Interleukin 18 Receptor Accessory Protein (IL18RAP)

Interleukin 18 receptor accessory protein is an accessory subunit of the heterodimeric receptor for IL18. This protein enhances the IL18 binding activity of IL18R1 (IL1RRP), a ligand binding subunit of IL18 receptor. The coexpression of IL18R1 and this protein is required for the activation of NF-kappa B and MAPK8 (JNK) in response to IL18. IL18RAP is predicted to contain a 14-amino acid signal peptide, a 342-amino acid extracellular (Ig superfamily-like) segment, a single transmembrane region, and a 222-amino acid cytoplasmic domain that is 32% identical to IL1R1. Northern blot analysis revealed that IL18RAP mRNA, present predominantly as a 3.8-kb product, was expressed strongly in peripheral blood leukocytes, spleen, lung, and, to a lesser extent, in colon, but not in any other tissue tested.