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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Grinstein, Sergio Steinberg, Benjamin E. Vargas-caballero, Mariana Touret, Nicolas |
| Description | Author Affiliation: Steinberg BE ( Programs in Cell Biology, Hospital for Sick Children, Toronto, ON, Canada.); |
| Abstract | Phagosomes employ lytic enzymes, cationic peptides, and reactive oxygen intermediates to eliminate invading microorganisms. The effectiveness of these microbicidal mechanisms is potentiated by the acidic pH created by H(+)-pumping vacuolar-type ATPases (V-ATPases) on the phagosomal membrane. The degree of phagosomal acidification varies greatly among neutrophils, macrophages, and dendritic cells and can be affected by diseases like cystic fibrosis. The determinants of phagosomal pH are not completely understood, but the permeability to ions that neutralize the electrogenic effect of the V-ATPase has been proposed to play a central role. When counterion conductance is limiting, generation of a large membrane potential will dominate the proton-motive force (pmf), with a proportionally diminished pH gradient. Validation of this notion requires direct measurement of the electrical potential that develops across the phagosomal membrane (Psi(Phi)). We describe a noninvasive procedure to estimate Psi(Phi) in intact cells, based on fluorescence resonance energy transfer. This approach, in combination with measurements of phagosomal pH, enabled us to calculate the pmf across phagosomes of murine macrophages and to analyze the factors that limit acidification. At steady state, Psi(Phi) averaged 27 mV (lumen positive) and was only partially dissipated by inhibition of the V-ATPase with concanamycin A. The comparatively small contribution of the potential to the pmf suggests that proton pumping is not limited by the counterion permeability, a notion that was validated independently by using ionophores. Instead, phagosomal pH stabilizes when the rate of proton pumping, which decreases gradually as the lumen acidifies, is matched by the passive leak of proton equivalents. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 22 |
| Volume Number | 104 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2007-05-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Intracellular Membranes Metabolism Membrane Potentials Phagosomes Proton-Motive Force Animals Cell Line Cell Survival Fluorescence Resonance Energy Transfer Mice Vacuolar Proton-Translocating ATPases Research Support, Non-U.S. Gov't Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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