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Pereira AJ, Xing H, de Campos LJ, Seleem MA, de Oliveira KMP, Obaro SK, Conda-Sheridan M. Structure-Activity Relationship Study to Develop Peptide Amphiphiles as Species-Specific Antimicrobials. Chemistry 2024; 30:e202303986. [PMID: 38221408 PMCID: PMC10939825 DOI: 10.1002/chem.202303986] [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: 11/29/2023] [Revised: 01/05/2024] [Accepted: 01/09/2024] [Indexed: 01/16/2024]
Abstract
Antimicrobial peptide amphiphiles (PAs) are a promising class of molecules that can disrupt the bacterial membrane or act as drug nanocarriers. In this study, we prepared 33 PAs to establish supramolecular structure-activity relationships. We studied the morphology and activity of the nanostructures against different Gram-positive and Gram-negative bacterial strains (such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii). Next, we used principal component analysis (PCA) to determine the key contributors to activity. We found that for S. aureus, the zeta potential was the major contributor to the activity while Gram-negative bacteria were more influenced by the partition coefficient (LogP) with the following order P. aeruginosa>E. coli>A. baumannii. We also performed a study of the mechanism of action of selected PAs on the bacterial membrane assessing the membrane permeability and depolarization, changes in zeta potential and overall integrity. We studied the toxicity of the nanostructures against mammalian cells. Finally, we performed an in vivo study using the wax moth larvae to determine the therapeutic efficacy of the active PAs. This study shows cationic PA nanostructures can be an intriguing platform for the development of nanoantibacterials.
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Affiliation(s)
- Aramis J. Pereira
- A. J. Pereira, Dr. H. Xing, L. J. de Campos, Prof. Dr. M. Conda-Sheridan, Department of Pharmaceutical Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE 68198 (USA)
| | - Huihua Xing
- A. J. Pereira, Dr. H. Xing, L. J. de Campos, Prof. Dr. M. Conda-Sheridan, Department of Pharmaceutical Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE 68198 (USA)
| | - Luana J. de Campos
- A. J. Pereira, Dr. H. Xing, L. J. de Campos, Prof. Dr. M. Conda-Sheridan, Department of Pharmaceutical Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE 68198 (USA)
| | - Mohamed A. Seleem
- Dr. M.A. Seleem, Department of Pharmaceutical Organic Chemistry, Al-Azhar University, Cairo, 4434003 (Egypt)
| | - Kelly M. P. de Oliveira
- Prof. Dr. K. M. P. de Oliveira, Department of Biological and Environmental Science, Federal University of Grande Dourados (UFGD), Dourados, MS 79804-970 (Brazil)
| | - Stephen K. Obaro
- Prof. Dr. S. K. Obaro, Division of Pediatric Infectious Diseases, University of Alabama at Birmingham (UAB), Birmingham, AL 35233 (USA), International Foundation against Infectious Diseases in Nigeria (IFAIN), Abuja, 900108 (Nigeria)
| | - Martin Conda-Sheridan
- A. J. Pereira, Dr. H. Xing, L. J. de Campos, Prof. Dr. M. Conda-Sheridan, Department of Pharmaceutical Sciences, University of Nebraska Medical Center (UNMC), Omaha, NE 68198 (USA)
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2
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Kumar G, Engle K. Natural products acting against S. aureus through membrane and cell wall disruption. Nat Prod Rep 2023; 40:1608-1646. [PMID: 37326041 DOI: 10.1039/d2np00084a] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Covering: 2015 to 2022Staphylococcus aureus (S. aureus) is responsible for several community and hospital-acquired infections with life-threatening complications such as bacteraemia, endocarditis, meningitis, liver abscess, and spinal cord epidural abscess. In recent decades, the abuse and misuse of antibiotics in humans, animals, plants, and fungi and the treatment of nonmicrobial diseases have led to the rapid emergence of multidrug-resistant pathogens. The bacterial wall is a complex structure consisting of the cell membrane, peptidoglycan cell wall, and various associated polymers. The enzymes involved in bacterial cell wall synthesis are established antibiotic targets and continue to be a central focus for antibiotic development. Natural products play a vital role in drug discovery and development. Importantly, natural products provide a starting point for active/lead compounds that sometimes need modification based on structural and biological properties to meet the drug criteria. Notably, microorganisms and plant metabolites have contributed as antibiotics for noninfectious diseases. In this study, we have summarized the recent advances in understanding the activity of the drugs or agents of natural origin that directly inhibit the bacterial membrane, membrane components, and membrane biosynthetic enzymes by targeting membrane-embedded proteins. We also discussed the unique aspects of the active mechanisms of established antibiotics or new agents.
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Affiliation(s)
- Gautam Kumar
- Department of Natural Products, Chemical Sciences, National Institute of Pharmaceutical Education and Research-Hyderabad, Hyderabad, Balanagar, 500037, India.
| | - Kritika Engle
- Department of Natural Products, Chemical Sciences, National Institute of Pharmaceutical Education and Research-Hyderabad, Hyderabad, Balanagar, 500037, India.
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3
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Reid DJ, Dash T, Wang Z, Aspinwall CA, Marty MT. Investigating Daptomycin-Membrane Interactions Using Native MS and Fast Photochemical Oxidation of Peptides in Nanodiscs. Anal Chem 2023; 95:4984-4991. [PMID: 36888920 PMCID: PMC10033427 DOI: 10.1021/acs.analchem.2c05222] [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] [Indexed: 03/10/2023]
Abstract
Daptomycin is a cyclic lipopeptide antibiotic that targets the lipid membrane of Gram-positive bacteria. Membrane fluidity and charge can affect daptomycin activity, but its mechanisms are poorly understood because it is challenging to study daptomycin interactions within lipid bilayers. Here, we combined native mass spectrometry (MS) and fast photochemical oxidation of peptides (FPOP) to study daptomycin-membrane interactions with different lipid bilayer nanodiscs. Native MS suggests that daptomycin incorporates randomly and does not prefer any specific oligomeric states when integrated into bilayers. FPOP reveals significant protection in most bilayer environments. Combining the native MS and FPOP results, we observed that stronger membrane interactions are formed with more rigid membranes, and pore formation may occur in more fluid membranes to expose daptomycin to FPOP oxidation. Electrophysiology measurements further supported the observation of polydisperse pore complexes from the MS data. Together, these results demonstrate the complementarity of native MS, FPOP, and membrane conductance experiments to shed light on how antibiotic peptides interact with and within lipid membranes.
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Affiliation(s)
- Deseree J. Reid
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Tapasyatanu Dash
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Zhihan Wang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Craig A. Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, University of Arizona, Tucson, AZ 85721, USA
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Bio5 Institute, University of Arizona, Tucson, AZ 85721, USA
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4
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García de la Mària C, Cañas MA, Fernández-Pittol M, Dahl A, García-González J, Hernández-Meneses M, Cuervo G, Moreno A, Miró JM, Marco F. Emerging issues on Staphylococcus aureus endocarditis and the role in therapy of daptomycin plus fosfomycin. Expert Rev Anti Infect Ther 2023; 21:281-293. [PMID: 36744387 DOI: 10.1080/14787210.2023.2174969] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Methicillin-resistant and -susceptible Staphylococcus aureus (MRSA/MSSA) infections are a major global health-care problem. Bacteremia with S. aureus exhibits high rates of morbidity and mortality and can cause complicated infections such as infective endocarditis (IE). The emerging resistance profile of S. aureus is worrisome, and several international agencies have appealed for new treatment approaches to be developed. AREAS COVERED Daptomycin presents a rapid bactericidal effect against MRSA and has been considered at least as effective as vancomycin in treating MRSA bacteremia. However, therapy failure is often related to deep-seated infections, e.g. endocarditis, with high bacterial inocula and daptomycin regimens <10 mg/kg/day. Current antibiotic options for treating invasive S. aureus infections have limitations in monotherapy. Daptomycin in combination with other antibiotics, e.g. fosfomycin, may be effective in improving clinical outcomes in patients with MRSA IE. EXPERT OPINION Exploring therapeutic combinations has shown fosfomycin to have a unique mechanism of action and to be the most effective option in preventing the onset of resistance to and optimizing the efficacy of daptomycin, suggesting the synergistic combination of fosfomycin with daptomycin is a useful alternative treatment option for MSSA or MRSA IE.
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Affiliation(s)
- Cristina García de la Mària
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | - Maria-Alexandra Cañas
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | | | - Anders Dahl
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain.,Department of Cardiology, Bispebjerg University Hospital, Copenhagen, Denmark
| | - Javier García-González
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | - Marta Hernández-Meneses
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | - Guillermo Cuervo
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | - Asunción Moreno
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain
| | - Jose M Miró
- Infectious Diseases Service, Hospital Clinic - Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). University of Barcelona, Barcelona, Spain.,CIBERINFEC, Instituto de Salud Carlos III, Madrid, Spain
| | - Francesc Marco
- Microbiology Department, Centre Diagnòstic Biomèdic (CDB) Hospital Clínic, Barcelona, Spain.,ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
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5
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Moreira R, Taylor SD. A54145 Factor D Is Not Less Susceptible to Inhibition by Lung Surfactant than Daptomycin. ACS Infect Dis 2022; 8:1935-1947. [PMID: 36001599 DOI: 10.1021/acsinfecdis.2c00313] [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: 01/29/2023]
Abstract
A54145 factor D (A5D) is a cyclic lipopeptide antibiotic that shares several structural and mechanistic features with the clinically important antibiotic daptomycin, such as their requirement for calcium and phosphatidylglycerol (PG) for activity. Studies by others have suggested that daptomycin's activity is strongly inhibited by lung surfactant while A5D's activity is not. This finding has inspired efforts, albeit unsuccessful, to develop an A5D analogue that is highly active in the presence of lung surfactant and can be used for treating community acquired pneumonia (CAP). Here we demonstrate that A5D, like daptomycin, has a strong preference for the 1,2-diacyl-sn-glycero-3-phospho-1'-sn-glycerol stereoisomer (2R,2'S configuration) of PG. This PG stereoisomer was determined to be the only stereoisomer of PG in lung surfactant. Both antibiotics are completely antagonized by approximately 1-2 mol equiv of 2R,2'S-PG. Studies performed in the presence of lung surfactant revealed that the antagonism of these peptides by surfactant is mainly due to their interaction with PG and that A5D is not significantly less susceptible to inhibition by lung surfactant than daptomycin.
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Affiliation(s)
- Ryan Moreira
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Scott D Taylor
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
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6
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Miller LN, Blake MJ, Page EF, Castillo HB, Calhoun TR. Phosphate Ions Alter the Binding of Daptomycin to Living Bacterial Cell Surfaces. ACS Infect Dis 2021; 7:3088-3095. [PMID: 34605244 DOI: 10.1021/acsinfecdis.1c00397] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Advancements in antibiotic drug design are often hindered by missing information on how these small molecules interact with living cells. The antibiotic, daptomycin, has found clinical success and an emerging resistance, but a comprehensive picture of its mechanism of action has remained elusive. Using a surface-specific spectroscopy technique, second harmonic generation, we are able to quantitatively assess the binding of daptomycin to living cell membranes without the addition of exogenous labels. Our results reveal similar binding affinities for both Gram-positive and Gram-negative bacteria studied, including Escherichia coli. More importantly, we show that the presence of phosphate ions influences the binding of daptomycin to the Gram-positive bacterium Enterococcus faecalis. The role of environmental phosphate has not previously been considered in any proposed mechanism, and its implications are expected to be important in vivo.
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Affiliation(s)
- Lindsey N. Miller
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Marea J. Blake
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Eleanor F. Page
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Hannah B. Castillo
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Tessa R. Calhoun
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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7
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Kotsogianni I, Wood TM, Alexander FM, Cochrane SA, Martin NI. Binding Studies Reveal Phospholipid Specificity and Its Role in the Calcium-Dependent Mechanism of Action of Daptomycin. ACS Infect Dis 2021; 7:2612-2619. [PMID: 34406007 PMCID: PMC8438661 DOI: 10.1021/acsinfecdis.1c00316] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Multidrug-resistant bacteria pose a serious global health threat as antibiotics are increasingly losing their clinical efficacy. A molecular level understanding of the mechanism of action of antimicrobials plays a key role in developing new agents to combat the threat of antimicrobial resistance. Daptomycin, the only clinically used calcium-dependent lipopeptide antibiotic, selectively disrupts Gram-positive bacterial membranes to illicit its bactericidal effect. In this study, we use isothermal titration calorimetry to further characterize the structural features of the target bacterial phospholipids that drive daptomycin binding. Our studies reveal that daptomycin shows a clear preference for the phosphoglycerol headgroup. Furthermore, unlike other calcium-dependent lipopeptide antibiotics, calcium binding by daptomycin is strongly dependent on the presence of phosphatidylglycerol. These investigations provide new insights into daptomycin's phospholipid specificity and calcium binding behavior.
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Affiliation(s)
- Ioli Kotsogianni
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Thomas M. Wood
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Francesca M. Alexander
- School of Chemistry and Chemical Engineering, David Keir Building, Stranmillis Road, Queen’s University Belfast, Belfast, BT9 5AG, United Kingdom
| | - Stephen A. Cochrane
- School of Chemistry and Chemical Engineering, David Keir Building, Stranmillis Road, Queen’s University Belfast, Belfast, BT9 5AG, United Kingdom
| | - Nathaniel I. Martin
- Biological Chemistry Group, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
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8
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Noden M, Taylor SD. Enantioselective Synthesis and Application of Small and Environmentally Sensitive Fluorescent Amino Acids for Probing Biological Interactions. J Org Chem 2021; 86:11407-11418. [PMID: 34387500 DOI: 10.1021/acs.joc.1c00907] [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
Environmentally sensitive fluorescent amino acids (FlAAs) have been used extensively to probe biological interactions. However, most of these amino acids are large and do not resemble amino acid side chains. Here, we report the enantioselective synthesis of two small and environmentally sensitive fluorescent amino acids bearing 7-dialkylaminocoumarin side chains by alkylation of a Ni(II) glycine Schiff base complex. These amino acids exhibit a large increase in fluorescence as environment polarity decreases. One of these FLAAs was incorporated into a highly active analog of the cyclic lipopeptide antibiotic paenibacterin by Fmoc solid-phase peptide synthesis via a new and very efficient route. This peptide was used to probe the interaction of the antibiotic with model liposomes, lipopolysaccharides, and live bacteria.
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Affiliation(s)
- Michael Noden
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Scott D Taylor
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
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9
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Blasco P, Zhang C, Chow HY, Chen G, Wu Y, Li X. An atomic perspective on improving daptomycin's activity. Biochim Biophys Acta Gen Subj 2021; 1865:129918. [PMID: 33965439 DOI: 10.1016/j.bbagen.2021.129918] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 05/03/2021] [Accepted: 05/03/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Recently, through comprehensive medicinal chemistry efforts, we have found a new daptomycin analogue, termed kynomycin, showing enhanced activity against both methicillin-resistant S. aureus and vancomycin-resistant Enterococcus in vitro and in vivo, with improved pharmacokinetics and lower cytotoxicity than daptomycin. METHODS In this study we compared the physicochemical properties of kynomycin with those of daptomycin from an atomic perspective by using Nuclear Magnetic Resonance spectroscopy and Molecular Dynamics simulations. RESULTS AND CONCLUSION We observed that kynurenine methylation changes daptomycin's key physicochemical properties; its calcium dependent oligomerization efficiency is improved and the modified kynurenine strengths contacts with the lipid tail and tryptophan residues. In addition, it is observed that, compared to daptomycin, kynomycin tetramer is more stable and binds stronger to calcium. The combined experiments provide key clues for the improved antibacterial activity of kynomycin. GENERAL SIGNIFICANCE We expect that this approach will help study the calcium binding and oligomerization features of new calcium dependent peptide antibiotics.
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Affiliation(s)
- Pilar Blasco
- Department of Chemistry, State Key Lab of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Chunlei Zhang
- Department of Chemistry, State Key Lab of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Hoi Yee Chow
- Department of Chemistry, State Key Lab of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Guanhua Chen
- Department of Chemistry, State Key Lab of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
| | - Yongsheng Wu
- Mudanjiang YouBo Pharmaceutical Co., Ltd, Mudanjiang, PR China
| | - Xuechen Li
- Department of Chemistry, State Key Lab of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong; Laboratory for Marine Drugs and Bioproducts, Qingdao National Laboratory for Marine Science and Technology, Qingdao, PR China.
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10
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Pokorny A, Almeida PF. The Antibiotic Peptide Daptomycin Functions by Reorganizing the Membrane. J Membr Biol 2021; 254:97-108. [DOI: 10.1007/s00232-021-00175-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 01/21/2021] [Indexed: 10/22/2022]
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11
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Karas JA, Carter GP, Howden BP, Turner AM, Paulin OKA, Swarbrick JD, Baker MA, Li J, Velkov T. Structure–Activity Relationships of Daptomycin Lipopeptides. J Med Chem 2020; 63:13266-13290. [DOI: 10.1021/acs.jmedchem.0c00780] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- John A. Karas
- Department of Pharmacology & Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Glen P. Carter
- Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, VIC 3000, Australia
| | - Benjamin P. Howden
- Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, VIC 3000, Australia
| | - Adrianna M. Turner
- Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, VIC 3000, Australia
| | - Olivia K. A. Paulin
- Department of Pharmacology & Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - James D. Swarbrick
- Department of Pharmacology & Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Mark. A. Baker
- Priority Research Centre in Reproductive Science, School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Jian Li
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia
| | - Tony Velkov
- Department of Pharmacology & Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
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12
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Gray DA, Wenzel M. More Than a Pore: A Current Perspective on the In Vivo Mode of Action of the Lipopeptide Antibiotic Daptomycin. Antibiotics (Basel) 2020; 9:E17. [PMID: 31947747 PMCID: PMC7168178 DOI: 10.3390/antibiotics9010017] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 12/29/2019] [Accepted: 12/31/2019] [Indexed: 12/19/2022] Open
Abstract
Daptomycin is a cyclic lipopeptide antibiotic, which was discovered in 1987 and entered the market in 2003. To date, it serves as last resort antibiotic to treat complicated skin infections, bacteremia, and right-sided endocarditis caused by Gram-positive pathogens, most prominently methicillin-resistant Staphylococcus aureus. Daptomycin was the last representative of a novel antibiotic class that was introduced to the clinic. It is also one of the few membrane-active compounds that can be applied systemically. While membrane-active antibiotics have long been limited to topical applications and were generally excluded from systemic drug development, they promise slower resistance development than many classical drugs that target single proteins. The success of daptomycin together with the emergence of more and more multi-resistant superbugs attracted renewed interest in this compound class. Studying daptomycin as a pioneering systemic membrane-active compound might help to pave the way for future membrane-targeting antibiotics. However, more than 30 years after its discovery, the exact mechanism of action of daptomycin is still debated. In particular, there is a prominent discrepancy between in vivo and in vitro studies. In this review, we discuss the current knowledge on the mechanism of daptomycin against Gram-positive bacteria and try to offer explanations for these conflicting observations.
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Affiliation(s)
- Declan Alan Gray
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK;
| | - Michaela Wenzel
- Division of Chemical Biology, Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden
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13
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Aktas G. In Vitro Synergistic Effect of Vancomycin Combined with Daptomycin Against Vancomycin-Resistant Enterococci. Microb Drug Resist 2019; 25:1484-1489. [PMID: 31343391 DOI: 10.1089/mdr.2019.0033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
New antimicrobial agents are being designed to treat infections of multidrug-resistant pathogens and have been introduced in the past few years, but there has been a worldwide increase in the incidence of vancomycin-resistant enterococci (VRE) infections, and treatment options are still limited. In this study, it was aimed to investigate the in vitro activity of vancomycin combined with daptomycin against 30 VRE strains. The minimum inhibitory concentration (MIC) values of antibiotics were determined using broth microdilution assay as described by the Clinical and Laboratory Standards Institute (CLSI). The activities of antibiotics in combination were assessed using a broth microcheckerboard method. In addition, 4 of the 30 strains were randomly selected to determine the time-kill curves at 1 × MIC concentrations and 2 of 4 strains at ½ × MIC concentrations. Viable counts were determined at 0-, 4-, 8-, 12-, 24-, 48-, and 72-hr intervals. This was accomplished by subculturing 0.1 mL from repetitive serial dilutions in Eppendorf tubes, followed by subculturing 0.1 mL from tubes onto Tryptic Soy Agar plates. All plates were incubated at 35°C for 24 hr. The synergistic effect was found 100% using the broth microcheckerboard method, and in strains tested using the time-kill method at both 1 × MIC and ½ × MIC concentrations. The results of this study suggest that this combination could be effective in the treatment of the VRE-associated infection.
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Affiliation(s)
- Gulseren Aktas
- Department of Medical Microbiology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey
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14
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Wood TM, Martin NI. The calcium-dependent lipopeptide antibiotics: structure, mechanism, & medicinal chemistry. MEDCHEMCOMM 2019; 10:634-646. [PMID: 31191855 PMCID: PMC6533798 DOI: 10.1039/c9md00126c] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 03/20/2019] [Indexed: 12/19/2022]
Abstract
To push back the growing tide of antibacterial resistance the discovery and development of new antibiotics is a must. In recent years the calcium-dependent lipopeptide antibiotics (CDAs) have emerged as a potential source of new antibacterial agents rich in structural and mechanistic diversity. All CDAs share a common lipidated cyclic peptide motif containing amino acid side chains that specifically chelate calcium. It is only in the calcium bound state that the CDAs achieve their potent antibacterial activities. Interestingly, despite their common structural features, the mechanisms by which different CDAs target bacteria can vary dramatically. This review provides both a historic context for the CDAs while also addressing the state of the art with regards to their discovery, optimization, and antibacterial mechanisms.
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Affiliation(s)
- Thomas M Wood
- Department of Chemical Biology & Drug Discovery , Utrecht Institute for Pharmaceutical Sciences , Utrecht University , Universiteitsweg 99 , 3584 CG Utrecht , The Netherlands
- Biological Chemistry Group , Institute of Biology Leiden , Leiden University , Sylvius Laboratories , Sylviusweg 72 , 2333 BE Leiden , The Netherlands . ; Tel: +31 (0)6 1878 5274
| | - Nathaniel I Martin
- Biological Chemistry Group , Institute of Biology Leiden , Leiden University , Sylvius Laboratories , Sylviusweg 72 , 2333 BE Leiden , The Netherlands . ; Tel: +31 (0)6 1878 5274
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15
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Daptomycin Pore Formation and Stoichiometry Depend on Membrane Potential of Target Membrane. Antimicrob Agents Chemother 2018; 63:AAC.01589-18. [PMID: 30323037 DOI: 10.1128/aac.01589-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/06/2018] [Indexed: 12/14/2022] Open
Abstract
Daptomycin is a calcium-dependent lipodepsipeptide antibiotic clinically used to treat serious infections caused by Gram-positive pathogens. Its precise mode of action is somewhat controversial; the biggest issue is daptomycin pore formation, which we directly investigated here. We first performed a screening experiment using propidium iodide (PI) entry to Bacillus subtilis cells and chose the optimum and therapeutically relevant conditions (10 µg/ml daptomycin and 1.25 mM CaCl2) for the subsequent analyses. Using conductance measurements on planar lipid bilayers, we show that daptomycin forms nonuniform oligomeric pores with conductance ranging from 120 pS to 14 nS. The smallest conductance unit is probably a dimer; however, tetramers and pentamers occur in the membrane most frequently. Moreover, daptomycin pore-forming activity is exponentially dependent on the applied membrane voltage. We further analyzed the membrane-permeabilizing activity in B. subtilis cells using fluorescence methods [PI and DiSC3(5)]. Daptomycin most rapidly permeabilizes cells with high initial membrane potential and dissipates it within a few minutes. Low initial membrane potential hinders daptomycin pore formation.
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Lee MT, Yang PY, Charron NE, Hsieh MH, Chang YY, Huang HW. Comparison of the Effects of Daptomycin on Bacterial and Model Membranes. Biochemistry 2018; 57:5629-5639. [PMID: 30153001 DOI: 10.1021/acs.biochem.8b00818] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Daptomycin is a phosphatidylglycerol specific, calcium-dependent membrane-active antibiotic that has been approved for the treatment of Gram-positive infections. A recent Bacillus subtilis study found that daptomycin clustered into fluid lipid domains of bacterial membranes and the membrane binding was correlated with dislocation of peripheral membrane proteins and depolarization of membrane potential. In particular, the study disproved the existence of daptomycin ion channels. Our purpose here is to study how daptomycin interacts with lipid bilayers to understand the observed phenomena on bacterial membranes. We performed new types of experiments using aspirated giant vesicles with an ion leakage indicator, making comparisons between daptomycin and ionomycin, performing vesicle-vesicle transfers, and measuring daptomycin binding to fluid phase versus gel phase bilayers and bilayers including cholesterol. Our findings are entirely consistent with the observations for bacterial membranes. In addition, daptomycin is found to cause ion leakage through the membrane only if its concentration in the membrane is over a certain threshold. The ion leakage caused by daptomycin is transient. It occurs only when daptomycin binds the membrane for the first time; afterward, they cease to induce ion leakage. The ion leakage effect of daptomycin cannot be transferred from one membrane to another. The level of membrane binding of daptomycin is reduced in the gel phase versus the fluid phase. Cholesterol also weakens the membrane binding of daptomycin. The combination of membrane concentration threshold and differential binding is significant. This could be a reason why daptomycin discriminates between eukaryotic and prokaryotic cell membranes.
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Affiliation(s)
- Ming-Tao Lee
- National Synchrotron Radiation Research Center , Hsinchu , Taiwan 300.,Department of Physics , National Central University , Jhongli , Taiwan 320
| | - Pei-Yin Yang
- Department of Physics and Astronomy , Rice University , Houston , Texas 77005 , United States
| | - Nicholas E Charron
- Department of Physics and Astronomy , Rice University , Houston , Texas 77005 , United States
| | - Meng-Hsuan Hsieh
- Institute of Biotechnology , National Taiwan University , Taipei , Taiwan 10617
| | - Yu-Yung Chang
- National Synchrotron Radiation Research Center , Hsinchu , Taiwan 300
| | - Huey W Huang
- Department of Physics and Astronomy , Rice University , Houston , Texas 77005 , United States
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17
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Update on prevalence and mechanisms of resistance to linezolid, tigecycline and daptomycin in enterococci in Europe: Towards a common nomenclature. Drug Resist Updat 2018; 40:25-39. [DOI: 10.1016/j.drup.2018.10.002] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 08/10/2018] [Accepted: 10/30/2018] [Indexed: 01/04/2023]
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18
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Kreutzberger MA, Pokorny A, Almeida PF. Daptomycin-Phosphatidylglycerol Domains in Lipid Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13669-13679. [PMID: 29130685 PMCID: PMC5710797 DOI: 10.1021/acs.langmuir.7b01841] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Daptomycin is an acidic, 13-amino acid, cyclic polypeptide that contains a number of nonproteinogenic residues and is modified at its N-terminus with a decanoyl chain. It has been in clinical use since 2003 against selected drug-resistant Staphylococcus aureus and Enterococcus spp infections. In vitro, daptomycin is active against Gram-positive pathogens at low concentrations but its antibiotic activity depends critically on the presence of calcium ions. This dependence has been thought to arise from binding of one or two Ca2+ ions to daptomycin as a required step in its interaction with the bacterial membrane. Here, we investigated the interaction of daptomycin with giant unilamellar vesicles (GUVs) composed 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG). We used fluorescence confocal microscopy to monitor binding of the peptide to GUVs and follow its effect on the membrane of the vesicle. We found that in the absence of POPG or Ca2+ daptomycin does not bind measurably to the lipid membrane. In the presence of 20-30% PG in the membrane and 2 mM Ca2+, daptomycin induces the formation of membrane domains rich in acidic lipids. This effect is not induced by Ca2+ alone. In addition, daptomycin causes GUV collapse, but it does not translocate across the membrane to the inside of intact POPC/POPG vesicles. We conclude that pore formation is probably not the mechanism by which the peptide functions. On the other hand, we found that daptomycin coclusters with the anionic phospholipid POPG and the fluorescent probes used, leading to extensive formation of daptomycin-POPG domains in the membrane.
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19
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Taylor R, Beriashvili D, Taylor S, Palmer M. Daptomycin Pore Formation Is Restricted by Lipid Acyl Chain Composition. ACS Infect Dis 2017; 3:797-801. [PMID: 29048870 DOI: 10.1021/acsinfecdis.7b00138] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Daptomycin is a calcium-dependent lipopeptide antibiotic that is used clinically against various Gram-positive pathogens. It acts on bacterial cell membranes, whose susceptibility varies with the content of phosphatidylglycerol (PG). Some studies have reported that daptomycin permeabilizes and depolarizes bacterial cell membranes, while others have found no evidence of membrane permeabilization and thus proposed different mechanisms of antibacterial action. Divergent observations have also been reported regarding the effect of daptomycin on model membranes, which were found to be permeabilized nonselectively, selectively for small cations, or not at all. While these diverging model studies did consider the functional roles of different lipid head groups, they assumed that the acyl chains were interchangeable. We here show this assumption to be erroneous. In equimolar mixtures of PG and phosphatidylcholine (PC), dimyristoyl lipids support membrane permeabilization, whereas dioleyl and palmitoleyl lipids do not, even though daptomycin does bind to and form oligomers on all of these membranes. These observations help reconcile some of the discrepant findings in the literature.
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Affiliation(s)
- Robert Taylor
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - David Beriashvili
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Scott Taylor
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Michael Palmer
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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20
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Lee MT, Hung WC, Hsieh MH, Chen H, Chang YY, Huang HW. Molecular State of the Membrane-Active Antibiotic Daptomycin. Biophys J 2017; 113:82-90. [PMID: 28700928 DOI: 10.1016/j.bpj.2017.05.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/19/2017] [Accepted: 05/22/2017] [Indexed: 11/27/2022] Open
Abstract
Membrane-active antibiotics are potential alternatives to the resistance-prone conventional antibiotics. Daptomycin, a cyclic lipopeptide, is the only membrane-active antibiotic approved by the U.S. Food and Drug Administration so far. The drug interacts with the cytoplasmic membranes of Gram-positive pathogens, causing membrane permeabilization to ions and cell death. The antibiotic activity is calcium-ion dependent and correlates with the target membrane's content of phosphatidylglycerol (PG). For such a complex reaction with membranes, it has been difficult to uncover the molecular process that underlies its antibacterial activity. The role of the cofactor, calcium ions, has been confusing. Many have proposed that calcium ions binding to daptomycin is a precondition for membrane interaction. Here, we report our findings on the molecular state of daptomycin before and after its membrane-binding reaction, particularly at therapeutic concentrations in the low micromolar range. We were able to perform small-angle x-ray scattering at sufficiently low daptomycin concentrations to determine that the molecules are monomeric before membrane binding. By careful circular dichroism (CD) analyses of daptomycin with Ca2+ and PG-containing membranes, we found that there are only two states identifiable by CD, one before and another after membrane binding; all other CD spectra are linear combinations of the two. Before membrane binding, the molecular state of daptomycin as defined by CD is the same with or without calcium ions. We are able to determine the stoichiometric ratios of the membrane-binding reaction. The stoichiometric ratio of daptomycin to calcium is 2:3. The stoichiometric ratio of daptomycin to PG is ∼1:1 if only the PG lipids in the outer leaflets of membranes are accessible to daptomycin.
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Affiliation(s)
- Ming-Tao Lee
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan; Department of Physics, National Central University, Jhongli, Taiwan
| | - Wei-Chin Hung
- Department of Physics, R. O. C. Military Academy, Fengshan, Kaohsiung, Taiwan
| | - Meng-Hsuan Hsieh
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Hsiung Chen
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Yu-Yung Chang
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Huey W Huang
- Department of Physics and Astronomy, Rice University, Houston, Texas.
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Zhang J, Scott WRP, Gabel F, Wu M, Desmond R, Bae J, Zaccai G, Algar WR, Straus SK. On the quest for the elusive mechanism of action of daptomycin: Binding, fusion, and oligomerization. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:1490-1499. [PMID: 28844744 DOI: 10.1016/j.bbapap.2017.07.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 07/05/2017] [Accepted: 07/31/2017] [Indexed: 01/27/2023]
Abstract
Daptomycin, sold under the trade name CUBICIN, is the first lipopeptide antibiotic to be approved for use against Gram-positive organisms, including a number of highly resistant species. Over the last few decades, a number of studies have tried to pinpoint the mechanism of action of daptomycin. These proposed modes of action often have points in common (e.g. the requirement for Ca2+ and lipid membranes containing a high proportion of phosphatidylglycerol (PG) headgroups), but also points of divergence (e.g. oligomerization in solution and in membranes, membrane perturbation vs. inhibition of cell envelope synthesis). In this study, we investigate how concentration effects may have an impact on the interpretation of the biophysical data used to support a given mechanism of action. Results obtained from small angle neutron scattering (SANS) experiments and molecular dynamics (MD) simulations show that daptomycin oligomerizes at high concentrations (both with and without Ca2+) in solution, but that this oligomer readily falls apart. Photon correlation spectroscopy (PCS) experiments demonstrate that daptomycin causes fusion more readily in DMPC/PG membranes than in POPC/PG, suggesting that the latter may be a better model system. Finally, fluorescence and Förster resonance energy transfer (FRET) experiments reveal that daptomycin binds strongly to the lipid membrane and that oligomerization occurs in a concentration-dependent manner. The combined experiments provide an improved framework for more general and rigorous biophysical studies toward understanding the elusive mechanism of action of daptomycin. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman.
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Affiliation(s)
- Jin Zhang
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Walter R P Scott
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Frank Gabel
- Institut de Biologie Structurale, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France; Institut Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - Miao Wu
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Ruqaiba Desmond
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - JungHwan Bae
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Giuseppe Zaccai
- Institut Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - W Russ Algar
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada.
| | - Suzana K Straus
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada.
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Taylor RM, Scott B, Taylor S, Palmer M. An Acyl-Linked Dimer of Daptomycin Is Strongly Inhibited by the Bacterial Cell Wall. ACS Infect Dis 2017; 3:462-466. [PMID: 28350438 DOI: 10.1021/acsinfecdis.7b00019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The lipopeptide antibiotic daptomycin is active against Gram-positive pathogens. It permeabilizes bacterial cell membranes, which involves the formation of membrane-associated oligomers. We here studied a dimer of daptomycin whose two subunits were linked through a bivalent aliphatic acyl chain. Unexpectedly, the dimer had very low activity on vegetative Staphylococcus aureus and Bacillus subtilis cells. However, activity resembled that of monomeric daptomycin on liposomes and on B. subtilis L-forms. These findings underscore the importance of the bacterial cell wall in daptomycin resistance.
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Affiliation(s)
- Robert M. Taylor
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Bradley Scott
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Scott Taylor
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Michael Palmer
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
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Zhang T, Taylor SD, Palmer M, Duhamel J. Membrane Binding and Oligomerization of the Lipopeptide A54145 Studied by Pyrene Fluorescence. Biophys J 2017; 111:1267-1277. [PMID: 27653485 DOI: 10.1016/j.bpj.2016.07.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 07/11/2016] [Accepted: 07/15/2016] [Indexed: 11/30/2022] Open
Abstract
A54145 is a lipopeptide antibiotic related to daptomycin that permeabilizes bacterial cell membranes. Its action requires both calcium and phosphatidylglycerol in the target membrane, and it is accompanied by the formation of membrane-associated oligomers. We here probed the interaction of A54145 with model membranes composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol, using the steady-state and time-resolved fluorescence of a pyrene-labeled derivative (Py-A54145). In solution, the labeled peptide was found to exist as a monomer. Its membrane interaction occurred in two stages that could be clearly distinguished by varying the calcium concentration. In the first stage, which was observed between 0.15 and 1 mM calcium, Py-A54145 bound to the membrane, as indicated by a strong increase in pyrene monomer emission. At the same calcium concentration, excimer emission increased also, suggesting that Py-A54145 had oligomerized. A global analysis of the time-resolved pyrene monomer and excimer fluorescence confirmed that Py-A54145 forms oligomers quantitatively and concomitantly with membrane binding. When calcium was raised beyond 1 mM, a distinct second transition was observed that may correspond to a doubling of the number of oligomer subunits. The collective findings confirm and extend our understanding of the action mode of A54145 and daptomycin.
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Affiliation(s)
- TianHua Zhang
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
| | - Scott D Taylor
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
| | - Michael Palmer
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada.
| | - Jean Duhamel
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada.
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Mitochondria-targeted antioxidants as highly effective antibiotics. Sci Rep 2017; 7:1394. [PMID: 28469140 PMCID: PMC5431119 DOI: 10.1038/s41598-017-00802-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/13/2017] [Indexed: 12/17/2022] Open
Abstract
Mitochondria-targeted antioxidants are known to alleviate mitochondrial oxidative damage that is associated with a variety of diseases. Here, we showed that SkQ1, a decyltriphenyl phosphonium cation conjugated to a quinone moiety, exhibited strong antibacterial activity towards Gram-positive Bacillus subtilis, Mycobacterium sp. and Staphylococcus aureus and Gram-negative Photobacterium phosphoreum and Rhodobacter sphaeroides in submicromolar and micromolar concentrations. SkQ1 exhibited less antibiotic activity towards Escherichia coli due to the presence of the highly effective multidrug resistance pump AcrAB-TolC. E. coli mutants lacking AcrAB-TolC showed similar SkQ1 sensitivity, as B. subtilis. Lowering of the bacterial membrane potential by SkQ1 might be involved in the mechanism of its bactericidal action. No significant cytotoxic effect on mammalian cells was observed at bacteriotoxic concentrations of SkQ1. Therefore, SkQ1 may be effective in protection of the infected mammals by killing invading bacteria.
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Daptomycin inhibits cell envelope synthesis by interfering with fluid membrane microdomains. Proc Natl Acad Sci U S A 2016; 113:E7077-E7086. [PMID: 27791134 DOI: 10.1073/pnas.1611173113] [Citation(s) in RCA: 265] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Daptomycin is a highly efficient last-resort antibiotic that targets the bacterial cell membrane. Despite its clinical importance, the exact mechanism by which daptomycin kills bacteria is not fully understood. Different experiments have led to different models, including (i) blockage of cell wall synthesis, (ii) membrane pore formation, and (iii) the generation of altered membrane curvature leading to aberrant recruitment of proteins. To determine which model is correct, we carried out a comprehensive mode-of-action study using the model organism Bacillus subtilis and different assays, including proteomics, ionomics, and fluorescence light microscopy. We found that daptomycin causes a gradual decrease in membrane potential but does not form discrete membrane pores. Although we found no evidence for altered membrane curvature, we confirmed that daptomycin inhibits cell wall synthesis. Interestingly, using different fluorescent lipid probes, we showed that binding of daptomycin led to a drastic rearrangement of fluid lipid domains, affecting overall membrane fluidity. Importantly, these changes resulted in the rapid detachment of the membrane-associated lipid II synthase MurG and the phospholipid synthase PlsX. Both proteins preferentially colocalize with fluid membrane microdomains. Delocalization of these proteins presumably is a key reason why daptomycin blocks cell wall synthesis. Finally, clustering of fluid lipids by daptomycin likely causes hydrophobic mismatches between fluid and more rigid membrane areas. This mismatch can facilitate proton leakage and may explain the gradual membrane depolarization observed with daptomycin. Targeting of fluid lipid domains has not been described before for antibiotics and adds another dimension to our understanding of membrane-active antibiotics.
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