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Demey LM, Sinha R, DiRita VJ. An essential host dietary fatty acid promotes TcpH inhibition of TcpP proteolysis promoting virulence gene expression in Vibrio cholerae. mBio 2024:e0072124. [PMID: 38958446 DOI: 10.1128/mbio.00721-24] [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: 04/11/2024] [Accepted: 05/03/2024] [Indexed: 07/04/2024] Open
Abstract
Vibrio cholerae is a Gram-negative gastrointestinal pathogen responsible for the diarrheal disease cholera. Expression of key virulence factors, cholera toxin and toxin-coregulated pilus, is regulated directly by ToxT and indirectly by two transmembrane transcription regulators (TTRs), ToxR and TcpP, that promote the expression of toxT. TcpP abundance and activity are controlled by TcpH, a single-pass transmembrane protein, which protects TcpP from a two-step proteolytic process known as regulated intramembrane proteolysis (RIP). The mechanism of TcpH-mediated protection of TcpP represents a major gap in our understanding of V. cholerae pathogenesis. The absence of tcpH leads to unimpeded degradation of TcpP in vitro and a colonization defect in a neonate mouse model of V. cholerae colonization. Here, we show that TcpH protects TcpP from RIP via direct interaction. We also demonstrate that α-linolenic acid, a dietary fatty acid, promotes TcpH-dependent inhibition of RIP via co-association of TcpP and TcpH molecules within detergent-resistant membranes (DRMs) in a mechanism requiring the TcpH transmembrane domain. Taken together, our data support a model where V. cholerae cells use exogenous α-linolenic acid to remodel the phospholipid bilayer in vivo, leading to co-association of TcpP and TcpH within DRMs where RIP of TcpP is inhibited by TcpH, thereby promoting V. cholerae pathogenicity. IMPORTANCE Vibrio cholerae continues to pose a significant global burden on health and an alternative therapeutic approach is needed, due to evolving multidrug resistance strains. Transcription of toxT, stimulated by TcpP and ToxR, is essential for V. cholerae pathogenesis. Our results show that TcpP, one of the major regulators of toxT gene expression, is protected from proteolysis by TcpH, via direct interaction. Furthermore, we identified a gut metabolite, α-linolenic acid, that stimulates the co-association of TcpP and TcpH within detergent-resistant membranes (also known as lipid-ordered membrane domains), thereby supporting TcpH-dependent antagonism of TcpP proteolysis. Data presented here extend our knowledge of RIP, virulence gene regulation in V. cholerae, and, to the best of our knowledge, provides the first evidence that lipid-ordered membranes exist within V. cholerae. The model presented here also suggests that TTRs, common among bacteria and archaea, and co-component signal transduction systems present in Enterobacteria, could also be influenced similarly.
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Affiliation(s)
- Lucas M Demey
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Ritam Sinha
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Victor J DiRita
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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2
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Gubensäk N, Sagmeister T, Buhlheller C, Geronimo BD, Wagner GE, Petrowitsch L, Gräwert MA, Rotzinger M, Berger TMI, Schäfer J, Usón I, Reidl J, Sánchez-Murcia PA, Zangger K, Pavkov-Keller T. Vibrio cholerae's ToxRS bile sensing system. eLife 2023; 12:e88721. [PMID: 37768326 PMCID: PMC10624426 DOI: 10.7554/elife.88721] [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: 04/20/2023] [Accepted: 09/27/2023] [Indexed: 09/29/2023] Open
Abstract
The seventh pandemic of the diarrheal cholera disease, which began in 1960, is caused by the Gram-negative bacterium Vibrio cholerae. Its environmental persistence provoking recurring sudden outbreaks is enabled by V. cholerae's rapid adaption to changing environments involving sensory proteins like ToxR and ToxS. Located at the inner membrane, ToxR and ToxS react to environmental stimuli like bile acid, thereby inducing survival strategies for example bile resistance and virulence regulation. The presented crystal structure of the sensory domains of ToxR and ToxS in combination with multiple bile acid interaction studies, reveals that a bile binding pocket of ToxS is only properly folded upon binding to ToxR. Our data proposes an interdependent functionality between ToxR transcriptional activity and ToxS sensory function. These findings support the previously suggested link between ToxRS and VtrAC-like co-component systems. Besides VtrAC, ToxRS is now the only experimentally determined structure within this recently defined superfamily, further emphasizing its significance. In-depth analysis of the ToxRS complex reveals its remarkable conservation across various Vibrio species, underlining the significance of conserved residues in the ToxS barrel and the more diverse ToxR sensory domain. Unravelling the intricate mechanisms governing ToxRS's environmental sensing capabilities, provides a promising tool for disruption of this vital interaction, ultimately inhibiting Vibrio's survival and virulence. Our findings hold far-reaching implications for all Vibrio strains that rely on the ToxRS system as a shared sensory cornerstone for adapting to their surroundings.
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Affiliation(s)
- Nina Gubensäk
- Institute of Molecular Biosciences, University of GrazGrazAustria
| | - Theo Sagmeister
- Institute of Molecular Biosciences, University of GrazGrazAustria
| | | | - Bruno Di Geronimo
- Laboratory of Computer-Aided Molecular Design, Division of Medicinal Chemistry, Otto-Loewi Research Center, Medical University of GrazGrazAustria
| | - Gabriel E Wagner
- Institute of Chemistry / Organic and Bioorganic Chemistry, Medical University of GrazGrazAustria
- Diagnostic and Research Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of GrazGrazAustria
| | | | | | - Markus Rotzinger
- Institute of Chemistry / Organic and Bioorganic Chemistry, Medical University of GrazGrazAustria
| | | | | | - Isabel Usón
- Institute of Molecular Biology of BarcelonaBarcelonaSpain
- ICREA, Institució Catalana de Recerca i Estudis AvançatsBarcelonaSpain
| | - Joachim Reidl
- Institute of Molecular Biosciences, University of GrazGrazAustria
- BioHealth Field of Excellence, University of GrazGrazAustria
- BioTechMed-GrazGrazAustria
| | - Pedro A Sánchez-Murcia
- Laboratory of Computer-Aided Molecular Design, Division of Medicinal Chemistry, Otto-Loewi Research Center, Medical University of GrazGrazAustria
| | - Klaus Zangger
- Institute of Chemistry / Organic and Bioorganic Chemistry, Medical University of GrazGrazAustria
- BioHealth Field of Excellence, University of GrazGrazAustria
- BioTechMed-GrazGrazAustria
| | - Tea Pavkov-Keller
- Institute of Molecular Biosciences, University of GrazGrazAustria
- BioHealth Field of Excellence, University of GrazGrazAustria
- BioTechMed-GrazGrazAustria
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3
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Kristensen SS, Diep DB, Kjos M, Mathiesen G. The role of site-2-proteases in bacteria: a review on physiology, virulence, and therapeutic potential. MICROLIFE 2023; 4:uqad025. [PMID: 37223736 PMCID: PMC10202637 DOI: 10.1093/femsml/uqad025] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/21/2023] [Accepted: 05/02/2023] [Indexed: 05/25/2023]
Abstract
Site-2-proteases are a class of intramembrane proteases involved in regulated intramembrane proteolysis. Regulated intramembrane proteolysis is a highly conserved signaling mechanism that commonly involves sequential digestion of an anti-sigma factor by a site-1- and site-2-protease in response to external stimuli, resulting in an adaptive transcriptional response. Variation of this signaling cascade continues to emerge as the role of site-2-proteases in bacteria continues to be explored. Site-2-proteases are highly conserved among bacteria and play a key role in multiple processes, including iron uptake, stress response, and pheromone production. Additionally, an increasing number of site-2-proteases have been found to play a pivotal role in the virulence properties of multiple human pathogens, such as alginate production in Pseudomonas aeruginosa, toxin production in Vibrio cholerae, resistance to lysozyme in enterococci and antimicrobials in several Bacillus spp, and cell-envelope lipid composition in Mycobacterium tuberculosis. The prominent role of site-2-proteases in bacterial pathogenicity highlights the potential of site-2-proteases as novel targets for therapeutic intervention. In this review, we summarize the role of site-2-proteases in bacterial physiology and virulence, as well as evaluate the therapeutic potential of site-2-proteases.
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Affiliation(s)
- Sofie S Kristensen
- Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), 1433 Ås, Norway
| | | | - Morten Kjos
- Corresponding author. NMBU, P.O. Box 5003, 1433 Ås, Norway. E-mail:
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4
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Midgett CR, Kull FJ. Structural Insights into Regulation of Vibrio Virulence Gene Networks. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1404:269-294. [PMID: 36792881 DOI: 10.1007/978-3-031-22997-8_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
One of the best studied aspects of pathogenic Vibrios are the virulence cascades that lead to the production of virulence factors and, ultimately, clinical outcomes. In this chapter, we will examine the regulation of Vibrio virulence gene networks from a structural and biochemical perspective. We will discuss the recent research into the numerous proteins that contribute to regulating virulence in Vibrio spp such as quorum sensing regulator HapR, the transcription factors AphA and AphB, or the virulence regulators ToxR and ToxT. We highlight how insights gained from these studies are already illuminating the basic molecular mechanisms by which the virulence cascade of pathogenic Vibrios unfold and contend that understanding how protein interactions contribute to the host-pathogen communications will enable the development of new antivirulence compounds that can effectively target these pathogens.
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Affiliation(s)
| | - F Jon Kull
- Chemistry Department, Dartmouth College, Hanover, NH, USA.
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5
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Kinch LN, Cong Q, Jaishankar J, Orth K. Co-component signal transduction systems: Fast-evolving virulence regulation cassettes discovered in enteric bacteria. Proc Natl Acad Sci U S A 2022; 119:e2203176119. [PMID: 35648808 PMCID: PMC9214523 DOI: 10.1073/pnas.2203176119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/08/2022] [Indexed: 01/31/2023] Open
Abstract
Bacterial signal transduction systems sense changes in the environment and transmit these signals to control cellular responses. The simplest one-component signal transduction systems include an input sensor domain and an output response domain encoded in a single protein chain. Alternatively, two-component signal transduction systems transmit signals by phosphorelay between input and output domains from separate proteins. The membrane-tethered periplasmic bile acid sensor that activates the Vibrio parahaemolyticus type III secretion system adopts an obligate heterodimer of two proteins encoded by partially overlapping VtrA and VtrC genes. This co-component signal transduction system binds bile acid using a lipocalin-like domain in VtrC and transmits the signal through the membrane to a cytoplasmic DNA-binding transcription factor in VtrA. Using the domain and operon organization of VtrA/VtrC, we identify a fast-evolving superfamily of co-component systems in enteric bacteria. Accurate machine learning–based fold predictions for the candidate co-components support their homology in the twilight zone of rapidly evolving sequences and provide mechanistic hypotheses about previously unrecognized lipid-sensing functions.
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Affiliation(s)
- Lisa N. Kinch
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Qian Cong
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Jananee Jaishankar
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
- HHMI, University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390
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6
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Gao C, Garren M, Penn K, Fernandez VI, Seymour JR, Thompson JR, Raina JB, Stocker R. Coral mucus rapidly induces chemokinesis and genome-wide transcriptional shifts toward early pathogenesis in a bacterial coral pathogen. THE ISME JOURNAL 2021; 15:3668-3682. [PMID: 34168314 PMCID: PMC8630044 DOI: 10.1038/s41396-021-01024-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 05/12/2021] [Accepted: 05/25/2021] [Indexed: 02/06/2023]
Abstract
Elevated seawater temperatures have contributed to the rise of coral disease mediated by bacterial pathogens, such as the globally distributed Vibrio coralliilyticus, which utilizes coral mucus as a chemical cue to locate stressed corals. However, the physiological events in the pathogens that follow their entry into the coral host environment remain unknown. Here, we present simultaneous measurements of the behavioral and transcriptional responses of V. coralliilyticus BAA-450 incubated in coral mucus. Video microscopy revealed a strong and rapid chemokinetic behavioral response by the pathogen, characterized by a two-fold increase in average swimming speed within 6 min of coral mucus exposure. RNA sequencing showed that this bacterial behavior was accompanied by an equally rapid differential expression of 53% of the genes in the V. coralliilyticus genome. Specifically, transcript abundance 10 min after mucus exposure showed upregulation of genes involved in quorum sensing, biofilm formation, and nutrient metabolism, and downregulation of flagella synthesis and chemotaxis genes. After 60 min, we observed upregulation of genes associated with virulence, including zinc metalloproteases responsible for causing coral tissue damage and algal symbiont photoinactivation, and secretion systems that may export toxins. Together, our results suggest that V. coralliilyticus employs a suite of behavioral and transcriptional responses to rapidly shift into a distinct infection mode within minutes of exposure to the coral microenvironment.
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Affiliation(s)
- Cherry Gao
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Civil and Environmental Engineering, Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Zurich, Switzerland
| | - Melissa Garren
- Working Ocean Strategies LLC, Carmel, CA, USA
- Department of Applied Environmental Science, California State University Monterey Bay, Seaside, CA, USA
| | - Kevin Penn
- Department of Civil and Environmental Engineering, Ralph M. Parsons Laboratory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Vicente I Fernandez
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Zurich, Switzerland
| | - Justin R Seymour
- Climate Change Cluster (C3), University of Technology Sydney, Ultimo, NSW, Australia
| | - Janelle R Thompson
- Singapore Center for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- Asian School of the Environment, Nanyang Technological University, Singapore, Singapore
| | - Jean-Baptiste Raina
- Climate Change Cluster (C3), University of Technology Sydney, Ultimo, NSW, Australia
| | - Roman Stocker
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Zurich, Switzerland.
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7
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Abstract
Vibrio cholerae is a Gram-negative bacterium that causes the enteric disease cholera. V. cholerae colonization of the human intestine is dependent on the expression of both virulence genes and environmental adaptation genes involved in antimicrobial resistance. The expression of virulence genes, including the genes encoding for the main virulence factors cholera toxin (CT) and the toxin coregulated pilus (TCP), are coordinately regulated by the ToxR regulon. Tripartite transport systems belonging to the ATP binding cassette, major facilitator, and Resistance-Nodulation-Division families are critical for V. cholerae pathogenesis. Transport systems belonging to these families contribute to myriad phenotypes including protein secretion, antimicrobial resistance and virulence. TolC plays a central role in bacterial physiology by functioning as the outer membrane pore protein for tripartite transport systems. Consistent with this, V. cholerae tolC was previously found to be required for MARTX toxin secretion and antimicrobial resistance. Herein we investigated the contribution of TolC to V. cholerae virulence. We documented that tolC was required for CT and TCP production in O1 El Tor V. cholerae. This phenotype was linked to repression of the critical ToxR regulon transcription factor aphA. Decreased aphA transcription correlated with increased expression of the LysR-family transcription factor leuO. Deletion of leuO restored aphA expression, and CT and TCP production, in a tolC mutant. The collective results document that tolC is required for ToxR regulon expression and further suggest that tolC may participate in a efflux-dependent feedback circuit to regulate virulence gene expression.
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8
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Quinn JD, Weening EH, Miller VL. PsaF Is a Membrane-Localized pH Sensor That Regulates psaA Expression in Yersinia pestis. J Bacteriol 2021; 203:e0016521. [PMID: 34060904 PMCID: PMC8407435 DOI: 10.1128/jb.00165-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 05/21/2021] [Indexed: 12/30/2022] Open
Abstract
The Yersinia pestis pH 6 antigen (PsaA) forms fimbria-like structures and is required for full virulence during bubonic plague. High temperature and low pH regulate PsaA production, and while recent work has uncovered the molecular aspects of temperature control, the mechanisms underlying this unusual regulation by pH are poorly understood. Using defined growth conditions, we recently showed that high levels of PsaE and PsaF (two regulatory proteins required for expression of psaA) are present at mildly acidic pH, but these levels are greatly reduced at neutral pH, resulting in low psaA expression. In prior work, the use of translational reporters suggested that pH had no impact on translation of psaE and psaF, but rather affected protein stability of PsaE and/or PsaF. Here, we investigated the pH-dependent posttranslational mechanisms predicted to regulate PsaE and PsaF stability. Using antibodies that recognize the endogenous proteins, we showed that the amount of PsaE and PsaF is defined by a distinct pH threshold. Analysis of histidine residues in the periplasmic domain of PsaF suggested that it functions as a pH sensor and indicated that the presence of PsaF is important for PsaE stability. At neutral pH, when PsaF is absent, PsaE appears to be targeted for proteolytic degradation by regulated intramembrane proteolysis. Together, our work shows that Y. pestis utilizes PsaF as a pH sensor to control psaA expression by enhancing the stability of PsaE, an essential psaA regulatory protein. IMPORTANCE Yersinia pestis is a bacterial pathogen that causes bubonic plague in humans. As Y. pestis cycles between fleas and mammals, it senses the environment within each host to appropriately control gene expression. PsaA is a protein that forms fimbria-like structures and is required for virulence. High temperature and low pH together stimulate psaA transcription by increasing the levels of two essential integral membrane regulators, PsaE and PsaF. Histidine residues in the PsaF periplasmic domain enable it to function as a pH sensor. In the absence of PsaF, PsaE (a DNA-binding protein) appears to be targeted for proteolytic degradation, thus preventing expression of psaA. This work offers insight into the mechanisms that bacteria use to sense pH and control virulence gene expression.
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Affiliation(s)
- Joshua D. Quinn
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Eric H. Weening
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Virginia L. Miller
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USA
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina, USA
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9
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ToxR Mediates the Antivirulence Activity of Phenyl-Arginine-β-Naphthylamide To Attenuate Vibrio cholerae Virulence. Infect Immun 2021; 89:e0014721. [PMID: 33941578 DOI: 10.1128/iai.00147-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multidrug efflux systems belonging to the resistance-nodulation-cell division (RND) family are ubiquitous in Gram-negative bacteria and are critical for antimicrobial resistance. This realization has led to efforts to develop efflux pump inhibitors (EPI) for use as adjuvants for antibiotic treatment of resistant organisms. However, the functions of RND transporters extend beyond antimicrobial resistance to include physiological functions that are critical for pathogenesis, suggesting that EPIs could also be used as antivirulence therapeutics. This was documented in the enteric pathogen Vibrio cholerae, in which EPIs were shown to attenuate the production of the critical virulence factors cholera toxin (CT) and the toxin-coregulated pilus (TCP). In this study, we investigated the antivirulence mechanism of action of the EPI phenyl-arginine-β-naphthylamide (PAβN) on V. cholerae. Using bioassays, we documented that PAβN inhibited virulence factor production in three epidemic V. cholerae isolates. Transcriptional reporter studies and mutant analysis indicated that PAβN initiated a ToxR-dependent regulatory circuit to activate leuO expression and that LeuO repressed the expression of the critical virulence activator aphA to attenuate CT and TCP production. The antivirulence activity of PAβN was found to be dependent on the ToxR periplasmic sensing domain (PPD), suggesting that a feedback mechanism was involved in its activity. Collectively, the data indicated that PAβN inhibited V. cholerae virulence factor production by activating a ToxR-dependent metabolic feedback mechanism to repress the expression of the ToxR virulence regulon. This suggests that efflux pump inhibitors could be used as antivirulence therapeutics for the treatment of cholera and perhaps that of other Gram-negative pathogens.
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10
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Gubensäk N, Wagner GE, Schrank E, Falsone FS, Berger TMI, Pavkov-Keller T, Reidl J, Zangger K. The periplasmic domains of Vibriocholerae ToxR and ToxS are forming a strong heterodimeric complex independent on the redox state of ToxR cysteines. Mol Microbiol 2021; 115:1277-1291. [PMID: 33368680 PMCID: PMC8359183 DOI: 10.1111/mmi.14673] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/18/2020] [Accepted: 12/18/2020] [Indexed: 01/24/2023]
Abstract
The transmembrane protein ToxR plays a key role in the virulence expression system of Vibrio cholerae. The activity of ToxR is dependent on its periplasmic sensor domain (ToxRp) and on the inner membrane protein ToxS. Herein, we present the Nuclear Magnetic Resonance NMR solution structure of the sensory ToxRp containing an intramolecular disulfide bond. The presented structural and dynamic experiments with reduced and oxidized ToxRp propose an explanation for the increased proteolytic sensitivity of reduced ToxR. Additionally, for the first time, we could identify the formation of a strong heterodimer complex between the periplasmic domains of ToxR and ToxS in solution. NMR interaction studies reveal that binding of ToxS is not dependent on the redox state of ToxR cysteines, and formed complexes are structurally similar. By monitoring the proteolytic cleavage of ToxRp with NMR, we additionally provide a direct evidence of ToxS protective function. Taken together our results suggest that ToxR activity is regulated by its stability which is, on the one hand, dependent on the redox states of its cysteines, influencing the stability of its fold, and on the other hand, on its interaction with ToxS, which binds independent on the cysteines and acts as a protection against proteases.
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Affiliation(s)
- Nina Gubensäk
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria.,Institute of Molecular Biosciences, University of Graz, Graz, Austria
| | - Gabriel E Wagner
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria.,Diagnostic and Research Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria
| | - Evelyne Schrank
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria
| | - Fabio S Falsone
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria.,KAGes Healthcare, Graz, Austria
| | | | - Tea Pavkov-Keller
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria.,Field of Excellence BioHealth, University of Graz, Graz, Austria
| | - Joachim Reidl
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria.,Field of Excellence BioHealth, University of Graz, Graz, Austria
| | - Klaus Zangger
- Institute of Chemistry/Organic and Bioorganic Chemistry, University of Graz, Graz, Austria.,BioTechMed-Graz, Graz, Austria.,Field of Excellence BioHealth, University of Graz, Graz, Austria
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11
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Zhou Y, Lee ZL, Zhu J. On or Off: Life-Changing Decisions Made by Vibrio cholerae Under Stress. INFECTIOUS MICROBES & DISEASES 2020; 2:127-135. [PMID: 38630076 PMCID: PMC7769058 DOI: 10.1097/im9.0000000000000037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/20/2020] [Accepted: 08/23/2020] [Indexed: 11/25/2022]
Abstract
Vibrio cholerae, the causative agent of the infectious disease, cholera, is commonly found in brackish waters and infects human hosts via the fecal-oral route. V. cholerae is a master of stress resistance as V. cholerae's dynamic lifestyle across different physical environments constantly exposes it to diverse stressful circumstances. Specifically, V. cholerae has dedicated genetic regulatory networks to sense different environmental cues and respond to these signals. With frequent outbreaks costing a tremendous amount of lives and increased global water temperatures providing more suitable aquatic habitats for V. cholerae, cholera pandemics remain a probable catastrophic threat to humanity. Understanding how V. cholerae copes with different environmental stresses broadens our repertoire of measures against infectious diseases and expands our general knowledge of prokaryotic stress responses. In this review, we summarize the regulatory mechanisms of how V. cholerae fights against stresses in vivo and in vitro.
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12
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Hsiao A, Zhu J. Pathogenicity and virulence regulation of Vibrio cholerae at the interface of host-gut microbiome interactions. Virulence 2020; 11:1582-1599. [PMID: 33172314 PMCID: PMC7671094 DOI: 10.1080/21505594.2020.1845039] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 12/12/2022] Open
Abstract
The Gram-negative bacterium Vibrio cholerae is responsible for the severe diarrheal pandemic disease cholera, representing a major global public health concern. This pathogen transitions from aquatic reservoirs into epidemics in human populations, and has evolved numerous mechanisms to sense this transition in order to appropriately regulate its gene expression for infection. At the intersection of pathogen and host in the gastrointestinal tract lies the community of native gut microbes, the gut microbiome. It is increasingly clear that the diversity of species and biochemical activities within the gut microbiome represents a driver of infection outcome, through their ability to manipulate the signals used by V. cholerae to regulate virulence and fitness in vivo. A better mechanistic understanding of how commensal microbial action interacts with V. cholerae pathogenesis may lead to novel prophylactic and therapeutic interventions for cholera. Here, we review a subset of this burgeoning field of research.
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Affiliation(s)
- Ansel Hsiao
- Department of Microbiology & Plant Pathology, University of California Riverside, Riverside, CA, USA
| | - Jun Zhu
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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13
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Wettstadt S, Llamas MA. Role of Regulated Proteolysis in the Communication of Bacteria With the Environment. Front Mol Biosci 2020; 7:586497. [PMID: 33195433 PMCID: PMC7593790 DOI: 10.3389/fmolb.2020.586497] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 09/22/2020] [Indexed: 12/29/2022] Open
Abstract
For bacteria to flourish in different niches, they need to sense signals from the environment and translate these into appropriate responses. Most bacterial signal transduction systems involve proteins that trigger the required response through the modification of gene transcription. These proteins are often produced in an inactive state that prevents their interaction with the RNA polymerase and/or the DNA in the absence of the inducing signal. Among other mechanisms, regulated proteolysis is becoming increasingly recognized as a key process in the modulation of the activity of these signal response proteins. Regulated proteolysis can either produce complete degradation or specific cleavage of the target protein, thus modifying its function. Because proteolysis is a fast process, the modulation of signaling proteins activity by this process allows for an immediate response to a given signal, which facilitates adaptation to the surrounding environment and bacterial survival. Moreover, regulated proteolysis is a fundamental process for the transmission of extracellular signals to the cytosol through the bacterial membranes. By a proteolytic mechanism known as regulated intramembrane proteolysis (RIP) transmembrane proteins are cleaved within the plane of the membrane to liberate a cytosolic domain or protein able to modify gene transcription. This allows the transmission of a signal present on one side of a membrane to the other side where the response is elicited. In this work, we review the role of regulated proteolysis in the bacterial communication with the environment through the modulation of the main bacterial signal transduction systems, namely one- and two-component systems, and alternative σ factors.
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Affiliation(s)
- Sarah Wettstadt
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - María A Llamas
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
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14
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M Jayakumar J, Balasubramanian D, Reddi G, Almagro-Moreno S. Synergistic role of abiotic factors driving viable but non-culturable Vibrio cholerae. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:454-465. [PMID: 32542975 DOI: 10.1111/1758-2229.12861] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/06/2020] [Accepted: 06/13/2020] [Indexed: 06/11/2023]
Abstract
Vibrio cholerae O1, a natural inhabitant of estuarine environments, is found in a dormant, viable but non-culturable (VBNC) state during interepidemic periods. Although the individual roles of abiotic factors affecting VBNC formation have been extensively studied, their interplay in driving this phenomenon remains largely unaddressed. Here, we identified that major abiotic factors synergize with low nutrient conditions governing entry of cells into the VBNC state. Specifically, V. cholerae cells exposed to a combination of alkaline pH and high salinity under aeration at low temperatures (VBNC-inducing conditions) synergize to facilitate rapid entry into VBNC, whereas the opposite conditions prevented entry into the state. The major virulence regulator ToxR, and the stringent response protein RelA played opposing roles, repressing and facilitating VBNC entry respectively. Further, VBNC-inducing conditions negated the effects of ToxR and RelA, facilitating rapid formation of VBNC cells. In summary, this study highlights the synergy between critical abiotic factors and identified ToxR and RelA as two associated regulators, allowing for the persistence of V. cholerae in aquatic environments. Insights obtained in this study will help better understand environmental survival non-sporulating bacteria and transmission of facultative bacterial pathogens.
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Affiliation(s)
- Jane M Jayakumar
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816
- National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL, 32816
| | - Deepak Balasubramanian
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816
- National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL, 32816
| | - Geethika Reddi
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816
- National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL, 32816
| | - Salvador Almagro-Moreno
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816
- National Center for Integrated Coastal Research, University of Central Florida, Orlando, FL, 32816
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15
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Midgett CR, Swindell RA, Pellegrini M, Jon Kull F. A disulfide constrains the ToxR periplasmic domain structure, altering its interactions with ToxS and bile-salts. Sci Rep 2020; 10:9002. [PMID: 32488093 PMCID: PMC7265457 DOI: 10.1038/s41598-020-66050-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 05/13/2020] [Indexed: 11/10/2022] Open
Abstract
ToxR is a transmembrane transcription factor that, together with its integral membrane periplasmic binding partner ToxS, is conserved across the Vibrionaceae family. In some pathogenic Vibrios, including V. parahaemolyticus and V. cholerae, ToxR is required for bile resistance and virulence, and ToxR is fully activated and protected from degradation by ToxS. ToxS achieves this in part by ensuring formation of an intra-chain disulfide bond in the C-terminal periplasmic domain of ToxR (dbToxRp). In this study, biochemical analysis showed dbToxRp to have a higher affinity for the ToxS periplasmic domain than the non-disulfide bonded conformation. Analysis of our dbToxRp crystal structure showed this is due to disulfide bond stabilization. Furthermore, dbToxRp is structurally homologous to the V. parahaemolyticus VtrA periplasmic domain. These results highlight the critical structural role of disulfide bond in ToxR and along with VtrA define a domain fold involved in environmental sensing conserved across the Vibrionaceae family.
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Affiliation(s)
| | | | | | - F Jon Kull
- Department of Chemistry, Dartmouth College, Hanover, NH, USA
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16
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Stringent response interacts with the ToxR regulon to regulate Vibrio cholerae virulence factor expression. Arch Microbiol 2020; 202:1359-1368. [DOI: 10.1007/s00203-020-01847-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 02/03/2020] [Accepted: 02/25/2020] [Indexed: 10/24/2022]
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17
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Morgan SJ, French EL, Plecha SC, Krukonis ES. The wing of the ToxR winged helix-turn-helix domain is required for DNA binding and activation of toxT and ompU. PLoS One 2019; 14:e0221936. [PMID: 31498842 PMCID: PMC6733452 DOI: 10.1371/journal.pone.0221936] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 08/19/2019] [Indexed: 02/02/2023] Open
Abstract
ToxR and TcpP, two winged helix-turn-helix (w-HTH) family transcription factors, co-activate expression of the toxT promoter in Vibrio cholerae. ToxT then directly regulates a number of genes required for virulence. In addition to co-activation of toxT, ToxR can directly activate the ompU promoter and repress the ompT promoter. Based on a previous study suggesting that certain wing residues of ToxR are preferentially involved in toxT co-activation compared to direct ompU activation, we employed alanine-scanning mutagenesis to determine which residues in the wing of ToxR are required for activation of each promoter. All of the ToxR wing residues tested that were critical for transcriptional activation of toxT and/or ompU were also critical for DNA binding. While some ToxR wing mutants had reduced interaction with TcpP, that reduced interaction did not correlate with a specific defect in toxT activation. Rather, such mutants also affected ompU activation and DNA binding. Based on these findings we conclude that the primary role of the wing of ToxR is to bind DNA, along with the DNA recognition helix of ToxR, and this function is required both for direct activation of ompU and co-activation of toxT.
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Affiliation(s)
- Sarah J. Morgan
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, United States of America
| | - Emily L. French
- Division of Integrated Biomedical Sciences, University of Detroit Mercy School of Dentistry, Detroit, MI, United States of America
| | - Sarah C. Plecha
- Division of Integrated Biomedical Sciences, University of Detroit Mercy School of Dentistry, Detroit, MI, United States of America
| | - Eric S. Krukonis
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, United States of America
- Division of Integrated Biomedical Sciences, University of Detroit Mercy School of Dentistry, Detroit, MI, United States of America
- Department of Biochemistry, Microbiology and Immunology, Wayne State University, Detroit, MI, United States of America
- * E-mail:
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18
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Temperature Control of psaA Expression by PsaE and PsaF in Yersinia pestis. J Bacteriol 2019; 201:JB.00217-19. [PMID: 31138630 PMCID: PMC6657601 DOI: 10.1128/jb.00217-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 05/22/2019] [Indexed: 12/19/2022] Open
Abstract
Y. pestis is a Gram-negative bacterial pathogen that causes bubonic plague. As a vector-borne pathogen, Y. pestis fluctuates between an arthropod vector (flea) and mammalian host. As such, Y. pestis must recognize environmental signals encountered within each host environment and respond by appropriately regulating gene expression. PsaA is a key Y. pestis mammalian virulence determinant that forms fimbriae. Our work provides evidence that Y. pestis utilizes multiple posttranscriptional mechanisms to regulate the levels of two PsaA regulatory proteins in response to both temperature and pH. This study offers insight into mechanisms that bacteria utilize to sense environmental cues and regulate the expression of determinants required for mammalian disease. PsaA, the subunit of the fimbria originally referred to as the “pH 6 antigen,” is required for full virulence of Yersinia pestis during bubonic plague. The expression of psaA is dependent upon specific environmental signals, and while the signals (high temperature and acidic pH) are defined, the mechanisms underlying this regulation remain unclear. In the closely related species Yersinia pseudotuberculosis, psaA transcription requires two regulatory genes, psaE and psaF, and it is speculated that posttranscriptional regulation of PsaE and/or PsaF contributes to the regulation of psaA transcription. Few studies have examined the regulation of psaA expression in Y. pestis, and prior to this work, the roles of psaE and psaF in Y. pestis had not been defined. The data presented here show that both psaE and psaF are required for psaA transcription in Y. pestis and that the impact of temperature and pH is mediated through discrete posttranscriptional effects on PsaE and PsaF. By generating antibodies that recognize endogenous PsaE and PsaF, we determined that the levels of both proteins are impacted by temperature and pH. High temperature is required for psaE and psaF translation via discrete mechanisms mediated by the mRNA 5′ untranslated region (UTR) upstream of each gene. Additionally, levels of PsaE and PsaF are impacted by pH. We show that PsaF enhances the stability of PsaE, and thus, both PsaE and PsaF are required for psaA transcription. Our data indicate that the environmental signals (temperature and pH) impact the expression of psaA by affecting the translation of psaE and psaF and the stability of PsaE and PsaF. IMPORTANCEY. pestis is a Gram-negative bacterial pathogen that causes bubonic plague. As a vector-borne pathogen, Y. pestis fluctuates between an arthropod vector (flea) and mammalian host. As such, Y. pestis must recognize environmental signals encountered within each host environment and respond by appropriately regulating gene expression. PsaA is a key Y. pestis mammalian virulence determinant that forms fimbriae. Our work provides evidence that Y. pestis utilizes multiple posttranscriptional mechanisms to regulate the levels of two PsaA regulatory proteins in response to both temperature and pH. This study offers insight into mechanisms that bacteria utilize to sense environmental cues and regulate the expression of determinants required for mammalian disease.
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19
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Pennetzdorfer N, Lembke M, Pressler K, Matson JS, Reidl J, Schild S. Regulated Proteolysis in Vibrio cholerae Allowing Rapid Adaptation to Stress Conditions. Front Cell Infect Microbiol 2019; 9:214. [PMID: 31293982 PMCID: PMC6598108 DOI: 10.3389/fcimb.2019.00214] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 06/03/2019] [Indexed: 12/30/2022] Open
Abstract
The lifecycle of the causative agent of the severe secretory diarrheal disease cholera, Vibrio cholerae, is characterized by the transition between two dissimilar habitats, i.e., as a natural inhabitant of aquatic ecosystems and as a pathogen in the human gastrointestinal tract. Vibrio cholerae faces diverse stressors along its lifecycle, which require effective adaptation mechanisms to facilitate the survival fitness. Not surprisingly, the pathogen's transcriptome undergoes global changes during the different stages of the lifecycle. Moreover, recent evidence indicates that several of the transcription factors (i.e., ToxR, TcpP, and ToxT) and alternative sigma factors (i.e., FliA, RpoS, and RpoE) involved in transcriptional regulations along the lifecycle are controlled by regulated proteolysis. This post-translational control ensures a fast strategy by the pathogen to control cellular checkpoints and thereby rapidly respond to changing conditions. In this review, we discuss selected targets for regulated proteolysis activated by various stressors, which represent a key feature for fast adaptation of V. cholerae.
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Affiliation(s)
| | - Mareike Lembke
- Institute of Molecular Microbiology, University of Graz, Graz, Austria
| | | | - Jyl S Matson
- Department of Medical Microbiology and Immunology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States
| | - Joachim Reidl
- Institute of Molecular Microbiology, University of Graz, Graz, Austria.,BioTechMed Graz, Graz, Austria
| | - Stefan Schild
- Institute of Molecular Microbiology, University of Graz, Graz, Austria.,BioTechMed Graz, Graz, Austria
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20
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Lembke M, Pennetzdorfer N, Tutz S, Koller M, Vorkapic D, Zhu J, Schild S, Reidl J. Proteolysis of ToxR is controlled by cysteine-thiol redox state and bile salts in Vibrio cholerae. Mol Microbiol 2018; 110:796-810. [PMID: 30218472 PMCID: PMC6242745 DOI: 10.1111/mmi.14125] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 09/07/2018] [Accepted: 09/07/2018] [Indexed: 01/25/2023]
Abstract
In Vibrio cholerae, virulence gene expression is regulated by a transmembrane-localized transcription factor complex designated as ToxRS. ToxR harbours two cysteines in the periplasmic domain that can form inter- and intramolecular disulfide bonds. In this study, we investigated the σE -dependent inner membrane proteolysis of ToxR, which occurs via the periplasmic-localized proteases DegS and DegP. Both proteases respond to the redox state of the two cysteine thiol groups of ToxR. Interestingly, in the presence of sodium deoxycholate, ToxR proteolysis is blocked independently of ToxS, whereas ToxR activation by bile salts requires ToxS function. From these data, we identified at least two levels of control for ToxR activation by sodiumdeoxycholate. First, bile inhibits ToxR degradation under starvation and alkaline pH or under conditions in which DegPS responds to the reduced disulfide bonds of ToxR. The second level links bile to ToxRS complex formation and further activation of its transcription factor activity. Overall, our data suggest a comprehensive bile sensory function for the ToxRS complex during host colonization.
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Affiliation(s)
- Mareike Lembke
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
| | - Nina Pennetzdorfer
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
| | - Sarah Tutz
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
| | - Michael Koller
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
| | - Dina Vorkapic
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
| | - Jun Zhu
- Department of MicrobiologyUniversity of PennsylvaniaPhiladelphiaPA19104‐6076USA
| | - Stefan Schild
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
- BioTechMed‐GrazGrazA‐8010Austria
| | - Joachim Reidl
- Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 50GrazA‐8010Austria
- BioTechMed‐GrazGrazA‐8010Austria
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21
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Peterson KM, Gellings PS. Multiple intraintestinal signals coordinate the regulation of Vibrio cholerae virulence determinants. Pathog Dis 2018; 76:4791527. [PMID: 29315383 DOI: 10.1093/femspd/ftx126] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 12/27/2017] [Indexed: 12/17/2022] Open
Abstract
Vibrio cholerae is a Gram-negative motile bacterium capable of causing fatal pandemic disease in humans via oral ingestion of contaminated water or food. Within the human intestine, the motile vibrios must evade the innate host defense mechanisms, penetrate the mucus layer covering the small intestine, adhere to and multiply on the surface of the microvilli and cause disease via the action of cholera toxin. The explosive diarrhea associated with V. cholerae intestinal colonization leads to dissemination of the vibrios back into the environment to complete this phase of the life cycle. The host phase of the vibrio life cycle is made possible via the concerted action of a signaling cascade that controls the synthesis of V. cholerae colonization determinants. These virulence proteins are coordinately synthesized in response to specific host signals that are still largely undefined. A more complete understanding of the molecular events involved in the V. cholerae recognition of intraintestinal signals and the subsequent transcriptional response will provide important information regarding how pathogenic bacteria establish infection and provide novel methods for treating and/or preventing bacterial infections such as Asiatic cholera. This review will summarize what is currently known in regard to host intraintestinal signals that inform the complex ToxR regulatory cascade in order to coordinate in a spatial and temporal fashion virulence protein synthesis within the human small intestine.
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Affiliation(s)
- Kenneth M Peterson
- Department of Microbiology and Immunology, Louisiana State University Health Science Center, Shreveport, LA 71130, USA
| | - Patrick S Gellings
- Department of Microbiology and Immunology, Louisiana State University Health Science Center, Shreveport, LA 71130, USA
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22
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Herbst S, Lorkowski M, Sarenko O, Nguyen TKL, Jaenicke T, Hengge R. Transmembrane redox control and proteolysis of PdeC, a novel type of c-di-GMP phosphodiesterase. EMBO J 2018; 37:e97825. [PMID: 29514851 PMCID: PMC5897775 DOI: 10.15252/embj.201797825] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 01/31/2018] [Accepted: 02/08/2018] [Indexed: 12/17/2022] Open
Abstract
The nucleotide second messenger c-di-GMP nearly ubiquitously promotes bacterial biofilm formation, with enzymes that synthesize and degrade c-di-GMP being controlled by diverse N-terminal sensor domains. Here, we describe a novel class of widely occurring c-di-GMP phosphodiesterases (PDE) that feature a periplasmic "CSS domain" with two highly conserved cysteines that is flanked by two transmembrane regions (TM1 and TM2) and followed by a cytoplasmic EAL domain with PDE activity. Using PdeC, one of the five CSS domain PDEs of Escherichia coli K-12, we show that DsbA/DsbB-promoted disulfide bond formation in the CSS domain reduces PDE activity. By contrast, the free thiol form is enzymatically highly active, with the TM2 region promoting dimerization. Moreover, this form is processed by periplasmic proteases DegP and DegQ, yielding a highly active TM2 + EAL fragment that is slowly removed by further proteolysis. Similar redox control and proteolysis was also observed for a second CSS domain PDE, PdeB. At the physiological level, CSS domain PDEs modulate production and supracellular architecture of extracellular matrix polymers in the deeper layers of mature E. coli biofilms.
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Affiliation(s)
- Susanne Herbst
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Martin Lorkowski
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Olga Sarenko
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Thi Kim Loan Nguyen
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Tina Jaenicke
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Regine Hengge
- Institut für Biologie/Mikrobiologie, Humboldt-Universität zu Berlin, Berlin, Germany
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23
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Sakib SN, Reddi G, Almagro-Moreno S. Environmental role of pathogenic traits in Vibrio cholerae. J Bacteriol 2018; 200:e00795-17. [PMID: 29581410 PMCID: PMC6040180 DOI: 10.1128/jb.00795-17] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Vibrio cholerae is a natural inhabitant of aquatic ecosystems. Some strains of V. cholerae can colonize the human host and cause cholera, a profuse watery diarrhea. The major pathogenicity factors and virulence regulators of V. cholerae are either encoded in mobile genetic elements acquired in the environment (e.g. pathogenicity islands or lysogenic phages) or in the core genome. Several lines of evidence indicate that the emergence of numerous virulence traits of V. cholerae occurred in its natural environment due to biotic and abiotic pressures. Here, we discuss the connection between the human host and the potential ecological role of these virulent traits. Unraveling these connections will help us understand the emergence of this organism and other facultative bacterial pathogens.
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Affiliation(s)
- S Nazmus Sakib
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32816, USA
| | - Geethika Reddi
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32816, USA
| | - Salvador Almagro-Moreno
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32816, USA.
- National Center for Integrated Coastal Research, University of Central Florida, Orlando, Florida 32816, USA
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24
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Midgett CR, Almagro-Moreno S, Pellegrini M, Taylor RK, Skorupski K, Kull FJ. Bile salts and alkaline pH reciprocally modulate the interaction between the periplasmic domains of Vibrio cholerae ToxR and ToxS. Mol Microbiol 2017; 105:258-272. [PMID: 28464377 DOI: 10.1111/mmi.13699] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/21/2017] [Indexed: 12/31/2022]
Abstract
ToxR is a transmembrane transcription factor that is essential for virulence gene expression and human colonization by Vibrio cholerae. ToxR requires its operon partner ToxS, a periplasmic integral membrane protein, for full activity. These two proteins are thought to interact through their respective periplasmic domains, ToxRp and ToxSp. In addition, ToxR is thought to be responsive to various environmental cues, such as bile salts and alkaline pH, but how these factors influence ToxR is not yet understood. Using NMR and reciprocal pull down assays, we present the first direct evidence that ToxR and ToxS physically interact. Furthermore, using NMR and DSF, it was shown that the bile salts cholate and chenodeoxycholate interact with purified ToxRp and destabilize it. Surprisingly, bile salt destabilization of ToxRp enhanced the interaction between ToxRp and ToxSp. In contrast, alkaline pH, which is one of the factors that leads to ToxR proteolysis, decreased the interaction between ToxRp and ToxSp. Taken together, these data suggest a model whereby bile salts or other detergents destabilize ToxR, increasing its interaction with ToxS to promote full ToxR activity. Subsequently, as V. cholerae alkalinizes its environment in late stationary phase, the interaction between the two proteins decreases, allowing ToxR proteolysis to proceed.
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Affiliation(s)
| | - Salvador Almagro-Moreno
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32816, USA
| | - Maria Pellegrini
- Department of Chemistry, Dartmouth College, Hanover, NH, 03755, USA
| | - Ronald K Taylor
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH, 03755, USA
| | - Karen Skorupski
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, NH, 03755, USA
| | - F Jon Kull
- Department of Chemistry, Dartmouth College, Hanover, NH, 03755, USA
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25
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Rivera-Cancel G, Orth K. Biochemical basis for activation of virulence genes by bile salts in Vibrio parahaemolyticus. Gut Microbes 2017; 8:366-373. [PMID: 28129014 PMCID: PMC5570421 DOI: 10.1080/19490976.2017.1287655] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Bile salts act as a stressor to bacteria that transit the intestinal tract. Enteric pathogens have hijacked bile as an intestinal signal to regulate virulence factors. We recently demonstrated that Vibrio parahemolyticus senses bile salts via a heterodimeric receptor formed by the periplasmic domains of inner-membrane proteins VtrA and VtrC. Crystal structures of the periplasmic complex reveal that VtrA and VtrC form a β-barrel that binds bile salts in its hydrophobic interior to activate the VtrA cytoplasmic DNA-binding domain. Proteins with the same domain arrangement as VtrA and VtrC are widespread in Vibrio and related bacteria, where they are involved in regulating virulence and other unknown functions. Here we discuss our findings and review current knowledge on VtrA and VtrC homologs. We propose that signaling by these membrane-bound transcription factors can be advantageous for the regulation of membrane and secretory proteins.
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Affiliation(s)
- Giomar Rivera-Cancel
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA,CONTACT Kim Orth
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26
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Pressler K, Vorkapic D, Lichtenegger S, Malli G, Barilich BP, Cakar F, Zingl FG, Reidl J, Schild S. AAA+ proteases and their role in distinct stages along the Vibrio cholerae lifecycle. Int J Med Microbiol 2016; 306:452-62. [PMID: 27345492 DOI: 10.1016/j.ijmm.2016.05.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 05/09/2016] [Accepted: 05/24/2016] [Indexed: 12/29/2022] Open
Abstract
The facultative human pathogen Vibrio cholerae has to adapt to different environmental conditions along its lifecycle by means of transcriptional, translational and post-translational regulation. This study provides a first comprehensive analysis regarding the contribution of the cytoplasmic AAA+ proteases Lon, ClpP and HslV to distinct features of V. cholerae behaviour, including biofilm formation, motility, cholera toxin expression and colonization fitness in the mouse model. While absence of HslV did not yield to any altered phenotype compared to wildtype, absence of Lon or ClpP resulted in significantly reduced colonization in vivo. In addition, a Δlon deletion mutant showed altered biofilm formation and increased motility, which could be correlated with higher expression of V. cholerae flagella gene class IV. Concordantly, we could show by immunoblot analysis, that Lon is the main protease responsible for proteolytic control of FliA, which is required for class IV flagella gene transcription, but also downregulates virulence gene expression. FliA becomes highly sensitive to proteolytic degradation in absence of its anti-sigma factor FlgM, a scenario reported to occur during mucosal penetration due to FlgM secretion through the broken flagellum. Our results confirm that the high stability of FliA in the absence of Lon results in less cholera toxin and toxin corgulated pilus production under virulence gene inducing conditions and in the presence of a damaged flagellum. Thus, the data presented herein provide a molecular explanation on how V. cholerae can achieve full expression of virulence genes during early stages of colonization, despite FliA getting liberated from the anti-sigma factor FlgM.
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Affiliation(s)
- Katharina Pressler
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Dina Vorkapic
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Sabine Lichtenegger
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Gerald Malli
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Benjamin P Barilich
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Fatih Cakar
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Franz G Zingl
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Joachim Reidl
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria
| | - Stefan Schild
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, A-8010 Graz, Austria.
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Abstract
Vibrio parahaemolyticus is the most common cause of seafood-borne gastroenteritis worldwide and a blight on global aquaculture. This organism requires a horizontally acquired type III secretion system (T3SS2) to infect the small intestine, but knowledge of additional factors that underlie V. parahaemolyticus pathogenicity is limited. We used transposon-insertion sequencing to screen for genes that contribute to viability of V. parahaemolyticus in vitro and in the mammalian intestine. Our analysis enumerated and controlled for the host infection bottleneck, enabling robust assessment of genetic contributions to in vivo fitness. We identified genes that contribute to V. parahaemolyticus colonization of the intestine independent of known virulence mechanisms in addition to uncharacterized components of T3SS2. Our study revealed that toxR, an ancestral locus in Vibrio species, is required for V. parahaemolyticus fitness in vivo and for induction of T3SS2 gene expression. The regulatory mechanism by which V. parahaemolyticus ToxR activates expression of T3SS2 resembles Vibrio cholerae ToxR regulation of distinct virulence elements acquired via lateral gene transfer. Thus, disparate horizontally acquired virulence systems have been placed under the control of this ancestral transcription factor across independently evolved human pathogens.
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