1
|
Xander C, Rajagopalan S, Jacobs WR, Braunstein M. The SapM phosphatase can arrest phagosome maturation in an ESX-1 independent manner in Mycobacterium tuberculosis and BCG. Infect Immun 2024; 92:e0021724. [PMID: 38884474 PMCID: PMC11238552 DOI: 10.1128/iai.00217-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 06/18/2024] Open
Abstract
Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that survives and grows in macrophages. A mechanism used by Mtb to achieve intracellular survival is to secrete effector molecules that arrest the normal process of phagosome maturation. Through phagosome maturation arrest (PMA), Mtb remains in an early phagosome and avoids delivery to degradative phagolysosomes. One PMA effector of Mtb is the secreted SapM phosphatase. Because the host target of SapM, phosphatidylinositol-3-phosphate (PI3P), is located on the cytosolic face of the phagosome, SapM needs to not only be released by the mycobacteria but also travel out of the phagosome to carry out its function. To date, the only mechanism known for Mtb molecules to leave the phagosome is phagosome permeabilization by the ESX-1 secretion system. To understand this step of SapM function in PMA, we generated identical in-frame sapM mutants in both the attenuated Mycobacterium bovis bacille Calmette-Guérin (BCG) vaccine strain, which lacks the ESX-1 system, and Mtb. Characterization of these mutants demonstrated that SapM is required for PMA in BCG and Mtb. Further, by establishing a role for SapM in PMA in BCG, and subsequently in a Mtb mutant lacking the ESX-1 system, we demonstrated that the role of SapM does not require ESX-1. We further determined that ESX-2 or ESX-4 is also not required for SapM to function in PMA. These results indicate that SapM is a secreted effector of PMA in both BCG and Mtb, and that it can function independent of the known mechanism for Mtb molecules to leave the phagosome.
Collapse
Affiliation(s)
- Christian Xander
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Saranathan Rajagopalan
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - William R. Jacobs
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Miriam Braunstein
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA
| |
Collapse
|
2
|
Jones BS, Pareek V, Hu DD, Weaver SD, Syska C, Galfano G, Champion MM, Champion PA. N - acetyl-transferases required for iron uptake and aminoglycoside resistance promote virulence lipid production in M. marinum. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.05.602253. [PMID: 39005365 PMCID: PMC11245092 DOI: 10.1101/2024.07.05.602253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Phagosomal lysis is a key aspect of mycobacterial infection of host macrophages. Acetylation is a protein modification mediated enzymatically by N-acetyltransferases (NATs) that impacts bacterial pathogenesis and physiology. To identify NATs required for lytic activity, we leveraged Mycobacterium marinum, a nontubercular pathogen and an established model for M. tuberculosis. M. marinum hemolysis is a proxy for phagolytic activity. We generated M. marinum strains with deletions in conserved NAT genes and screened for hemolytic activity. Several conserved lysine acetyltransferases (KATs) contributed to hemolysis. Hemolysis is mediated by the ESX-1 secretion system and by phthiocerol dimycocerosate (PDIM), a virulence lipid. For several strains, the hemolytic activity was restored by the addition of second copy of the ESX-1 locus. Using thin-layer chromatography (TLC), we found a single NAT required for PDIM and phenolic glycolipid (PGL) production. MbtK is a conserved KAT required for mycobactin siderophore synthesis and virulence. Mycobactin J exogenously complemented PDIM/PGL production in the Δ mbtK strain. The Δ mbtK M. marinum strain was attenuated in macrophage and Galleria mellonella infection models. Constitutive expression of either eis or papA5, which encode a KAT required for aminoglycoside resistance and a PDIM/PGL biosynthetic enzyme, rescued PDIM/PGL production and virulence of the Δ mbtK strain. Eis N-terminally acetylated PapA5 in vitro , supporting a mechanism for restored lipid production. Overall, our study establishes connections between the MbtK and Eis NATs, and between iron uptake and PDIM and PGL synthesis in M. marinum . Our findings underscore the multifunctional nature of mycobacterial NATs and their connection to key virulence pathways. Significance Statement Acetylation is a modification of protein N-termini, lysine residues, antibiotics and lipids. Many of the enzymes that promote acetylation belong to the GNAT family of proteins. M. marinum is a well-established as a model to understand how M. tuberculosis causes tuberculosis. In this study we sought to identify conserved GNAT proteins required for early stages of mycobacterial infection. Using M. marinum, we determined that several GNAT proteins are required for the lytic activity of M. marinum. We uncovered previously unknown connections between acetyl-transferases required for iron uptake and antimicrobial resistance, and the production of the unique mycobacterial lipids, PDIM and PGLOur data support that acetyl-transferases from the GNAT family are interconnected, and have activities beyond those previously reported.
Collapse
|
3
|
Jones BS, Hu DD, Nicholson KR, Cronin RM, Weaver SD, Champion MM, Champion PA. The loss of the PDIM/PGL virulence lipids causes differential secretion of ESX-1 substrates in Mycobacterium marinum. mSphere 2024; 9:e0000524. [PMID: 38661343 PMCID: PMC11237470 DOI: 10.1128/msphere.00005-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 03/21/2024] [Indexed: 04/26/2024] Open
Abstract
The mycobacterial cell envelope is a major virulence determinant in pathogenic mycobacteria. Specific outer lipids play roles in pathogenesis, modulating the immune system and promoting the secretion of virulence factors. ESX-1 (ESAT-6 system-1) is a conserved protein secretion system required for mycobacterial pathogenesis. Previous studies revealed that mycobacterial strains lacking the outer lipid PDIM have impaired ESX-1 function during laboratory growth and infection. The mechanisms underlying changes in ESX-1 function are unknown. We used a proteo-genetic approach to measure phthiocerol dimycocerosate (PDIM)- and phenolic glycolipid (PGL)-dependent protein secretion in M. marinum, a non-tubercular mycobacterial pathogen that causes tuberculosis-like disease in ectothermic animals. Importantly, M. marinum is a well-established model for mycobacterial pathogenesis. Our findings showed that M. marinum strains without PDIM and PGL showed specific, significant reductions in protein secretion compared to the WT and complemented strains. We recently established a hierarchy for the secretion of ESX-1 substrates in four (I-IV) groups. Loss of PDIM differentially impacted secretion of Group III and IV ESX-1 substrates, which are likely the effectors of pathogenesis. Our data suggest that the altered secretion of specific ESX-1 substrates is responsible for the observed ESX-1-related effects in PDIM-deficient strains.IMPORTANCEMycobacterium tuberculosis, the cause of human tuberculosis, killed an estimated 1.3 million people in 2022. Non-tubercular mycobacterial species cause acute and chronic human infections. Understanding how these bacteria cause disease is critical. Lipids in the cell envelope are essential for mycobacteria to interact with the host and promote disease. Strains lacking outer lipids are attenuated for infection, but the reasons are unclear. Our research aims to identify a mechanism for attenuation of mycobacterial strains without the PDIM and PGL outer lipids in M. marinum. These findings will enhance our understanding of the importance of lipids in pathogenesis and how these lipids contribute to other established virulence mechanisms.
Collapse
Affiliation(s)
- Bradley S. Jones
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
| | - Daniel D. Hu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Kathleen R. Nicholson
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Rachel M. Cronin
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Simon D. Weaver
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Matthew M. Champion
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Patricia A. Champion
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, USA
| |
Collapse
|
4
|
Lefrançois LH, Nitschke J, Wu H, Panis G, Prados J, Butler RE, Mendum TA, Hanna N, Stewart GR, Soldati T. Temporal genome-wide fitness analysis of Mycobacterium marinum during infection reveals the genetic requirement for virulence and survival in amoebae and microglial cells. mSystems 2024; 9:e0132623. [PMID: 38270456 PMCID: PMC10878075 DOI: 10.1128/msystems.01326-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Accepted: 12/15/2023] [Indexed: 01/26/2024] Open
Abstract
Tuberculosis remains the most pervasive infectious disease and the recent emergence of drug-resistant strains emphasizes the need for more efficient drug treatments. A key feature of pathogenesis, conserved between the human pathogen Mycobacterium tuberculosis and the model pathogen Mycobacterium marinum, is the metabolic switch to lipid catabolism and altered expression of virulence genes at different stages of infection. This study aims to identify genes involved in sustaining viable intracellular infection. We applied transposon sequencing (Tn-Seq) to M. marinum, an unbiased genome-wide strategy combining saturation insertional mutagenesis and high-throughput sequencing. This approach allowed us to identify the localization and relative abundance of insertions in pools of transposon mutants. Gene essentiality and fitness cost of mutations were quantitatively compared between in vitro growth and different stages of infection in two evolutionary distinct phagocytes, the amoeba Dictyostelium discoideum and the murine BV2 microglial cells. In the M. marinum genome, 57% of TA sites were disrupted and 568 genes (10.2%) were essential, which is comparable to previous Tn-Seq studies on M. tuberculosis and M. bovis. Major pathways involved in the survival of M. marinum during infection of D. discoideum are related to DNA damage repair, lipid and vitamin metabolism, the type VII secretion system (T7SS) ESX-1, and the Mce1 lipid transport system. These pathways, except Mce1 and some glycolytic enzymes, were similarly affected in BV2 cells. These differences suggest subtly distinct nutrient availability or requirement in different host cells despite the known predominant use of lipids in both amoeba and microglial cells.IMPORTANCEThe emergence of biochemically and genetically tractable host model organisms for infection studies holds the promise to accelerate the pace of discoveries related to the evolution of innate immunity and the dissection of conserved mechanisms of cell-autonomous defenses. Here, we have used the genetically and biochemically tractable infection model system Dictyostelium discoideum/Mycobacterium marinum to apply a genome-wide transposon-sequencing experimental strategy to reveal comprehensively which mutations confer a fitness advantage or disadvantage during infection and compare these to a similar experiment performed using the murine microglial BV2 cells as host for M. marinum to identify conservation of virulence pathways between hosts.
Collapse
Affiliation(s)
- Louise H. Lefrançois
- Department of Biochemistry, Faculty of Science, University of Geneva, Science II, Geneva, Switzerland
| | - Jahn Nitschke
- Department of Biochemistry, Faculty of Science, University of Geneva, Science II, Geneva, Switzerland
| | - Huihai Wu
- Department of Microbial Sciences, School of Biosciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Gaël Panis
- Department of Microbiology and Molecular Medicine, Faculty of Medicine/CMU, University of Geneva, Institute of Genetics and Genomics in Geneva (iGE3), Genève, Switzerland
| | - Julien Prados
- Department of Microbiology and Molecular Medicine, Faculty of Medicine/CMU, University of Geneva, Institute of Genetics and Genomics in Geneva (iGE3), Genève, Switzerland
- Bioinformatics Support Platform for data analysis, Geneva University, Medicine Faculty, Geneva, Switzerland
| | - Rachel E. Butler
- Department of Microbial Sciences, School of Biosciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Tom A. Mendum
- Department of Microbial Sciences, School of Biosciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Nabil Hanna
- Department of Biochemistry, Faculty of Science, University of Geneva, Science II, Geneva, Switzerland
| | - Graham R. Stewart
- Department of Microbial Sciences, School of Biosciences, University of Surrey, Guildford, Surrey, United Kingdom
| | - Thierry Soldati
- Department of Biochemistry, Faculty of Science, University of Geneva, Science II, Geneva, Switzerland
| |
Collapse
|
5
|
Parmar S, Tocheva EI. The cell envelope of Mycobacterium abscessus and its role in pathogenesis. PLoS Pathog 2023; 19:e1011318. [PMID: 37200238 DOI: 10.1371/journal.ppat.1011318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023] Open
Abstract
Mycobacterium abscessus is a nontuberculosis mycobacterium (NTM) that has shown an exponential rise in its ability to cause disease. Due to its ubiquitous presence in the environment, M. abscessus is widely implicated in secondary exacerbations of many nosocomial infections and genetic respiratory disorders, such as cystic fibrosis (CF). Contrary to other rapidly growing NTMs, the cell envelope of M. abscessus harbors several prominent features and undergoes modifications that are responsible for its pathogenesis. Compositional changes of the mycobacterial outer membrane (MOM) significantly decrease the presence of glycopeptidolipids (GPLs) and enable the transition from a colonizing, smooth morphotype into a virulent, rough morphotype. The GPLs are transported to the MOM by the Mycobacterial membrane proteins Large (MmpL), which further act as drug efflux pumps and confer antibiotic resistance. Lastly, M. abscessus possesses 2 type VII secretion systems (T7SS): ESX-3 and ESX-4, both of which have recently been implicated in host-pathogen interactions and virulence. This review summarizes the current knowledge of M. abscessus pathogenesis and highlights the clinically relevant association between the structure and functions of its cell envelope.
Collapse
Affiliation(s)
- Shweta Parmar
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | - Elitza I Tocheva
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| |
Collapse
|
6
|
Mittal E, Roth AT, Seth A, Singamaneni S, Beatty W, Philips JA. Single cell preparations of Mycobacterium tuberculosis damage the mycobacterial envelope and disrupt macrophage interactions. eLife 2023; 12:e85416. [PMID: 36852737 PMCID: PMC9998084 DOI: 10.7554/elife.85416] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 01/11/2023] [Indexed: 03/01/2023] Open
Abstract
For decades, investigators have studied the interaction of Mycobacterium tuberculosis (Mtb) with macrophages, which serve as a major cellular niche for the bacilli. Because Mtb are prone to aggregation, investigators rely on varied methods to disaggregate the bacteria for these studies. Here, we examined the impact of routinely used preparation methods on bacterial cell envelope integrity, macrophage inflammatory responses, and intracellular Mtb survival. We found that both gentle sonication and filtering damaged the mycobacterial cell envelope and markedly impacted the outcome of infections in mouse bone marrow-derived macrophages. Unexpectedly, sonicated bacilli were hyperinflammatory, eliciting dramatically higher TLR2-dependent gene expression and elevated secretion of IL-1β and TNF-α. Despite evoking enhanced inflammatory responses, sonicated bacilli replicated normally in macrophages. In contrast, Mtb that had been passed through a filter induced little inflammatory response, and they were attenuated in macrophages. Previous work suggests that the mycobacterial cell envelope lipid, phthiocerol dimycocerosate (PDIM), dampens macrophage inflammatory responses to Mtb. However, we found that the impact of PDIM depended on the method used to prepare Mtb. In conclusion, widely used methodologies to disaggregate Mtb may introduce experimental artifacts in Mtb-host interaction studies, including alteration of host inflammatory signaling, intracellular bacterial survival, and interpretation of bacterial mutants.
Collapse
Affiliation(s)
- Ekansh Mittal
- Division of Infectious Diseases, Department of Medicine, Washington University School of MedicineSt LouisUnited States
- Department of Molecular Microbiology, Washington University School of MedicineSt LouisUnited States
| | - Andrew T Roth
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Washington University School of MedicineSt LouisUnited States
| | - Anushree Seth
- Department of Mechanical Engineering and Materials Science, Institute of Materials Science and Engineering, Washington University in St. LouisSt LouisUnited States
| | - Srikanth Singamaneni
- Department of Mechanical Engineering and Materials Science, Institute of Materials Science and Engineering, Washington University in St. LouisSt LouisUnited States
- Siteman Cancer Center, Washington UniversitySt. LouisUnited States
| | - Wandy Beatty
- Department of Molecular Microbiology, Washington University School of MedicineSt LouisUnited States
| | - Jennifer A Philips
- Division of Infectious Diseases, Department of Medicine, Washington University School of MedicineSt LouisUnited States
- Department of Molecular Microbiology, Washington University School of MedicineSt LouisUnited States
| |
Collapse
|
7
|
Barisch C, Holthuis JCM, Cosentino K. Membrane damage and repair: a thin line between life and death. Biol Chem 2023; 404:467-490. [PMID: 36810295 DOI: 10.1515/hsz-2022-0321] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 02/03/2023] [Indexed: 02/24/2023]
Abstract
Bilayered membranes separate cells from their surroundings and form boundaries between intracellular organelles and the cytosol. Gated transport of solutes across membranes enables cells to establish vital ion gradients and a sophisticated metabolic network. However, an advanced compartmentalization of biochemical reactions makes cells also particularly vulnerable to membrane damage inflicted by pathogens, chemicals, inflammatory responses or mechanical stress. To avoid potentially lethal consequences of membrane injuries, cells continuously monitor the structural integrity of their membranes and readily activate appropriate pathways to plug, patch, engulf or shed the damaged membrane area. Here, we review recent insights into the cellular mechanisms that underly an effective maintenance of membrane integrity. We discuss how cells respond to membrane lesions caused by bacterial toxins and endogenous pore-forming proteins, with a primary focus on the intimate crosstalk between membrane proteins and lipids during wound formation, detection and elimination. We also discuss how a delicate balance between membrane damage and repair determines cell fate upon bacterial infection or activation of pro-inflammatory cell death pathways.
Collapse
Affiliation(s)
- Caroline Barisch
- Molecular Infection Biology Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| | - Joost C M Holthuis
- Molecular Cell Biology Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| | - Katia Cosentino
- Molecular Cell Biophysics Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| |
Collapse
|
8
|
Pagán AJ, Lee LJ, Edwards-Hicks J, Moens CB, Tobin DM, Busch-Nentwich EM, Pearce EL, Ramakrishnan L. mTOR-regulated mitochondrial metabolism limits mycobacterium-induced cytotoxicity. Cell 2022; 185:3720-3738.e13. [PMID: 36103894 PMCID: PMC9596383 DOI: 10.1016/j.cell.2022.08.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 06/17/2022] [Accepted: 08/16/2022] [Indexed: 02/01/2023]
Abstract
Necrosis of macrophages in the granuloma, the hallmark immunological structure of tuberculosis, is a major pathogenic event that increases host susceptibility. Through a zebrafish forward genetic screen, we identified the mTOR kinase, a master regulator of metabolism, as an early host resistance factor in tuberculosis. We found that mTOR complex 1 protects macrophages from mycobacterium-induced death by enabling infection-induced increases in mitochondrial energy metabolism fueled by glycolysis. These metabolic adaptations are required to prevent mitochondrial damage and death caused by the secreted mycobacterial virulence determinant ESAT-6. Thus, the host can effectively counter this early critical mycobacterial virulence mechanism simply by regulating energy metabolism, thereby allowing pathogen-specific immune mechanisms time to develop. Our findings may explain why Mycobacterium tuberculosis, albeit humanity's most lethal pathogen, is successful in only a minority of infected individuals.
Collapse
Affiliation(s)
- Antonio J. Pagán
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK,MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK,Department of Microbiology, University of Washington, Seattle, WA 98195, USA,Corresponding author
| | - Lauren J. Lee
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK,MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Joy Edwards-Hicks
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Cecilia B. Moens
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - David M. Tobin
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Elisabeth M. Busch-Nentwich
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
| | - Erika L. Pearce
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg im Breisgau, Germany
| | - Lalita Ramakrishnan
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK,MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK,Department of Microbiology, University of Washington, Seattle, WA 98195, USA,Corresponding author
| |
Collapse
|
9
|
Proteo-genetic analysis reveals clear hierarchy of ESX-1 secretion in Mycobacterium marinum. Proc Natl Acad Sci U S A 2022; 119:e2123100119. [PMID: 35671426 PMCID: PMC9214503 DOI: 10.1073/pnas.2123100119] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The ESX-1 (ESAT-6-system-1) system and the protein substrates it transports are essential for mycobacterial pathogenesis. The precise ways that ESX-1 substrates contribute to virulence remains unknown. Several known ESX-1 substrates are also required for the secretion of other proteins. We used a proteo-genetic approach to construct high-resolution dependency relationships for the roles of individual ESX-1 substrates in secretion and virulence in Mycobacterium marinum, a pathogen of humans and animals. Characterizing a collection of M. marinum strains with in-frame deletions in each of the known ESX-1 substrate genes and the corresponding complementation strains, we demonstrate that ESX-1 substrates are differentially required for ESX-1 activity and for virulence. Using isobaric-tagged proteomics, we quantified the degree of requirement of each substrate on protein secretion. We conclusively defined distinct contributions of ESX-1 substrates in protein secretion. Our data reveal a hierarchy of ESX-1 substrate secretion, which supports a model for the composition of the extracytoplasmic ESX-1 secretory machinery. Overall, our proteo-genetic analysis demonstrates discrete roles for ESX-1 substrates in ESX-1 function and secretion in M. marinum.
Collapse
|
10
|
Osman MM, Shanahan JK, Chu F, Takaki KK, Pinckert ML, Pagán AJ, Brosch R, Conrad WH, Ramakrishnan L. The C terminus of the mycobacterium ESX-1 secretion system substrate ESAT-6 is required for phagosomal membrane damage and virulence. Proc Natl Acad Sci U S A 2022; 119:e2122161119. [PMID: 35271388 PMCID: PMC8931374 DOI: 10.1073/pnas.2122161119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 01/15/2022] [Indexed: 12/21/2022] Open
Abstract
SignificanceTuberculosis (TB), an ancient disease of humanity, continues to be a major cause of worldwide death. The causative agent of TB, Mycobacterium tuberculosis, and its close pathogenic relative Mycobacterium marinum, initially infect, evade, and exploit macrophages, a major host defense against invading pathogens. Within macrophages, mycobacteria reside within host membrane-bound compartments called phagosomes. Mycobacterium-induced damage of the phagosomal membranes is integral to pathogenesis, and this activity has been attributed to the specialized mycobacterial secretion system ESX-1, and particularly to ESAT-6, its major secreted protein. Here, we show that the integrity of the unstructured ESAT-6 C terminus is required for macrophage phagosomal damage, granuloma formation, and virulence.
Collapse
Affiliation(s)
- Morwan M. Osman
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Jonathan K. Shanahan
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Frances Chu
- Department of Microbiology, University of Washington, Seattle, WA 98105
| | - Kevin K. Takaki
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Malte L. Pinckert
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Antonio J. Pagán
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Roland Brosch
- Institut Pasteur, Université de Paris, CNRS UMR 3525, Unit for Integrated Mycobacterial Pathogenomics, 75724 Paris Cedex 15, France
| | - William H. Conrad
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
| | - Lalita Ramakrishnan
- Molecular Immunity Unit, Cambridge Institute of Therapeutic Immunology and Infectious Diseases, Department of Medicine, University of Cambridge, CB2 OQH Cambridge, United Kingdom
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, CB2 0QH Cambridge, United Kingdom
- Department of Microbiology, University of Washington, Seattle, WA 98105
| |
Collapse
|
11
|
Bell SL, Lopez KL, Cox JS, Patrick KL, Watson RO. Galectin-8 Senses Phagosomal Damage and Recruits Selective Autophagy Adapter TAX1BP1 To Control Mycobacterium tuberculosis Infection in Macrophages. mBio 2021; 12:e0187120. [PMID: 34225486 PMCID: PMC8406326 DOI: 10.1128/mbio.01871-20] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 06/03/2021] [Indexed: 12/26/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb) causes one of the deadliest infectious diseases worldwide. Upon infection, Mtb is phagocytosed by macrophages and uses its virulence-associated ESX-1 secretion system to modulate the host cell. We showed previously that the ESX-1 secretion system perturbs the Mtb-containing phagosome, and a population (∼30%) of intracellular Mtb is tagged with ubiquitin and targeted to selective autophagy. However, our understanding of how macrophages sense and respond to damaged Mtb-containing phagosomes remains incomplete. Here, we demonstrate that several cytosolic glycan-binding proteins called galectins recognize Mtb-containing phagosomes; in macrophage cell lines and in primary macrophages, galectin-3, -8, and -9 are all recruited to the same Mtb population that colocalizes with selective autophagy markers (ubiquitin, p62, and LC3). To test whether galectins are required for controlling Mtb replication in macrophages, we generated CRISPR/Cas9 knockouts and found that galectin-8-/- and galectin-3/8/9-/- macrophages were similarly defective in targeting Mtb to selective autophagy and controlling replication. This suggests galectin-8 plays a unique role in anti-Mtb autophagy. In investigating galectin-8's role, we identified a novel and specific interaction between galectin-8 and the selective autophagy adapter TAX1BP1 and found that this galectin-8/TAX1BP1 interaction was necessary for macrophages to efficiently target Mtb to selective autophagy. Remarkably, overexpressing galectin-8 increased targeting of Mtb to autophagy and limited Mtb replication. Taken together, these data demonstrate that while several galectins are capable of recognizing damaged Mtb-containing phagosomes, galectin-8 plays a privileged role in recruiting downstream autophagy machinery and may represent a promising target for host-directed tuberculosis therapies. IMPORTANCE Mycobacterium tuberculosis (Mtb) infects one-quarter of the global population and causes one of the deadliest infectious diseases worldwide. Macrophages are the first line of defense against Mtb infection and are typically incredibly efficient at destroying intracellular pathogens, but Mtb has evolved to survive and replicate in this harsh environment. Previous work has found that a portion of intracellular Mtb bacilli damage their phagosomes, leaving them vulnerable to detection by the host and delivery to an antibacterial pathway called selective autophagy. Here, we show that in macrophages, galectin-8 recognizes damaged Mtb-containing phagosomes and targets Mtb to selective autophagy; we found that galectin-8, unlike other highly similar and closely related galectins, is required for targeting and controlling Mtb in macrophages. The specific role for galectin-8 appears to stem from its interaction with TAX1BP1, a selective autophagy adapter protein. Interestingly, overexpressing galectin-8 helps macrophages target and control Mtb, highlighting the importance of galectin-8 in the innate immune response to Mtb.
Collapse
Affiliation(s)
- Samantha L. Bell
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M Health Science Center, Bryan, Texas, USA
| | - Kayla L. Lopez
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M Health Science Center, Bryan, Texas, USA
| | - Jeffery S. Cox
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Kristin L. Patrick
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M Health Science Center, Bryan, Texas, USA
| | - Robert O. Watson
- Department of Microbial Pathogenesis and Immunology, College of Medicine, Texas A&M Health Science Center, Bryan, Texas, USA
| |
Collapse
|
12
|
Lagune M, Petit C, Sotomayor FV, Johansen MD, Beckham KSH, Ritter C, Girard-Misguich F, Wilmanns M, Kremer L, Maurer FP, Herrmann JL. Conserved and specialized functions of Type VII secretion systems in non-tuberculous mycobacteria. MICROBIOLOGY-SGM 2021; 167. [PMID: 34224347 DOI: 10.1099/mic.0.001054] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Non-tuberculous mycobacteria (NTM) are a large group of micro-organisms comprising more than 200 individual species. Most NTM are saprophytic organisms and are found mainly in terrestrial and aquatic environments. In recent years, NTM have been increasingly associated with infections in both immunocompetent and immunocompromised individuals, prompting significant efforts to understand the diverse pathogenic and signalling traits of these emerging pathogens. Since the discovery of Type VII secretion systems (T7SS), there have been significant developments regarding the role of these complex systems in mycobacteria. These specialised systems, also known as Early Antigenic Secretion (ESX) systems, are employed to secrete proteins across the inner membrane. They also play an essential role in virulence, nutrient uptake and conjugation. Our understanding of T7SS in mycobacteria has significantly benefited over the last few years, from the resolution of ESX-3 structure in Mycobacterium smegmatis, to ESX-5 structures in Mycobacterium xenopi and Mycobacterium tuberculosis. In addition, ESX-4, considered until recently as a non-functional system in both pathogenic and non-pathogenic mycobacteria, has been proposed to play an important role in the virulence of Mycobacterium abscessus; an increasingly recognized opportunistic NTM causing severe lung diseases. These major findings have led to important new insights into the functional mechanisms of these biological systems, their implication in virulence, nutrient acquisitions and cell wall shaping, and will be discussed in this review.
Collapse
Affiliation(s)
- Marion Lagune
- Université Paris-Saclay, UVSQ, Inserm, Infection et inflammation, 78180, Montigny-Le-Bretonneux, France
| | - Cecile Petit
- European Molecular Biology Laboratory, Hamburg Unit, Notkestraße 85, 22607 Hamburg, Germany
| | - Flor Vásquez Sotomayor
- National and WHO Supranational Reference Center for Mycobacteria, Research Center Borstel, Leibniz Lung Center, Borstel, Germany
| | - Matt D Johansen
- Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, 1919 route de Mende, 34293, Montpellier, France.,Present address: Centre for Inflammation, Centenary Institute and University of Technology Sydney, Faculty of Science, Sydney, NSW, Australia
| | - Kathrine S H Beckham
- European Molecular Biology Laboratory, Hamburg Unit, Notkestraße 85, 22607 Hamburg, Germany
| | - Christina Ritter
- European Molecular Biology Laboratory, Hamburg Unit, Notkestraße 85, 22607 Hamburg, Germany
| | - Fabienne Girard-Misguich
- Université Paris-Saclay, UVSQ, Inserm, Infection et inflammation, 78180, Montigny-Le-Bretonneux, France
| | - Matthias Wilmanns
- European Molecular Biology Laboratory, Hamburg Unit, Notkestraße 85, 22607 Hamburg, Germany.,University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20251 Hamburg, Germany
| | - Laurent Kremer
- Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, 1919 route de Mende, 34293, Montpellier, France.,INSERM, IRIM, 34293 Montpellier, France
| | - Florian P Maurer
- National and WHO Supranational Reference Center for Mycobacteria, Research Center Borstel, Leibniz Lung Center, Borstel, Germany.,Institute of Medical Microbiology, Virology and Hospital Hygiene, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jean-Louis Herrmann
- Université Paris-Saclay, UVSQ, Inserm, Infection et inflammation, 78180, Montigny-Le-Bretonneux, France.,APHP, GHU Paris-Saclay, Hôpital Raymond Poincaré, Service de Microbiologie, Garches, France
| |
Collapse
|
13
|
A Small Protein but with Diverse Roles: A Review of EsxA in Mycobacterium-Host Interaction. Cells 2021; 10:cells10071645. [PMID: 34209120 PMCID: PMC8305481 DOI: 10.3390/cells10071645] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/27/2021] [Accepted: 06/28/2021] [Indexed: 12/20/2022] Open
Abstract
As a major effector of the ESX-1 secretion system, EsxA is essential for the virulence of pathogenic mycobacteria, such as Mycobacterium tuberculosis (Mtb) and Mycobacterium marinum (Mm). EsxA possesses an acidic pH-dependent membrane permeabilizing activity and plays an essential role by mediating mycobacterial escape from the phagosome and translocation to the cytosol for intracellular replication. Moreover, EsxA regulates host immune responses as a potent T-cell antigen and a strong immunoregulator. EsxA interacts with multiple cellular proteins and stimulates several signal pathways, such as necrosis, apoptosis, autophagy, and antigen presentation. Interestingly, there is a co-dependency in the expression and secretion of EsxA and other mycobacterial factors, which greatly increases the complexity of dissecting the precise roles of EsxA and other factors in mycobacterium-host interaction. In this review, we summarize the current understandings of the roles and functions of EsxA in mycobacterial infection and discuss the challenges and future directions.
Collapse
|
14
|
Holzheimer M, Buter J, Minnaard AJ. Chemical Synthesis of Cell Wall Constituents of Mycobacterium tuberculosis. Chem Rev 2021; 121:9554-9643. [PMID: 34190544 PMCID: PMC8361437 DOI: 10.1021/acs.chemrev.1c00043] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
The pathogen Mycobacterium tuberculosis (Mtb), causing
tuberculosis disease, features an extraordinary
thick cell envelope, rich in Mtb-specific lipids,
glycolipids, and glycans. These cell wall components are often directly
involved in host–pathogen interaction and recognition, intracellular
survival, and virulence. For decades, these mycobacterial natural
products have been of great interest for immunology and synthetic
chemistry alike, due to their complex molecular structure and the
biological functions arising from it. The synthesis of many of these
constituents has been achieved and aided the elucidation of their
function by utilizing the synthetic material to study Mtb immunology. This review summarizes the synthetic efforts of a quarter
century of total synthesis and highlights how the synthesis layed
the foundation for immunological studies as well as drove the field
of organic synthesis and catalysis to efficiently access these complex
natural products.
Collapse
Affiliation(s)
- Mira Holzheimer
- Stratingh Institute for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Jeffrey Buter
- Stratingh Institute for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Adriaan J Minnaard
- Stratingh Institute for Chemistry, University of Groningen, 9747 AG Groningen, The Netherlands
| |
Collapse
|
15
|
Patrick KL, Watson RO. Mitochondria: Powering the Innate Immune Response to Mycobacterium tuberculosis Infection. Infect Immun 2021; 89:e00687-20. [PMID: 33558322 PMCID: PMC8090963 DOI: 10.1128/iai.00687-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Within the last decade, we have learned that damaged mitochondria activate many of the same innate immune pathways that evolved to sense and respond to intracellular pathogens. These shared responses include cytosolic nucleic acid sensing and type I interferon (IFN) expression, inflammasome activation that leads to pyroptosis, and selective autophagy (called mitophagy when mitochondria are the cargo). Because mitochondria were once bacteria, parallels between how cells respond to mitochondrial and bacterial ligands are not altogether surprising. However, the potential for cross talk or synergy between bacterium- and mitochondrion-driven innate immune responses during infection remains poorly understood. This interplay is particularly striking, and intriguing, in the context of infection with the intracellular bacterial pathogen Mycobacterium tuberculosis (Mtb). Multiple studies point to a role for Mtb infection and/or specific Mtb virulence factors in disrupting the mitochondrial network in macrophages, leading to metabolic changes and triggering potent innate immune responses. Research from our laboratories and others argues that mutations in mitochondrial genes can exacerbate mycobacterial disease severity by hyperactivating innate responses or activating them at the wrong time. Indeed, growing evidence supports a model whereby different mitochondrial defects or mutations alter Mtb infection outcomes in distinct ways. By synthesizing the current literature in this minireview, we hope to gain insight into the molecular mechanisms driving, and consequences of, mitochondrion-dependent immune polarization so that we might better predict tuberculosis patient outcomes and develop host-directed therapeutics designed to correct these imbalances.
Collapse
Affiliation(s)
- Kristin L Patrick
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, College of Medicine, Bryan, Texas, USA
| | - Robert O Watson
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, College of Medicine, Bryan, Texas, USA
| |
Collapse
|
16
|
Fevereiro J, Fraga AG, Pedrosa J. Genetics in the Host-Mycobacterium ulcerans interaction. Immunol Rev 2021; 301:222-241. [PMID: 33682158 DOI: 10.1111/imr.12958] [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: 01/05/2021] [Revised: 01/30/2021] [Accepted: 02/01/2021] [Indexed: 11/30/2022]
Abstract
Buruli ulcer is an emerging infectious disease associated with high morbidity and unpredictable outbreaks. It is caused by Mycobacterium ulcerans, a slow-growing pathogen evolutionarily shaped by the acquisition of a plasmid involved in the production of a potent macrolide-like cytotoxin and by genome rearrangements and downsizing. These events culminated in an uncommon infection pattern, whereby M. ulcerans is both able to induce the initiation of the inflammatory cascade and the cell death of its proponents, as well as to survive within the phagosome and in the extracellular milieu. In such extreme conditions, the host is sentenced to rely on a highly orchestrated genetic landscape to be able to control the infection. We here revisit the dynamics of M. ulcerans infection, drawing parallels from other mycobacterioses and integrating the most recent knowledge on its evolution and pathogenicity in its interaction with the host immune response.
Collapse
Affiliation(s)
- João Fevereiro
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Alexandra G Fraga
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Jorge Pedrosa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| |
Collapse
|
17
|
Bao Y, Wang L, Sun J. Post-translational knockdown and post-secretional modification of EsxA determine contribution of EsxA membrane permeabilizing activity for mycobacterial intracellular survival. Virulence 2021; 12:312-328. [PMID: 33356823 PMCID: PMC7808419 DOI: 10.1080/21505594.2020.1867438] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Current genetic studies (e.g. gene knockout) have suggested that EsxA and EsxB function as secreted virulence factors that are essential for Mycobaterium tuberculosis (Mtb) intracellular survival, specifically in mediating phagosome rupture and translocation of Mtb to the cytosol of host cells, which further facilitates Mtb intracellular replicating and cell-to-cell spreading. The EsxA-mediated intracellular survival is presumably achieved by its pH-dependent membrane-permeabilizing activity (MPA). However, the data from other studies have generated a discrepancy regarding the role of EsxA MPA in mycobacterial intracellular survival, which has raised a concern that genetic manipulations, such as deletion of esxB-esxA operon or RD-1 locus, may affect other codependently secreted factors that could be also directly involved cytosolic translocation, or stimulate extended disturbance on other genes’ expression. To avoid the drawbacks of gene knockout, we first engineered a Mycobacterium marinum (Mm) strain, in which a DAS4+ tag was fused to the C-terminus of EsxB to allow inducible knockdown of EsxB (also EsxA) at the post-translational level. We also engineered an Mm strain by fusing a SpyTag (ST) to the C-terminus of EsxA, which allowed inhibition of EsxA-ST MPA at the post-secretional level through a covalent linkage to SpyCatcher-GFP. Both post-translational knockdown and functional inhibition of EsxA resulted in attenuation of Mm intracellular survival in lung epithelial cells or macrophages, which unambiguously confirms the direct role of EsxA MPA in mycobacterial intracellular survival.
Collapse
Affiliation(s)
- Yanqing Bao
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso , El Paso, Texas, USA
| | - Lin Wang
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso , El Paso, Texas, USA
| | - Jianjun Sun
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso , El Paso, Texas, USA
| |
Collapse
|
18
|
Cambier CJ, Banik SM, Buonomo JA, Bertozzi CR. Spreading of a mycobacterial cell-surface lipid into host epithelial membranes promotes infectivity. eLife 2020; 9:60648. [PMID: 33226343 PMCID: PMC7735756 DOI: 10.7554/elife.60648] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 11/23/2020] [Indexed: 12/31/2022] Open
Abstract
Several virulence lipids populate the outer cell wall of pathogenic mycobacteria. Phthiocerol dimycocerosate (PDIM), one of the most abundant outer membrane lipids, plays important roles in both defending against host antimicrobial programs and in evading these programs altogether. Immediately following infection, mycobacteria rely on PDIM to evade Myd88-dependent recruitment of microbicidal monocytes which can clear infection. To circumvent the limitations in using genetics to understand virulence lipids, we developed a chemical approach to track PDIM during Mycobacterium marinum infection of zebrafish. We found that PDIM's methyl-branched lipid tails enabled it to spread into host epithelial membranes to prevent immune activation. Additionally, PDIM’s affinity for cholesterol promoted this phenotype; treatment of zebrafish with statins, cholesterol synthesis inhibitors, decreased spreading and provided protection from infection. This work establishes that interactions between host and pathogen lipids influence mycobacterial infectivity and suggests the use of statins as tuberculosis preventive therapy by inhibiting PDIM spread.
Collapse
Affiliation(s)
- C J Cambier
- Department of Chemistry, Stanford University, Stanford, United States
| | - Steven M Banik
- Department of Chemistry, Stanford University, Stanford, United States
| | - Joseph A Buonomo
- Department of Chemistry, Stanford University, Stanford, United States
| | - Carolyn R Bertozzi
- Department of Chemistry, Stanford University, Stanford, United States.,Howard Hughes Medical Institute, Stanford University, Stanford, United States
| |
Collapse
|
19
|
Conserved ESX-1 Substrates EspE and EspF Are Virulence Factors That Regulate Gene Expression. Infect Immun 2020; 88:IAI.00289-20. [PMID: 32900815 DOI: 10.1128/iai.00289-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 08/28/2020] [Indexed: 12/12/2022] Open
Abstract
Mycobacterium tuberculosis, the cause of human tuberculosis, and Mycobacterium marinum, a nontubercular pathogen with a broad host range, require the ESX-1 secretion system for virulence. The ESX-1 system secretes proteins which cause phagosomal lysis within the macrophage via an unknown mechanism. As reported elsewhere (R. E. Bosserman et al., Proc Natl Acad Sci U S A 114:E10772-E10781, 2017, https://doi.org/10.1073/pnas.1710167114), we recently discovered that the ESX-1 system regulates gene expression in M. marinum This finding was confirmed in M. tuberculosis in reports by C. Sala et al. (PLoS Pathog 14:e1007491, 2018, https://doi.org/10.1371/journal.ppat.1007491) and A. M. Abdallah et al. (PLoS One 14:e0211003, 2019, https://doi.org/10.1371/journal.pone.0211003). We further demonstrated that a feedback control mechanism connects protein secretion to WhiB6-dependent expression of the esx-1 genes via an unknown mechanism. Here, we connect protein secretion and gene expression by showing for the first time that specific ESX-1 substrates have dual functions inside and outside the mycobacterial cell. We demonstrate that the EspE and EspF substrates negatively control esx-1 gene expression in the M. marinum cytoplasm through the conserved WhiB6 transcription factor. We found that EspE and EspF are required for virulence and promote lytic activity independently of the major EsxA and EsxB substrates. We show that the dual functions of EspE and EspF are conserved in the orthologous proteins from M. tuberculosis Our findings support a role for EspE and EspF in virulence that is independent of the EsxA and EsxB substrates and demonstrate that ESX-1 substrates have a conserved role in regulating gene expression.
Collapse
|