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Caprini D, Battista F, Zajdel P, Di Muccio G, Guardiani C, Trump B, Carter M, Yakovenko AA, Amayuelas E, Bartolomé L, Meloni S, Grosu Y, Casciola CM, Giacomello A. Bubbles enable volumetric negative compressibility in metastable elastocapillary systems. Nat Commun 2024; 15:5076. [PMID: 38871721 DOI: 10.1038/s41467-024-49136-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 05/21/2024] [Indexed: 06/15/2024] Open
Abstract
Although coveted in applications, few materials expand when subject to compression or contract under decompression, i.e., exhibit negative compressibility. A key step to achieve such counterintuitive behaviour is the destabilisations of (meta)stable equilibria of the constituents. Here, we propose a simple strategy to obtain negative compressibility exploiting capillary forces both to precompress the elastic material and to release such precompression by a threshold phenomenon - the reversible formation of a bubble in a hydrophobic flexible cavity. We demonstrate that the solid part of such metastable elastocapillary systems displays negative compressibility across different scales: hydrophobic microporous materials, proteins, and millimetre-sized laminae. This concept is applicable to fields such as porous materials, biomolecules, sensors and may be easily extended to create unexpected material susceptibilities.
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Affiliation(s)
- Davide Caprini
- Center for Life Nano- & Neuro-Science, Istituto Italiano di Tecnologia, Viale Regina Elena 291, Rome, Italy
| | - Francesco Battista
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Via Eudossiana 18, Rome, Italy
| | - Paweł Zajdel
- A. Chełkowski Institute of Physics, University of Silesia, ul 75 Pułku Piechoty 1, Chorzów, Poland
| | - Giovanni Di Muccio
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Via Eudossiana 18, Rome, Italy
| | - Carlo Guardiani
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Via Eudossiana 18, Rome, Italy
| | - Benjamin Trump
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Marcus Carter
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Andrey A Yakovenko
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, USA
| | - Eder Amayuelas
- Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, Vitoria-Gasteiz, Spain
| | - Luis Bartolomé
- Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, Vitoria-Gasteiz, Spain
| | - Simone Meloni
- Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Ferrara, Via Luigi Borsari 46, Ferrara, Italy.
| | - Yaroslav Grosu
- Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48, Vitoria-Gasteiz, Spain.
- Institute of Chemistry, University of Silesia, Katowice, Poland.
| | - Carlo Massimo Casciola
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Via Eudossiana 18, Rome, Italy.
| | - Alberto Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Via Eudossiana 18, Rome, Italy.
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2
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Sawada Y, Nomura T, Martinac B, Sokabe M. A novel force transduction pathway from a tension sensor to the gate in the mechano-gating of MscL channel. Front Chem 2023; 11:1175443. [PMID: 37347044 PMCID: PMC10279863 DOI: 10.3389/fchem.2023.1175443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/22/2023] [Indexed: 06/23/2023] Open
Abstract
The bacterial mechanosensitive channel of large conductance MscL is activated exclusively by increased tension in the membrane bilayer. Despite many proposed models for MscL opening, its precise mechano-gating mechanism, particularly how the received force at the tension sensor transmits to the gate remains incomplete. Previous studies have shown that along with amphipathic N-terminus located near the cytoplasmic surface of the membrane, Phe78 residue near the outer surface also acts as a "tension sensor," while Gly22 is a central constituent of the "hydrophobic gate." Present study focused on elucidating the force transmission mechanism from the sensor Phe78 in the outer transmembrane helix (TM2) to the gate in the inner transmembrane helix (TM1) of MscL by applying the patch clamp and molecular dynamics (MD) simulations to the wild type MscL channel and its single mutants at the sensor (F78N), the gate (G22N) and their combination (G22N/F78N) double mutant. F78N MscL resulted in a severe loss-of-function, while G22N MscL caused a gain-of-function channel exhibiting spontaneous openings at the resting membrane tension. We initially speculated that the spontaneous opening in G22N mutant might occur without tension acting on Phe78 residue. To test this hypothesis, we examined the (G22N/F78N) double mutant, which unexpectedly exhibited neither spontaneous activity nor activity by a relatively high membrane tension. To understand the underlying mechanism, we conducted MD simulations and analyzed the force transduction pathway. Results showed that the mutation at the tension sensor (F78N) in TM2 caused decreased interaction of this residue not only with lipids, but also with a group of amino acids (Ile32-Leu36-Ile40) in the neighboring TM1 helix, which resulted in an inefficient force transmission to the gate-constituting amino acids on TM1. This change also induced a slight tilting of TM1 towards the membrane plane and decreased the size of the channel pore at the gate, which seems to be the major mechanism for the inhibition of spontaneous opening of the double mutant channel. More importantly, the newly identified interaction between the TM2 (Phe78) and adjacent TM1 (Ile32-Leu36-Ile40) helices seems to be an essential force transmitting mechanism for the stretch-dependent activation of MscL given that substitution of any one of these four amino acids with Asn resulted in severe loss-of-function MscL as reported in our previous work.
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Affiliation(s)
- Yasuyuki Sawada
- Department of Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Institute of Materials Innovation, Institutes of Innovation for Future Society, Nagoya University, Nagoya, Japan
| | - Takeshi Nomura
- International Cooperative Research Project, Solution Oriented Research for Science and Technology (ICORP/SORST), Cell Mechanosensing, Japan Science and Technology Agency (JST), Nagoya, Japan
- Molecular Cardiology and Biophysics Division, Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
- School of Human Science and Environment, University of Hyogo, Himeji, Japan
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Masahiro Sokabe
- Department of Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- International Cooperative Research Project, Solution Oriented Research for Science and Technology (ICORP/SORST), Cell Mechanosensing, Japan Science and Technology Agency (JST), Nagoya, Japan
- Human Information Systems Laboratories, Kanazawa Institute of Technology, Hakusan, Ishikawa, Japan
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3
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Li J, Jamieson WD, Dimitriou P, Xu W, Rohde P, Martinac B, Baker M, Drinkwater BW, Castell OK, Barrow DA. Building programmable multicompartment artificial cells incorporating remotely activated protein channels using microfluidics and acoustic levitation. Nat Commun 2022; 13:4125. [PMID: 35840619 PMCID: PMC9287423 DOI: 10.1038/s41467-022-31898-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 07/06/2022] [Indexed: 01/25/2023] Open
Abstract
Intracellular compartments are functional units that support the metabolism within living cells, through spatiotemporal regulation of chemical reactions and biological processes. Consequently, as a step forward in the bottom-up creation of artificial cells, building analogous intracellular architectures is essential for the expansion of cell-mimicking functionality. Herein, we report the development of a droplet laboratory platform to engineer complex emulsion-based, multicompartment artificial cells, using microfluidics and acoustic levitation. Such levitated models provide free-standing, dynamic, definable droplet networks for the compartmentalisation of chemical species. Equally, they can be remotely operated with pneumatic, heating, and magnetic elements for post-processing, including the incorporation of membrane proteins; alpha-hemolysin; and mechanosensitive channel of large-conductance. The assembly of droplet networks is three-dimensionally patterned with fluidic input configurations determining droplet contents and connectivity, whilst acoustic manipulation can be harnessed to reconfigure the droplet network in situ. The mechanosensitive channel can be repeatedly activated and deactivated in the levitated artificial cell by the application of acoustic and magnetic fields to modulate membrane tension on demand. This offers possibilities beyond one-time chemically mediated activation to provide repeated, non-contact, control of membrane protein function. Collectively, this expands our growing capability to program and operate increasingly sophisticated artificial cells as life-like materials.
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Affiliation(s)
- Jin Li
- School of Engineering, Cardiff University, The Parade, Cardiff, CF24 3AA, UK.
| | - William D Jamieson
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, King Edward VII Ave, Cardiff, CF10 3NB, UK
| | | | - Wen Xu
- Cardiff Business School, Cardiff University, Aberconway Building, Colum Dr, Cardiff, CF10 3EU, UK
| | - Paul Rohde
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinhurst, NSW, 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool St, Darlinhurst, NSW, 2010, Australia.,School of Clinical Medicine, UNSW, Sydney, NSW, 2052, Australia
| | - Matthew Baker
- School of Biotechnology and Biomolecular Science, UNSW, Sydney, NSW, 2052, Australia
| | - Bruce W Drinkwater
- Department of Mechanical Engineering, University of Bristol, University Walk, Bristol, BS8 1TR, UK.
| | - Oliver K Castell
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, King Edward VII Ave, Cardiff, CF10 3NB, UK.
| | - David A Barrow
- School of Engineering, Cardiff University, The Parade, Cardiff, CF24 3AA, UK.
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4
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Lynch CI, Klesse G, Rao S, Tucker SJ, Sansom MSP. Water Nanoconfined in a Hydrophobic Pore: Molecular Dynamics Simulations of Transmembrane Protein 175 and the Influence of Water Models. ACS NANO 2021; 15:19098-19108. [PMID: 34784172 PMCID: PMC7612143 DOI: 10.1021/acsnano.1c06443] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Water molecules within biological ion channels are in a nanoconfined environment and therefore exhibit behaviors which differ from that of bulk water. Here, we investigate the phenomenon of hydrophobic gating, the process by which a nanopore may spontaneously dewet to form a "vapor lock" if the pore is sufficiently hydrophobic and/or narrow. This occurs without steric occlusion of the pore. Using molecular dynamics simulations with both rigid fixed-charge and polarizable (AMOEBA) force fields, we investigate this wetting/dewetting behavior in the transmembrane protein 175 ion channel. We examine how a range of rigid fixed-charge and polarizable water models affect wetting/dewetting in both the wild-type structure and in mutants chosen to cover a range of nanopore radii and pore-lining hydrophobicities. Crucially, we find that the rigid fixed-charge water models lead to similar wetting/dewetting behaviors, but that the polarizable water model resulted in an increased wettability of the hydrophobic gating region of the pore. This has significant implications for molecular simulations of nanoconfined water, as it implies that polarizability may need to be included if we are to gain detailed mechanistic insights into wetting/dewetting processes. These findings are of importance for the design of functionalized biomimetic nanopores (e.g., sensing or desalination) as well as for furthering our understanding of the mechanistic processes underlying biological ion channel function.
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Affiliation(s)
- Charlotte I. Lynch
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK, OX1 3QU
| | - Gianni Klesse
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, UK, OX1 3PU
| | - Shanlin Rao
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK, OX1 3QU
| | - Stephen J. Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, UK, OX1 3PU
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK, OX1 3QU
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5
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Ion Channels in Biophysics and Physiology: Methods & Challenges to Study Mechanosensitive Ion Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:33-49. [DOI: 10.1007/978-981-16-4254-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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6
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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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7
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Brooker HR, Gyamfi IA, Wieckowska A, Brooks NJ, Mulvihill DP, Geeves MA. A novel live-cell imaging system reveals a reversible hydrostatic pressure impact on cell-cycle progression. J Cell Sci 2018; 131:jcs.212167. [PMID: 29930079 PMCID: PMC6104828 DOI: 10.1242/jcs.212167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 06/04/2018] [Indexed: 11/20/2022] Open
Abstract
Life is dependent upon the ability of a cell to rapidly respond to changes in the environment. Small perturbations in local environments change the ability of molecules to interact and, hence, communicate. Hydrostatic pressure provides a rapid non-invasive, fully reversible method for modulating affinities between molecules both in vivo and in vitro. We have developed a simple fluorescence imaging chamber that allows intracellular protein dynamics and molecular events to be followed at pressures <200 bar in living cells. By using yeast, we investigated the impact of hydrostatic pressure upon cell growth and cell-cycle progression. While 100 bar has no effect upon viability, it induces a delay in chromosome segregation, resulting in the accumulation of long undivided cells that are also bent, consistent with disruption of the cytoskeletons. This delay is independent of stress signalling and induces synchronisation of cell-cycle progression. Equivalent effects were observed in Candida albicans, with pressure inducing a reversible cell-cycle delay and hyphal growth. We present a simple novel non-invasive fluorescence microscopy-based approach to transiently impact molecular dynamics in order to visualise, dissect and study signalling pathways and cellular processes in living cells. Summary: Development of a simple fluorescence imaging chamber allowing observation of intracellular protein dynamics and molecular events in living cells at pressure up to 200 bar.
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Affiliation(s)
- Holly R Brooker
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Irene A Gyamfi
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | | | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, London SW7 2AZ, UK
| | | | - Michael A Geeves
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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8
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Petrov E, Menon G, Rohde PR, Battle AR, Martinac B, Solioz M. Xenon-inhibition of the MscL mechano-sensitive channel and the CopB copper ATPase under different conditions suggests direct effects on these proteins. PLoS One 2018; 13:e0198110. [PMID: 29864148 PMCID: PMC5986136 DOI: 10.1371/journal.pone.0198110] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 05/14/2018] [Indexed: 11/18/2022] Open
Abstract
Xenon is frequently used as a general anesthetic in humans, but the mechanism remains an issue of debate. While for some membrane proteins, a direct interaction of xenon with the protein has been shown to be the inhibitory mechanism, other membrane protein functions could be affected by changes of membrane properties due to partitioning of the gas into the lipid bilayer. Here, the effect of xenon on a mechanosensitive ion channel and a copper ion-translocating ATPase was compared under different conditions. Xenon inhibited spontaneous gating of the Escherichia coli mechano-sensitive mutant channel MscL-G22E, as shown by patch-clamp recording techniques. Under high hydrostatic pressure, MscL-inhibition was reversed. Similarly, the activity of the Enterococcus hirae CopB copper ATPase, reconstituted into proteoliposomes, was inhibited by xenon. However, the CopB ATPase activity was also inhibited by xenon when CopB was in a solubilized state. These findings suggest that xenon acts by directly interacting with these proteins, rather than via indirect effects by altering membrane properties. Also, inhibition of copper transport may be a novel effect of xenon that contributes to anesthesia.
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Affiliation(s)
- Evgeny Petrov
- Laboratory of Biochemistry and Molecular Biology, Tomsk State University, Tomsk, Russia
| | - Gopalakrishnan Menon
- Laboratory of Biochemistry and Molecular Biology, Tomsk State University, Tomsk, Russia
| | - Paul R Rohde
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Andrew R Battle
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia.,School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia.,St Vincent's Clinical School, University of New South Wales, Darlinghurst, Australia
| | - Marc Solioz
- Laboratory of Biochemistry and Molecular Biology, Tomsk State University, Tomsk, Russia.,Department Clinical Research, University of Bern, Bern, Switzerland
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9
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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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10
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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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11
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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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12
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Inducible release of particulates from liposomes using the mechanosensitive channel of large conductance and L-α-lysophosphatidylcholine. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:521-30. [PMID: 26143502 DOI: 10.1007/s00249-015-1055-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 06/07/2015] [Accepted: 06/17/2015] [Indexed: 01/05/2023]
Abstract
The mechanosensitive channel of large conductance (MscL) from Escherichia coli is a prototype for the mechanosensitive class of ion channels and opens one of the largest known gated transmembrane pores. As such, MscL offers the structural framework for the development of liposomal nanovalves for biotechnological applications. Here we incorporated MscL into liposomes and investigated the effects of L-α-lysophosphatidylcholine (LPC) with varying acyl chain lengths or saturation on its pore gating. This was measured by the efflux of encapsulated 5,6-carboxyfluorescein (CF) from the MscL proteoliposomes. Efflux improved in the presence of shorter and double-bonded LPC acyl chains. It was also dependent on the detergent concentration employed during MscL purification. MscL purified in 2 mM dodecyl β-D-maltopyranoside (DDM) had a marked increase in CF efflux compared to MscL purified in 1 mM DDM when treated with LPC. The purification conditions also resulted in increased efflux from proteoliposomes containing the G22C-MscL pore mutant channel, which requires higher membrane tension for its activation compared to WT-MscL.
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13
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Abstract
We review the combined effect of temperature and pressure on the structure, dynamics and phase behavior of lipid bilayers, differing in chain length, headgroup structure and composition as revealed by thermodynamic, spectroscopic and scattering experiments. The effect of additives, such as ions, cholesterol, and anaesthetics is discussed as well. Our data include also reports on the effect of pressure on the lateral organization of heterogeneous lipid membranes and lipid extracts from cellular membranes, as well as the influence of peptide and protein incorporation on the pressure-dependent structure and phase behavior of lipid membranes. Moreover, the effects of pressure on membrane protein function are summarized. Finally, we introduce pressure as a kinetic variable for studying the kinetics of various lipid phase transformations.
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Affiliation(s)
- Roland Winter
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Otto-Hahn Str. 6, D-44227, Dortmund, Germany,
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Strahl H, Bürmann F, Hamoen LW. The actin homologue MreB organizes the bacterial cell membrane. Nat Commun 2014; 5:3442. [PMID: 24603761 PMCID: PMC3955808 DOI: 10.1038/ncomms4442] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/13/2014] [Indexed: 02/07/2023] Open
Abstract
The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes. The formation of lipid domains in eukaryotic cells is controlled by the cortical actin cytoskeleton. Here, the authors show that the bacterial actin homologue MreB has a comparable activity, influencing the formation of regions of increased fluidity that determine the distribution of membrane proteins.
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Affiliation(s)
- Henrik Strahl
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle NE2 4AX, UK
| | - Frank Bürmann
- Max Planck Institute of Biochemistry, Chromosome Organization and Dynamics, Am Klopferspitz 18, Martinsried D-82152, Germany
| | - Leendert W Hamoen
- 1] Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle NE2 4AX, UK [2] Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Amsterdam 1098 XH, The Netherlands
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Chen SK, Chung CA, Cheng YC, Huang CJ, Ruaan RC, Chen WY, Li C, Tsao CW, Hu WW, Chien CC. Hydrostatic pressure enhances mitomycin C induced apoptosis in urothelial carcinoma cells. Urol Oncol 2013; 32:26.e17-24. [PMID: 23403205 DOI: 10.1016/j.urolonc.2012.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 09/13/2012] [Accepted: 09/13/2012] [Indexed: 10/27/2022]
Abstract
OBJECTIVES Urothelial carcinoma (UC) of the bladder is the second most common cancer of the genitourinary system. Clinical UC treatment usually involves transurethral resection of the bladder tumor followed by adjuvant intravesical immunotherapy or chemotherapy to prevent recurrence. Intravesical chemotherapy induces fewer side effects than immunotherapy but is less effective at preventing tumor recurrence. Improvement to intravesical chemotherapy is, therefore, needed. METHODS AND MATERIALS Cellular effects of mitomycin C (MMC) and hydrostatic pressure on UC BFTC905 cells were assessed. The viability of the UC cells was determined using cellular proliferation assay. Changes in apoptotic function were evaluated by caspase 3/7 activities, expression of FasL, and loss of mitochondrial membrane potential. RESULTS Reduced cell viability was associated with increasing hydrostatic pressure. Caspase 3/7 activities were increased following treatment of the UC cells with MMC or hydrostatic pressure. In combination with 10 kPa hydrostatic pressure, MMC treatment induced increasing FasL expression. The mitochondria of UC cells displayed increasingly impaired membrane potentials following a combined treatment with 10 μg/ml MMC and 10 kPa hydrostatic pressure. CONCLUSIONS Both MMC and hydrostatic pressure can induce apoptosis in UC cells through an extrinsic pathway. Hydrostatic pressure specifically increases MMC-induced apoptosis and might minimize the side effects of the chemotherapy by reducing the concentration of the chemical agent. This study provides a new and alternative approach for treatment of patients with UC following transurethral resection of the bladder tumor.
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Affiliation(s)
- Shao-Kuan Chen
- Department of Urology, Sijhih Cathay General Hospital, New Taipei City, Taiwan; Department of Mechanical Engineering, National Central University, Jhongli, Taiwan; School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Chih-Ang Chung
- Department of Mechanical Engineering, National Central University, Jhongli, Taiwan; Institute of Biomedical Engineering, National Central University, Jhongli, Taiwan
| | - Yu-Che Cheng
- Institute of Biomedical Engineering, National Central University, Jhongli, Taiwan; Department of Medical Research, Cathay General Hospital, Taipei, Taiwan
| | - Chi-Jung Huang
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Department of Medical Research, Cathay General Hospital, Taipei, Taiwan; Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Ruoh-Chyu Ruaan
- Institute of Biomedical Engineering, National Central University, Jhongli, Taiwan; Department of Chemical and Materials Engineering, National Central University, Jhongli, Taiwan
| | - Wen-Yih Chen
- Department of Chemical and Materials Engineering, National Central University, Jhongli, Taiwan
| | - Chuan Li
- Department of Mechanical Engineering, National Central University, Jhongli, Taiwan
| | - Chia-Wen Tsao
- Department of Mechanical Engineering, National Central University, Jhongli, Taiwan
| | - Wei-Wen Hu
- Department of Chemical and Materials Engineering, National Central University, Jhongli, Taiwan
| | - Chih-Cheng Chien
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Institute of Biomedical Engineering, National Central University, Jhongli, Taiwan; Department of Medical Research, Cathay General Hospital, Taipei, Taiwan; Department of Anesthesiology, Sijhih Cathay General Hospital, Sijhih District, New Taipei City, Taiwan.
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Hydrophobic gating of mechanosensitive channel of large conductance evidenced by single-subunit resolution. Proc Natl Acad Sci U S A 2012; 109:12944-9. [PMID: 22826215 DOI: 10.1073/pnas.1205270109] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mechanosensitive (MS) ion channels are membrane proteins that detect and respond to membrane tension in all branches of life. In bacteria, MS channels prevent cells from lysing upon sudden hypoosmotic shock by opening and releasing solutes and water. Despite the importance of MS channels and ongoing efforts to explain their functioning, the molecular mechanism of MS channel gating remains elusive and controversial. Here we report a method that allows single-subunit resolution for manipulating and monitoring "mechanosensitive channel of large conductance" from Escherichia coli. We gradually changed the hydrophobicity of the pore constriction in this homopentameric protein by modifying a critical pore residue one subunit at a time. Our experimental results suggest that both channel opening and closing are initiated by the transmembrane 1 helix of a single subunit and that the participation of each of the five identical subunits in the structural transitions between the closed and open states is asymmetrical. Such a minimal change in the pore environment seems ideal for a fast and energy-efficient response to changes in the membrane tension.
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