Abstract
Interleukin-33 (IL-33) is a novel member of the IL-1 family of cytokines that plays diverse roles in the regulation of immune responses. IL-33 exerts its effects through a heterodimeric receptor complex resulting in the production and release of pro-inflammatory cytokines. A detailed understanding of the signaling pathways activated by IL-33 is still unclear. To gain insights into the IL-33 mediated signaling mechanisms, we carried out a SILAC-based global quantitative phosphoproteomic analysis that resulted in the identification of 7,191 phosphorylation sites derived from 2,746 proteins. We observed alterations in the level of phosphorylation in 1,050 sites corresponding to 672 proteins upon IL-33 stimulation. We report, for the first time, phosphorylation of multiple protein kinases, including Mitogen-activated protein kinase-activated protein kinase 2 (Mapkapk2), Receptor (TNFRSF)-interacting serine-threonine kinase 1 (Ripk1) and NAD kinase (Nadk) that are induced by IL-33. In addition, we observed IL-33-induced phosphorylation of several protein phosphatases including Protein tyrosine phosphatase, Non-receptor type 12 (Ptpn12) and Inositol polyphosphate-5-phosphatase D (Inpp5d), which have not been reported previously. Network analysis revealed an enrichment of actin binding and cytoskeleton reorganization that could be important in macrophage activation induced by IL-33. Our study is the first quantitative analysis of IL-33-regulated phosphoproteome. Our findings significantly expand the understanding of IL-33 mediated signaling events and have the potential to provide novel therapeutic targets pertaining to immune related diseases such as asthma where dysregulation of IL-33 is observed.