The type II interleukin-1 receptor (IL-1RII) of the bony fish gilthead seabream Sparus aurata is strongly induced after infection and tightly regulated at transcriptional and post-transcriptional levels.
Interleukin-1beta (IL-1beta) is the prototypic pro-inflammatory cytokine. All the biological effects of IL-1beta are mediated through interaction with type 1 IL-1 receptor (IL-1RI), whereas another receptor, called type 2 IL-1R (IL-1RII), lacks an intracellular signalling domain and acts as a decoy receptor that down-regulates responses to IL-1beta. Although both receptors are present in bony fish, their expression and biological role in the regulation of IL-1beta activity in non-mammalian vertebrates remain to be established. In this study, a homologue of mammalian IL-1RII was isolated and characterized in the gilthead seabream (Sparus aurata). The seabream IL-1RII harboured two Ig-like domains in its extracellular region and a short cytoplasmic tail lacking a signalling domain. The seabream IL-1RII cDNA showed an unexpectedly long 3'UTR compared with that from other species and contained three ATTTA instability motifs, which seem to be responsible for its relatively short half-life (less than 2h). The expression of seabream IL-1RII was dramatically up-regulated after infection with Vibrio anguillarum in all the immune tissues examined and was even more strongly induced than the IL-1beta gene in the head kidney, spleen and liver. Strikingly, the mRNA levels of IL-1RII were 15-fold higher than those of IL-1beta in the liver, suggesting a role for this organ in the neutralization of IL-1beta leaking into the systemic circulation from the sites of inflammation. In vitro, bacterial DNA and flagellin increased the mRNA levels of IL-1RII in macrophages, while only flagellin was able to weakly induce its expression in acidophilic granulocytes. Finally, the seabream IL-1RII was localized in the plasma membrane when expressed in HEK293 cells and was able to bind IL-1beta.
López-Castejón
Gloria
G
Department of Cell Biology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain.
Sepulcre
M Pilar
MP
Roca
Francisco J
FJ
Castellana
Barbara
B
Planas
Josep V
JV
Meseguer
José
J
Mulero
Victoriano
V
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D005393:Fish Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D005786:Gene Expression Regulation; D006801:Humans; D053583:Interleukin-1beta / Q000276:immunology; D008969:Molecular Sequence Data; D010802:Phylogeny; D053574:Receptors, Interleukin-1 Type II / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D021541:Sea Bream / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D014158:Transcription, Genetic; D015854:Up-Regulation; D014735:Vibrio Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary*
D053583:Interleukin-1beta; D053574:Receptors, Interleukin-1 Type II