1
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Jarva TM, Phillips NM, Von Eiff C, Poulakis GR, Naylor G, Feldheim KA, Flynt AS. Gene expression, evolution, and the genetics of electrosensing in the smalltooth sawfish, Pristis pectinata. Ecol Evol 2024; 14:e11260. [PMID: 38694751 PMCID: PMC11057056 DOI: 10.1002/ece3.11260] [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: 04/10/2023] [Revised: 03/14/2024] [Accepted: 03/28/2024] [Indexed: 05/04/2024] Open
Abstract
Sawfishes (Pristidae) are large, highly threatened rays named for their tooth-studded rostrum, which is used for prey sensing and capture. Of all five species, the smalltooth sawfish, Pristis pectinata, has experienced the greatest decline in range, currently found in only ~20% of its historic range. To better understand the genetic underpinnings of these taxonomically and morphologically unique animals, we collected transcriptomic data from several tissue types, mapped them to the recently completed reference genome, and contrasted the patterns observed with comparable data from other elasmobranchs. Evidence of positive selection was detected in 79 genes in P. pectinata, several of which are involved in growth factor/receptor tyrosine kinase signaling and body symmetry and may be related to the unique morphology of sawfishes. Changes in these genes may impact cellular responses to environmental conditions such as temperature, dissolved oxygen, and salinity. Data acquired also allow for examination of the molecular components of P. pectinata electrosensory systems, which are highly developed in sawfishes and have likely been influential in their evolutionary success.
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Affiliation(s)
- Taiya M. Jarva
- School of Biological, Environmental, and Earth SciencesThe University of Southern MississippiHattiesburgMississippiUSA
| | - Nicole M. Phillips
- School of Biological, Environmental, and Earth SciencesThe University of Southern MississippiHattiesburgMississippiUSA
| | - Cory Von Eiff
- School of Biological, Environmental, and Earth SciencesThe University of Southern MississippiHattiesburgMississippiUSA
| | - Gregg R. Poulakis
- Charlotte Harbor Field LaboratoryFish and Wildlife Research Institute, Florida Fish and Wildlife Conservation CommissionPort CharlotteFloridaUSA
| | - Gavin Naylor
- Florida Program for Shark ResearchUniversity of FloridaGainesvilleFloridaUSA
| | - Kevin A. Feldheim
- Pritzker Laboratory for Molecular Systematics and Evolution, the Field MuseumChicagoIllinoisUSA
| | - Alex S. Flynt
- School of Biological, Environmental, and Earth SciencesThe University of Southern MississippiHattiesburgMississippiUSA
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2
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Li Q, Chen G, Yan J. Transmembrane determinants of voltage-gating differences between BK (Slo1) and Slo3 channels. Biophys J 2024:S0006-3495(24)00278-9. [PMID: 38637987 DOI: 10.1016/j.bpj.2024.04.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 02/01/2024] [Accepted: 04/15/2024] [Indexed: 04/20/2024] Open
Abstract
Voltage-gated potassium channels are critical in modulating cellular excitability, with Slo (slowpoke) channels forming a unique family characterized by their large conductance and dual regulation by electrical signals and intracellular messengers. Despite their structural and evolutionary similarities, Slo1 and Slo3 channels exhibit significant differences in their voltage-gating properties. This study investigates the molecular determinants that differentiate the voltage-gating properties of human Slo1 and mouse Slo3 channels. Utilizing Slo1/Slo3 chimeras, we pinpointed the selectivity filter region as a key factor in the Slo3 channel's reduced conductance at negative voltages. The S6 transmembrane (TM) segment was identified as pivotal for the Slo3 channel's biphasic deactivation kinetics at these voltages. Additionally, the S4 and S6 TM segments were found to be responsible for the gradual slope in the Slo3 channel's conductance-voltage relationship, while multiple TM regions appear to be involved in the Slo3 channel's requirement of strong depolarization for activation. Mutations in the Slo1's S5 and S6 TM segments revealed three residues (I233, L302, and M304) that likely play a crucial role in the allosteric coupling between the voltage sensors and the pore gate.
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Affiliation(s)
- Qin Li
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas
| | - Guanxing Chen
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas; Molecular & Translational Biology and Neuroscience Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, Texas.
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3
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Echeverría F, Gonzalez-Sanabria N, Alvarado-Sanchez R, Fernández M, Castillo K, Latorre R. Large conductance voltage-and calcium-activated K + (BK) channel in health and disease. Front Pharmacol 2024; 15:1373507. [PMID: 38584598 PMCID: PMC10995336 DOI: 10.3389/fphar.2024.1373507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/12/2024] [Indexed: 04/09/2024] Open
Abstract
Large Conductance Voltage- and Calcium-activated K+ (BK) channels are transmembrane pore-forming proteins that regulate cell excitability and are also expressed in non-excitable cells. They play a role in regulating vascular tone, neuronal excitability, neurotransmitter release, and muscle contraction. Dysfunction of the BK channel can lead to arterial hypertension, hearing disorders, epilepsy, and ataxia. Here, we provide an overview of BK channel functioning and the implications of its abnormal functioning in various diseases. Understanding the function of BK channels is crucial for comprehending the mechanisms involved in regulating vital physiological processes, both in normal and pathological conditions, controlled by BK. This understanding may lead to the development of therapeutic interventions to address BK channelopathies.
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Affiliation(s)
- Felipe Echeverría
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Naileth Gonzalez-Sanabria
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sanchez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Miguel Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Centro de Investigación de Estudios Avanzados del Maule, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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4
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Van NTH, Kim WK, Nam JH. Challenges in the Therapeutic Targeting of KCa Channels: From Basic Physiology to Clinical Applications. Int J Mol Sci 2024; 25:2965. [PMID: 38474212 PMCID: PMC10932353 DOI: 10.3390/ijms25052965] [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: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Calcium-activated potassium (KCa) channels are ubiquitously expressed throughout the body and are able to regulate membrane potential and intracellular calcium concentrations, thereby playing key roles in cellular physiology and signal transmission. Consequently, it is unsurprising that KCa channels have been implicated in various diseases, making them potential targets for pharmaceutical interventions. Over the past two decades, numerous studies have been conducted to develop KCa channel-targeting drugs, including those for disorders of the central and peripheral nervous, cardiovascular, and urinary systems and for cancer. In this review, we synthesize recent findings regarding the structure and activating mechanisms of KCa channels. We also discuss the role of KCa channel modulators in therapeutic medicine. Finally, we identify the major reasons behind the delay in bringing these modulators to the pharmaceutical market and propose new strategies to promote their application.
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Affiliation(s)
- Nhung Thi Hong Van
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
- Department of Internal Medicine, Graduate School of Medicine, Dongguk University, Goyang 10326, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
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5
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Yamanouchi D, Kasuya G, Nakajo K, Kise Y, Nureki O. Dual allosteric modulation of voltage and calcium sensitivities of the Slo1-LRRC channel complex. Mol Cell 2023; 83:4555-4569.e4. [PMID: 38035882 DOI: 10.1016/j.molcel.2023.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 09/15/2023] [Accepted: 11/06/2023] [Indexed: 12/02/2023]
Abstract
Modulation of large conductance intracellular ligand-activated potassium (BK) channel family (Slo1-3) by auxiliary subunits allows diverse physiological functions in excitable and non-excitable cells. Cryoelectron microscopy (cryo-EM) structures of voltage-gated potassium (Kv) channel complexes have provided insights into how voltage sensitivity is modulated by auxiliary subunits. However, the modulation mechanisms of BK channels, particularly as ligand-activated ion channels, remain unknown. Slo1 is a Ca2+-activated and voltage-gated BK channel and is expressed in neurons, muscle cells, and epithelial cells. Using cryo-EM and electrophysiology, we show that the LRRC26-γ1 subunit modulates not only voltage but also Ca2+ sensitivity of Homo sapiens Slo1. LRRC26 stabilizes the active conformation of voltage-senor domains of Slo1 by an extracellularly S4-locking mechanism. Furthermore, it also stabilizes the active conformation of Ca2+-sensor domains of Slo1 intracellularly, which is functionally equivalent to intracellular Ca2+ in the activation of Slo1. Such a dual allosteric modulatory mechanism may be general in regulating the intracellular ligand-activated BK channel complexes.
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Affiliation(s)
- Daichi Yamanouchi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Go Kasuya
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 329-0498, Japan.
| | - Koichi Nakajo
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke-shi, Tochigi 329-0498, Japan
| | - Yoshiaki Kise
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Osamu Nureki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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6
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Kallure GS, Pal K, Zhou Y, Lingle CJ, Chowdhury S. High-resolution structures illuminate key principles underlying voltage and LRRC26 regulation of Slo1 channels. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572542. [PMID: 38187713 PMCID: PMC10769243 DOI: 10.1101/2023.12.20.572542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Multi-modal regulation of Slo1 channels by membrane voltage, intracellular calcium, and auxiliary subunits enables its pleiotropic physiological functions. Our understanding of how voltage impacts Slo1 conformational dynamics and the mechanisms by which auxiliary subunits, particularly of the LRRC (Leucine Rich Repeat containing) family of proteins, modulate its voltage gating remain unresolved. Here, we used single particle cryo-electron microscopy to determine structures of human Slo1 mutants which functionally stabilize the closed pore (F315A) or the activated voltage-sensor (R207A). Our structures, obtained under calcium-free conditions, reveal that a key step in voltage-sensing by Slo1 involves a rotameric flip of the voltage-sensing charges (R210 and R213) moving them by ∼6 Å across a hydrophobic gasket. Next we obtained reconstructions of a complex of human Slo1 with the human LRRC26 (γ1) subunit in absence of calcium. Together with extensive biochemical tests, we show that the extracellular domains of γ1 form a ring of interlocked dominos that stabilizes the quaternary assembly of the complex and biases Slo1:γ1 assembly towards high stoichiometric complexes. The transmembrane helix of γ1 is kinked and tightly packed against the Slo1 voltage-sensor. We hypothesize that γ1 subunits exert relatively small effects on early steps in voltage-gating but structurally stabilize non-S4 helices of Slo1 voltage-sensor which energetically facilitate conformational rearrangements that occur late in voltage stimulated transitions.
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7
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Pham T, Hussein T, Calis D, Bischof H, Skrabak D, Cruz Santos M, Maier S, Spähn D, Kalina D, Simonsig S, Ehinger R, Groschup B, Knipper M, Plesnila N, Ruth P, Lukowski R, Matt L. BK channels sustain neuronal Ca 2+ oscillations to support hippocampal long-term potentiation and memory formation. Cell Mol Life Sci 2023; 80:369. [PMID: 37989805 PMCID: PMC10663188 DOI: 10.1007/s00018-023-05016-y] [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: 05/15/2023] [Revised: 09/25/2023] [Accepted: 10/24/2023] [Indexed: 11/23/2023]
Abstract
Mutations of large conductance Ca2+- and voltage-activated K+ channels (BK) are associated with cognitive impairment. Here we report that CA1 pyramidal neuron-specific conditional BK knock-out (cKO) mice display normal locomotor and anxiety behavior. They do, however, exhibit impaired memory acquisition and retrieval in the Morris Water Maze (MWM) when compared to littermate controls (CTRL). In line with cognitive impairment in vivo, electrical and chemical long-term potentiation (LTP) in cKO brain slices were impaired in vitro. We further used a genetically encoded fluorescent K+ biosensor and a Ca2+-sensitive probe to observe cultured hippocampal neurons during chemical LTP (cLTP) induction. cLTP massively reduced intracellular K+ concentration ([K+]i) while elevating L-Type Ca2+ channel- and NMDA receptor-dependent Ca2+ oscillation frequencies. Both, [K+]i decrease and Ca2+ oscillation frequency increase were absent after pharmacological BK inhibition or in cells lacking BK. Our data suggest that L-Type- and NMDAR-dependent BK-mediated K+ outflow significantly contributes to hippocampal LTP, as well as learning and memory.
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Affiliation(s)
- Thomas Pham
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Tamara Hussein
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Dila Calis
- Department of Otolaryngology, Head and Neck Surgery, Molecular Physiology of Hearing, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Helmut Bischof
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - David Skrabak
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Melanie Cruz Santos
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Selina Maier
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - David Spähn
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Daniel Kalina
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Stefanie Simonsig
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Rebekka Ehinger
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Bernhard Groschup
- Laboratory of Experimental Stroke Research, Institute for Stroke and Dementia Research (ISD), University Hospital, Ludwig-Maximilians-University Munich (LMU), Munich, Germany
| | - Marlies Knipper
- Department of Otolaryngology, Head and Neck Surgery, Molecular Physiology of Hearing, Tübingen Hearing Research Centre, University of Tübingen, Tübingen, Germany
| | - Nikolaus Plesnila
- Laboratory of Experimental Stroke Research, Institute for Stroke and Dementia Research (ISD), University Hospital, Ludwig-Maximilians-University Munich (LMU), Munich, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Lucas Matt
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Tübingen, Germany.
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8
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Chen G, Li Q, Webb TI, Hollywood MA, Yan J. BK channel modulation by positively charged peptides and auxiliary γ subunits mediated by the Ca2+-bowl site. J Gen Physiol 2023; 155:e202213237. [PMID: 37130264 PMCID: PMC10163825 DOI: 10.1085/jgp.202213237] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 01/12/2023] [Accepted: 04/13/2023] [Indexed: 05/04/2023] Open
Abstract
The large-conductance, Ca2+-, and voltage-activated K+ (BK) channel consists of the pore-forming α (BKα) subunit and regulatory β and γ subunits. The γ1-3 subunits facilitate BK channel activation by shifting the voltage-dependence of channel activation toward the hyperpolarization direction by about 50-150 mV in the absence of Ca2+. We previously found that the intracellular C-terminal positively charged regions of the γ subunits play important roles in BK channel modulation. In this study, we found that the intracellular C-terminal region of BKα is indispensable in BK channel modulation by the γ1 subunit. Notably, synthetic peptide mimics of the γ1-3 subunits' C-terminal positively charged regions caused 30-50 mV shifts in BKα channel voltage-gating toward the hyperpolarization direction. The cationic cell-penetrating HIV-1 Tat peptide exerted a similar BK channel-activating effect. The BK channel-activating effects of the synthetic peptides were reduced in the presence of Ca2+ and markedly ablated by both charge neutralization of the Ca2+-bowl site and high ionic strength, suggesting the involvement of electrostatic interactions. The efficacy of the γ subunits in BK channel modulation was reduced by charge neutralization of the Ca2+-bowl site. However, BK channel modulation by the γ1 subunit was little affected by high ionic strength and the positively charged peptide remained effective in BK channel modulation in the presence of the γ1 subunit. These findings identify positively charged peptides as BK channel modulators and reveal a role for the Ca2+-bowl site in BK channel modulation by positively charged peptides and the C-terminal positively charged regions of auxiliary γ subunits.
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Affiliation(s)
- Guanxing Chen
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Qin Li
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Timothy I. Webb
- The Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Mark A. Hollywood
- The Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Neuroscience and Biochemistry and Cell Biology Graduate Programs, MD Anderson UT Health Graduate School of Biomedical Sciences, Houston, TX, USA
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9
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Wang ZW, Trussell LO, Vedantham K. Regulation of Neurotransmitter Release by K + Channels. ADVANCES IN NEUROBIOLOGY 2023; 33:305-331. [PMID: 37615872 DOI: 10.1007/978-3-031-34229-5_12] [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] [Indexed: 08/25/2023]
Abstract
K+ channels play potent roles in the process of neurotransmitter release by influencing the action potential waveform and modulating neuronal excitability and release probability. These diverse effects of K+ channel activation are ensured by the wide variety of K+ channel genes and their differential expression in different cell types. Accordingly, a variety of K+ channels have been implicated in regulating neurotransmitter release, including the Ca2+- and voltage-gated K+ channel Slo1 (also known as BK channel), voltage-gated K+ channels of the Kv3 (Shaw-type), Kv1 (Shaker-type), and Kv7 (KCNQ) families, G-protein-gated inwardly rectifying K+ (GIRK) channels, and SLO-2 (a Ca2+-. Cl-, and voltage-gated K+ channel in C. elegans). These channels vary in their expression patterns, subcellular localization, and biophysical properties. Their roles in neurotransmitter release may also vary depending on the synapse and physiological or experimental conditions. This chapter summarizes key findings about the roles of K+ channels in regulating neurotransmitter release.
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Affiliation(s)
- Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA.
| | - Laurence O Trussell
- Oregon Hearing Research Center & Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Kiranmayi Vedantham
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
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10
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Mapping the functional expression of auxiliary subunits of K Ca1.1 in glioblastoma. Sci Rep 2022; 12:22023. [PMID: 36539587 PMCID: PMC9768140 DOI: 10.1038/s41598-022-26196-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022] Open
Abstract
Glioblastoma (GBM) is the most aggressive glial tumor, where ion channels, including KCa1.1, are candidates for new therapeutic options. Since the auxiliary subunits linked to KCa1.1 in GBM are largely unknown we used electrophysiology combined with pharmacology and gene silencing to address the functional expression of KCa1.1/β subunits complexes in both primary tumor cells and in the glioblastoma cell line U-87 MG. The pattern of the sensitivity (activation/inhibition) of the whole-cell currents to paxilline, lithocholic acid, arachidonic acid, and iberiotoxin; the presence of inactivation of the whole-cell current along with the loss of the outward rectification upon exposure to the reducing agent DTT collectively argue that KCa1.1/β3 complex is expressed in U-87 MG. Similar results were found using human primary glioblastoma cells isolated from patient samples. Silencing the β3 subunit expression inhibited carbachol-induced Ca2+ transients in U-87 MG thereby indicating the role of the KCa1.1/β3 in the Ca2+ signaling of glioblastoma cells. Functional expression of the KCa1.1/β3 complex, on the other hand, lacks cell cycle dependence. We suggest that the KCa1.1/β3 complex may have diagnostic and therapeutic potential in glioblastoma in the future.
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11
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Pereira da Silva EA, Martín-Aragón Baudel M, Navedo MF, Nieves-Cintrón M. Ion channel molecular complexes in vascular smooth muscle. Front Physiol 2022; 13:999369. [PMID: 36091375 PMCID: PMC9459047 DOI: 10.3389/fphys.2022.999369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 08/02/2022] [Indexed: 11/30/2022] Open
Abstract
Ion channels that influence membrane potential and intracellular calcium concentration control vascular smooth muscle excitability. Voltage-gated calcium channels (VGCC), transient receptor potential (TRP) channels, voltage (KV), and Ca2+-activated K+ (BK) channels are key regulators of vascular smooth muscle excitability and contractility. These channels are regulated by various signaling cues, including protein kinases and phosphatases. The effects of these ubiquitous signaling molecules often depend on the formation of macromolecular complexes that provide a platform for targeting and compartmentalizing signaling events to specific substrates. This manuscript summarizes our current understanding of specific molecular complexes involving VGCC, TRP, and KV and BK channels and their contribution to regulating vascular physiology.
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12
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Bae EJ, Jo H, Kim SS, Shin DS, Yang JY, Bae MA, Jeong P, Park CS, Ahn JH. Novel Thioxothiazolo[3,4- a]quinazolin-5(4 H)-one Derivatives as BK Ca Channel Activators for Urinary Incontinence. ACS Med Chem Lett 2022; 13:1052-1061. [DOI: 10.1021/acsmedchemlett.2c00070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Eun Jung Bae
- Department of Chemistry, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Heeji Jo
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Seong Soon Kim
- Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
| | - Dae-Seop Shin
- Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
| | - Jung Yoon Yang
- Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
| | - Myung Ae Bae
- Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology, Daejeon 34114, Korea
| | - Pyeonghwa Jeong
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | - Chul-Seung Park
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Jin Hee Ahn
- Department of Chemistry, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
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13
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Discovery and characterization of a potent activator of the BK Ca channel that relives overactive bladder syndrome in rats. Eur J Pharmacol 2022; 927:175055. [PMID: 35644420 DOI: 10.1016/j.ejphar.2022.175055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 05/13/2022] [Accepted: 05/19/2022] [Indexed: 11/21/2022]
Abstract
The large-conductance Ca2+-activated K+ channel (BKCa channel) is involved in repolarizing the membrane potential and has a variety of cellular functions. The BKCa channel is highly expressed in bladder smooth muscle and mediates muscle relaxation. Compounds that activate the BKCa channel have therapeutic potential against pathological symptoms associated with the overactivity of bladder smooth muscle. In this regard, we screened a chemical library of 9938 compounds to identify novel BKCa channel activators. A cell-based fluorescence assay identified a structural family of compounds containing a common tricyclic quinazoline ring that activated the BKCa channel. The most potent compound TTQC-1 (7-bromo-N-(3-methylphenyl)-5-oxo-1-thioxo-4,5-dihydro[1,3]thiazolo[3,4-a]quinazoline-3-carboxamide) directly and reversibly activated the macroscopic current of BKCa channels expressed in Xenopus oocytes from both sides of the cellular membrane. TTQC-1 increased the maximum conductance and shifted the half activation voltage to the left. The apparent half-maximal effective concentration and dissociation constant were 2.8 μM and 7.95 μM, respectively. TTQC-1 delayed the kinetics of channel deactivation without affecting channel activation. The activation effects were observed over a wide range of intracellular Ca2+ concentrations and dependent on the co-expression of β1 and β4 auxiliary subunits, which are highly expressed in urinary bladder. In the isolated smooth muscle cells of rat urinary bladder, TTQC-1 increased the K+ currents which can be blocked by iberiotoxin. Finally, oral administration of TTQC-1 to hypertensive rats decreased the urination frequency. Therefore, TTQC-1 is a BKCa channel activator with a novel structure that is a potential therapeutic candidate for BKCa channel-related diseases, such as overactive bladder syndrome.
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Zuccolini P, Gavazzo P, Pusch M. BK Channel in the Physiology and in the Cancer of Pancreatic Duct: Impact and Reliability of BK Openers. Front Pharmacol 2022; 13:906608. [PMID: 35685628 PMCID: PMC9171006 DOI: 10.3389/fphar.2022.906608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
BK (KCa 1.1, Slo-1) is a K+ channel characterized by an allosteric regulation of the gating mechanism by Ca2+ binding and voltage, and a high unitary conductance. The channel is expressed in many different tissues, where it is involved in the regulation or the fine-tuning of many physiological processes. Among other organs, BK is expressed in the pancreatic duct, a part of the gland important for the correct ionic composition of the pancreatic juice. Unfortunately, the pancreatic duct is also the site where one of the deadliest cancer types, the pancreatic duct adenocarcinoma (PDAC), develops. In the past years, it has been reported that continuous exposure of cancer cells to BK openers can have a significant impact on cell viability as well as on the ability to proliferate and migrate. Here, we first summarize the main BK channel properties and its roles in pancreatic duct physiology. Then we focus on the potential role of BK as a pharmacological target in PDAC. Moreover, we discuss how results obtained when employing BK activators on cancer cells can, in some cases, be misleading.
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15
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Gonzalez-Perez V, Zhou Y, Ciorba MA, Lingle CJ. The LRRC family of BK channel regulatory subunits: potential roles in health and disease. J Physiol 2022; 600:1357-1371. [PMID: 35014034 PMCID: PMC8930516 DOI: 10.1113/jp281952] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 01/04/2022] [Indexed: 11/08/2022] Open
Abstract
Large conductance K+ channels, termed BK channels, regulate a variety of cellular and physiological functions. Although universally activated by changes in voltage or [Ca2+ ]i , the threshold for BK channel activation varies among loci of expression, often arising from cell-specific regulatory subunits including a family of leucine rich repeat-containing (LRRC) γ subunits (LRRC26, LRRC52, LRRC55 and LRRC38). The 'founding' member of this family, LRRC26, was originally identified as a tumour suppressor in various cancers. An LRRC26 knockout (KO) mouse model recently revealed that LRRC26 is also highly expressed in secretory epithelial cells and partners with BK channels in the salivary gland and colonic goblet cells to promote sustained K+ fluxes likely essential for normal secretory function. To accomplish this, LRRC26 negatively shifts the range of BK channel activation such that channels contribute to K+ flux near typical epithelial cell resting conditions. In colon, the absence of LRRC26 increases vulnerability to colitis. LRRC26-containing BK channels are also likely important regulators of epithelial function in other loci, including airways, female reproductive tract and mammary gland. Based on an LRRC52 KO mouse model, LRRC52 regulation of large conductance K+ channels plays a role both in sperm function and in cochlear inner hair cells. Although our understanding of LRRC-containing BK channels remains rudimentary, KO mouse models may help define other organs in which LRRC-containing channels support normal function. A key topic for future work concerns identification of endogenous mechanisms, whether post-translational or via gene regulation, that may impact LRRC-dependent pathologies.
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Affiliation(s)
- Vivian Gonzalez-Perez
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., Saint Louis, MO 63110 USA
| | - Yu Zhou
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., Saint Louis, MO 63110 USA
| | - Matthew A. Ciorba
- Department of Internal Medicine, Division of Gastroenterology, Washington University School of Medicine, St. Louis MO 63110 USA
| | - Christopher J. Lingle
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave., Saint Louis, MO 63110 USA
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16
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Chen G, Li Q, Yan J. The leucine-rich repeat domains of BK channel auxiliary γ subunits regulate their expression, trafficking, and channel-modulation functions. J Biol Chem 2022; 298:101664. [PMID: 35104503 PMCID: PMC8892010 DOI: 10.1016/j.jbc.2022.101664] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/16/2022] [Accepted: 01/26/2022] [Indexed: 11/25/2022] Open
Abstract
As high-conductance calcium- and voltage-dependent potassium channels, BK channels consist of pore-forming, voltage-, and Ca2+-sensing α and auxiliary subunits. The leucine-rich repeat (LRR) domain-containing auxiliary γ subunits potently modulate the voltage dependence of BK channel activation. Despite their dominant size in whole protein masses, the function of the LRR domain in BK channel γ subunits is unknown. We here investigated the function of these LRR domains in BK channel modulation by the auxiliary γ1-3 (LRRC26, LRRC52, and LRRC55) subunits. Using cell surface protein immunoprecipitation, we validated the predicted extracellular localization of the LRR domains. We then refined the structural models of mature proteins on the membrane via molecular dynamic simulations. By replacement of the LRR domain with extracellular regions or domains of non-LRR proteins, we found that the LRR domain is nonessential for the maximal channel-gating modulatory effect but is necessary for the all-or-none phenomenon of BK channel modulation by the γ1 subunit. Mutational and enzymatic blockade of N-glycosylation in the γ1-3 subunits resulted in a reduction or loss of BK channel modulation by γ subunits. Finally, by analyzing their expression in whole cells and on the plasma membrane, we found that blockade of N-glycosylation drastically reduced total expression of the γ2 subunit and the cell surface expression of the γ1 and γ3 subunits. We conclude that the LRR domains play key roles in the regulation of the expression, cell surface trafficking, and channel-modulation functions of the BK channel γ subunits.
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Affiliation(s)
- Guanxing Chen
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Qin Li
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Jiusheng Yan
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA; Graduate Programs of Neuroscience and Biochemistry and Cell Biology, The University of Texas MD Anderson Cancer Center UT Health Graduate School of Biomedical Sciences, Houston, Texas, USA.
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17
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Zuccolini P, Ferrera L, Remigante A, Picco C, Barbieri R, Bertelli S, Moran O, Gavazzo P, Pusch M. The VRAC blocker DCPIB directly gates the BK channels and increases intracellular Ca 2+ in Melanoma and Pancreatic Duct Adenocarcinoma (PDAC) cell lines. Br J Pharmacol 2022; 179:3452-3469. [PMID: 35102550 DOI: 10.1111/bph.15810] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 01/18/2022] [Accepted: 01/24/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The Volume Regulated Anion Channel (VRAC) is known to be involved in different aspects of cancer cell behavior and response to therapies. For this reason, we investigated the effect of DCPIB, a presumably specific blocker of VRAC, in two types of cancer: pancreatic duct adenocarcinoma (PDAC) and melanoma. EXPERIMENTAL APPROACH For this investigation, we used patch-clamp electrophysiology, supported by Ca2+ imaging, gene expression analysis, docking simulation and mutagenesis. We employed two PDAC lines (Panc-1 and MiaPaCa-2), as well as a primary (IGR39) and a metastatic (IGR37) melanoma line. KEY RESULTS Surprisingly, DCPIB induced a dramatic increase of whole-cell currents in Panc-1, MiaPaca2 and IGR39, but not in IGR37 cells. The currents were mostly mediated by the KCa1.1 channel, commonly known as BK. We verified DCPIB activation of BK also in HEK293 cells transfected with the α subunit of the channel. Further experiments showed that in IGR39, and to a smaller degree also in Panc-1 cells, DCPIB induces a rapid Ca2+ influx. This, in turn, indirectly potentiates BK and, in IGR39 cells, additionally activates other Ca2+ -dependent channels. However, the Ca2+ influx is not required for BK activation by DCPIB: indeed, we found that the activation of BK by DCPIB involves the extracellular part of the protein and identified two residues crucial for binding. CONCLUSION AND IMPLICATIONS DCPIB directly targets BK channels and, in addition, can acutely increase intracellular Ca2+ . Our findings elongate the list of DCPIB effects that have to be taken into consideration for future development of DCPIB-based modulators of ion channels and other membrane proteins.
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Affiliation(s)
- Paolo Zuccolini
- Institute of Biophysics, National Research Council, Genova, Italy
| | - Loretta Ferrera
- Institute of Biophysics, National Research Council, Genova, Italy.,U.O.C. Genetica Medica, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto Giannina Gaslini, Genova, Italy
| | | | - Cristiana Picco
- Institute of Biophysics, National Research Council, Genova, Italy
| | | | - Sara Bertelli
- Institute of Biophysics, National Research Council, Genova, Italy
| | - Oscar Moran
- Institute of Biophysics, National Research Council, Genova, Italy
| | - Paola Gavazzo
- Institute of Biophysics, National Research Council, Genova, Italy
| | - Michael Pusch
- Institute of Biophysics, National Research Council, Genova, Italy
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18
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Shah KR, Guan X, Yan J. Structural and Functional Coupling of Calcium-Activated BK Channels and Calcium-Permeable Channels Within Nanodomain Signaling Complexes. Front Physiol 2022; 12:796540. [PMID: 35095560 PMCID: PMC8795833 DOI: 10.3389/fphys.2021.796540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 12/28/2021] [Indexed: 11/13/2022] Open
Abstract
Biochemical and functional studies of ion channels have shown that many of these integral membrane proteins form macromolecular signaling complexes by physically associating with many other proteins. These macromolecular signaling complexes ensure specificity and proper rates of signal transduction. The large-conductance, Ca2+-activated K+ (BK) channel is dually activated by membrane depolarization and increases in intracellular free Ca2+ ([Ca2+]i). The activation of BK channels results in a large K+ efflux and, consequently, rapid membrane repolarization and closing of the voltage-dependent Ca2+-permeable channels to limit further increases in [Ca2+]i. Therefore, BK channel-mediated K+ signaling is a negative feedback regulator of both membrane potential and [Ca2+]i and plays important roles in many physiological processes and diseases. However, the BK channel formed by the pore-forming and voltage- and Ca2+-sensing α subunit alone requires high [Ca2+]i levels for channel activation under physiological voltage conditions. Thus, most native BK channels are believed to co-localize with Ca2+-permeable channels within nanodomains (a few tens of nanometers in distance) to detect high levels of [Ca2+]i around the open pores of Ca2+-permeable channels. Over the last two decades, advancement in research on the BK channel’s coupling with Ca2+-permeable channels including recent reports involving NMDA receptors demonstrate exemplary models of nanodomain structural and functional coupling among ion channels for efficient signal transduction and negative feedback regulation. We hereby review our current understanding regarding the structural and functional coupling of BK channels with different Ca2+-permeable channels.
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Affiliation(s)
- Kunal R. Shah
- Department of Anesthesiology & Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Xin Guan
- Department of Anesthesiology & Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Jiusheng Yan
- Department of Anesthesiology & Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
- Neuroscience Program, Graduate School of Biomedical Sciences, UT Health, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
- Biochemistry and Cell Biology Program, Graduate School of Biomedical Sciences, UT Health, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
- *Correspondence: Jiusheng Yan,
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19
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Wrzosek A, Gałecka S, Żochowska M, Olszewska A, Kulawiak B. Alternative Targets for Modulators of Mitochondrial Potassium Channels. Molecules 2022; 27:299. [PMID: 35011530 PMCID: PMC8746388 DOI: 10.3390/molecules27010299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/30/2021] [Accepted: 12/31/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondrial potassium channels control potassium influx into the mitochondrial matrix and thus regulate mitochondrial membrane potential, volume, respiration, and synthesis of reactive oxygen species (ROS). It has been found that pharmacological activation of mitochondrial potassium channels during ischemia/reperfusion (I/R) injury activates cytoprotective mechanisms resulting in increased cell survival. In cancer cells, the inhibition of these channels leads to increased cell death. Therefore, mitochondrial potassium channels are intriguing targets for the development of new pharmacological strategies. In most cases, however, the substances that modulate the mitochondrial potassium channels have a few alternative targets in the cell. This may result in unexpected or unwanted effects induced by these compounds. In our review, we briefly present the various classes of mitochondrial potassium (mitoK) channels and describe the chemical compounds that modulate their activity. We also describe examples of the multidirectional activity of the activators and inhibitors of mitochondrial potassium channels.
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Affiliation(s)
- Antoni Wrzosek
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.W.); (S.G.); (M.Ż.)
| | - Shur Gałecka
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.W.); (S.G.); (M.Ż.)
| | - Monika Żochowska
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.W.); (S.G.); (M.Ż.)
| | - Anna Olszewska
- Department of Histology, Medical University of Gdansk, 1a Debinki, 80-211 Gdansk, Poland;
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.W.); (S.G.); (M.Ż.)
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20
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Lu T, Lee HC. Coronary Large Conductance Ca 2+-Activated K + Channel Dysfunction in Diabetes Mellitus. Front Physiol 2021; 12:750618. [PMID: 34744789 PMCID: PMC8567020 DOI: 10.3389/fphys.2021.750618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/14/2021] [Indexed: 11/24/2022] Open
Abstract
Diabetes mellitus (DM) is an independent risk of macrovascular and microvascular complications, while cardiovascular diseases remain a leading cause of death in both men and women with diabetes. Large conductance Ca2+-activated K+ (BK) channels are abundantly expressed in arteries and are the key ionic determinant of vascular tone and organ perfusion. It is well established that the downregulation of vascular BK channel function with reduced BK channel protein expression and altered intrinsic BK channel biophysical properties is associated with diabetic vasculopathy. Recent efforts also showed that diabetes-associated changes in signaling pathways and transcriptional factors contribute to the downregulation of BK channel expression. This manuscript will review our current understandings on the molecular, physiological, and biophysical mechanisms that underlie coronary BK channelopathy in diabetes mellitus.
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Affiliation(s)
- Tong Lu
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, United States
| | - Hon-Chi Lee
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, MN, United States
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21
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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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22
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Control of Biophysical and Pharmacological Properties of Potassium Channels by Ancillary Subunits. Handb Exp Pharmacol 2021; 267:445-480. [PMID: 34247280 DOI: 10.1007/164_2021_512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Potassium channels facilitate and regulate physiological processes as diverse as electrical signaling, ion, solute and hormone secretion, fluid homeostasis, hearing, pain sensation, muscular contraction, and the heartbeat. Potassium channels are each formed by either a tetramer or dimer of pore-forming α subunits that co-assemble to create a multimer with a K+-selective pore that in most cases is capable of functioning as a discrete unit to pass K+ ions across the cell membrane. The reality in vivo, however, is that the potassium channel α subunit multimers co-assemble with ancillary subunits to serve specific physiological functions. The ancillary subunits impart specific physiological properties that are often required for a particular activity in vivo; in addition, ancillary subunit interaction often alters the pharmacology of the resultant complex. In this chapter the modes of action of ancillary subunits on K+ channel physiology and pharmacology are described and categorized into various mechanistic classes.
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23
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Sek A, Kampa RP, Kulawiak B, Szewczyk A, Bednarczyk P. Identification of the Large-Conductance Ca 2+-Regulated Potassium Channel in Mitochondria of Human Bronchial Epithelial Cells. Molecules 2021; 26:molecules26113233. [PMID: 34072205 PMCID: PMC8199365 DOI: 10.3390/molecules26113233] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/19/2021] [Accepted: 05/24/2021] [Indexed: 12/18/2022] Open
Abstract
Mitochondria play a key role in energy metabolism within the cell. Potassium channels such as ATP-sensitive, voltage-gated or large-conductance Ca2+-regulated channels have been described in the inner mitochondrial membrane. Several hypotheses have been proposed to describe the important roles of mitochondrial potassium channels in cell survival and death pathways. In the current study, we identified two populations of mitochondrial large-conductance Ca2+-regulated potassium (mitoBKCa) channels in human bronchial epithelial (HBE) cells. The biophysical properties of the channels were characterized using the patch-clamp technique. We observed the activity of the channel with a mean conductance close to 285 pS in symmetric 150/150 mM KCl solution. Channel activity was increased upon application of the potassium channel opener NS11021 in the micromolar concentration range. The channel activity was completely inhibited by 1 µM paxilline and 300 nM iberiotoxin, selective inhibitors of the BKCa channels. Based on calcium and iberiotoxin modulation, we suggest that the C-terminus of the protein is localized to the mitochondrial matrix. Additionally, using RT-PCR, we confirmed the presence of α pore-forming (Slo1) and auxiliary β3-β4 subunits of BKCa channel in HBE cells. Western blot analysis of cellular fractions confirmed the mitochondrial localization of α pore-forming and predominately β3 subunits. Additionally, the regulation of oxygen consumption and membrane potential of human bronchial epithelial mitochondria in the presence of the potassium channel opener NS11021 and inhibitor paxilline were also studied. In summary, for the first time, the electrophysiological and functional properties of the mitoBKCa channel in a bronchial epithelial cell line were described.
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Affiliation(s)
- Aleksandra Sek
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.S.); (R.P.K.); (B.K.); (A.S.)
- Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland
| | - Rafal P. Kampa
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.S.); (R.P.K.); (B.K.); (A.S.)
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences—SGGW, 02-776 Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.S.); (R.P.K.); (B.K.); (A.S.)
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland; (A.S.); (R.P.K.); (B.K.); (A.S.)
| | - Piotr Bednarczyk
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences—SGGW, 02-776 Warsaw, Poland
- Correspondence: ; Tel.: +48-22-593-8620
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24
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Gałecka S, Kulawiak B, Bednarczyk P, Singh H, Szewczyk A. Single channel properties of mitochondrial large conductance potassium channel formed by BK-VEDEC splice variant. Sci Rep 2021; 11:10925. [PMID: 34035423 PMCID: PMC8149700 DOI: 10.1038/s41598-021-90465-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 05/10/2021] [Indexed: 01/15/2023] Open
Abstract
The activation of mitochondrial large conductance calcium-activated potassium (mitoBKCa) channels increases cell survival during ischemia/reperfusion injury of cardiac cells. The basic biophysical and pharmacological properties of mitoBKCa correspond to the properties of the BKCa channels from the plasma membrane. It has been suggested that the VEDEC splice variant of the KCNMA1 gene product encoding plasma membrane BKCa is targeted toward mitochondria. However there has been no direct evidence that this protein forms a functional channel in mitochondria. In our study, we used HEK293T cells to express the VEDEC splice variant and observed channel activity in mitochondria using the mitoplast patch-clamp technique. For the first time, we found that transient expression with the VEDEC isoform resulted in channel activity with the conductance of 290 ± 3 pS. The channel was voltage-dependent and activated by calcium ions. Moreover, the activity of the channel was stimulated by the potassium channel opener NS11021 and inhibited by hemin and paxilline, which are known BKCa channel blockers. Immunofluorescence experiments confirmed the partial colocalization of the channel within the mitochondria. From these results, we conclude that the VEDEC isoform of the BKCa channel forms a functional channel in the inner mitochondrial membrane. Additionally, our data show that HEK293T cells are a promising experimental model for expression and electrophysiological studies of mitochondrial potassium channels.
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Affiliation(s)
- Shur Gałecka
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur St., 02-093, Warsaw, Poland
| | - Bogusz Kulawiak
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur St., 02-093, Warsaw, Poland.
| | - Piotr Bednarczyk
- Department of Physics and Biophysics, Institute of Biology, Warsaw, University of Life Sciences-SGGW, Nowoursynowska 166, 02-787, Warsaw, Poland
| | - Harpreet Singh
- Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, 43210, USA
| | - Adam Szewczyk
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur St., 02-093, Warsaw, Poland
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25
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North KC, Bukiya AN, Dopico AM. BK channel-forming slo1 proteins mediate the brain artery constriction evoked by the neurosteroid pregnenolone. Neuropharmacology 2021; 192:108603. [PMID: 34023335 DOI: 10.1016/j.neuropharm.2021.108603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 04/15/2021] [Accepted: 04/29/2021] [Indexed: 01/24/2023]
Abstract
Pregnenolone is a neurosteroid that modulates glial growth and differentiation, neuronal firing, and several brain functions, these effects being attributed to pregnenolone actions on the neurons and glial cells themselves. Despite the vital role of the cerebral circulation for brain function and the fact that pregnenolone is a vasoactive agent, pregnenolone action on brain arteries remain unknown. Here, we obtained in vivo concentration response curves to pregnenolone on middle cerebral artery (MCA) diameter in anesthetized male and female C57BL/6J mice. In both male and female animals, pregnenolone (1 nM-100 μM) constricted MCA in a concentration-dependent manner, its maximal effect reaching ~22-35% decrease in diameter. Pregnenolone action was replicated in intact and de-endothelialized, in vitro pressurized MCA segments with pregnenolone evoking similar constriction in intact and de-endothelialized MCA. Neurosteroid action was abolished by 1 μM paxilline, a selective blocker of Ca2+ - and voltage-gated K+ channels of large conductance (BK). Cell-attached, patch-clamp recordings on freshly isolated smooth muscle cells from mouse MCAs demonstrated that pregnenolone at concentrations that constricted MCAs in vitro and in vivo (10 μM), reduced BK activity (NPo), with an average decrease in NPo reaching 24.2%. The concentration-dependence of pregnenolone constriction of brain arteries and inhibition of BK activity in intact cells were paralleled by data obtained in cell-free, inside-out patches, with maximal inhibition reached at 10 μM pregnenolone. MCA smooth muscle BKs include channel-forming α (slo1 proteins) and regulatory β1 subunits, encoded by KCNMA1 and KCNMB1, respectively. However, pregnenolone-driven decrease in NPo was still evident in MCA myocytes from KCNMB1-/- mice. Following reconstitution of slo1 channels into artificial, binary phospholipid bilayers, 10 μM pregnenolone evoked slo1 NPo inhibition which was similar to that seen in native membranes. Lastly, pregnenolone failed to constrict MCA from KCNMA1-/- mice. In conclusion, pregnenolone constricts MCA independently of neuronal, glial, endothelial and circulating factors, as well as of cell integrity, organelles, complex membrane cytoarchitecture, and the continuous presence of cytosolic signals. Rather, this action involves direct inhibition of SM BK channels, which does not require β1 subunits but is mediated through direct sensing of the neurosteroid by the channel-forming α subunit.
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Affiliation(s)
- Kelsey C North
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, 38103, USA
| | - Anna N Bukiya
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, 38103, USA
| | - Alex M Dopico
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, 38103, USA.
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Mondéjar-Parreño G, Cogolludo A, Perez-Vizcaino F. Potassium (K +) channels in the pulmonary vasculature: Implications in pulmonary hypertension Physiological, pathophysiological and pharmacological regulation. Pharmacol Ther 2021; 225:107835. [PMID: 33744261 DOI: 10.1016/j.pharmthera.2021.107835] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/26/2021] [Accepted: 03/02/2021] [Indexed: 02/06/2023]
Abstract
The large K+ channel functional diversity in the pulmonary vasculature results from the multitude of genes expressed encoding K+ channels, alternative RNA splicing, the post-transcriptional modifications, the presence of homomeric or heteromeric assemblies of the pore-forming α-subunits and the existence of accessory β-subunits modulating the functional properties of the channel. K+ channels can also be regulated at multiple levels by different factors controlling channel activity, trafficking, recycling and degradation. The activity of these channels is the primary determinant of membrane potential (Em) in pulmonary artery smooth muscle cells (PASMC), providing an essential regulatory mechanism to dilate or contract pulmonary arteries (PA). K+ channels are also expressed in pulmonary artery endothelial cells (PAEC) where they control resting Em, Ca2+ entry and the production of different vasoactive factors. The activity of K+ channels is also important in regulating the population and phenotype of PASMC in the pulmonary vasculature, since they are involved in cell apoptosis, survival and proliferation. Notably, K+ channels play a major role in the development of pulmonary hypertension (PH). Impaired K+ channel activity in PH results from: 1) loss of function mutations, 2) downregulation of its expression, which involves transcription factors and microRNAs, or 3) decreased channel current as a result of increased vasoactive factors (e.g., hypoxia, 5-HT, endothelin-1 or thromboxane), exposure to drugs with channel-blocking properties, or by a reduction in factors that positively regulate K+ channel activity (e.g., NO and prostacyclin). Restoring K+ channel expression, its intracellular trafficking and the channel activity is an attractive therapeutic strategy in PH.
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Affiliation(s)
- Gema Mondéjar-Parreño
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain
| | - Angel Cogolludo
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain
| | - Francisco Perez-Vizcaino
- Department of Pharmacology and Toxicology, School of Medicine, University Complutense of Madrid, Spain; Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), Madrid, Spain; Ciber Enfermedades Respiratorias (CIBERES), Spain.
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27
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BK Channel Regulation of Afterpotentials and Burst Firing in Cerebellar Purkinje Neurons. J Neurosci 2021; 41:2854-2869. [PMID: 33593855 DOI: 10.1523/jneurosci.0192-20.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 01/13/2021] [Accepted: 02/05/2021] [Indexed: 11/21/2022] Open
Abstract
BK calcium-activated potassium channels have complex kinetics because they are activated by both voltage and cytoplasmic calcium. The timing of BK activation and deactivation during action potentials determines their functional role in regulating firing patterns but is difficult to predict a priori. We used action potential clamp to characterize the kinetics of voltage-dependent calcium current and BK current during action potentials in Purkinje neurons from mice of both sexes, using acutely dissociated neurons that enabled rapid voltage clamp at 37°C. With both depolarizing voltage steps and action potential waveforms, BK current was entirely dependent on calcium entry through voltage-dependent calcium channels. With voltage steps, BK current greatly outweighed the triggering calcium current, with only a brief, small net inward calcium current before Ca-activated BK current dominated the total Ca-dependent current. During action potential waveforms, although BK current activated with only a short (∼100 μs) delay after calcium current, the two currents were largely separated, with calcium current flowing during the falling phase of the action potential and most BK current flowing over several milliseconds after repolarization. Step depolarizations activated both an iberiotoxin-sensitive BK component with rapid activation and deactivation kinetics and a slower-gating iberiotoxin-resistant component. During action potential firing, however, almost all BK current came from the faster-gating iberiotoxin-sensitive channels, even during bursts of action potentials. Inhibiting BK current had little effect on action potential width or a fast afterhyperpolarization but converted a medium afterhyperpolarization to an afterdepolarization and could convert tonic firing of single action potentials to burst firing.SIGNIFICANCE STATEMENT BK calcium-activated potassium channels are widely expressed in central neurons. Altered function of BK channels is associated with epilepsy and other neuronal disorders, including cerebellar ataxia. The functional role of BK in regulating neuronal firing patterns is highly dependent on the context of other channels and varies widely among different types of neurons. Most commonly, BK channels are activated during action potentials and help produce a fast afterhyperpolarization. We find that in Purkinje neurons BK current flows primarily after the fast afterhyperpolarization and helps to prevent a later afterdepolarization from producing rapid burst firing, enabling typical regular tonic firing.
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28
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Simkin D, Marshall KA, Vanoye CG, Desai RR, Bustos BI, Piyevsky BN, Ortega JA, Forrest M, Robertson GL, Penzes P, Laux LC, Lubbe SJ, Millichap JJ, George AL, Kiskinis E. Dyshomeostatic modulation of Ca 2+-activated K + channels in a human neuronal model of KCNQ2 encephalopathy. eLife 2021; 10:64434. [PMID: 33544076 PMCID: PMC7864629 DOI: 10.7554/elife.64434] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 01/20/2021] [Indexed: 12/22/2022] Open
Abstract
Mutations in KCNQ2, which encodes a pore-forming K+ channel subunit responsible for neuronal M-current, cause neonatal epileptic encephalopathy, a complex disorder presenting with severe early-onset seizures and impaired neurodevelopment. The condition is exceptionally difficult to treat, partially because the effects of KCNQ2 mutations on the development and function of human neurons are unknown. Here, we used induced pluripotent stem cells (iPSCs) and gene editing to establish a disease model and measured the functional properties of differentiated excitatory neurons. We find that patient iPSC-derived neurons exhibit faster action potential repolarization, larger post-burst afterhyperpolarization and a functional enhancement of Ca2+-activated K+ channels. These properties, which can be recapitulated by chronic inhibition of M-current in control neurons, facilitate a burst-suppression firing pattern that is reminiscent of the interictal electroencephalography pattern in patients. Our findings suggest that dyshomeostatic mechanisms compound KCNQ2 loss-of-function leading to alterations in the neurodevelopmental trajectory of patient iPSC-derived neurons.
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Affiliation(s)
- Dina Simkin
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States.,Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Kelly A Marshall
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Carlos G Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Reshma R Desai
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Bernabe I Bustos
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Brandon N Piyevsky
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Juan A Ortega
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Marc Forrest
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States.,Center for Autism and Neurodevelopment, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Gabriella L Robertson
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Peter Penzes
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States.,Center for Autism and Neurodevelopment, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Linda C Laux
- Epilepsy Center and Division of Neurology, Departments of Pediatrics and Neurology, Ann & Robert H. Lurie Children's Hospital of Chicago, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Steven J Lubbe
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - John J Millichap
- Epilepsy Center and Division of Neurology, Departments of Pediatrics and Neurology, Ann & Robert H. Lurie Children's Hospital of Chicago, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Alfred L George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Evangelos Kiskinis
- The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, United States.,Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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29
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Application of Machine-Learning Methods to Recognize mitoBK Channels from Different Cell Types Based on the Experimental Patch-Clamp Results. Int J Mol Sci 2021; 22:ijms22020840. [PMID: 33467711 PMCID: PMC7831025 DOI: 10.3390/ijms22020840] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 01/03/2021] [Accepted: 01/11/2021] [Indexed: 12/03/2022] Open
Abstract
(1) Background: In this work, we focus on the activity of large-conductance voltage- and Ca2+-activated potassium channels (BK) from the inner mitochondrial membrane (mitoBK). The characteristic electrophysiological features of the mitoBK channels are relatively high single-channel conductance (ca. 300 pS) and types of activating and deactivating stimuli. Nevertheless, depending on the isoformal composition of mitoBK channels in a given membrane patch and the type of auxiliary regulatory subunits (which can be co-assembled to the mitoBK channel protein) the characteristics of conformational dynamics of the channel protein can be altered. Consequently, the individual features of experimental series describing single-channel activity obtained by patch-clamp method can also vary. (2) Methods: Artificial intelligence approaches (deep learning) were used to classify the patch-clamp outputs of mitoBK activity from different cell types. (3) Results: Application of the K-nearest neighbors algorithm (KNN) and the autoencoder neural network allowed to perform the classification of the electrophysiological signals with a very good accuracy, which indicates that the conformational dynamics of the analyzed mitoBK channels from different cell types significantly differs. (4) Conclusion: We displayed the utility of machine-learning methodology in the research of ion channel gating, even in cases when the behavior of very similar microbiosystems is analyzed. A short excerpt from the patch-clamp recording can serve as a “fingerprint” used to recognize the mitoBK gating dynamics in the patches of membrane from different cell types.
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30
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Martín P, Moncada M, Castillo K, Orsi F, Ducca G, Fernández-Fernández JM, González C, Milesi V. Arachidonic acid effect on the allosteric gating mechanism of BK (Slo1) channels associated with the β1 subunit. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183550. [PMID: 33417967 DOI: 10.1016/j.bbamem.2021.183550] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 12/04/2020] [Accepted: 12/30/2020] [Indexed: 11/30/2022]
Abstract
Arachidonic acid (AA) is a fatty acid involved in the modulation of several ion channels. Previously, we reported that AA activates the high conductance Ca2+- and voltage-dependent K+ channel (BK) in vascular smooth muscle depending on the expression of the auxiliary β1 subunit. Here, using the patch-clamp technique on BK channel co-expressed with β1 subunit in a heterologous cell expression system, we analyzed whether AA modifies the three functional modules involved in the channel gating: the voltage sensor domain (VSD), the pore domain (PD), and the intracellular calcium sensor domain (CSD). We present evidence that AA activates BK channel in a direct way, inducing VSD stabilization on its active configuration observed as a significant left shift in the Q-V curve obtained from gating currents recordings. Moreover, AA facilitates the channel opening transitions when VSD are at rest, and the CSD are unoccupied. Furthermore, the activation was independent of the intracellular Ca2+ concentration and reduced when the BK channel was co-expressed with the Y74A mutant of the β1 subunit. These results allow us to present new insigths in the mechanism by which AA modulates BK channels co-expressed with its auxiliary β1 subunit.
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Affiliation(s)
- Pedro Martín
- Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, Facultad de Ciencias Exactas, La Plata, Argentina.
| | - Melisa Moncada
- Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, Facultad de Ciencias Exactas, La Plata, Argentina.
| | - Karen Castillo
- CINV: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
| | - Federico Orsi
- Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, Facultad de Ciencias Exactas, La Plata, Argentina.
| | - Gerónimo Ducca
- Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, Facultad de Ciencias Exactas, La Plata, Argentina.
| | - José Manuel Fernández-Fernández
- Laboratory of Molecular Physiology, Department of Experimental and Health Sciences, University Pompeu Fabra, 08003 Barcelona, Spain.
| | - Carlos González
- CINV: Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
| | - Verónica Milesi
- Instituto de Estudios Inmunológicos y Fisiopatológicos (IIFP), UNLP, CONICET, asociado CIC PBA, Facultad de Ciencias Exactas, La Plata, Argentina.
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31
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Szteyn K, Singh H. BK Ca Channels as Targets for Cardioprotection. Antioxidants (Basel) 2020; 9:antiox9080760. [PMID: 32824463 PMCID: PMC7463653 DOI: 10.3390/antiox9080760] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 12/16/2022] Open
Abstract
The large-conductance calcium- and voltage-activated K+ channel (BKCa) are encoded by the Kcnma1 gene. They are ubiquitously expressed in neuronal, smooth muscle, astrocytes, and neuroendocrine cells where they are known to play an important role in physiological and pathological processes. They are usually localized to the plasma membrane of the majority of the cells with an exception of adult cardiomyocytes, where BKCa is known to localize to mitochondria. BKCa channels couple calcium and voltage responses in the cell, which places them as unique targets for a rapid physiological response. The expression and activity of BKCa have been linked to several cardiovascular, muscular, and neurological defects, making them a key therapeutic target. Specifically in the heart muscle, pharmacological and genetic activation of BKCa channels protect the heart from ischemia-reperfusion injury and also facilitate cardioprotection rendered by ischemic preconditioning. The mechanism involved in cardioprotection is assigned to the modulation of mitochondrial functions, such as regulation of mitochondrial calcium, reactive oxygen species, and membrane potential. Here, we review the progress made on BKCa channels and cardioprotection and explore their potential roles as therapeutic targets for preventing acute myocardial infarction.
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32
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Direct and indirect cholesterol effects on membrane proteins with special focus on potassium channels. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158706. [DOI: 10.1016/j.bbalip.2020.158706] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 03/19/2020] [Accepted: 03/30/2020] [Indexed: 12/16/2022]
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33
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Chen S, Feng X, Chen X, Zhuang Z, Xiao J, Fu H, Klein JD, Wang XH, Hoover RS, Eaton DC, Cai H. 14-3-3γ, a novel regulator of the large-conductance Ca 2+-activated K + channel. Am J Physiol Renal Physiol 2020; 319:F52-F62. [PMID: 32463725 DOI: 10.1152/ajprenal.00584.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
14-3-3γ is a small protein regulating its target proteins through binding to phosphorylated serine/threonine residues. Sequence analysis of large-conductance Ca2+-activated K+ (BK) channels revealed a putative 14-3-3 binding site in the COOH-terminal region. Our previous data showed that 14-3-3γ is widely expressed in the mouse kidney. Therefore, we hypothesized that 14-3-3γ has a novel role in the regulation of BK channel activity and protein expression. We used electrophysiology, Western blot analysis, and coimmunoprecipitation to examine the effects of 14-3-3γ on BK channels both in vitro and in vivo. We demonstrated the interaction of 14-3-3γ with BK α-subunits (BKα) by coimmunoprecipitation. In human embryonic kidney-293 cells stably expressing BKα, overexpression of 14-3-3γ significantly decreased BK channel activity and channel open probability. 14-3-3γ inhibited both total and cell surface BKα protein expression while enhancing ERK1/2 phosphorylation in Cos-7 cells cotransfected with flag-14-3-3γ and myc-BK. Knockdown of 14-3-3γ by siRNA transfection markedly increased BKα expression. Blockade of the ERK1/2 pathway by incubation with the MEK-specific inhibitor U0126 partially abolished 14-3-3γ-mediated inhibition of BK protein expression. Similarly, pretreatment of the lysosomal inhibitor bafilomycin A1 reversed the inhibitory effects of 14-3-3γ on BK protein expression. Furthermore, overexpression of 14-3-3γ significantly increased BK protein ubiquitination in embryonic kidney-293 cells stably expressing BKα. Additionally, 3 days of dietary K+ challenge reduced 14-3-3γ expression and ERK1/2 phosphorylation while enhancing renal BK protein expression and K+ excretion. These data suggest that 14-3-3γ modulates BK channel activity and protein expression through an ERK1/2-mediated ubiquitin-lysosomal pathway.
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Affiliation(s)
- Shan Chen
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiuyan Feng
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Department of Pathology and Translational Pathobiology, Louisiana State University Health Sciences Center, Shreveport, Louisiana
| | - Xinxin Chen
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Zhizhi Zhuang
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Jia Xiao
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Haian Fu
- Department of Pharmacology, Emory University, School of Medicine, Atlanta, Georgia
| | - Janet D Klein
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Xiaonan H Wang
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Robert S Hoover
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.,Physiology, Emory University, School of Medicine, Atlanta, Georgia
| | - Douglas C Eaton
- Physiology, Emory University, School of Medicine, Atlanta, Georgia
| | - Hui Cai
- Renal Divison, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia.,Section of Nephrology, Atlanta Veterans Administration Medical Center, Decatur, Georgia.,Physiology, Emory University, School of Medicine, Atlanta, Georgia
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Mohr CJ, Schroth W, Mürdter TE, Gross D, Maier S, Stegen B, Dragoi A, Steudel FA, Stehling S, Hoppe R, Madden S, Ruth P, Huber SM, Brauch H, Lukowski R. Subunits of BK channels promote breast cancer development and modulate responses to endocrine treatment in preclinical models. Br J Pharmacol 2020; 179:2906-2924. [PMID: 32468618 DOI: 10.1111/bph.15147] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Revised: 03/20/2020] [Accepted: 05/13/2020] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE Pore-forming α subunits of the voltage- and Ca2+ -activated K+ channel with large conductance (BKα) promote malignant phenotypes of breast tumour cells. Auxiliary subunits such as the leucine-rich repeat containing 26 (LRRC26) protein, also termed BKγ1, may be required to permit activation of BK currents at a depolarized resting membrane potential that frequently occur in non-excitable tumour cells. EXPERIMENTAL APPROACH Anti-tumour effects of BKα loss were investigated in breast tumour-bearing MMTV-PyMT transgenic BKα knockout (KO) mice, primary MMTV-PyMT cell cultures, and in a syngeneic transplantation model of breast cancer derived from these cells. The therapeutic relevance of BK channels in the context of endocrine treatment was assessed in human breast cancer cell lines expressing either low (MCF-7) or high (MDA-MB-453) levels of BKα and BKγ1, as well as in BKα-negative MDA-MB-157. KEY RESULTS BKα promoted breast cancer onset and overall survival in preclinical models. Conversely, lack of BKα and/or knockdown of BKγ1 attenuated proliferation of murine and human breast cancer cells in vitro. At low concentrations, tamoxifen and its major active metabolites stimulated proliferation of BKα/γ1-positive breast cancer cells, independent of the genomic signalling controlled by the oestrogen receptor. Finally, tamoxifen increased the relative survival time of BKα KO but not of wild-type tumour cell recipient mice. CONCLUSION AND IMPLICATIONS Breast cancer initiation, progression, and tamoxifen sensitivity depend on functional BK channels thereby providing a rationale for the future exploration of the oncogenic actions of BK channels in clinical outcomes with anti-oestrogen therapy.
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Affiliation(s)
- Corinna J Mohr
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.,Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Werner Schroth
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Thomas E Mürdter
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Dominic Gross
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Selina Maier
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany.,Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Benjamin Stegen
- Department of Radiation Oncology, University of Tuebingen, Tuebingen, Germany
| | - Alice Dragoi
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Friederike A Steudel
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Severine Stehling
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Reiner Hoppe
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany
| | - Stephen Madden
- RCSI Division of Population Health Sciences, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
| | - Stephan M Huber
- Department of Radiation Oncology, University of Tuebingen, Tuebingen, Germany
| | - Hiltrud Brauch
- Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Stuttgart and University of Tuebingen, Germany.,German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany.,iFIT-Cluster of Excellence, University of Tuebingen, Tuebingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tuebingen, Tuebingen, Germany
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35
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Affiliation(s)
- Rachel G Scheraga
- Respiratory Instituteand.,Lerner Research InstituteCleveland Clinic FoundationCleveland, Ohio
| | - Mitchell A Olman
- Respiratory Instituteand.,Lerner Research InstituteCleveland Clinic FoundationCleveland, Ohio
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36
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Noda S, Chikazawa K, Suzuki Y, Imaizumi Y, Yamamura H. Involvement of the γ1 subunit of the large-conductance Ca 2+-activated K + channel in the proliferation of human somatostatinoma cells. Biochem Biophys Res Commun 2020; 525:1032-1037. [PMID: 32178873 DOI: 10.1016/j.bbrc.2020.02.176] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 02/28/2020] [Indexed: 10/24/2022]
Abstract
Pancreatic neuroendocrine tumors (pNETs) occur due to the abnormal growth of pancreatic islet cells and predominantly develop in the duodenal-pancreatic region. Somatostatinoma is one of the pNETs associated with tumors of pancreatic δ cells, which produce and secrete somatostatin. Limited information is currently available on the pathogenic mechanisms of somatostatinoma. The large-conductance Ca2+-activated K+ (BKCa) channel is expressed in several types of cancer cells and regulates cell proliferation, migration, invasion, and metastasis. In the present study, the functional expression of the BKCa channel was examined in a human somatostatinoma QGP-1 cell line. In QGP-1 cells, outward currents were elicited by membrane depolarization at pCa 6.5 (300 nM) in the pipette solution and inhibited by the specific BKCa channel blocker, paxilline. Paxilline-sensitive currents were detected, even at pCa 8.0 (10 nM) in the pipette solution, in QGP-1 cells. In addition to the α and β2-4 subunits of the BKCa channel, the novel regulatory γ1 subunit (BKCaγ1) was co-localized with the α subunit in QGP-1 cells. Paxilline-sensitive currents at pCa 8.0 in the pipette solution were reduced by the siRNA knockdown of BKCaγ1. Store-operated Ca2+ entry was smaller in BKCaγ1 siRNA-treated QGP-1 cells. The proliferation of QGP-1 cells was attenuated by paxilline or the siRNA knockdown of BKCaγ1. These results strongly suggest that BKCaγ1 facilitates the proliferation of human somatostatinoma cells. Therefore, BKCaγ1 may be a novel therapeutic target for somatostatinoma.
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Affiliation(s)
- Sayuri Noda
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori Mizuhoku, Nagoya, 467-8603, Japan
| | - Kana Chikazawa
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori Mizuhoku, Nagoya, 467-8603, Japan
| | - Yoshiaki Suzuki
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori Mizuhoku, Nagoya, 467-8603, Japan
| | - Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori Mizuhoku, Nagoya, 467-8603, Japan
| | - Hisao Yamamura
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori Mizuhoku, Nagoya, 467-8603, Japan.
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Plante AE, Lai MH, Lu J, Meredith AL. Effects of Single Nucleotide Polymorphisms in Human KCNMA1 on BK Current Properties. Front Mol Neurosci 2019; 12:285. [PMID: 31849601 PMCID: PMC6901604 DOI: 10.3389/fnmol.2019.00285] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 11/12/2019] [Indexed: 12/14/2022] Open
Abstract
BK Ca2+-activated K+ channels are important regulators of membrane excitability. Multiple regulatory mechanisms tailor BK current properties across tissues, such as alternative splicing, posttranslational modifications, and auxiliary subunits. Another potential mechanism for modulating BK channel activity is genetic variation due to single nucleotide polymorphisms (SNPs). The gene encoding the human BK α subunit, KCNMA1, contains hundreds of SNPs. However, the variation in BK channel activity due to SNPs is not well studied. Here, we screened the effects of four SNPs (A138V, C495G, N599D, and R800W) on BK currents in HEK293T cells, selected based on predicted protein pathogenicity or disease linkage. We found that the SNPs C495G and R800W had the largest effects on BK currents, affecting the conductance–voltage relationship across multiple Ca2+ conditions in the context of two BK channel splice variants. In symmetrical K+, C495G shifted the V1/2 to more hyperpolarized potentials (by −15 to −20 mV) and accelerated activation, indicating C495G confers some gain-of-function properties. R800W shifted the V1/2 to more depolarized potentials (+15 to +35 mV) and slowed activation, conferring loss-of-function properties. Moreover, the C495G and R800W effects on current properties were found to persist with posttranslational modifications. In contrast, A138V and N599D had smaller and more variable effects on current properties. Neither application of alkaline phosphatase to patches, which results in increased BK channel activity attributed to channel dephosphorylation, nor bidirectional redox modulations completely abrogated SNP effects on BK currents. Lastly, in physiological K+, C495G increased the amplitude of action potential (AP)-evoked BK currents, while R800W had a more limited effect. However, the introduction of R800W in parallel with the epilepsy-linked mutation D434G (D434G/R800W) decreased the amplitude of AP-evoked BK currents compared with D434G alone. These results suggest that in a physiological context, C495G could increase BK activation, while the effects of the loss-of-function SNP R800W could oppose the gain-of-function effects of an epilepsy-linked mutation. Together, these results implicate naturally occurring human genetic variation as a potential modifier of BK channel activity across a variety of conditions.
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Affiliation(s)
- Amber E Plante
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Michael H Lai
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jessica Lu
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Andrea L Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, United States
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38
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Numata T, Sato-Numata K, Okada Y. Herbal components of Japanese Kampo medicines exert laxative actions in colonic epithelium cells via activation of BK and CFTR channels. Sci Rep 2019; 9:15554. [PMID: 31664151 PMCID: PMC6820752 DOI: 10.1038/s41598-019-52171-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/12/2019] [Indexed: 11/20/2022] Open
Abstract
Japanese Kampo medicines Junchoto and Mashiningan are mixtures of numerous herbal plant extracts and empirically known to exert laxative actions by stimulating fluid secretion in the colonic epithelium. However, it is unknown which and how the herbal components of these crude Kampo drugs are effective to stimulate ion effluxes causing fluid secretion. Here, we selected four herbal components of Junchoto and Mashiningan, Mashinin (MSN), Kyonin (KYN), Tonin (TON), and Daio (DIO), which are putatively laxatives, and examined their effects on the ion channel activity of human colonic epithelial Caco-2 cells. Patch clamp analyses revealed that MSN activated whole-cell current characteristics of the cystic fibrosis transmembrane conductance regulator (CFTR) channel, whereas KYN, TON, and DIO activated the large-conductance and voltage-activated K+ (BK) channel. Furthermore, electronic cell sizing showed that MSN induced secretory volume decrease (SVD) sensitivity to a CFTR blocker, whereas TON, KYN, and DIO induced SVD sensitivity to a K+ channel blocker. In conclusion, MSN and TON, KYN, and DIO promote fluid secretion from colonic epithelial cells by activating CFTR and BK channels. Thus, Japanese Kampo medicines, Junchoto and Mashiningan, exert anti-constipation actions by inducing KCl efflux through the combined actions of CFTR- and BK-stimulating herbal components.
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Affiliation(s)
- Tomohiro Numata
- Department of Physiology, Graduate School of Medical Sciences, Fukuoka University, Fukuoka, 814-0180, Japan.
| | - Kaori Sato-Numata
- Department of Physiology, Graduate School of Medical Sciences, Fukuoka University, Fukuoka, 814-0180, Japan.,Japan Society for the Promotion of Science, Tokyo, 102-0083, Japan
| | - Yasunobu Okada
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, 602-8566, Japan.,National Institute for Physiological Sciences, Okazaki, 444-8585, Japan
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Djokic V, Jankovic-Raznatovic S, Novakovic R, Kostic M, Rajkovic J, Labudovic-Borovic M, Rakocevic J, Stanisic J, Djuric M, Gojkovic-Bukarica L. Effect of gestational diabetes mellitus and pregnancy-induced hypertension on human umbilical vein smooth muscle K ATP channels. Exp Mol Pathol 2019; 111:104323. [PMID: 31669131 DOI: 10.1016/j.yexmp.2019.104323] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 09/03/2019] [Accepted: 10/21/2019] [Indexed: 01/25/2023]
Abstract
Gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH) can jeopardize mother and/or fetus. Vascular ATP-sensitive potassium (KATP) channels most likely participate in the processes of diabetes and hypertension. The aim of this research was to examine whether GDM and PIH cause changes in the expression and function of KATP channels in vascular smooth muscle of human umbilical vein (HUV). Western blot and immunohistochemistry detected significantly decreased expression of Kir6.1 subunit of KATP channels in GDM and PIH, while the expression of SUR2B was unchanged. In GDM, a K+ channel opener, pinacidil caused reduced relaxation of the endothelium-denuded HUVs compared to normal pregnancy. However, its effects in HUVs from PIH subjects were similar to normal pregnancy. In all groups KATP channel blocker glibenclamide antagonized the relaxation of HUV induced by pinacidil without change in the maximal relaxations indicating additional KATP channel-independent mechanisms of pinacidil action. Iberiotoxin, a selective antagonist of large-conductance calcium-activated potassium channels, inhibited the relaxant effect of pinacidil in PIH, but not in normal pregnancy and GDM. Experiments performed in K+-rich solution confirmed the existence of K+-independent effects of pinacidil, which also appear to be impaired in GDM and PIH. Thus, the expression of KATP channels is decreased in GDM and PIH. In GDM, vasorelaxant response of HUV to pinacidil is reduced, while in PIH it remains unchanged. It is very likely that KATP channels modulation and more detailed insight in KATP channel-independent actions of pinacidil may be precious in the therapy of pathological pregnancies.
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Affiliation(s)
- Vladimir Djokic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia.
| | - Svetlana Jankovic-Raznatovic
- Department of Obstetrics and Gynecology "Narodni front", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Radmila Novakovic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Milan Kostic
- Vinca Institute of Nuclear Sciences, 11000 Belgrade, Serbia
| | - Jovana Rajkovic
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Milica Labudovic-Borovic
- Institute of Histology and Embryology "Aleksandar Dj. Kostic", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Jelena Rakocevic
- Institute of Histology and Embryology "Aleksandar Dj. Kostic", Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | | | - Milos Djuric
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Ljiljana Gojkovic-Bukarica
- Department of Pharmacology, Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
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40
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Lang I, Jung M, Niemeyer BA, Ruth P, Engel J. Expression of the LRRC52 γ subunit (γ2) may provide Ca 2+-independent activation of BK currents in mouse inner hair cells. FASEB J 2019; 33:11721-11734. [PMID: 31348683 DOI: 10.1096/fj.201900701rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Mammalian inner hair cells (IHCs) transduce sound into depolarization and transmitter release. Big conductance and voltage- and Ca2+-activated K+ (BK) channels are responsible for fast membrane repolarization and small time constants of mature IHCs. For unknown reasons, they activate at around -75 mV with a voltage of half-maximum activation (Vhalf) of -50 mV although being largely insensitive to Ca2+ influx. Ca2+-independent activation of BK channels was observed by others in heterologous expression systems if γ subunits leucine-rich repeat-containing protein (LRRC)26 (γ1) and LRRC52 (γ2) were coexpressed with the pore-forming BKα subunit, which shifted Vhalf by -140 and -100 mV, respectively. Using nested PCR, we consistently detected transcripts for LRRC52 but not for LRRC26 in IHCs of 3-wk-old mice. Confocal immunohistochemistry showed synchronous up-regulation of LRRC52 protein with BKα at the onset of hearing. Colocalization of LRRC52 protein and BKα at the IHC neck within ≤40 nm was specified using an in situ proximity ligation assay. Mice deficient for the voltage-gated Cav1.3 Ca2+ channel encoded by Cacna1d do not express BKα protein. LRRC52 protein was neither expressed in IHCs of BKα nor in IHCs of Cav1.3 knockout mice. Together, LRRC52 is a γ2 subunit of BK channel complexes and is a strong candidate for causing the Ca2+-independent activation of BK currents at negative membrane potentials in mouse IHCs.-Lang, I., Jung, M., Niemeyer, B. A., Ruth, P., Engel, J. Expression of the LRRC52 γ subunit (γ2) may provide Ca2+-independent activation of BK currents in mouse inner hair cells.
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Affiliation(s)
- Isabelle Lang
- Hearing Research, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Martin Jung
- Department of Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Barbara A Niemeyer
- Molecular Biophysics, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Peter Ruth
- Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy, University of Tübingen, Tübingen, Germany
| | - Jutta Engel
- Hearing Research, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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41
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Haworth AS, Brackenbury WJ. Emerging roles for multifunctional ion channel auxiliary subunits in cancer. Cell Calcium 2019; 80:125-140. [PMID: 31071485 PMCID: PMC6553682 DOI: 10.1016/j.ceca.2019.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 02/07/2023]
Abstract
Several superfamilies of plasma membrane channels which regulate transmembrane ion flux have also been shown to regulate a multitude of cellular processes, including proliferation and migration. Ion channels are typically multimeric complexes consisting of conducting subunits and auxiliary, non-conducting subunits. Auxiliary subunits modulate the function of conducting subunits and have putative non-conducting roles, further expanding the repertoire of cellular processes governed by ion channel complexes to processes such as transcellular adhesion and gene transcription. Given this expansive influence of ion channels on cellular behaviour it is perhaps no surprise that aberrant ion channel expression is a common occurrence in cancer. This review will focus on the conducting and non-conducting roles of the auxiliary subunits of various Ca2+, K+, Na+ and Cl- channels and the burgeoning evidence linking such auxiliary subunits to cancer. Several subunits are upregulated (e.g. Cavβ, Cavγ) and downregulated (e.g. Kvβ) in cancer, while other subunits have been functionally implicated as oncogenes (e.g. Navβ1, Cavα2δ1) and tumour suppressor genes (e.g. CLCA2, KCNE2, BKγ1) based on in vivo studies. The strengthening link between ion channel auxiliary subunits and cancer has exposed these subunits as potential biomarkers and therapeutic targets. However further mechanistic understanding is required into how these subunits contribute to tumour progression before their therapeutic potential can be fully realised.
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Affiliation(s)
- Alexander S Haworth
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK
| | - William J Brackenbury
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, Heslington, York, YO10 5DD, UK.
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42
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Bukiya AN, Dopico AM. Regulation of BK Channel Activity by Cholesterol and Its Derivatives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1115:53-75. [DOI: 10.1007/978-3-030-04278-3_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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43
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Miranda P, Holmgren M, Giraldez T. Voltage-dependent dynamics of the BK channel cytosolic gating ring are coupled to the membrane-embedded voltage sensor. eLife 2018; 7:40664. [PMID: 30526860 PMCID: PMC6301790 DOI: 10.7554/elife.40664] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 12/11/2018] [Indexed: 12/21/2022] Open
Abstract
In humans, large conductance voltage- and calcium-dependent potassium (BK) channels are regulated allosterically by transmembrane voltage and intracellular Ca2+. Divalent cation binding sites reside within the gating ring formed by two Regulator of Conductance of Potassium (RCK) domains per subunit. Using patch-clamp fluorometry, we show that Ca2+ binding to the RCK1 domain triggers gating ring rearrangements that depend on transmembrane voltage. Because the gating ring is outside the electric field, this voltage sensitivity must originate from coupling to the voltage-dependent channel opening, the voltage sensor or both. Here we demonstrate that alterations of the voltage sensor, either by mutagenesis or regulation by auxiliary subunits, are paralleled by changes in the voltage dependence of the gating ring movements, whereas modifications of the relative open probability are not. These results strongly suggest that conformational changes of RCK1 domains are specifically coupled to the voltage sensor function during allosteric modulation of BK channels.
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Affiliation(s)
- Pablo Miranda
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Miguel Holmgren
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Teresa Giraldez
- Departamento de Ciencias Medicas Basicas, Universidad de La Laguna, San Cristóbal de La Laguna, Spain.,Instituto de Tecnologias Biomedicas, Universidad de La Laguna, San Cristóbal de La Laguna, Spain
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44
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Yu M, Guo L, Li N, Henzel KS, Gu H, Ran X, Sun W, Liu S, Lu Y, Ehninger D, Zhou Y. Overexpression of Kcnmb2 in Dorsal CA1 of Offspring Mice Rescues Hippocampal Dysfunction Caused by a Methyl Donor-Rich Paternal Diet. Front Cell Neurosci 2018; 12:360. [PMID: 30405352 PMCID: PMC6206260 DOI: 10.3389/fncel.2018.00360] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 09/25/2018] [Indexed: 01/06/2023] Open
Abstract
BK channels are known regulators of neuronal excitability, synaptic plasticity, and memory. Our previous study showed that a paternal methyl donor-rich diet reduced the expression of Kcnmb2, which encodes BK channel subunit beta 2, and caused memory deficits in offspring mice. To explore the underlying cellular mechanisms, we investigated the intrinsic and synaptic properties of CA1 pyramidal neurons of the F1 offspring mice whose fathers were fed with either a methyl donor-rich diet (MD) or regular control diet (CD) for 6 weeks before mating. Whole-cell patch-clamp recordings of CA1 pyramidal neurons revealed a decrease in intrinsic excitability and reduced frequency of inhibitory post-synaptic currents in MD F1 mice compared to the CD F1 controls. AAV-based overexpression of Kcnmb2 in dorsal CA1 ameliorated changes in neuronal excitability, synaptic transmission, and plasticity in MD F1 mice. Our findings thus indicate that a transient paternal exposure to a methyl donor-rich diet prior to mating alters Kcnmb2-sensitive hippocampal functions in offspring animals.
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Affiliation(s)
- Ming Yu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Li Guo
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China.,Department of Physiology, Binzhou Medical University, Yantai, China
| | - Nan Li
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Kristin S Henzel
- Molecular and Cellular Cognition Lab, German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Huating Gu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Xiufang Ran
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Wei Sun
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Shuai Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Yingchang Lu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China
| | - Dan Ehninger
- Molecular and Cellular Cognition Lab, German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Yu Zhou
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Qingdao University, Qingdao, China.,Institute of Brain Sciences and Related Disorders, Qingdao University, Qingdao, China
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45
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Ohya S, Kito H. Ca 2+-Activated K + Channel K Ca3.1 as a Therapeutic Target for Immune Disorders. Biol Pharm Bull 2018; 41:1158-1163. [PMID: 30068864 DOI: 10.1248/bpb.b18-00078] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In lymphoid and myeloid cells, membrane hyperpolarization by the opening of K+ channels increases the activity of Ca2+ release-activated Ca2+ (CRAC) channels and transient receptor potential (TRP) Ca2+ channels. The intermediate-conductance Ca2+-activated K+ channel KCa3.1 plays an important role in cell proliferation, differentiation, migration, and cytokine production in innate and adaptive immune systems. KCa3.1 is therefore an attractive therapeutic target for allergic, inflammatory, and autoimmune disorders. In the past several years, studies have provided new insights into 1) KCa3.1 pharmacology and its auxiliary regulators; 2) post-transcriptional and proteasomal regulation of KCa3.1; 3) KCa3.1 as a regulator of immune cell migration, cytokine production, and phenotypic polarization; 4) the role of KCa3.1 in the phosphorylation and nuclear translocation of Smad2/3; and 5) KCa3.1 as a therapeutic target for cancer immunotherapy. In this review, we have assembled a comprehensive overview of current research on the physiological and pathophysiological significance of KCa3.1 in the immune system.
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Affiliation(s)
- Susumu Ohya
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University
| | - Hiroaki Kito
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University
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46
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Xin F, Cheng Y, Ren J, Zhang S, Liu P, Zhao H, Huang H, Wang W. The extracellular loop of the auxiliary β1-subunit is involved in the regulation of BKCa channel mechanosensitivity. Am J Physiol Cell Physiol 2018; 315:C485-C493. [DOI: 10.1152/ajpcell.00037.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The large conductance Ca2+-activated potassium (BKCa) channel is activated by stretch. The stress-regulated exon (STREX) in α-subunits is known to affect the mechanosensitivity of BKCa channels. However, in human colonic smooth muscle cells (HCoSMCs), we found that the α-subunits without STREX (ZERO-BK) and β1-subunits could be detected yet the cells were mechanosensitive. Whether the β1-subunit is involved in the regulation of BKCa mechanosensitivity is unclear. In the present study, ZERO-BK and β1-subunits were individually expressed or coexpressed in HEK293 cells and cell-attached patch-clamp techniques were used to measure BKCa currents defining mechanosensitivity. Single-channel patch-clamp recordings from HEK293 cells cotransfected with ZERO-BK and β1-subunits showed stretch sensitivity, but there was no mechanosensitivity in HEK293 cells transfected only with ZERO-BK. We also showed that expression of the β1-subunit could increase mechanosensitivity of the STREX-type α-subunits (STREX-BK). To identify the domain in β1-subunits responsible for affecting stretch sensitivity, we expressed β1- LoopDel (chimeric β1-subunits without the extracellular loop) or β1- C TermDel (chimeric β1-subunits without COOH terminus) with ZERO-BK in HEK293 cells. The data showed that deletion of the extracellular loop but not the COOH terminus of β1-subunits virtually abolished the mechanosensitivity. These results suggest that the extracellular loop of the β1-subunit is involved in the regulation of BKCa channel mechanosensitivity and that role is independent of STREX.
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Affiliation(s)
- Fang Xin
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Yuan Cheng
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Jie Ren
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Sitao Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Ping Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
| | - Haiyan Zhao
- Yanjing Medical College, Capital Medical University, Beijing, People’s Republic of China
| | - Haixia Huang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
- Beijing Key Laboratory of Metabolic Disorders Related Cardiovascular Diseases, Capital Medical University, Beijing, People’s Republic of China
| | - Wei Wang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, People’s Republic of China
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Abstract
The large-conductance calcium- and voltage-activated K+ (BK) channel has a requirement of high intracellular free Ca2+ concentrations for its activation in neurons under physiological conditions. The Ca2+ sources for BK channel activation are not well understood. In this study, we showed by coimmunopurification and colocalization analyses that BK channels form complexes with NMDA receptors (NMDARs) in both rodent brains and a heterologous expression system. The BK-NMDAR complexes are broadly present in different brain regions. The complex formation occurs between the obligatory BKα and GluN1 subunits likely via a direct physical interaction of the former's intracellular S0-S1 loop with the latter's cytosolic regions. By patch-clamp recording on mouse brain slices, we observed BK channel activation by NMDAR-mediated Ca2+ influx in dentate gyrus granule cells. BK channels modulate excitatory synaptic transmission via functional coupling with NMDARs at postsynaptic sites of medial perforant path-dentate gyrus granule cell synapses. A synthesized peptide of the BKα S0-S1 loop region, when loaded intracellularly via recording pipette, abolished the NMDAR-mediated BK channel activation and effect on synaptic transmission. These findings reveal the broad expression of the BK-NMDAR complexes in brain, the potential mechanism underlying the complex formation, and the NMDAR-mediated activation and function of postsynaptic BK channels in neurons.
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48
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Patel NH, Johannesen J, Shah K, Goswami SK, Patel NJ, Ponnalagu D, Kohut AR, Singh H. Inhibition of BK Ca negatively alters cardiovascular function. Physiol Rep 2018; 6:e13748. [PMID: 29932499 PMCID: PMC6014461 DOI: 10.14814/phy2.13748] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/15/2018] [Accepted: 05/28/2018] [Indexed: 12/19/2022] Open
Abstract
Large conductance calcium and voltage-activated potassium channels (BKCa ) are transmembrane proteins, ubiquitously expressed in the majority of organs, and play an active role in regulating cellular physiology. In the heart, BKCa channels are known to play a role in regulating the heart rate and protect it from ischemia-reperfusion injury. In vascular smooth muscle cells, the opening of BKCa channels results in membrane hyperpolarization which eventually results in vasodilation mediated by a reduction in Ca2+ influx due to the closure of voltage-dependent Ca2+ channels. Ex vivo studies have shown that BKCa channels play an active role in the regulation of the function of the majority of blood vessels. However, in vivo role of BKCa channels in cardiovascular function is not completely deciphered. Here, we have evaluated the rapid in vivo role of BKCa channels in regulating the cardiovascular function by using two well-established, rapid-acting, potent blockers, paxilline and iberiotoxin. Our results show that BKCa channels are actively involved in regulating the heart rate, the function of the left and right heart as well as major vessels. We also found that the effect on BKCa channels by blockers is completely reversible, and hence, BKCa channels can be exploited as potential targets for clinical applications for modulating heart rate and cardiac contractility.
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Affiliation(s)
- Nishi H. Patel
- Department of Internal MedicineDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Justin Johannesen
- Department of Internal MedicineDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Kajol Shah
- Department of Pharmacology and PhysiologyDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Sumanta K. Goswami
- Department of Pharmacology and PhysiologyDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Neel J. Patel
- Department of Internal MedicineDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Devasena Ponnalagu
- Department of Pharmacology and PhysiologyDrexel University College of MedicinePhiladelphiaPennsylvania
| | - Andrew R. Kohut
- Penn Heart and Vascular CenterUniversity of PennsylvaniaPhiladelphiaPennsylvania
| | - Harpreet Singh
- Department of Pharmacology and PhysiologyDrexel University College of MedicinePhiladelphiaPennsylvania
- Division of CardiologyDrexel University College of MedicinePhiladelphiaPennsylvania
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49
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Dopico AM, Bukiya AN, Jaggar JH. Calcium- and voltage-gated BK channels in vascular smooth muscle. Pflugers Arch 2018; 470:1271-1289. [PMID: 29748711 DOI: 10.1007/s00424-018-2151-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 04/27/2018] [Indexed: 02/04/2023]
Abstract
Ion channels in vascular smooth muscle regulate myogenic tone and vessel contractility. In particular, activation of calcium- and voltage-gated potassium channels of large conductance (BK channels) results in outward current that shifts the membrane potential toward more negative values, triggering a negative feed-back loop on depolarization-induced calcium influx and SM contraction. In this short review, we first present the molecular basis of vascular smooth muscle BK channels and the role of subunit composition and trafficking in the regulation of myogenic tone and vascular contractility. BK channel modulation by endogenous signaling molecules, and paracrine and endocrine mediators follows. Lastly, we describe the functional changes in smooth muscle BK channels that contribute to, or are triggered by, common physiological conditions and pathologies, including obesity, diabetes, and systemic hypertension.
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Affiliation(s)
- Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA.
| | - Anna N Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St., Memphis, TN, 38163, USA
| | - Jonathan H Jaggar
- Department of Physiology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
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Wang Y, Lan W, Yan Z, Gao J, Liu X, Wang S, Guo X, Wang C, Zhou H, Ding J, Cao C. Solution structure of extracellular loop of human β4 subunit of BK channel and its biological implication on ChTX sensitivity. Sci Rep 2018; 8:4571. [PMID: 29545539 PMCID: PMC5854672 DOI: 10.1038/s41598-018-23016-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 03/05/2018] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-dependent K+ (BK) channels display diverse biological functions while their pore-forming α subunit is coded by a single Slo1 gene. The variety of BK channels is correlated with the effects of BKα coexpression with auxiliary β (β1-β4) subunits, as well as newly defined γ subunits. Charybdotoxin (ChTX) blocks BK channel through physically occluding the K+-conduction pore. Human brain enriched β4 subunit (hβ4) alters the conductance-voltage curve, slows activation and deactivation time courses of BK channels. Its extracellular loop (hβ4-loop) specifically impedes ChTX to bind BK channel pore. However, the structure of β4 subunit's extracellular loop and the molecular mechanism for gating kinetics, toxin sensitivity of BK channels regulated by β4 are still unclear. To address them, here, we first identified four disulfide bonds in hβ4-loop by mass spectroscopy and NMR techniques. Then we determined its three-dimensional solution structure, performed NMR titration and electrophysiological analysis, and found that residue Asn123 of β4 subunit regulated the gating and pharmacological characteristics of BK channel. Finally, by constructing structure models of BKα/β4 and thermodynamic double-mutant cycle analysis, we proposed that BKα subunit might interact with β4 subunit through the conserved residue Glu264(BKα) coupling with residue Asn123(β4).
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Affiliation(s)
- Yanting Wang
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China.,Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, Hubei, China
| | - Wenxian Lan
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China
| | - Zhenzhen Yan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, Hubei, China
| | - Jing Gao
- Department of Analytical Chemistry, Shanghai Institute of Materia Medica, CAS, 555 Zuchongzhi Road, Shanghai, 201203, China
| | - Xinlian Liu
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China
| | - Sheng Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, Hubei, China
| | - Xiying Guo
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, Hubei, China
| | - Chunxi Wang
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China
| | - Hu Zhou
- Department of Analytical Chemistry, Shanghai Institute of Materia Medica, CAS, 555 Zuchongzhi Road, Shanghai, 201203, China
| | - Jiuping Ding
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, Hubei, China
| | - Chunyang Cao
- State Key Laboratory of Bioorganic and Natural Product Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China. .,University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing, 100049, China. .,Collaborative Innovation Center of Chemistry for Life Sciences, Chinese Academy of Sciences (CAS), 345 Lingling Road, Shanghai, 200032, China.
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