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Yakhnitsa V, Thompson J, Ponomareva O, Ji G, Kiritoshi T, Mahimainathan L, Molehin D, Pruitt K, Neugebauer V. Dysfunction of Small-Conductance Ca 2+-Activated Potassium (SK) Channels Drives Amygdala Hyperexcitability and Neuropathic Pain Behaviors: Involvement of Epigenetic Mechanisms. Cells 2024; 13:1055. [PMID: 38920682 PMCID: PMC11201618 DOI: 10.3390/cells13121055] [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: 04/29/2024] [Revised: 06/07/2024] [Accepted: 06/10/2024] [Indexed: 06/27/2024] Open
Abstract
Neuroplasticity in the amygdala and its central nucleus (CeA) is linked to pain modulation and pain behaviors, but cellular mechanisms are not well understood. Here, we addressed the role of small-conductance Ca2+-activated potassium (SK) channels in pain-related amygdala plasticity. The facilitatory effects of the intra-CeA application of an SK channel blocker (apamin) on the pain behaviors of control rats were lost in a neuropathic pain model, whereas an SK channel activator (NS309) inhibited pain behaviors in neuropathic rats but not in sham controls, suggesting the loss of the inhibitory behavioral effects of amygdala SK channels. Brain slice electrophysiology found hyperexcitability of CeA neurons in the neuropathic pain condition due to the loss of SK channel-mediated medium afterhyperpolarization (mAHP), which was accompanied by decreased SK2 channel protein and mRNA expression, consistent with a pretranscriptional mechanisms. The underlying mechanisms involved the epigenetic silencing of the SK2 gene due to the increased DNA methylation of the CpG island of the SK2 promoter region and the change in methylated CpG sites in the CeA in neuropathic pain. This study identified the epigenetic dysregulation of SK channels in the amygdala (CeA) as a novel mechanism of neuropathic pain-related plasticity and behavior that could be targeted to control abnormally enhanced amygdala activity and chronic neuropathic pain.
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Affiliation(s)
- Vadim Yakhnitsa
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Jeremy Thompson
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Olga Ponomareva
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Guangchen Ji
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Takaki Kiritoshi
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Lenin Mahimainathan
- Department of Pathology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Deborah Molehin
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Kevin Pruitt
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
- Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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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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Sang Y, Niu C, Xu J, Zhu T, You S, Wang J, Zhang L, Du X, Zhang H. PI4KIIIβ-Mediated Phosphoinositides Metabolism Regulates Function of the VTA Dopaminergic Neurons and Depression-Like Behavior. J Neurosci 2024; 44:e0555232024. [PMID: 38267258 PMCID: PMC10941068 DOI: 10.1523/jneurosci.0555-23.2024] [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: 03/27/2023] [Revised: 12/18/2023] [Accepted: 01/11/2024] [Indexed: 01/26/2024] Open
Abstract
Phosphoinositides, including phosphatidylinositol-4,5-bisphosphate (PIP2), play a crucial role in controlling key cellular functions such as membrane and vesicle trafficking, ion channel, and transporter activity. Phosphatidylinositol 4-kinases (PI4K) are essential enzymes in regulating the turnover of phosphoinositides. However, the functional role of PI4Ks and mediated phosphoinositide metabolism in the central nervous system has not been fully revealed. In this study, we demonstrated that PI4KIIIβ, one of the four members of PI4Ks, is an important regulator of VTA dopaminergic neuronal activity and related depression-like behavior of mice by controlling phosphoinositide turnover. Our findings provide new insights into possible mechanisms and potential drug targets for neuropsychiatric diseases, including depression. Both sexes were studied in basic behavior tests, but only male mice could be used in the social defeat depression model.
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Affiliation(s)
- Yuqi Sang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Chenxu Niu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Jiaxi Xu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Department of Physiology and Pathophysiology, Xi'an Jiaotong University Health Science Center, Xi'an, Shanxi 710061, China
| | - Tiantian Zhu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Shuangzhu You
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Jing Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Ludi Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Collaborative Innovation Center of Hebei Province for Mechanism, Diagnosis and Treatment of Neuropsychiatric Diseases, Hebei Medical University, Shijiazhuang, Hebei 050011, China
- Department of Psychiatry, The First Hospital of Hebei Medical University, Mental Health Institute of Hebei Medical University, Shijiazhuang, Hebei 050000, China
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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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Rahman MA, Orfali R, Dave N, Lam E, Naguib N, Nam YW, Zhang M. K Ca 2.2 (KCNN2): A physiologically and therapeutically important potassium channel. J Neurosci Res 2023; 101:1699-1710. [PMID: 37466411 PMCID: PMC10932612 DOI: 10.1002/jnr.25233] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 07/05/2023] [Accepted: 07/08/2023] [Indexed: 07/20/2023]
Abstract
One group of the K+ ion channels, the small-conductance Ca2+ -activated potassium channels (KCa 2.x, also known as SK channels family), is widely expressed in neurons as well as the heart, endothelial cells, etc. They are named small-conductance Ca2+ -activated potassium channels (SK channels) due to their comparatively low single-channel conductance of about ~10 pS. These channels are insensitive to changes in membrane potential and are activated solely by rises in the intracellular Ca2+ . According to the phylogenic research done on the KCa 2.x channels family, there are three channels' subtypes: KCa 2.1, KCa 2.2, and KCa 2.3, which are encoded by KCNN1, KCNN2, and KCNN3 genes, respectively. The KCa 2.x channels regulate neuronal excitability and responsiveness to synaptic input patterns. KCa 2.x channels inhibit excitatory postsynaptic potentials (EPSPs) in neuronal dendrites and contribute to the medium afterhyperpolarization (mAHP) that follows the action potential bursts. Multiple brain regions, including the hippocampus, express the KCa 2.2 channel encoded by the KCNN2 gene on chromosome 5. Of particular interest, rat cerebellar Purkinje cells express KCa 2.2 channels, which are crucial for various cellular processes during development and maturation. Patients with a loss-of-function of KCNN2 mutations typically exhibit extrapyramidal symptoms, cerebellar ataxia, motor and language developmental delays, and intellectual disabilities. Studies have revealed that autosomal dominant neurodevelopmental movement disorders resembling rodent symptoms are caused by heterozygous loss-of-function mutations, which are most likely to induce KCNN2 haploinsufficiency. The KCa 2.2 channel is a promising drug target for spinocerebellar ataxias (SCAs). SCAs exhibit the dysregulation of firing in cerebellar Purkinje cells which is one of the first signs of pathology. Thus, selective KCa 2.2 modulators are promising potential therapeutics for SCAs.
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Affiliation(s)
- Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Nikita Dave
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Elyn Lam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Nadeen Naguib
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, California 92618, USA
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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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Vasileva V, Chubinskiy-Nadezhdin V. Regulation of PIEZO1 channels by lipids and the structural components of extracellular matrix/cell cytoskeleton. J Cell Physiol 2023; 238:918-930. [PMID: 36947588 DOI: 10.1002/jcp.31001] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 01/31/2023] [Accepted: 03/02/2023] [Indexed: 03/23/2023]
Abstract
PIEZO1 is a mechanosensitive channel widely presented in eukaryotic organisms. Although the PIEZO family was discovered in 2010, main questions related to the molecular structure as well as to specific activation mechanisms and regulating pathways remain open. Two hypotheses of PIEZO1 gating were formulated: the first, as a dominant hypothesis, through the plasma membrane (force-from-lipids) and the second, via the participation of the cytoskeleton and the components of the extracellular matrix (ECM) (force-from-filaments). Many researchers provide convincing evidence for both hypotheses. It was demonstrated that PIEZO1 has a propeller-like shape forming a membrane curvature within the lipid bilayer. That suggests the participation of lipids in channel modulation, and many studies demonstrate the critical role of lipids and compounds that modify the lipid bilayer in the regulation of PIEZO1 properties. At the same time, the components of ECM and cortical cytoskeleton can be affected by the membrane curvature and thus have an impact on PIEZO1 properties. In living cells, PIEZO1 properties are reported to be critically dependent on channel microenvironment that is on combinatorial influence of plasma membrane, cytoskeleton and ECM. Thus, it is necessary to understand which factors can affect PIEZO1 and consider them when interpreting the role of PIEZO1 in various physiological processes. This review summarizes the current knowledge about regulation of Piezo1 by lipids and the components of ECM and cytoskeleton.
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Affiliation(s)
- Valeria Vasileva
- Group of Ionic Mechanisms of Cell Signalling, Department of Intracellular Signalling and Transport, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
| | - Vladislav Chubinskiy-Nadezhdin
- Group of Ionic Mechanisms of Cell Signalling, Department of Intracellular Signalling and Transport, Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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Yuan Z, Hansen SB. Cholesterol Regulation of Membrane Proteins Revealed by Two-Color Super-Resolution Imaging. MEMBRANES 2023; 13:membranes13020250. [PMID: 36837753 PMCID: PMC9966874 DOI: 10.3390/membranes13020250] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/05/2023] [Accepted: 02/07/2023] [Indexed: 05/15/2023]
Abstract
Cholesterol and phosphatidyl inositol 4,5-bisphosphate (PIP2) are hydrophobic molecules that regulate protein function in the plasma membrane of all cells. In this review, we discuss how changes in cholesterol concentration cause nanoscopic (<200 nm) movements of membrane proteins to regulate their function. Cholesterol is known to cluster many membrane proteins (often palmitoylated proteins) with long-chain saturated lipids. Although PIP2 is better known for gating ion channels, in this review, we will discuss a second independent function as a regulator of nanoscopic protein movement that opposes cholesterol clustering. The understanding of the movement of proteins between nanoscopic lipid domains emerged largely through the recent advent of super-resolution imaging and the establishment of two-color techniques to label lipids separate from proteins. We discuss the labeling techniques for imaging, their strengths and weakness, and how they are used to reveal novel mechanisms for an ion channel, transporter, and enzyme function. Among the mechanisms, we describe substrate and ligand presentation and their ability to activate enzymes, gate channels, and transporters rapidly and potently. Finally, we define cholesterol-regulated proteins (CRP) and discuss the role of PIP2 in opposing the regulation of cholesterol, as seen through super-resolution imaging.
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Affiliation(s)
- Zixuan Yuan
- Department of Molecular Medicine, Department of Neuroscience, UF Scripps, Jupiter, FL 33458, USA
- Department of Neuroscience UF Scripps, Jupiter, FL 33458, USA
- Skaggs Graduate School of Chemical and Biological Sciences, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Scott B. Hansen
- Department of Molecular Medicine, Department of Neuroscience, UF Scripps, Jupiter, FL 33458, USA
- Department of Neuroscience UF Scripps, Jupiter, FL 33458, USA
- Correspondence:
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Tiffner A, Hopl V, Derler I. CRAC and SK Channels: Their Molecular Mechanisms Associated with Cancer Cell Development. Cancers (Basel) 2022; 15:cancers15010101. [PMID: 36612099 PMCID: PMC9817886 DOI: 10.3390/cancers15010101] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/16/2022] [Accepted: 12/19/2022] [Indexed: 12/28/2022] Open
Abstract
Cancer represents a major health burden worldwide. Several molecular targets have been discovered alongside treatments with positive clinical outcomes. However, the reoccurrence of cancer due to therapy resistance remains the primary cause of mortality. Endeavors in pinpointing new markers as molecular targets in cancer therapy are highly desired. The significance of the co-regulation of Ca2+-permeating and Ca2+-regulated ion channels in cancer cell development, proliferation, and migration make them promising molecular targets in cancer therapy. In particular, the co-regulation of the Orai1 and SK3 channels has been well-studied in breast and colon cancer cells, where it finally leads to an invasion-metastasis cascade. Nevertheless, many questions remain unanswered, such as which key molecular components determine and regulate their interplay. To provide a solid foundation for a better understanding of this ion channel co-regulation in cancer, we first shed light on the physiological role of Ca2+ and how this ion is linked to carcinogenesis. Then, we highlight the structure/function relationship of Orai1 and SK3, both individually and in concert, their role in the development of different types of cancer, and aspects that are not yet known in this context.
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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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PKC regulation of ion channels: The involvement of PIP 2. J Biol Chem 2022; 298:102035. [PMID: 35588786 PMCID: PMC9198471 DOI: 10.1016/j.jbc.2022.102035] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022] Open
Abstract
Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate. The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various PKC isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on phosphatidylinositol (4,5) bisphosphate as a mechanistic endpoint to control channel gating.
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12
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Fluck EC, Yazici AT, Rohacs T, Moiseenkova-Bell VY. Structural basis of TRPV5 regulation by physiological and pathophysiological modulators. Cell Rep 2022; 39:110737. [PMID: 35476976 PMCID: PMC9088182 DOI: 10.1016/j.celrep.2022.110737] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/02/2022] [Accepted: 04/05/2022] [Indexed: 12/11/2022] Open
Abstract
Transient receptor potential vanilloid 5 (TRPV5) is a kidney-specific Ca2+-selective ion channel that plays a key role in Ca2+ homeostasis. The basal activity of TRPV5 is balanced through activation by phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and inhibition by Ca2+-bound calmodulin (CaM). Parathyroid hormone (PTH), the key extrinsic regulator of Ca2+ homeostasis, increases the activity of TRPV5 via protein kinase A (PKA)-mediated phosphorylation. Metabolic acidosis leads to reduced TRPV5 activity independent of PTH, causing hypercalciuria. Using cryoelectron microscopy (cryo-EM), we show that low pH inhibits TRPV5 by precluding PI(4,5)P2 activation. We capture intermediate conformations at low pH, revealing a transition from open to closed state. In addition, we demonstrate that PI(4,5)P2 is the primary modulator of channel gating, yet PKA controls TRPV5 activity by preventing CaM binding and channel inactivation. Our data provide detailed molecular mechanisms for regulation of TRPV5 by two key extrinsic modulators, low pH and PKA.
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Affiliation(s)
- Edwin C Fluck
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Aysenur Torun Yazici
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ 07103, USA
| | - Vera Y Moiseenkova-Bell
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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13
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Maltan L, Andova AM, Derler I. The Role of Lipids in CRAC Channel Function. Biomolecules 2022; 12:biom12030352. [PMID: 35327543 PMCID: PMC8944985 DOI: 10.3390/biom12030352] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/12/2022] [Accepted: 02/20/2022] [Indexed: 11/28/2022] Open
Abstract
The composition and dynamics of the lipid membrane define the physical properties of the bilayer and consequently affect the function of the incorporated membrane transporters, which also applies for the prominent Ca2+ release-activated Ca2+ ion channel (CRAC). This channel is activated by receptor-induced Ca2+ store depletion of the endoplasmic reticulum (ER) and consists of two transmembrane proteins, STIM1 and Orai1. STIM1 is anchored in the ER membrane and senses changes in the ER luminal Ca2+ concentration. Orai1 is the Ca2+-selective, pore-forming CRAC channel component located in the plasma membrane (PM). Ca2+ store-depletion of the ER triggers activation of STIM1 proteins, which subsequently leads to a conformational change and oligomerization of STIM1 and its coupling to as well as activation of Orai1 channels at the ER-PM contact sites. Although STIM1 and Orai1 are sufficient for CRAC channel activation, their efficient activation and deactivation is fine-tuned by a variety of lipids and lipid- and/or ER-PM junction-dependent accessory proteins. The underlying mechanisms for lipid-mediated CRAC channel modulation as well as the still open questions, are presented in this review.
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14
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Tiffner A, Hopl V, Schober R, Sallinger M, Grabmayr H, Höglinger C, Fahrner M, Lunz V, Maltan L, Frischauf I, Krivic D, Bhardwaj R, Schindl R, Hediger MA, Derler I. Orai1 Boosts SK3 Channel Activation. Cancers (Basel) 2021; 13:6357. [PMID: 34944977 PMCID: PMC8699475 DOI: 10.3390/cancers13246357] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 12/13/2021] [Indexed: 12/20/2022] Open
Abstract
The interplay of SK3, a Ca2+ sensitive K+ ion channel, with Orai1, a Ca2+ ion channel, has been reported to increase cytosolic Ca2+ levels, thereby triggering proliferation of breast and colon cancer cells, although a molecular mechanism has remained elusive to date. We show in the current study, via heterologous protein expression, that Orai1 can enhance SK3 K+ currents, in addition to constitutively bound calmodulin (CaM). At low cytosolic Ca2+ levels that decrease SK3 K+ permeation, co-expressed Orai1 potentiates SK3 currents. This positive feedback mechanism of SK3 and Orai1 is enabled by their close co-localization. Remarkably, we discovered that loss of SK3 channel activity due to overexpressed CaM mutants could be restored by Orai1, likely via its interplay with the SK3-CaM binding site. Mapping for interaction sites within Orai1, we identified that the cytosolic strands and pore residues are critical for a functional communication with SK3. Moreover, STIM1 has a bimodal role in SK3-Orai1 regulation. Under physiological ionic conditions, STIM1 is able to impede SK3-Orai1 interplay by significantly decreasing their co-localization. Forced STIM1-Orai1 activity and associated Ca2+ influx promote SK3 K+ currents. The dynamic regulation of Orai1 to boost endogenous SK3 channels was also determined in the human prostate cancer cell line LNCaP.
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Affiliation(s)
- Adéla Tiffner
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Valentina Hopl
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Romana Schober
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
- Gottfried Schatz Research Centre, Medical University of Graz, A-8010 Graz, Austria; (D.K.); (R.S.)
| | - Matthias Sallinger
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Herwig Grabmayr
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Carmen Höglinger
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Marc Fahrner
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Victoria Lunz
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Lena Maltan
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Irene Frischauf
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
| | - Denis Krivic
- Gottfried Schatz Research Centre, Medical University of Graz, A-8010 Graz, Austria; (D.K.); (R.S.)
| | - Rajesh Bhardwaj
- Department of Nephrology and Hypertension, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland; (R.B.); (M.A.H.)
- Department of Biomedical Research, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland
| | - Rainer Schindl
- Gottfried Schatz Research Centre, Medical University of Graz, A-8010 Graz, Austria; (D.K.); (R.S.)
| | - Matthias A. Hediger
- Department of Nephrology and Hypertension, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland; (R.B.); (M.A.H.)
- Department of Biomedical Research, University of Bern, Inselspital, Freiburgstrasse 15, CH-3010 Bern, Switzerland
| | - Isabella Derler
- JKU Life Science Center, Institute of Biophysics, Johannes Kepler University Linz, A-4020 Linz, Austria; (A.T.); (V.H.); (R.S.); (M.S.); (H.G.); (C.H.); (M.F.); (V.L.); (L.M.); (I.F.)
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15
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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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Kulawiak B, Bednarczyk P, Szewczyk A. Multidimensional Regulation of Cardiac Mitochondrial Potassium Channels. Cells 2021; 10:1554. [PMID: 34205420 PMCID: PMC8235349 DOI: 10.3390/cells10061554] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 06/11/2021] [Accepted: 06/15/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondria play a fundamental role in the energetics of cardiac cells. Moreover, mitochondria are involved in cardiac ischemia/reperfusion injury by opening the mitochondrial permeability transition pore which is the major cause of cell death. The preservation of mitochondrial function is an essential component of the cardioprotective mechanism. The involvement of mitochondrial K+ transport in this complex phenomenon seems to be well established. Several mitochondrial K+ channels in the inner mitochondrial membrane, such as ATP-sensitive, voltage-regulated, calcium-activated and Na+-activated channels, have been discovered. This obliges us to ask the following question: why is the simple potassium ion influx process carried out by several different mitochondrial potassium channels? In this review, we summarize the current knowledge of both the properties of mitochondrial potassium channels in cardiac mitochondria and the current understanding of their multidimensional functional role. We also critically summarize the pharmacological modulation of these proteins within the context of cardiac ischemia/reperfusion injury and cardioprotection.
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Affiliation(s)
- Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Pasteura 3, 02-093 Warsaw, Poland;
| | - Piotr Bednarczyk
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland;
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Pasteura 3, 02-093 Warsaw, Poland;
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17
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Dwivedi D, Bhalla US. Physiology and Therapeutic Potential of SK, H, and M Medium AfterHyperPolarization Ion Channels. Front Mol Neurosci 2021; 14:658435. [PMID: 34149352 PMCID: PMC8209339 DOI: 10.3389/fnmol.2021.658435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/13/2021] [Indexed: 12/19/2022] Open
Abstract
SK, HCN, and M channels are medium afterhyperpolarization (mAHP)-mediating ion channels. The three channels co-express in various brain regions, and their collective action strongly influences cellular excitability. However, significant diversity exists in the expression of channel isoforms in distinct brain regions and various subcellular compartments, which contributes to an equally diverse set of specific neuronal functions. The current review emphasizes the collective behavior of the three classes of mAHP channels and discusses how these channels function together although they play specialized roles. We discuss the biophysical properties of these channels, signaling pathways that influence the activity of the three mAHP channels, various chemical modulators that alter channel activity and their therapeutic potential in treating various neurological anomalies. Additionally, we discuss the role of mAHP channels in the pathophysiology of various neurological diseases and how their modulation can alleviate some of the symptoms.
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Affiliation(s)
- Deepanjali Dwivedi
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India.,Department of Neurobiology, Harvard Medical School, Boston, MA, United States.,Stanley Center at the Broad, Cambridge, MA, United States
| | - Upinder S Bhalla
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India
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18
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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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19
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The regulation of the small-conductance calcium-activated potassium current and the mechanisms of sex dimorphism in J wave syndrome. Pflugers Arch 2021; 473:491-506. [PMID: 33411079 DOI: 10.1007/s00424-020-02500-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/16/2022]
Abstract
Apamin-sensitive small-conductance calcium-activated potassium (SK) current (IKAS) plays an important role in cardiac repolarization under a variety of physiological and pathological conditions. The regulation of cardiac IKAS relies on SK channel expression, intracellular Ca2+, and interaction between SK channel and intracellular Ca2+. IKAS activation participates in multiple types of arrhythmias, including atrial fibrillation, ventricular tachyarrhythmias, and automaticity and conduction abnormality. Recently, sex dimorphisms in autonomic control have been noticed in IKAS activation, resulting in sex-differentiated action potential morphology and arrhythmogenesis. This review provides an update on the Ca2+-dependent regulation of cardiac IKAS and the role of IKAS on arrhythmias, with a special focus on sex differences in IKAS activation. We propose that sex dimorphism in autonomic control of IKAS may play a role in J wave syndrome.
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20
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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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21
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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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22
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Tiffner A, Derler I. Molecular Choreography and Structure of Ca 2+ Release-Activated Ca 2+ (CRAC) and K Ca2+ Channels and Their Relevance in Disease with Special Focus on Cancer. MEMBRANES 2020; 10:E425. [PMID: 33333945 PMCID: PMC7765462 DOI: 10.3390/membranes10120425] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/16/2022]
Abstract
Ca2+ ions play a variety of roles in the human body as well as within a single cell. Cellular Ca2+ signal transduction processes are governed by Ca2+ sensing and Ca2+ transporting proteins. In this review, we discuss the Ca2+ and the Ca2+-sensing ion channels with particular focus on the structure-function relationship of the Ca2+ release-activated Ca2+ (CRAC) ion channel, the Ca2+-activated K+ (KCa2+) ion channels, and their modulation via other cellular components. Moreover, we highlight their roles in healthy signaling processes as well as in disease with a special focus on cancer. As KCa2+ channels are activated via elevations of intracellular Ca2+ levels, we summarize the current knowledge on the action mechanisms of the interplay of CRAC and KCa2+ ion channels and their role in cancer cell development.
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Affiliation(s)
| | - Isabella Derler
- Institute of Biophysics, JKU Life Science Center, Johannes Kepler University Linz, A-4020 Linz, Austria;
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23
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Ko W, Jung SR, Kim KW, Yeon JH, Park CG, Nam JH, Hille B, Suh BC. Allosteric modulation of alternatively spliced Ca 2+-activated Cl - channels TMEM16A by PI(4,5)P 2 and CaMKII. Proc Natl Acad Sci U S A 2020; 117:30787-30798. [PMID: 33199590 PMCID: PMC7720229 DOI: 10.1073/pnas.2014520117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Transmembrane 16A (TMEM16A, anoctamin1), 1 of 10 TMEM16 family proteins, is a Cl- channel activated by intracellular Ca2+ and membrane voltage. This channel is also regulated by the membrane phospholipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. We find that two splice variants of TMEM16A show different sensitivity to endogenous PI(4,5)P2 degradation, where TMEM16A(ac) displays higher channel activity and more current inhibition by PI(4,5)P2 depletion than TMEM16A(a). These two channel isoforms differ in the alternative splicing of the c-segment (exon 13). The current amplitude and PI(4,5)P2 sensitivity of both TMEM16A(ac) and (a) are significantly strengthened by decreased free cytosolic ATP and by conditions that decrease phosphorylation by Ca2+/calmodulin-dependent protein kinase II (CaMKII). Noise analysis suggests that the augmentation of currents is due to a rise of single-channel current (i), but not of channel number (N) or open probability (PO). Mutagenesis points to arginine 486 in the first intracellular loop as a putative binding site for PI(4,5)P2, and to serine 673 in the third intracellular loop as a site for regulatory channel phosphorylation that modulates the action of PI(4,5)P2 In silico simulation suggests how phosphorylation of S673 allosterically and differently changes the structure of the distant PI(4,5)P2-binding site between channel splice variants with and without the c-segment exon. In sum, our study reveals the following: differential regulation of alternatively spliced TMEM16A(ac) and (a) by plasma membrane PI(4,5)P2, modification of these effects by channel phosphorylation, identification of the molecular sites, and mechanistic explanation by in silico simulation.
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Affiliation(s)
- Woori Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea
| | - Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Kwon-Woo Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea
| | - Jun-Hee Yeon
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea
| | - Cheon-Gyu Park
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, College of Medicine, Dongguk University, Gyeongju 38066, Republic of Korea
- Ion Channel Disease Research Center, College of Medicine, Dongguk University, Goyang, Gyeonggi-do 10326, Republic of Korea
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, Republic of Korea;
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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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PIP 2: A critical regulator of vascular ion channels hiding in plain sight. Proc Natl Acad Sci U S A 2020; 117:20378-20389. [PMID: 32764146 PMCID: PMC7456132 DOI: 10.1073/pnas.2006737117] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2), has long been established as a major contributor to intracellular signaling, primarily by virtue of its role as a substrate for phospholipase C (PLC). Signaling by Gq-protein-coupled receptors triggers PLC-mediated hydrolysis of PIP2 into inositol 1,4,5-trisphosphate and diacylglycerol, which are well known to modulate vascular ion channel activity. Often overlooked, however, is the role PIP2 itself plays in this regulation. Although numerous reports have demonstrated that PIP2 is critical for ion channel regulation, how it impacts vascular function has received scant attention. In this review, we focus on PIP2 as a regulator of ion channels in smooth muscle cells and endothelial cells-the two major classes of vascular cells. We further address the concerted effects of such regulation on vascular function and blood flow control. We close with a consideration of current knowledge regarding disruption of PIP2 regulation of vascular ion channels in disease.
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26
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Signaling pathways targeting mitochondrial potassium channels. Int J Biochem Cell Biol 2020; 125:105792. [PMID: 32574707 DOI: 10.1016/j.biocel.2020.105792] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/08/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022]
Abstract
In this review, we describe key signaling pathways regulating potassium channels present in the inner mitochondrial membrane. The signaling cascades covered here include phosphorylation, redox reactions, modulation by calcium ions and nucleotides. The following types of potassium channels have been identified in the inner mitochondrial membrane of various tissues: ATP-sensitive, Ca2+-activated, voltage-gated and two-pore domain potassium channels. The direct roles of these channels involve regulation of mitochondrial respiration, membrane potential and synthesis of reactive oxygen species (ROS). Changes in channel activity lead to diverse pro-life and pro-death responses in different cell types. Hence, characterizing the signaling pathways regulating mitochondrial potassium channels will facilitate understanding the physiological role of these proteins. Additionally, we describe in this paper certain regulatory mechanisms, which are unique to mitochondrial potassium channels.
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27
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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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28
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Shim H, Brown BM, Singh L, Singh V, Fettinger JC, Yarov-Yarovoy V, Wulff H. The Trials and Tribulations of Structure Assisted Design of K Ca Channel Activators. Front Pharmacol 2019; 10:972. [PMID: 31616290 PMCID: PMC6764326 DOI: 10.3389/fphar.2019.00972] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 07/29/2019] [Indexed: 11/13/2022] Open
Abstract
Calcium-activated K+ channels constitute attractive targets for the treatment of neurological and cardiovascular diseases. To explain why certain 2-aminobenzothiazole/oxazole-type KCa activators (SKAs) are KCa3.1 selective we previously generated homology models of the C-terminal calmodulin-binding domain (CaM-BD) of KCa3.1 and KCa2.3 in complex with CaM using Rosetta modeling software. We here attempted to employ this atomistic level understanding of KCa activator binding to switch selectivity around and design KCa2.2 selective activators as potential anticonvulsants. In this structure-based drug design approach we used RosettaLigand docking and carefully compared the binding poses of various SKA compounds in the KCa2.2 and KCa3.1 CaM-BD/CaM interface pocket. Based on differences between residues in the KCa2.2 and KCa.3.1 models we virtually designed 168 new SKA compounds. The compounds that were predicted to be both potent and KCa2.2 selective were synthesized, and their activity and selectivity tested by manual or automated electrophysiology. However, we failed to identify any KCa2.2 selective compounds. Based on the full-length KCa3.1 structure it was recently demonstrated that the C-terminal crystal dimer was an artefact and suggested that the "real" binding pocket for the KCa activators is located at the S4-S5 linker. We here confirmed this structural hypothesis through mutagenesis and now offer a new, corrected binding site model for the SKA-type KCa channel activators. SKA-111 (5-methylnaphtho[1,2-d]thiazol-2-amine) is binding in the interface between the CaM N-lobe and the S4-S5 linker where it makes van der Waals contacts with S181 and L185 in the S45A helix of KCa3.1.
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Affiliation(s)
- Heesung Shim
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Chemistry, University of California, Davis, Davis, CA, United States
| | - Brandon M Brown
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Latika Singh
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Vikrant Singh
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - James C Fettinger
- Department of Chemistry, University of California, Davis, Davis, CA, United States
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA, United States
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States
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29
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Jang H, Banerjee A, Marcus K, Makowski L, Mattos C, Gaponenko V, Nussinov R. The Structural Basis of the Farnesylated and Methylated KRas4B Interaction with Calmodulin. Structure 2019; 27:1647-1659.e4. [PMID: 31495533 DOI: 10.1016/j.str.2019.08.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/31/2019] [Accepted: 08/16/2019] [Indexed: 02/07/2023]
Abstract
Ca2+-calmodulin (CaM) extracts KRas4B from the plasma membrane, suggesting that KRas4B/CaM interaction plays a role in regulating Ras signaling. To gain mechanistic insight, we provide a computational model, supported by experimental structural data, of farnesylated/methylated KRas4B1-185 interacting with CaM in solution and at anionic membranes including signaling lipids. Due to multiple interaction modes, we observe diverse conformational ensembles of the KRas4B-CaM complex. A highly populated conformation reveals the catalytic domain interacting with the N-lobe and the hypervariable region (HVR) wrapping around the linker with the farnesyl docking to the extended CaM's C-lobe pocket. Alternatively, KRas4B can interact with collapsed CaM with the farnesyl penetrating CaM's center. At anionic membranes, CaM interacts with the catalytic domain with large fluctuations, drawing the HVR. Signaling lipids establishing strong salt bridges with CaM prevent membrane departure. Membrane-interacting KRas4B-CaM complex can productively recruit phosphatidylinositol 3-kinase α (PI3Kα) to the plasma membrane, serving as a coagent in activating PI3Kα/Akt signaling.
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Affiliation(s)
- Hyunbum Jang
- Computational Structural Biology Section, Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA
| | - Avik Banerjee
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Kendra Marcus
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Lee Makowski
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Carla Mattos
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA
| | - Vadim Gaponenko
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Ruth Nussinov
- Computational Structural Biology Section, Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA; Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
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30
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Brown BM, Shim H, Christophersen P, Wulff H. Pharmacology of Small- and Intermediate-Conductance Calcium-Activated Potassium Channels. Annu Rev Pharmacol Toxicol 2019; 60:219-240. [PMID: 31337271 DOI: 10.1146/annurev-pharmtox-010919-023420] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The three small-conductance calcium-activated potassium (KCa2) channels and the related intermediate-conductance KCa3.1 channel are voltage-independent K+ channels that mediate calcium-induced membrane hyperpolarization. When intracellular calcium increases in the channel vicinity, it calcifies the flexible N lobe of the channel-bound calmodulin, which then swings over to the S4-S5 linker and opens the channel. KCa2 and KCa3.1 channels are highly druggable and offer multiple binding sites for venom peptides and small-molecule blockers as well as for positive- and negative-gating modulators. In this review, we briefly summarize the physiological role of KCa channels and then discuss the pharmacophores and the mechanism of action of the most commonly used peptidic and small-molecule KCa2 and KCa3.1 modulators. Finally, we describe the progress that has been made in advancing KCa3.1 blockers and KCa2.2 negative- and positive-gating modulators toward the clinic for neurological and cardiovascular diseases and discuss the remaining challenges.
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Affiliation(s)
- Brandon M Brown
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | - Heesung Shim
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | | | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA;
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31
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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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32
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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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33
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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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34
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Liu L, Bonventre JV, Rittenhouse AR. cPLA2α-/- sympathetic neurons exhibit increased membrane excitability and loss of N-Type Ca2+ current inhibition by M1 muscarinic receptor signaling. PLoS One 2018; 13:e0201322. [PMID: 30557348 PMCID: PMC6296557 DOI: 10.1371/journal.pone.0201322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 07/11/2018] [Indexed: 11/18/2022] Open
Abstract
Group IVa cytosolic phospholipase A2 (cPLA2α) mediates GPCR-stimulated arachidonic acid (AA) release from phosphatidylinositol 4,5-bisphosphate (PIP2) located in plasma membranes. We previously found in superior cervical ganglion (SCG) neurons that PLA2 activity is required for voltage-independent N-type Ca2+ (N-) current inhibition by M1 muscarinic receptors (M1Rs). These findings are at odds with an alternative model, previously observed for M-current inhibition, where PIP2 dissociation from channels and subsequent metabolism by phospholipase C suffices for current inhibition. To resolve cPLA2α’s importance, we have investigated its role in mediating voltage-independent N-current inhibition (~40%) that follows application of the muscarinic agonist oxotremorine-M (Oxo-M). Preincubation with different cPLA2α antagonists or dialyzing cPLA2α antibodies into cells minimized N-current inhibition by Oxo-M, whereas antibodies to Ca2+-independent PLA2 had no effect. Taking a genetic approach, we found that SCG neurons from cPLA2α-/- mice exhibited little N-current inhibition by Oxo-M, confirming a role for cPLA2α. In contrast, cPLA2α antibodies or the absence of cPLA2α had no effect on voltage-dependent N-current inhibition by M2/M4Rs or on M-current inhibition by M1Rs. These findings document divergent M1R signaling mediating M-current and voltage-independent N-current inhibition. Moreover, these differences suggest that cPLA2α acts locally to metabolize PIP2 intimately associated with N- but not M-channels. To determine cPLA2α’s functional importance more globally, we examined action potential firing of cPLA2α+/+ and cPLA2α-/- SCG neurons, and found decreased latency to first firing and interspike interval resulting in a doubling of firing frequency in cPLA2α-/- neurons. These unanticipated findings identify cPLA2α as a tonic regulator of neuronal membrane excitability.
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Affiliation(s)
- Liwang Liu
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Joseph V. Bonventre
- Harvard Institute of Medicine, Harvard Medical School & Brigham and Women's Hospital, Boston, Massachusetts, United States of America
| | - Ann R. Rittenhouse
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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35
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Chen M, Xu DZ, Wu AZ, Guo S, Wan J, Yin D, Lin SF, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Concomitant SK current activation and sodium current inhibition cause J wave syndrome. JCI Insight 2018; 3:122329. [PMID: 30429367 PMCID: PMC6302939 DOI: 10.1172/jci.insight.122329] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/18/2022] Open
Abstract
The mechanisms of J wave syndrome (JWS) are incompletely understood. Here, we showed that the concomitant activation of small-conductance calcium-activated potassium (SK) current (IKAS) and inhibition of sodium current by cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) recapitulate the phenotypes of JWS in Langendorff-perfused rabbit hearts. CyPPA induced significant J wave elevation and frequent spontaneous ventricular fibrillation (SVF), as well as sinus bradycardia, atrioventricular block, and intraventricular conduction delay. IKAS activation by CyPPA resulted in heterogeneous shortening of action potential (AP) duration (APD) and repolarization alternans. CyPPA inhibited cardiac sodium current (INa) and decelerated AP upstroke and intracellular calcium transient. SVFs were typically triggered by short-coupled premature ventricular contractions, initiated with phase 2 reentry and originated more frequently from the right than the left ventricles. Subsequent IKAS blockade by apamin reduced J wave elevation and eliminated SVF. β-Adrenergic stimulation was antiarrhythmic in CyPPA-induced electrical storm. Like CyPPA, hypothermia (32.0°C) also induced J wave elevation and SVF. It facilitated negative calcium-voltage coupling and phase 2 repolarization alternans with spatial and electromechanical discordance, which were ameliorated by apamin. These findings suggest that IKAS activation contributes to the development of JWS in rabbit ventricles.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Adonis Z. Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiothoracic Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael Rubart-von der Lohe
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Thomas H. Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - James N. Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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36
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Hughes TET, Pumroy RA, Yazici AT, Kasimova MA, Fluck EC, Huynh KW, Samanta A, Molugu SK, Zhou ZH, Carnevale V, Rohacs T, Moiseenkova-Bell VY. Structural insights on TRPV5 gating by endogenous modulators. Nat Commun 2018; 9:4198. [PMID: 30305626 PMCID: PMC6179994 DOI: 10.1038/s41467-018-06753-6] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/14/2018] [Indexed: 11/10/2022] Open
Abstract
TRPV5 is a transient receptor potential channel involved in calcium reabsorption. Here we investigate the interaction of two endogenous modulators with TRPV5. Both phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and calmodulin (CaM) have been shown to directly bind to TRPV5 and activate or inactivate the channel, respectively. Using cryo-electron microscopy (cryo-EM), we determined TRPV5 structures in the presence of dioctanoyl PI(4,5)P2 and CaM. The PI(4,5)P2 structure reveals a binding site between the N-linker, S4-S5 linker and S6 helix of TRPV5. These interactions with PI(4,5)P2 induce conformational rearrangements in the lower gate, opening the channel. The CaM structure reveals two TRPV5 C-terminal peptides anchoring a single CaM molecule and that calcium inhibition is mediated through a cation-π interaction between Lys116 on the C-lobe of calcium-activated CaM and Trp583 at the intracellular gate of TRPV5. Overall, this investigation provides insight into the endogenous modulation of TRPV5, which has the potential to guide drug discovery.
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Affiliation(s)
- Taylor E T Hughes
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Ruth A Pumroy
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Aysenur Torun Yazici
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Marina A Kasimova
- Institute for Computational Molecular Science, Temple University, Philadelphia, PA, 19122, USA
| | - Edwin C Fluck
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kevin W Huynh
- California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA
| | - Amrita Samanta
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Sudheer K Molugu
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA
| | - Vincenzo Carnevale
- Institute for Computational Molecular Science, Temple University, Philadelphia, PA, 19122, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Vera Y Moiseenkova-Bell
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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37
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Kshatri AS, Gonzalez-Hernandez A, Giraldez T. Physiological Roles and Therapeutic Potential of Ca 2+ Activated Potassium Channels in the Nervous System. Front Mol Neurosci 2018; 11:258. [PMID: 30104956 PMCID: PMC6077210 DOI: 10.3389/fnmol.2018.00258] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/06/2018] [Indexed: 12/21/2022] Open
Abstract
Within the potassium ion channel family, calcium activated potassium (KCa) channels are unique in their ability to couple intracellular Ca2+ signals to membrane potential variations. KCa channels are diversely distributed throughout the central nervous system and play fundamental roles ranging from regulating neuronal excitability to controlling neurotransmitter release. The physiological versatility of KCa channels is enhanced by alternative splicing and co-assembly with auxiliary subunits, leading to fundamental differences in distribution, subunit composition and pharmacological profiles. Thus, understanding specific KCa channels’ mechanisms in neuronal function is challenging. Based on their single channel conductance, KCa channels are divided into three subtypes: small (SK, 4–14 pS), intermediate (IK, 32–39 pS) and big potassium (BK, 200–300 pS) channels. This review describes the biophysical characteristics of these KCa channels, as well as their physiological roles and pathological implications. In addition, we also discuss the current pharmacological strategies and challenges to target KCa channels for the treatment of various neurological and psychiatric disorders.
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Affiliation(s)
- Aravind S Kshatri
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Alberto Gonzalez-Hernandez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Teresa Giraldez
- Department of Basic Medical Sciences, Medical School, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, Tenerife, Spain
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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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A V-to-F substitution in SK2 channels causes Ca 2+ hypersensitivity and improves locomotion in a C. elegans ALS model. Sci Rep 2018; 8:10749. [PMID: 30013223 PMCID: PMC6048120 DOI: 10.1038/s41598-018-28783-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 06/29/2018] [Indexed: 11/09/2022] Open
Abstract
Small-conductance Ca2+-activated K+ (SK) channels mediate medium afterhyperpolarization in the neurons and play a key role in the regulation of neuronal excitability. SK channels are potential drug targets for ataxia and Amyotrophic Lateral Sclerosis (ALS). SK channels are activated exclusively by the Ca2+-bound calmodulin. Previously, we identified an intrinsically disordered fragment that is essential for the mechanical coupling between Ca2+/calmodulin binding and channel opening. Here, we report that substitution of a valine to phenylalanine (V407F) in the intrinsically disordered fragment caused a ~6 fold increase in the Ca2+ sensitivity of SK2-a channels. This substitution resulted in a novel interaction between the ectopic phenylalanine and M411, which stabilized PIP2-interacting residue K405, and subsequently enhanced Ca2+ sensitivity. Also, equivalent valine to phenylalanine substitutions in SK1 or SK3 channels conferred Ca2+ hypersensitivity. An equivalent phenylalanine substitution in the Caenorhabditis elegans (C. elegans) SK2 ortholog kcnl-2 partially rescued locomotion defects in an existing C. elegans ALS model, in which human SOD1G85R is expressed at high levels in neurons, confirming that this phenylalanine substitution impacts channel function in vivo. This work for the first time provides a critical reagent for future studies: an SK channel that is hypersensitive to Ca2+ with increased activity in vivo.
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40
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Hilgemann DW, Dai G, Collins A, Lariccia V, Magi S, Deisl C, Fine M. Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis. J Gen Physiol 2018; 150:211-224. [PMID: 29326133 PMCID: PMC5806671 DOI: 10.1085/jgp.201711875] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence. Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Anthony Collins
- Saba University School of Medicine, The Bottom, Saba, Dutch Caribbean
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Christine Deisl
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
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41
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Shimizu K, Cao W, Saad G, Shoji M, Terada T. Comparative analysis of membrane protein structure databases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1077-1091. [PMID: 29331638 DOI: 10.1016/j.bbamem.2018.01.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Revised: 12/28/2017] [Accepted: 01/04/2018] [Indexed: 12/11/2022]
Abstract
BACKGROUND Membrane proteins play important roles in cell survival and cell communication, as they function as transporters, receptors, anchors and enzymes. They are also potential targets for drugs that block receptors or inhibit enzymes related to diseases. Although the number of known structures of membrane proteins is still small relative to the size of the proteome as a whole, many new membrane protein structures have been determined recently. SCOPE OF THE ARTICLE We compared and analyzed the widely used membrane protein databases, mpstruc, Orientations of Proteins in Membranes (OPM), and PDBTM, as well as the extended dataset of mpstruc based on sequence similarity, the PDB structures whose classification field indicates that they are "membrane proteins" and the proteins with Structural Classification of Proteins (SCOP) class-f domains. We evaluated the relationships between these databases or datasets based on the overlap in their contents and the degree of consistency in the structural, topological, and functional classifications and in the transmembrane domain assignment. MAJOR CONCLUSIONS The membrane databases differ from each other in their coverage, and in the criteria that they use for annotation and classification. To ensure the efficient use of these databases, it is important to understand their differences and similarities. The establishment of more detailed and consistent annotations for the sequence, structure, membrane association, and function of membrane proteins is still required. GENERAL SIGNIFICANCE Considering the recent growth of experimentally determined structures, a broad survey and cumulative analysis of the sum of knowledge as presented in the membrane protein structure databases can be helpful to elucidate structures and functions of membrane proteins. We also aim to provide a framework for future research and classification of membrane proteins.
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Affiliation(s)
- Kentaro Shimizu
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
| | - Wei Cao
- Faculty of Information Networking for Innovation and Design, Toyo University, Tokyo, Japan.
| | - Gull Saad
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
| | - Michiru Shoji
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
| | - Tohru Terada
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
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42
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Ha J, Xu Y, Kawano T, Hendon T, Baki L, Garai S, Papapetropoulos A, Thakur GA, Plant LD, Logothetis DE. Hydrogen sulfide inhibits Kir2 and Kir3 channels by decreasing sensitivity to the phospholipid phosphatidylinositol 4,5-bisphosphate (PIP 2). J Biol Chem 2018; 293:3546-3561. [PMID: 29317494 DOI: 10.1074/jbc.ra117.001679] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 01/07/2018] [Indexed: 11/06/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels establish and regulate the resting membrane potential of excitable cells in the heart, brain, and other peripheral tissues. Phosphatidylinositol 4,5-bisphosphate (PIP2) is a key direct activator of ion channels, including Kir channels. The gasotransmitter carbon monoxide has been shown to regulate Kir channel activity by altering channel-PIP2 interactions. Here, we tested in two cellular models the effects and mechanism of action of another gasotransmitter, hydrogen sulfide (H2S), thought to play a key role in cellular responses under ischemic conditions. Direct administration of sodium hydrogen sulfide as an exogenous H2S source and expression of cystathionine γ-lyase, a key enzyme that produces endogenous H2S in specific brain tissues, resulted in comparable current inhibition of several Kir2 and Kir3 channels. This effect resulted from changes in channel-gating kinetics rather than in conductance or cell-surface localization. The extent of H2S regulation depended on the strength of the channel-PIP2 interactions. H2S regulation was attenuated when channel-PIP2 interactions were strengthened and was increased when channel-PIP2 interactions were weakened by depleting PIP2 levels. These H2S effects required specific cytoplasmic cysteine residues in Kir3.2 channels. Mutation of these residues abolished H2S inhibition, and reintroduction of specific cysteine residues back into the background of the cytoplasmic cysteine-lacking mutant rescued H2S inhibition. Molecular dynamics simulation experiments provided mechanistic insights into how potential sulfhydration of specific cysteine residues could lead to changes in channel-PIP2 interactions and channel gating.
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Affiliation(s)
- Junghoon Ha
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298
| | - Yu Xu
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Takeharu Kawano
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Tyler Hendon
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298
| | - Lia Baki
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Sumanta Garai
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Andreas Papapetropoulos
- the Laboratory of Pharmacology, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece, and.,the Center of Clinical, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens 11527, Greece
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Leigh D Plant
- Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
| | - Diomedes E Logothetis
- From the Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, .,Department of Pharmaceutical Sciences in the School of Pharmacy, Northeastern University Bouvé College of Health Sciences, Boston, Massachusetts 02115
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43
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Nam YW, Orfali R, Liu T, Yu K, Cui M, Wulff H, Zhang M. Structural insights into the potency of SK channel positive modulators. Sci Rep 2017; 7:17178. [PMID: 29214998 PMCID: PMC5719431 DOI: 10.1038/s41598-017-16607-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 11/15/2017] [Indexed: 12/26/2022] Open
Abstract
Small-conductance Ca2+-activated K+ (SK) channels play essential roles in the regulation of cellular excitability and have been implicated in neurological and cardiovascular diseases through both animal model studies and human genetic association studies. Over the past two decades, positive modulators of SK channels such as NS309 and 1-EBIO have been developed. Our previous structural studies have identified the binding pocket of 1-EBIO and NS309 that is located at the interface between the channel and calmodulin. In this study, we took advantage of four compounds with potencies varying over three orders of magnitude, including 1-EBIO, NS309, SKS-11 (6-bromo-5-methyl-1H-indole-2,3-dione-3-oxime) and SKS-14 (7-fluoro-3-(hydroxyimino)indolin-2-one). A combination of x-ray crystallographic, computational and electrophysiological approaches was utilized to investigate the interactions between the positive modulators and their binding pocket. A strong trend exists between the interaction energy of the compounds within their binding site calculated from the crystal structures, and the potency of these compounds in potentiating the SK2 channel current determined by electrophysiological recordings. Our results further reveal that the difference in potency of the positive modulators in potentiating SK2 channel activity may be attributed primarily to specific electrostatic interactions between the modulators and their binding pocket.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Razan Orfali
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Tingting Liu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Kunqian Yu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, 02115, USA
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, 95616, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences & Structural Biology Research Center, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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44
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Tobelaim WS, Dvir M, Lebel G, Cui M, Buki T, Peretz A, Marom M, Haitin Y, Logothetis DE, Hirsch JA, Attali B. Ca 2+-Calmodulin and PIP2 interactions at the proximal C-terminus of Kv7 channels. Channels (Austin) 2017; 11:686-695. [PMID: 28976808 PMCID: PMC5786183 DOI: 10.1080/19336950.2017.1388478] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/18/2017] [Accepted: 09/29/2017] [Indexed: 10/18/2022] Open
Abstract
In the heart, co-assembly of Kv7.1 with KCNE1 produces the slow IKS potassium current, which repolarizes the cardiac action potential and mutations in human Kv7.1 and KCNE1 genes cause cardiac arrhythmias. The proximal Kv7.1 C-terminus binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2) and recently we revealed the competition of PIP2 with the calcified CaM N-lobe to a previously unidentified site in Kv7.1 helix B, also known to harbor a LQT mutation. Data indicated that PIP2 and Ca2+-CaM perform the same function on IKS channel gating to stabilize the channel open state. Here we show that similar features were observed for Kv7.1 currents expressed alone. We also find that conservation of homologous residues in helix B of other Kv7 subtypes confer similar competition of Ca2+-CaM with PIP2 binding to their proximal C-termini and suggest that PIP2-CaM interactions converge to Kv7 helix B to modulates channel activity in a Kv7 subtype-dependent manner.
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Affiliation(s)
- William S. Tobelaim
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Meidan Dvir
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Guy Lebel
- Department of Biochemistry & Molecular Biology, George S. Wise Faculty of Life Sciences, Institute of Structural Biology, Tel Aviv University, Tel Aviv, Israel
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, USA
| | - Tal Buki
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Asher Peretz
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
| | - Milit Marom
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yoni Haitin
- Laboratory of Structural Physiology, Department of Physiology & Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - Joel A. Hirsch
- Department of Biochemistry & Molecular Biology, George S. Wise Faculty of Life Sciences, Institute of Structural Biology, Tel Aviv University, Tel Aviv, Israel
| | - Bernard Attali
- Department of Physiology & Pharmacology, Sackler Faculty of Medicine and Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel
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Kirchner MK, Foehring RC, Wang L, Chandaka GK, Callaway JC, Armstrong WE. Phosphatidylinositol 4,5-bisphosphate (PIP 2 ) modulates afterhyperpolarizations in oxytocin neurons of the supraoptic nucleus. J Physiol 2017; 595:4927-4946. [PMID: 28383826 DOI: 10.1113/jp274219] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 04/04/2017] [Indexed: 01/19/2023] Open
Abstract
KEY POINTS Afterhyperpolarizations (AHPs) generated by repetitive action potentials in supraoptic magnocellular neurons regulate repetitive firing and spike frequency adaptation but relatively little is known about PIP2 's control of these AHPs. We examined how changes in PIP2 levels affected AHPs, somatic [Ca2+ ]i , and whole cell Ca2+ currents. Manipulations of PIP2 levels affected both medium and slow AHP currents in oxytocin (OT) neurons of the supraoptic nucleus. Manipulations of PIP2 levels did not modulate AHPs by influencing Ca2+ release from IP3 -triggered Ca2+ stores, suggesting more direct modulation of channels by PIP2 . PIP2 depletion reduced spike-evoked Ca2+ entry and voltage-gated Ca2+ currents. PIP2 appears to influence AHPs in OT neurons by reducing Ca2+ influx during spiking. ABSTRACT Oxytocin (OT)- and vasopressin (VP)-secreting magnocellular neurons of the supraoptic nucleus (SON) display calcium-dependent afterhyperpolarizations (AHPs) following a train of action potentials that are critical to shaping the firing patterns of these cells. Previous work demonstrated that the lipid phosphatidylinositol 4,5-bisphosphate (PIP2 ) enabled the slow AHP component (sAHP) in cortical pyramidal neurons. We investigated whether this phenomenon occurred in OT and VP neurons of the SON. Using whole cell recordings in coronal hypothalamic slices from adult female rats, we demonstrated that inhibition of PIP2 synthesis with wortmannin robustly blocked both the medium and slow AHP currents (ImAHP and IsAHP ) of OT, but not VP neurons with high affinity. We further tested this by introducing a water-soluble PIP2 analogue (diC8 -PIP2 ) into neurons, which in OT neurons not only prevented wortmannin's inhibitory effect, but slowed rundown of the ImAHP and IsAHP . Inhibition of phospholipase C (PLC) with U73122 did not inhibit either ImAHP or IsAHP in OT neurons, consistent with wortmannin's effects not being due to reducing diacylglycerol (DAG) or IP3 availability, i.e. PIP2 modulation of AHPs is not likely to involve downstream Ca2+ release from inositol 1,4,5-trisphosphate (IP3 )-triggered Ca2+ -store release, or channel modulation via DAG and protein kinase C (PKC). We found that wortmannin reduced [Ca2+ ]i increase induced by spike trains in OT neurons, but had no effect on AHPs evoked by uncaging intracellular Ca2+ . Finally, wortmannin selectively reduced whole cell Ca2+ currents in OT neurons while leaving VP neurons unaffected. The results indicate that PIP2 modulates both the ImAHP and IsAHP in OT neurons, most likely by controlling Ca2+ entry through voltage-gated Ca2+ channels opened during spike trains.
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Affiliation(s)
- Matthew K Kirchner
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Robert C Foehring
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Lie Wang
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Giri Kumar Chandaka
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Joseph C Callaway
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
| | - William E Armstrong
- Department of Anatomy and Neurobiology and Neuroscience Institute, University of Tennessee Health Science Center, Memphis, TN, USA
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Cannady R, McGonigal JT, Newsom RJ, Woodward JJ, Mulholland PJ, Gass JT. Prefrontal Cortex K Ca2 Channels Regulate mGlu 5-Dependent Plasticity and Extinction of Alcohol-Seeking Behavior. J Neurosci 2017; 37:4359-4369. [PMID: 28320841 PMCID: PMC5413180 DOI: 10.1523/jneurosci.2873-16.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 03/10/2017] [Accepted: 03/15/2017] [Indexed: 12/17/2022] Open
Abstract
Identifying novel treatments that facilitate extinction learning could enhance cue-exposure therapy and reduce high relapse rates in alcoholics. Activation of mGlu5 receptors in the infralimbic prefrontal cortex (IL-PFC) facilitates learning during extinction of cue-conditioned alcohol-seeking behavior. Small-conductance calcium-activated potassium (KCa2) channels have also been implicated in extinction learning of fear memories, and mGlu5 receptor activation can reduce KCa2 channel function. Using a combination of electrophysiological, pharmacological, and behavioral approaches, this study examined KCa2 channels as a novel target to facilitate extinction of alcohol-seeking behavior in rats. This study also explored related neuronal and synaptic mechanisms within the IL-PFC that underlie mGlu5-dependent enhancement of extinction learning. Using whole-cell patch-clamp electrophysiology, activation of mGlu5 in ex vivo slices significantly reduced KCa2 channel currents in layer V IL-PFC pyramidal neurons, confirming functional downregulation of KCa2 channel activity by mGlu5 receptors. Additionally, positive modulation of KCa2 channels prevented mGlu5 receptor-dependent facilitation of long-term potentiation in the IL-PFC. Systemic and intra-IL-PFC treatment with apamin (KCa2 channel allosteric inhibitor) significantly enhanced extinction of alcohol-seeking behavior across multiple extinction sessions, an effect that persisted for 3 weeks, but was not observed after apamin microinfusions into the prelimbic PFC. Positive modulation of IL-PFC KCa2 channels significantly attenuated mGlu5-dependent facilitation of alcohol cue-conditioned extinction learning. These data suggest that mGlu5-dependent facilitation of extinction learning and synaptic plasticity in the IL-PFC involves functional inhibition of KCa2 channels. Moreover, these findings demonstrate that KCa2 channels are a novel target to facilitate long-lasting extinction of alcohol-seeking behavior.SIGNIFICANCE STATEMENT Alcohol use disorder is a chronic relapsing disorder that is associated with compulsive alcohol-seeking behavior. One of the main causes of alcohol relapse is the craving caused by environmental cues that are associated with alcohol. These cues are formed by normal learning and memory principles, and the understanding of the brain mechanisms that help form these associations can lead to the development of drugs and/or behavior therapies that reduce the impact that these cues have on relapse in alcoholics.
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Affiliation(s)
- Reginald Cannady
- Department of Neuroscience
- Department of Psychiatry & Behavioral Sciences, and
| | | | | | - John J Woodward
- Department of Neuroscience
- Department of Psychiatry & Behavioral Sciences, and
| | | | - Justin T Gass
- Department of Neuroscience,
- Department of Psychiatry & Behavioral Sciences, and
- Charleston Alcohol Research Center, Addiction Sciences Division, College of Health Professions, Medical University of South Carolina, Charleston, South Carolina 29425
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47
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Competition of calcified calmodulin N lobe and PIP2 to an LQT mutation site in Kv7.1 channel. Proc Natl Acad Sci U S A 2017; 114:E869-E878. [PMID: 28096388 DOI: 10.1073/pnas.1612622114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Voltage-gated potassium 7.1 (Kv7.1) channel and KCNE1 protein coassembly forms the slow potassium current IKS that repolarizes the cardiac action potential. The physiological importance of the IKS channel is underscored by the existence of mutations in human Kv7.1 and KCNE1 genes, which cause cardiac arrhythmias, such as the long-QT syndrome (LQT) and atrial fibrillation. The proximal Kv7.1 C terminus (CT) binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2), but the role of CaM in channel function is still unclear, and its possible interaction with PIP2 is unknown. Our recent crystallographic study showed that CaM embraces helices A and B with the apo C lobe and calcified N lobe, respectively. Here, we reveal the competition of PIP2 and the calcified CaM N lobe to a previously unidentified site in Kv7.1 helix B, also known to harbor an LQT mutation. Protein pulldown, molecular docking, molecular dynamics simulations, and patch-clamp recordings indicate that residues K526 and K527 in Kv7.1 helix B form a critical site where CaM competes with PIP2 to stabilize the channel open state. Data indicate that both PIP2 and Ca2+-CaM perform the same function on IKS channel gating by producing a left shift in the voltage dependence of activation. The LQT mutant K526E revealed a severely impaired channel function with a right shift in the voltage dependence of activation, a reduced current density, and insensitivity to gating modulation by Ca2+-CaM. The results suggest that, after receptor-mediated PIP2 depletion and increased cytosolic Ca2+, calcified CaM N lobe interacts with helix B in place of PIP2 to limit excessive IKS current inhibition.
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48
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Salzer I, Erdem FA, Chen WQ, Heo S, Koenig X, Schicker KW, Kubista H, Lubec G, Boehm S, Yang JW. Phosphorylation regulates the sensitivity of voltage-gated Kv7.2 channels towards phosphatidylinositol-4,5-bisphosphate. J Physiol 2016; 595:759-776. [PMID: 27621207 PMCID: PMC5215842 DOI: 10.1113/jp273274] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 08/30/2016] [Indexed: 12/22/2022] Open
Abstract
Key points Phosphatidylinositol‐4,5‐bisphosphate (PIP2) is a key regulator of many membrane proteins, including voltage‐gated Kv7.2 channels. In this study, we identified the residues in five phosphorylation sites and their corresponding protein kinases, the former being clustered within one of four putative PIP2‐binding domains in Kv7.2. Dephosphorylation of these residues reduced the sensitivity of Kv7.2 channels towards PIP2. Dephosphorylation of Kv7.2 affected channel inhibition via M1 muscarinic receptors, but not via bradykinin receptors. Our data indicated that phosphorylation of the Kv7.2 channel was necessary to maintain its low affinity for PIP2, thereby ensuring the tight regulation of the channel via G protein‐coupled receptors.
Abstract The function of numerous ion channels is tightly controlled by G protein‐coupled receptors (GPCRs). The underlying signalling mechanisms may involve phosphorylation of channel proteins and participation of phosphatidylinositol‐4,5‐bisphosphate (PIP2). Although the roles of both mechanisms have been investigated extensively, thus far only little has been reported on their interaction in channel modulation. GPCRs govern Kv7 channels, the latter playing a major role in the regulation of neuronal excitability by determining the levels of PIP2 and through phosphorylation. Using liquid chromatography‐coupled mass spectrometry for Kv7.2 immunoprecipitates of rat brain membranes and transfected cells, we mapped a cluster of five phosphorylation sites in one of the PIP2‐binding domains. To evaluate the effect of phosphorylation on PIP2‐mediated Kv7.2 channel regulation, a quintuple alanine mutant of these serines (S427/S436/S438/S446/S455; A5 mutant) was generated to mimic the dephosphorylated state. Currents passing through these mutated channels were less sensitive towards PIP2 depletion via the voltage‐sensitive phosphatase Dr‐VSP than were wild‐type channels. In vitro phosphorylation assays with the purified C‐terminus of Kv7.2 revealed that CDK5, p38 MAPK, CaMKIIα and PKA were able to phosphorylate the five serines. Inhibition of these protein kinases reduced the sensitivity of wild‐type but not mutant Kv7.2 channels towards PIP2 depletion via Dr‐VSP. In superior cervical ganglion neurons, the protein kinase inhibitors attenuated Kv7 current regulation via M1 receptors, but left unaltered the control by B2 receptors. Our results revealed that the phosphorylation status of serines located within a putative PIP2‐binding domain determined the phospholipid sensitivity of Kv7.2 channels and supported GPCR‐mediated channel regulation. Phosphatidylinositol‐4,5‐bisphosphate (PIP2) is a key regulator of many membrane proteins, including voltage‐gated Kv7.2 channels. In this study, we identified the residues in five phosphorylation sites and their corresponding protein kinases, the former being clustered within one of four putative PIP2‐binding domains in Kv7.2. Dephosphorylation of these residues reduced the sensitivity of Kv7.2 channels towards PIP2. Dephosphorylation of Kv7.2 affected channel inhibition via M1 muscarinic receptors, but not via bradykinin receptors. Our data indicated that phosphorylation of the Kv7.2 channel was necessary to maintain its low affinity for PIP2, thereby ensuring the tight regulation of the channel via G protein‐coupled receptors.
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Affiliation(s)
- Isabella Salzer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Fatma Asli Erdem
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Wei-Qiang Chen
- Department of Pediatrics, Medical University of Vienna, 1090, Vienna, Austria
| | - Seok Heo
- Department of Pediatrics, Medical University of Vienna, 1090, Vienna, Austria
| | - Xaver Koenig
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Klaus W Schicker
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Helmut Kubista
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Gert Lubec
- Department of Pharmaceutical Chemistry, University of Vienna, 1090, Vienna, Austria
| | - Stefan Boehm
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
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49
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Greene DL, Hoshi N. Modulation of Kv7 channels and excitability in the brain. Cell Mol Life Sci 2016; 74:495-508. [PMID: 27645822 DOI: 10.1007/s00018-016-2359-y] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 08/25/2016] [Accepted: 09/06/2016] [Indexed: 11/26/2022]
Abstract
Neuronal Kv7 channels underlie a voltage-gated non-inactivating potassium current known as the M-current. Due to its particular characteristics, Kv7 channels show pronounced control over the excitability of neurons. We will discuss various factors that have been shown to drastically alter the activity of this channel such as protein and phospholipid interactions, phosphorylation, calcium, and numerous neurotransmitters. Kv7 channels locate to key areas for the control of action potential initiation and propagation. Moreover, we will explore the dynamic surface expression of the channel modulated by neurotransmitters and neural activity. We will also focus on known principle functions of neural Kv7 channels: control of resting membrane potential and spiking threshold, setting the firing frequency, afterhyperpolarization after burst firing, theta resonance, and transient hyperexcitability from neurotransmitter-induced suppression of the M-current. Finally, we will discuss the contribution of altered Kv7 activity to pathologies such as epilepsy and cognitive deficits.
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Affiliation(s)
- Derek L Greene
- Department of Pharmacology, University of California, 360 Med Surge II, Irvine, CA, 92697, USA
| | - Naoto Hoshi
- Department of Pharmacology, University of California, 360 Med Surge II, Irvine, CA, 92697, USA.
- Department of Physiology and Biophysics, University of California, Irvine, USA.
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50
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Lörinczi E, Helliwell M, Finch A, Stansfeld PJ, Davies NW, Mahaut-Smith M, Muskett FW, Mitcheson JS. Calmodulin Regulates Human Ether à Go-Go 1 (hEAG1) Potassium Channels through Interactions of the Eag Domain with the Cyclic Nucleotide Binding Homology Domain. J Biol Chem 2016; 291:17907-18. [PMID: 27325704 PMCID: PMC5016179 DOI: 10.1074/jbc.m116.733576] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 11/24/2022] Open
Abstract
The ether à go-go family of voltage-gated potassium channels is structurally distinct. The N terminus contains an eag domain (eagD) that contains a Per-Arnt-Sim (PAS) domain that is preceded by a conserved sequence of 25–27 amino acids known as the PAS-cap. The C terminus contains a region with homology to cyclic nucleotide binding domains (cNBHD), which is directly linked to the channel pore. The human EAG1 (hEAG1) channel is remarkably sensitive to inhibition by intracellular calcium (Ca2+i) through binding of Ca2+-calmodulin to three sites adjacent to the eagD and cNBHD. Here, we show that the eagD and cNBHD interact to modulate Ca2+-calmodulin as well as voltage-dependent gating. Sustained elevation of Ca2+i resulted in an initial profound inhibition of hEAG1 currents, which was followed by a phase when current amplitudes partially recovered, but activation gating was slowed and shifted to depolarized potentials. Deletion of either the eagD or cNBHD abolished the inhibition by Ca2+i. However, deletion of just the PAS-cap resulted in a >15-fold potentiation in response to elevated Ca2+i. Mutations of residues at the interface between the eagD and cNBHD have been linked to human cancer. Glu-600 on the cNBHD, when substituted with residues with a larger volume, resulted in hEAG1 currents that were profoundly potentiated by Ca2+i in a manner similar to the ΔPAS-cap mutant. These findings provide the first evidence that eagD and cNBHD interactions are regulating Ca2+-dependent gating and indicate that the binding of the PAS-cap with the cNBHD is required for the closure of the channels upon CaM binding.
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Affiliation(s)
- Eva Lörinczi
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN
| | - Matthew Helliwell
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN, the School of Physiology and Pharmacology, University of Bristol, Bristol BS5 1TD, and
| | - Alina Finch
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN
| | - Phillip J Stansfeld
- the Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Noel W Davies
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN
| | - Martyn Mahaut-Smith
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN
| | - Frederick W Muskett
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN
| | - John S Mitcheson
- From the Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN,
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