1
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Immadisetty K, Polasa A, Shelton R, Moradi M. Elucidating the molecular basis of spontaneous activation in an engineered mechanosensitive channel. Comput Struct Biotechnol J 2022; 20:2539-2550. [PMID: 35685356 PMCID: PMC9156883 DOI: 10.1016/j.csbj.2022.05.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 05/11/2022] [Accepted: 05/12/2022] [Indexed: 12/11/2022] Open
Abstract
Mechanosensitive channel of large conductance (MscL) detects and responds to changes in the pressure profile of cellular membranes and transduces the mechanical energy into electrical and/or chemical signals. MscL can be activated using ultrasonic or chemical activation methods to improve the absorption of medicines and bioactive compounds into cells. However, re-engineering chemical signals such as pH change can trigger channel activation in MscL. This study elucidates the activation mechanism of an engineered MscL at an atomic level through a combination of equilibrium and non-equilibrium (NE) molecular dynamics (MD) simulations. Comparing the wild-type (WT) and engineered MscL activation processes suggests that the two systems are likely associated with different active states and different transition pathways. These findings indicate that (1) periplasmic loops play a key role in the activation process of MscL, (2) the loss of various backbone-backbone hydrogen bonds and salt bridge interactions in the engineered MscL channel causes the spontaneous opening of the channel, and (3) the most significant interactions lost during the activation process are between the transmembrane helices 1 and 2 in engineered MscL channel. The orientation-based biasing approach for producing and optimizing an open MscL model used in this work is a promising way to characterize unknown protein functional states and investigate the activation processes in ion channels and transmembrane proteins in general. This work paves the way for a computational framework for engineering more efficient pH-sensing mechanosensitive channels.
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Affiliation(s)
- Kalyan Immadisetty
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
| | - Adithya Polasa
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
| | - Reid Shelton
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
| | - Mahmoud Moradi
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, AR 72701, United States
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2
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Wang B, Lane BJ, Kapsalis C, Ault JR, Sobott F, El Mkami H, Calabrese AN, Kalli AC, Pliotas C. Pocket delipidation induced by membrane tension or modification leads to a structurally analogous mechanosensitive channel state. Structure 2022; 30:608-622.e5. [PMID: 34986323 PMCID: PMC9033278 DOI: 10.1016/j.str.2021.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/13/2021] [Accepted: 12/07/2021] [Indexed: 01/06/2023]
Abstract
The mechanosensitive ion channel of large conductance MscL gates in response to membrane tension changes. Lipid removal from transmembrane pockets leads to a concerted structural and functional MscL response, but it remains unknown whether there is a correlation between the tension-mediated state and the state derived by pocket delipidation in the absence of tension. Here, we combined pulsed electron paramagnetic resonance spectroscopy and hydrogen-deuterium exchange mass spectrometry, coupled with molecular dynamics simulations under membrane tension, to investigate the structural changes associated with the distinctively derived states. Whether it is tension- or modification-mediated pocket delipidation, we find that MscL samples a similar expanded subconducting state. This is the final step of the delipidation pathway, but only an intermediate stop on the tension-mediated path, with additional tension triggering further channel opening. Our findings hint at synergistic modes of regulation by lipid molecules in membrane tension-activated mechanosensitive channels.
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Affiliation(s)
- Bolin Wang
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Benjamin J Lane
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Charalampos Kapsalis
- Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - James R Ault
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Frank Sobott
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Hassane El Mkami
- School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
| | - Antonio N Calabrese
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Antreas C Kalli
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9NL, UK
| | - Christos Pliotas
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK; Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, UK.
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3
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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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4
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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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5
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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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6
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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: 43] [Impact Index Per Article: 10.8] [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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7
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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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8
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Temperature-sensitive gating of TRPV1 channel as probed by atomistic simulations of its trans- and juxtamembrane domains. Sci Rep 2016; 6:33112. [PMID: 27612191 PMCID: PMC5017144 DOI: 10.1038/srep33112] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 08/22/2016] [Indexed: 12/20/2022] Open
Abstract
Heat-activated transient receptor potential channel TRPV1 is one of the most studied eukaryotic proteins involved in temperature sensation. Upon heating, it exhibits rapid reversible pore gating, which depolarizes neurons and generates action potentials. Underlying molecular details of such effects in the pore region of TRPV1 is of a crucial importance to control temperature responses of the organism. Despite the spatial structure of the channel in both open (O) and closed (C) states is known, microscopic nature of channel gating and mechanism of thermal sensitivity are still poorly understood. In this work, we used unrestrained atomistic molecular dynamics simulations of TRPV1 (without N- and C-terminal cytoplasmic domains) embedded into explicit lipid bilayer in its O- and C-states. We found that the pore domain with its neighboring loops undergoes large temperature-dependent conformational transitions in an asymmetric way, when fragments of only one monomer move with large amplitude, freeing the pore upon heating. Such an asymmetrical gating looks rather biologically relevant because it is faster and more reliable than traditionally proposed “iris-like” symmetric scheme of channel opening. Analysis of structural, dynamic, and hydrophobic organization of the pore domain revealed entropy growth upon TRPV1 gating, which is in line with current concepts of thermal sensitivity.
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9
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Kocer A. Mechanisms of mechanosensing - mechanosensitive channels, function and re-engineering. Curr Opin Chem Biol 2015; 29:120-7. [PMID: 26610201 DOI: 10.1016/j.cbpa.2015.10.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/30/2015] [Accepted: 10/06/2015] [Indexed: 10/22/2022]
Abstract
Sensing and responding to mechanical stimuli is an ancient behavior and ubiquitous to all forms of life. One of its players 'mechanosensitive ion channels' are involved in processes from osmosensing in bacteria to pain in humans. However, the mechanism of mechanosensing is yet to be elucidated. This review describes recent developments in the understanding of a bacterial mechanosensitive channel. Force from the lipid principle of mechanosensation, new methods to understand protein-lipid interactions, the role of water in the gating, the use of engineered mechanosensitive channels in the understanding of the gating mechanism and application of the accumulated knowledge in the field of drug delivery, drug design and sensor technologies are discussed.
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Affiliation(s)
- Armagan Kocer
- University of Groningen, University Medical Center Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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10
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Chandramouli B, Di Maio D, Mancini G, Barone V, Brancato G. Breaking the hydrophobicity of the MscL pore: insights into a charge-induced gating mechanism. PLoS One 2015; 10:e0120196. [PMID: 25825909 PMCID: PMC4380313 DOI: 10.1371/journal.pone.0120196] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/06/2015] [Indexed: 01/17/2023] Open
Abstract
The mechanosensitive channel of large conductance (MscL) is a protein that responds to membrane tension by opening a transient pore during osmotic downshock. Due to its large pore size and functional reconstitution into lipid membranes, MscL has been proposed as a promising artificial nanovalve suitable for biotechnological applications. For example, site-specific mutations and tailored chemical modifications have shown how MscL channel gating can be triggered in the absence of tension by introducing charged residues at the hydrophobic pore level. Recently, engineered MscL proteins responsive to stimuli like pH or light have been reported. Inspired by experiments, we present a thorough computational study aiming at describing, with atomistic detail, the artificial gating mechanism and the molecular transport properties of a light-actuated bacterial MscL channel, in which a charge-induced gating mechanism has been enabled through the selective cleavage of photo-sensitive alkylating agents. Properties such as structural transitions, pore dimension, ion flux and selectivity have been carefully analyzed. Besides, the effects of charge on alternative sites of the channel with respect to those already reported have been addressed. Overall, our results provide useful molecular insights into the structural events accompanying the engineered MscL channel gating and the interplay of electrostatic effects, channel opening and permeation properties. In addition, we describe how the experimentally observed ionic current in a single-subunit charged MscL mutant is obtained through a hydrophobicity breaking mechanism involving an asymmetric inter-subunit motion.
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Affiliation(s)
| | - Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Giordano Mancini
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
| | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- Istituto Nazionale di Fisica Nucleare (INFN), sezione di Pisa, Largo Bruno Pontecorvo 3, 56127, Pisa, Italy
- * E-mail:
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11
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Aryal P, Sansom MSP, Tucker SJ. Hydrophobic gating in ion channels. J Mol Biol 2015; 427:121-30. [PMID: 25106689 PMCID: PMC4817205 DOI: 10.1016/j.jmb.2014.07.030] [Citation(s) in RCA: 191] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 07/24/2014] [Accepted: 07/28/2014] [Indexed: 02/01/2023]
Abstract
Biological ion channels are nanoscale transmembrane pores. When water and ions are enclosed within the narrow confines of a sub-nanometer hydrophobic pore, they exhibit behavior not evident from macroscopic descriptions. At this nanoscopic level, the unfavorable interaction between the lining of a hydrophobic pore and water may lead to stochastic liquid-vapor transitions. These transient vapor states are "dewetted", i.e. effectively devoid of water molecules within all or part of the pore, thus leading to an energetic barrier to ion conduction. This process, termed "hydrophobic gating", was first observed in molecular dynamics simulations of model nanopores, where the principles underlying hydrophobic gating (i.e., changes in diameter, polarity, or transmembrane voltage) have now been extensively validated. Computational, structural, and functional studies now indicate that biological ion channels may also exploit hydrophobic gating to regulate ion flow within their pores. Here we review the evidence for this process and propose that this unusual behavior of water represents an increasingly important element in understanding the relationship between ion channel structure and function.
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Affiliation(s)
- Prafulla Aryal
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 2JD, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 2JD, UK.
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 2JD, UK.
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12
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Global structural changes of an ion channel during its gating are followed by ion mobility mass spectrometry. Proc Natl Acad Sci U S A 2014; 111:17170-5. [PMID: 25404294 DOI: 10.1073/pnas.1413118111] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mechanosensitive ion channels are sensors probing membrane tension in all species; despite their importance and vital role in many cell functions, their gating mechanism remains to be elucidated. Here, we determined the conditions for releasing intact mechanosensitive channel of large conductance (MscL) proteins from their detergents in the gas phase using native ion mobility-mass spectrometry (IM-MS). By using IM-MS, we could detect the native mass of MscL from Escherichia coli, determine various global structural changes during its gating by measuring the rotationally averaged collision cross-sections, and show that it can function in the absence of a lipid bilayer. We could detect global conformational changes during MscL gating as small as 3%. Our findings will allow studying native structure of many other membrane proteins.
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13
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Mukherjee N, Jose MD, Birkner JP, Walko M, Ingólfsson HI, Dimitrova A, Arnarez C, Marrink SJ, Koçer A. The activation mode of the mechanosensitive ion channel, MscL, by lysophosphatidylcholine differs from tension-induced gating. FASEB J 2014; 28:4292-302. [PMID: 24958207 DOI: 10.1096/fj.14-251579] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
One of the best-studied mechanosensitive channels is the mechanosensitive channel of large conductance (MscL). MscL senses tension in the membrane evoked by an osmotic down shock and directly couples it to large conformational changes leading to the opening of the channel. Spectroscopic techniques offer unique possibilities to monitor these conformational changes if it were possible to generate tension in the lipid bilayer, the native environment of MscL, during the measurements. To this end, asymmetric insertion of l-α-lysophosphatidylcholine (LPC) into the lipid bilayer has been effective; however, how LPC activates MscL is not fully understood. Here, the effects of LPC on tension-sensitive mutants of a bacterial MscL and on MscL homologs with different tension sensitivities are reported, leading to the conclusion that the mode of action of LPC is different from that of applied tension. Our results imply that LPC shifts the free energy of gating by interfering with MscL-membrane coupling. Furthermore, we demonstrate that the fine-tuned addition of LPC can be used for controlled activation of MscL in spectroscopic studies.
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Affiliation(s)
- Nobina Mukherjee
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Mac Donald Jose
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Jan Peter Birkner
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands; Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands; and
| | - Martin Walko
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Helgi I Ingólfsson
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Anna Dimitrova
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Clément Arnarez
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands
| | - Armağan Koçer
- Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, The Netherlands; Neuroscience Department, University Medical Centre Groningen, Groningen, The Netherlands
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14
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Tan N, Lansman JB. Utrophin regulates modal gating of mechanosensitive ion channels in dystrophic skeletal muscle. J Physiol 2014; 592:3303-23. [PMID: 24879867 DOI: 10.1113/jphysiol.2014.274332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dystrophin is a large, submembrane cytoskeletal protein, absence of which causes Duchenne muscular dystrophy. Utrophin is a dystrophin homologue found in both muscle and brain whose physiological function is unknown. Recordings of single-channel activity were made from membrane patches on skeletal muscle from mdx, mdx/utrn(+/-) heterozygotes and mdx/utrn(-/-) double knockout mice to investigate the role of these cytoskeletal proteins in mechanosensitive (MS) channel gating. We find complex, gene dose-dependent effects of utrophin depletion in dystrophin-deficient mdx muscle: (1) increased MS channel open probability, (2) a shift of MS channel gating to larger pressures, (3) appearance of modal gating of MS channels and small conductance channels and (4) expression of large conductance MS channels. We suggest a physical model in which utrophin acts as a scaffolding protein that stabilizes lipid microdomains and clusters MS channel subunits. Depletion of utrophin disrupts domain composition in a manner that favours open channel area expansion, as well as allowing diffusion and aggregation of additional MS channel subunits.
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Affiliation(s)
- Nhi Tan
- Department of Cellular and Molecular Pharmacology, School of Medicine, University of California, San Francisco, San Francisco, CA, 94143-0450, USA
| | - Jeffry B Lansman
- Department of Cellular and Molecular Pharmacology, School of Medicine, University of California, San Francisco, San Francisco, CA, 94143-0450, USA
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15
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MscL: channeling membrane tension. Pflugers Arch 2014; 467:15-25. [PMID: 24859800 DOI: 10.1007/s00424-014-1535-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 05/06/2014] [Accepted: 05/09/2014] [Indexed: 10/25/2022]
Abstract
Mechanosensitive channels are integral components for the response of bacteria to osmotic shock. The mechanosensitive channel of large conductance (MscL) responds to extreme turgor pressure increase that would otherwise lyse the cellular membrane. MscL has been studied as a model mechanosensitive channel using both structural and functional approaches. We will summarize the structural data and discuss outstanding questions surrounding the gating mechanism of this homo-oligomeric channel that has ~3 nS conductance. Specifically, we will explore the following: (1) the variability in oligomeric state that has been observed, (2) the open pore size measurements, and (3) the role of the C-terminal coiled coil domain for channel function. The oligomeric state of MscL has been characterized using various techniques, with a pentamer being the predominant form; however, the presence of mixtures of oligomers in the membrane is still uncertain. In the absence of structural data for the open state of MscL, the diameter of the open state pore has been estimated by several different approaches, leading to a current estimate between 25 and 30 Å. While the C-terminal domain is highly conserved among MscL homologues, it is not required for activity in vivo or in vitro. This domain is likely to remain intact during the gating transition and perform a filtering function that retains valuable osmolytes in the cytosol. Overall, studies of MscL have provided significant insight to the field, and serve as a paradigm for the analysis of non-homologous, eukaryotic mechanosensitive channel proteins.
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16
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Velásquez J, Schuurman-Wolters G, Birkner JP, Abee T, Poolman B. Bacillus subtilisspore protein SpoVAC functions as a mechanosensitive channel. Mol Microbiol 2014; 92:813-23. [DOI: 10.1111/mmi.12591] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Jeanette Velásquez
- Department of Biochemistry; Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- TI Food and Nutrition; Wageningen The Netherlands
| | - Gea Schuurman-Wolters
- Department of Biochemistry; Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Jan Peter Birkner
- Department of Biochemistry; Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Tjakko Abee
- TI Food and Nutrition; Wageningen The Netherlands
- Laboratory of Food Microbiology; Wageningen University; Wageningen The Netherlands
| | - Bert Poolman
- Department of Biochemistry; Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
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17
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Urban M, Kleefen A, Mukherjee N, Seelheim P, Windschiegl B, Vor der Brüggen M, Koçer A, Tampé R. Highly parallel transport recordings on a membrane-on-nanopore chip at single molecule resolution. NANO LETTERS 2014; 14:1674-80. [PMID: 24524682 PMCID: PMC3953990 DOI: 10.1021/nl5002873] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 02/08/2014] [Indexed: 05/21/2023]
Abstract
Membrane proteins are prime drug targets as they control the transit of information, ions, and solutes across membranes. Here, we present a membrane-on-nanopore platform to analyze nonelectrogenic channels and transporters that are typically not accessible by electrophysiological methods in a multiplexed manner. The silicon chip contains 250,000 femtoliter cavities, closed by a silicon dioxide top layer with defined nanopores. Lipid vesicles containing membrane proteins of interest are spread onto the nanopore-chip surface. Transport events of ligand-gated channels were recorded at single-molecule resolution by high-parallel fluorescence decoding.
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Affiliation(s)
- Michael Urban
- Institute
of Biochemistry, Biocenter, Goethe-University, Frankfurt, Germany
| | - Alexander Kleefen
- Institute
of Biochemistry, Biocenter, Goethe-University, Frankfurt, Germany
| | - Nobina Mukherjee
- Department
of Biochemistry, University of Groningen, The Netherlands
| | | | | | | | - Armagan Koçer
- Department
of Biochemistry, University of Groningen, The Netherlands
| | - Robert Tampé
- Institute
of Biochemistry, Biocenter, Goethe-University, Frankfurt, Germany
- Cluster
of Excellence − Macromolecular Complexes, Goethe-University, Frankfurt, Germany
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