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Parkhill SL, Johnson EO. Integrating bacterial molecular genetics with chemical biology for renewed antibacterial drug discovery. Biochem J 2024; 481:839-864. [PMID: 38958473 DOI: 10.1042/bcj20220062] [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: 05/07/2024] [Revised: 06/20/2024] [Accepted: 06/24/2024] [Indexed: 07/04/2024]
Abstract
The application of dyes to understanding the aetiology of infection inspired antimicrobial chemotherapy and the first wave of antibacterial drugs. The second wave of antibacterial drug discovery was driven by rapid discovery of natural products, now making up 69% of current antibacterial drugs. But now with the most prevalent natural products already discovered, ∼107 new soil-dwelling bacterial species must be screened to discover one new class of natural product. Therefore, instead of a third wave of antibacterial drug discovery, there is now a discovery bottleneck. Unlike natural products which are curated by billions of years of microbial antagonism, the vast synthetic chemical space still requires artificial curation through the therapeutics science of antibacterial drugs - a systematic understanding of how small molecules interact with bacterial physiology, effect desired phenotypes, and benefit the host. Bacterial molecular genetics can elucidate pathogen biology relevant to therapeutics development, but it can also be applied directly to understanding mechanisms and liabilities of new chemical agents with new mechanisms of action. Therefore, the next phase of antibacterial drug discovery could be enabled by integrating chemical expertise with systematic dissection of bacterial infection biology. Facing the ambitious endeavour to find new molecules from nature or new-to-nature which cure bacterial infections, the capabilities furnished by modern chemical biology and molecular genetics can be applied to prospecting for chemical modulators of new targets which circumvent prevalent resistance mechanisms.
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Affiliation(s)
- Susannah L Parkhill
- Systems Chemical Biology of Infection and Resistance Laboratory, The Francis Crick Institute, London, U.K
- Faculty of Life Sciences, University College London, London, U.K
| | - Eachan O Johnson
- Systems Chemical Biology of Infection and Resistance Laboratory, The Francis Crick Institute, London, U.K
- Faculty of Life Sciences, University College London, London, U.K
- Department of Chemistry, Imperial College, London, U.K
- Department of Chemistry, King's College London, London, U.K
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2
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Ongwae GM, Lepori I, Chordia MD, Dalesandro BE, Apostolos AJ, Siegrist MS, Pires MM. Measurement of Small Molecule Accumulation into Diderm Bacteria. ACS Infect Dis 2023; 9:97-110. [PMID: 36530146 DOI: 10.1021/acsinfecdis.2c00435] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Some of the most dangerous bacterial pathogens (Gram-negative and mycobacterial) deploy a formidable secondary membrane barrier to reduce the influx of exogenous molecules. For Gram-negative bacteria, this second exterior membrane is known as the outer membrane (OM), while for the Gram-indeterminate Mycobacteria, it is known as the "myco" membrane. Although different in composition, both the OM and mycomembrane are key structures that restrict the passive permeation of small molecules into bacterial cells. Although it is well-appreciated that such structures are principal determinants of small molecule permeation, it has proven to be challenging to assess this feature in a robust and quantitative way or in complex, infection-relevant settings. Herein, we describe the development of the bacterial chloro-alkane penetration assay (BaCAPA), which employs the use of a genetically encoded protein called HaloTag, to measure the uptake and accumulation of molecules into model Gram-negative and mycobacterial species, Escherichia coli and Mycobacterium smegmatis, respectively, and into the human pathogen Mycobacterium tuberculosis. The HaloTag protein can be directed to either the cytoplasm or the periplasm of bacteria. This offers the possibility of compartmental analysis of permeation across individual cell membranes. Significantly, we also showed that BaCAPA can be used to analyze the permeation of molecules into host cell-internalized E. coli and M. tuberculosis, a critical capability for analyzing intracellular pathogens. Together, our results show that BaCAPA affords facile measurement of permeability across four barriers: the host plasma and phagosomal membranes and the diderm bacterial cell envelope.
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Affiliation(s)
- George M Ongwae
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Irene Lepori
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Mahendra D Chordia
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Brianna E Dalesandro
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Alexis J Apostolos
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - M Sloan Siegrist
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, United States.,Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Marcos M Pires
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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3
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Ooi JMF, Fairhall JM, Spangler B, Chong DJW, Feng BY, Gamble AB, Hook S. Development of a bioorthogonal fluorescence-based assay for assessing drug uptake and delivery in bacteria. RSC Adv 2022; 12:15631-15642. [PMID: 35685699 PMCID: PMC9126673 DOI: 10.1039/d2ra02272a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/09/2022] [Indexed: 11/21/2022] Open
Abstract
Bioorthogonal chemistry can facilitate the development of fluorescent probes that can be used to sensitively and specifically detect the presence of biological targets. In this study, such an assay was developed to evaluate the uptake and delivery of antimicrobials into Escherichia coli, building on and extending previous work which utilised more resource intensive LCMS detection. The bacteria were genetically engineered to express streptavidin in the periplasmic or cytoplasmic compartments, which was used to localise a bioorthogonal probe (BCN-biotin). Azido-compounds which are delivered to these compartments react with the localised BCN-biotin–streptavidin in a concentration-dependent manner via a strain-promoted alkyne–azide cycloaddition. The amount of azido-compound taken up by bacteria was determined by quantifying unreacted BCN-biotin–streptavidin via an inverse electron demand Diels–Alder reaction between remaining BCN-biotin and a tetrazine-containing fluorescent dye. Following optimisation and validation, the assay was used to assess uptake of liposome-formulated azide-functionalised luciferin and cefoxitin. The results demonstrated that formulation into cationic liposomes improved the uptake of azide-functionalised compounds into the periplasm of E. coli, providing insight on the uptake mechanism of liposomes in the bacteria. This newly developed bioorthogonal fluorescence plate-reader based assay provides a bioactivity-independent, medium-to-high throughput tool for screening compound uptake/delivery. Bioorthogonal alkyne–azide and alkyne–tetrazine chemistries were used to assess drug uptake in bacteria. Azido-drug reacts with streptavidin bound alkyne-biotin within bacteria, the remaining unreacted alkyne is then quantified with a tetrazine-dye.![]()
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Affiliation(s)
| | | | - Benjamin Spangler
- Novartis Institutes for BioMedical Research (NIBR) in Emeryville California USA
| | | | - Brian Y Feng
- Novartis Institutes for BioMedical Research (NIBR) in Emeryville California USA
| | - Allan B Gamble
- School of Pharmacy, University of Otago Dunedin New Zealand
| | - Sarah Hook
- School of Pharmacy, University of Otago Dunedin New Zealand
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4
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Verma VA, Wang L, Labadie SS, Liang J, Sellers BD, Wang J, Dong L, Wang Q, Zhang S, Xu Z, Zhang Y, Niu Y, Wang X, Wai J, Koehler MFT, Hu H, Alexander MK, Nishiyama M, Miu A, Xu Y, Pang J, Katakam AK, Reichelt M, Austin CD, Ho H, Payandeh J, Koth CM. Discovery of Inhibitors of the Lipopolysaccharide Transporter MsbA: From a Screening Hit to Potent Wild-Type Gram-Negative Activity. J Med Chem 2022; 65:4085-4120. [DOI: 10.1021/acs.jmedchem.1c01909] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Vishal A. Verma
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Lan Wang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Sharada S. Labadie
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jun Liang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Benjamin D. Sellers
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jian Wang
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Liting Dong
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Qiuyue Wang
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Shuang Zhang
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Zhongya Xu
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Yexia Zhang
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Yanan Niu
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - Xinxin Wang
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | - John Wai
- WuXi AppTec Co., Ltd., 288 Fute Zhong Road, Waigaoqiao Free Trade Zone, Shanghai 200131, People’s Republic of China
| | | | - Huiyong Hu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Mary Kate Alexander
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Mireille Nishiyama
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Anh Miu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Yiming Xu
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jodie Pang
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Anand K. Katakam
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Michael Reichelt
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Cary D. Austin
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Hoangdung Ho
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Jian Payandeh
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Christopher M. Koth
- Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
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5
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Mastering the Gram-negative bacterial barrier - Chemical approaches to increase bacterial bioavailability of antibiotics. Adv Drug Deliv Rev 2021; 172:339-360. [PMID: 33705882 DOI: 10.1016/j.addr.2021.02.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 02/08/2021] [Accepted: 02/18/2021] [Indexed: 02/07/2023]
Abstract
To win the battle against resistant, pathogenic bacteria, novel classes of anti-infectives and targets are urgently needed. Bacterial uptake, distribution, metabolic and efflux pathways of antibiotics in Gram-negative bacteria determine what we here refer to as bacterial bioavailability. Understanding these mechanisms from a chemical perspective is essential for anti-infective activity and hence, drug discovery as well as drug delivery. A systematic and critical discussion of in bacterio, in vitro and in silico assays reveals that a sufficiently accurate holistic approach is still missing. We expect new findings based on Gram-negative bacterial bioavailability to guide future anti-infective research.
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Prajapati JD, Kleinekathöfer U, Winterhalter M. How to Enter a Bacterium: Bacterial Porins and the Permeation of Antibiotics. Chem Rev 2021; 121:5158-5192. [PMID: 33724823 DOI: 10.1021/acs.chemrev.0c01213] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite tremendous successes in the field of antibiotic discovery seen in the previous century, infectious diseases have remained a leading cause of death. More specifically, pathogenic Gram-negative bacteria have become a global threat due to their extraordinary ability to acquire resistance against any clinically available antibiotic, thus urging for the discovery of novel antibacterial agents. One major challenge is to design new antibiotics molecules able to rapidly penetrate Gram-negative bacteria in order to achieve a lethal intracellular drug accumulation. Protein channels in the outer membrane are known to form an entry route for many antibiotics into bacterial cells. Up until today, there has been a lack of simple experimental techniques to measure the antibiotic uptake and the local concentration in subcellular compartments. Hence, rules for translocation directly into the various Gram-negative bacteria via the outer membrane or via channels have remained elusive, hindering the design of new or the improvement of existing antibiotics. In this review, we will discuss the recent progress, both experimentally as well as computationally, in understanding the structure-function relationship of outer-membrane channels of Gram-negative pathogens, mainly focusing on the transport of antibiotics.
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Affiliation(s)
| | | | - Mathias Winterhalter
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen 28759, Germany
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Metier C, Dow J, Wootton H, Lynham S, Wren B, Wagner GK. Profiling of Haemophilus influenzae strain R2866 with carbohydrate-based covalent probes. Org Biomol Chem 2021; 19:476-485. [PMID: 33355321 DOI: 10.1039/d0ob01971b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate the application of four covalent probes based on anomerically pure d-galactosamine and d-glucosamine scaffolds for the profiling of Haemophilus influenzae strain R2866. The probes have been used successfully for the labelling of target proteins not only in cell lysates, but also in intact cells. Differences in the labelling patterns between lysates and intact cells indicate that the probes can penetrate into the periplasm, but not the cytoplasm of H. influenzae. Analysis of selected target proteins by LC-MS/MS suggests predominant labelling of nucleotide-binding proteins, including several known antibacterial drug targets. Our protocols will aid the identification of molecular determinants of bacterial pathogenicity in Haemophilus influenzae and other bacterial pathogens.
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Affiliation(s)
- Camille Metier
- King's College London, Department of Chemistry, Britannia House, 7 Trinity Street, London, SE1 1DB, UK
| | - Jennifer Dow
- London School of Hygiene and Tropical Medicine, Department of Infection Biology, Keppel Street, London, WC1E, 7HT, UK
| | - Hayley Wootton
- King's College London, Department of Chemistry, Britannia House, 7 Trinity Street, London, SE1 1DB, UK
| | - Steven Lynham
- Proteomics Facility, Centre of Excellence for Mass Spectrometry, King's College London, The James Black Centre, 125 Coldharbour Lane, London, SE5 9NU, UK
| | - Brendan Wren
- London School of Hygiene and Tropical Medicine, Department of Infection Biology, Keppel Street, London, WC1E, 7HT, UK
| | - Gerd K Wagner
- Queen's University Belfast, School of Pharmacy, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK.
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8
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Winterhalter M. Antibiotic uptake through porins located in the outer membrane of Gram-negative bacteria. Expert Opin Drug Deliv 2020; 18:449-457. [PMID: 33161750 DOI: 10.1080/17425247.2021.1847080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Introduction: Making selective inhibitors of novel Gram-negative targets is not a substantial challenge - getting them into Gram-negative bacteria to reach their lethal target is the bottleneck. Poor permeability of the antibiotic requires high concentration causing off target activity. The lack of simple experimental techniques to measure antibiotic uptake as well as the local concentration at the target site creates a particular bottleneck in understanding and in improving the antibiotic activity.Areas covered: Here we recall current approaches to quantify the uptake. For a few antibiotics with known evidence for channel-limited permeation, the flux across a single OmpF or OmpC channel has been measured. For a typical concentration gradient of 1 µM of antibiotics the uptake varies between one up to few hundred molecules per second and per channel.Expert opinion: The current research effort is on quantifying the flux for a larger list of compounds on a cellular (mass spectra, fluorescence) or at single channel level (electrophysiology). A larger dataset of single channel permeabilities under various condition will be a powerful tool for understanding and improving the activity of antibiotics.
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9
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McDowell LL, Quinn CL, Leeds JA, Silverman JA, Silver LL. Perspective on Antibacterial Lead Identification Challenges and the Role of Hypothesis-Driven Strategies. SLAS DISCOVERY 2020; 24:440-456. [PMID: 30890054 DOI: 10.1177/2472555218818786] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
For the past three decades, the pharmaceutical industry has undertaken many diverse approaches to discover novel antibiotics, with limited success. We have witnessed and personally experienced many mistakes, hurdles, and dead ends that have derailed projects and discouraged scientists and business leaders. Of the many factors that affect the outcomes of screening campaigns, a lack of understanding of the properties that drive efflux and permeability requirements across species has been a major barrier for advancing hits to leads. Hits that possess bacterial spectrum have seldom also possessed druglike properties required for developability and safety. Persistence in solving these two key barriers is necessary for the reinvestment into discovering antibacterial agents. This perspective narrates our experience in antibacterial discovery-our lessons learned about antibacterial challenges as well as best practices for screening strategies. One of the tenets that guides us is that drug discovery is a hypothesis-driven science. Application of this principle, at all steps in the antibacterial discovery process, should improve decision making and possibly the odds of what has become, in recent decades, an increasingly challenging endeavor with dwindling success rates.
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Affiliation(s)
- Laura L McDowell
- 1 Novartis Institutes for Biomedical Research, Emeryville, CA, USA
| | | | - Jennifer A Leeds
- 1 Novartis Institutes for Biomedical Research, Emeryville, CA, USA
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Breaching the Barrier: Quantifying Antibiotic Permeability across Gram-negative Bacterial Membranes. J Mol Biol 2019; 431:3531-3546. [DOI: 10.1016/j.jmb.2019.03.031] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/29/2019] [Accepted: 03/28/2019] [Indexed: 11/22/2022]
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11
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Gayen A, Kumar D, Matheshwaran S, Chandra M. Unveiling the Modulating Role of Extracellular pH in Permeation and Accumulation of Small Molecules in Subcellular Compartments of Gram-negative Escherichia coli using Nonlinear Spectroscopy. Anal Chem 2019; 91:7662-7671. [PMID: 30986344 DOI: 10.1021/acs.analchem.9b00574] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Quantitative evaluation of small molecule permeation and accumulation in Gram-negative bacteria is important for drug development against these bacteria. While these measurements are commonly performed at physiological pH, Escherichia coli and many other Enterobacteriaceae infect human gastrointestinal and urinary tracts, where they encounter different pH conditions. To understand how external pH affects permeation and accumulation of small molecules in E. coli cells, we apply second harmonic generation (SHG) spectroscopy using SHG-active antimicrobial compound malachite green as the probe molecule. Using SHG, we quantify periplasmic and cytoplasmic accumulations separately in live E. coli cells, which was never done before. Compartment-wise measurements reveal accumulation of the probe molecule in cytoplasm at physiological and alkaline pH, while entrapment in periplasm at weakly acidic pH and retention in external solution at highly acidic pH. Behind such disparity in localizations, up to 2 orders of magnitude reduction in permeability across the inner membrane at weakly acidic pH and outer membrane at highly acidic pH are found to play key roles. Our results unequivocally demonstrate the control of external pH over entry and compartment-wise distribution of small molecules in E. coli cells, which is a vital information and should be taken into account in antibiotic screening against E. coli and other Enterobacteriaceae members. In addition, our results demonstrate the ability of malachite green as an excellent SHG-indicator of changes of individual cell membrane and periplasm properties of live E. coli cells in response to external pH change from acidic to alkaline. This finding, too, has great importance, as there is barely any other molecular probe that can provide similar information.
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12
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Spangler B, Yang S, Baxter Rath CM, Reck F, Feng BY. A Unified Framework for the Incorporation of Bioorthogonal Compound Exposure Probes within Biological Compartments. ACS Chem Biol 2019; 14:725-734. [PMID: 30908011 DOI: 10.1021/acschembio.9b00008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Compartmentalization is a crucial facet of many biological systems, and key aspects of cellular processes rely on spatial segregation within the cell. While many drug targets reside in specific intracellular compartments, the tools available for assessing compound exposure are generally limited to whole-cell measurements. To address this gap, we recently developed a bioorthogonal chemistry-based method to assess compartment-specific compound exposure and demonstrated its use in Gram-negative bacteria. To expand the applicability of this approach, we report here novel bioorthogonal probe modalities which enable diverse probe incorporation strategies. The probes we developed utilize a cleavable thiocarbamate linker to connect localizing elements such as metabolic substrates to a cyclooctyne moiety which enables the detection of azide-containing molecules. Adducts between the probe and azide-bearing compounds can be recovered and affinity purified after exposure experiments, thus facilitating the mass-spectrometry based analysis used to assess compound exposure. The bioorthogonal system reported here thus provides a valuable new tool for interrogating compartment-specific compound exposure in a variety of biological contexts while retaining a simple and unified sample preparation and analysis workflow.
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Affiliation(s)
- Benjamin Spangler
- Novartis Institutes for BioMedical Research, Emerville, California 94608, United States
| | - Shengtian Yang
- Novartis Institutes for BioMedical Research, Emerville, California 94608, United States
| | | | - Folkert Reck
- Novartis Institutes for BioMedical Research, Emerville, California 94608, United States
| | - Brian Y. Feng
- Novartis Institutes for BioMedical Research, Emerville, California 94608, United States
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Widya M, Pasutti WD, Sachdeva M, Simmons RL, Tamrakar P, Krucker T, Six DA. Development and Optimization of a Higher-Throughput Bacterial Compound Accumulation Assay. ACS Infect Dis 2019; 5:394-405. [PMID: 30624052 DOI: 10.1021/acsinfecdis.8b00299] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The Gram-negative bacterial permeability barrier, coupled with efflux, raises formidable challenges to antibiotic drug discovery. The absence of efficient assays to determine compound penetration into the cell and impact of efflux makes the process resource-intensive, small-scale, and lacking much success. Here, we present BacPK: a label-free, solid phase extraction-mass spectrometry (SPE-MS)-based assay that measures total cellular compound accumulation in Escherichia coli. The BacPK assay is a 96-well accumulation assay that takes advantage of 9 s/sample SPE-MS throughput. This enables the analysis of each compound in a four-point dose-response in isogenic strain pairs along with a no-cell control and 16-point external standard curve, all in triplicate. To validate the assay, differences in accumulation were examined for tetracycline (Tet) and two analogs, confirming that close analogs can differ greatly in accumulation. Tet cellular accumulation was also compared for isogenic strains exhibiting Tet resistance due to the expression of an efflux pump (TetA) or ribosomal protection protein (TetM), confirming only TetA affected cellular Tet accumulation. Finally, using a diverse set of antibacterial compounds, we confirmed the assay's ability to quantify differences in accumulation for isogenic strain pairs with efflux or permeability alterations that are consistent with differences in susceptibility seen for the compounds.
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14
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Iyer R, Ye Z, Ferrari A, Duncan L, Tanudra MA, Tsao H, Wang T, Gao H, Brummel CL, Erwin AL. Evaluating LC-MS/MS To Measure Accumulation of Compounds within Bacteria. ACS Infect Dis 2018; 4:1336-1345. [PMID: 29961312 DOI: 10.1021/acsinfecdis.8b00083] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A general method for determining bacterial uptake of compounds independent of antibacterial activity would be a valuable tool in antibacterial drug discovery. LC-MS/MS assays have been described, but it has not been shown whether the data can be used directly to inform medicinal chemistry. We describe the evaluation of an LC-MS/MS assay measuring association of compounds with bacteria, using a set of over a hundred compounds (inhibitors of NAD-dependent DNA ligase, LigA) for which in vitro potency and antibacterial activity had been determined. All compounds were active against an efflux-deficient strain of Escherichia coli with reduced LigA activity ( E. coli ligA251 Δ tolC). Testing a single compound concentration and incubation time, we found that, for equipotent compounds, LC-MS/MS values were not predictive of antibacterial activity. This indicates that measured bacteria-associated compound was not necessarily exposed to the target enzyme. Our data suggest that, while exclusion from bacteria is a major reason for poor antibacterial activity of potent compounds, the distribution of compound within the bacterial cell may also be a problem. The relative importance of these factors is likely to vary from one chemical series to another. Our observations provide directions for further study of this difficult issue.
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Affiliation(s)
- Ramkumar Iyer
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Zhengqi Ye
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Annette Ferrari
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Leonard Duncan
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - M. Angela Tanudra
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Hong Tsao
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Tiansheng Wang
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Hong Gao
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Christopher L. Brummel
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
| | - Alice L. Erwin
- Vertex Pharmaceuticals Incorporated, 50 Northern Avenue, Boston, Massachusetts 02210, United States
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