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Sinha AK, Lee C, Holt JC. KCNQ2/3 regulates efferent mediated slow excitation of vestibular afferents in mammals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.30.573731. [PMID: 38260489 PMCID: PMC10802244 DOI: 10.1101/2023.12.30.573731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Primary vestibular afferents transmit information from hair cells about head position and movement to the CNS, which is critical for maintaining balance, gaze stability and spatial navigation. The CNS, in turn, modulates hair cells and afferents via the efferent vestibular system (EVS) and its activation of several cholinergic signaling mechanisms. Electrical stimulation of EVS neurons gives rise to three kinetically- and mechanistically-distinct afferent responses including a slow excitation, a fast excitation, and a fast inhibition. EVS-mediated slow excitation is attributed to odd-numbered muscarinic acetylcholine receptors (mAChRs) on the afferent whose activation leads to the closure of a potassium conductance and increased afferent discharge. Likely effector candidates include low-threshold, voltage-gated potassium channels belonging to the KCNQ (Kv7.X) family, which are involved in neuronal excitability across the nervous system and are subject to mAChR modulation. Specifically, KCNQ2/3 heteromeric channels may be the molecular correlates for the M-current, a potassium current that is blocked following the activation of odd-numbered mAChRs. To this end, multiple members of the KCNQ channel family, including KCNQ2 and KCNQ3, are localized to several microdomains within vestibular afferent endings, where they influence afferent excitability and could be targeted by EVS neurons. Additionally, the relative expression of KCNQ subunits appears to vary across the sensory epithelia and among different afferent types. However, it is unclear which KCNQ channel subunits are targeted by mAChR activation and whether that also varies among different afferent classes. Here we show that EVS-mediated slow excitation is blocked and enhanced by the non-selective KCNQ channel blocker XE991 and opener retigabine, respectively. Using KCNQ subunit-selective drugs, we observed that a KCNQ2 blocker blocks the slow response in irregular afferents, while a KCNQ2/3 opener enhances slow responses in regular afferents. The KCNQ2 blockers did not appear to affect resting afferent discharge rates, while KCNQ2/3 or KCNQ2/4 openers decreased afferent excitability. Here, we show pharmacological evidence that KCNQ2/3 subunits are likely targeted by mAChR activation in mammalian vestibular afferents. Additionally, we show that KCNQ3 KO mice have altered resting discharge rate as well as EVS-mediated slow response. These data together suggest that KCNQ channels play a role in slow response and discharge rate of vestibular afferents, which can be modulated by EVS in mammals.
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Nuñez E, Jones F, Muguruza-Montero A, Urrutia J, Aguado A, Malo C, Bernardo-Seisdedos G, Domene C, Millet O, Gamper N, Villarroel A. Redox regulation of K V7 channels through EF3 hand of calmodulin. eLife 2023; 12:e81961. [PMID: 36803414 PMCID: PMC9988260 DOI: 10.7554/elife.81961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 02/10/2023] [Indexed: 02/22/2023] Open
Abstract
Neuronal KV7 channels, important regulators of cell excitability, are among the most sensitive proteins to reactive oxygen species. The S2S3 linker of the voltage sensor was reported as a site-mediating redox modulation of the channels. Recent structural insights reveal potential interactions between this linker and the Ca2+-binding loop of the third EF-hand of calmodulin (CaM), which embraces an antiparallel fork formed by the C-terminal helices A and B, constituting the calcium responsive domain (CRD). We found that precluding Ca2+ binding to the EF3 hand, but not to EF1, EF2, or EF4 hands, abolishes oxidation-induced enhancement of KV7.4 currents. Monitoring FRET (Fluorescence Resonance Energy Transfer) between helices A and B using purified CRDs tagged with fluorescent proteins, we observed that S2S3 peptides cause a reversal of the signal in the presence of Ca2+ but have no effect in the absence of this cation or if the peptide is oxidized. The capacity of loading EF3 with Ca2+ is essential for this reversal of the FRET signal, whereas the consequences of obliterating Ca2+ binding to EF1, EF2, or EF4 are negligible. Furthermore, we show that EF3 is critical for translating Ca2+ signals to reorient the AB fork. Our data are consistent with the proposal that oxidation of cysteine residues in the S2S3 loop relieves KV7 channels from a constitutive inhibition imposed by interactions between the EF3 hand of CaM which is crucial for this signaling.
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Affiliation(s)
| | - Frederick Jones
- School of Biomedical Sciences, Faculty of Biological Sciences, University of LeedsLeedsUnited Kingdom
| | | | | | | | | | | | - Carmen Domene
- Department of Chemistry, University of BathBathUnited Kingdom
- Department of Chemistry, University of OxfordOxfordUnited Kingdom
| | - Oscar Millet
- Protein Stability and Inherited Disease Laboratory, CIC bioGUNEDerioSpain
| | - Nikita Gamper
- School of Biomedical Sciences, Faculty of Biological Sciences, University of LeedsLeedsUnited Kingdom
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3
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Yang X, Chen S, Zhang S, Shi S, Zong R, Gao Y, Guan B, Gamper N, Gao H. Intracellular zinc protects Kv7 K + channels from Ca 2+/calmodulin-mediated inhibition. J Biol Chem 2022; 299:102819. [PMID: 36549648 PMCID: PMC9852549 DOI: 10.1016/j.jbc.2022.102819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/24/2022] Open
Abstract
Zinc (Zn) is an essential trace element; it serves as a cofactor for a great number of enzymes, transcription factors, receptors, and other proteins. Zinc is also an important signaling molecule, which can be released from intracellular stores into the cytosol or extracellular space, for example, during synaptic transmission. Amongst cellular effects of zinc is activation of Kv7 (KCNQ, M-type) voltage-gated potassium channels. Here, we investigated relationships between Kv7 channel inhibition by Ca2+/calmodulin (CaM) and zinc-mediated potentiation. We show that Zn2+ ionophore, zinc pyrithione (ZnPy), can prevent or reverse Ca2+/CaM-mediated inhibition of Kv7.2. In the presence of both Ca2+ and Zn2+, the Kv7.2 channels lose most of their voltage dependence and lock in an open state. In addition, we demonstrate that mutations that interfere with CaM binding to Kv7.2 and Kv7.3 reduced channel membrane abundance and activity, but these mutants retained zinc sensitivity. Moreover, the relative efficacy of ZnPy to activate these mutants was generally greater, compared with the WT channels. Finally, we show that zinc sensitivity was retained in Kv7.2 channels assembled with mutant CaM with all four EF hands disabled, suggesting that it is unlikely to be mediated by CaM. Taken together, our findings indicate that zinc is a potent Kv7 stabilizer, which may protect these channels from physiological inhibitory effects of neurotransmitters and neuromodulators, protecting neurons from overactivity.
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Affiliation(s)
- Xinhe Yang
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China,CSPC ZhongQi Pharmaceutical Technology (Shijiazhuang) Co, Ltd, Shijiazhuang, Hebei, China
| | - Shuai Chen
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Shuo Zhang
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Sai Shi
- Tianjin Key Laboratory of Function and Application of Biological Macromolecular Structures, School of Life Sciences, Tianjin University, Tianjin, China
| | - Rui Zong
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yiting Gao
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Bingcai Guan
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Nikita Gamper
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China; Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK.
| | - Haixia Gao
- Department of Pharmacology, Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei, China.
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4
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Kampa RP, Sęk A, Bednarczyk P, Szewczyk A, Calderone V, Testai L. Flavonoids as new regulators of mitochondrial potassium channels: contribution to cardioprotection. J Pharm Pharmacol 2022; 75:466-481. [PMID: 36508341 DOI: 10.1093/jpp/rgac093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/18/2022] [Indexed: 12/14/2022]
Abstract
Abstract
Objectives
Acute myocardial ischemia is one of the major causes of illness in western society. Reduced coronary blood supply leads to cell death and loss of cardiomyocyte population, resulting in serious and often irreversible consequences on myocardial function. Mitochondrial potassium (mitoK) channels have been identified as fine regulators of mitochondrial function and, consequently, in the metabolism of the whole cell, and in the mechanisms underlying the cardioprotection. Interestingly, mitoK channels represent a novel putative target for treating cardiovascular diseases, particularly myocardial infarction, and their modulators represent an interesting tool for pharmacological intervention. In this review, we took up the challenge of selecting flavonoids that show cardioprotective properties through the activation of mitoK channels.
Key findings
A brief overview of the main information on mitoK channels and their participation in the induction of cytoprotective processes was provided. Then, naringenin, quercetin, morin, theaflavin, baicalein, epigallocatechin gallate, genistein, puerarin, luteolin and proanthocyanidins demonstrated to be effective modulators of mitoK channels activity, mediating many beneficial effects.
Summary
The pathophysiological role of mitoK channels has been investigated as well as the impact of flavonoids on this target with particular attention to their potential role in the prevention of cardiovascular disorders.
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Affiliation(s)
- Rafał P Kampa
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS , Warsaw , Poland
- Department of Pharmacy, University of Pisa , Italy
| | - Aleksandra Sęk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS , Warsaw , Poland
- Faculty of Chemistry, University of Warsaw , Warsaw , Poland
| | - Piotr Bednarczyk
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences, SGGW , Warsaw , Poland
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology PAS , Warsaw , Poland
| | | | - Lara Testai
- Department of Pharmacy, University of Pisa , Italy
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5
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Emerging mechanisms involving brain Kv7 channel in the pathogenesis of hypertension. Biochem Pharmacol 2022; 206:115318. [PMID: 36283445 DOI: 10.1016/j.bcp.2022.115318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/15/2022] [Accepted: 10/17/2022] [Indexed: 12/14/2022]
Abstract
Hypertension is a prevalent health problem inducing many organ damages. The pathogenesis of hypertension involves a complex integration of different organ systems including the brain. The elevated sympathetic nerve activity is closely related to the etiology of hypertension. Ion channels are critical regulators of neuronal excitability. Several mechanisms have been proposed to contribute to hypothalamic-driven elevated sympathetic activity, including altered ion channel function. Recent findings indicate one of the voltage-gated potassium channels, Kv7 channels (M channels), plays a vital role in regulating cardiovascular-related neurons activity, and the expression of Kv7 channels is downregulated in hypertension. This review highlights recent findings that the Kv7 channels in the brain, blood vessels, and kidneys are emerging targets involved in the pathogenesis of hypertension, suggesting new therapeutic targets for treating drug-resistant, neurogenic hypertension.
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Zhuang W, Yan Z. The S2-S3 Loop of Kv7.4 Channels Is Essential for Calmodulin Regulation of Channel Activation. Front Physiol 2021; 11:604134. [PMID: 33551832 PMCID: PMC7854705 DOI: 10.3389/fphys.2020.604134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 12/23/2020] [Indexed: 11/16/2022] Open
Abstract
Kv7.4 (KCNQ4) voltage-gated potassium channels control excitability in the inner ear and the central auditory pathway. Mutations in Kv7.4 channels result in inherited progressive deafness in humans. Calmodulin (CaM) is crucial for regulating Kv7 channels, but how CaM affects Kv7 activity has remained unclear. Here, based on electrophysiological recordings, we report that the third EF hand (EF3) of CaM controls the calcium-dependent regulation of Kv7.4 activation and that the S2–S3 loop of Kv7.4 is essential for the regulation mediated by CaM. Overexpression of the mutant CaM1234, which loses the calcium binding ability of all four EF hands, facilitates Kv7.4 activation by accelerating activation kinetics and shifting the voltage dependence of activation leftwards. The single mutant CaM3, which loses the calcium binding ability of the EF3, phenocopies facilitating effects of CaM1234 on Kv7.4 activation. Kv7.4 channels co-expressed with wild-type (WT) CaM show inhibited activation when intracellular calcium levels increase, while Kv7.4 channels co-expressed with CaM1234 or CaM3 are insensitive to calcium. Mutations C156A, C157A, C158V, R159, and R161A, which are located within the Kv7.4 S2–S3 loop, dramatically facilitate activation of Kv7.4 channels co-expressed with WT CaM but have no effect on activation of Kv7.4 channels co-expressed with CaM3, indicating that these five mutations decrease the inhibitory effect of Ca2+/CaM. The double mutation C156A/R159A decreases Ca2+/CaM binding and completely abolishes CaM-mediated calcium-dependent regulation of Kv7.4 activation. Taken together, our results provide mechanistic insights into CaM regulation of Kv7.4 activation and highlight the crucial role of the Kv7.4 S2–S3 loop in CaM regulation.
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Affiliation(s)
- Wenhui Zhuang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China
| | - Zhiqiang Yan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Department of Physiology and Biophysics, School of Life Sciences, Human Phenome Institute, Fudan University, Shanghai, China.,Shenzhen Bay Laboratory, Institute of Molecular Physiology, Shenzhen, China
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7
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Abstract
Kv7.1-Kv7.5 (KCNQ1-5) K+ channels are voltage-gated K+ channels with major roles in neurons, muscle cells and epithelia where they underlie physiologically important K+ currents, such as neuronal M current and cardiac IKs. Specific biophysical properties of Kv7 channels make them particularly well placed to control the activity of excitable cells. Indeed, these channels often work as 'excitability breaks' and are targeted by various hormones and modulators to regulate cellular activity outputs. Genetic deficiencies in all five KCNQ genes result in human excitability disorders, including epilepsy, arrhythmias, deafness and some others. Not surprisingly, this channel family attracts considerable attention as potential drug targets. Here we will review biophysical properties and tissue expression profile of Kv7 channels, discuss recent advances in the understanding of their structure as well as their role in various neurological, cardiovascular and other diseases and pathologies. We will also consider a scope for therapeutic targeting of Kv7 channels for treatment of the above health conditions.
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8
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Kang PW, Westerlund AM, Shi J, White KM, Dou AK, Cui AH, Silva JR, Delemotte L, Cui J. Calmodulin acts as a state-dependent switch to control a cardiac potassium channel opening. SCIENCE ADVANCES 2020; 6:6/50/eabd6798. [PMID: 33310856 PMCID: PMC7732179 DOI: 10.1126/sciadv.abd6798] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/27/2020] [Indexed: 05/09/2023]
Abstract
Calmodulin (CaM) and phosphatidylinositol 4,5-bisphosphate (PIP2) are potent regulators of the voltage-gated potassium channel KCNQ1 (KV7.1), which conducts the cardiac I Ks current. Although cryo-electron microscopy structures revealed intricate interactions between the KCNQ1 voltage-sensing domain (VSD), CaM, and PIP2, the functional consequences of these interactions remain unknown. Here, we show that CaM-VSD interactions act as a state-dependent switch to control KCNQ1 pore opening. Combined electrophysiology and molecular dynamics network analysis suggest that VSD transition into the fully activated state allows PIP2 to compete with CaM for binding to VSD. This leads to conformational changes that alter VSD-pore coupling to stabilize open states. We identify a motif in the KCNQ1 cytosolic domain, which works downstream of CaM-VSD interactions to facilitate the conformational change. Our findings suggest a gating mechanism that integrates PIP2 and CaM in KCNQ1 voltage-dependent activation, yielding insights into how KCNQ1 gains the phenotypes critical for its physiological function.
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Affiliation(s)
- Po Wei Kang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Annie M Westerlund
- Department of Applied Physics, KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden
| | - Jingyi Shi
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Kelli McFarland White
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Alex K Dou
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Amy H Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Jonathan R Silva
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA
| | - Lucie Delemotte
- Department of Applied Physics, KTH Royal Institute of Technology, Science for Life Laboratory, Stockholm, Sweden.
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, and Cardiac Bioelectricity, and Arrhythmia Center, Washington University, St. Louis, MO 63130, USA.
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Núñez E, Muguruza-Montero A, Villarroel A. Atomistic Insights of Calmodulin Gating of Complete Ion Channels. Int J Mol Sci 2020; 21:ijms21041285. [PMID: 32075037 PMCID: PMC7072864 DOI: 10.3390/ijms21041285] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/07/2020] [Accepted: 02/12/2020] [Indexed: 12/13/2022] Open
Abstract
Intracellular calcium is essential for many physiological processes, from neuronal signaling and exocytosis to muscle contraction and bone formation. Ca2+ signaling from the extracellular medium depends both on membrane potential, especially controlled by ion channels selective to K+, and direct permeation of this cation through specialized channels. Calmodulin (CaM), through direct binding to these proteins, participates in setting the membrane potential and the overall permeability to Ca2+. Over the past years many structures of complete channels in complex with CaM at near atomic resolution have been resolved. In combination with mutagenesis-function, structural information of individual domains and functional studies, different mechanisms employed by CaM to control channel gating are starting to be understood at atomic detail. Here, new insights regarding four types of tetrameric channels with six transmembrane (6TM) architecture, Eag1, SK2/SK4, TRPV5/TRPV6 and KCNQ1–5, and its regulation by CaM are described structurally. Different CaM regions, N-lobe, C-lobe and EF3/EF4-linker play prominent signaling roles in different complexes, emerging the realization of crucial non-canonical interactions between CaM and its target that are only evidenced in the full-channel structure. Different mechanisms to control gating are used, including direct and indirect mechanical actuation over the pore, allosteric control, indirect effect through lipid binding, as well as direct plugging of the pore. Although each CaM lobe engages through apparently similar alpha-helices, they do so using different docking strategies. We discuss how this allows selective action of drugs with great therapeutic potential.
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Alaimo A, Etxeberria A, Gómez-Posada JC, Gomis-Perez C, Fernández-Orth J, Malo C, Villarroel A. Lack of correlation between surface expression and currents in epileptogenic AB-calmodulin binding domain Kv7.2 potassium channel mutants. Channels (Austin) 2019; 12:299-310. [PMID: 30126342 PMCID: PMC6161613 DOI: 10.1080/19336950.2018.1511512] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Heteromers of Kv7.2/Kv7.3 subunits constitute the main substrate of the neuronal M-current that limits neuronal hyper-excitability and firing frequency. Calmodulin (CaM) binding is essential for surface expression of Kv7 channels, and disruption of this interaction leads to diseases ranging from mild epilepsy to early onset encephalopathy. In this study, we addressed the impact of a charge neutralizing mutation located at the periphery of helix B (K526N). We found that, CaM binding and surface expression was impaired, although current amplitude was not altered. Currents were reduced at a faster rate after activation of a voltage-dependent phosphatase, suggesting that phosphatidylinositol-4,5-bisphosphate (PIP2) binding was weaker. In contrast, a charge neutralizing mutation located at the periphery of helix A (R333Q) did not affect CaM binding, but impaired trafficking and led to a reduction in current amplitude. Taken together, these results suggest that disruption of CaM-dependent or CaM-independent trafficking of Kv7.2/Kv7.3 channels can lead to pathology regardless of the consequences on the macroscopic ionic flow through the channel.
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Affiliation(s)
- Alessandro Alaimo
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Ainhoa Etxeberria
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Juan Camilo Gómez-Posada
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Carolina Gomis-Perez
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Juncal Fernández-Orth
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Covadonga Malo
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
| | - Alvaro Villarroel
- a Instituto Biofisika , Consejo Superior de Investigaciones Científicas, CSIC, UPV/EHU , Leioa , Spain
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11
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Calmodulin: A Multitasking Protein in Kv7.2 Potassium Channel Functions. Biomolecules 2018; 8:biom8030057. [PMID: 30022004 PMCID: PMC6164012 DOI: 10.3390/biom8030057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/13/2018] [Accepted: 07/14/2018] [Indexed: 02/06/2023] Open
Abstract
The ubiquitous calcium transducer calmodulin (CaM) plays a pivotal role in many cellular processes, regulating a myriad of structurally different target proteins. Indeed, it is unquestionable that CaM is the most relevant transductor of calcium signals in eukaryotic cells. During the last two decades, different studies have demonstrated that CaM mediates the modulation of several ion channels. Among others, it has been indicated that Kv7.2 channels, one of the members of the voltage gated potassium channel family that plays a critical role in brain excitability, requires CaM binding to regulate the different mechanisms that govern its functions. The purpose of this review is to provide an overview of the most recent advances in structure–function studies on the role of CaM regulation of Kv7.2 and the other members of the Kv7 family.
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12
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Chang A, Abderemane-Ali F, Hura GL, Rossen ND, Gate RE, Minor DL. A Calmodulin C-Lobe Ca 2+-Dependent Switch Governs Kv7 Channel Function. Neuron 2018; 97:836-852.e6. [PMID: 29429937 DOI: 10.1016/j.neuron.2018.01.035] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/07/2017] [Accepted: 01/12/2018] [Indexed: 12/22/2022]
Abstract
Kv7 (KCNQ) voltage-gated potassium channels control excitability in the brain, heart, and ear. Calmodulin (CaM) is crucial for Kv7 function, but how this calcium sensor affects activity has remained unclear. Here, we present X-ray crystallographic analysis of CaM:Kv7.4 and CaM:Kv7.5 AB domain complexes that reveal an Apo/CaM clamp conformation and calcium binding preferences. These structures, combined with small-angle X-ray scattering, biochemical, and functional studies, establish a regulatory mechanism for Kv7 CaM modulation based on a common architecture in which a CaM C-lobe calcium-dependent switch releases a shared Apo/CaM clamp conformation. This C-lobe switch inhibits voltage-dependent activation of Kv7.4 and Kv7.5 but facilitates Kv7.1, demonstrating that mechanism is shared by Kv7 isoforms despite the different directions of CaM modulation. Our findings provide a unified framework for understanding how CaM controls different Kv7 isoforms and highlight the role of membrane proximal domains for controlling voltage-gated channel function. VIDEO ABSTRACT.
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Affiliation(s)
- Aram Chang
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Fayal Abderemane-Ali
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Greg L Hura
- Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Nathan D Rossen
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Rachel E Gate
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA
| | - Daniel L Minor
- Cardiovascular Research Institute, University of California San Francisco, San Francisco, CA 94158, USA; Molecular Biophysics and Integrated Bio-imaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Departments of Biochemistry and Biophysics, and Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA 94158, USA; California Institute for Quantitative Biomedical Research, University of California San Francisco, San Francisco, CA 94158, USA; Kavli Institute for Fundamental Neuroscience, University of California San Francisco, San Francisco, CA 94158, USA.
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Muscarinic Acetylcholine Receptors and M-Currents Underlie Efferent-Mediated Slow Excitation in Calyx-Bearing Vestibular Afferents. J Neurosci 2017; 37:1873-1887. [PMID: 28093476 DOI: 10.1523/jneurosci.2322-16.2017] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 01/09/2017] [Accepted: 01/10/2017] [Indexed: 11/21/2022] Open
Abstract
Stimulation of vestibular efferent neurons excites calyx and dimorphic (CD) afferents. This excitation consists of fast and slow components that differ >100-fold in activation kinetics and response duration. In the turtle, efferent-mediated fast excitation arises in CD afferents when the predominant efferent neurotransmitter acetylcholine (ACh) activates calyceal nicotinic ACh receptors (nAChRs); however, it is unclear whether the accompanying efferent-mediated slow excitation is also attributed to cholinergic mechanisms. To identify synaptic processes underlying efferent-mediated slow excitation, we recorded from CD afferents innervating the turtle posterior crista during electrical stimulation of efferent neurons, in combination with pharmacological probes and mechanical stimulation. Efferent-mediated slow excitation was unaffected by nAChR compounds that block efferent-mediated fast excitation, but were mimicked by muscarine and antagonized by atropine, indicating that it requires ACh and muscarinic ACh receptor (mAChR) activation. Efferent-mediated slow excitation or muscarine application enhanced the sensitivity of CD afferents to mechanical stimulation, suggesting that mAChR activation increases afferent input impedance by closing calyceal potassium channels. These observations were consistent with suppression of a muscarinic-sensitive K+-current, or M-current. Immunohistochemistry for putative M-current candidates suggested that turtle CD afferents express KCNQ3, KCNQ4, and ERG1-3 potassium channel subunits. KCNQ channels were favored as application of the selective antagonist XE991 mimicked and occluded efferent-mediated slow excitation in CD afferents. These data highlight an efferent-mediated mechanism for enhancing afferent sensitivity. They further suggest that the clinical effectiveness of mAChR antagonists in treating balance disorders may also target synaptic mechanisms in the vestibular periphery, and that KCNQ channel modulators might offer similar therapeutic value.SIGNIFICANCE STATEMENT Targeting the efferent vestibular system (EVS) pharmacologically might prove useful in ameliorating some forms of vestibular dysfunction by modifying ongoing primary vestibular input. EVS activation engages several kinetically distinct synaptic processes that profoundly alter the discharge rate and sensitivity of first-order vestibular neurons. Efferent-mediated slow excitation of vestibular afferents is of considerable interest given its ability to elevate afferent activity over an extended time course. We demonstrate for the first time that efferent-mediated slow excitation of vestibular afferents is mediated by muscarinic acetylcholine receptor (mAChR) activation and the subsequent closure of KCNQ potassium channels. The clinical effectiveness of some anti-mAChR drugs in treating motion sickness suggest that we may, in fact, already be targeting the peripheral EVS.
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Augustynek B, Kunz WS, Szewczyk A. Guide to the Pharmacology of Mitochondrial Potassium Channels. Handb Exp Pharmacol 2017; 240:103-127. [PMID: 27838853 DOI: 10.1007/164_2016_79] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This chapter provides a critical overview of the available literature on the pharmacology of mitochondrial potassium channels. In the first part, the reader is introduced to the topic, and eight known protein contributors to the potassium permeability of the inner mitochondrial membrane are presented. The main part of this chapter describes the basic characteristics of each channel type mentioned in the introduction. However, the most important and valuable information included in this chapter concerns the pharmacology of mitochondrial potassium channels. Several available channel modulators are critically evaluated and rated by suitability for research use. The last figure of this chapter shows the results of this evaluation at a glance. Thus, this chapter can be very useful for beginners in this field. It is intended to be a time- and resource-saving guide for those searching for proper modulators of mitochondrial potassium channels.
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Affiliation(s)
- Bartłomiej Augustynek
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland
| | - Wolfram S Kunz
- Department of Epileptology, University of Bonn, Sigmund-Freud-Str. 25, 53105, Bonn, Germany
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Department of Biochemistry, Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093, Warsaw, Poland.
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Greene DL, Hoshi N. Modulation of Kv7 channels and excitability in the brain. Cell Mol Life Sci 2016; 74:495-508. [PMID: 27645822 DOI: 10.1007/s00018-016-2359-y] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/25/2016] [Accepted: 09/06/2016] [Indexed: 11/26/2022]
Abstract
Neuronal Kv7 channels underlie a voltage-gated non-inactivating potassium current known as the M-current. Due to its particular characteristics, Kv7 channels show pronounced control over the excitability of neurons. We will discuss various factors that have been shown to drastically alter the activity of this channel such as protein and phospholipid interactions, phosphorylation, calcium, and numerous neurotransmitters. Kv7 channels locate to key areas for the control of action potential initiation and propagation. Moreover, we will explore the dynamic surface expression of the channel modulated by neurotransmitters and neural activity. We will also focus on known principle functions of neural Kv7 channels: control of resting membrane potential and spiking threshold, setting the firing frequency, afterhyperpolarization after burst firing, theta resonance, and transient hyperexcitability from neurotransmitter-induced suppression of the M-current. Finally, we will discuss the contribution of altered Kv7 activity to pathologies such as epilepsy and cognitive deficits.
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Affiliation(s)
- Derek L Greene
- Department of Pharmacology, University of California, 360 Med Surge II, Irvine, CA, 92697, USA
| | - Naoto Hoshi
- Department of Pharmacology, University of California, 360 Med Surge II, Irvine, CA, 92697, USA.
- Department of Physiology and Biophysics, University of California, Irvine, USA.
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