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Luczo JM, Hamidou Soumana I, Reagin KL, Dihle P, Ghedin E, Klonowski KD, Harvill ET, Tompkins SM. Bordetella bronchiseptica-Mediated Interference Prevents Influenza A Virus Replication in the Murine Nasal Cavity. Microbiol Spectr 2023; 11:e0473522. [PMID: 36728413 PMCID: PMC10100957 DOI: 10.1128/spectrum.04735-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Accepted: 01/09/2023] [Indexed: 02/03/2023] Open
Abstract
Colonization resistance, also known as pathogen interference, describes the ability of a colonizing microbe to interfere with the ability of an incoming microbe to establish infection, and in the case of pathogenic organisms, cause disease in a susceptible host. Furthermore, colonization-associated dysbiosis of the commensal microbiota can alter host immunocompetence and infection outcomes. Here, we investigated the role of Bordetella bronchiseptica nasal colonization and associated disruption of the nasal microbiota on the ability of influenza A virus to establish infection in the murine upper respiratory tract. Targeted sequencing of the microbial 16S rRNA gene revealed that B. bronchiseptica colonization of the nasal cavity efficiently displaced the resident commensal microbiota-the peak of this effect occurring 7 days postcolonization-and was associated with reduced influenza associated-morbidity and enhanced recovery from influenza-associated clinical disease. Anti-influenza A virus hemagglutinin-specific humoral immune responses were not affected by B. bronchiseptica colonization, although the cellular influenza PA-specific CD8+ immune responses were dampened. Notably, influenza A virus replication in the nasal cavity was negated in B. bronchiseptica-colonized mice. Collectively, this work demonstrates that B. bronchiseptica-mediated pathogen interference prevents influenza A virus replication in the murine nasal cavity. This may have direct implications for controlling influenza A virus replication in, and transmission events originating from, the upper respiratory tract. IMPORTANCE The interplay of microbial species in the upper respiratory tract is important for the ability of an incoming pathogen to establish and, in the case of pathogenic organisms, cause disease in a host. Here, we demonstrate that B. bronchiseptica efficiently colonizes and concurrently displaces the commensal nasal cavity microbiota, negating the ability of influenza A virus to establish infection. Furthermore, B. bronchiseptica colonization also reduced influenza-associated morbidity and enhanced recovery from influenza-associated disease. Collectively, this study indicates that B. bronchiseptica-mediated interference prevents influenza A virus replication in the upper respiratory tract. This result demonstrates the potential for respiratory pathogen-mediated interference to control replication and transmission dynamics of a clinically important respiratory pathogen like influenza A virus.
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Affiliation(s)
- Jasmina M. Luczo
- Center for Vaccines and Immunology, University of Georgia, Athens, Georgia, USA
- Emory-UGA Centers of Excellence for Influenza Research and Surveillance (CEIRS), Athens, Georgia, USA
| | | | - Katie L. Reagin
- Department of Cellular Biology, University of Georgia, Athens, Georgia, USA
| | - Preston Dihle
- Center for Genomics and Systems Biology, New York University, New York City, New York, USA
| | - Elodie Ghedin
- Center for Genomics and Systems Biology, New York University, New York City, New York, USA
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | | | - Eric T. Harvill
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
| | - Stephen M. Tompkins
- Center for Vaccines and Immunology, University of Georgia, Athens, Georgia, USA
- Emory-UGA Centers of Excellence for Influenza Research and Surveillance (CEIRS), Athens, Georgia, USA
- Department of Infectious Diseases, University of Georgia, Athens, Georgia, USA
- Center for Influenza Disease and Emergence Response (CIDER), Athens, Georgia, USA
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Tietze L, Mangold A, Hoff MW, Lale R. Identification and Cross-Characterisation of Artificial Promoters and 5' Untranslated Regions in Vibrio natriegens. Front Bioeng Biotechnol 2022; 10:826142. [PMID: 35155395 PMCID: PMC8830501 DOI: 10.3389/fbioe.2022.826142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 01/07/2022] [Indexed: 11/13/2022] Open
Abstract
Vibrio natriegens has recently gained attention as a novel fast-growing bacterium in synthetic biology applications. Currently, a limited set of genetic elements optimised for Escherichia coli are used in V. natriegens due to the lack of DNA parts characterised in this novel host. In this study, we report the identification and cross-characterisation of artificial promoters and 5' untranslated regions (artificial regulatory sequence, ARES) that lead to production of fluorescent proteins with a wide-range of expression levels. We identify and cross-characterise 52 constructs in V. natriegens and E. coli. Furthermore, we report the DNA sequence and motif analysis of the ARESs using various algorithms. With this study, we expand the pool of characterised genetic DNA parts that can be used for different biotechnological applications using V. natriegens as a host microorganism.
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Affiliation(s)
| | | | | | - Rahmi Lale
- Department of Biotechnology and Food Science, Faculty of Natural Sciences, Norwegian University of Science and Technology, Trondheim, Norway
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Abstract
Filamentous hemagglutinin (FhaB) is a critical virulence factor for both Bordetella pertussis, the causal agent of whooping cough, and the closely related species Bordetella bronchiseptica. FhaB is an adhesin, suppresses inflammatory cytokine production, and protects against phagocytic cell clearance during infection. Regulated degradation of the FhaB C-terminal prodomain is required to establish a persistent infection in mice. Two proteases, CtpA in the periplasm and SphB1 on the bacterial surface, are known to mediate FhaB processing, and we recently determined that CtpA functions before, and controls the FhaB cleavage site of, SphB1. However, the data indicate that another periplasmic protease must initiate degradation of the prodomain by removing a portion of the FhaB C terminus that inhibits CtpA-mediated degradation. Using a candidate approach, we identified DegP as the initiating protease. Deletion of degP or substitution of its predicted catalytic residue resulted in reduced creation of FHA′ (the main product of FhaB processing) and an accumulation of full-length FhaB in whole-cell lysates. Also, FHA′ was no longer released into culture supernatants in degP mutants. Alterations of the FhaB C terminus that relieve inhibition of CtpA abrogate the need for DegP, consistent with DegP functioning prior to CtpA in the processing pathway. DegP is not required for secretion of FhaB through FhaC or for adherence of the bacteria to host cells, indicating that DegP acts primarily as a protease and not a chaperone for FhaB in B. bronchiseptica. Our results highlight a role for HtrA family proteases in activation of virulence factors in pathogenic bacteria.
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Gestal MC, Howard LK, Dewan K, Johnson HM, Barbier M, Bryant C, Soumana IH, Rivera I, Linz B, Blas-Machado U, Harvill ET. Enhancement of immune response against Bordetella spp. by disrupting immunomodulation. Sci Rep 2019; 9:20261. [PMID: 31889098 PMCID: PMC6937331 DOI: 10.1038/s41598-019-56652-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 12/12/2019] [Indexed: 12/27/2022] Open
Abstract
Well-adapted pathogens must evade clearance by the host immune system and the study of how they do this has revealed myriad complex strategies and mechanisms. Classical bordetellae are very closely related subspecies that are known to modulate adaptive immunity in a variety of ways, permitting them to either persist for life or repeatedly infect the same host. Exploring the hypothesis that exposure to immune cells would cause bordetellae to induce expression of important immunomodulatory mechanisms, we identified a putative regulator of an immunomodulatory pathway. The deletion of btrS in B. bronchiseptica did not affect colonization or initial growth in the respiratory tract of mice, its natural host, but did increase activation of the inflammasome pathway, and recruitment of inflammatory cells. The mutant lacking btrS recruited many more B and T cells into the lungs, where they rapidly formed highly organized and distinctive Bronchial Associated Lymphoid Tissue (BALT) not induced by any wild type Bordetella species, and a much more rapid and strong antibody response than observed with any of these species. Immunity induced by the mutant was measurably more robust in all respiratory organs, providing completely sterilizing immunity that protected against challenge infections for many months. Moreover, the mutant induced sterilizing immunity against infection with other classical bordetellae, including B. pertussis and B. parapertussis, something the current vaccines do not provide. These findings reveal profound immunomodulation by bordetellae and demonstrate that by disrupting it much more robust protective immunity can be generated, providing a pathway to greatly improve vaccines and preventive treatments against these important pathogens.
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Affiliation(s)
- Monica C Gestal
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
| | - Laura K Howard
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Kalyan Dewan
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Hannah M Johnson
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Mariette Barbier
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States of America
- Vaccine Development Center at West Virginia University Health Sciences Center, Morgantown, West Virginia, United States of America
| | - Clare Bryant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, CB3 0ES, United Kingdom
| | - Illiassou Hamidou Soumana
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Israel Rivera
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Bodo Linz
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Uriel Blas-Machado
- Department of Pathology, Athens Veterinary Diagnostic Laboratory, University of Georgia, Athens, Georgia, United States of America
| | - Eric T Harvill
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America.
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Huang L, Zhang Y, He R, Zuo Z, Luo Z, Xu W, Yan Q. Phenotypic characterization, virulence, and immunogenicity of Pseudomonas plecoglossicida rpoE knock-down strain. FISH & SHELLFISH IMMUNOLOGY 2019; 87:772-777. [PMID: 30776544 DOI: 10.1016/j.fsi.2019.02.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 02/13/2019] [Accepted: 02/15/2019] [Indexed: 06/09/2023]
Abstract
Pseudomonas plecoglossicida, a temperature dependent bacterial pathogen in fish, expresses rpoE gene that is sensitive to temperature and probably critical for pathogen virulence and disease development. In this study, the rpoE silence strain rpoE-RNAi-1 was constructed by gene knock-down. The rpoE-RNAi-1 displayed significant changes in biofilm formation, swarming motility, adhesion and virulence. Meanwhile, vaccination of grouper with rpoE-RNAi-1 led to a relative percent survival (RPS) value of 85% after challenged with the wild-type P. plecoglossicida. qRT-PCR assays showed that vaccination with rpoE-RNAi-1 enhanced the expression of immune-related genes, including MHC-I, MHC-II, IgM, and IL-1β, indicating that it was able to induce humoral and cell-mediated immune response in grouper. These results validated the possibility of rpoE as a potential target for constructing P. plecoglossicida live attenuated vaccine.
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Affiliation(s)
- Lixing Huang
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, PR China.
| | - Youyu Zhang
- Institute of Electromagnetics and Acoustics, School of Electronic Science and Engineering, Xiamen University, Xiamen, Fujian, PR China
| | - Rongchao He
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, PR China
| | - Zhenghong Zuo
- School of Life Sciences, Xiamen University, Xiamen, Fujian, PR China
| | - Zhuhua Luo
- Third Institute of Oceanography, State Oceanic Administration, Xiamen, 361005, PR China
| | - Wei Xu
- Third Institute of Oceanography, State Oceanic Administration, Xiamen, 361005, PR China
| | - Qingpi Yan
- Fisheries College, Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture, Jimei University, Xiamen, Fujian, PR China.
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Gestal MC, Whitesides LT, Harvill ET. Integrated Signaling Pathways Mediate Bordetella Immunomodulation, Persistence, and Transmission. Trends Microbiol 2018; 27:118-130. [PMID: 30661570 DOI: 10.1016/j.tim.2018.09.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/17/2018] [Accepted: 09/28/2018] [Indexed: 01/01/2023]
Abstract
The mammalian immune system includes a sophisticated array of antimicrobial mechanisms. However, successful pathogens have developed subversive strategies to detect, modulate, and/or evade immune control and clearance. Independent disciplines study host immunology and bacterial pathogenesis, but interkingdom signaling between bacteria and host during natural infection remains poorly understood. An efficient natural host infection system has revealed complex communication between Bordetella spp. and mice, identified novel regulatory mechanisms, and demonstrated that bordetellae can respond to microenvironment and inflammatory status cues. Understanding these bacterial signaling pathways and their complex network that allows precisely timed expression of numerous immunomodulatory factors will serve as a paradigm for other organisms lacking such a powerful experimental infection system. VIDEO ABSTRACT.
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Affiliation(s)
- M C Gestal
- Deaprtment of Infectious Diseases, College of Veterinary Medicine, University of Georgia. 501 DW Brooks Drive, 30602, Athens, Georgia, USA.
| | - L T Whitesides
- Deaprtment of Infectious Diseases, College of Veterinary Medicine, University of Georgia. 501 DW Brooks Drive, 30602, Athens, Georgia, USA
| | - E T Harvill
- Deaprtment of Infectious Diseases, College of Veterinary Medicine, University of Georgia. 501 DW Brooks Drive, 30602, Athens, Georgia, USA.
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Barbier M, Boehm DT, Sen-Kilic E, Bonnin C, Pinheiro T, Hoffman C, Gray M, Hewlett E, Damron FH. Modulation of Pertussis and Adenylate Cyclase Toxins by Sigma Factor RpoE in Bordetella pertussis. Infect Immun 2017; 85:e00565-16. [PMID: 27849178 PMCID: PMC5203664 DOI: 10.1128/iai.00565-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 11/07/2016] [Indexed: 12/23/2022] Open
Abstract
Bordetella pertussis is a human pathogen that can infect the respiratory tract and cause the disease known as whooping cough. B. pertussis uses pertussis toxin (PT) and adenylate cyclase toxin (ACT) to kill and modulate host cells to allow the pathogen to survive and persist. B. pertussis encodes many uncharacterized transcription factors, and very little is known about their functions. RpoE is a sigma factor which, in other bacteria, responds to oxidative, heat, and other environmental stresses. RseA is a negative regulator of RpoE that sequesters the sigma factor to regulate gene expression based on conditions. In B. pertussis, deletion of the rseA gene results in high transcriptional activity of RpoE and large amounts of secretion of ACT. By comparing parental B. pertussis to an rseA gene deletion mutant (PM18), we sought to characterize the roles of RpoE in virulence and determine the regulon of genes controlled by RpoE. Despite high expression of ACT, the rseA mutant strain did not infect the murine airway as efficiently as the parental strain and PM18 was killed more readily when inside phagocytes. RNA sequencing analysis was performed and 263 genes were differentially regulated by RpoE, and surprisingly, the rseA mutant strain where RpoE activity was elevated expressed very little pertussis toxin. Western blots and proteomic analysis corroborated the inverse relationship of PT to ACT expression in the high-RpoE-activity rseA deletion strain. Our data suggest that RpoE can modulate PT and ACT expression indirectly through unidentified mechanisms in response to conditions.
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Affiliation(s)
- Mariette Barbier
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Dylan T Boehm
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Emel Sen-Kilic
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Claire Bonnin
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Theo Pinheiro
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Casey Hoffman
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
| | - Mary Gray
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
| | - Erik Hewlett
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
| | - F Heath Damron
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
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Dayao DAE, Seddon JM, Gibson JS, Blackall PJ, Turni C. Whole Genome Sequence Analysis of Pig Respiratory Bacterial Pathogens with Elevated Minimum Inhibitory Concentrations for Macrolides. Microb Drug Resist 2016; 22:531-537. [DOI: 10.1089/mdr.2015.0214] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Jennifer M. Seddon
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Justine S. Gibson
- School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia
| | - Patrick J. Blackall
- Queensland Alliance for Agriculture and Food Innovation, EcoSciences Precinct, The University of Queensland, Dutton Park, Queensland, Australia
| | - Conny Turni
- Queensland Alliance for Agriculture and Food Innovation, EcoSciences Precinct, The University of Queensland, Dutton Park, Queensland, Australia
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9
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The RpoE Stress Response Pathway Mediates Reduction of the Virulence of Enteropathogenic Escherichia coli by Zinc. Appl Environ Microbiol 2015; 81:3766-74. [PMID: 25819956 DOI: 10.1128/aem.00507-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 03/19/2015] [Indexed: 11/20/2022] Open
Abstract
Zinc supplements are an effective clinical treatment for infantile diarrheal disease caused by enteric pathogens. Previous studies demonstrated that zinc acts on enteropathogenic Escherichia coli (EPEC) bacteria directly to suppress several virulence-related genes at a concentration that can be achieved by oral delivery of dietary zinc supplements. Our in vitro studies showed that a micromolar concentration of zinc induced the envelope stress response and suppressed virulence in EPEC, providing a possible mechanistic explanation for zinc's therapeutic action. In this report, we investigated the molecular and physiological changes in EPEC induced by zinc. We found that micromolar concentrations of zinc reduced the bacterial growth rate without affecting viability. We observed increased membrane permeability caused by zinc. Zinc upregulated the RpoE-dependent envelope stress response pathway and suppressed EPEC virulence gene expression. RpoE alone was sufficient to inhibit virulence factor expression and to attenuate attaching and effacing lesion formation on human host cells. By mutational analysis we demonstrate that the DNA-binding motif of RpoE is necessary for suppression of the LEE1, but not the LEE4, operon. Predictably, inhibition of the RpoE-mediated envelope stress response in combination with micromolar concentrations of zinc reduced EPEC viability. In conclusion, zinc induces the RpoE and stress response pathways in EPEC, and the alternate sigma factor RpoE downregulates EPEC LEE and non-LEE virulence genes by multiple mechanisms.
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Hanawa T, Yonezawa H, Kawakami H, Kamiya S, Armstrong SK. Role of Bordetella pertussis RseA in the cell envelope stress response and adenylate cyclase toxin release. Pathog Dis 2013; 69:7-20. [PMID: 23821542 DOI: 10.1111/2049-632x.12061] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 11/28/2022] Open
Abstract
Bordetella pertussis is the bacterial agent of the human disease such as whooping cough. In many bacteria, the extracellular function sigma factor σE is central to the response to envelope stress, and its activity is negatively controlled by the RseA anti-sigma factor. In this study, the role of RseA in B. pertussis envelope stress responses was investigated. Compared with the wild-type strain, an rseA mutant showed elevated resistance to envelope stress and enhanced growth at 25 °C. rpoH and other predicted σE target genes demonstrated increased transcription in the rseA mutant compared with the wild-type parent. Transcription of those genes was also increased in wild-type B. pertussis and Escherichia coli under envelope stress, whereas no stress-induced increase in transcription was observed in the rseA mutant. rseA inactivation was also associated with altered levels of certain proteins in culture supernatant fluids, which showed increased adenylate cyclase toxin (CyaA) levels. The increased CyaA in the mutant was correlated with an apparent increased stability of the extracellular toxin and increased production of CyaA-containing outer membrane vesicles. Consistent with this, compared with the wild-type strain, rseA mutant cells produced increased numbers of large surface-associated vesicles.
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Affiliation(s)
- Tomoko Hanawa
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Hideo Yonezawa
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Hayato Kawakami
- Department of Anatomy, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Shigeru Kamiya
- Department of Infectious Diseases, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
| | - Sandra K Armstrong
- Department of Microbiology, University of Minnesota Medical School, Minneapolis, MN, USA
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Barchinger SE, Ades SE. Regulated proteolysis: control of the Escherichia coli σ(E)-dependent cell envelope stress response. Subcell Biochem 2013; 66:129-60. [PMID: 23479440 DOI: 10.1007/978-94-007-5940-4_6] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Over the past decade, regulatory proteolysis has emerged as a paradigm for transmembrane signal transduction in all organisms, from bacteria to humans. These conserved proteolytic pathways share a common design that involves the sequential proteolysis of a membrane-bound regulatory protein by two proteases. Proteolysis releases the regulator, which is inactive in its membrane-bound form, into the cytoplasm where it performs its cellular function. One of the best-characterized examples of signal transduction via regulatory proteolysis is the pathway governing the σ(E)-dependent cell envelope stress response in Escherichia coli. In unstressed cells, σ(E) is sequestered at the membrane by the transmembrane anti-sigma factor, RseA. Stresses that compromise the cell envelope and interfere with the proper folding of outer membrane proteins (OMPs) activate the proteolytic pathway. The C-terminal residues of unfolded OMPs bind to the inner membrane protease, DegS, to initiate the proteolytic cascade. DegS removes the periplasmic domain of RseA creating a substrate for the next protease in the pathway, RseP. RseP cleaves RseA in the periplasmic region in a process called regulated intramembrane proteolysis (RIP). The remaining fragment of RseA is released into the cytoplasm and fully degraded by the ATP-dependent protease, ClpXP, with the assistance of the adaptor protein, SspB, thereby freeing σ(E) to reprogram gene expression. A growing body of evidence indicates that the overall proteolytic framework that governs the σ(E) response is used to regulate similar anti-sigma factor/sigma factor pairs throughout the bacterial world and has been adapted to recognize a wide variety of signals and control systems as diverse as envelope stress responses, sporulation, virulence, and iron-siderophore uptake. In this chapter, we review the extensive physiological, biochemical, and structural studies on the σ(E) system that provide remarkable insights into the mechanistic underpinnings of this regulated proteolytic signal transduction pathway. These studies reveal design principles that are applicable to related proteases and regulatory proteolytic pathways in all domains of life.
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Affiliation(s)
- Sarah E Barchinger
- Graduate Program in BMMB, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
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