Molecular cloning and expression analysis of sea bass (Dicentrarchus labrax L.) tumor necrosis factor-α (TNF-α)

In the search for pro-inflammatory genes in sea bass a TNF-α gene was cloned and sequenced. The sea bass TNF-α (sbTNF-α) putative protein conserves the TNF-α family signature, as well as the two cysteines usually involved in the formation of a disulfide bond. The mouse TNF-α Thr-Leu cleavage sequence and a potential transmembrane domain were also found, suggesting that sbTNF-α exists as two forms: a ∼28 kDa membrane-bound form and a ∼18.4 kDa soluble protein. The single copy sbTNF-α gene contains a four exon-three intron structure similar to other known TNF-α genes. Homology modeling of sbTNF-α is compatible with the trimeric quaternary architecture of its mammalian counterparts. SbTNF-α is constitutively expressed in several unstimulated tissues, and was not up-regulated in the spleen and head-kidney, in response to UV-killed Photobacterium damselae subsp. piscicida. However, an increase of sbTNF-α expression was detected in the head-kidney during an experimental infection using the same pathogen.