Molecular characteristics and functional study of tumor necrosis factor receptor-associated factor 2 from the orange-spotted grouper (Epinephelus coioides).

In mammals, tumor necrosis factor receptor-associated factor 2 (TRAF2) is a crucial intracellular adaptor protein, which performs a vital role in numerous signaling pathways that activate NF-κB, MAPKs, and IRFs. In the present study, three TRAF2 sequences were identified from the orange-spotted grouper (Epinephelus coioides), and named EcTRAF2-1, EcTRAF2-2, and EcTRAF2-3. These sequences contained conserved structure features that were similar to those of mammals. EcTRAF2-1 shared relatively low sequence identity with the other two EcTRAF2s. In healthy E. coioides, EcTRAF2s were widely expressed in all tissues tested, but with distinct expression profiles. After infection with Cryptocaryon irritans, EcTRAF2s was markedly upregulated in the gill and head kidney at most time points, implying that EcTRAF2s may be involved in host defense against C. irritans infection. In HEK293T cells, EcTRAF2s were scattered in the cytoplasm. EcTRAF2-1 and EcTRAF2-2 increased the activity of NF-κB, while EcTRAF2-3 reduced NF-κB activation mediated by EcTRAF2-1 implying that EcTRAF2-3 might be a negative regulator of EcTRAF2-1.