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Muraoka T. Biofunctional Molecules Inspired by Protein Mimicry and Manipulation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20190315] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Takahiro Muraoka
- Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan
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52
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Comert F, Greenwood A, Maramba J, Acevedo R, Lucas L, Kulasinghe T, Cairns LS, Wen Y, Fu R, Hammer J, Blazyk J, Sukharev S, Cotten ML, Mihailescu M. The host-defense peptide piscidin P1 reorganizes lipid domains in membranes and decreases activation energies in mechanosensitive ion channels. J Biol Chem 2019; 294:18557-18570. [PMID: 31619519 PMCID: PMC6901303 DOI: 10.1074/jbc.ra119.010232] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 10/01/2019] [Indexed: 11/06/2022] Open
Abstract
The host-defense peptide (HDP) piscidin 1 (P1), isolated from the mast cells of striped bass, has potent activities against bacteria, viruses, fungi, and cancer cells and can also modulate the activity of membrane receptors. Given its broad pharmacological potential, here we used several approaches to better understand its interactions with multicomponent bilayers representing models of bacterial (phosphatidylethanolamine (PE)/phosphatidylglycerol) and mammalian (phosphatidylcholine/cholesterol (PC/Chol)) membranes. Using solid-state NMR, we solved the structure of P1 bound to PC/Chol and compared it with that of P3, a less potent homolog. The comparison disclosed that although both peptides are interfacially bound and α-helical, they differ in bilayer orientations and depths of insertion, and these differences depend on bilayer composition. Although Chol is thought to make mammalian membranes less susceptible to HDP-mediated destabilization, we found that Chol does not affect the permeabilization effects of P1. X-ray diffraction experiments revealed that both piscidins produce a demixing effect in PC/Chol membranes by increasing the fraction of the Chol-depleted phase. Furthermore, P1 increased the temperature required for the lamellar-to-hexagonal phase transition in PE bilayers, suggesting that it imposes positive membrane curvature. Patch-clamp measurements on the inner Escherichia coli membrane showed that P1 and P3, at concentrations sufficient for antimicrobial activity, substantially decrease the activating tension for bacterial mechanosensitive channels. This indicated that piscidins can cause lipid redistribution and restructuring in the microenvironment near proteins. We conclude that the mechanism of piscidin's antimicrobial activity extends beyond simple membrane destabilization, helping to rationalize its broader spectrum of pharmacological effects.
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Affiliation(s)
- Fatih Comert
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Alexander Greenwood
- Department of Applied Science, William and Mary, Williamsburg, Virginia 23185
| | - Joseph Maramba
- Biology Department, University of Maryland, College Park, Maryland 20742
| | - Roderico Acevedo
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Laura Lucas
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Thulasi Kulasinghe
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Leah S Cairns
- Department of Biochemistry and Molecular Biology, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Yi Wen
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Riqiang Fu
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310
| | - Janet Hammer
- Department of Biomedical Sciences, Ohio University, Athens, Ohio 45701
| | - Jack Blazyk
- Department of Biomedical Sciences, Ohio University, Athens, Ohio 45701
| | - Sergei Sukharev
- Biology Department, University of Maryland, College Park, Maryland 20742
| | - Myriam L Cotten
- Department of Applied Science, William and Mary, Williamsburg, Virginia 23185.
| | - Mihaela Mihailescu
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850.
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53
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Hu JP, Wu ZX, Xie T, Liu XY, Yan X, Sun X, Liu W, Liang L, He G, Gan Y, Gou XJ, Shi Z, Zou Q, Wan H, Shi HB, Chang S. Applications of Molecular Simulation in the Discovery of Antituberculosis Drugs: A Review. Protein Pept Lett 2019; 26:648-663. [PMID: 31218945 DOI: 10.2174/0929866526666190620145919] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 04/10/2019] [Accepted: 05/03/2019] [Indexed: 02/05/2023]
Abstract
After decades of efforts, tuberculosis has been well controlled in most places. The existing drugs are no longer sufficient for the treatment of drug-resistant Mycobacterium tuberculosis due to significant toxicity and selective pressure, especially for XDR-TB. In order to accelerate the development of high-efficiency, low-toxic antituberculosis drugs, it is particularly important to use Computer Aided Drug Design (CADD) for rational drug design. Here, we systematically reviewed the specific role of molecular simulation in the discovery of new antituberculosis drugs. The purpose of this review is to overview current applications of molecular simulation methods in the discovery of antituberculosis drugs. Furthermore, the unique advantages of molecular simulation was discussed in revealing the mechanism of drug resistance. The comprehensive use of different molecular simulation methods will help reveal the mechanism of drug resistance and improve the efficiency of rational drug design. With the help of molecular simulation methods such as QM/MM method, the mechanisms of biochemical reactions catalyzed by enzymes at atomic level in Mycobacterium tuberculosis has been deeply analyzed. QSAR and virtual screening both accelerate the development of highefficiency, low-toxic potential antituberculosis drugs. Improving the accuracy of existing algorithms and developing more efficient new methods for CADD will always be a hot topic in the future. It is of great value to utilize molecular dynamics simulation to investigate complex systems that cannot be studied in experiments, especially for drug resistance of Mycobacterium tuberculosis.
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Affiliation(s)
- Jian-Ping Hu
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Zhi-Xiang Wu
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Tao Xie
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Xin-Yu Liu
- Laboratory of Tumor Targeted and Immune Therapy, Clinical Research Center for Breast, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, China
| | - Xiao Yan
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Xin Sun
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Wei Liu
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Li Liang
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Gang He
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Ya Gan
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Xiao-Jun Gou
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Zheng Shi
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Qiang Zou
- College of Pharmacy and Biological Engineering, Sichuan Industrial Institute of Antibiotics, Key Laboratory of Medicinal and Edible Plants Resources Development of Sichuan Education Department, Chengdu University, Chengdu, China
| | - Hua Wan
- College of Mathematics and Informatics, South China Agricultural University, Guangzhou, China
| | - Hu-Bing Shi
- Laboratory of Tumor Targeted and Immune Therapy, Clinical Research Center for Breast, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center, Chengdu, China
| | - Shan Chang
- Institute of Bioinformatics and Medical Engineering, School of Electrical and Information Engineering, Jiangsu University of Technology, Changzhou, China
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54
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R Ferreira R, Fukui H, Chow R, Vilfan A, Vermot J. The cilium as a force sensor-myth versus reality. J Cell Sci 2019; 132:132/14/jcs213496. [PMID: 31363000 DOI: 10.1242/jcs.213496] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cells need to sense their mechanical environment during the growth of developing tissues and maintenance of adult tissues. The concept of force-sensing mechanisms that act through cell-cell and cell-matrix adhesions is now well established and accepted. Additionally, it is widely believed that force sensing can be mediated through cilia. Yet, this hypothesis is still debated. By using primary cilia sensing as a paradigm, we describe the physical requirements for cilium-mediated mechanical sensing and discuss the different hypotheses of how this could work. We review the different mechanosensitive channels within the cilium, their potential mode of action and their biological implications. In addition, we describe the biological contexts in which cilia are acting - in particular, the left-right organizer - and discuss the challenges to discriminate between cilium-mediated chemosensitivity and mechanosensitivity. Throughout, we provide perspectives on how quantitative analysis and physics-based arguments might help to better understand the biological mechanisms by which cells use cilia to probe their mechanical environment.
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Affiliation(s)
- Rita R Ferreira
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U1258, 67404 Illkirch, France.,Université de Strasbourg, 67404 Illkirch, France
| | - Hajime Fukui
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U1258, 67404 Illkirch, France.,Université de Strasbourg, 67404 Illkirch, France
| | - Renee Chow
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U1258, 67404 Illkirch, France.,Université de Strasbourg, 67404 Illkirch, France
| | - Andrej Vilfan
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Department of Living Matter Physics, 37077 Göttingen, Germany .,J. Stefan Institute, 1000 Ljubljana, Slovenia
| | - Julien Vermot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France .,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U1258, 67404 Illkirch, France.,Université de Strasbourg, 67404 Illkirch, France
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55
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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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56
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Rasmussen T, Rasmussen A, Yang L, Kaul C, Black S, Galbiati H, Conway SJ, Miller S, Blount P, Booth IR. Interaction of the Mechanosensitive Channel, MscS, with the Membrane Bilayer through Lipid Intercalation into Grooves and Pockets. J Mol Biol 2019; 431:3339-3352. [PMID: 31173776 DOI: 10.1016/j.jmb.2019.05.043] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/14/2019] [Accepted: 05/29/2019] [Indexed: 10/26/2022]
Abstract
All membrane proteins have dynamic and intimate relationships with the lipids of the bilayer that may determine their activity. Mechanosensitive channels sense tension through their interaction with the lipids of the membrane. We have proposed a mechanism for the bacterial channel of small conductance, MscS, that envisages variable occupancy of pockets in the channel by lipid chains. Here, we analyze protein-lipid interactions for MscS by quenching of tryptophan fluorescence with brominated lipids. By this strategy, we define the limits of the bilayer for TM1, which is the most lipid exposed helix of this protein. In addition, we show that residues deep in the pockets, created by the oligomeric assembly, interact with lipid chains. On the cytoplasmic side, lipids penetrate as far as the pore-lining helices and lipid molecules can align along TM3b perpendicular to lipids in the bilayer. Cardiolipin, free fatty acids, and branched lipids can access the pockets where the latter have a distinct effect on function. Cholesterol is excluded from the pockets. We demonstrate that introduction of hydrophilic residues into TM3b severely impairs channel function and that even "conservative" hydrophobic substitutions can modulate the stability of the open pore. The data provide important insights into the interactions between phospholipids and MscS and are discussed in the light of recent developments in the study of Piezo1 and TrpV4.
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Affiliation(s)
- Tim Rasmussen
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
| | - Akiko Rasmussen
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Limin Yang
- Department of Physiology, U.T. Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9040, USA.
| | - Corinna Kaul
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Susan Black
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Heloisa Galbiati
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Stuart J Conway
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK.
| | - Samantha Miller
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
| | - Paul Blount
- Department of Physiology, U.T. Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9040, USA.
| | - Ian Rylance Booth
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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57
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Nakayama Y, Hashimoto KI, Kawasaki H, Martinac B. "Force-From-Lipids" mechanosensation in Corynebacterium glutamicum. Biophys Rev 2019; 11:327-333. [PMID: 31055761 PMCID: PMC6557938 DOI: 10.1007/s12551-019-00524-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 04/15/2019] [Indexed: 02/07/2023] Open
Abstract
Since the mechanosensitive channel MscCG has been identified as the major glutamate efflux system in Corynebacterium glutamicum, studies of mechanotransduction processes in this bacterium have helped to unpuzzle a long-unresolved mystery of glutamate efflux that has been utilised for industrial monosodium glutamate production. The patch clamp recording from C. glutamicum giant spheroplasts revealed the existence of three types of mechanosensitive (MS) channels in the cell membrane of this bacterium. The experiments demonstrated that the MS channels could be activated by membrane tension, indicating that the channel gating by mechanical force followed the "Force-From-Lipids (FFL)" principle characteristic of ion channels inherently sensitive to transbilayer pressure profile changes in the mechanically stressed membrane bilayer. Mechanical properties of the C. glutamicum membrane are characteristics of very soft membranes, which in the C. glutamicum membrane are due to negatively charged lipids as its exclusive constituents. Given that membrane lipids are significantly altered during the fermentation process in the monosodium glutamate production, MS channels seem to respond to changes in force transmission through the membrane bilayer due to membrane lipid dynamics. In this review, we describe the recent results describing corynebacterial FFL-dependent mechanosensation originating from the particular lipid composition of the C. glutamicum membrane and unique structure of MscCG-type channels.
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Affiliation(s)
- Yoshitaka Nakayama
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool St, Darlinghurst, NSW, 2010, Australia
| | - Ken-Ichi Hashimoto
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Hisashi Kawasaki
- Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
- Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool St, Darlinghurst, NSW, 2010, Australia.
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW, 2010, Australia.
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58
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Almanjahie IM, Khan RN, Milne RK, Nomura T, Martinac B. Moving average filtering with deconvolution (MAD) for hidden Markov model with filtering and correlated noise. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2019; 48:383-393. [PMID: 31028435 DOI: 10.1007/s00249-019-01368-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 02/14/2019] [Accepted: 04/22/2019] [Indexed: 11/28/2022]
Abstract
Ion channel data recorded using the patch clamp technique are low-pass filtered to remove high-frequency noise. Almanjahie et al. (Eur Biophys J 44:545-556, 2015) based statistical analysis of such data on a hidden Markov model (HMM) with a moving average adjustment for the filter but without correlated noise, and used the EM algorithm for parameter estimation. In this paper, we extend their model to include correlated noise, using signal processing methods and deconvolution to pre-whiten the noise. The resulting data can be modelled as a standard HMM and parameter estimates are again obtained using the EM algorithm. We evaluate this approach using simulated data and also apply it to real data obtained from the mechanosensitive channel of large conductance (MscL) in Escherichia coli. Estimates of mean conductances are comparable to literature values. The key advantages of this method are that it is much simpler and computationally considerably more efficient than currently used HMM methods that include filtering and correlated noise.
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Affiliation(s)
- Ibrahim M Almanjahie
- Department of Mathematics and Statistics, University of Western Australia, Crawley, WA, 6009, Australia.,Department of Mathematics, King Khalid University, Abha, 61413, Saudi Arabia
| | - Ramzan Nazim Khan
- Department of Mathematics and Statistics, University of Western Australia, Crawley, WA, 6009, Australia.
| | - Robin K Milne
- Department of Mathematics and Statistics, University of Western Australia, Crawley, WA, 6009, Australia
| | - Takeshi Nomura
- Department of Rehabilitation, Kyushu Nutrition Welfare University, Kitakyushu, 800-029, Japan
| | - Boris Martinac
- Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
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59
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Romero LO, Massey AE, Mata-Daboin AD, Sierra-Valdez FJ, Chauhan SC, Cordero-Morales JF, Vásquez V. Dietary fatty acids fine-tune Piezo1 mechanical response. Nat Commun 2019; 10:1200. [PMID: 30867417 PMCID: PMC6416271 DOI: 10.1038/s41467-019-09055-7] [Citation(s) in RCA: 144] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 02/18/2019] [Indexed: 12/18/2022] Open
Abstract
Mechanosensitive ion channels rely on membrane composition to transduce physical stimuli into electrical signals. The Piezo1 channel mediates mechanoelectrical transduction and regulates crucial physiological processes, including vascular architecture and remodeling, cell migration, and erythrocyte volume. The identity of the membrane components that modulate Piezo1 function remain largely unknown. Using lipid profiling analyses, we here identify dietary fatty acids that tune Piezo1 mechanical response. We find that margaric acid, a saturated fatty acid present in dairy products and fish, inhibits Piezo1 activation and polyunsaturated fatty acids (PUFAs), present in fish oils, modulate channel inactivation. Force measurements reveal that margaric acid increases membrane bending stiffness, whereas PUFAs decrease it. We use fatty acid supplementation to abrogate the phenotype of gain-of-function Piezo1 mutations causing human dehydrated hereditary stomatocytosis. Beyond Piezo1, our findings demonstrate that cell-intrinsic lipid profile and changes in the fatty acid metabolism can dictate the cell's response to mechanical cues.
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Affiliation(s)
- Luis O Romero
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 71S. Manassas St., Memphis, TN, 38163, USA
| | - Andrew E Massey
- Department of Pharmaceutical Sciences and Institute of Biomarker and Molecular Therapeutics (IBMT), College of Pharmacy, University of Tennessee Health Science Center, 881 Madison Ave., Memphis, TN, 38163, USA
| | - Alejandro D Mata-Daboin
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 71S. Manassas St., Memphis, TN, 38163, USA
| | - Francisco J Sierra-Valdez
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 71S. Manassas St., Memphis, TN, 38163, USA
- Centro de Investigación Biomédica, Hospital Zambrano Hellion, TecSalud, Ave. Batallon de San Patricio 112, 66278, San Pedro Garza García, Nuevo León, Mexico
- Tecnólogico de Monterrey, Escuela de Ingeniería y Ciencias, Ave. Eugenio Garza Sada 2501 Sur, 64849, Monterrey, Nuevo León, Mexico
| | - Subhash C Chauhan
- Department of Pharmaceutical Sciences and Institute of Biomarker and Molecular Therapeutics (IBMT), College of Pharmacy, University of Tennessee Health Science Center, 881 Madison Ave., Memphis, TN, 38163, USA
| | - Julio F Cordero-Morales
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 71S. Manassas St., Memphis, TN, 38163, USA
| | - Valeria Vásquez
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, 71S. Manassas St., Memphis, TN, 38163, USA.
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60
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Constitutive boost of a K + channel via inherent bilayer tension and a unique tension-dependent modality. Proc Natl Acad Sci U S A 2018; 115:13117-13122. [PMID: 30509986 DOI: 10.1073/pnas.1812282115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular mechanisms underlying channel-membrane interplay have been extensively studied. Cholesterol, as a major component of the cell membrane, participates either in specific binding to channels or via modification of membrane physical features. Here, we examined the action of various sterols (cholesterol, epicholesterol, etc.) on a prototypical potassium channel (KcsA). Single-channel current recordings of the KcsA channel were performed in a water-in-oil droplet bilayer (contact bubble bilayer) with a mixed phospholipid composition (azolectin). Upon membrane perfusion of sterols, the activated gate at acidic pH closed immediately, irrespective of the sterol species. During perfusion, we found that the contacting bubbles changed their shapes, indicating alterations in membrane physical features. Absolute bilayer tension was measured according to the principle of surface chemistry, and inherent bilayer tension was ∼5 mN/m. All tested sterols decreased the tension, and the nonspecific sterol action to the channel was likely mediated by the bilayer tension. Purely mechanical manipulation that reduced bilayer tension also closed the gate, whereas the resting channel at neutral pH never activated upon increased tension. Thus, rather than conventional stretch activation, the channel, once ready to activate by acidic pH, changes the open probability through the action of bilayer tension. This constitutes a channel regulating modality by two successive stimuli. In the contact bubble bilayer, inherent bilayer tension was high, and the channel remained boosted. In the cell membrane, resting tension is low, and it is anticipated that the ready-to-activate channel remains closed until bilayer tension reaches a few millinewton/meter during physiological and pathological cellular activities.
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61
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Haselwandter CA, MacKinnon R. Piezo's membrane footprint and its contribution to mechanosensitivity. eLife 2018; 7:41968. [PMID: 30480546 PMCID: PMC6317911 DOI: 10.7554/elife.41968] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 11/26/2018] [Indexed: 02/03/2023] Open
Abstract
Piezo1 is an ion channel that gates open when mechanical force is applied to a cell membrane, thus allowing cells to detect and respond to mechanical stimulation. Molecular structures of Piezo1 reveal a large ion channel with an unusually curved shape. This study analyzes how such a curved ion channel interacts energetically with the cell membrane. Through membrane mechanical calculations, we show that Piezo1 deforms the membrane shape outside the perimeter of the channel into a curved 'membrane footprint'. This membrane footprint amplifies the sensitivity of Piezo1 to changes in membrane tension, rendering it exquisitely responsive. We assert that the shape of the Piezo channel is an elegant example of molecular form evolved to optimize a specific function, in this case tension sensitivity. Furthermore, the predicted influence of the membrane footprint on Piezo gating is consistent with the demonstrated importance of membrane-cytoskeletal attachments to Piezo gating.
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Affiliation(s)
- Christoph A Haselwandter
- Department of Physics & Astronomy, University of Southern California, Los Angeles, United States.,Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
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62
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Wang Z, Jumper JM, Wang S, Freed KF, Sosnick TR. A Membrane Burial Potential with H-Bonds and Applications to Curved Membranes and Fast Simulations. Biophys J 2018; 115:1872-1884. [PMID: 30413241 DOI: 10.1016/j.bpj.2018.10.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 09/21/2018] [Accepted: 10/10/2018] [Indexed: 10/28/2022] Open
Abstract
We use the statistics of a large and curated training set of transmembrane helical proteins to develop a knowledge-based potential that accounts for the dependence on both the depth of burial of the protein in the membrane and the degree of side-chain exposure. Additionally, the statistical potential includes depth-dependent energies for unsatisfied backbone hydrogen bond donors and acceptors, which are found to be relatively small, ∼2 RT. Our potential accurately places known proteins within the bilayer. The potential is applied to the mechanosensing MscL channel in membranes of varying thickness and curvature, as well as to the prediction of protein structure. The potential is incorporated into our new Upside molecular dynamics algorithm. Notably, we account for the exchange of protein-lipid interactions for protein-protein interactions as helices contact each other, thereby avoiding overestimating the energetics of helix association within the membrane. Simulations of most multimeric complexes find that isolated monomers and the oligomers retain the same orientation in the membrane, suggesting that the assembly of prepositioned monomers presents a viable mechanism of oligomerization.
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Affiliation(s)
- Zongan Wang
- Department of Chemistry, The University of Chicago, Chicago, Illinois; James Franck Institute, The University of Chicago, Chicago, Illinois
| | - John M Jumper
- Department of Chemistry, The University of Chicago, Chicago, Illinois; James Franck Institute, The University of Chicago, Chicago, Illinois; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois
| | - Sheng Wang
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia; Toyota Technological Institute at Chicago, Chicago, Illinois
| | - Karl F Freed
- Department of Chemistry, The University of Chicago, Chicago, Illinois; James Franck Institute, The University of Chicago, Chicago, Illinois.
| | - Tobin R Sosnick
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois; Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
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63
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Najem JS, Rowe I, Anishkin A, Leo DJ, Sukharev S. The voltage-dependence of MscL has dipolar and dielectric contributions and is governed by local intramembrane electric field. Sci Rep 2018; 8:13607. [PMID: 30206263 PMCID: PMC6133944 DOI: 10.1038/s41598-018-31945-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 08/29/2018] [Indexed: 02/01/2023] Open
Abstract
Channels without canonical voltage sensors can be modulated by voltage acting on other domains. Here we show that besides protein dipoles, pore hydration can be affected by electric fields. In patches, both WT MscL and its V23T mutant show a decrease in the tension midpoint with hyperpolarization. The mutant exhibits a stronger parabolic dependence of transition energy on voltage, highly consistent with the favourable dielectric contribution from water filling the expanding pore. Purified V23T MscL in DPhPC droplet interface bilayers shows a similar voltage dependence. When reconstituted in an asymmetric DOPhPC/DPhPC bilayer carrying a permanent bias of ~130 mV due to a dipole potential difference between the interfaces, the channel behaved as if the local intramembrane electric field sets the tension threshold for gating rather than just the externally applied voltage. The data emphasize the roles of polarized water in the pore and interfacial lipid dipoles in channel gating thermodynamics.
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Affiliation(s)
- Joseph S Najem
- Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37830, United States.,Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, Tennessee, 37916, United States
| | - Ian Rowe
- Department of Biology, University of Maryland, College Park, MD, 20817, United States
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD, 20817, United States
| | - Donald J Leo
- College of Engineering, University of Georgia, Athens, Georgia, 30605, United States
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, MD, 20817, United States.
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64
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Martinac B, Bavi N, Ridone P, Nikolaev YA, Martinac AD, Nakayama Y, Rohde PR, Bavi O. Tuning ion channel mechanosensitivity by asymmetry of the transbilayer pressure profile. Biophys Rev 2018; 10:1377-1384. [PMID: 30182202 DOI: 10.1007/s12551-018-0450-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 08/15/2018] [Indexed: 01/04/2023] Open
Abstract
Mechanical stimuli acting on the cellular membrane are linked to intracellular signaling events and downstream effectors via different mechanoreceptors. Mechanosensitive (MS) ion channels are the fastest known primary mechano-electrical transducers, which convert mechanical stimuli into meaningful intracellular signals on a submillisecond time scale. Much of our understanding of the biophysical principles that underlie and regulate conversion of mechanical force into conformational changes in MS channels comes from studies based on MS channel reconstitution into lipid bilayers. The bilayer reconstitution methods have enabled researchers to investigate the structure-function relationship in MS channels and probe their specific interactions with their membrane lipid environment. This brief review focuses on close interactions between MS channels and the lipid bilayer and emphasizes the central role that the transbilayer pressure profile plays in mechanosensitivity and gating of these fascinating membrane proteins.
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Affiliation(s)
- Boris Martinac
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW, 2010, Australia.
- St Vincent's Clinical School, University of New South Wales, 405 Liverpool St, Darlinghurst, NSW, 2010, Australia.
| | - Navid Bavi
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, 60637, USA
| | - Pietro Ridone
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW, 2010, Australia
- St Vincent's Clinical School, University of New South Wales, 405 Liverpool St, Darlinghurst, NSW, 2010, Australia
| | - Yury A Nikolaev
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW, 2010, Australia
- Dept. of Cellular & Molecular Physiology, Yale University, 333 Cedar Street, New Haven, CT 06520-8026, USA
| | - Adam D Martinac
- NeuRA, Margarete Ainsworth Building, Barker St, Randwick, NSW, 2031, Australia
| | - Yoshitaka Nakayama
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW, 2010, Australia
| | - Paul R Rohde
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW, 2010, Australia
| | - Omid Bavi
- Institute for Nanoscience and Nanotechnology, Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, 7155713876, Iran
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65
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Nakayama Y, Komazawa K, Bavi N, Hashimoto KI, Kawasaki H, Martinac B. Evolutionary specialization of MscCG, an MscS-like mechanosensitive channel, in amino acid transport in Corynebacterium glutamicum. Sci Rep 2018; 8:12893. [PMID: 30150671 PMCID: PMC6110860 DOI: 10.1038/s41598-018-31219-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 08/14/2018] [Indexed: 11/09/2022] Open
Abstract
MscCG, a mechanosensitive channel of Corynebacterium glutamicum provides a major export mechanism for glutamate in this Gram-positive bacterium, which has for many years been used for industrial production of glutamate and other amino acids. The functional characterization of MscCG is therefore, of great significance to understand its conductive properties for different amino acids. Here we report the first successful giant spheroplast preparation of C. glutamicum amenable to the patch clamp technique, which enabled us to investigate mechanosensitive channel activities of MscCG in the native membrane of this bacterium. Single channel recordings from these spheroplasts revealed the presence of three types of mechanosensitive channels, MscCG, MscCG2, and CgMscL, which differ largely from each other in their conductance and mechanosensitivity. MscCG has a relatively small conductance of ~340 pS followed by an intermediate MscCG2 conductance of ~1.0 nS and comparably very large conductance of 3.7 nS exhibited by CgMscL. By applying Laplace's law, we determined that very moderate membrane tension of ~5.5 mN/m was required for half activation of MscCG compared to ~12 mN/m required for half activation of both MscCG2 and CgMscL. Furthermore, by combining the micropipette aspiration technique with molecular dynamics simulations we measured mechanical properties of the C. glutamicum membrane, whose area elasticity module of KA ≈ 15 mN/m is characteristic of a very soft membrane compared to the three times larger area expansion modulus of KA ≈ 44 mN/m of the more elastic E. coli membrane. Moreover, we demonstrate that the "soft" properties of the C. glutamicum membrane have a significant impact on the MscCG gating characterized by a strong voltage-dependent hysteresis in the membrane of C. glutamicum compared to a complete absence of the hysteresis in the E. coli cell membrane. We thus propose that MscCG has evolved and adapted as an MscS-like channel to the mechanical properties of the C. glutamicum membrane enabling the channel to specialize in transport of amino acids such as glutamate, which are major osmolytes helping the bacterial cells survive extreme osmotic stress.
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Affiliation(s)
- Yoshitaka Nakayama
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Kosuke Komazawa
- Department of Green and Sustainable Chemistry, Tokyo Denki University, 5 Asahi-cho, Senju, Adachi-ku, Tokyo, 120-8551, Japan
| | - Navid Bavi
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia.,St Vincent's Clinical School, Faculty of Medicine, The University of New South Wales, Darlinghurst, NSW, 2010, Australia.,Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, 60637, USA
| | - Ken-Ichi Hashimoto
- Department of Green and Sustainable Chemistry, Tokyo Denki University, 5 Asahi-cho, Senju, Adachi-ku, Tokyo, 120-8551, Japan
| | - Hisashi Kawasaki
- Department of Green and Sustainable Chemistry, Tokyo Denki University, 5 Asahi-cho, Senju, Adachi-ku, Tokyo, 120-8551, Japan
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia. .,St Vincent's Clinical School, Faculty of Medicine, The University of New South Wales, Darlinghurst, NSW, 2010, Australia.
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66
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Amar A, Pezzoni M, Pizarro RA, Costa CS. New envelope stress factors involved in σ E activation and conditional lethality of rpoE mutations in Salmonella enterica. MICROBIOLOGY-SGM 2018; 164:1293-1307. [PMID: 30084765 DOI: 10.1099/mic.0.000701] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Salmonella enterica serovar Typhimurium (S. typhimurium) can cause food- and water-borne illness with diverse clinical manifestations. One key factor for S. typhimurium pathogenesis is the alternative sigma factor σE, which is encoded by the rpoE gene and controls the transcription of genes required for outer-membrane integrity in response to alterations in the bacterial envelope. The canonical pathway for σE activation involves proteolysis of the antisigma factor RseA, which is triggered by unfolded outer-membrane porins (OMPs) and lipopolysaccharides (LPS) that have accumulated in the periplasm. This study reports new stress factors that are able to activate σE expression. We demonstrate that UVA radiation induces σE activity in a pathway that is dependent on the stringent response regulator ppGpp. Survival assays revealed that rpoE has a role in the defence against lethal UVA doses that is mediated by functions that are dependent on and independent of the alternative sigma factor RpoS. We also report that the envelope stress generated by phage infection requires a functional rpoE gene for optimal bacterial tolerance and that it is able to induce σE activity in an RseA-dependent fashion. σE activity is also induced by hypo-osmotic shock in the absence of osmoregulated periplasmic glucans (OPGs). It is known that the rpoE gene is not essential in S. typhimurium. However, we report here two cases of the conditional lethality of rpoE mutations in this micro-organism. We demonstrate that rpoE mutations are not tolerated in the absence of OPGs (at low to moderate osmolarity) or LPS O-antigen. The latter case resembles that of the prototypic Escherichia coli strain K12, which neither synthesizes a complete LPS nor tolerates null rpoE mutations.
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Affiliation(s)
- Agustina Amar
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Magdalena Pezzoni
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Ramón A Pizarro
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
| | - Cristina S Costa
- Dpto. de Radiobiología, Comisión Nacional de Energía Atómica, General San Martín, Argentina
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67
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Spatiotemporal relationships defining the adaptive gating of the bacterial mechanosensitive channel MscS. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2018; 47:663-677. [DOI: 10.1007/s00249-018-1303-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 03/27/2018] [Accepted: 04/13/2018] [Indexed: 12/13/2022]
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68
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Sachs F. Mechanical Transduction and the Dark Energy of Biology. Biophys J 2018; 114:3-9. [PMID: 29320693 PMCID: PMC5984904 DOI: 10.1016/j.bpj.2017.10.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 09/26/2017] [Accepted: 10/11/2017] [Indexed: 12/27/2022] Open
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69
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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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70
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Abstract
Bacteria represent one of the most evolutionarily successful groups of organisms to inhabit Earth. Their world is awash with mechanical cues, probably the most ancient form of which are osmotic forces. As a result, they have developed highly robust mechanosensors in the form of bacterial mechanosensitive (MS) channels. These channels are essential in osmoregulation, and in this setting, provide one of the simplest paradigms for the study of mechanosensory transduction. We explore the past, present, and future of bacterial MS channels, including the alternate mechanosensory roles that they may play in complex microbial communities. Central to all of these functions is their ability to change conformation in response to mechanical stimuli. We discuss their gating according to the force-from-lipids principle and its applicability to eukaryotic MS channels. This includes the new paradigms emerging for bilayer-mediated channel mechanosensitivity and how this molecular detail may provide advances in both industry and medicine.
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Affiliation(s)
- Charles D Cox
- Victor Chang Cardiac Research Institute, Sydney, New South Wales 2010, Australia; , , .,St. Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2010, Australia
| | - Navid Bavi
- Victor Chang Cardiac Research Institute, Sydney, New South Wales 2010, Australia; , , .,St. Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Sydney, New South Wales 2010, Australia; , , .,St. Vincent's Clinical School, University of New South Wales, Sydney, New South Wales 2010, Australia
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71
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Ackermann K, Pliotas C, Valera S, Naismith JH, Bode BE. Sparse Labeling PELDOR Spectroscopy on Multimeric Mechanosensitive Membrane Channels. Biophys J 2017; 113:1968-1978. [PMID: 29117521 PMCID: PMC5685675 DOI: 10.1016/j.bpj.2017.09.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 08/31/2017] [Accepted: 09/05/2017] [Indexed: 11/17/2022] Open
Abstract
Pulse electron paramagnetic resonance (EPR) is being applied to ever more complex biological systems comprising multiple subunits. Membrane channel proteins are of great interest as pulse EPR reports on functionally significant but distinct conformational states in a native environment without the need for crystallization. Pulse EPR, in the form of pulsed electron-electron double resonance (PELDOR), using site-directed spin labeling, is most commonly employed to accurately determine distances (in the nanometer range) between different regions of the structure. However, PELDOR data analysis is more challenging in systems containing more than two spins (e.g., homomultimers) due to distorting multispin effects. Without suppression of these effects, much of the information contained in PELDOR data cannot be reliably retrieved. Thus, it is of utmost importance for future PELDOR applications in structural biology to develop suitable approaches that can overcome the multispin problem. Here, two different approaches for suppressing multispin effects in PELDOR, sparse labeling of the protein (reducing the labeling efficiency f) and reducing the excitation probability of spins (λ), are compared on two distinct bacterial mechanosensitive channels. For both the pentameric channel of large conductance (MscL) and the heptameric channel of small conductance (MscS) of Escherichia coli, mutants containing a spin label in the cytosolic or the transmembrane region were tested. Data demonstrate that distance distributions can be significantly improved with either approach compared to the standard PELDOR measurement, and confirm that λ < 1/(n−1) is needed to sufficiently suppress multispin effects (with n being the number of spins in the system). A clear advantage of the sparse labeling approach is demonstrated for the cytosolic mutants due to a significantly smaller loss in sensitivity. For the transmembrane mutants, this advantage is less pronounced but still useful for MscS, but performance is inferior for MscL possibly due to structural perturbations by the bulkier diamagnetic spin label analog.
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Affiliation(s)
- Katrin Ackermann
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Christos Pliotas
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Silvia Valera
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - James H Naismith
- Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom
| | - Bela E Bode
- Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom; Biomedical Sciences Research Complex and EaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife, United Kingdom.
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72
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Muraoka T, Umetsu K, Tabata KV, Hamada T, Noji H, Yamashita T, Kinbara K. Mechano-Sensitive Synthetic Ion Channels. J Am Chem Soc 2017; 139:18016-18023. [DOI: 10.1021/jacs.7b09515] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Takahiro Muraoka
- School
of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
- Precursory
Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Kaori Umetsu
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1,
Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Kazuhito V. Tabata
- Department
of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Tsutomu Hamada
- School
of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan
| | - Hiroyuki Noji
- Department
of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Takashi Yamashita
- Department
of Pure and Applied Chemistry, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
| | - Kazushi Kinbara
- School
of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1,
Katahira, Aoba-ku, Sendai 980-8577, Japan
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73
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Song Y, Zhang B, Guo F, Yang M, Li Y, Liu ZQ. Identification of Intracellular β-Barrel Residues Involved in Ion Selectivity in the Mechanosensitive Channel of Thermoanaerobacter tengcongensis. Front Physiol 2017; 8:832. [PMID: 29118717 PMCID: PMC5661003 DOI: 10.3389/fphys.2017.00832] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 10/06/2017] [Indexed: 11/13/2022] Open
Abstract
The mechanosensitive channel of small conductance (MscS) is a bacterial membrane pore that senses membrane tension and protects cells from lysis by releasing osmolytes. MscS is a homoheptameric channel with a cytoplasmic domain with seven portals and a β-barrel opening to the cytoplasm. TtMscS, an MscS channel from Thermoanaerobacter tengcongensis, is an anion-selective channel. A previous study from our laboratory has defined the crucial role of β-barrel in the anion selectivity of TtMscS (Zhang et al., 2012). However, the mechanistic details by which the β-barrel determines anion selectivity remain unclear. Here, using mutagenesis and patch-clamp recordings, we investigated the function and structural correlations between β-barrels and the anion selectivity of TtMscS at the atomic level. Our results indicated that mutation of V274, a residue at the center of the inner wall of the β-barrel in TtMscS, caused the anion selectivity of TtMscS reverse to cation selectivity. Moreover, the electrostatic potential (T272) and physical size (L276) of residues in the inner wall of β-barrel also determine the anion selectivity of TtMscS. In summary, the present study confirmed that the β-barrel region of TtMscS acts as a “selective filter” that renders TtMscS anion selectivity.
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Affiliation(s)
- Yingcai Song
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China
| | - Bing Zhang
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Fei Guo
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Maojun Yang
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yang Li
- Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Zhi-Qiang Liu
- Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China
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74
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Shapovalov G, Ritaine A, Bidaux G, Slomianny C, Borowiec AS, Gordienko D, Bultynck G, Skryma R, Prevarskaya N. Organelle membrane derived patches: reshaping classical methods for new targets. Sci Rep 2017; 7:14082. [PMID: 29074990 PMCID: PMC5658434 DOI: 10.1038/s41598-017-13968-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/04/2017] [Indexed: 12/12/2022] Open
Abstract
Intracellular ion channels are involved in multiple signaling processes, including such crucial ones as regulation of cellular motility and fate. With 95% of the cellular membrane belonging to intracellular organelles, it is hard to overestimate the importance of intracellular ion channels. Multiple studies have been performed on these channels over the years, however, a unified approach allowing not only to characterize their activity but also to study their regulation by partner proteins, analogous to the patch clamp “golden standard”, is lacking. Here, we present a universal approach that combines the extraction of intracellular membrane fractions with the preparation of patchable substrates that allows to characterize these channels in endogenous protein environment and to study their regulation by partner proteins. We validate this method by characterizing activity of multiple intracellular ion channels localized to different organelles and by providing detailed electrophysiological characterization of the regulation of IP3R activity by endogenous Bcl-2. Thus, after synthesis and reshaping of the well-established approaches, organelle membrane derived patch clamp provides the means to assess ion channels from arbitrary cellular membranes at the single channel level.
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Affiliation(s)
- George Shapovalov
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Abigaël Ritaine
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Gabriel Bidaux
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Christian Slomianny
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Anne-Sophie Borowiec
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Dmitri Gordienko
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Herestraat 49, BE-3000, Leuven, Belgium
| | - Roman Skryma
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Natalia Prevarskaya
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France. .,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.
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75
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Chen Y, Ju L, Rushdi M, Ge C, Zhu C. Receptor-mediated cell mechanosensing. Mol Biol Cell 2017; 28:3134-3155. [PMID: 28954860 PMCID: PMC5687017 DOI: 10.1091/mbc.e17-04-0228] [Citation(s) in RCA: 124] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 09/06/2017] [Accepted: 09/19/2017] [Indexed: 12/22/2022] Open
Abstract
Mechanosensing depicts the ability of a cell to sense mechanical cues, which under some circumstances is mediated by the surface receptors. In this review, a four-step model is described for receptor-mediated mechanosensing. Platelet GPIb, T-cell receptor, and integrins are used as examples to illustrate the key concepts and players in this process. Mechanosensing describes the ability of a cell to sense mechanical cues of its microenvironment, including not only all components of force, stress, and strain but also substrate rigidity, topology, and adhesiveness. This ability is crucial for the cell to respond to the surrounding mechanical cues and adapt to the changing environment. Examples of responses and adaptation include (de)activation, proliferation/apoptosis, and (de)differentiation. Receptor-mediated cell mechanosensing is a multistep process that is initiated by binding of cell surface receptors to their ligands on the extracellular matrix or the surface of adjacent cells. Mechanical cues are presented by the ligand and received by the receptor at the binding interface; but their transmission over space and time and their conversion into biochemical signals may involve other domains and additional molecules. In this review, a four-step model is described for the receptor-mediated cell mechanosensing process. Platelet glycoprotein Ib, T-cell receptor, and integrins are used as examples to illustrate the key concepts and players in this process.
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Affiliation(s)
- Yunfeng Chen
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332.,Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332
| | - Lining Ju
- Charles Perkins Centre and Heart Research Institute, University of Sydney, Camperdown, NSW 2006, Australia
| | - Muaz Rushdi
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332.,Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
| | - Chenghao Ge
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332.,Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
| | - Cheng Zhu
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 .,Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332.,Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332
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76
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Çetiner U, Rowe I, Schams A, Mayhew C, Rubin D, Anishkin A, Sukharev S. Tension-activated channels in the mechanism of osmotic fitness in Pseudomonas aeruginosa. J Gen Physiol 2017; 149:595-609. [PMID: 28424229 PMCID: PMC5412531 DOI: 10.1085/jgp.201611699] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 01/16/2017] [Accepted: 03/20/2017] [Indexed: 12/14/2022] Open
Abstract
Pseudomonas aeruginosa is resistant to drastic osmotic changes because of its ability to quickly jettison small osmolytes through osmotic release channels. Çetiner et al. reveal that it uses one MscL-like and at least two types of MscS-like channels during its osmotic response. Pseudomonas aeruginosa (PA) is an opportunistic pathogen with an exceptional ability to adapt to a range of environments. Part of its adaptive potential is the ability to survive drastic osmolarity changes. Upon a sudden dilution of external medium, such as during exposure to rain, bacteria evade mechanical rupture by engaging tension-activated channels that act as osmolyte release valves. In this study, we compare fast osmotic permeability responses in suspensions of wild-type PA and Escherichia coli (EC) strains in stopped-flow experiments and provide electrophysiological descriptions of osmotic-release channels in PA. Using osmotic dilution experiments, we first show that PA tolerates a broader range of shocks than EC. We record the kinetics of cell equilibration reported by light scattering responses to osmotic up- and down-shocks. PA exhibits a lower water permeability and faster osmolyte release rates during large osmotic dilutions than EC, which correlates with better survival. To directly characterize the PA tension-activated channels, we generate giant spheroplasts from this microorganism and record current responses in excised patches. Unlike EC, which relies primarily on two types of channels, EcMscS and EcMscL, to generate a distinctive two-wave pressure ramp response, PA exhibits a more gradual response that is dominated by MscL-type channels. Genome analysis, cloning, and expression reveal that PA possesses one MscL-type (PaMscL) and two MscS-type (PaMscS-1 and 2) proteins. In EC spheroplasts, both PaMscS channels exhibit a slightly earlier activation by pressure compared with EcMscS. Unitary currents reveal that PaMscS-2 has a smaller conductance, higher anionic preference, stronger inactivation, and slower recovery compared with PaMscS-1. We conclude that PA relies on MscL as the major valve defining a high rate of osmolyte release sufficient to curb osmotic swelling under extreme shocks, but it still requires MscS-type channels with a strong propensity to inactivation to properly terminate massive permeability response.
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Affiliation(s)
- Uğur Çetiner
- Department of Biology, University of Maryland, College Park, MD 20742.,Institute of Physical Science and Technology, University of Maryland, College Park, MD 20742.,Maryland Biophysics Program, University of Maryland, College Park, MD 20742
| | - Ian Rowe
- Department of Biology, University of Maryland, College Park, MD 20742.,Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742
| | - Anthony Schams
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Christina Mayhew
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Deanna Rubin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, MD 20742 .,Institute of Physical Science and Technology, University of Maryland, College Park, MD 20742.,Maryland Biophysics Program, University of Maryland, College Park, MD 20742
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77
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Rosholm KR, Baker MAB, Ridone P, Nakayama Y, Rohde PR, Cuello LG, Lee LK, Martinac B. Activation of the mechanosensitive ion channel MscL by mechanical stimulation of supported Droplet-Hydrogel bilayers. Sci Rep 2017; 7:45180. [PMID: 28345591 PMCID: PMC5366917 DOI: 10.1038/srep45180] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 02/17/2017] [Indexed: 11/29/2022] Open
Abstract
The droplet on hydrogel bilayer (DHB) is a novel platform for investigating the function of ion channels. Advantages of this setup include tight control of all bilayer components, which is compelling for the investigation of mechanosensitive (MS) ion channels, since they are highly sensitive to their lipid environment. However, the activation of MS ion channels in planar supported lipid bilayers, such as the DHB, has not yet been established. Here we present the activation of the large conductance MS channel of E. coli, (MscL), in DHBs. By selectively stretching the droplet monolayer with nanolitre injections of buffer, we induced quantifiable DHB tension, which could be related to channel activity. The MscL activity response revealed that the droplet monolayer tension equilibrated over time, likely by insertion of lipid from solution. Our study thus establishes a method to controllably activate MS channels in DHBs and thereby advances studies of MS channels in this novel platform.
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Affiliation(s)
- Kadla R Rosholm
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia
| | - Matthew A B Baker
- School of Medical Sciences, University of New South Wales, Kensington, NSW 2052, Australia
| | - Pietro Ridone
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia
| | - Yoshitaka Nakayama
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia
| | - Paul R Rohde
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia
| | - Luis G Cuello
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Lawrence K Lee
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia.,School of Medical Sciences, University of New South Wales, Kensington, NSW 2052, Australia
| | - Boris Martinac
- The Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinghurst, NSW 2010, Australia.,St Vincent's Clinical School, Darlinghurst, NSW 2010, Australia
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78
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Gnanasambandam R, Gottlieb PA, Sachs F. The Kinetics and the Permeation Properties of Piezo Channels. CURRENT TOPICS IN MEMBRANES 2017; 79:275-307. [PMID: 28728821 DOI: 10.1016/bs.ctm.2016.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Piezo channels are eukaryotic, cation-selective mechanosensitive channels (MSCs), which show rapid activation and voltage-dependent inactivation. The kinetics of these channels are largely consistent across multiple cell types and different stimulation paradigms with some minor variability. No accessory subunits that associate with Piezo channels have been reported. They are homotrimers and each ∼300kD monomer has an N-terminal propeller blade-like mechanosensing module, which can confer mechanosensing capabilities on ASIC-1 (the trimeric non-MSC, acid-sensing ion channel-1) and a C-terminal pore module, which influences conductance, selectivity, and channel inactivation. Repeated stimulation can cause domain fracture and diffusion of these channels leading to synchronous loss of inactivation. The reconstituted channels spontaneously open only in asymmetric bilayers but lack inactivation. Mutations that cause hereditary xerocytosis alter PIEZO1 kinetics. The kinetics of the wild-type PIEZO1 and alterations thereof in mutants (M2225R, R2456K, and DhPIEZO1) are summarized in the form of a quantitative model and hosted online. The pore is permeable to alkali ions although Li+ permeates poorly. Divalent cations, notably Ca2+, traverse the channel and inhibit the flux of monovalents. The large monovalent organic cations such as tetramethyl ammonium and tetraethyl ammonium can traverse the channel, but slowly, suggesting a pore diameter of ∼8Å, and the estimated in-plane area change upon opening is around 6-20nm2. Ruthenium red can enter the channel only from the extracellular side and seems to bind in a pocket close to residue 2496.
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Affiliation(s)
- R Gnanasambandam
- State University of New York at Buffalo, Buffalo, NY, United States
| | - P A Gottlieb
- State University of New York at Buffalo, Buffalo, NY, United States
| | - F Sachs
- State University of New York at Buffalo, Buffalo, NY, United States
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79
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80
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Dynamics of Escherichia coli's passive response to a sudden decrease in external osmolarity. Proc Natl Acad Sci U S A 2016; 113:E5838-E5846. [PMID: 27647888 DOI: 10.1073/pnas.1522185113] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For most cells, a sudden decrease in external osmolarity results in fast water influx that can burst the cell. To survive, cells rely on the passive response of mechanosensitive channels, which open under increased membrane tension and allow the release of cytoplasmic solutes and water. Although the gating and the molecular structure of mechanosensitive channels found in Escherichia coli have been extensively studied, the overall dynamics of the whole cellular response remain poorly understood. Here, we characterize E. coli's passive response to a sudden hypoosmotic shock (downshock) on a single-cell level. We show that initial fast volume expansion is followed by a slow volume recovery that can end below the initial value. Similar response patterns were observed at downshocks of a wide range of magnitudes. Although wild-type cells adapted to osmotic downshocks and resumed growing, cells of a double-mutant ([Formula: see text]) strain expanded, but failed to fully recover, often lysing or not resuming growth at high osmotic downshocks. We propose a theoretical model to explain our observations by simulating mechanosensitive channels opening, and subsequent solute efflux and water flux. The model illustrates how solute efflux, driven by mechanical pressure and solute chemical potential, competes with water influx to reduce cellular osmotic pressure and allow volume recovery. Our work highlights the vital role of mechanosensation in bacterial survival.
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81
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Abstract
Patch clamp recordings from ion channels often show periods of repetitive activity, known as bursts, which are noticeably separated from each other by periods of inactivity. Depending on the type of channel, such recordings may exhibit (conductance) levels between the closed (zero) level and the fully open level. Properties of bursts are less subject to problems that arise from recording than are properties for individual sojourns at different levels, and study of bursting behaviour provides important information about the finer structure of the underlying channel gating process. For a general finite state space continuous-time Markov chain model allowing one or more nonzero conductance levels, the present paper establishes results about the semi-Markov structure of a single burst and of a sequence of bursts, and uses this in a unified approach to properties of both theoretical and empirical bursts. The distribution and moments of particular burst properties, including the total charge transfer, the total sojourn time and the total number of visits to specified conductance levels during a burst, are derived. Various extensions are also described.
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82
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Freeman EC, Najem JS, Sukharev S, Philen MK, Leo DJ. The mechanoelectrical response of droplet interface bilayer membranes. SOFT MATTER 2016; 12:3021-3031. [PMID: 26905644 DOI: 10.1039/c5sm02779a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Mechanotransduction and interfacial properties in unsupported liquid biomimetic membranes are explored using the droplet-interface bilayer technique. The fluidic monolayer-membrane system afforded by this technique allows for dynamic control over the membrane dimensions and curvature, which under periodic deformations generates capacitive currents (akin to a Kelvin probe), and permits a detailed electrostatic characterization of the boundary layers as well as observation of flexoelectric effects. Both high and low displacement frequency regimes are examined, and the results show that the mechanoelectric signals generated by the membranes may be linked to the membrane electrostatic structure. In addition, we show that periodic membrane bending in a high-frequency regime generates tension sufficient to activate reconstituted mechanosensitive channels.
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Affiliation(s)
- E C Freeman
- College of Engineering, University of Georgia, USA.
| | - J S Najem
- Department of Mechanical Engineering, Virginia Tech, USA
| | - S Sukharev
- Department of Biology, University of Maryland, USA
| | - M K Philen
- Department of Aerospace and Ocean Engineering, Virginia Tech, USA
| | - D J Leo
- College of Engineering, University of Georgia, USA.
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83
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Zhu L, Wu J, Liu L, Liu Y, Yan Y, Cui Q, Chen X. Gating mechanism of mechanosensitive channel of large conductance: a coupled continuum mechanical-continuum solvation approach. Biomech Model Mechanobiol 2016; 15:1557-1576. [PMID: 27009075 DOI: 10.1007/s10237-016-0783-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 03/09/2016] [Indexed: 10/22/2022]
Abstract
Gating transition of the mechanosensitive channel of large conductance (MscL) represents a good example of important biological processes that are difficult to describe using atomistic simulations due to the large (submicron) length scale and long (millisecond) time scale. Here we develop a novel computational framework that tightly couples continuum mechanics with continuum solvation models to study the detailed gating behavior of E. coli-MscL. The components of protein molecules are modeled by continuum elements that properly describe their shape, material properties and physicochemical features (e.g., charge distribution). The lipid membrane is modeled as a three-layer material in which the lipid head group and tail regions are treated separately, taking into account the fact that fluidic lipid bilayers do not bear shear stress. Coupling between mechanical and chemical responses of the channel is realized by an iterative integration of continuum mechanics (CM) modeling and continuum solvation (CS) computation. Compared to previous continuum mechanics studies, the present model is capable of capturing the most essential features of the gating process in a much more realistic fashion: due mainly to the apolar solvation contribution, the membrane tension for full opening of MscL is reduced substantially to the experimental measured range. Moreover, the pore size stabilizes constantly during gating because of the intricate interactions of the multiple components of the system, implying the mechanism for sub-conducting states of MscL gating. A significant fraction ([Formula: see text]2/3) of the gating membrane strain is required to reach the first sub-conducting state of our model, which is featured with a relative conductance of 0.115 to the fully opened state. These trends agree well with experimental observations. We anticipate that the coupled CM/CS modeling framework is uniquely suited for the analysis of many biomolecules and their assemblies under external mechanical stimuli.
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Affiliation(s)
- Liangliang Zhu
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, People's Republic of China.,Columbia Nanomechanics Research Center, Department of Earth and Environmental Engineering, Columbia University, New York, NY, 10027, USA
| | - Jiazhong Wu
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, People's Republic of China
| | - Ling Liu
- Department of Mechanical and Aerospace Engineering, Utah State University, Logan, UT, 84322, USA
| | - Yilun Liu
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, People's Republic of China
| | - Yuan Yan
- International Center for Applied Mechanics, State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace, Xi'an Jiaotong University, Xi'an, 710049, People's Republic of China
| | - Qiang Cui
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Xi Chen
- Columbia Nanomechanics Research Center, Department of Earth and Environmental Engineering, Columbia University, New York, NY, 10027, USA.
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84
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Cox CD, Bae C, Ziegler L, Hartley S, Nikolova-Krstevski V, Rohde PR, Ng CA, Sachs F, Gottlieb PA, Martinac B. Removal of the mechanoprotective influence of the cytoskeleton reveals PIEZO1 is gated by bilayer tension. Nat Commun 2016; 7:10366. [PMID: 26785635 PMCID: PMC4735864 DOI: 10.1038/ncomms10366] [Citation(s) in RCA: 330] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 12/04/2015] [Indexed: 12/18/2022] Open
Abstract
Mechanosensitive ion channels are force-transducing enzymes that couple mechanical stimuli to ion flux. Understanding the gating mechanism of mechanosensitive channels is challenging because the stimulus seen by the channel reflects forces shared between the membrane, cytoskeleton and extracellular matrix. Here we examine whether the mechanosensitive channel PIEZO1 is activated by force-transmission through the bilayer. To achieve this, we generate HEK293 cell membrane blebs largely free of cytoskeleton. Using the bacterial channel MscL, we calibrate the bilayer tension demonstrating that activation of MscL in blebs is identical to that in reconstituted bilayers. Utilizing a novel PIEZO1-GFP fusion, we then show PIEZO1 is activated by bilayer tension in bleb membranes, gating at lower pressures indicative of removal of the cortical cytoskeleton and the mechanoprotection it provides. Thus, PIEZO1 channels must sense force directly transmitted through the bilayer.
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Affiliation(s)
- Charles D. Cox
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Chilman Bae
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Lynn Ziegler
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Silas Hartley
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | | | - Paul R. Rohde
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
| | - Chai-Ann Ng
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
| | - Frederick Sachs
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
- The Centre for Single Molecule Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Philip A. Gottlieb
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
- The Centre for Single Molecule Biophysics, State University of New York at Buffalo, Buffalo, New York 14214, USA
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Darlinghurst, New South Wales 2010, Australia
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85
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Nazarski RB, Wałejko P, Witkowski S. Multi-conformer molecules in solutions: an NMR-based DFT/MP2 conformational study of two glucopyranosides of a vitamin E model compound. Org Biomol Chem 2016; 14:3142-58. [DOI: 10.1039/c5ob01865j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Overall geometries of both glucosyl derivatives of PMC were found on the basis of their NMR spectra in CDCl3and relatedδH,C/nJHHIEF-PCM(UFF,CHCl3)/DFT calculational results.
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Affiliation(s)
- Ryszard B. Nazarski
- University of Łódź
- Faculty of Chemistry
- Department of Theoretical and Structural Chemistry
- 90-236 Łódź
- Poland
| | - Piotr Wałejko
- University of Białystok
- Institute of Chemistry
- 15-245 Białystok
- Poland
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86
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87
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Kayal A, Chandra A. Wetting and dewetting of narrow hydrophobic channels by orthogonal electric fields: Structure, free energy, and dynamics for different water models. J Chem Phys 2015; 143:224708. [DOI: 10.1063/1.4936939] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Abhijit Kayal
- Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
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88
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Lewis AH, Grandl J. Mechanical sensitivity of Piezo1 ion channels can be tuned by cellular membrane tension. eLife 2015; 4. [PMID: 26646186 PMCID: PMC4718726 DOI: 10.7554/elife.12088] [Citation(s) in RCA: 244] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/26/2015] [Indexed: 12/17/2022] Open
Abstract
Piezo1 ion channels mediate the conversion of mechanical forces into electrical signals and are critical for responsiveness to touch in metazoans. The apparent mechanical sensitivity of Piezo1 varies substantially across cellular environments, stimulating methods and protocols, raising the fundamental questions of what precise physical stimulus activates the channel and how its stimulus sensitivity is regulated. Here, we measured Piezo1 currents evoked by membrane stretch in three patch configurations, while simultaneously visualizing and measuring membrane geometry. Building on this approach, we developed protocols to minimize resting membrane curvature and tension prior to probing Piezo1 activity. We find that Piezo1 responds to lateral membrane tension with exquisite sensitivity as compared to other mechanically activated channels and that resting tension can drive channel inactivation, thereby tuning overall mechanical sensitivity of Piezo1. Our results explain how Piezo1 can function efficiently and with adaptable sensitivity as a sensor of mechanical stimulation in diverse cellular contexts. DOI:http://dx.doi.org/10.7554/eLife.12088.001 Piezo ion channels are proteins that are embedded in the cell membranes of many types of tissue, including the heart, lung, skin and kidney. These proteins are essential for many biological processes, including sensing gentle touches and ensuring that blood vessels develop properly. When stimulated by mechanical forces, a central pore in the Piezo channel opens to allow positively charged ions to flow into the cell, which triggers electrical and chemical signaling processes inside the cell. However, it was not known exactly what type of mechanical stimulus is sensed by Piezo ion channels. Lewis and Grandl expressed Piezo ion channels in cultured human kidney cells, and opened them by applying pressure to parts of the cell membrane inside a glass pipette. This causes a number of changes to the membrane, including to its curvature and tension, either of which could potentially open the Piezo channels. However, Lewis and Grandl were able to calculate from images of the cell membrane inside the pipette that tension is the activating stimulus. Further experiments unexpectedly revealed that the tension that is usually present in the cell membrane is sufficient to inactivate Piezo channels and prevent them from responding to an additional mechanical stimulus. This suggests that Piezo ion channels are inherently more sensitive to tension than previously realized, which could explain why different cell types appear to have different sensitivities to pressure. Although Lewis and Grandl have now shown that Piezo channels are activated by tension, more work is needed to investigate how the Piezo ion channel senses this force, and how this leads to the channel pore opening. DOI:http://dx.doi.org/10.7554/eLife.12088.002
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Affiliation(s)
- Amanda H Lewis
- Department of Neurobiology, Duke University Medical Center, Durham, United States
| | - Jörg Grandl
- Department of Neurobiology, Duke University Medical Center, Durham, United States
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89
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Pliotas C, Dahl ACE, Rasmussen T, Mahendran KR, Smith TK, Marius P, Gault J, Banda T, Rasmussen A, Miller S, Robinson CV, Bayley H, Sansom MSP, Booth IR, Naismith JH. The role of lipids in mechanosensation. Nat Struct Mol Biol 2015; 22:991-8. [PMID: 26551077 PMCID: PMC4675090 DOI: 10.1038/nsmb.3120] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 10/06/2015] [Indexed: 12/13/2022]
Abstract
The ability of proteins to sense membrane tension is pervasive in biology. A higher-resolution structure of the Escherichia coli small-conductance mechanosensitive channel MscS identifies alkyl chains inside pockets formed by the transmembrane helices (TMs). Purified MscS contains E. coli lipids, and fluorescence quenching demonstrates that phospholipid acyl chains exchange between bilayer and TM pockets. Molecular dynamics and biophysical analyses show that the volume of the pockets and thus the number of lipid acyl chains within them decreases upon channel opening. Phospholipids with one acyl chain per head group (lysolipids) displace normal phospholipids (with two acyl chains) from MscS pockets and trigger channel opening. We propose that the extent of acyl-chain interdigitation in these pockets determines the conformation of MscS. When interdigitation is perturbed by increased membrane tension or by lysolipids, the closed state becomes unstable, and the channel gates.
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Affiliation(s)
- Christos Pliotas
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | | | - Tim Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Terry K Smith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Phedra Marius
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
| | - Joseph Gault
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Thandiwe Banda
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Akiko Rasmussen
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Samantha Miller
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | | | - Hagan Bayley
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Ian R Booth
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA
| | - James H Naismith
- Biomedical Sciences Research Complex, University of St. Andrews, St. Andrews, UK
- State Key Laboratory of Biotherapy, Sichuan University, Chengdu, China
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90
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Najem JS, Dunlap MD, Yasmann A, Freeman EC, Grant JW, Sukharev S, Leo DJ. Multifunctional, Micropipette-based Method for Incorporation And Stimulation of Bacterial Mechanosensitive Ion Channels in Droplet Interface Bilayers. J Vis Exp 2015. [PMID: 26650467 PMCID: PMC4692740 DOI: 10.3791/53362] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
MscL, a large conductance mechanosensitive channel (MSC), is a ubiquitous osmolyte release valve that helps bacteria survive abrupt hypo-osmotic shocks. It has been discovered and rigorously studied using the patch-clamp technique for almost three decades. Its basic role of translating tension applied to the cell membrane into permeability response makes it a strong candidate to function as a mechanoelectrical transducer in artificial membrane-based biomolecular devices. Serving as building blocks to such devices, droplet interface bilayers (DIBs) can be used as a new platform for the incorporation and stimulation of MscL channels. Here, we describe a micropipette-based method to form DIBs and measure the activity of the incorporated MscL channels. This method consists of lipid-encased aqueous droplets anchored to the tips of two opposing (coaxially positioned) borosilicate glass micropipettes. When droplets are brought into contact, a lipid bilayer interface is formed. This technique offers control over the chemical composition and the size of each droplet, as well as the dimensions of the bilayer interface. Having one of the micropipettes attached to a harmonic piezoelectric actuator provides the ability to deliver a desired oscillatory stimulus. Through analysis of the shapes of the droplets during deformation, the tension created at the interface can be estimated. Using this technique, the first activity of MscL channels in a DIB system is reported. Besides MS channels, activities of other types of channels can be studied using this method, proving the multi-functionality of this platform. The method presented here enables the measurement of fundamental membrane properties, provides a greater control over the formation of symmetric and asymmetric membranes, and is an alternative way to stimulate and study mechanosensitive channels.
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Affiliation(s)
- Joseph S Najem
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University
| | - Myles D Dunlap
- School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University
| | | | | | - John W Grant
- Department of Engineering Sciences and Mechanics, Virginia Polytechnic Institute and State University
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91
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Abstract
Escherichia coli and Salmonella encounter osmotic pressure variations in natural environments that include host tissues, food, soil, and water. Osmotic stress causes water to flow into or out of cells, changing their structure, physics, and chemistry in ways that perturb cell functions. E. coli and Salmonella limit osmotically induced water fluxes by accumulating and releasing electrolytes and small organic solutes, some denoted compatible solutes because they accumulate to high levels without disturbing cell functions. Osmotic upshifts inhibit membrane-based energy transduction and macromolecule synthesis while activating existing osmoregulatory systems and specifically inducing osmoregulatory genes. The osmoregulatory response depends on the availability of osmoprotectants (exogenous organic compounds that can be taken up to become compatible solutes). Without osmoprotectants, K+ accumulates with counterion glutamate, and compatible solute trehalose is synthesized. Available osmoprotectants are taken up via transporters ProP, ProU, BetT, and BetU. The resulting compatible solute accumulation attenuates the K+ glutamate response and more effectively restores cell hydration and growth. Osmotic downshifts abruptly increase turgor pressure and strain the cytoplasmic membrane. Mechanosensitive channels like MscS and MscL open to allow nonspecific solute efflux and forestall cell lysis. Research frontiers include (i) the osmoadaptive remodeling of cell structure, (ii) the mechanisms by which osmotic stress alters gene expression, (iii) the mechanisms by which transporters and channels detect and respond to osmotic pressure changes, (iv) the coordination of osmoregulatory programs and selection of available osmoprotectants, and (v) the roles played by osmoregulatory mechanisms as E. coli and Salmonella survive or thrive in their natural environments.
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92
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Najem JS, Dunlap MD, Rowe ID, Freeman EC, Grant JW, Sukharev S, Leo DJ. Activation of bacterial channel MscL in mechanically stimulated droplet interface bilayers. Sci Rep 2015; 5:13726. [PMID: 26348441 PMCID: PMC4562232 DOI: 10.1038/srep13726] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 08/03/2015] [Indexed: 02/01/2023] Open
Abstract
MscL, a stretch-activated channel, saves bacteria experiencing hypo-osmotic shocks from lysis. Its high conductance and controllable activation makes it a strong candidate to serve as a transducer in stimuli-responsive biomolecular materials. Droplet interface bilayers (DIBs), flexible insulating scaffolds for such materials, can be used as a new platform for incorporation and activation of MscL. Here, we report the first reconstitution and activation of the low-threshold V23T mutant of MscL in a DIB as a response to axial compressions of the droplets. Gating occurs near maximum compression of both droplets where tension in the membrane is maximal. The observed 0.1-3 nS conductance levels correspond to the V23T-MscL sub-conductive and fully open states recorded in native bacterial membranes or liposomes. Geometrical analysis of droplets during compression indicates that both contact angle and total area of the water-oil interfaces contribute to the generation of tension in the bilayer. The measured expansion of the interfaces by 2.5% is predicted to generate a 4-6 mN/m tension in the bilayer, just sufficient for gating. This work clarifies the principles of interconversion between bulk and surface forces in the DIB, facilitates the measurements of fundamental membrane properties, and improves our understanding of MscL response to membrane tension.
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Affiliation(s)
- Joseph S. Najem
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Myles D. Dunlap
- School of Biomedical Engineering and Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Ian D. Rowe
- Department of Biology, University of Maryland, College Park, Maryland 20742, United States
| | - Eric C. Freeman
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
| | - John W. Grant
- Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Sergei Sukharev
- Department of Biology, University of Maryland, College Park, Maryland 20742, United States
| | - Donald J. Leo
- College of Engineering, University of Georgia, Athens, Georgia 30602, United States
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93
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Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion. Proc Natl Acad Sci U S A 2015; 112:10726-31. [PMID: 26261325 PMCID: PMC4553819 DOI: 10.1073/pnas.1503202112] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 Å wide, exhibiting a large unitary conductance of ∼ 3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an ω-shaped loop and a short β-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands.
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94
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Hidden Markov analysis of improved bandwidth mechanosensitive ion channel data. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:545-56. [PMID: 26233758 DOI: 10.1007/s00249-015-1060-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 07/04/2015] [Indexed: 10/23/2022]
Abstract
The gating behaviour of a single ion channel can be described by hidden Markov models (HMMs), forming the basis for statistical analysis of patch clamp data. Extensive improved bandwidth (25 kHz, 50 kHz) data from the mechanosensitive channel of large conductance in Escherichia coli were analysed using HMMs, and HMMs with a moving average adjustment for filtering. The aim was to determine the number of levels, and mean current, mean dwell time and proportion of time at each level. Parameter estimates for HMMs with a moving average adjustment for low-pass filtering were obtained using an expectation-maximisation algorithm that depends on a generalisation of Baum's forward-backward algorithm. This results in a simpler algorithm than those based on meta-states and a much smaller parameter space; hence, the computational load is substantially reduced. In addition, this algorithm maximises the actual log-likelihood rather than that for a related meta-state process. Comprehensive data analyses and comparisons across all our data sets have consistently shown five subconducting levels in addition to the fully open and closed levels for this channel.
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95
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Damodaran S. Beyond the hydrophobic effect: Critical function of water at biological phase boundaries--A hypothesis. Adv Colloid Interface Sci 2015; 221:22-33. [PMID: 25888225 DOI: 10.1016/j.cis.2015.03.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 03/24/2015] [Accepted: 03/25/2015] [Indexed: 11/29/2022]
Abstract
Many life-sustaining processes in living cells occur at the membrane-water interface. The pertinent questions that need to be asked are what is the evolutionary reason for biology to choose the membrane-water interface as the site for performing and/or controlling crucial biological reactions and what is the key physical principle that is singular to the membrane-water interface that biology exploits for regulating metabolic processes in cells? In this review, a hypothesis is developed, which espouses that cells control activities of membrane-bound enzymes and receptor activated processes via manipulating the thermodynamic activity of water at the membrane-water interfacial region. In support of this hypothesis, first we establish that the surface pressure of a lipid monolayer is a direct measure of a reduction in the thermodynamic activity of interfacial water. Second, we show that the surface pressure-dependent activation/inactivation of interfacial enzymes is fundamentally related to their dependence on interfacial water activity. We extend this argument to infer that cells might manipulate activities of membrane-associated biological processes via manipulating the activity of interfacial water via localized compression or expansion of the interface. In this paper, we critically analyze literature data on mechano-activation of large pore ion channels in Escherichia coli spheroplasts and G-proteins in reconstituted lipid vesicles, and show that these pressure-induced activation processes are fundamentally and quantitatively related to changes in the thermodynamic state of interfacial water, caused by mechanical stretching of the bilayer.
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Affiliation(s)
- Srinivasan Damodaran
- University of Wisconsin-Madison, Department of Food Science, 1605 Linden Drive, Madison, WI 53706, United States.
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96
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Ridone P, Nakayama Y, Martinac B, Battle AR. Patch clamp characterization of the effect of cardiolipin on MscS of E. coli. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:567-76. [DOI: 10.1007/s00249-015-1020-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 03/01/2015] [Accepted: 03/15/2015] [Indexed: 12/12/2022]
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97
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Saddhe AA, Kumar K. In silico identification and expression analysis of MscS like gene family in rice. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.plgene.2014.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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98
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Lee LM, Liu AP. A microfluidic pipette array for mechanophenotyping of cancer cells and mechanical gating of mechanosensitive channels. LAB ON A CHIP 2015; 15:264-73. [PMID: 25361042 PMCID: PMC4256121 DOI: 10.1039/c4lc01218f] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Micropipette aspiration measures the mechanical properties of single cells. A traditional micropipette aspiration system requires a bulky infrastructure and has a low throughput and limited potential for automation. We have developed a simple microfluidic device which is able to trap and apply pressure to single cells in designated aspiration arrays. By changing the volume flow rate using a syringe pump, we can accurately exert a pressure difference across the trapped cells for pipette aspiration. By examining cell deformation and protrusion length into the pipette under an optical microscope, several important cell mechanical properties, such as the cortical tension and the Young's modulus, can be measured quantitatively using automated image analysis. Using the microfluidic pipette array, the stiffness of breast cancer cells and healthy breast epithelial cells was measured and compared. Finally, we applied our device to examine the gating threshold of the mechanosensitive channel MscL expressed in mammalian cells. Together, the development of a microfluidic pipette array could enable rapid mechanophenotyping of individual cells and for mechanotransduction studies.
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Affiliation(s)
- Lap Man Lee
- Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, MI 48105, USA.
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99
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Sokabe M, Sawada Y, Kobayashi T. Ion Channels Activated by Mechanical Forces in Bacterial and Eukaryotic Cells. Subcell Biochem 2015; 72:613-26. [PMID: 26174401 DOI: 10.1007/978-94-017-9918-8_28] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Since the first discovery of mechanosensitive ion channel (MSC) in non-sensory cells in 1984, a variety of MSCs has been identified both in prokaryotic and eukaryotic cells. One of the central issues concerning MSCs is to understand the molecular and biophysical mechanisms of how mechanical forces activate/open MSCs. It has been well established that prokaryotic (mostly bacterial) MSCs are activated exclusively by membrane tension. Thus the problem to be solved with prokaryotic MSCs is the mechanisms how the MSC proteins receive tensile forces from the lipid bilayer and utilize them for channel opening. On the other hand, the activation of many eukaryotic MSCs crucially depends on tension in the actin cytoskeleton. By using the actin cytoskeleton as a force sensing antenna, eukaryotic MSCs have obtained sophisticated functions such as remote force sensing and force-direction sensing, which bacterial MSCs do not have. Actin cytoskeletons also give eukaryotic MSCs an interesting and important function called "active touch sensing", by which cells can sense rigidity of their substrates. The contractile actin cytoskeleton stress fiber (SF) anchors its each end to a focal adhesion (FA) and pulls the substrate to generate substrate-rigidity-dependent stresses in the FA. It has been found that those stresses are sensed by some Ca2+-permeable MSCs existing in the vicinity of FAs, thus the MSCs work as a substrate rigidity sensor that can transduce the rigidity into intracellular Ca2+ levels. This short review, roughly constituting of two parts, deals with molecular and biophysical mechanisms underlying the MSC activation process mostly based on our recent studies; (1) structure-function in bacterial MSCs activation at the atomic level, and (2) roles of actin cytoskeletons in the activation of eukaryotic MSCs.
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Affiliation(s)
- Masahiro Sokabe
- Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya, Japan,
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100
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Water at Biological Phase Boundaries: Its Role in Interfacial Activation of Enzymes and Metabolic Pathways. Subcell Biochem 2015; 71:233-61. [PMID: 26438268 DOI: 10.1007/978-3-319-19060-0_10] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Many life-sustaining activities in living cells occur at the membrane-water interface. The pertinent questions that we need to ask are, what are the evolutionary reasons in biology for choosing the membrane-water interface as the site for performing and/or controlling crucial biological reactions, and what is the key physical principle that is very singular to the membrane-water interface that biology exploits for regulating metabolic processes in cells? In this chapter, a hypothesis is developed, which espouses that cells control activities of membrane-bound enzymes through manipulation of the thermodynamic activity of water in the lipid-water interfacial region. The hypothesis is based on the fact that the surface pressure of a lipid monolayer is a direct measure of the thermodynamic activity of water at the lipid-water interface. Accordingly, the surface pressure-dependent activation or inactivation of interfacial enzymes is directly related to changes in the thermodynamic activity of interfacial water. Extension of this argument suggests that cells may manipulate conformations (and activities) of membrane-bound enzymes by manipulating the (re)activity of interfacial water at various locations in the membrane by localized compression or expansion of the interface. In this respect, cells may use the membrane-bound hormone receptors, lipid phase transition, and local variations in membrane lipid composition as effectors of local compression and/or expansion of membrane, and thereby local water activity. Several experimental data in the literature will be reexamined in the light of this hypothesis.
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