Identification and characterization of a novel IκB-ɛ-like gene from Lamprey (Lampetra japonica) with a role in immune response

Nuclear factor of kappa B (NF-κB) is a stimuli-activated transcription factor, regulates the expression of a diverse array of genes. Inhibitor of kappa B-epsilon (IκB-ɛ) is an inhibitor of NF-κB, which retains NF-κB in an inactive state in the cytoplasm. Lampreys (Lampetra japonica) belong to the lowest class of vertebrates with little information about its IκBs. We have identified a cDNA sequence IκB-ɛ-like in the lamprey and the deduced amino acid sequence of IκB-ɛ-like. It contains a conserved DSGxxS motif and six consecutive ankyrin repeats, which are necessary for signal-induced degradation of the molecule. Phylogenetic analysis indicated it had high sequence homology with IκB-ɛs from other vertebrates. FACS analysis showed that IκB-ɛ-like located in cytoplasm of leukocytes. The degradation of IκB-ɛ-like could be observed in leukocytes of L. japonica stimulated with lipopolysaccharide. These results indicate that IκB-ɛ proteins are conserved across vertebrates and the NF-κB-like signaling pathway may exist in the oldest agnatha.