Journal article
Cytosolic clearance of replication-deficient mutants reveals Francisella tularensis interactions with the autophagic pathway
Autophagy, Vol.8(9), pp.1342-1356
09/01/2012
Handle:
https://hdl.handle.net/2376/104741
PMCID: PMC3442881
PMID: 22863802
Abstract
Cytosolic bacterial pathogens must evade intracellular innate immune recognition and clearance systems such as autophagy to ensure their survival and proliferation. The intracellular cycle of the bacterium
Francisella tularensis
is characterized by rapid phagosomal escape followed by extensive proliferation in the macrophage cytoplasm. Cytosolic replication, but not phagosomal escape, requires the locus FTT0369c, which encodes the
dipA
gene (
d
eficient in
i
ntracellular
r
eplication
A
). Here, we show that a replication-deficient, ∆
dipA
mutant of the prototypical SchuS4 strain is eventually captured from the cytosol of murine and human macrophages into double-membrane vacuoles displaying the late endosomal marker, LAMP1, and the autophagy-associated protein, LC3, coinciding with a reduction in viable intracellular bacteria. Capture of SchuS4Δ
dipA
was not
dipA-
specific as other replication-deficient bacteria, such as chloramphenicol-treated SchuS4 and a purine auxotroph mutant SchuS4Δ
purMCD
, were similarly targeted to autophagic vacuoles. Vacuoles containing replication-deficient bacteria were labeled with ubiquitin and the autophagy receptors SQSTM1/p62 and NBR1, and their formation was decreased in macrophages from either ATG5-, LC3B- or SQSTM1-deficient mice, indicating recognition by the ubiquitin-SQSTM1-LC3 pathway. While a fraction of both the wild-type and the replication-impaired strains were ubiquitinated and recruited SQSTM1, only the replication-defective strains progressed to autophagic capture, suggesting that wild-type Francisella interferes with the autophagic cascade. Survival of replication-deficient strains was not restored in autophagy-deficient macrophages, as these bacteria died in the cytosol prior to autophagic capture. Collectively, our results demonstrate that replication-impaired strains of Francisella are cleared by autophagy, while replication-competent bacteria seem to interfere with autophagic recognition, therefore ensuring survival and proliferation.
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Details
- Title
- Cytosolic clearance of replication-deficient mutants reveals Francisella tularensis interactions with the autophagic pathway
- Creators
- Audrey Chong - Tularemia Pathogenesis Section; Laboratory of Intracellular Parasites; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Hamilton, MT USATara D Wehrly - Tularemia Pathogenesis Section; Laboratory of Intracellular Parasites; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Hamilton, MT USARobert Child - Tularemia Pathogenesis Section; Laboratory of Intracellular Parasites; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Hamilton, MT USABryan Hansen - Electron Microscopy Unit; Research Technologies Branch; Rocky Mountain Laboratories; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Hamilton, MT USASeungmin Hwang - Department of Pathology and Immunology; University School of Medicine; St. Louis, MO USAHerbert W Virgin - Department of Pathology and Immunology; University School of Medicine; St. Louis, MO USAJean Celli - Tularemia Pathogenesis Section; Laboratory of Intracellular Parasites; National Institute of Allergy and Infectious Diseases; National Institutes of Health; Hamilton, MT USA
- Publication Details
- Autophagy, Vol.8(9), pp.1342-1356
- Academic Unit
- Paul G. Allen School for Global Animal Health
- Publisher
- Landes Bioscience
- Identifiers
- 99900546947801842
- Language
- English
- Resource Type
- Journal article