Neuronal JNK pathway activation by IL-1 is mediated through IL1RAPL1, a protein required for development of cognitive functions.

Interleukin-1-Receptor Accessory Protein Like 1 (IL1RAPL1) gene mutations are associated to cognitive impairment ranging from non-syndromic X-linked mental retardation to autism. Functionally IL1RAPL1 belongs to a novel family of Toll/IL-1 Receptors, but its ligand is unknown. In a recent study, we have shown that IL1RAPL1 is present in dendritic spine where it interacts with PSD-95, a major scaffold protein of excitatory post-synaptic density. We demonstrated that IL1RAPL1 regulates the synaptic localization of PSD-95 by controlling JNK (c-Jun terminal Kinase) activity and PSD-95 phosphorylation. Loss of IL1RAPL1 in mouse not only led to a reduction of excitatory synapses but also to specific deficits in hippocampal long-term synaptic plasticity. Here we report that activation of JNK pathway in neurons by Interleukin-1 (IL-1) is mediated by IL1RAPL1. The interaction of IL1RAPL1 with PSD-95 discloses a novel pathophysiological mechanism underlying cognitive impairment associated with alterations of the JNK pathway in response to IL-1 and leading to the mislocalization of PSD-95, that subsequently result in abnormal synaptic organization and function.