A conserved sugar bridge connected to the WSXWS motif has an important role for transport of IL-21R to the plasma membrane.
Genes Immun. 2015 Jun 4;
Authors: Siupka P, Hamming OT, Kang L, Gad HH, Hartmann R
Abstract
Interleukin-21 (IL-21) is a class I cytokine that belongs to the γc-subfamily of cytokines and regulates immune responses. It signals through a heterodimeric receptor complex composed of the IL-21R1 and γc-receptor chains. A characteristic feature of class I cytokine receptors is the presence of a consensus motif WSXWS (WS motif) in the membrane proximal fibronectin type III domain (FNIII) of these receptors. We recently described the structure of the IL-21R:IL-21 complex and showed that the first tryptophan of the WS motif of IL-21R is mannosylated and involved in formation of a sugar bridge that connects the two FNIII domains of the receptor. Furthermore, a mutation within the WS motif of IL-21R was recently shown to cause a novel kind of primary immunodeficiency syndrome (PID). Here, we report the structure of IL-21R alone, which shows that the sugar bridge forms independently of whether IL-21R binds IL-21 or not, and we furthermore investigate the role of this bridge in the export of IL-21R and γC to the plasma membrane. Thus, we provide a molecular explanation for how mutations in the WS motif may cause PIDs.Genes and Immunity advance online publication, 4 June 2015; doi:10.1038/gene.2015.22.
PMID: 26043171 [PubMed – as supplied by publisher]
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