Involvement of the autophagy pathway in trafficking of Mycobacterium tuberculosis bacilli through cultured human type II epithelial cells

Kari L. Fine, Maureen G. Metcalfe, Elizabeth White, Mumtaz Virji, Russell K. Karls, Frederick D. Quinn*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

27 Citations (Scopus)

Abstract

Interactions between Mycobacterium tuberculosis bacilli and alveolar macrophages have been extensively characterized, while similar analyses in epithelial cells have not been performed. In this study, we microscopically examined endosomal trafficking of M.?tuberculosis strain Erdman in A549 cells, a human type II pneumocyte cell line. Immuno-electron microscopic (IEM) analyses indicate that M.?tuberculosis bacilli are internalized to a compartment labelled first with Rab5 and then with Rab7 small GTPase proteins. This suggests that, unlike macrophages, M.?tuberculosis bacilli traffic to late endosomes in epithelial cells. However, fusion of lysosomes with the bacteria-containing compartment appears to be inhibited, as illustrated by IEM studies employing LAMP-2 and cathepsin-L antibodies. Examination by transmission electron microscopy and IEM revealed M.?tuberculosis-containing compartments surrounded by double membranes and labelled with antibodies against the autophagy marker Lc3, providing evidence for involvement and intersection of the autophagy and endosomal pathways. Interestingly, inhibition of the autophagy pathway using 3-methyladenine improved host cell viability and decreased numbers of viable intracellular bacteria recovered after 72?h post infection. Collectively, these datasuggest that trafficking patterns for M.?tuberculosis bacilli in alveolar epithelial cells differ from macrophages, and that autophagy is involved this process.

Original languageEnglish
Pages (from-to)1402-1414
Number of pages13
JournalCellular Microbiology
Volume14
Issue number9
Early online date25 May 2012
DOIs
Publication statusPublished - Sep 2012

Keywords

  • PHAGOSOME-LYSOSOME FUSION
  • HUMAN MACROPHAGES
  • IN-VITRO
  • INTRACELLULAR PATHOGENS
  • LEGIONELLA-PNEUMOPHILA
  • INFECTION
  • MATURATION
  • VIRULENCE
  • INHIBITION
  • SURVIVAL
  • Mycobacterium tuberculosis
  • autophagy pathway
  • host pathogen
  • interactions

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