Characterization of the interleukin 1 receptor-associated kinase 4 (IRAK4)-encoding gene in salmonid fish: the functional copy is rearranged in Oncorhynchus mykiss and that factor can impair TLR signaling in mammalian cells.
The interleukin 1 receptor-associated kinase 4 (IRAK4) is an essential factor for TLR-mediated activation of the host's immune functions subsequent to pathogen contact. We have characterized the respective cDNA and gene sequences from three salmonid species, salmon, rainbow trout and maraena whitefish. The gene from salmon is structured into eleven exons, as is the mammalian homologue, while exons have been fused in the genes from the two other salmonid species. Rainbow trout expresses also a pseudogene at low levels. Its basic structure resembles more closely the primordial gene than the functional copy does. The N-terminal death domain and the C-terminal protein kinase domain of the factors are better conserved throughout evolution than the linker domain. The deduced amino acid sequences of the factors from all three species group together in an evolutionary tree of IRAK4 factors. Scrutinizing expression and function of IRAK4 from rainbow trout, we found its highest expression in head kidney and spleen and lowest expression in muscle tissue. Infecting fish with Aeromonas salmonicida did not modulate its expression during 72 h of observation. Expression of a GFP-tagged trout IRAK4 revealed, expectedly, its cytoplasmic localization in human HEK-293 cells. However, this factor significantly quenched in a dose-dependent fashion not only the pathogen-induced stimulation of NF-κB factors in the HEK-293 reconstitution system of TLR2 signaling, but also the basal NF-κB levels in unstimulated control cells. Our data unexpectedly imply that IRAK4 is involved in establishing threshold levels of active NF-κB in resting cells.
Leibniz Institute for Farm Animal Biology, Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Andreas
A
Brietzke
Leibniz Institute for Farm Animal Biology, Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Tom
T
Goldammer
Rostock University Medical Center, Department of Cell Biology, Schillingallee 69, 18057 Rostock, Germany.
Henrike
H
Rebl
Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Institute of Immunology, Südufer 10, 17493 Greifswald, Insel Riems, Germany.
Tomáš
T
Korytář
Friedrich-Loeffler-Institute (FLI), Federal Research Institute for Animal Health, Institute of Immunology, Südufer 10, 17493 Greifswald, Insel Riems, Germany.
Bernd
B
Köllner
Department of Anesthesiology, Duke University Medical Center, PO Box 3094, Durham, NC 27710, USA.
Wei
W
Yang
Leibniz Institute for Farm Animal Biology, Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany. Electronic address: rebl@fbn-dummerstorf.de.
Alexander
A
Rebl
Leibniz Institute for Farm Animal Biology, Institute for Genome Biology, Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Hans-Martin
HM
Seyfert
D048409:Aeromonas salmonicida / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005393:Fish Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D015321:Gene Rearrangement / Q000276:immunology; D016905:Gram-Negative Bacterial Infections / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D057809:HEK293 Cells; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012487:Salmonidae; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000276:immunology; D051193:Toll-Like Receptors / Q000276:immunology
D012333:RNA, Messenger; D051193:Toll-Like Receptors; D053592:Interleukin-1 Receptor-Associated Kinases
Aeromonas salmonicida; DD; HEK-293; IRAK4; IRAK4s; Innate immunity; Interleukin 1 receptor-associated kinase 4; Myddosome; ORF; PKc; RLU; Rainbow trout; TIR; TLR; Toll-like receptor; Toll/interleukin-1 receptor domain; death domain; hours post infection; hpi; human embryonic kidney 293 cells; open reading frame; protein kinase domain; relative light units; short form of IRAK4