The alpha inhibitor of NF-kappaB (IkappaBalpha) from the mandarin fish binds with p65 NF-kappaB.

The NF-kappaB/IkappaBalpha pathway plays an important role in the regulation of immune and inflammatory responses. IkappaBalpha is an inhibitory molecule that sequesters transcription activator NF-kappaB dimer in the cytoplasm of unstimulated cells. Here, we isolated the full-length cDNAs of the mandarin fish (Siniperca chuatsi) alpha inhibitor of NF-kappaB (ScIkappaBalpha) and p65 NF-kappaB (Scp65). Multiple sequence alignments showed that the amino acid sequences of both ScIkappaBalpha and Scp65 contain conserved domains similar to those of mammalian counterparts. Protein pull-down and coimmunoprecipitation assays showed that ScIkappaBalpha directly bound with Scp65. Real-time quantitative PCR analysis showed that ScIkappaBalpha mRNA was constitutive in all mandarin fish tissues detected. After challenge with infectious spleen and kidney necrosis virus (ISKNV), the mRNA level of ScIkappaBalpha was decreased nearly 6 fold in the spleen. This result suggests that the NF-kappaB/IkappaBalpha pathway in mandarin fish may play a role in the immune response against ISKNV.