title: A cation counterflux supports lysosomal acidification.
abstract: 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.
authors.affiliation: Program in Cell Biology, Hospital for Sick Children, Toronto, Canada M5G 1X8.
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Steinberg
authors.forename: Kassidy K
authors.initials: KK
authors.lastname: Huynh
authors.forename: Alexandre
authors.initials: A
authors.lastname: Brodovitch
authors.forename: Sabrina
authors.initials: S
authors.lastname: Jabs
authors.forename: Tobias
authors.initials: T
authors.lastname: Stauber
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Jentsch
authors.forename: Sergio
authors.initials: S
authors.lastname: Grinstein
mesh_terms: 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
chemical_list: D000838:Anions; D002412:Cations; D002712:Chlorides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator