Cg-IkappaB, a new member of the IkappaB protein family characterized in the pacific oyster Crassostrea gigas.

Inhibitors of NF-kappaB (IkappaBs) have been implicated as major components of the Rel/NF-kappaB signaling pathway, which is an important mediator of immune responses throughout much of the animal kingdom. Here we report the first characterization of a bivalve mollusc cDNA that encodes a novel IkappaB member called Cg-IkappaB showing the conservation of most IkappaB protein characteristics. Sequences as well as phylogenetic analyses reveal a high level of identity between not only Cg-IkappaB and other mollusc and insect IkappaB-like proteins but also similarities to vertebrate IkappaB-alpha and -epsilon isoforms. Expression analyses demonstrated that the transcript is widely expressed in all oyster tissues. This work is consistent with our previous discovery of several members of an NF-kappaB pathway in Crassostrea gigas and further sustains the hypothesis of a conserved scheme of immune gene regulation through most of the metazoans.