title: Internalization, phagolysosomal biogenesis and killing of mycobacteria in enucleated epithelial cells.
abstract: Bacterial and parasitic intracellular pathogens or their secreted products have been shown to induce host cell transcriptional responses, which may benefit the host, favour the microorganism or be unrelated to the infection. In most instances, however, it is not known if the host cell nucleus is proximately required for the development of an intracellular infection. This information can be obtained by the infection of artificially enucleated host cells (cytoplasts). This model, although rather extensively used in studies of viral infection, has only been applied to few bacterial pathogens, which do not include Mycobacterium spp. Here, we investigate the internalization, phagosome biogenesis and survival of M. smegmatis in enucleated type II alveolar epithelial cells. Cytoplasts were infected with M. smegmatis, but the percentage of infection was significantly lower than that of nucleated cells. Scanning electron microscopy indicated that in both cells and cytoplasts, bacteria were internalized by a phagocytosis-like mechanism. Interestingly, phagosome fusion with lysosomes and mycobacterial killing were both more efficient in enucleated than in nucleated cells, a finding that may be correlated with the increased number of autophagic vesicles developed in cytoplasts. We provide evidence that although quantitative changes were observed, the full development of the infection, as well as mycobacterial killing did not require the presence of the host cell nucleus.
authors.affiliation: Department of Vaccinology and Applied Microbiology, Research Group Phagosome Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
authors.forename: Cristiane
authors.initials: C
authors.lastname: de Souza Carvalho
authors.forename: Bahram
authors.initials: B
authors.lastname: Kasmapour
authors.forename: Achim
authors.initials: A
authors.lastname: Gronow
authors.forename: Manfred
authors.initials: M
authors.lastname: Rohde
authors.forename: Michel
authors.initials: M
authors.lastname: Rabinovitch
authors.forename: Maximiliano Gabriel
authors.initials: MG
authors.lastname: Gutierrez
mesh_terms: D002460:Cell Line; D002467:Cell Nucleus / Q000502:physiology; D004705:Endocytosis; D004847:Epithelial Cells / Q000382:microbiology*; D006801:Humans; D008247:Lysosomes / Q000382:microbiology*; D050296:Microbial Viability; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D020102:Mycobacterium smegmatis / Q000472:pathogenicity*; D010588:Phagosomes / Q000382:microbiology*