title: Assessment of cation trapping by cellular acidic compartments.
abstract: All nucleated cells, from yeast to animal cells, concentrate cationic chemicals (weak bases with a pKa~8-10) into acidic cell compartments (low retro-diffusion under a protonated form at low pH=ion trapping). The proton pump vacuolar (V)-ATPase is the driving force of this pseudotransport that concerns acidic organelles (mainly late endosomes and lysosomes). The latter rapidly become swollen (osmotic vacuolization) and macroautophagic. Cation concentration in cells is not proved to involve membrane transporters, but is prevented or reversed by inhibitors of V-ATPase, such as bafilomycin A1. Lipophilicity is a major determinant of the apparent affinity of this pseudotransport because simple diffusion of the uncharged form supports it. Quinacrine is a formerly used antiparasitic drug that is intensely fluorescent, lipophilic, and a tertiary amine. The drug, at micromolar concentrations, is proposed as a superior probe for assessing cation trapping by cellular acidic compartments, being readily quantified using fluorometry in cell extracts and analyzed using microscopy and cytofluorometry (fluorescence settings for fluorescein being applicable). Further, cells respond to micromolar levels of quinacrine by autophagic accumulation (e.g., accumulation of the activated macroautophagic effector LC3 II, immunoblots), an objective and universal response to sequestered amines.
authors.affiliation: Centre de recherche en rhumatologie et immunologie, Centre Hospitalier Universitaire de Québec, Québec, Canada. Electronic address: francois.marceau@crchul.ulaval.ca.
authors.forename: François
authors.initials: F
authors.lastname: Marceau
authors.affiliation: Centre de recherche en rhumatologie et immunologie, Centre Hospitalier Universitaire de Québec, Québec, Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Roy
authors.affiliation: Centre de recherche en rhumatologie et immunologie, Centre Hospitalier Universitaire de Québec, Québec, Canada.
authors.forename: Johanne
authors.initials: J
authors.lastname: Bouthillier
mesh_terms: D001343:Autophagy / Q000235:genetics; D002412:Cations; D002448:Cell Adhesion; D002478:Cells, Cultured; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D007700:Kinetics; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011796:Quinacrine / Q000378:metabolism* / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002412:Cations; D004791:Enzyme Inhibitors; C477012:MAP1LC3A protein, human; D018942:Macrolides; D008869:Microtubule-Associated Proteins; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases; D011796:Quinacrine
keywords: Autophagy; Cationic drugs; Ion trapping; Phospholipidosis; Quinacrine; Vacuolar ATPase