Characterization of the Core Elements of the NF-κB Signaling Pathway of the Sea Anemone Nematostella vectensis

The sea anemone Nematostella vectensis is the leading developmental and genomic model for the phylum Cnidaria, which includes anemones, hydras, jellyfish, and corals. In insects and vertebrates, the NF-kappa B pathway is required for cellular and organismal responses to various stresses, including pathogens and chemicals, as well as for several developmental processes. Herein, we have characterized proteins that comprise the core NF-kappa B pathway in Nematostella, including homologs of NF-kappa B, I kappa B, Bcl-3, and I kappa B kinase (IKK). We show that N. vectensis NF-kappa B (Nv-NF-kappa B) can bind to kappa B sites and activate transcription of reporter genes containing multimeric kappa B sites or the Nv-I kappa B promoter. Both Nv-I kappa B and Nv-Bcl-3 interact with Nv-NF-kappa B and block its ability to activate reporter gene expression. Nv-IKK is most similar to human IKK epsilon/TBK kinases and, in vitro, can phosphorylate Ser47 of Nv-I kappa B. Nv-NF-kappa B is expressed in a subset of ectodermal cells in juvenile and adult Nematostella anemones. A bioinformatic analysis suggests that homologs of many mammalian NF-kappa B target genes are targets for Nv-NF-kappa B, including genes involved in apoptosis and responses to organic compounds and endogenous stimuli. These results indicate that NF-kappa B pathway proteins in Nematostella are similar to their vertebrate homologs, and these results also provide a framework for understanding the evolutionary origins of NF-kappa B signaling.