title: pH-dependent perforation of macrophage phagosomes by listeriolysin O from Listeria monocytogenes.
abstract: The pore-forming toxin listeriolysin O (LLO) is a major virulence factor implicated in escape of Listeria monocytogenes from phagocytic vacuoles. Here we describe the pH-dependence of vacuolar perforation by LLO, using the membrane-impermeant fluorophore 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) to monitor the pH and integrity of vacuoles in mouse bone marrow-derived macrophages. Perforation was observed when acidic vacuoles containing wild-type L. monocytogenes displayed sudden increases in pH and release of HPTS into the cytosol. These changes were not seen with LLO-deficient mutants. Perforation occurred at acidic vacuolar pH (4.9-6.7) and was reduced in frequency or prevented completely when macrophages were treated with the lysosomotropic agents ammonium chloride or bafilomycin A1. We conclude that acidic pH facilitates LLO activity in vivo.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Beauregard
authors.forename: K D
authors.initials: KD
authors.lastname: Lee
authors.forename: R J
authors.initials: RJ
authors.lastname: Collier
authors.forename: J A
authors.initials: JA
authors.lastname: Swanson
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001190:Arylsulfonates / Q000378:metabolism; D001426:Bacterial Proteins / Q000502:physiology; D001427:Bacterial Toxins; D002463:Cell Membrane Permeability; D005456:Fluorescent Dyes / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000502:physiology*; D006460:Hemolysin Proteins; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000235:genetics / Q000472:pathogenicity*; D018942:Macrolides; D008264:Macrophages / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D010588:Phagosomes / Q000378:metabolism*; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D001190:Arylsulfonates; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005456:Fluorescent Dyes; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D018942:Macrolides; D000643:Ammonium Chloride; C040929:bafilomycin A1; C005047:pyranine; C038705:hlyA protein, Listeria monocytogenes