A novel H(+) conductance in eosinophils: unique characteristics and absence in chronic granulomatous disease.
Efficient mechanisms of H(+) ion extrusion are crucial for normal NADPH oxidase function. However, whether the NADPH oxidase-in analogy with mitochondrial cytochromes-has an inherent H(+) channel activity remains uncertain: electrophysiological studies did not find altered H(+) currents in cells from patients with chronic granulomatous disease (CGD), challenging earlier reports in intact cells. In this study, we describe the presence of two different types of H(+) currents in human eosinophils. The "classical" H(+) current had properties similar to previously described H(+) conductances and was present in CGD cells. In contrast, the "novel" type of H(+) current had not been described previously and displayed unique properties: (a) it was absent in cells from gp91- or p47-deficient CGD patients; (b) it was only observed under experimental conditions that allowed NADPH oxidase activation; (c) because of its low threshold of voltage activation, it allowed proton influx and cytosolic acidification; (d) it activated faster and deactivated with slower and distinct kinetics than the classical H(+) currents; and (e) it was approximately 20-fold more sensitive to Zn(2+) and was blocked by the histidine-reactive agent, diethylpyrocarbonate (DEPC). In summary, our results demonstrate that the NADPH oxidase or a closely associated protein provides a novel type of H(+) conductance during phagocyte activation. The unique properties of this conductance suggest that its physiological function is not restricted to H(+) extrusion and repolarization, but might include depolarization, pH-dependent signal termination, and determination of the phagosomal pH set point.
Bánfi
B
B
Division of Infectious Diseases, Geneva University Hospitals, CH-1211 Geneva 4, Switzerland.
Schrenzel
J
J
Nüsse
O
O
Lew
D P
DP
Ligeti
E
E
Krause
K H
KH
Demaurex
N
N
D000328:Adult; D002648:Child; D004579:Electron Transport; D004789:Enzyme Activation; D004804:Eosinophils / Q000378:metabolism*; D005260:Female; D006105:Granulomatous Disease, Chronic / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics; D008564:Membrane Potentials; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency / Q000235:genetics; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics; D016897:Respiratory Burst
D008562:Membrane Glycoproteins; D010750:Phosphoproteins; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1