Phosphoproteomic Analyses Provide Insight into Molecular Mechanisms Underlying NETosis

NETosis, a novel cell death mechanism which leads to neutrophil extracellular trap (NET) formation, is involved in both infectious and noninfectious diseases. However, its underlying mechanisms remain unclear. To explore the mechanisms and common factors associated with NADPH oxidase (NOX)-dependent and NOX-independent NETosis, global proteomics and phosphoproteomics analyses are conducted in neutrophils treated with phorbol 12-myristate 13-acetate (PMA), ionomycin, and monosodium urate (MSU). Global proteomic analyses identify 64, 97, and 141 proteins differentially regulated in the PMA, ionomycin, and MSU groups compared with the control group, respectively. Phosphoproteomic analysis identifies 931, 565, and 201 phosphorylation sites differentially regulated in the PMA, ionomycin, and MSU groups, compared with the control, respectively. Overlap analysis of the three comparisons identifies nine proteins and 49 phosphorylation sites derived from 41 phosphoproteins. Among the 41 differentially regulated phosphoproteins, 23 are associated with nuclear function, five with chromatin binding, and 13 with poly(A) RNA binding activities based on GO annotation. Among these, DEK, methyl-CpG-binding protein 2 (MECP2), and structure-specific recognition protein 1 (SSRP1) are involved in both chromatin and poly(A) RNA binding. In conclusion, this study provides insight into molecular mechanisms of NETosis and a useful dataset for the guidance of future studies.