Recombinant Mouse IL-36 alpha/IL-1F6 (aa 8-160) Protein

IL‑36 alpha, previously called IL‑1F6 and FIL1 epsilon (family of IL‑1 member epsilon), is a member of the IL‑1 family which includes IL‑1 beta, IL‑1 alpha, IL‑1ra, IL‑18, and novel family members IL‑36 Ra (IL‑1F5), IL‑36 beta (IL‑1F8), IL‑36 gamma (IL‑1F9), IL‑37 (IL‑1F7) and IL‑1F10 (14). All family members show a 12  beta‑strand, beta‑trefoil configuration, and are believed to have arisen from a common ancestral gene (1, 2). IL‑36 alpha is an 18‑22 kDa, 160 amino acid (aa) intracellular and secreted protein that contains no signal sequence, no prosegment and no potential N‑linked glycosylation sites (1‑3). It can be externalized non‑specifically in response to LPS and ATP‑induced activation of the P2X7 receptor (5). Full‑length recombinant IL‑36 alpha is less active than endogenous IL‑36 alpha, but trimming of the N‑termini enhances its activity (6). Mouse IL‑36 alpha (aa 8‑160) shares 83% aa sequence identity with rat IL‑36 alpha, 54‑60% with human, rabbit, equine and bovine IL‑36 alpha, and 27‑57% aa sequence identity with other novel IL‑1 family members. IL‑36 alpha is mainly found in skin and lymphoid tissues, but also in fetal brain, trachea, stomach and intestine (1, 3, 7). It is expressed by monocytes, B and T cells (1, 2).  The receptor for IL‑36 alpha is a combination of IL‑1 Rrp2 (also called IL‑1 RL2 or IL‑1 R6), mainly found in epithelia and keratinocytes, and the widely expressed IL‑1 RAcP (3, 6, 7). IL‑36 alpha, beta and gamma all activate NF‑ kappaB and MAPK pathways in an IL‑1 Rrp2 dependent manner, and induce production of inflammatory cytokines and chemokines such as CXCL8/IL‑8 (7). IL‑36 alpha and other family members are overexpressed in psoriatic skin lesions, and transgenic overexpression of IL‑36 alpha in skin keratinocytes produces epidermal hyperplasia (6‑9). IL‑36 alpha is present in kidney tubule epithelia; it is highly overexpressed in tubulointerstitial lesions in mouse models of chronic glomerulonephritis, lupus nephritis and diabetic nephritis (10). IL‑36 alpha is induced by inflammation in adipose tissue‑resident alternately activated (M2) macrophages, and reduces adipocyte differentiation (11).