title: Alkalinity of neutrophil phagocytic vacuoles is modulated by HVCN1 and has consequences for myeloperoxidase activity.
abstract: The NADPH oxidase of neutrophils, essential for innate immunity, passes electrons across the phagocytic membrane to form superoxide in the phagocytic vacuole. Activity of the oxidase requires that charge movements across the vacuolar membrane are balanced. Using the pH indicator SNARF, we measured changes in pH in the phagocytic vacuole and cytosol of neutrophils. In human cells, the vacuolar pH rose to ~9, and the cytosol acidified slightly. By contrast, in Hvcn1 knock out mouse neutrophils, the vacuolar pH rose above 11, vacuoles swelled, and the cytosol acidified excessively, demonstrating that ordinarily this channel plays an important role in charge compensation. Proton extrusion was not diminished in Hvcn1-/- mouse neutrophils arguing against its role in maintaining pH homeostasis across the plasma membrane. Conditions in the vacuole are optimal for bacterial killing by the neutral proteases, cathepsin G and elastase, and not by myeloperoxidase, activity of which was unphysiologically low at alkaline pH.
authors.affiliation: Division of Medicine, University College London, London, United Kingdom.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Levine
authors.affiliation: Department of Cell and Developmental Biology, University College London, London, United Kingdom.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Duchen
authors.affiliation: Glynn Laboratory of Bioenergetics, Department of Biology, University College London, London, United Kingdom.
authors.forename: Simon
authors.initials: S
authors.lastname: de Villiers
authors.affiliation: Glynn Laboratory of Bioenergetics, Department of Biology, University College London, London, United Kingdom.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Rich
authors.affiliation: Division of Medicine, University College London, London, United Kingdom.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Segal
mesh_terms: D000818:Animals; D056649:Cathepsin G / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000378:metabolism* / Q000502:physiology; D010196:Pancreatic Elastase / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism*; D010587:Phagocytosis; D016897:Respiratory Burst; D014617:Vacuoles / Q000737:chemistry / Q000378:metabolism*
chemical_list: C540876:Hv1 proton channel, mouse; D007473:Ion Channels; D009195:Peroxidase; D056649:Cathepsin G; C534096:Ctsg protein, mouse; D010196:Pancreatic Elastase