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Berude JC, Kennouche P, Reniere ML, Portnoy DA. Listeria monocytogenes utilizes glutathione and limited inorganic sulfur compounds as sources of essential cysteine. Infect Immun 2024; 92:e0042223. [PMID: 38289071 PMCID: PMC10929415 DOI: 10.1128/iai.00422-23] [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: 10/13/2023] [Accepted: 12/13/2023] [Indexed: 02/13/2024] Open
Abstract
Listeria monocytogenes (Lm) is a Gram-positive facultative intracellular pathogen that leads a biphasic lifecycle, transitioning its metabolism and selectively inducing virulence genes when it encounters mammalian hosts. Virulence gene expression is controlled by the master virulence regulator PrfA, which is allosterically activated by the host- and bacterially derived glutathione (GSH). The amino acid cysteine is the rate-limiting substrate for GSH synthesis in bacteria and is essential for bacterial growth. Unlike many bacteria, Lm is auxotrophic for cysteine and must import exogenous cysteine for growth and virulence. GSH is enriched in the host cytoplasm, and previous work suggests that Lm utilizes exogenous GSH for PrfA activation. Despite these observations, the import mechanism(s) for GSH remains elusive. Analysis of known GSH importers predicted a homologous importer in Lm comprised of the Ctp ABC transporter and the OppDF ATPases of the Opp oligopeptide importer. Here, we demonstrated that the Ctp complex is a high-affinity GSH/GSSG importer that is required for Lm growth at physiologically relevant concentrations. Furthermore, we demonstrated that OppDF is required for GSH/GSSG import in an Opp-independent manner. These data support a model where Ctp and OppDF form a unique complex for GSH/GSSG import that supports growth and pathogenesis. In addition, we show that Lm utilizes the inorganic sulfur sources thiosulfate and H2S for growth in a CysK-dependent manner in the absence of other cysteine sources. These findings suggest a pathoadaptive role for partial cysteine auxotrophy in Lm, where locally high GSH/GSSG or inorganic sulfur concentrations may signal arrival to distinct host niches.
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Affiliation(s)
- John C. Berude
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Paul Kennouche
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Michelle L. Reniere
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
| | - Daniel A. Portnoy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
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2
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Berude JC, Kennouche P, Reniere ML, Portnoy DA. Listeria monocytogenes utilizes glutathione and limited inorganic sulfur compounds as a source of essential L-cysteine. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.16.562582. [PMID: 37905006 PMCID: PMC10614801 DOI: 10.1101/2023.10.16.562582] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Listeria monocytogenes ( Lm ) is a Gram-positive facultative intracellular pathogen that leads a biphasic lifecycle, transitioning its metabolism and selectively inducing virulence genes when it encounters mammalian hosts. Virulence gene expression is controlled by the master virulence regulator PrfA, which is allosterically activated by host- and bacterially-derived glutathione (GSH). The amino acid L-cysteine is the rate-limiting substrate for GSH synthesis in bacteria and is essential for bacterial growth. Unlike many bacteria, Lm is auxotrophic for L-cysteine and must import exogenous cysteine for growth and virulence. GSH is enriched in the host cytoplasm, and previous work suggests that Lm utilizes exogenous GSH for PrfA activation. Despite these observations, the import mechanism(s) for GSH remains elusive. Analysis of known GSH importers predicted a homologous importer in Lm comprised of the Ctp ABC transporter and the OppDF ATPases of the Opp oligopeptide importer. Here, we demonstrated that the Ctp complex is a high-affinity GSH/GSSG importer that is required for Lm growth at physiologically relevant concentrations. Further, we demonstrated that OppDF are required for GSH/GSSG import in an Opp-independent manner. These data support a model where Ctp and OppDF form a unique complex for GSH/GSSG import that supports growth and pathogenesis. Additionally, we show that Lm utilizes the inorganic sulfur sources thiosulfate and H 2 S for growth in a CysK-dependent manner in the absence of other L-cysteine sources. These findings suggest a pathoadaptive role for partial cysteine auxotrophy in Lm , where locally high GSH/GSSG or inorganic sulfur concentrations may signal arrival to distinct host niches.
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Abdelhamed H, Nho SW, Kim SW, Reddy JS, Park SB, Jung TS, Lawrence ML. Serotype-identifying ions in Listeria monocytogenes using matrix-associated laser desorption ionization-time of flight mass spectrometry. Heliyon 2022; 8:e11769. [DOI: 10.1016/j.heliyon.2022.e11769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 08/23/2022] [Accepted: 11/13/2022] [Indexed: 11/21/2022] Open
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Abdelhamed H, Ramachandran R, Narayanan L, Islam S, Ozan O, Freitag N, Lawrence ML. Role of FruR transcriptional regulator in virulence of Listeria monocytogenes and identification of its regulon. PLoS One 2022; 17:e0274005. [PMID: 36054213 PMCID: PMC9439231 DOI: 10.1371/journal.pone.0274005] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/19/2022] [Indexed: 11/29/2022] Open
Abstract
Listeria monocytogenes is a ubiquitous opportunistic foodborne pathogen capable of survival in various adverse environmental conditions. Pathogenesis of L. monocytogenes is tightly controlled by a complex regulatory network of transcriptional regulators that are necessary for survival and adaptations to harsh environmental conditions both inside and outside host cells. Among these regulatory pathways are members of the DeoR-family transcriptional regulators that are known to play a regulatory role in sugar metabolism. In this study, we deciphered the role of FruR, a DeoR family protein, which is a fructose operon transcriptional repressor protein, in L. monocytogenes pathogenesis and growth. Following intravenous (IV) inoculation in mice, a mutant strain with deletion of fruR exhibited a significant reduction in bacterial burden in liver and spleen tissues compared to the parent strain. Further, the ΔfruR strain had a defect in cell-to-cell spread in L2 fibroblast monolayers. Constitutive activation of PrfA, a pleiotropic activator of L. monocytogenes virulence factors, did not restore virulence to the ΔfruR strain, suggesting that the attenuation was not a result of impaired PrfA activation. Transcriptome analysis revealed that FruR functions as a positive regulator for genes encoding enzymes involved in the pentose phosphate pathway (PPP) and as a repressor for genes encoding enzymes in the glycolysis pathway. These results suggested that FruR may function to facilitate NADPH regeneration, which is necessary for full protection from oxidative stress. Interestingly, deletion of fruR increased sensitivity of L. monocytogenes to H2O2, confirming a role for FruR in survival of L. monocytogenes during oxidative stress. Using anti-mouse neutrophil/monocyte monoclonal antibody RB6-8C5 (RB6) in an in vivo infection model, we found that FruR has a specific function in protecting L. monocytogenes from neutrophil/monocyte-mediated killing. Overall, this work clarifies the role of FruR in controlling L. monocytogenes carbon flow between glycolysis and PPP for NADPH homeostasis, which provides a new mechanism allowing metabolic adaptation of L. monocytogenes to oxidative stress.
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Affiliation(s)
- Hossam Abdelhamed
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
- * E-mail:
| | - Reshma Ramachandran
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
- Department of Poultry Science, Mississippi State University, Starkville, MS, United States of America
| | - Lakshmi Narayanan
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Shamima Islam
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Ozdemir Ozan
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
| | - Nancy Freitag
- Department of Pharmaceutical Sciences, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Mark L. Lawrence
- Department of Comparative Biomedical Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States of America
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Cardiotropic Isolates of Listeria monocytogenes with Enhanced Vertical Transmission Dependent upon the Bacterial Surface Protein InlB. Infect Immun 2021; 89:IAI.00321-20. [PMID: 33139387 DOI: 10.1128/iai.00321-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/28/2020] [Indexed: 12/17/2022] Open
Abstract
Listeria monocytogenes is a facultative Gram-positive intracellular bacterium that is capable of causing serious invasive infections in pregnant women, resulting in abortion, still-birth, and disseminated fetal infection. Previously, a clinical L. monocytogenes isolate, 07PF0776, was identified as having an enhanced ability to target cardiac tissue. This tissue tropism appeared to correlate with amino acid variations found within internalin B (InlB), a bacterial surface protein associated with host cell invasion. Given that the mammalian receptor bound by InlB, Met, is abundantly expressed by placental tissue, we assessed isolate 07PF0776 for its ability to be transmitted from mother to fetus. Pregnant Swiss Webster mice were infected on gestational day E13 via tail vein injection with the standard isolate 10403S, a noncardiotropic strain, or 07PF0776, the cardiac isolate. Pregnant mice infected with 07PF0776 exhibited significantly enhanced transmission of L. monocytogenes to placentas and fetuses compared to 10403S. Both bacterial burdens and the frequency of placental and fetal infection were increased in mice infected with the cardiac isolate. Strain 07PF0776 also exhibited an enhanced ability to invade Jar human trophoblast tissue culture cells in comparison to 10403S, and was found to have increased levels of InlB associated with the bacterial cell surface. Overexpression of surface InlB via genetic manipulation was sufficient to confer enhanced invasion of the placenta and fetus to both 10403S and 07PF0776. These data support a central role for surface InlB in promoting vertical transmission of L. monocytogenes.
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Cross Talk between SigB and PrfA in Listeria monocytogenes Facilitates Transitions between Extra- and Intracellular Environments. Microbiol Mol Biol Rev 2019; 83:83/4/e00034-19. [PMID: 31484692 DOI: 10.1128/mmbr.00034-19] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The foodborne pathogen Listeria monocytogenes can modulate its transcriptome and proteome to ensure its survival during transmission through vastly differing environmental conditions. While L. monocytogenes utilizes a large array of regulators to achieve survival and growth in different intra- and extrahost environments, the alternative sigma factor σB and the transcriptional activator of virulence genes protein PrfA are two key transcriptional regulators essential for responding to environmental stress conditions and for host infection. Importantly, emerging evidence suggests that the shift from extrahost environments to the host gastrointestinal tract and, subsequently, to intracellular environments requires regulatory interplay between σB and PrfA at transcriptional, posttranscriptional, and protein activity levels. Here, we review the current evidence for cross talk and interplay between σB and PrfA and their respective regulons and highlight the plasticity of σB and PrfA cross talk and the role of this cross talk in facilitating successful transition of L. monocytogenes from diverse extrahost to diverse extra- and intracellular host environments.
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Vertical Transmission of Listeria monocytogenes: Probing the Balance between Protection from Pathogens and Fetal Tolerance. Pathogens 2018; 7:pathogens7020052. [PMID: 29799503 PMCID: PMC6027155 DOI: 10.3390/pathogens7020052] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 05/16/2018] [Accepted: 05/22/2018] [Indexed: 12/19/2022] Open
Abstract
Protection of the developing fetus from pathogens is one of the many critical roles of the placenta. Listeria monocytogenes is one of a select number of pathogens that can cross the placental barrier and cause significant harm to the fetus, leading to spontaneous abortion, stillbirth, preterm labor, and disseminated neonate infection despite antibiotic treatment. Such severe outcomes serve to highlight the importance of understanding how L. monocytogenes mediates infiltration of the placental barrier. Here, we review what is currently known regarding vertical transmission of L. monocytogenes as a result of cell culture and animal models of infection. In vitro cell culture and organ models have been useful for the identification of L. monocytogenes virulence factors that contribute to placental invasion. Examples include members of the Internalin family of bacterial surface proteins such as Interalin (Inl)A, InlB, and InlP that promote invasion of cells at the maternal-fetal interface. A number of animal models have been used to interrogate L. monocytogenes vertical transmission, including mice, guinea pigs, gerbils, and non-human primates; each of these models has advantages while still not providing a comprehensive understanding of L. monocytogenes invasion of the human placenta and/or fetus. These models do, however, allow for the molecular investigation of the balance between fetal tolerance and immune protection from L. monocytogenes during pregnancy.
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McMullen PD, Freitag NE. Assessing bacterial invasion of cardiac cells in culture and heart colonization in infected mice using Listeria monocytogenes. J Vis Exp 2015:e52497. [PMID: 26065439 DOI: 10.3791/52497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised patients, the elderly, and pregnant women. The most common manifestations of listeriosis in humans include meningitis, encephalitis, and fetal abortion. A significant but much less documented sequelae of invasive L. monocytogenes infection involves the heart. The death rate from cardiac illness can be up to 35% despite treatment, however very little is known regarding L. monocytogenes colonization of cardiac tissue and its resultant pathologies. In addition, it has recently become apparent that subpopulations of L. monocytogenes have an enhanced capacity to invade and grow within cardiac tissue. This protocol describes in detail in vitro and in vivo methods that can be used for assessing cardiotropism of L. monocytogenes isolates. Methods are presented for the infection of H9c2 rat cardiac myoblasts in tissue culture as well as for the determination of bacterial colonization of the hearts of infected mice. These methods are useful not only for identifying strains with the potential to colonize cardiac tissue in infected animals, but may also facilitate the identification of bacterial gene products that serve to enhance cardiac cell invasion and/or drive changes in heart pathology. These methods also provide for the direct comparison of cardiotropism between multiple L. monocytogenes strains.
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Affiliation(s)
- P David McMullen
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago
| | - Nancy E Freitag
- Department of Microbiology and Immunology, College of Medicine, University of Illinois at Chicago;
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Xayarath B, Alonzo F, Freitag NE. Identification of a peptide-pheromone that enhances Listeria monocytogenes escape from host cell vacuoles. PLoS Pathog 2015; 11:e1004707. [PMID: 25822753 PMCID: PMC4379056 DOI: 10.1371/journal.ppat.1004707] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 01/26/2015] [Indexed: 02/05/2023] Open
Abstract
Listeria monocytogenes is a Gram-positive facultative intracellular bacterial pathogen that invades mammalian cells and escapes from membrane-bound vacuoles to replicate within the host cell cytosol. Gene products required for intracellular bacterial growth and bacterial spread to adjacent cells are regulated by a transcriptional activator known as PrfA. PrfA becomes activated following L. monocytogenes entry into host cells, however the signal that stimulates PrfA activation has not yet been defined. Here we provide evidence for L. monocytogenes secretion of a small peptide pheromone, pPplA, which enhances the escape of L. monocytogenes from host cell vacuoles and may facilitate PrfA activation. The pPplA pheromone is generated via the proteolytic processing of the PplA lipoprotein secretion signal peptide. While the PplA lipoprotein is dispensable for pathogenesis, bacteria lacking the pPplA pheromone are significantly attenuated for virulence in mice and have a reduced efficiency of bacterial escape from the vacuoles of nonprofessional phagocytic cells. Mutational activation of PrfA restores virulence and eliminates the need for pPplA-dependent signaling. Experimental evidence suggests that the pPplA peptide may help signal to L. monocytogenes its presence within the confines of the host cell vacuole, stimulating the expression of gene products that contribute to vacuole escape and facilitating PrfA activation to promote bacterial growth within the cytosol.
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Affiliation(s)
- Bobbi Xayarath
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Francis Alonzo
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Nancy E. Freitag
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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Xayarath B, Freitag NE. Optimizing the balance between host and environmental survival skills: lessons learned from Listeria monocytogenes. Future Microbiol 2014; 7:839-52. [PMID: 22827306 DOI: 10.2217/fmb.12.57] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Environmental pathogens - organisms that survive in the outside environment but maintain the capacity to cause disease in mammals - navigate the challenges of life in habitats that range from water and soil to the cytosol of host cells. The bacterium Listeria monocytogenes has served for decades as a model organism for studies of host-pathogen interactions and for fundamental paradigms of cell biology. This ubiquitous saprophyte has recently become a model for understanding how an environmental bacterium switches to life within human cells. This review describes how L. monocytogenes balances life in disparate environments with the help of a critical virulence regulator known as PrfA. Understanding L. monocytogenes survival strategies is important for gaining insight into how environmental microbes become pathogens.
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Affiliation(s)
- Bobbi Xayarath
- Department of Microbiology & Immunology, University of Illinois at Chicago, Chicago, IL, USA
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11
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Bruno JC, Freitag NE. Listeria monocytogenes adapts to long-term stationary phase survival without compromising bacterial virulence. FEMS Microbiol Lett 2011; 323:171-9. [PMID: 22092717 DOI: 10.1111/j.1574-6968.2011.02373.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 07/26/2011] [Accepted: 07/27/2011] [Indexed: 11/30/2022] Open
Abstract
Bacteria withstand starvation during long-term stationary phase through the acquisition of mutations that increase bacterial fitness. The evolution of the growth advantage in stationary phase (GASP) phenotype results in the ability of bacteria from an aged culture to outcompete bacteria from a younger culture when the two are mixed together. The GASP phenotype was first described for Escherichia coli, but has not been examined for an environmental bacterial pathogen, which must balance long-term survival strategies that promote fitness in the outside environment with those that promote fitness within the host. Listeria monocytogenes is an environmental bacterium that lives as a saprophyte in soil, but is capable of replicating within the cytosol of mammalian cells. Herein, we demonstrate the ability of L. monocytogenes to express GASP via the acquisition of mutations during long-term stationary growth. Listeria monocytogenes GASP occurred through mechanisms that were both dependent and independent of the stress-responsive alternative sigma factor SigB. Constitutive activation of the central virulence transcriptional regulator PrfA interfered with the development of GASP; however, L. monocytogenes GASP cultures retained full virulence in mice. These results indicate that L. monocytogenes can accrue mutations that optimize fitness during long-term stationary growth without negatively impacting virulence.
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Affiliation(s)
- Joseph C Bruno
- Department of Global Health, University of Washington, Seattle, WA, USA
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12
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Probing the role of protein surface charge in the activation of PrfA, the central regulator of Listeria monocytogenes pathogenesis. PLoS One 2011; 6:e23502. [PMID: 21858145 PMCID: PMC3155570 DOI: 10.1371/journal.pone.0023502] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 07/19/2011] [Indexed: 02/05/2023] Open
Abstract
Listeria monocytogenes is a food-borne intracellular bacterial pathogen capable of causing serious human disease. L. monocytogenes survival within mammalian cells depends upon the synthesis of a number of secreted virulence factors whose expression is regulated by the transcriptional activator PrfA. PrfA becomes activated following bacterial entry into host cells where it induces the expression of gene products required for bacterial spread to adjacent cells. Activation of PrfA appears to occur via the binding of a small molecule cofactor whose identity remains unknown. Electrostatic modeling of the predicted PrfA cofactor binding pocket revealed a highly positively charged region with two lysine residues, K64 and K122, located at the edge of the pocket and another (K130) located deep within the interior. Mutational analysis of these residues indicated that K64 and K122 contribute to intracellular activation of PrfA, whereas a K130 substitution abolished protein activity. The requirement of K64 and K122 for intracellular PrfA activation could be bypassed via the introduction of the prfA G145S mutation that constitutively activates PrfA in the absence of cofactor binding. Our data indicate that the positive charge of the PrfA binding pocket contributes to intracellular activation of PrfA, presumably by facilitating binding of an anionic cofactor.
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13
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Xayarath B, Smart JI, Mueller KJ, Freitag NE. A novel C-terminal mutation resulting in constitutive activation of the Listeria monocytogenes central virulence regulatory factor PrfA. MICROBIOLOGY-SGM 2011; 157:3138-3149. [PMID: 21835879 DOI: 10.1099/mic.0.049957-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The environmental bacterium Listeria monocytogenes survives and replicates in a variety of diverse ecological niches that range from the soil to the cytosol of infected mammalian cells. The ability of L. monocytogenes to replicate within an infected host requires the expression of a number of secreted bacterial gene products whose expression is regulated by the transcriptional activator PrfA. PrfA becomes activated following bacterial entry into host cells; however, the mechanism by which this activation occurs remains unknown. Here we describe a novel C-terminal mutation that results in the high-level constitutive activation of PrfA and yet, in contrast with other described prfA* activation mutations, only modestly increases PrfA DNA binding affinity. L. monocytogenes strains containing the prfA P219S mutation exhibited high levels of PrfA-dependent virulence gene expression, were hyperinvasive in tissue culture models of infection, were fully motile and were hypervirulent in mice. In contrast with PrfA G145S and other mutationally activated PrfA proteins, the PrfA P219S protein readily formed homodimers and did not exhibit a dramatic increase in its DNA-binding affinity for target promoters. Interestingly, the prfA P219S mutation is located adjacent to the prfA K220 residue that has been previously reported to contribute to PrfA DNA binding activity. prfA P219S therefore appears to constitutively activate PrfA via a novel mechanism which minimally affects PrfA DNA binding in vitro.
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Affiliation(s)
- Bobbi Xayarath
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
| | - Jennifer I Smart
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
| | - Kimberly J Mueller
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
| | - Nancy E Freitag
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
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Alonzo F, Xayarath B, Whisstock JC, Freitag NE. Functional analysis of the Listeria monocytogenes secretion chaperone PrsA2 and its multiple contributions to bacterial virulence. Mol Microbiol 2011; 80:1530-48. [PMID: 21545417 DOI: 10.1111/j.1365-2958.2011.07665.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
As an organism that has evolved to live in environments ranging from soil to the cytosol of mammalian cells, Listeria monocytogenes must regulate the secretion and activity of protein products that promote survival within these habitats. The post-translocation chaperone PrsA2 has been adapted to assist in the folding and activity of L. monocytogenes secreted proteins required for bacterial replication within host cells. Here we present the first structure/function investigation of the contributions of PrsA2 to protein secretion and activity as well as to bacterial virulence. Domain swap experiments with the closely related L. monocytogenes PrsA1 protein combined with targeted mutagenesis indicate distinct functional roles for the PrsA2 peptidyl-prolyl isomerase (PPIase) and the N- and C-terminal domains in pathogenesis. In contrast to other PrsA-like proteins described thus far in the literature, an absolute in vivo requirement for PrsA2 PPIase activity is evident in mouse infection models. This work illustrates the diversity of function associated with L. monocytogenes PrsA2 that serves to promote bacterial life within the infected host.
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Affiliation(s)
- Francis Alonzo
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
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15
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Branched-chain fatty acids promote Listeria monocytogenes intracellular infection and virulence. Infect Immun 2010; 78:4667-73. [PMID: 20823206 DOI: 10.1128/iai.00546-10] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Anteiso-branched-chain fatty acids (BCFA) represent the dominant group of membrane fatty acids and have been established as crucial determinants in resistance against environmental stresses in Listeria monocytogenes, a facultative intracellular pathogen. Here, we investigate the role of anteiso-BCFA in L. monocytogenes virulence by using mutants deficient in branched-chain alpha-keto acid dehydrogenase (BKD), an enzyme complex involved in the synthesis of BCFA. In tissue culture models of infection, anteiso-BCFA contributed to intracellular growth and survival in macrophages and significantly enhanced plaque formation upon prolonged infection in L2 fibroblasts. The intracellular defects observed could be attributed partially to insufficient listeriolysin O (LLO) production, indicating a requirement for anteiso-BCFA in regulating virulence factor production. In a murine model of infection, the BKD-deficient mutant was highly attenuated, further emphasizing the importance of BKD-mediated metabolism in L. monocytogenes virulence. This study demonstrates an underappreciated role for BCFA in bacterial pathogenesis, which may provide insight into the development and application of antimicrobial agents.
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Listeria monocytogenes PrsA2 is required for virulence factor secretion and bacterial viability within the host cell cytosol. Infect Immun 2010; 78:4944-57. [PMID: 20823208 DOI: 10.1128/iai.00532-10] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the course of establishing its replication niche within the cytosol of infected host cells, the facultative intracellular bacterial pathogen Listeria monocytogenes must efficiently regulate the secretion and activity of multiple virulence factors. L. monocytogenes encodes two predicted posttranslocation secretion chaperones, PrsA1 and PrsA2, and evidence suggests that PrsA2 has been specifically adapted for bacterial pathogenesis. PrsA-like chaperones have been identified in a number of Gram-positive bacteria, where they are reported to function at the bacterial membrane-cell wall interface to assist in the folding of proteins translocated across the membrane; in some cases, these proteins have been found to be essential for bacterial viability. In this study, the contributions of PrsA2 and PrsA1 to L. monocytogenes growth and protein secretion were investigated in vitro and in vivo. Neither PrsA2 nor PrsA1 was found to be essential for L. monocytogenes growth in broth culture; however, optimal bacterial viability was found to be dependent upon PrsA2 for L. monocytogenes located within the cytosol of host cells. Proteomic analyses of prsA2 mutant strains in the presence of a mutationally activated allele of the virulence regulator PrfA revealed a critical requirement for PrsA2 activity under conditions of PrfA activation, an event which normally takes place within the host cell cytosol. Despite a high degree of amino acid similarity, no detectable degree of functional overlap was observed between PrsA2 and PrsA1. Our results indicate a critical requirement for PrsA2 under conditions relevant to host cell infection.
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17
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Listeria monocytogenes as a rare cause of mycotic aortic aneurysm. J Vasc Surg 2010; 52:456-9. [PMID: 20670778 DOI: 10.1016/j.jvs.2010.03.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 03/16/2010] [Accepted: 03/20/2010] [Indexed: 11/20/2022]
Abstract
Mycotic aneurysms represent a diagnostic and therapeutic challenge still lacking general recommendations for optimal therapy. So far, Listeria monocytogenes (L. monocytogenes) is very rarely reported to be the causative organism of mycotic aortic aneurysms. We report 2 cases of mycotic abdominal aortic aneurysms due to L. monocytogenes infection being treated by radical debridement, open in situ reconstruction with aorto-bi-iliac Dacron grafts, and long-term antibiotic therapy. Both patients recovered well from surgery. Interestingly, the long-time follow-up for the first patient 9 years after surgery was entirely uneventful. Open debridement in an in situ reconstruction with Dacron grafts followed by antibiotic therapy seems to be a suitable therapeutic regime for mycotic aneurysms due to L. monocytogenes.
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The behaviour of both Listeria monocytogenes and rat ciliated ependymal cells is altered during their co-culture. PLoS One 2010; 5:e10450. [PMID: 20454610 PMCID: PMC2864257 DOI: 10.1371/journal.pone.0010450] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 04/06/2010] [Indexed: 11/19/2022] Open
Abstract
Background Ciliated ependymal cells line the cerebral ventricles and aqueducts separating the infected CSF from the brain parenchyma in meningitis. Principal Findings Investigation of the interaction of Listeria monocytogenes with cultured rat brain ependymal cells showed that certain strains reduced the beat frequency of the cilia but all the strains studied significantly reduced the ciliary beat amplitude (the linear distance travelled by the tip of each cilium per beat cycle). Conclusion The presence of the ependyma caused aggregation of some listeria strains and in some cases extracellular material also was seen in association with bacterial aggregates. These observations were dependent on the expression of genes required for invasion, intracellular survival and listerial cell to cell spread that are regulated by the transcriptional activator, positive regulatory factor A (PrfA).
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Pyruvate carboxylase plays a crucial role in carbon metabolism of extra- and intracellularly replicating Listeria monocytogenes. J Bacteriol 2010; 192:1774-84. [PMID: 20097852 DOI: 10.1128/jb.01132-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The human pathogen L. monocytogenes is a facultatively intracellular bacterium that survives and replicates in the cytosol of many mammalian cells. The listerial metabolism, especially under intracellular conditions, is still poorly understood. Recent studies analyzed the carbon metabolism of L. monocytogenes by the (13)C isotopologue perturbation method in a defined minimal medium containing [U-(13)C(6)]glucose. It was shown that these bacteria produce oxaloacetate mainly by carboxylation of pyruvate due to an incomplete tricarboxylic acid cycle. Here, we report that a pycA insertion mutant defective in pyruvate carboxylase (PYC) still grows, albeit at a reduced rate, in brain heart infusion (BHI) medium but is unable to multiply in a defined minimal medium with glucose or glycerol as a carbon source. Aspartate and glutamate of the pycA mutant, in contrast to the wild-type strain, remain unlabeled when [U-(13)C(6)]glucose is added to BHI, indicating that the PYC-catalyzed carboxylation of pyruvate is the predominant reaction leading to oxaloacetate in L. monocytogenes. The pycA mutant is also unable to replicate in mammalian cells and exhibits high virulence attenuation in the mouse sepsis model.
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Xayarath B, Marquis H, Port GC, Freitag NE. Listeria monocytogenes CtaP is a multifunctional cysteine transport-associated protein required for bacterial pathogenesis. Mol Microbiol 2009; 74:956-73. [PMID: 19818015 DOI: 10.1111/j.1365-2958.2009.06910.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The bacterial pathogen Listeria monocytogenes survives under a myriad of conditions in the outside environment and within the human host where infections can result in severe disease. Bacterial life within the host requires the expression of genes with roles in nutrient acquisition as well as the biosynthesis of bacterial products required to support intracellular growth. A gene product identified as the substrate-binding component of a novel oligopeptide transport system (encoded by lmo0135) was recently shown to be required for L. monocytogenes virulence. Here we demonstrate that lmo0135 encodes a multifunctional protein that is associated with cysteine transport, acid resistance, bacterial membrane integrity and adherence to host cells. The lmo0135 gene product (designated CtaP, for cysteine transport associated protein) was required for bacterial growth in the presence of low concentrations of cysteine in vitro, but was not required for bacterial replication within the host cytosol. Loss of CtaP increased membrane permeability and acid sensitivity, and reduced bacterial adherence to host cells. ctaP deletion mutants were severely attenuated following intragastric and intravenous inoculation of mice. Taken together, the data presented indicate that CtaP contributes to multiple facets of L. monocytogenes physiology, growth and survival both inside and outside of animal cells.
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Affiliation(s)
- Bobbi Xayarath
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA
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Freitag NE, Port GC, Miner MD. Listeria monocytogenes - from saprophyte to intracellular pathogen. Nat Rev Microbiol 2009; 7:623-8. [PMID: 19648949 DOI: 10.1038/nrmicro2171] [Citation(s) in RCA: 404] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Listeria monocytogenes is a bacterium that lives in the soil as a saprophyte but is capable of making the transition into a pathogen following its ingestion by susceptible humans or animals. Recent studies suggest that L. monocytogenes mediates its saprophyte-to-cytosolic-parasite transition through the careful modulation of the activity of a virulence regulatory protein known as PrfA, using a range of environmental cues that include available carbon sources. In this Progress article we describe the regulation of PrfA and its role in the L. monocytogenes transition from the saprophytic stage to the virulent intracellular stage.
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Affiliation(s)
- Nancy E Freitag
- Department of Microbiology and Immunology (MC790), University of Illinois at Chicago, 835 South Wolcott Avenue, Chicago, Illinois 606127344, USA.
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Miner MD, Port GC, Freitag NE. Functional impact of mutational activation on the Listeria monocytogenes central virulence regulator PrfA. MICROBIOLOGY-SGM 2008; 154:3579-3589. [PMID: 18957610 DOI: 10.1099/mic.0.2008/021063-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The transcriptional activator PrfA is required for the expression of virulence factors necessary for Listeria monocytogenes pathogenesis. PrfA is believed to become activated following L. monocytogenes entry into the cytosol of infected host cells, resulting in the induction of target genes whose products are required for bacterial intracellular growth and cell-to-cell spread. Several mutations have been identified that appear to lock PrfA into its highly activated cytosolic form (known as prfA* mutations). In this study PrfA and five PrfA* mutant proteins exhibiting differing degrees of activity were purified and analysed to define the influences of the mutations on distinct aspects of PrfA activity. Based on limited proteolytic digestion, conformational changes were detected for the PrfA* mutant proteins in comparison to wild-type PrfA. For all but one mutant (PrfA Y63C), the DNA binding affinity as measured by electophoretic mobility shift assay appeared to directly correlate with levels of PrfA mutational activation, such that the high-activity mutants exhibited the largest increases in DNA binding affinity and moderately activated mutants exhibited more moderate increases. Surprisingly, the ability of PrfA and PrfA* mutants to form dimers in solution appeared to inversely correlate with levels of PrfA-dependent gene expression. Based on comparisons of protein activity and structural similarities with PrfA family members Crp and CooA, the prfA* mutations modify distinct aspects of PrfA activity that include DNA binding and protein-protein interactions.
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Affiliation(s)
- Maurine D Miner
- Seattle Biomedical Research Institute, Seattle, WA, USA.,Program in Pathobiology, University of Washington, Seattle, WA, USA
| | - Gary C Port
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA.,Seattle Biomedical Research Institute, Seattle, WA, USA
| | - Nancy E Freitag
- Seattle Biomedical Research Institute, Seattle, WA, USA.,Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA.,Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA.,Program in Pathobiology, University of Washington, Seattle, WA, USA
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Selected prfA* mutations in recombinant attenuated Listeria monocytogenes strains augment expression of foreign immunogens and enhance vaccine-elicited humoral and cellular immune responses. Infect Immun 2008; 76:3439-50. [PMID: 18474644 DOI: 10.1128/iai.00245-08] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
While recombinant Listeria monocytogenes strains can be explored as vaccine candidates, it is important to develop attenuated but highly immunogenic L. monocytogenes vaccine vectors. Here, prfA* mutations selected on the basis of upregulated expression of L. monocytogenes PrfA-dependent genes and proteins were assessed to determine their abilities to augment expression of foreign immunogens in recombinant L. monocytogenes vectors and therefore enhance vaccine-elicited immune responses (a prfA* mutation is a mutation that results in constitutive overexpression of PrfA and PrfA-dependent virulence genes; the asterisk distinguishes the mutation from inactivation or stop mutations). A total of 63 recombinant L. monocytogenes vaccine vectors expressing seven individual viral or bacterial immunogens each in nine different L. monocytogenes strains carrying wild-type prfA or having prfA* mutations were constructed and investigated. Mutations selected on the basis of increased PrfA activation in recombinant L. monocytogenes prfA* vaccine vectors augmented expression of seven individual protein immunogens remarkably. Consistently, prime and boost vaccination studies with mice indicated that the prfA(G155S) mutation in recombinant L. monocytogenes DeltaactA prfA* strains enhanced vaccine-elicited cellular immune responses. Surprisingly, the prfA(G155S) mutation was found to enhance vaccine-elicited humoral immune responses as well. The highly immunogenic recombinant L. monocytogenes DeltaactA prfA* vaccine strains were as attenuated as the recombinant parent L. monocytogenes DeltaactA vaccine vector. Thus, recombinant attenuated L. monocytogenes DeltaactA prfA* vaccine vectors potentially are better antimicrobial and anticancer vaccines.
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