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Peixoto-Neves D, Jaggar JH. Physiological functions and pathological involvement of ion channel trafficking in the vasculature. J Physiol 2024; 602:3275-3296. [PMID: 37818949 PMCID: PMC11006830 DOI: 10.1113/jp285007] [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: 08/09/2023] [Accepted: 09/28/2023] [Indexed: 10/13/2023] Open
Abstract
A variety of ion channels regulate membrane potential and calcium influx in arterial smooth muscle and endothelial cells to modify vascular functions, including contractility. The current (I) generated by a population of ion channels is equally dependent upon their number (N), open probability (Po) and single channel current (i), such that I = N.PO.i. A conventional view had been that ion channels traffic to the plasma membrane in a passive manner, resulting in a static surface population. It was also considered that channels assemble with auxiliary subunits prior to anterograde trafficking of the multimeric complex to the plasma membrane. Recent studies have demonstrated that physiological stimuli can regulate the surface abundance (N) of several different ion channels in arterial smooth muscle and endothelial cells to control arterial contractility. Physiological stimuli can also regulate the number of auxiliary subunits present in the plasma membrane to modify the biophysical properties, regulatory mechanisms and physiological functions of some ion channels. Furthermore, ion channel trafficking becomes dysfunctional in the vasculature during hypertension, which negatively impacts the regulation of contractility. The temporal kinetics of ion channel and auxiliary subunit trafficking can also vary depending on the signalling mechanisms and proteins involved. This review will summarize recent work that has uncovered the mechanisms, functions and pathological modifications of ion channel trafficking in arterial smooth muscle and endothelial cells.
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Affiliation(s)
| | - Jonathan H. Jaggar
- Department of Physiology, University of Tennessee Health Science Center, Memphis TN 38139
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2
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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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3
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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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4
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Jiang L, Li J, Reilly S, Xin H, Guo N, Zhang X. Role of organellar Ca2+-activated K+ channels in disease development. Life Sci 2023; 316:121433. [PMID: 36708987 DOI: 10.1016/j.lfs.2023.121433] [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: 11/09/2022] [Revised: 01/16/2023] [Accepted: 01/19/2023] [Indexed: 01/27/2023]
Abstract
The organellar Ca2+-activated K+ channels share a similar ability to transfer the alteration of Ca2+ concentration to membrane conductance of potassium. Multiple effects of Ca2+-activated K+ channels on cell metabolism and complex signaling pathways during organ development have been explored. The organellar Ca2+-activated K+ channels are able to control the ionic equilibrium and are always associated with oxidative stress in different organelles and the whole cells. Some drugs targeting Ca2+-activated K+ channels have been tested for various diseases in clinical trials. In this review, the known roles of organellar Ca2+-activated K+ channels were described, and their effects on different diseases, particularly on diabetes, cardiovascular diseases, and neurological diseases were discussed. It was attempted to summarize the currently known operational modes with the involvement of organellar Ca2+-activated K+ channels. This review may assist scholars to more comprehensively understand organellar Ca2+-activated K+ channels and related diseases.
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Affiliation(s)
- Lan Jiang
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Jiawei Li
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Svetlana Reilly
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, John Radcliffe Hospital, University of Oxford, Oxford, UK
| | - Hong Xin
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China
| | - Nan Guo
- Department of Pharmacy, Minhang hospital, Fudan University, Shanghai, China.
| | - Xuemei Zhang
- Department of Pharmacology, School of Pharmacy, Fudan University, Shanghai, China.
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5
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Ancatén-González C, Segura I, Alvarado-Sánchez R, Chávez AE, Latorre R. Ca 2+- and Voltage-Activated K + (BK) Channels in the Nervous System: One Gene, a Myriad of Physiological Functions. Int J Mol Sci 2023; 24:3407. [PMID: 36834817 PMCID: PMC9967218 DOI: 10.3390/ijms24043407] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/18/2023] [Accepted: 01/21/2023] [Indexed: 02/11/2023] Open
Abstract
BK channels are large conductance potassium channels characterized by four pore-forming α subunits, often co-assembled with auxiliary β and γ subunits to regulate Ca2+ sensitivity, voltage dependence and gating properties. BK channels are abundantly expressed throughout the brain and in different compartments within a single neuron, including axons, synaptic terminals, dendritic arbors, and spines. Their activation produces a massive efflux of K+ ions that hyperpolarizes the cellular membrane. Together with their ability to detect changes in intracellular Ca2+ concentration, BK channels control neuronal excitability and synaptic communication through diverse mechanisms. Moreover, increasing evidence indicates that dysfunction of BK channel-mediated effects on neuronal excitability and synaptic function has been implicated in several neurological disorders, including epilepsy, fragile X syndrome, mental retardation, and autism, as well as in motor and cognitive behavior. Here, we discuss current evidence highlighting the physiological importance of this ubiquitous channel in regulating brain function and its role in the pathophysiology of different neurological disorders.
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Affiliation(s)
- Carlos Ancatén-González
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ignacio Segura
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Rosangelina Alvarado-Sánchez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Doctorado en Ciencias Mención Biofísica y Biología Computacional, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Andrés E. Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso 2340000, Chile
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6
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Staruschenko A, Ma R, Palygin O, Dryer SE. Ion channels and channelopathies in glomeruli. Physiol Rev 2023; 103:787-854. [PMID: 36007181 PMCID: PMC9662803 DOI: 10.1152/physrev.00013.2022] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 08/15/2022] [Accepted: 08/21/2022] [Indexed: 11/22/2022] Open
Abstract
An essential step in renal function entails the formation of an ultrafiltrate that is delivered to the renal tubules for subsequent processing. This process, known as glomerular filtration, is controlled by intrinsic regulatory systems and by paracrine, neuronal, and endocrine signals that converge onto glomerular cells. In addition, the characteristics of glomerular fluid flow, such as the glomerular filtration rate and the glomerular filtration fraction, play an important role in determining blood flow to the rest of the kidney. Consequently, disease processes that initially affect glomeruli are the most likely to lead to end-stage kidney failure. The cells that comprise the glomerular filter, especially podocytes and mesangial cells, express many different types of ion channels that regulate intrinsic aspects of cell function and cellular responses to the local environment, such as changes in glomerular capillary pressure. Dysregulation of glomerular ion channels, such as changes in TRPC6, can lead to devastating glomerular diseases, and a number of channels, including TRPC6, TRPC5, and various ionotropic receptors, are promising targets for drug development. This review discusses glomerular structure and glomerular disease processes. It also describes the types of plasma membrane ion channels that have been identified in glomerular cells, the physiological and pathophysiological contexts in which they operate, and the pathways by which they are regulated and dysregulated. The contributions of these channels to glomerular disease processes, such as focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy, as well as the development of drugs that target these channels are also discussed.
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Affiliation(s)
- Alexander Staruschenko
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida
- Hypertension and Kidney Research Center, University of South Florida, Tampa, Florida
- James A. Haley Veterans Hospital, Tampa, Florida
| | - Rong Ma
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Oleg Palygin
- Division of Nephrology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Stuart E Dryer
- Department of Biology and Biochemistry, University of Houston, Houston, Texas
- Department of Biomedical Sciences, Tilman J. Fertitta Family College of Medicine, University of Houston, Houston, Texas
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7
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The Effect of 40-Hz White LED Therapy on Structure-Function of Brain Mitochondrial ATP-Sensitive Ca-Activated Large-Conductance Potassium Channel in Amyloid Beta Toxicity. Neurotox Res 2022; 40:1380-1392. [PMID: 36057039 DOI: 10.1007/s12640-022-00565-9] [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: 04/06/2022] [Revised: 06/07/2022] [Accepted: 08/19/2022] [Indexed: 10/14/2022]
Abstract
Photobiomodulation therapy has become the focus of medical research in many areas such as Alzheimer's disease (AD), because of its modulatory effect on cellular processes through light energy absorption via photoreceptors/chromophores located in the mitochondria. However, there are still many questions around the underlying mechanisms. This study was carried out to unravel whether the function-structure of ATP-sensitive mitoBKCa channels, as crucial components for maintenance of mitochondrial homeostasis, can be altered subsequent to light therapy in AD. Induction of Aβ neurotoxicity in male Wistar rats was done by intracerebroventricular injection of Aβ1-42. After a week, light-treated rats were exposed to 40-Hz white light LEDs, 15 min for 7 days. Electrophysiological properties of mitoBKCa channel were investigated using a channel incorporated into the bilayer lipid membrane, and mitoBKCa-β2 subunit expression was determined using western blot analysis in Aβ-induced toxicity and light-treated rats. Our results describe that conductance and open probability (Po) of mitoBKCa channel decreased significantly and was accompanied by a Po curve rightward shift in mitochondrial preparation in Aβ-induced toxicity rats. We also showed a significant reduction in expression of mitoBKCa-β2 subunit, which is partly responsible for a leftward shift in BKCa Po curve in low calcium status. Interestingly, we provided evidence of a significant improvement in channel conductance and Po after light therapy. We also found that light therapy improved mitoBKCa-β2 subunit expression, increasing it close to saline group. The current study explains a light therapy improvement in brain mitoBKCa channel function in the Aβ-induced neurotoxicity rat model, an effect that can be linked to increased expression of β2 subunit.
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8
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Slayden AV, Dyer CL, Ma D, Li W, Bukiya AN, Parrill AL, Dopico AM. Discovery of agonist-antagonist pairs for the modulation of Ca [2]+ and voltage-gated K + channels of large conductance that contain beta1 subunits. Bioorg Med Chem 2022; 68:116876. [PMID: 35716586 PMCID: PMC10464842 DOI: 10.1016/j.bmc.2022.116876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/31/2022] [Accepted: 06/03/2022] [Indexed: 11/02/2022]
Abstract
Large conductance, calcium/voltage-gated potassium channels (BK) regulate critical body processes, including neuronal, secretory and smooth muscle (SM) function. While BK-forming alpha subunits are ubiquitous, accessory beta1 subunits are highly expressed in SM. This makes beta1 an attractive target for pharmaceutical development to treat SM disorders, such as hypertension or cerebrovascular spasm. Compounds activating BK via beta1 have been identified, yet they exhibit low potency and off-target effects while antagonists that limit agonist activity via beta 1 remain unexplored. Beta1-dependent BK ligand-based pharmacophore modeling and ZINC database searches identified 15 commercially available hits. Concentration-response curves on BK alpha + beta1 subunit-mediated currents were obtained in CHO cells. One potent (EC50 = 20 nM) and highly efficacious activator (maximal activation = ×10.3 of control) was identified along with a potent antagonist (KB = 3.02 nM), both of which were dependent on beta1. Our study provides the first proof-of-principle that an agonist/antagonist pair can be used to control beta1-containing BK activity.
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Affiliation(s)
- Alexandria V Slayden
- Department of Pharmacology, Addiction Science and Toxicology, College of Medicine, The University of Tennessee Health Science Center, Memphis TN, 38103, USA
| | - Christy L Dyer
- Department of Chemistry, The University of Memphis, Memphis TN, 38152, USA
| | - Dejian Ma
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Tennessee Health Science Center, Memphis TN, 38163, USA
| | - Wei Li
- Department of Pharmaceutical Sciences, College of Pharmacy, The University of Tennessee Health Science Center, Memphis TN, 38163, 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
| | - Abby L Parrill
- Department of Chemistry, The University of Memphis, Memphis TN, 38152, 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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9
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Anxiety and hippocampal neuronal activity: Relationship and potential mechanisms. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2022; 22:431-449. [PMID: 34873665 DOI: 10.3758/s13415-021-00973-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/11/2021] [Indexed: 12/15/2022]
Abstract
The hippocampus has been implicated in modulating anxiety. It interacts with a variety of brain regions, both cortical and subcortical areas regulating emotion and stress responses, including prefrontal cortex, amygdala, hypothalamus, and the nucleus accumbens, to adjust anxiety levels in response to a variety of stressful conditions. Growing evidence indicates that anxiety is associated with increased neuronal excitability in the hippocampus, and alterations in local regulation of hippocampal excitability have been suggested to underlie behavioral disruptions characteristic of certain anxiety disorders. Furthermore, studies have shown that some anxiolytics can treat anxiety by altering the excitability and plasticity of hippocampal neurons. Hence, identifying cellular and molecular mechanisms and neural circuits that regulate hippocampal excitability in anxiety may be beneficial for developing targeted interventions for treatment of anxiety disorders particularly for the treatment-resistant cases. We first briefly review a role of the hippocampus in fear. We then review the evidence indicating a relationship between the hippocampal activity and fear/anxiety and discuss some possible mechanisms underlying stress-induced hippocampal excitability and anxiety-related behavior.
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10
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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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11
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Ochoa SV, Otero L, Aristizabal-Pachon AF, Hinostroza F, Carvacho I, Torres YP. Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK. Front Physiol 2022; 12:780206. [PMID: 35002762 PMCID: PMC8727448 DOI: 10.3389/fphys.2021.780206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/15/2021] [Indexed: 11/15/2022] Open
Abstract
Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.
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Affiliation(s)
- Sara V Ochoa
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Liliana Otero
- Center of Dental Research Dentistry Faculty, Pontificia Universidad Javeriana, Bogotá, Colombia
| | | | - Fernando Hinostroza
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile.,Centro de Investigación de Estudios Avanzados del Maule, CIEAM, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile.,Facultad de Ciencias de la Salud, Centro de Investigación en Neuropsicología y Neurociencias Cognitivas, Universidad Católica del Maule, Talca, Chile
| | - Ingrid Carvacho
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
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12
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González-Sanabria N, Echeverría F, Segura I, Alvarado-Sánchez R, Latorre R. BK in Double-Membrane Organelles: A Biophysical, Pharmacological, and Functional Survey. Front Physiol 2021; 12:761474. [PMID: 34764886 PMCID: PMC8577798 DOI: 10.3389/fphys.2021.761474] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 09/29/2021] [Indexed: 12/04/2022] Open
Abstract
In the 1970s, calcium-activated potassium currents were recorded for the first time. In 10years, this Ca2+-activated potassium channel was identified in rat skeletal muscle, chromaffin cells and characterized in skeletal muscle membranes reconstituted in lipid bilayers. This calcium- and voltage-activated potassium channel, dubbed BK for “Big K” due to its large ionic conductance between 130 and 300 pS in symmetric K+. The BK channel is a tetramer where the pore-forming α subunit contains seven transmembrane segments. It has a modular architecture containing a pore domain with a highly potassium-selective filter, a voltage-sensor domain and two intracellular Ca2+ binding sites in the C-terminus. BK is found in the plasma membrane of different cell types, the inner mitochondrial membrane (mitoBK) and the nuclear envelope’s outer membrane (nBK). Like BK channels in the plasma membrane (pmBK), the open probability of mitoBK and nBK channels are regulated by Ca2+ and voltage and modulated by auxiliary subunits. BK channels share common pharmacology to toxins such as iberiotoxin, charybdotoxin, paxilline, and agonists of the benzimidazole family. However, the precise role of mitoBK and nBK remains largely unknown. To date, mitoBK has been reported to play a role in protecting the heart from ischemic injury. At the same time, pharmacology suggests that nBK has a role in regulating nuclear Ca2+, membrane potential and expression of eNOS. Here, we will discuss at the biophysical level the properties and differences of mitoBK and nBK compared to those of pmBK and their pharmacology and function.
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Affiliation(s)
- Naileth González-Sanabria
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Echeverría
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ignacio Segura
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sánchez
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramon Latorre
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
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13
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Sancho M, Kyle BD. The Large-Conductance, Calcium-Activated Potassium Channel: A Big Key Regulator of Cell Physiology. Front Physiol 2021; 12:750615. [PMID: 34744788 PMCID: PMC8567177 DOI: 10.3389/fphys.2021.750615] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/29/2021] [Indexed: 12/01/2022] Open
Abstract
Large-conductance Ca2+-activated K+ channels facilitate the efflux of K+ ions from a variety of cells and tissues following channel activation. It is now recognized that BK channels undergo a wide range of pre- and post-translational modifications that can dramatically alter their properties and function. This has downstream consequences in affecting cell and tissue excitability, and therefore, function. While finding the “silver bullet” in terms of clinical therapy has remained elusive, ongoing research is providing an impressive range of viable candidate proteins and mechanisms that associate with and modulate BK channel activity, respectively. Here, we provide the hallmarks of BK channel structure and function generally, and discuss important milestones in the efforts to further elucidate the diverse properties of BK channels in its many forms.
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Affiliation(s)
- Maria Sancho
- Department of Pharmacology, University of Vermont, Burlington, VT, United States
| | - Barry D Kyle
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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14
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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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15
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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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16
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Granados ST, Latorre R, Torres YP. The Membrane Cholesterol Modulates the Interaction Between 17-βEstradiol and the BK Channel. Front Pharmacol 2021; 12:687360. [PMID: 34177597 PMCID: PMC8226216 DOI: 10.3389/fphar.2021.687360] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 05/24/2021] [Indexed: 11/13/2022] Open
Abstract
BK channels are composed by the pore forming α subunit and, in some tissues, is associated with different accessory β subunits. These proteins modify the biophysical properties of the channel, amplifying the range of BK channel activation according to the physiological context. In the vascular cells, the pore forming BKα subunit is expressed with the β1 subunit, where they play an essential role in the modulation of arterial tone and blood pressure. In eukaryotes, cholesterol is a structural lipid of the cellular membrane. Changes in the ratio of cholesterol content in the plasma membrane (PM) regulates the BK channel activation altering its open probability, and hence, vascular contraction. It has been shown that the estrogen 17β-Estradiol (E2) causes a vasodilator effect in vascular cells, inducing a leftward shift in the V0.5 of the GV curve. Here, we evaluate whether changes in the membrane cholesterol concentration modify the effect that E2 induces on the BKα/β1 channel activity. Using binding and electrophysiology assays after cholesterol depletion or enrichment, we show that the cholesterol enrichment significantly decreases the expression of the α subunit, while cholesterol depletion increased the expression of that α subunit. Additionally, we demonstrated that changes in the membrane cholesterol cause the loss of the modulatory effect of E2 on the BKα/β1 channel activity, without affecting the E2 binding to the complex. Our data suggest that changes in membrane cholesterol content could affect channel properties related to the E2 effect on BKα/β1 channel activity. Finally, the results suggest that an optimal membrane cholesterol content is essential for the activation of BK channels through the β1 subunit.
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Affiliation(s)
- Sara T Granados
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
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17
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Wang X, Xiao Q, Zhu Y, Qi H, Qu D, Yao Y, Jia Y, Guo J, Cheng J, Ji Y, Li G, Tao J. Glycosylation of β1 subunit plays a pivotal role in the toxin sensitivity and activation of BK channels. J Venom Anim Toxins Incl Trop Dis 2021; 27:e20200182. [PMID: 34149831 PMCID: PMC8183112 DOI: 10.1590/1678-9199-jvatitd-2020-0182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Background: The accessory β1 subunits, regulating the pharmacological and biophysical properties of BK channels, always undergo post-translational modifications, especially glycosylation. To date, it remains elusive whether the glycosylation contributes to the regulation of BK channels by β1 subunits. Methods: Herein, we combined the electrophysiological approach with molecular mutations and biochemical manipulation to investigate the function roles of N-glycosylation in β1 subunits. Results: The results show that deglycosylation of β1 subunits through double-site mutations (β1 N80A/N142A or β1 N80Q/N142Q) could significantly increase the inhibitory potency of iberiotoxin, a specific BK channel blocker. The deglycosylated channels also have a different sensitivity to martentoxin, another BK channel modulator with some remarkable effects as reported before. On the contrary to enhancing effects of martentoxin on glycosylated BK channels under the presence of cytoplasmic Ca2+, deglycosylated channels were not affected by the toxin. However, the deglycosylated channels were surprisingly inhibited by martentoxin under the absence of cytoplasmic Ca2+, while the glycosylated channels were not inhibited under this same condition. In addition, wild type BK (α+β1) channels treated with PNGase F also showed the same trend of pharmacological results to the mutants. Similar to this modulation of glycosylation on BK channel pharmacology, the deglycosylated forms of the channels were activated at a faster speed than the glycosylated ones. However, the V1/2 and slope were not changed by the glycosylation. Conclusion: The present study reveals that glycosylation is an indispensable determinant of the modulation of β1-subunit on BK channel pharmacology and its activation. The loss of glycosylation of β1 subunits could lead to the dysfunction of BK channel, resulting in a pathological state.
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Affiliation(s)
- Xiaoli Wang
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Qian Xiao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yudan Zhu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Hong Qi
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Dongxiao Qu
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Yao
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Yuxiang Jia
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China
| | - Jingkan Guo
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Jiwei Cheng
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Yonghua Ji
- Institute of Biomembrane and Biopharmaceutics, Shanghai University, Shanghai, China.,Xinhua Translational Institute for Cancer Pain, Shanghai, China
| | - Guoyi Li
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
| | - Jie Tao
- Department of Neurology and Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Putuo Clinical Medical School, Anhui Medical University, Shanghai, China
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18
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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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19
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Abstract
Ca2+- and voltage-gated K+ channels of large conductance (BK channels) are expressed in a diverse variety of both excitable and inexcitable cells, with functional properties presumably uniquely calibrated for the cells in which they are found. Although some diversity in BK channel function, localization, and regulation apparently arises from cell-specific alternative splice variants of the single pore-forming α subunit ( KCa1.1, Kcnma1, Slo1) gene, two families of regulatory subunits, β and γ, define BK channels that span a diverse range of functional properties. We are just beginning to unravel the cell-specific, physiological roles served by BK channels of different subunit composition.
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Affiliation(s)
- Vivian Gonzalez-Perez
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
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20
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Zhao H, Xue Q, Li C, Wang Q, Han S, Zhou Y, Yang T, Xie Y, Fu H, Lu C, Meng F, Zhang M, Zhang Y, Wu X, Wu S, Zhuo M, Xu H. Upregulation of Beta4 subunit of BK Ca channels in the anterior cingulate cortex contributes to mechanical allodynia associated anxiety-like behaviors. Mol Brain 2020; 13:22. [PMID: 32070382 PMCID: PMC7029562 DOI: 10.1186/s13041-020-0555-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 01/19/2020] [Indexed: 12/02/2022] Open
Abstract
The anterior cingulate cortex (ACC) serves as a critical hub for the anxiety and pain perception. The large-conductance Ca2+-activated potassium channels, or BKCa channels, are ubiquitously expressed throughout the central nervous system including the cingulate cortex. However, what changes of cortical BKCa channels undergo in the ACC remains unknown in pain-related anxiety. In the present study, a significant upregulation of synaptic and non-synaptic BKCa channel accessory β4 subunits in the ACC was accompanied with pain-associated anxiety-like behaviors in the chronic compression of multiple dorsal root ganglia (mCCD) of the rat. NS1619, an opener of BKCa channels, significantly rescued the alteration of fAHP and AP duration of ACC pyramidal neurons in mCCD rats. The mRNA expression of BKCa β4 subunits was extremely upregulated in the ACC after mCCD with the increased amount of both synaptic and non-synaptic BKCa β4 subunit protein. Meanwhile, NS1619 reversed the enhanced AMPA receptor-mediated spontaneous excitatory postsynaptic current (sEPSC) frequency and the attenuated PPR of ACC neurons in mCCD rats. Local activation of BKCa channels in the ACC reversed mechanical allodynia and anxiety-like behaviors. These results suggest that the upregulation of postsynaptic and presynaptic BKCa β4 subunit may contribute to neuronal hyperexcitability and the enhanced synaptic transmission in the ACC in neuropathic pain state, and then may result in anxiety-like behavior induced by neuropathic pain.
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Affiliation(s)
- Huan Zhao
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China.,Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.,Department of Anesthesiology, Heze Municipal Hospital, Heze, 274031, Shandong, China
| | - Qian Xue
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Cong Li
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China.,Department of Anesthesiology, Heze Municipal Hospital, Heze, 274031, Shandong, China.,Shandong First Medcial University & Shandong Academy of Medical Sciences, Taian, 271000, Shandong, China
| | - Qingchuan Wang
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China.,Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Shichao Han
- Department of Burns and Cutaneous Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
| | - Yongsheng Zhou
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Tao Yang
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yingli Xie
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Hao Fu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Changbo Lu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Fancheng Meng
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Ming Zhang
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yan Zhang
- Department of Anesthesiology, Heze Municipal Hospital, Heze, 274031, Shandong, China
| | - Xianglong Wu
- Key Laboratory for Space Bioscience and Biotechnology, School of Life Sciences, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Shengxi Wu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Min Zhuo
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.,Department of Phsyiology, University of Toronto, Toronto, Canada
| | - Hui Xu
- Department of Neurobiology and Collaborative Innovation Center for Brain Science, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China. .,Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710049, China.
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21
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Tao X, MacKinnon R. Molecular structures of the human Slo1 K + channel in complex with β4. eLife 2019; 8:51409. [PMID: 31815672 PMCID: PMC6934384 DOI: 10.7554/elife.51409] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 12/06/2019] [Indexed: 12/16/2022] Open
Abstract
Slo1 is a Ca2+- and voltage-activated K+ channel that underlies skeletal and smooth muscle contraction, audition, hormone secretion and neurotransmitter release. In mammals, Slo1 is regulated by auxiliary proteins that confer tissue-specific gating and pharmacological properties. This study presents cryo-EM structures of Slo1 in complex with the auxiliary protein, β4. Four β4, each containing two transmembrane helices, encircle Slo1, contacting it through helical interactions inside the membrane. On the extracellular side, β4 forms a tetrameric crown over the pore. Structures with high and low Ca2+ concentrations show that identical gating conformations occur in the absence and presence of β4, implying that β4 serves to modulate the relative stabilities of 'pre-existing' conformations rather than creating new ones. The effects of β4 on scorpion toxin inhibition kinetics are explained by the crown, which constrains access but does not prevent binding.
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Affiliation(s)
- Xiao Tao
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, New York, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, New York, United States
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22
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Granados ST, Castillo K, Bravo-Moraga F, Sepúlveda RV, Carrasquel-Ursulaez W, Rojas M, Carmona E, Lorenzo-Ceballos Y, González-Nilo F, González C, Latorre R, Torres YP. The molecular nature of the 17β-Estradiol binding site in the voltage- and Ca 2+-activated K + (BK) channel β1 subunit. Sci Rep 2019; 9:9965. [PMID: 31292456 PMCID: PMC6620312 DOI: 10.1038/s41598-019-45942-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 06/17/2019] [Indexed: 01/14/2023] Open
Abstract
The accessory β1 subunit modulates the Ca2+- and voltage-activated K+ (BK) channel gating properties mainly by increasing its apparent Ca2+ sensitivity. β1 plays an important role in the modulation of arterial tone and blood pressure by vascular smooth muscle cells (SMCs). 17β-estradiol (E2) increases the BK channel open probability (Po) in SMCs, through a β1 subunit-dependent modulatory effect. Here, using molecular modeling, bioinformatics, mutagenesis, and electrophysiology, we identify a cluster of hydrophobic residues in the second transmembrane domain of the β1 subunit, including the residues W163 and F166, as the binding site for E2. We further show that the increase in Po induced by E2 is associated with a stabilization of the voltage sensor in its active configuration and an increase in the coupling between the voltage sensor activation and pore opening. Since β1 is a key molecular player in vasoregulation, the findings reported here are of importance in the design of novel drugs able to modulate BK channels.
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Affiliation(s)
- Sara T Granados
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Felipe Bravo-Moraga
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés, Bello, Chile
| | - Romina V Sepúlveda
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés, Bello, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Maximiliano Rojas
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés, Bello, Chile
| | - Emerson Carmona
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Yenisleidy Lorenzo-Ceballos
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Fernando González-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Center for Bioinformatics and Integrative Biology, Facultad de Ciencias de la Vida, Universidad Andrés, Bello, Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Ramón Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile.
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.
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23
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Abstract
Ca2+- and voltage-gated K+ channels of large conductance (BK channels) are expressed in a diverse variety of both excitable and inexcitable cells, with functional properties presumably uniquely calibrated for the cells in which they are found. Although some diversity in BK channel function, localization, and regulation apparently arises from cell-specific alternative splice variants of the single pore-forming α subunit ( KCa1.1, Kcnma1, Slo1) gene, two families of regulatory subunits, β and γ, define BK channels that span a diverse range of functional properties. We are just beginning to unravel the cell-specific, physiological roles served by BK channels of different subunit composition.
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Affiliation(s)
- Vivian Gonzalez-Perez
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
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24
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Cell Cycle Regulation by Ca 2+-Activated K⁺ (BK) Channels Modulators in SH-SY5Y Neuroblastoma Cells. Int J Mol Sci 2018; 19:ijms19082442. [PMID: 30126198 PMCID: PMC6121591 DOI: 10.3390/ijms19082442] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 08/02/2018] [Accepted: 08/13/2018] [Indexed: 12/28/2022] Open
Abstract
The effects of Ca2+-activated K+ (BK) channel modulation by Paxilline (PAX) (10−7–10−4 M), Iberiotoxin (IbTX) (0.1–1 × 10−6 M) and Resveratrol (RESV) (1–2 × 10−4 M) on cell cycle and proliferation, AKT1pSer473 phosphorylation, cell diameter, and BK currents were investigated in SH-SY5Y cells using Operetta-high-content-Imaging-System, ELISA-assay, impedentiometric counting method and patch-clamp technique, respectively. IbTX (4 × 10−7 M), PAX (5 × 10−5 M) and RESV (10−4 M) caused a maximal decrease of the outward K+ current at +30 mV (Vm) of −38.3 ± 10%, −31.9 ± 9% and −43 ± 8%, respectively, which was not reversible following washout and cell depolarization. After 6h of incubation, the drugs concentration dependently reduced proliferation. A maximal reduction of cell proliferation, respectively of −60 ± 8% for RESV (2 × 10−4 M) (IC50 = 1.50 × 10−4 M), −65 ± 6% for IbTX (10−6 M) (IC50 = 5 × 10−7 M), −97 ± 6% for PAX (1 × 10−4 M) (IC50 = 1.06 × 10−5 M) and AKT1pser473 dephosphorylation was observed. PAX induced a G1/G2 accumulation and contraction of the S-phase, reducing the nuclear area and cell diameter. IbTX induced G1 contraction and G2 accumulation reducing diameter. RESV induced G2 accumulation and S contraction reducing diameter. These drugs share common actions leading to a block of the surface membrane BK channels with cell depolarization and calcium influx, AKT1pser473 dephosphorylation by calcium-dependent phosphatase, accumulation in the G2 phase, and a reduction of diameter and proliferation. In addition, the PAX action against nuclear membrane BK channels potentiates its antiproliferative effects with early apoptosis.
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Rosa P, Catacuzzeno L, Sforna L, Mangino G, Carlomagno S, Mincione G, Petrozza V, Ragona G, Franciolini F, Calogero A. BK channels blockage inhibits hypoxia-induced migration and chemoresistance to cisplatin in human glioblastoma cells. J Cell Physiol 2018; 233:6866-6877. [PMID: 29319175 DOI: 10.1002/jcp.26448] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 01/05/2018] [Indexed: 12/25/2022]
Abstract
Glioblastoma (GBM) cells express large-conductance, calcium-activated potassium (BK) channels, whose activity is important for several critical aspects of the tumor, such as migration/invasion and cell death. GBMs are also characterized by a heavy hypoxic microenvironment that exacerbates tumor aggressiveness. Since hypoxia modulates the activity of BK channels in many tissues, we hypothesized that a hypoxia-induced modulation of these channels may contribute to the hypoxia-induced GBM aggressiveness. In U87-MG cells, hypoxia induced a functional upregulation of BK channel activity, without interfering with their plasma membrane expression. Wound healing and transwell migration assays showed that hypoxia increased the migratory ability of U87-MG cells, an effect that could be prevented by BK channel inhibition. Toxicological experiments showed that hypoxia was able to induce chemoresistance to cisplatin in U87-MG cells and that the inhibition of BK channels prevented the hypoxia-induced chemoresistance. Clonogenic assays showed that BK channels are also used to increase the clonogenic ability of U87-MG GBM cells in presence, but not in absence, of cisplatin. BK channels were also found to be essential for the hypoxia-induced de-differentiation of GBM cells. Finally, using immunohistochemical analysis, we highlighted the presence of BK channels in hypoxic areas of human GBM tissues, suggesting that our findings may have physiopathological relevance in vivo. In conclusion, our data show that BK channels promote several aspects of the aggressive potential of GBM cells induced by hypoxia, such as migration and chemoresistance to cisplatin, suggesting it as a potential therapeutic target in the treatment of GBM.
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Affiliation(s)
- Paolo Rosa
- Department of Medical-Surgical Sciences and Biotechnologies, University of Rome "Sapienza", Polo Pontino, Latina, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Luigi Sforna
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Giorgio Mangino
- Department of Medical-Surgical Sciences and Biotechnologies, University of Rome "Sapienza", Polo Pontino, Latina, Italy
| | - Silvia Carlomagno
- Department of Medical-Surgical Sciences and Biotechnologies, University of Rome "Sapienza", Polo Pontino, Latina, Italy
| | - Gabriella Mincione
- Department of Medical, Oral and Biotechnological Sciences, University "G. d'Annunzio" Chieti-Pescara, Italy
| | - Vincenzo Petrozza
- Department of Medical-Surgical Sciences and Biotechnologies, University of Rome "Sapienza", Polo Pontino, Latina, Italy.,Istituto Chirurgico Ortopedico Traumatologico, ICOT, Latina, Italy
| | - Giuseppe Ragona
- Istituto Chirurgico Ortopedico Traumatologico, ICOT, Latina, Italy.,Department of Experimental Medicine, University of Rome "Sapienza", Rome, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Antonella Calogero
- Department of Medical-Surgical Sciences and Biotechnologies, University of Rome "Sapienza", Polo Pontino, Latina, Italy.,Istituto Chirurgico Ortopedico Traumatologico, ICOT, Latina, Italy
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26
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Shipston MJ. Control of anterior pituitary cell excitability by calcium-activated potassium channels. Mol Cell Endocrinol 2018; 463:37-48. [PMID: 28596131 DOI: 10.1016/j.mce.2017.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 06/02/2017] [Accepted: 06/02/2017] [Indexed: 01/01/2023]
Abstract
In anterior pituitary endocrine cells, large (BK), small (SK) and intermediate (IK) conductance calcium activated potassium channels are key determinants in shaping cellular excitability in a cell type- and context-specific manner. Indeed, these channels are targeted by multiple signaling pathways that stimulate or inhibit cellular excitability. BK channels can, paradoxically, both promote electrical bursting as well as terminate bursting and spiking dependent upon intrinsic BK channel properties and proximity to voltage gated calcium channels in somatotrophs, lactotrophs and corticotrophs. In contrast, SK channels are predominantly activated by calcium released from intracellular IP3-sensitive calcium stores and mediate membrane hyperpolarization in cells including gonadotrophs and corticotrophs. IK channels are predominantly expressed in corticotrophs where they limit membrane excitability. A major challenge for the future is to determine the cell-type specific molecular composition of calcium-activated potassium channels and how they control anterior pituitary hormone secretion as well as other calcium-dependent processes.
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Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, EH89XD, UK.
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27
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Activation of human smooth muscle BK channels by hydrochlorothiazide requires cell integrity and the presence of BK β 1 subunit. Acta Pharmacol Sin 2018; 39:371-381. [PMID: 29188803 DOI: 10.1038/aps.2017.133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 08/28/2017] [Indexed: 12/13/2022] Open
Abstract
Thiazide-like diuretics are the most commonly used drugs to treat arterial hypertension, with their efficacy being linked to their chronic vasodilatory effect. Previous studies suggest that activation of the large conductance voltage- and Ca2+-dependent K+ (BK) channel (Slo 1, MaxiK channel) is responsible for the thiazide-induced vasodilatory effect. But the direct electrophysiological evidence supporting this claim is lacking. BK channels can be associated with one small accessory β-subunit (β1-β4) that confers specific biophysical and pharmacological characteristics to the current phenotype. The β1-subunit is primarily expressed in smooth muscle cells (SMCs). In this study we investigated the effect of hydrochlorothiazide (HCTZ) on BK channel activity in native SMCs from human umbilical artery (HUASMCs) and HEK293T cells expressing the BK channel (with and without the β1-subunit). Bath application of HCTZ (10 μmol/L) significantly augmented the BK current in HUASMCs when recorded using the whole-cell configurations, but it did not affect the unitary conductance and open probability of the BK channel in HUASMCs evaluated in the inside-out configuration, suggesting an indirect mechanism requiring cell integrity. In HEK293T cells expressing BK channels, HCTZ-augmented BK channel activity was only observed when the β1-subunit was co-expressed, being concentration-dependent with an EC50 of 28.4 μmol/L, whereas membrane potential did not influence the concentration relationship. Moreover, HCTZ did not affect the BK channel current in HEK293T cells evaluated in the inside-out configuration, but significantly increases the open probability in the cell-attached configuration. Our data demonstrate that a β1-subunit-dependent mechanism that requires SMC integrity leads to HCTZ-induced BK channel activation.
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Zhang YY, Han X, Liu Y, Chen J, Hua L, Ma Q, Huang YYX, Tang QY, Zhang Z. +mRNA expression of LRRC55 protein (leucine-rich repeat-containing protein 55) in the adult mouse brain. PLoS One 2018; 13:e0191749. [PMID: 29370300 PMCID: PMC5784982 DOI: 10.1371/journal.pone.0191749] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/10/2018] [Indexed: 01/14/2023] Open
Abstract
LRRC55 (leucine-rich repeat-containing protein 55) protein is an auxiliary γ subunit of BK (Big conductance potassium channel) channels, which leftward shifts GVs of BK channels around 50 mV in the absence of cytosolic Ca2+. LRRC55 protein is also the only γ subunit of BK channels that is expressed in mammalian nervous system. However, the expression pattern of LRRC55 gene in adult mammalian brain remains elusive. In this study, we investigated the distribution of LRRC55 mRNA in the adult mouse brain by using in situ hybridization. We found that LRRC55 mRNA is richly expressed in the adult mouse medial habenula nucleus (MHb), cerebellum and pons. However, the potential role of LRRC55 in MHb and cerebellum could be different based on the function of BK channels in these brain regions.
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Affiliation(s)
- Ying-Ying Zhang
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Xue Han
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Ye Liu
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Jian Chen
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Lei Hua
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Qian Ma
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Yang-Yu-Xin Huang
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Qiong-Yao Tang
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
| | - Zhe Zhang
- School of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application Technology, Xuzhou Medical University, Xuzhou, Jiangsu Province, China
- * E-mail:
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Tanner MR, Beeton C. Differences in ion channel phenotype and function between humans and animal models. FRONT BIOSCI-LANDMRK 2018; 23:43-64. [PMID: 28930537 PMCID: PMC5626566 DOI: 10.2741/4581] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ion channels play crucial roles in regulating a broad range of physiological processes. They form a very large family of transmembrane proteins. Their diversity results from not only a large number of different genes encoding for ion channel subunits but also the ability of subunits to assemble into homo- or heteromultimers, the existence of splice variants, and the expression of different regulatory subunits. These characteristics and the existence of very selective modulators make ion channels very attractive targets for therapy in a wide variety of pathologies. Some ion channels are already being targeted in the clinic while many more are being evaluated as novel drug targets in both clinical and preclinical studies. Advancing ion channel modulators from the bench to the clinic requires their assessment for safety and efficacy in animal models. While extrapolating results from one species to another is tempting, doing such without careful evaluation of the ion channels in different species presents a risk as the translation is not always straightforward. Here, we discuss differences between species in terms of ion channels expressed in selected tissues, differing roles of ion channels in some cell types, variable response to pharmacological agents, and human channelopathies that cannot fully be replicated in animal models.
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Affiliation(s)
- Mark R Tanner
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston TX 77030, and Interdepartmental Graduate Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston TX 77030
| | - Christine Beeton
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston TX 77030, and Center for Drug Discovery and Biology of Inflammation Center, Baylor College of Medicine, Houston TX 77030,
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30
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Kuntamallappanavar G, Dopico AM. BK β1 subunit-dependent facilitation of ethanol inhibition of BK current and cerebral artery constriction is mediated by the β1 transmembrane domain 2. Br J Pharmacol 2017; 174:4430-4448. [PMID: 28940182 DOI: 10.1111/bph.14046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 09/11/2017] [Accepted: 09/14/2017] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Ethanol at concentrations obtained in the circulation during moderate-heavy episodic drinking (30-60 mM) causes cerebral artery constriction in several species, including humans. In rodents, ethanol-induced cerebral artery constriction results from ethanol inhibition of large conductance voltage/Ca2+i -gated K+ (BK) channels in cerebral artery myocytes. Moreover, the smooth muscle-abundant BK β1 accessory subunit is required for ethanol to inhibit cerebral artery myocyte BK channels under physiological Ca2+i and voltages and thus constrict cerebral arteries. The molecular bases of these ethanol actions remain unknown. Here, we set to identify the BK β1 region(s) that mediates ethanol-induced inhibition of cerebral artery myocyte BK channels and eventual arterial constriction. EXPERIMENTAL APPROACH We used protein biochemistry, patch-clamp on engineered channel subunits, reversible cDNA permeabilization of KCNMB1 K/O mouse arteries and artery in vitro pressurization. KEY RESULTS Ethanol inhibition of BK current was facilitated by β1 but not β4 subunits. Furthermore, only BK complexes containing β chimeras with β1 transmembrane (TM) domains on a β4 background or with a β1 TM2 domain on a β4 background displayed ethanol responses identical to those of BK complexes including wild-type β1. Moreover, β1 TM2 itself but not other β regions were necessary for ethanol-induced cerebral artery constriction. CONCLUSIONS AND IMPLICATIONS BK β1 TM2 is necessary for this subunit to enable ethanol-induced inhibition of myocyte BK channels and cerebral artery constriction at physiological Ca2+ and voltages. Thus, novel agents that target β1 TM2 may be considered to counteract ethanol-induced cerebral artery constriction and associated cerebrovascular conditions.
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Affiliation(s)
- Guruprasad Kuntamallappanavar
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
| | - Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, USA
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31
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Zhao QY, Peng YB, Luo XJ, Luo X, Xu H, Wei MY, Jiang QJ, Li WE, Ma LQ, Xu JC, Liu XC, Zang DA, She YS, Zhu H, Shen J, Zhao P, Xue L, Yu MF, Chen W, Zhang P, Fu X, Chen J, Nie X, Shen C, Chen S, Chen S, Chen J, Hu S, Zou C, Qin G, Fang Y, Ding J, Ji G, Zheng YM, Song T, Wang YX, Liu QH. Distinct Effects of Ca 2+ Sparks on Cerebral Artery and Airway Smooth Muscle Cell Tone in Mice and Humans. Int J Biol Sci 2017; 13:1242-1253. [PMID: 29104491 PMCID: PMC5666523 DOI: 10.7150/ijbs.21475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 08/10/2017] [Indexed: 11/21/2022] Open
Abstract
The effects of Ca2+ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone, as well as the underlying mechanisms, are not clear. In this investigation, we elucidated the underlying mechanisms of the distinct effects of Ca2+ sparks on cerebral artery smooth muscle cells (CASMCs) and airway smooth muscle cells (ASMCs) tone. In CASMCs, owing to the functional loss of Ca2+-activated Cl- (Clca) channels, Ca2+ sparks activated large-conductance Ca2+-activated K+ channels (BKs), resulting in a decreases in tone against a spontaneous depolarization-caused high tone in the resting state. In ASMCs, Ca2+ sparks induced relaxation through BKs and contraction via Clca channels. However, the integrated result was contraction because Ca2+ sparks activated BKs prior to Clca channels and Clca channels-induced depolarization was larger than BKs-caused hyperpolarization. However, the effects of Ca2+ sparks on both cell types were determined by L-type voltage-dependent Ca2+ channels (LVDCCs). In addition, compared with ASMCs, CASMCs had great and higher amplitude Ca2+ sparks, a higher density of BKs, and higher Ca2+ and voltage sensitivity of BKs. These differences enhanced the ability of Ca2+ sparks to decrease CASMC and to increase ASMC tone. The higher Ca2+ and voltage sensitivity of BKs in CASMCs than ASMCs were determined by the β1 subunits. Moreover, Ca2+ sparks showed the similar effects on human CASMC and ASMC tone. In conclusions, Ca2+ sparks decrease CASMC tone and increase ASMC tone, mediated by BKs and Clca channels, respectively, and finally determined by LVDCCs.
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Affiliation(s)
- Qing-Yang Zhao
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Yong-Bo Peng
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Xiao-Jing Luo
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Xi Luo
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Hao Xu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Ming-Yu Wei
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Qiu-Ju Jiang
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Wen-Er Li
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Li-Qun Ma
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Jin-Chao Xu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Xiao-Cao Liu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Dun-An Zang
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Yu-San She
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - He Zhu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Jinhua Shen
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Ping Zhao
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Lu Xue
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Meng-Fei Yu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Weiwei Chen
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Ping Zhang
- Department of Cerebral Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430032, Hubei, China
| | - Xiangning Fu
- Department of Thoracic Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430032, Hubei, China
| | - Jingyu Chen
- Wuxi &Jiangsu Key Laboratory of Organ Transplantation, Department of Cardiothoracic Surgery, Lung Transplant Group, Wuxi People's Hospital, Nanjing Medical University, Jiangsu, China
| | - Xiaowei Nie
- Wuxi &Jiangsu Key Laboratory of Organ Transplantation, Department of Cardiothoracic Surgery, Lung Transplant Group, Wuxi People's Hospital, Nanjing Medical University, Jiangsu, China
| | - Chenyou Shen
- Wuxi &Jiangsu Key Laboratory of Organ Transplantation, Department of Cardiothoracic Surgery, Lung Transplant Group, Wuxi People's Hospital, Nanjing Medical University, Jiangsu, China
| | - Shu Chen
- Department of Cardiovascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430032, Hubei, China
| | - Shanshan Chen
- Department of Cardiovascular Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430032, Hubei, China
| | - Jingcao Chen
- Department of Cerebral Surgery, Zhongnan Hospital, Wuhan University Medical College, Wuhan, 430071, Hubei, China
| | - Sheng Hu
- Department of Medical Oncology, Hubei Cancer Hospital, Wuhan, 430079, Hubei, China
| | - Chunbin Zou
- Acute Lung Injury Center of Excellence, Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA
| | - Gangjian Qin
- Department of Biomedical Engineering, School of Medicine & School of Engineering, University of Alabama Birmingham, AL, 35294, USA
| | - Ying Fang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 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, Wuhan, Hubei, China
| | - Guangju Ji
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yun-Min Zheng
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, 12208, USA
| | - Tengyao Song
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, 12208, USA
| | - Yong-Xiao Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY, 12208, USA
| | - Qing-Hua Liu
- Institute for Medical Biology and Hubei Provincial Key Laboratory for Protection and Application of Special Plants in Wuling Area of China, College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China
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Dopico AM, Bukiya AN. Regulation of Ca 2+-Sensitive K + Channels by Cholesterol and Bile Acids via Distinct Channel Subunits and Sites. CURRENT TOPICS IN MEMBRANES 2017; 80:53-93. [PMID: 28863822 DOI: 10.1016/bs.ctm.2017.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Cholesterol (CLR) conversion into bile acids (BAs) in the liver constitutes the major pathway for CLR elimination from the body. Moreover, these steroids regulate each other's metabolism. While the roles of CLR and BAs in regulating metabolism and tissue function are well known, research of the last two decades revealed the existence of specific protein receptors for CLR or BAs in tissues with minor contribution to lipid metabolism, raising the possibility that these lipids serve as signaling molecules throughout the body. Among other lipids, CLR and BAs regulate ionic current mediated by the activity of voltage- and Ca2+-gated, K+ channels of large conductance (BK channels) and, thus, modulate cell physiology and participate in tissue pathophysiology. Initial work attributed modification of BK channel function by CLR or BAs to the capability of these steroids to directly interact with bilayer lipids and thus alter the physicochemical properties of the bilayer with eventual modification of BK channel function. Based on our own work and that of others, we now review evidence that supports direct interactions between CLR or BA and specific BK protein subunits, and the consequence of such interactions on channel activity and organ function, with a particular emphasis on arterial smooth muscle. For each steroid type, we will also briefly discuss several mechanisms that may underlie modification of channel steady-state activity. Finally, we will present novel computational data that provide a chemical basis for differential recognition of CLR vs lithocholic acid by distinct BK channel subunits and recognition sites.
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Affiliation(s)
- Alex M Dopico
- College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, United States.
| | - Anna N Bukiya
- College of Medicine, The University of Tennessee Health Science Center, Memphis, TN, United States
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33
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The Slo(w) path to identifying the mitochondrial channels responsible for ischemic protection. Biochem J 2017; 474:2067-2094. [PMID: 28600454 DOI: 10.1042/bcj20160623] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 02/10/2017] [Accepted: 02/13/2017] [Indexed: 12/19/2022]
Abstract
Mitochondria play an important role in tissue ischemia and reperfusion (IR) injury, with energetic failure and the opening of the mitochondrial permeability transition pore being the major causes of IR-induced cell death. Thus, mitochondria are an appropriate focus for strategies to protect against IR injury. Two widely studied paradigms of IR protection, particularly in the field of cardiac IR, are ischemic preconditioning (IPC) and volatile anesthetic preconditioning (APC). While the molecular mechanisms recruited by these protective paradigms are not fully elucidated, a commonality is the involvement of mitochondrial K+ channel opening. In the case of IPC, research has focused on a mitochondrial ATP-sensitive K+ channel (mitoKATP), but, despite recent progress, the molecular identity of this channel remains a subject of contention. In the case of APC, early research suggested the existence of a mitochondrial large-conductance K+ (BK, big conductance of potassium) channel encoded by the Kcnma1 gene, although more recent work has shown that the channel that underlies APC is in fact encoded by Kcnt2 In this review, we discuss both the pharmacologic and genetic evidence for the existence and identity of mitochondrial K+ channels, and the role of these channels both in IR protection and in regulating normal mitochondrial function.
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Sun X, Hirano AA, Brecha NC, Barnes S. Calcium-activated BK Ca channels govern dynamic membrane depolarizations of horizontal cells in rodent retina. J Physiol 2017; 595:4449-4465. [PMID: 28374528 DOI: 10.1113/jp274132] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/17/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Large conductance, Ca2+ -activated K+ (BKCa ) channels play important roles in mammalian retinal neurons, including photoreceptors, bipolar cells, amacrine cells and ganglion cells, but they have not been identified in horizontal cells. BKCa channel blockers paxilline and iberiotoxin, as well as Ca2+ free solutions and divalent cation Cav channel blockers, eliminate the outwardly rectifying current, while NS1619 enhances it. In symmetrical 150 mm K+ , single channels had a conductance close to 250 pS, within the range of all known BKCa channels. In current clamped horizontal cells, BKCa channels subdue depolarizing membrane potential excursions, reduce the average resting potential and decrease oscillations. The results show that BKCa channel activation puts a ceiling on horizontal cell depolarization and regulates the temporal responsivity of the cells. ABSTRACT Large conductance, calcium-activated potassium (BKCa ) channels have numerous roles in neurons including the regulation of membrane excitability, intracellular [Ca2+ ] regulation, and neurotransmitter release. In the retina, they have been identified in photoreceptors, bipolar cells, amacrine cells and ganglion cells, but have not been conclusively identified in mammalian horizontal cells. We found that outward current recorded between -30 and +60 mV is carried primarily in BKCa channels in isolated horizontal cells of rats and mice. Whole-cell outward currents were maximal at +50 mV and declined at membrane potentials positive to this value. This current was eliminated by the selective BKCa channel blocker paxilline (100 nm), iberiotoxin (10 μm), Ca2+ free solutions and divalent cation Cav channel blockers. It was activated by the BKCa channel activator NS1619 (30 μm). Single channel recordings revealed the conductance of the channels to be 244 ± 11 pS (n = 17; symmetrical 150 mm K+ ) with open probability being both voltage- and Ca2+ -dependent. The channels showed fast activation kinetics in response to Ca2+ influx and inactivation gating that could be modified by intracellular protease treatment, which suggests β subunit involvement. Under current clamp, block of BKCa current increased depolarizing membrane potential excursions, raising the average resting potential and producing oscillations. BKCa current activation with NS1619 inhibited oscillations and hyperpolarized the resting potential. These effects underscore the functional role of BKCa current in limiting depolarization of the horizontal cell membrane potential and suggest actions of these channels in regulating the temporal responsivity of the cells.
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Affiliation(s)
- Xiaoping Sun
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Arlene A Hirano
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | - Nicholas C Brecha
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Departments of Medicine, Ophthalmology and Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Steven Barnes
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Departments of Physiology & Biophysics and Ophthalmology & Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada
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35
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Wang W, Zhang X, Gao Q, Lawas M, Yu L, Cheng X, Gu M, Sahoo N, Li X, Li P, Ireland S, Meredith A, Xu H. A voltage-dependent K + channel in the lysosome is required for refilling lysosomal Ca 2+ stores. J Cell Biol 2017; 216:1715-1730. [PMID: 28468834 PMCID: PMC5461029 DOI: 10.1083/jcb.201612123] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/05/2017] [Accepted: 04/10/2017] [Indexed: 01/04/2023] Open
Abstract
Ion-dependent channels and transporters have been identified in lysosomes, including the V-ATPase H+ pump and transient receptor potential mucolipin channels (TRPMLs), the principle Ca2+ release channels in the lysosome, but much less is understood about the roles of Na+ and K+ in lysosomal physiology. Wang et al. describe a voltage-sensitive, Ca2+-activated K+ current in the lysosome (LysoKVCa) and show that LysoKVCa regulates lysosomal membrane potential and refilling of lysosomal Ca2+ stores. The resting membrane potential (Δψ) of the cell is negative on the cytosolic side and determined primarily by the plasma membrane’s selective permeability to K+. We show that lysosomal Δψ is set by lysosomal membrane permeabilities to Na+ and H+, but not K+, and is positive on the cytosolic side. An increase in juxta-lysosomal Ca2+ rapidly reversed lysosomal Δψ by activating a large voltage-dependent and K+-selective conductance (LysoKVCa). LysoKVCa is encoded molecularly by SLO1 proteins known for forming plasma membrane BK channels. Opening of single LysoKVCa channels is sufficient to cause the rapid, striking changes in lysosomal Δψ. Lysosomal Ca2+ stores may be refilled from endoplasmic reticulum (ER) Ca2+ via ER–lysosome membrane contact sites. We propose that LysoKVCa serves as the perilysosomal Ca2+ effector to prime lysosomes for the refilling process. Consistently, genetic ablation or pharmacological inhibition of LysoKVCa, or abolition of its Ca2+ sensitivity, blocks refilling and maintenance of lysosomal Ca2+ stores, resulting in lysosomal cholesterol accumulation and a lysosome storage phenotype.
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Affiliation(s)
- Wuyang Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Xiaoli Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Qiong Gao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Maria Lawas
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Lu Yu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Xiping Cheng
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Mingxue Gu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Nirakar Sahoo
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Xinran Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Ping Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109.,Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014, China
| | - Stephen Ireland
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Andrea Meredith
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
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36
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Rosa P, Sforna L, Carlomagno S, Mangino G, Miscusi M, Pessia M, Franciolini F, Calogero A, Catacuzzeno L. Overexpression of Large-Conductance Calcium-Activated Potassium Channels in Human Glioblastoma Stem-Like Cells and Their Role in Cell Migration. J Cell Physiol 2017; 232:2478-2488. [PMID: 27606467 DOI: 10.1002/jcp.25592] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 09/07/2016] [Indexed: 01/24/2023]
Abstract
Glioblastomas (GBMs) are brain tumors characterized by diffuse invasion of cancer cells into the healthy brain parenchyma, and establishment of secondary foci. GBM cells abundantly express large-conductance, calcium-activated potassium (BK) channels that are thought to promote cell invasion. Recent evidence suggests that the GBM high invasive potential mainly originates from a pool of stem-like cells, but the expression and function of BK channels in this cell subpopulation have not been studied. We investigated the expression of BK channels in GBM stem-like cells using electrophysiological and immunochemical techniques, and assessed their involvement in the migratory process of this important cell subpopulation. In U87-MG cells, BK channel expression and function were markedly upregulated by growth conditions that enriched the culture in GBM stem-like cells (U87-NS). Cytofluorimetric analysis further confirmed the appearance of a cell subpopulation that co-expressed high levels of BK channels and CD133, as well as other stem cell markers. A similar association was also found in cells derived from freshly resected GBM biopsies. Finally, transwell migration tests showed that U87-NS cells migration was much more sensitive to BK channel block than U87-MG cells. Our data show that BK channels are highly expressed in GBM stem-like cells, and participate to their high migratory activity. J. Cell. Physiol. 232: 2478-2488, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Paolo Rosa
- Department of Medico-Surgical Sciences and Biotechnologies, "La Sapienza" University, Latina, Italy
| | - Luigi Sforna
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Silvia Carlomagno
- Department of Medico-Surgical Sciences and Biotechnologies, "La Sapienza" University, Latina, Italy
| | - Giorgio Mangino
- Department of Medico-Surgical Sciences and Biotechnologies, "La Sapienza" University, Latina, Italy
| | - Massimo Miscusi
- Department of Medico-Surgical Sciences and Biotechnologies, "La Sapienza" University, Latina, Italy
| | - Mauro Pessia
- Department of Experimental Medicine, University of Perugia, Perugia, Italy.,Department of Physiology and Biochemistry, University of Malta, Msida, Malta
| | - Fabio Franciolini
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
| | - Antonella Calogero
- Department of Medico-Surgical Sciences and Biotechnologies, "La Sapienza" University, Latina, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry Biology and Biotechnology, University of Perugia, Perugia, Italy
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37
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Tricarico D, Mele A. Commentary: A BK (Slo1) channel journey from molecule to physiology. Front Pharmacol 2017; 8:188. [PMID: 28424624 PMCID: PMC5380717 DOI: 10.3389/fphar.2017.00188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 03/23/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Antonietta Mele
- Department of Pharmacy-Drug Science, University of BariBari, Italy
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38
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Chen L, Bi D, Lu ZH, McClafferty H, Shipston MJ. Distinct domains of the β1-subunit cytosolic N terminus control surface expression and functional properties of large-conductance calcium-activated potassium (BK) channels. J Biol Chem 2017; 292:8694-8704. [PMID: 28373283 PMCID: PMC5448097 DOI: 10.1074/jbc.m116.769505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 03/17/2017] [Indexed: 11/06/2022] Open
Abstract
The properties and function of large-conductance calcium- and voltage-activated potassium (BK) channels are modified by the tissue-specific expression of regulatory β1-subunits. Although the short cytosolic N-terminal domain of the β1-subunit is important for controlling both BK channel trafficking and function, whether the same, or different, regions of the N terminus control these distinct processes remains unknown. Here we demonstrate that the first six N-terminal residues including Lys-3, Lys-4, and Leu-5 are critical for controlling functional regulation, but not trafficking, of BK channels. This membrane-distal region has features of an amphipathic helix that is predicted to control the orientation of the first transmembrane-spanning domain (TM1) of the β1-subunit. In contrast, a membrane-proximal leucine residue (Leu-17) controls trafficking without affecting functional coupling, an effect that is in part dependent on controlling efficient endoplasmic reticulum exit of the pore-forming α-subunit. Thus cell surface trafficking and functional coupling with BK channels are controlled by distinct domains of the β1-subunit N terminus.
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Affiliation(s)
- Lie Chen
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.,PAPRSB Institute of Health Sciences, Universiti Brunei Darussalam, Jalan Tungku Link BE1410, Brunei Darussalam
| | - Danlei Bi
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.,Neurodegenerative Disease Research Center, School of Life Sciences, University of Science and Technology of China, Hefei 230026, China,and
| | - Zen Huat Lu
- PAPRSB Institute of Health Sciences, Universiti Brunei Darussalam, Jalan Tungku Link BE1410, Brunei Darussalam.,Division of Genetics and Genomics, The Roslin Institute, University of Edinburgh, Edinburgh EH25 9RG, Scotland, United Kingdom
| | - Heather McClafferty
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom
| | - Michael J Shipston
- From the Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom,
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39
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Unravelling the complexities of vascular smooth muscle ion channels: Fine tuning of activity by ancillary subunits. Pharmacol Ther 2017; 178:57-66. [PMID: 28336473 DOI: 10.1016/j.pharmthera.2017.03.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Which ion channel is the most important for regulating vascular tone? Which one is responsible for controlling the resting membrane potential or repolarization? Which channels are recruited by different intracellular signalling pathways or change in certain vascular diseases? Many different ion channels have been identified in the vasculature over the years and claimed as future therapeutic targets. Unfortunately, several of these ion channels are not just found in the vasculature, with many of them also found to have prominent functional roles in different organs of the body, which then leads to off-target effects. As cardiovascular diseases are expected to increase worldwide to epidemic proportions, ion channel research and the hunt for the next major therapeutic target to treat different vascular diseases has never been more important. However, I believe that the question we should now be asking is: which ancillary subunits are involved in regulating specific ion channels in the vasculature and do they have the potential to be new therapeutic targets?
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40
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Guan X, Li Q, Yan J. Relationship between auxiliary gamma subunits and mallotoxin on BK channel modulation. Sci Rep 2017; 7:42240. [PMID: 28165042 PMCID: PMC5292707 DOI: 10.1038/srep42240] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 01/03/2017] [Indexed: 01/20/2023] Open
Abstract
The large-conductance, calcium- and voltage-activated K+(BK) channel consists of the pore-forming α subunits (BKα) and auxiliary subunits. The auxiliary γ1-3 subunits potently modulate the BK channel by shifting its voltage-dependence of channel activation toward the hyperpolarizing direction by approximately 145 mV (γ1), 100 mV (γ2), and 50 mV (γ3). Mallotoxin is a potent small-molecule BK channel activator. We analyzed the relationship between mallotoxin and the γ subunits in their BK channel-activating effects in membrane patches excised from HEK-293 cells. We found that mallotoxin, when applied extracellularly, shifted the half-activation voltage (V1/2) of BKα channels by −72 mV. The channel-activating effect of mallotoxin was greatly attenuated in the presence of the γ1, γ2, or γ3 subunit, with resultant ΔV1/2 (+/− mallotoxin) values of −9, −28, or −15 mV, respectively. Most examined γ1 mutant subunits antagonized mallotoxin’s channel-activating effect in a manner that was largely dependent on its own modulatory function. However, mallotoxin caused an irreversible functional and structural disengagement of the γ1-F273S mutant from BK channels. We infer that the auxiliary γ subunit effectively interferes with mallotoxin on BK channel modulation via either a direct steric competition or an indirect allosteric influence on mallotoxin’s binding and action on BKα.
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Affiliation(s)
- Xin Guan
- 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
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41
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Latorre R, Castillo K, Carrasquel-Ursulaez W, Sepulveda RV, Gonzalez-Nilo F, Gonzalez C, Alvarez O. Molecular Determinants of BK Channel Functional Diversity and Functioning. Physiol Rev 2017; 97:39-87. [DOI: 10.1152/physrev.00001.2016] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Large-conductance Ca2+- and voltage-activated K+ (BK) channels play many physiological roles ranging from the maintenance of smooth muscle tone to hearing and neurosecretion. BK channels are tetramers in which the pore-forming α subunit is coded by a single gene ( Slowpoke, KCNMA1). In this review, we first highlight the physiological importance of this ubiquitous channel, emphasizing the role that BK channels play in different channelopathies. We next discuss the modular nature of BK channel-forming protein, in which the different modules (the voltage sensor and the Ca2+ binding sites) communicate with the pore gates allosterically. In this regard, we review in detail the allosteric models proposed to explain channel activation and how the models are related to channel structure. Considering their extremely large conductance and unique selectivity to K+, we also offer an account of how these two apparently paradoxical characteristics can be understood consistently in unison, and what we have learned about the conduction system and the activation gates using ions, blockers, and toxins. Attention is paid here to the molecular nature of the voltage sensor and the Ca2+ binding sites that are located in a gating ring of known crystal structure and constituted by four COOH termini. Despite the fact that BK channels are coded by a single gene, diversity is obtained by means of alternative splicing and modulatory β and γ subunits. We finish this review by describing how the association of the α subunit with β or with γ subunits can change the BK channel phenotype and pharmacology.
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Affiliation(s)
- Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Romina V. Sepulveda
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Fernando Gonzalez-Nilo
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Carlos Gonzalez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Osvaldo Alvarez
- Centro Interdisciplinario de Neurociencia de Valparaíso and Doctorado en Ciencias Mención Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile; Universidad Andres Bello, Facultad de Ciencias Biologicas, Center for Bioinformatics and Integrative Biology, Avenida Republica 239, Santiago, Chile and Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
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42
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Kuntamallappanavar G, Bisen S, Bukiya AN, Dopico AM. Differential distribution and functional impact of BK channel beta1 subunits across mesenteric, coronary, and different cerebral arteries of the rat. Pflugers Arch 2016; 469:263-277. [PMID: 28012000 DOI: 10.1007/s00424-016-1929-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 12/06/2016] [Accepted: 12/12/2016] [Indexed: 12/12/2022]
Abstract
Large conductance, Ca2+i- and voltage-gated K+ (BK) channels regulate myogenic tone and, thus, arterial diameter. In smooth muscle (SM), BK channels include channel-forming α and auxiliary β1 subunits. BK β1 increases the channel's Ca2+ sensitivity, allowing BK channels to negatively feedback on depolarization-induced Ca2+ entry, oppose SM contraction and favor vasodilation. Thus, endothelial-independent vasodilation can be evoked though targeting of SM BK β1 by endogenous ligands, including lithocholate (LCA). Here, we investigated the expression of BK β1 across arteries of the cerebral and peripheral circulations, and the contribution of such expression to channel function and BK β1-mediated vasodilation. Data demonstrate that endothelium-independent, BK β1-mediated vasodilation by LCA is larger in coronary (CA) and basilar (BA) arteries than in anterior cerebral (ACA), middle cerebral (MCA), posterior cerebral (PCA), and mesenteric (MA) arteries, all arterial segments having a similar diameter. Thus, differential dilation occurs in extracranial arteries which are subjected to similar vascular pressure (CA vs. MA) and in arteries that irrigate different brain regions (BA vs. ACA, MCA, and PCA). SM BK channels from BA and CA displayed increased basal activity and LCA responses, indicating increased BK β1 functional presence. Indeed, in the absence of detectable changes in BK α, BA and CA myocytes showed an increased location of BK β1 in the plasmalemma/subplasmalemma. Moreover, these myocytes distinctly showed increased BK β1 messenger RNA (mRNA) levels. Supporting a major role of enhanced BK β1 transcripts in artery dilation, LCA-induced dilation of MCA transfected with BK β1 complementary DNA (cDNA) was as high as LCA-induced dilation of untransfected BA or CA.
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Affiliation(s)
- Guruprasad Kuntamallappanavar
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St, Memphis, TN, 38103, USA
| | - Shivantika Bisen
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St, Memphis, TN, 38103, USA
| | - Anna N Bukiya
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St, Memphis, TN, 38103, USA
| | - Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, 71 South Manassas St, Memphis, TN, 38103, USA.
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43
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Atomic determinants of BK channel activation by polyunsaturated fatty acids. Proc Natl Acad Sci U S A 2016; 113:13905-13910. [PMID: 27849612 DOI: 10.1073/pnas.1615562113] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Docosahexaenoic acid (DHA), a polyunsaturated ω-3 fatty acid enriched in oily fish, contributes to better health by affecting multiple targets. Large-conductance Ca2+- and voltage-gated Slo1 BK channels are directly activated by nanomolar levels of DHA. We investigated DHA-channel interaction by manipulating both the fatty acid structure and the channel composition through the site-directed incorporation of unnatural amino acids. Electrophysiological measurements show that the para-group of a Tyr residue near the ion conduction pathway has a critical role. To robustly activate the channel, ionization must occur readily by a fatty acid for a good efficacy, and a long nonpolar acyl tail with a Z double bond present at the halfway position for a high affinity. The results suggest that DHA and the channel form an ion-dipole bond to promote opening and demonstrate the channel druggability. DHA, a marine-derived nutraceutical, represents a promising lead compound for rational drug design and discovery.
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44
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Kuntamallappanavar G, Dopico AM. Alcohol modulation of BK channel gating depends on β subunit composition. J Gen Physiol 2016; 148:419-440. [PMID: 27799321 PMCID: PMC5089933 DOI: 10.1085/jgp.201611594] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 10/14/2016] [Indexed: 01/01/2023] Open
Abstract
In most mammalian tissues, Ca2+i/voltage-gated, large conductance K+ (BK) channels consist of channel-forming slo1 and auxiliary (β1-β4) subunits. When Ca2+i (3-20 µM) reaches the vicinity of BK channels and increases their activity at physiological voltages, β1- and β4-containing BK channels are, respectively, inhibited and potentiated by intoxicating levels of ethanol (50 mM). Previous studies using different slo1s, lipid environments, and Ca2+i concentrations-all determinants of the BK response to ethanol-made it impossible to determine the specific contribution of β subunits to ethanol action on BK activity. Furthermore, these studies measured ethanol action on ionic current under a limited range of stimuli, rendering no information on the gating processes targeted by alcohol and their regulation by βs. Here, we used identical experimental conditions to obtain single-channel and macroscopic currents of the same slo1 channel ("cbv1" from rat cerebral artery myocytes) in the presence and absence of 50 mM ethanol. First, we assessed the role five different β subunits (1,2,2-IR, 3-variant d, and 4) in ethanol action on channel function. Thus, two phenotypes were identified: (1) ethanol potentiated cbv1-, cbv1+β3-, and cbv1+β4-mediated currents at low Ca2+i while inhibiting current at high Ca2+i, the potentiation-inhibition crossover occurring at 20 µM Ca2+i; (2) for cbv1+β1, cbv1+wt β2, and cbv1+β2-IR, this crossover was shifted to ∼3 µM Ca2+i Second, applying Horrigan-Aldrich gating analysis on both phenotypes, we show that ethanol fails to modify intrinsic gating and the voltage-dependent parameters under examination. For cbv1, however, ethanol (a) drastically increases the channel's apparent Ca2+ affinity (nine-times decrease in Kd) and (b) very mildly decreases allosteric coupling between Ca2+ binding and channel opening (C). The decreased Kd leads to increased channel activity. For cbv1+β1, ethanol (a) also decreases Kd, yet this decrease (two times) is much smaller than that of cbv1; (b) reduces C; and (c) decreases coupling between Ca2+ binding and voltage sensing (parameter E). Decreased allosteric coupling leads to diminished BK activity. Thus, we have identified critical gating modifications that lead to the differential actions of ethanol on slo1 with and without different β subunits.
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Affiliation(s)
- Guruprasad Kuntamallappanavar
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
| | - Alex M Dopico
- Department of Pharmacology, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38103
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Pethő Z, Tanner MR, Tajhya RB, Huq R, Laragione T, Panyi G, Gulko PS, Beeton C. Different expression of β subunits of the KCa1.1 channel by invasive and non-invasive human fibroblast-like synoviocytes. Arthritis Res Ther 2016; 18:103. [PMID: 27165430 PMCID: PMC4863321 DOI: 10.1186/s13075-016-1003-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Accepted: 04/26/2016] [Indexed: 12/20/2022] Open
Abstract
Background Fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA-FLS) contribute to joint inflammation and damage characteristic of the disease. RA-FLS express KCa1.1 (BK, Slo1, MaxiK, KCNMA1) as their major plasma membrane potassium channel. Blocking KCa1.1 reduces the invasive phenotype of RA-FLS and attenuates disease severity in animal models of RA. This channel has therefore emerged as a promising therapeutic target in RA. However, the pore-forming α subunit of KCa1.1 is widely distributed in the body, and blocking it induces severe side effects, thus limiting its value as a therapeutic target. On the other hand, KCa1.1 channels can also contain different accessory subunits with restricted tissue distribution that regulate channel kinetics and pharmacology. Identification of the regulatory subunits of KCa1.1 expressed by RA-FLS may therefore provide the opportunity for generating a selective target for RA treatment. Methods Highly invasive RA-FLS were isolated from patients with RA, and FLS from patients with osteoarthritis (OA) were used as minimally invasive controls. The β subunit expression by FLS was assessed by quantitative reverse transcription polymerase chain reactions, Western blotting, and patch-clamp electrophysiology combined with pharmacological agents. FLS were sorted by flow cytometry on the basis of their CD44 expression level for comparison of their invasiveness and with their expression of KCa1.1 α and β subunits. β1 and β3 subunit expression was reduced with small interfering RNA (siRNA) to assess their specific role in KCa1.1α expression and function and in FLS invasiveness. Results We identified functional β1 and β3b regulatory subunits in RA-FLS. KCa1.1 β3b subunits were expressed by 70 % of the cells and were associated with highly invasive CD44high RA-FLS, whereas minimally invasive CD44low RA-FLS and OA-FLS expressed either β1 subunit. Furthermore, we found that silencing the β3 but not the β1 subunit with siRNA reduced KCa1.1 channel density at the plasma membrane of RA-FLS and inhibited RA-FLS invasiveness. Conclusions Our findings suggest the KCa1.1 channel composed of α and β3b subunits as an attractive target for the therapy of RA.
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Affiliation(s)
- Zoltán Pethő
- Department of Molecular Physiology and Biophysics, Mail Stop BCM335, Room S409A, Baylor College of Medicine, Houston, TX, 77030, USA.,Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, 4032, Hungary
| | - Mark R Tanner
- Department of Molecular Physiology and Biophysics, Mail Stop BCM335, Room S409A, Baylor College of Medicine, Houston, TX, 77030, USA.,Interdepartmental Graduate Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Rajeev B Tajhya
- Department of Molecular Physiology and Biophysics, Mail Stop BCM335, Room S409A, Baylor College of Medicine, Houston, TX, 77030, USA.,Graduate Program in Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Redwan Huq
- Department of Molecular Physiology and Biophysics, Mail Stop BCM335, Room S409A, Baylor College of Medicine, Houston, TX, 77030, USA.,Graduate Program in Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Teresina Laragione
- Division of Rheumatology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, 4032, Hungary
| | - Pércio S Gulko
- Division of Rheumatology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Christine Beeton
- Department of Molecular Physiology and Biophysics, Mail Stop BCM335, Room S409A, Baylor College of Medicine, Houston, TX, 77030, USA. .,Biology of Inflammation Center, Baylor College of Medicine, Houston, TX, 77030, USA. .,Center for Drug Discovery, Baylor College of Medicine, Houston, TX, 77030, USA.
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Modulation of BK Channel Function by Auxiliary Beta and Gamma Subunits. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:51-90. [PMID: 27238261 DOI: 10.1016/bs.irn.2016.03.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The large-conductance, Ca(2+)- and voltage-activated K(+) (BK) channel is ubiquitously expressed in mammalian tissues and displays diverse biophysical or pharmacological characteristics. This diversity is in part conferred by channel modulation with different regulatory auxiliary subunits. To date, two distinct classes of BK channel auxiliary subunits have been identified: β subunits and γ subunits. Modulation of BK channels by the four auxiliary β (β1-β4) subunits has been well established and intensively investigated over the past two decades. The auxiliary γ subunits, however, were identified only very recently, which adds a new dimension to BK channel regulation and improves our understanding of the physiological functions of BK channels in various tissues and cell types. This chapter will review the current understanding of BK channel modulation by auxiliary β and γ subunits, especially the latest findings.
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Kis A, Krick S, Baumlin N, Salathe M. Airway Hydration, Apical K(+) Secretion, and the Large-Conductance, Ca(2+)-activated and Voltage-dependent Potassium (BK) Channel. Ann Am Thorac Soc 2016; 13 Suppl 2:S163-8. [PMID: 27115952 PMCID: PMC5015721 DOI: 10.1513/annalsats.201507-405kv] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 09/08/2015] [Indexed: 01/20/2023] Open
Abstract
Large-conductance, calcium-activated, and voltage-gated K(+) (BK) channels are expressed in many tissues of the human body, where they play important roles in signaling not only in excitable but also in nonexcitable cells. Because BK channel properties are rendered in part by their association with four β and four γ subunits, their channel function can differ drastically, depending on in which cellular system they are expressed. Recent studies verify the importance of apically expressed BK channels for airway surface liquid homeostasis and therefore of their significant role in mucociliary clearance. Here, we review evidence that inflammatory cytokines, which contribute to airway diseases, can lead to reduced BK activity via a functional down-regulation of the γ regulatory subunit LRRC26. Therefore, manipulation of LRRC26 and pharmacological opening of BK channels represent two novel concepts of targeting epithelial dysfunction in inflammatory airway diseases.
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Affiliation(s)
- Adrian Kis
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida
| | - Stefanie Krick
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida
| | - Nathalie Baumlin
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida
| | - Matthias Salathe
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida
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Kaczorowski G, Garcia M. Developing Molecular Pharmacology of BK Channels for Therapeutic Benefit. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 128:439-75. [DOI: 10.1016/bs.irn.2016.02.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hermann A, Sitdikova GF, Weiger TM. Oxidative Stress and Maxi Calcium-Activated Potassium (BK) Channels. Biomolecules 2015; 5:1870-911. [PMID: 26287261 PMCID: PMC4598779 DOI: 10.3390/biom5031870] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/17/2015] [Accepted: 07/20/2015] [Indexed: 01/13/2023] Open
Abstract
All cells contain ion channels in their outer (plasma) and inner (organelle) membranes. Ion channels, similar to other proteins, are targets of oxidative impact, which modulates ion fluxes across membranes. Subsequently, these ion currents affect electrical excitability, such as action potential discharge (in neurons, muscle, and receptor cells), alteration of the membrane resting potential, synaptic transmission, hormone secretion, muscle contraction or coordination of the cell cycle. In this chapter we summarize effects of oxidative stress and redox mechanisms on some ion channels, in particular on maxi calcium-activated potassium (BK) channels which play an outstanding role in a plethora of physiological and pathophysiological functions in almost all cells and tissues. We first elaborate on some general features of ion channel structure and function and then summarize effects of oxidative alterations of ion channels and their functional consequences.
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Affiliation(s)
- Anton Hermann
- Department of Cell Biology, Division of Cellular and Molecular Neurobiology, University of Salzburg, Salzburg 5020, Austria.
| | - Guzel F Sitdikova
- Department of Physiology of Man and Animals, Kazan Federal University, Kazan 420008, Russia.
| | - Thomas M Weiger
- Department of Cell Biology, Division of Cellular and Molecular Neurobiology, University of Salzburg, Salzburg 5020, Austria.
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Talwar S, Lynch JW. Investigating ion channel conformational changes using voltage clamp fluorometry. Neuropharmacology 2015; 98:3-12. [PMID: 25839896 DOI: 10.1016/j.neuropharm.2015.03.018] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 03/12/2015] [Accepted: 03/17/2015] [Indexed: 11/26/2022]
Abstract
Ion channels are membrane proteins whose functions are governed by conformational changes. The widespread distribution of ion channels, coupled with their involvement in most physiological and pathological processes and their importance as therapeutic targets, renders the elucidation of these conformational mechanisms highly compelling from a drug discovery perspective. Thanks to recent advances in structural biology techniques, we now have high-resolution static molecular structures for members of the major ion channel families. However, major questions remain to be resolved about the conformational states that ion channels adopt during activation, drug modulation and desensitization. Patch-clamp electrophysiology has long been used to define ion channel conformational states based on functional criteria. It achieves this by monitoring conformational changes at the channel gate and cannot detect conformational changes occurring in regions distant from the gate. Voltage clamp fluorometry involves labelling cysteines introduced into domains of interest with environmentally sensitive fluorophores and inferring structural rearrangements from voltage or ligand-induced fluorescence changes. Ion channel currents are monitored simultaneously to verify the conformational status. By defining real time conformational changes in domains distant from the gate, this technique provides unexpected new insights into ion channel structure and function. This review aims to summarise the methodology and highlight recent innovative applications of this powerful technique. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'.
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Affiliation(s)
- Sahil Talwar
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Joseph W Lynch
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia; School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
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