In our search for genes involved in oyster immunity we isolated a cDNA encoding a polypeptide closely related to the mammalian IκB kinase (IKK) family. IKK proteins play a central role in cell signaling by regulating nuclear factor-κB (NF-κB) activation. We report here the cloning of an oyster IKK-like protein (oIKK) which possesses the characteristic organization of the mammalian IKK proteins, namely an amino-terminal kinase domain followed by a leucine zipper region and a carboxyl-terminal helix-loop-helix motif. When transfected into human cell lines, oIKK activated the expression of NF-κB-controlled reporter gene, whereas transfections with mutants of oIKK deleted within the kinase domain or within the helix-loop-helix motif respectively abolished and greatly reduced reporter gene activation. These results indicate that oIKK can replace the hIKK-α in catalyzing NF-κB nuclear translocation, and in triggering gene expression. Our results sustain the concept of an evolutionarily conserved signaling machinery in which IKK plays a major role.
Escoubas, J. M., Briant, L., Montagnani, C., Hez, S., Devaux, C., & Roch, P. (1999). Oyster IKK-like protein shares structural and functional properties with its mammalian homologues. FEBS Letters, 453(3), 293–298. https://doi.org/10.1016/S0014-5793(99)00737-1