title: Characterization and intracellular trafficking pattern of vacuoles containing Chlamydia pneumoniae in human epithelial cells.
abstract: Chlamydiae are obligate intracellular pathogens that reside within a membrane-bound vacuole throughout their developmental cycle. In this study, the intraphagosomal pH of Chlamydia pneumoniae (Cpn) was qualitatively assessed, and the intracellular fate of the pathogen-containing vacuole and its interaction with endocytic organelles in human epithelial cells were analysed using conventional immunofluorescence and confocal microscopy. The pH-sensitive probes acridine orange (AO), LysoTracker (LyT) and DAMP did not accumulate in the bacterial inclusion. In addition, exposure of cells to bafilomycin A1(BafA1), a potent acidification inhibitor, did not inhibit or delay chlamydial growth. The chlamydial compartment was not accessible to the fluid-phase tracer Texas Red (TR)-dextran and did not exhibit any level of staining for the late endosomal marker cation-independent mannose-6-phosphate receptor (Ci-M6PR) or for the lysosomal-associated membrane proteins (LAMP-1 and -2) and CD63. In addition, transferrin receptor (TfR)-enriched vesicles were observed close to Cpn vacuoles, potentially indicating a specific translocation of these organelles through the cytoplasm to the vicinity of the vacuole. We conclude that Cpn, like other chlamydial spp., circumvents the host endocytic pathway and inhabits a non-acidic vacuole, which is dissociated from late endosomes and lysosomes, but selectively accumulates early endosomes.
authors.affiliation: Max-Planck-Institut für Infektionsbiologie, Abteilung Molekulare Biologie, Berlin, Germany.
authors.forename: H M
authors.initials: HM
authors.lastname: Al-Younes
authors.forename: T
authors.initials: T
authors.lastname: Rudel
authors.forename: T F
authors.initials: TF
authors.lastname: Meyer
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002460:Cell Line; D016993:Chlamydophila pneumoniae / Q000254:growth & development / Q000472:pathogenicity*; D002701:Chloramphenicol / Q000494:pharmacology; D003911:Dextrans / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism / Q000382:microbiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology*; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D002479:Inclusion Bodies / Q000187:drug effects / Q000382:microbiology; D008247:Lysosomes / Q000378:metabolism; D018942:Macrolides; D008561:Membrane Fusion / Q000187:drug effects; D018613:Microscopy, Confocal; D010588:Phagosomes / Q000378:metabolism / Q000382:microbiology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011990:Receptors, Transferrin / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D003911:Dextrans; D004791:Enzyme Inhibitors; D018942:Macrolides; D011500:Protein Synthesis Inhibitors; D011990:Receptors, Transferrin; D002701:Chloramphenicol; C040929:bafilomycin A1