beta-trefoil domain found in the family of interleukin-36 (IL-36) and similar proteins
The IL-36 family includes three members, IL-36 alpha (also called FIL1 epsilon, or interleukin-1 epsilon, or IL-1 epsilon, or interleukin-1 family member 6, or IL-1F6), IL-36 beta (also called FIL1 eta, or interleukin-1 eta, or IL-1 eta, or interleukin-1 family member 8, or IL-1F8, or interleukin-1 homolog 2, or IL-1H2), and IL-36 gamma (also called IL-1-related protein 2, or IL-1RP2, or interleukin-1 epsilon, or IL-1 epsilon, or interleukin-1 family member 9, or IL-1F9, or interleukin-1 homolog 1, or IL-1H1). They act as cytokines that bind to and signals through the IL1RL2/IL-36R receptor which in turn activates NF-kappa-B and MAPK signaling pathways in target cells linked to a pro-inflammatory response. They are parts of the IL-36 signaling system that is thought to be present in epithelial barriers and to take part in local inflammatory response; like the IL-1 system with which they share the co-receptor IL1RAP. They may be involved in skin inflammatory response by acting on keratinocytes, dendritic cells, and indirectly on T-cells to drive tissue infiltration, cell maturation and cell proliferation. Members in this family contain a beta-trefoil domain, which is characterized by 12 beta strands folded into three similar trefoil subdomains (alpha, beta, and gamma) associated to give an overall structure with pseudo-3-fold symmetry.
Jiyao W et al.(2023). "The conserved domain database in 2023.",