Backbone assignment and inhibitor binding studies of IL-33 mutants by NMR spectroscopy

Abstract

Abstract Interleukin-33 (IL-33) is an IL-1 family protein that induces a type-2 immune response. IL-33 is constitutively expressed in epithelial cells and released in response to the cell damage or stimulation by an allergen. The secreted protein is activated when the N-terminal domain is cleaved by a protease, and the active form signals downstream immune cells, such as eosinophils, by binding to the heterodimeric ST2:IL-1RAcP receptor complex on the cell surface. The binding stimulates an inflammatory response, and the abnormal inflammatory response can cause allergic diseases such as atopic dermatitis and asthma. Inhibition of the interaction between IL-33 and ST2 is an attractive target to control the inflammatory disease at the upstream of the signaling. However, discovering the chemical moieties that bind to the protein–protein interaction interface is a challenging task due to the relatively wide and shallow binding pocket compared to the enzyme’s active site. For the IL-33-specific binder discovery, a series of IL-33 mutants were designed, and an electrophile chemical library was screened. Herein, we described the backbone 1H, 15N, and 13C resonance assignments of three IL-33 (117–270) mutants. Based on the assignments, the binding site of a selected compound by this approach was determined by 2D NMR. These results provide valuable information for further studies in drug discovery targeting the IL-33 and ST2 interaction.