulatory effect on viruses in teleost fish remains unknown. Here, the role of the TRPV4-DEAD box RNA helicase 1 (DDX1) axis in viral infection was investigated in mandarin fish (Siniperca chuatsi). Our results showed that TRPV4 activation mediates Ca2+ influx and facilitates infectious spleen and kidney necrosis virus (ISKNV) replication, whereas this promotion was nearly eliminated by an M709D mutation in TRPV4, a channel Ca2+ permeability mutant. The concentration of cellular Ca2+ increased during ISKNV infection, and Ca2+ was critical for viral replication. TRPV4 interacted with DDX1, and the interaction was mediated primarily by the N-terminal domain (NTD) of TRPV4 and the C-terminal domain (CTD) of DDX1. This interaction was attenuated by TRPV4 activation, thereby enhancing ISKNV replication. DDX1 could bind to viral mRNAs and facilitate ISKNV replication, which required the ATPase/helicase activity of DDX1. Furthermore, the TRPV4-DDX1 axis was verified to regulate herpes simplex virus 1 replication in mammalian cells. These results suggested that the TRPV4-DDX1 axis plays an important role in viral replication. Our work provides a novel molecular mechanism for host involvement in viral regulation, which would be of benefit for new insights into the prevention and control of aquaculture diseases. IMPORTANCE In 2020, global aquaculture production reached a record of 122.6 million tons, with a total value of $281.5 billion. Meanwhile, frequent outbreaks of viral diseases have occurred in aquaculture, and about 10% of farmed aquatic animal production has been lost to infectious diseases, resulting in more than $10 billion in economic losses every year. Therefore, an understanding of the potential molecular mechanism of how aquatic organisms respond to and regulate viral replication is of great significance. Our study suggested that TRPV4 enables Ca2+ influx and interactions with DDX1 to collectively promote ISKNV replication, providing novel insights into the roles of the TRPV4-DDX1 axis in regulating the proviral effect of DDX1. This advances our understanding of viral disease outbreaks and would be of benefit for studies on preventing aquatic viral diseases.

Mandarin fish von Hippel-Lindau protein regulates the NF-κB signaling pathway via interaction with IκB to promote fish ranavirus replication.

The von Hippel-Lindau tumor suppressor protein (VHL), an E3 ubiquitin ligase, functions as a critical regulator of the oxygen-sensing pathway for targeting hypoxia-inducible factors. Recent evidence suggests that mammalian VHL may also be critical to the NF-κB signaling pathway, although the specific molecular mechanisms remain unclear. Herein, the roles of mandarin fish ( Siniperca chuatsi) VHL ( scVHL) in the NF-κB signaling pathway and mandarin fish ranavirus (MRV) replication were explored. The transcription of scVHL was induced by immune stimulation and MRV infection, indicating a potential role in innate immunity. Dual-luciferase reporter gene assays and reverse transcription quantitative PCR (RT-qPCR) results demonstrated that scVHL evoked and positively regulated the NF-κB signaling pathway. Treatment with NF-κB signaling pathway inhibitors indicated that the role of scVHL may be mediated through scIKKα, scIKKß, scIκBα, or scp65. Co-immunoprecipitation (Co-IP) analysis identified scIκBα as a novel target protein of scVHL. Moreover, scVHL targeted scIκBα to catalyze the formation of K63-linked polyubiquitin chains to activate the NF-κB signaling pathway. Following MRV infection, NF-κB signaling remained activated, which, in turn, promoted MRV replication. These findings suggest that scVHL not only positively regulates NF-κB but also significantly enhances MRV replication. This study reveals a novel function of scVHL in NF-κB signaling and viral infection in fish.