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Raisch T, Raunser S. The modes of action of ion-channel-targeting neurotoxic insecticides: lessons from structural biology. Nat Struct Mol Biol 2023; 30:1411-1427. [PMID: 37845413 DOI: 10.1038/s41594-023-01113-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 08/31/2023] [Indexed: 10/18/2023]
Abstract
Insecticides are indispensable tools for plant protection in modern agriculture. Despite having highly heterogeneous structures, many neurotoxic insecticides use similar principles to inhibit or deregulate neuronal ion channels. Insecticides targeting pentameric ligand-gated channels are structural mimetics of neurotransmitters or manipulate and deregulate the proteins. Those binding to (pseudo-)tetrameric voltage-gated(-like) channels, on the other hand, are natural or synthetic compounds that directly block the ion-conducting pore or prevent conformational changes in the transmembrane domain necessary for opening and closing the pore. The use of a limited number of inhibition mechanisms can be problematic when resistances arise and become more widespread. Therefore, there is a rising interest in the development of insecticides with novel mechanisms that evade resistance and are pest-insect-specific. During the last decade, most known insecticide targets, many with bound compounds, have been structurally characterized, bringing the rational design of novel classes of agrochemicals within closer reach than ever before.
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Affiliation(s)
- Tobias Raisch
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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2
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Zhang J, Liu S, Fan J, Yan R, Huang B, Zhou F, Yuan T, Gong J, Huang Z, Jiang D. Structural basis of human Slo2.2 channel gating and modulation. Cell Rep 2023; 42:112858. [PMID: 37494189 DOI: 10.1016/j.celrep.2023.112858] [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: 12/15/2022] [Revised: 06/16/2023] [Accepted: 07/07/2023] [Indexed: 07/28/2023] Open
Abstract
The sodium-activated Slo2.2 channel is abundantly expressed in the brain, playing a critical role in regulating neuronal excitability. The Na+-binding site and the underlying mechanisms of Na+-dependent activation remain unclear. Here, we present cryoelectron microscopy (cryo-EM) structures of human Slo2.2 in closed, open, and inhibitor-bound form at resolutions of 2.6-3.2 Å, revealing gating mechanisms of Slo2.2 regulation by cations and a potent inhibitor. The cytoplasmic gating ring domain of the closed Slo2.2 harbors multiple K+ and Zn2+ sites, which stabilize the channel in the closed conformation. The open Slo2.2 structure reveals at least two Na+-sensitive sites where Na+ binding induces expansion and rotation of the gating ring that opens the inner gate. Furthermore, a potent inhibitor wedges into a pocket formed by pore helix and S6 helix and blocks the pore. Together, our results provide a comprehensive structural framework for the investigation of Slo2.2 channel gating, Na+ sensation, and inhibition.
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Affiliation(s)
- Jiangtao Zhang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; College of Life Science and Technology, Key Laboratory of Molecular Biophysics of MOE, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Shiqi Liu
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, China; IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Junping Fan
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Synthetic and Functional Biomolecules Center, and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Rui Yan
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Bo Huang
- Beijing StoneWise Technology Co Ltd., Haidian District, Beijing, China
| | - Feng Zhou
- Beijing StoneWise Technology Co Ltd., Haidian District, Beijing, China
| | - Tian Yuan
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, China; IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Jianke Gong
- College of Life Science and Technology, Key Laboratory of Molecular Biophysics of MOE, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhuo Huang
- State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing 100191, China; IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China.
| | - Daohua Jiang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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3
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Al-Hassany L, Boucherie DM, Creeney H, van Drie RWA, Farham F, Favaretto S, Gollion C, Grangeon L, Lyons H, Marschollek K, Onan D, Pensato U, Stanyer E, Waliszewska-Prosół M, Wiels W, Chen HZ, Amin FM. Future targets for migraine treatment beyond CGRP. J Headache Pain 2023; 24:76. [PMID: 37370051 DOI: 10.1186/s10194-023-01567-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Accepted: 03/14/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND Migraine is a disabling and chronic neurovascular headache disorder. Trigeminal vascular activation and release of calcitonin gene-related peptide (CGRP) play a pivotal role in the pathogenesis of migraine. This knowledge has led to the development of CGRP(-receptor) therapies. Yet, a substantial proportion of patients do not respond to these treatments. Therefore, alternative targets for future therapies are warranted. The current narrative review provides a comprehensive overview of the pathophysiological role of these possible non-CGRP targets in migraine. FINDINGS We covered targets of the metabotropic receptors (pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), amylin, and adrenomedullin), intracellular targets (nitric oxide (NO), phosphodiesterase-3 (PDE3) and -5 (PDE5)), and ion channels (potassium, calcium, transient receptor potential (TRP), and acid-sensing ion channels (ASIC)). The majority of non-CGRP targets were able to induce migraine-like attacks, except for (i) calcium channels, as it is not yet possible to directly target channels to elucidate their precise involvement in migraine; (ii) TRP channels, activation of which can induce non-migraine headache; and (iii) ASICs, as their potential in inducing migraine attacks has not been investigated thus far. Drugs that target its receptors exist for PACAP, NO, and the potassium, TRP, and ASIC channels. No selective drugs exist for the other targets, however, some existing (migraine) treatments appear to indirectly antagonize responses to amylin, adrenomedullin, and calcium channels. Drugs against PACAP, NO, potassium channels, TRP channels, and only a PAC1 antibody have been tested for migraine treatment, albeit with ambiguous results. CONCLUSION While current research on these non-CGRP drug targets has not yet led to the development of efficacious therapies, human provocation studies using these targets have provided valuable insight into underlying mechanisms of migraine headaches and auras. Further studies are needed on these alternative therapies in non-responders of CGRP(-receptor) targeted therapies with the ultimate aim to pave the way towards a headache-free future for all migraine patients.
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Affiliation(s)
- Linda Al-Hassany
- Department of Internal Medicine, Division of Vascular Medicine and Pharmacology, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Deirdre M Boucherie
- Department of Internal Medicine, Division of Vascular Medicine and Pharmacology, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Hannah Creeney
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - Ruben W A van Drie
- Department of Internal Medicine, Division of Vascular Medicine and Pharmacology, Erasmus MC University Medical Center, Rotterdam, The Netherlands
- Department of Cardiology, Division of Experimental Cardiology, Erasmus MC University Medical Center, Rotterdam, The Netherlands
| | - Fatemeh Farham
- Department of Headache, Iranian Centre of Neurological Researchers, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Silvia Favaretto
- Headache Center, Neurology Clinic, University Hospital of Padua, Padua, Italy
| | - Cédric Gollion
- Department of Neurology, University Hospital of Toulouse, Toulouse, France
| | - Lou Grangeon
- Neurology Department, Rouen University Hospital, Rouen, France
| | - Hannah Lyons
- Institute of Metabolism and Systems Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Karol Marschollek
- Department of Neurology, Wroclaw Medical University, Wrocław, Poland
| | - Dilara Onan
- Spine Health Unit, Faculty of Physical Therapy and Rehabilitation, Hacettepe University, Ankara, Turkey
- Department of Clinical and Molecular Medicine, Sapienza University, Rome, Italy
| | - Umberto Pensato
- Neurology and Stroke Unit, IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy
- Humanitas University, Pieve Emanuele, Milan, Italy
| | - Emily Stanyer
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | | | - Wietse Wiels
- Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Hui Zhou Chen
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - Faisal Mohammad Amin
- Danish Headache Center, Department of Neurology, Faculty of Health and Medical Sciences, Rigshospitalet Glostrup, University of Copenhagen, Copenhagen, Denmark.
- Department of Neurorehabilitation/Traumatic Brain Injury, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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4
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Bundela R, Cameron RC, Singh AJ, McLellan RM, Richardson AT, Berry D, Nicholson MJ, Parker EJ. Generation of Alternate Indole Diterpene Architectures in Two Species of Aspergilli. J Am Chem Soc 2023; 145:2754-2758. [PMID: 36710518 PMCID: PMC9913125 DOI: 10.1021/jacs.2c11170] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Indexed: 01/31/2023]
Abstract
The significant structural diversity and potent bioactivity of the fungal indole diterpenes (IDTs) has attracted considerable interest in their biosynthesis. Although substantial skeletal diversity is generated by the action of noncanonical terpene cyclases, comparatively little is known about these enzymes, particularly those involved in the generation of the subgroup containing emindole SA and DA, which show alternate terpenoid skeletons. Here, we describe the IDT biosynthetic machinery generating these unusual IDT architectures from Aspergillus striatus and Aspergillus desertorum. The function of four putative cyclases was interrogated via heterologous expression. Two specific cyclases were identified that catalyze the formation of epimers emindole SA and DA from A. striatus and A. desertorum, respectively. These cyclases are both clustered along with all the elements required for basic IDT biosynthesis yet catalyze an unusual Markovnikov-like cyclization cascade with alternate stereochemical control. Their identification reveals that these alternate architectures are not generated by mechanistically sloppy or promiscuous enzymes, but by cyclases capable of delivering precise regio- and stereospecificities.
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Affiliation(s)
- Rudranuj Bundela
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Rosannah C. Cameron
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - A. Jonathan Singh
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Rose M. McLellan
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Alistair T. Richardson
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Daniel Berry
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Matthew J. Nicholson
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
| | - Emily J. Parker
- Ferrier
Research Institute, Victoria University
of Wellington, PO Box 600, Wellington 6140, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand
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5
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Small molecule modulation of the Drosophila Slo channel elucidated by cryo-EM. Nat Commun 2021; 12:7164. [PMID: 34887422 PMCID: PMC8660915 DOI: 10.1038/s41467-021-27435-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 11/18/2021] [Indexed: 12/16/2022] Open
Abstract
Slowpoke (Slo) potassium channels display extraordinarily high conductance, are synergistically activated by a positive transmembrane potential and high intracellular Ca2+ concentrations and are important targets for insecticides and antiparasitic drugs. However, it is unknown how these compounds modulate ion translocation and whether there are insect-specific binding pockets. Here, we report structures of Drosophila Slo in the Ca2+-bound and Ca2+-free form and in complex with the fungal neurotoxin verruculogen and the anthelmintic drug emodepside. Whereas the architecture and gating mechanism of Slo channels are conserved, potential insect-specific binding pockets exist. Verruculogen inhibits K+ transport by blocking the Ca2+-induced activation signal and precludes K+ from entering the selectivity filter. Emodepside decreases the conductance by suboptimal K+ coordination and uncouples ion gating from Ca2+ and voltage sensing. Our results expand the mechanistic understanding of Slo regulation and lay the foundation for the rational design of regulators of Slo and other voltage-gated ion channels. Slowpoke (Slo) channels are voltage-gated potassium channels that are activated by high intracellular Ca2+ concentrations, and they are targets for insecticides and antiparasitic drugs. Here, the authors present the cryo-EM structures of the Drosophila melanogaster Slo channel in the Ca2+-bound and Ca2+-free conformations, as well as in complex with the fungal neurotoxin verruculogen and the anthelmintic drug emodepside and discuss the mechanisms by which they affect the activity of Slo.
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6
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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7
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Uray IP, Uray K. Mechanotransduction at the Plasma Membrane-Cytoskeleton Interface. Int J Mol Sci 2021; 22:11566. [PMID: 34768998 PMCID: PMC8584042 DOI: 10.3390/ijms222111566] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/19/2021] [Accepted: 10/21/2021] [Indexed: 02/08/2023] Open
Abstract
Mechanical cues are crucial for survival, adaptation, and normal homeostasis in virtually every cell type. The transduction of mechanical messages into intracellular biochemical messages is termed mechanotransduction. While significant advances in biochemical signaling have been made in the last few decades, the role of mechanotransduction in physiological and pathological processes has been largely overlooked until recently. In this review, the role of interactions between the cytoskeleton and cell-cell/cell-matrix adhesions in transducing mechanical signals is discussed. In addition, mechanosensors that reside in the cell membrane and the transduction of mechanical signals to the nucleus are discussed. Finally, we describe two examples in which mechanotransduction plays a significant role in normal physiology and disease development. The first example is the role of mechanotransduction in the proliferation and metastasis of cancerous cells. In this system, the role of mechanotransduction in cellular processes, including proliferation, differentiation, and motility, is described. In the second example, the role of mechanotransduction in a mechanically active organ, the gastrointestinal tract, is described. In the gut, mechanotransduction contributes to normal physiology and the development of motility disorders.
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Affiliation(s)
- Iván P. Uray
- Department of Clinical Oncology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
| | - Karen Uray
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
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8
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Thompson B, Satin LS. Beta-Cell Ion Channels and Their Role in Regulating Insulin Secretion. Compr Physiol 2021; 11:1-21. [PMID: 34636409 PMCID: PMC8935893 DOI: 10.1002/cphy.c210004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Beta cells of the pancreatic islet express many different types of ion channels. These channels reside in the β-cell plasma membrane as well as subcellular organelles and their coordinated activity and sensitivity to metabolism regulate glucose-dependent insulin secretion. Here, we review the molecular nature, expression patterns, and functional roles of many β-cell channels, with an eye toward explaining the ionic basis of glucose-induced insulin secretion. Our primary focus is on KATP and voltage-gated Ca2+ channels as these primarily regulate insulin secretion; other channels in our view primarily help to sculpt the electrical patterns generated by activated β-cells or indirectly regulate metabolism. Lastly, we discuss why understanding the physiological roles played by ion channels is important for understanding the secretory defects that occur in type 2 diabetes. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.
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9
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Shi J, Shi S, Shi S, Jia Q, Yuan G, Chu Y, Wang H, Hu Y, Cui H. Bibliometric analysis of potassium channel research. Channels (Austin) 2021; 14:18-27. [PMID: 31842669 PMCID: PMC7039634 DOI: 10.1080/19336950.2019.1705055] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
ABSTRACT Objective: To explore the research status, hotspots, and trends in research on potassium channel. Methods: The Web of Science core collection database was used as the data source and the visual analysis software Citespace5.4 R3 was used to visualize the studies of potassium channel in the past 10 years. The national/institutional distribution, journal distribution, authors, and related research were discussed. Results 17,392 articles were obtained. The USA, Peoples R China, Germany, England, and Japan were the main countries in the field and University of California was the most important institution for the study of potassium channel. PLoS One was the most productive journal and proceedings of the national academy of sciences of the united states of america was the most frequently cited journal in potassium channel research. The author with the highest number was Colin G Nichols and the author with the highest co- cited frequency was Sanguinetti MC. The three hot spots of potassium channel research were gene expression, Ca2+ activated k+ channel and nitric oxide. The top four research frontiers of potassium channel research were bk channel,blood pressure,oxidative stress and electrophysiology. Conclusion The study provides a perspective for understanding the potassium channel research and provides valuable information for potassium channel researchers to identify potential collaborators, partner institutions, hot topics and research frontiers.
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Affiliation(s)
- Jingjing Shi
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Shuqing Shi
- Graduate School of Beijing University of Chinese Medicine, Beijing, China
| | - Shuai Shi
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Qiulei Jia
- Graduate School of Beijing University of Chinese Medicine, Beijing, China
| | - Guozhen Yuan
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuguang Chu
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Huan Wang
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuanhui Hu
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Hanming Cui
- Guanganmen Hospital, China Academy of Chinese Medical Sciences, Beijing, China
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10
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Zhang RG, Yip CY, Pan KW, Cai MY, Ko WH. β 2 adrenoceptor signaling regulates ion transport in 16HBE14o- human airway epithelial cells. J Cell Physiol 2020; 235:8387-8401. [PMID: 32239700 DOI: 10.1002/jcp.29683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 03/15/2020] [Indexed: 11/09/2022]
Abstract
We investigated the regulation of Cl- secretion by adrenoceptors in polarized 16HBE14o- human bronchial epithelial cells. Treatment with the nonselective β adrenoceptor agonist isoprenaline stimulated an increase in short-circuit current (ISC ), which was inhibited by the β adrenoceptor blocker propranolol. Treatment with procaterol, an agonist specific for the β2 adrenoceptor subtype, stimulated a similar increase in ISC , which was inhibited by the β2 adrenoceptor antagonist ICI 118551. Inhibitors of cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated Cl- channel (CaCC), but not K+ channel blockers, were able to inhibit the increase in ISC . "Trimultaneous" recording of ISC and intracellular cyclic adenosine monophosphate (cAMP) and Ca2+ levels in 16HBE14o- epithelia confirmed that the ISC induced by isoprenaline or procaterol involved both cAMP and Ca2+ signaling. Our results demonstrate that β2 adrenoceptors regulate Cl- secretion in the human airway epithelium by activating apical CFTRs and CaCCs via cAMP-dependent and intracellular Ca2+ -dependent mechanisms, respectively.
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Affiliation(s)
- Rui-Gang Zhang
- Department of Physiology, Basic Medical School, Guangdong Medical University, China
| | - Chung-Yin Yip
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Ke-Wu Pan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Meng-Yun Cai
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Wing-Hung Ko
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
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11
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Kopec W, Rothberg BS, de Groot BL. Molecular mechanism of a potassium channel gating through activation gate-selectivity filter coupling. Nat Commun 2019; 10:5366. [PMID: 31772184 PMCID: PMC6879586 DOI: 10.1038/s41467-019-13227-w] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 10/24/2019] [Indexed: 01/08/2023] Open
Abstract
Potassium channels are presumed to have two allosterically coupled gates, the activation gate and the selectivity filter gate, that control channel opening, closing, and inactivation. However, the molecular mechanism of how these gates regulate K+ ion flow through the channel remains poorly understood. An activation process, occurring at the selectivity filter, has been recently proposed for several potassium channels. Here, we use X-ray crystallography and extensive molecular dynamics simulations, to study ion permeation through a potassium channel MthK, for various opening levels of both gates. We find that the channel conductance is controlled at the selectivity filter, whose conformation depends on the activation gate. The crosstalk between the gates is mediated through a collective motion of channel helices, involving hydrophobic contacts between an isoleucine and a conserved threonine in the selectivity filter. We propose a gating model of selectivity filter-activated potassium channels, including pharmacologically relevant two-pore domain (K2P) and big potassium (BK) channels.
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Affiliation(s)
- Wojciech Kopec
- Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.
| | - Brad S Rothberg
- Department of Medical Genetics and Molecular Biochemistry, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA
| | - Bert L de Groot
- Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.
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12
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Zhuang Z, Xiao J, Chen X, Hu X, Li R, Chen S, Feng X, Shen S, Ma HP, Zhuang J, Cai H. G protein pathway suppressor 2 enhanced the renal large-conductance Ca 2+-activated potassium channel expression via inhibiting ERK1/2 signaling pathway. Am J Physiol Renal Physiol 2018; 315:F503-F511. [PMID: 29767559 DOI: 10.1152/ajprenal.00041.2018] [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] [Indexed: 12/16/2022] Open
Abstract
G protein pathway suppressor 2 (GPS2) is a multifunctional protein and transcriptional regulation factor that is involved in the G protein MAPK signaling pathway. It has been shown that the MAPK signaling pathway plays an important role in the regulation of renal large-conductance Ca2+-activated potassium (BK) channels. In this study, we investigated the effects of GPS2 on BK channel activity and protein expression. In human embryonic kidney (HEK) BK stably expressing cells transfected with either GPS2 or its vector control, a single-cell recording showed that GPS2 significantly increased BK channel activity ( NPo), increasing BK open probability ( Po), and channel number ( N) compared with the control. In Cos-7 cells and HEK 293 T cells, GPS2 overexpression significantly enhanced the total protein expression of BK in a dose-dependent manner. Knockdown of GPS2 expression significantly decreased BK protein expression, while increasing ERK1/2 phosphorylation. Knockdown of ERK1/2 expression reversed the GPS2 siRNA-mediated inhibition of BK protein expression in Cos-7 cells. Pretreatments of Cos-7 cells with either the lysosomal inhibitor bafilomycin A1 or the proteasomal inhibitor MG132 partially reversed the inhibitory effects of GPS2 siRNA on BK protein expression. In addition, feeding a high-potassium diet significantly increased both GPS2 and BK protein abundance in mice. These data suggest that GPS2 enhances BK channel activity and its protein expression by reducing ERK1/2 signaling-mediated degradation of the channel.
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Affiliation(s)
- Zhizhi Zhuang
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Jia Xiao
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Xiangya Hospital, Central South University, Hunan, China
| | - Xinxin Chen
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Xiaohan Hu
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Ruidian Li
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Shan Chen
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia
| | - Xiuyan Feng
- Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Xiangya Hospital, Central South University, Hunan, China
| | - Saier Shen
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine , Atlanta, Georgia
| | - Jieqiu Zhuang
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China
| | - Hui Cai
- Renal Division, the Second Affiliated Hospital, Wenzhou Medical University , Zhejiang , China.,Renal Division, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia
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13
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Chloroform Extract of Artemisia annua L. Relaxes Mouse Airway Smooth Muscle. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2017; 2017:9870414. [PMID: 29259649 PMCID: PMC5702405 DOI: 10.1155/2017/9870414] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 09/06/2017] [Accepted: 10/10/2017] [Indexed: 11/18/2022]
Abstract
Artemisia annua L. belongs to the Asteraceae family, which is indigenous to China. It has valuable pharmacological properties, such as antimalarial, anti-inflammatory, and anticancer properties. However, whether it possesses antiasthma properties is unknown. In the current study, chloroform extract of Artemisia annua L. (CEAA) was prepared, and we found that CEAA completely eliminated acetylcholine (ACh) or high K+-elicited (80 mM) contractions of mouse tracheal rings (TRs). Patch-clamp technique and ion channel blockers were employed to explore the underlying mechanisms of the relaxant effect of CEAA. In whole-cell current recording, CEAA almost fully abolished voltage-dependent Ca2+ channel (VDCC) currents and markedly enhanced large conductance Ca2+-activated K+ (BK) channel currents on airway smooth muscle cells (ASMCs). In single channel current recording, CEAA increased the opening probability but had no effect on the single channel conductance of BK channels. However, under paxilline-preincubated (a selective BK channel blocker) conditions, CEAA only slightly increased BK channel currents. These results indicate that CEAA may contain active components with potent antiasthma activity. The abolished VDCCs by CEAA may mainly contribute to the underlying mechanism through which it acts as an effective antiasthmatic compound, but the enhanced BK currents might play a less important role in the antiasthmatic effects.
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14
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Paeger L, Pippow A, Hess S, Paehler M, Klein AC, Husch A, Pouzat C, Brüning JC, Kloppenburg P. Energy imbalance alters Ca 2+ handling and excitability of POMC neurons. eLife 2017; 6. [PMID: 28762947 PMCID: PMC5538824 DOI: 10.7554/elife.25641] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Accepted: 06/29/2017] [Indexed: 01/16/2023] Open
Abstract
Satiety-signaling, pro-opiomelanocortin (POMC)-expressing neurons in the arcuate nucleus of the hypothalamus play a pivotal role in the regulation of energy homeostasis. Recent studies reported altered mitochondrial dynamics and decreased mitochondria- endoplasmic reticulum contacts in POMC neurons during diet-induced obesity. Since mitochondria play a crucial role in Ca2+ signaling, we investigated whether obesity alters Ca2+ handling of these neurons in mice. In diet-induced obesity, cellular Ca2+ handling properties including mitochondrial Ca2+ uptake capacity are impaired, and an increased resting level of free intracellular Ca2+ is accompanied by a marked decrease in neuronal excitability. Experimentally increasing or decreasing intracellular Ca2+ concentrations reproduced electrophysiological properties observed in diet-induced obesity. Taken together, we provide the first direct evidence for a diet-dependent deterioration of Ca2+ homeostasis in POMC neurons during obesity development resulting in impaired function of these critical energy homeostasis-regulating neurons. DOI:http://dx.doi.org/10.7554/eLife.25641.001
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Affiliation(s)
- Lars Paeger
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Andreas Pippow
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Simon Hess
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Moritz Paehler
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Andreas C Klein
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Andreas Husch
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Christophe Pouzat
- MAP5 - Mathématiques Appliquées à Paris 5, CNRS UMR 8145, Paris, France
| | - Jens C Brüning
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany.,Department of Mouse Genetics and Metabolism, Institute for Genetics, Center of Molecular Medicine Cologne, Center for Endocrinology, Diabetes and Preventive Medicine, University Hospital of Cologne, Cologne, Germany.,Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Peter Kloppenburg
- Biocenter, Institute for Zoology, University of Cologne, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
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15
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Kaczmarek LK, Aldrich RW, Chandy KG, Grissmer S, Wei AD, Wulff H. International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 2017; 69:1-11. [PMID: 28267675 PMCID: PMC11060434 DOI: 10.1124/pr.116.012864] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Richard W Aldrich
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - K George Chandy
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Stephan Grissmer
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Aguan D Wei
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Heike Wulff
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
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16
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Seydel U, Scheel O, Müller M, Brandenburg K, Blunck R. A K+ channel is involved in LPS signaling. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/09680519010070030901] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We previously showed a clear correlation between the molecular conformation of the lipid A moiety of endotoxin molecules and their cytokine-inducing capacity in mononuclear cells. While conically shaped lipid A moieties exhibit a high agonistic activity, a shift to a more cylindrically shaped lipid A leads to a decrease in agonistic and increase in antagonistic activity of the endotoxin molecules. Here, we show the involvement of a high-conductance Ca2+-activated potassium (MaxiK) channel in LPS signaling in macrophages. Corresponding to their biological activity, endotoxins activate a MaxiK channel as shown in outside-out patch-clamp experiments. LPS antagonists and anti-CD14 antibodies inhibit the LPS-induced activation of the channel. Blocking of the channel by specific channel blockers in macrophage cultures leads to inhibition of cytokine mRNA production. In particular, this result implies that there is no other independent transmembrane signaling pathway operative in macrophages. A shift of the molecular conformation of an a priori antagonistic lipid A from a cylindrical to a conical shape by adding the membrane-active compound chlorpromazine increases the activity of the MaxiK channel and the biological activity of the lipid A. We conclude that the activation of the MaxiK channel is a very early step in LPS-induced signaling in macrophages.
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Affiliation(s)
- U. Seydel
- Division of Biophysics, Research Center Borstel, Borstel, Germany,
| | - O. Scheel
- Division of Biophysics, Research Center Borstel, Borstel, Germany
| | - M. Müller
- Division of Biophysics, Research Center Borstel, Borstel, Germany
| | - K. Brandenburg
- Division of Biophysics, Research Center Borstel, Borstel, Germany
| | - R. Blunck
- Division of Biophysics, Research Center Borstel, Borstel, Germany
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17
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Bradler C, Warren B, Bardos V, Schleicher S, Klein A, Kloppenburg P. Properties and physiological function of Ca2+-dependent K+ currents in uniglomerular olfactory projection neurons. J Neurophysiol 2016; 115:2330-40. [PMID: 26823514 DOI: 10.1152/jn.00840.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 01/27/2016] [Indexed: 11/22/2022] Open
Abstract
Ca(2+)-activated potassium currents [IK(Ca)] are an important link between the intracellular signaling system and the membrane potential, which shapes intrinsic electrophysiological properties. To better understand the ionic mechanisms that mediate intrinsic firing properties of olfactory uniglomerular projection neurons (uPNs), we used whole cell patch-clamp recordings in an intact adult brain preparation of the male cockroach Periplaneta americana to analyze IK(Ca) In the insect brain, uPNs form the principal pathway from the antennal lobe to the protocerebrum, where centers for multimodal sensory processing and learning are located. In uPNs the activation of IK(Ca) was clearly voltage and Ca(2+) dependent. Thus under physiological conditions IK(Ca) is strongly dependent on Ca(2+) influx kinetics and on the membrane potential. The biophysical characterization suggests that IK(Ca) is generated by big-conductance (BK) channels. A small-conductance (SK) channel-generated current could not be detected. IK(Ca) was sensitive to charybdotoxin (CTX) and iberiotoxin (IbTX) but not to apamin. The functional role of IK(Ca) was analyzed in occlusion experiments under current clamp, in which portions of IK(Ca) were blocked by CTX or IbTX. Blockade of IK(Ca) showed that IK(Ca) contributes significantly to intrinsic electrophysiological properties such as the action potential waveform and membrane excitability.
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Affiliation(s)
- Cathleen Bradler
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Ben Warren
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Viktor Bardos
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Sabine Schleicher
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Andreas Klein
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Peter Kloppenburg
- Biocenter, Institute for Zoology, and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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18
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Yu M, Liu SL, Sun PB, Pan H, Tian CL, Zhang LH. Peptide toxins and small-molecule blockers of BK channels. Acta Pharmacol Sin 2016; 37:56-66. [PMID: 26725735 DOI: 10.1038/aps.2015.139] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 10/13/2015] [Indexed: 12/21/2022] Open
Abstract
Large conductance, Ca(2+)-activated potassium (BK) channels play important roles in the regulation of neuronal excitability and the control of smooth muscle contractions. BK channels can be activated by changes in both the membrane potential and intracellular Ca(2+) concentrations. Here, we provide an overview of the structural and pharmacological properties of BK channel blockers. First, the properties of different venom peptide toxins from scorpions and snakes are described, with a focus on their characteristic structural motifs, including their disulfide bond formation pattern, the binding interface between the toxin and BK channel, and the functional consequence of the blockage of BK channels by these toxins. Then, some representative non-peptide blockers of BK channels are also described, including their molecular formula and pharmacological effects on BK channels. The detailed categorization and descriptions of these BK channel blockers will provide mechanistic insights into the blockade of BK channels. The structures of peptide toxins and non-peptide compounds could provide templates for the design of new channel blockers, and facilitate the optimization of lead compounds for further therapeutic applications in neurological disorders or cardiovascular diseases.
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19
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Tanner MR, Hu X, Huq R, Tajhya RB, Sun L, Khan FS, Laragione T, Horrigan FT, Gulko PS, Beeton C. KCa1.1 inhibition attenuates fibroblast-like synoviocyte invasiveness and ameliorates disease in rat models of rheumatoid arthritis. Arthritis Rheumatol 2015; 67:96-106. [PMID: 25252152 DOI: 10.1002/art.38883] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 09/11/2014] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Fibroblast-like synoviocytes (FLS) participate in joint inflammation and damage in rheumatoid arthritis (RA) and its animal models. The purpose of this study was to define the importance of KCa1.1 (BK, Maxi-K, Slo1, KCNMA1) channel expression and function in FLS and to establish these channels as potential new targets for RA therapy. METHODS We compared KCa1.1 expression levels in FLS from rats with pristane-induced arthritis (PIA) and in FLS from healthy rats. We then used ex vivo functional assays combined with small interfering RNA-induced knockdown, overexpression, and functional modulation of KCa1.1 in PIA FLS. Finally, we determined the effectiveness of modulating KCa1.1 in 2 rat models of RA, moderate PIA and severe collagen-induced arthritis (CIA). RESULTS We found that PIA FLS expressed the KCa1.1 channel as their major potassium channel, as has been found in FLS from patients with RA. In contrast, FLS from healthy rats expressed fewer of these channels. Inhibiting the function or expression of KCa1.1 ex vivo reduced proliferation and invasive properties of, as well as protease production by, PIA FLS, whereas opening native KCa1.1 or overexpressing the channel enhanced the invasiveness of both FLS from rats with PIA and FLS from healthy rats. Treatment with a KCa1.1 channel blocker at the onset of clinical signs stopped disease progression in the PIA and CIA models, reduced joint and bone damage, and inhibited FLS invasiveness and proliferation. CONCLUSION Our results demonstrate a critical role of KCa1.1 channels in the regulation of FLS invasiveness and suggest that KCa1.1 channels represent potential therapeutic targets in RA.
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20
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Hsu HT, Tseng YT, Lo YC, Wu SN. Ability of naringenin, a bioflavonoid, to activate M-type potassium current in motor neuron-like cells and to increase BKCa-channel activity in HEK293T cells transfected with α-hSlo subunit. BMC Neurosci 2014; 15:135. [PMID: 25539574 PMCID: PMC4288500 DOI: 10.1186/s12868-014-0135-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 12/11/2014] [Indexed: 12/17/2022] Open
Abstract
Background Naringenin (NGEN) is a citrus bioflavonoid known to have beneficial health properties; however, the ionic mechanism of its actions remains largely unclear. In this study, we attempted to evaluate the possible effects of NGEN on K+ currents in NSC-34 neuronal cells and in HEK293T cells expressing α-hSlo. Results NGEN increased M-type K+ current (IK(M)) in a concentration-dependent manner with an EC50 value of 9.8 μM in NSC-34 cells. NGEN shifted the activation curve of IK(M) conductance to the more negative potentials. In cell-attached recordings, NGEN or flupirtine enhanced the activity of M-type K+ (KM) channels with no changes in single-channel amplitude. NGEN (10 μM) had minimal effect on erg-mediated K+ currents. Under cell-attached voltage-clamp recordings, NGEN decreased the frequency of spontaneous action currents and further application of linopirdine can reverse NGEN-induced inhibition of firing. In HEK293T cells expressing α-hSlo, this compound increased the amplitude of Ca2+-activated K+ current (IK(Ca)). Under inside-out recordings, NGEN applied to the intracellular side of the detached patch enhanced the activity of large-conductance Ca2+-activated K+ (BKCa) channels. Moreover, from the study of a modeled neuron, burst firing of simulated action potentials (APs) was reduced in the presence of the increased conductances of both KM and KCa channels. Fast-slow analysis of AP bursting from this model also revealed that as the conductances of both KM and BKCa channels were increased by two-fold, the voltage nullcline was shifted in an upward direction accompanied by the compression of burst trajectory. Conclusions The present results demonstrate that activation of both KM and BKCa channels caused by NGEN might combine to influence neuronal activity if similar channels were functionally co-expressed in central neurons in vivo.
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Affiliation(s)
- Hung-Te Hsu
- Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan. .,Department of Anesthesia, Kaohsiung Medical University Hospital, Kaohsiung City, 80708, Taiwan.
| | - Yu-Ting Tseng
- Department of Pharmacology, School of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan. .,Graduate Institute of Natural Products, School of Pharmacy, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
| | - Yi-Ching Lo
- Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan. .,Department of Pharmacology, School of Medicine, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan. .,Graduate Institute of Natural Products, School of Pharmacy, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan.
| | - Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, 70101, Taiwan. .,Institute of Basic Medical Sciences, National Cheng Kung University Medical College, Tainan City, 70101, Taiwan.
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21
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Wang B, Jaffe DB, Brenner R. Current understanding of iberiotoxin-resistant BK channels in the nervous system. Front Physiol 2014; 5:382. [PMID: 25346692 PMCID: PMC4190997 DOI: 10.3389/fphys.2014.00382] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 09/15/2014] [Indexed: 11/13/2022] Open
Abstract
While most large-conductance, calcium-, and voltage-activated potassium channels (BK or Maxi-K type) are blocked by the scorpion venom iberiotoxin, the so-called “type II” subtype has the property of toxin resistance. This property is uniquely mediated by channel assembly with one member of the BK accessory β subunit family, the neuron-enriched β4 subunit. This review will focus on current understanding of iberiotoxin-resistant, β4-containing BK channel properties and their function in the CNS. Studies have shown that β4 dramatically promotes BK channel opening by shifting voltage sensor activation to more negative voltage ranges, but also slows activation to timescales that theoretically preclude BK ability to shape action potentials (APs). In addition, β4 membrane trafficking is regulated through an endoplasmic retention signal and palmitoylation. More recently, the challenge has been to understand the functional role of the iberiotoxin-resistant BK subtype utilizing computational modeling of neurons and neurophysiological approaches. Utilizing iberiotoxin-resistance as a footprint for these channels, they have been identified in dentate gyrus granule neurons and in purkinje neurons of the cerebellum. In these neurons, the role of these channels is largely consistent with slow-gated channels that reduce excitability either through an interspike conductance, such as in purkinje neurons, or by replacing fast-gating BK channels that otherwise facilitate high frequency AP firing, such as in dentate gyrus neurons. They are also observed in presynaptic mossy fiber terminals of the dentate gyrus and posterior pituitary terminals. More recent studies suggest that β4 subunits may also be expressed in some neurons lacking iberiotoxin-resistant BK channels, such as in CA3 hippocampus neurons. Ongoing research using novel, specific blockers and agonists of BK/β4, and β4 knockout mice, will continue to move the field forward in understanding the function of these channels.
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Affiliation(s)
- Bin Wang
- Department of Physiology, University of Texas Health Science Center at San Antonio San Antonio, TX, USA
| | - David B Jaffe
- Department of Biology and the UTSA Neurosciences Institute, University of Texas at San Antonio San Antonio, TX, USA
| | - Robert Brenner
- Department of Physiology, University of Texas Health Science Center at San Antonio San Antonio, TX, USA
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22
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Liu Y, Song X, Shi Y, Shi Z, Niu W, Feng X, Gu D, Bao HF, Ma HP, Eaton DC, Zhuang J, Cai H. WNK1 activates large-conductance Ca2+-activated K+ channels through modulation of ERK1/2 signaling. J Am Soc Nephrol 2014; 26:844-54. [PMID: 25145935 DOI: 10.1681/asn.2014020186] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
With no lysine (WNK) kinases are members of the serine/threonine kinase family. We previously showed that WNK4 inhibits renal large-conductance Ca(2+)-activated K(+) (BK) channel activity by enhancing its degradation through a lysosomal pathway. In this study, we investigated the effect of WNK1 on BK channel activity. In HEK293 cells stably expressing the α subunit of BK (HEK-BKα cells), siRNA-mediated knockdown of WNK1 expression significantly inhibited both BKα channel activity and open probability. Knockdown of WNK1 expression also significantly inhibited BKα protein expression and increased ERK1/2 phosphorylation, whereas overexpression of WNK1 significantly enhanced BKα expression and decreased ERK1/2 phosphorylation in a dose-dependent manner in HEK293 cells. Knockdown of ERK1/2 prevented WNK1 siRNA-mediated inhibition of BKα expression. Similarly, pretreatment of HEK-BKα cells with the lysosomal inhibitor bafilomycin A1 reversed the inhibitory effects of WNK1 siRNA on BKα expression in a dose-dependent manner. Knockdown of WNK1 expression also increased the ubiquitination of BKα channels. Notably, mice fed a high-K(+) diet for 10 days had significantly higher renal protein expression levels of BKα and WNK1 and lower levels of ERK1/2 phosphorylation compared with mice fed a normal-K(+) diet. These data suggest that WNK1 enhances BK channel function by reducing ERK1/2 signaling-mediated lysosomal degradation of the channel.
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Affiliation(s)
- Yingli Liu
- Renal Division, Department of Medicine, and Department of Nephrology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine
| | - Xiang Song
- Department of Cardiology, The Fourth Affiliated Hospital, Harbin Medical University, Heilongjiang, China; and
| | | | - Zhen Shi
- Department of Nephrology, The Second Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
| | - Weihui Niu
- Department of Nephrology, The Second Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
| | - Xiuyan Feng
- Renal Division, Department of Medicine, and Renal Section, Atlanta Veterans Affairs Medical Center, Decatur, Georgia
| | - Dingying Gu
- Department of Nephrology, The Second Affiliated Hospital, Wenzhou Medical University, Zhejiang, China
| | - Hui-Fang Bao
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Douglas C Eaton
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
| | - Jieqiu Zhuang
- Department of Nephrology, The Second Affiliated Hospital, Wenzhou Medical University, Zhejiang, China;
| | - Hui Cai
- Renal Division, Department of Medicine, and Renal Section, Atlanta Veterans Affairs Medical Center, Decatur, Georgia Department of Physiology, Emory University School of Medicine, Atlanta, Georgia;
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23
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KCa and Ca(2+) channels: the complex thought. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2322-33. [PMID: 24613282 DOI: 10.1016/j.bbamcr.2014.02.019] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/13/2014] [Accepted: 02/26/2014] [Indexed: 01/30/2023]
Abstract
Potassium channels belong to the largest and the most diverse super-families of ion channels. Among them, Ca(2+)-activated K(+) channels (KCa) comprise many members. Based on their single channel conductance they are divided into three subfamilies: big conductance (BKCa), intermediate conductance (IKCa) and small conductance (SKCa; SK1, SK2 and SK3). Ca(2+) channels are divided into two main families, voltage gated/voltage dependent Ca(2+) channels and non-voltage gated/voltage independent Ca(2+) channels. Based on their electrophysiological and pharmacological properties and on the tissue where there are expressed, voltage gated Ca(2+) channels (Cav) are divided into 5 families: T-type, L-type, N-type, P/Q-type and R-type Ca(2+). Non-voltage gated Ca(2+) channels comprise the TRP (TRPC, TRPV, TRPM, TRPA, TRPP, TRPML and TRPN) and Orai (Orai1 to Orai3) families and their partners STIM (STIM1 to STIM2). A depolarization is needed to activate voltage-gated Ca(2+) channels while non-voltage gated Ca(2+) channels are activated by Ca(2+) depletion of the endoplasmic reticulum stores (SOCs) or by receptors (ROCs). These two Ca(2+) channel families also control constitutive Ca(2+) entries. For reducing the energy consumption and for the fine regulation of Ca(2+), KCa and Ca(2+) channels appear associated as complexes in excitable and non-excitable cells. Interestingly, there is now evidence that KCa-Ca(2+) channel complexes are also found in cancer cells and contribute to cancer-associated functions such as cell proliferation, cell migration and the capacity to develop metastases. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Takahashi K, Naruse K. Stretch-activated BK channel and heart function. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2013; 110:239-44. [PMID: 23281538 DOI: 10.1016/j.pbiomolbio.2012.08.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The heart is an organ that is exposed to extreme dynamic mechanical stimuli. From birth till death, the heart indefinitely repeats periodic contraction and dilation, i.e., shortening and elongation of cardiomyocytes. Mechanical stretch elicits a change in heart rate and may cause arrhythmia if it is excessive. Thus, mechanosensitivity is crucial to heart function. The molecule that is substantially involved in mechanosensitivity is a stretch-activated ion channel. Among several ion channels believed to be activated by stretch in the heart, the stretch-activated KCa (SAKCA) channel, a member of the group of large conductance (Big Potassium, BK) channels, shows a mechanosensitive (MS) response to membrane stretch. As BK channels respond to voltage and intracellular calcium concentration with large conductance, they are considered to be involved in repolarization after depolarization. Some BK channels are known to be activated by stretch and are expressed in a number of cells, including human osteoblasts and guinea pig intestinal neurons. The SAKCA channel was found to be sensitive to stretch in the chick heart. Given that the cardiomyocyte is unremittingly exposed to contraction and dilation and that it generates action potential and its contractility is modulated by intracellular calcium concentration, the SAKCA channel, which is dependent voltage and calcium, may be involved in action potential generation. It was recently reported that a BK channel is involved in the modulation of heart rate in the mouse. Further studies regarding the role of MS BK channels, including SAKCA, in the modulation of heart rate and contractility are expected.
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Affiliation(s)
- Ken Takahashi
- Department of Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
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25
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Mannowetz N, Naidoo NM, Choo SAS, Smith JF, Lishko PV. Slo1 is the principal potassium channel of human spermatozoa. eLife 2013; 2:e01009. [PMID: 24137539 PMCID: PMC3789364 DOI: 10.7554/elife.01009] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/02/2013] [Indexed: 12/21/2022] Open
Abstract
Mammalian spermatozoa gain competence to fertilize an oocyte as they travel through the female reproductive tract. This process is accompanied by an elevation of sperm intracellular calcium and a membrane hyperpolarization. The latter is evoked by K(+) efflux; however, the molecular identity of the potassium channel of human spermatozoa (hKSper) is unknown. Here, we characterize hKSper, reporting that it is regulated by intracellular calcium but is insensitive to intracellular alkalinization. We also show that human KSper is inhibited by charybdotoxin, iberiotoxin, and paxilline, while mouse KSper is insensitive to these compounds. Such unique properties suggest that the Slo1 ion channel is the molecular determinant for hKSper. We show that Slo1 is localized to the sperm flagellum and is inhibited by progesterone. Inhibition of hKSper by progesterone may depolarize the spermatozoon to open the calcium channel CatSper, thus raising [Ca(2+)] to produce hyperactivation and allowing sperm to fertilize an oocyte. DOI:http://dx.doi.org/10.7554/eLife.01009.001.
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Affiliation(s)
- Nadja Mannowetz
- Department of Molecular and Cell Biology , University of California, Berkeley , Berkeley , United States
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26
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Shi P, Li D, Lai C, Zhang L, Tian C. Intracellular segment between transmembrane helices S0 and S1 of BK channel α subunit contains two amphipathic helices connected by a flexible loop. Biochem Biophys Res Commun 2013; 437:408-12. [PMID: 23831469 DOI: 10.1016/j.bbrc.2013.06.091] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 06/24/2013] [Indexed: 01/31/2023]
Abstract
The BK channel, a tetrameric potassium channel with very high conductance, has a central role in numerous physiological functions. The BK channel can be activated by intracellular Ca(2+) and Mg(2+), as well as by membrane depolarization. Unlike other tetrameric potassium channels, the BK channel has seven transmembrane helices (S0-S6) including an extra helix S0. The intracellular segment between S0 and S1 (BK-IS1) is essential to BK channel functions and Asp99 in BK-IS1 is reported to be responsible for Mg(2+) coordination. In this study, BK-IS1 (44-113) was over-expressed using a bacterial system and purified in the presence of detergent micelles for multidimensional heteronuclear nuclear magnetic resonance (NMR) structural studies. Backbone resonance assignment and secondary structure analysis showed that BK-IS1 contains two amphipathic helices connected by a 36-residue loop. Amide (1)H-(15)N heteronuclear NOE analysis indicated that the loop is very flexible, while the two amphipathic helices are possibly stabilized through interaction with the membrane. A solution NMR-based titration assay of BK-IS1 was performed with various concentrations of Mg(2+). Two residues (Thr45 and Leu46) with chemical shift changes were observed but no, or very minor, chemical shift difference was observed for Asp99, indicating a possible site for binding divalent ions or other modulation partners.
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Affiliation(s)
- Pan Shi
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230027, PR China
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Wu RS, Liu G, Zakharov SI, Chudasama N, Motoike H, Karlin A, Marx SO. Positions of β2 and β3 subunits in the large-conductance calcium- and voltage-activated BK potassium channel. ACTA ACUST UNITED AC 2013; 141:105-17. [PMID: 23277477 PMCID: PMC3536527 DOI: 10.1085/jgp.201210891] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Large-conductance voltage- and Ca2+-gated K+ channels are negative-feedback regulators of excitability in many cell types. They are complexes of α subunits and of one of four types of modulatory β subunits. These have intracellular N- and C-terminal tails and two transmembrane (TM) helices, TM1 and TM2, connected by an ∼100-residue extracellular loop. Based on endogenous disulfide formation between engineered cysteines (Cys), we found that in β2 and β3, as in β1 and β4, TM1 is closest to αS1 and αS2 and TM2 is closest to αS0. Mouse β3 (mβ3) has seven Cys in its loop, one of which is free, and this Cys readily forms disulfides with Cys substituted in the extracellular flanks of each of αS0–αS6. We identified by elimination mβ3-loop Cys152 as the only free Cys. We inferred the disulfide-bonding pattern of the other six Cys. Using directed proteolysis and fragment sizing, we determined this pattern first among the four loop Cys in β1. These are conserved in β2–β4, which have four additional Cys (eight in total), except that mβ3 has one fewer. In β1, disulfides form between Cys at aligned positions 1 and 8 and between Cys at aligned positions 5 and 6. In mβ3, the free Cys is at position 7; position 2 lacks a Cys present in all other β2–β4; and the disulfide pattern is 1–8, 3–4, and 5–6. Presumably, Cys 2 cross-links to Cys 7 in all other β2–β4. Cross-linking of mβ3 Cys152 to Cys substituted in the flanks of αS0–S5 attenuated the protection against iberiotoxin (IbTX); cross-linking of Cys152 to K296C in the αS6 flank and close to the pore enhanced protection against IbTX. In no case was N-type inactivation by the N-terminal tail of mβ3 perturbed. Although the mβ3 loop can move, its position with Cys152 near αK296, in which it blocks IbTX binding, is likely favored.
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Affiliation(s)
- Roland S Wu
- Division of Cardiology, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Choi SH, Lee BH, Kim HJ, Hwang SH, Lee SM, Nah SY. Activation of lysophosphatidic Acid receptor is coupled to enhancement of ca(2+)-activated potassium channel currents. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2013; 17:223-8. [PMID: 23776399 PMCID: PMC3682083 DOI: 10.4196/kjpp.2013.17.3.223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 05/07/2013] [Accepted: 05/22/2013] [Indexed: 11/15/2022]
Abstract
The calcium-activated K(+) (BKCa) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. Ca(2+) is the main regulator of BKCa channel activation. The BKCa channel contains two high affinity Ca(2+) binding sites, namely, regulators of K(+) conductance, RCK1 and the Ca(2+) bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein-coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular Ca(2+) levels through diverse G proteins such as Gαq/11, Gαi, Gα12/13, and Gαs and the related signal transduction pathway. In the present study, we examined LPA effects on BKCa channel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated BKCa channel activation was also attenuated by the PLC inhibitor U-73122, IP3 inhibitor 2-APB, Ca(2+) chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated BKCa channel activation. The present study indicates that LPA-mediated activation of the BKCa channel is achieved through the PLC, IP3, Ca(2+), and PKC pathway and that LPA-mediated activation of the BKCa channel could be one of the biological effects of LPA in the nervous and vascular systems.
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Affiliation(s)
- Sun-Hye Choi
- Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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Molecular mechanisms of large-conductance ca (2+) -activated potassium channel activation by ginseng gintonin. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:323709. [PMID: 23662129 PMCID: PMC3638619 DOI: 10.1155/2013/323709] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/05/2013] [Accepted: 03/12/2013] [Indexed: 01/12/2023]
Abstract
Gintonin is a unique lysophosphatidic acid (LPA) receptor ligand
found in Panax ginseng. Gintonin induces transient
[Ca2+]i
through G protein-coupled LPA receptors. Large-conductance Ca2+-activated
K+ (BKCa)
channels are expressed in blood vessels and neurons and
play important roles in blood vessel relaxation and attenuation of
neuronal excitability. BKCa channels are activated by transient
[Ca2+]i
and are regulated by various Ca2+-dependent kinases. We
investigated the molecular mechanisms of BKCa channel activation
by gintonin. BKCa channels are heterologously expressed in
Xenopus oocytes. Gintonin treatment induced BKCa channel activation in
oocytes expressing the BKCa channel α subunit in a
concentration-dependent manner (EC50 = 0.71 ± 0.08 µg/mL).
Gintonin-mediated BKCa channel activation was blocked by a PKC
inhibitor, calphostin, and by the calmodulin inhibitor,
calmidazolium. Site-directed mutations in BKCa channels targeting
CaM kinase II or PKC phosphorylation sites but not PKA
phosphorylation sites attenuated gintonin action. Mutations in the
Ca2+ bowl and the regulator of K+ conductance (RCK) site also
blocked gintonin action. These results indicate that
gintonin-mediated BKCa channel activations are achieved through
LPA1 receptor-phospholipase C-IP3-Ca2+-PKC-calmodulin-CaM kinase
II pathways and calcium binding to the Ca2+ bowl and RCK domain.
Gintonin could be a novel contributor against blood vessel
constriction and over-excitation of neurons.
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Scornik FS, Bucciero RS, Wu Y, Selga E, Bosch Calero C, Brugada R, Pérez GJ. DiBAC₄(3) hits a "sweet spot" for the activation of arterial large-conductance Ca²⁺-activated potassium channels independently of the β₁-subunit. Am J Physiol Heart Circ Physiol 2013; 304:H1471-82. [PMID: 23542916 DOI: 10.1152/ajpheart.00939.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The voltage-sensitive dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC₄(3)] has been reported as a novel large-conductance Ca²⁺-activated K⁺ (BK) channel activator with selectivity for its β₁- or β₄-subunits. In arterial smooth muscle, BK channels are formed by a pore-forming α-subunit and a smooth muscle-abundant regulatory β₁-subunit. This tissue specificity has driven extensive pharmacological research aimed at regulating arterial tone. Using animals with a disruption of the gene for the β₁-subunit, we explored the effects of DiBAC₄(3) in native channels from arterial smooth muscle. We tested the hypothesis that, in native BK channels, activation by DiBAC₄(3) relies mostly on its α-subunit. We studied BK channels from wild-type and transgenic β₁-knockout mice in excised patches. BK channels from brain arteries, with or without the β₁-subunit, were similarly activated by DiBAC₄(3). In addition, we found that saturating concentrations of DiBAC₄(3) (~30 μM) promote an unprecedented persistent activation of the channel that negatively shifts its voltage dependence by as much as -300 mV. This "sweet spot" for persistent activation is independent of Ca²⁺ and/or the β₁₋₄-subunits and is fully achieved when DiBAC₄(3) is applied to the intracellular side of the channel. Arterial BK channel response to DiBAC₄(3) varies across species and/or vascular beds. DiBAC₄(3) unique effects can reveal details of BK channel gating mechanisms and help in the rational design of BK channel activators.
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Affiliation(s)
- Fabiana S Scornik
- Cardiovascular Genetics Center, Institut de Investigació Biomèdica de Girona, and Department of Medical Sciences, School of Medicine, University of Girona, Girona, Spain
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Bury M, Girault A, Mégalizzi V, Spiegl-Kreinecker S, Mathieu V, Berger W, Evidente A, Kornienko A, Gailly P, Vandier C, Kiss R. Ophiobolin A induces paraptosis-like cell death in human glioblastoma cells by decreasing BKCa channel activity. Cell Death Dis 2013; 4:e561. [PMID: 23538442 PMCID: PMC3615734 DOI: 10.1038/cddis.2013.85] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 02/19/2013] [Accepted: 02/25/2013] [Indexed: 01/31/2023]
Abstract
Glioblastoma multiforme (GBM) is the most lethal and common malignant human brain tumor. The intrinsic resistance of highly invasive GBM cells to radiation- and chemotherapy-induced apoptosis accounts for the generally dismal treatment outcomes. This study investigated ophiobolin A (OP-A), a fungal metabolite from Bipolaris species, for its promising anticancer activity against human GBM cells exhibiting varying degrees of resistance to proapoptotic stimuli. We found that OP-A induced marked changes in the dynamic organization of the F-actin cytoskeleton, and inhibited the proliferation and migration of GBM cells, likely by inhibiting big conductance Ca(2+)-activated K(+) channel (BKCa) channel activity. Moreover, our results indicated that OP-A induced paraptosis-like cell death in GBM cells, which correlated with the vacuolization, possibly brought about by the swelling and fusion of mitochondria and/or the endoplasmic reticulum (ER). In addition, the OP-A-induced cell death did not involve the activation of caspases. We also showed that the expression of BKCa channels colocalized with these two organelles (mitochondria and ER) was affected in this programmed cell death pathway. Thus, this study reveals a novel mechanism of action associated with the anticancer effects of OP-A, which involves the induction of paraptosis through the disruption of internal potassium ion homeostasis. Our findings offer a promising therapeutic strategy to overcome the intrinsic resistance of GBM cells to proapoptotic stimuli.
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Affiliation(s)
- M Bury
- Laboratoire de Toxicologie, Faculté de Pharmacie, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - A Girault
- INSERM U1069, Laboratoire Nutrition Croissance Cancer, Université de Tours, Tours, France
| | - V Mégalizzi
- Laboratoire de Toxicologie, Faculté de Pharmacie, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - S Spiegl-Kreinecker
- Department of Neurosurgery, Landesnervenklinik Wagner-Jauregg Hospital, Linz, Austria
| | - V Mathieu
- Laboratoire de Toxicologie, Faculté de Pharmacie, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - W Berger
- Department of Medicine I, Comprehensive Cancer Center and Institute of Cancer Research, Medical University Vienna, Vienna, Austria
| | - A Evidente
- Dipartimento di Scienze Chimiche, Complesso Universitario Monte Sant'Angelo, Napoli, Italy
| | - A Kornienko
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, USA
| | - P Gailly
- Laboratoire de Physiologie Cellulaire, Institut des Neurosciences, Université Catholique de Louvain, Brussels, Belgium
| | - C Vandier
- INSERM U1069, Laboratoire Nutrition Croissance Cancer, Université de Tours, Tours, France
| | - R Kiss
- Laboratoire de Toxicologie, Faculté de Pharmacie, Université Libre de Bruxelles (ULB), Brussels, Belgium
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Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol. Pharmacol Ther 2012; 135:133-50. [PMID: 22584144 DOI: 10.1016/j.pharmthera.2012.05.002] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/09/2012] [Indexed: 11/21/2022]
Abstract
Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease.
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Ma Z, Liu T. Myricetin facilitates potassium currents and inhibits neuronal activity of PVN neurons. Neurochem Res 2012; 37:1450-6. [PMID: 22382814 DOI: 10.1007/s11064-012-0732-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 02/01/2012] [Accepted: 02/15/2012] [Indexed: 10/28/2022]
Abstract
The effects of myricetin on hypothalamic paraventricular nucleus (PVN) neurons in rats were investigated. By whole-cell patch clamp detection in hypothalamic brain slices, we showed that the action potential frequency in type-I PVN neurons dose-dependently decreased after myricetin treatment. Further studies demonstrated that myricetin may enhance potassium currents and shifts the voltage-dependence of activation of potassium currents to more negative potentials by 6.07 mV. Using calcium free/cadmium perfusion solution could reverse myricetin-induced enhancement of potassium currents in PVN neurons. These results suggested that inhibition of hypothalamic PVN neurons by myricetin might be attributed to the enhancement of potassium currents.
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Affiliation(s)
- ZeGang Ma
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, Medical College of Qingdao University, Qingdao, 266071, China.
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Gruslova A, Semenov I, Wang B. An extracellular domain of the accessory β1 subunit is required for modulating BK channel voltage sensor and gate. ACTA ACUST UNITED AC 2011; 139:57-67. [PMID: 22155735 PMCID: PMC3250105 DOI: 10.1085/jgp.201110698] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A family of tissue-specific auxiliary β subunits modulates large conductance voltage- and calcium-activated potassium (BK) channel gating properties to suit their diverse functions. Paradoxically, β subunits both promote BK channel activation through a stabilization of voltage sensor activation and reduce BK channel openings through an increased energetic barrier of the closed-to-open transition. The molecular determinants underlying β subunit function, including the dual gating effects, remain unknown. In this study, we report the first identification of a β1 functional domain consisting of Y74, S104, Y105, and I106 residues located in the extracellular loop of β1. These amino acids reside within two regions of highest conservation among related β1, β2, and β4 subunits. Analysis in the context of the Horrigan-Aldrich gating model revealed that this domain functions to both promote voltage sensor activation and also reduce intrinsic gating. Free energy calculations suggest that the dual effects of the β1 Y74 and S104–I106 domains can be largely accounted for by a relative destabilization of channels in open states that have few voltage sensors activated. These results suggest a unique and novel mechanism for β subunit modulation of voltage-gated potassium channels wherein interactions between extracellular β subunit residues with the external portions of the gate and voltage sensor regulate channel opening.
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Affiliation(s)
- Aleksandra Gruslova
- Department of Physiology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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36
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Yuan P, Leonetti MD, Hsiung Y, MacKinnon R. Open structure of the Ca2+ gating ring in the high-conductance Ca2+-activated K+ channel. Nature 2011; 481:94-7. [PMID: 22139424 PMCID: PMC3319005 DOI: 10.1038/nature10670] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 10/24/2011] [Indexed: 12/30/2022]
Abstract
High-conductance voltage- and Ca(2+)-activated K(+) channels function in many physiological processes that link cell membrane voltage and intracellular Ca(2+) concentration, including neuronal electrical activity, skeletal and smooth muscle contraction, and hair cell tuning. Like other voltage-dependent K(+) channels, Ca(2+)-activated K(+) channels open when the cell membrane depolarizes, but in contrast to other voltage-dependent K(+) channels, they also open when intracellular Ca(2+) concentrations rise. Channel opening by Ca(2+) is made possible by a structure called the gating ring, which is located in the cytoplasm. Recent structural studies have defined the Ca(2+)-free, closed, conformation of the gating ring, but the Ca(2+)-bound, open, conformation is not yet known. Here we present the Ca(2+)-bound conformation of the gating ring. This structure shows how one layer of the gating ring, in response to the binding of Ca(2+), opens like the petals of a flower. The degree to which it opens explains how Ca(2+) binding can open the transmembrane pore. These findings present a molecular basis for Ca(2+) activation of K(+) channels and suggest new possibilities for targeting the gating ring to treat conditions such as asthma and hypertension.
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Affiliation(s)
- Peng Yuan
- Laboratory of Molecular Neurobiology and Biophysics, Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, New York 10065, USA
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37
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Wolstenholme AJ. Ion channels and receptor as targets for the control of parasitic nematodes. Int J Parasitol Drugs Drug Resist 2011; 1:2-13. [PMID: 24533259 PMCID: PMC3898135 DOI: 10.1016/j.ijpddr.2011.09.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 09/14/2011] [Accepted: 09/21/2011] [Indexed: 01/19/2023]
Abstract
Many of the anthelmintic drugs in use today act on the nematode nervous system. Ion channel targets have some obvious advantages. They tend to act quickly, which means that they will clear many infections rapidly. They produce very obvious effects on the worms, typically paralyzing them, and these effects are suitable for use in rapid and high-throughput assays. Many of the ion channels and enzymes targeted can also be incorporated into such assays. The macrocyclic lactones bind to an allosteric site on glutamate-gated chloride channels, either directly activating the channel or enhancing the effect of the normal agonist, glutamate. Many old and new anthelmintics, including tribendimidine and the amino-acetonitrile derivatives, act as agonists at nicotinic acetylcholine receptors; derquantel is an antagonist at these receptors. Nematodes express many different types of nicotinic receptor and this diversity means that they are likely to remain important targets for the foreseeable future. Emodepside may have multiple effects, affecting both a potassium channel and a pre-synaptic G protein-coupled receptor; although few other current drugs act at such targets, this example indicates that they may be more important in the future. The nematode nervous system contains many other ion channels and receptors that have not so far been exploited in worm control but which should be explored in the development of effective new compounds.
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Affiliation(s)
- Adrian J. Wolstenholme
- Dept. of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
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On benzofuroindole analogues as smooth muscle relaxants. J Biomed Biotechnol 2011; 2011:389056. [PMID: 21941431 PMCID: PMC3177241 DOI: 10.1155/2011/389056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 07/14/2011] [Indexed: 11/18/2022] Open
Abstract
At least two laboratories have independently reported the synthesis of benzofuroindole compounds having potential therapeutic implications in many disease states including those that involve smooth muscle hyperactivity. Through a series of in vitro screenings, they demonstrated the efficacy (and selectivity) of these compounds to potentiate large conductance calcium- (Ca2+-) activated K+ (BKCa) channels, by far, the most characterized of all Ca2+-dependent K+ channels. Interestingly, promising benzofuroindole derivatives such as compound 7 (10H-benzo[4,5]furo[3,2-b]indole) and compound 22 (4-chloro-7-trifluoromethyl-10H-benzo[4,5]furo[3,2-b]indole-1-carboxylic acid) both exhibited high bladder (versus aorta) selectivity, making them attractive alternative treatments for bladder overactivity. In recent reports, compound 22 (LDD175 or TBIC) also showed inhibition of ileum and uterine contractions, indicating multiple target tissues, which is not surprising as BKCa channels are ubiquitously expressed in the animal and human tissues. In this paper, the authors discuss the value of benzofuroindole compounds and the challenges that need to be overcome if they were considered as smooth muscle relaxants.
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Medina P, Segarra G, Mauricio MD, Vila JM, Chuan P, Lluch S. Role of Ca2+-activated K+ channels and Na+,K+-ATPase in prostaglandin E1- and E2-induced inhibition of the adrenergic response in human vas deferens. Biochem Pharmacol 2011; 82:65-71. [DOI: 10.1016/j.bcp.2011.03.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 03/21/2011] [Accepted: 03/22/2011] [Indexed: 10/18/2022]
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40
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Zhuang J, Zhang X, Wang D, Li J, Zhou B, Shi Z, Gu D, Denson DD, Eaton DC, Cai H. WNK4 kinase inhibits Maxi K channel activity by a kinase-dependent mechanism. Am J Physiol Renal Physiol 2011; 301:F410-9. [PMID: 21613417 DOI: 10.1152/ajprenal.00518.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
WNK [with no lysine (k)] kinase is a serine/threonine kinase subfamily. Mutations in two of the WNK kinases result in pseudohypoaldosteronism type II (PHA II) characterized by hypertension, hyperkalemia, and metabolic acidosis. Recent studies showed that both WNK1 and WNK4 inhibit ROMK activity. However, little is known about the effect of WNK kinases on Maxi K, a large-conductance Ca(2+) and voltage-activated potassium (K) channel. Here, we report that WNK4 wild-type (WT) significantly inhibits Maxi K channel activity in HEK αBK stable cell lines compared with the control group. However, a WNK4 dead-kinase mutant, D321A, has no inhibitory effect on Maxi K activity. We further found that WNK4 inhibits total and cell surface protein expression of Maxi K equally compared with control groups. A dominant-negative dynamin mutant, K44A, did not alter the WNK4-mediated inhibitory effect on Maxi K surface expression. Treatment with bafilomycin A1 (a proton pump inhibitor) and leupeptin (a lysosomal inhibitor) reversed WNK4 WT-mediated inhibition of Maxi K total protein expression. These findings suggest that WNK4 WT inhibits Maxi K activity by reducing Maxi K protein at the membrane, but that the inhibition is not due to an increase in clathrin-mediated endocytosis of Maxi K, but likely due to enhancing its lysosomal degradation. Also, WNK4's inhibitory effect on Maxi K activity is dependent on its kinase activity.
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Affiliation(s)
- Jieqiu Zhuang
- Department of Nephrology, The Second Affiliated Hospital, Wenzhou Medical College, Zhejiang, China
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41
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Palmer ML, Peitzman ER, Maniak PJ, Sieck GC, Prakash YS, O'Grady SM. K(Ca)3.1 channels facilitate K+ secretion or Na+ absorption depending on apical or basolateral P2Y receptor stimulation. J Physiol 2011; 589:3483-94. [PMID: 21606112 DOI: 10.1113/jphysiol.2011.207548] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Human mammary epithelial (HME) cells express several P2Y receptor subtypes located in both apical and basolateral membranes. Apical UTP or ATP-γ-S stimulation of monolayers mounted in Ussing chambers evoked a rapid, but transient decrease in short circuit current (I(sc)), consistent with activation of an apical K+ conductance. In contrast, basolateral P2Y receptor stimulation activated basolateral K+ channels and increased transepithelial Na+ absorption. Chelating intracellular Ca2+ using the membrane-permeable compound BAPTA-AM, abolished the effects of purinoceptor activation on I(sc). Apical pretreatment with charybdotoxin also blocked the I(sc) decrease by >90% and similar magnitudes of inhibition were observed with clotrimazole and TRAM-34. In contrast, iberiotoxin and apamin did not block the effects of apical P2Y receptor stimulation. Silencing the expression of K(Ca)3.1 produced ∼70% inhibition of mRNA expression and a similar reduction in the effects of apical purinoceptor agonists on I(sc). In addition, silencing P2Y2 receptors reduced the level of P2Y2 mRNA by 75% and blocked the effects of ATP-γ-S by 65%. These results suggest that P2Y2 receptors mediate the effects of purinoceptor agonists on K+ secretion by regulating the activity of K(Ca)3.1 channels expressed in the apical membrane of HME cells. The results also indicate that release of ATP or UTP across the apical or basolateral membrane elicits qualitatively different effects on ion transport that may ultimately determine the [Na+]/[K+] composition of fluid within the mammary ductal network.
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Affiliation(s)
- Melissa L Palmer
- Biology Program, College of Biological Sciences, University of Minnesota, Minneapolis, MN 55455, USA
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42
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Semenov I, Wang B, Herlihy JT, Brenner R. BK channel β1 subunits regulate airway contraction secondary to M2 muscarinic acetylcholine receptor mediated depolarization. J Physiol 2011; 589:1803-17. [PMID: 21300746 DOI: 10.1113/jphysiol.2010.204347] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The large conductance calcium- and voltage-activated potassium channel (BK channel) and its smooth muscle-specific β1 subunit regulate excitation–contraction coupling in many types of smooth muscle cells. However, the relative contribution of BK channels to control of M2- or M3-muscarinic acetylcholine receptor mediated airway smooth muscle contraction is poorly understood. Previously, we showed that knockout of the BK channel β1 subunit enhances cholinergic-evoked trachea contractions. Here, we demonstrate that the enhanced contraction of the BK β1 knockout can be ascribed to a defect in BK channel opposition of M2 receptor-mediated contractions. Indeed, the enhanced contraction of β1 knockout is eliminated by specific M2 receptor antagonism. The role of BK β1 to oppose M2 signalling is evidenced by a greater than fourfold increase in the contribution of L-type voltage-dependent calcium channels to contraction that otherwise does not occur with M2 antagonist or with β1 containing BK channels. The mechanism through which BK channels oppose M2-mediated recruitment of calcium channels is through a negative shift in resting voltage that offsets, rather than directly opposes, M2-mediated depolarization. The negative shift in resting voltage is reduced to similar extents by BK β1 knockout or by paxilline block of BK channels. Normalization of β1 knockout baseline voltage with low external potassium eliminated the enhanced M2-receptor mediated contraction. In summary, these findings indicate that an important function of BK/β1 channels is to oppose cholinergic M2 receptor-mediated depolarization and activation of calcium channels by restricting excitation–contraction coupling to more negative voltage ranges.
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Affiliation(s)
- Iurii Semenov
- Department of Physiology, UT Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA
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Choi SH, Shin TJ, Lee BH, Hwang SH, Lee SM, Lee BC, Park CS, Ha TS, Nah SY. Ginsenoside Rg3 enhances large conductance Ca2+-activated potassium channel currents: a role of Tyr360 residue. Mol Cells 2011; 31:133-40. [PMID: 21191818 PMCID: PMC3932677 DOI: 10.1007/s10059-011-0017-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 10/25/2010] [Accepted: 11/13/2010] [Indexed: 10/18/2022] Open
Abstract
Ginsenosides, active ingredients of Panax ginseng, are known to exhibit neuroprotective effects. Large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels are key modulators of cellular excitability of neurons and vascular smooth muscle cells. In the present study, we examined the effects of ginsenosides on rat brain BK(Ca) (rSlo) channel activity heterologously expressed in Xenopus oocytes to elucidate the molecular mechanisms how ginsenoside regulates the BK(Ca) channel activity. Ginsenoside Rg(3) (Rg(3)) enhanced outward BK(Ca) channel currents. The Rg(3)-enhancement of outward BK(Ca) channel currents was concentration-dependent, voltage-dependent, and reversible. The EC(50) was 15.1 ± 3.1 μM. Rg(3) actions were not desensitized by repeated treatment. Tetraetylammonium (TEA), a K(+) channel blocker, inhibited BK(Ca) channel currents. We examined whether extracellular TEA treatment could alter the Rg(3) action and vice versa. TEA caused a rightward shift of the Rg(3) concentration-response curve (i.e., much higher concentration of Rg(3) is required for the activation of BK(Ca) channel compared to the absence of TEA), while Rg(3) caused a rightward shift of the TEA concentration-response curve in wild-type channels. Mutation of the extracellular TEA binding site Y360 to Y360I caused a rightward shift of the TEA concentration-response curve and almost abolished both the Rg(3) action and Rg(3)-induced rightward shift of TEA concentration-response curve. These results indicate that Tyr360 residue of BK(Ca) channel plays an important role in the Rg(3)-enhancement of BK(Ca) channel currents.
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Affiliation(s)
- Sun-Hye Choi
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Tae-Joon Shin
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Byung-Hwan Lee
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Sung Hee Hwang
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Sang-Mok Lee
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
| | - Byung-Cheol Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Cheol-Seung Park
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
| | - Tal Soo Ha
- Department of Molecular Biology, College of Natural Science, Daegu University, Gyeongsan 712-714, Korea
| | - Seung-Yeol Nah
- Ginsentology Research Laboratory and Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
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Cui YM, Yasutomi E, Otani Y, Ido K, Yoshinaga T, Sawada K, Ohwada T. Design, synthesis, and characterization of BK channel openers based on oximation of abietane diterpene derivatives. Bioorg Med Chem 2010; 18:8642-59. [DOI: 10.1016/j.bmc.2010.09.072] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 09/30/2010] [Indexed: 01/19/2023]
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45
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Ermolinsky BS, Skinner F, Garcia I, Arshadmansab MF, Otalora LFP, Zarei MM, Garrido-Sanabria ER. Upregulation of STREX splice variant of the large conductance Ca2+-activated potassium (BK) channel in a rat model of mesial temporal lobe epilepsy. Neurosci Res 2010; 69:73-80. [PMID: 20933547 DOI: 10.1016/j.neures.2010.09.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 09/29/2010] [Accepted: 09/30/2010] [Indexed: 02/04/2023]
Abstract
Functional properties of large conductance Ca(2+) activated potassium (BK) channels are determined by complex alternative splicing of the Kcnma1 gene encoding the alpha pore-forming subunit. Inclusion of the STREX exon in a C-terminal splice site is dynamically regulated and confers enhanced Ca(2+) sensitivity and channel inhibition via cAMP-dependent phosphorylation. Here, we describe a real time quantitative PCR (qPCR) approach to investigate relative changes in the expression of STREX and ZERO splice variants using a newly designed set of probes and primers for TaqMan-based qPCR analysis of cDNA from the rat dentate gyrus at different time points following pilocarpine-induced status epilepticus. Reduction in Kcnma1 gene expression is associated with a relative increase of STREX splice variant. Relative expression of STREX variant mRNA was increased at 10 days and at more than 1 month following status epilepticus. The biological consequences of seizure-related changes in alternative splicing of Kcnma1 deserve additional investigation.
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Affiliation(s)
- Boris S Ermolinsky
- Department of Biological Sciences, University of Texas at Brownsville/Texas Southmost College, Brownsville, TX 78520, USA
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46
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Zuidema MY, Yang Y, Wang M, Kalogeris T, Liu Y, Meininger CJ, Hill MA, Davis MJ, Korthuis RJ. Antecedent hydrogen sulfide elicits an anti-inflammatory phenotype in postischemic murine small intestine: role of BK channels. Am J Physiol Heart Circ Physiol 2010; 299:H1554-67. [PMID: 20833953 DOI: 10.1152/ajpheart.01229.2009] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The objectives of this study were to determine the role of calcium-activated, small (SK), intermediate (IK), and large (BK) conductance potassium channels in initiating the development of an anti-inflammatory phenotype elicited by preconditioning with an exogenous hydrogen sulfide (H(2)S) donor, sodium hydrosulfide (NaHS). Intravital microscopy was used to visualize rolling and firmly adherent leukocytes in vessels of the small intestine of mice preconditioned with NaHS (in the absence and presence of SK, IK, and BK channel inhibitors, apamin, TRAM-34, and paxilline, respectively) or SK/IK (NS-309) or BK channel activators (NS-1619) 24 h before ischemia-reperfusion (I/R). I/R induced marked increases in leukocyte rolling and adhesion, effects that were largely abolished by preconditioning with NaHS, NS-309, or NS-1619. The postischemic anti-inflammatory effects of NaHS-induced preconditioning were mitigated by BKB channel inhibitor treatment coincident with NaHS, but not by apamin or TRAM-34, 24 h before I/R. Confocal imaging and immunohistochemistry were used to demonstrate the presence of BKα subunit staining in both endothelial and vascular smooth muscle cells of isolated, pressurized mesenteric venules. Using patch-clamp techniques, we found that BK channels in cultured endothelial cells were activated after exposure to NaHS. Bath application of the same concentration of NaHS used in preconditioning protocols led to a rapid increase in a whole cell K(+) current; specifically, the component of K(+) current blocked by the selective BK channel antagonist iberiotoxin. The activation of BK current by NaHS could also be demonstrated in single channel recording mode where it was independent of a change in intracellular Ca(+) concentration. Our data are consistent with the concept that H(2)S induces the development of an anti-adhesive state in I/R in part mediated by a BK channel-dependent mechanism.
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Affiliation(s)
- Mozow Y Zuidema
- Department of Medical Pharmacology and Physiology, Dalton Cardiovascular Research Center, University of Missouri School of Medicine, Columbia, Missouri 65212, USA
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47
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Martire M, Barrese V, D'Amico M, Iannotti FA, Pizzarelli R, Samengo I, Viggiano D, Ruth P, Cherubini E, Taglialatela M. Pre-synaptic BK channels selectively control glutamate versus GABA release from cortical and hippocampal nerve terminals. J Neurochem 2010; 115:411-22. [PMID: 20681950 DOI: 10.1111/j.1471-4159.2010.06938.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present study, by means of genetic, biochemical, morphological, and electrophysiological approaches, the role of large-conductance voltage- and Ca(2+)-dependent K(+) channels (BK channels) in the release of excitatory and non-excitatory neurotransmitters at hippocampal and non-hippocampal sites has been investigated. The results obtained show that the pharmacological modulation of pre-synaptic BK channels selectively regulates [(3)H]D-aspartate release from cortical and hippocampal rat synaptosomes, but it fails to influence the release of excitatory neurotransmitters from cerebellar nerve endings or that of [(3)H]GABA, [(3)H]Noradrenaline, or [(3)H]Dopamine from any of the brain regions investigated. Confocal immunofluorescence experiments in hippocampal or cerebrocortical nerve terminals revealed that the main pore-forming BK α subunit was more abundantly expressed in glutamatergic (vGLUT1(+)) versus GABAergic (GAD(65-67)(+)) nerve terminals. Double patch recordings in monosynaptically connected hippocampal neurons in culture confirmed a preferential control exerted by BK channels on glutamate over GABA release. Altogether, the present results highlight a high degree of specificity in the regulation of the release of various neurotransmitters from distinct brain regions by BK channels, supporting the concept that BK channel modulators can be used to selectively limit excessive excitatory amino acid release, a major pathogenetic mechanism in several neuropsychiatric disorders.
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Affiliation(s)
- Maria Martire
- Institute of Pharmacology, Catholic University of Sacred Heart, Rome, Italy
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48
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Ohbuchi T, Yokoyama T, Saito T, Suzuki H, Fujihara H, Katoh A, Otsubo H, Ishikura T, Suzuki H, Ueta Y. Modulators of BK and SK channels alter electrical activity in vitro in single vasopressin neurons isolated from the rat supraoptic nucleus. Neurosci Lett 2010; 484:26-9. [PMID: 20708068 DOI: 10.1016/j.neulet.2010.08.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 08/03/2010] [Accepted: 08/04/2010] [Indexed: 12/23/2022]
Abstract
Release of arginine vasopressin (AVP) from magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) is controlled by the electrical activities of the MNCs. Ca(2+)-activated K(+) channels, such as the BK and SK channels, are K(+)-selective ion channels that are activated in response to increased intracellular calcium concentrations. Intrinsic affinities for Ca(2+) permit these channels to exert a negative feedback effect on cellular excitability. In the present study, we used the whole-cell patch-clamp technique to examine the effects of BK or SK channel modulators on neuronal activity in single isolated rat SON MNCs that express an AVP-enhanced green fluorescent protein (eGFP) transgene. Application of BK or SK channel activators abolished the action potentials and induced hyperpolarization. In contrast, the number of action potentials was significantly increased after application of BK or SK channel blockers. Our results suggest that BK and SK channels in AVP neurons may play a role in the regulatory mechanisms of neural activity.
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Affiliation(s)
- Toyoaki Ohbuchi
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
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49
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Houamed KM, Sweet IR, Satin LS. BK channels mediate a novel ionic mechanism that regulates glucose-dependent electrical activity and insulin secretion in mouse pancreatic β-cells. J Physiol 2010; 588:3511-23. [PMID: 20643769 DOI: 10.1113/jphysiol.2009.184341] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
BK channels are large unitary conductance K(+) channels cooperatively activated by intracellular calcium and membrane depolarisation. We show that BK channels regulate electrical activity in β-cells of mouse pancreatic islets exposed to elevated glucose. In 11.1 mM glucose, the non-peptidyl BK channel blocker paxilline increased the height of β-cell action potentials (APs) by 21 mV without affecting burst- or silent-period durations. In isolated β-cells, paxilline increased AP height by 16 mV without affecting resting membrane potential. In voltage clamp, paxilline blocked a transient component of outward current activated by a short depolarisation, which accounted for at least 90% of the initial outward K(+) current. This BK current (I(BK)) was blocked by the Ca(2+) channel blockers Cd(2+) (200 μM) or nimodipine (1 μM), and potentiated by FPL-64176 (1 μM). I(BK) was also 56% blocked by the BK channel blocker iberiotoxin (100 nM). I(BK) activated more than 10-fold faster than the delayed rectifier I(Kv) over the physiological voltage range, and partially inactivated. An AP-like command revealed that I(BK) activated and deactivated faster than I(Kv) and accounted for 86% of peak I(K), explaining why I(BK) block increased AP height. A higher amplitude AP-like command, patterned on an AP recorded in 11.1 mM glucose plus paxilline, activated 4-fold more I(Kv) and significantly increased Ca(2+) entry. Paxilline increased insulin secretion in islets exposed to 11.1 mM glucose by 67%, but did not affect basal secretion in 2.8 mM glucose. These data suggest a modified model of β-cell AP generation where I(BK) and I(Kv) coordinate the AP repolarisation.
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Affiliation(s)
- Khaled M Houamed
- Department of Pharmacology and Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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50
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Wu Y, Yang Y, Ye S, Jiang Y. Structure of the gating ring from the human large-conductance Ca(2+)-gated K(+) channel. Nature 2010; 466:393-7. [PMID: 20574420 PMCID: PMC2910425 DOI: 10.1038/nature09252] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 06/07/2010] [Indexed: 12/11/2022]
Abstract
Large-conductance Ca(2+)-gated K(+) (BK) channels are essential for many biological processes such as smooth muscle contraction and neurotransmitter release. This group of channels can be activated synergistically by both voltage and intracellular Ca(2+), with the large carboxy-terminal intracellular portion being responsible for Ca(2+) sensing. Here we present the crystal structure of the entire cytoplasmic region of the human BK channel in a Ca(2+)-free state. The structure reveals four intracellular subunits, each comprising two tandem RCK domains, assembled into a gating ring similar to that seen in the MthK channel and probably representing its physiological assembly. Three Ca(2+) binding sites including the Ca(2+) bowl are mapped onto the structure based on mutagenesis data. The Ca(2+) bowl, located within the second RCK domain, forms an EF-hand-like motif and is strategically positioned close to the assembly interface between two subunits. The other two Ca(2+) (or Mg(2+)) binding sites, Asp 367 and Glu 374/Glu 399, are located on the first RCK domain. The Asp 367 site has high Ca(2+) sensitivity and is positioned in the groove between the amino- and carboxy-terminal subdomains of RCK1, whereas the low-affinity Mg(2+)-binding Glu 374/Glu 399 site is positioned on the upper plateau of the gating ring and close to the membrane. Our structure also contains the linker connecting the transmembrane and intracellular domains, allowing us to dock a voltage-gated K(+) channel pore of known structure onto the gating ring with reasonable accuracy and generate a structural model for the full BK channel.
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Affiliation(s)
- Yunkun Wu
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040
| | - Yi Yang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040
| | - Sheng Ye
- Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, P.R. China
| | - Youxing Jiang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040
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