GTPases and reactive oxygen species: switches for killing and signaling

In neutrophils and other phagocytic cells, the small GTPase Rac is an essential regulator of a multi-component NADPH oxidase that produces high levels of superoxide, which kills invading pathogens. In many other cell types, Rac and newly discovered relatives of the neutrophil burst oxidase and its subunits have been found associated with production of reactive oxygen species, implicating superoxide production in a wide range of cellular processes not related to host defense. Although the precise role played by Rac in the regulation of these novel oxidases is not known, Rac does control the cellular redox state. Through these pro-oxidant mechanisms, Rac and the novel oxidases modify gene expression, cell proliferation, adhesion and many cell-specific functions.