Evolution of the IL17 receptor family in chordates: a new subfamily IL17REL
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The human interleukin 17 receptor (IL17R) family plays a critical role in inflammatory responses and contributes to the pathology of many autoimmune diseases. So far, five members, IL17RA to IL17RE, have been identified. Recently, some IL17R genes have been identified in non-mammalian species, such as zebrafish IL17RD; however, there are no reports on the evolutionary history of this complex gene family through comparative phylogenetic approaches. Here, we concentrated on the IL17R evolution in chordates. There are two IL17Rs in the genome of the basal chordate amphioxus: IL17RA and IL17RD. After two rounds of whole genome duplications, these two IL17R genes expanded into five early vertebrate IL17R genes, IL17RA to IL17RE. IL17RA and IL17RD are found in most vertebrates, whereas the other three, IL17RB, ILR17RC, and IL17RE, underwent some loss in vertebrates during evolution. Our sequence and structure analyses reveal functional similarities and distinctions between the different IL17Rs. Based on similarity searches for IL17R-like proteins within chordate sequences, a group of IL17RE-like (IL17REL) proteins were identified from mammalians to lower vertebrates. In silico and expression analyses on the novel IL17RELs showed that this group of receptors is highly conserved across species, indicating that IL17REL may represent a unique subfamily of IL17Rs.
KeywordsInterleukin 17 receptor IL17REL Chordate Evolution
We thank Hong Yu for the artwork and Dr. Jing Gong and Guang Li for scientific advice. This work was supported by the Chinese National ‘863’ Project under grant no. 2008AA092603 and the China Postdoctoral Science Foundation under grant no. 20110491591. The work conducted by the U.S. Department of Energy Joint Genome Institute is supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231.
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