1
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Lane BJ, Ma Y, Yan N, Wang B, Ackermann K, Karamanos TK, Bode BE, Pliotas C. Monitoring the conformational ensemble and lipid environment of a mechanosensitive channel under cyclodextrin-induced membrane tension. Structure 2024; 32:739-750.e4. [PMID: 38521071 DOI: 10.1016/j.str.2024.02.020] [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: 09/14/2023] [Revised: 12/29/2023] [Accepted: 02/27/2024] [Indexed: 03/25/2024]
Abstract
Membrane forces shift the equilibria of mechanosensitive channels enabling them to convert mechanical cues into electrical signals. Molecular tools to stabilize and methods to capture their highly dynamic states are lacking. Cyclodextrins can mimic tension through the sequestering of lipids from membranes. Here we probe the conformational ensemble of MscS by EPR spectroscopy, the lipid environment with NMR, and function with electrophysiology under cyclodextrin-induced tension. We show the extent of MscS activation depends on the cyclodextrin-to-lipid ratio, and that lipids are depleted slower when MscS is present. This has implications in MscS' activation kinetics when distinct membrane scaffolds such as nanodiscs or liposomes are used. We find MscS transits from closed to sub-conducting state(s) before it desensitizes, due to the lack of lipid availability in its vicinity required for closure. Our approach allows for monitoring tension-sensitive states in membrane proteins and screening molecules capable of inducing molecular tension in bilayers.
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Affiliation(s)
- Benjamin J Lane
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Yue Ma
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Nana Yan
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Bolin Wang
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK
| | - Katrin Ackermann
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, St Andrews KY16 9ST, UK
| | - Theodoros K Karamanos
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Bela E Bode
- EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews, St Andrews KY16 9ST, UK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK; School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester M13 9PT, UK; Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, UK.
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2
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Fu YH, Hu YF, Lin T, Zhuang GW, Wang YL, Chen WX, Li ZT, Hou JL. Constructing artificial gap junctions to mediate intercellular signal and mass transport. Nat Chem 2024:10.1038/s41557-024-01519-8. [PMID: 38658798 DOI: 10.1038/s41557-024-01519-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 03/25/2024] [Indexed: 04/26/2024]
Abstract
Natural gap junctions are a type of channel protein responsible for intercellular signalling and mass communication. However, the scope of applications for these proteins is limited as they cannot be prepared at a large scale and are unable to spontaneously insert into cell membranes in vitro. The construction of artificial gap junctions may provide an alternative strategy for preparing analogues of the natural proteins and bottom-up building blocks necessary for the synthesis of artificial cells. Here we show the construction of artificial gap junction channels from unimolecular tubular molecules consisting of alternately arranged positively and negatively charged pillar[5]arene motifs. These molecules feature a hydrophobic-hydrophilic-hydrophobic triblock structure that allows them to efficiently insert into two adjacent plasma membranes and stretch across the gap between the two membranes to form gap junctions. Similar to natural gap junction channels, the synthetic channels could mediate intercellular signal coupling and reactive oxygen species transmission, leading to cellular activity.
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Affiliation(s)
- Yong-Hong Fu
- Department of Chemistry, Fudan University, Shanghai, China
| | - Yi-Fei Hu
- Department of Chemistry, Fudan University, Shanghai, China
| | - Tao Lin
- Department of Chemistry, Fudan University, Shanghai, China
| | - Guo-Wei Zhuang
- Department of Chemistry, Fudan University, Shanghai, China
| | - Ying-Lan Wang
- Department of Chemistry, Fudan University, Shanghai, China
| | - Wen-Xue Chen
- Department of Chemistry, Fudan University, Shanghai, China
| | - Zhan-Ting Li
- Department of Chemistry, Fudan University, Shanghai, China
| | - Jun-Li Hou
- Department of Chemistry, Fudan University, Shanghai, China.
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3
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Kumar D, Gayen A, Chandra M. Hypo-osmotic Stress Increases Permeability of Individual Barriers in Escherichia coli Cell Envelope, Enabling Rapid Drug Transport. ACS Infect Dis 2023; 9:2471-2481. [PMID: 37950691 DOI: 10.1021/acsinfecdis.3c00326] [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] [Indexed: 11/13/2023]
Abstract
Survival of foodborne Gram-negative bacteria during osmotic stress often leads to multidrug resistance development. However, despite the concern, how osmoadaptation alters drug penetration across the Gram-negative bacterial cell envelope has remained inconclusive for years. Here, we have investigated drug permeation and accumulation inside hypo-osmotically shocked Escherichia coli. Three different quaternary ammonium compounds (QACs) are used as cationic amine-containing drug representatives; they also serve as envelope permeability indicators in different assays. Propidium iodide fluorescence reveals cytoplasmic accumulation and overall envelope permeability, while crystal violet sorption and second harmonic generation (SHG) spectroscopy reveal periplasmic accumulation and outer membrane permeability. Malachite green sorption and SHG results reveal transport across both the outer and inner membranes and accumulation in the periplasm as well as cytoplasm. The findings are found to be complementary to one another, collectively revealing enhanced permeabilities of both membranes and the periplasmic space in response to hypo-osmotic stress in E. coli. Enhanced permeability leads to faster QACs transport and higher accumulation in subcellular compartments, whereas transport and accumulation both are negligible under isosmotic conditions. The QACs' transport rates are found to be highly influenced by the osmolytes used, where phosphate ion emerges as a key facilitator of transport across the periplasm into the cytoplasm. E. coli is found viable, with morphology unchanged under extreme hypo-osmotic stress; i.e., it adapts to the situation. The outcome shows that the hypo-osmotic shock to E. coli, specifically using phosphate as an osmolyte, can be beneficial for drug delivery.
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Affiliation(s)
- Deepak Kumar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, Uttar Pradesh, India
| | - Anindita Gayen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, Uttar Pradesh, India
| | - Manabendra Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, Uttar Pradesh, India
- Center of Excellence: Tropical and Infectious Diseases, Gangwal School of Medical Sciences and Technology, Indian Institute of Technology Kanpur, Kanpur-208016, Uttar Pradesh, India
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4
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Dhar R, Bowman AM, Hatungimana B, Sg Slusky J. Evolutionary Engineering a Larger Porin Using a Loop-to-Hairpin Mechanism. J Mol Biol 2023; 435:168292. [PMID: 37769963 PMCID: PMC11215794 DOI: 10.1016/j.jmb.2023.168292] [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: 06/14/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023]
Abstract
In protein evolution, diversification is generally driven by genetic duplication. The hallmarks of this mechanism are visible in the repeating topology of various proteins. In outer membrane β-barrels, duplication is visible with β-hairpins as the repeating unit of the barrel. In contrast to the overall use of duplication in diversification, a computational study hypothesized evolutionary mechanisms other than hairpin duplications leading to increases in the number of strands in outer membrane β-barrels. Specifically, the topology of some 16- and 18-stranded β-barrels appear to have evolved through a loop to β-hairpin transition. Here we test this novel evolutionary mechanism by creating a chimeric protein from an 18-stranded β-barrel and an evolutionarily related 16-stranded β-barrel. The chimeric combination of the two was created by replacing loop L3 of the 16-stranded barrel with the sequentially matched transmembrane β-hairpin region of the 18-stranded barrel. We find the resulting chimeric protein is stable and has characteristics of increased strand number. This study provides the first experimental evidence supporting the evolution through a loop to β-hairpin transition.
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Affiliation(s)
- Rik Dhar
- Department of Molecular Biosciences, The University of Kansas, Lawrence, KS 66045, USA. https://twitter.com/Rik_Skywalker
| | - Alexander M Bowman
- Department of Molecular Biosciences, The University of Kansas, Lawrence, KS 66045, USA
| | - Brunojoel Hatungimana
- Department of Molecular Biosciences, The University of Kansas, Lawrence, KS 66045, USA
| | - Joanna Sg Slusky
- Department of Molecular Biosciences, The University of Kansas, Lawrence, KS 66045, USA; Computational Biology Program, The University of Kansas, Lawrence, KS 66047, USA.
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5
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Dhar R, Bowman AM, Hatungimana B, Slusky JS. Evolutionary engineering a larger porin using a loop-to-hairpin mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.14.544993. [PMID: 37398247 PMCID: PMC10312768 DOI: 10.1101/2023.06.14.544993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
In protein evolution, diversification is generally driven by genetic duplication. The hallmarks of this mechanism are visible in the repeating topology of various proteins. In outer membrane β-barrels, duplication is visible with β-hairpins as the repeating unit of the barrel. In contrast to the overall use of duplication in diversification, a computational study hypothesized evolutionary mechanisms other than hairpin duplications leading to increases in the number of strands in outer membrane β-barrels. Specifically, the topology of some 16- and 18-stranded β-barrels appear to have evolved through a loop to β-hairpin transition. Here we test this novel evolutionary mechanism by creating a chimeric protein from an 18-stranded β-barrel and an evolutionarily related 16-stranded β-barrel. The chimeric combination of the two was created by replacing loop L3 of the 16-stranded barrel with the sequentially matched transmembrane β-hairpin region of the 18-stranded barrel. We find the resulting chimeric protein is stable and has characteristics of increased strand number. This study provides the first experimental evidence supporting the evolution through a loop to β-hairpin transition. Highlights We find evidence supporting a novel diversification mechanism in membrane β-barrelsThe mechanism is the conversion of an extracellular loop to transmembrane β-hairpinA chimeric protein modeling this mechanism folds stably in the membraneThe chimera has more β-structure and a larger pore, consistent with a loop-to-hairpin transition.
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Affiliation(s)
- Rik Dhar
- Department of Molecular Biosciences, The University of Kansas, Lawrence KS 66045
| | - Alexander M Bowman
- Department of Molecular Biosciences, The University of Kansas, Lawrence KS 66045
| | | | - Joanna Sg Slusky
- Department of Molecular Biosciences, The University of Kansas, Lawrence KS 66045
- Computational Biology Program, The University of Kansas, Lawrence KS 66047
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6
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Ramirez VI, Wray R, Blount P, King MD. The Effects of Airflow on the Mechanosensitive Channels of Escherichia coli MG1655 and the Impact of Survival Mechanisms Triggered. Microorganisms 2023; 11:2236. [PMID: 37764080 PMCID: PMC10534522 DOI: 10.3390/microorganisms11092236] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 09/01/2023] [Accepted: 09/01/2023] [Indexed: 09/29/2023] Open
Abstract
Understanding how bacteria respond to ventilated environments is a crucial concept, especially when considering accurate airflow modeling and detection limits. To properly design facilities for aseptic conditions, we must minimize the parameters for pathogenic bacteria to thrive. Identifying how pathogenic bacteria continue to survive, particularly due to their multi-drug resistance characteristics, is necessary for designing sterile environments and minimizing pathogen exposure. A conserved characteristic among bacterial organisms is their ability to maintain intracellular homeostasis for survival and growth in hostile environments. Mechanosensitive (MS) channels are one of the characteristics that guide this phenomenon. Interestingly, during extreme stress, bacteria will forgo favorable homeostasis to execute fast-acting survival strategies. Physiological sensors, such as MS channels, that trigger this survival mechanism are not clearly understood, leaving a gap in how bacteria translate physical stress to an intracellular response. In this paper, we study the role of mechanosensitive ion channels that are potentially triggered by aerosolization. We hypothesize that change in antimicrobial uptake is affected by aerosolization stress. Bacteria regulate their defense mechanisms against antimicrobials, which leads to varying susceptibility. Based on this information we hypothesize that aerosolization stress affects the antimicrobial resistance defense mechanisms of Escherichia coli (E. coli). We analyzed the culturability of knockout E. coli strains with different numbers of mechanosensitive channels and compared antibiotic susceptibility under stressed and unstressed airflow conditions. As a result of this study, we can identify how the defensive mechanisms of resistant bacteria are triggered for their survival in built environments. By changing ventilation airflow velocity and observing the change in antibiotic responses, we show how pathogenic bacteria respond to ventilated environments via mechanosensitive ion channels.
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Affiliation(s)
- Violette I. Ramirez
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, TX 77845, USA
| | - Robin Wray
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Maria D. King
- Department of Biological and Agricultural Engineering, Texas A&M University, College Station, TX 77845, USA
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7
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Ebrahimi A, Ergün T, Kaygusuz İzgördü Ö, Darcan C, Avci H, Öztürk B, Güner HR, Ghorbanpoor H, Doğan Güzel F. Revealing the single-channel characteristics of OprD (OccAB1) porins from hospital strains of Acinetobacter baumannii. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2023:10.1007/s00249-023-01651-2. [PMID: 37052656 DOI: 10.1007/s00249-023-01651-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 03/28/2023] [Accepted: 04/07/2023] [Indexed: 04/14/2023]
Abstract
Nowadays, reports of antimicrobial resistance (AMR) against many antibiotics are increasing because of their misapplication. With this rise, there is a serious decrease in the discovery and development of new types of antibiotics amid an increase in multi-drug resistance. Unfermented Acinetobacter baumannii from gram-negative bacteria, which is one of the main causes of nosocomial infections and multi-drug resistance, has 4 main kinds of antibiotic resistance mechanism: inactivating antibiotics by enzymes, reduced numbers of porins and changing of their target or cellular functions due to mutations, and efflux pumps. In this study, characterization of the possible mutations in OprD (OccAB1) porins from hospital strains of A. baumannii were investigated using single channel electrophysiology and compared with the standard OprD isolated from wild type ATCC 19,606. For this aim, 5 A. baumannii bacteria samples were obtained from patients infected with A. baumannii, after which OprD porins were isolated from these A. baumannii strains. OprD porins were then inserted in an artificial lipid bilayer and the current-voltage curves were obtained using electrical recordings through a pair of Ag/AgCl electrodes. We observed that each porin has a characteristic conductance and single channel recording, which then leads to differences in channel diameter. Finally, the single channel data have been compared with the gene sequences of each porin. It was interesting to find out that each porin isolated has a unique porin diameter and decreased anion selectivity compared to the wild type.
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Affiliation(s)
- Aliakbar Ebrahimi
- Faculty of Engineering and Natural Sciences, Department of Biomedical Engineering, Ankara Yildirim Beyazit University, Ankara, Turkey
- Cellular Therapy and Stem Cell Research Center and Translational Medicine Research and Clinical Center (ESTEM), Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Tuğçe Ergün
- Faculty of Engineering and Natural Sciences, Department of Biomedical Engineering, Ankara Yildirim Beyazit University, Ankara, Turkey
- Department of Biotechnology and Biosafety, Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Özge Kaygusuz İzgördü
- Biotechnology Application and Research Center, Bilecik Şeyh Edebali University, Bilecik, Turkey
| | - Cihan Darcan
- Faculty of Science and Literature, Department of Molecular Biology and Genetics, Bilecik Seyh Edebali University, Bilecik, Turkey
| | - Hüseyin Avci
- Cellular Therapy and Stem Cell Research Center and Translational Medicine Research and Clinical Center (ESTEM), Eskisehir Osmangazi University, Eskisehir, Turkey
- Faculty of Engineering and Architecture, Department of Metallurgical and Material Engineering, Eskisehir Osmangazi University, Eskisehir, Turkey
- Department of Stem Cell, Institute of Health Sciences, Eskisehir Osmangazi University, Eskisehir, Turkey
- Translational Medicine Research and Clinical Center (TATUM), Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Barçin Öztürk
- Faculty of Medicine, Department of Infectious Diseases and Clinical Microbiology, Adnan Menderes University, Aydin, Turkey
| | - Hatice Rahmet Güner
- Faculty of Medicine, Department of Infectious Diseases and Clinical Microbiology, Ankara Yildirim Beyazit University, Ankara, Turkey
| | - Hamed Ghorbanpoor
- Cellular Therapy and Stem Cell Research Center and Translational Medicine Research and Clinical Center (ESTEM), Eskisehir Osmangazi University, Eskisehir, Turkey
- Department of Biomedical Engineering, Eskisehir Osmangazi University, Eskisehir, Turkey
| | - Fatma Doğan Güzel
- Faculty of Engineering and Natural Sciences, Department of Biomedical Engineering, Ankara Yildirim Beyazit University, Ankara, Turkey.
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8
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Lane BJ, Pliotas C. Approaches for the modulation of mechanosensitive MscL channel pores. Front Chem 2023; 11:1162412. [PMID: 37021145 PMCID: PMC10069478 DOI: 10.3389/fchem.2023.1162412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/03/2023] [Indexed: 03/17/2023] Open
Abstract
MscL was the first mechanosensitive ion channel identified in bacteria. The channel opens its large pore when the turgor pressure of the cytoplasm increases close to the lytic limit of the cellular membrane. Despite their ubiquity across organisms, their importance in biological processes, and the likelihood that they are one of the oldest mechanisms of sensory activation in cells, the exact molecular mechanism by which these channels sense changes in lateral tension is not fully understood. Modulation of the channel has been key to understanding important aspects of the structure and function of MscL, but a lack of molecular triggers of these channels hindered early developments in the field. Initial attempts to activate mechanosensitive channels and stabilize functionally relevant expanded or open states relied on mutations and associated post-translational modifications that were often cysteine reactive. These sulfhydryl reagents positioned at key residues have allowed the engineering of MscL channels for biotechnological purposes. Other studies have modulated MscL by altering membrane properties, such as lipid composition and physical properties. More recently, a variety of structurally distinct agonists have been shown bind to MscL directly, close to a transmembrane pocket that has been shown to have an important role in channel mechanical gating. These agonists have the potential to be developed further into antimicrobial therapies that target MscL, by considering the structural landscape and properties of these pockets.
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Affiliation(s)
- Benjamin J. Lane
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- School of Biological Sciences, Faculty of Biology, Medicine and Health, Manchester Academic and Health Science Centre, The University of Manchester, Manchester, United Kingdom
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
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9
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Ma S, Zhang Y, Zhang X, Xie H, Tong Q, Yu K, Yang J. Dynamic Interactions Between Brilliant Green and MscL Investigated by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations. Chemistry 2023; 29:e202202106. [PMID: 36251739 DOI: 10.1002/chem.202202106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Indexed: 11/22/2022]
Abstract
The mechanosensitive ion channel of large conductance (MscL) is a promising template for the development of new antibiotics due to its high conservation and uniqueness to microbes. Brilliant green (BG), a triarylmethane dye, has been identified as a new antibiotic targeted MscL. However, the detailed binding sites to MscL and the dynamic pathway of BG through the MscL channel remain unknown. Here, the dynamic interactions between BG and MscL were investigated using solid-state NMR spectroscopy and molecule dynamics (MD) simulations. Residue site-specific binding sites of BG to the MscL channel were identified by solid-state NMR. In addition, MD simulations revealed that BG conducts through the MscL channel via residues along the inner surface of the pore sequentially, in which the strong hydrophobic interactions between BG and hydrophobic residues F23 and I27 in the hydrophobic gate region of the MscL channel are major restrictions. Particularly, it was demonstrated that BG activates the MscL channel by reducing the hydrophobicity of the F23 in the gate region by water molecules that are bound to BG. Taken together, these simulations and experimental data provide novel insights into the dynamic interactions between BG and MscL, based on which new hydrophobic antibiotics and adjuvants targeting MscL can be developed.
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Affiliation(s)
- Shaojie Ma
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, P.R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China
| | - Yan Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Xuning Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China
| | - Huayong Xie
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
| | - Qiong Tong
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China
| | - Kunqian Yu
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, P.R. China
| | - Jun Yang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.,Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China.,Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, P. R. China.,University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
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10
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Wang J, Blount P. Feeling the Tension: The Bacterial Mechanosensitive Channel MscL as a Model System and Drug Target. CURRENT OPINION IN PHYSIOLOGY 2022. [DOI: 10.1016/j.cophys.2022.100627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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11
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Wray R, Wang J, Blount P, Iscla I. Activation of a Bacterial Mechanosensitive Channel, MscL, Underlies the Membrane Permeabilization of Dual-Targeting Antibacterial Compounds. Antibiotics (Basel) 2022; 11:antibiotics11070970. [PMID: 35884223 PMCID: PMC9312261 DOI: 10.3390/antibiotics11070970] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/13/2022] [Accepted: 07/15/2022] [Indexed: 01/27/2023] Open
Abstract
Resistance to antibiotics is a serious and worsening threat to human health worldwide, and there is an urgent need to develop new antibiotics that can avert it. One possible solution is the development of compounds that possess multiple modes of action, requiring at least two mutations to acquire resistance. Compound SCH-79797 both avoids resistance and has two mechanisms of action: one inhibiting the folate pathway, and a second described as “membrane permeabilization”; however, the mechanism by which membranes from bacterial cells, but not the host, are disrupted has remained mysterious. The opening of the bacterial mechanosensitive channel of large conductance, MscL, which ordinarily serves the physiological role of osmotic emergency release valves gated by hypoosmotic shock, has been previously demonstrated to affect bacterial membrane permeabilization. MscL allows the rapid permeabilization of both ions and solutes through the opening of the largest known gated pore, which has a diameter of 30 Å. We found that SCH-79797 and IRS-16, a more potent derivative, directly bind to the MscL channel and produce membrane permeabilization as a result of its activation. These findings suggest that possessing or adding an MscL-activating component to an antibiotic compound could help to lower toxicity and evade antibiotic resistance.
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Affiliation(s)
- Robin Wray
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA;
| | - Junmei Wang
- Computational Chemical Genomics Screening Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburg, PA 15261, USA
- Correspondence: (J.W.); (P.B.); (I.I.)
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA;
- Correspondence: (J.W.); (P.B.); (I.I.)
| | - Irene Iscla
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA;
- Correspondence: (J.W.); (P.B.); (I.I.)
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12
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Bavi O, Zhou Z, Bavi N, Mehdi Vaez Allaei S, Cox CD, Martinac B. Asymmetric effects of amphipathic molecules on mechanosensitive channels. Sci Rep 2022; 12:9976. [PMID: 35705645 PMCID: PMC9200802 DOI: 10.1038/s41598-022-14446-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 06/06/2022] [Indexed: 12/30/2022] Open
Abstract
Mechanosensitive (MS) ion channels are primary transducers of mechanical force into electrical and/or chemical intracellular signals. Many diverse MS channel families have been shown to respond to membrane forces. As a result of this intimate relationship with the membrane and proximal lipids, amphipathic compounds exert significant effects on the gating of MS channels. Here, we performed all-atom molecular dynamics (MD) simulations and employed patch-clamp recording to investigate the effect of two amphipaths, Fluorouracil (5-FU) a chemotherapy agent, and the anaesthetic trifluoroethanol (TFE) on structurally distinct mechanosensitive channels. We show that these amphipaths have a profound effect on the bilayer order parameter as well as transbilayer pressure profile. We used bacterial mechanosensitive channels (MscL/MscS) and a eukaryotic mechanosensitive channel (TREK-1) as force-from-lipids reporters and showed that these amphipaths have differential effects on these channels depending on the amphipaths' size and shape as well as which leaflet of the bilayer they incorporate into. 5-FU is more asymmetric in shape and size than TFE and does not penetrate as deep within the bilayer as TFE. Thereby, 5-FU has a more profound effect on the bilayer and channel activity than TFE at much lower concentrations. We postulate that asymmetric effects of amphipathic molecules on mechanosensitive membrane proteins through the bilayer represents a general regulatory mechanism for these proteins.
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Affiliation(s)
- Omid Bavi
- grid.444860.a0000 0004 0600 0546Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, Iran
| | - Zijing Zhou
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia
| | - Navid Bavi
- grid.170205.10000 0004 1936 7822Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL USA
| | - S. Mehdi Vaez Allaei
- grid.46072.370000 0004 0612 7950Department of Physics, University of Tehran, 1439955961 Tehran, Iran
| | - Charles D. Cox
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia ,grid.1005.40000 0004 4902 0432Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW 2010 Australia
| | - B. Martinac
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia ,grid.1005.40000 0004 4902 0432Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW 2010 Australia
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13
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OzTracs: Optical Osmolality Reporters Engineered from Mechanosensitive Ion Channels. Biomolecules 2022; 12:biom12060787. [PMID: 35740912 PMCID: PMC9221499 DOI: 10.3390/biom12060787] [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: 04/26/2022] [Revised: 05/18/2022] [Accepted: 06/02/2022] [Indexed: 02/01/2023] Open
Abstract
Interactions between physical forces and membrane proteins underpin many forms of environmental sensation and acclimation. Microbes survive osmotic stresses with the help of mechanically gated ion channels and osmolyte transporters. Plant mechanosensitive ion channels have been shown to function in defense signaling. Here, we engineered genetically encoded osmolality sensors (OzTracs) by fusing fluorescent protein spectral variants to the mechanosensitive ion channels MscL from E. coli or MSL10 from A. thaliana. When expressed in yeast cells, the OzTrac sensors reported osmolality changes as a proportional change in the emission ratio of the two fluorescent protein domains. Live-cell imaging revealed an accumulation of fluorescent sensors in internal aggregates, presumably derived from the endomembrane system. Thus, OzTrac sensors serve as osmolality-dependent reporters through an indirect mechanism, such as effects on molecular crowding or fluorophore solvation.
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14
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In Silico Screen Identifies a New Family of Agonists for the Bacterial Mechanosensitive Channel MscL. Antibiotics (Basel) 2022; 11:antibiotics11040433. [PMID: 35453186 PMCID: PMC9030384 DOI: 10.3390/antibiotics11040433] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 12/10/2022] Open
Abstract
MscL is a highly conserved mechanosensitive channel found in the majority of bacterial species, including pathogens. It functions as a biological emergency release valve, jettisoning solutes from the cytoplasm upon acute hypoosmotic stress. It opens the largest known gated pore and has been heralded as an antibacterial target. Although there are no known endogenous ligands, small compounds have recently been shown to specifically bind to and open the channel, leading to decreased cell growth and viability. Their binding site is at the cytoplasmic/membrane and subunit interfaces of the protein, which has been recently been proposed to play an essential role in channel gating. Here, we have targeted this pocket using in silico screening, resulting in the discovery of a new family of compounds, distinct from other known MscL-specific agonists. Our findings extended the study of this functional region, the progression of MscL as a viable drug target, and demonstrated the power of in silico screening for identifying and improving the design of MscL agonists.
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15
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Ahmed T, Nisler CR, Fluck EC, Walujkar S, Sotomayor M, Moiseenkova-Bell VY. Structure of the ancient TRPY1 channel from Saccharomyces cerevisiae reveals mechanisms of modulation by lipids and calcium. Structure 2022; 30:139-155.e5. [PMID: 34453887 PMCID: PMC8741645 DOI: 10.1016/j.str.2021.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/29/2021] [Accepted: 08/10/2021] [Indexed: 01/14/2023]
Abstract
Transient receptor potential (TRP) channels emerged in fungi as mechanosensitive osmoregulators. The Saccharomyces cerevisiae vacuolar TRP yeast 1 (TRPY1) is the most studied TRP channel from fungi, but the structure and details of channel modulation remain elusive. Here, we describe the full-length cryoelectron microscopy structure of TRPY1 at 3.1 Å resolution in a closed state. The structure, despite containing an evolutionarily conserved and archetypical transmembrane domain, reveals distinctive structural folds for the cytosolic N and C termini, compared with other eukaryotic TRP channels. We identify an inhibitory phosphatidylinositol 3-phosphate (PI(3)P) lipid-binding site, along with two Ca2+-binding sites: a cytosolic site, implicated in channel activation and a vacuolar lumen site, implicated in inhibition. These findings, together with data from microsecond-long molecular dynamics simulations and a model of a TRPY1 open state, provide insights into the basis of TRPY1 channel modulation by lipids and Ca2+, and the molecular evolution of TRP channels.
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Affiliation(s)
- Tofayel Ahmed
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Collin R Nisler
- Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210, USA; Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Edwin C Fluck
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sanket Walujkar
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Chemical Physics Graduate Program, The Ohio State University, Columbus, OH 43210, USA
| | - Marcos Sotomayor
- Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210, USA; Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Chemical Physics Graduate Program, The Ohio State University, Columbus, OH 43210, USA
| | - Vera Y Moiseenkova-Bell
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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16
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Qiu Z, Kala S, Guo J, Xian Q, Zhu J, Zhu T, Hou X, Wong KF, Yang M, Wang H, Sun L. Targeted Neurostimulation in Mouse Brains with Non-invasive Ultrasound. Cell Rep 2021; 32:108033. [PMID: 32814040 DOI: 10.1016/j.celrep.2020.108033] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 09/11/2019] [Accepted: 07/23/2020] [Indexed: 01/17/2023] Open
Abstract
Recently developed brain stimulation techniques have significantly advanced our ability to manipulate the brain's function. However, stimulating specific neurons in a desired region without significant surgical invasion remains a challenge. Here, we demonstrate a neuron-specific and region-targeted neural excitation strategy using non-invasive ultrasound through activation of heterologously expressed mechanosensitive ion channels (MscL-G22S). Low-intensity ultrasound is significantly better at inducing Ca2+ influx and neuron activation in vitro and at evoking electromyogram (EMG) responses in vivo in targeted cells expressing MscL-G22S. Neurons in the cerebral cortex or dorsomedial striatum of mice are made to express MscL-G22S and stimulated ultrasonically. We find significant upregulation of c-Fos in neuron nuclei only in the regions expressing MscL-G22S compared with the non-MscL controls, as well as in various other regions in the same brain. Thus, we detail an effective approach for activating specific regions and cell types in intact mouse brains by sensitizing them to ultrasound using a mechanosensitive ion channel.
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Affiliation(s)
- Zhihai Qiu
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Shashwati Kala
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Jinghui Guo
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Quanxiang Xian
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Jiejun Zhu
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Ting Zhu
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Xuandi Hou
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Kin Fung Wong
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Minyi Yang
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Haoru Wang
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077
| | - Lei Sun
- Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, P. R. China, 999077.
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17
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Zhang X, Zhang Y, Tang S, Ma S, Shen Y, Chen Y, Tong Q, Li Y, Yang J. Hydrophobic Gate of Mechanosensitive Channel of Large Conductance in Lipid Bilayers Revealed by Solid-State NMR Spectroscopy. J Phys Chem B 2021; 125:2477-2490. [DOI: 10.1021/acs.jpcb.0c07487] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Xuning Zhang
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yan Zhang
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Siyang Tang
- Children’s Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Shaojie Ma
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
| | - Yang Shen
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Yanke Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiong Tong
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yuezhou Li
- Children’s Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China
| | - Jun Yang
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
- National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, P. R. China
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18
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Zecchi KA, Heimburg T. Non-linear Conductance, Rectification, and Mechanosensitive Channel Formation of Lipid Membranes. Front Cell Dev Biol 2021; 8:592520. [PMID: 33575253 PMCID: PMC7870788 DOI: 10.3389/fcell.2020.592520] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 12/10/2020] [Indexed: 01/04/2023] Open
Abstract
There is mounting evidence that lipid bilayers display conductive properties. However, when interpreting the electrical response of biological membranes to voltage changes, they are commonly considered as inert insulators. Lipid bilayers under voltage-clamp conditions display current traces with discrete conduction-steps, which are indistinguishable from those attributed to the presence of protein channels. In current-voltage (I-V) plots they may also display outward rectification, i.e., voltage-gating. Surprisingly, this has even been observed in chemically symmetric lipid bilayers. Here, we investigate this phenomenon using a theoretical framework that models the electrostrictive effect of voltage on lipid membranes in the presence of a spontaneous polarization, which can be recognized by a voltage offset in electrical measurements. It can arise from an asymmetry of the membrane, for example from a non-zero spontaneous curvature of the membrane. This curvature can be caused by voltage via the flexoelectric effect, or by hydrostatic pressure differences across the membrane. Here, we describe I-V relations for lipid membranes formed at the tip of patch pipettes situated close to an aqueous surface. We measured at different depths relative to air/water surface, resulting in different pressure gradients across the membrane. Both linear and non-linear I-V profiles were observed. Non-linear conduction consistently takes the form of outward rectified currents. We explain the conductance properties by two mechanisms: One leak current with constant conductance without pores, and a second process that is due to voltage-gated pore opening correlating with the appearance of channel-like conduction steps. In some instances, these non-linear I-V relations display a voltage regime in which dI/dV is negative. This has also been previously observed in the presence of sodium channels. Experiments at different depths reveal channel formation that depends on pressure gradients. Therefore, we find that the channels in the lipid membrane are both voltage-gated and mechanosensitive. We also report measurements on black lipid membranes that also display rectification. In contrast to the patch experiments they are always symmetric and do not display a voltage offset.
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Affiliation(s)
- Karis Amata Zecchi
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Heimburg
- Membrane Biophysics Group, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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19
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Strutt R, Hindley JW, Gregg J, Booth PJ, Harling JD, Law RV, Friddin MS, Ces O. Activating mechanosensitive channels embedded in droplet interface bilayers using membrane asymmetry. Chem Sci 2021; 12:2138-2145. [PMID: 34163978 PMCID: PMC8179348 DOI: 10.1039/d0sc03889j] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 12/03/2020] [Indexed: 11/21/2022] Open
Abstract
Droplet microcompartments linked by lipid bilayers show great promise in the construction of synthetic minimal tissues. Central to controlling the flow of information in these systems are membrane proteins, which can gate in response to specific stimuli in order to control the molecular flux between membrane separated compartments. This has been demonstrated with droplet interface bilayers (DIBs) using several different membrane proteins combined with electrical, mechanical, and/or chemical activators. Here we report the activation of the bacterial mechanosensitive channel of large conductance (MscL) in a dioleoylphosphatidylcholine:dioleoylphosphatidylglycerol DIB by controlling membrane asymmetry. We show using electrical measurements that the incorporation of lysophosphatidylcholine (LPC) into one of the bilayer leaflets triggers MscL gating in a concentration-dependent manner, with partial and full activation observed at 10 and 15 mol% LPC respectively. Our findings could inspire the design of new minimal tissues where flux pathways are dynamically defined by lipid composition.
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Affiliation(s)
- Robert Strutt
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Institute of Chemical Biology, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
| | - James W Hindley
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Institute of Chemical Biology, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- FabriCELL, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
| | - Jordan Gregg
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
| | - Paula J Booth
- FabriCELL, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Department of Chemistry, King's College London SE1 1DB London UK
| | - John D Harling
- Medicinal Chemistry, GSK Gunnels Wood Road, Stevenage SG1 2NY UK
| | - Robert V Law
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Institute of Chemical Biology, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- FabriCELL, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
| | - Mark S Friddin
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Dyson School of Design Engineering, Imperial College London Imperial College Road SW7 2AZ UK
| | - Oscar Ces
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- Institute of Chemical Biology, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
- FabriCELL, Imperial College London, Molecular Sciences Research Hub Shepherd's Bush London W12 0BZ UK
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20
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Rajeshwar T R, Anishkin A, Sukharev S, Vanegas JM. Mechanical Activation of MscL Revealed by a Locally Distributed Tension Molecular Dynamics Approach. Biophys J 2020; 120:232-242. [PMID: 33333032 DOI: 10.1016/j.bpj.2020.11.2274] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/20/2020] [Accepted: 11/30/2020] [Indexed: 02/02/2023] Open
Abstract
Membrane tension perceived by mechanosensitive (MS) proteins mediates cellular responses to mechanical stimuli and osmotic stresses, and it also guides multiple biological functions including cardiovascular control and development. In bacteria, MS channels function as tension-activated pores limiting excessive turgor pressure, with MS channel of large conductance (MscL) acting as an emergency release valve preventing cell lysis. Previous attempts to simulate gating transitions in MscL by either directly applying steering forces to the protein or by increasing the whole-system tension were not fully successful and often disrupted the integrity of the system. We present a novel, to our knowledge, locally distributed tension molecular dynamics (LDT-MD) simulation method that allows application of forces continuously distributed among lipids surrounding the channel using a specially constructed collective variable. We report reproducible and reversible transitions of MscL to the open state with measured parameters of lateral expansion and conductivity that exactly satisfy experimental values. The LDT-MD method enables exploration of the MscL-gating process with different pulling velocities and variable tension asymmetry between the inner and outer membrane leaflets. We use LDT-MD in combination with well-tempered metadynamics to reconstruct the tension-dependent free-energy landscape for the opening transition in MscL. The flexible definition of the LDT collective variable allows general application of our method to study mechanical activation of any membrane-embedded protein.
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Affiliation(s)
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, Maryland
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, Maryland
| | - Juan M Vanegas
- Department of Physics, University of Vermont, Burlington, Vermont.
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21
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Farrugia MY, Caruana M, Ghio S, Camilleri A, Farrugia C, Cauchi RJ, Cappelli S, Chiti F, Vassallo N. Toxic oligomers of the amyloidogenic HypF-N protein form pores in mitochondrial membranes. Sci Rep 2020; 10:17733. [PMID: 33082392 PMCID: PMC7575562 DOI: 10.1038/s41598-020-74841-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 10/06/2020] [Indexed: 12/30/2022] Open
Abstract
Studies on the amyloidogenic N-terminal domain of the E. coli HypF protein (HypF-N) have contributed significantly to a detailed understanding of the pathogenic mechanisms in neurodegenerative diseases characterised by the formation of misfolded oligomers, by proteins such as amyloid-β, α-synuclein and tau. Given that both cell membranes and mitochondria are increasingly recognised as key targets of oligomer toxicity, we investigated the damaging effects of aggregates of HypF-N on mitochondrial membranes. Essentially, we found that HypF-N oligomers characterised by high surface hydrophobicity (type A) were able to trigger a robust permeabilisation of mito-mimetic liposomes possessing cardiolipin-rich membranes and dysfunction of isolated mitochondria, as demonstrated by a combination of mitochondrial shrinking, lowering of mitochondrial membrane potential and cytochrome c release. Furthermore, using single-channel electrophysiology recordings we obtained evidence that the type A aggregates induced currents reflecting formation of ion-conducting pores in mito-mimetic planar phospholipid bilayers, with multi-level conductances ranging in the hundreds of pS at negative membrane voltages. Conversely, HypF-N oligomers with low surface hydrophobicity (type B) could not permeabilise or porate mitochondrial membranes. These results suggest an inherent toxicity of membrane-active aggregates of amyloid-forming proteins to mitochondria, and that targeting of oligomer-mitochondrial membrane interactions might therefore afford protection against such damage.
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Affiliation(s)
- Maria Ylenia Farrugia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Mario Caruana
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Stephanie Ghio
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Angelique Camilleri
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | | | - Ruben J Cauchi
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Sara Cappelli
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, 50134, Florence, Italy
| | - Fabrizio Chiti
- Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences, University of Florence, 50134, Florence, Italy
| | - Neville Vassallo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta.
- Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta.
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22
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Carniello V, Peterson BW, van der Mei HC, Busscher HJ. Role of adhesion forces in mechanosensitive channel gating in Staphylococcus aureus adhering to surfaces. NPJ Biofilms Microbiomes 2020; 6:31. [PMID: 32826897 PMCID: PMC7442641 DOI: 10.1038/s41522-020-00141-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 07/30/2020] [Indexed: 01/18/2023] Open
Abstract
Mechanosensitive channels in bacterial membranes open or close in response to environmental changes to allow transmembrane transport, including antibiotic uptake and solute efflux. In this paper, we hypothesize that gating of mechanosensitive channels is stimulated by forces through which bacteria adhere to surfaces. Hereto, channel gating is related with adhesion forces to different surfaces of a Staphylococcus aureus strain and its isogenic ΔmscL mutant, deficient in MscL (large) channel gating. Staphylococci becoming fluorescent due to uptake of calcein, increased with adhesion force and were higher in the parent strain (66% when adhering with an adhesion force above 4.0 nN) than in the ΔmscL mutant (40% above 1.2 nN). This suggests that MscL channels open at a higher critical adhesion force than at which physically different, MscS (small) channels open and contribute to transmembrane transport. Uptake of the antibiotic dihydrostreptomycin was monitored by staphylococcal killing. The parent strain exposed to dihydrostreptomycin yielded a CFU reduction of 2.3 log-units when adhering with an adhesion force above 3.5 nN, but CFU reduction remained low (1.0 log-unit) in the mutant, independent of adhesion force. This confirms that large channels open at a higher critical adhesion-force than small channels, as also concluded from calcein transmembrane transport. Collectively, these observations support our hypothesis that adhesion forces to surfaces play an important role, next to other established driving forces, in staphylococcal channel gating. This provides an interesting extension of our understanding of transmembrane antibiotic uptake and solute efflux in infectious staphylococcal biofilms in which bacteria experience adhesion forces from a wide variety of surfaces, like those of other bacteria, tissue cells, or implanted biomaterials.
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Affiliation(s)
- Vera Carniello
- Department of BioMedical Engineering, University of Groningen and University Medical Center Groningen, Groningen, Netherlands
| | - Brandon W Peterson
- Department of BioMedical Engineering, University of Groningen and University Medical Center Groningen, Groningen, Netherlands.
| | - Henny C van der Mei
- Department of BioMedical Engineering, University of Groningen and University Medical Center Groningen, Groningen, Netherlands
| | - Henk J Busscher
- Department of BioMedical Engineering, University of Groningen and University Medical Center Groningen, Groningen, Netherlands
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23
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Haylock S, Friddin MS, Hindley JW, Rodriguez E, Charalambous K, Booth PJ, Barter LMC, Ces O. Membrane protein mediated bilayer communication in networks of droplet interface bilayers. Commun Chem 2020; 3:77. [PMID: 34113722 PMCID: PMC7610947 DOI: 10.1038/s42004-020-0322-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Droplet interface bilayers (DIBs) are model membranes formed between lipid monolayer-encased water droplets in oil. Compared to conventional methods, one of the most unique properties of DIBs is that they can be connected together to generate multi-layered ‘tissue-like’ networks, however introducing communication pathways between these compartments typically relies on water-soluble pores that are unable to gate. Here, we show that network connectivity can instead be achieved using a water-insoluble membrane protein by successfully reconstituting a chemically activatable mutant of the mechanosensitive channel MscL into a network of DIBs. Moreover, we also show how the small molecule activator can diffuse through an open channel and across the neighbouring droplet to activate MscL present in an adjacent bilayer. This demonstration of membrane protein mediated bilayer communication could prove key toward developing the next generation of responsive bilayer networks capable of defining information flow inside a minimal tissue.
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Affiliation(s)
- Stuart Haylock
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
| | - Mark S Friddin
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
| | - James W Hindley
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,fabriCELL, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
| | - Enrique Rodriguez
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
| | - Kalypso Charalambous
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
| | - Paula J Booth
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
| | - Laura M C Barter
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
| | - Oscar Ces
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, 80 Wood Lane, London W12 0BZ, UK.,fabriCELL, Imperial College London, 80 Wood Lane, London W12 0BZ, UK
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24
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Younger S, Jang H, Davies HA, Niemiec MJ, Garcia JGN, Nussinov R, Migrino RQ, Madine J, Arce FT. Medin Oligomer Membrane Pore Formation: A Potential Mechanism of Vascular Dysfunction. Biophys J 2020; 118:2769-2782. [PMID: 32402244 PMCID: PMC7264854 DOI: 10.1016/j.bpj.2020.04.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 04/11/2020] [Accepted: 04/17/2020] [Indexed: 12/12/2022] Open
Abstract
Medin, a 50-amino-acid cleavage product of the milk fat globule-EGF factor 8 protein, is one of the most common forms of localized amyloid found in the vasculature of individuals older than 50 years. Medin induces endothelial dysfunction and vascular inflammation, yet despite its prevalence in the human aorta and multiple arterial beds, little is known about the nature of its pathology. Medin oligomers have been implicated in the pathology of aortic aneurysm, aortic dissection, and more recently, vascular dementia. Recent in vitro biomechanical measurements found increased oligomer levels in aneurysm patients with altered aortic wall integrity. Our results suggest an oligomer-mediated toxicity mechanism for medin pathology. Using lipid bilayer electrophysiology, we show that medin oligomers induce ionic membrane permeability by pore formation. Pore activity was primarily observed for preaggregated medin species from the growth-phase and rarely for lag-phase species. Atomic force microscopy (AFM) imaging of medin aggregates at different stages of aggregation revealed the gradual formation of flat domains resembling the morphology of supported lipid bilayers. Transmission electron microscopy images showed the coexistence of compact oligomers, largely consistent with the AFM data, and larger protofibrillar structures. Circular dichroism spectroscopy revealed the presence of largely disordered species and suggested the presence of β-sheets. This observation and the significantly lower thioflavin T fluorescence emitted by medin aggregates compared to amyloid-β fibrils, along with the absence of amyloid fibers in the AFM and transmission electron microscopy images, suggest that medin aggregation into pores follows a nonamyloidogenic pathway. In silico modeling by molecular dynamics simulations provides atomic-level structural detail of medin pores with the CNpNC barrel topology and diameters comparable to values estimated from experimental pore conductances.
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Affiliation(s)
- Scott Younger
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Hyunbum Jang
- Computational Structural Biology Section, Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | - Hannah A Davies
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Martin J Niemiec
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona
| | - Joe G N Garcia
- Department of Medicine, University of Arizona, Tucson, Arizona
| | - Ruth Nussinov
- Computational Structural Biology Section, Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland; Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Raymond Q Migrino
- Office of Research, Phoenix Veterans Affairs Health Care System, Phoenix, Arizona; Department of Medicine, University of Arizona College of Medicine-Phoenix, Arizona
| | - Jillian Madine
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Fernando T Arce
- Department of Biomedical Engineering, University of Arizona, Tucson, Arizona; Department of Medicine, University of Arizona, Tucson, Arizona.
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25
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Paraschiv A, Hegde S, Ganti R, Pilizota T, Šarić A. Dynamic Clustering Regulates Activity of Mechanosensitive Membrane Channels. PHYSICAL REVIEW LETTERS 2020; 124:048102. [PMID: 32058787 DOI: 10.1103/physrevlett.124.048102] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Indexed: 06/10/2023]
Abstract
Experiments have suggested that bacterial mechanosensitive channels separate into 2D clusters, the role of which is unclear. By developing a coarse-grained computer model we find that clustering promotes the channel closure, which is highly dependent on the channel concentration and membrane stress. This behaviour yields a tightly regulated gating system, whereby at high tensions channels gate individually, and at lower tensions the channels spontaneously aggregate and inactivate. We implement this positive feedback into the model for cell volume regulation, and find that the channel clustering protects the cell against excessive loss of cytoplasmic content.
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Affiliation(s)
- Alexandru Paraschiv
- Department of Physics and Astronomy, Institute for the Physics of Living Systems University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
| | - Smitha Hegde
- Centre for Synthetic and Systems Biology University of Edinburgh, Edinburgh EH9 3FF, United Kingdom
| | - Raman Ganti
- Institute for Medical Engineering and Science Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Teuta Pilizota
- Centre for Synthetic and Systems Biology University of Edinburgh, Edinburgh EH9 3FF, United Kingdom
| | - Anđela Šarić
- Department of Physics and Astronomy, Institute for the Physics of Living Systems University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
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26
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Wray R, Wang J, Iscla I, Blount P. Novel MscL agonists that allow multiple antibiotics cytoplasmic access activate the channel through a common binding site. PLoS One 2020; 15:e0228153. [PMID: 31978161 PMCID: PMC6980572 DOI: 10.1371/journal.pone.0228153] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 01/09/2020] [Indexed: 12/20/2022] Open
Abstract
The antibiotic resistance crisis is becoming dire, yet in the past several years few potential antibiotics or adjuvants with novel modes of action have been identified. The bacterial mechanosensitive channel of large conductance, MscL, found in the majority of bacterial species, including pathogens, normally functions as an emergency release valve, sensing membrane tension upon low-osmotic stress and discharging cytoplasmic solutes before cell lysis. Opening the huge ~30Å diameter pore of MscL inappropriately is detrimental to the cell, allowing solutes from and even passage of drugs into to cytoplasm. Thus, MscL is a potential novel drug target. However, there are no known natural agonists, and small compounds that modulate MscL activity are just now being identified. Here we describe a small compound, K05, that specifically modulates MscL activity and we compare results with those obtained for the recently characterized MscL agonist 011A. While the structure of K05 only vaguely resembles 011A, many of the findings, including the binding pocket, are similar. On the other hand, both in vivo and molecular dynamic simulations indicate that the two compounds modulate MscL activity in significantly different ways.
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Affiliation(s)
- Robin Wray
- Department of Physiology, UT Southwestern Medical Center, Dallas, Texas, United States of America
| | - Junmei Wang
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, University of Pittsburgh School of Pharmacy, Pittsburg, Pennsylvania, United States of America
| | - Irene Iscla
- Department of Physiology, UT Southwestern Medical Center, Dallas, Texas, United States of America
| | - Paul Blount
- Department of Physiology, UT Southwestern Medical Center, Dallas, Texas, United States of America
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27
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Life with Bacterial Mechanosensitive Channels, from Discovery to Physiology to Pharmacological Target. Microbiol Mol Biol Rev 2020; 84:84/1/e00055-19. [PMID: 31941768 DOI: 10.1128/mmbr.00055-19] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
General principles in biology have often been elucidated from the study of bacteria. This is true for the bacterial mechanosensitive channel of large conductance, MscL, the channel highlighted in this review. This channel functions as a last-ditch emergency release valve discharging cytoplasmic solutes upon decreases in osmotic environment. Opening the largest gated pore, MscL passes molecules up to 30 Å in diameter; exaggerated conformational changes yield advantages for study, including in vivo assays. MscL contains structural/functional themes that recur in higher organisms and help elucidate how other, structurally more complex, channels function. These features of MscL include (i) the ability to directly sense, and respond to, biophysical changes in the membrane, (ii) an α helix ("slide helix") or series of charges ("knot in a rope") at the cytoplasmic membrane boundary to guide transmembrane movements, and (iii) important subunit interfaces that, when disrupted, appear to cause the channel to gate inappropriately. MscL may also have medical applications: the modality of the MscL channel can be changed, suggesting its use as a triggered nanovalve in nanodevices, including those for drug targeting. In addition, recent studies have shown that the antibiotic streptomycin opens MscL and uses it as one of the primary paths to the cytoplasm. Moreover, the recent identification and study of novel specific agonist compounds demonstrate that the channel is a valid drug target. Such compounds may serve as novel-acting antibiotics and adjuvants, a way of permeabilizing the bacterial cell membrane and, thus, increasing the potency of commonly used antibiotics.
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28
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Martinac B, Nikolaev YA, Silvani G, Bavi N, Romanov V, Nakayama Y, Martinac AD, Rohde P, Bavi O, Cox CD. Cell membrane mechanics and mechanosensory transduction. CURRENT TOPICS IN MEMBRANES 2020; 86:83-141. [DOI: 10.1016/bs.ctm.2020.08.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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29
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Allosteric activation of an ion channel triggered by modification of mechanosensitive nano-pockets. Nat Commun 2019; 10:4619. [PMID: 31601809 PMCID: PMC6787021 DOI: 10.1038/s41467-019-12591-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 09/17/2019] [Indexed: 11/08/2022] Open
Abstract
Lipid availability within transmembrane nano-pockets of ion channels is linked with mechanosensation. However, the effect of hindering lipid-chain penetration into nano-pockets on channel structure has not been demonstrated. Here we identify nano-pockets on the large conductance mechanosensitive channel MscL, the high-pressure threshold channel. We restrict lipid-chain access to the nano-pockets by mutagenesis and sulfhydryl modification, and monitor channel conformation by PELDOR/DEER spectroscopy. For a single site located at the entrance of the nano-pockets and distal to the channel pore we generate an allosteric response in the absence of tension. Single-channel recordings reveal a significant decrease in the pressure activation threshold of the modified channel and a sub-conducting state in the absence of applied tension. Threshold is restored to wild-type levels upon reduction of the sulfhydryl modification. The modification associated with the conformational change restricts lipid access to the nano-pocket, interrupting the contact between the membrane and the channel that mediates mechanosensitivity.
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30
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Mayer SF, Ducrey J, Dupasquier J, Haeni L, Rothen-Rutishauser B, Yang J, Fennouri A, Mayer M. Targeting specific membranes with an azide derivative of the pore-forming peptide ceratotoxin A. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183023. [DOI: 10.1016/j.bbamem.2019.07.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/01/2019] [Accepted: 07/09/2019] [Indexed: 10/26/2022]
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31
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Owada N, Yoshida M, Morita K, Yoshimura K. Temperature-sensitive mutants of MscL mechanosensitive channel. J Biochem 2019; 166:281-288. [PMID: 31143940 DOI: 10.1093/jb/mvz035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/25/2019] [Indexed: 01/15/2023] Open
Abstract
MscL is a mechanosensitive channel that undergoes a global conformational change upon application of membrane stretching. To elucidate how the structural stability and flexibility occur, we isolated temperature-sensitive (Ts) mutants of Escherichia coli MscL that allowed cell growth at 32°C but not at 42°C. Two Ts mutants, L86P and D127V, were identified. The L86P mutation occurred in the second transmembrane helix, TM2. Substitution of residues neighbouring L86 with proline also led to a Ts mutation, but the substitution of L86 with other amino acids did not result in a Ts phenotype, indicating that the Ts phenotype was due to a structural change of TM2 helix by the introduction of a proline residue. The D127V mutation was localized in the electrostatic belt of the bundle of cytoplasmic helices, indicating that stability of the pentameric bundle of the cytoplasmic helix affects MscL structure. Together, this study described a novel class of MscL mutations that were correlated with the thermodynamic stability of the MscL structure.
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Affiliation(s)
- Naoto Owada
- Department of Machinery and Control Systems, College of Systems Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama, Japan
| | - Megumi Yoshida
- Department of Machinery and Control Systems, College of Systems Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama, Japan
| | - Kohei Morita
- Department of Machinery and Control Systems, College of Systems Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama, Japan
| | - Kenjiro Yoshimura
- Department of Machinery and Control Systems, College of Systems Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama-shi, Saitama, Japan
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32
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Katsuta H, Sawada Y, Sokabe M. Biophysical Mechanisms of Membrane-Thickness-Dependent MscL Gating: An All-Atom Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:7432-7442. [PMID: 30113845 DOI: 10.1021/acs.langmuir.8b02074] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The bacterial mechanosensitive channel, MscL, is activated by membrane tension, acting as a safety valve to prevent cell lysis against hypotonic challenge. It has been established that its activation threshold decreases with membrane thickness, while the underlying mechanism remains to be solved. We performed all-atom molecular dynamics (MD) simulations for the initial opening process of MscL embedded in four different types of lipid bilayers with different thicknesses: 1,2-dilauroyl- sn-glycero-3-phosphocholine (DLPC)), 1,2-dimyristoyl-glycero-3-phosphorylcholine (DMPC), 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), and 1,2-distearoyl- sn-glycero-3-phosphocholine (DSPC). In response to membrane stretching, channel opening occurred only in the thinner membranes (DLPC and DMPC) in a thickness-dependent way. We found that the MscL opening was governed by the rate and degree of membrane thinning and that the channel opening was tightly associated with the tilting of transmembrane (TM) helices of MscL toward the membrane plane. Upon membrane stretching, the order parameter of acyl chains of thinner membranes (DLPC and DMPC) became smaller, whereas other thicker membranes (DPPC and DSPC) showed interdigitation with little changes in the order parameter. The decreased order parameter contributed much more to membrane thinning than did interdigitation. We conclude that the membrane-thickness-dependent MscL opening mainly arises from structural changes in MscL to match the altered membrane thickness by stretching.
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33
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Wray R, Herrera N, Iscla I, Wang J, Blount P. An agonist of the MscL channel affects multiple bacterial species and increases membrane permeability and potency of common antibiotics. Mol Microbiol 2019; 112:896-905. [PMID: 31177589 DOI: 10.1111/mmi.14325] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/06/2019] [Indexed: 12/18/2022]
Abstract
The bacterial MscL channel normally functions as an emergency release valve discharging cytoplasmic solutes upon osmotic stress. The channel opens and passes molecules up to 30 Å and its pore is the largest of any gated channel. Opening the MscL pore inappropriately is detrimental to the bacterial cell, suggesting MscL as a potential novel drug target. A small-molecule compound, 011A, has been shown to increase sensitivity of the Escherichia coli MscL channel, slow growth, and even decrease viability of quiescent cultures. The mscL gene is highly conserved and found in the vast majority of bacterial species, including pathogens. Here, we test the hypothesis that 011A can influence the growth and viability of other bacterial species, specifically Staphylococcus aureus and Mycobacterium smegmatis, in a MscL-dependent manner. Furthermore, we demonstrate that the 011A compound can increase potency of other antibiotics, presumably by permeabilizing the membrane and allowing easier access of the antibiotic into the cytoplasm. Thus, MscL activators have potential as novel broad-spectrum antibiotics or adjuvants that work with antibiotics to selectively allow passage across bacterial membranes.
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Affiliation(s)
- Robin Wray
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, USA
| | - Nadia Herrera
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, USA
| | - Irene Iscla
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, USA
| | - Junmei Wang
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, Pittsburgh, PA, USA
| | - Paul Blount
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, USA
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34
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Maruf A, Wang Y, Yin T, Huang J, Wang N, Durkan C, Tan Y, Wu W, Wang G. Atherosclerosis Treatment with Stimuli-Responsive Nanoagents: Recent Advances and Future Perspectives. Adv Healthc Mater 2019; 8:e1900036. [PMID: 30945462 DOI: 10.1002/adhm.201900036] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 03/06/2019] [Indexed: 01/04/2023]
Abstract
Atherosclerosis is the root of approximately one-third of global mortalities. Nanotechnology exhibits splendid prospects to combat atherosclerosis at the molecular level by engineering smart nanoagents with versatile functionalizations. Significant advances in nanoengineering enable nanoagents to autonomously navigate in the bloodstream, escape from biological barriers, and assemble with their nanocohort at the targeted lesion. The assembly of nanoagents with endogenous and exogenous stimuli breaks down their shells, facilitates intracellular delivery, releases their cargo to kill the corrupt cells, and gives imaging reports. All these improvements pave the way toward personalized medicine for atherosclerosis. This review systematically summarizes the recent advances in stimuli-responsive nanoagents for atherosclerosis management and its progress in clinical trials.
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Affiliation(s)
- Ali Maruf
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
| | - Yi Wang
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
| | - Tieyin Yin
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
| | - Junli Huang
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
| | - Nan Wang
- The Nanoscience CentreUniversity of Cambridge Cambridge CB3 0FF UK
| | - Colm Durkan
- The Nanoscience CentreUniversity of Cambridge Cambridge CB3 0FF UK
| | - Youhua Tan
- Department of Biomedical EngineeringThe Hong Kong Polytechnic University Hong Kong SAR 999077 China
| | - Wei Wu
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
| | - Guixue Wang
- Key Laboratory for Biorheological Science and Technology of Ministry of EducationState and Local Joint Engineering Laboratory for Vascular ImplantsBioengineering College of Chongqing University Chongqing 400030 China
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35
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Hong F, Li Y. [Application of mechanosensitive channels in sonogenetics]. Zhejiang Da Xue Xue Bao Yi Xue Ban 2019; 48:34-38. [PMID: 31102355 PMCID: PMC8800646 DOI: 10.3785/j.issn.1008-9292.2019.02.06] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 09/23/2018] [Indexed: 06/09/2023]
Abstract
As a non-invasive approach, sonogenetics is applied to control neuronal activity. The mechanosensitive channel(MSC), which has low threshold of responding to ultrasound, may be the alternative solution. Sonogenetics is the technique that activates the MSC expressed in targeted neurons by low intensity ultrasound, thus achieve the neuromodulation. In this review, we introduce the mechanosensitive channel of large conductance, transient receptor potential, channels of the two-pore-domain potassium family, Piezo and the recent progress on their application in sonogenetics.
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Affiliation(s)
- Feifan Hong
- 1. Department of Biophysics, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Yuezhou Li
- 1. Department of Biophysics, Zhejiang University School of Medicine, Hangzhou 310058, China
- Department of Laboratory, Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310052, China
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36
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Wray R, Iscla I, Kovacs Z, Wang J, Blount P. Novel compounds that specifically bind and modulate MscL: insights into channel gating mechanisms. FASEB J 2019; 33:3180-3189. [PMID: 30359098 PMCID: PMC6404570 DOI: 10.1096/fj.201801628r] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/01/2018] [Indexed: 12/14/2022]
Abstract
The bacterial mechanosensitive channel of large conductance (MscL) normally functions as an emergency release valve discharging cytoplasmic solutes upon osmotic stress. Opening the large pore of MscL inappropriately is detrimental to the cell, and thus it has been speculated to be a potential antibiotic target. Although MscL is one of the best studied mechanosensitive channels, no chemical that influenced bacterial growth by modulating MscL is known. We therefore used a high-throughput screen to identify compounds that slowed growth in an MscL-dependent manner. We characterized 2 novel sulfonamide compounds identified in the screen. We demonstrated that, although both increase MscL gating, one of these compounds does not work through the folate pathway, as other antimicrobial sulfonamides; indeed, the sulfonamide portion of the compound is not needed for activity. The only mode of action appears to be MscL activation. The binding pocket is where an α-helix runs along the cytoplasmic membrane and interacts with a neighboring subunit; analogous motifs have been observed in several prokaryotic and eukaryotic channels. The data not only demonstrate that MscL is a viable antibiotic target, but also give insight into the gating mechanisms of MscL, and they may have implications for developing agonists for other channels.-Wray, R., Iscla, I., Kovacs, Z., Wang, J., Blount, P. Novel compounds that specifically bind and modulate MscL: insights into channel gating mechanisms.
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Affiliation(s)
- Robin Wray
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Irene Iscla
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Zoltan Kovacs
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Junmei Wang
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, Pittsburgh, Pennsylvania, USA
| | - Paul Blount
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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37
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Panatala R, Barbato S, Kozai T, Luo J, Kapinos LE, Lim RYH. Nuclear Pore Membrane Proteins Self-Assemble into Nanopores. Biochemistry 2019; 58:484-488. [DOI: 10.1021/acs.biochem.8b01179] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Radhakrishnan Panatala
- Biozentrum and Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Suncica Barbato
- Biozentrum and Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Toshiya Kozai
- Biozentrum and Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Jinghui Luo
- Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Larisa E. Kapinos
- Biozentrum and Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Roderick Y. H. Lim
- Biozentrum and Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
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38
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Chure G, Lee HJ, Rasmussen A, Phillips R. Connecting the Dots between Mechanosensitive Channel Abundance, Osmotic Shock, and Survival at Single-Cell Resolution. J Bacteriol 2018; 200:e00460-18. [PMID: 30201782 PMCID: PMC6222198 DOI: 10.1128/jb.00460-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/05/2018] [Indexed: 12/17/2022] Open
Abstract
Rapid changes in extracellular osmolarity are one of many insults microbial cells face on a daily basis. To protect against such shocks, Escherichia coli and other microbes express several types of transmembrane channels that open and close in response to changes in membrane tension. In E. coli, one of the most abundant channels is the mechanosensitive channel of large conductance (MscL). While this channel has been heavily characterized through structural methods, electrophysiology, and theoretical modeling, our understanding of its physiological role in preventing cell death by alleviating high membrane tension remains tenuous. In this work, we examine the contribution of MscL alone to cell survival after osmotic shock at single-cell resolution using quantitative fluorescence microscopy. We conducted these experiments in an E. coli strain which is lacking all mechanosensitive channel genes save for MscL, whose expression was tuned across 3 orders of magnitude through modifications of the Shine-Dalgarno sequence. While theoretical models suggest that only a few MscL channels would be needed to alleviate even large changes in osmotic pressure, we find that between 500 and 700 channels per cell are needed to convey upwards of 80% survival. This number agrees with the average MscL copy number measured in wild-type E. coli cells through proteomic studies and quantitative Western blotting. Furthermore, we observed zero survival events in cells with fewer than ∼100 channels per cell. This work opens new questions concerning the contribution of other mechanosensitive channels to survival, as well as regulation of their activity.IMPORTANCE Mechanosensitive (MS) channels are transmembrane protein complexes which open and close in response to changes in membrane tension as a result of osmotic shock. Despite extensive biophysical characterization, the contribution of these channels to cell survival remains largely unknown. In this work, we used quantitative video microscopy to measure the abundance of a single species of MS channel in single cells, followed by their survival after a large osmotic shock. We observed total death of the population with fewer than ∼100 channels per cell and determined that approximately 500 to 700 channels were needed for 80% survival. The number of channels we found to confer nearly full survival is consistent with the counts of the numbers of channels in wild-type cells in several earlier studies. These results prompt further studies to dissect the contribution of other channel species to survival.
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Affiliation(s)
- Griffin Chure
- Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - Heun Jin Lee
- Department of Applied Physics, California Institute of Technology, Pasadena, California, USA
| | - Akiko Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, United Kingdom
| | - Rob Phillips
- Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
- Department of Physics, California Institute of Technology, Pasadena, California, USA
- Department of Applied Physics, California Institute of Technology, Pasadena, California, USA
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Babakhanian M, Yang L, Nowroozi B, Saddik G, Boodaghians L, Blount P, Grundfest W. Effects of Low Intensity Focused Ultrasound on Liposomes Containing Channel proteins. Sci Rep 2018; 8:17250. [PMID: 30467339 PMCID: PMC6250712 DOI: 10.1038/s41598-018-35486-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 10/06/2018] [Indexed: 02/08/2023] Open
Abstract
The ability to reversibly and non-invasively modulate region-specific brain activity in vivo suggests Low Intensity Focused Ultrasound (LIFU) as potential therapeutics for neurological dysfunctions such as epilepsy and Parkinson's disease. While in vivo studies provide evidence of the bioeffects of LIFU on neuronal activity, they merely hint at potential mechanisms but do not fully explain how this technology achieves these effects. One potential hypothesis is that LIFU produces local membrane depolarization by mechanically perturbing the neuronal cell membrane, or activating channels or other proteins embedded in the membrane. Proteins that sense mechanical perturbations of the membrane, such as those gated by membrane tension, are prime candidates for activating in response to LIFU and thus leading to the neurological responses that have been measured. Here we use the bacterial mechanosensitive channel MscL, which has been purified and reconstituted in liposomes, to determine how LIFU may affect the activation of this membrane-tension gated channel. Two bacterial voltage-gated channels, KvAP and NaK2K F92A channels were also studied. Surprisingly, the results suggest that ultrasound modulation and membrane perturbation does not induce channel gating, but rather induces pore formation at the membrane protein-lipid interface. However, in vesicles with high MscL mechanosensitive channel concentrations, apparent decreases in pore formation are observed, suggesting that this membrane-tension-sensitive protein may serve to increase the elasticity of the membrane, presumably because of expansion of the channel in the plane of the membrane independent of channel gating.
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Affiliation(s)
- Meghedi Babakhanian
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA
- Center for Advanced Surgical and Interventional Technology (CASIT), University of California, Los Angeles, CA, 90095, USA
| | - Limin Yang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX, 75390-9040, USA
| | - Bryan Nowroozi
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA
- Center for Advanced Surgical and Interventional Technology (CASIT), University of California, Los Angeles, CA, 90095, USA
| | - George Saddik
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA
- Center for Advanced Surgical and Interventional Technology (CASIT), University of California, Los Angeles, CA, 90095, USA
| | - Lilian Boodaghians
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA
- Center for Advanced Surgical and Interventional Technology (CASIT), University of California, Los Angeles, CA, 90095, USA
| | - Paul Blount
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX, 75390-9040, USA.
| | - Warren Grundfest
- Department of Bioengineering, University of California, Los Angeles, CA, 90095, USA.
- Center for Advanced Surgical and Interventional Technology (CASIT), University of California, Los Angeles, CA, 90095, USA.
- Department of Electrical Engineering, University of California, Los Angeles, CA, 90095, USA.
- David Geffen School of Medicine, University of California, Los Angeles, USA.
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Herrera N, Maksaev G, Haswell ES, Rees DC. Elucidating a role for the cytoplasmic domain in the Mycobacterium tuberculosis mechanosensitive channel of large conductance. Sci Rep 2018; 8:14566. [PMID: 30275500 PMCID: PMC6167328 DOI: 10.1038/s41598-018-32536-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 08/31/2018] [Indexed: 12/04/2022] Open
Abstract
Microbial survival in dynamic environments requires the ability to successfully respond to abrupt changes in osmolarity. The mechanosensitive channel of large conductance (MscL) is a ubiquitous channel that facilitates the survival of bacteria and archaea under severe osmotic downshock conditions by relieving excess turgor pressure in response to increased membrane tension. A prominent structural feature of MscL, the cytoplasmic C-terminal domain, has been suggested to influence channel assembly and function. In this report, we describe the X-ray crystal structure and electrophysiological properties of a C-terminal domain truncation of the Mycobacterium tuberculosis MscL (MtMscLΔC). A crystal structure of MtMscLΔC solubilized in the detergent n-dodecyl-β-D-maltopyranoside reveals the pentameric, closed state-like architecture for the membrane spanning region observed in the previously solved full-length MtMscL. Electrophysiological characterization demonstrates that MtMscLΔC retains mechanosensitivity, but with conductance and tension sensitivity more closely resembling full length EcMscL than MtMscL. This study establishes that the C-terminal domain of MtMscL is not required for oligomerization of the full-length channel, but rather influences the tension sensitivity and conductance properties of the channel. The collective picture that emerges from these data is that each MscL channel structure has characteristic features, highlighting the importance of studying multiple homologs.
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Affiliation(s)
- Nadia Herrera
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA.,Division of Infectious Diseases, Department of Medicine University of California, San Francisco, San Francisco, CA, 94143-0654, USA
| | - Grigory Maksaev
- Department of Biology, NSF Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, 63130, USA.,Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Elizabeth S Haswell
- Department of Biology, NSF Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Douglas C Rees
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA.
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Ye J, Tang S, Meng L, Li X, Wen X, Chen S, Niu L, Li X, Qiu W, Hu H, Jiang M, Shang S, Shu Q, Zheng H, Duan S, Li Y. Ultrasonic Control of Neural Activity through Activation of the Mechanosensitive Channel MscL. NANO LETTERS 2018; 18:4148-4155. [PMID: 29916253 DOI: 10.1021/acs.nanolett.8b00935] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Externally controlling the excitation of a neuronal subset through ion channels activation can modulate the firing pattern of an entire neural circuit in vivo. As nanovalves in the cell membrane, ion channels can be opened by light (optogenetics) or ultrasonic (sonogenetics) means. A thoroughly analyzed force sensor is the Escherichia coli mechano sensitive channel of large conductance (MscL). Here we expressed MscL in rat hippocampal neurons in a primary culture and showed that it could be activated by low-pressure ultrasound pulses. The gain-of-function mutation, I92L, sensitized MscL's sonic response, triggering action potentials at a peak negative pressure as low as 0.25 MPa. Further, the I92L MscL reliably elicited individual spikes by timed brief pulses, making excitation programmable. Because MscL opens to tension in the lipid bilayer, requiring no other proteins or ligands, it could be developed into a general noninvasive sonogenetic tool to manipulate the activities of neurons or other cells and potential nanodevices.
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Affiliation(s)
- Jia Ye
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Siyang Tang
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Long Meng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI , Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences , Shenzhen , 518005 , China
| | - Xia Li
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Xiaoxu Wen
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Sihan Chen
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Lili Niu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI , Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences , Shenzhen , 518005 , China
| | - Xiangyao Li
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Weibao Qiu
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI , Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences , Shenzhen , 518005 , China
| | - Hailan Hu
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Mizu Jiang
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Shiqiang Shang
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Qiang Shu
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Hairong Zheng
- Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Key Laboratory for MRI , Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences , Shenzhen , 518005 , China
| | - Shumin Duan
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
| | - Yuezhou Li
- Children's Hospital and Department of Biophysics, NHC and CAMS Key Laboratory of Medical Neurobiology , Zhejiang University School of Medicine , Hangzhou , Zhejiang 310058 , China
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Yang LM, Zheng H, Ratnakar JS, Adebesin BY, Do QN, Kovacs Z, Blount P. Engineering a pH-Sensitive Liposomal MRI Agent by Modification of a Bacterial Channel. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1704256. [PMID: 29638039 PMCID: PMC6140348 DOI: 10.1002/smll.201704256] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 01/31/2018] [Indexed: 06/08/2023]
Abstract
MscL is a bacterial mechanosensitive channel that serves as a cellular emergency release valve, protecting the cell from lysis upon a drop in external osmolarity. The channel has an extremely large pore (30 Å) and can be purified and reconstituted into artificial membranes. Moreover, MscL is modified to open in response to alternative external stimuli including changes in pH. These properties suggest this channel's potential as a triggered "nanopore" for localized release of vesicular contents such as magnetic resonance imaging (MRI) contrast agents and drugs. Toward this end, several variants of pH-triggered MscL nanovalves are engineered. Stealth vesicles previously been shown to evade normal in vivo clearance and passively accumulate in inflamed and malignant tissues are reconstituted. These vesicles are loaded with 1,4,7,10-tetraazacyclododecane tetraacetic acid gadolinium complex (Gd-DOTA), an MRI contrast reagent, and the resulting nanodevices tested for their ability to release Gd-DOTA as evidenced by enhancement of the longitudinal relaxation rate (R1 ) of the bulk water proton spins. Nanovalves that are responsive to physiological pH changes are identified, but differ in sensitivity and efficacy, thus giving an array of nanovalves that could potentially be useful in different settings. These triggered nanodevices may be useful in delivering both diagnostic and therapeutic agents.
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Affiliation(s)
- Li-Min Yang
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Hui Zheng
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - James S Ratnakar
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Bukola Y Adebesin
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Quyen N Do
- Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Zoltan Kovacs
- Advanced Imaging Research Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
| | - Paul Blount
- Department of Physiology, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390, USA
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Single-channel recordings of RyR1 at microsecond resolution in CMOS-suspended membranes. Proc Natl Acad Sci U S A 2018; 115:E1789-E1798. [PMID: 29432144 DOI: 10.1073/pnas.1712313115] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Single-channel recordings are widely used to explore functional properties of ion channels. Typically, such recordings are performed at bandwidths of less than 10 kHz because of signal-to-noise considerations, limiting the temporal resolution available for studying fast gating dynamics to greater than 100 µs. Here we present experimental methods that directly integrate suspended lipid bilayers with high-bandwidth, low-noise transimpedance amplifiers based on complementary metal-oxide-semiconductor (CMOS) integrated circuits (IC) technology to achieve bandwidths in excess of 500 kHz and microsecond temporal resolution. We use this CMOS-integrated bilayer system to study the type 1 ryanodine receptor (RyR1), a Ca2+-activated intracellular Ca2+-release channel located on the sarcoplasmic reticulum. We are able to distinguish multiple closed states not evident with lower bandwidth recordings, suggesting the presence of an additional Ca2+ binding site, distinct from the site responsible for activation. An extended beta distribution analysis of our high-bandwidth data can be used to infer closed state flicker events as fast as 35 ns. These events are in the range of single-file ion translocations.
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Abstract
Mechanosensitive (MS) channels protect bacteria against hypo-osmotic shock and fulfil additional functions. Hypo-osmotic shock leads to high turgor pressure that can cause cell rupture and death. MS channels open under these conditions and release unspecifically solutes and consequently the turgor pressure. They can recognise the raised pressure via the increased tension in the cell membrane. Currently, a better understanding how MS channels can sense tension on molecular level is developing because the interaction of the lipid bilayer with the channel is being investigated in detail. The MS channel of large conductance (MscL) and of small conductance (MscS) have been distinguished and studied in molecular detail. In addition, larger channels were found that contain a homologous region corresponding to MscS so that MscS represents a family of channels. Often several members of this family are present in a species. The importance of this family is underlined by the fact that members can be found not only in bacteria but also in higher organisms. While MscL and MscS have been studied for years in particular by electrophysiology, mutagenesis, molecular dynamics, X-ray crystallography and other biophysical techniques, only recently more details are emerging about other members of the MscS-family.
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Bavi N, Martinac AD, Cortes DM, Bavi O, Ridone P, Nomura T, Hill AP, Martinac B, Perozo E. Structural Dynamics of the MscL C-terminal Domain. Sci Rep 2017; 7:17229. [PMID: 29222414 PMCID: PMC5722894 DOI: 10.1038/s41598-017-17396-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 11/16/2017] [Indexed: 12/17/2022] Open
Abstract
The large conductance mechanosensitive channel (MscL), acts as an osmoprotective emergency valve in bacteria by opening a large, water-filled pore in response to changes in membrane tension. In its closed configuration, the last 36 residues at the C-terminus form a bundle of five α-helices co-linear with the five-fold axis of symmetry. Here, we examined the structural dynamics of the C-terminus of EcMscL using site-directed spin labelling electron paramagnetic resonance (SDSL EPR) spectroscopy. These experiments were complemented with computational modelling including molecular dynamics (MD) simulations and finite element (FE) modelling. Our results show that under physiological conditions, the C-terminus is indeed an α-helical bundle, located near the five-fold symmetry axis of the molecule. Both experiments and computational modelling demonstrate that only the top part of the C-terminal domain (from the residue A110 to E118) dissociates during the channel gating, while the rest of the C-terminus stays assembled. This result is consistent with the view that the C-terminus functions as a molecular sieve and stabilizer of the oligomeric MscL structure as previously suggested.
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Affiliation(s)
- Navid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Adam D Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- School of Mechanical & Mining Engineering, University of Queensland, St. Lucia (Brisbane), QLD 4072, Brisbane, Australia
| | - D Marien Cortes
- Texas Tech University Health Sciences Center, Lubbock, Texas, 79430, USA
| | - Omid Bavi
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Physics, University of Tehran, Tehran, 1439955961, Iran
| | - Pietro Ridone
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Takeshi Nomura
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- Department of Rehabilitation, Kyushu Nutrition Welfare University, Kitakyushu, 800-029, Japan
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, New South Wales, 2010, Australia.
- St. Vincent's Clinical School, The University of New South Wales, Darlinghurst (Sydney), New South Wales, 2010, Australia.
| | - Eduardo Perozo
- Department of Biochemistry and Molecular Biology, University of Chicago, 929 E 57th St, Chicago, Illinois, 60637, USA.
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Wu H, Tito N, Giraldo JP. Anionic Cerium Oxide Nanoparticles Protect Plant Photosynthesis from Abiotic Stress by Scavenging Reactive Oxygen Species. ACS NANO 2017; 11:11283-11297. [PMID: 29099581 DOI: 10.1021/acsnano.7b05723] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Plant abiotic stress leads to accumulation of reactive oxygen species (ROS) and a consequent decrease in photosynthetic performance. We demonstrate that a plant nanobionics approach of localizing negatively charged, sub-11 nm, spherical cerium oxide nanoparticles (nanoceria) inside chloroplasts in vivo augments ROS scavenging and photosynthesis of Arabidopsis thaliana plants under excess light (2000 μmol m-2 s-1, 1.5 h), heat (35 °C, 2.5 h), and dark chilling (4 °C, 5 days). Poly(acrylic acid) nanoceria (PNC) with a hydrodynamic diameter (10.3 nm)-lower than the maximum plant cell wall porosity-and negative ζ-potential (-16.9 mV) exhibit significantly higher colocalization (46%) with chloroplasts in leaf mesophyll cells than aminated nanoceria (ANC) (27%) of similar size (12.6 nm) but positive charge (9.7 mV). Nanoceria are transported into chloroplasts via nonendocytic pathways, influenced by the electrochemical gradient of the plasma membrane potential. PNC with a low Ce3+/Ce4+ ratio (35.0%) reduce leaf ROS levels by 52%, including hydrogen peroxide, superoxide anion, and hydroxyl radicals. For the latter ROS, there is no known plant enzyme scavenger. Plants embedded with these PNC that were exposed to abiotic stress exhibit an increase up to 19% in quantum yield of photosystem II, 67% in carbon assimilation rates, and 61% in Rubisco carboxylation rates relative to plants without nanoparticles. In contrast, PNC with high Ce3+/Ce4+ ratio (60.8%) increase overall leaf ROS levels and do not protect photosynthesis from oxidative damage during abiotic stress. This study demonstrates that anionic, spherical, sub-11 nm PNC with low Ce3+/Ce4+ ratio can act as a tool to study the impact of oxidative stress on plant photosynthesis and to protect plants from abiotic stress.
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Affiliation(s)
- Honghong Wu
- Department of Botany and Plant Sciences, University of California , Riverside, California 92521, United States
| | - Nicholas Tito
- Department of Botany and Plant Sciences, University of California , Riverside, California 92521, United States
| | - Juan P Giraldo
- Department of Botany and Plant Sciences, University of California , Riverside, California 92521, United States
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Martinac AD, Bavi N, Bavi O, Martinac B. Pulling MscL open via N-terminal and TM1 helices: A computational study towards engineering an MscL nanovalve. PLoS One 2017; 12:e0183822. [PMID: 28859093 PMCID: PMC5578686 DOI: 10.1371/journal.pone.0183822] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/11/2017] [Indexed: 11/18/2022] Open
Abstract
There are great opportunities in the manipulation of bacterial mechanosensitive (MS) ion channels for specific and targeted drug delivery purposes. Recent research has shown that these ion channels have the potential to be converted into nanovalves through clever use of magnetic nanoparticles and magnetic fields. Using a combination of molecular dynamics (MD) simulations and the finite element (FE) modelling, this study investigates the theoretical feasibility of opening the MscL channel (MS channel of large conductance of E. coli) by applying mechanical force directly to its N-terminus. This region has already been reported to function as a major mechanosensor in this channel. The stress-strain behaviour of each MscL helix was obtained using all atom MD simulations. Using the same method, we simulated two models, the wild-type (WT) MscL and the G22N mutant MscL, both embedded in a POPE lipid bilayer. In addition to indicating the main interacting residues at the hydrophobic pore, their pairwise interaction energies were monitored during the channel gating. We implemented these inputs into our FE model of MscL using curve-fitting codes and continuum mechanics equations. In the FE model, the channel could be fully opened via pulling directly on the N-terminus and bottom of TM1 by mutating dominant van der Waals interactions in the channel pore; otherwise the stress generated on the channel protein can irreversibly unravel the N-secondary structure. This is a significant finding suggesting that applying force in this manner is sufficient to open an MscL nanovalve delivering various drugs used, for example, in cancer chemotherapy. More importantly, the FE model indicates that to fully operate an MscL nanovalve by pulling directly on the N-terminus and bottom of TM1, gain-of-function (GOF) mutants (e.g., G22N MscL) would have to be employed rather than the WT MscL channel.
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Affiliation(s)
- Adam D. Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Navid Bavi
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW, Australia
| | - Omid Bavi
- Department of Physics, University of Tehran, Tehran, Iran
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW, Australia
- * E-mail:
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48
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Pohorille A, Wilson MA, Shannon G. Flexible Proteins at the Origin of Life. Life (Basel) 2017; 7:E23. [PMID: 28587235 PMCID: PMC5492145 DOI: 10.3390/life7020023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/10/2017] [Accepted: 05/24/2017] [Indexed: 11/17/2022] Open
Abstract
Almost all modern proteins possess well-defined, relatively rigid scaffolds that provide structural preorganization for desired functions. Such scaffolds require the sufficient length of a polypeptide chain and extensive evolutionary optimization. How ancestral proteins attained functionality, even though they were most likely markedly smaller than their contemporary descendants, remains a major, unresolved question in the origin of life. On the basis of evidence from experiments and computer simulations, we argue that at least some of the earliest water-soluble and membrane proteins were markedly more flexible than their modern counterparts. As an example, we consider a small, evolved in vitro ligase, based on a novel architecture that may be the archetype of primordial enzymes. The protein does not contain a hydrophobic core or conventional elements of the secondary structure characteristic of modern water-soluble proteins, but instead is built of a flexible, catalytic loop supported by a small hydrophilic core containing zinc atoms. It appears that disorder in the polypeptide chain imparts robustness to mutations in the protein core. Simple ion channels, likely the earliest membrane protein assemblies, could also be quite flexible, but still retain their functionality, again in contrast to their modern descendants. This is demonstrated in the example of antiamoebin, which can serve as a useful model of small peptides forming ancestral ion channels. Common features of the earliest, functional protein architectures discussed here include not only their flexibility, but also a low level of evolutionary optimization and heterogeneity in amino acid composition and, possibly, the type of peptide bonds in the protein backbone.
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Affiliation(s)
- Andrew Pohorille
- Exobiology Branch, MS 239-4, NASA Ames Research Center, Moffett Field, CA 94035, USA.
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94132, USA.
| | - Michael A Wilson
- Exobiology Branch, MS 239-4, NASA Ames Research Center, Moffett Field, CA 94035, USA.
- SETI Institute, 189 N Bernardo Ave #200, Mountain View, CA 94043, USA.
| | - Gareth Shannon
- Exobiology Branch, MS 239-4, NASA Ames Research Center, Moffett Field, CA 94035, USA.
- NASA Postdoctoral Program Fellow, NASA Ames Research Center, Moffett Field, CA 94035, USA.
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49
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Bode DC, Baker MD, Viles JH. Ion Channel Formation by Amyloid-β42 Oligomers but Not Amyloid-β40 in Cellular Membranes. J Biol Chem 2016; 292:1404-1413. [PMID: 27927987 DOI: 10.1074/jbc.m116.762526] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 11/24/2016] [Indexed: 12/23/2022] Open
Abstract
A central hallmark of Alzheimer's disease is the presence of extracellular amyloid plaques chiefly consisting of amyloid-β (Aβ) peptides in the brain interstitium. Aβ largely exists in two isoforms, 40 and 42 amino acids long, but a large body of evidence points to Aβ(1-42) rather than Aβ(1-40) as the cytotoxic form. One proposed mechanism by which Aβ exerts toxicity is the formation of ion channel pores that disrupt intracellular Ca2+ homeostasis. However, previous studies using membrane mimetics have not identified any notable difference in the channel forming properties between Aβ(1-40) and Aβ(1-42). Here, we tested whether a more physiological environment, membranes excised from HEK293 cells of neuronal origin, would reveal differences in the relative channel forming ability of monomeric, oligomeric, and fibrillar forms of both Aβ(1-40) and Aβ(1-42). Aβ preparations were characterized with transmission electron microscopy and thioflavin T fluorescence. Aβ was then exposed to the extracellular face of excised membranes, and transmembrane currents were monitored using patch clamp. Our data indicated that Aβ(1-42) assemblies in oligomeric preparations form voltage-independent, non-selective ion channels. In contrast, Aβ(1-40) oligomers, fibers, and monomers did not form channels. Ion channel conductance results suggested that Aβ(1-42) oligomers, but not monomers and fibers, formed three distinct pore structures with 1.7-, 2.1-, and 2.4-nm pore diameters. Our findings demonstrate that only Aβ(1-42) contains unique structural features that facilitate membrane insertion and channel formation, now aligning ion channel formation with the differential neurotoxic effect of Aβ(1-40) and Aβ(1-42) in Alzheimer's disease.
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Affiliation(s)
- David C Bode
- From the School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom and
| | - Mark D Baker
- the Blizard Institute, Centre for Neuroscience and Trauma, Barts and The London School of Medicine and Dentistry, Queen Mary, University of London, 4 Newark Street, London E1 2AT, United Kingdom
| | - John H Viles
- From the School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom and
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50
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Zhang XC, Liu Z, Li J. From membrane tension to channel gating: A principal energy transfer mechanism for mechanosensitive channels. Protein Sci 2016; 25:1954-1964. [PMID: 27530280 DOI: 10.1002/pro.3017] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 08/10/2016] [Indexed: 12/17/2022]
Abstract
Mechanosensitive (MS) channels are evolutionarily conserved membrane proteins that play essential roles in multiple cellular processes, including sensing mechanical forces and regulating osmotic pressure. Bacterial MscL and MscS are two prototypes of MS channels. Numerous structural studies, in combination with biochemical and cellular data, provide valuable insights into the mechanism of energy transfer from membrane tension to gating of the channel. We discuss these data in a unified two-state model of thermodynamics. In addition, we propose a lipid diffusion-mediated mechanism to explain the adaptation phenomenon of MscS.
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Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China.
| | - Zhenfeng Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China
| | - Jie Li
- National Laboratory of Biomacromolecules, Institute of Biophysics Chinese Academy of Sciences, CAS Center for Excellence in Biomacromolecules, Beijing, 100101, China
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