The role of EaIκB-α, an IκB-α homologue in Epinephelus akaara, involved in innate immune response

The inhibitor κB (IκB) protein is an important component of the nuclear factor kB (NF-κB) signaling pathway. We have cloned and characterized the IκB-α homologue gene (named EaIκB-α) from grouper (Epinephelus akaara), expressed it in Escherichia coli and generated a rabbit polyclonal antibody. EaIκB-α encodes a 308-amino acid protein with evolutionarily and functionally homology to mammalian IκB-α. Over-expression of wild-type EaIκB-α or a mutated, nondegradable EaIκB-α (EaIκB-αM) in Escherichia coli both inhibited the degradation of cellular EaIκB-α, activation of NF-κB and expression of tumor necrosis factor α (TNF-α). EaIκB-α protein is restricted to the cytoplasm in unstimulated cell. Activated by diverse stimuli, EaIκB-α is degraded, thereby releasing NF-κB into nucleus and activating NF-κB-mediated transcripts. EaIκB-α and other studied NF-κB target genes are induced by LPS in kidney and liver, which suggests that EaIκB-α may play an important role in immune response of grouper.