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

Abstract

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 (<italic>Siniperca chuatsi</italic>) VHL (<italic>sc</italic>VHL) in the NF-κB signaling pathway and mandarin fish ranavirus (MRV) replication were explored. The transcription of <italic>sc</italic>VHL 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 <italic>sc</italic>VHL evoked and positively regulated the NF-κB signaling pathway. Treatment with NF-κB signaling pathway inhibitors indicated that the role of <italic>sc</italic>VHL may be mediated through <italic>sc</italic>IKKα, <italic>sc</italic>IKKβ, <italic>sc</italic>IκBα, or <italic>sc</italic>p65. Co-immunoprecipitation (Co-IP) analysis identified <italic>sc</italic>IκBα as a novel target protein of <italic>sc</italic>VHL. Moreover, <italic>sc</italic>VHL targeted <italic>sc</italic>IκBα 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 <italic>sc</italic>VHL not only positively regulates NF-κB but also significantly enhances MRV replication. This study reveals a novel function of <italic>sc</italic>VHL in NF-κB signaling and viral infection in fish.