Interleukin-1β gene in orange-spotted grouper, Epinephelus coioides: Molecular cloning, expression, biological activities and signal transduction

IL-1β, a key mediator of inflammation, orchestrates a variety of immune responses by initiating gene expression. Herein, we have cloned and sequenced the IL-1β in orange-spotted grouper (Epinephelus coioides), produced soluble mature recombinant IL-1β in Escherichia coli, and characterized its biological properties and downstream signal transduction. The grouper IL-1β cDNA was 1364 bp in length, containing an open reading frame of 765 bp. The predicted protein of 254 amino acids revealed the presence of the IL-1 family signature motif and the absence of a conventional ICE cut site. Phylogenetically, the grouper IL-1β clustered closely with those of teleost belonging to Perciformes and apart from those of mammals. The grouper IL-1β was constitutively expressed in almost all tissues examined, and was augmented in PBL after the addition of LPS or Poly I:C in vitro. The prokaryotically produced rIL-1β significantly stimulated the proliferation of grouper head kidney cells, and activated gene expression of IL-1β and COX-2. Moreover, the rIL-1β-induced IL-1β and COX-2 expression were reduced by p38 MAPK inhibitor (SB203580) and JNK inhibitor (SP600125), respectively. Taken together, the present study indicated that grouper IL-1β may have an important role in grouper immune system and activate similar downstream cascades as its mammalian counterparts.