A cation counterflux supports lysosomal acidification.
The profound luminal acidification essential for the degradative function of lysosomes requires a counter-ion flux to dissipate an opposing voltage that would prohibit proton accumulation. It has generally been assumed that a parallel anion influx is the main or only counter-ion transport that enables acidification. Indeed, defective anion conductance has been suggested as the mechanism underlying attenuated lysosome acidification in cells deficient in CFTR or ClC-7. To assess the individual contribution of counter-ions to acidification, we devised means of reversibly and separately permeabilizing the plasma and lysosomal membranes to dialyze the cytosol and lysosome lumen in intact cells, while ratiometrically monitoring lysosomal pH. Replacement of cytosolic Cl(-) with impermeant anions did not significantly alter proton pumping, while the presence of permeant cations in the lysosomal lumen supported acidification. Accordingly, the lysosomes were found to acidify to the same pH in both CFTR- and ClC-7-deficient cells. We conclude that cations, in addition to chloride, can support lysosomal acidification and defects in lysosomal anion conductance cannot explain the impaired microbicidal capacity of CF phagocytes.
Steinberg
Benjamin E
BE
Program in Cell Biology, Hospital for Sick Children, Toronto, Canada M5G 1X8.
Huynh
Kassidy K
KK
Brodovitch
Alexandre
A
Jabs
Sabrina
S
Stauber
Tobias
T
Jentsch
Thomas J
TJ
Grinstein
Sergio
S
D000818:Animals; D000838:Anions; D002412:Cations / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes; D008247:Lysosomes / Q000378:metabolism*; D008264:Macrophages; D051379:Mice; D008822:Mice, Transgenic; D010539:Permeability
D000838:Anions; D002412:Cations; D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator