1
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Fan X, Ye Y, Saha A, Peng L, Pindi C, Wang Q, Yang L, Liu J, Tang X, Palermo G, Liao J, Xu T, Lu Y, Du G. Fine-tuning pH sensor H98 by remote essential residues in the hydrogen-bond network of mTASK-3. Int J Biol Macromol 2024; 273:132892. [PMID: 38878921 DOI: 10.1016/j.ijbiomac.2024.132892] [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] [Received: 11/15/2023] [Revised: 05/21/2024] [Accepted: 06/02/2024] [Indexed: 06/23/2024]
Abstract
TASK-3 generates a background K+ conductance which when inhibited by acidification depolarizes membrane potential and increases cell excitability. These channels sense pH by protonation of histidine residue H98, but recent evidence revealed that several other amino acid residues also contribute to TASK-3 pH sensitivity, suggesting that the pH sensitivity is determined by an intermolecular network. Here we use electrophysiology and molecular modeling to characterize the nature and requisite role(s) of multiple amino acids in pH sensing by TASK-3. Our results suggest that the pH sensor H98 and consequently pH sensitivity is influenced by remote amino acids that function as a hydrogen-bonding network to modulate ionic conductivity. Among the residues in the network, E30 and K79 are the most important for passing external signals near residue S31 to H98. The hydrogen-bond network plays a key role in selectivity or pH sensing in mTASK-3, and E30 and S31 in the network can modulate the conductive properties (E30) or reverse the pH sensitivity and selectivity of the channel (S31). Molecular dynamics simulations and pK1/2 calculation revealed that double mutants involving H98 + S31 primarily regulate the structure stability of the pore selectivity filter and pore loop regions, further strengthen the stability of the cradle suspension system, and alter the ionization state of E30 and K79, thereby preventing pore conformational change that normally occurs in response to varying extracellular pH. These results demonstrate that crucial residues in the hydrogen-bond network can remotely tune the pH sensing of mTASK-3 and may be a potential allosteric regulatory site for therapeutic molecule development.
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Affiliation(s)
- Xueming Fan
- Department of Pain Management, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Yifei Ye
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Aakash Saha
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Li Peng
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Chinmai Pindi
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Qi Wang
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Linghui Yang
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Jin Liu
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Xiangdong Tang
- Sleep Medicine Center, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; Mental Health Center, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; State Key Laboratory of Biotherapy, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Giulia Palermo
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Jiayu Liao
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States; Huaxi-Cal Research Center for Predictive Intervention Medicine, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Tingting Xu
- Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guizhou, Guangdong 510530, China
| | - Yongzhi Lu
- Guangzhou National Laboratory, Guangzhou International Bio Island, Guangzhou, Guangdong 510005, China.
| | - Guizhi Du
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China.
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2
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Elliott ER, Brock KE, Vacassenno RM, Harrison DA, Cooper RL. The effects of doxapram and its potential interactions with K2P channels in experimental model preparations. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024:10.1007/s00359-024-01705-6. [PMID: 38802613 DOI: 10.1007/s00359-024-01705-6] [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: 02/05/2024] [Revised: 05/15/2024] [Accepted: 05/18/2024] [Indexed: 05/29/2024]
Abstract
The channels commonly responsible for maintaining cell resting membrane potentials are referred to as K2P (two-P-domain K+ subunit) channels. These K+ ion channels generally remain open but can be modulated by their local environment. These channels are classified based on pharmacology, pH sensitivity, mechanical stretch, and ionic permeability. Little is known about the physiological nature of these K2P channels in invertebrates. Acidic conditions depolarize neurons and muscle fibers, which may be caused by K2P channels given that one subtype can be blocked by acidic conditions. Doxapram is used clinically as a respiratory aid known to block acid-sensitive K2P channels; thus, the effects of doxapram on the muscle fibers and synaptic transmission in larval Drosophila and crawfish were monitored. A dose-dependent response was observed via depolarization of the larval Drosophila muscle and an increase in evoked synaptic transmission, but doxapram blocked the production of action potentials in the crawfish motor neuron and had a minor effect on the resting membrane potential of the crawfish muscle. This indicates that the nerve and muscle tissues in larval Drosophila and crawfish likely express different K2P channel subtypes. Since these organisms serve as physiological models for neurobiology and physiology, it would be of interest to further investigate what types of K2P channel are expressed in these tissues. (212 words).
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Affiliation(s)
- Elizabeth R Elliott
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Kaitlyn E Brock
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | | | - Douglas A Harrison
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Robin L Cooper
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA.
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3
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Kim SS, Park J, Kim E, Hwang EM, Park JY. β-COP Suppresses the Surface Expression of the TREK2. Cells 2023; 12:1500. [PMID: 37296621 PMCID: PMC10252889 DOI: 10.3390/cells12111500] [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] [Received: 04/14/2023] [Revised: 05/18/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023] Open
Abstract
K2P channels, also known as two-pore domain K+ channels, play a crucial role in maintaining the cell membrane potential and contributing to potassium homeostasis due to their leaky nature. The TREK, or tandem of pore domains in a weak inward rectifying K+ channel (TWIK)-related K+ channel, subfamily within the K2P family consists of mechanical channels regulated by various stimuli and binding proteins. Although TREK1 and TREK2 within the TREK subfamily share many similarities, β-COP, which was previously known to bind to TREK1, exhibits a distinct binding pattern to other members of the TREK subfamily, including TREK2 and the TRAAK (TWIK-related acid-arachidonic activated K+ channel). In contrast to TREK1, β-COP binds to the C-terminus of TREK2 and reduces its cell surface expression but does not bind to TRAAK. Furthermore, β-COP cannot bind to TREK2 mutants with deletions or point mutations in the C-terminus and does not affect the surface expression of these TREK2 mutants. These results emphasize the unique role of β-COP in regulating the surface expression of the TREK family.
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Affiliation(s)
- Seong-Seop Kim
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Republic of Korea; (S.-S.K.); (J.P.)
| | - Jimin Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Republic of Korea; (S.-S.K.); (J.P.)
- BK21FOUR R&E Center for Learning Health Systems, Korea University, Seoul 02841, Republic of Korea
| | - Eunju Kim
- Brain Science Institute (BSI), Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea;
| | - Eun Mi Hwang
- Brain Science Institute (BSI), Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea;
| | - Jae-Yong Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Republic of Korea; (S.-S.K.); (J.P.)
- BK21FOUR R&E Center for Learning Health Systems, Korea University, Seoul 02841, Republic of Korea
- ASTRION, Inc., Seoul 02842, Republic of Korea
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4
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Herrera-Pérez S, Lamas JA. TREK channels in Mechanotransduction: a Focus on the Cardiovascular System. Front Cardiovasc Med 2023; 10:1180242. [PMID: 37288256 PMCID: PMC10242076 DOI: 10.3389/fcvm.2023.1180242] [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: 03/06/2023] [Accepted: 04/26/2023] [Indexed: 06/09/2023] Open
Abstract
Mechano-electric feedback is one of the most important subsystems operating in the cardiovascular system, but the underlying molecular mechanism remains rather unknown. Several proteins have been proposed to explain the molecular mechanism of mechano-transduction. Transient receptor potential (TRP) and Piezo channels appear to be the most important candidates to constitute the molecular mechanism behind of the inward current in response to a mechanical stimulus. However, the inhibitory/regulatory processes involving potassium channels that operate on the cardiac system are less well known. TWIK-Related potassium (TREK) channels have emerged as strong candidates due to their capacity for the regulation of the flow of potassium in response to mechanical stimuli. Current data strongly suggest that TREK channels play a role as mechano-transducers in different components of the cardiovascular system, not only at central (heart) but also at peripheral (vascular) level. In this context, this review summarizes and highlights the main existing evidence connecting this important subfamily of potassium channels with the cardiac mechano-transduction process, discussing molecular and biophysical aspects of such a connection.
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Affiliation(s)
- Salvador Herrera-Pérez
- Laboratory of Neuroscience, CINBIO, University of Vigo, Vigo, Spain
- Laboratory of Neuroscience, Galicia Sur Health Research Institute (IISGS), Vigo, Spain
| | - José Antonio Lamas
- Laboratory of Neuroscience, CINBIO, University of Vigo, Vigo, Spain
- Laboratory of Neuroscience, Galicia Sur Health Research Institute (IISGS), Vigo, Spain
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5
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Kim SS, Bae Y, Kwon O, Kwon SH, Seo JB, Hwang EM, Park JY. β-COP Regulates TWIK1/TREK1 Heterodimeric Channel-Mediated Passive Conductance in Astrocytes. Cells 2022; 11:cells11203322. [PMID: 36291187 PMCID: PMC9600989 DOI: 10.3390/cells11203322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/16/2022] [Accepted: 10/19/2022] [Indexed: 11/16/2022] Open
Abstract
Mature astrocytes are characterized by a K+ conductance (passive conductance) that changes with a constant slope with voltage, which is involved in K+ homeostasis in the brain. Recently, we reported that the tandem of pore domains in a weak inward rectifying K+ channel (TWIK1 or KCNK1) and TWIK-related K+ channel 1 (TREK1 or KCNK2) form heterodimeric channels that mediate passive conductance in astrocytes. However, little is known about the binding proteins that regulate the function of the TWIK1/TREK1 heterodimeric channels. Here, we found that β-coat protein (COP) regulated the surface expression and activity of the TWIK1/TREK1 heterodimeric channels in astrocytes. β-COP binds directly to TREK1 but not TWIK1 in a heterologous expression system. However, β-COP also interacts with the TWIK1/TREK1 heterodimeric channel in a TREK1 dependent manner and enhances the surface expression of the heterodimeric channel in astrocytes. Consequently, it regulates TWIK1/TREK1 heterodimeric channel-mediated passive conductance in astrocytes in the mouse brain. Taken together, these results suggest that β-COP is a potential regulator of astrocytic passive conductance in the brain.
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Affiliation(s)
- Seong-Seop Kim
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea
| | - Yeonju Bae
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Osung Kwon
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea
| | - Seung-Hae Kwon
- Seoul Center, Korea Basic Science Institute (KBSI), Seoul 02841, Korea
| | - Jong Bok Seo
- Seoul Center, Korea Basic Science Institute (KBSI), Seoul 02841, Korea
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Jae-Yong Park
- School of Biosystems and Biomedical Sciences, College of Health Sciences, Korea University, Seoul 02841, Korea
- Correspondence: ; Tel.: +82-2-3290-5637
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6
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Reddi R, Matulef K, Riederer EA, Whorton MR, Valiyaveetil FI. Structural basis for C-type inactivation in a Shaker family voltage-gated K + channel. SCIENCE ADVANCES 2022; 8:eabm8804. [PMID: 35452285 PMCID: PMC9032944 DOI: 10.1126/sciadv.abm8804] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 03/08/2022] [Indexed: 06/14/2023]
Abstract
C-type inactivation is a process by which ion flux through a voltage-gated K+ (Kv) channel is regulated at the selectivity filter. While prior studies have indicated that C-type inactivation involves structural changes at the selectivity filter, the nature of the changes has not been resolved. Here, we report the crystal structure of the Kv1.2 channel in a C-type inactivated state. The structure shows that C-type inactivation involves changes in the selectivity filter that disrupt the outer two ion binding sites in the filter. The changes at the selectivity filter propagate to the extracellular mouth and the turret regions of the channel pore. The structural changes observed are consistent with the functional hallmarks of C-type inactivation. This study highlights the intricate interplay between K+ occupancy at the ion binding sites and the interactions of the selectivity filter in determining the balance between the conductive and the inactivated conformations of the filter.
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Affiliation(s)
- Ravikumar Reddi
- Program in Chemical Biology, Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA
| | - Kimberly Matulef
- Program in Chemical Biology, Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA
| | - Erika A. Riederer
- Program in Chemical Biology, Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA
| | - Matthew R. Whorton
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA
| | - Francis I. Valiyaveetil
- Program in Chemical Biology, Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, Portland, OR 97239, USA
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7
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Zhang Q, Fu J, Zhang S, Guo P, Liu S, Shen J, Guo J, Yang H. 'C-type' closed state and gating mechanisms of K2P channels revealed by conformational changes of the TREK-1 channel. J Mol Cell Biol 2022; 14:6504012. [PMID: 35022758 PMCID: PMC9021975 DOI: 10.1093/jmcb/mjac002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/04/2022] [Accepted: 01/07/2022] [Indexed: 01/10/2023] Open
Abstract
Two-pore domain potassium (K2P) channels gate primarily within the selectivity filter, termed ‘C-type’ gating. Due to the lack of structural insights into the nonconductive (closed) state, ‘C-type’ gating mechanisms remain elusive. Here, molecular dynamics (MD) simulations on TREK-1, a K2P channel, revealed that M4 helix movements induce filter closing in a novel ‘deeper-down’ structure that represents a ‘C-type’ closed state. The ‘down’ structure does not represent the closed state as previously proposed and instead acts as an intermediate state in gating. The study identified the allosteric ‘seesaw’ mechanism of M4 helix movements in modulating filter closing. Finally, guided by this recognition of K2P gating mechanisms, MD simulations revealed that gain-of-function mutations and small-molecule activators activate TREK-1 by perturbing state transitions from open to closed states. Together, we reveal a ‘C-type’ closed state and provide mechanical insights into gating procedures and allosteric regulations for K2P channels.
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Affiliation(s)
- Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Jie Fu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Shaoying Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Peipei Guo
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Shijie Liu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Juwen Shen
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Jiangtao Guo
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai 200241, China
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8
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Control of Biophysical and Pharmacological Properties of Potassium Channels by Ancillary Subunits. Handb Exp Pharmacol 2021; 267:445-480. [PMID: 34247280 DOI: 10.1007/164_2021_512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Potassium channels facilitate and regulate physiological processes as diverse as electrical signaling, ion, solute and hormone secretion, fluid homeostasis, hearing, pain sensation, muscular contraction, and the heartbeat. Potassium channels are each formed by either a tetramer or dimer of pore-forming α subunits that co-assemble to create a multimer with a K+-selective pore that in most cases is capable of functioning as a discrete unit to pass K+ ions across the cell membrane. The reality in vivo, however, is that the potassium channel α subunit multimers co-assemble with ancillary subunits to serve specific physiological functions. The ancillary subunits impart specific physiological properties that are often required for a particular activity in vivo; in addition, ancillary subunit interaction often alters the pharmacology of the resultant complex. In this chapter the modes of action of ancillary subunits on K+ channel physiology and pharmacology are described and categorized into various mechanistic classes.
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9
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Mathie A, Veale EL, Golluscio A, Holden RG, Walsh Y. Pharmacological Approaches to Studying Potassium Channels. Handb Exp Pharmacol 2021; 267:83-111. [PMID: 34195873 DOI: 10.1007/164_2021_502] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this review, we consider the pharmacology of potassium channels from the perspective of these channels as therapeutic targets. Firstly, we describe the three main families of potassium channels in humans and disease states where they are implicated. Secondly, we describe the existing therapeutic agents which act on potassium channels and outline why these channels represent an under-exploited therapeutic target with potential for future drug development. Thirdly, we consider the evidence desired in order to embark on a drug discovery programme targeting a particular potassium channel. We have chosen two "case studies": activators of the two-pore domain potassium (K2P) channel TREK-2 (K2P10.1), for the treatment of pain and inhibitors of the voltage-gated potassium channel KV1.3, for use in autoimmune diseases such as multiple sclerosis. We describe the evidence base to suggest why these are viable therapeutic targets. Finally, we detail the main technical approaches available to characterise the pharmacology of potassium channels and identify novel regulatory compounds. We draw particular attention to the Comprehensive in vitro Proarrhythmia Assay initiative (CiPA, https://cipaproject.org ) project for cardiac safety, as an example of what might be both desirable and possible in the future, for ion channel regulator discovery projects.
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Affiliation(s)
- Alistair Mathie
- Medway School of Pharmacy, University of Kent, Kent, UK. .,Medway School of Pharmacy, University of Greenwich, London, UK. .,School of Engineering, Arts, Science and Technology, University of Suffolk, Ipswich, UK.
| | - Emma L Veale
- Medway School of Pharmacy, University of Kent, Kent, UK.,Medway School of Pharmacy, University of Greenwich, London, UK
| | - Alessia Golluscio
- Medway School of Pharmacy, University of Kent, Kent, UK.,Medway School of Pharmacy, University of Greenwich, London, UK
| | - Robyn G Holden
- Medway School of Pharmacy, University of Kent, Kent, UK.,Medway School of Pharmacy, University of Greenwich, London, UK
| | - Yvonne Walsh
- Medway School of Pharmacy, University of Kent, Kent, UK.,Medway School of Pharmacy, University of Greenwich, London, UK
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10
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Natale AM, Deal PE, Minor DL. Structural Insights into the Mechanisms and Pharmacology of K 2P Potassium Channels. J Mol Biol 2021; 433:166995. [PMID: 33887333 PMCID: PMC8436263 DOI: 10.1016/j.jmb.2021.166995] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/08/2021] [Accepted: 04/09/2021] [Indexed: 01/10/2023]
Abstract
Leak currents, defined as voltage and time independent flows of ions across cell membranes, are central to cellular electrical excitability control. The K2P (KCNK) potassium channel class comprises an ion channel family that produces potassium leak currents that oppose excitation and stabilize the resting membrane potential in cells in the brain, cardiovascular system, immune system, and sensory organs. Due to their widespread tissue distribution, K2Ps contribute to many physiological and pathophysiological processes including anesthesia, pain, arrythmias, ischemia, hypertension, migraine, intraocular pressure regulation, and lung injury responses. Structural studies of six homomeric K2Ps have established the basic architecture of this channel family, revealed key moving parts involved in K2P function, uncovered the importance of asymmetric pinching and dilation motions in the K2P selectivity filter (SF) C-type gate, and defined two K2P structural classes based on the absence or presence of an intracellular gate. Further, a series of structures characterizing K2P:modulator interactions have revealed a striking polysite pharmacology housed within a relatively modestly sized (~70 kDa) channel. Binding sites for small molecules or lipids that control channel function are found at every layer of the channel structure, starting from its extracellular side through the portion that interacts with the membrane bilayer inner leaflet. This framework provides the basis for understanding how gating cues sensed by different channel parts control function and how small molecules and lipids modulate K2P activity. Such knowledge should catalyze development of new K2P modulators to probe function and treat a wide range of disorders.
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Affiliation(s)
- Andrew M Natale
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA
| | - Parker E Deal
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA; California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA 94158, USA; Kavli Institute for Fundamental Neuroscience University of California, San Francisco, CA 94158, USA; Molecular Biophysics and Integrated Bio-imaging Division Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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11
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Lee H, Lolicato M, Arrigoni C, Minor DL. Production of K 2P2.1 (TREK-1) for structural studies. Methods Enzymol 2021; 653:151-188. [PMID: 34099170 DOI: 10.1016/bs.mie.2021.02.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
K2P (KCNK) potassium channels form 'background' or 'leak' currents that are important for controlling cell excitability in the brain, cardiovascular system, and somatosensory neurons. K2P2.1 (TREK-1) is one of the founding members of this family and one of the first well-characterized polymodal ion channels capable of responding to a variety of physical and chemical gating cues. Of the six K2P subfamilies, the thermo-and mechano-sensitive TREK subfamily comprising K2P2.1 (TREK-1), K2P4.1 (TRAAK), and K2P10.1 (TREK-2) is the first to have structures determined for each subfamily member. These structural studies have revealed key architectural features that provide a framework for understanding how gating cues sensed by different channel elements converge on the K2P selectivity filter C-type gate. TREK family structural studies have also revealed numerous sites where small molecules or lipids bind and affect channel function. This rich structural landscape provides the framework for probing K2P function and for the development of new K2P-directed agents. Such molecules may be useful for affecting processes where TREK channels are important such as anesthesia, pain, arrythmia, ischemia, migraine, intraocular pressure, and lung injury. Production of high quality protein samples is key to addressing new questions about K2P function and pharmacology. Here, we present methods for producing pure K2P2.1 (TREK-1) suitable for advancing towards these goals through structural and biochemical studies.
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Affiliation(s)
- Haerim Lee
- Cardiovascular Research Institute, University of California, San Francisco, CA, United States
| | - Marco Lolicato
- Cardiovascular Research Institute, University of California, San Francisco, CA, United States
| | - Cristina Arrigoni
- Cardiovascular Research Institute, University of California, San Francisco, CA, United States
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California, San Francisco, CA, United States; Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, University of California, San Francisco, CA, United States; California Institute for Quantitative Biomedical Research, University of California, San Francisco, CA, United States; Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, CA, United States; Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
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12
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Mondéjar-Parreño G, Cogolludo A, Perez-Vizcaino F. Potassium (K +) channels in the pulmonary vasculature: Implications in pulmonary hypertension Physiological, pathophysiological and pharmacological regulation. Pharmacol Ther 2021; 225:107835. [PMID: 33744261 DOI: 10.1016/j.pharmthera.2021.107835] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/26/2021] [Accepted: 03/02/2021] [Indexed: 02/06/2023]
Abstract
The large K+ channel functional diversity in the pulmonary vasculature results from the multitude of genes expressed encoding K+ channels, alternative RNA splicing, the post-transcriptional modifications, the presence of homomeric or heteromeric assemblies of the pore-forming α-subunits and the existence of accessory β-subunits modulating the functional properties of the channel. K+ channels can also be regulated at multiple levels by different factors controlling channel activity, trafficking, recycling and degradation. The activity of these channels is the primary determinant of membrane potential (Em) in pulmonary artery smooth muscle cells (PASMC), providing an essential regulatory mechanism to dilate or contract pulmonary arteries (PA). K+ channels are also expressed in pulmonary artery endothelial cells (PAEC) where they control resting Em, Ca2+ entry and the production of different vasoactive factors. The activity of K+ channels is also important in regulating the population and phenotype of PASMC in the pulmonary vasculature, since they are involved in cell apoptosis, survival and proliferation. Notably, K+ channels play a major role in the development of pulmonary hypertension (PH). Impaired K+ channel activity in PH results from: 1) loss of function mutations, 2) downregulation of its expression, which involves transcription factors and microRNAs, or 3) decreased channel current as a result of increased vasoactive factors (e.g., hypoxia, 5-HT, endothelin-1 or thromboxane), exposure to drugs with channel-blocking properties, or by a reduction in factors that positively regulate K+ channel activity (e.g., NO and prostacyclin). Restoring K+ channel expression, its intracellular trafficking and the channel activity is an attractive therapeutic strategy in PH.
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Affiliation(s)
- Gema Mondéjar-Parreño
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain
| | - Angel Cogolludo
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain
| | - Francisco Perez-Vizcaino
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain.
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13
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Abstract
Aberrant function or expression of potassium channels can be underlying in pathologies such as cardiac arrhythmia, diabetes mellitus, hypertension, preterm birth, and various types of cancer. The expression of potassium channels is altered in many types of diseases. Also, we have previously shown that natural polyphenols, such as resveratrol, and selective synthetic modulators of potassium channels, like pinacidil, can alter their function and lead to the desired outcome. Therefore, targeting potassium channels with substance, which has an influence on their function, is promising access to cancer, diabetes mellitus, preterm birth, or hypertension therapy. In this chapter, we could discuss strategies for targeting different types of potassium channels as potential targets for synthetic and natural molecules therapy.
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14
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Pons-Bennaceur A, Tsintsadze V, Bui TT, Tsintsadze T, Minlebaev M, Milh M, Scavarda D, Giniatullin R, Giniatullina R, Shityakov S, Wright M, Miller AD, Lozovaya N, Burnashev N. Diadenosine-Polyphosphate Analogue AppCH2ppA Suppresses Seizures by Enhancing Adenosine Signaling in the Cortex. Cereb Cortex 2020; 29:3778-3795. [PMID: 30295710 DOI: 10.1093/cercor/bhy257] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 08/15/2018] [Accepted: 09/14/2018] [Indexed: 01/16/2023] Open
Abstract
Epilepsy is a multifactorial disorder associated with neuronal hyperexcitability that affects more than 1% of the human population. It has long been known that adenosine can reduce seizure generation in animal models of epilepsies. However, in addition to various side effects, the instability of adenosine has precluded its use as an anticonvulsant treatment. Here we report that a stable analogue of diadenosine-tetraphosphate: AppCH2ppA effectively suppresses spontaneous epileptiform activity in vitro and in vivo in a Tuberous Sclerosis Complex (TSC) mouse model (Tsc1+/-), and in postsurgery cortical samples from TSC human patients. These effects are mediated by enhanced adenosine signaling in the cortex post local neuronal adenosine release. The released adenosine induces A1 receptor-dependent activation of potassium channels thereby reducing neuronal excitability, temporal summation, and hypersynchronicity. AppCH2ppA does not cause any disturbances of the main vital autonomous functions of Tsc1+/- mice in vivo. Therefore, we propose this compound to be a potent new candidate for adenosine-related treatment strategies to suppress intractable epilepsies.
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Affiliation(s)
- Alexandre Pons-Bennaceur
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
| | - Vera Tsintsadze
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France.,Knight Cardiovascular Institute, Oregon Health and Science University, OR, USA
| | - Thi-Thien Bui
- B&A Therapeutics, Ben-Ari Institute of Neuroarcheology, Batiment Beret-Delaage, Zone Luminy Biotech Entreprises, Marseille, Cedex 09, France
| | - Timur Tsintsadze
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
| | - Marat Minlebaev
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France.,Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia
| | - Mathieu Milh
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, Marseille Cedex 5, France
| | - Didier Scavarda
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, Marseille Cedex 5, France
| | - Rashid Giniatullin
- Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia.,A.I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Eastern Finland, Kuopio, Finland
| | - Raisa Giniatullina
- A.I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Eastern Finland, Kuopio, Finland
| | - Sergey Shityakov
- Department of Anaesthesia and Critical Care, University of Würzburg, Josef-Schneider-Street 2, Würzburg, Germany
| | - Michael Wright
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, Waterloo Campus, 150 Stamford Street, London, UK
| | - Andrew D Miller
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, Waterloo Campus, 150 Stamford Street, London, UK.,Veterinary Research Institute, Hudcova 296/70, Brno, Czech Republic.,KP Therapeutics Ltd, 86 Deansgate, Manchester, UK
| | - Natalia Lozovaya
- B&A Therapeutics, Ben-Ari Institute of Neuroarcheology, Batiment Beret-Delaage, Zone Luminy Biotech Entreprises, Marseille, Cedex 09, France
| | - Nail Burnashev
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
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15
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Maltby CJ, Schofield JPR, Houghton SD, O’Kelly I, Vargas-Caballero M, Deinhardt K, Coldwell MJ. A 5' UTR GGN repeat controls localisation and translation of a potassium leak channel mRNA through G-quadruplex formation. Nucleic Acids Res 2020; 48:9822-9839. [PMID: 32870280 PMCID: PMC7515701 DOI: 10.1093/nar/gkaa699] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 08/28/2020] [Indexed: 12/18/2022] Open
Abstract
RNA G-quadruplexes (G4s) are secondary structures proposed to function as regulators of post-transcriptional mRNA localisation and translation. G4s within some neuronal mRNAs are known to control distal localisation and local translation, contributing to distinct local proteomes that facilitate the synaptic remodelling attributed to normal cellular function. In this study, we characterise the G4 formation of a (GGN)13 repeat found within the 5' UTR of the potassium 2-pore domain leak channel Task3 mRNA. Biophysical analyses show that this (GGN)13 repeat forms a parallel G4 in vitro exhibiting the stereotypical potassium specificity of G4s, remaining thermostable under physiological ionic conditions. Through mouse brain tissue G4-RNA immunoprecipitation, we further confirm that Task3 mRNA forms a G4 structure in vivo. The G4 is inhibitory to translation of Task3 in vitro and is overcome through activity of a G4-specific helicase DHX36, increasing K+ leak currents and membrane hyperpolarisation in HEK293 cells. Further, we observe that this G4 is fundamental to ensuring delivery of Task3 mRNA to distal primary cortical neurites. It has been shown that aberrant Task3 expression correlates with neuronal dysfunction, we therefore posit that this G4 is important in regulated local expression of Task3 leak channels that maintain K+ leak within neurons.
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Affiliation(s)
- Connor J Maltby
- School of Biological Sciences, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | - James P R Schofield
- School of Biological Sciences, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | - Steven D Houghton
- School of Biological Sciences, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | - Ita O’Kelly
- Centre for Human Development, Stem Cells and Regeneration, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | | | - Katrin Deinhardt
- School of Biological Sciences, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
| | - Mark J Coldwell
- School of Biological Sciences, University of Southampton, Southampton, Hampshire SO17 1BJ, UK
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16
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Imbrici P, Nematian-Ardestani E, Hasan S, Pessia M, Tucker SJ, D'Adamo MC. Altered functional properties of a missense variant in the TRESK K + channel (KCNK18) associated with migraine and intellectual disability. Pflugers Arch 2020; 472:923-930. [PMID: 32394190 DOI: 10.1007/s00424-020-02382-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/16/2020] [Accepted: 04/22/2020] [Indexed: 12/16/2022]
Abstract
Mutations in the KCNK18 gene that encodes the TRESK K2P potassium channel have previously been linked with typical familial migraine with aura. Recently, an atypical clinical case has been reported in which a male individual carrying the p.Trp101Arg (W101R) missense mutation in the KCNK18 gene was diagnosed with intellectual disability and migraine with brainstem aura. Here we report the functional characterization of this new missense variant. This mutation is located in a highly conserved residue close to the selectivity filter, and our results show although these mutant channels retain their K+ selectivity and calcineurin-dependent regulation, the variant causes an overall dramatic loss of TRESK channel function as well as an initial dominant-negative effect when co-expressed with wild-type channels in Xenopus laevis oocytes. The dramatic functional consequences of this mutation thereby support a potentially pathogenic role for this variant and provide further insight into the relationship between the structure and function of this ion channel.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Ehsan Nematian-Ardestani
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta
| | - Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Mauro Pessia
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.,Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Maria Cristina D'Adamo
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.
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17
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Gu RX, de Groot BL. Lipid-protein interactions modulate the conformational equilibrium of a potassium channel. Nat Commun 2020; 11:2162. [PMID: 32358584 PMCID: PMC7195391 DOI: 10.1038/s41467-020-15741-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/18/2020] [Indexed: 01/17/2023] Open
Abstract
Cell membranes actively participate in the regulation of protein structure and function. In this work, we conduct molecular dynamics simulations to investigate how different membrane environments affect protein structure and function in the case of MthK, a potassium channel. We observe different ion permeation rates of MthK in membranes with different properties, and ascribe them to a shift of the conformational equilibrium between two states of the channel that differ according to whether a transmembrane helix has a kink. Further investigations indicate that two key residues in the kink region mediate a crosstalk between two gates at the selectivity filter and the central cavity, respectively. Opening of one gate eventually leads to closure of the other. Our simulations provide an atomistic model of how lipid-protein interactions affect the conformational equilibrium of a membrane protein. The gating mechanism revealed for MthK may also apply to other potassium channels.
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Affiliation(s)
- Ruo-Xu Gu
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Bert L de Groot
- Department of Theoretical and Computational Biophysics, Max-Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.
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18
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Al-Moubarak E, Veale EL, Mathie A. Pharmacologically reversible, loss of function mutations in the TM2 and TM4 inner pore helices of TREK-1 K2P channels. Sci Rep 2019; 9:12394. [PMID: 31455781 PMCID: PMC6712037 DOI: 10.1038/s41598-019-48855-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 08/09/2019] [Indexed: 01/21/2023] Open
Abstract
A better understanding of the gating of TREK two pore domain potassium (K2P) channels and their activation by compounds such as the negatively charged activator, flufenamic acid (FFA) is critical in the search for more potent and selective activators of these channels. Currents through wild-type and mutated human K2P channels expressed in tsA201 cells were measured using whole-cell patch-clamp recordings in the presence and absence of FFA. Mutation of the TM2.6 residue of TREK-1 to a phenylalanine (G171F) and a similar mutation of TM4.6 (A286F) substantially reduced current through TREK-1 channels. In complementary experiments, replacing the natural F residues at the equivalent position in TRESK channels, significantly enhanced current. Known, gain of function mutations of TREK-1 (G137I, Y284A) recovered current through these mutated channels. This reduction in current could be also be reversed pharmacologically, by FFA. However, an appropriate length MTS (MethaneThioSulfonate) cross-linking reagent (MTS14) restricted the activation of TREK-1_A286C channels by repeated application of FFA. This suggests that the cross-linker stabilises the channel in a conformation which blunts FFA activation. Pharmacologically reversible mutations of TREK channels will help to clarify the importance of these channels in pathophysiological conditions such as pain and depression.
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Affiliation(s)
- Ehab Al-Moubarak
- Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Emma L Veale
- Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Alistair Mathie
- Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.
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19
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Riedelsberger J, Obando PA, Gonzalez W. Yeast strain Saccharomyces cerevisiae BYT45 lacking the cation extrusion systems ENA1-5 and NHA1 is suitable for the characterization of TASK-3 potassium channel antagonists. FEMS Yeast Res 2019; 19:5524363. [PMID: 31247642 DOI: 10.1093/femsyr/foz044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 06/24/2019] [Indexed: 11/13/2022] Open
Abstract
Finding new potential antagonists of potassium channels is a continuing task. TASK potassium channels operate over a large physiological range of membrane voltages, why they are thought to contribute to the excitability and resting potential of mammalian membrane potentials. Additionally, they are regulated by extracellular stimuli like changes in pH and K+ concentrations. TASK malfunctions are associated with diseases, which makes them popular targets for the search of new antagonists. Identification of channel inhibitors can be a time-consuming and expensive project. Here, we present an easy-to-use and inexpensive yeast system for the expression of the two-pore domain K+ channel TASK-3, and for the characterization of TASK-3 antagonists. The Saccharomyces cerevisiae strain BYT45 was used to express guinea pig TASK-3. The system allowed the expression and characterization of TASK-3 at variable pH values and K+ concentrations. Three known TASK-3 antagonists have been tested in the BYT45 yeast system: PK-THPP, ZnCl2 and Bupivacaine. Their inhibitory effect on TASK-3 was tested in solid and liquid media assays, and half maximal inhibitory concentrations were estimated. Although the system is less sensitive than more refined systems, the antagonistic activity could be confirmed for all three inhibitors.
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Affiliation(s)
- Janin Riedelsberger
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 3460000 Talca, Chile
| | - Patricia A Obando
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 3460000 Talca, Chile
| | - Wendy Gonzalez
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, 3460000 Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Centro de Bioinformática y Simulación Molecular, Universidad de Talca, 2 Norte 685, 3460000 Talca, Chile
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20
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Abbott GW. Chansporter complexes in cell signaling. FEBS Lett 2017; 591:2556-2576. [PMID: 28718502 DOI: 10.1002/1873-3468.12755] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/03/2017] [Accepted: 07/12/2017] [Indexed: 12/11/2022]
Abstract
Ion channels facilitate diffusion of ions across cell membranes for such diverse purposes as neuronal signaling, muscular contraction, and fluid homeostasis. Solute transporters often utilize ionic gradients to move aqueous solutes up their concentration gradient, also fulfilling a wide variety of tasks. Recently, an increasing number of ion channel-transporter ('chansporter') complexes have been discovered. Chansporter complex formation may overcome what could otherwise be considerable spatial barriers to rapid signal integration and feedback between channels and transporters, the ions and other substrates they transport, and environmental factors to which they must respond. Here, current knowledge in this field is summarized, covering both heterologous expression structure/function findings and potential mechanisms by which chansporter complexes fulfill contrasting roles in cell signaling in vivo.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
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21
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Membrane Transport. TEXTBOOK OF MEMBRANE BIOLOGY 2017. [PMCID: PMC7119958 DOI: 10.1007/978-981-10-7101-0_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Every living cell has to exchange molecules across the membrane for cellular functions. The hydrophobic or lipophilic molecules do not require energy for crossing the membrane. They can diffuse freely from higher to lower concentration till equilibrium is established. This process is called passive transport or diffusion.
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22
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White SH, Sturgeon RM, Magoski NS. Nicotine inhibits potassium currents in Aplysia bag cell neurons. J Neurophysiol 2016; 115:2635-48. [PMID: 26864763 DOI: 10.1152/jn.00816.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 02/09/2016] [Indexed: 11/22/2022] Open
Abstract
Acetylcholine and the archetypal cholinergic agonist, nicotine, are typically associated with the opening of ionotropic receptors. In the bag cell neurons, which govern the reproductive behavior of the marine snail, Aplysia californica, there are two cholinergic responses: a relatively large acetylcholine-induced current and a relatively small nicotine-induced current. Both currents are readily apparent at resting membrane potential and result from the opening of distinct ionotropic receptors. We now report a separate current response elicited by applying nicotine to cultured bag cell neurons under whole cell voltage-clamp. This current was ostensibly inward, best resolved at depolarized voltages, presented a noncooperative dose-response with a half-maximal concentration near 1.5 mM, and associated with a decrease in membrane conductance. The unique nicotine-evoked response was not altered by intracellular perfusion with the G protein blocker GDPβS or exposure to classical nicotinic antagonists but was occluded by replacing intracellular K(+) with Cs(+) Consistent with an underlying mechanism of direct inhibition of one or more K(+) channels, nicotine was found to rapidly reduce the fast-inactivating A-type K(+) current as well as both components of the delayed-rectifier K(+) current. Finally, nicotine increased bag cell neuron excitability, which manifested as reduction in spike threshold, greater action potential height and width, and markedly more spiking to continuous depolarizing current injection. In contrast to conventional transient activation of nicotinic ionotropic receptors, block of K(+) channels could represent a nonstandard means for nicotine to profoundly alter the electrical properties of neurons over prolonged periods of time.
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Affiliation(s)
- Sean H White
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Raymond M Sturgeon
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
| | - Neil S Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Queen's University, Kingston, Ontario, Canada
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23
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Abstract
Hippocampal area CA2 has several features that distinguish it from CA1 and CA3, including a unique gene expression profile, failure to display long-term potentiation and relative resistance to cell death. A recent increase in interest in the CA2 region, combined with the development of new methods to define and manipulate its neurons, has led to some exciting new discoveries on the properties of CA2 neurons and their role in behaviour. Here, we review these findings and call attention to the idea that the definition of area CA2 ought to be revised in light of gene expression data.
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24
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Grafting voltage and pharmacological sensitivity in potassium channels. Cell Res 2016; 26:935-45. [PMID: 27174053 DOI: 10.1038/cr.2016.57] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 03/04/2016] [Accepted: 03/29/2016] [Indexed: 11/08/2022] Open
Abstract
A classical voltage-gated ion channel consists of four voltage-sensing domains (VSDs). However, the roles of each VSD in the channels remain elusive. We developed a GVTDT (Graft VSD To Dimeric TASK3 channels that lack endogenous VSDs) strategy to produce voltage-gated channels with a reduced number of VSDs. TASK3 channels exhibit a high host tolerance to VSDs of various voltage-gated ion channels without interfering with the intrinsic properties of the TASK3 selectivity filter. The constructed channels, exemplified by the channels grafted with one or two VSDs from Kv7.1 channels, exhibit classical voltage sensitivity, including voltage-dependent opening and closing. Furthermore, the grafted Kv7.1 VSD transfers the potentiation activity of benzbromarone, an activator that acts on the VSDs of the donor channels, to the constructed channels. Our study indicates that one VSD is sufficient to voltage-dependently gate the pore and provides new insight into the roles of VSDs.
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25
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Veale EL, Mathie A. Aristolochic acid, a plant extract used in the treatment of pain and linked to Balkan endemic nephropathy, is a regulator of K2P channels. Br J Pharmacol 2016; 173:1639-52. [PMID: 26914156 PMCID: PMC4842925 DOI: 10.1111/bph.13465] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 02/08/2016] [Accepted: 02/15/2016] [Indexed: 01/08/2023] Open
Abstract
Background and Purpose Aristolochic acid (AristA) is found in plants used in traditional medicines to treat pain. We investigated the action of AristA on TREK and TRESK, potassium (K2P) channels, which are potential therapeutic targets in pain. Balkan endemic nephropathy (BEN) is a renal disease associated with AristA consumption. A mutation of TASK‐2 (K2P5.1) channels (T108P) is seen in some patients susceptible to BEN, so we investigated how both this mutation and AristA affected TASK‐2 channels. Experimental Approach Currents through wild‐type and mutated human K2P channels expressed in tsA201 cells were measured using whole‐cell patch‐clamp recordings in the presence and absence of AristA. Key Results TREK‐1‐ and TREK‐2‐mediated currents were enhanced by AristA (100 μM), whereas TRESK was inhibited. Inhibition of TRESK did not depend on the phosphorylation of key intracellular serines but was completely blocked by mutation of bulky residues in the inner pore (F145A_F352A). The TASK‐2_T108P mutation markedly reduced both current density and ion selectivity. A related mutation (T108C) had similar but less marked effects. External alkalization and application of flufenamic acid enhanced TASK‐2 and TASK‐2_T108C current but did not affect TASK‐2_T108P current. AristA (300 μM) produced a modest enhancement of TASK‐2 current. Conclusions and Implications Enhancement of TREK‐1 and TREK‐2 and inhibition of TRESK by AristA may contribute to therapeutically useful effects of this compound in pain. Whilst AristA is unlikely to interact directly with TASK‐2 channels in BEN, loss of functional TASK‐2 channels may indirectly increase susceptibility to AristA toxicity.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, University of Kent, Kent, UK
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26
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Hover S, King B, Hall B, Loundras EA, Taqi H, Daly J, Dallas M, Peers C, Schnettler E, McKimmie C, Kohl A, Barr JN, Mankouri J. Modulation of Potassium Channels Inhibits Bunyavirus Infection. J Biol Chem 2015; 291:3411-22. [PMID: 26677217 PMCID: PMC4751384 DOI: 10.1074/jbc.m115.692673] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Indexed: 11/06/2022] Open
Abstract
Bunyaviruses are considered to be emerging pathogens facilitated by the segmented nature of their genome that allows reassortment between different species to generate novel viruses with altered pathogenicity. Bunyaviruses are transmitted via a diverse range of arthropod vectors, as well as rodents, and have established a global disease range with massive importance in healthcare, animal welfare, and economics. There are no vaccines or anti-viral therapies available to treat human bunyavirus infections and so development of new anti-viral strategies is urgently required. Bunyamwera virus (BUNV; genus Orthobunyavirus) is the model bunyavirus, sharing aspects of its molecular and cellular biology with all Bunyaviridae family members. Here, we show for the first time that BUNV activates and requires cellular potassium (K(+)) channels to infect cells. Time of addition assays using K(+) channel modulating agents demonstrated that K(+) channel function is critical to events shortly after virus entry but prior to viral RNA synthesis/replication. A similar K(+) channel dependence was identified for other bunyaviruses namely Schmallenberg virus (Orthobunyavirus) as well as the more distantly related Hazara virus (Nairovirus). Using a rational pharmacological screening regimen, two-pore domain K(+) channels (K2P) were identified as the K(+) channel family mediating BUNV K(+) channel dependence. As several K2P channel modulators are currently in clinical use, our work suggests they may represent a new and safe drug class for the treatment of potentially lethal bunyavirus disease.
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Affiliation(s)
- Samantha Hover
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Barnabas King
- School of Life Sciences, University of Nottingham, Nottingham NG7 2UH
| | - Bradley Hall
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Eleni-Anna Loundras
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Hussah Taqi
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Janet Daly
- Veterinary Medicine and Science, University of Nottingham, Nottingham NG7 2RD
| | - Mark Dallas
- School of Pharmacy, University of Reading, Reading RG6 6AP, and
| | - Chris Peers
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT
| | - Esther Schnettler
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - Clive McKimmie
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Scotland, Glasgow G61 1QH, United Kingdom
| | - John N Barr
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT,
| | - Jamel Mankouri
- From the School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT,
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27
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Abbott GW. Pharmacogenetic diversification by alternative translation initiation: background channels to the fore: Commentary on Kisselbach et al., Br J Pharmacol 171: 5182-5194. Br J Pharmacol 2015; 172:4591-4593. [DOI: 10.1111/bph.12630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 02/06/2014] [Indexed: 11/27/2022] Open
Affiliation(s)
- G W Abbott
- Bioelectricity Laboratory; Departments of Pharmacology and Physiology and Biophysics; School of Medicine; University of California; Irvine CA USA
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28
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Dadi PK, Luo B, Vierra NC, Jacobson DA. TASK-1 Potassium Channels Limit Pancreatic α-Cell Calcium Influx and Glucagon Secretion. MOLECULAR ENDOCRINOLOGY (BALTIMORE, MD.) 2015. [PMID: 25849724 DOI: 10.1210/me.2014‐1321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Glucose regulation of pancreatic α-cell Ca(2+) entry through voltage-dependent Ca(2+) channels is essential for normal glucagon secretion and becomes defective during the pathogenesis of diabetes mellitus. The 2-pore domain K(+) channel, TWIK-related acid-sensitive K(+) channel 1 (TASK-1), is an important modulator of membrane voltage and Ca(2+) entry. However, its role in α-cells has not been determined. Therefore, we addressed how TASK-1 channels regulate α-cell electrical activity, Ca(2+) entry, and glucagon secretion. We find that TASK-1 channels expressed in human and rodent α-cells are blocked by the TASK-1 channel inhibitor A1899. Alpha-cell 2-pore domain K(+) currents were also significantly reduced after ablation of mouse α-cell TASK-1 channels. Inhibition of TASK-1 channels with A1899 caused plasma membrane potential depolarization in both human and mouse α-cells, which resulted in increased electrical excitability. Moreover, ablation of α-cell TASK-1 channels increased α-cell electrical excitability under elevated glucose (11 mM) conditions compared with control α-cells. This resulted in significantly elevated α-cell Ca(2+) influx when TASK-1 channels were inhibited in the presence of high glucose (14 mM). However, there was an insignificant change in α-cell Ca(2+) influx after TASK-1 inhibition in low glucose (1 mM). Glucagon secretion from mouse and human islets was also elevated specifically in high (11 mM) glucose after acute TASK-1 inhibition. Interestingly, mice deficient for α-cell TASK-1 showed improvements in both glucose inhibition of glucagon secretion and glucose tolerance, which resulted from the chronic loss of α-cell TASK-1 currents. Therefore, these data suggest an important role for TASK-1 channels in limiting α-cell excitability and glucagon secretion during glucose stimulation.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics (P.K.D., N.C.V., D.A.J.), Vanderbilt University, Nashville, Tennessee 37232-0615; and University of Oklahoma College of Medicine (B.L.), Oklahoma City, Oklahoma 73104-5042
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29
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Dadi PK, Luo B, Vierra NC, Jacobson DA. TASK-1 Potassium Channels Limit Pancreatic α-Cell Calcium Influx and Glucagon Secretion. Mol Endocrinol 2015; 29:777-87. [PMID: 25849724 DOI: 10.1210/me.2014-1321] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Glucose regulation of pancreatic α-cell Ca(2+) entry through voltage-dependent Ca(2+) channels is essential for normal glucagon secretion and becomes defective during the pathogenesis of diabetes mellitus. The 2-pore domain K(+) channel, TWIK-related acid-sensitive K(+) channel 1 (TASK-1), is an important modulator of membrane voltage and Ca(2+) entry. However, its role in α-cells has not been determined. Therefore, we addressed how TASK-1 channels regulate α-cell electrical activity, Ca(2+) entry, and glucagon secretion. We find that TASK-1 channels expressed in human and rodent α-cells are blocked by the TASK-1 channel inhibitor A1899. Alpha-cell 2-pore domain K(+) currents were also significantly reduced after ablation of mouse α-cell TASK-1 channels. Inhibition of TASK-1 channels with A1899 caused plasma membrane potential depolarization in both human and mouse α-cells, which resulted in increased electrical excitability. Moreover, ablation of α-cell TASK-1 channels increased α-cell electrical excitability under elevated glucose (11 mM) conditions compared with control α-cells. This resulted in significantly elevated α-cell Ca(2+) influx when TASK-1 channels were inhibited in the presence of high glucose (14 mM). However, there was an insignificant change in α-cell Ca(2+) influx after TASK-1 inhibition in low glucose (1 mM). Glucagon secretion from mouse and human islets was also elevated specifically in high (11 mM) glucose after acute TASK-1 inhibition. Interestingly, mice deficient for α-cell TASK-1 showed improvements in both glucose inhibition of glucagon secretion and glucose tolerance, which resulted from the chronic loss of α-cell TASK-1 currents. Therefore, these data suggest an important role for TASK-1 channels in limiting α-cell excitability and glucagon secretion during glucose stimulation.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics (P.K.D., N.C.V., D.A.J.), Vanderbilt University, Nashville, Tennessee 37232-0615; and University of Oklahoma College of Medicine (B.L.), Oklahoma City, Oklahoma 73104-5042
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30
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Renigunta V, Schlichthörl G, Daut J. Much more than a leak: structure and function of K₂p-channels. Pflugers Arch 2015; 467:867-94. [PMID: 25791628 DOI: 10.1007/s00424-015-1703-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 11/27/2022]
Abstract
Over the last decade, we have seen an enormous increase in the number of experimental studies on two-pore-domain potassium channels (K2P-channels). The collection of reviews and original articles compiled for this special issue of Pflügers Archiv aims to give an up-to-date summary of what is known about the physiology and pathophysiology of K2P-channels. This introductory overview briefly describes the structure of K2P-channels and their function in different organs. Its main aim is to provide some background information for the 19 reviews and original articles of this special issue of Pflügers Archiv. It is not intended to be a comprehensive review; instead, this introductory overview focuses on some unresolved questions and controversial issues, such as: Do K2P-channels display voltage-dependent gating? Do K2P-channels contribute to the generation of action potentials? What is the functional role of alternative translation initiation? Do K2P-channels have one or two or more gates? We come to the conclusion that we are just beginning to understand the extremely complex regulation of these fascinating channels, which are often inadequately described as 'leak channels'.
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Affiliation(s)
- Vijay Renigunta
- Institute of Physiology and Pathophysiology, Marburg University, 35037, Marburg, Germany
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31
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Dong YY, Pike ACW, Mackenzie A, McClenaghan C, Aryal P, Dong L, Quigley A, Grieben M, Goubin S, Mukhopadhyay S, Ruda GF, Clausen MV, Cao L, Brennan PE, Burgess-Brown NA, Sansom MSP, Tucker SJ, Carpenter EP. K2P channel gating mechanisms revealed by structures of TREK-2 and a complex with Prozac. Science 2015; 347:1256-9. [PMID: 25766236 DOI: 10.1126/science.1261512] [Citation(s) in RCA: 212] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
TREK-2 (KCNK10/K2P10), a two-pore domain potassium (K2P) channel, is gated by multiple stimuli such as stretch, fatty acids, and pH and by several drugs. However, the mechanisms that control channel gating are unclear. Here we present crystal structures of the human TREK-2 channel (up to 3.4 angstrom resolution) in two conformations and in complex with norfluoxetine, the active metabolite of fluoxetine (Prozac) and a state-dependent blocker of TREK channels. Norfluoxetine binds within intramembrane fenestrations found in only one of these two conformations. Channel activation by arachidonic acid and mechanical stretch involves conversion between these states through movement of the pore-lining helices. These results provide an explanation for TREK channel mechanosensitivity, regulation by diverse stimuli, and possible off-target effects of the serotonin reuptake inhibitor Prozac.
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Affiliation(s)
- Yin Yao 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
| | - Alexandra Mackenzie
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - 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 3PN, UK
| | - Prafulla Aryal
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK. OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Liang Dong
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Andrew Quigley
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Mariana Grieben
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Solenne Goubin
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | | | - Gian Filippo Ruda
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | - Michael V Clausen
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Lishuang Cao
- Pfizer Neusentis, Granta Park, Cambridge CB21 6GS, UK
| | - Paul E Brennan
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK. Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7FZ, UK
| | | | - Mark S P Sansom
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PN, UK. Department of Biochemistry, University of Oxford, Oxford OX1 3QU, 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 3PN, UK.
| | - 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.
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32
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Bouhadfane M, Kaszás A, Rózsa B, Harris-Warrick RM, Vinay L, Brocard F. Sensitization of neonatal rat lumbar motoneuron by the inflammatory pain mediator bradykinin. eLife 2015; 4:e06195. [PMID: 25781633 PMCID: PMC4410746 DOI: 10.7554/elife.06195] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 03/16/2015] [Indexed: 11/27/2022] Open
Abstract
Bradykinin (Bk) is a potent inflammatory mediator that causes hyperalgesia. The action of Bk on the sensory system is well documented but its effects on motoneurons, the final pathway of the motor system, are unknown. By a combination of patch-clamp recordings and two-photon calcium imaging, we found that Bk strongly sensitizes spinal motoneurons. Sensitization was characterized by an increased ability to generate self-sustained spiking in response to excitatory inputs. Our pharmacological study described a dual ionic mechanism to sensitize motoneurons, including inhibition of a barium-sensitive resting K+ conductance and activation of a nonselective cationic conductance primarily mediated by Na+. Examination of the upstream signaling pathways provided evidence for postsynaptic activation of B2 receptors, G protein activation of phospholipase C, InsP3 synthesis, and calmodulin activation. This study questions the influence of motoneurons in the assessment of hyperalgesia since the withdrawal motor reflex is commonly used as a surrogate pain model. DOI:http://dx.doi.org/10.7554/eLife.06195.001 When we accidentally place our hand on a hot stove, we normally experience a painful sensation that starts with the sensory nerves under our skin. These nerves respond by transmitting electrical impulses to our brain, where the painful sensation is then processed. At the same time, these impulses are also transmitted to the motor nerves that control the muscles in our hand to trigger an immediate reflex to withdraw the hand from the hot stove. Pain therefore has a useful role as it can reduce how bad an injury is. People with a condition called hyperalgesia have an increased sensitivity to pain. This condition can result from a chemical called bradykinin ‘sensitizing’ the sensory nerves, causing them to transmit more electrical impulses in response to pain than normal. This makes the injury feel much more painful, and can make the pain last for longer than is beneficial. It was less clear whether bradykinin also affects motor nerves and so triggers a withdrawal reflex. By recording the electrical activity of motor nerve cells taken from the spinal cords of newborn rats, Bouhadfane et al. now show that these motor nerves become more active when exposed to bradykinin. Nerve cells generate electrical signals when ions—such as potassium, sodium, and calcium ions—move through channels in the membranes of the cell. Therefore, to investigate how bradykinin influences the electrical activity of motor nerves, Bouhadfane et al. exposed the cells to drugs that inhibit particular ion channels. This revealed that bradykinin sensitizes the motor nerves by blocking a type of potassium ion channel and activating another ion channel that mainly transports sodium ions. Furthermore, Bouhadfane et al. were able to identify the signaling pathways that allow bradykinin to affect the motor nerve cells. The study implies that the neuronal circuitry for pain does not rely exclusively on sensory nerve cells but should also integrate motor nerve cells. A future challenge remains in developing a protocol to resolve the contribution of motor nerve cells to hyperalgesia assessed by reflex withdrawal. DOI:http://dx.doi.org/10.7554/eLife.06195.002
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Affiliation(s)
- Mouloud Bouhadfane
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
| | - Attila Kaszás
- Institut de Neuroscience des Systèmes (UMR1106), Aix Marseille Université and INSERM, Marseille, France
| | - Balázs Rózsa
- Two-Photon Imaging Center, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | | | - Laurent Vinay
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
| | - Frédéric Brocard
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille, France
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33
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Peers C, Boyle JP, Scragg JL, Dallas ML, Al-Owais MM, Hettiarachichi NT, Elies J, Johnson E, Gamper N, Steele DS. Diverse mechanisms underlying the regulation of ion channels by carbon monoxide. Br J Pharmacol 2015; 172:1546-56. [PMID: 24818840 PMCID: PMC4369263 DOI: 10.1111/bph.12760] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 04/14/2014] [Accepted: 04/21/2014] [Indexed: 12/19/2022] Open
Abstract
Carbon monoxide (CO) is firmly established as an important, physiological signalling molecule as well as a potent toxin. Through its ability to bind metal-containing proteins, it is known to interfere with a number of intracellular signalling pathways, and such actions can account for its physiological and pathological effects. In particular, CO can modulate the intracellular production of reactive oxygen species, NO and cGMP levels, as well as regulate MAPK signalling. In this review, we consider ion channels as more recently discovered effectors of CO signalling. CO is now known to regulate a growing number of different ion channel types, and detailed studies of the underlying mechanisms of action are revealing unexpected findings. For example, there are clear areas of contention surrounding its ability to increase the activity of high conductance, Ca(2+) -sensitive K(+) channels. More recent studies have revealed the ability of CO to inhibit T-type Ca(2+) channels and have unveiled a novel signalling pathway underlying tonic regulation of this channel. It is clear that the investigation of ion channels as effectors of CO signalling is in its infancy, and much more work is required to fully understand both the physiological and the toxic actions of this gas. Only then can its emerging use as a therapeutic tool be fully and safely exploited.
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Affiliation(s)
- C Peers
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - J P Boyle
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - J L Scragg
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - M L Dallas
- School of Pharmacy, University of ReadingReading, UK
| | - M M Al-Owais
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - N T Hettiarachichi
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - J Elies
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - E Johnson
- Division of Cardiovascular and Diabetes Research, LIGHT, Faculty of Medicine and Health, University of LeedsLeeds, UK
| | - N Gamper
- Faculty of Biological Sciences, University of LeedsLeeds, UK
| | - D S Steele
- Faculty of Biological Sciences, University of LeedsLeeds, UK
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Sepúlveda FV, Pablo Cid L, Teulon J, Niemeyer MI. Molecular aspects of structure, gating, and physiology of pH-sensitive background K2P and Kir K+-transport channels. Physiol Rev 2015; 95:179-217. [PMID: 25540142 DOI: 10.1152/physrev.00016.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
K(+) channels fulfill roles spanning from the control of excitability to the regulation of transepithelial transport. Here we review two groups of K(+) channels, pH-regulated K2P channels and the transport group of Kir channels. After considering advances in the molecular aspects of their gating based on structural and functional studies, we examine their participation in certain chosen physiological and pathophysiological scenarios. Crystal structures of K2P and Kir channels reveal rather unique features with important consequences for the gating mechanisms. Important tasks of these channels are discussed in kidney physiology and disease, K(+) homeostasis in the brain by Kir channel-equipped glia, and central functions in the hearing mechanism in the inner ear and in acid secretion by parietal cells in the stomach. K2P channels fulfill a crucial part in central chemoreception probably by virtue of their pH sensitivity and are central to adrenal secretion of aldosterone. Finally, some unorthodox behaviors of the selectivity filters of K2P channels might explain their normal and pathological functions. Although a great deal has been learned about structure, molecular details of gating, and physiological functions of K2P and Kir K(+)-transport channels, this has been only scratching at the surface. More molecular and animal studies are clearly needed to deepen our knowledge.
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Affiliation(s)
- Francisco V Sepúlveda
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - L Pablo Cid
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - Jacques Teulon
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - María Isabel Niemeyer
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
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35
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Feliciangeli S, Chatelain FC, Bichet D, Lesage F. The family of K2P channels: salient structural and functional properties. J Physiol 2015; 593:2587-603. [PMID: 25530075 DOI: 10.1113/jphysiol.2014.287268] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 12/10/2014] [Indexed: 12/11/2022] Open
Abstract
Potassium channels participate in many biological functions, from ion homeostasis to generation and modulation of the electrical membrane potential. They are involved in a large variety of diseases. In the human genome, 15 genes code for K(+) channels with two pore domains (K2P ). These channels form dimers of pore-forming subunits that produce background conductances finely regulated by a range of natural and chemical effectors, including signalling lipids, temperature, pressure, pH, antidepressants and volatile anaesthetics. Since the cloning of TWIK1, the prototypical member of this family, a lot of work has been carried out on their structure and biology. These studies are still in progress, but data gathered so far show that K2P channels are central players in many processes, including ion homeostasis, hormone secretion, cell development and excitability. A growing number of studies underline their implication in physiopathological mechanisms, such as vascular and pulmonary hypertension, cardiac arrhythmias, nociception, neuroprotection and depression. This review gives a synthetic view of the most noticeable features of these channels.
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Affiliation(s)
- Sylvain Feliciangeli
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Frank C Chatelain
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Delphine Bichet
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Florian Lesage
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
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36
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Transmembrane helix straightening and buckling underlies activation of mechanosensitive and thermosensitive K(2P) channels. Neuron 2014; 84:1198-212. [PMID: 25500157 DOI: 10.1016/j.neuron.2014.11.017] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2014] [Indexed: 01/23/2023]
Abstract
Mechanical and thermal activation of ion channels is central to touch, thermosensation, and pain. The TRAAK/TREK K(2P) potassium channel subfamily produces background currents that alter neuronal excitability in response to pressure, temperature, signaling lipids, and anesthetics. How such diverse stimuli control channel function is unclear. Here we report structures of K(2P)4.1 (TRAAK) bearing C-type gate-activating mutations that reveal a tilting and straightening of the M4 inner transmembrane helix and a buckling of the M2 transmembrane helix. These conformational changes move M4 in a direction opposite to that in classical potassium channel activation mechanisms and open a passage lateral to the pore that faces the lipid bilayer inner leaflet. Together, our findings uncover a unique aspect of K(2P) modulation, indicate a means for how the K(2P) C-terminal cytoplasmic domain affects the C-type gate which lies ∼40Å away, and suggest how lipids and bilayer inner leaflet deformations may gate the channel.
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37
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Nishizuka M, Hayashi T, Asano M, Osada S, Imagawa M. KCNK10, a tandem pore domain potassium channel, is a regulator of mitotic clonal expansion during the early stage of adipocyte differentiation. Int J Mol Sci 2014; 15:22743-56. [PMID: 25501330 PMCID: PMC4284734 DOI: 10.3390/ijms151222743] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 11/10/2014] [Accepted: 11/26/2014] [Indexed: 01/13/2023] Open
Abstract
KCNK10, a member of tandem pore domain potassium channel family, gives rise to leak K+ currents. It plays important roles in stabilizing the negative resting membrane potential and in counterbalancing depolarization. We previously demonstrated that kcnk10 expression is quickly elevated during the early stage of adipogenesis of 3T3-L1 cells and that reduction of kcnk10 expression inhibits adipocyte differentiation. However, the molecular mechanism of KCNK10 in adipocyte differentiation remains unclear. Here we revealed that kcnk10 is induced by 3-isobutyl-1-methylxanthine, a cyclic nucleotide phosphodiesterase inhibitor and a potent inducer of adipogenesis, during the early stage of adipocyte differentiation. We also demonstrated that KCNK10 functions as a positive regulator of mitotic clonal expansion (MCE), a necessary process for terminal differentiation. The reduction of kcnk10 expression repressed the expression levels of CCAAT/enhancer-binding protein β (C/EBPβ) and C/EBPδ as well as the phosphorylation level of Akt during the early phase of adipogenesis. In addition, knockdown of kcnk10 expression suppressed insulin-induced Akt phosphorylation. These results indicate that KCNK10 contributes to the regulation of MCE through the control of C/EBPβ and C/EBPδ expression and insulin signaling.
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Affiliation(s)
- Makoto Nishizuka
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
| | - Takahiro Hayashi
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
| | - Mami Asano
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
| | - Shigehiro Osada
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
| | - Masayoshi Imagawa
- Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
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The role of K₂p channels in anaesthesia and sleep. Pflugers Arch 2014; 467:907-16. [PMID: 25482669 PMCID: PMC4428837 DOI: 10.1007/s00424-014-1654-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Revised: 11/11/2014] [Accepted: 11/12/2014] [Indexed: 12/20/2022]
Abstract
Tandem two-pore potassium channels (K2Ps) have widespread expression in the central nervous system and periphery where they contribute to background membrane conductance. Some general anaesthetics promote the opening of some of these channels, enhancing potassium currents and thus producing a reduction in neuronal excitability that contributes to the transition to unconsciousness. Similarly, these channels may be recruited during the normal sleep-wake cycle as downstream effectors of wake-promoting neurotransmitters such as noradrenaline, histamine and acetylcholine. These transmitters promote K2P channel closure and thus an increase in neuronal excitability. Our understanding of the roles of these channels in sleep and anaesthesia has been largely informed by the study of mouse K2P knockout lines and what is currently predicted by in vitro electrophysiology and channel structure and gating.
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Mathie A, Veale EL. Two-pore domain potassium channels: potential therapeutic targets for the treatment of pain. Pflugers Arch 2014; 467:931-43. [DOI: 10.1007/s00424-014-1655-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 11/11/2014] [Accepted: 11/13/2014] [Indexed: 01/01/2023]
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Bayliss DA, Barhanin J, Gestreau C, Guyenet PG. The role of pH-sensitive TASK channels in central respiratory chemoreception. Pflugers Arch 2014; 467:917-29. [PMID: 25346157 DOI: 10.1007/s00424-014-1633-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 10/08/2014] [Accepted: 10/12/2014] [Indexed: 01/16/2023]
Abstract
A number of the subunits within the family of K2P background K(+) channels are sensitive to changes in extracellular pH in the physiological range, making them likely candidates to mediate various pH-dependent processes. Based on expression patterns within several brainstem neuronal cell groups that are believed to function in CO2/H(+) regulation of breathing, three TASK subunits-TASK-1, TASK-2, and TASK-3-were specifically hypothesized to contribute to this central respiratory chemoreflex. For the acid-sensitive TASK-1 and TASK-3 channels, despite widespread expression at multiple levels within the brainstem respiratory control system (including presumptive chemoreceptor populations), experiments in knockout mice provided no evidence for their involvement in CO2 regulation of breathing. By contrast, the alkaline-activated TASK-2 channel has a more restricted brainstem distribution and was localized to the Phox2b-expressing chemoreceptor neurons of the retrotrapezoid nucleus (RTN). Remarkably, in a Phox2b(27Ala/+) mouse genetic model of congenital central hypoventilation syndrome (CCHS) that is characterized by reduced central respiratory chemosensitivity, selective ablation of Phox2b-expressing RTN neurons was accompanied by a corresponding loss of TASK-2 expression. Furthermore, genetic deletion of TASK-2 blunted RTN neuronal pH sensitivity in vitro, reduced alkaline-induced respiratory network inhibition in situ and diminished the ventilatory response to CO2/H(+) in vivo. Notably, a subpopulation of RTN neurons from TASK-2(-/-) mice retained their pH sensitivity, at least in part due to a residual pH-sensitive background K(+) current, suggesting that other mechanisms (and perhaps other K2P channels) for RTN neuronal pH sensitivity are yet to be identified.
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Affiliation(s)
- Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, 22908-0735, USA,
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41
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Dadi PK, Vierra NC, Jacobson DA. Pancreatic β-cell-specific ablation of TASK-1 channels augments glucose-stimulated calcium entry and insulin secretion, improving glucose tolerance. Endocrinology 2014; 155:3757-68. [PMID: 24932805 PMCID: PMC4164933 DOI: 10.1210/en.2013-2051] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calcium entry through voltage-dependent Ca(2+) channels (VDCCs) is required for pancreatic β-cell insulin secretion. The 2-pore-domain acid-sensitive potassium channel (TASK-1) regulates neuronal excitability and VDCC activation by hyperpolarizing the plasma membrane potential (Δψp); however, a role for pancreatic β-cell TASK-1 channels is unknown. Here we examined the influence of TASK-1 channel activity on the β-cell Δψp and insulin secretion during secretagogue stimulation. TASK-1 channels were found to be highly expressed in human and rodent islets and localized to the plasma membrane of β-cells. TASK-1-like currents of mouse and human β-cells were blocked by the potent TASK-1 channel inhibitor, A1899 (250nM). Although inhibition of TASK-1 currents did not influence the β-cell Δψp in the presence of low (2mM) glucose, A1899 significantly enhanced glucose-stimulated (14mM) Δψp depolarization of human and mouse β-cells. TASK-1 inhibition also resulted in greater secretagogue-stimulated Ca(2+) influx in both human and mouse islets. Moreover, conditional ablation of mouse β-cell TASK-1 channels reduced K2P currents, increased glucose-stimulated Δψp depolarization, and augmented secretagogue-stimulated Ca(2+) influx. The Δψp depolarization caused by TASK-1 inhibition resulted in a transient increase in glucose-stimulated mouse β-cell action potential (AP) firing frequency. However, secretagogue-stimulated β-cell AP duration eventually increased in the presence of A1899 as well as in β-cells without TASK-1, causing a decrease in AP firing frequency. Ablation or inhibition of mouse β-cell TASK-1 channels also significantly enhanced glucose-stimulated insulin secretion, which improved glucose tolerance. Conversely, TASK-1 ablation did not perturb β-cell Δψp, Ca(2+) influx, or insulin secretion under low-glucose conditions (2mM). These results reveal a glucose-dependent role for β-cell TASK-1 channels of limiting glucose-stimulated Δψp depolarization and insulin secretion, which modulates glucose homeostasis.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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Czirják G, Enyedi P. The LQLP calcineurin docking site is a major determinant of the calcium-dependent activation of human TRESK background K+ channel. J Biol Chem 2014; 289:29506-18. [PMID: 25202008 DOI: 10.1074/jbc.m114.577684] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-dependent activation of human TRESK (TWIK-related spinal cord K(+) channel, K2P18.1) depends on direct targeting of calcineurin to the PQIIIS motif. In the present study we demonstrate that TRESK also contains another functionally relevant docking site for the phosphatase, the LQLP amino acid sequence. Combined mutations of the PQIIIS and LQLP motifs were required to eliminate the calcium-dependent regulation of the channel. In contrast to the alanine substitutions of PQIIIS, the mutation of LQLP to AQAP alone did not significantly change the amplitude of TRESK activation evoked by the substantial elevation of cytoplasmic calcium concentration. However, the AQAP mutation slowed down the response to high calcium. In addition, modest elevation of [Ca(2+)], which effectively regulated the wild type channel, failed to activate TRESK-AQAP. This indicates that the AQAP mutation diminished the sensitivity of TRESK to calcium. Even if PQIIIS was replaced by the PVIVIT sequence of high calcineurin binding affinity, the effect of the AQAP mutation was clearly detected in this TRESK-PVIVIT context. Substitution of the LQLP region with the corresponding fragment of NFAT transcription factor, perfectly matching the previously described LXVP calcineurin-binding consensus sequence, increased the calcium-sensitivity of TRESK-PVIVIT. Thus the enhancement of the affinity of TRESK for calcineurin by the incorporation of PVIVIT could not compensate for or prevent the effects of LQLP sequence modifications, suggesting that the two calcineurin-binding regions play distinct roles in the regulation. Our results indicate that the LQLP site is a fundamental determinant of the calcium-sensitivity of human TRESK.
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Affiliation(s)
- Gábor Czirják
- From the Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Péter Enyedi
- From the Department of Physiology, Semmelweis University, Budapest, Hungary
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Guo Z, Liu P, Ren F, Cao YQ. Nonmigraine-associated TRESK K+ channel variant C110R does not increase the excitability of trigeminal ganglion neurons. J Neurophysiol 2014; 112:568-79. [PMID: 24805079 DOI: 10.1152/jn.00267.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent genetic studies suggest that dysfunction of ion channels and transporters may contribute to migraine pathophysiology. A migraine-associated frameshift mutation in the TWIK-related spinal cord K+ (TRESK) channel results in nonfunctional channels. Moreover, mutant TRESK subunits exert a dominant-negative effect on whole cell TRESK currents and result in hyperexcitability of small-diameter trigeminal ganglion (TG) neurons, suggesting that mutant TRESK may increase the gain of the neuronal circuit underlying migraine headache. However, the nonmigraine-associated TRESK C110R variant exhibits the same effect on TRESK currents as the mutant subunits in Xenopus oocytes, suggesting that dysfunction of TRESK is not sufficient to cause migraine. Here, we confirmed that the C110R variant formed nonfunctional channels and exerted a dominant-negative effect on TRESK currents in HEK293T cells, similar to the migraine-associated mutant TRESK. To compare the functional consequences of TRESK mutations/variants in a more physiological setting, we expressed the mutant TRESK and the C110R variant in cultured mouse TG neurons and investigated their effects on background K+ currents and neuronal excitability. Both mutant TRESK and the C110R variant reduced the endogenous TRESK currents in TG neurons, but the effect of the C110R variant was significantly smaller. Importantly, only TG neurons expressing mutant TRESK subunits, but not those expressing the C110R variant, exhibited a significant increase in excitability. Thus only the migraine-associated TRESK mutation, but not the C110R variant, reduces the endogenous TRESK currents to a degree that affects TG excitability. Our results support a potential causal relationship between the frameshift TRESK mutation and migraine susceptibility.
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Affiliation(s)
- Zhaohua Guo
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Ping Liu
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Fei Ren
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Yu-Qing Cao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
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Retailleau K, Duprat F. Polycystins and partners: proposed role in mechanosensitivity. J Physiol 2014; 592:2453-71. [PMID: 24687583 DOI: 10.1113/jphysiol.2014.271346] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mutations of the two polycystins, PC1 and PC2, lead to polycystic kidney disease. Polycystins are able to form complexes with numerous families of proteins that have been suggested to participate in mechanical sensing. The proposed role of polycystins and their partners in the kidney primary cilium is to sense urine flow. A role for polycystins in mechanosensing has also been shown in other cell types such as vascular smooth muscle cells and cardiac myocytes. At the plasma membrane, polycystins interact with diverse ion channels of the TRP family and with stretch-activated channels (Piezos, TREKs). The actin cytoskeleton and its interacting proteins, such as filamin A, have been shown to be essential for these interactions. Numerous proteins involved in cell-cell and cell-extracellular matrix junctions interact with PC1 and/or PC2. These multimeric protein complexes are important for cell structure integrity, the transmission of force, as well as for mechanosensing and mechanotransduction. A group of polycystin partners are also involved in subcellular trafficking mechanisms. Finally, PC1 and especially PC2 interact with elements of the endoplasmic reticulum and are essential components of calcium homeostasis. In conclusion, we propose that both PC1 and PC2 act as conductors to tune the overall cellular mechanosensitivity.
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Affiliation(s)
- Kevin Retailleau
- CNRS Institute of Molecular and Cellular Pharmacology (IPMC), Valbonne, France
| | - Fabrice Duprat
- CNRS Institute of Molecular and Cellular Pharmacology (IPMC), Valbonne, France
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45
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de la Cruz IP, Ma L, Horvitz HR. The Caenorhabditis elegans iodotyrosine deiodinase ortholog SUP-18 functions through a conserved channel SC-box to regulate the muscle two-pore domain potassium channel SUP-9. PLoS Genet 2014; 10:e1004175. [PMID: 24586202 PMCID: PMC3930498 DOI: 10.1371/journal.pgen.1004175] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Accepted: 12/28/2013] [Indexed: 02/04/2023] Open
Abstract
Loss-of-function mutations in the Caenorhabditis elegans gene sup-18 suppress the defects in muscle contraction conferred by a gain-of-function mutation in SUP-10, a presumptive regulatory subunit of the SUP-9 two-pore domain K+ channel associated with muscle membranes. We cloned sup-18 and found that it encodes the C. elegans ortholog of mammalian iodotyrosine deiodinase (IYD), an NADH oxidase/flavin reductase that functions in iodine recycling and is important for the biosynthesis of thyroid hormones that regulate metabolism. The FMN-binding site of mammalian IYD is conserved in SUP-18, which appears to require catalytic activity to function. Genetic analyses suggest that SUP-10 can function with SUP-18 to activate SUP-9 through a pathway that is independent of the presumptive SUP-9 regulatory subunit UNC-93. We identified a novel evolutionarily conserved serine-cysteine-rich region in the C-terminal cytoplasmic domain of SUP-9 required for its specific activation by SUP-10 and SUP-18 but not by UNC-93. Since two-pore domain K+ channels regulate the resting membrane potentials of numerous cell types, we suggest that the SUP-18 IYD regulates the activity of the SUP-9 channel using NADH as a coenzyme and thus couples the metabolic state of muscle cells to muscle membrane excitability. Iodotyrosine deiodinase (IYD) controls the recycling of iodide in the biogenesis of thyroid hormones that regulate metabolism. Defects in IYD result in congenital hypothyroidism, a multisystem disorder that can lead to growth failure and severe mental retardation. We identified the gene sup-18 of the nematode Caenorhabditis elegans as a regulator of the SUP-9/UNC-93/SUP-10 two-pore domain potassium channel complex and showed that SUP-18 is an ortholog of IYD, a member of the NADH oxidase/flavin reductase family. SUP-18 IYD is required for the activation of the channel complex by a gain-of-function mutation of the SUP-10 protein. SUP-9 channel activation by SUP-18 requires a conserved serine-cysteine-rich region in the C-terminus of SUP-9 and is independent of the function of the conserved multi-transmembrane protein UNC-93. We propose that SUP-18 uses NADH as a coenzyme to activate the SUP-9 channel in response to the activity of SUP-10 and the metabolic state of muscle cells.
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Affiliation(s)
- Ignacio Perez de la Cruz
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Long Ma
- State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - H. Robert Horvitz
- Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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46
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Veale EL, Al-Moubarak E, Bajaria N, Omoto K, Cao L, Tucker SJ, Stevens EB, Mathie A. Influence of the N Terminus on the Biophysical Properties and Pharmacology of TREK1 Potassium Channels. Mol Pharmacol 2014; 85:671-81. [DOI: 10.1124/mol.113.091199] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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47
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Laursen WJ, Bagriantsev SN, Gracheva EO. TRPA1 channels: chemical and temperature sensitivity. CURRENT TOPICS IN MEMBRANES 2014; 74:89-112. [PMID: 25366234 DOI: 10.1016/b978-0-12-800181-3.00004-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Transient receptor potential ankyrin 1 (TRPA1) is a polymodal excitatory ion channel found in sensory neurons of different organisms, ranging from worms to humans. Since its discovery as an uncharacterized transmembrane protein in human fibroblasts, TRPA1 has become one of the most intensively studied ion channels. Its function has been linked to regulation of heat and cold perception, mechanosensitivity, hearing, inflammation, pain, circadian rhythms, chemoreception, and other processes. Some of these proposed functions remain controversial, while others have gathered considerable experimental support. A truly polymodal ion channel, TRPA1 is activated by various stimuli, including electrophilic chemicals, oxygen, temperature, and mechanical force, yet the molecular mechanism of TRPA1 gating remains obscure. In this review, we discuss recent advances in the understanding of TRPA1 physiology, pharmacology, and molecular function.
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Affiliation(s)
- Willem J Laursen
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA; Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, USA
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA; Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, USA
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Veale EL, Hassan M, Walsh Y, Al-Moubarak E, Mathie A. Recovery of current through mutated TASK3 potassium channels underlying Birk Barel syndrome. Mol Pharmacol 2013; 85:397-407. [PMID: 24342771 DOI: 10.1124/mol.113.090530] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
TASK3 (TWIK-related acid-sensitive K(+) channel 3) potassium channels are members of the two-pore-domain potassium channel family. They are responsible for background leak potassium currents found in many cell types. TASK3 channels are genetically imprinted, and a mutation in TASK3 (G236R) is responsible for Birk Barel mental retardation dysmorphism syndrome, a maternally transmitted developmental disorder. This syndrome may arise from a neuronal migration defect during development caused by dysfunctional TASK3 channels. Through the use of whole-cell electrophysiologic recordings, we have found that, although G236R mutated TASK3 channels give rise to a functional current, this current is significantly smaller in an outward direction when compared with wild-type (WT) TASK3 channels. In contrast to WT TASK3 channels, the current is inwardly rectifying. Furthermore, the current through mutated channels is differentially sensitive to a number of regulators, such as extracellular acidification, extracellular zinc, and activation of Gαq-coupled muscarinic (M3) receptors, compared with WT TASK3 channels. The reduced outward current through mutated TASK3_G236R channels can be overcome, at least in part, by both a gain-of-function additional mutation of TASK3 channels (A237T) or by application of the nonsteroidal anti-inflammatory drug flufenamic acid (FFA; 2-{[3-(trifluoromethyl)phenyl]amino}benzoic acid). FFA produces a significantly greater enhancement of current through mutated channels than through WT TASK3 channels. We propose that pharmacologic enhancement of mutated TASK3 channel current during development may, therefore, provide a potentially useful therapeutic strategy in the treatment of Birk Barel syndrome.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, University of Kent and University of Greenwich, Kent, United Kingdom
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El Hachmane MF, Rees KA, Veale EL, Sumbayev VV, Mathie A. Enhancement of TWIK-related acid-sensitive potassium channel 3 (TASK3) two-pore domain potassium channel activity by tumor necrosis factor α. J Biol Chem 2013; 289:1388-401. [PMID: 24307172 DOI: 10.1074/jbc.m113.500033] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TASK3 two-pore domain potassium (K2P) channels are responsible for native leak K channels in many cell types which regulate cell resting membrane potential and excitability. In addition, TASK3 channels contribute to the regulation of cellular potassium homeostasis. Because TASK3 channels are important for cell viability, having putative roles in both neuronal apoptosis and oncogenesis, we sought to determine their behavior under inflammatory conditions by investigating the effect of TNFα on TASK3 channel current. TASK3 channels were expressed in tsA-201 cells, and the current through them was measured using whole cell voltage clamp recordings. We show that THP-1 human myeloid leukemia monocytes, co-cultured with hTASK3-transfected tsA-201 cells, can be activated by the specific Toll-like receptor 7/8 activator, R848, to release TNFα that subsequently enhances hTASK3 current. Both hTASK3 and mTASK3 channel activity is increased by incubation with recombinant TNFα (10 ng/ml for 2-15 h), but other K2P channels (hTASK1, hTASK2, hTREK1, and hTRESK) are unaffected. This enhancement by TNFα is not due to alterations in levels of channel expression at the membrane but rather to an alteration in channel gating. The enhancement by TNFα can be blocked by extracellular acidification but persists for mutated TASK3 (H98A) channels that are no longer acid-sensitive even in an acidic extracellular environment. TNFα action on TASK3 channels is mediated through the intracellular C terminus of the channel. Furthermore, it occurs through the ASK1 pathway and is JNK- and p38-dependent. In combination, TNFα activation and TASK3 channel activity can promote cellular apoptosis.
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Affiliation(s)
- Mickael-F El Hachmane
- From the Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, ME4 4TB Kent, United Kingdom
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Beltrán LR, Dawid C, Beltrán M, Gisselmann G, Degenhardt K, Mathie K, Hofmann T, Hatt H. The pungent substances piperine, capsaicin, 6-gingerol and polygodial inhibit the human two-pore domain potassium channels TASK-1, TASK-3 and TRESK. Front Pharmacol 2013; 4:141. [PMID: 24302912 PMCID: PMC3831292 DOI: 10.3389/fphar.2013.00141] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 10/23/2013] [Indexed: 01/26/2023] Open
Abstract
For a long time, the focus of trigeminal chemoperception has rested almost exclusively on TRP channels. However, two-pore domain (K2P) potassium channels have recently been identified as targets for substances associated with typical trigeminal sensations, such as numbing and tingling. In addition, they have been shown to be modulated by several TRP agonists. We investigated whether the pungent substances piperine, capsaicin, 6-gingerol and polygodial have an effect on human K2P channels. For this purpose, we evaluated the effects of these pungent substances on both wild-type and mutant K2P channels by means of two-electrode voltage-clamp experiments using Xenopus laevis oocytes. All four pungent substances were found to inhibit the basal activity of TASK-1 (K2P 3.1), TASK-3 (K2P 9.1), and TRESK (K2P 18.1) channels. This inhibitory effect was dose-dependent and, with the exception of polygodial on TASK-1, fully reversible. However, only piperine exhibited an IC50 similar to its reported EC50 on TRP channels. Finally, we observed for TASK-3 that mutating H98 to E markedly decreased the inhibition induced by piperine, capsaicin, and 6-gingerol, but not by polygodial. Our data contribute to the relatively sparse knowledge concerning the pharmacology of K2P channels and also raise the question of whether K2P channels could be involved in the pungency perception of piperine.
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