Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1757, Issue 8, Pages 996-1011Publisher
ELSEVIER
DOI: 10.1016/j.bbabio.2006.01.005
Keywords
respiratory burst; phagocyte; proton channel; NADPH oxidase; electron current; pH
Categories
Funding
- NHLBI NIH HHS [HL52671, HL61437, R01 HL061437] Funding Source: Medline
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The phagocyte NADPH oxidase produces superoxide anion (O-2(.-)) by the electrogenic process of moving electrons across the cell membrane. This charge translocation must be compensated to prevent self-inhibition by extreme membrane depolarization. Examination of the mechanisms of charge compensation reveals that these mechanisms perform several other vital functions beyond simply supporting oxidase activity. Voltage-gated proton channels compensate most of the charge translocated by the phagocyte NADPH oxidase in human neutrophils and eosinophils. Quantitative modeling of NADPH oxidase in the plasma membrane supports this conclusion and shows that if any other conductance is present, it must be miniscule. In addition to charge compensation, proton flux from the cytoplasm into the phagosome (a) helps prevent large pH excursions both in the cytoplasm and in the phagosome, (b) minimizes osmotic disturbances, and (c) provides essential substrate protons for the conversion of 0(2)(.-) to H2O2 and then to HOCL A small contribution by K+ or Cl- fluxes may offset the acidity of granule contents to keep the phagosome pH near neutral, facilitating release of bactericidal enzymes. In summary, the mechanisms used by phagocytes for charge compensation during the respiratory burst would still be essential to phagocyte function, even if NADPH oxidase were not electrogenic. (c) 2006 Elsevier B.V. All rights reserved.
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