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Plaza N, Pérez-Reytor D, Corsini G, García K, Urrutia ÍM. Contribution of the Type III Secretion System (T3SS2) of Vibrio parahaemolyticus in Mitochondrial Stress in Human Intestinal Cells. Microorganisms 2024; 12:813. [PMID: 38674757 PMCID: PMC11051933 DOI: 10.3390/microorganisms12040813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/08/2024] [Accepted: 04/15/2024] [Indexed: 04/28/2024] Open
Abstract
Vibrio parahaemolyticus is an important human pathogen that is currently the leading cause of shellfish-borne gastroenteritis in the world. Particularly, the pandemic strain has the capacity to induce cytotoxicity and enterotoxicity through its Type 3 Secretion System (T3SS2) that leads to massive cell death. However, the specific mechanism by which the T3SS2 induces cell death remains unclear and its contribution to mitochondrial stress is not fully understood. In this work, we evaluated the contribution of the T3SS2 of V. parahaemolyticus in generating mitochondrial stress during infection in human intestinal HT-29 cells. To evaluate the contribution of the T3SS2 of V. parahaemolyticus in mitochondrial stress, infection assays were carried out to evaluate mitochondrial transition pore opening, mitochondrial fragmentation, ATP quantification, and cell viability during infection. Our results showed that the Δvscn1 (T3SS2+) mutant strain contributes to generating the sustained opening of the mitochondrial transition pore. Furthermore, it generates perturbations in the ATP production in infected cells, leading to a significant decrease in cell viability and loss of membrane integrity. Our results suggest that the T3SS2 from V. parahaemolyticus plays a role in generating mitochondrial stress that leads to cell death in human intestinal HT-29 cells. It is important to highlight that this study represents the first report indicating the possible role of the V. parahaemolyticus T3SS2 and its effector proteins involvement in generating mitochondrial stress, its impact on the mitochondrial pore, and its effect on ATP production in human cells.
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Affiliation(s)
| | | | | | | | - Ítalo M. Urrutia
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago 8320000, Chile; (N.P.); (D.P.-R.); (G.C.); (K.G.)
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2
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Abstract
Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that can cause severe invasive infections upon ingestion with contaminated food. Clinically, listerial disease, or listeriosis, most often presents as bacteremia, meningitis or meningoencephalitis, and pregnancy-associated infections manifesting as miscarriage or neonatal sepsis. Invasive listeriosis is life-threatening and a main cause of foodborne illness leading to hospital admissions in Western countries. Sources of contamination can be identified through international surveillance systems for foodborne bacteria and strains' genetic data sharing. Large-scale whole genome studies have increased our knowledge on the diversity and evolution of L. monocytogenes, while recent pathophysiological investigations have improved our mechanistic understanding of listeriosis. In this article, we present an overview of human listeriosis with particular focus on relevant features of the causative bacterium, epidemiology, risk groups, pathogenesis, clinical manifestations, and treatment and prevention.
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Affiliation(s)
- Merel M Koopmans
- Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Matthijs C Brouwer
- Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - José A Vázquez-Boland
- Infection Medicine, Edinburgh Medical School (Biomedical Sciences), University of Edinburgh, Edinburgh, United Kingdom
| | - Diederik van de Beek
- Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam, the Netherlands
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3
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Role of mitochondria in regulating immune response during bacterial infection. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2023; 374:159-200. [PMID: 36858655 DOI: 10.1016/bs.ircmb.2022.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mitochondria are dynamic organelles of eukaryotes involved in energy production and fatty acid oxidation. Besides maintaining ATP production, calcium signaling, cellular apoptosis, and fatty acid synthesis, mitochondria are also known as the central hub of the immune system as it regulates the innate immune pathway during infection. Mitochondria mediated immune functions mainly involve regulation of reactive oxygen species production, inflammasome activation, cytokine secretion, and apoptosis of infected cells. Recent findings indicate that cellular mitochondria undergo constant biogenesis, fission, fusion and degradation, and these dynamics regulate cellular immuno-metabolism. Several intracellular pathogens target and modulate these normal functions of mitochondria to facilitate their own survival and growth. De-regulation of mitochondrial functions and dynamics favors bacterial infection and pathogens are able to protect themselves from mitochondria mediated immune responses. Here, we will discuss how mitochondria mediated anti-bacterial immune pathways help the host to evade pathogenic insult. In addition, examples of bacterial pathogens modulating mitochondrial metabolism and dynamics will also be elaborated. Study of these interactions between the mitochondria and bacterial pathogens during infection will lead to a better understanding of the mitochondrial metabolism pathways and dynamics important for the establishment of bacterial diseases. In conclusion, detailed studies on how mitochondria regulate the immune response during bacterial infection can open up new avenues to develop mitochondria centric anti-bacterial therapeutics.
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4
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Smith KP, Lee W, Tonelli M, Lee Y, Light SH, Cornilescu G, Chakravarthy S. Solution structure and dynamics of the mitochondrial-targeted GTPase-activating protein (GAP) VopE by an integrated NMR/SAXS approach. Protein Sci 2022; 31:e4282. [PMID: 35137487 PMCID: PMC9047041 DOI: 10.1002/pro.4282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 01/17/2022] [Accepted: 01/27/2022] [Indexed: 11/11/2022]
Abstract
The bacterial pathogen Vibrio cholerae use a type III secretion system to inject effector proteins into a host cell. Recently, a putative Toxic GTPase Activating Protein (ToxGAP) called VopE was identified as a T3SS substrate and virulence factor that affected host mitochondrial dynamics and immune response. However, biophysical and structural characterization has been absent. Here, we describe solution NMR structure of the putative GAP domain (73-204) of VopE. Using SEC-SAXS and RDC data, we restrained the MD process to efficiently determine the overall fold and improve the quality of the output calculated structures. Comparing the structure of VopE with other ToxGAP's revealed a similar overall fold with several features unique to VopE. Specifically, the "Bulge 1", α1 helix, and noteworthy "backside linker" elements on the N-terminus are dissimilar to the other ToxGAP's. By using NMR relaxation dispersion experiments, we demonstrate that these regions undergo motions on a >6 s-1 timescale. Based on the disposition of these mobile regions relative to the putative catalytic arginine residue, we hypothesize the protein may undergo structural changes to bind cognate GTPases. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Kyle P Smith
- Current, Xilio Therapeutics, Waltham, MA, USA.,Former, Department of Cell & Developmental Biology, Northwestern University Chicago, IL, USA
| | - Woonghee Lee
- Department of Chemistry, University of Colorado-Denver, Denver, CO, USA
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Yeongjoon Lee
- Department of Chemistry, University of Colorado-Denver, Denver, CO, USA
| | - Samuel H Light
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Gabriel Cornilescu
- Advanced Technology Research Facility, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., National Cancer Institute, National Institutes of Health, Frederick, MD, USA
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5
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Unrath N, McCabe E, Macori G, Fanning S. Application of Whole Genome Sequencing to Aid in Deciphering the Persistence Potential of Listeria monocytogenes in Food Production Environments. Microorganisms 2021; 9:1856. [PMID: 34576750 PMCID: PMC8464834 DOI: 10.3390/microorganisms9091856] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/23/2021] [Accepted: 08/25/2021] [Indexed: 01/26/2023] Open
Abstract
Listeria monocytogenes is the etiological agent of listeriosis, a foodborne illness associated with high hospitalizations and mortality rates. This bacterium can persist in food associated environments for years with isolates being increasingly linked to outbreaks. This review presents a discussion of genomes of Listeria monocytogenes which are commonly regarded as persisters within food production environments, as well as genes which are involved in mechanisms aiding this phenotype. Although criteria for the detection of persistence remain undefined, the advent of whole genome sequencing (WGS) and the development of bioinformatic tools have revolutionized the ability to find closely related strains. These advancements will facilitate the identification of mechanisms responsible for persistence among indistinguishable genomes. In turn, this will lead to improved assessments of the importance of biofilm formation, adaptation to stressful conditions and tolerance to sterilizers in relation to the persistence of this bacterium, all of which have been previously associated with this phenotype. Despite much research being published around the topic of persistence, more insights are required to further elucidate the nature of true persistence and its implications for public health.
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Affiliation(s)
- Natalia Unrath
- UCD-Centre for Food Safety, School of Public Health, Physiotherapy & Sports Science, University College Dublin, D04 N2E5 Dublin, Ireland; (N.U.); (E.M.); (G.M.)
| | - Evonne McCabe
- UCD-Centre for Food Safety, School of Public Health, Physiotherapy & Sports Science, University College Dublin, D04 N2E5 Dublin, Ireland; (N.U.); (E.M.); (G.M.)
- Department of Microbiology, St. Vincent’s University Hospital, D04 T6F4 Dublin, Ireland
| | - Guerrino Macori
- UCD-Centre for Food Safety, School of Public Health, Physiotherapy & Sports Science, University College Dublin, D04 N2E5 Dublin, Ireland; (N.U.); (E.M.); (G.M.)
| | - Séamus Fanning
- UCD-Centre for Food Safety, School of Public Health, Physiotherapy & Sports Science, University College Dublin, D04 N2E5 Dublin, Ireland; (N.U.); (E.M.); (G.M.)
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6
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Khan S, Raj D, Jaiswal K, Lahiri A. Modulation of host mitochondrial dynamics during bacterial infection. Mitochondrion 2020; 53:140-149. [PMID: 32470613 DOI: 10.1016/j.mito.2020.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/15/2020] [Accepted: 05/22/2020] [Indexed: 12/15/2022]
Abstract
Mitochondria is a dynamic organelle of the cell that can regulate and maintain cellular ATP level, ROS production, calcium signaling and immune response. In order to retain their shape and distribution, mitochondria go through coordinated cycles of fission and fusion. Further, dysfunctional mitochondria are selectively eliminated from the cell via mitophagy to synchronize mitochondrial quality control and cellular homeostasis. In addition, mitochondria when in close proximity with the endoplasmic reticulum can alter the signaling pathways and some recent findings also reveal a direct correlation between the mitochondrial localization in the cell to the immune response elicited against the invading pathogen. These modulations in the mitochondrial network are collectively termed as 'mitochondrial dynamics'. Diverse bacteria, virus and parasitic pathogens upon infecting a cell can alter the host mitochondrial dynamics in favor of their multiplication and this in turn can be a major determinant of the disease outcome. Pharmacological perturbations in these pathways thus could lead to generation of additional therapeutic opportunities. This review will focus on the pathogenic modulation of the host mitochondrial dynamics, specifically during the bacterial infections and describes how dysregulated mitochondrial dynamics facilitates the pathogen's ability to establish efficient infection.
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Affiliation(s)
- Shaziya Khan
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Desh Raj
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India
| | - Kritika Jaiswal
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow 226031, India
| | - Amit Lahiri
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow 226031, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi 110001, India.
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Soultawi C, Fortier Y, Soundaramourty C, Estaquier J, Laforge M. Mitochondrial Bioenergetics and Dynamics During Infection. EXPERIENTIA. SUPPLEMENTUM 2019; 109:221-233. [PMID: 30535601 DOI: 10.1007/978-3-319-74932-7_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Microbes have developed a series of strategies to overcome the defense mechanisms of the infected host. During pathogen-host coevolution, they develop strategy to manipulate cellular machinery particularly in subverting mitochondrion function. Mitochondria are highly dynamic organelles that constantly remodel their structure. In particular, shaping and cellular distribution of the mitochondrial network is maintained in large part by the conserved activities of mitochondrial division, fusion, motility, and tethering. Mitochondria have been long recognized for their role in providing energy production, calcium metabolism, and apoptosis. More recently, mitochondria have been also shown to serve as a platform for innate immune response. In this context, mitochondrial dynamics and shaping is not only essential to maintain cristae structure and bioenergetic to fuel cellular demands but contribute to regulate cellular function such as innate immune response and mitochondrial permeabilization. Due to their key role in cell survival, mitochondria represent attractive targets for pathogens. Therefore, microbes by manipulating mitochondrial dynamics may escape to host cellular control. Herein, we describe how mitochondrial bioenergetics, dynamics, and shaping are impacted during microbe infections and how this interplay benefits to pathogens contributing to the diseases.
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Affiliation(s)
- Cynthia Soultawi
- CNRS FR3636, Faculty of Medecine des Saint-Pères, Paris Descartes University, Paris, France
| | - Yasmina Fortier
- CNRS FR3636, Faculty of Medecine des Saint-Pères, Paris Descartes University, Paris, France
| | | | - Jérôme Estaquier
- CNRS FR3636, Faculty of Medecine des Saint-Pères, Paris Descartes University, Paris, France. .,Centre Hospitalier Universitaire (CHU) de Québec Research Center, Faculty of Medicine, Laval University, Québec, QC, Canada.
| | - Mireille Laforge
- CNRS FR3636, Faculty of Medecine des Saint-Pères, Paris Descartes University, Paris, France.
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8
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Abstract
The Gram-positive pathogen Listeria monocytogenes is able to promote its entry into a diverse range of mammalian host cells by triggering plasma membrane remodeling, leading to bacterial engulfment. Upon cell invasion, L. monocytogenes disrupts its internalization vacuole and translocates to the cytoplasm, where bacterial replication takes place. Subsequently, L. monocytogenes uses an actin-based motility system that allows bacterial cytoplasmic movement and cell-to-cell spread. L. monocytogenes therefore subverts host cell receptors, organelles and the cytoskeleton at different infection steps, manipulating diverse cellular functions that include ion transport, membrane trafficking, post-translational modifications, phosphoinositide production, innate immune responses as well as gene expression and DNA stability.
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9
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Kühbacher A, Novy K, Quereda JJ, Sachse M, Moya-Nilges M, Wollscheid B, Cossart P, Pizarro-Cerdá J. Listeriolysin O-dependent host surfaceome remodeling modulates Listeria monocytogenes invasion. Pathog Dis 2018; 76:5184460. [PMID: 30445439 PMCID: PMC6282100 DOI: 10.1093/femspd/fty082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/13/2018] [Indexed: 02/06/2023] Open
Abstract
Listeria monocytogenes is a pathogenic bacterium that invades epithelial cells by activating host signaling cascades, which promote bacterial engulfment within a phagosome. The pore-forming toxin listeriolysin O (LLO), which is required for bacteria phagosomal escape, has also been associated with the activation of several signaling pathways when secreted by extracellular bacteria, including Ca2+ influx and promotion of L. monocytogenes entry. Quantitative host surfaceome analysis revealed significant quantitative remodeling of a defined set of cell surface glycoproteins upon LLO treatment, including a subset previously identified to play a role in the L. monocytogenes infection process. Our data further shows that the lysosomal-associated membrane proteins LAMP-1 and LAMP-2 are translocated to the cellular surface and those LLO-induced Ca2+ fluxes are required to trigger the surface relocalization of LAMP-1. Finally, we identify late endosomes/lysosomes as the major donor compartments of LAMP-1 upon LLO treatment and by perturbing their function, we suggest that these organelles participate in L. monocytogenes invasion.
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Affiliation(s)
- Andreas Kühbacher
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France.,INSERM, U604, Paris F-75015, France.,INRA, USC2020, Paris F-75015, France
| | - Karel Novy
- Institute of Molecular Systems Biology and Department of Health Sciences and Technology, ETH Zürich, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Juan J Quereda
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France.,INSERM, U604, Paris F-75015, France.,INRA, USC2020, Paris F-75015, France
| | - Martin Sachse
- Institut Pasteur, UTechS Ultrastructural BioImaging, Paris F-75015, France
| | - Maryse Moya-Nilges
- Institut Pasteur, UTechS Ultrastructural BioImaging, Paris F-75015, France
| | - Bernd Wollscheid
- Institute of Molecular Systems Biology and Department of Health Sciences and Technology, ETH Zürich, Otto-Stern-Weg 3, 8093 Zürich, Switzerland
| | - Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France.,INSERM, U604, Paris F-75015, France.,INRA, USC2020, Paris F-75015, France
| | - Javier Pizarro-Cerdá
- Institut Pasteur, Unité des Interactions Bactéries Cellules, Paris F-75015, France.,INSERM, U604, Paris F-75015, France.,INRA, USC2020, Paris F-75015, France.,Institut Pasteur, Unité de Recherche Yersinia, Paris F-75015, France
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10
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Listeria monocytogenes and Shigella flexneri Activate the NLRP1B Inflammasome. Infect Immun 2017; 85:IAI.00338-17. [PMID: 28808162 DOI: 10.1128/iai.00338-17] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/10/2017] [Indexed: 11/20/2022] Open
Abstract
Activation of the innate immune receptor NLRP1B leads to the formation of an inflammasome, which induces autoproteolytic processing of pro-caspase-1, and ultimately to the release of inflammatory cytokines and to the execution of pyroptosis. One of the signals to which NLRP1B responds is metabolic stress that occurs in cells deprived of glucose or treated with metabolic inhibitors. NLRP1B might therefore sense microbial infection, as intracellular pathogens such as Listeria monocytogenes and Shigella flexneri cause metabolic stress as a result of nutrient scavenging and host cell damage. Here we addressed whether these pathogens activate the NLRP1B inflammasome. We found that Listeria infection activated the NLRP1B inflammasome in a reconstituted fibroblast model. Activation of NLRP1B by Listeria was diminished in an NLRP1B mutant shown previously to be defective at detecting energy stress and was dependent on the expression of listeriolysin O (LLO), a protein required for vacuolar escape. Infections of either Listeria or Shigella activated NLRP1B in the RAW264.7 murine macrophage line, which expresses endogenous NLRP1B. We conclude that NLRP1B senses cellular infection by distinct invasive pathogens.
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11
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Odendall C, Kagan JC. Activation and pathogenic manipulation of the sensors of the innate immune system. Microbes Infect 2017; 19:229-237. [PMID: 28093320 DOI: 10.1016/j.micinf.2017.01.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/06/2017] [Indexed: 12/13/2022]
Abstract
The innate immune system detects the presence of microbes through different families of pattern-recognition receptors (PRRs). PRRs detect pathogens of all origins and trigger signaling events that activate innate and adaptive immunity. These events need to be tightly regulated in order to ensure optimal activation when required, and minimal signaling in the absence of microbial encounters. This regulation is achieved, at least in part, through the precise subcellular positioning of receptors and downstream signaling proteins. Consequently, mislocalization of these proteins inhibits innate immune pathways, and pathogens have evolved to alter host protein localization as a strategy to evade immune detection. This review describes the importance of subcellular localization of various PRR families and their adaptors, and highlights pathogenic immune evasion strategies that operate by altering immune protein localization.
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Affiliation(s)
- Charlotte Odendall
- Department of Infectious Diseases, King's College London, London SE1 9RT, UK
| | - Jonathan C Kagan
- Harvard Medical School and Division of Gastroenterology, Boston Children's Hospital, Boston, MA 02115, USA.
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12
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Phobalysin, a Small β-Pore-Forming Toxin of Photobacterium damselae subsp. damselae. Infect Immun 2015; 83:4335-48. [PMID: 26303391 DOI: 10.1128/iai.00277-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 08/15/2015] [Indexed: 12/16/2022] Open
Abstract
Photobacterium damselae subsp. damselae, an important pathogen of marine animals, may also cause septicemia or hyperaggressive necrotizing fasciitis in humans. We previously showed that hemolysin genes are critical for virulence of this organism in mice and fish. In the present study, we characterized the hlyA gene product, a putative small β-pore-forming toxin, and termed it phobalysin P (PhlyP), for "photobacterial lysin encoded on a plasmid." PhlyP formed stable oligomers and small membrane pores, causing efflux of K(+), with no significant leakage of lactate dehydrogenase but entry of vital dyes. The latter feature distinguished PhlyP from the related Vibrio cholerae cytolysin. Attack by PhlyP provoked a loss of cellular ATP, attenuated translation, and caused profound morphological changes in epithelial cells. In coculture experiments with epithelial cells, Photobacterium damselae subsp. damselae led to rapid hemolysin-dependent membrane permeabilization. Unexpectedly, hemolysins also promoted the association of P. damselae subsp. damselae with epithelial cells. The collective observations of this study suggest that membrane-damaging toxins commonly enhance bacterial adherence.
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13
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Fine-Coulson K, Giguère S, Quinn FD, Reaves BJ. Infection of A549 human type II epithelial cells with Mycobacterium tuberculosis induces changes in mitochondrial morphology, distribution and mass that are dependent on the early secreted antigen, ESAT-6. Microbes Infect 2015; 17:689-97. [PMID: 26092385 DOI: 10.1016/j.micinf.2015.06.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 04/20/2015] [Accepted: 06/08/2015] [Indexed: 11/28/2022]
Abstract
Pulmonary infection by Mycobacterium tuberculosis (Mtb) involves the invasion of alveolar epithelial cells (AECs). We used Mitotracker Red(®) to assess changes in mitochondrial morphology/distribution and mass from 6 to 48 h post infection (hpi) by confocal microscopy and flow cytometry in Mtb-infected A549 type II AECs. During early infection there was no effect on mitochondrial morphology, however, by 48 hpi mitochondria appeared fragmented and concentrated around the nucleus. In flow cytometry experiments, the median fluorescence intensity (MFI) decreased by 44% at 48 hpi; double-labelling using antibodies to the integral membrane protein COXIV revealed that these changes were due to a decrease in mitochondrial mass. These changes did not occur with the apathogenic strain, Mycobacterium bovis BCG. ESAT-6 is a virulence factor present in Mtb Erdman but lacking in M. bovis BCG. We performed similar experiments using Mtb Erdman, an ESAT-6 deletion mutant and its complement. MFI decreased at 48 hpi in the parent and complemented strains versus uninfected controls by 52% and 36% respectively; no decrease was detected in the deletion mutant. These results indicate an involvement of ESAT-6 in the perturbation of mitochondria induced by virulent Mtb in AECs and suggest mitophagy may play a role in the infection process.
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Affiliation(s)
- Kari Fine-Coulson
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Steeve Giguère
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Frederick D Quinn
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
| | - Barbara J Reaves
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
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