title: Reversible activation of NADPH oxidase in membranes of HL-60 human leukemic cells.
abstract: NADPH oxidase in membranes of undifferentiated and dimethylsulphoxide-differentiated HL-60 cells was activated by arachidonic acid (AA) in the presence of Mg2+ and a cytosolic cofactor (CF) found in differentiated HL-60 cells. Basal superoxide (O2-) formation was enhanced several-fold by addition of the stable GTP-analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), prior to AA and was completely prevented by that of GDP. Basal and GTP gamma S-stimulated O2- formation was terminated by GDP. In the presence of Mg2+ or EDTA, basal O2- formation ceased after 25 or 10 min, respectively, and was reinitiated by GTP gamma S or GTP gamma S plus Mg2+. Albumin terminated O2- formation, which was reactivated by AA in the presence of GTP gamma S. Our results show that (1) activation of NADPH oxidase in HL-60 membranes is dependent on endogenous GTP, Mg2+, AA and CF, which is induced during myeloid differentiation, and that (2) NADPH oxidase activation is a reversible process modulated by exogenous guanine nucleotides at various stages of activity of NADPH oxidase. We suggest crucial roles of guanine nucleotide-binding proteins in the activation, deactivation and reactivation of the enzyme.
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D007700:Kinetics; D007951:Leukemia, Myeloid; D008274:Magnesium / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases
chemical_list: D004492:Edetic Acid; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D008274:Magnesium; D004121:Dimethyl Sulfoxide