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Kavanaugh LG, Dey D, Shafer WM, Conn GL. Structural and functional diversity of Resistance-Nodulation-Division (RND) efflux pump transporters with implications for antimicrobial resistance. Microbiol Mol Biol Rev 2024:e0008923. [PMID: 39235227 DOI: 10.1128/mmbr.00089-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2024] Open
Abstract
SUMMARYThe discovery of bacterial efflux pumps significantly advanced our understanding of how bacteria can resist cytotoxic compounds that they encounter. Within the structurally and functionally distinct families of efflux pumps, those of the Resistance-Nodulation-Division (RND) superfamily are noteworthy for their ability to reduce the intracellular concentration of structurally diverse antimicrobials. RND systems are possessed by many Gram-negative bacteria, including those causing serious human disease, and frequently contribute to resistance to multiple antibiotics. Herein, we review the current literature on the structure-function relationships of representative transporter proteins of tripartite RND efflux pumps of clinically important pathogens. We emphasize their contribution to bacterial resistance to clinically used antibiotics, host defense antimicrobials and other biocides, as well as highlighting structural similarities and differences among efflux transporters that help bacteria survive in the face of antimicrobials. Furthermore, we discuss technical advances that have facilitated and advanced efflux pump research and suggest future areas of investigation that will advance antimicrobial development efforts.
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Affiliation(s)
- Logan G Kavanaugh
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
- Graduate Program in Microbiology and Molecular Genetics, Emory University, Atlanta, Georgia, USA
| | - Debayan Dey
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
| | - William M Shafer
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
- Laboratories of Microbial Pathogenesis, VA Medical Research Service, Veterans Affairs Medical Center, Decatur, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Graeme L Conn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
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2
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Unemo M, Sánchez-Busó L, Golparian D, Jacobsson S, Shimuta K, Lan PT, Eyre DW, Cole M, Maatouk I, Wi T, Lahra MM. The novel 2024 WHO Neisseria gonorrhoeae reference strains for global quality assurance of laboratory investigations and superseded WHO N. gonorrhoeae reference strains-phenotypic, genetic and reference genome characterization. J Antimicrob Chemother 2024; 79:1885-1899. [PMID: 38889110 PMCID: PMC11290888 DOI: 10.1093/jac/dkae176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 05/15/2024] [Indexed: 06/20/2024] Open
Abstract
OBJECTIVES MDR and XDR Neisseria gonorrhoeae strains remain major public health concerns internationally, and quality-assured global gonococcal antimicrobial resistance (AMR) surveillance is imperative. The WHO global Gonococcal Antimicrobial Surveillance Programme (GASP) and WHO Enhanced GASP (EGASP), including metadata and WGS, are expanding internationally. We present the phenotypic, genetic and reference genome characteristics of the 2024 WHO gonococcal reference strains (n = 15) for quality assurance worldwide. All superseded WHO gonococcal reference strains (n = 14) were identically characterized. MATERIAL AND METHODS The 2024 WHO reference strains include 11 of the 2016 WHO reference strains, which were further characterized, and four novel strains. The superseded WHO reference strains include 11 WHO reference strains previously unpublished. All strains were characterized phenotypically and genomically (single-molecule PacBio or Oxford Nanopore and Illumina sequencing). RESULTS The 2024 WHO reference strains represent all available susceptible and resistant phenotypes and genotypes for antimicrobials currently and previously used (n = 22), or considered for future use (n = 3) in gonorrhoea treatment. The novel WHO strains include internationally spreading ceftriaxone resistance, ceftriaxone resistance due to new penA mutations, ceftriaxone plus high-level azithromycin resistance and azithromycin resistance due to mosaic MtrRCDE efflux pump. AMR, serogroup, prolyliminopeptidase, genetic AMR determinants, plasmid types, molecular epidemiological types and reference genome characteristics are presented for all strains. CONCLUSIONS The 2024 WHO gonococcal reference strains are recommended for internal and external quality assurance in laboratory examinations, especially in the WHO GASP, EGASP and other GASPs, but also in phenotypic and molecular diagnostics, AMR prediction, pharmacodynamics, epidemiology, research and as complete reference genomes in WGS analysis.
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Affiliation(s)
- Magnus Unemo
- Department of Laboratory Medicine, Faculty of Medicine and Health, WHO Collaborating Centre for Gonorrhoea and Other STIs, National Reference Laboratory for STIs, Microbiology, Örebro University, Örebro, Sweden
- Institute for Global Health, University College London (UCL), London, UK
| | - Leonor Sánchez-Busó
- Joint Research Unit ‘Infection and Public Health’, FISABIO-University of Valencia, Institute for Integrative Systems Biology (I2SysBio), Valencia, Spain
- CIBERESP, ISCIII, Madrid, Spain
| | - Daniel Golparian
- Department of Laboratory Medicine, Faculty of Medicine and Health, WHO Collaborating Centre for Gonorrhoea and Other STIs, National Reference Laboratory for STIs, Microbiology, Örebro University, Örebro, Sweden
| | - Susanne Jacobsson
- Department of Laboratory Medicine, Faculty of Medicine and Health, WHO Collaborating Centre for Gonorrhoea and Other STIs, National Reference Laboratory for STIs, Microbiology, Örebro University, Örebro, Sweden
| | - Ken Shimuta
- Department of Bacteriology I, National Institute of Infectious Diseases, Tokyo, Japan
| | - Pham Thi Lan
- Hanoi Medical University, National Hospital of Dermatology and Venereology, Hanoi, Vietnam
| | - David W Eyre
- Big Data Institute, University of Oxford, Oxford, UK
- Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | | | - Ismael Maatouk
- Department of the Global HIV, Hepatitis and STI Programmes, WHO, Geneva, Switzerland
| | - Teodora Wi
- Department of the Global HIV, Hepatitis and STI Programmes, WHO, Geneva, Switzerland
| | - Monica M Lahra
- WHO Collaborating Centre for Sexually Transmitted Infections and Antimicrobial Resistance, New South Wales Health Pathology, Microbiology, Randwick, NSW, Australia
- Faculty of Medicine, The University of New South Wales, Sydney, Australia
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3
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Klenotic PA, Yu EW. Structural analysis of resistance-nodulation cell division transporters. Microbiol Mol Biol Rev 2024; 88:e0019823. [PMID: 38551344 PMCID: PMC11332337 DOI: 10.1128/mmbr.00198-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2024] Open
Abstract
SUMMARYInfectious bacteria have both intrinsic and acquired mechanisms to combat harmful biocides that enter the cell. Through adaptive pressures, many of these pathogens have become resistant to many, if not all, of the current antibiotics used today to treat these often deadly infections. One prominent mechanism is the upregulation of efflux systems, especially the resistance-nodulation-cell division class of exporters. These tripartite systems consist of an inner membrane transporter coupled with a periplasmic adaptor protein and an outer membrane channel to efficiently transport a diverse array of substrates from inside the cell to the extracellular space. Detailed mechanistic insight into how these inner membrane transporters recognize and shuttle their substrates can ultimately inform both new antibiotic and efflux pump inhibitor design. This review examines the structural basis of substrate recognition of these pumps and the molecular mechanisms underlying multidrug extrusion, which in turn mediate antimicrobial resistance in bacterial pathogens.
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Affiliation(s)
- Philip A. Klenotic
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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Tajer L, Paillart JC, Dib H, Sabatier JM, Fajloun Z, Abi Khattar Z. Molecular Mechanisms of Bacterial Resistance to Antimicrobial Peptides in the Modern Era: An Updated Review. Microorganisms 2024; 12:1259. [PMID: 39065030 PMCID: PMC11279074 DOI: 10.3390/microorganisms12071259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Revised: 06/10/2024] [Accepted: 06/18/2024] [Indexed: 07/28/2024] Open
Abstract
Antimicrobial resistance (AMR) poses a serious global health concern, resulting in a significant number of deaths annually due to infections that are resistant to treatment. Amidst this crisis, antimicrobial peptides (AMPs) have emerged as promising alternatives to conventional antibiotics (ATBs). These cationic peptides, naturally produced by all kingdoms of life, play a crucial role in the innate immune system of multicellular organisms and in bacterial interspecies competition by exhibiting broad-spectrum activity against bacteria, fungi, viruses, and parasites. AMPs target bacterial pathogens through multiple mechanisms, most importantly by disrupting their membranes, leading to cell lysis. However, bacterial resistance to host AMPs has emerged due to a slow co-evolutionary process between microorganisms and their hosts. Alarmingly, the development of resistance to last-resort AMPs in the treatment of MDR infections, such as colistin, is attributed to the misuse of this peptide and the high rate of horizontal genetic transfer of the corresponding resistance genes. AMP-resistant bacteria employ diverse mechanisms, including but not limited to proteolytic degradation, extracellular trapping and inactivation, active efflux, as well as complex modifications in bacterial cell wall and membrane structures. This review comprehensively examines all constitutive and inducible molecular resistance mechanisms to AMPs supported by experimental evidence described to date in bacterial pathogens. We also explore the specificity of these mechanisms toward structurally diverse AMPs to broaden and enhance their potential in developing and applying them as therapeutics for MDR bacteria. Additionally, we provide insights into the significance of AMP resistance within the context of host-pathogen interactions.
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Affiliation(s)
- Layla Tajer
- Laboratory of Applied Biotechnology (LBA3B), Azm Center for Research in Biotechnology and Its Applications, Department of Cell Culture, EDST, Lebanese University, Tripoli 1300, Lebanon; (L.T.); (Z.F.)
| | - Jean-Christophe Paillart
- CNRS, Architecture et Réactivité de l’ARN, UPR 9002, Université de Strasbourg, 2 Allée Konrad Roentgen, F-67000 Strasbourg, France;
| | - Hanna Dib
- College of Engineering and Technology, American University of the Middle East, Egaila 54200, Kuwait;
| | - Jean-Marc Sabatier
- CNRS, INP, Inst Neurophysiopathol, Aix-Marseille Université, 13385 Marseille, France
| | - Ziad Fajloun
- Laboratory of Applied Biotechnology (LBA3B), Azm Center for Research in Biotechnology and Its Applications, Department of Cell Culture, EDST, Lebanese University, Tripoli 1300, Lebanon; (L.T.); (Z.F.)
- Department of Biology, Faculty of Sciences 3, Lebanese University, Campus Michel Slayman Ras Maska, Tripoli 1352, Lebanon
| | - Ziad Abi Khattar
- Faculty of Medicine and Medical Sciences, University of Balamand, Kalhat, P.O. Box 100, Tripoli, Lebanon
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Rice J, Gibson J, Young E, Souder K, Cunningham K, Schmitt DM. Low Oxygen Concentration Reduces Neisseria gonorrhoeae Susceptibility to Resazurin. Antibiotics (Basel) 2024; 13:395. [PMID: 38786124 PMCID: PMC11117329 DOI: 10.3390/antibiotics13050395] [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: 03/08/2024] [Revised: 04/18/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024] Open
Abstract
Neisseria gonorrhoeae has developed resistance to every antibiotic currently approved for the treatment of gonorrhea, prompting the development of new therapies. The phenoxazine dye resazurin exhibits robust antimicrobial activity against N. gonorrhoeae in vitro but fails to limit vaginal colonization by N. gonorrhoeae in a mouse model. The lack of in vivo efficacy may be due to oxygen limitation as in vitro susceptibility assays with resazurin are conducted under atmospheric oxygen while a microaerophilic environment is present in the vagina. Here, we utilized broth microdilution assays to determine the susceptibility of N. gonorrhoeae to resazurin under low and atmospheric oxygen conditions. The minimal inhibitory concentration of resazurin for multiple N. gonorrhoeae clinical isolates was significantly higher under low oxygen. This effect was specific to resazurin as N. gonorrhoeae was equally susceptible to other antibiotics under low and atmospheric oxygen conditions. The reduced susceptibility of N. gonorrhoeae to resazurin under low oxygen was largely attributed to reduced oxidative stress, as the addition of antioxidants under atmospheric oxygen mimicked the reduced susceptibility to resazurin observed under low oxygen. Together, these data suggest oxygen concentration is an important factor to consider when evaluating the efficacy of new antibiotics against N. gonorrhoeae in vitro.
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Affiliation(s)
| | | | | | | | | | - Deanna M. Schmitt
- Department of Biomedical Sciences, West Liberty University, West Liberty, WV 26074, USA
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6
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Wilhelm J, Pos KM. Molecular insights into the determinants of substrate specificity and efflux inhibition of the RND efflux pumps AcrB and AdeB. MICROBIOLOGY (READING, ENGLAND) 2024; 170:001438. [PMID: 38358391 PMCID: PMC10924465 DOI: 10.1099/mic.0.001438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/30/2024] [Indexed: 02/16/2024]
Abstract
Gram-negative bacterial members of the Resistance Nodulation and cell Division (RND) superfamily form tripartite efflux pump systems that span the cell envelope. One of the intriguing features of the multiple drug efflux members of this superfamily is their ability to recognize different classes of antibiotics, dyes, solvents, bile salts, and detergents. This review provides an overview of the molecular mechanisms of multiple drug efflux catalysed by the tripartite RND efflux system AcrAB-TolC from Eschericha coli. The determinants for sequential or simultaneous multiple substrate binding and efflux pump inhibitor binding are discussed. A comparison is made with the determinants for substrate binding of AdeB from Acinetobacter baumannii, which acts within the AdeABC multidrug efflux system. There is an apparent general similarity between the structures of AcrB and AdeB and their substrate specificity. However, the presence of distinct conformational states and different drug efflux capacities as revealed by single-particle cryo-EM and mutational analysis suggest that the drug binding and transport features exhibited by AcrB may not be directly extrapolated to the homolog AdeB efflux pump.
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Affiliation(s)
- Julia Wilhelm
- Institute of Biochemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
| | - Klaas Martinus Pos
- Institute of Biochemistry, Goethe-University Frankfurt, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
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Allgood SC, Su CC, Crooks AL, Meyer CT, Zhou B, Betterton MD, Barbachyn MR, Yu EW, Detweiler CS. Bacterial efflux pump modulators prevent bacterial growth in macrophages and under broth conditions that mimic the host environment. mBio 2023; 14:e0249223. [PMID: 37921493 PMCID: PMC10746280 DOI: 10.1128/mbio.02492-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 09/21/2023] [Indexed: 11/04/2023] Open
Abstract
IMPORTANCE Bacterial efflux pumps are critical for resistance to antibiotics and for virulence. We previously identified small molecules that inhibit efflux pumps (efflux pump modulators, EPMs) and prevent pathogen replication in host cells. Here, we used medicinal chemistry to increase the activity of the EPMs against pathogens in cells into the nanomolar range. We show by cryo-electron microscopy that these EPMs bind an efflux pump subunit. In broth culture, the EPMs increase the potency (activity), but not the efficacy (maximum effect), of antibiotics. We also found that bacterial exposure to the EPMs appear to enable the accumulation of a toxic metabolite that would otherwise be exported by efflux pumps. Thus, inhibitors of bacterial efflux pumps could interfere with infection not only by potentiating antibiotics, but also by allowing toxic waste products to accumulate within bacteria, providing an explanation for why efflux pumps are needed for virulence in the absence of antibiotics.
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Affiliation(s)
- Samual C. Allgood
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Amy L. Crooks
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
| | - Christian T. Meyer
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
- Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado, USA
- Duet Biosystems, Nashville, Tennessee, USA
- Antimicrobial Research Consortium (ARC) Labs, Boulder, Colorado, USA
| | - Bojun Zhou
- Department of Physics, University of Colorado, Boulder, Colorado, USA
| | - Meredith D. Betterton
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
- Department of Physics, University of Colorado, Boulder, Colorado, USA
- Center for Computational Biology, Flatiron Institute, New York, New York, USA
| | | | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Corrella S. Detweiler
- Molecular, Cellular, and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
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8
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Allgood SC, Su CC, Crooks AL, Meyer CT, Zhou B, Betterton MD, Barbachyn MR, Yu EW, Detweiler CS. Bacterial Efflux Pump Modulators Prevent Bacterial Growth in Macrophages and Under Broth Conditions that Mimic the Host Environment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.20.558466. [PMID: 37786697 PMCID: PMC10541609 DOI: 10.1101/2023.09.20.558466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
New approaches for combatting microbial infections are needed. One strategy for disrupting pathogenesis involves developing compounds that interfere with bacterial virulence. A critical molecular determinant of virulence for Gram-negative bacteria are efflux pumps of the resistance-nodulation-division (RND) family, which includes AcrAB-TolC. We previously identified small molecules that bind AcrB, inhibit AcrAB-TolC, and do not appear to damage membranes. These efflux pump modulators (EPMs) were discovered in an in-cell screening platform called SAFIRE (Screen for Anti-infectives using Fluorescence microscopy of IntracellulaR Enterobacteriaceae). SAFIRE identifies compounds that disrupt the growth of a Gram-negative human pathogen, Salmonella enterica serotype Typhimurium (S. Typhimurium) in macrophages. We used medicinal chemistry to iteratively design ~200 EPM35 analogs and test them for activity in SAFIRE, generating compounds with nanomolar potency. Analogs were demonstrated to bind AcrB in a substrate binding pocket by cryo-electron microscopy (cryo-EM). Despite having amphipathic structures, the EPM analogs do not disrupt membrane voltage, as monitored by FtsZ localization to the cell septum. The EPM analogs had little effect on bacterial growth in standard Mueller Hinton Broth. However, under broth conditions that mimic the micro-environment of the macrophage phagosome, acrAB is required for growth, the EPM analogs are bacteriostatic, and increase the potency of antibiotics. These data suggest that under macrophage-like conditions the EPM analogs prevent the export of a toxic bacterial metabolite(s) through AcrAB-TolC. Thus, compounds that bind AcrB could disrupt infection by specifically interfering with the export of bacterial toxic metabolites, host defense factors, and/or antibiotics.
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Affiliation(s)
- Samual C Allgood
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Amy L Crooks
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Christian T Meyer
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
- Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO, USA
- Duet Biosystems, Nashville, TN, USA
- Antimicrobial Research Consortium (ARC) Labs, Boulder, CO, USA
| | - Bojun Zhou
- Department of Physics, University of Colorado, Boulder, CO, USA
| | - Meredith D Betterton
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
- Department of Physics, University of Colorado, Boulder, CO, USA
- Center for Computational Biology, Flatiron Institute, New York, NY, USA
| | | | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Corrella S Detweiler
- Molecular, Cellular Developmental Biology, University of Colorado Boulder, Boulder, CO, USA
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9
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Zhang Z, Lizer N, Wu Z, Morgan CE, Yan Y, Zhang Q, Yu EW. Cryo-Electron Microscopy Structures of a Campylobacter Multidrug Efflux Pump Reveal a Novel Mechanism of Drug Recognition and Resistance. Microbiol Spectr 2023; 11:e0119723. [PMID: 37289051 PMCID: PMC10434076 DOI: 10.1128/spectrum.01197-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023] Open
Abstract
Campylobacter jejuni is a bacterium that is commonly present in the intestinal tracts of animals. It is also a major foodborne pathogen that causes gastroenteritis in humans. The most predominant and clinically important multidrug efflux system in C. jejuni is the CmeABC (Campylobacter multidrug efflux) pump, a tripartite system that includes an inner membrane transporter (CmeB), a periplasmic fusion protein (CmeA), and an outer membrane channel protein (CmeC). This efflux protein machinery mediates resistance to a number of structurally diverse antimicrobial agents. A recently identified CmeB variant, termed resistance enhancing CmeB (RE-CmeB), can increase its multidrug efflux pump activity, likely by influencing antimicrobial recognition and extrusion. Here, we report structures of RE-CmeB in its apo form as well as in the presence of four different drugs by using single-particle cryo-electron microscopy (cryo-EM). Coupled with mutagenesis and functional studies, this structural information allows us to identify critical amino acids that are important for drug resistance. We also report that RE-CmeB utilizes a somewhat unique subset of residues to bind different drugs, thereby optimizing its ability to accommodate different compounds with distinct scaffolds. These findings provide insights into the structure-function relationship of this newly emerged antibiotic efflux transporter variant in Campylobacter. IMPORTANCE Campylobacter jejuni has emerged as one of the most problematic and highly antibiotic-resistant pathogens, worldwide. The Centers for Disease Control and Prevention have designated antibiotic-resistant C. jejuni as a serious antibiotic resistance threat in the United States. We recently identified a C. jejuni resistance enhancing CmeB (RE-CmeB) variant that can increase its multidrug efflux pump activity and confers an exceedingly high-level of resistance to fluoroquinolones. Here, we report the cryo-EM structures of this prevalent and clinically important C. jejuni RE-CmeB multidrug efflux pump in both the absence and presence of four antibiotics. These structures allow us to understand the action mechanism for multidrug recognition in this pump. Our studies will ultimately inform an era in structure-guided drug design to combat multidrug resistance in these Gram-negative pathogens.
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Affiliation(s)
- Zhemin Zhang
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Nicholas Lizer
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Zuowei Wu
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Christopher E. Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Yuqi Yan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Qijing Zhang
- Department of Veterinary Microbiology, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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10
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Kato T, Okada U, Hung LW, Yamashita E, Kim HB, Kim CY, Terwilliger TC, Schweizer HP, Murakami S. Crystal structures of multidrug efflux transporters from Burkholderia pseudomallei suggest details of transport mechanism. Proc Natl Acad Sci U S A 2023; 120:e2215072120. [PMID: 37428905 PMCID: PMC10629574 DOI: 10.1073/pnas.2215072120] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 05/24/2023] [Indexed: 07/12/2023] Open
Abstract
BpeB and BpeF are multidrug efflux transporters from Burkholderia pseudomallei that enable multidrug resistance. Here, we report the crystal structures of BpeB and BpeF at 2.94 Å and 3.0 Å resolution, respectively. BpeB was found as an asymmetric trimer, consistent with the widely-accepted functional rotation mechanism for this type of transporter. One of the monomers has a distinct structure that we interpret as an intermediate along this functional cycle. Additionally, a detergent molecule bound in a previously undescribed binding site provides insights into substrate translocation through the pathway. BpeF shares structural similarities with the crystal structure of OqxB from Klebsiella pneumoniae, where both are symmetric trimers composed of three "binding"-state monomers. The structures of BpeB and BpeF further our understanding of the functional mechanisms of transporters belonging to the HAE1-RND superfamily.
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Affiliation(s)
- Takaaki Kato
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama226-8501, Japan
| | - Ui Okada
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama226-8501, Japan
| | - Li-Wei Hung
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM87545
| | - Eiki Yamashita
- Institute for Protein Research, Osaka University, Osaka565-0871, Japan
| | - Heung-Bok Kim
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM87545
| | - Chang-Yub Kim
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM87545
| | - Thomas C. Terwilliger
- Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM87545
- New Mexico Consortium, Los Alamos, NM87544
| | - Herbert P. Schweizer
- The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ86011
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ86011
| | - Satoshi Murakami
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama226-8501, Japan
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11
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Waltmann A, Balthazar JT, Begum AA, Hua N, Jerse AE, Shafer WM, Hobbs MM, Duncan JA. Neisseria gonorrhoeae MtrCDE Efflux Pump During In Vivo Experimental Genital Tract Infection in Men and Mice Reveals the Presence of Within-Host Colonization Bottleneck. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.06.23.23291824. [PMID: 37425726 PMCID: PMC10327229 DOI: 10.1101/2023.06.23.23291824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The MtrCDE efflux pump of Neisseria gonorrhoeae exports a wide range of antimicrobial compounds that the gonococcus encounters at mucosal surfaces during colonization and infection. Here, we evaluate the role of this efflux pump system in strain FA1090 in human male urethral infection with a Controlled Human Infection Model. Using the strategy of competitive multi-strain infection with wild-type FA1090 and an isogenic mutant strain that does not contain a functional MtrCDE pump, we found that the presence of the efflux pump during human experimental infection did not confer a competitive advantage. This finding is in contrast to previous findings in female mice, which demonstrated that gonococci of strain FA19 lacking a functional MtrCDE pump had a significantly reduced fitness compared to the wild type strain in the lower genital tract of female mice. We conducted competitive infections in female mice with FA19 and FA1090 strains, including mutants that do not assemble a functional Mtr efflux pump, demonstrating the fitness advantage provided byt the MtrCDE efflux pump during infection of mice is strain dependent. Our data indicate that new gonorrhea treatment strategies targeting the MtrCDE efflux pump functions may not be universally efficacious in naturally occurring infections. Owing to the equal fitness of FA1090 strains in men, our experiments unexpectedly demonstrated the likely presence of an early colonization bottleneck of N. gonorrhoeae in the human male urethra. TRIAL REGISTRATION Clinicaltrials.gov NCT03840811 .
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12
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Silva KPT, Sundar G, Khare A. Efflux pump gene amplifications bypass necessity of multiple target mutations for resistance against dual-targeting antibiotic. Nat Commun 2023; 14:3402. [PMID: 37296157 PMCID: PMC10256781 DOI: 10.1038/s41467-023-38507-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 05/05/2023] [Indexed: 06/12/2023] Open
Abstract
Antibiotics that have multiple cellular targets theoretically reduce the frequency of resistance evolution, but adaptive trajectories and resistance mechanisms against such antibiotics are understudied. Here we investigate these in methicillin resistant Staphylococcus aureus (MRSA) using experimental evolution upon exposure to delafloxacin (DLX), a novel fluoroquinolone that targets both DNA gyrase and topoisomerase IV. We show that selection for coding sequence mutations and genomic amplifications of the gene encoding a poorly characterized efflux pump, SdrM, leads to high DLX resistance, circumventing the requirement for mutations in both target enzymes. In the evolved populations, sdrM overexpression due to genomic amplifications containing sdrM and two adjacent genes encoding efflux pumps results in high DLX resistance, while the adjacent hitchhiking efflux pumps contribute to streptomycin cross-resistance. Further, lack of sdrM necessitates mutations in both target enzymes to evolve DLX resistance, and sdrM thus increases the frequency of resistance evolution. Finally, sdrM mutations and amplifications are similarly selected in two diverse clinical isolates, indicating the generality of this DLX resistance mechanism. Our study highlights that instead of reduced rates of resistance, evolution of resistance to multi-targeting antibiotics can involve alternate high-frequency evolutionary paths, that may cause unexpected alterations of the fitness landscape, including antibiotic cross-resistance.
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Affiliation(s)
- Kalinga Pavan T Silva
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Ganesh Sundar
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Anupama Khare
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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13
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Trampari E, Prischi F, Vargiu AV, Abi-Assaf J, Bavro VN, Webber MA. Functionally distinct mutations within AcrB underpin antibiotic resistance in different lifestyles. NPJ ANTIMICROBIALS AND RESISTANCE 2023; 1:2. [PMID: 38686215 PMCID: PMC11057200 DOI: 10.1038/s44259-023-00001-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/27/2023] [Indexed: 05/02/2024]
Abstract
Antibiotic resistance is a pressing healthcare challenge and is mediated by various mechanisms, including the active export of drugs via multidrug efflux systems, which prevent drug accumulation within the cell. Here, we studied how Salmonella evolved resistance to two key antibiotics, cefotaxime and azithromycin, when grown planktonically or as a biofilm. Resistance to both drugs emerged in both conditions and was associated with different substitutions within the efflux-associated transporter, AcrB. Azithromycin exposure selected for an R717L substitution, while cefotaxime for Q176K. Additional mutations in ramR or envZ accumulated concurrently with the R717L or Q176K substitutions respectively, resulting in clinical resistance to the selective antibiotics and cross-resistance to other drugs. Structural, genetic, and phenotypic analysis showed the two AcrB substitutions confer their benefits in profoundly different ways. R717L reduces steric barriers associated with transit through the substrate channel 2 of AcrB. Q176K increases binding energy for cefotaxime, improving recognition in the distal binding pocket, resulting in increased efflux efficiency. Finally, we show the R717 substitution is present in isolates recovered around the world.
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Affiliation(s)
- Eleftheria Trampari
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
| | - Filippo Prischi
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ UK
| | - Attilio V. Vargiu
- Department of Physics, University of Cagliari, S. P. 8, km. 0.700, 09042 Monserrato, Italy
| | - Justin Abi-Assaf
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
| | - Vassiliy N. Bavro
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ UK
| | - Mark A. Webber
- Quadram Institute Bioscience, Norwich Research Park, Norwich, Norfolk NR4 7UQ UK
- Medical School, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7UA UK
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14
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Reimche JL, Clemons AA, Chivukula VL, Joseph SJ, Schmerer MW, Pham CD, Schlanger K, St Cyr SB, Kersh EN, Gernert KM. Genomic analysis of 1710 surveillance-based Neisseria gonorrhoeae isolates from the USA in 2019 identifies predominant strain types and chromosomal antimicrobial-resistance determinants. Microb Genom 2023; 9. [PMID: 37171855 DOI: 10.1099/mgen.0.001006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023] Open
Abstract
This study characterized high-quality whole-genome sequences of a sentinel, surveillance-based collection of 1710 Neisseria gonorrhoeae (GC) isolates from 2019 collected in the USA as part of the Gonococcal Isolate Surveillance Project (GISP). It aims to provide a detailed report of strain diversity, phylogenetic relationships and resistance determinant profiles associated with reduced susceptibilities to antibiotics of concern. The 1710 isolates represented 164 multilocus sequence types and 21 predominant phylogenetic clades. Common genomic determinants defined most strains' phenotypic, reduced susceptibility to current and historic antibiotics (e.g. bla TEM plasmid for penicillin, tetM plasmid for tetracycline, gyrA for ciprofloxacin, 23S rRNA and/or mosaic mtr operon for azithromycin, and mosaic penA for cefixime and ceftriaxone). The most predominant phylogenetic clade accounted for 21 % of the isolates, included a majority of the isolates with low-level elevated MICs to azithromycin (2.0 µg ml-1), carried a mosaic mtr operon and variants in PorB, and showed expansion with respect to data previously reported from 2018. The second largest clade predominantly carried the GyrA S91F variant, was largely ciprofloxacin resistant (MIC ≥1.0 µg ml-1), and showed significant expansion with respect to 2018. Overall, a low proportion of isolates had medium- to high-level elevated MIC to azithromycin ((≥4.0 µg ml-1), based on C2611T or A2059G 23S rRNA variants). One isolate carried the penA 60.001 allele resulting in elevated MICs to cefixime and ceftriaxone of 1.0 µg ml-1. This high-resolution snapshot of genetic profiles of 1710 GC sequences, through a comparison with 2018 data (1479 GC sequences) within the sentinel system, highlights change in proportions and expansion of select GC strains and the associated genetic mechanisms of resistance. The knowledge gained through molecular surveillance may support rapid identification of outbreaks of concern. Continued monitoring may inform public health responses to limit the development and spread of antibiotic-resistant gonorrhoea.
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Affiliation(s)
- Jennifer L Reimche
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
- Oak Ridge Institute for Science and Education Research Participation and Fellowship Program, Oak Ridge, TN, USA
| | - Arvon A Clemons
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
- Oak Ridge Institute for Science and Education Research Participation and Fellowship Program, Oak Ridge, TN, USA
| | - Vasanta L Chivukula
- Oak Ridge Institute for Science and Education Research Participation and Fellowship Program, Oak Ridge, TN, USA
- Division of Preparedness and Emerging Infections, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Sandeep J Joseph
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Matthew W Schmerer
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Cau D Pham
- Antimicrobial Resistance Coordination and Strategy Unit, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Karen Schlanger
- Division of HIV Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Sancta B St Cyr
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Ellen N Kersh
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Kim M Gernert
- Division of STD Prevention, National Center for HIV, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
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15
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Muenks A, Zepeda S, Zhou G, Veesler D, DiMaio F. Automatic and accurate ligand structure determination guided by cryo-electron microscopy maps. Nat Commun 2023; 14:1164. [PMID: 36859493 PMCID: PMC9976687 DOI: 10.1038/s41467-023-36732-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 02/15/2023] [Indexed: 03/03/2023] Open
Abstract
Advances in cryo-electron microscopy (cryoEM) and deep-learning guided protein structure prediction have expedited structural studies of protein complexes. However, methods for accurately determining ligand conformations are lacking. In this manuscript, we develop EMERALD, a tool for automatically determining ligand structures guided by medium-resolution cryoEM density. We show this method is robust at predicting ligands along with surrounding side chains in maps as low as 4.5 Å local resolution. Combining this with a measure of placement confidence and running on all protein/ligand structures in the EMDB, we show that 57% of ligands replicate the deposited model, 16% confidently find alternate conformations, 22% have ambiguous density where multiple conformations might be present, and 5% are incorrectly placed. For five cases where our approach finds an alternate conformation with high confidence, high-resolution crystal structures validate our placement. EMERALD and the resulting analysis should prove critical in using cryoEM to solve protein-ligand complexes.
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Affiliation(s)
- Andrew Muenks
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
- Institute for Protein Design, University of Washington, Seattle, WA, 98195, USA
| | - Samantha Zepeda
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Guangfeng Zhou
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
- Institute for Protein Design, University of Washington, Seattle, WA, 98195, USA
| | - David Veesler
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, 98195, USA
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA.
- Institute for Protein Design, University of Washington, Seattle, WA, 98195, USA.
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16
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Cryo-EM Structures of AcrD Illuminate a Mechanism for Capturing Aminoglycosides from Its Central Cavity. mBio 2023; 14:e0338322. [PMID: 36625574 PMCID: PMC9973356 DOI: 10.1128/mbio.03383-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The Escherichia coli acriflavine resistance protein D (AcrD) is an efflux pump that belongs to the resistance-nodulation-cell division (RND) superfamily. Its primary function is to provide resistance to aminoglycoside-based drugs by actively extruding these noxious compounds out of E. coli cells. AcrD can also mediate resistance to a limited range of other amphiphilic agents, including bile acids, novobiocin, and fusidic acids. As there is no structural information available for any aminoglycoside-specific RND pump, here we describe cryo-electron microscopy (cryo-EM) structures of AcrD in the absence and presence of bound gentamicin. These structures provide new information about the RND superfamily of efflux pumps, specifically, that three negatively charged residues central to the aminoglycoside-binding site are located within the ceiling of the central cavity of the AcrD trimer. Thus, it is likely that AcrD is capable of picking up aminoglycosides via this central cavity. Through the combination of cryo-EM structural determination, mutagenesis analysis, and molecular simulation, we show that charged residues are critically important for this pump to shuttle drugs directly from the central cavity to the funnel of the AcrD trimer for extrusion. IMPORTANCE Here, we report cryo-EM structures of the AcrD aminoglycoside efflux pump in the absence and presence of bound gentamicin, posing the possibility that this pump is capable of capturing aminoglycosides from the central cavity of the AcrD trimer. The results indicate that AcrD utilizes charged residues to bind and export drugs, mediating resistance to these antibiotics.
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17
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RND Pump-Mediated Efflux of Amotosalen, a Compound Used in Pathogen Inactivation Technology to Enhance Safety of Blood Transfusion Products, May Compromise Its Gram-Negative Anti-Bacterial Activity. mSphere 2023; 8:e0067322. [PMID: 36853056 PMCID: PMC10117049 DOI: 10.1128/msphere.00673-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
Pathogen inactivation is a strategy to improve the safety of transfusion products. The only pathogen reduction technology for blood products currently approved in the US utilizes a psoralen compound, called amotosalen, in combination with UVA light to inactivate bacteria, viruses, and protozoa. Psoralens have structural similarity to bacterial multidrug efflux pump substrates. As these efflux pumps are often overexpressed in multidrug-resistant pathogens, we tested whether contemporary drug-resistant pathogens might show resistance to amotosalen and other psoralens based on multidrug efflux mechanisms through genetic, biophysical, and molecular modeling analysis. The main efflux systems in Enterobacterales, Acinetobacter baumannii, and Pseudomonas aeruginosa are tripartite resistance-nodulation-cell division (RND) systems, which span the inner and outer membranes of Gram-negative pathogens, and expel antibiotics from the bacterial cytoplasm into the extracellular space. We provide evidence that amotosalen is an efflux substrate for the E. coli AcrAB, Acinetobacter baumannii AdeABC, and P. aeruginosa MexXY RND efflux pumps. Furthermore, we show that the MICs for contemporary Gram-negative bacterial isolates for these species and others in vitro approached and exceeded the concentration of amotosalen used in the approved platelet and plasma inactivation procedures. These findings suggest that otherwise safe and effective inactivation methods should be further studied to identify possible gaps in their ability to inactivate contemporary, multidrug-resistant bacterial pathogens. IMPORTANCE Pathogen inactivation is a strategy to enhance the safety of transfused blood products. We identify the compound, amotosalen, widely used for pathogen inactivation, as a bacterial multidrug efflux substrate. Specifically, experiments suggest that amotosalen is pumped out of bacteria by major efflux pumps in E. coli, Acinetobacter baumannii, and Pseudomonas aeruginosa. Such efflux pumps are often overexpressed in multidrug-resistant pathogens. Importantly, the MICs for contemporary multidrug-resistant Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa, Burkholderia spp., and Stenotrophomonas maltophilia isolates approached or exceeded the amotosalen concentration used in approved platelet and plasma inactivation procedures, potentially as a result of efflux pump activity. Although there are important differences in methodology between our experiments and blood product pathogen inactivation, these findings suggest that otherwise safe and effective inactivation methods should be further studied to identify possible gaps in their ability to inactivate contemporary, multidrug-resistant bacterial pathogens.
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18
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Chen X, Han J, Cai X, Wang S. Antimicrobial peptides: Sustainable application informed by evolutionary constraints. Biotechnol Adv 2022; 60:108012. [PMID: 35752270 DOI: 10.1016/j.biotechadv.2022.108012] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/02/2022] [Accepted: 06/19/2022] [Indexed: 01/10/2023]
Abstract
The proliferation and global expansion of multidrug-resistant (MDR) bacteria have deepened the need to develop novel antimicrobials. Antimicrobial peptides (AMPs) are regarded as promising antibacterial agents because of their broad-spectrum antibacterial activity and multifaceted mechanisms of action with non-specific targets. However, if AMPs are to be applied sustainably, knowledge of how they induce resistance in pathogenic bacteria must be mastered to avoid repeating the traditional antibiotic resistance mistakes currently faced. Furthermore, the evolutionary constraints on the acquisition of AMP resistance by microorganisms in the natural environment, such as functional compatibility and fitness trade-offs, inform the translational application of AMPs. Consequently, the shortcut to achieve sustainable utilization of AMPs is to uncover the evolutionary constraints of bacteria on AMP resistance in nature and find the tricks to exploit these constraints, such as applying AMP cocktails to minimize the efficacy of selection for resistance or combining nanomaterials to maximize the costs of AMP resistance. Altogether, this review dissects the benefits, challenges, and opportunities of utilizing AMPs against disease-causing bacteria, and highlights the use of AMP cocktails or nanomaterials to proactively address potential AMP resistance crises in the future.
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Affiliation(s)
- Xuan Chen
- College of Chemical Engineering, Fuzhou University, Fuzhou, Fujian 350108, China; College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China
| | - Jinzhi Han
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China
| | - Xixi Cai
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China
| | - Shaoyun Wang
- College of Biological Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108, China.
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19
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Structural Basis of Peptide-Based Antimicrobial Inhibition of a Resistance-Nodulation-Cell Division Multidrug Efflux Pump. Microbiol Spectr 2022; 10:e0299022. [PMID: 36121287 PMCID: PMC9603588 DOI: 10.1128/spectrum.02990-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Bacterial efflux pumps in the resistance-nodulation-cell division (RND) family of Gram-negative bacteria contribute significantly to the development of antimicrobial resistance by many pathogens. In this study, we selected the MtrD transporter protein of Neisseria gonorrhoeae as it is the sole RND pump possessed by this strictly human pathogen and can export multiple antimicrobials, including antibiotics, bile salts, detergents, dyes, and antimicrobial peptides. Using knowledge from our previously published structures of MtrD in the presence or absence of bound antibiotics as a model and the known ability of MtrCDE to export cationic antimicrobial peptides, we hypothesized that cationic peptides could be accommodated within MtrD binding sites. Furthermore, we thought that MtrD-bound peptides lacking antibacterial action could sensitize bacteria to an antibiotic normally exported by the MtrCDE efflux pump or other similar RND-type pumps possessed by different Gram-negative bacteria. We now report the identification of a novel nonantimicrobial cyclic cationic antimicrobial peptide, which we termed CASP (cationic antibiotic-sensitizing peptide). By single-particle cryo-electron microscopy, we found that CASP binds within the periplasmic cleft region of MtrD using overlapping and distinct amino acid contact sites that interact with another cyclic peptide (colistin) or a linear human cationic antimicrobial peptide derived from human LL-37. While CASP could not sensitize Neisseria gonorrhoeae to an antibiotic (novobiocin) that is a substrate for RND pumps, it could do so against multiple Gram-negative, rod-shaped bacteria. We propose that CASP (or future derivatives) could serve as an adjuvant for the antibiotic treatment of certain Gram-negative infections previously thwarted by RND transporters. IMPORTANCE RND efflux pumps can export numerous antimicrobials that enter Gram-negative bacteria, and their action can reduce the efficacy of antibiotics and provide decreased susceptibility to various host antimicrobials. Here, we identified a cationic antibiotic-sensitizing peptide (CASP) that binds within the periplasmic cleft of an RND transporter protein (MtrD) produced by Neisseria gonorrhoeae. Surprisingly, CASP was able to render rod-shaped Gram-negative bacteria, but not gonococci, susceptible to an antibiotic that is a substrate for the gonococcal MtrCDE efflux pump. CASP (or its future derivatives) could be used as an adjuvant to treat infections for which RND efflux contributes to multidrug resistance.
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20
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Ayala JC, Balthazar JT, Shafer WM. Transcriptional regulation of the mtrCDE efflux pump operon: importance for Neisseria gonorrhoeae antimicrobial resistance. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35916832 DOI: 10.1099/mic.0.001231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This review focuses on the mechanisms of transcriptional control of an important multidrug efflux pump system (MtrCDE) possessed by Neisseria gonorrhoeae, the aetiological agent of the sexually transmitted infection termed gonorrhoea. The mtrCDE operon that encodes this tripartite protein efflux pump is subject to both cis- and trans-acting transcriptional factors that negatively or positively influence expression. Critically, levels of MtrCDE can influence levels of gonococcal susceptibility to classical antibiotics, host-derived antimicrobials and various biocides. The regulatory systems that control mtrCDE can have profound influences on the capacity of gonococci to resist current and past antibiotic therapy regimens as well as virulence. The emergence, mechanisms of action and clinical significance of the transcriptional regulatory systems that impact mtrCDE expression in gonococci are reviewed here with the aim of linking bacterial antimicrobial resistance with multidrug efflux capability.
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Affiliation(s)
- Julio C Ayala
- Department of Microbiology and Immunology Emory University School of Medicine, Atlanta, Georgia, 30322, USA
| | - Jacqueline T Balthazar
- Department of Microbiology and Immunology Emory University School of Medicine, Atlanta, Georgia, 30322, USA
| | - William M Shafer
- Department of Microbiology and Immunology Emory University School of Medicine, Atlanta, Georgia, 30322, USA.,Laboratories of Bacterial Pathogenesis, VA Medical Center (Atlanta), Decatur, Georgia, 30033, USA.,The Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA
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21
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Blair JMA, Zeth K, Bavro VN, Sancho-Vaello E. The role of bacterial transport systems in the removal of host antimicrobial peptides in Gram-negative bacteria. FEMS Microbiol Rev 2022; 46:6617596. [PMID: 35749576 PMCID: PMC9629497 DOI: 10.1093/femsre/fuac032] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 05/23/2022] [Accepted: 06/22/2022] [Indexed: 01/09/2023] Open
Abstract
Antibiotic resistance is a global issue that threatens our progress in healthcare and life expectancy. In recent years, antimicrobial peptides (AMPs) have been considered as promising alternatives to the classic antibiotics. AMPs are potentially superior due to their lower rate of resistance development, since they primarily target the bacterial membrane ('Achilles' heel' of the bacteria). However, bacteria have developed mechanisms of AMP resistance, including the removal of AMPs to the extracellular space by efflux pumps such as the MtrCDE or AcrAB-TolC systems, and the internalization of AMPs to the cytoplasm by the Sap transporter, followed by proteolytic digestion. In this review, we focus on AMP transport as a resistance mechanism compiling all the experimental evidence for the involvement of efflux in AMP resistance in Gram-negative bacteria and combine this information with the analysis of the structures of the efflux systems involved. Finally, we expose some open questions with the aim of arousing the interest of the scientific community towards the AMPs-efflux pumps interactions. All the collected information broadens our understanding of AMP removal by efflux pumps and gives some clues to assist the rational design of AMP-derivatives as inhibitors of the efflux pumps.
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Affiliation(s)
- Jessica M A Blair
- College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
| | - Kornelius Zeth
- Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark
| | - Vassiliy N Bavro
- School of Life Sciences, University of Essex, Colchester, CO4 3SQ, United Kingdom
| | - Enea Sancho-Vaello
- Corresponding author. College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom. E-mail:
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22
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Cartee JC, Joseph SJ, Weston E, Pham CD, Thomas JC, Schlanger K, St Cyr SB, Farley MM, Moore AE, Tunali AK, Cloud C, Raphael BH. Phylogenomic comparison of Neisseria gonorrhoeae causing disseminated gonococcal infections and uncomplicated gonorrhea in Georgia, United States. Open Forum Infect Dis 2022; 9:ofac247. [DOI: 10.1093/ofid/ofac247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/11/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Disseminated gonococcal infection (DGI) is a rare complication caused by the systemic dissemination of Neisseria gonorrhoeae (Ng) to normally sterile anatomical sites. Little is known about the genetic diversity of DGI gonococcal strains and how they relate to other gonococcal strains causing uncomplicated mucosal infections. We used whole genome sequencing to characterize DGI isolates (n = 30) collected from a surveillance system in Georgia (GA), USA during 2017-2020 to understand phylogenetic clustering among DGI as well as uncomplicated uro-and-extragenital gonococcal (UGI) isolates (n = 110) collected in Fulton County, GA during 2017-2019. We also investigated the presence or absence of genetic markers related to antimicrobial resistance (AMR) as well as surveyed the genomes for putative virulence genetic factors associated with normal human-serum (NHS) resistance that might facilitate DGI. We found that DGI strains demonstrated significant genetic variability similar to the population structure of isolates causing UGI, with sporadic incidences of geographically clustered DGI strains. DGI isolates contained various AMR markers and genetic mechanisms associated with NHS resistance. DGI isolates had a higher frequency of the porB1A allele compared with UGI (67% vs. 9%, p < 0.0001); however, no single NHS resistance marker was found in all DGI isolates. Continued DGI surveillance with genome-based characterization of DGI isolates is necessary to better understand specific factors that promote systemic dissemination.
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Affiliation(s)
- John C. Cartee
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Sandeep J. Joseph
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Emily Weston
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
- Current affiliation: Division of Global Health and Protection, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Cau D. Pham
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Jesse C. Thomas
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Karen Schlanger
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Sancta B. St Cyr
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
| | - Monica M. Farley
- Emory University School of Medicine, Department of Medicine, Atlanta, GA, 30322, United States
- Atlanta VA Medical Center, Atlanta, GA, 30033, United States
| | - Ashley E. Moore
- Georgia Department of Public Health, Atlanta, GA, 30303, United States
| | - Amy K. Tunali
- Emory University School of Medicine, Department of Medicine, Atlanta, GA, 30322, United States
- Atlanta VA Medical Center, Atlanta, GA, 30033, United States
| | - Charletta Cloud
- Georgia Department of Public Health, Atlanta, GA, 30303, United States
| | - Brian H. Raphael
- Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, 30329, United States
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23
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de Block T, González N, Abdellati S, Laumen JGE, Van Dijck C, De Baetselier I, Van den Bossche D, Manoharan-Basil SS, Kenyon C. Successful Intra- but Not Inter-species Recombination of msr(D) in Neisseria subflava. Front Microbiol 2022; 13:855482. [PMID: 35432273 PMCID: PMC9007320 DOI: 10.3389/fmicb.2022.855482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/02/2022] [Indexed: 11/23/2022] Open
Abstract
Resistance acquisition via natural transformation is a common process in the Neisseria genus. Transformation has played an important role in the emergence of resistance to many antimicrobials in Neisseria gonorrhoeae and Neisseria meningitidis. In a previous study, we found that currently circulating isolates of Neisseria subflava had acquired an msr(D) gene that has been found to result in macrolide resistance in other bacteria but never found in Neisseria species before. To determine if this resistance mechanism is transferable among Neisseria species, we assessed if we could transform the msr(D) gene into other commensal and pathogenic Neisseria under low dose azithromycin pressure. Intraspecies recombination in commensal N. subflava was confirmed with PCR and resulted in high-level macrolide resistance. Whole-genome sequencing of these transformed strains identified the complete uptake of the msr(D) integration fragment. Sequence analysis showed that a large fragment of DNA (5 and 12 kb) was transferred through a single horizontal gene transfer event. Furthermore, uptake of the msr(D) gene had no apparent fitness cost. Interspecies transformation of msr(D) from N. subflava to N. gonorrhoeae was, however, not successful.
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Affiliation(s)
- Tessa de Block
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Natalia González
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Saïd Abdellati
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Jolein Gyonne Elise Laumen
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
| | - Christophe Van Dijck
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
| | - Irith De Baetselier
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | | | | | - Chris Kenyon
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Medicine, University of Cape Town, Cape Town, South Africa
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24
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Jain N, Sk MF, Mishra A, Kar P, Kumar A. Identification of novel Efflux pump inhibitors for Neisseria gonorrhoeae via multiple ligand-based pharmacophores, e-pharmacophore, molecular docking, density functional theory, and Molecular dynamics approaches. Comput Biol Chem 2022; 98:107682. [DOI: 10.1016/j.compbiolchem.2022.107682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/30/2022] [Accepted: 04/04/2022] [Indexed: 11/24/2022]
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25
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Proximal Binding Pocket Arg717 Substitutions in Escherichia coli AcrB Cause Clinically Relevant Divergencies in Resistance Profiles. Antimicrob Agents Chemother 2022; 66:e0239221. [PMID: 35311521 PMCID: PMC9017336 DOI: 10.1128/aac.02392-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Recent mutations in RND efflux pumps in clinical strains have further increased multidrug resistance. We show that R717L and R717Q substitutions (found in azithromycin-resistant Salmonella enterica spp.) in the Escherichia coli efflux pump AcrB dramatically increase macrolide, as well as fluoroquinolone, resistance. On the other hand, cells became more susceptible to novobiocin and β-lactam cloxacillin. We urge the control of, and adjustments to, treatments with antibiotics and the need for novel antibiotics and efflux pump inhibitors.
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26
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Ammerman L, Mertz SB, Park C, Wise JG. Transport Dynamics of MtrD: An RND Multidrug Efflux Pump from Neisseria gonorrheae. Biochemistry 2021; 60:3098-3113. [PMID: 34609833 DOI: 10.1021/acs.biochem.1c00399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The MtrCDE system confers multidrug resistance to Neisseria gonorrheae, the causative agent of gonorrhea. Using free and directed molecular dynamics (MD) simulations, we analyzed the interactions between MtrD and azithromycin, a transport substrate of MtrD, and a last-resort clinical treatment for multidrug-resistant gonorrhea. We then simulated the interactions between MtrD and streptomycin, an apparent nonsubstrate of MtrD. Using known conformations of MtrD homologues, we simulated a potential dynamic transport cycle of MtrD using targeted MD techniques (TMD), and we noted that forces were not applied to ligands of interest. In these TMD simulations, we observed the transport of azithromycin and the rejection of streptomycin. In an unbiased, long-time scale simulation of AZY-bound MtrD, we observed the spontaneous diffusion of azithromycin through the periplasmic cleft. Our simulations show how the peristaltic motions of the periplasmic cleft facilitate the transport of substrates by MtrD. Our data also suggest that multiple transport pathways for macrolides may exist within the periplasmic cleft of MtrD.
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Affiliation(s)
- Lauren Ammerman
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Research Computing, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas 75275-0376, United States
| | - Sarah B Mertz
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Research Computing, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas 75275-0376, United States
| | - Chanyang Park
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas 75275-0376, United States
| | - John G Wise
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Research Computing, Southern Methodist University, Dallas, Texas 75275-0376, United States.,Center for Drug Discovery, Design and Delivery, Southern Methodist University, Dallas, Texas 75275-0376, United States
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27
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A Unique Sequence Is Essential for Efficient Multidrug Efflux Function of the MtrD Protein of Neisseria gonorrhoeae. mBio 2021; 12:e0167521. [PMID: 34465021 PMCID: PMC8406276 DOI: 10.1128/mbio.01675-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antimicrobial resistance in Neisseria gonorrhoeae has reached an alarming level, severely impacting the effective treatment of gonorrhea. Belonging to the resistance-nodulation-cell division (RND) superfamily of efflux transporters, the MtrD membrane protein of N. gonorrhoeae provides resistance to a broad range of antimicrobial compounds. A unique feature of MtrD is an 11-residue sequence (from N917 to P927 [N917-P927]) that connects transmembrane helices (TMS) 9 and 10; this sequence is not present in homologous RND proteins. This study explores the structural and functional roles of the N917-P927 region by means of mutant analysis and molecular dynamics simulations. We show that N917-P927 plays a key role in modulating substrate access to the binding cleft and influences the overall orientation of the protein within the inner membrane necessary for optimal functioning. Removal of N917-P927 significantly reduced MtrD-mediated resistance to a range of antimicrobials and mutations of three single amino acids impacted MtrD-mediated multidrug resistance. Furthermore, molecular dynamics simulations showed deletion of N917-P927 in MtrD may dysregulate access of the substrate to the binding cleft and closure of the substrate-binding pocket during the transport cycle. These findings indicate that N917-P927 is a key region for interacting with the inner membrane, conceivably influencing substrate capture from the membrane-periplasm interface and thus is essential for full multidrug resistance capacity of MtrD. IMPORTANCE The historical sexually transmitted infection gonorrhea continues to be a major public health concern with an estimated global annual incidence of 86.9 million cases. N. gonorrhoeae has been identified by the World Health Organization as one of the 12 antimicrobial-resistant bacterial species that poses the greatest risk to human health. As the major efflux pump in gonococci, the MtrD transporter contributes to the cell envelope barrier in this organism and pumps antimicrobials from the periplasm and inner membrane, resulting in resistance. This study demonstrates that a unique region of the MtrD protein that connects TMS 9 and TMS 10 forms a structure that may interact with the inner membrane positioning TMS 9 and stabilizing the protein facilitating substrate capture from the inner membrane-periplasm interface. Analysis of mutants of this region identified that it was essential for MtrD-mediated multidrug resistance. Characterization of the structure and function of this unique local region of MtrD has implications for drug efflux mechanisms used by related proteins and is important knowledge for development of antibiotics that bypass efflux.
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28
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Guo Y. Detergent-free systems for structural studies of membrane proteins. Biochem Soc Trans 2021; 49:1361-1374. [PMID: 34110369 PMCID: PMC8276625 DOI: 10.1042/bst20201080] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 05/03/2021] [Accepted: 05/17/2021] [Indexed: 11/17/2022]
Abstract
Membrane proteins play vital roles in living organisms, serving as targets for most currently prescribed drugs. Membrane protein structural biology aims to provide accurate structural information to understand their mechanisms of action. The advance of membrane protein structural biology has primarily relied on detergent-based methods over the past several decades. However, detergent-based approaches have significant drawbacks because detergents often damage the native protein-lipid interactions, which are often crucial for maintaining the natural structure and function of membrane proteins. Detergent-free methods recently have emerged as alternatives with a great promise, e.g. for high-resolution structure determinations of membrane proteins in their native cell membrane lipid environments. This minireview critically examines the current status of detergent-free methods by a comparative analysis of five groups of membrane protein structures determined using detergent-free and detergent-based methods. This analysis reveals that current detergent-free systems, such as the styrene-maleic acid lipid particles (SMALP), the diisobutyl maleic acid lipid particles (DIBMALP), and the cycloalkane-modified amphiphile polymer (CyclAPol) technologies are not better than detergent-based approaches in terms of maintenance of native cell membrane lipids on the transmembrane domain and high-resolution structure determination. However, another detergent-free technology, the native cell membrane nanoparticles (NCMN) system, demonstrated improved maintenance of native cell membrane lipids with the studied membrane proteins, and produced particles that were suitable for high-resolution structural analysis. The ongoing development of new membrane-active polymers and their optimization will facilitate the maturation of these new detergent-free systems.
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Affiliation(s)
- Youzhong Guo
- Department of Medicinal Chemistry and Institute for Structural Biology, Drug Discovery and Development, Virginia Commonwealth University, Richmond, VA 23298-0540, USA
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29
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Tam HK, Foong WE, Oswald C, Herrmann A, Zeng H, Pos KM. Allosteric drug transport mechanism of multidrug transporter AcrB. Nat Commun 2021; 12:3889. [PMID: 34188038 PMCID: PMC8242077 DOI: 10.1038/s41467-021-24151-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 06/02/2021] [Indexed: 12/27/2022] Open
Abstract
Gram-negative bacteria maintain an intrinsic resistance mechanism against entry of noxious compounds by utilizing highly efficient efflux pumps. The E. coli AcrAB-TolC drug efflux pump contains the inner membrane H+/drug antiporter AcrB comprising three functionally interdependent protomers, cycling consecutively through the loose (L), tight (T) and open (O) state during cooperative catalysis. Here, we present 13 X-ray structures of AcrB in intermediate states of the transport cycle. Structure-based mutational analysis combined with drug susceptibility assays indicate that drugs are guided through dedicated transport channels toward the drug binding pockets. A co-structure obtained in the combined presence of erythromycin, linezolid, oxacillin and fusidic acid shows binding of fusidic acid deeply inside the T protomer transmembrane domain. Thiol cross-link substrate protection assays indicate that this transmembrane domain-binding site can also accommodate oxacillin or novobiocin but not erythromycin or linezolid. AcrB-mediated drug transport is suggested to be allosterically modulated in presence of multiple drugs. Gram-negative bacteria can display intrinsic antibiotic resistance due to the action of tripartite efflux pumps, which include a H+/drug antiporter component. Here, the authors present a structure-function analysis of antiporter AcrB in intermediate states of the transport cycle, showing novel drug-binding sites and transport pathways.
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Affiliation(s)
- Heng-Keat Tam
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany. .,Hengyang Medical College, University of South China, Hengyang, Hunan Province, China.
| | - Wuen Ee Foong
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Christine Oswald
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany.,Sosei Heptares, Steinmetz Building, Granta Park, Great Abington, Cambridge, UK
| | - Andrea Herrmann
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Hui Zeng
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany
| | - Klaas M Pos
- Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt am Main, Germany.
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30
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Zwama M, Nishino K. Ever-Adapting RND Efflux Pumps in Gram-Negative Multidrug-Resistant Pathogens: A Race against Time. Antibiotics (Basel) 2021; 10:774. [PMID: 34201908 PMCID: PMC8300642 DOI: 10.3390/antibiotics10070774] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/11/2021] [Accepted: 06/14/2021] [Indexed: 01/13/2023] Open
Abstract
The rise in multidrug resistance (MDR) is one of the greatest threats to human health worldwide. MDR in bacterial pathogens is a major challenge in healthcare, as bacterial infections are becoming untreatable by commercially available antibiotics. One of the main causes of MDR is the over-expression of intrinsic and acquired multidrug efflux pumps, belonging to the resistance-nodulation-division (RND) superfamily, which can efflux a wide range of structurally different antibiotics. Besides over-expression, however, recent amino acid substitutions within the pumps themselves-causing an increased drug efflux efficiency-are causing additional worry. In this review, we take a closer look at clinically, environmentally and laboratory-evolved Gram-negative bacterial strains and their decreased drug sensitivity as a result of mutations directly in the RND-type pumps themselves (from Escherichia coli, Salmonella enterica, Neisseria gonorrhoeae, Pseudomonas aeruginosa, Acinetobacter baumannii and Legionella pneumophila). We also focus on the evolution of the efflux pumps by comparing hundreds of efflux pumps to determine where conservation is concentrated and where differences in amino acids can shed light on the broad and even broadening drug recognition. Knowledge of conservation, as well as of novel gain-of-function efflux pump mutations, is essential for the development of novel antibiotics and efflux pump inhibitors.
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Affiliation(s)
- Martijn Zwama
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Kunihiko Nishino
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Ibaraki, Osaka 567-0047, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan
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31
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Fairweather SJ, Gupta V, Chitsaz M, Booth L, Brown MH, O’Mara ML. Coordination of Substrate Binding and Protonation in the N. gonorrhoeae MtrD Efflux Pump Controls the Functionally Rotating Transport Mechanism. ACS Infect Dis 2021; 7:1833-1847. [PMID: 33980014 DOI: 10.1021/acsinfecdis.1c00149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Multidrug resistance is a serious problem that threatens the effective treatment of the widespread sexually transmitted disease gonorrhea, caused by the Gram-negative bacterium Neisseria gonorrhoeae. The drug efflux pump primarily implicated in N. gonorrhoeae antimicrobial resistance is the inner membrane transporter MtrD, which forms part of the tripartite multiple transferable resistance (Mtr) CDE efflux system. A structure of MtrD was first solved in 2014 as a symmetrical homotrimer, and then, recently, as an asymmetrical homotrimer. Through a series of molecular dynamics simulations and mutagenesis experiments, we identify the combination of substrate binding and protonation states of the proton relay network that drives the transition from the symmetric to the asymmetric conformation of MtrD. We characterize the allosteric coupling between the functionally important local regions that control conformational changes between the access, binding, and extrusion states and allow for transition to the asymmetric MtrD conformation. We also highlight a significant rotation of the transmembrane helices caused by protonation of the proton relay network, which widens the intermonomeric gap that is a hallmark of the rotational transporter mechanism. This is the first analysis and description of the transport mechanism for the N. gonorrhoeae MtrD transporter and provides evidence that antimicrobial efflux in MtrD follows the functionally rotating transport mechanism seen in protein homologues from the same transport protein superfamily.
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Affiliation(s)
- Stephen J. Fairweather
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
- Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
| | - Vrinda Gupta
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
| | - Mohsen Chitsaz
- College of Science and Engineering, Flinders University, Bedford Park, SA 5042, Australia
| | - Lauren Booth
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
| | - Melissa H. Brown
- College of Science and Engineering, Flinders University, Bedford Park, SA 5042, Australia
| | - Megan L. O’Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia
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32
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Cryo-EM Determination of Eravacycline-Bound Structures of the Ribosome and the Multidrug Efflux Pump AdeJ of Acinetobacter baumannii. mBio 2021; 12:e0103121. [PMID: 34044590 PMCID: PMC8263017 DOI: 10.1128/mbio.01031-21] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic-resistant strains of the Gram-negative pathogen Acinetobacter baumannii have emerged as a significant global health threat. One successful therapeutic option to treat bacterial infections has been to target the bacterial ribosome. However, in many cases, multidrug efflux pumps within the bacterium recognize and extrude these clinically important antibiotics designed to inhibit the protein synthesis function of the bacterial ribosome. Thus, multidrug efflux within A. baumannii and other highly drug-resistant strains is a major cause of failure of drug-based treatments of infectious diseases. We here report the first structures of the Acinetobacterdrug efflux (Ade)J pump in the presence of the antibiotic eravacycline, using single-particle cryo-electron microscopy (cryo-EM). We also describe cryo-EM structures of the eravacycline-bound forms of the A. baumannii ribosome, including the 70S, 50S, and 30S forms. Our data indicate that the AdeJ pump primarily uses hydrophobic interactions to bind eravacycline, while the 70S ribosome utilizes electrostatic interactions to bind this drug. Our work here highlights how an antibiotic can bind multiple bacterial targets through different mechanisms and potentially enables drug optimization by taking advantage of these different modes of ligand binding.
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33
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Klenotic PA, Moseng MA, Morgan CE, Yu EW. Structural and Functional Diversity of Resistance-Nodulation-Cell Division Transporters. Chem Rev 2021; 121:5378-5416. [PMID: 33211490 PMCID: PMC8119314 DOI: 10.1021/acs.chemrev.0c00621] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Multidrug resistant (MDR) bacteria are a global threat with many common infections becoming increasingly difficult to eliminate. While significant effort has gone into the development of potent biocides, the effectiveness of many first-line antibiotics has been diminished due to adaptive resistance mechanisms. Bacterial membrane proteins belonging to the resistance-nodulation-cell division (RND) superfamily play significant roles in mediating bacterial resistance to antimicrobials. They participate in multidrug efflux and cell wall biogenesis to transform bacterial pathogens into "superbugs" that are resistant even to last resort antibiotics. In this review, we summarize the RND superfamily of efflux transporters with a primary focus on the assembly and function of the inner membrane pumps. These pumps are critical for extrusion of antibiotics from the cell as well as the transport of lipid moieties to the outer membrane to establish membrane rigidity and stability. We analyze recently solved structures of bacterial inner membrane efflux pumps as to how they bind and transport their substrates. Our cumulative data indicate that these RND membrane proteins are able to utilize different oligomerization states to achieve particular activities, including forming MDR pumps and cell wall remodeling machineries, to ensure bacterial survival. This mechanistic insight, combined with simulated docking techniques, allows for the design and optimization of new efflux pump inhibitors to more effectively treat infections that today are difficult or impossible to cure.
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Affiliation(s)
- Philip A. Klenotic
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Mitchell A. Moseng
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Christopher E. Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
| | - Edward W. Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland OH 44106, USA
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34
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Alav I, Kobylka J, Kuth MS, Pos KM, Picard M, Blair JMA, Bavro VN. Structure, Assembly, and Function of Tripartite Efflux and Type 1 Secretion Systems in Gram-Negative Bacteria. Chem Rev 2021; 121:5479-5596. [PMID: 33909410 PMCID: PMC8277102 DOI: 10.1021/acs.chemrev.1c00055] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Indexed: 12/11/2022]
Abstract
Tripartite efflux pumps and the related type 1 secretion systems (T1SSs) in Gram-negative organisms are diverse in function, energization, and structural organization. They form continuous conduits spanning both the inner and the outer membrane and are composed of three principal components-the energized inner membrane transporters (belonging to ABC, RND, and MFS families), the outer membrane factor channel-like proteins, and linking the two, the periplasmic adaptor proteins (PAPs), also known as the membrane fusion proteins (MFPs). In this review we summarize the recent advances in understanding of structural biology, function, and regulation of these systems, highlighting the previously undescribed role of PAPs in providing a common architectural scaffold across diverse families of transporters. Despite being built from a limited number of basic structural domains, these complexes present a staggering variety of architectures. While key insights have been derived from the RND transporter systems, a closer inspection of the operation and structural organization of different tripartite systems reveals unexpected analogies between them, including those formed around MFS- and ATP-driven transporters, suggesting that they operate around basic common principles. Based on that we are proposing a new integrated model of PAP-mediated communication within the conformational cycling of tripartite systems, which could be expanded to other types of assemblies.
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Affiliation(s)
- Ilyas Alav
- Institute
of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Jessica Kobylka
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Miriam S. Kuth
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Klaas M. Pos
- Institute
of Biochemistry, Biocenter, Goethe Universität
Frankfurt, Max-von-Laue-Straße 9, D-60438 Frankfurt, Germany
| | - Martin Picard
- Laboratoire
de Biologie Physico-Chimique des Protéines Membranaires, CNRS
UMR 7099, Université de Paris, 75005 Paris, France
- Fondation
Edmond de Rothschild pour le développement de la recherche
Scientifique, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Jessica M. A. Blair
- Institute
of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Vassiliy N. Bavro
- School
of Life Sciences, University of Essex, Colchester, CO4 3SQ United Kingdom
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35
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Structural Insights into Transporter-Mediated Drug Resistance in Infectious Diseases. J Mol Biol 2021; 433:167005. [PMID: 33891902 DOI: 10.1016/j.jmb.2021.167005] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/12/2021] [Accepted: 04/12/2021] [Indexed: 02/07/2023]
Abstract
Infectious diseases present a major threat to public health globally. Pathogens can acquire resistance to anti-infectious agents via several means including transporter-mediated efflux. Typically, multidrug transporters feature spacious, dynamic, and chemically malleable binding sites to aid in the recognition and transport of chemically diverse substrates across cell membranes. Here, we discuss recent structural investigations of multidrug transporters involved in resistance to infectious diseases that belong to the ATP-binding cassette (ABC) superfamily, the major facilitator superfamily (MFS), the drug/metabolite transporter (DMT) superfamily, the multidrug and toxic compound extrusion (MATE) family, the small multidrug resistance (SMR) family, and the resistance-nodulation-division (RND) superfamily. These structural insights provide invaluable information for understanding and combatting multidrug resistance.
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36
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Beggs GA, Ayala JC, Kavanaugh LG, Read T, Hooks G, Schumacher M, Shafer W, Brennan R. Structures of Neisseria gonorrhoeae MtrR-operator complexes reveal molecular mechanisms of DNA recognition and antibiotic resistance-conferring clinical mutations. Nucleic Acids Res 2021; 49:4155-4170. [PMID: 33784401 PMCID: PMC8053128 DOI: 10.1093/nar/gkab213] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/08/2021] [Accepted: 03/16/2021] [Indexed: 11/13/2022] Open
Abstract
Mutations within the mtrR gene are commonly found amongst multidrug resistant clinical isolates of Neisseria gonorrhoeae, which has been labelled a superbug by the Centers for Disease Control and Prevention. These mutations appear to contribute to antibiotic resistance by interfering with the ability of MtrR to bind to and repress expression of its target genes, which include the mtrCDE multidrug efflux transporter genes and the rpoH oxidative stress response sigma factor gene. However, the DNA-recognition mechanism of MtrR and the consensus sequence within these operators to which MtrR binds has remained unknown. In this work, we report the crystal structures of MtrR bound to the mtrCDE and rpoH operators, which reveal a conserved, but degenerate, DNA consensus binding site 5'-MCRTRCRN4YGYAYGK-3'. We complement our structural data with a comprehensive mutational analysis of key MtrR-DNA contacts to reveal their importance for MtrR-DNA binding both in vitro and in vivo. Furthermore, we model and generate common clinical mutations of MtrR to provide plausible biochemical explanations for the contribution of these mutations to multidrug resistance in N. gonorrhoeae. Collectively, our findings unveil key biological mechanisms underlying the global stress responses of N. gonorrhoeae.
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Affiliation(s)
- Grace A Beggs
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Julio C Ayala
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Logan G Kavanaugh
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Timothy D Read
- Department of Medicine, and the Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA 30322, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Grace M Hooks
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Maria A Schumacher
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - William M Shafer
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA 30322, USA
- Laboratories of Bacterial Pathogenesis, VA Medical Center, Decatur, GA 30033, USA
| | - Richard G Brennan
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
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Abstract
Gram-negative bacteria utilize the resistance-nodulation-cell division (RND) superfamily of efflux pumps to expel a variety of toxic compounds from the cell. The Escherichia coli CusA membrane protein, which recognizes and extrudes biocidal Cu(I) and Ag(I) ions, belongs to the heavy-metal efflux (HME) subfamily of RND efflux pumps. We here report four structures of the trimeric CusA heavy-metal efflux pump in the presence of Cu(I) using single-particle cryo-electron microscopy (cryo-EM). We discover that different CusA protomers within the trimer are able to bind Cu(I) ions simultaneously. Our structural data combined with molecular dynamics (MD) simulations allow us to propose a mechanism for ion transport where each CusA protomer functions independently within the trimer.IMPORTANCE The bacterial RND superfamily of efflux pumps mediate resistance to a variety of biocides, including Cu(I) and Ag(I) ions. Here we report four cryo-EM structures of the trimeric CusA pump in the presence of Cu(I). Combined with MD simulations, our data indicate that each CusA protomer within the trimer recognizes and extrudes Cu(I) independently.
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Laumen JGE, Manoharan-Basil SS, Verhoeven E, Abdellati S, De Baetselier I, Crucitti T, Xavier BB, Chapelle S, Lammens C, Van Dijck C, Malhotra-Kumar S, Kenyon C. Molecular pathways to high-level azithromycin resistance in Neisseria gonorrhoeae. J Antimicrob Chemother 2021; 76:1752-1758. [DOI: 10.1093/jac/dkab084] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/28/2021] [Indexed: 01/02/2023] Open
Abstract
Abstract
Background
The prevalence of azithromycin resistance in Neisseria gonorrhoeae is increasing in numerous populations worldwide.
Objectives
To characterize the genetic pathways leading to high-level azithromycin resistance.
Methods
A customized morbidostat was used to subject two N. gonorrhoeae reference strains (WHO-F and WHO-X) to dynamically sustained azithromycin pressure. We tracked stepwise evolution of resistance by whole genome sequencing.
Results
Within 26 days, all cultures evolved high-level azithromycin resistance. Typically, the first step towards resistance was found in transitory mutations in genes rplD, rplV and rpmH (encoding the ribosomal proteins L4, L22 and L34 respectively), followed by mutations in the MtrCDE-encoded efflux pump and the 23S rRNA gene. Low- to high-level resistance was associated with mutations in the ribosomal proteins and MtrCDE efflux pump. However, high-level resistance was consistently associated with mutations in the 23S ribosomal RNA, mainly the well-known A2059G and C2611T mutations, but also at position A2058G.
Conclusions
This study enabled us to track previously reported mutations and identify novel mutations in ribosomal proteins (L4, L22 and L34) that may play a role in the genesis of azithromycin resistance in N. gonorrhoeae.
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Affiliation(s)
- J G E Laumen
- Institute of Tropical Medicine, Department of Clinical Sciences, STI Unit, Antwerp, Belgium
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - S S Manoharan-Basil
- Institute of Tropical Medicine, Department of Clinical Sciences, STI Unit, Antwerp, Belgium
| | - E Verhoeven
- Institute of Tropical Medicine, Department of Clinical Sciences, STI Unit, Antwerp, Belgium
- Pfizer, Puurs, Belgium
| | - S Abdellati
- Institute of Tropical Medicine, Department of Clinical Sciences, Clinical Reference Laboratory, Antwerp, Belgium
| | - I De Baetselier
- Institute of Tropical Medicine, Department of Clinical Sciences, Clinical Reference Laboratory, Antwerp, Belgium
| | - T Crucitti
- Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - B B Xavier
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - S Chapelle
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - C Lammens
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - C Van Dijck
- Institute of Tropical Medicine, Department of Clinical Sciences, STI Unit, Antwerp, Belgium
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - S Malhotra-Kumar
- University of Antwerp, Laboratory of Medical Microbiology, Vaccine and Infectious Disease Institute, Antwerp, Belgium
| | - C Kenyon
- Institute of Tropical Medicine, Department of Clinical Sciences, STI Unit, Antwerp, Belgium
- Department of Medicine, University of Cape Town, Cape Town, South Africa
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Klenotic PA, Morgan CE, Yu EW. Cryo-EM as a tool to study bacterial efflux systems and the membrane proteome. Fac Rev 2021; 10:24. [PMID: 33718941 PMCID: PMC7946387 DOI: 10.12703/r/10-24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Antibiotic resistance is an emerging threat to global health. Current treatment regimens for these types of bacterial infections are becoming increasingly inadequate. Thus, new innovative technologies are needed to help identify and characterize novel drugs and drug targets which are critical in order to combat multidrug-resistant bacterial strains. Bacterial efflux systems have emerged as an attractive target for drug design, as blocking their export function significantly increases the potency of administered antibiotics. However, in order to develop potent and tolerable efflux pump inhibitors with high efficacy, detailed structural information is required for both the apo- and substrate-bound forms of these membrane proteins. The emergence of cryo-electron microscopy (cryo-EM) has greatly advanced the field of membrane protein structural biology. It has significantly enhanced the ability to solve large multi-protein complexes as well as extract meaningful data from a heterogeneous sample, such as identification of several assembly states of the bacterial ribosome, from a single data set. This technique can be expanded to solve the structures of substrate-bound efflux pumps and entire efflux systems from previously unusable membrane protein sample preparations. Subsequently, cryo-EM combined with other biophysical techniques has the potential to markedly advance the field of membrane protein structural biology. The ability to discern complete transport machineries, enzymatic signal transduction pathways, and other membrane-associated complexes will help us fully understand the complexities of the membrane proteome.
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Affiliation(s)
- Philip A Klenotic
- Department of Pharmacology, Case Western Reserve University School of Medicine, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
| | - Christopher E Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
| | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, 2109 Adelbert Rd, Cleveland, OH 44106-4965, USA
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Morgan CE, Glaza P, Leus IV, Trinh A, Su CC, Cui M, Zgurskaya HI, Yu EW. Cryoelectron Microscopy Structures of AdeB Illuminate Mechanisms of Simultaneous Binding and Exporting of Substrates. mBio 2021; 12:e03690-20. [PMID: 33622726 PMCID: PMC8545137 DOI: 10.1128/mbio.03690-20] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/31/2022] Open
Abstract
Acinetobacter baumannii is a Gram-negative pathogen that has emerged as one of the most highly antibiotic-resistant bacteria worldwide. Multidrug efflux within these highly drug-resistant strains and other opportunistic pathogens is a major cause of failure of drug-based treatments of infectious diseases. The best-characterized multidrug efflux system in A. baumannii is the prevalent Acinetobacterdrug efflux B (AdeB) pump, which is a member of the resistance-nodulation-cell division (RND) superfamily. Here, we report six structures of the trimeric AdeB multidrug efflux pump in the presence of ethidium bromide using single-particle cryoelectron microscopy (cryo-EM). These structures allow us to directly observe various novel conformational states of the AdeB trimer, including the transmembrane region of trimeric AdeB can be associated with form a trimer assembly or dissociated into "dimer plus monomer" and "monomer plus monomer plus monomer" configurations. We also discover that a single AdeB protomer can simultaneously anchor a number of ethidium ligands and that different AdeB protomers can bind ethidium molecules simultaneously. Combined with molecular dynamics (MD) simulations, we reveal a drug transport mechanism that involves multiple multidrug-binding sites and various transient states of the AdeB membrane protein. Our data suggest that each AdeB protomer within the trimer binds and exports drugs independently.IMPORTANCEAcinetobacter baumannii has emerged as one of the most highly antibiotic-resistant Gram-negative pathogens. The prevalent AdeB multidrug efflux pump mediates resistance to a broad spectrum of clinically relevant antimicrobial agents. Here, we report six cryo-EM structures of the trimeric AdeB pump in the presence of ethidium bromide. We discover that a single AdeB protomer can simultaneously anchor a number of ligands, and different AdeB protomers can bind ethidium molecules simultaneously. The results indicate that each AdeB protomer within the trimer recognizes and extrudes drugs independently.
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Affiliation(s)
- Christopher E Morgan
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Przemyslaw Glaza
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Inga V Leus
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Anhthu Trinh
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Chih-Chia Su
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, Massachusetts, USA
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Edward W Yu
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA
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41
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An Analysis of the Novel Fluorocycline TP-6076 Bound to Both the Ribosome and Multidrug Efflux Pump AdeJ from Acinetobacter baumannii. mBio 2021; 13:e0373221. [PMID: 35100868 PMCID: PMC8805024 DOI: 10.1128/mbio.03732-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Antibiotic resistance among bacterial pathogens continues to pose a serious global health threat. Multidrug-resistant (MDR) strains of the Gram-negative organism Acinetobacter baumannii utilize a number of resistance determinants to evade current antibiotics. One of the major resistance mechanisms employed by these pathogens is the use of multidrug efflux pumps. These pumps extrude xenobiotics directly out of bacterial cells, resulting in treatment failures when common antibiotics are administered. Here, the structure of the novel tetracycline antibiotic TP-6076, bound to both the Acinetobacter drug efflux pump AdeJ and the ribosome from Acinetobacter baumannii, using single-particle cryo-electron microscopy (cryo-EM), is elucidated. In this work, the structure of the AdeJ-TP-6076 complex is solved, and we show that AdeJ utilizes a network of hydrophobic interactions to recognize this fluorocycline. Concomitant with this, we elucidate three structures of TP-6076 bound to the A. baumannii ribosome and determine that its binding is stabilized largely by electrostatic interactions. We then compare the differences in binding modes between TP-6076 and the related tetracycline antibiotic eravacycline in both targets. These differences suggest that modifications to the tetracycline core may be able to alter AdeJ binding while maintaining interactions with the ribosome. Together, this work highlights how different mechanisms are used to stabilize the binding of tetracycline-based compounds to unique bacterial targets and provides guidance for the future clinical development of tetracycline antibiotics. IMPORTANCE Treatment of antibiotic-resistant organisms such as A. baumannii represents an ongoing issue for modern medicine. The multidrug efflux pump AdeJ serves as a major resistance determinant in A. baumannii through its action of extruding antibiotics from the cell. In this work, we use cryo-EM to show how AdeJ recognizes the experimental tetracycline antibiotic TP-6076 and prevents this drug from interacting with the A. baumannii ribosome. Since AdeJ and the ribosome use different binding modes to stabilize interactions with TP-6076, exploiting these differences may guide future drug development for combating antibiotic-resistant A. baumannii and potentially other strains of MDR bacteria.
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HIV susceptibility in women: The roles of genital inflammation, sexually transmitted infections and the genital microbiome. J Reprod Immunol 2021; 145:103291. [PMID: 33647576 DOI: 10.1016/j.jri.2021.103291] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 01/29/2021] [Accepted: 02/12/2021] [Indexed: 12/24/2022]
Abstract
Given that heterosexual transmission of HIV across the genital mucosa is the most common route of infection in women, an in-depth understanding of the biological mechanisms associated with HIV risk in the female genital tract (FGT) is essential for effective control of the epidemic. Genital pro-inflammatory cytokines are well-described biological co-factors to HIV risk. Increased levels of pro-inflammatory cytokines in the FGT have been associated with a 3-fold higher-risk of acquiring HIV, presumably through involvement in barrier compromise and the recruitment of highly activated HIV target cells to the site of initial viral infection and replication. Sexually transmitted infections (STIs) and bacterial vaginosis (BV) are suggested possible contributors to genital inflammation in the FGT, and this, coupled with the relationship between genital inflammation and HIV risk, underscores the importance of effective treatment of STI and BV in the promotion of women's health. In most low- and middle-income countries, STIs are treated syndromically, a practice providing rapid treatment without identifying the infection source. However, this approach has been associated with over-diagnosis and the overuse of drugs. Further, because many women with STIs are asymptomatic, syndromic management also fails to treat a vast proportion of infected women. Although several studies have explored the role of STIs and the vaginal microbiome on genital inflammation and HIV risk, the impact of STI and BV management on genital inflammation remains poorly understood. This review aimed to collate the evidence on how BV and STI management efforts affect genital inflammation and the genital microbiome in women.
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43
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Lim KYL, Mullally CA, Haese EC, Kibble EA, McCluskey NR, Mikucki EC, Thai VC, Stubbs KA, Sarkar-Tyson M, Kahler CM. Anti-Virulence Therapeutic Approaches for Neisseria gonorrhoeae. Antibiotics (Basel) 2021; 10:antibiotics10020103. [PMID: 33494538 PMCID: PMC7911339 DOI: 10.3390/antibiotics10020103] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/18/2021] [Accepted: 01/20/2021] [Indexed: 01/15/2023] Open
Abstract
While antimicrobial resistance (AMR) is seen in both Neisseria gonorrhoeae and Neisseria meningitidis, the former has become resistant to commonly available over-the-counter antibiotic treatments. It is imperative then to develop new therapies that combat current AMR isolates whilst also circumventing the pathways leading to the development of AMR. This review highlights the growing research interest in developing anti-virulence therapies (AVTs) which are directed towards inhibiting virulence factors to prevent infection. By targeting virulence factors that are not essential for gonococcal survival, it is hypothesized that this will impart a smaller selective pressure for the emergence of resistance in the pathogen and in the microbiome, thus avoiding AMR development to the anti-infective. This review summates the current basis of numerous anti-virulence strategies being explored for N. gonorrhoeae.
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Affiliation(s)
- Katherine Y. L. Lim
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Christopher A. Mullally
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Ethan C. Haese
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Emily A. Kibble
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA 6150, Australia
| | - Nicolie R. McCluskey
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA 6150, Australia
| | - Edward C. Mikucki
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Van C. Thai
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Keith A. Stubbs
- School of Molecular Sciences, University of Western Australia, Crawley, WA 6009, Australia;
| | - Mitali Sarkar-Tyson
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
| | - Charlene M. Kahler
- Marshall Centre for Infectious Disease Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (K.Y.L.L.); (C.A.M.); (E.C.H.); (E.A.K.); (N.R.M.); (E.C.M.); (V.C.T.); (M.S.-T.)
- Correspondence:
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A small molecule that mitigates bacterial infection disrupts Gram-negative cell membranes and is inhibited by cholesterol and neutral lipids. PLoS Pathog 2020; 16:e1009119. [PMID: 33290418 PMCID: PMC7748285 DOI: 10.1371/journal.ppat.1009119] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 12/18/2020] [Accepted: 11/01/2020] [Indexed: 01/01/2023] Open
Abstract
Infections caused by Gram-negative bacteria are difficult to fight because these pathogens exclude or expel many clinical antibiotics and host defense molecules. However, mammals have evolved a substantial immune arsenal that weakens pathogen defenses, suggesting the feasibility of developing therapies that work in concert with innate immunity to kill Gram-negative bacteria. Using chemical genetics, we recently identified a small molecule, JD1, that kills Salmonella enterica serovar Typhimurium (S. Typhimurium) residing within macrophages. JD1 is not antibacterial in standard microbiological media, but rapidly inhibits growth and curtails bacterial survival under broth conditions that compromise the outer membrane or reduce efflux pump activity. Using a combination of cellular indicators and super resolution microscopy, we found that JD1 damaged bacterial cytoplasmic membranes by increasing fluidity, disrupting barrier function, and causing the formation of membrane distortions. We quantified macrophage cell membrane integrity and mitochondrial membrane potential and found that disruption of eukaryotic cell membranes required approximately 30-fold more JD1 than was needed to kill bacteria in macrophages. Moreover, JD1 preferentially damaged liposomes with compositions similar to E. coli inner membranes versus mammalian cell membranes. Cholesterol, a component of mammalian cell membranes, was protective in the presence of neutral lipids. In mice, intraperitoneal administration of JD1 reduced tissue colonization by S. Typhimurium. These observations indicate that during infection, JD1 gains access to and disrupts the cytoplasmic membrane of Gram-negative bacteria, and that neutral lipids and cholesterol protect mammalian membranes from JD1-mediated damage. Thus, it may be possible to develop therapeutics that exploit host innate immunity to gain access to Gram-negative bacteria and then preferentially damage the bacterial cell membrane over host membranes.
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45
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Ozorowski G, Torres JL, Santos-Martins D, Forli S, Ward AB. A Strain-Specific Inhibitor of Receptor-Bound HIV-1 Targets a Pocket near the Fusion Peptide. Cell Rep 2020; 33:108428. [PMID: 33238117 PMCID: PMC7701285 DOI: 10.1016/j.celrep.2020.108428] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 10/07/2020] [Accepted: 11/03/2020] [Indexed: 01/18/2023] Open
Abstract
Disruption of viral fusion represents a viable, albeit under-explored, target for HIV therapeutics. Here, while studying the receptor-bound envelope glycoprotein conformation by cryoelectron microscopy (cryo-EM), we identify a pocket near the base of the trimer containing a bound detergent molecule and perform in silico drug screening by using a library of drug-like and commercially available molecules. After down-selection, we solve cryo-EM structures that validate the binding of two small molecule hits in very similar manners to the predicted binding poses, including interactions with aromatic residues within the fusion peptide. One of the molecules demonstrates low micromolar inhibition of the autologous virus by using a very rare phenylalanine in the fusion peptide and stabilizing the surrounding region. This work demonstrates that small molecules can target the fusion process, providing an additional target for anti-HIV therapeutics, and highlights the need to explore how fusion peptide sequence variations affect receptor-mediated conformational states across diverse HIV strains.
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Affiliation(s)
- Gabriel Ozorowski
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, International AIDS Vaccine Initiative Neutralizing Antibody Center, and Collaboration for AIDS Vaccine Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jonathan L Torres
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, International AIDS Vaccine Initiative Neutralizing Antibody Center, and Collaboration for AIDS Vaccine Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Diogo Santos-Martins
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Stefano Forli
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, International AIDS Vaccine Initiative Neutralizing Antibody Center, and Collaboration for AIDS Vaccine Discovery, The Scripps Research Institute, La Jolla, CA 92037, USA.
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46
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Ma KC, Mortimer TD, Grad YH. Efflux Pump Antibiotic Binding Site Mutations Are Associated with Azithromycin Nonsusceptibility in Clinical Neisseria gonorrhoeae Isolates. mBio 2020; 11:e01509-20. [PMID: 32843551 PMCID: PMC7448274 DOI: 10.1128/mbio.01509-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Kevin C Ma
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Tatum D Mortimer
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Yonatan H Grad
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts, USA
- Division of Infectious Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
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47
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Du Toit A. Taking a closer look. Nat Rev Microbiol 2020; 18:412. [DOI: 10.1038/s41579-020-0398-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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