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Structure of Vibrio cholerae ToxT reveals a mechanism for fatty acid regulation of virulence genes. Proc Natl Acad Sci U S A 2010; 107:2860-5. [PMID: 20133655 DOI: 10.1073/pnas.0915021107] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. In order for V. cholerae to cause disease, it must produce two virulence factors, the toxin-coregulated pilus (TCP) and cholera toxin (CT), whose expression is controlled by a transcriptional cascade culminating with the expression of the AraC-family regulator, ToxT. We have solved the 1.9 A resolution crystal structure of ToxT, which reveals folds in the N- and C-terminal domains that share a number of features in common with AraC, MarA, and Rob as well as the unexpected presence of a buried 16-carbon fatty acid, cis-palmitoleate. The finding that cis-palmitoleic acid reduces TCP and CT expression in V. cholerae and prevents ToxT from binding to DNA in vitro provides a direct link between the host environment of V. cholerae and regulation of virulence gene expression.
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202
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Antivirulence drugs to target bacterial secretion systems. Curr Opin Microbiol 2010; 13:100-5. [DOI: 10.1016/j.mib.2009.12.003] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 11/29/2009] [Accepted: 12/01/2009] [Indexed: 02/03/2023]
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203
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Abstract
Antibiotic resistance is one of the greatest challenges of the twenty-first century. However, the increasing understanding of bacterial pathogenesis and intercellular communication has revealed many potential strategies to develop novel drugs to treat bacteria-mediated disease. Interference with bacterial virulence and/or cell-to-cell signalling pathways is an especially compelling approach, as it is thought to apply less selective pressure for the development of bacterial resistance than traditional strategies, which are aimed at killing bacteria or preventing their growth. Here, we discuss the mechanisms of bacterial virulence and present promising anti-virulence strategies and compounds for the future treatment of bacterial infections.
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Higueruelo AP, Schreyer A, Bickerton GRJ, Pitt WR, Groom CR, Blundell TL. Atomic interactions and profile of small molecules disrupting protein-protein interfaces: the TIMBAL database. Chem Biol Drug Des 2009; 74:457-67. [PMID: 19811506 DOI: 10.1111/j.1747-0285.2009.00889.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Growing evidence of the possibility of modulating protein-protein interactions with small molecules is opening the door to new approaches and concepts in drug discovery. In this paper, we describe the creation of TIMBAL, a hand-curated database holding an up to date collection of small molecules inhibiting multi-protein complexes. This database has been analysed and profiled in terms of molecular properties. Protein-protein modulators tend to be large lipophilic molecules with few hydrogen bond features. An analysis of TIMBAL's intersection with other structural databases, including CREDO (protein-small molecule from the PDB) and PICCOLO (protein-protein from the PDB) reveals that TIMBAL molecules tend to form mainly hydrophobic interactions with only a few hydrogen bonding contacts. With respect to potency, TIMBAL molecules are slightly less efficient than an average medicinal chemistry hit or lead. The database provides a resource that will allow further insights into the types of molecules favoured by protein interfaces and provide a background to continuing work in this area. Access at http://www-cryst.bioc.cam.ac.uk/timbal.
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205
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Ho Sui SJ, Fedynak A, Hsiao WWL, Langille MGI, Brinkman FSL. The association of virulence factors with genomic islands. PLoS One 2009; 4:e8094. [PMID: 19956607 PMCID: PMC2779486 DOI: 10.1371/journal.pone.0008094] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 11/07/2009] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND It has been noted that many bacterial virulence factor genes are located within genomic islands (GIs; clusters of genes in a prokaryotic genome of probable horizontal origin). However, such studies have been limited to single genera or isolated observations. We have performed the first large-scale analysis of multiple diverse pathogens to examine this association. We additionally identified genes found predominantly in pathogens, but not non-pathogens, across multiple genera using 631 complete bacterial genomes, and we identified common trends in virulence for genes in GIs. Furthermore, we examined the relationship between GIs and clustered regularly interspaced palindromic repeats (CRISPRs) proposed to confer resistance to phage. METHODOLOGY/PRINCIPAL FINDINGS We show quantitatively that GIs disproportionately contain more virulence factors than the rest of a given genome (p<1E-40 using three GI datasets) and that CRISPRs are also over-represented in GIs. Virulence factors in GIs and pathogen-associated virulence factors are enriched for proteins having more "offensive" functions, e.g. active invasion of the host, and are disproportionately components of type III/IV secretion systems or toxins. Numerous hypothetical pathogen-associated genes were identified, meriting further study. CONCLUSIONS/SIGNIFICANCE This is the first systematic analysis across diverse genera indicating that virulence factors are disproportionately associated with GIs. "Offensive" virulence factors, as opposed to host-interaction factors, may more often be a recently acquired trait (on an evolutionary time scale detected by GI analysis). Newly identified pathogen-associated genes warrant further study. We discuss the implications of these results, which cement the significant role of GIs in the evolution of many pathogens.
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Affiliation(s)
- Shannan J. Ho Sui
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Amber Fedynak
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - William W. L. Hsiao
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Morgan G. I. Langille
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Fiona S. L. Brinkman
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail:
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206
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Saenz JB, Li J, Haslam DB. The MAP kinase-activated protein kinase 2 (MK2) contributes to the Shiga toxin-induced inflammatory response. Cell Microbiol 2009; 12:516-29. [PMID: 19951368 DOI: 10.1111/j.1462-5822.2009.01414.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infection with Shiga toxin (STx)-producing bacteria can progress to a toxemic, extraintestinal injury cascade known as haemolytic uremic syndrome (HUS), the leading cause of acute renal failure in children. Mounting evidence suggests that STx activates stress response pathways in susceptible cells and has implicated the p38 mitogen-activated protein kinase (MAPK) pathway. More importantly, some of the pathology associated with HUS is believed to be a result of a STx-induced inflammatory response. From a siRNA screen of the human kinome adapted to a high-throughput format, we found that knock-down of the MAPK-activated protein kinase 2 (MK2), a downstream target of the p38 MAPK, protected against Shiga toxicity. Further characterization of the in vitro role of MK2 revealed that STx activates the p38-MK2 stress response pathway in both p38- and MK2-dependent manners in two distinct cell lines. MK2 activation was specific to damage to the ribosome by an enzymatically active toxin and did not result from translational inhibition per se. Genetic and chemical inhibition of MK2 significantly decreased the inflammatory response to STx. These findings suggest that MK2 inhibition might play a valuable role in decreasing the immuopathological component of STx-mediated disease.
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Affiliation(s)
- Jose B Saenz
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
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207
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Swoboda JG, Meredith TC, Campbell J, Brown S, Suzuki T, Bollenbach T, Malhowski AJ, Kishony R, Gilmore MS, Walker S. Discovery of a small molecule that blocks wall teichoic acid biosynthesis in Staphylococcus aureus. ACS Chem Biol 2009; 4:875-83. [PMID: 19689117 DOI: 10.1021/cb900151k] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Both Gram-positive and Gram-negative bacteria contain bactoprenol-dependent biosynthetic pathways expressing non-essential cell surface polysaccharides that function as virulence factors. Although these polymers are not required for bacterial viability in vitro, genes in many of the biosynthetic pathways are conditionally essential: they cannot be deleted except in strains incapable of initiating polymer synthesis. We report a cell-based, pathway-specific strategy to screen for small molecule inhibitors of conditionally essential enzymes. The screen identifies molecules that prevent the growth of a wildtype bacterial strain but do not affect the growth of a mutant strain incapable of initiating polymer synthesis. We have applied this approach to discover inhibitors of wall teichoic acid (WTA) biosynthesis in Staphylococcus aureus. WTAs are anionic cell surface polysaccharides required for host colonization that have been suggested as targets for new antimicrobials. We have identified a small molecule, 7-chloro-N,N-diethyl-3-(phenylsulfonyl)-[1,2,3]triazolo[1,5-a]quinolin-5-amine (1835F03), that inhibits the growth of a panel of S. aureus strains (MIC = 1-3 microg mL(-1)), including clinical methicillin-resistant S. aureus (MRSA) isolates. Using a combination of biochemistry and genetics, we have identified the molecular target as TarG, the transmembrane component of the ABC transporter that exports WTAs to the cell surface. We also show that preventing the completion of WTA biosynthesis once it has been initiated triggers growth arrest. The discovery of 1835F03 validates our chemical genetics strategy for identifying inhibitors of conditionally essential enzymes, and the strategy should be applicable to many other bactoprenol-dependent biosynthetic pathways in the pursuit of novel antibacterials and probes of bacterial stress responses.
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Affiliation(s)
- Jonathan G. Swoboda
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Timothy C. Meredith
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Jennifer Campbell
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Stephanie Brown
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Takashi Suzuki
- The Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, 20 Staniford Street, Boston, Massachusetts 02114
| | - Tobias Bollenbach
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Amy J. Malhowski
- Department of Medicine, Tufts Medical Center, Boston, Massachusetts 02111
| | - Roy Kishony
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
| | - Michael S. Gilmore
- The Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, 20 Staniford Street, Boston, Massachusetts 02114
| | - Suzanne Walker
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115
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208
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Stanley SA, Hung DT. Chemical tools for dissecting bacterial physiology and virulence. Biochemistry 2009; 48:8776-86. [PMID: 19653697 DOI: 10.1021/bi9009083] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Increasingly, chemical biology is being used in the context of bacterial virulence and the host-pathogen interaction, as small molecule inhibitors provide a number of unique advantages for the study of bacterial pathogens that complement powerful, existing classical genetic approaches. Small molecules have the potential to inhibit targets rapidly and reversibly, with a high degree of specificity. They are therefore well suited for studying the role of essential genes in bacterial physiology and virulence in both genetically tractable and intractable organisms, with the capacity to reveal novel phenotypes and insights into the function of essential factors during infection. The use of small molecule inhibitors during infection is also deepening our understanding of the role that host factors play in bacterial pathogenesis. In the future, the utility of chemical biology will grow as technologies for rapid identification of targets of interesting bioactive small molecules are developed. In this review, we highlight recent work in which small molecule inhibitors are used to study essential genes and genetically intractable organisms, to reveal novel phenotypes related to bacterial physiology, and to probe the role of bacterial and host factors during infection. In addition, we review recent advances in biochemical, genetic, and genomic techniques for target identification.
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Affiliation(s)
- Sarah A Stanley
- Infectious Disease Initiative, The Broad Institute, 7 Cambridge Center, Cambridge, Massachusetts 02142, USA
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209
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Puri AW, Bogyo M. Using small molecules to dissect mechanisms of microbial pathogenesis. ACS Chem Biol 2009; 4:603-16. [PMID: 19606820 DOI: 10.1021/cb9001409] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the ways in which pathogens invade and neutralize their hosts is of great interest from both an academic and a clinical perspective. However, in many cases genetic tools are unavailable or insufficient to fully characterize the detailed mechanisms of pathogenesis. Small molecule approaches are particularly powerful due to their ability to modulate specific biological functions in a highly controlled manner and their potential to broadly target conserved processes across species. Recently, two approaches that make use of small molecules, activity-based protein profiling and high-throughput phenotypic screening, have begun to find applications in the study of pathways involved in pathogenesis. In this Review we highlight ways in which these techniques have been applied to examine bacterial and parasitic pathogenesis and discuss possible ways in which these efforts can be expanded in the near future.
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Affiliation(s)
| | - Matthew Bogyo
- Chemical and Systems Biology
- Pathology
- Microbiology and Immunology, Stanford University School of Medicine, 300 Pasteur Dr., Stanford, California 94305
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210
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Abstract
Bacteria have been long considered primitive organisms, with a lifestyle focused on the survival and propagation of single cells. However, in the past few decades it became obvious that bacteria can display sophisticated group behaviors. For instance, bacteria can communicate amongst themselves and with their hosts, by producing, sensing, and responding to chemical signals. By doing so, they can sense their surroundings and adapt as to increase their chances of survival and propagation. Here, we review the discovery of bacterial intercellular communication, some of the signaling molecules identified to date, the role of intercellular signaling in symbiotic and pathogenic relationships between bacteria and their hosts and its implications for the development of new therapeutic strategies against human disease.
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Affiliation(s)
- L Caetano M Antunes
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada.
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211
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Productive steps toward an antimicrobial targeting virulence. Curr Opin Microbiol 2009; 12:490-6. [PMID: 19631578 DOI: 10.1016/j.mib.2009.06.012] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 06/05/2009] [Indexed: 01/19/2023]
Abstract
Targeting virulence factors has gained increasing attention as a potential approach to new antibiotics. Small molecule inhibitors of virulence have been shown to change the course of disease in whole organism infection models. Recently, key advances in the field include the identification of novel targets within cell signaling pathways, a new class of anti-virulence compounds that target bacterial defenses against host immunity, and a growing body of in vivo data to support the general approach of anti-virulence therapies. Additionally, there has been a distinct trend toward developing broader spectrum anti-virulence compounds, in particular agents with activity against diverse Gram-negative organisms. Herein we provide an update on the status of the field with a focus on recent advancements.
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212
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Omeprazole antagonizes virulence and inflammation in Salmonella enterica-infected RAW264.7 cells. Antimicrob Agents Chemother 2009; 53:2402-9. [PMID: 19307359 DOI: 10.1128/aac.01483-08] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The proton pump inhibitor omeprazole reduced the intracellular replication of Salmonella enterica serovar Typhimurium in RAW264.7 cells without affecting bacterial growth in vitro or the viability of the host cells. The mechanism was bacteriostatic and interfered with replication mediated by the virulence-associated SPI2 type III secretion system. The proton pump inhibitor bafilomycin A(1), in contrast, mediated killing of intracellular bacteria and imposed a marked cytotoxicity on RAW264.7 cells. The two compounds also differentially affected the proinflammatory responses of the infected cells. Bafilomycin A(1) enhanced nitric oxide production, whereas omeprazole delayed IkappaB degradation and blocked nitric oxide production and the secretion of proinflammatory cytokines. These results imply that omeprazole can be used to block the virulence factor-mediated intracellular replication of S. Typhimurium, and that its mechanism of growth inhibition is different from that mediated by bafilomycin A(1).
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213
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Rasko DA, Sperandio V. Novel approaches to bacterial infection therapy by interfering with cell-to-cell signaling. ACTA ACUST UNITED AC 2009; Chapter 17:Unit17.3. [PMID: 19235150 DOI: 10.1002/9780471729259.mc1703s12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The identification of cell-to-cell signaling inhibitors among bacteria is a novel mechanism used to control the virulence of pathogens. Signaling inhibitors have a significant potential to be used as therapeutics in that they will exert less biological pressure to develop resistance than classic antibiotics, which attempt to eradicate or significantly inhibit bacterial growth. Decreasing the virulence of pathogens by inhibiting signaling provides a mechanism by which the bacteria will be "misled" into not activating virulence factors. If virulence factors are not activated, these pathogens will either pass through the host without incidence or be controlled by the host's immune system. In this unit, we discuss the general principles for the design and implementation of a high-throughput screen to identify inhibitors of bacterial cell-to-cell communication. We also provide a detailed protocol using a specific example of signaling inhibitor identification using enterohemorrhagic Escherichia coli as a model system.
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Affiliation(s)
- David A Rasko
- University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
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214
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Direct regulation by the Vibrio cholerae regulator ToxT to modulate colonization and anticolonization pilus expression. Infect Immun 2009; 77:1383-8. [PMID: 19168737 DOI: 10.1128/iai.01156-08] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The pathogen Vibrio cholerae uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host and establish itself at its preferred colonization site at the host intestinal mucosa. The key regulator in this process is the AraC/XylS family transcription factor, ToxT, which plays critical roles in pathogenesis, including the regulation of two type IV pili, the anticolonization factor mannose-sensitive hemagglutinin and the toxin-coregulated pilus. Previously, it was thought ToxT required dimerization in order to effect transcriptional regulation at its cognate promoters. Here, we present evidence that ToxT directly represses transcription of the msh operon by binding to three promoters within this operon and that dimerization may not be required for transcriptional repression of target promoters by ToxT, suggesting that this regulator uses different mechanisms to modulate the transcriptional repertoire of V. cholerae.
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215
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Abstract
PURPOSE OF REVIEW Incidences of antimicrobial-resistant infections have increased dramatically over the past several decades and are associated with adverse patient outcomes. Alternative approaches to combat infection are critical and have led to the development of more specific drugs targeted at particular bacterial virulence systems or essential regulatory pathways. The purpose of this review is to highlight the recent developments in antibacterial therapy and the novel approaches toward increasing our therapeutic armory against bacterial infection. RECENT FINDINGS Although classic antibiotic development is not occurring rapidly, alternative therapeutics that target specific bacterial virulence systems are progressing from the discovery stage through the Food and Drug Administration approval process. Here we review novel antibodies that target specific virulence systems as well as a variety of newly discovered small molecules that block bacterial attachment, communication systems (quorum sensing) or important regulatory processes associated with virulence gene expression. SUMMARY The success of novel therapeutics could significantly change clinical practice. Furthermore, the complications of collateral damage due to antibiotic administration, for example, suprainfections or decreased host immunity due to loss of synergistic bacterial communities, may be minimized using therapeutics that specifically target pathogenic behavior.
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216
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A small-molecule screen identifies the antipsychotic drug pimozide as an inhibitor of Listeria monocytogenes infection. Antimicrob Agents Chemother 2008; 53:756-64. [PMID: 19015342 DOI: 10.1128/aac.00607-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We developed a screening procedure to identify small-molecule compounds that altered infection by Listeria monocytogenes to gain insights into bacterial/host cellular processes required for intracellular pathogenesis. A small-molecule library of 480 compounds with known biological functions was screened, and 21 compounds that altered the L. monocytogenes infection of murine bone marrow-derived macrophages (BMM) were identified. The identified compounds affected various cellular functions, such as actin polymerization, kinase/phosphatase activity, calcium signaling, and apoptosis. Pimozide, an FDA-approved drug used to treat severe Tourette's syndrome and schizophrenia, was further examined and shown to decrease the bacterial uptake and vacuole escape of L. monocytogenes in BMM. The inhibitory effect of pimozide on internalization was not specific for L. monocytogenes, as the phagocytosis of other bacterial species (Bacillus subtilis, Salmonella enterica serovar Typhimurium, and Escherichia coli K12) was significantly inhibited in the presence of pimozide. The invasion and cell-to-cell spread of L. monocytogenes during the infection of nonprofessional phagocytic cells also was decreased by pimozide treatment. Although pimozide has been reported to be an antagonist of mammalian cell calcium channels, the infection of BMM in a calcium-free medium did not relieve the inhibitory effects of pimozide on L. monocytogenes infection. Our results provide a generalizable screening approach for identifying small-molecule compounds that affect cellular pathways that are required for intracellular bacterial pathogenesis. We also have identified pimozide, a clinically approved antipsychotic drug, as a compound that may be suitable for further development as a therapeutic for intracellular bacterial infections.
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217
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Bench-to-bedside review: Bacterial virulence and subversion of host defences. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2008; 12:234. [PMID: 19014410 PMCID: PMC2646333 DOI: 10.1186/cc7091] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Bacterial pathogens possess an array of specific mechanisms that confer virulence and the capacity to avoid host defence mechanisms. Mechanisms of virulence are often mediated by the subversion of normal aspects of host biology. In this way the pathogen modifies host function so as to promote the pathogen's survival or proliferation. Such subversion is often mediated by the specific interaction of bacterial effector molecules with host encoded proteins and other molecules. The importance of these mechanisms for bacterial pathogens that cause infections leading to severe community-acquired infections is well established. In contrast, the importance of specialised mechanisms of virulence in the genesis of nosocomial bacterial infections, which occur in the context of local or systemic defects in host immune defences, is less well established. Specific mechanisms of bacterial resistance to host immunity might represent targets for therapeutic intervention. The clinical utility of such an approach for either prevention or treatment of bacterial infection, however, has not been determined.
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218
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Bodero MD, Harden EA, Munson GP. Transcriptional regulation of subclass 5b fimbriae. BMC Microbiol 2008; 8:180. [PMID: 18854044 PMCID: PMC2579436 DOI: 10.1186/1471-2180-8-180] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Accepted: 10/14/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Enterotoxigenic Escherichia coli (ETEC) is a major cause of infant and child mortality in developing countries. This enteric pathogen causes profuse watery diarrhea by elaborating one or more enterotoxins that intoxicate eukaryotic cells and ultimately leads to a loss of water to the intestinal lumen. Virulence is also dependent upon fimbrial adhesins that facilitate colonization of the small intestine. RESULTS The expression of CS1 fimbriae is positively regulated by Rns, a member of the AraC/XylS superfamily of transcriptional regulators. Based on fimbrial protein homology, CS1 fimbriae have been categorized as subclass 5b along with CS17, CS19, and PCFO71 fimbriae. In this study we show that Rns positively regulates the expression of these other subclass 5b members. DNase I footprinting revealed a Rns binding site adjacent to the -35 hexamer of each fimbrial promoter. The CS17 and PCFO71 fimbrial promoters carry a second Rns binding site centered at -109.5, relative to the Rns-dependent transcription start site. This second binding site is centered at -108.5 for the CS19 promoter. Mutagenesis of either site reduced Rns-dependent transcription from each promoter indicating that the molecules bound to these sites apparently function independently of one another, with each having an additive effect upon fimbrial promoter activation. CONCLUSION This study demonstrates that the ETEC virulence regulator Rns is required for the expression of all known 5b fimbriae. Since Rns is also known to control the expression of additional ETEC fimbriae, including those within subclasses 5a and 5c, the inactivation or inhibition of Rns could be an effective strategy to prevent ETEC infections.
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Affiliation(s)
- Maria D Bodero
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
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219
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Flexibility of Vibrio cholerae ToxT in transcription activation of genes having altered promoter spacing. J Bacteriol 2008; 190:7925-31. [PMID: 18849430 DOI: 10.1128/jb.00512-08] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cholera, a severe diarrheal disease, is caused by ingestion of the gram-negative bacterium Vibrio cholerae. Expression of V. cholerae virulence factors is highly regulated at the transcriptional and posttranscriptional levels by a complex network of proteins and small noncoding RNAs. The direct activator of transcription of most V. cholerae virulence genes is the ToxT protein. ToxT binds to a 13-bp sequence, the toxbox, located upstream of genes in its regulon. However, the organization of toxboxes relative to each other and to the core promoter elements at different genes varies dramatically. At different ToxT-activated genes a single toxbox may be necessary and sufficient for full activation, or pairs of toxboxes organized as either inverted or direct repeats may be required for full activation. Although all toxboxes are located at positions consistent with a class I promoter architecture, the locations of toxboxes relative to the transcription start site also vary from gene to gene. To further assess the ability of ToxT to activate transcription from different configurations relative to the core promoter elements, we constructed promoter-lacZ fusions having altered spacing both between toxbox pairs and between the promoter-proximal toxbox and the -35 box at five different ToxT-activated promoters. Our results suggest that that ToxT has remarkable flexibility in its positioning as a transcription activator and that different interactions between ToxT and RNA polymerase occur during transcription activation of promoters having different toxbox configurations.
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220
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Shen DK, Filopon D, Chaker H, Boullanger S, Derouazi M, Polack B, Toussaint B. High-cell-density regulation of the Pseudomonas aeruginosa type III secretion system: implications for tryptophan catabolites. MICROBIOLOGY-SGM 2008; 154:2195-2208. [PMID: 18667553 DOI: 10.1099/mic.0.2007/013680-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The Pseudomonas aeruginosa type III secretion system (T3SS) is known to be a very important virulence factor in acute human infections, but it is less important in maintaining chronic infections in which T3SS genes are downregulated. In vitro, the activation of T3SS expression involves a positive activating loop that acts on the transcriptional regulator ExsA. We have observed that in vivo T3SS expression is cell density-dependent in a manner that does not need known quorum-sensing (QS) signals. In addition, stationary-phase culture supernatants added to exponential-phase growing strains can inhibit T3SS expression. The analysis of transposon insertion mutants showed that the production of such T3SS-inhibiting signals might depend on tryptophan synthase and hence tryptophan, which is the precursor of signalling molecules such as indole-3-acetic acid (IAA), kynurenine and Pseudomonas quinolone signal (PQS). Commercially available tryptophan-derived molecules were tested for their role in the regulation of T3SS expression. At millimolar concentrations, IAA, 1-naphthalacetic acid (NAA) and 3-hydroxykynurenine inhibited T3SS expression. Inactivation of the tryptophan dioxygenase-encoding kynA gene resulted in a decrease in the T3SS-inhibiting activity of supernatants. These observations suggest that tryptophan catabolites are involved in the downregulation of T3SS expression in the transition from a low- to a high-cell-density state.
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Affiliation(s)
- Da-Kang Shen
- Department of Microbiology and Parasitology, Shanghai Jiao-Tong University School of Medicine, Shanghai 200025, PR China.,GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Didier Filopon
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Hichem Chaker
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Stephanie Boullanger
- Service Spectrométrie de Masse, CERMAV-CNRS, BP53, 38041 Grenoble cedex 9, France
| | - Madiha Derouazi
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Benoit Polack
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
| | - Bertrand Toussaint
- GREPI, TIMC-IMAG, UMR5525 CNRS/Université Joseph Fourier Faculté de Médecine, Bat. J Roget, Domaine de la Merci, 38700 La Tronche, France
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The bile response repressor BreR regulates expression of the Vibrio cholerae breAB efflux system operon. J Bacteriol 2008; 190:7441-52. [PMID: 18776020 DOI: 10.1128/jb.00584-08] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enteric pathogens have developed several resistance mechanisms to survive the antimicrobial action of bile. We investigated the transcriptional profile of Vibrio cholerae O1 El Tor strain C6706 under virulence gene-inducing conditions in the presence and absence of bile. Microarray analysis revealed that the expression of 119 genes was affected by bile. The mRNA levels of genes encoding proteins involved in transport were increased in the presence of bile, whereas the mRNA levels of genes encoding proteins involved in pathogenesis and chemotaxis were decreased. This study identified genes encoding transcriptional regulators from the TetR family (vexR and breR) and multidrug efflux pumps from the resistance-nodulation-cell division superfamily (vexB and vexD [herein renamed breB]) that were induced in response to bile. Further analysis regarding vexAB and breAB expression in the presence of various antimicrobial compounds established that vexAB was induced in the presence of bile, sodium dodecyl sulfate, or novobiocin and that the induction of breAB was specific to bile. BreR is a direct repressor of the breAB promoter and is able to regulate its own expression, as demonstrated by transcriptional and electrophoretic mobility shift assays (EMSA). The expression of breR and breAB is induced in the presence of the bile salts cholate, deoxycholate, and chenodeoxycholate, and EMSA showed that deoxycholate is able to abolish the formation of BreR-P(breR) complexes. We propose that deoxycholate is able to interact with BreR and induce a conformational change that interferes with the DNA binding ability of BreR, resulting in breAB and breR expression. These results provide new insight into a transcriptional regulator and a transport system that likely play essential roles in the ability of V. cholerae to resist the action of bile in the host.
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222
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Walsh CT, Fischbach MA. Inhibitors of sterol biosynthesis as Staphylococcus aureus antibiotics. Angew Chem Int Ed Engl 2008; 47:5700-2. [PMID: 18576462 DOI: 10.1002/anie.200801801] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Christopher T Walsh
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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223
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Rasko DA, Moreira CG, Li DR, Reading NC, Ritchie JM, Waldor MK, Williams N, Taussig R, Wei S, Roth M, Hughes DT, Huntley JF, Fina MW, Falck JR, Sperandio V. Targeting QseC signaling and virulence for antibiotic development. Science 2008; 321:1078-80. [PMID: 18719281 PMCID: PMC2605406 DOI: 10.1126/science.1160354] [Citation(s) in RCA: 383] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Many bacterial pathogens rely on a conserved membrane histidine sensor kinase, QseC, to respond to host adrenergic signaling molecules and bacterial signals in order to promote the expression of virulence factors. Using a high-throughput screen, we identified a small molecule, LED209, that inhibits the binding of signals to QseC, preventing its autophosphorylation and consequently inhibiting QseC-mediated activation of virulence gene expression. LED209 is not toxic and does not inhibit pathogen growth; however, this compound markedly inhibits the virulence of several pathogens in vitro and in vivo in animals. Inhibition of signaling offers a strategy for the development of broad-spectrum antimicrobial drugs.
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Affiliation(s)
- David A. Rasko
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Cristiano G. Moreira
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - De Run Li
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Nicola C. Reading
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jennifer M. Ritchie
- Channing Laboratory, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Matthew K. Waldor
- Channing Laboratory, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Noelle Williams
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ron Taussig
- Department of Pharmacology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Shuguang Wei
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Michael Roth
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - David T. Hughes
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jason F. Huntley
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Maggy W. Fina
- Department of Pharmacology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - John R. Falck
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
| | - Vanessa Sperandio
- Department of Microbiology, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biochemistry, University of Texas (UT) Southwestern Medical Center, Dallas, TX 75390, USA
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224
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Walsh C, Fischbach M. Inhibitoren der Sterolbiosynthese als Antibiotika gegen Staphylococcus aureus. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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225
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Vibrio cholerae RND family efflux systems are required for antimicrobial resistance, optimal virulence factor production, and colonization of the infant mouse small intestine. Infect Immun 2008; 76:3595-605. [PMID: 18490456 DOI: 10.1128/iai.01620-07] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Vibrio cholerae is a gram-negative human intestinal pathogen that causes the diarrheal disease cholera. Humans acquire cholera by ingesting V. cholerae-contaminated food or water. Upon ingestion, V. cholerae encounters several barriers to colonization, including bile acid toxicity and antimicrobial products of the innate immune system. In many gram-negative bacteria, resistance to the antimicrobial effects of these products is mediated by RND (resistance-nodulation-division) family efflux systems. In this study we tested the hypothesis that the V. cholerae RND efflux systems are required for antimicrobial resistance and virulence. The six V. cholerae genes encoding RND efflux pumps were deleted from the genome of the O1 El Tor strain N16961, resulting in the generation of 14 independent RND deletion mutants, including one RND-null strain. Determination of the antimicrobial susceptibilities of the mutants revealed that the RND efflux systems were responsible for resistance to multiple antimicrobial compounds, including bile acids, antimicrobial peptides, and antibiotics. VexB (VC0164) was found to be the RND efflux pump primarily responsible for the resistance of V. cholerae to multiple antimicrobial compounds in vitro. In contrast, VexD (VC1757) and VexK (VC1673) encoded efflux pumps with detergent-specific substrate specificities that were redundant with VexB. A strain lacking VexB, VexD, and VexK was attenuated in the infant mouse model, and its virulence factor production was unaffected. In contrast, a V. cholerae RND-null strain produced significantly less cholera toxin and fewer toxin-coregulated pili than the wild type and was unable to colonize the infant mouse. The decreased virulence factor production in the RND-null strain was linked to reduced transcription of tcpP and toxT. Our findings show that the V. cholerae RND efflux systems are required for antimicrobial resistance, optimal virulence factor production, and colonization of the infant mouse.
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226
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Brown S, Zhang YH, Walker S. A revised pathway proposed for Staphylococcus aureus wall teichoic acid biosynthesis based on in vitro reconstitution of the intracellular steps. ACTA ACUST UNITED AC 2008; 15:12-21. [PMID: 18215769 DOI: 10.1016/j.chembiol.2007.11.011] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2007] [Revised: 11/09/2007] [Accepted: 11/14/2007] [Indexed: 11/15/2022]
Abstract
Resistance to every family of clinically used antibiotics has emerged, and there is a pressing need to explore unique antibacterial targets. Wall teichoic acids (WTAs) are anionic polymers that coat the cell walls of many Gram-positive bacteria. Because WTAs play an essential role in Staphylococcus aureus colonization and infection, the enzymes involved in WTA biosynthesis are proposed to be targets for antibiotic development. To facilitate the discovery of WTA inhibitors, we have reconstituted the intracellular steps of S. aureus WTA biosynthesis. We show that two intracellular steps in the biosynthetic pathway are different from what was proposed. The work reported here lays the foundation for the discovery and characterization of inhibitors of WTA biosynthetic enzymes to assess their potential for treating bacterial infections.
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Affiliation(s)
- Stephanie Brown
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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227
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228
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da Silva APG, Unks D, Lyu SC, Ma J, Zbozien-Pacamaj R, Chen X, Krensky AM, Clayberger C. In vitro and in vivo antimicrobial activity of granulysin-derived peptides against Vibrio cholerae. J Antimicrob Chemother 2008; 61:1103-9. [PMID: 18310138 DOI: 10.1093/jac/dkn058] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
OBJECTIVES To determine the antibacterial activity of synthetic peptides derived from the cationic antimicrobial peptide granulysin against Vibrio cholerae. METHODS The antibacterial activity of granulysin-derived peptides was assessed in vitro by microtitre and cfu assays. Toxicity against human peripheral blood mononuclear cells (PBMCs) was measured by propidium iodide uptake and haemolysis by measuring the levels of haemoglobin released after incubation of red blood cells (RBCs) with granulysin peptides. The ability of granulysin peptides to control bacterial growth in vivo was tested by the treatment of suckling mice infected with V. cholerae with granulysin peptides, administered by gavage 1 h after infection and determining the number of bacteria in the small and large intestines 24 h after infection. RESULTS All peptides tested inhibited V. cholerae growth in vitro, and they were more effective against stationary phase cells. Two peptides, G12.21 and G14.15, effectively controlled bacterial growth in vivo. The peptides did not lyse RBCs and, with the exception of two peptides, exhibited very little toxicity against human PBMCs. CONCLUSIONS These results suggest that granulysin-derived peptides are candidates for the development of new agents for the treatment of V. cholerae infection.
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Affiliation(s)
- Ana Paula Galvão da Silva
- Division of Immunology and Transplantation Biology, Department of Pediatrics, CCSR 2105, Stanford University School of Medicine, Stanford, CA 94305, USA
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229
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Arnoldo A, Curak J, Kittanakom S, Chevelev I, Lee VT, Sahebol-Amri M, Koscik B, Ljuma L, Roy PJ, Bedalov A, Giaever G, Nislow C, Merrill RA, Lory S, Stagljar I. Identification of small molecule inhibitors of Pseudomonas aeruginosa exoenzyme S using a yeast phenotypic screen. PLoS Genet 2008; 4:e1000005. [PMID: 18454192 PMCID: PMC2265467 DOI: 10.1371/journal.pgen.1000005] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 01/17/2008] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen that is a key factor in the mortality of cystic fibrosis patients, and infection represents an increased threat for human health worldwide. Because resistance of Pseudomonas aeruginosa to antibiotics is increasing, new inhibitors of pharmacologically validated targets of this bacterium are needed. Here we demonstrate that a cell-based yeast phenotypic assay, combined with a large-scale inhibitor screen, identified small molecule inhibitors that can suppress the toxicity caused by heterologous expression of selected Pseudomonas aeruginosa ORFs. We identified the first small molecule inhibitor of Exoenzyme S (ExoS), a toxin involved in Type III secretion. We show that this inhibitor, exosin, modulates ExoS ADP-ribosyltransferase activity in vitro, suggesting the inhibition is direct. Moreover, exosin and two of its analogues display a significant protective effect against Pseudomonas infection in vivo. Furthermore, because the assay was performed in yeast, we were able to demonstrate that several yeast homologues of the known human ExoS targets are likely ADP-ribosylated by the toxin. For example, using an in vitro enzymatic assay, we demonstrate that yeast Ras2p is directly modified by ExoS. Lastly, by surveying a collection of yeast deletion mutants, we identified Bmh1p, a yeast homologue of the human FAS, as an ExoS cofactor, revealing that portions of the bacterial toxin mode of action are conserved from yeast to human. Taken together, our integrated cell-based, chemical-genetic approach demonstrates that such screens can augment traditional drug screening approaches and facilitate the discovery of new compounds against a broad range of human pathogens.
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Affiliation(s)
- Anthony Arnoldo
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Jasna Curak
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Saranya Kittanakom
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Igor Chevelev
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Vincent T. Lee
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Mehdi Sahebol-Amri
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Becky Koscik
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Lana Ljuma
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Peter J. Roy
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
| | - Antonio Bedalov
- Clinical Research and Human Biology Divisions, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Guri Giaever
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
- Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada
| | - Corey Nislow
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
- Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada
| | - Rod A. Merrill
- Department of Molecular and Cellular Biology, University of Guelph, Ontario, Canada
| | - Stephen Lory
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Igor Stagljar
- Terrence Donnelly Centre for Cellular and Biomolecular Research, Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Ontario, Canada
- * E-mail:
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230
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Zhong Z, Yu X, Zhu J. Red bayberry extract inhibits growth and virulence gene expression of the human pathogen Vibrio cholerae. J Antimicrob Chemother 2008; 61:753-4. [DOI: 10.1093/jac/dkm540] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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231
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Cegelski L, Marshall GR, Eldridge GR, Hultgren SJ. The biology and future prospects of antivirulence therapies. Nat Rev Microbiol 2008; 6:17-27. [PMID: 18079741 DOI: 10.1038/nrmicro1818] [Citation(s) in RCA: 572] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The emergence and increasing prevalence of bacterial strains that are resistant to available antibiotics demand the discovery of new therapeutic approaches. Targeting bacterial virulence is an alternative approach to antimicrobial therapy that offers promising opportunities to inhibit pathogenesis and its consequences without placing immediate life-or-death pressure on the target bacterium. Certain virulence factors have been shown to be potential targets for drug design and therapeutic intervention, whereas new insights are crucial for exploiting others. Targeting virulence represents a new paradigm to empower the clinician to prevent and treat infectious diseases.
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Affiliation(s)
- Lynette Cegelski
- Department of Molecular Microbiology, Washington University, Saint Louis, Missouri 63110, USA
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232
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Abstract
Clinically significant antibiotic resistance has evolved against virtually every antibiotic deployed. Yet the development of new classes of antibiotics has lagged far behind our growing need for such drugs. Rather than focusing on therapeutics that target in vitro viability, much like conventional antibiotics, an alternative approach is to target functions essential for infection, such as virulence factors required to cause host damage and disease. This approach has several potential advantages including expanding the repertoire of bacterial targets, preserving the host endogenous microbiome, and exerting less selective pressure, which may result in decreased resistance. We review new approaches to targeting virulence, discuss their advantages and disadvantages, and propose that in addition to targeting virulence, new antimicrobial development strategies should be expanded to include targeting bacterial gene functions that are essential for in vivo viability. We highlight both new advances in identifying these functions and prospects for antimicrobial discovery targeting this unexploited area.
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Affiliation(s)
- Anne E Clatworthy
- Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, 185 Cambridge St., Boston, Massachusetts 02114, USA
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233
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Abstract
Vibrio cholerae is a gram-negative bacterium that is the causative agent of cholera. This disease consists of enormous fluid loss through stools, which can be fatal. Cholera epidemics appear in explosive outbreaks that have occurred repeatedly throughout history. The virulence factors toxin coregulated pilus (TCP) and cholera toxin (CT) are essential for colonization of the host and enterotoxicity, respectively. These virulence factors are under the control of ToxT, an AraC/XylS family protein that activates transcription of the genes encoding TCP and CT. ToxT is under the control of a virulence regulatory cascade known as the ToxR regulon, which responds to environmental stimuli to ensure maximal virulence-factor induction within the human intestine. An understanding of this intricate signaling pathway is essential for the development of methods to treat and prevent this devastating disease.
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Affiliation(s)
- Brandon M Childers
- Department of Microbiology & Immunology, San Antonio, TX 78229-3900, USA.
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234
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Abstract
Steven Opal reviews the phenomenon of bacterial communities and discusses the role played by bacterial communication and cooperation in host-pathogen interactions, particularly in urinary tract infection.
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Affiliation(s)
- Steven M Opal
- Warren Alpert Medical School of Brown University, Infectious Disease Division, Memorial Hospital of Rhode Island, Pawtucket, Rhode Island, United States of America.
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235
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Abstract
High-affinity iron acquisition is mediated by siderophore-dependent pathways in the majority of pathogenic and nonpathogenic bacteria and fungi. Considerable progress has been made in characterizing and understanding mechanisms of siderophore synthesis, secretion, iron scavenging, and siderophore-delivered iron uptake and its release. The regulation of siderophore pathways reveals multilayer networks at the transcriptional and posttranscriptional levels. Due to the key role of many siderophores during virulence, coevolution led to sophisticated strategies of siderophore neutralization by mammals and (re)utilization by bacterial pathogens. Surprisingly, hosts also developed essential siderophore-based iron delivery and cell conversion pathways, which are of interest for diagnostic and therapeutic studies. In the last decades, natural and synthetic compounds have gained attention as potential therapeutics for iron-dependent treatment of infections and further diseases. Promising results for pathogen inhibition were obtained with various siderophore-antibiotic conjugates acting as "Trojan horse" toxins and siderophore pathway inhibitors. In this article, general aspects of siderophore-mediated iron acquisition, recent findings regarding iron-related pathogen-host interactions, and current strategies for iron-dependent pathogen control will be reviewed. Further concepts including the inhibition of novel siderophore pathway targets are discussed.
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Affiliation(s)
- Marcus Miethke
- Philipps Universität Marburg, FB Chemie Biochemie, Hans Meerwein Strasse, D-35032 Marburg, Germany
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236
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Shakhnovich EA, Sturtevant D, Mekalanos JJ. Molecular mechanisms of virstatin resistance by non-O1/non-O139 strains of Vibrio cholerae. Mol Microbiol 2007; 66:1331-41. [DOI: 10.1111/j.1365-2958.2007.05984.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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237
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Kauppi AM, Andersson CD, Norberg HA, Sundin C, Linusson A, Elofsson M. Inhibitors of type III secretion in Yersinia: Design, synthesis and multivariate QSAR of 2-arylsulfonylamino-benzanilides. Bioorg Med Chem 2007; 15:6994-7011. [PMID: 17851084 DOI: 10.1016/j.bmc.2007.07.047] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 07/18/2007] [Accepted: 07/25/2007] [Indexed: 11/19/2022]
Abstract
Compound 1, 2-(benzo[1,2,5]thiadiazole-4-sulfonylamino)-5-chloro-N-(3,4-dichloro-phenyl)-benzamide, was identified as a putative type III secretion inhibitor in Yersinia, and the compound thus has a potential to be used to prevent or treat bacterial infections. A set of seven analogues was synthesized and evaluated in a type III secretion dependent reporter-gene assay with viable bacterial to give basic SAR. A second set of 19 compounds was obtained by statistical molecular design in the building block and product space and by subsequent synthesis. Evaluation in the reporter-gene assay showed that the compounds ranged from non-active to compounds more potent than 1. Based on the data multivariate QSAR models were established and the final Hi-PLS model showed good correlation between experimentally determined % inhibition and the calculated % inhibition of the reporter-gene signal.
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Affiliation(s)
- Anna M Kauppi
- Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden
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238
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Abstract
Campylobacter jejuni is a foodborne bacterial pathogen that is common in the developed world. However, we know less about its biology and pathogenicity than we do about other less prevalent pathogens. Interest in C. jejuni has increased in recent years as a result of the growing appreciation of its importance as a pathogen and the availability of new model systems and genetic and genomic technologies. C. jejuni establishes persistent, benign infections in chickens and is rapidly cleared by many strains of laboratory mouse, but causes significant inflammation and enteritis in humans. Comparing the different host responses to C. jejuni colonization should increase our understanding of this organism.
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Affiliation(s)
- Kathryn T Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 48109, USA
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239
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Matson JS, Withey JH, DiRita VJ. Regulatory networks controlling Vibrio cholerae virulence gene expression. Infect Immun 2007; 75:5542-9. [PMID: 17875629 PMCID: PMC2168339 DOI: 10.1128/iai.01094-07] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Jyl S Matson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-0620, USA
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240
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Mellies JL, Barron AMS, Carmona AM. Enteropathogenic and enterohemorrhagic Escherichia coli virulence gene regulation. Infect Immun 2007; 75:4199-210. [PMID: 17576759 PMCID: PMC1951183 DOI: 10.1128/iai.01927-06] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Jay L Mellies
- Biology Department, Reed College, 3203 S.E. Woodstock Boulevard, Portland, OR 97202, USA.
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241
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Saenz JB, Doggett TA, Haslam DB. Identification and characterization of small molecules that inhibit intracellular toxin transport. Infect Immun 2007; 75:4552-61. [PMID: 17576758 PMCID: PMC1951202 DOI: 10.1128/iai.00442-07] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Shiga toxin (Stx), cholera toxin (Ctx), and the plant toxin ricin are among several toxins that reach their intracellular destinations via a complex route. Following endocytosis, these toxins travel in a retrograde direction through the endosomal system to the trans-Golgi network, Golgi apparatus, and endoplasmic reticulum (ER). There the toxins are transported across the ER membrane to the cytosol, where they carry out their toxic effects. Transport via the ER from the cell surface to the cytosol is apparently unique to pathogenic toxins, raising the possibility that various stages in the transport pathway can be therapeutically targeted. We have applied a luciferase-based high-throughput screen to a chemical library of small-molecule compounds in order to identify inhibitors of Stx. We report two novel compounds that protect against Stx and ricin inhibition of protein synthesis, and we demonstrate that these compounds reversibly inhibit bacterial transport at various stages in the endocytic pathway. One compound (compound 75) inhibited transport at an early stage of Stx and Ctx transport and also provided protection against diphtheria toxin, which enters the cytosol from early endosomes. In contrast, compound 134 inhibited transport from recycling endosomes through the Golgi apparatus and protected only against toxins that access the ER. Small-molecule compounds such as these will provide insight into the mechanism of toxin transport and lead to the identification of compounds with therapeutic potential against toxins routed through the ER.
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Affiliation(s)
- Jose B Saenz
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
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242
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Negrea A, Bjur E, Ygberg SE, Elofsson M, Wolf-Watz H, Rhen M. Salicylidene acylhydrazides that affect type III protein secretion in Salmonella enterica serovar typhimurium. Antimicrob Agents Chemother 2007; 51:2867-76. [PMID: 17548496 PMCID: PMC1932493 DOI: 10.1128/aac.00223-07] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A collection of nine salicylidene acylhydrazide compounds were tested for their ability to inhibit the activity of virulence-associated type III secretion systems (T3SSs) in Salmonella enterica serovar Typhimurium. The compounds strongly affected Salmonella pathogenicity island 1 (SPI1) T3SS-mediated invasion of epithelial cells and in vitro secretion of SPI1 invasion-associated effector proteins. The use of a SPI1 effector beta-lactamase fusion protein implicated intracellular entrapment of the protein construct upon application of a salicylidene acylhydrazide, whereas the use of chromosomal transcriptional gene fusions revealed a compound-mediated transcriptional silencing of SPI1. Salicylidene acylhydrazides also affected intracellular bacterial replication in murine macrophage-like cells and blocked the transport of an epitope-tagged SPI2 effector protein. Two of the compounds significantly inhibited bacterial motility and expression of extracellular flagellin. We conclude that salicylidene acylhydrazides affect bacterial T3SS activity in S. enterica and hence could be used as lead substances when designing specific inhibitors of bacterial T3SSs in order to pharmaceutically intervene with bacterial virulence.
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Affiliation(s)
- Aurel Negrea
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Nobels väg 16, Stockholm, Sweden
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243
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Wright GD, Sutherland AD. New strategies for combating multidrug-resistant bacteria. Trends Mol Med 2007; 13:260-7. [PMID: 17493872 DOI: 10.1016/j.molmed.2007.04.004] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 04/03/2007] [Accepted: 04/30/2007] [Indexed: 11/24/2022]
Abstract
Antibiotic resistance is a problem that continues to challenge the healthcare sector. In particular, multidrug resistance is now common in familiar pathogens such as Staphylococcus aureus and Mycobacterium tuberculosis, as well as emerging pathogens such as Acinetobacter baumannii. New antibiotics and new therapeutic strategies are needed to address this challenge. Advances in identifying new sources of antibiotic natural products and expanding antibiotic chemical diversity are providing chemical leads for new drugs. Inhibitors of resistance mechanisms and microbial virulence are orthogonal strategies that are also generating new chemicals that can extend the life of existing antibiotics. This new chemistry, coupled with a growing understanding of the mechanisms, origins and distribution of antibiotic resistance, position us to tackle the challenges of antibiotic resistance in the 21st century.
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Affiliation(s)
- Gerard D Wright
- Antimicrobial Research Centre, Department of Biochemistry and Biomedical Sciences, DeGroote School of Medicine, McMaster University, 1200 Main St W, Hamilton, Ontario, L8N 3Z5, Canada.
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244
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Zhang Q, Major MB, Takanashi S, Camp ND, Nishiya N, Peters EC, Ginsberg MH, Jian X, Randazzo PA, Schultz PG, Moon RT, Ding S. Small-molecule synergist of the Wnt/beta-catenin signaling pathway. Proc Natl Acad Sci U S A 2007; 104:7444-8. [PMID: 17460038 PMCID: PMC1863490 DOI: 10.1073/pnas.0702136104] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Indexed: 11/18/2022] Open
Abstract
The Wnt/beta-catenin signaling pathway regulates cell fate and behavior during embryogenesis, adult tissue homeostasis, and regeneration. When inappropriately activated, the pathway has been linked to colorectal cancer and melanoma, and when attenuated it may contribute to Alzheimer's disease and osteoporosis. Small molecules that modulate Wnt signaling will likely provide new insights into the regulation of this key developmental pathway and ultimately provide pharmacological agents to control Wnt signaling in vivo. To this end, we screened a library of 100,000 small molecules for activity in a cell-based assay of Wnt/beta-catenin signaling and discovered a purine derivative, QS11, that synergizes with Wnt-3a ligand in the activation of Wnt/beta-catenin signal transduction. Through affinity chromatography and subsequent functional assays, we showed that QS11 binds and inhibits the GTPase activating protein of ADP-ribosylation factor 1 (ARFGAP1), suggesting that QS11 modulates Wnt/beta-catenin signaling through an effect on protein trafficking. Consistent with its function as an ARFGAP inhibitor, QS11 inhibits migration of ARFGAP overexpressing breast cancer cells.
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Affiliation(s)
- Qisheng Zhang
- *Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Michael B. Major
- Howard Hughes Medical Institute, Department of Pharmacology, and the Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, WA 98195
| | - Shinichi Takanashi
- *Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Nathan D. Camp
- Howard Hughes Medical Institute, Department of Pharmacology, and the Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, WA 98195
| | - Naoyuki Nishiya
- Department of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093
| | - Eric C. Peters
- Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, CA 92121; and
| | - Mark H. Ginsberg
- Department of Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Paul A. Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | - Peter G. Schultz
- *Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
- Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, CA 92121; and
| | - Randall T. Moon
- Howard Hughes Medical Institute, Department of Pharmacology, and the Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, WA 98195
| | - Sheng Ding
- *Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
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245
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Benghezal M, Adam E, Lucas A, Burn C, Orchard MG, Deuschel C, Valentino E, Braillard S, Paccaud JP, Cosson P. Inhibitors of bacterial virulence identified in a surrogate host model. Cell Microbiol 2007; 9:1336-42. [PMID: 17474906 DOI: 10.1111/j.1462-5822.2006.00877.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Antibiotic resistance continues to reduce the number of available antibiotics, increasing the need for novel antibacterial drugs. Since the seminal work of Sir Alexander Fleming, antibiotic identification has been based exclusively on the inhibition of bacterial growth in vitro. Recently, inhibitors of bacterial virulence which interfere with bacterial pathogenesis mechanisms have been proposed as an alternative to antibiotics, and a few were discovered using assays targeting specific virulence mechanisms. Here we designed a simple surrogate host model for the measurement of virulence and systematic discovery of anti-virulence molecules, based on the interaction of Tetrahymena pyriformis and Klebsiella pneumoniae cells. We screened a library of small molecules and identified several inhibitors of virulence. In a mouse pneumonia model we confirmed that an anti-virulence molecule displayed antibacterial activity against Klebsiella pneumoniae and Pseudomonas aeruginosa, by reducing dramatically the bacterial load in the lungs. This molecule did not inhibit bacterial growth in vitro but prevented biosynthesis of the Klebsiella capsule and lipopolysaccharides, a key requirement for virulence. Our results demonstrate that anti-virulence molecules represent an alternative to antibiotics and those can be discovered using non-animal host models.
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246
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Abstract
In a time of emerging bacterial resistance there is a vital need for new targets and strategies in antibacterial therapy. Using uropathogenic Escherichia coli as a model pathogen we have developed a class of compounds, pilicides, which inhibit the formation of virulence-associated organelles termed pili. The pilicides interfere with a highly conserved bacterial assembly and secretion system called the chaperone-usher pathway, which is abundant in a vast number of Gram-negative pathogens and serves to assemble multi-protein surface fibers (pili/fimbriae). This class of compounds provides a platform to gain insight into important biological processes such as the molecular mechanisms of the chaperone-usher pathway and the sophisticated function of pili. Pili are primarily involved in bacterial adhesion, invasion and persistence to host defenses. On this basis, pilicides can aid the development of new antibacterial agents.
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Affiliation(s)
- Veronica Aberg
- Department of Chemistry, Umeå University, SE-90187, Umeå, Sweden.
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247
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Zhang L, Yan K, Zhang Y, Huang R, Bian J, Zheng C, Sun H, Chen Z, Sun N, An R, Min F, Zhao W, Zhuo Y, You J, Song Y, Yu Z, Liu Z, Yang K, Gao H, Dai H, Zhang X, Wang J, Fu C, Pei G, Liu J, Zhang S, Goodfellow M, Jiang Y, Kuai J, Zhou G, Chen X. High-throughput synergy screening identifies microbial metabolites as combination agents for the treatment of fungal infections. Proc Natl Acad Sci U S A 2007; 104:4606-11. [PMID: 17360571 PMCID: PMC1838648 DOI: 10.1073/pnas.0609370104] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Indexed: 11/18/2022] Open
Abstract
The high mortality rate of immunocompromised patients with fungal infections and the limited availability of highly efficacious and safe agents demand the development of new antifungal therapeutics. To rapidly discover such agents, we developed a high-throughput synergy screening (HTSS) strategy for novel microbial natural products. Specifically, a microbial natural product library was screened for hits that synergize the effect of a low dosage of ketoconazole (KTC) that alone shows little detectable fungicidal activity. Through screening of approximately 20,000 microbial extracts, 12 hits were identified with broad-spectrum antifungal activity. Seven of them showed little cytotoxicity against human hepatoma cells. Fractionation of the active extracts revealed beauvericin (BEA) as the most potent component, because it dramatically synergized KTC activity against diverse fungal pathogens by a checkerboard assay. Significantly, in our immunocompromised mouse model, combinations of BEA (0.5 mg/kg) and KTC (0.5 mg/kg) prolonged survival of the host infected with Candida parapsilosis and reduced fungal colony counts in animal organs including kidneys, lungs, and brains. Such an effect was not achieved even with the high dose of 50 mg/kg KTC. These data support synergism between BEA and KTC and thereby a prospective strategy for antifungal therapy.
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Affiliation(s)
- Lixin Zhang
- Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, China.
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248
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Abstract
Many potential drugs that specifically target a particular protein considered to underlie a given disease have been found to be less effective than hoped, or to cause significant side effects. The intrinsic robustness of living systems against various perturbations is a key factor that prevents such compounds from being successful. By studying complex network systems and reformulating control and communication theories that are well established in engineering, a theoretical foundation for a systems-oriented approach to more effectively control the robustness of living systems, particularly at the cellular level, could be developed. Here, I use examples that are based on existing drugs to illustrate the concept of robustness, and then discuss how a greater consideration of the importance of robustness could influence the design of new drugs that will be intended to control complex systems.
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Affiliation(s)
- Hiroaki Kitano
- Sony Computer Science Laboratories Inc., 3-14-13 Higashi-Gotanda, Shinagawa, Tokyo 141-0022, Japan.
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249
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Abstract
Can weakly active phytochemicals be combined synergistically to produce new antibacterial treatments?
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Affiliation(s)
- Kim Lewis
- Antimicrobial Discovery Center and Department of Biology, Northeastern University, Boston, Massachusetts 02115, USA.
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250
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Shakhnovich EA, Hung DT, Pierson E, Lee K, Mekalanos JJ. Virstatin inhibits dimerization of the transcriptional activator ToxT. Proc Natl Acad Sci U S A 2007; 104:2372-7. [PMID: 17283330 PMCID: PMC1892951 DOI: 10.1073/pnas.0611643104] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The development of antimicrobials is critical in this time of increasing antibiotic resistance of most clinically relevant bacteria. To date, all current antibiotics focus on inhibiting crucial enzymatic activities of their protein targets (i.e., trimethoprim for dihydrofolate reductase), thus disrupting in vitro essential gene functions. In contrast, we have previously reported the identification of virstatin, a small molecule that inhibits virulence regulation in Vibrio cholerae, thereby preventing intestinal colonization in an infant mouse model for cholera. Virstatin prevents expression of the two major V. cholerae virulence factors, cholera toxin (CT) and the toxin coregulated pilus, by inhibiting the virulence transcriptional activator ToxT. It has previously been described that the N-terminal domain of ToxT has the ability to form homodimers. We now demonstrate that virstatin inhibits ToxT dimerization, thus demonstrating that it further falls into a unique class of inhibitors that works by disrupting protein-protein interactions, particularly homodimerization. Using virstatin, truncation mutants of ToxT, and a virstatin-resistant mutant, we show that dimerization is required for ToxT activation of the ctx promoter. In contrast, ToxT dimerization does not appear to be required at all of the other ToxT-regulated promoters, suggesting multiple mechanisms may exist for its transcriptional activity.
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Affiliation(s)
- Elizabeth A. Shakhnovich
- *Department of Microbiology and Molecular Genetics, Harvard Medical School, Armenise Building, Room 425, 200 Longwood Avenue, Boston, MA 02115
| | - Deborah T. Hung
- *Department of Microbiology and Molecular Genetics, Harvard Medical School, Armenise Building, Room 425, 200 Longwood Avenue, Boston, MA 02115
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Simches Research Building 7208, 185 Cambridge Street, Boston, MA 02114
- Broad Institute of Massachusetts Institute of Technology and Harvard, 7 Cambridge Center, Cambridge, MA 02142; and
| | - Emily Pierson
- *Department of Microbiology and Molecular Genetics, Harvard Medical School, Armenise Building, Room 425, 200 Longwood Avenue, Boston, MA 02115
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Simches Research Building 7208, 185 Cambridge Street, Boston, MA 02114
- Broad Institute of Massachusetts Institute of Technology and Harvard, 7 Cambridge Center, Cambridge, MA 02142; and
| | - Kyungae Lee
- New England Regional Center of Excellence, 200 Longwood Avenue, Boston, MA 02114
| | - John J. Mekalanos
- *Department of Microbiology and Molecular Genetics, Harvard Medical School, Armenise Building, Room 425, 200 Longwood Avenue, Boston, MA 02115
- To whom correspondence should be addressed. E-mail:
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