Nitric oxide regulates phagocytosis through S-nitrosylation of Rab5

AbstractPhagocytosis is mediated mainly by immune cells, such as macrophages, monocytes and neutrophils, that function to clear large pathogens including bacteria. The small GTP-binding protein Rab5 is crucial for clathrin-dependent endocytosis as well as phagocytosis. However, the role and mechanism of Rab5 activation during phagocytosis are poorly understood. Here we report that nitric oxide (NO), a novel regulator of Rab5, regulates phagocytosis through S-nitrosylation of Rab5. NO can promote phagocytosis by activating Rab5 in cultured cells, and it potently S-nitrosylates active Rab5 compared to inactive Rab5. Moreover, we demonstrate that two cysteine residues in the C terminus of Rab5 are S-nitrosylated and are important for phagocytosis. Experiments involving mice also showed that NO activates Rab5 and increases levels of S-nitrosylated Rab5 and that NO is involved in phagocytic bacterial clearance mediated by peritoneal macrophages. These data suggest that NO promotes S-nitrosylation of Rab5 to act as a novel Rab5 activator and a key regulator of phagocytosis.HighlightsNO promotes phagocytosisNO directly activates Rab5 and increases Rab5 S-nitrosylationS-nitrosylation C-terminal Rab5 cysteines residues is involved in phagocytosisNO increases Rab5 S-nitrosylation and activity to promote bacterial clearance in vivo