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Zhang X, Tu B, Cao Z, Fang M, Zhang G, Yang J, Ying Y, Sun Z, Hou J, Fang Q, Tang Z, Li L. Anomalous Mechanical and Electrical Interplay in a Covalent Organic Framework Monolayer Membrane. J Am Chem Soc 2023; 145:17786-17794. [PMID: 37537964 DOI: 10.1021/jacs.3c04655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Ion transport through nanoconfinement, driven by both electrical and mechanical forces, has drawn ever-increasing attention, due to its high similarity to stress-sensitive ion channels in biological systems. Previous studies have reported only pressure-induced enhancement in ion conductance in low-permeable systems such as nanotubes, nanoslits, or single nanopores. This enhancement is generally explained by the ion accumulation caused by the capacitive effect in low-permeable systems. Here, we fabricate a highly permeable COF monolayer membrane to investigate ion transport behavior driven by both electrical and mechanical forces. Our results show an anomalous conductance reduction activated by external mechanical force, which is contrary to the capacitive effect-dominated conductance enhancement observed in low-permeable nanopores or channels. Through simulations, we uncovered a distinct electrical-mechanical interplay mechanism that depends on the relative rate between the ion diffusion from the boundary layer to the membrane surface and the ion transport through the membrane. The high pore density of the COF monolayer membrane reduces the charge accumulation caused by the capacitive effect, resulting in fewer accumulated ions near the membrane surface. Additionally, the high membrane permeability greatly accelerates the dissipation of the accumulated ions under mechanical pressure, weakening the effect of the capacitive layer on the streaming current. As a result, the ions accumulated on the electrodes, rather than in the capacitive layer, dominating the streaming current and giving rise to a distinct electrical-mechanical interplay mechanism compared to that in low-permeable nanopores or channels. Our study provides new insights into the interplay between electrical and mechanical forces in ultra-permeable systems.
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Affiliation(s)
- Xiaopeng Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
| | - Bin Tu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhouwen Cao
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Munan Fang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Guangjie Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jinlei Yang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Yue Ying
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhifei Sun
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Junjun Hou
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Qiaojun Fang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Zhiyong Tang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Lianshan Li
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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Nedumaran B, Pineda RH, Rudra P, Lee S, Malykhina AP. Association of genetic polymorphisms in the pore domains of mechano-gated TREK-1 channel with overactive lower urinary tract symptoms in humans. Neurourol Urodyn 2018; 38:144-150. [PMID: 30350878 DOI: 10.1002/nau.23862] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 09/03/2018] [Indexed: 12/12/2022]
Abstract
AIMS Mechanosensitivity of the urinary bladder is regulated by many factors including mechano-gated two-pore domain (K2 P, KCNK) potassium channels. TWIK-related K+ channel, TREK-1, is a predominantly expressed member of K2 P channel family in the human detrusor, and its expression and function are diminished in patients with overactive lower urinary tract symptoms (LUTS). The changes in channel activity may result from spontaneously occurring gene mutations. The aim of this study was to compare single nucleotide polymorphisms (SNPs) in TREK-1 channel between patients with LUTS and healthy donors. METHODS Six SNPs (rs370266806, rs373919966, rs758937019, rs769301539, rs772497750, and rs775158737) in two pore domains of human TREK-1 gene were analyzed using TaqMan SNP genotyping assay with manufacturer-designed primers and allele-specific probes. The screening was done in control bladders and detrusor specimens from patients with overactive LUTS. Statistical analyses were performed using R, Fisher's exact test and Hardy-Weinberg Equilibrium. RESULTS Six SNPs in two pore domains of the human TREK-1 gene were analyzed in human bladder specimens. The frequencies of rs758937019-CT genotype (P = 0.0016) and rs758937019-T allele (P = 0.0022) were significantly higher in the group with overactive LUTS. There was no significant association of rs775158737-GA genotype and rs775158737-A allele with the overactive LUTS, though they were present only in the overactive LUTS group. CONCLUSIONS Our results provide evidence that altered expression and function of TREK-1 channel in patients with overactive LUTS could be due to genetic polymorphisms in the pore domains of TREK-1 channel (rs758937019).
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Affiliation(s)
- Balachandar Nedumaran
- Division of Urology, Department of Surgery, University of Colorado Denver, Aurora, Colorado.,Division of Cardiothoracic Surgery, Department of Surgery, University of Colorado Denver, Aurora, Colorado
| | - Ricardo H Pineda
- Division of Urology, Department of Surgery, University of Colorado Denver, Aurora, Colorado
| | - Pratyaydipta Rudra
- Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Denver, Aurora, Colorado
| | - Sanghee Lee
- Department of Urology, University of California San Diego, La Jolla, California
| | - Anna P Malykhina
- Division of Urology, Department of Surgery, University of Colorado Denver, Aurora, Colorado
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3
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Do TT, Dao UP, Bui HT, Nguyen TT. Effect of electrostatic interaction between fluoxetine and lipid membranes on the partitioning of fluoxetine investigated using second derivative spectrophotometry and FTIR. Chem Phys Lipids 2017; 207:10-23. [DOI: 10.1016/j.chemphyslip.2017.07.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 06/25/2017] [Accepted: 07/01/2017] [Indexed: 12/26/2022]
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4
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Vivier D, Soussia IB, Rodrigues N, Lolignier S, Devilliers M, Chatelain FC, Prival L, Chapuy E, Bourdier G, Bennis K, Lesage F, Eschalier A, Busserolles J, Ducki S. Development of the First Two-Pore Domain Potassium Channel TWIK-Related K+ Channel 1-Selective Agonist Possessing in Vivo Antinociceptive Activity. J Med Chem 2017; 60:1076-1088. [DOI: 10.1021/acs.jmedchem.6b01285] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Delphine Vivier
- Université Clermont Auvergne, CNRS, SIGMA Clermont, ICCF, F-63000 Clermont-Ferrand, France
| | - Ismail Ben Soussia
- Labex
ICST, Institut de Pharmacologie Moléculaire et Cellulaire, UMR CNRS 7275, Université Côte d’Azur, F-06560 Valbonne, France
| | - Nuno Rodrigues
- Université Clermont Auvergne, CNRS, SIGMA Clermont, ICCF, F-63000 Clermont-Ferrand, France
| | - Stéphane Lolignier
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
| | - Maïly Devilliers
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
| | - Franck C. Chatelain
- Labex
ICST, Institut de Pharmacologie Moléculaire et Cellulaire, UMR CNRS 7275, Université Côte d’Azur, F-06560 Valbonne, France
| | - Laetitia Prival
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
| | - Eric Chapuy
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
| | - Geoffrey Bourdier
- Université Clermont Auvergne, CNRS, SIGMA Clermont, ICCF, F-63000 Clermont-Ferrand, France
| | - Khalil Bennis
- Université Clermont Auvergne, CNRS, SIGMA Clermont, ICCF, F-63000 Clermont-Ferrand, France
| | - Florian Lesage
- Labex
ICST, Institut de Pharmacologie Moléculaire et Cellulaire, UMR CNRS 7275, Université Côte d’Azur, F-06560 Valbonne, France
| | - Alain Eschalier
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
- CHU Clermont-Ferrand, Service de Pharmacologie, F-63003 Clermont-Ferrand, France
| | - Jérôme Busserolles
- Université Clermont Auvergne, Inserm, Neuro-Dol, F-63000 Clermont-Ferrand, France
| | - Sylvie Ducki
- Université Clermont Auvergne, CNRS, SIGMA Clermont, ICCF, F-63000 Clermont-Ferrand, France
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Wu J, Lewis AH, Grandl J. Touch, Tension, and Transduction - The Function and Regulation of Piezo Ion Channels. Trends Biochem Sci 2016; 42:57-71. [PMID: 27743844 DOI: 10.1016/j.tibs.2016.09.004] [Citation(s) in RCA: 326] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 09/07/2016] [Accepted: 09/08/2016] [Indexed: 02/03/2023]
Abstract
In 2010, two proteins, Piezo1 and Piezo2, were identified as the long-sought molecular carriers of an excitatory mechanically activated current found in many cells. This discovery has opened the floodgates for studying a vast number of mechanotransduction processes. Over the past 6 years, groundbreaking research has identified Piezos as ion channels that sense light touch, proprioception, and vascular blood flow, ruled out roles for Piezos in several other mechanotransduction processes, and revealed the basic structural and functional properties of the channel. Here, we review these findings and discuss the many aspects of Piezo function that remain mysterious, including how Piezos convert a variety of mechanical stimuli into channel activation and subsequent inactivation, and what molecules and mechanisms modulate Piezo function.
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Affiliation(s)
- Jason Wu
- Duke University Medical Center, Department of Neurobiology, Durham, NC 27710, USA
| | - Amanda H Lewis
- Duke University Medical Center, Department of Neurobiology, Durham, NC 27710, USA
| | - Jörg Grandl
- Duke University Medical Center, Department of Neurobiology, Durham, NC 27710, USA.
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6
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Viswanath ANI, Jung SY, Hwang EM, Park KD, Lim SM, Min SJ, Cho YS, Pae AN. Identification of the firstin silico-designed TREK1 antagonists that block channel currents dose dependently. Chem Biol Drug Des 2016; 88:807-819. [DOI: 10.1111/cbdd.12810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 05/03/2016] [Accepted: 06/18/2016] [Indexed: 02/01/2023]
Affiliation(s)
- Ambily Nath Indu Viswanath
- Convergence Research Center for Diagnosis, Treatment and Care System of Dementia; Korea Institute of Science and Technology; Seoul Korea
- Department of Biological Chemistry; Korea University of Science and Technology; Daejeon Korea
| | - Seo Yun Jung
- Convergence Research Center for Diagnosis, Treatment and Care System of Dementia; Korea Institute of Science and Technology; Seoul Korea
| | - Eun Mi Hwang
- Department of Biological Chemistry; Korea University of Science and Technology; Daejeon Korea
- Center for Functional Connectomics; Korea Institute of Science and Technology; Seoul Korea
| | - Ki Duk Park
- Convergence Research Center for Diagnosis, Treatment and Care System of Dementia; Korea Institute of Science and Technology; Seoul Korea
- Department of Biological Chemistry; Korea University of Science and Technology; Daejeon Korea
| | - Sang Min Lim
- Center for Neuro-Medicine; Korea Institute of Science and Technology; Seoul Korea
| | - Sun-Joon Min
- Department of Applied Chemistry; Hanyang University ERICA Campus; Sangnok-gu, Ansan Gyeonggi-do Korea
| | - Yong Seo Cho
- Center for Neuro-Medicine; Korea Institute of Science and Technology; Seoul Korea
| | - Ae Nim Pae
- Convergence Research Center for Diagnosis, Treatment and Care System of Dementia; Korea Institute of Science and Technology; Seoul Korea
- Department of Biological Chemistry; Korea University of Science and Technology; Daejeon Korea
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8
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Vivier D, Bennis K, Lesage F, Ducki S. Perspectives on the Two-Pore Domain Potassium Channel TREK-1 (TWIK-Related K(+) Channel 1). A Novel Therapeutic Target? J Med Chem 2015; 59:5149-57. [PMID: 26588045 DOI: 10.1021/acs.jmedchem.5b00671] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Potassium (K(+)) channels are membrane proteins expressed in most living cells that selectively control the flow of K(+) ions. More than 80 genes encode the K(+) channel subunits in the human genome. The TWIK-related K(+) channel (TREK-1) belongs to the two-pore domain K(+) channels (K2P) and displays various properties including sensitivity to physical (membrane stretch, acidosis, temperature) and chemical stimuli (signaling lipids, volatile anesthetics). The distribution of TREK-1 in the central nervous system, coupled with the physiological consequences of its opening and closing, leads to the emergence of this channel as an attractive therapeutic target. We review the TREK-1 channel, its structural and functional properties, and the pharmacological agents (agonists and antagonists) able to modulate its gating.
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Affiliation(s)
- Delphine Vivier
- Université Clermont Auvergne, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS, UMR6296, ICCF, F-63171 Aubiere, France
| | - Khalil Bennis
- Université Clermont Auvergne, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS, UMR6296, ICCF, F-63171 Aubiere, France
| | - Florian Lesage
- Labex ICST, Institut de Pharmacologie Moléculaire et Cellulaire, UMR CNRS 7275, Université de Nice Sophia Antipolis, F-06560 Valbonne, France
| | - Sylvie Ducki
- Université Clermont Auvergne, ENSCCF, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand, France.,CNRS, UMR6296, ICCF, F-63171 Aubiere, France
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9
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Booth IR, Miller S, Müller A, Lehtovirta-Morley L. The evolution of bacterial mechanosensitive channels. Cell Calcium 2014; 57:140-50. [PMID: 25591932 DOI: 10.1016/j.ceca.2014.12.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Revised: 12/16/2014] [Accepted: 12/17/2014] [Indexed: 01/17/2023]
Abstract
Mechanosensitive channels are ubiquitous and highly studied. However, the evolution of the bacterial channels remains enigmatic. It can be argued that mechanosensitivity might be a feature of all membrane proteins with some becoming progressively less sensitive to membrane tension over the course of evolution. Bacteria and archaea exhibit two main classes of channels, MscS and MscL. Present day channels suggest that the evolution of MscL may be highly constrained, whereas MscS has undergone elaboration via gene fusion (and potentially gene fission) events to generate a diversity of channel structures. Some of these channel variants are constrained to a small number of genera or species. Some are only found in higher organisms. Only exceptionally have these diverse channels been investigated in any detail. In this review we consider both the processes that might have led to the evolved complexity but also some of the methods exploiting the explosion of genome sequences to understand (and/or track) their distribution. The role of MscS-related channels in calcium-mediated cell biology events is considered.
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Affiliation(s)
- Ian R Booth
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA.
| | - Samantha Miller
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
| | - Axel Müller
- Division of Chemistry and Chemical Engineering, Broad Institute, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA.
| | - Laura Lehtovirta-Morley
- Institute of Biological and Environmental Sciences, Cruikshank Building, University of Aberdeen, St Machar Drive, Aberdeen AB24 3UU, UK.
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10
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Feeling the hidden mechanical forces in lipid bilayer is an original sense. Proc Natl Acad Sci U S A 2014; 111:7898-905. [PMID: 24850861 DOI: 10.1073/pnas.1313364111] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Life's origin entails enclosing a compartment to hoard material, energy, and information. The envelope necessarily comprises amphipaths, such as prebiotic fatty acids, to partition the two aqueous domains. The self-assembled lipid bilayer comes with a set of properties including its strong anisotropic internal forces that are chemically or physically malleable. Added bilayer stretch can alter force vectors on embedded proteins to effect conformational change. The force-from-lipid principle was demonstrated 25 y ago when stretches opened purified Escherichia coli MscL channels reconstituted into artificial bilayers. This reductionistic exercise has rigorously been recapitulated recently with two vertebrate mechanosensitive K(+) channels (TREK1 and TRAAK). Membrane stretches have also been known to activate various voltage-, ligand-, or Ca(2+)-gated channels. Careful analyses showed that Kv, the canonical voltage-gated channel, is in fact exquisitely sensitive even to very small tension. In an unexpected context, the canonical transient-receptor-potential channels in the Drosophila eye, long presumed to open by ligand binding, is apparently opened by membrane force due to PIP2 hydrolysis-induced changes in bilayer strain. Being the intimate medium, lipids govern membrane proteins by physics as well as chemistry. This principle should not be a surprise because it parallels water's paramount role in the structure and function of soluble proteins. Today, overt or covert mechanical forces govern cell biological processes and produce sensations. At the genesis, a bilayer's response to osmotic force is likely among the first senses to deal with the capricious primordial sea.
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11
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Novel electrophysiological properties of dronedarone: inhibition of human cardiac two-pore-domain potassium (K2P) channels. Naunyn Schmiedebergs Arch Pharmacol 2012; 385:1003-16. [DOI: 10.1007/s00210-012-0780-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 06/29/2012] [Indexed: 12/27/2022]
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12
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Noël J, Sandoz G, Lesage F. Molecular regulations governing TREK and TRAAK channel functions. Channels (Austin) 2011; 5:402-9. [PMID: 21829087 DOI: 10.4161/chan.5.5.16469] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
K+ channels with two-pore domain (K2p) form a large family of hyperpolarizing channels. They produce background currents that oppose membrane depolarization and cell excitability. They are involved in cellular mechanisms of apoptosis, vasodilatation, anesthesia, pain, neuroprotection and depression. This review focuses on TREK-1, TREK-2 and TRAAK channels subfamily and on the mechanisms that contribute to their molecular heterogeneity and functional regulations. Their molecular diversity is determined not only by the number of genes but also by alternative splicing and alternative initiation of translation. These channels are sensitive to a wide array of biophysical parameters that affect their activity such as unsaturated fatty acids, intra- and extracellular pH, membrane stretch, temperature, and intracellular signaling pathways. They interact with partner proteins that influence their activity and their plasma membrane expression. Molecular heterogeneity, regulatory mechanisms and protein partners are all expected to contribute to cell specific functions of TREK currents in many tissues.
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Affiliation(s)
- Jacques Noël
- Université de Nice Sophia Antipolis, UFR Sciences, Nice, France.
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13
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Piechotta PL, Rapedius M, Stansfeld PJ, Bollepalli MK, Ehrlich G, Erhlich G, Andres-Enguix I, Fritzenschaft H, Decher N, Sansom MSP, Tucker SJ, Baukrowitz T. The pore structure and gating mechanism of K2P channels. EMBO J 2011; 30:3607-19. [PMID: 21822218 PMCID: PMC3181484 DOI: 10.1038/emboj.2011.268] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 07/04/2011] [Indexed: 12/26/2022] Open
Abstract
Two-pore domain (K2P) potassium channels are important regulators of cellular electrical excitability. However, the structure of these channels and their gating mechanism, in particular the role of the bundle-crossing gate, are not well understood. Here, we report that quaternary ammonium (QA) ions bind with high-affinity deep within the pore of TREK-1 and have free access to their binding site before channel activation by intracellular pH or pressure. This demonstrates that, unlike most other K(+) channels, the bundle-crossing gate in this K2P channel is constitutively open. Furthermore, we used QA ions to probe the pore structure of TREK-1 by systematic scanning mutagenesis and comparison of these results with different possible structural models. This revealed that the TREK-1 pore most closely resembles the open-state structure of KvAP. We also found that mutations close to the selectivity filter and the nature of the permeant ion profoundly influence TREK-1 channel gating. These results demonstrate that the primary activation mechanisms in TREK-1 reside close to, or within the selectivity filter and do not involve gating at the cytoplasmic bundle crossing.
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Affiliation(s)
- Paula L Piechotta
- Universitätsklinikum Jena, Institute of Physiology II, Jena, Germany
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Maksaev G, Milac A, Anishkin A, Guy HR, Sukharev S. Analyses of gating thermodynamics and effects of deletions in the mechanosensitive channel TREK-1: comparisons with structural models. Channels (Austin) 2011; 5:34-42. [PMID: 21057213 DOI: 10.4161/chan.5.1.13906] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
TREK-1, a mechanosensitive K channel from the two-pore family (K(2)P), is involved in protective regulation of the resting potential in CNS neurons and other tissues. The structure of TREK-1 and the basis of its sensitivity to stretch and variety of lipid-soluble factors remain unknown. Using existing K channel structures as modeling templates, TREK-1 was envisioned as a two-fold symmetrical complex with the gate formed primarily by the centrally positioned TM2b helices of the second homologous repeat. Opening was modeled as a conical expansion of the barrel separating TM2b's accompanied by extension of TM2a helices with the cytoplasmic TM2a-TM1b connector. Seeking first experimental support to the models we have accomplished thermodynamic analysis of mouse TREK-1 gating and functional testing of several deletion mutants. The predicted increase of the channel in-plane area (ΔA) of ~5 nm(2) in models was supported by the experimental ΔA of ~4 nm(2) derived from the slope of open probability versus membrane tension in HEK-293T cells and their cytoskeleton-depleted blebs. In response to steps of suction, wild-type channel produced transient currents in cell-attached patches and mostly sustained currents upon patch excision. TREK-1 motifs not present in canonical K channels include divergent cytoplasmic N- and C-termini, and a characteristic 50-residue extracellular loop in the first homologous repeat. Deletion of the extracellular loop (Δ76-124) reduced the average current density in patches, increased spontaneous activity and generated a larger sub-population of high-conductance channels, while activation by tension augmented by arachidonic acid was fully retained. Further deletion of the C-terminal end (Δ76-124/Δ334-411) removed voltage dependency but otherwise produced no additional effect. In an attempt to generate a cysteine-free version of the channel, we mutated two remaining cysteines 159 and 219 in the transmembrane region. C219A did not compromise channel activity, whereas the C159A/S mutants were essentially inactive. Treatment with β-mercaptoethanol suggested that none of these cysteines form functionally-important disulfides.
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Affiliation(s)
- Grigory Maksaev
- Department of Biology, University of Maryland, College Park, USA
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