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Hussain A, Ong EBB, Balaram P, Ismail A, Kien PK. TolC facilitates the intracellular survival and immunomodulation of Salmonella Typhi in human host cells. Virulence 2024; 15:2395831. [PMID: 39185619 PMCID: PMC11385165 DOI: 10.1080/21505594.2024.2395831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 06/29/2024] [Accepted: 08/19/2024] [Indexed: 08/27/2024] Open
Abstract
Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever, a systemic infection that affects millions of people worldwide. S. Typhi can invade and survive within host cells, such as intestinal epithelial cells and macrophages, by modulating their immune responses. However, the immunomodulatory capability of S. Typhi in relation to TolC-facilitated efflux pump function remains unclear. The role of TolC, an outer membrane protein that facilitates efflux pump function, in the invasion and immunomodulation of S. Typhi, was studied in human intestinal epithelial cells and macrophages. The tolC deletion mutant of S. Typhi was compared with the wild-type and its complemented strain in terms of their ability to invade epithelial cells, survive and induce cytotoxicity in macrophages, and elicit proinflammatory cytokine production in macrophages. The tolC mutant, which has a defective outer membrane, was impaired in invading epithelial cells compared to the wild-type strain, but the intracellular presence of the tolC mutant exhibited greater cytotoxicity and induced higher levels of proinflammatory cytokines (IL-1β and IL-8) in macrophages compared to the wild-type strain. These effects were reversed by complementing the tolC mutant with a functional tolC gene. Our results suggest that TolC plays a role in S. Typhi to efficiently invade epithelial cells and suppress host immune responses during infection. TolC may be a potential target for the development of novel therapeutics against typhoid fever.
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Affiliation(s)
- Ashraf Hussain
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL USA
| | - Eugene Boon Beng Ong
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia
| | - Prabha Balaram
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia
| | - Asma Ismail
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia
| | - Phua Kia Kien
- Institute for Research in Molecular Medicine (INFORMM), Universiti Sains Malaysia, Penang, Malaysia
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2
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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; 88:e0008923. [PMID: 39235227 PMCID: PMC11426026 DOI: 10.1128/mmbr.00089-23] [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: 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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3
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Johnson TS, Bourdine AA, Deber CM. Hydrophobic moment drives penetration of bacterial membranes by transmembrane peptides. J Biol Chem 2023; 299:105266. [PMID: 37734555 PMCID: PMC10585379 DOI: 10.1016/j.jbc.2023.105266] [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: 07/30/2023] [Revised: 09/11/2023] [Accepted: 09/13/2023] [Indexed: 09/23/2023] Open
Abstract
With antimicrobial resistance (AMR) remaining a persistent and growing threat to human health worldwide, membrane-active peptides are gaining traction as an alternative strategy to overcome the issue. Membrane-embedded multi-drug resistant (MDR) efflux pumps are a prime target for membrane-active peptides, as they are a well-established contributor to clinically relevant AMR infections. Here, we describe a series of transmembrane peptides (TMs) to target the oligomerization motif of the AcrB component of the AcrAB-TolC MDR efflux pump from Escherichia coli. These peptides contain an N-terminal acetyl-A-(Sar)3 (sarcosine; N-methylglycine) tag and a C-terminal lysine tag-a design strategy our lab has utilized to improve the solubility and specificity of targeting for TMs previously. While these peptides have proven useful in preventing AcrB-mediated substrate efflux, the mechanisms by which these peptides associate with and penetrate the bacterial membrane remained unknown. In this study, we have shown peptide hydrophobic moment (μH)-the measure of concentrated hydrophobicity on one face of a lipopathic α-helix-drives bacterial membrane permeabilization and depolarization, likely through lateral-phase separation of negatively-charged POPG lipids and the disruption of lipid packing. Our results show peptide μH is an important consideration when designing membrane-active peptides and may be the determining factor in whether a TM will function in a permeabilizing or non-permeabilizing manner when embedded in the bacterial membrane.
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Affiliation(s)
- Tyler S Johnson
- Program in Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Aleksandra A Bourdine
- Program in Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Charles M Deber
- Program in Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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4
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Zheng M, Lupoli TJ. Counteracting antibiotic resistance enzymes and efflux pumps. Curr Opin Microbiol 2023; 75:102334. [PMID: 37329679 DOI: 10.1016/j.mib.2023.102334] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/02/2023] [Accepted: 05/17/2023] [Indexed: 06/19/2023]
Abstract
Bacterial pathogens are constantly evolving new resistance mechanisms against antibiotics; hence, strategies to potentiate existing antibiotics or combat mechanisms of resistance using adjuvants are always in demand. Recently, inhibitors have been identified that counteract enzymatic modification of the drugs isoniazid and rifampin, which have implications in the study of multi-drug-resistant mycobacteria. A wealth of structural studies on efflux pumps from diverse bacteria has also fueled the design of new small-molecule and peptide-based agents to prevent the active transport of antibiotics. We envision that these findings will inspire microbiologists to apply existing adjuvants to clinically relevant resistant strains, or to use described platforms to discover novel antibiotic adjuvant scaffolds.
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Affiliation(s)
- Meng Zheng
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA
| | - Tania J Lupoli
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003, USA.
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5
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Jang S. AcrAB-TolC, a major efflux pump in Gram negative bacteria: toward understanding its operation mechanism. BMB Rep 2023; 56:326-334. [PMID: 37254571 PMCID: PMC10315565 DOI: 10.5483/bmbrep.2023-0070] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 05/18/2023] [Accepted: 05/30/2023] [Indexed: 08/27/2023] Open
Abstract
Antibiotic resistance (AR) is a silent pandemic that kills millions worldwide. Although the development of new therapeutic agents against antibiotic resistance is in urgent demand, this has presented a great challenge, especially for Gram-negative bacteria that have inherent drug-resistance mediated by impermeable outer membranes and multidrug efflux pumps that actively extrude various drugs from the bacteria. For the last two decades, multidrug efflux pumps, including AcrAB-TolC, the most clinically important efflux pump in Gram-negative bacteria, have drawn great attention as strategic targets for re-sensitizing bacteria to the existing antibiotics. This article aims to provide a concise overview of the AcrAB-TolC operational mechanism, reviewing its architecture and substrate specificity, as well as the recent development of AcrAB-TolC inhibitors. [BMB Reports 2023; 56(6): 326-334].
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Affiliation(s)
- Soojin Jang
- Department of Discovery Biology, Antibacterial Resistance Laboratory, Institut Pasteur Korea, Seongnam 13488, Korea
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6
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Update on the Discovery of Efflux Pump Inhibitors against Critical Priority Gram-Negative Bacteria. Antibiotics (Basel) 2023; 12:antibiotics12010180. [PMID: 36671381 PMCID: PMC9854755 DOI: 10.3390/antibiotics12010180] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/18/2023] Open
Abstract
Antimicrobial resistance (AMR) has become a major problem in public health leading to an estimated 4.95 million deaths in 2019. The selective pressure caused by the massive and repeated use of antibiotics has led to bacterial strains that are partially or even entirely resistant to known antibiotics. AMR is caused by several mechanisms, among which the (over)expression of multidrug efflux pumps plays a central role. Multidrug efflux pumps are transmembrane transporters, naturally expressed by Gram-negative bacteria, able to extrude and confer resistance to several classes of antibiotics. Targeting them would be an effective way to revive various options for treatment. Many efflux pump inhibitors (EPIs) have been described in the literature; however, none of them have entered clinical trials to date. This review presents eight families of EPIs active against Escherichia coli or Pseudomonas aeruginosa. Structure-activity relationships, chemical synthesis, in vitro and in vivo activities, and pharmacological properties are reported. Their binding sites and their mechanisms of action are also analyzed comparatively.
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7
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Chetri S. The culmination of multidrug-resistant efflux pumps vs. meager antibiotic arsenal era: Urgent need for an improved new generation of EPIs. Front Microbiol 2023; 14:1149418. [PMID: 37138605 PMCID: PMC10149990 DOI: 10.3389/fmicb.2023.1149418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 03/13/2023] [Indexed: 05/05/2023] Open
Abstract
Efflux pumps function as an advanced defense system against antimicrobials by reducing the concentration of drugs inside the bacteria and extruding the substances outside. Various extraneous substances, including antimicrobials, toxic heavy metals, dyes, and detergents, have been removed by this protective barrier composed of diverse transporter proteins found in between the cell membrane and the periplasm within the bacterial cell. In this review, multiple efflux pump families have been analytically and widely outlined, and their potential applications have been discussed in detail. Additionally, this review also discusses a variety of biological functions of efflux pumps, including their role in the formation of biofilms, quorum sensing, their survivability, and the virulence in bacteria, and the genes/proteins associated with efflux pumps have also been explored for their potential relevance to antimicrobial resistance and antibiotic residue detection. A final discussion centers around efflux pump inhibitors, particularly those derived from plants.
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8
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Mitchell CJ, Johnson TS, Deber CM. Transmembrane peptide effects on bacterial membrane integrity and organization. Biophys J 2022; 121:3253-3262. [PMID: 35923102 PMCID: PMC9463641 DOI: 10.1016/j.bpj.2022.07.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 07/10/2022] [Accepted: 07/21/2022] [Indexed: 11/02/2022] Open
Abstract
As the bacterial multidrug resistance crisis continues, membrane-active antimicrobial peptides are being explored as an alternate treatment to conventional antibiotics. In contrast to antimicrobial peptides, which function by a nonspecific membrane disruption mechanism, here we describe a series of transmembrane (TM) peptides that are designed to act as drug efflux inhibitors by aligning with and out-competing a conserved TM4-TM4 homodimerization motif within bacterial small multidrug resistance proteins. The peptides contain two terminal tags: a C-terminal lysine tag to direct the peptides toward the negatively charged bacterial membrane, and an uncharged N-terminal sarcosine (N-methyl-glycine) tag to promote membrane insertion. While effective at inhibiting efflux activity, ostensibly through their designed mechanism of action, the impact of the peptides on the bacterial inner membrane remains undetermined. To evaluate the extant peptide-membrane interactions, we performed a series of biophysical measurements. Circular dichroism spectroscopy and Trp fluorescence showed that the peptides insert into the membrane generally in helical form. Interestingly, differential scanning calorimetry of the peptides added to bacterial-like membranes (POPE:POPG 3:1) revealed the peptides' ability to demix the POPE and POPG lipids, creating two pools, one of which is likely a peptide-POPG conglomerate, and the other a POPE-rich component where the native POPG content has been depleted. However, dye leakage assays confirmed that these events occur without causing significant membrane disruption both in vitro and in vivo, indicating that the peptides can target the small multidrug resistance TM4-TM4 motif without nonspecific membrane disruption. In related studies, DiOC2(3) fluorescence indicated moderate peptide-mediated reduction of the proton motive force for all peptides, including control peptides that did not display inhibitory activity. The overall findings suggest that peptides designed with suitable tags, sequence hydrophobicity, and charge distribution can be directed more generally to impact proteins whose function involves membrane-embedded protein-protein interactions.
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Affiliation(s)
- Chloe J Mitchell
- Program in Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Ontario, Canada
| | - Tyler S Johnson
- Program in Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Ontario, Canada
| | - Charles M Deber
- Program in Molecular Medicine, Research Institute, Hospital for Sick Children, Toronto M5G 0A4, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto M5S 1A8, Ontario, Canada.
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9
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MacDermott-Opeskin HI, Gupta V, O’Mara ML. Lipid-mediated antimicrobial resistance: a phantom menace or a new hope? Biophys Rev 2022; 14:145-162. [PMID: 35251360 PMCID: PMC8880301 DOI: 10.1007/s12551-021-00912-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/14/2021] [Indexed: 02/06/2023] Open
Abstract
Abstract The proposition of a post-antimicrobial era is all the more realistic with the continued rise of antimicrobial resistance. The development of new antimicrobials is failing to counter the ever-increasing rates of bacterial antimicrobial resistance. This necessitates novel antimicrobials and drug targets. The bacterial cell membrane is an essential and highly conserved cellular component in bacteria and acts as the primary barrier for entry of antimicrobials into the cell. Although previously under-exploited as an antimicrobial target, the bacterial cell membrane is attractive for the development of novel antimicrobials due to its importance in pathogen viability. Bacterial cell membranes are diverse assemblies of macromolecules built around a central lipid bilayer core. This lipid bilayer governs the overall membrane biophysical properties and function of its membrane-embedded proteins. This mini-review will outline the mechanisms by which the bacterial membrane causes and controls resistance, with a focus on alterations in the membrane lipid composition, chemical modification of constituent lipids, and the efflux of antimicrobials by membrane-embedded efflux systems. Thorough insight into the interplay between membrane-active antimicrobials and lipid-mediated resistance is needed to enable the rational development of new antimicrobials. In particular, the union of computational approaches and experimental techniques for the development of innovative and efficacious membrane-active antimicrobials is explored.
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Affiliation(s)
- Hugo I. MacDermott-Opeskin
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Vrinda Gupta
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601 Australia
| | - Megan L. O’Mara
- Research School of Chemistry, College of Science, The Australian National University, Canberra, ACT 2601 Australia
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10
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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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11
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Zgurskaya HI, Malloci G, Chandar B, Vargiu AV, Ruggerone P. Bacterial efflux transporters' polyspecificity - a gift and a curse? Curr Opin Microbiol 2021; 61:115-123. [PMID: 33940284 DOI: 10.1016/j.mib.2021.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 03/26/2021] [Accepted: 03/30/2021] [Indexed: 12/24/2022]
Abstract
All mechanisms of clinical antibiotic resistance benefit from activities of polyspecific efflux pumps acting to reduce intracellular accumulation of toxins and antibiotics. In Gram-negative bacteria, the major polyspecific efflux transporters belong to the Resistance-Nodulation-cell Division (RND) superfamily of proteins, which are capable of expelling thousands of structurally diverse compounds. Recent structural and functional advances generated novel insights into mechanisms underlying the biochemical versatility of RND transporters. This opinion article reviews these mechanisms and discusses implications of the polyspecificity of RND transporters for bacterial survival and for the development of efflux pump inhibitors effective in clinics.
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Affiliation(s)
- Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73072, United States.
| | - Giuliano Malloci
- Department of Physics, University of Cagliari, 09042 Monserrato (Cagliari), Italy
| | - Brinda Chandar
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73072, United States
| | - Attilio V Vargiu
- Department of Physics, University of Cagliari, 09042 Monserrato (Cagliari), Italy
| | - Paolo Ruggerone
- Department of Physics, University of Cagliari, 09042 Monserrato (Cagliari), Italy
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