1
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Yu M, Schewe M, Bauer G, Rembe C. Improved demodulated phase signal resolution for carrier signals with small modulation index by clipping and synchronous sampling for heterodyne interferometers. Sci Rep 2023; 13:8570. [PMID: 37237111 DOI: 10.1038/s41598-023-35000-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
Digitization of phase-modulated carrier signals with a commercially available analog-to-digital converter (ADC) is a common task in many communication and sensor applications. ADCs deliver phase-modulated digital carrier signals, which are numerically demodulated in order to extract the relevant information. However, the limited dynamic ranges of available ADCs limit the carrier-to-noise ratio of carrier signals after digitization. Correspondingly, the resolution of the demodulated digital signal is degraded. We demonstrate a sampling method with a simple demodulation scheme for phase-modulated signals with a small modulation index. Our new scheme overcomes the limitation due to digital noise defined by the ADC. Through simulations and experiments, we provide evidence that our method can improve the resolution of the demodulated digital signal significantly, when the carrier-to-noise ratio of phase-modulated signals is limited by digital noise. We employ our sampling and demodulation scheme to solve the problem of a possible degradation of measurement resolution after digital demodulation in heterodyne interferometers measuring small vibration amplitudes.
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Affiliation(s)
- M Yu
- Department of Applied Metrology, Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld, Germany.
| | - M Schewe
- Department of Applied Metrology, Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld, Germany
| | - G Bauer
- Department of Applied Metrology, Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld, Germany
| | - C Rembe
- Department of Applied Metrology, Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld, Germany
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2
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Schroeter CB, Nelke C, Schewe M, Spohler L, Herrmann AM, Müntefering T, Huntemann N, Kuzikov M, Gribbon P, Albrecht S, Bock S, Hundehege P, Neelsen LC, Baukrowitz T, Seebohm G, Wünsch B, Bittner S, Ruck T, Budde T, Meuth SG. Validation of TREK1 ion channel activators as an immunomodulatory and neuroprotective strategy in neuroinflammation. Biol Chem 2023; 404:355-375. [PMID: 36774650 DOI: 10.1515/hsz-2022-0266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/16/2023] [Indexed: 02/13/2023]
Abstract
Modulation of two-pore domain potassium (K2P) channels has emerged as a novel field of therapeutic strategies as they may regulate immune cell activation and metabolism, inflammatory signals, or barrier integrity. One of these ion channels is the TWIK-related potassium channel 1 (TREK1). In the current study, we report the identification and validation of new TREK1 activators. Firstly, we used a modified potassium ion channel assay to perform high-throughput-screening of new TREK1 activators. Dose-response studies helped to identify compounds with a high separation between effectiveness and toxicity. Inside-out patch-clamp measurements of Xenopus laevis oocytes expressing TREK1 were used for further validation of these activators regarding specificity and activity. These approaches yielded three substances, E1, B3 and A2 that robustly activate TREK1. Functionally, we demonstrated that these compounds reduce levels of adhesion molecules on primary human brain and muscle endothelial cells without affecting cell viability. Finally, we studied compound A2 via voltage-clamp recordings as this activator displayed the strongest effect on adhesion molecules. Interestingly, A2 lacked TREK1 activation in the tested neuronal cell type. Taken together, this study provides data on novel TREK1 activators that might be employed to pharmacologically modulate TREK1 activity.
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Affiliation(s)
- Christina B Schroeter
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Christopher Nelke
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Marcus Schewe
- Institute of Physiology, Christian-Albrechts University Kiel, Hermann-Rodewald-Straße 5, 24118 Kiel, Germany
| | - Lucas Spohler
- Department of Neurology with Institute for Translational Neurology, University Hospital Münster, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany
| | - Alexander M Herrmann
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Thomas Müntefering
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Niklas Huntemann
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Maria Kuzikov
- Fraunhofer Institute for Translational Medicine and Pharmacology (ITMP), Schnackenburgallee 114, D-22525 Hamburg, Germany
- Fraunhofer Cluster of Excellence for Immune mediated diseases (CIMD), Theodor-Stern-Kai 7, D-60596 Frankfurt, Germany
| | - Philip Gribbon
- Fraunhofer Institute for Translational Medicine and Pharmacology (ITMP), Schnackenburgallee 114, D-22525 Hamburg, Germany
- Fraunhofer Cluster of Excellence for Immune mediated diseases (CIMD), Theodor-Stern-Kai 7, D-60596 Frankfurt, Germany
| | - Sarah Albrecht
- Department of Neurology with Institute for Translational Neurology, University Hospital Münster, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany
| | - Stefanie Bock
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Petra Hundehege
- Department of Neurology with Institute for Translational Neurology, University Hospital Münster, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany
| | - Lea Christine Neelsen
- Institute of Physiology, Christian-Albrechts University Kiel, Hermann-Rodewald-Straße 5, 24118 Kiel, Germany
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts University Kiel, Hermann-Rodewald-Straße 5, 24118 Kiel, Germany
| | - Guiscard Seebohm
- IfGH-Cellular Electrophysiology, Department of Cardiology and Angiology, University Hospital of Münster, Albert-Schweitzer-Campus 1, D-48149 Münster, Germany
| | - Bernhard Wünsch
- Institute for Pharmaceutical and Medicinal Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstraße 48, D-48149 Münster, Germany
| | - Stefan Bittner
- Department of Neurology, University Medical Center Mainz, Langenbeckstraße 1, D-55131 Mainz, Germany
| | - Tobias Ruck
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Thomas Budde
- Institute of Physiology I, University of Münster, Robert-Koch-Straße 27A, D-48149 Münster, Germany
| | - Sven G Meuth
- Department of Neurology, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstr. 5, D-40225 Düsseldorf, Germany
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3
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Riel EB, Jürs BC, Cordeiro S, Musinszki M, Schewe M, Baukrowitz T. The versatile regulation of K2P channels by polyanionic lipids of the phosphoinositide and fatty acid metabolism. J Gen Physiol 2022; 154:212926. [PMID: 34928298 PMCID: PMC8693234 DOI: 10.1085/jgp.202112989] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 12/01/2021] [Indexed: 12/29/2022] Open
Abstract
Work over the past three decades has greatly advanced our understanding of the regulation of Kir K+ channels by polyanionic lipids of the phosphoinositide (e.g., PIP2) and fatty acid metabolism (e.g., oleoyl-CoA). However, comparatively little is known regarding the regulation of the K2P channel family by phosphoinositides and by long-chain fatty acid–CoA esters, such as oleoyl-CoA. We screened 12 mammalian K2P channels and report effects of polyanionic lipids on all tested channels. We observed activation of members of the TREK, TALK, and THIK subfamilies, with the strongest activation by PIP2 for TRAAK and the strongest activation by oleoyl-CoA for TALK-2. By contrast, we observed inhibition for members of the TASK and TRESK subfamilies. Our results reveal that TASK-2 channels have both activatory and inhibitory PIP2 sites with different affinities. Finally, we provided evidence that PIP2 inhibition of TASK-1 and TASK-3 channels is mediated by closure of the recently identified lower X-gate as critical mutations within the gate (i.e., L244A, R245A) prevent PIP2-induced inhibition. Our findings establish that K+ channels of the K2P family are highly sensitive to polyanionic lipids, extending our knowledge of the mechanisms of lipid regulation and implicating the metabolism of these lipids as possible effector pathways to regulate K2P channel activity.
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Affiliation(s)
- Elena B Riel
- Institute of Physiology, Kiel University, Kiel, Germany
| | - Björn C Jürs
- Institute of Physiology, Kiel University, Kiel, Germany.,Medical School Hamburg, University of Applied Sciences and Medical University, Hamburg, Germany
| | | | | | - Marcus Schewe
- Institute of Physiology, Kiel University, Kiel, Germany
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4
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Proks P, Schewe M, Conrad LJ, Rao S, Rathje K, Rödström KEJ, Carpenter EP, Baukrowitz T, Tucker SJ. Norfluoxetine inhibits TREK-2 K2P channels by multiple mechanisms including state-independent effects on the selectivity filter gate. J Gen Physiol 2021; 153:212184. [PMID: 34032848 PMCID: PMC8155809 DOI: 10.1085/jgp.202012812] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 05/06/2021] [Indexed: 12/25/2022] Open
Abstract
The TREK subfamily of two-pore domain K+ (K2P) channels are inhibited by fluoxetine and its metabolite, norfluoxetine (NFx). Although not the principal targets of this antidepressant, TREK channel inhibition by NFx has provided important insights into the conformational changes associated with channel gating and highlighted the role of the selectivity filter in this process. However, despite the availability of TREK-2 crystal structures with NFx bound, the precise mechanisms underlying NFx inhibition remain elusive. NFx has previously been proposed to be a state-dependent inhibitor, but its binding site suggests many possible ways in which this positively charged drug might inhibit channel activity. Here we show that NFx exerts multiple effects on single-channel behavior that influence both the open and closed states of the channel and that the channel can become highly activated by 2-APB while remaining in the down conformation. We also show that the inhibitory effects of NFx are unrelated to its positive charge but can be influenced by agonists which alter filter stability, such as ML335, as well as by an intrinsic voltage-dependent gating process within the filter. NFx therefore not only inhibits channel activity by altering the equilibrium between up and down conformations but also can directly influence filter gating. These results provide further insight into the complex allosteric mechanisms that modulate filter gating in TREK K2P channels and highlight the different ways in which filter gating can be regulated to permit polymodal regulation.
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Affiliation(s)
- Peter Proks
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
| | - Marcus Schewe
- Department of Physiology, University of Kiel, Kiel, Germany
| | - Linus J Conrad
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
| | - Shanlin Rao
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Kristin Rathje
- Department of Physiology, University of Kiel, Kiel, Germany
| | | | - Elisabeth P Carpenter
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK.,Centre for Medicines Discovery, University of Oxford, UK
| | | | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, UK
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5
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Schewe M, Riel EB, Rinné S, Kopec W, Langer J, Lindemann P, Jürs BC, Nazaré M, Groot BLD, Decher N, Baukrowitz T. Structural Basis for Gating of the Two-Pore Domain K+ (K2P) Channels TASK-1 and TALK-2. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.1850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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6
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Nematian-Ardestani E, Abd-Wahab F, Chatelain FC, Sun H, Schewe M, Baukrowitz T, Tucker SJ. Selectivity filter instability dominates the low intrinsic activity of the TWIK-1 K2P K + channel. J Biol Chem 2019; 295:610-618. [PMID: 31806709 DOI: 10.1074/jbc.ra119.010612] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 12/04/2019] [Indexed: 12/24/2022] Open
Abstract
Two-pore domain K+ (K2P) channels have many important physiological functions. However, the functional properties of the TWIK-1 (K2P1.1/KCNK1) K2P channel remain poorly characterized because heterologous expression of this ion channel yields only very low levels of functional activity. Several underlying reasons have been proposed, including TWIK-1 retention in intracellular organelles, inhibition by posttranslational sumoylation, a hydrophobic barrier within the pore, and a low open probability of the selectivity filter (SF) gate. By evaluating these potential mechanisms, we found that the latter dominates the low intrinsic functional activity of TWIK-1. Investigating this further, we observed that the low activity of the SF gate appears to arise from the inefficiency of K+ in stabilizing an active (i.e. conductive) SF conformation. In contrast, other permeant ion species, such as Rb+, NH4 +, and Cs+, strongly promoted a pH-dependent activated conformation. Furthermore, many K2P channels are activated by membrane depolarization via an SF-mediated gating mechanism, but we found here that only very strong nonphysiological depolarization produces voltage-dependent activation of heterologously expressed TWIK-1. Remarkably, we also observed that TWIK-1 Rb+ currents are potently inhibited by intracellular K+ (IC50 = 2.8 mm). We conclude that TWIK-1 displays unique SF gating properties among the family of K2P channels. In particular, the apparent instability of the conductive conformation of the TWIK-1 SF in the presence of K+ appears to dominate the low levels of intrinsic functional activity observed when the channel is expressed at the cell surface.
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Affiliation(s)
- Ehsan Nematian-Ardestani
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Firdaus Abd-Wahab
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Franck C Chatelain
- Université Côte d'Azur, Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Labex ICST, 06560 Valbonne, France
| | - Han Sun
- Department of Structural Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, 13125 Berlin, Germany
| | - Marcus Schewe
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom.
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7
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Nematian-ardestani E, Abd-wahab MF, Chatelain FC, Sun H, Schewe M, Baukrowitz T, Tucker SJ. Selectivity filter instability dominates the low intrinsic activity of the TWIK-1 K2P K + Channel.. [DOI: 10.1101/735704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
ABSTRACTTwo-pore domain (K2P) K+ channels have many important physiological functions. However, the functional properties of the TWIK-1 (K2P1.1/KCNK1) K2P channel remain poorly characterized because heterologous expression of this ion channel yields only very low levels of functional activity. Several underlying reasons have been proposed, including TWIK-1 retention in intracellular organelles, inhibition by post-translational sumoylation, a hydrophobic barrier within the pore, and a low open probability of the selectivity filter (SF) gate. By evaluating these various potential mechanisms, we found that the latter dominates the low intrinsic functional activity of TWIK-1. Investigating the underlying mechanism, we observed that the low activity of the SF gate appears to arise from the inefficiency of K+ in stabilizing an active (i.e. conductive) SF conformation. In contrast, other permeant ion species, such as Rb+, NH4+, and Cs+, strongly promoted a pH-dependent activated conformation. Furthermore, many K2P channels are activated by membrane depolarization via a SF-mediated gating mechanism, but we found here that only very strong, non-physiological depolarization produces voltage-dependent activation of heterologously expressed TWIK-1. Remarkably, we also observed that TWIK-1 Rb+ currents are potently inhibited by intracellular K+ (IC50 = 2.8 mM). We conclude that TWIK-1 displays unique SF gating properties among the family of K2P channels. In particular, the apparent instability of the conductive conformation of the TWIK-1 SF in the presence of K+ appears to dominate the low levels of intrinsic functional activity observed when the channel is expressed at the cell surface.
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8
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Schewe M, Sun H, Mert Ü, Mackenzie A, Pike ACW, Schulz F, Constantin C, Vowinkel KS, Conrad LJ, Kiper AK, Gonzalez W, Musinszki M, Tegtmeier M, Pryde DC, Belabed H, Nazare M, de Groot BL, Decher N, Fakler B, Carpenter EP, Tucker SJ, Baukrowitz T. A pharmacological master key mechanism that unlocks the selectivity filter gate in K + channels. Science 2019; 363:875-880. [PMID: 30792303 DOI: 10.1126/science.aav0569] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 01/28/2019] [Indexed: 12/13/2022]
Abstract
Potassium (K+) channels have been evolutionarily tuned for activation by diverse biological stimuli, and pharmacological activation is thought to target these specific gating mechanisms. Here we report a class of negatively charged activators (NCAs) that bypass the specific mechanisms but act as master keys to open K+ channels gated at their selectivity filter (SF), including many two-pore domain K+ (K2P) channels, voltage-gated hERG (human ether-à-go-go-related gene) channels and calcium (Ca2+)-activated big-conductance potassium (BK)-type channels. Functional analysis, x-ray crystallography, and molecular dynamics simulations revealed that the NCAs bind to similar sites below the SF, increase pore and SF K+ occupancy, and open the filter gate. These results uncover an unrecognized polypharmacology among K+ channel activators and highlight a filter gating machinery that is conserved across different families of K+ channels with implications for rational drug design.
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Affiliation(s)
- Marcus Schewe
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany.
| | - Han Sun
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Structural Biology, 13125 Berlin, Germany
| | - Ümit Mert
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Alexandra Mackenzie
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK.,Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Ashley C W Pike
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Friederike Schulz
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Cristina Constantin
- Institute of Physiology II, Albert-Ludwigs University of Freiburg, 79104 Freiburg, Germany.,Centers for Biological Signaling Studies CIBSS and BIOSS, 79104 Freiburg, Germany
| | - Kirsty S Vowinkel
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, 35037 Marburg, Germany
| | - Linus J Conrad
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK.,Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Aytug K Kiper
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, 35037 Marburg, Germany
| | - Wendy Gonzalez
- Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, 3465548 Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, 3465548 Talca, Chile
| | - Marianne Musinszki
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Marie Tegtmeier
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - David C Pryde
- Pfizer Worldwide Medicinal Chemistry, Neuroscience and Pain Research Unit, Portway Building, Granta Park, Great Abington, Cambridgeshire CB21 6GS, UK
| | - Hassane Belabed
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Medicinal Chemistry, 13125 Berlin, Germany
| | - Marc Nazare
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Medicinal Chemistry, 13125 Berlin, Germany
| | - Bert L de Groot
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, 35037 Marburg, Germany
| | - Bernd Fakler
- Institute of Physiology II, Albert-Ludwigs University of Freiburg, 79104 Freiburg, Germany.,Centers for Biological Signaling Studies CIBSS and BIOSS, 79104 Freiburg, Germany
| | - Elisabeth P Carpenter
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK
| | - Stephen J Tucker
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK.,Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany.
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9
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Rinné S, Kiper AK, Vowinkel KS, Ramírez D, Schewe M, Bedoya M, Aser D, Gensler I, Netter MF, Stansfeld PJ, Baukrowitz T, Gonzalez W, Decher N. The molecular basis for an allosteric inhibition of K +-flux gating in K 2P channels. eLife 2019; 8:39476. [PMID: 30803485 PMCID: PMC6391080 DOI: 10.7554/elife.39476] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 02/06/2019] [Indexed: 01/05/2023] Open
Abstract
Two-pore-domain potassium (K2P) channels are key regulators of many physiological and pathophysiological processes and thus emerged as promising drug targets. As for other potassium channels, there is a lack of selective blockers, since drugs preferentially bind to a conserved binding site located in the central cavity. Thus, there is a high medical need to identify novel drug-binding sites outside the conserved lipophilic central cavity and to identify new allosteric mechanisms of channel inhibition. Here, we identified a novel binding site and allosteric inhibition mechanism, disrupting the recently proposed K+-flux gating mechanism of K2P channels, which results in an unusual voltage-dependent block of leak channels belonging to the TASK subfamily. The new binding site and allosteric mechanism of inhibition provide structural and mechanistic insights into the gating of TASK channels and the basis for the drug design of a new class of potent blockers targeting specific types of K2P channels.
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Affiliation(s)
- Susanne Rinné
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Aytug K Kiper
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Kirsty S Vowinkel
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - David Ramírez
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.,Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Talca, Chile
| | - Marcus Schewe
- Institute of Physiology, University of Kiel, Kiel, Germany
| | - Mauricio Bedoya
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile
| | - Diana Aser
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Isabella Gensler
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Michael F Netter
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Phillip J Stansfeld
- Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Wendy Gonzalez
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Niels Decher
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
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10
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Schewe M, Sun H, Mackenzie A, Pike AC, Schulz F, Constantin C, Kiper AK, Conrad LJ, Gonzalez W, de Groot BL, Decher N, Fakler B, Carpenter EP, Tucker SJ, Baukrowitz T. A Pharmacological Masterkey Mechanism to Unlock the Selectivity Filter Gate in K+ Channels. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.1635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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11
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Silbernagel N, Walecki M, Schäfer MKH, Kessler M, Zobeiri M, Rinné S, Kiper AK, Komadowski MA, Vowinkel KS, Wemhöner K, Fortmüller L, Schewe M, Dolga AM, Scekic-Zahirovic J, Matschke LA, Culmsee C, Baukrowitz T, Monassier L, Ullrich ND, Dupuis L, Just S, Budde T, Fabritz L, Decher N. The VAMP-associated protein VAPB is required for cardiac and neuronal pacemaker channel function. FASEB J 2018; 32:6159-6173. [PMID: 29879376 PMCID: PMC6629115 DOI: 10.1096/fj.201800246r] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels encode neuronal and cardiac pacemaker currents. The composition of pacemaker channel complexes in different tissues is poorly understood, and the presence of additional HCN modulating subunits was speculated. Here we show that vesicle-associated membrane protein-associated protein B (VAPB), previously associated with a familial form of amyotrophic lateral sclerosis 8, is an essential HCN1 and HCN2 modulator. VAPB significantly increases HCN2 currents and surface expression and has a major influence on the dendritic neuronal distribution of HCN2. Severe cardiac bradycardias in VAPB-deficient zebrafish and VAPB-/- mice highlight that VAPB physiologically serves to increase cardiac pacemaker currents. An altered T-wave morphology observed in the ECGs of VAPB-/- mice supports the recently proposed role of HCN channels for ventricular repolarization. The critical function of VAPB in native pacemaker channel complexes will be relevant for our understanding of cardiac arrhythmias and epilepsies, and provides an unexpected link between these diseases and amyotrophic lateral sclerosis.-Silbernagel, N., Walecki, M., Schäfer, M.-K. H., Kessler, M., Zobeiri, M., Rinné, S., Kiper, A. K., Komadowski, M. A., Vowinkel, K. S., Wemhöner, K., Fortmüller, L., Schewe, M., Dolga, A. M., Scekic-Zahirovic, J., Matschke, L. A., Culmsee, C., Baukrowitz, T., Monassier, L., Ullrich, N. D., Dupuis, L., Just, S., Budde, T., Fabritz, L., Decher, N. The VAMP-associated protein VAPB is required for cardiac and neuronal pacemaker channel function.
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Affiliation(s)
- Nicole Silbernagel
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Magdalena Walecki
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Martin K-H Schäfer
- Institute of Anatomy and Cell Biology, Philipps University, Marburg, Germany
| | - Mirjam Kessler
- Molecular Cardiology, Department of Internal Medicine II, University Hospital Ulm, Ulm, Germany
| | | | - Susanne Rinné
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Aytug K Kiper
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Marlene A Komadowski
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany.,Institute of Anatomy and Cell Biology, Philipps University, Marburg, Germany
| | - Kirsty S Vowinkel
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Konstantin Wemhöner
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Lisa Fortmüller
- Department of Cardiology II - Electrophysiology, University Hospital Münster, University of Münster, Munster, Germany
| | - Marcus Schewe
- Institute of Physiology, Christian-Albrechts University, Kiel, Germany
| | - Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, Phillips University, Marburg, Germany
| | - Jelena Scekic-Zahirovic
- Laboratoire de Pharmacologie et Toxicologie NeuroCardiovasculaire, Faculté de Médecine, Université de Strasbourg, Strasbourg, France
| | - Lina A Matschke
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, Phillips University, Marburg, Germany
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts University, Kiel, Germany
| | - Laurent Monassier
- Laboratoire de Pharmacologie et Toxicologie NeuroCardiovasculaire, Faculté de Médecine, Université de Strasbourg, Strasbourg, France
| | - Nina D Ullrich
- Institute of Physiology and Pathophysiology, University of Heidelberg, Heidelberg, Germany
| | - Luc Dupuis
- Laboratoire de Neurobiologie et Pharmacologie Cardiovasculaire, Faculté de Médecine, Université de Strasbourg, Strasbourg, France.,INSERM, Faculté de Médecine, Université de Strasbourg, Strasbourg, France
| | - Steffen Just
- Molecular Cardiology, Department of Internal Medicine II, University Hospital Ulm, Ulm, Germany
| | - Thomas Budde
- Institute for Physiology I, University of Münster, Munster, Germany
| | - Larissa Fabritz
- Department of Cardiology II - Electrophysiology, University Hospital Münster, University of Münster, Munster, Germany.,Institute of Cardiovascular Sciences, University Hospital Birmingham, University of Birmingham, Birmingham, United Kingdom.,Department of Cardiology, University Hospital Birmingham, University of Birmingham, Birmingham, United Kingdom.,Division of Rhythmology, Department of Genetic Epidemiology, University Hospital Münster, University of Münster, Munster, Germany.,Institute of Human Genetics, Department of Genetic Epidemiology, University Hospital Münster, University of Münster, Munster, Germany
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Phillips University, Marburg, Germany
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12
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McClenaghan C, Schewe M, Aryal P, Carpenter EP, Baukrowitz T, Tucker SJ. Polymodal activation of the TREK-2 K2P channel produces structurally distinct open states. J Gen Physiol 2017; 147:497-505. [PMID: 27241700 PMCID: PMC4886281 DOI: 10.1085/jgp.201611601] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 05/09/2016] [Indexed: 01/08/2023] Open
Abstract
TREK channels, which are gated open by a wide range of stimuli, exist in at least two conformations known as “up” and “down.” McClenaghan et al. show that the channel can be open in both of these conformations and that gating is primarily achieved by the channel’s selectivity filter. The TREK subfamily of two-pore domain (K2P) K+ channels exhibit polymodal gating by a wide range of physical and chemical stimuli. Crystal structures now exist for these channels in two main states referred to as the “up” and “down” conformations. However, recent studies have resulted in contradictory and mutually exclusive conclusions about the functional (i.e., conductive) status of these two conformations. To address this problem, we have used the state-dependent TREK-2 inhibitor norfluoxetine that can only bind to the down state, thereby allowing us to distinguish between these two conformations when activated by different stimuli. Our results reconcile these previously contradictory gating models by demonstrating that activation by pressure, temperature, voltage, and pH produce more than one structurally distinct open state and reveal that channel activation does not simply involve switching between the up and down conformations. These results also highlight the diversity of structural mechanisms that K2P channels use to integrate polymodal gating signals.
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Affiliation(s)
- Conor McClenaghan
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, England, UK OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PU, England, UK
| | - Marcus Schewe
- Department of Physiology, University of Kiel, 24118 Kiel, Germany
| | - Prafulla Aryal
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, England, UK OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PU, England, UK
| | - Elisabeth P Carpenter
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PU, England, UK Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, England, UK
| | | | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, England, UK OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PU, England, UK
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13
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Decher N, Ortiz-Bonnin B, Friedrich C, Schewe M, Kiper AK, Rinné S, Seemann G, Peyronnet R, Zumhagen S, Bustos D, Kockskämper J, Kohl P, Just S, González W, Baukrowitz T, Stallmeyer B, Schulze-Bahr E. Sodium permeable and "hypersensitive" TREK-1 channels cause ventricular tachycardia. EMBO Mol Med 2017; 9:403-414. [PMID: 28242754 PMCID: PMC5376757 DOI: 10.15252/emmm.201606690] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In a patient with right ventricular outflow tract (RVOT) tachycardia, we identified a heterozygous point mutation in the selectivity filter of the stretch-activated K2P potassium channel TREK-1 (KCNK2 or K2P2.1). This mutation introduces abnormal sodium permeability to TREK-1. In addition, mutant channels exhibit a hypersensitivity to stretch-activation, suggesting that the selectivity filter is directly involved in stretch-induced activation and desensitization. Increased sodium permeability and stretch-sensitivity of mutant TREK-1 channels may trigger arrhythmias in areas of the heart with high physical strain such as the RVOT We present a pharmacological strategy to rescue the selectivity defect of the TREK-1 pore. Our findings provide important insights for future studies of K2P channel stretch-activation and the role of TREK-1 in mechano-electrical feedback in the heart.
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Affiliation(s)
- Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Beatriz Ortiz-Bonnin
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Corinna Friedrich
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Marcus Schewe
- Institute of Physiology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Aytug K Kiper
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Susanne Rinné
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Gunnar Seemann
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sven Zumhagen
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Daniel Bustos
- Center for Bioinformatics and Molecular Simulation, University of Talca, Talca, Chile
| | - Jens Kockskämper
- Institute of Pharmacology and Clinical Pharmacy, Biochemical and Pharmacological Center (BPC) Philipps-University of Marburg, Marburg, Germany
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Steffen Just
- Molecular Cardiology, University Hospital Ulm, Ulm, Germany
| | - Wendy González
- Center for Bioinformatics and Molecular Simulation, University of Talca, Talca, Chile
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Birgit Stallmeyer
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Eric Schulze-Bahr
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
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14
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Aryal P, Jarerattanachat V, Clausen MV, Schewe M, McClenaghan C, Argent L, Conrad LJ, Dong YY, Pike ACW, Carpenter EP, Baukrowitz T, Sansom MSP, Tucker SJ. Bilayer-Mediated Structural Transitions Control Mechanosensitivity of the TREK-2 K2P Channel. Structure 2017; 25:708-718.e2. [PMID: 28392258 PMCID: PMC5415359 DOI: 10.1016/j.str.2017.03.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/01/2017] [Accepted: 03/10/2017] [Indexed: 11/25/2022]
Abstract
The mechanosensitive two-pore domain (K2P) K+ channels (TREK-1, TREK-2, and TRAAK) are important for mechanical and thermal nociception. However, the mechanisms underlying their gating by membrane stretch remain controversial. Here we use molecular dynamics simulations to examine their behavior in a lipid bilayer. We show that TREK-2 moves from the “down” to “up” conformation in direct response to membrane stretch, and examine the role of the transmembrane pressure profile in this process. Furthermore, we show how state-dependent interactions with lipids affect the movement of TREK-2, and how stretch influences both the inner pore and selectivity filter. Finally, we present functional studies that demonstrate why direct pore block by lipid tails does not represent the principal mechanism of mechanogating. Overall, this study provides a dynamic structural insight into K2P channel mechanosensitivity and illustrates how the structure of a eukaryotic mechanosensitive ion channel responds to changes in forces within the bilayer. Mechanogating of TREK-2 involves movement from the down to up conformation Simulations sample a wide range of mechanosensitive K2P channel structures Changes in the pressure profile and state-dependent lipid interactions play a key role Lipid block of the inner pore does not mediate stretch activation
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Affiliation(s)
- Prafulla Aryal
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Viwan Jarerattanachat
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Michael V Clausen
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Marcus Schewe
- Department of Physiology, University of Kiel, 24118 Kiel, Germany
| | - Conor McClenaghan
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Liam Argent
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Linus J Conrad
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK
| | - Yin Y Dong
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Ashley C W Pike
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Elisabeth P Carpenter
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK; Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | | | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK.
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, UK.
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15
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Schewe M, Nematian-Ardestani E, Sun H, Musinszki M, Cordeiro S, Bucci G, de Groot BL, Tucker SJ, Rapedius M, Baukrowitz T. A Non-canonical Voltage-Sensing Mechanism Controls Gating in K2P K(+) Channels. Cell 2016; 164:937-49. [PMID: 26919430 PMCID: PMC4771873 DOI: 10.1016/j.cell.2016.02.002] [Citation(s) in RCA: 130] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 09/23/2015] [Accepted: 01/29/2016] [Indexed: 12/21/2022]
Abstract
Two-pore domain (K2P) K(+) channels are major regulators of excitability that endow cells with an outwardly rectifying background "leak" conductance. In some K2P channels, strong voltage-dependent activation has been observed, but the mechanism remains unresolved because they lack a canonical voltage-sensing domain. Here, we show voltage-dependent gating is common to most K2P channels and that this voltage sensitivity originates from the movement of three to four ions into the high electric field of an inactive selectivity filter. Overall, this ion-flux gating mechanism generates a one-way "check valve" within the filter because outward movement of K(+) induces filter opening, whereas inward movement promotes inactivation. Furthermore, many physiological stimuli switch off this flux gating mode to convert K2P channels into a leak conductance. These findings provide insight into the functional plasticity of a K(+)-selective filter and also refine our understanding of K2P channels and the mechanisms by which ion channels can sense voltage.
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Affiliation(s)
- Marcus Schewe
- Institute of Physiology, Christian-Albrechts University, 24118 Kiel, Germany
| | | | - Han Sun
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Leibniz-Institut für Molekulare Pharmakologie, 13125 Berlin, Germany
| | - Marianne Musinszki
- Institute of Physiology, Christian-Albrechts University, 24118 Kiel, Germany
| | - Sönke Cordeiro
- Institute of Physiology, Christian-Albrechts University, 24118 Kiel, Germany
| | - Giovanna Bucci
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Bert L de Groot
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative, University of Oxford, Oxford OX1 3PU, UK
| | - Markus Rapedius
- Institute of Physiology, Christian-Albrechts University, 24118 Kiel, Germany; Nanion Technologies GmbH, 80636 Munich, Germany
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts University, 24118 Kiel, Germany.
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16
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Schewe M, Nematian-Ardestani E, Sun H, Musinszki M, Cordeiro S, Bucci G, de Groot BL, Tucker SJ, Rapedius M, Baukrowitz T. A Non-Canonical Voltage Sensor Controls Gating in K2P K+ Channels. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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17
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McClenaghan C, Schewe M, Baukrowitz T, Tucker SJ. Polymodal Gating of the TREK-2 K2P Potassium Channel Involves Structurally Distinct Open States. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.3241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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18
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Schewe M, Nematian-Ardestani E, Linke T, Benndorf K, Tucker SJ, Rapedius M, Baukrowitz T. Sensing the Electrochemical K+ Gradient: The Voltage Gating Mechanism in K2P Potassium Channels. Biophys J 2015. [DOI: 10.1016/j.bpj.2014.11.2338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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19
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Schewe M, Müller P, Korte T, Herrmann A. The role of phospholipid asymmetry in calcium-phosphate-induced fusion of human erythrocytes. J Biol Chem 1992; 267:5910-5. [PMID: 1556105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
To elucidate the role of phospholipid asymmetry in calcium-phosphate-induced fusion of human erythrocytes, we examined the interaction of erythrocyte membranes with asymmetric and symmetric bilayer distributions of phospholipids. Fusion of human erythrocytes was monitored by light microscopy as well as spectrophotometrically by the octadecylrhodamine dequenching assay. Phospholipid translocation and distribution between the inner and the outer leaflet of intact red blood cells were determined with spin-labeled phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). Significant fusion of lipid-asymmetric red blood cells where PS and PE are predominantly oriented to the inner leaflet was only observed at Ca2+ concentrations greater than or equal to 10 mM (in the presence of 10 mM phosphate buffer) while fusion of lipid-symmetric erythrocyte membranes was established at greater than or equal to 1.5 mM Ca2+. The Ca2+ threshold of fusion of lipid-asymmetric red blood cells was significantly reduced (i) after exposure of PS to the outer layer but not after redistribution of PE alone, and (ii) upon incorporation of spin-labeled PS into the outer leaflet of red blood cells. Spin-labeled PE or PC did not affect fusion, suggesting that the serine headgroup is an important factor in calcium-phosphate-induced fusion.
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Affiliation(s)
- M Schewe
- Institut für Biophysik, Humbolt-Universität Berlin, Germany
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20
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Schewe M, Müller P, Korte T, Herrmann A. The role of phospholipid asymmetry in calcium-phosphate-induced fusion of human erythrocytes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)42640-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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21
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Mehnert D, Koch E, Paufler D, Schewe M. [Electromyographic studies of muscle activity in wind instrument players]. Z Gesamte Hyg 1983; 29:209-14. [PMID: 6868696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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