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Schmidt CC, Tong R, Emptage NJ. GluN2A- and GluN2B-containing pre-synaptic N-methyl-d-aspartate receptors differentially regulate action potential-evoked Ca 2+ influx via modulation of SK channels. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230222. [PMID: 38853550 DOI: 10.1098/rstb.2023.0222] [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: 09/29/2023] [Accepted: 01/02/2024] [Indexed: 06/11/2024] Open
Abstract
N-methyl-d-aspartate receptors (NMDARs) play a pivotal role in synaptic plasticity. While the functional role of post-synaptic NMDARs is well established, pre-synaptic NMDAR (pre-NMDAR) function is largely unexplored. Different pre-NMDAR subunit populations are documented at synapses, suggesting that subunit composition influences neuronal transmission. Here, we used electrophysiological recordings at Schaffer collateral-CA1 synapses partnered with Ca2+ imaging and glutamate uncaging at boutons of CA3 pyramidal neurones to reveal two populations of pre-NMDARs that contain either the GluN2A or GluN2B subunit. Activation of the GluN2B population decreases action potential-evoked Ca2+ influx via modulation of small-conductance Ca2+-activated K+ channels, while activation of the GluN2A population does the opposite. Critically, the level of functional expression of the subunits is subject to homeostatic regulation, bidirectionally affecting short-term facilitation, thus providing a capacity for a fine adjustment of information transfer. This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
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Affiliation(s)
- Carla C Schmidt
- Department of Pharmacology, University of Oxford , Oxford OX1 3QT, UK
| | - Rudi Tong
- Department of Pharmacology, University of Oxford , Oxford OX1 3QT, UK
- Montreal Neurological Institute, 3801 University Street , Montreal, Quebec H3A 2B4, Canada
| | - Nigel J Emptage
- Department of Pharmacology, University of Oxford , Oxford OX1 3QT, UK
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Segura É, Zhao J, Broszczak M, Audet F, Sauvé R, Parent L. Investigating the Impact of Electrostatic Interactions on Calmodulin Binding and Ca 2+-Dependent Activation of the Calcium-Gated Potassium SK4 Channel. Int J Mol Sci 2024; 25:4255. [PMID: 38673845 PMCID: PMC11050286 DOI: 10.3390/ijms25084255] [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: 03/08/2024] [Revised: 04/03/2024] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
Ca2+ binding to the ubiquitous Ca2+ sensing protein calmodulin (CaM) activates the intermediate conductance Ca2+-activated SK4 channel. Potential hydrophilic pockets for CaM binding have been identified at the intracellular HA and HB helices in the C-terminal of SK4 from the three published cryo-EM structures of SK4. Single charge reversal substitutions at either site, significantly weakened the pull-down of SK4 by CaM wild-type (CaM), and decreased the TRAM-34 sensitive outward K+ current densities in native HEK293T cells when compared with SK4 WT measured under the same conditions. Only the doubly substituted SK4 R352D/R355D (HB helix) obliterated the CaM-mediated pull-down and thwarted outward K+ currents. However, overexpression of CaM E84K/E87K, which had been predicted to face the arginine doublet, restored the CaM-mediated pull-down of SK4 R352D/R355D and normalized its whole-cell current density. Virtual analysis of the putative salt bridges supports a unique role for the positively charged arginine doublet at the HB helix into anchoring the interaction with the negatively charged CaM glutamate 84 and 87 CaM. Our findings underscore the unique contribution of electrostatic interactions in carrying CaM binding onto SK4 and support the role of the C-terminal HB helix to the Ca2+-dependent gating process.
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Affiliation(s)
- Émilie Segura
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
| | - Juan Zhao
- Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (J.Z.); (M.B.)
| | - Marlena Broszczak
- Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (J.Z.); (M.B.)
| | - Frédéric Audet
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
| | - Rémy Sauvé
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Université de Montréal, 2900 Bd Édouard-Montpetit, Montréal, QC H3T 1J4, Canada;
| | - Lucie Parent
- Département de Pharmacologie et Physiologie, Faculté de Médecine, Centre de Recherche de l’Institut de Cardiologie de Montréal, Université de Montréal, Montréal, QC H1T 1C8, Canada; (É.S.); (F.A.)
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Cozzolino M, Panyi G. Intracellular acidity impedes KCa3.1 activation by Riluzole and SKA-31. Front Pharmacol 2024; 15:1380655. [PMID: 38638868 PMCID: PMC11024243 DOI: 10.3389/fphar.2024.1380655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/05/2024] [Indexed: 04/20/2024] Open
Abstract
Background The unique microenvironment in tumors inhibits the normal functioning of tumor-infiltrating lymphocytes, leading to immune evasion and cancer progression. Over-activation of KCa3.1 using positive modulators has been proposed to rescue the anti-tumor response. One of the key characteristics of the tumor microenvironment is extracellular acidity. Herein, we analyzed how intra- and extracellular pH affects K+ currents through KCa3.1 and if the potency of two of its positive modulators, Riluzole and SKA-31, is pH sensitive. Methods Whole-cell patch-clamp was used to measure KCa3.1 currents either in activated human peripheral lymphocytes or in CHO cells transiently transfected with either the H192A mutant or wild-type hKCa3.1 in combination with T79D-Calmodulin, or with KCa2.2. Results We found that changes in the intra- and extracellular pH minimally influenced the KCa3.1-mediated K+ current. Extracellular pH, in the range of 6.0-8.0, does not interfere with the capacity of Riluzole and SKA-31 to robustly activate the K+ currents through KCa3.1. Contrariwise, an acidic intracellular solution causes a slow, but irreversible loss of potency of both the activators. Using different protocols of perfusion and depolarization we demonstrated that the loss of potency is strictly time and pH-dependent and that this peculiar effect can be observed with a structurally similar channel KCa2.2. While two different point mutations of both KCa3.1 (H192A) and its associated protein Calmodulin (T79D) do not limit the effect of acidity, increasing the cytosolic Ca2+ concentration to saturating levels eliminated the loss-of-potency phenotype. Conclusion Based on our data we conclude that KCa3.1 currents are not sensitive the either the intracellular or the extracellular pH in the physiological and pathophysiological range. However, intracellular acidosis in T cells residing in the tumor microenvironment could hinder the potentiating effect of KCa3.1 positive modulators administered to boost their activity. Further research is warranted both to clarify the molecular interactions between the modulators and KCa3.1 at different intracellular pH conditions and to define whether this loss of potency can be observed in cancer models as well.
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Affiliation(s)
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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Liu Y, Xia D, Zhong L, Chen L, Zhang L, Ai M, Mei R, Pang R. Casein Kinase 2 Affects Epilepsy by Regulating Ion Channels: A Potential Mechanism. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2024; 23:894-905. [PMID: 37350003 DOI: 10.2174/1871527322666230622124618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 03/31/2023] [Accepted: 04/10/2023] [Indexed: 06/24/2023]
Abstract
Epilepsy, characterized by recurrent seizures and abnormal brain discharges, is the third most common chronic disorder of the Central Nervous System (CNS). Although significant progress has been made in the research on antiepileptic drugs (AEDs), approximately one-third of patients with epilepsy are refractory to these drugs. Thus, research on the pathogenesis of epilepsy is ongoing to find more effective treatments. Many pathological mechanisms are involved in epilepsy, including neuronal apoptosis, mossy fiber sprouting, neuroinflammation, and dysfunction of neuronal ion channels, leading to abnormal neuronal excitatory networks in the brain. CK2 (Casein kinase 2), which plays a critical role in modulating neuronal excitability and synaptic transmission, has been shown to be associated with epilepsy. However, there is limited research on the mechanisms involved. Recent studies have suggested that CK2 is involved in regulating the function of neuronal ion channels by directly phosphorylating them or their binding partners. Therefore, in this review, we will summarize recent research advances regarding the potential role of CK2 regulating ion channels in epilepsy, aiming to provide more evidence for future studies.
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Affiliation(s)
- Yan Liu
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
| | - Di Xia
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
| | - Lianmei Zhong
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
| | - Ling Chen
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
- Yunnan Provincial Clinical Research Center for Neurological Disease, Kunming, Yunnan, 650032, China
| | - Linming Zhang
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
| | - Mingda Ai
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
| | - Rong Mei
- Department of Neurology, the First People's Hospital of Yunnan Province, Kunming, Yunnan, 650034, China
| | - Ruijing Pang
- Department of Neurology, the First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, 650032, China
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Blankenship HE, Carter KA, Cassidy NT, Markiewicz AN, Thellmann MI, Sharpe AL, Freeman WM, Beckstead MJ. VTA dopamine neurons are hyperexcitable in 3xTg-AD mice due to casein kinase 2-dependent SK channel dysfunction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.16.567486. [PMID: 38014232 PMCID: PMC10680865 DOI: 10.1101/2023.11.16.567486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Alzheimer's disease (AD) patients exhibit neuropsychiatric symptoms that extend beyond classical cognitive deficits, suggesting involvement of subcortical areas. Here, we investigated the role of midbrain dopamine (DA) neurons in AD using the amyloid + tau-driven 3xTg-AD mouse model. We found deficits in reward-based operant learning in AD mice, suggesting possible VTA DA neuron dysregulation. Physiological assessment revealed hyperexcitability and disrupted firing in DA neurons caused by reduced activity of small-conductance calcium-activated potassium (SK) channels. RNA sequencing from contents of single patch-clamped DA neurons (Patch-seq) identified up-regulation of the SK channel modulator casein kinase 2 (CK2). Pharmacological inhibition of CK2 restored SK channel activity and normal firing patterns in 3xTg-AD mice. These findings shed light on a complex interplay between neuropsychiatric symptoms and subcortical circuits in AD, paving the way for novel treatment strategies.
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Kant S, Xing H, Liu Y, Harrington EO, Sellke FW, Feng J. Acute protein kinase C beta inhibition preserves coronary endothelial function after cardioplegic hypoxia/reoxygenation. JTCVS OPEN 2023; 15:242-251. [PMID: 37808045 PMCID: PMC10556935 DOI: 10.1016/j.xjon.2023.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 06/18/2023] [Accepted: 06/27/2023] [Indexed: 10/10/2023]
Abstract
Objective Protein kinase C (PKC) influences myocardial contractility and susceptibility to long-term cardiac dysfunction after ischemia-reperfusion injury. In diabetes, PKC inhibition has a protective effect in terms of microvascular dysfunction. SK-channel dysfunction also influences endothelial dysfunction in cardioplegic hypoxia-reoxygenation (CP-H/R). Here, we examine whether acute inhibition of PKC beta protects against CP-H/R-induced coronary endothelial and SK channel dysfunction. Methods Isolated mouse coronary arterioles, half pretreated with selective PKC inhibitor ruboxistaurin (RBX), were subjected to hyperkalemic, cardioplegic hypoxia (1 hour), and reoxygenation (1 hour) with Krebs buffer. Sham control vessels were continuously perfused with oxygenated Krebs buffer without CP-H/R. After 1 hour of reoxygenation, responses to the endothelium-dependent vasodilator adenosine-diphosphate (ADP) and the SK-channel activator NS309 were examined. Endothelial SK-specific potassium currents from mouse heart endothelial cells were examined using whole-cell path clamp configurations in response to NS309 and SK channel blockers apamin and TRAM34. Results CP-H/R significantly decreased coronary relaxation responses to ADP (P = .006) and NS309 (P = .0001) compared with the sham control group. Treatment with selective PKC beta inhibitor RBX significantly increased recovery of coronary relaxation responses to ADP (P = .031) and NS309 (P = .004) after CP-H/R. Treatment with RBX significantly increased NS309-mediated potassium currents following CP-H/R (P = .0415). Apamin and TRAM34 sensitive currents were significantly greater in CP-H/R + RBX versus CP-H/R mouse heart endothelial cells (P = .0027). Conclusions Acute inhibition of PKC beta significantly protected mouse coronary endothelial function after CP-H/R injury. This suggests that acute PKC beta inhibition may be a novel approach for preventing microvascular dysfunction during CP-H/R.
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Affiliation(s)
- Shawn Kant
- Division of Cardiothoracic Surgery, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI
| | - Hang Xing
- Division of Cardiothoracic Surgery, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI
| | - Yuhong Liu
- Division of Cardiothoracic Surgery, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI
| | - Elizabeth O. Harrington
- Vascular Research Laboratory, Department of Medicine, Providence VA Medical Center, Alpert Medical School of Brown University, Providence, RI
| | - Frank W. Sellke
- Division of Cardiothoracic Surgery, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI
| | - Jun Feng
- Division of Cardiothoracic Surgery, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RI
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Ma X, Miraucourt LS, Qiu H, Sharif-Naeini R, Khadra A. Modulation of SK Channels via Calcium Buffering Tunes Intrinsic Excitability of Parvalbumin Interneurons in Neuropathic Pain: A Computational and Experimental Investigation. J Neurosci 2023; 43:5608-5622. [PMID: 37451982 PMCID: PMC10401647 DOI: 10.1523/jneurosci.0426-23.2023] [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: 03/07/2023] [Revised: 05/11/2023] [Accepted: 05/18/2023] [Indexed: 07/18/2023] Open
Abstract
Parvalbumin-expressing interneurons (PVINs) play a crucial role within the dorsal horn of the spinal cord by preventing touch inputs from activating pain circuits. In both male and female mice, nerve injury decreases PVINs' output via mechanisms that are not fully understood. In this study, we show that PVINs from nerve-injured male mice change their firing pattern from tonic to adaptive. To examine the ionic mechanisms responsible for this decreased output, we used a reparametrized Hodgkin-Huxley type model of PVINs, which predicted (1) the firing pattern transition is because of an increased contribution of small conductance calcium-activated potassium (SK) channels, enabled by (2) impairment in intracellular calcium buffering systems. Analyzing the dynamics of the Hodgkin-Huxley type model further demonstrated that a generalized Hopf bifurcation differentiates the two types of state transitions observed in the transient firing of PVINs. Importantly, this predicted mechanism holds true when we embed the PVIN model within the neuronal circuit model of the spinal dorsal horn. To experimentally validate this hypothesized mechanism, we used pharmacological modulators of SK channels and demonstrated that (1) tonic firing PVINs from naive male mice become adaptive when exposed to an SK channel activator, and (2) adapting PVINs from nerve-injured male mice return to tonic firing on SK channel blockade. Our work provides important insights into the cellular mechanism underlying the decreased output of PVINs in the spinal dorsal horn after nerve injury and highlights potential pharmacological targets for new and effective treatment approaches to neuropathic pain.SIGNIFICANCE STATEMENT Parvalbumin-expressing interneurons (PVINs) exert crucial inhibitory control over Aβ fiber-mediated nociceptive pathways at the spinal dorsal horn. The loss of their inhibitory tone leads to neuropathic symptoms, such as mechanical allodynia, via mechanisms that are not fully understood. This study identifies the reduced intrinsic excitability of PVINs as a potential cause for their decreased inhibitory output in nerve-injured condition. Combining computational and experimental approaches, we predict a calcium-dependent mechanism that modulates PVINs' electrical activity following nerve injury: a depletion of cytosolic calcium buffer allows for the rapid accumulation of intracellular calcium through the active membranes, which in turn potentiates SK channels and impedes spike generation. Our results therefore pinpoint SK channels as potential therapeutic targets for treating neuropathic symptoms.
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Affiliation(s)
- Xinyue Ma
- Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Alan Edwards Center for Research on Pain, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Loïs S Miraucourt
- Alan Edwards Center for Research on Pain, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Haoyi Qiu
- Alan Edwards Center for Research on Pain, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Reza Sharif-Naeini
- Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Alan Edwards Center for Research on Pain, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Anmar Khadra
- Integrated Program in Neuroscience, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
- Department of Quantitative Life Sciences, McGill University, Montreal, Quebec H3G 1Y6, Canada
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8
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Zhang M, Luo Y, Wang J, Sun Y, Xie B, Zhang L, Cong B, Ma C, Wen D. Roles of nucleus accumbens shell small-conductance calcium-activated potassium channels in the conditioned fear freezing. J Psychiatr Res 2023; 163:180-194. [PMID: 37216772 DOI: 10.1016/j.jpsychires.2023.05.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 04/27/2023] [Accepted: 05/15/2023] [Indexed: 05/24/2023]
Abstract
BACKGROUND Posttraumatic stress disorder (PTSD), a psychiatric disorder caused by stressful events, is characterized by long-lasting fear memory. The nucleus accumbens shell (NAcS) is a key brain region that regulates fear-associated behavior. Small-conductance calcium-activated potassium channels (SK channels) play a key role in regulating the excitability of NAcS medium spiny neurons (MSNs) but their mechanisms of action in fear freezing are unclear. METHOD We established an animal model of traumatic memory using conditioned fear freezing paradigm, and investigated the alterations in SK channels of NAc MSNs subsequent to fear conditioning in mice. We then utilized an adeno-associated virus (AAV) transfection system to overexpress the SK3 subunit and explore the function of the NAcS MSNs SK3 channel in conditioned fear freezing. RESULTS Fear conditioning activated NAcS MSNs with enhanced excitability and reduced the SK channel-mediated medium after-hyperpolarization (mAHP) amplitude. The expression of NAcS SK3 were also reduced time-dependently. The overexpression of NAcS SK3 impaired conditioned fear consolidation without affecting conditioned fear expression, and blocked fear conditioning-induced alterations in NAcS MSNs excitability and mAHP amplitude. Additionally, the amplitudes of mEPSC, AMPAR/NMDAR ratio, and membrane surface GluA1/A2 expression in NAcS MSNs was increased by fear conditioning and returned to normal levels upon SK3 overexpression, indicating that fear conditioning-induced decrease of SK3 expression caused postsynaptic excitation by facilitating AMPAR transmission to the membrane. CONCLUSION These findings show that the NAcS MSNs SK3 channel plays a critical role in conditioned fear consolidation and that it may influence PTSD pathogenesis, making it a potential therapeutic target against PTSD.
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Affiliation(s)
- Minglong Zhang
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Yixiao Luo
- Hunan Province People's Hospital, The First-Affiliated Hospital of Hunan Normal University, Changsha, 410081, PR China
| | - Jian Wang
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Yufei Sun
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Bing Xie
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Ludi Zhang
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Bin Cong
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China
| | - Chunling Ma
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China.
| | - Di Wen
- College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Hebei Province, Shijiazhuang, 050017, PR China.
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Nam YW, Downey M, Rahman MA, Cui M, Zhang M. Channelopathy of small- and intermediate-conductance Ca 2+-activated K + channels. Acta Pharmacol Sin 2023; 44:259-267. [PMID: 35715699 PMCID: PMC9889811 DOI: 10.1038/s41401-022-00935-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 05/31/2022] [Indexed: 02/04/2023] Open
Abstract
Small- and intermediate-conductance Ca2+-activated K+ (KCa2.x/KCa3.1 also called SK/IK) channels are gated exclusively by intracellular Ca2+. The Ca2+ binding protein calmodulin confers sub-micromolar Ca2+ sensitivity to the channel-calmodulin complex. The calmodulin C-lobe is constitutively associated with the proximal C-terminus of the channel. Interactions between calmodulin N-lobe and the channel S4-S5 linker are Ca2+-dependent, which subsequently trigger conformational changes in the channel pore and open the gate. KCNN genes encode four subtypes, including KCNN1 for KCa2.1 (SK1), KCNN2 for KCa2.2 (SK2), KCNN3 for KCa2.3 (SK3), and KCNN4 for KCa3.1 (IK). The three KCa2.x channel subtypes are expressed in the central nervous system and the heart. The KCa3.1 subtype is expressed in the erythrocytes and the lymphocytes, among other peripheral tissues. The impact of dysfunctional KCa2.x/KCa3.1 channels on human health has not been well documented. Human loss-of-function KCa2.2 mutations have been linked with neurodevelopmental disorders. Human gain-of-function mutations that increase the apparent Ca2+ sensitivity of KCa2.3 and KCa3.1 channels have been associated with Zimmermann-Laband syndrome and hereditary xerocytosis, respectively. This review article discusses the physiological significance of KCa2.x/KCa3.1 channels, the pathophysiology of the diseases linked with KCa2.x/KCa3.1 mutations, the structure-function relationship of the mutant KCa2.x/KCa3.1 channels, and potential pharmacological therapeutics for the KCa2.x/KCa3.1 channelopathy.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Myles Downey
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, 02115, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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10
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Allosteric inhibitors targeting the calmodulin-PIP2 interface of SK4 K + channels for atrial fibrillation treatment. Proc Natl Acad Sci U S A 2022; 119:e2202926119. [PMID: 35969786 PMCID: PMC9407317 DOI: 10.1073/pnas.2202926119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Ca2+-activated SK4 K+ channel is gated by Ca2+-calmodulin (CaM) and is expressed in immune cells, brain, and heart. A cryoelectron microscopy (cryo-EM) structure of the human SK4 K+ channel recently revealed four CaM molecules per channel tetramer, where the apo CaM C-lobe and the holo CaM N-lobe interact with the proximal carboxyl terminus and the linker S4-S5, respectively, to gate the channel. Here, we show that phosphatidylinositol 4-5 bisphosphate (PIP2) potently activates SK4 channels by docking to the boundary of the CaM-binding domain. An allosteric blocker, BA6b9, was designed to act to the CaM-PIP2-binding domain, a previously untargeted region of SK4 channels, at the interface of the proximal carboxyl terminus and the linker S4-S5. Site-directed mutagenesis, molecular docking, and patch-clamp electrophysiology indicate that BA6b9 inhibits SK4 channels by interacting with two specific residues, Arg191 and His192 in the linker S4-S5, not conserved in SK1-SK3 subunits, thereby conferring selectivity and preventing the Ca2+-CaM N-lobe from properly interacting with the channel linker region. Immunohistochemistry of the SK4 channel protein in rat hearts showed a widespread expression in the sarcolemma of atrial myocytes, with a sarcomeric striated Z-band pattern, and a weaker occurrence in the ventricle but a marked incidence at the intercalated discs. BA6b9 significantly prolonged atrial and atrioventricular effective refractory periods in rat isolated hearts and reduced atrial fibrillation induction ex vivo. Our work suggests that inhibition of SK4 K+ channels by targeting drugs to the CaM-PIP2-binding domain provides a promising anti-arrhythmic therapy.
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11
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Metabolic regulation and dysregulation of endothelial small conductance calcium activated potassium channels. Eur J Cell Biol 2022; 101:151208. [DOI: 10.1016/j.ejcb.2022.151208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 02/06/2022] [Accepted: 02/07/2022] [Indexed: 12/13/2022] Open
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12
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Martucci LL, Cancela JM. Neurophysiological functions and pharmacological tools of acidic and non-acidic Ca2+ stores. Cell Calcium 2022; 104:102582. [DOI: 10.1016/j.ceca.2022.102582] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/07/2022] [Accepted: 03/23/2022] [Indexed: 02/08/2023]
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13
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Luján R, Merchán-Pérez A, Soriano J, Martín-Belmonte A, Aguado C, Alfaro-Ruiz R, Moreno-Martínez AE, DeFelipe J. Neuron Class and Target Variability in the Three-Dimensional Localization of SK2 Channels in Hippocampal Neurons as Detected by Immunogold FIB-SEM. Front Neuroanat 2022; 15:781314. [PMID: 34975419 PMCID: PMC8715088 DOI: 10.3389/fnana.2021.781314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 11/19/2021] [Indexed: 11/22/2022] Open
Abstract
Small-conductance calcium-activated potassium (SK) channels are crucial for learning and memory. However, many aspects of their spatial organization in neurons are still unknown. In this study, we have taken a novel approach to answering these questions combining a pre-embedding immunogold labeling with an automated dual-beam electron microscope that integrates focused ion beam milling and scanning electron microscopy (FIB/SEM) to gather 3D map ultrastructural and biomolecular information simultaneously. Using this new approach, we evaluated the number and variability in the density of extrasynaptic SK2 channels in 3D reconstructions from six dendritic segments of excitatory neurons and six inhibitory neurons present in the stratum radiatum of the CA1 region of the mouse. SK2 immunoparticles were observed throughout the surface of hippocampal neurons, either scattered or clustered, as well as at intracellular sites. Quantitative volumetric evaluations revealed that the extrasynaptic SK2 channel density in spines was seven times higher than in dendritic shafts and thirty-five times higher than in interneurons. Spines showed a heterogeneous population of SK2 expression, some spines having a high SK2 content, others having a low content and others lacking SK2 channels. SK2 immunonegative spines were significantly smaller than those immunopositive. These results show that SK2 channel density differs between excitatory and inhibitory neurons and demonstrates a large variability in the density of SK2 channels in spines. Furthermore, we demonstrated that SK2 expression was associated with excitatory synapses, but not with inhibitory synapses in CA1 pyramidal cells. Consequently, regulation of excitability and synaptic plasticity by SK2 channels is expected to be neuron class- and target-specific. These data show that immunogold FIB/SEM represent a new powerful EM tool to correlate structure and function of ion channels with nanoscale resolution.
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Affiliation(s)
- Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Angel Merchán-Pérez
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain
| | - Joaquim Soriano
- CRIB-Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Alejandro Martín-Belmonte
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Rocío Alfaro-Ruiz
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Ana Esther Moreno-Martínez
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
| | - Javier DeFelipe
- Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain.,Instituto Cajal (CSIC), Madrid, Spain
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14
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Yang CF, Tsai WC. Calmodulin: The switch button of calcium signaling. Tzu Chi Med J 2022; 34:15-22. [PMID: 35233351 PMCID: PMC8830543 DOI: 10.4103/tcmj.tcmj_285_20] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 03/17/2021] [Accepted: 05/06/2021] [Indexed: 11/25/2022] Open
Abstract
Calmodulin (CaM), a calcium sensor, decodes the critical calcium-dependent signals and converts them into the driving force to control various important cellular functions, such as ion transport. This small protein has a short central linker to connect two globular lobes and each unit is composed of a pair of homologous domains (HD) which are responsible for calcium binding. The conformation of each HD is sensitive to the levels of the intracellular Ca2+ concentrations while the flexible structure of the central domain enables its interactions with hundreds of cellular proteins. Apart from calcium binding, posttranslational modifications (PTMs) also contribute to the modulations of CaM functions by affecting its protein-protein interaction networks and hence drawing out the various downstream signaling cascades. In this mini-review, we first aim to elucidate the structural features of CaM and then overview the recent studies on the engagements of calcium binding and PTMs in Ca2+/CaM-mediated conformational alterations and signaling events. The mechanistic understanding of CaM working models is expected to be a key to decipher the precise role of CaM in cardiac physiology and disease pathology.
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15
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Barak-Broner N, Singer-Lahat D, Chikvashvili D, Lotan I. CK2 Phosphorylation Is Required for Regulation of Syntaxin 1A Activity in Ca 2+-Triggered Release in Neuroendocrine Cells. Int J Mol Sci 2021; 22:ijms222413556. [PMID: 34948351 PMCID: PMC8708312 DOI: 10.3390/ijms222413556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 12/29/2022] Open
Abstract
The polybasic juxtamembrane region (5RK) of the plasma membrane neuronal SNARE, syntaxin1A (Syx), was previously shown by us to act as a fusion clamp in PC12 cells, as charge neutralization of 5RK promotes spontaneous and inhibits Ca2+-triggered release. Using a Syx-based FRET probe (CSYS), we demonstrated that 5RK is required for a depolarization-induced Ca+2-dependent opening (close-to-open transition; CDO) of Syx, which involves the vesicular SNARE synaptobrevin2 and occurs concomitantly with Ca2+-triggered release. Here, we investigated the mechanism underlying the CDO requirement for 5RK and identified phosphorylation of Syx at Ser-14 (S14) by casein kinase 2 (CK2) as a crucial molecular determinant. Thus, following biochemical verification that both endogenous Syx and CSYS are constitutively S14 phosphorylated in PC12 cells, dynamic FRET analysis of phospho-null and phospho-mimetic mutants of CSYS and the use of a CK2 inhibitor revealed that the S14 phosphorylation confers the CDO requirement for 5RK. In accord, amperometric analysis of catecholamine release revealed that the phospho-null mutant does not support Ca2+-triggered release. These results identify a functionally important CK2 phosphorylation of Syx that is required for the 5RK-regulation of CDO and for concomitant Ca2+-triggered release. Further, also spontaneous release, conferred by charge neutralization of 5RK, was abolished in the phospho-null mutant.
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Affiliation(s)
- Noa Barak-Broner
- Department of Neurobiology Biochemistry & Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel;
| | - Dafna Singer-Lahat
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Dodo Chikvashvili
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Ilana Lotan
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
- Sagol School of Neuroscience, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel
- Correspondence:
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16
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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17
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Wang H, Zhao H, Chu Y, Feng J, Sun K. Assessing evidence for adaptive evolution in two hearing-related genes important for high-frequency hearing in echolocating mammals. G3 (BETHESDA, MD.) 2021; 11:jkab069. [PMID: 33784395 PMCID: PMC8049434 DOI: 10.1093/g3journal/jkab069] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 02/28/2021] [Indexed: 11/29/2022]
Abstract
High-frequency hearing is particularly important for echolocating bats and toothed whales. Previously, studies of the hearing-related genes Prestin, KCNQ4, and TMC1 documented that adaptive evolution of high-frequency hearing has taken place in echolocating bats and toothed whales. In this study, we present two additional candidate hearing-related genes, Shh and SK2, that may also have contributed to the evolution of echolocation in mammals. Shh is a member of the vertebrate Hedgehog gene family and is required in the specification of the mammalian cochlea. SK2 is expressed in both inner and outer hair cells, and it plays an important role in the auditory system. The coding region sequences of Shh and SK2 were obtained from a wide range of mammals with and without echolocating ability. The topologies of phylogenetic trees constructed using Shh and SK2 were different; however, multiple molecular evolutionary analyses showed that those two genes experienced different selective pressures in echolocating bats and toothed whales compared to nonecholocating mammals. In addition, several nominally significant positively selected sites were detected in the nonfunctional domain of the SK2 gene, indicating that different selective pressures were acting on different parts of the SK2 gene. This study has expanded our knowledge of the adaptive evolution of high-frequency hearing in echolocating mammals.
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Affiliation(s)
- Hui Wang
- College of Life Science, Jilin Agricultural University, Changchun 130118, China
| | - Hanbo Zhao
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun 130117, China
| | - Yujia Chu
- College of Life Science, Jilin Agricultural University, Changchun 130118, China
| | - Jiang Feng
- College of Life Science, Jilin Agricultural University, Changchun 130118, China
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun 130117, China
| | - Keping Sun
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun 130117, China
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18
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Etchepare L, Gréa H, Durand P, Bouchet D, Groc L. NMDA receptor membrane dynamics tunes the firing pattern of midbrain dopaminergic neurons. J Physiol 2021; 599:2933-2951. [PMID: 33651437 DOI: 10.1113/jp281104] [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: 11/21/2020] [Accepted: 02/22/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS NMDA receptors (NMDARs) expressed by dopamine neurons of the ventral tegmental area (VTA) play a central role in glutamate synapse plasticity, neuronal firing and adaptative behaviours. The NMDAR surface dynamics shapes synaptic adaptation in hippocampal networks, as well as associative memory. We investigated the basic properties and role of the NMDAR surface dynamics on cultured mesencephalic and VTA dopamine neurons in rodents. Using a combination of single molecule imaging and electrophysiological recordings, we demonstrate that NMDARs are highly diffusive at the surface of mesencephalic dopamine neurons. Unexpectedly, the NMDAR membrane dynamics per se regulates the firing pattern of VTA dopaminergic neurons, probably through a functional interplay between NMDARs receptors and small-conductance calcium-dependent potassium (SK) channels. ABSTRACT Midbrain dopaminergic (DA) neurons play a central role in major physiological brain functions, and their dysfunctions have been associated with neuropsychiatric diseases. The activity of midbrain DA neurons is controlled by ion channels and neurotransmitter receptors, such as the glutamate NMDA receptor (NMDAR) and small-conductance calcium-dependent potassium (SK) channels. However, the cellular mechanisms through which these channels tune the firing pattern of midbrain DA neurons remain unclear. Here, we investigated whether the surface dynamics and distribution of NMDARs tunes the firing pattern of midbrain DA neurons. Using a combination of single molecule imaging and electrophysiological recordings, we report that NMDARs are highly diffusive at the surface of cultured midbrain DA neurons from rodents and humans. Reducing acutely the NMDAR membrane dynamics, which leaves the ionotropic function of the receptor intact, robustly altered the firing pattern of midbrain DA neurons without altering synaptic glutamatergic transmission. The reduction of NMDAR surface dynamics reduced apamin (SK channel blocker)-induced firing change and the distribution of SK3 channels in DA neurons. Together, these data show that the surface dynamics of NMDAR, and not solely its ionotropic function, tune the firing pattern of midbrain DA neurons partly through a functional interplay with SK channel function.
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Affiliation(s)
- Laetitia Etchepare
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.,CNRS, IINS UMR 5297, Bordeaux, France
| | - Hélène Gréa
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.,CNRS, IINS UMR 5297, Bordeaux, France
| | - Pauline Durand
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.,CNRS, IINS UMR 5297, Bordeaux, France
| | - Delphine Bouchet
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.,CNRS, IINS UMR 5297, Bordeaux, France
| | - Laurent Groc
- Interdisciplinary Institute for Neuroscience, Université de Bordeaux, UMR 5297, Bordeaux, F-33000, France.,CNRS, IINS UMR 5297, Bordeaux, France
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19
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Zhang XD, Thai PN, Lieu DK, Chiamvimonvat N. Cardiac small-conductance calcium-activated potassium channels in health and disease. Pflugers Arch 2021; 473:477-489. [PMID: 33624131 PMCID: PMC7940285 DOI: 10.1007/s00424-021-02535-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 12/22/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK, KCa2) channels are encoded by KCNN genes, including KCNN1, 2, and 3. The channels play critical roles in the regulation of cardiac excitability and are gated solely by beat-to-beat changes in intracellular Ca2+. The family of SK channels consists of three members with differential sensitivity to apamin. All three isoforms are expressed in human hearts. Studies over the past two decades have provided evidence to substantiate the pivotal roles of SK channels, not only in healthy heart but also with diseases including atrial fibrillation (AF), ventricular arrhythmia, and heart failure (HF). SK channels are prominently expressed in atrial myocytes and pacemaking cells, compared to ventricular cells. However, the channels are significantly upregulated in ventricular myocytes in HF and pulmonary veins in AF models. Interests in cardiac SK channels are further fueled by recent studies suggesting the possible roles of SK channels in human AF. Therefore, SK channel may represent a novel therapeutic target for atrial arrhythmias. Furthermore, SK channel function is significantly altered by human calmodulin (CaM) mutations, linked to life-threatening arrhythmia syndromes. The current review will summarize recent progress in our understanding of cardiac SK channels and the roles of SK channels in the heart in health and disease.
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Affiliation(s)
- Xiao-Dong Zhang
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
| | - Phung N Thai
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA
| | - Deborah K Lieu
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, One Shields Avenue, GBSF 6315, Davis, CA, 95616, USA.
- Department of Veterans Affairs, Northern California Health Care System, 10535 Hospital Way, Mather, CA, 95655, USA.
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, 95616, USA.
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20
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Nam YW, Kong D, Wang D, Orfali R, Sherpa RT, Totonchy J, Nauli SM, Zhang M. Differential modulation of SK channel subtypes by phosphorylation. Cell Calcium 2021; 94:102346. [PMID: 33422768 PMCID: PMC8415101 DOI: 10.1016/j.ceca.2020.102346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 12/23/2020] [Accepted: 12/23/2020] [Indexed: 01/01/2023]
Abstract
Small-conductance Ca2+-activated K+ (SK) channels are voltage-independent and are activated by Ca2+ binding to the calmodulin constitutively associated with the channels. Both the pore-forming subunits and the associated calmodulin are subject to phosphorylation. Here, we investigated the modulation of different SK channel subtypes by phosphorylation, using the cultured endothelial cells as a tool. We report that casein kinase 2 (CK2) negatively modulates the apparent Ca2+ sensitivity of SK1 and IK channel subtypes by more than 5-fold, whereas the apparent Ca2+ sensitivity of the SK3 and SK2 subtypes is only reduced by ∼2-fold, when heterologously expressed on the plasma membrane of cultured endothelial cells. The SK2 channel subtype exhibits limited cell surface expression in these cells, partly as a result of the phosphorylation of its C-terminus by cyclic AMP-dependent protein kinase (PKA). SK2 channels expressed on the ER and mitochondria membranes may protect against cell death. This work reveals the subtype-specific modulation of the apparent Ca2+ sensitivity and subcellular localization of SK channels by phosphorylation in cultured endothelial cells.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Dezhi Kong
- Institute of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Dong Wang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Rinzhin T Sherpa
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Jennifer Totonchy
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Surya M Nauli
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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21
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Gripp KW, Smithson SF, Scurr IJ, Baptista J, Majumdar A, Pierre G, Williams M, Henderson LB, Wentzensen IM, McLaughlin H, Leeuwen L, Simon MEH, van Binsbergen E, Dinulos MBP, Kaplan JD, McRae A, Superti-Furga A, Good JM, Kutsche K. Syndromic disorders caused by gain-of-function variants in KCNH1, KCNK4, and KCNN3-a subgroup of K + channelopathies. Eur J Hum Genet 2021; 29:1384-1395. [PMID: 33594261 PMCID: PMC8440610 DOI: 10.1038/s41431-021-00818-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/18/2021] [Accepted: 01/22/2021] [Indexed: 12/13/2022] Open
Abstract
Decreased or increased activity of potassium channels caused by loss-of-function and gain-of-function (GOF) variants in the corresponding genes, respectively, underlies a broad spectrum of human disorders affecting the central nervous system, heart, kidney, and other organs. While the association of epilepsy and intellectual disability (ID) with variants affecting function in genes encoding potassium channels is well known, GOF missense variants in K+ channel encoding genes in individuals with syndromic developmental disorders have only recently been recognized. These syndromic phenotypes include Zimmermann–Laband and Temple–Baraitser syndromes, caused by dominant variants in KCNH1, FHEIG syndrome due to dominant variants in KCNK4, and the clinical picture associated with dominant variants in KCNN3. Here we review the presentation of these individuals, including five newly reported with variants in KCNH1 and three additional individuals with KCNN3 variants, all variants likely affecting function. There is notable overlap in the phenotypic findings of these syndromes associated with dominant KCNN3, KCNH1, and KCNK4 variants, sharing developmental delay and/or ID, coarse facial features, gingival enlargement, distal digital hypoplasia, and hypertrichosis. We suggest to combine the phenotypes and define a new subgroup of potassium channelopathies caused by increased K+ conductance, referred to as syndromic neurodevelopmental K+ channelopathies due to dominant variants in KCNH1, KCNK4, or KCNN3.
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Affiliation(s)
- Karen W Gripp
- Division of Medical Genetics, Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Sarah F Smithson
- Department of Clinical Genetics, University Hospitals Bristol and Weston, Bristol, UK
| | - Ingrid J Scurr
- Department of Clinical Genetics, University Hospitals Bristol and Weston, Bristol, UK
| | - Julia Baptista
- Exeter Genomics Laboratory, Royal Devon & Exeter NHS Foundation Trust, Exeter, UK.,College of Medicine and Health, University of Exeter, Exeter, UK
| | - Anirban Majumdar
- Department of Paediatric Neurology, Bristol Royal Hospital for Children, Bristol, UK
| | - Germaine Pierre
- Department of Paediatric Metabolic Medicine, Bristol Royal Hospital for Children, Bristol, UK
| | - Maggie Williams
- Bristol Genetics Laboratory, North Bristol NHS Trust, Bristol, UK
| | | | | | | | - Lisette Leeuwen
- Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Marleen E H Simon
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Ellen van Binsbergen
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Mary Beth P Dinulos
- Section of Genetics and Child Development, Children's Hospital at Dartmouth, Lebanon, NH, USA
| | - Julie D Kaplan
- Division of Medical Genetics, Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Anne McRae
- Division of Genetics, Birth Defects and Metabolism, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, IL, USA
| | - Andrea Superti-Furga
- Division of Genetic Medicine, Lausanne University Hospital, Lausanne, Switzerland
| | - Jean-Marc Good
- Division of Genetic Medicine, Lausanne University Hospital, Lausanne, Switzerland
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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22
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Nam YW, Cui M, Orfali R, Viegas A, Nguyen M, Mohammed EHM, Zoghebi KA, Rahighi S, Parang K, Zhang M. Hydrophobic interactions between the HA helix and S4-S5 linker modulate apparent Ca 2+ sensitivity of SK2 channels. Acta Physiol (Oxf) 2021; 231:e13552. [PMID: 32865319 PMCID: PMC7736289 DOI: 10.1111/apha.13552] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 08/09/2020] [Accepted: 08/20/2020] [Indexed: 12/11/2022]
Abstract
AIM Small-conductance Ca2+ -activated potassium (SK) channels are activated exclusively by increases in intracellular Ca2+ that binds to calmodulin constitutively associated with the channel. Wild-type SK2 channels are activated by Ca2+ with an EC50 value of ~0.3 μmol/L. Here, we investigate hydrophobic interactions between the HA helix and the S4-S5 linker as a major determinant of channel apparent Ca2+ sensitivity. METHODS Site-directed mutagenesis, electrophysiological recordings and molecular dynamic (MD) simulations were utilized. RESULTS Mutations that decrease hydrophobicity at the HA-S4-S5 interface lead to Ca2+ hyposensitivity of SK2 channels. Mutations that increase hydrophobicity result in hypersensitivity to Ca2+ . The Ca2+ hypersensitivity of the V407F mutant relies on the interaction of the cognate phenylalanine with the S4-S5 linker in the SK2 channel. Replacing the S4-S5 linker of the SK2 channel with the S4-S5 linker of the SK4 channel results in loss of the hypersensitivity caused by V407F. This difference between the S4-S5 linkers of SK2 and SK4 channels can be partially attributed to I295 equivalent to a valine in the SK4 channel. A N293A mutation in the S4-S5 linker also increases hydrophobicity at the HA-S4-S5 interface and elevates the channel apparent Ca2+ sensitivity. The double N293A/V407F mutations generate a highly Ca2+ sensitive channel, with an EC50 of 0.02 μmol/L. The MD simulations of this double-mutant channel revealed a larger channel cytoplasmic gate. CONCLUSION The electrophysiological data and MD simulations collectively suggest a crucial role of the interactions between the HA helix and S4-S5 linker in the apparent Ca2+ sensitivity of SK2 channels.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Adam Viegas
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Misa Nguyen
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Eman H M Mohammed
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Khalid A Zoghebi
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Simin Rahighi
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Keykavous Parang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
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Luo T, Li L, Peng Y, Xie R, Yan N, Fan H, Zhang Q. The MORN domain of Junctophilin2 regulates functional interactions with small-conductance Ca 2+ -activated potassium channel subtype2 (SK2). Biofactors 2021; 47:69-79. [PMID: 31904168 DOI: 10.1002/biof.1608] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 12/17/2019] [Indexed: 01/15/2023]
Abstract
Small-conductance Ca2+ -activated K+ channel subtype2 (SK2) are stable macromolecular complexes that regulate myocardial excitability and Ca2+ homeostasis. Junctophilin-2 (JP2) is a membrane-binding protein, which provides functional crosstalk by physically linking with the cell-surface and intracellular ion channels. We previously demonstrated that the MORN domain of JP2 interacts with SK2 channels. However, the roles of the JP2 MORN domain in regulating the precise subcellular localization and molecular modulation of SK2 have not yet been incompletely understood. In the present study, in vitro and in vivo assays were used to confirm the physical interactions between the SK2 channel and JP2 in H9c2 and HEK293 cells, with a concentration on the association between the C-terminus of SK2 channels and the MORN domain of JP2. Furthermore, the membrane expression of SK2 were found to be significantly impaired by the mutation or knockdown of JP2. Using immunofluorescence staining along with Golgi/early endosome markers, we studied the mechanisms of JP2-regulated SK2 membrane trafficking, which indicates that the JP2 MORN domain is probably necessary for the retrograde trafficking of SK2 channels. The functional study demonstrates that whole cell SK2 current densities recorded from the HEK293 cells co-expressing the JP2-MORN domain with SK2 were significantly augmented, compared with cells expressing SK2 alone. Our findings suggest that the MORN domain of JP2 directly modulates SK2 channel current amplitude and trafficking, through its interaction with an overlapping region of the JP2 MORN domain on the SK2 C-terminus.
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Affiliation(s)
- Tianxia Luo
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Liren Li
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Yanghao Peng
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Rongrong Xie
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Ningning Yan
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Hongkun Fan
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Qian Zhang
- Department of Physiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
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24
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Montenarh M, Götz C. Protein kinase CK2 and ion channels (Review). Biomed Rep 2020; 13:55. [PMID: 33082952 PMCID: PMC7560519 DOI: 10.3892/br.2020.1362] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/28/2020] [Indexed: 12/18/2022] Open
Abstract
Protein kinase CK2 appears as a tetramer or higher molecular weight oligomer composed of catalytic CK2α, CK2α' subunits and non-catalytic regulatory CK2β subunits or as individual subunits. It is implicated in a variety of different regulatory processes, such as Akt signalling, splicing and DNA repair within eukaryotic cells. The present review evaluates the influence of CK2 on ion channels in the plasma membrane. CK2 phosphorylates platform proteins such as calmodulin and ankyrin G, which bind to channel proteins for a physiological transport to and positioning into the membrane. In addition, CK2 directly phosphorylates a variety of channel proteins directly to regulate opening and closing of the channels. Thus, modulation of CK2 activities by specific inhibitors, by siRNA technology or by CRISPR/Cas technology has an influence on intracellular ion concentrations and thereby on cellular signalling. The physiological regulation of the intracellular ion concentration is important for cell survival and correct intracellular signalling. Disturbance of this regulation results in a variety of different diseases including epilepsy, heart failure, cystic fibrosis and diabetes. Therefore, these effects should be considered when using CK2 inhibition as a treatment option for cancer.
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Affiliation(s)
- Mathias Montenarh
- Medical Biochemistry and Molecular Biology, Saarland University, D-66424 Homburg, Saarland, Germany
| | - Claudia Götz
- Medical Biochemistry and Molecular Biology, Saarland University, D-66424 Homburg, Saarland, Germany
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25
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Impact of I SK Voltage and Ca 2+/Mg 2+-Dependent Rectification on Cardiac Repolarization. Biophys J 2020; 119:690-704. [PMID: 32668235 DOI: 10.1016/j.bpj.2020.06.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 06/02/2020] [Accepted: 06/10/2020] [Indexed: 10/24/2022] Open
Abstract
Cardiac small conductance Ca2+-activated K+ (SK) channels are activated solely by Ca2+, but the SK current (ISK) is inwardly rectified. However, the impact of inward rectification in shaping action potentials (APs) in ventricular cardiomyocytes under β-adrenergic stimulation or in disease states remains undefined. Two processes underlie this inward rectification: an intrinsic rectification caused by an electrostatic energy barrier from positively charged amino acids at the inner pore and a voltage-dependent Ca2+/Mg2+ block. Thus, Ca2+ has a biphasic effect on ISK, activating at low [Ca2+] yet inhibiting ISK at high [Ca2+]. We examined the effect of ISK rectification on APs in rat cardiomyocytes by simultaneously recording whole-cell apamin-sensitive currents and Ca2+ transients during an AP waveform and developed a computer model of SK channels with rectification features. The typical profile of ISK during AP clamp included an initial peak (mean 1.6 pA/pF) followed by decay to the point that submembrane [Ca2+] reached ∼10 μM. During the rest of the AP stimulus, ISK either plateaued or gradually increased as the cell repolarized and submembrane [Ca2+] decreased further. We used a six-state gating model combined with intrinsic and Ca2+/Mg2+-dependent rectification to simulate ISK and investigated the relative contributions of each type of rectification to AP shape. This SK channel model replicates key features of ISK recording during AP clamp showing that intrinsic rectification limits ISK at high Vm during the early and plateau phase of APs. Furthermore, the initial rise of Ca2+ transients activates, but higher [Ca2+] blocks SK channels, yielding a transient outward-like ISK trajectory. During the decay phase of Ca2+, the Ca2+-dependent block is released, causing ISK to rise again and contribute to repolarization. Therefore, ISK is an important repolarizing current, and the rectification characteristics of an SK channel determine its impact on early, plateau, and repolarization phases of APs.
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26
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Shrestha A, Sultana R, Adeniyi PA, Lee CC, Ogundele OM. Positive Modulation of SK Channel Impedes Neuron-Specific Cytoskeletal Organization and Maturation. Dev Neurosci 2020; 42:59-71. [PMID: 32580196 PMCID: PMC7486235 DOI: 10.1159/000507989] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 04/15/2020] [Indexed: 01/01/2023] Open
Abstract
N-methyl-D-aspartate receptor (NMDAR) modulates the structural plasticity of dendritic spines by impacting cytoskeletal organization and kinase signaling. In the developing nervous system, activation of NMDAR is pertinent for neuronal migration, neurite differentiation, and cellular organization. Given that small conductance potassium channels (SK2/3) repress NMDAR ionotropic signaling, this study highlights the impact of neonatal SK channel potentiation on adult cortical and hippocampal organization. Neonatal SK channel potentiation was performed by one injection of SK2/3 agonist (CyPPA) into the pallium of mice on postnatal day 2 (P2). When the animals reached adulthood (P55), the hippocampus and cortex were examined to assess neuronal maturation, lamination, and the distribution of synaptic cytoskeletal proteins. Immunodetection of neuronal markers in the brain of P2-treated P55 mice revealed the presence of immature neurons in the upper cortical layers (layers II-IV) and CA1 (hippocampus). Also, layer-dependent cortical-cell density was attenuated due to the ectopic localization of mature (NeuN+) and immature (Doublecortin+ [DCX+]) neurons in cortical layers II-IV. Similarly, the decreased count of NeuN+ neurons in the CA1 is accompanied by an increase in the number of immature DCX+ neurons. Ectopic localization of neurons in the upper cortex and CA1 caused the dramatic expression of neuron-specific cytoskeletal proteins. In line with this, structural deformity of neuronal projections and the loss of postsynaptic densities suggests that postsynaptic integrity is compromised in the SK2/3+ brain. From these results, we deduced that SK channel activity in the developing brain likely impacts neuronal maturation through its effects on cytoskeletal formation.
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Affiliation(s)
- Amita Shrestha
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, USA
| | - Razia Sultana
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, USA
| | - Philip A Adeniyi
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, USA
| | - Charles C Lee
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, USA
| | - Olalekan M Ogundele
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana, USA,
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27
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Kessi M, Chen B, Peng J, Tang Y, Olatoutou E, He F, Yang L, Yin F. Intellectual Disability and Potassium Channelopathies: A Systematic Review. Front Genet 2020; 11:614. [PMID: 32655623 PMCID: PMC7324798 DOI: 10.3389/fgene.2020.00614] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/20/2020] [Indexed: 01/15/2023] Open
Abstract
Intellectual disability (ID) manifests prior to adulthood as severe limitations to intellectual function and adaptive behavior. The role of potassium channelopathies in ID is poorly understood. Therefore, we aimed to evaluate the relationship between ID and potassium channelopathies. We hypothesized that potassium channelopathies are strongly associated with ID initiation, and that both gain- and loss-of-function mutations lead to ID. This systematic review explores the burden of potassium channelopathies, possible mechanisms, advancements using animal models, therapies, and existing gaps. The literature search encompassed both PubMed and Embase up to October 2019. A total of 75 articles describing 338 cases were included in this review. Nineteen channelopathies were identified, affecting the following genes: KCNMA1, KCNN3, KCNT1, KCNT2, KCNJ10, KCNJ6, KCNJ11, KCNA2, KCNA4, KCND3, KCNH1, KCNQ2, KCNAB1, KCNQ3, KCNQ5, KCNC1, KCNB1, KCNC3, and KCTD3. Twelve of these genes presented both gain- and loss-of-function properties, three displayed gain-of-function only, three exhibited loss-of-function only, and one had unknown function. How gain- and loss-of-function mutations can both lead to ID remains largely unknown. We identified only a few animal studies that focused on the mechanisms of ID in relation to potassium channelopathies and some of the few available therapeutic options (channel openers or blockers) appear to offer limited efficacy. In conclusion, potassium channelopathies contribute to the initiation of ID in several instances and this review provides a comprehensive overview of which molecular players are involved in some of the most prominent disease phenotypes.
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Affiliation(s)
- Miriam Kessi
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China.,Kilimanjaro Christian Medical University College, Moshi, Tanzania.,Mawenzi Regional Referral Hospital, Moshi, Tanzania
| | - Baiyu Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Yulin Tang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Eleonore Olatoutou
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fang He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Lifen Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China.,Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
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28
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Schulze F, Müller S, Guli X, Schumann L, Brehme H, Riffert T, Rohde M, Goerss D, Rackow S, Einsle A, Kirschstein T, Köhling R. CK2 Inhibition Prior to Status Epilepticus Persistently Enhances K Ca2 Function in CA1 Which Slows Down Disease Progression. Front Cell Neurosci 2020; 14:33. [PMID: 32174814 PMCID: PMC7054465 DOI: 10.3389/fncel.2020.00033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 02/04/2020] [Indexed: 12/19/2022] Open
Abstract
Purpose Epilepsy therapy is currently based on anti-seizure drugs that do not modify the course of the disease, i.e., they are not anti-epileptogenic in nature. Previously, we observed that in vivo casein kinase 2 (CK2) inhibition with 4,5,6,7-tetrabromotriazole (TBB) had anti-epileptogenic effects in the acute epilepsy slice model. Methods Here, we pretreated rats with TBB in vivo prior to the establishment of a pilocarpine-induced status epilepticus (SE) in order to analyze the long-term sequelae of such a preventive TBB administration. Results We found that TBB pretreatment delayed onset of seizures after pilocarpine and slowed down disease progression during epileptogenesis. This was accompanied with a reduced proportion of burst firing neurons in the CA1 area. Western blot analyses demonstrated that CA1 tissue from TBB-pretreated epileptic animals contained significantly less CK2 than TBB-pretreated controls. On the transcriptional level, TBB pretreatment led to differential gene expression changes of KCa2.2, but also of HCN1 and HCN3 channels. Thus, in the presence of the HCN channel blocker ZD7288, pretreatment with TBB rescued the afterhyperpolarizing potential (AHP) as well as spike frequency adaptation in epileptic animals, both of which are prominent functions of KCa2 channels. Conclusion These data indicate that TBB pretreatment prior to SE slows down disease progression during epileptogenesis involving increased KCa2 function, probably due to a persistently decreased CK2 protein expression.
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Affiliation(s)
- Felix Schulze
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Steffen Müller
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Xiati Guli
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Lukas Schumann
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Hannes Brehme
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Till Riffert
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Marco Rohde
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Doreen Goerss
- Department of Psychosomatic Medicine, Rostock University Medical Center, Rostock, Germany.,German Center for Neurodegenerative Diseases (DZNE), Göttingen, Germany
| | - Simone Rackow
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Anne Einsle
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Timo Kirschstein
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany.,Center of Transdisciplinary Neurosciences Rostock, University of Rostock, Rostock, Germany
| | - Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany.,Center of Transdisciplinary Neurosciences Rostock, University of Rostock, Rostock, Germany
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29
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Gill DF, Hansel C. Muscarinic Modulation of SK2-Type K + Channels Promotes Intrinsic Plasticity in L2/3 Pyramidal Neurons of the Mouse Primary Somatosensory Cortex. eNeuro 2020; 7:ENEURO.0453-19.2020. [PMID: 32005752 PMCID: PMC7294454 DOI: 10.1523/eneuro.0453-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 01/09/2020] [Accepted: 01/17/2020] [Indexed: 11/21/2022] Open
Abstract
Muscarinic acetylcholine receptors (mAChRs) inhibit small-conductance calcium-activated K+ channels (SK channels) and enhance synaptic weight via this mechanism. SK channels are also involved in activity-dependent plasticity of membrane excitability ("intrinsic plasticity"). Here, we investigate whether mAChR activation can drive SK channel-dependent intrinsic plasticity in L2/3 cortical pyramidal neurons. Using whole-cell patch-clamp recordings from these neurons in slices prepared from mouse primary somatosensory cortex (S1), we find that brief bath application of the mAChR agonist oxotremorine-m (oxo-m) causes long-term enhancement of excitability in wild-type mice that is not observed in mice deficient of SK channels of the SK2 isoform. Similarly, repeated injection of depolarizing current pulses into the soma triggers intrinsic plasticity that is absent from SK2 null mice. Intrinsic plasticity lowers spike frequency adaptation and attenuation of spike firing upon prolonged activation, consistent with SK channel modulation. Depolarization-induced plasticity is prevented by bath application of the protein kinase A (PKA) inhibitor H89, and the casein kinase 2 (CK2) inhibitor TBB, respectively. These findings point toward a recruitment of two known signaling pathways in SK2 regulation: SK channel trafficking (PKA) and reduction of the calcium sensitivity (CK2). Using mice with an inactivation of CaMKII (T305D mice), we show that intrinsic plasticity does not require CaMKII. Finally, we demonstrate that repeated injection of depolarizing pulses in the presence of oxo-m causes intrinsic plasticity that surpasses the plasticity amplitude reached by either manipulation alone. Our findings show that muscarinic activation enhances membrane excitability in L2/3 pyramidal neurons via a downregulation of SK2 channels.
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Affiliation(s)
- Daniel F Gill
- Department of Neurobiology, University of Chicago, Chicago, IL 60637
| | - Christian Hansel
- Department of Neurobiology, University of Chicago, Chicago, IL 60637
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30
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Oliver DK, Intson K, Sargin D, Power SK, McNabb J, Ramsey AJ, Lambe EK. Chronic social isolation exerts opposing sex-specific consequences on serotonin neuronal excitability and behaviour. Neuropharmacology 2020; 168:108015. [PMID: 32092443 DOI: 10.1016/j.neuropharm.2020.108015] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 02/07/2020] [Accepted: 02/18/2020] [Indexed: 12/18/2022]
Abstract
Social isolation raises the risk for mood disorders associated with serotonergic disruption. Yet, the underlying mechanisms by which the stress of social isolation increases risk are not well understood. Men and women are differently vulnerable; however, this modulating role of sex is challenging to study in humans under carefully controlled conditions. Therefore, we investigated this question in mice of both sexes, asking how the long-term stress of social isolation (from weaning into adulthood) affects the excitability of serotonin neurons in the dorsal raphe nucleus as well as mouse behaviour. The electrophysiological experiments and the first set of behavioural tests were conducted in young adult mice, with additional behavioural assays completed as the mice matured to assess the stability of their behavioural phenotype. We found that social isolation exerted seemingly-opposite effects in male and female mice, relative to their respective group-housed littermate controls. This distinctive pattern was observed for the effect of social isolation on the control of serotonergic neuron excitability via the SK family of calcium-activated potassium channels. Furthermore, we observed a similar and consistent pattern on tests relevant to assessing the efficacy of anti-depressant medicines, including the forced swim test, the novelty-suppressed feeding test, and the sucrose preference test. These findings underscore the concept that stress-elicited illness manifests distinctly in males and females and that treatments aimed at restoring serotonergic function may require a sex-specific approach. This article is part of the special issue entitled 'Serotonin Research: Crossing Scales and Boundaries'.
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Affiliation(s)
- David K Oliver
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Katheron Intson
- Department of Pharmacology and Toxicology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Derya Sargin
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Saige K Power
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Janice McNabb
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Amy J Ramsey
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of Pharmacology and Toxicology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Evelyn K Lambe
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of OBGYN, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of Psychiatry, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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31
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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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32
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Gain-of-Function Mutations in KCNN3 Encoding the Small-Conductance Ca 2+-Activated K + Channel SK3 Cause Zimmermann-Laband Syndrome. Am J Hum Genet 2019; 104:1139-1157. [PMID: 31155282 DOI: 10.1016/j.ajhg.2019.04.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/15/2019] [Indexed: 01/16/2023] Open
Abstract
Zimmermann-Laband syndrome (ZLS) is characterized by coarse facial features with gingival enlargement, intellectual disability (ID), hypertrichosis, and hypoplasia or aplasia of nails and terminal phalanges. De novo missense mutations in KCNH1 and KCNK4, encoding K+ channels, have been identified in subjects with ZLS and ZLS-like phenotype, respectively. We report de novo missense variants in KCNN3 in three individuals with typical clinical features of ZLS. KCNN3 (SK3/KCa2.3) constitutes one of three members of the small-conductance Ca2+-activated K+ (SK) channels that are part of a multiprotein complex consisting of the pore-forming channel subunits, the constitutively bound Ca2+ sensor calmodulin, protein kinase CK2, and protein phosphatase 2A. CK2 modulates Ca2+ sensitivity of the channels by phosphorylating SK-bound calmodulin. Patch-clamp whole-cell recordings of KCNN3 channel-expressing CHO cells demonstrated that disease-associated mutations result in gain of function of the mutant channels, characterized by increased Ca2+ sensitivity leading to faster and more complete activation of KCNN3 mutant channels. Pretreatment of cells with the CK2 inhibitor 4,5,6,7-tetrabromobenzotriazole revealed basal inhibition of wild-type and mutant KCNN3 channels by CK2. Analogous experiments with the KCNN3 p.Val450Leu mutant previously identified in a family with portal hypertension indicated basal constitutive channel activity and thus a different gain-of-function mechanism compared to the ZLS-associated mutant channels. With the report on de novo KCNK4 mutations in subjects with facial dysmorphism, hypertrichosis, epilepsy, ID, and gingival overgrowth, we propose to combine the phenotypes caused by mutations in KCNH1, KCNK4, and KCNN3 in a group of neurological potassium channelopathies caused by an increase in K+ conductance.
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33
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Hamilton S, Polina I, Terentyeva R, Bronk P, Kim TY, Roder K, Clements RT, Koren G, Choi BR, Terentyev D. PKA phosphorylation underlies functional recruitment of sarcolemmal SK2 channels in ventricular myocytes from hypertrophic hearts. J Physiol 2019; 598:2847-2873. [PMID: 30771223 PMCID: PMC7496687 DOI: 10.1113/jp277618] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Accepted: 02/08/2019] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes are dormant in health, yet become functional in cardiac disease. SK channels are voltage independent and their gating is controlled by intracellular [Ca2+ ] in a biphasic manner. Submicromolar [Ca2+ ] activates the channel via constitutively-bound calmodulin, whereas higher [Ca2+ ] exerts inhibitory effect during depolarization. Using a rat model of cardiac hypertrophy induced by thoracic aortic banding, we found that functional upregulation of SK2 channels in hypertrophic rat ventricular cardiomyocytes is driven by protein kinase A (PKA) phosphorylation. Using site-directed mutagenesis, we identified serine-465 as the site conferring PKA-dependent effects on SK2 channel function. PKA phosphorylation attenuates ISK rectification by reducing the Ca2+ /voltage-dependent inhibition of SK channels without changing their sensitivity to activating submicromolar [Ca2+ ]i . This mechanism underlies the functional recruitment of SK channels not only in cardiac disease, but also in normal physiology, contributing to repolarization under conditions of enhanced adrenergic drive. ABSTRACT Small-conductance Ca2+ -activated K+ (SK) channels expressed in ventricular myocytes (VMs) are dormant in health, yet become functional in cardiac disease. We aimed to test the hypothesis that post-translational modification of SK channels under conditions accompanied by enhanced adrenergic drive plays a central role in disease-related activation of the channels. We investigated this phenomenon using a rat model of hypertrophy induced by thoracic aortic banding (TAB). Western blot analysis using anti-pan-serine/threonine antibodies demonstrated enhanced phosphorylation of immunoprecipitated SK2 channels in VMs from TAB rats vs. Shams, which was reversible by incubation of the VMs with PKA inhibitor H89 (1 μmol L-1 ). Patch clamped VMs under basal conditions from TABs but not Shams exhibited outward current sensitive to the specific SK inhibitor apamin (100 nmol L-1 ), which was eliminated by inhibition of PKA (1 μmol L-1 ). Beta-adrenergic stimulation (isoproterenol, 100 nmol L-1 ) evoked ISK in VMs from Shams, resulting in shortening of action potentials in VMs and ex vivo optically mapped Sham hearts. Using adenoviral gene transfer, wild-type and mutant SK2 channels were overexpressed in adult rat VMs, revealing serine-465 as the site that elicits PKA-dependent phosphorylation effects on SK2 channel function. Concurrent confocal Ca2+ imaging experiments established that PKA phosphorylation lessens rectification of ISK via reduction Ca2+ /voltage-dependent inhibition of the channels at high [Ca2+ ] without affecting their sensitivity to activation by Ca2+ in the submicromolar range. In conclusion, upregulation of SK channels in diseased VMs is mediated by hyperadrenergic drive in cardiac hypertrophy, with functional effects on the channel conferred by PKA-dependent phosphorylation at serine-465.
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Affiliation(s)
- Shanna Hamilton
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Iuliia Polina
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Medical University of South Carolina, Department of Medicine, Division of Nephrology, Charleston, SC, USA
| | - Radmila Terentyeva
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
| | - Peter Bronk
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Tae Yun Kim
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Karim Roder
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Richard T Clements
- Department of Surgery, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Vascular Research Laboratory, Providence Veterans Affairs Medical Center, Providence, RI, USA
| | - Gideon Koren
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Bum-Rak Choi
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA
| | - Dmitry Terentyev
- Department of Medicine, The Warren Alpert Medical School of Brown University, Rhode Island Hospital, Cardiovascular Research Center, Providence, RI, USA.,Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH, USA.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA
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The multifunctional role of phospho-calmodulin in pathophysiological processes. Biochem J 2018; 475:4011-4023. [PMID: 30578290 PMCID: PMC6305829 DOI: 10.1042/bcj20180755] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 11/23/2018] [Accepted: 11/30/2018] [Indexed: 02/06/2023]
Abstract
Calmodulin (CaM) is a versatile Ca2+-sensor/transducer protein that modulates hundreds of enzymes, channels, transport systems, transcription factors, adaptors and other structural proteins, controlling in this manner multiple cellular functions. In addition to its capacity to regulate target proteins in a Ca2+-dependent and Ca2+-independent manner, the posttranslational phosphorylation of CaM by diverse Ser/Thr- and Tyr-protein kinases has been recognized as an important additional manner to regulate this protein by fine-tuning its functionality. In this review, we shall cover developments done in recent years in which phospho-CaM has been implicated in signalling pathways that are relevant for the onset and progression of diverse pathophysiological processes. These include diverse systems playing a major role in carcinogenesis and tumour development, prion-induced encephalopathies and brain hypoxia, melatonin-regulated neuroendocrine disorders, hypertension, and heavy metal-induced cell toxicity.
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Foster WJ, Taylor HBC, Padamsey Z, Jeans AF, Galione A, Emptage NJ. Hippocampal mGluR1-dependent long-term potentiation requires NAADP-mediated acidic store Ca 2+ signaling. Sci Signal 2018; 11:11/558/eaat9093. [PMID: 30482851 DOI: 10.1126/scisignal.aat9093] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Acidic organelles, such as endosomes and lysosomes, store Ca2+ that is released in response to intracellular increases in the second messenger nicotinic acid adenine dinucleotide phosphate (NAADP). In neurons, NAADP and Ca2+ signaling contribute to synaptic plasticity, a process of activity-dependent long-term potentiation (LTP) [or, alternatively, long-term depression (LTD)] of synaptic strength and neuronal transmission that is critical for neuronal function and memory formation. We explored the function of and mechanisms regulating acidic Ca2+ store signaling in murine hippocampal neurons. We found that metabotropic glutamate receptor 1 (mGluR1) was coupled to NAADP signaling that elicited Ca2+ release from acidic stores. In turn, this released Ca2+-mediated mGluR1-dependent LTP by transiently inhibiting SK-type K+ channels, possibly through the activation of protein phosphatase 2A. Genetically removing two-pore channels (TPCs), which are endolysosomal-specific ion channels, switched the polarity of plasticity from LTP to LTD, indicating the importance of specific receptor store coupling and providing mechanistic insight into how mGluR1 can produce both synaptic potentiation and synaptic depression.
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Affiliation(s)
- William J Foster
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Henry B C Taylor
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Zahid Padamsey
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Alexander F Jeans
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Nigel J Emptage
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
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36
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Bajorat R, Porath K, Kuhn J, Goßla E, Goerss D, Sellmann T, Köhling R, Kirschstein T. Oral administration of the casein kinase 2 inhibitor TBB leads to persistent K Ca2.2 channel up-regulation in the epileptic CA1 area and cortex, but lacks anti-seizure efficacy in the pilocarpine epilepsy model. Epilepsy Res 2018; 147:42-50. [PMID: 30219695 DOI: 10.1016/j.eplepsyres.2018.08.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/31/2018] [Accepted: 08/29/2018] [Indexed: 02/04/2023]
Abstract
Temporal lobe epilepsy (TLE) is the most common epileptic syndrome in adults and often presents with seizures that prove intractable with currently available anticonvulsants. Thus, there is still a need for new anti-seizure drugs in this condition. Recently, we found that the casein kinase 2 inhibitor 4,5,6,7-tetrabromotriazole (TBB) prevented the emergence of spontaneous epileptic discharges in an acute in vitro epilepsy model. This prompted us to study the anti-seizure effects of TBB in the pilocarpine model of chronic epilepsy in vivo. To this end, we performed long-term video-EEG monitoring lasting 78-167 days of nine chronically epileptic rats and obtained a baseline seizure rate of 3.3 ± 1.3 per day (baseline of 27-80 days). We found a significant age effect with more pronounced seizure rates in older animals as compared to younger ones. However, the seizure rate increased to 6.3 ± 2.2 per day during the oral TBB administration (treatment period of 21-50 days), and following discontinuation of TBB, this rate remained stable with 5.2 ± 1.4 seizures per day (follow-up of 30-55 days). After completing the video-EEG during the follow-up the hippocampal tissue was prepared and studied for the expression of the Ca2+-activated K+ channel KCa2.2. We found a significant up-regulation of KCa2.2 in the epileptic CA1 region and in the neocortex, but in no other hippocampal subfield. Hence, our findings indicate that oral administration of TBB leads to persistent up-regulation of KCa2.2 in the epileptic CA1 subfield and in the neocortex, but lacks anti-seizure efficacy in the pilocarpine epilepsy model.
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Affiliation(s)
- Rika Bajorat
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany; Department of Anesthesiology and Intensive Care Medicine, Rostock University Medical Centre, Rostock, Germany.
| | - Katrin Porath
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
| | - Johannes Kuhn
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
| | - Elke Goßla
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
| | - Doreen Goerss
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany; Department of Psychosomatic and Psychotherapeutic Medicine, Rostock University Medical Centre, Rostock, Germany.
| | - Tina Sellmann
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
| | - Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
| | - Timo Kirschstein
- Oscar Langendorff Institute of Physiology, Rostock University Medical Centre, Rostock, Germany.
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37
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Ko JS, Guo S, Hassel J, Celestino-Soper P, Lynnes TC, Tisdale JE, Zheng JJ, Taylor SE, Foroud T, Murray MD, Kovacs RJ, Li X, Lin SF, Chen Z, Vatta M, Chen PS, Rubart M. Ondansetron blocks wild-type and p.F503L variant small-conductance Ca 2+-activated K + channels. Am J Physiol Heart Circ Physiol 2018; 315:H375-H388. [PMID: 29677462 PMCID: PMC6139629 DOI: 10.1152/ajpheart.00479.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 04/11/2018] [Accepted: 04/11/2018] [Indexed: 01/24/2023]
Abstract
Apamin-sensitive small-conductance Ca2+-activated K+ (SK) current ( IKAS) is encoded by Ca2+-activated K+ channel subfamily N ( KCNN) genes. IKAS importantly contributes to cardiac repolarization in conditions associated with reduced repolarization reserve. To test the hypothesis that IKAS inhibition contributes to drug-induced long QT syndrome (diLQTS), we screened for KCNN variants among patients with diLQTS, determined the properties of heterologously expressed wild-type (WT) and variant KCNN channels, and determined if the 5-HT3 receptor antagonist ondansetron blocks IKAS. We searched 2,306,335 records in the Indiana Network for Patient Care and found 11 patients with diLQTS who had DNA available in the Indiana Biobank. DNA sequencing discovered a heterozygous KCNN2 variant (p.F503L) in a 52-yr-old woman presenting with corrected QT interval prolongation at baseline (473 ms) and further corrected QT interval lengthening (601 ms) after oral administration of ondansetron. That patient was also heterozygous for the p.S38G and p.P2835S variants of the QT-controlling genes KCNE1 and ankyrin 2, respectively. Patch-clamp experiments revealed that the p.F503L KCNN2 variant heterologously expressed in human embryonic kidney (HEK)-293 cells augmented Ca2+ sensitivity, increasing IKAS density. The fraction of total F503L-KCNN2 protein retained in the membrane was higher than that of WT KCNN2 protein. Ondansetron at nanomolar concentrations inhibited WT and p.F503L SK2 channels expressed in HEK-293 cells as well as native SK channels in ventricular cardiomyocytes. Ondansetron-induced IKAS inhibition was also demonstrated in Langendorff-perfused murine hearts. In conclusion, the heterozygous p.F503L KCNN2 variant increases Ca2+ sensitivity and IKAS density in transfected HEK-293 cells. Ondansetron at therapeutic (i.e., nanomolar) concentrations is a potent IKAS blocker. NEW & NOTEWORTHY We showed that ondansetron, a 5-HT3 receptor antagonist, blocks small-conductance Ca2+-activated K+ (SK) current. Ondansetron may be useful in controlling arrhythmias in which increased SK current is a likely contributor. However, its SK-blocking effects may also facilitate the development of drug-induced long QT syndrome.
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Affiliation(s)
- Jum-Suk Ko
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Wonkwang University School of Medicine and Hospital, Iksan, South Korea
| | - Shuai Guo
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Jonathan Hassel
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Patricia Celestino-Soper
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Ty C Lynnes
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - James E Tisdale
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | | | - Stanley E Taylor
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Tatiana Foroud
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael D Murray
- Department of Pharmacy Practice, College of Pharmacy, Purdue University , West Lafayette, Indiana
- Regenstrief Institute , Indianapolis, Indiana
| | - Richard J Kovacs
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Xiaochun Li
- Department of Biostatistics, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Shien-Fong Lin
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Matteo Vatta
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Medical and Molecular Genetics, Indiana University School of Medicine , Indianapolis, Indiana
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
| | - Peng-Sheng Chen
- The Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine , Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine , Indianapolis, Indiana
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38
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Lee CH, MacKinnon R. Activation mechanism of a human SK-calmodulin channel complex elucidated by cryo-EM structures. Science 2018; 360:508-513. [PMID: 29724949 DOI: 10.1126/science.aas9466] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 03/16/2018] [Indexed: 12/17/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK) channels mediate neuron excitability and are associated with synaptic transmission and plasticity. They also regulate immune responses and the size of blood cells. Activation of SK channels requires calmodulin (CaM), but how CaM binds and opens SK channels has been unclear. Here we report cryo-electron microscopy (cryo-EM) structures of a human SK4-CaM channel complex in closed and activated states at 3.4- and 3.5-angstrom resolution, respectively. Four CaM molecules bind to one channel tetramer. Each lobe of CaM serves a distinct function: The C-lobe binds to the channel constitutively, whereas the N-lobe interacts with the S4-S5 linker in a Ca2+-dependent manner. The S4-S5 linker, which contains two distinct helices, undergoes conformational changes upon CaM binding to open the channel pore. These structures reveal the gating mechanism of SK channels and provide a basis for understanding SK channel pharmacology.
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Affiliation(s)
- Chia-Hsueh Lee
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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39
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Plasma membrane insertion of KCa2.3 (SK3) is dependent upon the SNARE proteins, syntaxin-4 and SNAP23. PLoS One 2018; 13:e0196717. [PMID: 29768434 PMCID: PMC5955555 DOI: 10.1371/journal.pone.0196717] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 04/18/2018] [Indexed: 02/03/2023] Open
Abstract
We previously demonstrated endocytosis of KCa2.3 is caveolin-1-, dynamin II- and Rab5-dependent. KCa2.3 then enters Rab35/EPI64C- and RME-1-containing recycling endosomes and is returned to the plasma membrane (PM). Herein, we report on the mechanism by which KCa2.3 is inserted into the PM during recycling and following exit from the Golgi. We demonstrate KCa2.3 colocalizes with SNAP-23 and Syntaxin-4 in the PM of HEK and endothelial cells by confocal immunofluorescence microscopy. We further show KCa2.3 can be co-immunoprecipitated with SNAP-23 and Syntaxin-4. Overexpression of either Syntaxin-4 or SNAP-23 increased PM expression of KCa2.3, whereas shRNA-mediated knockdown of these SNARE proteins significantly decreased PM KCa2.3 expression, as assessed by cell surface biotinylation. Whole-cell patch clamp studies confirmed knockdown of SNAP-23 significantly decreased the apamin sensitive, KCa2.3 current. Using standard biotinylation/stripping methods, we demonstrate shRNA mediated knockdown of SNAP-23 inhibits recycling of KCa2.3 following endocytosis, whereas scrambled shRNA had no effect. Finally, using biotin ligase acceptor peptide (BLAP)-tagged KCa2.3, coupled with ER-resident biotin ligase (BirA), channels could be biotinylated in the ER after which we evaluated their rate of insertion into the PM following Golgi exit. We demonstrate knockdown of SNAP-23 significantly slows the rate of Golgi to PM delivery of KCa2.3. The inhibition of both recycling and PM delivery of newly synthesized KCa2.3 channels likely accounts for the decreased PM expression observed following knockdown of these SNARE proteins. In total, our results suggest insertion of KCa2.3 into the PM depends upon the SNARE proteins, Syntaxin-4 and SNAP-23.
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40
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Wang L, Chandaka GK, Foehring RC, Callaway JC, Armstrong WE. Changes in potassium channel modulation may underlie afterhyperpolarization plasticity in oxytocin neurons during late pregnancy. J Neurophysiol 2018. [PMID: 29537926 DOI: 10.1152/jn.00608.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Oxytocin (OT) neurons exhibit larger afterhyperpolarizations (AHPs) following spike trains during late pregnancy and lactation, times when these neurons fire in bursts and release more OT associated with labor and lactation. Calcium-dependent AHPs mediated by SK channels show this plasticity, and are reduced when the channel complex is phosphorylated by casein kinase 2 (CK2), and increased when dephosphorylated by protein phosphatase (PP)2A, by altering Ca2+ sensitivity. We compared AHP currents in supraoptic OT neurons after CK2 inhibition with 4,5,6,7-tetrabromobenzotriazole (TBB), or PP1-PP2A inhibition with okadaic acid (OA), to determine the roles of these enzymes in AHP plasticity, focusing on the peak current at 100 ms representing the SK-mediated, medium AHP (ImAHP). In slices from virgin and two groups of pregnant rats [embryonic days (E18-19, or E20-21], ImAHPs were evoked with 3-, 10-, and 17-spike trains (20 Hz). With 3-spike trains, TBB increased the ImAHP to the greatest extent in virgin compared with both groups of pregnant animals. A difference between virgins and E20-21 rats was also evident with a 10-spike train but the increases in ImAHPs were similar among groups with 17-spike trains. In contrast, OA, while consistently reducing the ImAHP in all cases, showed no differential effects among groups. In Western blots, CK2α, CK2β, PP2A-A, PP2A-B, and PP2A-C were found in supraoptic lysates, and expression of CK2α and CK2β was reduced in E20-21 rats. Coimmunoprecipitation revealed that calmodulin, CK2α, and PP2A-C were associated with SK3 protein. The results suggest that a downregulation of SK3-associated CK2α during late pregnancy may increase the sensitivity of the SK calmodulin (Ca2+) sensor for ImAHP, contributing to the enhanced ImAHP. NEW & NOTEWORTHY The article demonstrates for the first time that enhancement in spike afterhyperpolarizations in oxytocin neurons during pregnancy may be related to a downregulation in the small-conductance Ca2+-activated potassium channels (SK)/calmodulin binding protein casein kinase 2, which phosphorylates the SK channel complex and reduces its Ca2+ sensitivity.
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Affiliation(s)
- Lie Wang
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee
| | - Giri Kumar Chandaka
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee
| | - Robert C Foehring
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee.,Neuroscience Institute, University of Tennessee Health Science Center , Memphis, Tennessee
| | - Joseph C Callaway
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee.,Neuroscience Institute, University of Tennessee Health Science Center , Memphis, Tennessee
| | - William E Armstrong
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, Tennessee.,Neuroscience Institute, University of Tennessee Health Science Center , Memphis, Tennessee
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Ogundele OM, Lee CC. CaMKIIα expression in a mouse model of NMDAR hypofunction schizophrenia: Putative roles for IGF-1R and TLR4. Brain Res Bull 2018; 137:53-70. [PMID: 29137928 PMCID: PMC5835406 DOI: 10.1016/j.brainresbull.2017.11.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 11/03/2017] [Accepted: 11/08/2017] [Indexed: 12/29/2022]
Abstract
Schizophrenia (SCZ) is a neuropsychiatric disorder that is linked to social behavioral deficits and other negative symptoms associated with hippocampal synaptic dysfunction. Synaptic mechanism of schizophrenia is characterized by loss of hippocampal N-Methyl-d-Aspartate Receptor (NMDAR) activity (NMDAR hypofunction) and dendritic spines. Previous studies show that genetic deletion of hippocampal synaptic regulatory calcium-calmodulin dependent kinase II alpha (CaMKIIα) cause synaptic and behavioral defects associated with schizophrenia in mice. Although CaMKIIα is involved in modulation of NMDAR activity, it is equally linked to inflammatory and neurotropin signaling in neurons. Based on these propositions, we speculate that non-neurotransmitter upstream receptors associated with neurotropic and inflammatory signaling activities of CaMKIIα may alter its synaptic function. Besides, how these receptors (i.e. inflammatory and neurotropic receptors) alter CaMKIIα function (phosphorylation) relative to hippocampal NMDAR activity in schizophrenia is poorly understood. Here, we examined the relationship between toll-like receptor (TLR4; inflammatory), insulin-like growth factor receptor 1 (IGF-1R; neurotropic) and CaMKIIα expression in the hippocampus of behaviorally deficient schizophrenic mice after we induced schizophrenia through NMDAR inhibition. Schizophrenia was induced in WT (C57BL/6) mice through intraperitoneal administration of 30mg/Kg ketamine (NMDAR antagonist) for 5days (WT/SCZ). Five days after the last ketamine treatment, wild type schizophrenic mice show deficiencies in sociability and social novelty behavior. Furthermore, there was a significant decrease in hippocampal CaMKIIα (p<0.001) and IGF-1R (p<0.001) expression when assessed through immunoblotting and confocal immunofluorescence microscopy. Additionally, WT schizophrenic mice show an increased percentage of phosphorylated CaMKIIα in addition to upregulated TLR4 signaling (TLR4, NF-κB, and MAPK/ErK) in the hippocampus. To ascertain the functional link between TLR4, IGF-1R and CaMKIIα relative to NMDAR hypofunction in schizophrenia, we created hippocampal-specific TLR4 knockdown mouse using AAV-driven Cre-lox technique (TLR4 KD). Subsequently, we inhibited NMDAR function in TLR4 KD mice in an attempt to induce schizophrenia (TLR4 KD SCZ). Interestingly, IGF-1R and CaMKIIα expressions were preserved in the TLR4 KD hippocampus after attenuation of NMDAR function. Furthermore, TLR4 KD SCZ mice showed no prominent defects in sociability and social novelty behavior when compared with the control (WT). Our results show that a sustained IGF-1R expression may preserve the synaptic activity of CaMKIIα while TLR4 signaling ablates hippocampal CaMKIIα expression in NMDAR hypofunction schizophrenia. Together, we infer that IGF-1R depletion and increased TLR4 signaling are non-neurotransmitter pro-schizophrenic cues that can reduce synaptic CaMKIIα activity in a pharmacologic mouse model of schizophrenia.
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Affiliation(s)
- O M Ogundele
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States.
| | - C C Lee
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States.
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Müller S, Guli X, Hey J, Einsle A, Pfanz D, Sudmann V, Kirschstein T, Köhling R. Acute epileptiform activity induced by gabazine involves proteasomal rather than lysosomal degradation of K Ca2.2 channels. Neurobiol Dis 2018; 112:79-84. [PMID: 29330041 DOI: 10.1016/j.nbd.2018.01.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/21/2017] [Accepted: 01/08/2018] [Indexed: 01/01/2023] Open
Abstract
Voltage-independent, Ca2+-activated K+ channels (KCa2.2, previously named SK2) are typically activated during a train of action potentials, and hence, are powerful regulators of cellular excitability by generating an afterhyperpolarizing potential (AHP) following prolonged excitation. In the acute in vitro epilepsy model induced in hippocampal brain slice preparations by exposure to the GABAA receptor blocker gabazine (GZ), the AHP was previously shown to be significantly decreased. Here, we asked the question whether KCa2.2 protein degradation occurs in this model and which pathways are involved. To this end, we applied either gabazine alone or gabazine together with inhibitors of proteasomal and lysosomal protein degradation pathways, Z-Leu-Leu-Leu-CHO (MG132) and chloroquine (CQ), respectively. Western blot analysis showed a significant decrease of total KCa2.2 protein content in GZ-treated slices which could be rescued by concomitant incubation with MG132 and CQ. Using HEK293 cells transfected with a green fluorescent protein-tagged KCa2.2 construct, we demonstrated that proteasomal rather than lysosomal degradation was involved in KCa2.2 reduction. We then recorded epileptiform afterdischarges at hippocampal Schaffer collateral-CA1 synapses and confirmed that the GZ-induced increase was significantly attenuated by both MG132 and CQ, with MG132 being significantly more effective than CQ. Epileptiform afterdischarges were almost prevented by co-application of protein degradation inhibitors. Furthermore, epileptiform afterdischarges could be re-established by using the KCa2.2 blocker UCL 1684 suggesting involvement of KCa2.2. We conclude that in GZ-induced acute epilepsy, KCa2.2 degradation by proteasomal rather than lysosomal pathways plays a major role in the generation of epileptiform afterdischarges.
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Affiliation(s)
- Steffen Müller
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Xiati Guli
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Judith Hey
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Anne Einsle
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Daniela Pfanz
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Victor Sudmann
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
| | - Timo Kirschstein
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany.
| | - Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock, Germany
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Sultana R, Ghandi T, M. Davila A, Lee CC, Ogundele OM. Upregulated SK2 Expression and Impaired CaMKII Phosphorylation Are Shared Synaptic Defects Between 16p11.2del and 129S: Δdisc1 Mutant Mice. ASN Neuro 2018; 10:1759091418817641. [PMID: 33592687 PMCID: PMC6295693 DOI: 10.1177/1759091418817641] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/07/2018] [Accepted: 11/09/2018] [Indexed: 12/29/2022] Open
Abstract
Ion channel gating and kinase regulation of N-methyl-D-aspartate receptor 1 activity are fundamental mechanisms that govern synaptic plasticity. In this study, we showed that two mutant models (16p11.2del and Δdisc1 ) that recapitulate aspects of human cognitive disorders shared a similar defect in N-methyl-D-aspartate receptor 1-dependent synaptic function. Our results demonstrate that the expression of small-conductance potassium channels (SK2 or KCa2.2) was significantly upregulated in the hippocampus and prefrontal cortex of 16p11.2del and 129S:Δdisc1 mutant mice. Likewise, both mutant strains exhibited an impairment of T286 phosphorylation of calcium-calmodulin-dependent kinase II (CaMKII) in the hippocampus and prefrontal cortex. In vivo neural recordings revealed that increased SK2 expression and impaired T286 phosphorylation of CaMKII coincide with a prolonged interspike interval in the hippocampal cornu ammonis-1 (CA1) field for both 16p11.2del and 129S:Δdisc1 mutant mice. These findings suggest that alteration of small conductance channels and T286 phosphorylation of CaMKII are likely shared factors underlying behavioral changes in these two genetic mouse models.
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Affiliation(s)
- Razia Sultana
- Department of Comparative Biomedical Sciences, Louisiana State
University School of Veterinary Medicine, Baton Rouge, LA, USA
| | - Tanya Ghandi
- Department of Comparative Biomedical Sciences, Louisiana State
University School of Veterinary Medicine, Baton Rouge, LA, USA
| | - Alexandra M. Davila
- Department of Comparative Biomedical Sciences, Louisiana State
University School of Veterinary Medicine, Baton Rouge, LA, USA
| | - Charles C. Lee
- Department of Comparative Biomedical Sciences, Louisiana State
University School of Veterinary Medicine, Baton Rouge, LA, USA
| | - Olalekan M. Ogundele
- Department of Comparative Biomedical Sciences, Louisiana State
University School of Veterinary Medicine, Baton Rouge, LA, USA
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The Slo(w) path to identifying the mitochondrial channels responsible for ischemic protection. Biochem J 2017; 474:2067-2094. [PMID: 28600454 DOI: 10.1042/bcj20160623] [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: 01/12/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/19/2022]
Abstract
Mitochondria play an important role in tissue ischemia and reperfusion (IR) injury, with energetic failure and the opening of the mitochondrial permeability transition pore being the major causes of IR-induced cell death. Thus, mitochondria are an appropriate focus for strategies to protect against IR injury. Two widely studied paradigms of IR protection, particularly in the field of cardiac IR, are ischemic preconditioning (IPC) and volatile anesthetic preconditioning (APC). While the molecular mechanisms recruited by these protective paradigms are not fully elucidated, a commonality is the involvement of mitochondrial K+ channel opening. In the case of IPC, research has focused on a mitochondrial ATP-sensitive K+ channel (mitoKATP), but, despite recent progress, the molecular identity of this channel remains a subject of contention. In the case of APC, early research suggested the existence of a mitochondrial large-conductance K+ (BK, big conductance of potassium) channel encoded by the Kcnma1 gene, although more recent work has shown that the channel that underlies APC is in fact encoded by Kcnt2 In this review, we discuss both the pharmacologic and genetic evidence for the existence and identity of mitochondrial K+ channels, and the role of these channels both in IR protection and in regulating normal mitochondrial function.
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Honrath B, Krabbendam IE, Culmsee C, Dolga AM. Small conductance Ca 2+-activated K + channels in the plasma membrane, mitochondria and the ER: Pharmacology and implications in neuronal diseases. Neurochem Int 2017; 109:13-23. [PMID: 28511953 DOI: 10.1016/j.neuint.2017.05.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 04/24/2017] [Accepted: 05/08/2017] [Indexed: 12/14/2022]
Abstract
Ca2+-activated K+ (KCa) channels regulate after-hyperpolarization in many types of neurons in the central and peripheral nervous system. Small conductance Ca2+-activated K+ (KCa2/SK) channels, a subfamily of KCa channels, are widely expressed in the nervous system, and in the cardiovascular system. Voltage-independent SK channels are activated by alterations in intracellular Ca2+ ([Ca2+]i) which facilitates the opening of these channels through binding of Ca2+ to calmodulin that is constitutively bound to the SK2 C-terminus. In neurons, SK channels regulate synaptic plasticity and [Ca2+]i homeostasis, and a number of recent studies elaborated on the emerging neuroprotective potential of SK channel activation in conditions of excitotoxicity and cerebral ischemia, as well as endoplasmic reticulum (ER) stress and oxidative cell death. Recently, SK channels were discovered in the inner mitochondrial membrane and in the membrane of the endoplasmic reticulum which sheds new light on the underlying molecular mechanisms and pathways involved in SK channel-mediated protective effects. In this review, we will discuss the protective properties of pharmacological SK channel modulation with particular emphasis on intracellularly located SK channels as potential therapeutic targets in paradigms of neuronal dysfunction.
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Affiliation(s)
- Birgit Honrath
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Inge E Krabbendam
- Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Carsten Culmsee
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany
| | - Amalia M Dolga
- Institute of Pharmacology and Clinical Pharmacy, University of Marburg, 35043 Marburg, Germany; Faculty of Science and Engineering, Groningen Research Institute of Pharmacy, Department of Molecular Pharmacology, University of Groningen, 9713 AV Groningen, The Netherlands.
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Mahrous AA, Elbasiouny SM. SK channel inhibition mediates the initiation and amplitude modulation of synchronized burst firing in the spinal cord. J Neurophysiol 2017; 118:161-175. [PMID: 28356481 DOI: 10.1152/jn.00929.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 03/06/2017] [Accepted: 03/25/2017] [Indexed: 11/22/2022] Open
Abstract
Burst firing in motoneurons represents the basis for generating meaningful movements. Neuromodulators and inhibitory receptor blocker cocktails have been used for years to induce burst firing in vitro; however, the ionic mechanisms in the motoneuron membrane that contribute to burst initiation and amplitude modulation are not fully understood. Small conductance Ca2+-activated potassium (SK) channels regulate excitatory inputs and firing output of motoneurons and interneurons and therefore, are a candidate for mediating bursting behavior. The present study examines the role of SK channels in the generation of synchronized bursting using an in vitro spinal cord preparation from adult mice. Our results show that SK channel inhibition is required for both initiation and amplitude modulation of burst firing. Specifically, administration of the synaptic inhibition blockers strychnine and picrotoxin amplified the spinal circuit excitatory drive but not enough to evoke bursting. However, when SK channels were inhibited using various approaches, the excitatory drive was further amplified, and synchronized bursting was always evoked. Furthermore, graded SK channel inhibition modulated the amplitude of the burst in a dose-dependent manner, which was reversed using SK channel activators. Importantly, modulation of neuronal excitability using multiple approaches failed to mimic the effects of SK modulators, suggesting a specific role for SK channel inhibition in generating bursting. Both NMDA (N-methyl-d-aspartate) and AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionate) receptors were found to drive the synchronized bursts. The blocking of gap junctions did not disturb the burst synchrony. These results demonstrate a novel mechanistic role for SK channels in initiating and modulating burst firing of spinal motoneurons.NEW & NOTEWORTHY This study demonstrates that cholinergic inhibition or direct blockade of small conductance Ca2+-activated potassium (SK) channels facilitates burst firing in spinal motoneurons. The data provide a novel mechanistic explanation for synchronized bursting initiation and amplitude modulation through SK channel inhibition. Evidence also shows that synchronized bursting is driven by NMDA (N-methyl-d-aspartate) and AMPA (α-amino-3-hydroxy-5-methylisoxazole-4-propionate) receptors and that gap junctions do not mediate motoneuron synchronization in this behavior.
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Affiliation(s)
- Amr A Mahrous
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, Ohio; and
| | - Sherif M Elbasiouny
- Department of Neuroscience, Cell Biology, and Physiology, Boonshoft School of Medicine and College of Science and Mathematics, Wright State University, Dayton, Ohio; and .,Department of Biomedical, Industrial, and Human Factors Engineering, College of Engineering and Computer Science, Wright State University, Dayton, Ohio
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Kaczmarek LK, Aldrich RW, Chandy KG, Grissmer S, Wei AD, Wulff H. International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 2017; 69:1-11. [PMID: 28267675 PMCID: PMC11060434 DOI: 10.1124/pr.116.012864] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Richard W Aldrich
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - K George Chandy
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Stephan Grissmer
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Aguan D Wei
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Heike Wulff
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
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Hypocretin/Orexin Peptides Alter Spike Encoding by Serotonergic Dorsal Raphe Neurons through Two Distinct Mechanisms That Increase the Late Afterhyperpolarization. J Neurosci 2016; 36:10097-115. [PMID: 27683906 DOI: 10.1523/jneurosci.0635-16.2016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 08/11/2016] [Indexed: 01/02/2023] Open
Abstract
UNLABELLED Orexins (hypocretins) are neuropeptides that regulate multiple homeostatic processes, including reward and arousal, in part by exciting serotonergic dorsal raphe neurons, the major source of forebrain serotonin. Here, using mouse brain slices, we found that, instead of simply depolarizing these neurons, orexin-A altered the spike encoding process by increasing the postspike afterhyperpolarization (AHP) via two distinct mechanisms. This orexin-enhanced AHP (oeAHP) was mediated by both OX1 and OX2 receptors, required Ca(2+) influx, reversed near EK, and decayed with two components, the faster of which resulted from enhanced SK channel activation, whereas the slower component decayed like a slow AHP (sAHP), but was not blocked by UCL2077, an antagonist of sAHPs in some neurons. Intracellular phospholipase C inhibition (U73122) blocked the entire oeAHP, but neither component was sensitive to PKC inhibition or altered PKA signaling, unlike classical sAHPs. The enhanced SK current did not depend on IP3-mediated Ca(2+) release but resulted from A-current inhibition and the resultant spike broadening, which increased Ca(2+) influx and Ca(2+)-induced-Ca(2+) release, whereas the slower component was insensitive to these factors. Functionally, the oeAHP slowed and stabilized orexin-induced firing compared with firing produced by a virtual orexin conductance lacking the oeAHP. The oeAHP also reduced steady-state firing rate and firing fidelity in response to stimulation, without affecting the initial rate or fidelity. Collectively, these findings reveal a new orexin action in serotonergic raphe neurons and suggest that, when orexin is released during arousal and reward, it enhances the spike encoding of phasic over tonic inputs, such as those related to sensory, motor, and reward events. SIGNIFICANCE STATEMENT Orexin peptides are known to excite neurons via slow postsynaptic depolarizations. Here we elucidate a significant new orexin action that increases and prolongs the postspike afterhyperpolarization (AHP) in 5-HT dorsal raphe neurons and other arousal-system neurons. Our mechanistic studies establish involvement of two distinct Ca(2+)-dependent AHP currents dependent on phospholipase C signaling but independent of IP3 or PKC. Our functional studies establish that this action preserves responsiveness to phasic inputs while attenuating responsiveness to tonic inputs. Thus, our findings bring new insight into the actions of an important neuropeptide and indicate that, in addition to producing excitation, orexins can tune postsynaptic excitability to better encode the phasic sensory, motor, and reward signals expected during aroused states.
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Abstract
Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti–atrial fibrillation principle.
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50
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Meadows JP, Guzman-Karlsson MC, Phillips S, Brown JA, Strange SK, Sweatt JD, Hablitz JJ. Dynamic DNA methylation regulates neuronal intrinsic membrane excitability. Sci Signal 2016; 9:ra83. [PMID: 27555660 DOI: 10.1126/scisignal.aaf5642] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Epigenetic modifications, such as DNA cytosine methylation, contribute to the mechanisms underlying learning and memory by coordinating adaptive gene expression and neuronal plasticity. Transcription-dependent plasticity regulated by DNA methylation includes synaptic plasticity and homeostatic synaptic scaling. Memory-related plasticity also includes alterations in intrinsic membrane excitability mediated by changes in the abundance or activity of ion channels in the plasma membrane, which sets the threshold for action potential generation. We found that prolonged inhibition of DNA methyltransferase (DNMT) activity increased intrinsic membrane excitability of cultured cortical pyramidal neurons. Knockdown of the cytosine demethylase TET1 or inhibition of RNA polymerase blocked the increased membrane excitability caused by DNMT inhibition, suggesting that this effect was mediated by subsequent cytosine demethylation and de novo transcription. Prolonged DNMT inhibition blunted the medium component of the after-hyperpolarization potential, an effect that would increase neuronal excitability, and was associated with reduced expression of the genes encoding small-conductance Ca(2+)-activated K(+) (SK) channels. Furthermore, the specific SK channel blocker apamin increased neuronal excitability but was ineffective after DNMT inhibition. Our results suggested that DNMT inhibition enables transcriptional changes that culminate in decreased expression of SK channel-encoding genes and decreased activity of SK channels, thus providing a mechanism for the regulation of neuronal intrinsic membrane excitability by dynamic DNA cytosine methylation. This study has implications for human neurological and psychiatric diseases associated with dysregulated intrinsic excitability.
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Affiliation(s)
- Jarrod P Meadows
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Mikael C Guzman-Karlsson
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Scott Phillips
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jordan A Brown
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Sarah K Strange
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - J David Sweatt
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA. Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - John J Hablitz
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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