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Infect Immun. 2018 Apr 23;86(5). pii: e00608-17. doi: 10.1128/IAI.00608-17. Print 2018 May.

Coxiella burnetii Subverts p62/Sequestosome 1 and Activates Nrf2 Signaling in Human Macrophages.

Author information

1
Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
2
Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
3
Arkansas Children's Hospital Research Institute, Little Rock, Arkansas, USA.
4
Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA dvoth@uams.edu.
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Contributed equally

Abstract

Coxiella burnetii is the causative agent of human Q fever, a debilitating flu-like illness that can progress to chronic disease presenting as endocarditis. Following inhalation, C. burnetii is phagocytosed by alveolar macrophages and generates a lysosome-like replication compartment termed the parasitophorous vacuole (PV). A type IV secretion system (T4SS) is required for PV generation and is one of the pathogen's few known virulence factors. We previously showed that C. burnetii actively recruits autophagosomes to the PV using the T4SS but does not alter macroautophagy. In the current study, we confirmed that the cargo receptor p62/sequestosome 1 (SQSTM-1) localizes near the PV in primary human alveolar macrophages infected with virulent C. burnetii p62 and LC3 typically interact to select cargo for autophagy-mediated degradation, resulting in p62 degradation and LC3 recycling. However, in C. burnetii-infected macrophages, p62 was not degraded when cells were starved, suggesting that the pathogen stabilizes the protein. In addition, phosphorylated p62 levels increased, indicative of activation, during infection. Small interfering RNA experiments indicated that p62 is not absolutely required for intracellular growth, suggesting that the protein serves a signaling role during infection. Indeed, the Nrf2-Keap1 cytoprotective pathway was activated during infection, as evidenced by sustained maintenance of Nrf2 levels and translocation of the protein to the nucleus in C. burnetii-infected cells. Collectively, our studies identify a new p62-regulated host signaling pathway exploited by C. burnetii during intramacrophage growth.

KEYWORDS:

Coxiella burnetii; Nrf2; autophagy; intracellular pathogen; p62

PMID:
29483292
PMCID:
PMC5913852
DOI:
10.1128/IAI.00608-17
[Indexed for MEDLINE]
Free PMC Article

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