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Matsuki Y, Takashima M, Ueki M, Iwamoto M, Oiki S. Probing membrane deformation energy by KcsA potassium channel gating under varied membrane thickness and tension. FEBS Lett 2024. [PMID: 38880762 DOI: 10.1002/1873-3468.14956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 06/18/2024]
Abstract
This study investigated how membrane thickness and tension modify the gating of KcsA potassium channels when simultaneously varied. The KcsA channel undergoes global conformational changes upon gating: expansion of the cross-sectional area and longitudinal shortening upon opening. Thus, membranes impose differential effects on the open and closed conformations, such as hydrophobic mismatches. Here, the single-channel open probability was recorded in the contact bubble bilayer, by which variable thickness membranes under a defined tension were applied. A fully open channel in thin membranes turned to sporadic openings in thick membranes, where the channel responded moderately to tension increase. Quantitative gating analysis prompted the hypothesis that tension augmented the membrane deformation energy when hydrophobic mismatch was enhanced in thick membranes.
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Affiliation(s)
- Yuka Matsuki
- Department of Anesthesiology and Reanimatology, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Japan
- Life Science Innovation Center, University of Fukui, Yoshida-gun, Japan
| | - Masako Takashima
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Japan
| | - Misuzu Ueki
- Life Science Innovation Center, University of Fukui, Yoshida-gun, Japan
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Japan
| | - Masayuki Iwamoto
- Life Science Innovation Center, University of Fukui, Yoshida-gun, Japan
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Japan
| | - Shigetoshi Oiki
- Biomedical Imaging Research Center, University of Fukui, Yoshida-gun, Japan
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Matsuki Y, Iwamoto M, Oiki S. Asymmetric Lipid Bilayers and Potassium Channels Embedded Therein in the Contact Bubble Bilayer. Methods Mol Biol 2024; 2796:1-21. [PMID: 38856892 DOI: 10.1007/978-1-0716-3818-7_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Cell membranes are highly intricate systems comprising numerous lipid species and membrane proteins, where channel proteins, lipid molecules, and lipid bilayers, as continuous elastic fabric, collectively engage in multi-modal interplays. Owing to the complexity of the native cell membrane, studying the elementary processes of channel-membrane interactions necessitates a bottom-up approach starting from forming simplified synthetic membranes. This is the rationale for establishing an in vitro membrane reconstitution system consisting of a lipid bilayer with a defined lipid composition and a channel molecule. Recent technological advancements have facilitated the development of asymmetric membranes, and the contact bubble bilayer (CBB) method allows single-channel current recordings under arbitrary lipid compositions in asymmetric bilayers. Here, we present an experimental protocol for the formation of asymmetric membranes using the CBB method. The KcsA potassium channel is a prototypical model channel with huge structural and functional information and thus serves as a reporter of membrane actions on the embedded channels. We demonstrate specific interactions of anionic lipids in the inner leaflet. Considering that the local lipid composition varies steadily in cell membranes, we `present a novel lipid perfusion technique that allows rapidly changing the lipid composition while monitoring the single-channel behavior. Finally, we demonstrate a leaflet perfusion method for modifying the composition of individual leaflets. These techniques with custom synthetic membranes allow for variable experiments, providing crucial insights into channel-membrane interplay in cell membranes.
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Affiliation(s)
- Yuka Matsuki
- Department of Anesthesiology and Reanimatology, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
| | - Masayuki Iwamoto
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Fukui, Japan
| | - Shigetoshi Oiki
- Biomedical Imaging Research Center, University of Fukui, Fukui, Japan.
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Iwamoto M, Morito M, Oiki S, Nishitani Y, Yamamoto D, Matsumori N. Cardiolipin binding enhances KcsA channel gating via both its specific and dianion-monoanion interchangeable sites. iScience 2023; 26:108471. [PMID: 38077151 PMCID: PMC10709135 DOI: 10.1016/j.isci.2023.108471] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 10/29/2023] [Accepted: 11/13/2023] [Indexed: 01/17/2024] Open
Abstract
KcsA is a potassium channel with a plethora of structural and functional information, but its activity in the KcsA-producing actinomycete membranes remains elusive. To determine lipid species involved in channel-modulation, a surface plasmon resonance (SPR)-based methodology, characterized by immobilization of membrane proteins under a membrane environment, was applied. Dianionic cardiolipin (CL) showed extremely higher affinity for KcsA than monoanionic lipids. The SPR experiments further demonstrated that CL bound not only to the N-terminal M0 helix, a lipid-sensor domain, but to the M0 helix-deleted mutant. In contrast, monoanionic lipids interacted primarily with the M0 helix. This indicates the presence of an alternative CL-binding site, plausibly in the transmembrane domain. Single-channel recordings demonstrated that CL enhanced channel opening in an M0-independent manner. Taken together, the action of monoanionic lipids is exclusively mediated by the M0 helix, while CL binds both the M0 helix and its specific site, further enhancing the channel activity.
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Affiliation(s)
- Masayuki Iwamoto
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Masayuki Morito
- Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395 Japan
| | - Shigetoshi Oiki
- Biomedial Imaging Research Center, University of Fukui, Fukui 910-1193, Japan
| | - Yudai Nishitani
- Department of Applied Physics, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan
| | - Daisuke Yamamoto
- Department of Applied Physics, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan
| | - Nobuaki Matsumori
- Department of Chemistry, Graduate School of Science, Kyushu University, Fukuoka 819-0395 Japan
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Chittari SS, Obermeyer AC, Knight AS. Investigating Fundamental Principles of Nonequilibrium Assembly Using Temperature-Sensitive Copolymers. J Am Chem Soc 2023; 145:6554-6561. [PMID: 36913711 DOI: 10.1021/jacs.3c00883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
Both natural biomaterials and synthetic materials benefit from complex energy landscapes that provide the foundation for structure-function relationships and environmental sensitivity. Understanding these nonequilibrium dynamics is important for the development of design principles to harness this behavior. Using a model system of poly(ethylene glycol) methacrylate-based thermoresponsive lower critical solution temperature (LCST) copolymers, we explored the impact of composition and stimulus path on nonequilibrium thermal hysteretic behavior. Through turbidimetry analysis of nonsuperimposable heat-cool cycles, we observe that LCST copolymers show clear hysteresis that varies as a function of pendent side chain length and hydrophobicity. Hysteresis is further impacted by the temperature ramp rate, as insoluble states can be kinetically trapped under optimized temperature protocols. This systematic study brings to light fundamental principles that can enable the harnessing of out-of-equilibrium effects in synthetic soft materials.
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Affiliation(s)
- Supraja S Chittari
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Allie C Obermeyer
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
| | - Abigail S Knight
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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Nakayama Y, Rohde PR, Martinac B. "Force-From-Lipids" Dependence of the MscCG Mechanosensitive Channel Gating on Anionic Membranes. Microorganisms 2023; 11:microorganisms11010194. [PMID: 36677485 PMCID: PMC9861469 DOI: 10.3390/microorganisms11010194] [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: 12/22/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 01/15/2023] Open
Abstract
Mechanosensory transduction in Corynebacterium glutamicum plays a major role in glutamate efflux for industrial MSG, whose production depends on the activation of MscCG-type mechanosensitive channels. Dependence of the MscCG channel activation by membrane tension on the membrane lipid content has to date not been functionally characterized. Here, we report the MscCG channel patch clamp recording from liposomes fused with C. glutamicum membrane vesicles as well as from proteoliposomes containing the purified MscCG protein. Our recordings demonstrate that mechanosensitivity of MscCG channels depends significantly on the presence of negatively charged lipids in the proteoliposomes. MscCG channels in liposome preparations fused with native membrane vesicles exhibited the activation threshold similar to the channels recorded from C. glutamicum giant spheroplasts. In comparison, the activation threshold of the MscCG channels reconstituted into azolectin liposomes was higher than the activation threshold of E. coli MscL, which is gated by membrane tension close to the bilayer lytic tension. The spheroplast-like activation threshold was restored when the MscCG channels were reconstituted into liposomes made of E. coli polar lipid extract. In liposomes made of polar lipids mixed with synthetic phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin, the activation threshold of MscCG was significantly reduced compared to the activation threshold recorded in azolectin liposomes, which suggests the importance of anionic lipids for the channel mechanosensitivity. Moreover, the micropipette aspiration technique combined with patch fluorometry demonstrated that membranes containing anionic phosphatidylglycerol are softer than membranes containing only polar non-anionic phosphatidylcholine and phosphatidylethanolamine. The difference in mechanosensitivity between C. glutamicum MscCG and canonical MscS of E. coli observed in proteoliposomes explains the evolutionary tuning of the force from lipids sensing in various bacterial membrane environments.
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Affiliation(s)
- Yoshitaka Nakayama
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
- Faculty of Medicine, St Vincent’s Clinical School, The University of New South Wales, Sydney 2010, Australia
| | - Paul R. Rohde
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
- Faculty of Medicine, St Vincent’s Clinical School, The University of New South Wales, Sydney 2010, Australia
- Correspondence: ; Tel.: +61-2-9295-8743
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Yano K, Iwamoto M, Koshiji T, Oiki S. Geometrical and electrophysiological data of the moving membrane method for the osmotic water permeability of a lipid bilayer. Data Brief 2021; 38:107309. [PMID: 34485640 PMCID: PMC8405959 DOI: 10.1016/j.dib.2021.107309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 06/29/2021] [Accepted: 08/16/2021] [Indexed: 11/22/2022] Open
Abstract
Data of the osmotic water permeability of a lipid bilayer (diphytanoylphosphaticylcholin) in the presence of cholesterol (30 mole%) are shown under the simultaneous measurement of bilayer tension. Detailed methods and procedures for evaluating the water permeability using the moving membrane method (K. Yano, M. Iwamoto, T. Koshiji & S. Oiki: Visualizing the Osmotic Water Permeability of a Lipid Bilayer under Measured Bilayer Tension Using a Moving Membrane Method. Journal of Membrane Science, 627 (2021) 119231) are presented. The planar lipid bilayer is formed in a glass capillary, separating two aqueous compartments with different osmolarities, and osmotically-driven water flux is visualized as membrane movements along the capillary. The water permeability was evaluated under constant membrane area and tension after correcting for the unstirred layer effect. In these measurements, geometrical features, such as the edge of the planar lipid bilayer and the contact angle between bilayer and monolayer, were image-analyzed. The unstirred layer was evaluated electrophysiologically, in which gramicidin A channel was employed. In the presence of an osmotic gradient, the gramicidin channel generates the streaming potential, and the measured streaming potential data and the derived water-ion coupling ratio (water flux/ion flux) are shown. Detailed descriptions of the integrated method of the moving membrane allow researchers to reproduce the experiment and give opportunities to examine water permeability of various types of membranes, including those containing aquaporins. The present data of osmotic water permeability are compared with the previously published data, while they neglected the bilayer tension.
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Affiliation(s)
- Keita Yano
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Masayuki Iwamoto
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
- Department of Surgery, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Takaaki Koshiji
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Shigetoshi Oiki
- Department of Molecular Physiology and Biophysics, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
- Biomedical Imaging Research Center, University of Fukui, Fukui 910-1193, Japan
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Ueki M, Iwamoto M. Fluorescent labeling in size-controlled liposomes reveals membrane curvature-induced structural changes in the KcsA potassium channel. FEBS Lett 2021; 595:1914-1919. [PMID: 34080704 DOI: 10.1002/1873-3468.14141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/28/2021] [Accepted: 05/29/2021] [Indexed: 11/06/2022]
Abstract
Biological structures with highly curved membranes, such as caveolae and transport vesicles, are essential for signal transduction and membrane trafficking. Although membrane proteins in these structures are subjected to physical stress due to the curvature of the lipid bilayers, the effect of this membrane curvature on protein structure and function remains unclear. In this study, we established an experimental procedure to evaluate membrane curvature-induced structural changes in the prototypical potassium channel KcsA. The effect of a large membrane curvature was estimated using fluorescently labeled KcsA by incorporating it into liposomes with a small diameter (< 30 nm). We found that a large membrane curvature significantly affects the activation gate conformation of the KcsA channel.
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Affiliation(s)
- Misuzu Ueki
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Japan
| | - Masayuki Iwamoto
- Department of Molecular Neuroscience, Faculty of Medical Sciences, University of Fukui, Japan
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