ZFYVE1 suppresses IRF3/7-mediated antiviral innate immunity in black carp

Zinc finger FYVE-type containing 1 (ZFYVE1), a FYVE-containing protein, exerts a significant function during autophagosome formation and lipid droplet metabolism. Nevertheless, it is currently unclear whether teleost ZFYVE1 influences antiviral innate immunity. In this paper, the black carp (Mylopharyngodon piceus) homolog of ZFYVE1 (bcZFYVE1) was cloned to explore its regulatory function within the interferon (IFN) signaling cascade of teleost fish. The coding region of bcZFYVE1 is composed of 2337 nucleotides and encodes 778 amino acids, including two zinc-binding FYVE domains and a guanylate-binding protein (GBP) domain. bcZFYVE1 transcription in host cells varied upon stimulation with LPS, grass carp reovirus (GCRV) and spring viremia of carp virus (SVCV), respectively. bcZFYVE1 migrated at approximately 86 kDa in immunoblot assay and was primarily detected in the cytoplasm in immunofluorescence staining assay. Upon the co-expression of bcZFYVE1 and bcIRF3/7 in EPC cells, bcZFYVE1 markedly reduced the transcription of the IFN promoter activated by bcIRF3/7. Correspondingly, the mRNA levels of interferon-stimulated genes (ISGs) downstream were reduced. And, overexpressed bcZFYVE1 markedly inhibited the antiviral activity mediated by bcIRF3/7. Additionally, knockdown of bcZFYVE1 attenuated SVCV replication and improved the antiviral capability of host cells. The co-immunoprecipitation assays verified the interaction between bcZFYVE1 and bcIRF3/7. Furthermore, we found that co-expression of bcZFYVE1 with bcIRF3/7 decreased the protein levels of bcIRF3/7 and both MG132 or chloroquine treatment could restore the protein levels. In summary, our data conclude that ZFYVE1 suppresses IRF3/7-mediated antiviral innate immune response in black carp, which expands the understanding of the function of ZFYVE1.