ACTIVATION OF H+ CONDUCTANCE IN NEUTROPHILS REQUIRES ASSEMBLY OF COMPONENTS OF THE RESPIRATORY BURST OXIDASE BUT NOT ITS REDOX FUNCTION

In phagocytes, superoxide generation by the NADPH oxidase is accompani ed by metabolic acid production. Cytoplasmic acidification during this metabolic burst is prevented by a combination of H+ extrusion mechani sms, including a unique H+ conductance. NADPH oxidase is deficient in chronic granulomatous disease (CGD) patients. The burst of acid produc tion is absent in CGD patients lacking the 47-kD (p47-phox) or the 91- kD (gp91-phox) subunits of the oxidase. Activation of the H+ conductan ce is also defective in these patients suggesting that (a) the oxidase itself undertakes H+ translocation or (b) oxidase assembly is require d to stimulate a separate H+ conducting entity. To discern between the se possibilities, three rare forms of CGD were studied. In neutrophils expressing nonfunctional cytochrome b, the conductance was activated to near-normal levels, implying that functional oxidase is not require d to activate H+ extrusion. CGD cells expressing diminished amounts of cytochrome displayed H+ conductance approaching normal levels, sugges ting that the oxidase itself does not translocate H+. Finally, the con ductance was only partially inhibited in patients lacking the 67-kD su bunit, indicating that this component is not essential for stimulation of H+ transport. We propose that normal assembly of the oxidase submi ts is required for optimal activation of a closely associated but dist inct H+ conducting entity.