Recombinant Mouse IL-1Rrp2/IL-1R6 Protein

IL-1 Rrp2, also known as IL-1 R6, is a member of the IL-1 R/TLR superfamily. Members of this superfamily have a characteristic Toll-IL-1 R (TIR) domain in their cytoplasmic region. This superfamily can be further divided into three subgroups based on extracellular region analogies. IL-1 Rrp2 belongs to Subgroup 1 which is characterized by the presence of at least one immunoglobulin-like domain (1). Mouse IL-1 Rrp2/IL-1R6 is a 70 kDa type I transmembrane glycoprotein that is synthesized as a 574 amino acid (aa) precursor. The precursor contains a 21 aa signal sequence, a 317 aa extracellular region, a 21 aa transmembrane segment, and a 215 aa cytoplasmic domain (2). The extracellular region contains three C-type Ig-like domains. Within the extracellular region, mouse IL-1 Rrp2 is 64% and 80% aa identical to human and rat IL-1 Rrp2, respectively. Expression of IL-1 Rrp2 is restricted to lung epithelium, monocytes, skin-derived keratinocytes, fibroblasts and, to a lesser extent, endothelial cells (3). Studies have demonstrated that the functional receptor for IL-1F6, IL-1F8 and IL-1F9 is a combination of IL-1 Rrp2 and IL-1 RAcP. This suggests that IL-1 Rrp2 ligands may signal in a similar fashion to IL-1 and IL-18. In each case, there is a binding receptor which, upon ligation, recruits a second receptor as a signaling component, forming an active heterodimeric receptor complex (4).