1
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Huang Y, Ma D, Yang Z, Zhao Y, Guo J. Voltage-gated potassium channels KCNQs: Structures, mechanisms, and modulations. Biochem Biophys Res Commun 2023; 689:149218. [PMID: 37976835 DOI: 10.1016/j.bbrc.2023.149218] [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: 08/09/2023] [Revised: 10/19/2023] [Accepted: 11/03/2023] [Indexed: 11/19/2023]
Abstract
KCNQ (Kv7) channels are voltage-gated, phosphatidylinositol 4,5-bisphosphate- (PIP2-) modulated potassium channels that play essential roles in regulating the activity of neurons and cardiac myocytes. Hundreds of mutations in KCNQ channels are closely related to various cardiac and neurological disorders, such as long QT syndrome, epilepsy, and deafness, which makes KCNQ channels important drug targets. During the past several years, the application of single-particle cryo-electron microscopy (cryo-EM) technique in the structure determination of KCNQ channels has greatly advanced our understanding of their molecular mechanisms. In this review, we summarize the currently available structures of KCNQ channels, analyze their special voltage gating mechanism, and discuss their activation mechanisms by both the endogenous membrane lipid and the exogenous synthetic ligands. These structural studies of KCNQ channels will guide the development of drugs targeting KCNQ channels.
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Affiliation(s)
- Yuan Huang
- Department of Cardiology, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Demin Ma
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Zhenni Yang
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Yiwen Zhao
- The Key Laboratory of Neural and Vascular Biology, The Key Laboratory of New Drug Pharmacology and Toxicology, Department of Pharmacology, Ministry of Education, Hebei Medical University, Shijiazhuang, 050011, China
| | - Jiangtao Guo
- Department of Biophysics and Department of Neurology of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, China.
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2
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Alam KA, Svalastoga P, Martinez A, Glennon JC, Haavik J. Potassium channels in behavioral brain disorders. Molecular mechanisms and therapeutic potential: A narrative review. Neurosci Biobehav Rev 2023; 152:105301. [PMID: 37414376 DOI: 10.1016/j.neubiorev.2023.105301] [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: 03/31/2023] [Revised: 06/26/2023] [Accepted: 06/30/2023] [Indexed: 07/08/2023]
Abstract
Potassium channels (K+-channels) selectively control the passive flow of potassium ions across biological membranes and thereby also regulate membrane excitability. Genetic variants affecting many of the human K+-channels are well known causes of Mendelian disorders within cardiology, neurology, and endocrinology. K+-channels are also primary targets of many natural toxins from poisonous organisms and drugs used within cardiology and metabolism. As genetic tools are improving and larger clinical samples are being investigated, the spectrum of clinical phenotypes implicated in K+-channels dysfunction is rapidly expanding, notably within immunology, neurosciences, and metabolism. K+-channels that previously were considered to be expressed in only a few organs and to have discrete physiological functions, have recently been found in multiple tissues and with new, unexpected functions. The pleiotropic functions and patterns of expression of K+-channels may provide additional therapeutic opportunities, along with new emerging challenges from off-target effects. Here we review the functions and therapeutic potential of K+-channels, with an emphasis on the nervous system, roles in neuropsychiatric disorders and their involvement in other organ systems and diseases.
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Affiliation(s)
| | - Pernille Svalastoga
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway; Children and Youth Clinic, Haukeland University Hospital, Bergen, Norway
| | | | - Jeffrey Colm Glennon
- Conway Institute for Biomolecular and Biomedical Research, School of Medicine, University College Dublin, Dublin, Ireland.
| | - Jan Haavik
- Department of Biomedicine, University of Bergen, Norway; Division of Psychiatry, Haukeland University Hospital, Norway.
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3
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Naffaa MM, Al-Ewaidat OA. Ligand modulation of KCNQ-encoded (K V7) potassium channels in the heart and nervous system. Eur J Pharmacol 2021; 906:174278. [PMID: 34174270 DOI: 10.1016/j.ejphar.2021.174278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/06/2021] [Accepted: 06/18/2021] [Indexed: 10/21/2022]
Abstract
KCNQ-encoded (KV7) potassium channels are diversely distributed in the human tissues, associated with many physiological processes and pathophysiological conditions. These channels are increasingly used as drug targets for treating diseases. More selective and potent molecules on various types of the KV7 channels are desirable for appropriate therapies. The recent knowledge of the structure and function of human KCNQ-encoded channels makes it more feasible to achieve these goals. This review discusses the role and mechanism of action of many molecules in modulating the function of the KCNQ-encoded potassium channels in the heart and nervous system. The effects of these compounds on KV7 channels help to understand their involvement in many diseases, and to search for more selective and potent ligands to be used in the treatment of many disorders such as various types of cardiac arrhythmias, epilepsy, and pain.
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Affiliation(s)
- Moawiah M Naffaa
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
| | - Ola A Al-Ewaidat
- Faculty of Medicine, The University of Jordan, Amman, 11942, Jordan
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4
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Borgini M, Mondal P, Liu R, Wipf P. Chemical modulation of Kv7 potassium channels. RSC Med Chem 2021; 12:483-537. [PMID: 34046626 PMCID: PMC8128042 DOI: 10.1039/d0md00328j] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 01/10/2023] Open
Abstract
The rising interest in Kv7 modulators originates from their ability to evoke fundamental electrophysiological perturbations in a tissue-specific manner. A large number of therapeutic applications are, in part, based on the clinical experience with two broad-spectrum Kv7 agonists, flupirtine and retigabine. Since precise molecular structures of human Kv7 channel subtypes in closed and open states have only very recently started to emerge, computational studies have traditionally been used to analyze binding modes and direct the development of more potent and selective Kv7 modulators with improved safety profiles. Herein, the synthetic and medicinal chemistry of small molecule modulators and the representative biological properties are summarized. Furthermore, new therapeutic applications supported by in vitro and in vivo assay data are suggested.
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Affiliation(s)
- Matteo Borgini
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Pravat Mondal
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Ruiting Liu
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh Pittsburgh PA 15260 USA
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5
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Li X, Zhang Q, Guo P, Fu J, Mei L, Lv D, Wang J, Lai D, Ye S, Yang H, Guo J. Molecular basis for ligand activation of the human KCNQ2 channel. Cell Res 2021; 31:52-61. [PMID: 32884139 PMCID: PMC7852908 DOI: 10.1038/s41422-020-00410-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 08/14/2020] [Indexed: 01/10/2023] Open
Abstract
The voltage-gated potassium channel KCNQ2 is responsible for M-current in neurons and is an important drug target to treat epilepsy, pain and several other diseases related to neuronal hyper-excitability. A list of synthetic compounds have been developed to directly activate KCNQ2, yet our knowledge of their activation mechanism is limited, due to lack of high-resolution structures. Here, we report cryo-electron microscopy (cryo-EM) structures of the human KCNQ2 determined in apo state and in complex with two activators, ztz240 or retigabine, which activate KCNQ2 through different mechanisms. The activator-bound structures, along with electrophysiology analysis, reveal that ztz240 binds at the voltage-sensing domain and directly stabilizes it at the activated state, whereas retigabine binds at the pore domain and activates the channel by an allosteric modulation. By accurately defining ligand-binding sites, these KCNQ2 structures not only reveal different ligand recognition and activation mechanisms, but also provide a structural basis for drug optimization and design.
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Affiliation(s)
- Xiaoxiao Li
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
| | - Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China
| | - Peipei Guo
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China
| | - Jie Fu
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China
| | - Lianghe Mei
- Suzhou Institute of Drug Innovation, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 108 Yuxin Road, Suzhou, Jiangsu, 215123, China
| | - Dashuai Lv
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Jiangqin Wang
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
| | - Dongwu Lai
- Department of Cardiology, Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310016, China
| | - Sheng Ye
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, 310058, China
- School of Life Sciences, Tianjin University, 92 Weijin Road, Nankai District, Tianjin, 300072, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences and School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
| | - Jiangtao Guo
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China.
- Department of Cardiology, Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310016, China.
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Kanyo R, Wang CK, Locskai LF, Li J, Allison WT, Kurata HT. Functional and behavioral signatures of Kv7 activator drug subtypes. Epilepsia 2020; 61:1678-1690. [PMID: 32652600 DOI: 10.1111/epi.16592] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 01/10/2023]
Abstract
OBJECTIVE Voltage-gated potassium channels of the KCNQ (Kv7) family are targeted by a variety of activator compounds with therapeutic potential for treatment of epilepsy. Exploration of this drug class has revealed a variety of effective compounds with diverse mechanisms. In this study, we aimed to clarify functional criteria for categorization of Kv7 activator compounds, and to compare the effects of prototypical drugs in a zebrafish larvae model. METHODS In vitro electrophysiological approaches with recombinant ion channels were used to highlight functional properties important for classification of drug mechanisms. We also benchmarked the effects of representative antiepileptic Kv7 activator drugs using behavioral seizure assays of zebrafish larvae and in vivo Ca2+ imaging with the ratiometric Ca2+ sensor CaMPARI. RESULTS Drug effects on channel gating kinetics, and drug sensitivity profiles to diagnostic channel mutations, were used to highlight properties for categorization of Kv7 activator drugs into voltage sensor-targeted or pore-targeted subtypes. Quantifying seizures and ratiometric Ca2+ imaging in freely swimming zebrafish larvae demonstrated that while all Kv7 activators tested lead to suppression of neuronal excitability, pore-targeted activators (like ML213 and retigabine) strongly suppress seizure behavior, whereas ICA-069673 triggers a seizure-like hypermotile behavior. SIGNIFICANCE This study suggests criteria to categorize antiepileptic Kv7 activator drugs based on their underlying mechanism. We also establish the use of in vivo CaMPARI as a tool for screening effects of anticonvulsant drugs on neuronal excitability in zebrafish. In summary, despite a shared ability to suppress neuronal excitability, our findings illustrate how mechanistic differences between Kv7 activator subtypes influence their effects on heteromeric channels and lead to vastly different in vivo outcomes.
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Affiliation(s)
- Richard Kanyo
- Department of Biological Sciences, Centre for Prions and Protein Folding Disease, University of Alberta, Edmonton, Alberta, Canada
| | - Caroline K Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Laszlo F Locskai
- Department of Biological Sciences, Centre for Prions and Protein Folding Disease, University of Alberta, Edmonton, Alberta, Canada
| | - Jingru Li
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - W Ted Allison
- Department of Biological Sciences, Centre for Prions and Protein Folding Disease, University of Alberta, Edmonton, Alberta, Canada
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
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7
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Zhang F, Liu Y, Tang F, Liang B, Chen H, Zhang H, Wang K. Electrophysiological and pharmacological characterization of a novel and potent neuronal Kv7 channel opener SCR2682 for antiepilepsy. FASEB J 2019; 33:9154-9166. [DOI: 10.1096/fj.201802848rr] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Fan Zhang
- The Key Laboratory of Neural and Vascular Biology Ministry of Education The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province Department of Pharmacology Hebei Medical University Shijiazhuang China
| | - Yani Liu
- Department of Pharmacology Qingdao University Qingdao China
| | - Feng Tang
- Medicinal Chemistry, Simcere Pharmaceutical Nanjing China
| | - Bo Liang
- Medicinal Chemistry Shanghai Zhimeng BioPharma Shanghai China
| | - Huanming Chen
- Medicinal Chemistry Shanghai Zhimeng BioPharma Shanghai China
| | - Hailin Zhang
- The Key Laboratory of Neural and Vascular Biology Ministry of Education The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province Department of Pharmacology Hebei Medical University Shijiazhuang China
| | - Kewei Wang
- Department of Pharmacology Qingdao University Qingdao China
- Institute of Innovative Drugs School of Pharmacy Qingdao University Qingdao China
- Center for Brain Science and Brain‐Inspired Intelligence Guangzhou China
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8
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Abstract
The highly structurally similar drugs flupirtine and retigabine have been regarded as safe and effective for many years but lately they turned out to exert intolerable side effects. While the twin molecules share the mode of action, both stabilize the open state of voltage-gated potassium channels, the form and severity of adverse effects is different. The analgesic flupirtine caused drug-induced liver injury in rare but fatal cases, whereas prolonged use of the antiepileptic retigabine led to blue tissue discoloration. Because the adverse effects seem unrelated to the mode of action, it is likely, that both drugs that occupied important therapeutic niches, could be replaced. Reasons for the clinically relevant toxicity will be clarified and future substitutes for these drugs presented in this review.
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9
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Gollasch M, Welsh DG, Schubert R. Perivascular adipose tissue and the dynamic regulation of K v 7 and K ir channels: Implications for resistant hypertension. Microcirculation 2018; 25. [PMID: 29211322 DOI: 10.1111/micc.12434] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 11/30/2017] [Indexed: 12/20/2022]
Abstract
Resistant hypertension is defined as high blood pressure that remains uncontrolled despite treatment with at least three antihypertensive drugs at adequate doses. Resistant hypertension is an increasingly common clinical problem in older age, obesity, diabetes, sleep apnea, and chronic kidney disease. Although the direct vasodilator minoxidil was introduced in the early 1970s, only recently has this drug been shown to be particularly effective in a subgroup of patients with treatment-resistant or uncontrolled hypertension. This pharmacological approach is interesting from a mechanistic perspective as minoxidil is the only clinically used K+ channel opener today, which targets a subclass of K+ channels, namely KATP channels in VSMCs. Beside KATP channels, two other classes of VSMC K+ channels could represent novel effective targets for treatment of resistant hypertension, namely Kv 7 (KCNQ) and inward rectifier potassium (Kir 2.1) channels. Interestingly, these channels are unique among VSMC potassium channels. First, both have been implicated in the control of microvascular tone by perivascular adipose tissue. Second, they exhibit biophysical properties strongly controlled and regulated by membrane voltage, but not intracellular calcium. This review focuses on Kv 7 (Kv 7.1-5) and Kir (Kir 2.1) channels in VSMCs as potential novel drug targets for treatment of resistant hypertension, particularly in comorbid conditions such as obesity and metabolic syndrome.
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Affiliation(s)
- Maik Gollasch
- Medical Clinic for Nephrology and Internal Intensive Care, Charité Campus Virchow Klinikum, Experimental and Clinical Research Center (ECRC) - a joint cooperation between the Charité - University Medicine Berlin and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Donald G Welsh
- Department of Physiology and Pharmacology, Western University, London, ON, Canada
| | - Rudolf Schubert
- Centre for Biomedicine and Medical Technology Mannheim (CBTM), Research Division Cardiovascular Physiology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
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10
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Wang CK, Lamothe SM, Wang AW, Yang RY, Kurata HT. Pore- and voltage sensor-targeted KCNQ openers have distinct state-dependent actions. J Gen Physiol 2018; 150:1722-1734. [PMID: 30373787 PMCID: PMC6279353 DOI: 10.1085/jgp.201812070] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/24/2018] [Accepted: 10/11/2018] [Indexed: 01/01/2023] Open
Abstract
Ion channels encoded by KCNQ2-5 generate a prominent K+ conductance in the central nervous system, referred to as the M current, which is controlled by membrane voltage and PIP2. The KCNQ2-5 voltage-gated potassium channels are targeted by a variety of activating compounds that cause negative shifts in the voltage dependence of activation. The underlying pharmacology of these effects is of growing interest because of possible clinical applications. Recent studies have revealed multiple binding sites and mechanisms of action of KCNQ activators. For example, retigabine targets the pore domain, but several compounds have been shown to influence the voltage-sensing domain. An important unexplored feature of these compounds is the influence of channel gating on drug binding or effects. In the present study, we compare the state-dependent actions of retigabine and ICA-069673 (ICA73, a voltage sensor-targeted activator). We assess drug binding to preopen states by applying drugs to homomeric KCNQ2 channels at different holding voltages, demonstrating little or no association of ICA73 with resting states. Using rapid solution switching, we also demonstrate that the rate of onset of ICA73 correlates with the voltage dependence of channel activation. Retigabine actions differ significantly, with prominent drug effects seen at very negative holding voltages and distinct voltage dependences of drug binding versus channel activation. Using similar approaches, we investigate the mechanistic basis for attenuation of ICA73 actions by the voltage-sensing domain mutation KCNQ2[A181P]. Our findings demonstrate different state-dependent actions of pore- versus voltage sensor-targeted KCNQ channel activators, which highlight that subtypes of this drug class operate with distinct mechanisms.
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Affiliation(s)
- Caroline K Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Shawn M Lamothe
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Alice W Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Runying Y Yang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
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11
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Wang AW, Yau MC, Wang CK, Sharmin N, Yang RY, Pless SA, Kurata HT. Four drug-sensitive subunits are required for maximal effect of a voltage sensor-targeted KCNQ opener. J Gen Physiol 2018; 150:1432-1443. [PMID: 30166313 PMCID: PMC6168237 DOI: 10.1085/jgp.201812014] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 08/06/2018] [Indexed: 12/28/2022] Open
Abstract
KCNQ2-5 (Kv7.2-Kv7.5) channels are strongly influenced by an emerging class of small-molecule channel activators. Retigabine is the prototypical KCNQ activator that is thought to bind within the pore. It requires the presence of a Trp side chain that is conserved among retigabine-sensitive channels but absent in the retigabine-insensitive KCNQ1 subtype. Recent work has demonstrated that certain KCNQ openers are insensitive to mutations of this conserved Trp, and that their effects are instead abolished or attenuated by mutations in the voltage-sensing domain (VSD). In this study, we investigate the stoichiometry of a VSD-targeted KCNQ2 channel activator, ICA-069673, by forming concatenated channel constructs with varying numbers of drug-insensitive subunits. In homomeric WT KCNQ2 channels, ICA-069673 strongly stabilizes an activated channel conformation, which is reflected in the pronounced deceleration of deactivation and leftward shift of the conductance-voltage relationship. A full complement of four drug-sensitive subunits is required for maximal sensitivity to ICA-069673-even a single drug-insensitive subunit leads to significantly weakened effects. In a companion article (see Yau et al. in this issue), we demonstrate very different stoichiometry for the action of retigabine on KCNQ3, for which a single retigabine-sensitive subunit enables near-maximal effect. Together, these studies highlight fundamental differences in the site and mechanism of activation between retigabine and voltage sensor-targeted KCNQ openers.
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Affiliation(s)
- Alice W Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Michael C Yau
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada.,Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Copenhagen, Denmark
| | - Caroline K Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Nazlee Sharmin
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Runying Y Yang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Stephan A Pless
- Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Copenhagen, Denmark
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
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12
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Yau MC, Kim RY, Wang CK, Li J, Ammar T, Yang RY, Pless SA, Kurata HT. One drug-sensitive subunit is sufficient for a near-maximal retigabine effect in KCNQ channels. J Gen Physiol 2018; 150:1421-1431. [PMID: 30166314 PMCID: PMC6168243 DOI: 10.1085/jgp.201812013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 08/06/2018] [Indexed: 12/31/2022] Open
Abstract
Retigabine is a widely studied potassium channel activator that is thought to interact with a conserved Trp side chain in the pore domain of Kv7 subunits. Yau et al. demonstrate that drug sensitivity in just one of the four subunits is sufficient for a near-maximal response to retigabine. Retigabine is an antiepileptic drug and the first voltage-gated potassium (Kv) channel opener to be approved for human therapeutic use. Retigabine is thought to interact with a conserved Trp side chain in the pore of KCNQ2–5 (Kv7.2–7.5) channels, causing a pronounced hyperpolarizing shift in the voltage dependence of activation. In this study, we investigate the functional stoichiometry of retigabine actions by manipulating the number of retigabine-sensitive subunits in concatenated KCNQ3 channel tetramers. We demonstrate that intermediate retigabine concentrations cause channels to exhibit biphasic conductance–voltage relationships rather than progressive concentration-dependent shifts. This suggests that retigabine can exert its effects in a nearly “all-or-none” manner, such that channels exhibit either fully shifted or unshifted behavior. Supporting this notion, concatenated channels containing only a single retigabine-sensitive subunit exhibit a nearly maximal retigabine effect. Also, rapid solution exchange experiments reveal delayed kinetics during channel closure, as retigabine dissociates from channels with multiple drug-sensitive subunits. Collectively, these data suggest that a single retigabine-sensitive subunit can generate a large shift of the KCNQ3 conductance–voltage relationship. In a companion study (Wang et al. 2018. J. Gen. Physiol.https://doi.org/10.1085/jgp.201812014), we contrast these findings with the stoichiometry of a voltage sensor-targeted KCNQ channel opener (ICA-069673), which requires four drug-sensitive subunits for maximal effect.
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Affiliation(s)
- Michael C Yau
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Copenhagen, Denmark
| | - Robin Y Kim
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Caroline K Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jingru Li
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Tarek Ammar
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Runying Y Yang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Stephan A Pless
- Department of Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Copenhagen, Denmark
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
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13
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Du X, Gao H, Jaffe D, Zhang H, Gamper N. M-type K + channels in peripheral nociceptive pathways. Br J Pharmacol 2018; 175:2158-2172. [PMID: 28800673 PMCID: PMC5980636 DOI: 10.1111/bph.13978] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 07/17/2017] [Accepted: 08/03/2017] [Indexed: 12/22/2022] Open
Abstract
Pathological pain is a hyperexcitability disorder. Since the excitability of a neuron is set and controlled by a complement of ion channels it expresses, in order to understand and treat pain, we need to develop a mechanistic insight into the key ion channels controlling excitability within the mammalian pain pathways and how these ion channels are regulated and modulated in various physiological and pathophysiological settings. In this review, we will discuss the emerging data on the expression in pain pathways, functional role and modulation of a family of voltage-gated K+ channels called 'M channels' (KCNQ, Kv 7). M channels are increasingly recognized as important players in controlling pain signalling, especially within the peripheral somatosensory system. We will also discuss the therapeutic potential of M channels as analgesic drug targets. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc/.
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Affiliation(s)
- Xiaona Du
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
| | - Haixia Gao
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
- School of Biomedical Sciences, Faculty of Biological SciencesUniversity of LeedsLeedsUK
| | - David Jaffe
- Department of Biology, UTSA Neurosciences InstituteUniversity of Texas at San AntonioSan AntonioTXUSA
| | - Hailin Zhang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
| | - Nikita Gamper
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
- School of Biomedical Sciences, Faculty of Biological SciencesUniversity of LeedsLeedsUK
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14
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Bai F, Pi X, Li P, Zhou P, Yang H, Wang X, Li M, Gao Z, Jiang H. A Statistical Thermodynamic Model for Ligands Interacting With Ion Channels: Theoretical Model and Experimental Validation of the KCNQ2 Channel. Front Pharmacol 2018; 9:150. [PMID: 29593528 PMCID: PMC5855359 DOI: 10.3389/fphar.2018.00150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 02/13/2018] [Indexed: 12/01/2022] Open
Abstract
Ion channels are important therapeutic targets, and their pharmacology is becoming increasingly important. However, knowledge of the mechanism of interaction of the activators and ion channels is still limited due to the complexity of the mechanisms. A statistical thermodynamic model has been developed in this study to characterize the cooperative binding of activators to ion channels. By fitting experimental concentration-response data, the model gives eight parameters for revealing the mechanism of an activator potentiating an ion channel, i.e., the binding affinity (KA), the binding cooperative coefficients for two to four activator molecules interacting with one channel (γ, μ, and ν), and the channel conductance coefficients for four activator binding configurations of the channel (a, b, c, and d). Values for the model parameters and the mechanism underlying the interaction of ztz240, a proven KCNQ2 activator, with the wild-type channel have been obtained and revealed by fitting the concentration-response data of this activator potentiating the outward current amplitudes of KCNQ2. With these parameters, our model predicted an unexpected bi-sigmoid concentration-response curve of ztz240 activation of the WT-F137A mutant heteromeric channel that was in good agreement with the experimental data determined in parallel in this study, lending credence to the assumptions on which the model is based and to the model itself. Our model can provide a better fit to the measured data than the Hill equation and estimates the binding affinity, as well as the cooperative coefficients for the binding of activators and conductance coefficients for binding states, which validates its use in studying ligand-channel interaction mechanisms.
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Affiliation(s)
- Fang Bai
- Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, and Faculty of Chemical, Environmental, and Biological Science and Technology, Dalian University of Technology, Dalian, China.,Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xiaoping Pi
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ping Li
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Pingzheng Zhou
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Huaiyu Yang
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xicheng Wang
- Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, and Faculty of Chemical, Environmental, and Biological Science and Technology, Dalian University of Technology, Dalian, China
| | - Min Li
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD, United States
| | - Zhaobing Gao
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hualiang Jiang
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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15
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Mehta P, Srivastava S, Choudhary BS, Sharma M, Malik R. Probing voltage sensing domain of KCNQ2 channel as a potential target to combat epilepsy: a comparative study. J Recept Signal Transduct Res 2017; 37:578-589. [DOI: 10.1080/10799893.2017.1369122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Pakhuri Mehta
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, Kishangarh, Ajmer, Rajasthan, India
| | - Shubham Srivastava
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, Kishangarh, Ajmer, Rajasthan, India
| | - Bhanwar Singh Choudhary
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, Kishangarh, Ajmer, Rajasthan, India
| | - Manish Sharma
- School of Pharmacy, Maharishi Markandeshwar University, Ambala, Haryana, India
| | - Ruchi Malik
- Department of Pharmacy, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, Kishangarh, Ajmer, Rajasthan, India
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16
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Effects of novel subtype selective M-current activators on spinal reflexes in vitro: Comparison with retigabine. Neuropharmacology 2016; 109:131-138. [DOI: 10.1016/j.neuropharm.2016.05.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 04/28/2016] [Accepted: 05/31/2016] [Indexed: 01/13/2023]
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17
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Wang AW, Yang R, Kurata HT. Sequence determinants of subtype-specific actions of KCNQ channel openers. J Physiol 2016; 595:663-676. [PMID: 27506413 DOI: 10.1113/jp272762] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/02/2016] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS Retigabine is a KCNQ voltage-gated potassium channel opener that was recently approved as an add-on therapeutic for patients with drug-resistant epilepsy. Retigabine exhibits very little specificity between most KCNQ channel subtypes, and there is interest in generating more potent and specific KCNQ channel openers. The present study describes the marked specificity of ICA069673 for KCNQ2 vs. KCNQ3, and exploits this property to investigate determinants of KCNQ subtype specificity. ICA069673 acts on a binding site in the voltage-sensing domain that is distinct from the putative retigabine site in the channel pore. ICA069673 has two separable effects on KCNQ channel activity. We identify two channel residues required for subtype specificity of KCNQ channel openers and show that these are sufficient to generate ICA069673 sensitivity in KCNQ3. ABSTRACT Retigabine (RTG) is the first approved anti-epileptic drug that acts via activation of voltage-gated potassium channels, targeting KCNQ channels that underlie the neuronal M-current. RTG exhibits little specificity between KCNQ2-5 as a result of conservation of a Trp residue in the pore domain that binds to the drug. The RTG analogue ICA-069673 ('ICA73') exhibits much stronger effects on KCNQ2 channels, including a large hyperpolarizing shift of the voltage-dependence of activation, an ∼2-fold enhancement of peak current and pronounced subtype specificity for KCNQ2 over KCNQ3. Based on ICA73 sensitivity of chimeric constructs of the transmembrane segments of KCNQ2 and KCNQ3, this drug appears to interact with the KCNQ2 voltage sensor (S1-S4) rather than the pore region targeted by RTG. KCNQ2 point mutants in the voltage sensor were generated based on KCNQ2/KCNQ3 sequence differences, and screened for ICA73 sensitivity. These experiments reveal that KCNQ2 residues F168 and A181 in the S3 segment are essential determinants of ICA73 subtype specificity. Mutations at either position in KCNQ2 abolish the ICA73-mediated gating shift, but preserve RTG sensitivity. Interestingly, A181P mutant channels show little ICA73-mediated gating shift but retain current potentiation by the drug. Mutations (L198F and P211A), which introduce these critical KCNQ2 residues at corresponding positions in KCNQ3, transplant partial ICA73 sensitivity. These findings demonstrate that RTG and ICA73 act via distinct mechanisms, and also reveal specific residues that underlie subtype specificity of KCNQ channel openers.
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Affiliation(s)
- Alice W Wang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Runying Yang
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
| | - Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
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18
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Liu T, Lu D, Zhang H, Zheng M, Yang H, Xu Y, Luo C, Zhu W, Yu K, Jiang H. Applying high-performance computing in drug discovery and molecular simulation. Natl Sci Rev 2016; 3:49-63. [PMID: 32288960 PMCID: PMC7107815 DOI: 10.1093/nsr/nww003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Revised: 01/03/2016] [Accepted: 01/05/2016] [Indexed: 12/31/2022] Open
Abstract
In recent decades, high-performance computing (HPC) technologies and supercomputers in China have significantly advanced, resulting in remarkable achievements. Computational drug discovery and design, which is based on HPC and combines pharmaceutical chemistry and computational biology, has become a critical approach in drug research and development and is financially supported by the Chinese government. This approach has yielded a series of new algorithms in drug design, as well as new software and databases. This review mainly focuses on the application of HPC to the fields of drug discovery and molecular simulation at the Chinese Academy of Sciences, including virtual drug screening, molecular dynamics simulation, and protein folding. In addition, the potential future application of HPC in precision medicine is briefly discussed.
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Affiliation(s)
- Tingting Liu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Dong Lu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Hao Zhang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Mingyue Zheng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Huaiyu Yang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yechun Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Cheng Luo
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Weiliang Zhu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Kunqian Yu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Hualiang Jiang
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
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19
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Kim RY, Yau MC, Galpin JD, Seebohm G, Ahern CA, Pless SA, Kurata HT. Atomic basis for therapeutic activation of neuronal potassium channels. Nat Commun 2015; 6:8116. [PMID: 26333338 PMCID: PMC4561856 DOI: 10.1038/ncomms9116] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 07/21/2015] [Indexed: 12/25/2022] Open
Abstract
Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2–5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific chemical interactions required for retigabine action. Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp. Supporting this model, substitution with fluorinated Trp analogues, with increased H-bonding propensity, strengthens retigabine potency. In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators. These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators. The antiepileptic drug retigabine potentiates neuronal KCNQ potassium channels. Here, the authors use a combination of unnatural amino acid mutagenesis and electrophysiology to show that retigabine acts by hydrogen bonding with a tryptophan indole nitrogen in the channel pore.
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Affiliation(s)
- Robin Y Kim
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - Michael C Yau
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - Jason D Galpin
- Department of Molecular Physiology and Biophysics, University of Iowa, 285 Newton Road, Iowa City, Iowa 52242, USA
| | - Guiscard Seebohm
- Department of Cardiovascular Medicine, University Hospital Münster, Albert-Schweitzer-Campus 1 (Gebäude D3), D-48149 Münster, Germany
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, 285 Newton Road, Iowa City, Iowa 52242, USA
| | - Stephan A Pless
- Department of Drug Design and Pharmacology (Center for Biopharmaceuticals), University of Copenhagen, Jagtvej 160, DK-2100 Copenhagen, Denmark
| | - Harley T Kurata
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
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20
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Miceli F, Soldovieri MV, Ambrosino P, De Maria M, Manocchio L, Medoro A, Taglialatela M. Molecular pathophysiology and pharmacology of the voltage-sensing module of neuronal ion channels. Front Cell Neurosci 2015; 9:259. [PMID: 26236192 PMCID: PMC4502356 DOI: 10.3389/fncel.2015.00259] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 06/22/2015] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated ion channels (VGICs) are membrane proteins that switch from a closed to open state in response to changes in membrane potential, thus enabling ion fluxes across the cell membranes. The mechanism that regulate the structural rearrangements occurring in VGICs in response to changes in membrane potential still remains one of the most challenging topic of modern biophysics. Na+, Ca2+ and K+ voltage-gated channels are structurally formed by the assembly of four similar domains, each comprising six transmembrane segments. Each domain can be divided into two main regions: the Pore Module (PM) and the Voltage-Sensing Module (VSM). The PM (helices S5 and S6 and intervening linker) is responsible for gate opening and ion selectivity; by contrast, the VSM, comprising the first four transmembrane helices (S1–S4), undergoes the first conformational changes in response to membrane voltage variations. In particular, the S4 segment of each domain, which contains several positively charged residues interspersed with hydrophobic amino acids, is located within the membrane electric field and plays an essential role in voltage sensing. In neurons, specific gating properties of each channel subtype underlie a variety of biological events, ranging from the generation and propagation of electrical impulses, to the secretion of neurotransmitters and to the regulation of gene expression. Given the important functional role played by the VSM in neuronal VGICs, it is not surprising that various VSM mutations affecting the gating process of these channels are responsible for human diseases, and that compounds acting on the VSM have emerged as important investigational tools with great therapeutic potential. In the present review we will briefly describe the most recent discoveries concerning how the VSM exerts its function, how genetically inherited diseases caused by mutations occurring in the VSM affects gating in VGICs, and how several classes of drugs and toxins selectively target the VSM.
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Affiliation(s)
- Francesco Miceli
- Department of Neuroscience, University of Naples Federico II Naples, Italy
| | | | - Paolo Ambrosino
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Michela De Maria
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Laura Manocchio
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Alessandro Medoro
- Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
| | - Maurizio Taglialatela
- Department of Neuroscience, University of Naples Federico II Naples, Italy ; Department of Medicine and Health Sciences, University of Molise Campobasso, Italy
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21
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Abstract
The voltage sensitive domain (VSD) is a pivotal structure of voltage-gated ion channels (VGICs) and plays an essential role in the generation of electrochemical signals by neurons, striated muscle cells, and endocrine cells. The VSD is not unique to VGICs. Recent studies have shown that a VSD regulates a phosphatase. Similarly, Hv1, a voltage-sensitive protein that lacks an apparent pore domain, is a self-contained voltage sensor that operates as an H⁺ channel. VSDs are formed by four transmembrane helices (S1-S4). The S4 helix is positively charged due to the presence of arginine and lysine residues. It is surrounded by two water crevices that extend into the membrane from both the extracellular and intracellular milieus. A hydrophobic septum disrupts communication between these water crevices thus preventing the permeation of ions. The septum is maintained by interactions between the charged residues of the S4 segment and the gating charge transfer center. Mutating the charged residue of the S4 segment allows the water crevices to communicate and generate gating pore or omega pore. Gating pore currents have been reported to underlie several neuronal and striated muscle channelopathies. Depending on which charged residue on the S4 segment is mutated, gating pores are permeant either at depolarized or hyperpolarized voltages. Gating pores are cation selective and seem to converge toward Eisenmann's first or second selectivity sequences. Most gating pores are blocked by guanidine derivatives as well as trivalent and quadrivalent cations. Gating pores can be used to study the movement of the voltage sensor and could serve as targets for novel small therapeutic molecules.
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22
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Wang J, Li Y, Hui Z, Cao M, Shi R, Zhang W, Geng L, Zhou X. Functional analysis of potassium channels in Kv7.2 G271V mutant causing early onset familial epilepsy. Brain Res 2015; 1616:112-22. [PMID: 25960349 DOI: 10.1016/j.brainres.2015.04.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 04/20/2015] [Accepted: 04/24/2015] [Indexed: 01/23/2023]
Abstract
Kv7 (KCNQ) channels underlying a class of voltage-gated K+ current are best known for regulating neuronal excitability. The first glycine (G) residue in the pore helix of Kv7.2 (KCNQ2) subunit is highly conserved among different classes of Kv7 channel family. A missense mutation causing the replacement of the corresponding G residues with a valine (p.G271V) in Kv7.2 was found in a large, four-generation pedigree. Here, we set out to examine the molecular pathomechanism of G271V mutants using patch clamp technology combined with biochemical and immunocytochemical techniques in transiently transfected human embryonic kidney (HEK) 293 cells. The expression of Kv7.2 protein had the same intensity for both wild type (WT) and G271V. In transfected HEK cells, G271V mutants induced large depolarizing shifts of the conductance-voltage relationships and marked slowing of current activation kinetics compared to WT. In addition, G271V mutants abolished currents in homomeric channels, and resulted in about 50% reduction of current in Kv7.2/G271V/Kv7.3 heteromultimeric condition, indicating a more severe functional defect. To test for G271V mutant channel expression in surface membrane, we performed fluorescence confocal microscopy imaging, which revealed no differences between the mutant and WT, suggesting that G271V channels fail to open in response to depolarization even though they are present in the membrane. Furthermore, pharmacologic intervention experiments revealed that upon specific incubation of transfected HEK 293 cells expressing G271V heteromultimeric channels in presence of Kv7 channel enhancer retigabine (ezogabine), the potassium currents increased significantly, suggesting the potential of retigabine as gene-specific therapy.
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Affiliation(s)
- Juanjuan Wang
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Yuan Li
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Zhiyan Hui
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Min Cao
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Ruiming Shi
- Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Wei Zhang
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Limeng Geng
- Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Xihui Zhou
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China.
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23
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Subramanian P, Indu S, Kaliappan KP. A One-Pot Copper Catalyzed Biomimetic Route to N-Heterocyclic Amides from Methyl Ketones via Oxidative C–C Bond Cleavage. Org Lett 2014; 16:6212-5. [DOI: 10.1021/ol5031266] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
| | - Satrajit Indu
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Krishna P. Kaliappan
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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24
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Zhou P, Zhang Y, Xu H, Chen F, Chen X, Li X, Pi X, Wang L, Zhan L, Nan F, Gao Z. P-retigabine: an N-propargyled retigabine with improved brain distribution and enhanced antiepileptic activity. Mol Pharmacol 2014; 87:31-8. [PMID: 25319542 DOI: 10.1124/mol.114.095190] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Retigabine (RTG, [ethyl N-[2-amino-4-[(4-fluorophenyl)methyl]amino] phenyl] carbamate]) is a first-in-class antiepileptic drug that acts by potentiating neuronal KCNQ potassium channels; however, it has less than optimal brain distribution. In this study, we report that P-RTG (ethyl N-[2-amino-4-((4-fluorobenzyl)(prop-2-ynyl)amino)phenyl]carbamate), an RTG derivative that incorporates a propargyl group at the N position of the RTG linker, exhibits an inverted brain distribution compared with RTG. The brain-to-plasma concentration ratio of P-RTG increased to 2.30 compared with 0.16 for RTG. However, the structural modification did not change the drug's potentiation potency, subtype selectivity, or RTG molecular determinants on KCNQ channels. In addition, in cultured hippocampal neurons, P-RTG exhibited a similar capability as RTG for suppressing both induced and spontaneous action potential firing. Notably, P-RTG antiepileptic activity in the maximal electroshock (MES)-induced mouse seizure model was significantly enhanced to a value 2.5 times greater than that of RTG. Additionally, the neurotoxicity of P-RTG in the rotarod test was comparable with that of RTG. Collectively, our results indicate that the incorporation of a propargyl group significantly improves the RTG brain distribution, supporting P-RTG as a promising antiepileptic drug candidate. The strategy for improving brain-to-plasma distribution of RTG might be applicable for the drug development of other central nervous system diseases.
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Affiliation(s)
- Pingzheng Zhou
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Yangming Zhang
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Haiyan Xu
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Fei Chen
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xueqin Chen
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xiaoying Li
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Xiaoping Pi
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Lipeng Wang
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Li Zhan
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Fajun Nan
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Zhaobing Gao
- State Key Laboratory of Drug Research (P.Z., H.X., X.C., X.P., L.W., L.Z., Z.G.), and National Center for Drug Screening (Y.Z., F.C., X.L., F.N.), State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, and Graduate School, Chinese Academy of Sciences, Shanghai, People's Republic of China
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Li P, Chen X, Zhang Q, Zheng Y, Jiang H, Yang H, Gao Z. The human ether-a-go-go-related gene activator NS1643 enhances epilepsy-associated KCNQ channels. J Pharmacol Exp Ther 2014; 351:596-604. [PMID: 25232191 DOI: 10.1124/jpet.114.217703] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Human ether-a-go-go-related gene (hERG) and KCNQ channels are two classes of voltage-gated potassium channels. Specific mutations have been identified that are causal for type II long QT (LQT2) syndrome, neonatal epilepsy, and benign familial neonatal convulsions. Increasing evidence from clinical studies suggests that LQT2 and epilepsy coexist in some patients. Therefore, an integral approach to investigating and treating the two diseases is likely more effective. In the current study, we found that NS1643 [1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea], a previously reported hERG activator, is also an activator of KCNQ channels. It potentiates the neuronal KCNQ2, KCNQ4, and KCNQ2/Q3 channels, but not the cardiac KCNQ1. The effects of NS1643 on the KCNQ2 channel include left shifting of voltage for reaching 50% of the maximum conductance and slowing of deactivation. Analysis of the dose-response curve of NS1643 revealed an EC50 value of 2.44 ± 0.25 μM. A hydrophobic phenylalanine (F137) located at the middle region of the voltage-sensing domain was identified as critical for NS1643 activity on KCNQ2. When testing NS1643 effects in rescuing LQT2 hERG mutants and the KCNQ2 BFNC mutants, we found it is particularly efficacious in some cases. Considering the substantial relationship between LQT2 and epilepsy, these findings reveal that NS1643 is a useful compound to elucidate the causal connection of LQT2 and epilepsy. More generally, this may provide a strategy in the development of therapeutics for LQT2 and epilepsy.
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Affiliation(s)
- Ping Li
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xueqin Chen
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Qiansen Zhang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yueming Zheng
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Hualiang Jiang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Huaiyu Yang
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Zhaobing Gao
- CAS Key Laboratory of Receptor Research (P.L., X.C., Y.Z., Z.G.), and State Key Laboratory of Drug Research (Q.Z., H.J., H.Y.), Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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Brueggemann LI, Haick JM, Cribbs LL, Byron KL. Differential activation of vascular smooth muscle Kv7.4, Kv7.5, and Kv7.4/7.5 channels by ML213 and ICA-069673. Mol Pharmacol 2014; 86:330-41. [PMID: 24944189 DOI: 10.1124/mol.114.093799] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent research suggests that smooth muscle cells express Kv7.4 and Kv7.5 voltage-activated potassium channels, which contribute to maintenance of their resting membrane voltage. New pharmacologic activators of Kv7 channels, ML213 (N-mesitybicyclo[2.2.1]heptane-2-carboxamide) and ICA-069673 N-(6-chloropyridin-3-yl)-3,4-difluorobenzamide), have been reported to discriminate among channels formed from different Kv7 subtypes. We compared the effects of ML213 and ICA-069673 on homomeric human Kv7.4, Kv7.5, and heteromeric Kv7.4/7.5 channels exogenously expressed in A7r5 vascular smooth muscle cells. We found that, despite its previous description as a selective activator of Kv7.2 and Kv7.4, ML213 significantly increased the maximum conductance of homomeric Kv7.4 and Kv7.5, as well as heteromeric Kv7.4/7.5 channels, and induced a negative shift of their activation curves. Current deactivation rates decreased in the presence of the ML213 (10 μM) for all three channel combinations. Mutants of Kv7.4 (W242L) and Kv7.5 (W235L), previously found to be insensitive to another Kv7 channel activator, retigabine, were also insensitive to ML213 (10 μM). In contrast to ML213, ICA-069673 robustly activated Kv7.4 channels but was significantly less effective on homomeric Kv7.5 channels. Heteromeric Kv7.4/7.5 channels displayed intermediate responses to ICA-069673. In each case, ICA-069673 induced a negative shift of the activation curves without significantly increasing maximal conductance. Current deactivation rates decreased in the presence of ICA-069673 in a subunit-specific manner. Kv7.4 W242L responded to ICA-069673-like wild-type Kv7.4, but a Kv7.4 F143A mutant was much less sensitive to ICA-069673. Based on these results, ML213 and ICA-069673 likely bind to different sites and are differentially selective among Kv7.4, Kv7.5, and Kv7.4/7.5 channel subtypes.
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Affiliation(s)
- Lyubov I Brueggemann
- Department of Molecular Pharmacology and Therapeutics (L.I.B., J.M.H., K.L.B.) and Cell and Molecular Physiology (L.L.C.); Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
| | - Jennifer M Haick
- Department of Molecular Pharmacology and Therapeutics (L.I.B., J.M.H., K.L.B.) and Cell and Molecular Physiology (L.L.C.); Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
| | - Leanne L Cribbs
- Department of Molecular Pharmacology and Therapeutics (L.I.B., J.M.H., K.L.B.) and Cell and Molecular Physiology (L.L.C.); Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
| | - Kenneth L Byron
- Department of Molecular Pharmacology and Therapeutics (L.I.B., J.M.H., K.L.B.) and Cell and Molecular Physiology (L.L.C.); Loyola University Chicago Stritch School of Medicine, Maywood, Illinois
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Khanamiri S, Soltysinska E, Jepps TA, Bentzen BH, Chadha PS, Schmitt N, Greenwood IA, Olesen SP. Contribution of Kv7 channels to basal coronary flow and active response to ischemia. Hypertension 2013; 62:1090-7. [PMID: 24082059 DOI: 10.1161/hypertensionaha.113.01244] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The goal of the present study was to determine the role of KCNQ-encoded Kv channels (Kv7 channels) in the passive and active regulation of coronary flow in normotensive and hypertensive rats. In left anterior descending coronary arteries from normotensive rats, structurally different Kv7.2 to 7.5 activators produced relaxations, which were considerably less in arteries from hypertensive rats and were not mimicked by the Kv7.1-specific activator R-L3. In isolated, perfused heart preparations, coronary flow rate increased in response to the Kv7.2 to 7.5 activator (S)-1 and was diminished in the presence of a Kv7 inhibitor. The expression levels of KCNQ1-5 and their known accessory KCNE1-5 subunits in coronary arteries were similar in normotensive and hypertensive rats as measured by quantitative polymerase chain reaction. However, Kv7.4 protein expression was reduced in hypertensive rats. Application of adenosine or A2A receptor agonist CGS-21680 produced concentration-dependent relaxations of coronary arteries from normotensive rats, which were attenuated by application of Kv7 inhibitors. Kv7 blockers also attenuated the ischemia-induced increase in coronary perfusion in Langendorff studies. Overall, these data establish Kv7 channels as crucial regulators of coronary flow at resting and after hypoxic insult.
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Affiliation(s)
- Saereh Khanamiri
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, Danish National Research Foundation Centre for Cardiac Arrhythmia, The Panum Institute, University of Copenhagen, 12.5.14, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
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Du X, Gamper N. Potassium channels in peripheral pain pathways: expression, function and therapeutic potential. Curr Neuropharmacol 2013; 11:621-40. [PMID: 24396338 PMCID: PMC3849788 DOI: 10.2174/1570159x113119990042] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Electrical excitation of peripheral somatosensory nerves is a first step in generation of most pain signals in mammalian nervous system. Such excitation is controlled by an intricate set of ion channels that are coordinated to produce a degree of excitation that is proportional to the strength of the external stimulation. However, in many disease states this coordination is disrupted resulting in deregulated peripheral excitability which, in turn, may underpin pathological pain states (i.e. migraine, neuralgia, neuropathic and inflammatory pains). One of the major groups of ion channels that are essential for controlling neuronal excitability is potassium channel family and, hereby, the focus of this review is on the K+ channels in peripheral pain pathways. The aim of the review is threefold. First, we will discuss current evidence for the expression and functional role of various K+ channels in peripheral nociceptive fibres. Second, we will consider a hypothesis suggesting that reduced functional activity of K+ channels within peripheral nociceptive pathways is a general feature of many types of pain. Third, we will evaluate the perspectives of pharmacological enhancement of K+ channels in nociceptive pathways as a strategy for new analgesic drug design.
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Affiliation(s)
- Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
- Faculty of Biological Sciences, University of Leeds, Leeds, UK
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Wan X, Lu Y, Chen X, Xiong J, Zhou Y, Li P, Xia B, Li M, Zhu MX, Gao Z. Bimodal voltage dependence of TRPA1: mutations of a key pore helix residue reveal strong intrinsic voltage-dependent inactivation. Pflugers Arch 2013; 466:1273-87. [PMID: 24092046 PMCID: PMC4062818 DOI: 10.1007/s00424-013-1345-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 12/03/2022]
Abstract
Transient receptor potential A1 (TRPA1) is implicated in somatosensory processing and pathological pain sensation. Although not strictly voltage-gated, ionic currents of TRPA1 typically rectify outwardly, indicating channel activation at depolarized membrane potentials. However, some reports also showed TRPA1 inactivation at high positive potentials, implicating voltage-dependent inactivation. Here we report a conserved leucine residue, L906, in the putative pore helix, which strongly impacts the voltage dependency of TRPA1. Mutation of the leucine to cysteine (L906C) converted the channel from outward to inward rectification independent of divalent cations and irrespective to stimulation by allyl isothiocyanate. The mutant, but not the wild-type channel, displayed exclusively voltage-dependent inactivation at positive potentials. The L906C mutation also exhibited reduced sensitivity to inhibition by TRPA1 blockers, HC030031 and ruthenium red. Further mutagenesis of the leucine to all natural amino acids individually revealed that most substitutions at L906 (15/19) resulted in inward rectification, with exceptions of three amino acids that dramatically reduced channel activity and one, methionine, which mimicked the wild-type channel. Our data are plausibly explained by a bimodal gating model involving both voltage-dependent activation and inactivation of TRPA1. We propose that the key pore helix residue, L906, plays an essential role in responding to the voltage-dependent gating.
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Affiliation(s)
- Xia Wan
- Department of Clinical Pharmacology, the First Affiliated Hospital, Chongqing Medical University, Chongqing, China
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30
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Boehlen A, Schwake M, Dost R, Kunert A, Fidzinski P, Heinemann U, Gebhardt C. The new KCNQ2 activator 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid displays anticonvulsant potential. Br J Pharmacol 2013; 168:1182-200. [PMID: 23176257 DOI: 10.1111/bph.12065] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 09/12/2012] [Accepted: 09/17/2012] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND AND PURPOSE KCNQ2-5 channels are voltage-gated potassium channels that regulate neuronal excitability and represent suitable targets for the treatment of hyperexcitability disorders. The effect of Chlor-N-(6-chlor-pyridin-3-yl)-benzamid was tested on KCNQ subtypes for its ability to alter neuronal excitability and for its anticonvulsant potential. EXPERIMENTAL APPROACH The effect of 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid was evaluated using whole-cell voltage-clamp recordings from CHO cells and Xenopus laevis oocytes expressing different types of KCNQ channels. Epileptiform afterdischarges were recorded in fully amygdala-kindled rats in vivo. Neuronal excitability was assessed using field potential and whole cell recording in rat hippocampus in vitro. KEY RESULTS 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid caused a hyperpolarizing shift of the activation curve and a pronounced slowing of deactivation in KCNQ2-mediated currents, whereas KCNQ3/5 heteromers remained unaffected. The effect was also apparent in the Retigabine-insensitive mutant KCNQ2-W236L. In fully amygdala-kindled rats, it elevated the threshold for induction of afterdischarges and reduced seizure severity and duration. In hippocampal CA1 cells, 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid strongly damped neuronal excitability caused by a membrane hyperpolarization and a decrease in membrane resistance and induced an increase of the somatic resonance frequency on the single cell level, whereas synaptic transmission was unaffected. On the network level, 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid caused a significant reduction of γ and θ oscillation peak power, with no significant change in oscillation frequency. CONCLUSION AND IMPLICATIONS Our data indicate that 4-Chlor-N-(6-chlor-pyridin-3-yl)-benzamid is a potent KCNQ activator with a selectivity for KCNQ2 containing channels. It strongly reduces neuronal excitability and displays anticonvulsant activity in vivo.
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Affiliation(s)
- A Boehlen
- Institute of Neurophysiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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31
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Faulkner MA, Burke RA. Safety profile of two novel antiepileptic agents approved for the treatment of refractory partial seizures: ezogabine (retigabine) and perampanel. Expert Opin Drug Saf 2013; 12:847-55. [DOI: 10.1517/14740338.2013.823399] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Zhang F, Mi Y, Qi JL, Li JW, Si M, Guan BC, Du XN, An HL, Zhang HL. Modulation of K(v)7 potassium channels by a novel opener pyrazolo[1,5-a]pyrimidin-7(4H)-one compound QO-58. Br J Pharmacol 2013; 168:1030-42. [PMID: 23013484 DOI: 10.1111/j.1476-5381.2012.02232.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 08/22/2012] [Accepted: 09/17/2012] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Modulation of K(v)7/M channel function represents a relatively new strategy to treat neuronal excitability disorders such as epilepsy and neuropathic pain. We designed and synthesized a novel series of pyrazolo[1,5-a] pyrimidin-7(4H)-one compounds, which activate K(v)7 channels. Here, we characterized the effects of the lead compound, QO-58, on K(v)7 channels and investigated its mechanism of action. EXPERIMENTAL APPROACH A perforated whole-cell patch technique was used to record K(v)7 currents expressed in mammalian cell lines and M-type currents from rat dorsal root ganglion neurons. The effects of QO-58 in a rat model of neuropathic pain, chronic constriction injury (CCI) of the sciatic nerve, were also examined. KEY RESULTS QO-58 increased the current amplitudes, shifted the voltage-dependent activation curve in a more negative direction and slowed the deactivation of K(v)7.2/K(v)7.3 currents. QO-58 activated K(v)7.1, K(v)7.2, K(v)7.4 and K(v)7.3/K(v)7.5 channels with a more selective effect on K(v)7.2 and K(v)7.4, but little effect on K(v)7.3. The mechanism of QO-58's activation of K(v)7 channels was clearly distinct from that used by retigabine. A chain of amino acids, Val(224)Val(225)Tyr(226), in K(v)7.2 was important for QO-58 activation of this channel. QO-58 enhanced native neuronal M currents, resulting in depression of evoked action potentials. QO-58 also elevated the pain threshold of neuropathic pain in the sciatic nerve CCI model. CONCLUSIONS AND IMPLICATIONS The results indicate that QO-58 is a potent modulator of K(v)7 channels with a mechanism of action different from those of known K(v)7 openers. Hence, QO-58 shows potential as a treatment for diseases associated with neuronal hyperexcitability.
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Affiliation(s)
- F Zhang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.
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Lasoń W, Chlebicka M, Rejdak K. Research advances in basic mechanisms of seizures and antiepileptic drug action. Pharmacol Rep 2013; 65:787-801. [DOI: 10.1016/s1734-1140(13)71060-0] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/11/2013] [Indexed: 10/25/2022]
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Li P, Chen Z, Xu H, Sun H, Li H, Liu H, Yang H, Gao Z, Jiang H, Li M. The gating charge pathway of an epilepsy-associated potassium channel accommodates chemical ligands. Cell Res 2013; 23:1106-18. [PMID: 23797855 PMCID: PMC3773576 DOI: 10.1038/cr.2013.82] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Revised: 04/16/2013] [Accepted: 05/09/2013] [Indexed: 01/05/2023] Open
Abstract
Voltage-gated potassium (Kv) channels derive their voltage sensitivity from movement of gating charges in voltage-sensor domains (VSDs). The gating charges translocate through a physical pathway in the VSD to open or close the channel. Previous studies showed that the gating charge pathways of Shaker and Kv1.2-2.1 chimeric channels are occluded, forming the structural basis for the focused electric field and gating charge transfer center. Here, we show that the gating charge pathway of the voltage-gated KCNQ2 potassium channel, activity reduction of which causes epilepsy, can accommodate various small molecule ligands. Combining mutagenesis, molecular simulation and electrophysiological recording, a binding model for the probe activator, ztz240, in the gating charge pathway was defined. This information was used to establish a docking-based virtual screening assay targeting the defined ligand-binding pocket. Nine activators with five new chemotypes were identified, and in vivo experiments showed that three ligands binding to the gating charge pathway exhibit significant anti-epilepsy activity. Identification of various novel activators by virtual screening targeting the pocket supports the presence of a ligand-binding site in the gating charge pathway. The capability of the gating charge pathway to accommodate small molecule ligands offers new insights into the gating charge pathway of the therapeutically relevant KCNQ2 channel.
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Affiliation(s)
- Ping Li
- CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
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Phosphatidylinositol 4,5-bisphosphate alters pharmacological selectivity for epilepsy-causing KCNQ potassium channels. Proc Natl Acad Sci U S A 2013; 110:8726-31. [PMID: 23650395 DOI: 10.1073/pnas.1302167110] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Pharmacological augmentation of neuronal KCNQ muscarinic (M) currents by drugs such as retigabine (RTG) represents a first-in-class therapeutic to treat certain hyperexcitatory diseases by dampening neuronal firing. Whereas all five potassium channel subtypes (KCNQ1-KCNQ5) are found in the nervous system, KCNQ2 and KCNQ3 are the primary players that mediate M currents. We investigated the plasticity of subtype selectivity by two M current effective drugs, retigabine and zinc pyrithione (ZnPy). Retigabine is more effective on KCNQ3 than KCNQ2, whereas ZnPy is more effective on KCNQ2 with no detectable effect on KCNQ3. In neurons, activation of muscarinic receptor signaling desensitizes effects by retigabine but not ZnPy. Importantly, reduction of phosphatidylinositol 4,5-bisphosphate (PIP2) causes KCNQ3 to become sensitive to ZnPy but lose sensitivity to retigabine. The dynamic shift of pharmacological selectivity caused by PIP2 may be induced orthogonally by voltage-sensitive phosphatase, or conversely, abolished by mutating a PIP2 site within the S4-S5 linker of KCNQ3. Therefore, whereas drug-channel binding is a prerequisite, the drug selectivity on M current is dynamic and may be regulated by receptor signaling pathways via PIP2.
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Amabile CM, Vasudevan A. Ezogabine: A Novel Antiepileptic for Adjunctive Treatment of Partial-Onset Seizures. Pharmacotherapy 2013; 33:187-94. [DOI: 10.1002/phar.1185] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
| | - Arvind Vasudevan
- Neurology Hospitalist; Carolinas Medical Center - Northeast; Concord; North Carolina
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Zhang XF, Zhang D, Surowy CS, Yao B, Jarvis MF, McGaraughty S, Neelands TR. Development and validation of a medium-throughput electrophysiological assay for KCNQ2/3 channel openers using QPatch HT. Assay Drug Dev Technol 2012; 11:17-24. [PMID: 23002961 DOI: 10.1089/adt.2012.446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The KCNQ2/3 channel has emerged as a drug target for a number of neurological disorders including pain and epilepsy. Known KCNQ2/3 openers have effects on two distinct biophysical properties of the channel: (1) a hyperpolarizing shift in the voltage dependence of channel activation (V(1/2)), and (2) an increase in channel open probability or peak whole-cell current. The current high-throughput screening assays for KCNQ2/3 openers measure changes of channel activity at sub-peak conductances and the output measure is a combination of effects on V(1/2) shift and peak current. Here, we describe a medium-throughput electrophysiological assay for screening KCNQ2/3 openers using the QPatch HT platform. We employed a double-pulse protocol that measures the shift in V(1/2) and the change in current amplitude at peak conductance voltage. Retigabine along with novel KCNQ2/3 openers were evaluated in this assay. Three classes of KCNQ2/3 openers were identified based on the hyperpolarizing shift in V(1/2) and the change in peak current. All three classes of compounds caused a hyperpolarizing shift in V(1/2), but they were differentiated by their respective effects on peak current amplitude (increase, decrease, or only modestly affecting peak current amplitude). KCNQ2/3 blockers were also identified with this assay. These compounds blocked currents without affecting voltage-dependent activation. In summary, we have developed a medium-throughput assay that can reliably detect changes in the biophysical properties of the KCNQ2/3 channel, V(1/2), and peak current amplitude, and therefore may serve as a reliable assay to evaluate KCNQ2/3 openers and blockers.
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Affiliation(s)
- Xu-Feng Zhang
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064-6125, USA.
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Ezogabine (Retigabine) and Its Role in the Treatment of Partial-Onset Seizures: A Review. Clin Ther 2012; 34:1845-56.e1. [DOI: 10.1016/j.clinthera.2012.07.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 07/10/2012] [Accepted: 07/20/2012] [Indexed: 11/21/2022]
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Mocilac P, Donnelly K, Gallagher JF. Structural systematics and conformational analyses of a 3 × 3 isomer grid of fluoro-N-(pyridyl)benzamides: physicochemical correlations, polymorphism and isomorphous relationships. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 2012; 68:189-203. [DOI: 10.1107/s0108768112006799] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Accepted: 02/15/2012] [Indexed: 11/10/2022]
Abstract
An isomer grid of nine fluoro-N-(pyridyl)benzamides (Fxx) (x = para-/meta-/ortho-) has been examined to correlate structural relationships between the experimental crystal structure and ab initio calculations, based on the effect of fluorine (Fx) and pyridine N-atom (x) substitution patterns on molecular conformation. Eight isomers form N—H...N hydrogen bonds, and only one (Fom) aggregates via intermolecular N—H...O=C interactions exclusively. The Fpm and Fom isomers both crystallize as two polymorphs with Fpm_O (N—H...O=C chains, P-syn
) and Fpm_N (N—H...N chains, P-anti
) both in P21/n (Z′ = 1) differing by their meta-N atom locations (P-syn
, P-anti
; Npyridine referenced to N—H), whereas the disordered Fom_O is mostly P-syn
(Z′ = 6) compared with Fom_F (P-anti
) (Z′ = 1). In the Fxo triad twisted dimers form cyclic R
2
2(8) rings via N—H...N interactions. Computational modelling and conformational preferences of the isomer grid demonstrate that the solid-state conformations generally conform with the most stable calculated conformations except for the Fxm triad, while calculations of the Fox triad predict the intramolecular N—H...F interaction established by spectroscopic and crystallographic data. Comparisons of Fxx with related isomer grids reveal a high degree of similarity in solid-state aggregation and physicochemical properties, while correlation of the melting point behaviour indicates the significance of the substituent position on melting point behaviour rather than the nature of the substituent.
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Rejdak K, Luszczki JJ, Błaszczyk B, Chwedorowicz R, Czuczwar SJ. Clinical utility of adjunctive retigabine in partial onset seizures in adults. Ther Clin Risk Manag 2012; 8:7-14. [PMID: 22298949 PMCID: PMC3269346 DOI: 10.2147/tcrm.s22605] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In ~30% of epileptic patients, full seizure control is not possible, which is why the search for novel antiepileptic drugs continues. Retigabine exhibits a mechanism of action that is not shared by the available antiepileptic drugs. This antiepileptic enhances potassium currents via Kv7.2–7.3 channels, which very likely results from destabilization of a closed conformation or stabilization of the open conformation of the channels. Generally, the pharmacokinetics of retigabine are linear and the drug undergoes glucuronidation and acetylation. Results from clinical trials indicate that, in the form of an add-on therapy, retigabine proves an effective drug in refractory epileptic patients. The major adverse effects of the add-on treatment are dizziness, somnolence, and fatigue. This epileptic drug is also considered for other conditions – neuropathic pain, affective disorders, stroke, or even Alzheimer’s disease.
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Affiliation(s)
- Konrad Rejdak
- Department of Neurology, Medical University of Lublin, Lublin
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Yu H, Wu M, Townsend SD, Zou B, Long S, Daniels JS, McManus OB, Li M, Lindsley CW, Hopkins CR. Discovery, Synthesis, and Structure Activity Relationship of a Series of N-Aryl- bicyclo[2.2.1]heptane-2-carboxamides: Characterization of ML213 as a Novel KCNQ2 and KCNQ4 Potassium Channel Opener. ACS Chem Neurosci 2011; 2:572-577. [PMID: 22125664 DOI: 10.1021/cn200065b] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Herein we report the discovery, synthesis and evaluation of a series of N-Aryl-bicyclo[2.2.1]heptane-2-carboxamides as selective KCNQ2 (K(v)7.2) and KCNQ4 (K(v)7.4) channel openers. The best compound, 1 (ML213) has an EC(50) of 230 nM (KCNQ2) and 510 nM (KCNQ4) and is selective for KCNQ2 and KCNQ4 channels versus a large battery of related potassium channels, as well as affording modest brain levels. This represents the first report of unique selectivity profile for KCNQ2 and KCNQ4 over the other channels (KCNQ1/3/5) and as such should prove to be a valuable tool compound for understanding these channels in regulating neuronal activity.
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Affiliation(s)
- Haibo Yu
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Meng Wu
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Steven D. Townsend
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Beiyan Zou
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Shunyou Long
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - J. Scott Daniels
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Owen B. McManus
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Min Li
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Craig W. Lindsley
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Corey R. Hopkins
- Department of Neuroscience, High Throughput Biology Center, ‡Johns Hopkins Ion Channel Center (JHICC), Johns Hopkins University, Baltimore, Maryland 21205, United States
- Department of Pharmacology, ∥Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee 37232, United States
- Department of Chemistry, #Vanderbilt Specialized Chemistry Center for Accelerated Probe Development (MLPCN), Vanderbilt University, Nashville, Tennessee 37232, United States
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Abstract
Ezogabine is a new drug for adjunctive therapy of partial-onset seizures with a novel mechanism of action. As a potassium-channel facilitator, it promotes membrane repolarization and thus opposes rapid repetitive discharges. Side effects are typical for antiepileptic drugs and the safety profile is good. Occasional instances of urinary difficulty may require surveillance.
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KCNQ2/3 openers show differential selectivity and site of action across multiple KCNQ channels. J Neurosci Methods 2011; 200:54-62. [PMID: 21723881 DOI: 10.1016/j.jneumeth.2011.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2011] [Revised: 06/12/2011] [Accepted: 06/16/2011] [Indexed: 12/20/2022]
Abstract
KCNQ2/3 voltage-gated potassium channels conduct low-threshold, slowly activating and non-inactivating currents to repolarize the neuronal resting membrane potential. The channels negatively regulate neuronal excitability and KCNQ2/3 openers are efficacious in hyperexcited states such as epilepsy and pain. We developed and utilized thallium influx assays to profile novel KCNQ2/3 channel openers with respect to selectivity across KCNQ subtypes and on requirement for tryptophan 236 of KCNQ2, a critical residue for activity of the KCNQ opener retigabine. Using distinct chemical series of openers, a quinazolinone series showed relatively poor selectivity across multiple KCNQ channels and lacked activity at the KCNQ2(W236L) mutant channel. In contrast, several novel benzimidazole openers showed selectivity for KCNQ2/3 and KCNQ2 and retain activity at KCNQ2(W236L). Profiling of several hundred KCNQ2/3 openers across multiple diverse chemical series revealed that openers show differential degrees of selectivity across subtypes, with selectivity most difficult to achieve against KCNQ2. In addition, we report the significant finding that KCNQ openers can pharmacologically differentiate between homomeric and heteromeric channels containing subtypes in common. Moreover, most openers assayed were dependent on the W236 for activity, whereas only a small number appear to use a distinct mechanism. Collectively, we provide novel insights into the molecular pharmacology of KCNQ channels by demonstrating differential selectivity and site of action for KCNQ2/3 openers. The high-throughput thallium influx assays should prove useful for rapid characterization of KCNQ openers and in guiding efforts to identify selective compounds for advancement towards the clinic.
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