Molecular characterization of interleukin-6 in the gilthead seabream (Sparus aurata).
A cDNA clone, designated sbIL-6 (seabream interleukin-6), was obtained from a cDNA library of enriched immune-stimulated sequences from gilthead seabream. The deduced sbIL-6 protein corresponds to a 225-amino acid protein with a putative 24-amino acid signal peptide, four conserved alpha helices and one N-linked glycosylation site. At the amino acid level sbIL-6 shares 23-26% identity with mammalian IL-6 sequences and 30-51% identity with other fish IL-6 sequences. The structure of the sbIL-6 gene consisted of 5 exons and 4 introns, spanning 2.4 kb. Healthy fish expressed sbIL-6 in white muscle, skin, spleen, anterior intestine and stomach, while no expression was detected in brain, gill, head kidney, posterior intestine and adipose tissue. A significant up-regulation of sbIL-6 expression was observed after lipopolysaccharide (LPS), Vibrio anguillarum DNA (VaDNA) and peptidoglycan treatment in cultured seabream head kidney leukocytes. Using purified immune cells, sbIL-6 expression was induced similarly in macrophages and acidophilic granulocytes by VaDNA but LPS was more effective in inducing sbIL-6 expression in acidophilic granulocytes than in macrophages. Furthermore, in vivo infection of seabream with live V. anguillarum caused significant increases in sbIL-6 mRNA expression in the thymus, peritoneal exudate, head kidney and gills. In summary, our study provides further evidence for the existence of distinct IL-6 genes in lower vertebrates and for the strong induction of their expression by immune stimuli, supporting the notion of a potentially important role for this cytokine in fish.
Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona and Institut de Biomedicina de la Universitat de Barcelona (IBUB), 08028 Barcelona, Spain.
Barbara
B
Castellana
Dimitar B
DB
Iliev
M Pilar
MP
Sepulcre
Simon
S
MacKenzie
Frederick W
FW
Goetz
Victoriano
V
Mulero
Josep V
JV
Planas
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D015850:Interleukin-6 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D021541:Sea Bream / Q000235:genetics* / Q000382:microbiology; D016415:Sequence Alignment; D014733:Vibrio
D015850:Interleukin-6; D012333:RNA, Messenger