The murine IRAK2 gene encodes four alternatively spliced isoforms, two of which are inhibitory.
The interleukin-1 receptor-associated kinases (IRAKs) are important downstream signaling components of Toll-like receptors (TLRs). To date, four mammalian IRAKs have been found, namely IRAK-1, IRAK-2, IRAK-4, and IRAK-M. Herein, we show a detailed analysis of the genomic region encompassing the murine Irak2 gene and the molecular cloning of four isoforms of Irak2 (designated Irak2a, Irak2b, Irak2c, and Irak2d) generated by alternative splicing at the 5'-end of the gene. This alternative splicing has direct effects on the expression of the N-terminal death domain and/or inter-domain. No evidence of similar alternative splicing was found for the human IRAK2 gene. When overexpressed, Irak2a and Irak2b potentiated NF-kappaB activation by lipopolysaccharide. Importantly, Irak2c and Irak2d were inhibitory. The promoter for Irak2c differed from that of the other Irak2 isoforms in that it contained putative NF-kappaB binding sites. Lipopolysaccharide induced the expression of Irak2c, indicating a possible negative feedback effect on the signaling pathway. Alternative splicing of the Irak2 gene in mice will therefore generate agonistic or antagonistic Irak2 isoforms, which is likely to have consequences for the regulation of TLR signaling. These observations identify another distinguishing feature between mice and humans in the TLR system that is likely to be due to differences in the selective pressure imposed by pathogens on each species during evolution.
Hardy
Matthew P
MP
Department of Biochemistry and the Biotechnology Institute, Trinity College Dublin, Dublin 2, Ireland.
O'Neill
Luke A J
LA
D016475:3T3 Cells; D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017353:Gene Deletion; D017930:Genes, Reporter / Q000235:genetics; D016678:Genome; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000235:genetics; D020033:Protein Isoforms; D011494:Protein Kinases / Q000235:genetics* / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014018:Tissue Distribution; D051193:Toll-Like Receptors
D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D051193:Toll-Like Receptors; D011494:Protein Kinases; C507771:IRAK3 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; C507772:Irak3 protein, mouse