title: Human monocytes use Rac1, not Rac2, in the NADPH oxidase complex.
abstract: Phagocyte NADPH oxidase is critical for defense against pathogens and contributes to inflammatory tissue injury. One component of the NADPH oxidase complex is the small GTP-binding protein Rac. There are two isoforms of Rac, and Rac2 is the predominant isoform in neutrophils and has been shown to be essential for NADPH oxidase activity. In primary human monocytes we report that in contrast to neutrophils, Rac1 is the predominantly expressed isoform. Upon monocyte activation by a variety of agents, we found that Rac1 dissociates from Rho GDP dissociation inhibitor (RhoGDI) and translocates to the membrane. We also found that Rac1 interacts with two other NADPH oxidase components, p67phox and p47phox, upon monocyte activation. These data indicate that Rac1, and not Rac2, is a component of the activated NADPH oxidase in monocytes. This finding suggests that it may be possible to selectively interfere with either monocyte or neutrophil NADPH oxidase activity, thereby selectively targeting chronic versus acute inflammatory processes.
authors.affiliation: Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Xiaoxian
authors.initials: X
authors.lastname: Zhao
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Carnevale
authors.forename: Martha K
authors.initials: MK
authors.lastname: Cathcart
mesh_terms: D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007249:Inflammation; D009000:Monocytes / Q000378:metabolism*; D019255:NADPH Oxidases / Q000737:chemistry* / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011233:Precipitin Tests; D020033:Protein Isoforms; D021381:Protein Transport; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D019255:NADPH Oxidases; D010750:Phosphoproteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011994:Recombinant Proteins; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D000097766:RAC2 GTP-Binding Protein; C079789:neutrophil cytosol factor 67K; C060505:neutrophil cytosolic factor 1