Human Receptor-Interacting Serine/Threonine-Protein Kinase 2 (RIPK2); A Target Enabling Package

RIPK2 inflammatory signalling downstream from the bacteria-sensing receptors NOD1 and NOD2 is associated with auto-immune and inflammatory conditions. RIPK2 inhibition has shown promise in disease models of inflammatory bowel disease and multiple sclerosis. In this TEP, we reveal a lack of correlation between inhibitor efficacy in cells and their potency using in vitro kinase assays. We show that RIPK2 kinase activity is in fact dispensable for NOD2 inflammatory signalling and that RIPK2 inhibitors function instead by antagonizing XIAP-binding and ubiquitination of RIPK2. We characterise the molecular basis for this effect. We also solved the first crystal structure of the RIPK2 kinase domain and applied a range of biochemical and cellular assays to profile type I and type II RIPK2 kinase inhibitors. Overall, our study illustrates how to target the ATP-binding pocket in RIPK2 to interfere with the RIPK2-XIAP interaction for modulation of NOD signalling.