Abnormal activation of H+ conductance in NADPH oxidase-defective neutrophils.
To combat bacterial infection, phagocytes generate superoxide (O2-) and other microbicidal oxygen radicals. NADPH oxidase, the enzyme responsible for O2- synthesis, is deficient in chronic granulomatous disease (CGD) patients. Although O2- generation is accompanied by a large burst of metabolic acid production, intracellular pH (pHi) remains near neutrality due to the concomitant stimulation of H+ extrusion. Three major pathways contribute to pHi regulation in activated phagocytes: Na+/H+ exchange, vacuolar-type H+ pumps, and a H+ conductance. The present study analyzed the relationship between activation of the NADPH oxidase and stimulation of the H+ extrusion mechanisms in human blood neutrophils. Phorbol ester-induced activation of Na+/H+ exchange and H+ pumping occurred normally in cells from CGD patients. Unlike normal individuals, however, CGD patients were unable to activate the H+ conductive pathway. Thus, activation of the H+ conductance appears to be contingent on the assembly of a functional NADPH oxidase. These findings imply a dual role of the NADPH oxidase in O2- synthesis and in the regulation of pHi. The oxidase (or some components thereof) may itself undertake H+ translocation or, alternatively, may signal the activation of a separate H+ conducting entity.
Nanda
A
A
Division of Cell Biology, Hospital for Sick Children, Toronto, Canada.
Grinstein
S
S
Curnutte
J T
JT
D001693:Biological Transport, Active; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005609:Free Radicals; D006105:Granulomatous Disease, Chronic / Q000503:physiopathology*; D006579:Heterozygote; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D009247:NADH, NADPH Oxidoreductases / Q000172:deficiency / Q000187:drug effects / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D017494:Proton Pumps / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D005609:Free Radicals; D017494:Proton Pumps; D009249:NADP; D012964:Sodium; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D013755:Tetradecanoylphorbol Acetate; D010100:Oxygen