title: Azithromycin, a lysosomotropic antibiotic, has distinct effects on fluid-phase and receptor-mediated endocytosis, but does not impair phagocytosis in J774 macrophages.
abstract: Pretreatment of J774 mouse macrophages by the dicationic macrolide antibiotic, azithromycin (AZ), selectively inhibited fluid-phase endocytosis of horseradish peroxidase and lucifer yellow, but not phagocytosis of latex beads. AZ delayed sequestration of receptor-bound transferrin and peroxidase-anti-peroxidase immune complexes into cell-surface endocytic pits and vesicles, but did not slow down the subsequent rate of receptor-mediated endocytosis. AZ down-regulated cell surface transferrin receptors, but not Fc gamma receptors, by causing a major delay in the accessibility of internalized transferrin receptors to the recycling route, without slowing down subsequent efflux, resulting in redistribution of the surface pool to an intracellular pool. Acidotropic accumulation of AZ was associated with an extensive vacuolation of late endosomes/lysosomes, and these compartments became inaccessible to horseradish peroxidase and immune complexes, but not to latex beads. The inhibitory profile of AZ cannot be solely accounted for by vacuolation and interference with acidification. AZ may help in dissecting various steps of the endocytic apparatus such as lateral mobility of receptors at the plasma membrane, formation of clathrin-independent endocytic vesicles, orientation of transferrin receptors into the recycling route, and fusogenicity with lysosomes.
authors.affiliation: Unité de Pharmacologie Cellulaire et Moléculaire, Université Catholique de Louvain, UCL 7370 Avenue E. Mounier 73, Brussels, Belgium.
authors.forename: Donatienne
authors.initials: D
authors.lastname: Tyteca
authors.forename: Patrick
authors.initials: P
authors.lastname: Van Der Smissen
authors.forename: Marcel
authors.initials: M
authors.lastname: Mettlen
authors.forename: Françoise
authors.initials: F
authors.lastname: Van Bambeke
authors.forename: Paul M
authors.initials: PM
authors.lastname: Tulkens
authors.forename: Marie Paule
authors.initials: MP
authors.lastname: Mingeot-Leclercq
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Courtoy
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D002451:Cell Compartmentation; D002460:Cell Line; D004705:Endocytosis / Q000187:drug effects*; D011992:Endosomes / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D008863:Microspheres; D010587:Phagocytosis / Q000187:drug effects*; D011961:Receptors, Fc / Q000037:antagonists & inhibitors / Q000378:metabolism; D017452:Receptors, IgG; D011990:Receptors, Transferrin / Q000037:antagonists & inhibitors / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; C445323:FCGR2A protein, human; C499173:FCGR2B protein, human; C499172:Fcgr2b protein, mouse; D011961:Receptors, Fc; D017452:Receptors, IgG; D011990:Receptors, Transferrin; D014168:Transferrin; D017963:Azithromycin; D006735:Horseradish Peroxidase