|M.Sc Student||Gazitt Tal|
|Subject||The Identification and Characterization of a New Splice-|
Variant of the Murine Interleukin-27 Receptor
|Department||Department of Medicine||Supervisor||Professor Nathan Karin|
WSX-1 is a member of the class I cytokine receptor family, and together with gp130, it serves to bind the pro-inflammatory cytokine IL-27. In this work, a novel splice isoform of mIL-27R, 297bp ORF, was isolated and characterized. Bioinformatics-derived tools were used to show that 297bp ORF is the expressed product of an extended first exon of mIL-27R, retaining a part of the first intron of the full-length mIL-27R gene. This intron, which is flanked by the weak, non-canonical splice site pair CG-GC, contains a STOP codon, hypothetically leading to the formation of a small and compact, globular isoform. Structurally, the retained intron introduces a major change in the encoded protein, namely, the addition of a second α helix motif, which displaces the β sheet motifs found in the full-length isoform. Despite its small size, 297bp ORF is predicted to contain several functional sites, including glycosaminoglycan and N-myristoylation attachment sites, and Protein Kinase C and Casein Kinase II phosphorylation sites.
Studies targeted at elucidating the biological function of the novel splice variant showed that it is expressed in cells of both innate and adaptive immunity. In vitro experiments showed that increasing concentrations of a fusion construct composed of 297bp ORF and mIgG1 added to cultured primary splenocytes derived from a C57BL/6 Experimental Autoimmune Encephalomyelitis (EAE) mouse stimulated the secretion of IL-4 in a dose-dependent manner and inhibited the secretion of IL-2. Moreover, a humoral immune response directed specifically against the unique portion of 297bp ORF exacerbated the course of on-going Adjuvant Induced Arthritis (AIA) in DNA vaccinated Lewis rats. The antibody titer generated against 297bp ORF by the immunized rats correlated with the clinical severity of systemic inflammation and with the marked mononuclear cell infiltration and cartilage destruction observed in histological sections taken from the DNA vaccinated rats. Taken together, these results suggest that 297bp ORF may play an anti-inflammatory role, perhaps by serving as a soluble decoy receptor for a pro-inflammatory cytokine such as IL-27.