Coreceptor for IL1RL2 in the IL-36 signaling system. Coreceptor with IL1R1 in the IL-1 signaling system. Associates with IL1R1 bound to IL1B to form the high affinity interleukin-1 receptor complex which mediates interleukin-1-dependent activation of NF-kappa-B and other pathways. Signaling involves the recruitment of adapter molecules such as TOLLIP, MYD88, and IRAK1 or IRAK2 via the respective TIR domains of the receptor/coreceptor subunits. Recruits TOLLIP to the signaling complex. Does not bind to interleukin-1 alone; binding of IL1RN to IL1R1, prevents its association with IL1R1 to form a signaling complex. The cellular response is modulated through a non-signaling association with the membrane IL1R2 decoy receptor. Secreted forms (isoforms 2 and 3) associate with secreted ligand-bound IL1R2 and increase the affinity of secreted IL1R2 for IL1B; this complex formation may be the dominant mechanism for neutralization of IL1B by secreted/soluble receptors. Coreceptor for IL1RL1 in the IL-33 signaling system. Can bidirectionally induce pre- and postsynaptic differentiation of neurons by trans-synaptically binding to PTPRD (PubMed:25908590). May play a role in IL1B-mediated costimulation of IFNG production from T-helper 1 (Th1) cells (By similarity). Associates with secreted ligand-bound IL1R2 and increases the affinity of secreted IL1R2 for IL1B; this complex formation may be the dominant mechanism for neutralization of IL1B by secreted/soluble receptors. Enhances the ability of secreted IL1R1 to inhibit IL-33 signaling. Required for Src phosphorylation by IL1B. Required for IL1B-potentiated NMDA-induced calcium influx in neurons acting in cooperation with IL1R1 isoform 2 to mediate Akt kinase activation. H2O + NAD(+) = ADP-D-ribose + H(+) + nicotinamide The interleukin-36 receptor complex is a heterodimer of IL1RL2 and IL1RAP; the association is inhibited by IL36RN. The interleukin-1 receptor complex is a heterodimer of IL1R1 and IL1RAP. Associates with IL1R2 to form a non-signaling interleukin-1 receptor complex. Interacts with IL-33-bound IL1RL1 to form the minimal interleukin-33 signaling complex with a 1:1:1 stoichiometry. Interacts with KIT (independently of stimulation with KITLG/SCF). A mast cell-specific KITLG/SCF-induced interleukin-33 signaling complex contains IL1RL1, IL1RAP, KIT and MYD88. Interacts (via the first immunoglobilin domain) with PTPRD (via the third immunoglobilin domain); induces pre- and postsynaptic differentiation of neurons (PubMed:25908590). Detected in lung, brain, spleen, thymus and liver. Expressed in brain endothelial cells, astrocytes, microglia and neurons. Isoform 3 is predominantly expressed in brain; expressed in hippocampal neurons. The TIR domain mediates NAD(+) hydrolase (NADase) activity. Self-association of TIR domains is required for NADase activity. Belongs to the interleukin-1 receptor family.