Involvement of eIF2α of Epinephelus coioides in the fish immune response to virus infection

The eukaryotic initiation factor 2 alpha subunit (eIF2 alpha) is a key translation regulator that plays an important role in different cellular pressures and stimuli, including virus infection. In the present study, an eIF2 alpha homolog (EcelF2 alpha) from the orange-spotted grouper (Epinephelus coioides) was cloned and its roles during fish viral infection were characterized. EcelF2 alpha encodes a putative protein of 315 amino acid residues, and shares a high degree of similarity with elF2 alpha s from other species. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that EcelF2 alpha was distributed in all examined tissues. Both of the expression levels of EceIF2 alpha in the spleen and head kidney of E. coioides were up-regulated when challenged with polyinosine-polycytidylic acid (poly[I:C]). EceIF2 alpha was abundantly distributed in both the cytoplasm and nucleus in grouper spleen (GS) cells. Over-expression of EceIF2 alpha improved the expression of red-spotted grouper nervous necrosis virus (RGNNV) genes in GS cells. In addition, EceIF2 alpha depressed the activation of NK-kappa B and IFN-beta. Furthermore, dephosphorylation inhibitor treatment led to a significant decrease of RGNNV gene transcription. Taken together, these results suggest that EcelF2 alpha might be involved in the fish immune response to virus challenge.