Interleukin-1 receptor accessory protein-like 1 (IL1RAPL1) belongs to the interleukin-1/Toll receptor family. It has extracellular Ig-like domains and an intracellular Toll/IL1R (TIR) domain. It regulates synapse formation of cortical neurons. Trans-synaptic interaction between postsynaptic IL1RAPL1 and presynaptic Receptor-type tyrosine-protein phosphatase delta (PTPRD) bidirectionally regulates excitatory synapse development. IL1RAPL2 is related to IL1RAPL1 and may also function in excitatory synapse organization although with less potency than IL1RAPL1 (Yoshida et al. 2011, Valnegri et al. 2011).
IL1RAPL1 is associated with cognitive diseases ranging from nonsyndromic X-linked mental retardation to autism (Hayashi et al. 2013, Piton et al. 2008, Carrie et al. 1999).