Functional characterization of two distinct interferon gamma structurally related protein IFNγrel 1 and IFNγrel 2, in ginbuna crucian carp

Abstract

Unlike mammals fish have two type II interferons, IFNγ and IFNγ‐related (IFNγrel). Both IFNγ and IFNγrel are structurally similar to human and mouse IFNγ and induce pro‐inflammatory responses. We previously identified two IFNγrel genes, IFNγrel 1 and IFNγrel 2 from ginbuna crucian carp, Carassius auratus langsdorfii. We produced recombinant IFNγrel 1 and IFNγrel 2 proteins using HEK cells and demonstrated that they possess high antiviral activities against CHNV hematopoietic necrosis virus. Both interferons have highly homologous sequences, however, they differ in the C‐terminus region, where IFNγrel has a nuclear localization site (NLS) and IFNγrel 2 does not. Here, we report that the NLS‐like sequence fused to GFP localized in nucleus of the GTS9 gibuna carp fibroblast cell line. Furthermore, we found that IFNγrel 1 translocated from cytosol to nucleus, despite the fact that IFNγrel 1 did not interact with known IFNγ receptors, IFNGR1‐1 and IFNGR1‐2. Pull‐down assay suggested the existence of a novel receptor for IFNγrel 1. These results indicate that IFNγrel 1 and IFNγrel 2 are functional, but appear to signal through different receptor(s) than IFNγ. It is probable that IFNγrel 1 and IFNγrel 2 use different signal transduction pathway(s).