Parkin is a critical factor in grouper immune response to virus infection

Parkin is an E3 ubiquitinated ligase that mainly participates in mitophagy and plays an essential biological role in organisms. To investigate Parkin's function in fish, a Parkin homolog was cloned from Epinephelus coioides (EcParkin). The open reading frame (ORF) of EcParkin consists of 1461 nucleotides and encodes a protein of 486 amino acids, with a predicted molecular weight of 53.32 kDa. EcParkin was highly expressed in the heart, kidney, and head kidney of healthy groupers, especially in the heart. The expression levels of EcParkin were upregulated after Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV) infection. Intracellular localization studies revealed that EcParkin is distributed in both the cytoplasm and nucleus of GS cells. Overexpression of EcParkin promoted SGIV and RGNNV replication in vitro, while knockdown of EcParkin inhibited SGIV and RGNNV replication. EcParkin suppressed the promoter activities of IFN-β, ISRE, and NF-κB, as well as the expression of interferon-related factors and inflammatory cytokines. EcParkin was found to colocalize and interact with EcMDA5, EcMAVS, EcTBK1, EcIRF3, and EcIRF7. Additionally, EcParkin enhanced LC3-II production in GS cells. These findings suggest that EcParkin may play a crucial role in the antiviral innate immunity and cellular autophagy of fish.