1
|
Speir M, Vogrin A, Seidi A, Abraham G, Hunot S, Han Q, Dorn GW, Masters SL, Flavell RA, Vince JE, Naderer T. Legionella pneumophila Strain 130b Evades Macrophage Cell Death Independent of the Effector SidF in the Absence of Flagellin. Front Cell Infect Microbiol 2017; 7:35. [PMID: 28261564 PMCID: PMC5311068 DOI: 10.3389/fcimb.2017.00035] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 01/30/2017] [Indexed: 01/08/2023] Open
Abstract
The human pathogen Legionella pneumophila must evade host cell death signaling to enable replication in lung macrophages and to cause disease. After bacterial growth, however, L. pneumophila is thought to induce apoptosis during egress from macrophages. The bacterial effector protein, SidF, has been shown to control host cell survival and death by inhibiting pro-apoptotic BNIP3 and BCL-RAMBO signaling. Using live-cell imaging to follow the L. pneumophila-macrophage interaction, we now demonstrate that L. pneumophila evades host cell apoptosis independent of SidF. In the absence of SidF, L. pneumophila was able to replicate, cause loss of mitochondria membrane potential, kill macrophages, and establish infections in lungs of mice. Consistent with this, deletion of BNIP3 and BCL-RAMBO did not affect intracellular L. pneumophila replication, macrophage death rates, and in vivo bacterial virulence. Abrogating mitochondrial cell death by genetic deletion of the effectors of intrinsic apoptosis, BAX, and BAK, or the regulator of mitochondrial permeability transition pore formation, cyclophilin-D, did not affect bacterial growth or the initial killing of macrophages. Loss of BAX and BAK only marginally limited the ability of L. pneumophila to efficiently kill all macrophages over extended periods. L. pneumophila induced killing of macrophages was delayed in the absence of capsase-11 mediated pyroptosis. Together, our data demonstrate that L. pneumophila evades host cell death responses independently of SidF during replication and can induce pyroptosis to kill macrophages in a timely manner.
Collapse
Affiliation(s)
- Mary Speir
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Adam Vogrin
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Azadeh Seidi
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Gilu Abraham
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| | - Stéphane Hunot
- Department of Immunobiology, Howard Hughes Medical Institute, Yale University School of MedicineNew Haven, CT, USA
- Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Institut du Cerveau et la Moelle - Hôpital Pitié-Salpêtrière, Boulevard de l'hôpital, Sorbonne Universités, UPMC Univ Paris 06Paris, France
| | - Qingqing Han
- Department of Immunobiology, Howard Hughes Medical Institute, Yale University School of MedicineNew Haven, CT, USA
| | - Gerald W. Dorn
- Department of Medicine, Center for Pharmacogenomics, Washington University School of MedicineSt. Louis, MO, USA
| | - Seth L. Masters
- Walter and Eliza Hall Institute of Medical ResearchParkville, VIC, Australia
- Department of Medical Biology, University of MelbourneParkville, VIC, Australia
| | - Richard A. Flavell
- Department of Immunobiology, Howard Hughes Medical Institute, Yale University School of MedicineNew Haven, CT, USA
| | - James E. Vince
- Walter and Eliza Hall Institute of Medical ResearchParkville, VIC, Australia
- Department of Medical Biology, University of MelbourneParkville, VIC, Australia
| | - Thomas Naderer
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash UniversityClayton, VIC, Australia
| |
Collapse
|