201
|
Abstract
Hypertension is a prevalent and major health problem, involving a complex integration of different organ systems, including the central nervous system (CNS). The CNS and the hypothalamus in particular are intricately involved in the pathogenesis of hypertension. In fact, evidence supports altered hypothalamic neuronal activity as a major factor contributing to increased sympathetic drive and increased blood pressure. Several mechanisms have been proposed to contribute to hypothalamic-driven sympathetic activity, including altered ion channel function. Ion channels are critical regulators of neuronal excitability and synaptic function in the brain and, thus, important for blood pressure homeostasis regulation. These include sodium channels, voltage-gated calcium channels, and potassium channels being some of them already identified in hypothalamic neurons. This brief review summarizes the hypothalamic ion channels that may be involved in hypertension, highlighting recent findings that suggest that hypothalamic ion channel modulation can affect the central control of blood pressure and, therefore, suggesting future development of interventional strategies designed to treat hypertension.
Collapse
Affiliation(s)
- Vera Geraldes
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal
| | - Sérgio Laranjo
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal
| | - Isabel Rocha
- Instituto de Fisiologia, Universidade de Lisboa, Faculdade de Medicina, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal. .,Centro Cardiovascular da Universidade de Lisboa, Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisbon, Portugal.
| |
Collapse
|
202
|
Abstract
Although the mechanism of sudden cardiac death (SCD) in heart failure is not completely known, genetic variations are known to play key roles in this process. Increasing numbers of mutations and variants are being discovered through genome-wide association studies. The genetic variations involved in the mechanisms of SCD have aroused widespread concern. Comprehensive understanding of the genetic variations involved in SCD may help prevent it. To this end, we briefly reviewed the genetic variations involved in SCD and their associations and interactions, and observed that cardiac ion channels are the core molecules involved in this process. Genetic variations involved in cardiac structure, cardiogenesis and development, cell division and differentiation, and DNA replication and transcription are all speculated to be loci involved in SCD. Additionally, the systems involved in neurohumoral regulation as well as substance and energy metabolism are also potentially responsible for susceptibility to SCD. They form an elaborate network and mutually interact with each other to govern the fate of SCD-susceptible individuals.
Collapse
|
203
|
Agasid MT, Wang X, Huang Y, Janczak CM, Bränström R, Saavedra SS, Aspinwall CA. Expression, purification, and electrophysiological characterization of a recombinant, fluorescent Kir6.2 in mammalian cells. Protein Expr Purif 2018; 146:61-68. [PMID: 29409958 DOI: 10.1016/j.pep.2018.01.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 11/27/2022]
Abstract
The inwardly rectifying K+ (Kir) channel, Kir6.2, plays critical roles in physiological processes in the brain, heart, and pancreas. Although Kir6.2 has been extensively studied in numerous expression systems, a comprehensive description of an expression and purification protocol has not been reported. We expressed and characterized a recombinant Kir6.2, with an N-terminal decahistidine tag, enhanced green fluorescent protein (eGFP) and deletion of C-terminal 26 amino acids, in succession, denoted eGFP-Kir6.2Δ26. eGFP-Kir6.2Δ26 was expressed in HEK293 cells and a purification protocol developed. Electrophysiological characterization showed that eGFP-Kir6.2Δ26 retains native single channel conductance (64 ± 3.3 pS), mean open times (τ1 = 0.72 ms, τ2 = 15.3 ms) and ATP affinity (IC50 = 115 ± 25 μM) when expressed in HEK293 cells. Detergent screening using size exclusion chromatography (SEC) identified Fos-choline-14 (FC-14) as the most suitable surfactant for protein solubilization, as evidenced by maintenance of the native tetrameric structure in SDS-PAGE and western blot analysis. A two-step scheme using Co2+-metal affinity chromatography and SEC was implemented for purification. Purified protein activity was assessed by reconstituting eGFP-Kir6.2Δ26 in black lipid membranes (BLMs) composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG), l-α-phosphatidylinositol-4,5-bisphosphate (PIP2) in a 89.5:10:0.5 mol ratio. Reconstituted eGFP-Kir6.2Δ26 displayed similar single channel conductance (61.8 ± 0.54 pS) compared to eGFP-Kir6.2Δ26 expressed in HEK293 membranes; however, channel mean open times increased (τ1 = 7.9 ms, τ2 = 61.9 ms) and ATP inhibition was significantly reduced for eGFP-Kir6.2Δ26 reconstituted into BLMs (IC50 = 3.14 ± 0.4 mM). Overall, this protocol should be foundational for the production of purified Kir6.2 for future structural and biochemical studies.
Collapse
Affiliation(s)
- Mark T Agasid
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Xuemin Wang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Yiding Huang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Colleen M Janczak
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States
| | - Robert Bränström
- Department of Molecular Medicine and Surgery, Karolinksa Institutet, Stockholm, Sweden
| | - S Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States; BIO5 Institute, University of Arizona, Tucson, AZ 85721, United States.
| | - Craig A Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, United States; BIO5 Institute, University of Arizona, Tucson, AZ 85721, United States; Department of Biomedical Engineering, University of Arizona, Tucson, AZ 85721, United States.
| |
Collapse
|
204
|
Modulation of Excitability of Stellate Neurons in the Ventral Cochlear Nucleus of Mice by ATP-Sensitive Potassium Channels. J Membr Biol 2018; 251:163-178. [PMID: 29379989 DOI: 10.1007/s00232-017-0011-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Accepted: 12/19/2017] [Indexed: 12/21/2022]
Abstract
Major voltage-activated ionic channels of stellate cells in the ventral part of cochlear nucleus (CN) were largely characterized previously. However, it is not known if these cells are equipped with other ion channels apart from the voltage-sensitive ones. In the current study, it was aimed to study subunit composition and function of ATP-sensitive potassium channels (KATP) in stellate cells of the ventral cochlear nucleus. Subunits of KATP channels, Kir6.1, Kir6.2, SUR1, and SUR2, were expressed at the mRNA level and at the protein level in the mouse VCN tissue. The specific and clearly visible bands for all subunits but that for Kir6.1 were seen in Western blot. Using immunohistochemical staining technique, stellate cells were strongly labeled with SUR1 and Kir6.2 antibodies and moderately labeled with SUR2 antibody, whereas the labeling signals for Kir6.1 were too weak. In patch clamp recordings, KATP agonists including cromakalim (50 µM), diazoxide (0.2 mM), 3-Amino-1,2,4-triazole (ATZ) (1 mM), 2,2-Dithiobis (5-nitro pyridine) (DTNP) (330 µM), 6-Chloro-3-isopropylamino- 4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NNC 55-0118) (1 µM), 6-chloro-3-(methylcyclopropyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NN414) (1 µM), and H2O2 (0.88 mM) induced marked responses in stellate cells, characterized by membrane hyperpolarization which were blocked by KATP antagonists. Blockers of KATP channels, glibenclamide (0.2 mM), tolbutamide (0.1 mM) as well as 5-hydroxydecanoic acid (1 mM), and catalase (500 IU/ml) caused depolarization of stellate cells, increasing spontaneous action potential firing. In conclusion, KATP channels seemed to be composed dominantly of Kir 6.2 subunit and SUR1 and SUR2 and activation or inhibition of KATP channels regulates firing properties of stellate cells by means of influencing resting membrane potential and input resistance.
Collapse
|
205
|
Abstract
Insulin secretion is initiated by activation of voltage-gated Ca2+ channels (VGCC) to trigger Ca2+-mediated insulin vesicle fusion with the β-cell plasma membrane. The firing of VGCC requires β-cell membrane depolarization, which is regulated by a balance of depolarizing and hyperpolarizing ionic currents. Here, we show that SWELL1 mediates a swell-activated, depolarizing chloride current (ICl,SWELL) in both murine and human β-cells. Hypotonic and glucose-stimulated β-cell swelling activates SWELL1-mediated ICl,SWELL and this contributes to membrane depolarization and activation of VGCC-dependent intracellular calcium signaling. SWELL1 depletion in MIN6 cells and islets significantly impairs glucose-stimulated insulin secretion. Tamoxifen-inducible β-cell-targeted Swell1 KO mice have normal fasting serum glucose and insulin levels but impaired glucose-stimulated insulin secretion and glucose tolerance; and this is further exacerbated in mild obesity. Our results reveal that β-cell SWELL1 modulates insulin secretion and systemic glycaemia by linking glucose-mediated β-cell swelling to membrane depolarization and activation of VGCC-triggered calcium signaling.
Collapse
|
206
|
Martínez-François JR, Fernández-Agüera MC, Nathwani N, Lahmann C, Burnham VL, Danial NN, Yellen G. BAD and K ATP channels regulate neuron excitability and epileptiform activity. eLife 2018; 7:32721. [PMID: 29368690 PMCID: PMC5785210 DOI: 10.7554/elife.32721] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 01/12/2018] [Indexed: 12/17/2022] Open
Abstract
Brain metabolism can profoundly influence neuronal excitability. Mice with genetic deletion or alteration of Bad (BCL-2 agonist of cell death) exhibit altered brain-cell fuel metabolism, accompanied by resistance to acutely induced epileptic seizures; this seizure protection is mediated by ATP-sensitive potassium (KATP) channels. Here we investigated the effect of BAD manipulation on KATP channel activity and excitability in acute brain slices. We found that BAD’s influence on neuronal KATP channels was cell-autonomous and directly affected dentate granule neuron (DGN) excitability. To investigate the role of neuronal KATP channels in the anticonvulsant effects of BAD, we imaged calcium during picrotoxin-induced epileptiform activity in entorhinal-hippocampal slices. BAD knockout reduced epileptiform activity, and this effect was lost upon knockout or pharmacological inhibition of KATP channels. Targeted BAD knockout in DGNs alone was sufficient for the antiseizure effect in slices, consistent with a ‘dentate gate’ function that is reinforced by increased KATP channel activity.
Collapse
Affiliation(s)
| | | | - Nidhi Nathwani
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Carolina Lahmann
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Veronica L Burnham
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Nika N Danial
- Department of Neurobiology, Harvard Medical School, Boston, United States.,Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, United States
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical School, Boston, United States
| |
Collapse
|
207
|
Kang C, Xie L, Gunasekar SK, Mishra A, Zhang Y, Pai S, Gao Y, Kumar A, Norris AW, Stephens SB, Sah R. SWELL1 is a glucose sensor regulating β-cell excitability and systemic glycaemia. Nat Commun 2018; 9:367. [PMID: 29371604 PMCID: PMC5785485 DOI: 10.1038/s41467-017-02664-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 12/15/2017] [Indexed: 12/11/2022] Open
Abstract
Insulin secretion is initiated by activation of voltage-gated Ca2+ channels (VGCC) to trigger Ca2+-mediated insulin vesicle fusion with the β-cell plasma membrane. The firing of VGCC requires β-cell membrane depolarization, which is regulated by a balance of depolarizing and hyperpolarizing ionic currents. Here, we show that SWELL1 mediates a swell-activated, depolarizing chloride current (ICl,SWELL) in both murine and human β-cells. Hypotonic and glucose-stimulated β-cell swelling activates SWELL1-mediated ICl,SWELL and this contributes to membrane depolarization and activation of VGCC-dependent intracellular calcium signaling. SWELL1 depletion in MIN6 cells and islets significantly impairs glucose-stimulated insulin secretion. Tamoxifen-inducible β-cell-targeted Swell1 KO mice have normal fasting serum glucose and insulin levels but impaired glucose-stimulated insulin secretion and glucose tolerance; and this is further exacerbated in mild obesity. Our results reveal that β-cell SWELL1 modulates insulin secretion and systemic glycaemia by linking glucose-mediated β-cell swelling to membrane depolarization and activation of VGCC-triggered calcium signaling.
Collapse
Affiliation(s)
- Chen Kang
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Litao Xie
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Susheel K Gunasekar
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Anil Mishra
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Yanhui Zhang
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Saachi Pai
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Yiwen Gao
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Ashutosh Kumar
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
| | - Andrew W Norris
- Department of Pediatrics, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
- Fraternal Order of the Eagles Diabetes Research Center, Iowa City, IA, 52242, USA
| | - Samuel B Stephens
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA
- Fraternal Order of the Eagles Diabetes Research Center, Iowa City, IA, 52242, USA
| | - Rajan Sah
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA, 52242, USA.
- Fraternal Order of the Eagles Diabetes Research Center, Iowa City, IA, 52242, USA.
- Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, IA, 52242, USA.
| |
Collapse
|
208
|
Yang HQ, Jana K, Rindler MJ, Coetzee WA. The trafficking protein, EHD2, positively regulates cardiac sarcolemmal K ATP channel surface expression: role in cardioprotection. FASEB J 2018; 32:1613-1625. [PMID: 29133341 DOI: 10.1096/fj.201700027r] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
ATP-sensitive K+ (KATP) channels uniquely link cellular energy metabolism to membrane excitability and are expressed in diverse cell types that range from the endocrine pancreas to neurons and smooth, skeletal, and cardiac muscle. A decrease in the surface expression of KATP channels has been linked to various disorders, including dysregulated insulin secretion, abnormal blood pressure, and impaired resistance to cardiac injury. In contrast, up-regulation of KATP channel surface expression may be protective, for example, by mediating the beneficial effect of ischemic preconditioning. Molecular mechanisms that regulate KATP channel trafficking are poorly understood. Here, we used cellular assays with immunofluorescence, surface biotinylation, and patch clamping to demonstrate that Eps15 homology domain-containing protein 2 (EHD2) is a novel positive regulator of KATP channel trafficking to increase surface KATP channel density. EHD2 had no effect on cardiac Na+ channels (Nav1.5). The effect is specific to EHD2 as other members of the EHD family-EHD1, EHD3, and EHD4-had no effect on KATP channel surface expression. EHD2 did not directly affect KATP channel properties as unitary conductance and ATP sensitivity were unchanged. Instead, we observed that the mechanism by which EHD2 increases surface expression is by stabilizing KATP channel-containing caveolar structures, which results in a reduced rate of endocytosis. EHD2 also regulated KATP channel trafficking in isolated cardiomyocytes, which validated the physiologic relevance of these observations. Pathophysiologically, EHD2 may be cardioprotective as a dominant-negative EHD2 mutant sensitized cardiomyocytes to ischemic damage. Our findings highlight EHD2 as a potential pharmacologic target in the treatment of diseases with KATP channel trafficking defects.-Yang, H. Q., Jana, K., Rindler, M. J., Coetzee, W. A. The trafficking protein, EHD2, positively regulates cardiac sarcolemmal KATP channel surface expression: role in cardioprotection.
Collapse
Affiliation(s)
- Hua Qian Yang
- Department of Pediatrics, New York University School of Medicine, New York, New York, USA
| | - Kundan Jana
- Department of Pediatrics, New York University School of Medicine, New York, New York, USA
| | - Michael J Rindler
- Department of Cell Biology, New York University School of Medicine, New York, New York, USA
| | - William A Coetzee
- Department of Pediatrics, New York University School of Medicine, New York, New York, USA.,Department of Physiology and Neuroscience, New York University School of Medicine, New York, New York, USA.,Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, USA
| |
Collapse
|
209
|
Kandasamy B, Shyng SL. Methods for Characterizing Disease-Associated ATP-Sensitive Potassium Channel Mutations. Methods Mol Biol 2018; 1684:85-104. [PMID: 29058186 DOI: 10.1007/978-1-4939-7362-0_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ATP-sensitive potassium (KATP) channel formed by the inwardly rectifying potassium channel Kir6.2 and the sulfonylurea receptor 1 (SUR1) plays a key role in regulating insulin secretion. Genetic mutations in KCNJ11 or ABCC8 which encode Kir6.2 and SUR1 respectively are major causes of insulin secretion disorders: those causing loss of channel function lead to congenital hyperinsulinism, whereas those causing gain of channel function result in neonatal diabetes and in some cases developmental delay, epilepsy, and neonatal diabetes, referred to as the DEND syndrome. Understanding how disease mutations disrupt channel expression and function is important for disease diagnosis and for devising effective therapeutic strategies. Here, we describe a workflow including several biochemical and functional assays to assess the effects of mutations on channel expression and function.
Collapse
Affiliation(s)
- Balamurugan Kandasamy
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Mail Code L224, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Physiology and Pharmacology, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Rd., Mail Code L224, Portland, OR, 97239, USA.
| |
Collapse
|
210
|
Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 424] [Impact Index Per Article: 70.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
Collapse
Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
211
|
Lee KPK, Chen J, MacKinnon R. Molecular structure of human KATP in complex with ATP and ADP. eLife 2017; 6:32481. [PMID: 29286281 PMCID: PMC5790381 DOI: 10.7554/elife.32481] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/29/2017] [Indexed: 12/20/2022] Open
Abstract
In many excitable cells, KATP channels respond to intracellular adenosine nucleotides: ATP inhibits while ADP activates. We present two structures of the human pancreatic KATP channel, containing the ABC transporter SUR1 and the inward-rectifier K+ channel Kir6.2, in the presence of Mg2+ and nucleotides. These structures, referred to as quatrefoil and propeller forms, were determined by single-particle cryo-EM at 3.9 Å and 5.6 Å, respectively. In both forms, ATP occupies the inhibitory site in Kir6.2. The nucleotide-binding domains of SUR1 are dimerized with Mg2+-ATP in the degenerate site and Mg2+-ADP in the consensus site. A lasso extension forms an interface between SUR1 and Kir6.2 adjacent to the ATP site in the propeller form and is disrupted in the quatrefoil form. These structures support the role of SUR1 as an ADP sensor and highlight the lasso extension as a key regulatory element in ADP’s ability to override ATP inhibition. A hormone called insulin finely controls the amount of sugar in the blood. When the blood sugar content is high, a group of cells in the pancreas release insulin; when it is low, they stop. In these cells, the level of sugar in the blood modifies the ratio of two molecules: ATP, the body’s energy currency, and ADP, a molecule closely related to ATP. Changes in the ATP/ADP ratio are therefore a proxy of the variations in blood sugar levels. In these pancreatic cells, a membrane protein called ATP sensitive potassium channel, KATP channel for short, acts as a switch that turns on and off the production of insulin. ATP and ADP control that switch, with the two molecules having opposite effects on the channel – ATP deactivates it, ADP activates it. The changes in ATP/ADP ratio – and by extension in blood sugar levels – are therefore coupled with the release of insulin. However, how KATP channels sense the changes in the ATP/ADP ratio in these cells is still unclear. In particular, ATP levels are usually high and constant: ATP is then continuously deactivating the channels, and it is unclear how ADP ever activates them. Here, Lee et al. use a microscopy technique that can image biological molecules at the atomic scale to look at the structure of human pancreatic KATP channels. The 3D reconstruction maps show that KATP channels have binding sites for ATP but also one for ADP. This ADP site acts as a sensor that can detect even small changes in ADP levels in the cell. The maps also reveal a dynamic lasso-like structure connecting the ATP and ADP binding areas. This domain may play a vital role in allowing ADP to override ATP’s control of the channel. The presence of the ADP sensor and the lasso structure could explain how KATP channels monitor changes in the ATP/ADP ratio and can therefore control the release of insulin based on blood sugar levels. Defects in the KATP channels of the pancreas are present in genetic diseases where infants produce too much or too little insulin. Understanding the structure of these channels and how they work may help scientists to design new drugs to treat these conditions.
Collapse
Affiliation(s)
- Kenneth Pak Kin Lee
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Jue Chen
- Laboratory of Membrane Biology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| |
Collapse
|
212
|
McClenaghan C, Hanson A, Sala-Rabanal M, Roessler HI, Josifova D, Grange DK, van Haaften G, Nichols CG. Cantu syndrome-associated SUR2 (ABCC9) mutations in distinct structural domains result in K ATP channel gain-of-function by differential mechanisms. J Biol Chem 2017; 293:2041-2052. [PMID: 29275331 DOI: 10.1074/jbc.ra117.000351] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/20/2017] [Indexed: 12/25/2022] Open
Abstract
The complex disorder Cantu syndrome (CS) arises from gain-of-function mutations in either KCNJ8 or ABCC9, the genes encoding the Kir6.1 and SUR2 subunits of ATP-sensitive potassium (KATP) channels, respectively. Recent reports indicate that such mutations can increase channel activity by multiple molecular mechanisms. In this study, we determined the mechanism by which KATP function is altered by several substitutions in distinct structural domains of SUR2: D207E in the intracellular L0-linker and Y985S, G989E, M1060I, and R1154Q/R1154W in TMD2. We engineered substitutions at their equivalent positions in rat SUR2A (D207E, Y981S, G985E, M1056I, and R1150Q/R1150W) and investigated functional consequences using macroscopic rubidium (86Rb+) efflux assays and patch-clamp electrophysiology. Our results indicate that D207E increases KATP channel activity by increasing intrinsic stability of the open state, whereas the cluster of Y981S/G985E/M1056I substitutions, as well as R1150Q/R1150W, augmented Mg-nucleotide activation. We also tested the responses of these channel variants to inhibition by the sulfonylurea drug glibenclamide, a potential pharmacotherapy for CS. None of the D207E, Y981S, G985E, or M1056I substitutions had a significant effect on glibenclamide sensitivity. However, Gln and Trp substitution at Arg-1150 significantly decreased glibenclamide potency. In summary, these results provide additional confirmation that mutations in CS-associated SUR2 mutations result in KATP gain-of-function. They help link CS genotypes to phenotypes and shed light on the underlying molecular mechanisms, including consequences for inhibitory drug sensitivity, insights that may inform the development of therapeutic approaches to manage CS.
Collapse
Affiliation(s)
| | - Alex Hanson
- From the Departments of Cell Biology and Physiology and
| | | | - Helen I Roessler
- the Department of Medical Genetics, University Medical Center Utrecht, Postbus 85500, 3508 GA Utrecht, The Netherlands, and
| | - Dragana Josifova
- the Guy's and St. Thomas NHS Trust, Clinical Genetics Department, Great Maze Pond, London SE1 9RT, United Kingdom
| | - Dorothy K Grange
- Pediatrics, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
| | - Gijs van Haaften
- the Department of Medical Genetics, University Medical Center Utrecht, Postbus 85500, 3508 GA Utrecht, The Netherlands, and
| | | |
Collapse
|
213
|
Bækgaard Nielsen O, de Paoli FV, Riisager A, Pedersen TH. Chloride Channels Take Center Stage in Acute Regulation of Excitability in Skeletal Muscle: Implications for Fatigue. Physiology (Bethesda) 2017; 32:425-434. [DOI: 10.1152/physiol.00006.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 07/14/2017] [Accepted: 08/02/2017] [Indexed: 01/28/2023] Open
Abstract
Initiation and propagation of action potentials in muscle fibers is a key element in the transmission of activating motor input from the central nervous system to their contractile apparatus, and maintenance of excitability is therefore paramount for their endurance during work. Here, we review current knowledge about the acute regulation of ClC-1 channels in active muscles and its importance for muscle excitability, function, and fatigue.
Collapse
Affiliation(s)
| | | | - Anders Riisager
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | |
Collapse
|
214
|
Abstract
Some anticancer agents induce immunogenic cell death that is accompanied by the emission of danger signals into the tumor microenvironment, thus attracting and activating innate immune effectors and finally inducing anticancer immunity. The release of extracellular nucleosides such as adenosine triphosphate (ATP) from the tumor in response to anticancer therapy plays a pivotal role in the attraction of antigen presenting cells and the activation of inflammasome-mediated proinflammatory cascades. In contrast, the ectonucleotidase-catalyzed phosphohydrolysis of nucleotides to nucleosides reduces the extracellular availability of nucleotides, hence limiting the recruitment and activation of antigen-presenting cells. In addition, the (over-)production of nucleosides including adenosine by ectonucleotidases located on cancer cells and regulatory T cells can induce immunosuppression, as adenosine directly inhibits the proliferation and activation of effector T cells. Here, we discuss the importance of death metabolites for immunomodulation in general, and the role of the purine nucleotide ATP and its derivative adenosine in particular. In addition, we provide an overview on therapeutic interventions that reinstate tumor immunogenicity in conditions where nucleotide-dependent immunostimulation is obstructed.
Collapse
Affiliation(s)
- Oliver Kepp
- Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France
- Equipe 11 Labellisée Ligue Contre le Cancer, Centre de Recherche des Cordeliers, INSERM U 1138, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Friedemann Loos
- Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France
- Equipe 11 Labellisée Ligue Contre le Cancer, Centre de Recherche des Cordeliers, INSERM U 1138, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Université Pierre et Marie Curie, Paris, France
| | - Peng Liu
- Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France
- Equipe 11 Labellisée Ligue Contre le Cancer, Centre de Recherche des Cordeliers, INSERM U 1138, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Université Pierre et Marie Curie, Paris, France
- University of Paris Sud XI, Kremlin Bicêtre, France
| | - Guido Kroemer
- Metabolomics and Cell Biology Platforms, Gustave Roussy Comprehensive Cancer Institute, Villejuif, France
- Equipe 11 Labellisée Ligue Contre le Cancer, Centre de Recherche des Cordeliers, INSERM U 1138, Paris, France
- Sorbonne Paris Cité, Université Paris Descartes, Paris, France
- Université Pierre et Marie Curie, Paris, France
- University of Paris Sud XI, Kremlin Bicêtre, France
- Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France
- Karolinska Institute, Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, Sweden
| |
Collapse
|
215
|
Bartoszewski R, Matalon S, Collawn JF. Ion channels of the lung and their role in disease pathogenesis. Am J Physiol Lung Cell Mol Physiol 2017; 313:L859-L872. [PMID: 29025712 PMCID: PMC5792182 DOI: 10.1152/ajplung.00285.2017] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 10/03/2017] [Accepted: 10/03/2017] [Indexed: 12/16/2022] Open
Abstract
Maintenance of normal epithelial ion and water transport in the lungs includes providing a thin layer of surface liquid that coats the conducting airways. This airway surface liquid is critical for normal lung function in a number of ways but, perhaps most importantly, is required for normal mucociliary clearance and bacterial removal. Preservation of the appropriate level of hydration, pH, and viscosity for the airway surface liquid requires the proper regulation and function of a battery of different types of ion channels and transporters. Here we discuss how alterations in ion channel/transporter function often lead to lung pathologies.
Collapse
Affiliation(s)
- Rafal Bartoszewski
- Department of Biology and Pharmaceutical Botany, Medical University of Gdansk, Gdansk, Poland
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Cell, Developmental, and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
- Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
- Gregory Fleming James Cystic Fibrosis Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - James F Collawn
- Department of Cell, Developmental, and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama;
- Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
- Gregory Fleming James Cystic Fibrosis Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| |
Collapse
|
216
|
Martin GM, Kandasamy B, DiMaio F, Yoshioka C, Shyng SL. Anti-diabetic drug binding site in a mammalian K ATP channel revealed by Cryo-EM. eLife 2017; 6:31054. [PMID: 29035201 PMCID: PMC5655142 DOI: 10.7554/elife.31054] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 10/11/2017] [Indexed: 12/25/2022] Open
Abstract
Sulfonylureas are anti-diabetic medications that act by inhibiting pancreatic KATP channels composed of SUR1 and Kir6.2. The mechanism by which these drugs interact with and inhibit the channel has been extensively investigated, yet it remains unclear where the drug binding pocket resides. Here, we present a cryo-EM structure of a hamster SUR1/rat Kir6.2 channel bound to a high-affinity sulfonylurea drug glibenclamide and ATP at 3.63 Å resolution, which reveals unprecedented details of the ATP and glibenclamide binding sites. Importantly, the structure shows for the first time that glibenclamide is lodged in the transmembrane bundle of the SUR1-ABC core connected to the first nucleotide binding domain near the inner leaflet of the lipid bilayer. Mutation of residues predicted to interact with glibenclamide in our model led to reduced sensitivity to glibenclamide. Our structure provides novel mechanistic insights of how sulfonylureas and ATP interact with the KATP channel complex to inhibit channel activity.
Collapse
Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, United States
| | - Balamurugan Kandasamy
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, United States
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, United States
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, United States
| |
Collapse
|
217
|
Abstract
Since the discovery of the KATP channel in 1983, numerous studies have revealed its physiological functions. The KATP channel is expressed in various organs, including the pancreas, brain and skeletal muscles. It functions as a "metabolic sensor" that converts the metabolic status to electrical activity. In pancreatic beta-cells, the KATP channel regulates the secretion of insulin by sensing a change in the blood glucose level and thus maintains glucose homeostasis. In 2004, heterozygous gain-of-function mutations in the KCNJ11 gene, which encodes the Kir6.2 subunit of the KATP channel, were found to cause neonatal diabetes. In some mutations, diabetes is accompanied by severe neurological symptoms [developmental delay, epilepsy, neonatal diabetes (DEND) syndrome]. This review focuses on mutations of Kir6.2, the pore-forming subunit and sulfonylurea receptor (SUR) 1, the regulatory subunit of the KATP channel, which cause neonatal diabetes/DEND syndrome and also discusses the findings of the pathological mechanisms that are associated with neonatal diabetes, and its neurological features.
Collapse
Affiliation(s)
- Kenju Shimomura
- Department of Medical Electrophysiology, Fukushima Medical University School of Medicine, Japan
| | - Yuko Maejima
- Department of Medical Electrophysiology, Fukushima Medical University School of Medicine, Japan
| |
Collapse
|
218
|
Glucose Sensing by Skeletal Myocytes Couples Nutrient Signaling to Systemic Homeostasis. Mol Cell 2017; 66:332-344.e4. [PMID: 28475869 PMCID: PMC5489118 DOI: 10.1016/j.molcel.2017.04.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 02/07/2017] [Accepted: 04/05/2017] [Indexed: 12/21/2022]
Abstract
Skeletal muscle is a major site of postprandial glucose disposal. Inadequate insulin action in skeletal myocytes contributes to hyperglycemia in diabetes. Although glucose is known to stimulate insulin secretion by β cells, whether it directly engages nutrient signaling pathways in skeletal muscle to maintain systemic glucose homeostasis remains largely unexplored. Here we identified the Baf60c-Deptor-AKT pathway as a target of muscle glucose sensing that augments insulin action in skeletal myocytes. Genetic activation of this pathway improved postprandial glucose disposal in mice, whereas its muscle-specific ablation impaired insulin action and led to postprandial glucose intolerance. Mechanistically, glucose triggers KATP channel-dependent calcium signaling, which promotes HDAC5 phosphorylation and nuclear exclusion, leading to Baf60c induction and insulin-independent AKT activation. This pathway is engaged by the anti-diabetic sulfonylurea drugs to exert their full glucose-lowering effects. These findings uncover an unexpected mechanism of glucose sensing in skeletal myocytes that contributes to homeostasis and therapeutic action.
Collapse
|
219
|
Youssef N, Campbell S, Barr A, Gandhi M, Hunter B, Dolinsky V, Dyck JRB, Clanachan AS, Light PE. Hearts lacking plasma membrane KATP channels display changes in basal aerobic metabolic substrate preference and AMPK activity. Am J Physiol Heart Circ Physiol 2017; 313:H469-H478. [DOI: 10.1152/ajpheart.00612.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 06/13/2017] [Accepted: 06/13/2017] [Indexed: 12/12/2022]
Abstract
Cardiac ATP-sensitive K+ (KATP) channels couple changes in cellular metabolism to membrane excitability and are activated during metabolic stress, although under basal aerobic conditions, KATP channels are thought to be predominately closed. Despite intense research into the roles of KATP channels during metabolic stress, their contribution to aerobic basal cardiac metabolism has not been previously investigated. Hearts from Kir6.2+/+ and Kir6.2−/− mice were perfused in working mode, and rates of glycolysis, fatty acid oxidation, and glucose oxidation were measured. Changes in activation/expression of proteins regulating metabolism were probed by Western blot analysis. Despite cardiac mechanical function and metabolic efficiency being similar in both groups, hearts from Kir6.2−/− mice displayed an approximately twofold increase in fatty acid oxidation and a 0.45-fold reduction in glycolytic rates but similar glucose oxidation rates compared with hearts from Kir6.2+/+ mice. Kir6.2−/− hearts also possessed elevated levels of activated AMP-activated protein kinase (AMPK), higher glycogen content, and reduced mitochondrial density. Moreover, activation of AMPK by isoproterenol or diazoxide was significantly blunted in Kir6.2−/− hearts. These data indicate that KATP channel ablation alters aerobic basal cardiac metabolism. The observed increase in fatty acid oxidation and decreased glycolysis before any metabolic insult may contribute to the poor recovery observed in Kir6.2−/− hearts in response to exercise or ischemia-reperfusion injury. Therefore, KATP channels may play an important role in the regulation of cardiac metabolism through AMPK signaling. NEW & NOTEWORTHY In this study, we show that genetic ablation of plasma membrane ATP-sensitive K+ channels results in pronounced changes in cardiac metabolic substrate preference and AMP-activated protein kinase activity. These results suggest that ATP-sensitive K+ channels may play a novel role in regulating metabolism in addition to their well-documented effects on ionic homeostasis during periods of stress.
Collapse
Affiliation(s)
- Nermeen Youssef
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Scott Campbell
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Amy Barr
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Manoj Gandhi
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Beth Hunter
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Vernon Dolinsky
- Children’s Hospital Research Institute of Manitoba, Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Jason R. B. Dyck
- Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and
| | - Alexander S. Clanachan
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E. Light
- Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
220
|
Cooper PE, McClenaghan C, Chen X, Stary-Weinzinger A, Nichols CG. Conserved functional consequences of disease-associated mutations in the slide helix of Kir6.1 and Kir6.2 subunits of the ATP-sensitive potassium channel. J Biol Chem 2017; 292:17387-17398. [PMID: 28842488 DOI: 10.1074/jbc.m117.804971] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 08/04/2017] [Indexed: 11/06/2022] Open
Abstract
Cantu syndrome (CS) is a condition characterized by a range of anatomical defects, including cardiomegaly, hyperflexibility of the joints, hypertrichosis, and craniofacial dysmorphology. CS is associated with multiple missense mutations in the genes encoding the regulatory sulfonylurea receptor 2 (SUR2) subunits of the ATP-sensitive K+ (KATP) channel as well as two mutations (V65M and C176S) in the Kir6.1 (KCNJ8) subunit. Previous analysis of leucine and alanine substitutions at the Val-65-equivalent site (Val-64) in Kir6.2 indicated no major effects on channel function. In this study, we characterized the effects of both valine-to-methionine and valine-to-leucine substitutions at this position in both Kir6.1 and Kir6.2 using ion flux and patch clamp techniques. We report that methionine substitution, but not leucine substitution, results in increased open state stability and hence significantly reduced ATP sensitivity and a marked increase of channel activity in the intact cell irrespective of the identity of the coassembled SUR subunit. Sulfonylurea inhibitors, such as glibenclamide, are potential therapies for CS. However, as a consequence of the increased open state stability, both Kir6.1(V65M) and Kir6.2(V64M) mutations essentially abolish high-affinity sensitivity to the KATP blocker glibenclamide in both intact cells and excised patches. This raises the possibility that, at least for some CS mutations, sulfonylurea therapy may not prove to be successful and highlights the need for detailed pharmacogenomic analyses of CS mutations.
Collapse
Affiliation(s)
- Paige E Cooper
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Conor McClenaghan
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
| | - Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110 and
| |
Collapse
|
221
|
Dhammika Bandara HM, Hua Z, Zhang M, Pauff SM, Miller SC, Colby Davie EA, Kobertz WR. Palladium-Mediated Synthesis of a Near-Infrared Fluorescent K + Sensor. J Org Chem 2017; 82:8199-8205. [PMID: 28664732 PMCID: PMC5715468 DOI: 10.1021/acs.joc.7b00845] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Potassium (K+) exits electrically excitable cells during normal and pathophysiological activity. Currently, K+-sensitive electrodes and electrical measurements are the primary tools to detect K+ fluxes. Here, we describe the synthesis of a near-IR, oxazine fluorescent K+ sensor (KNIR-1) with a dissociation constant suited for detecting changes in intracellular and extracellular K+ concentrations. KNIR-1 treatment of cells expressing voltage-gated K+ channels enabled the visualization of intracellular K+ depletion upon channel opening and restoration of cytoplasmic K+ after channel closing.
Collapse
Affiliation(s)
- H. M. Dhammika Bandara
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Zhengmao Hua
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Mei Zhang
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Steven M. Pauff
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Stephen C. Miller
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| | - Elizabeth A. Colby Davie
- Department of Natural Sciences, Assumption College, 500 Salisbury Street, Worcester MA 01609, United States
| | - William R. Kobertz
- Department of Biochemistry and Molecular Pharmacology, Programs in Neuroscience and Chemical Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, United States
| |
Collapse
|
222
|
Wang X, Fitts RH. Ventricular action potential adaptation to regular exercise: role of β-adrenergic and KATP channel function. J Appl Physiol (1985) 2017; 123:285-296. [DOI: 10.1152/japplphysiol.00197.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 04/21/2017] [Accepted: 05/15/2017] [Indexed: 01/06/2023] Open
Abstract
Regular exercise training is known to affect the action potential duration (APD) and improve heart function, but involvement of β-adrenergic receptor (β-AR) subtypes and/or the ATP-sensitive K+ (KATP) channel is unknown. To address this, female and male Sprague-Dawley rats were randomly assigned to voluntary wheel-running or control groups; they were anesthetized after 6–8 wk of training, and myocytes were isolated. Exercise training significantly increased APD of apex and base myocytes at 1 Hz and decreased APD at 10 Hz. Ca2+ transient durations reflected the changes in APD, while Ca2+ transient amplitudes were unaffected by wheel running. The nonselective β-AR agonist isoproterenol shortened the myocyte APD, an effect reduced by wheel running. The isoproterenol-induced shortening of APD was largely reversed by the selective β1-AR blocker atenolol, but not the β2-AR blocker ICI 118,551, providing evidence that wheel running reduced the sensitivity of the β1-AR. At 10 Hz, the KATP channel inhibitor glibenclamide prolonged the myocyte APD more in exercise-trained than control rats, implicating a role for this channel in the exercise-induced APD shortening at 10 Hz. A novel finding of this work was the dual importance of altered β1-AR responsiveness and KATP channel function in the training-induced regulation of APD. Of physiological importance to the beating heart, the reduced response to adrenergic agonists would enhance cardiac contractility at resting rates, where sympathetic drive is low, by prolonging APD and Ca2+ influx; during exercise, an increase in KATP channel activity would shorten APD and, thus, protect the heart against Ca2+ overload or inadequate filling. NEW & NOTEWORTHY Our data demonstrated that regular exercise prolonged the action potential and Ca2+ transient durations in myocytes isolated from apex and base regions at 1-Hz and shortened both at 10-Hz stimulation. Novel findings were that wheel running shifted the β-adrenergic receptor agonist dose-response curve rightward compared with controls by reducing β1-adrenergic receptor responsiveness and that, at the high activation rate, myocytes from trained animals showed higher KATP channel function.
Collapse
Affiliation(s)
- Xinrui Wang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| | - Robert H. Fitts
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| |
Collapse
|
223
|
Yildirim V, Vadrevu S, Thompson B, Satin LS, Bertram R. Upregulation of an inward rectifying K+ channel can rescue slow Ca2+ oscillations in K(ATP) channel deficient pancreatic islets. PLoS Comput Biol 2017; 13:e1005686. [PMID: 28749940 PMCID: PMC5549769 DOI: 10.1371/journal.pcbi.1005686] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 08/08/2017] [Accepted: 07/16/2017] [Indexed: 12/02/2022] Open
Abstract
Plasma insulin oscillations are known to have physiological importance in the regulation of blood glucose. In insulin-secreting β-cells of pancreatic islets, K(ATP) channels play a key role in regulating glucose-dependent insulin secretion. In addition, they convey oscillations in cellular metabolism to the membrane by sensing adenine nucleotides, and are thus instrumental in mediating pulsatile insulin secretion. Blocking K(ATP) channels pharmacologically depolarizes the β-cell plasma membrane and terminates islet oscillations. Surprisingly, when K(ATP) channels are genetically knocked out, oscillations in islet activity persist, and relatively normal blood glucose levels are maintained. Compensation must therefore occur to overcome the loss of K(ATP) channels in K(ATP) knockout mice. In a companion study, we demonstrated a substantial increase in Kir2.1 protein occurs in β-cells lacking K(ATP) because of SUR1 deletion. In this report, we demonstrate that β-cells of SUR1 null islets have an upregulated inward rectifying K+ current that helps to compensate for the loss of K(ATP) channels. This current is likely due to the increased expression of Kir2.1 channels. We used mathematical modeling to determine whether an ionic current having the biophysical characteristics of Kir2.1 is capable of rescuing oscillations that are similar in period to those of wild-type islets. By experimentally testing a key model prediction we suggest that Kir2.1 current upregulation is a likely mechanism for rescuing the oscillations seen in islets from mice deficient in K(ATP) channels. Pulsatile insulin secretion is important for the proper regulation of blood glucose, and disruption of this pulsatility is a hallmark of type II diabetes. An ion channel was discovered more than three decades ago that conveys the metabolic state of insulin-secreting β-cells to the plasma membrane because it is blocked by ATP and opened by ADP, and thereby controls the activity of these electrically-excitable cells on a rapid time scale according to the prevailing blood glucose level. In addition to setting the appropriate level of insulin secretion, K(ATP) channels play a key role in generating the oscillations in cellular activity that underlie insulin pulsatility. It is therefore surprising that oscillations in activity persist in islets in which the K(ATP) channels are genetically knocked out. In this combined modeling and experimental study, we demonstrate that the role played by K(ATP) current in wild-type β-cells can be taken over by an inward-rectifying K+ current which, we show here, is upregulated in β-cells from SUR1 knockout mice. This result helps to resolve a mystery in the field that has remained elusive for more than a decade, since the first studies showing oscillations in SUR1-/- islets.
Collapse
Affiliation(s)
- Vehpi Yildirim
- Department of Mathematics, Florida State University, Tallahassee, FL, United States of America
| | - Suryakiran Vadrevu
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Benjamin Thompson
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Leslie S. Satin
- Brehm Diabetes Center, University of Michigan Medical School, Ann Arbor, MI, United States of America
| | - Richard Bertram
- Department of Mathematics and Programs in Molecular Biophysics and Neuroscience, Florida State University, Tallahassee, FL, United States of America
- * E-mail:
| |
Collapse
|
224
|
High glucose stimulates cell proliferation and Collagen IV production in rat mesangial cells through inhibiting AMPK-K ATP signaling. Int Urol Nephrol 2017; 49:2079-2086. [PMID: 28748494 DOI: 10.1007/s11255-017-1654-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 07/06/2017] [Indexed: 01/22/2023]
Abstract
PURPOSE The present study investigated the putative mechanisms underlying effects of KATP channel on high glucose (HG)-induced mesangial cell proliferation and tissue inhibitors of metalloproteinases (TIMP)-2 and Collagen IV production. METHODS Rat mesangial cells were subjected to whole cell patch clamp to record the KATP channel currents under high glucose (HG, 30 mM) condition. Cell proliferation was measured using a CCK-8 assay. The production of TIMP-2 and Collagen IV and AMP-activated protein kinase (AMPK)-signaling pathway activity was assessed by ELISA and Western blotting, respectively. AMPK agonist (AICAR) was used to analyze the role of this kinase. The expression of KATP subunit (Kir6.1, Kir6.2, SUR1, SUR2A and SUR2B) was examined using quantitative real-time PCR (RT-PCR). RESULTS We found that HG was significant decreases in the expression of Kir6.1, SUB2A and SUB2B, three subunits of KATP, TIMP-2 production, KATP channel activity and AMPK activity, while it promoted the cell proliferation and Collagen IV production in rat mesangial cells. Pretreatment with KATP selective opener (diazoxide, DZX) significantly inhibited HG-induced mesangial cell proliferation, Collagen IV production and decrease in KATP channel activity in rat mesangial cells, which were reversed by pretreatment of 5-hydroxydecanoate, a selective inhibitor of KATP. Moreover, AICAR pretreatment inhibited HG-induced decrease in KATP channel activity. CONCLUSIONS Taken together, activating AMPK-KATP signaling may protect against HG-induced mesangial cell proliferation and Collagen IV production, and, thereby, provides new insights into the molecular mechanisms underlying early diabetic nephropathy (DN).
Collapse
|
225
|
Aharonovich Y, Scheinowitz M, Zlochiver S. Cardiac KATP channel modulation by 16Hz magnetic fields - A theoretical study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:161-164. [PMID: 28268304 DOI: 10.1109/embc.2016.7590665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Heart exposure to 16Hz magnetic fields (MFs) was shown to be cardio-protective for diseased hearts; still, the mechanism of this effect is unknown. We hypothesize that a possible one mechanism is an increased trans-membrane KATP channel open probability due to modulation of the degree of dissociation between K+ ions, having a resonance frequency of 16Hz, and the channel selectivity filter. The Fan-Makielski Markovian KATP channel model was adopted, and the MF bio-effect was manifested by modulating the open probability of the channel using the predictive MF bio-effect parameter based on Binhi's quantum mechanics model. The model was integrated in a ventricular single cell model and the MF effect on the calcium transients [Ca2+] was assessed. Periodic pacing (Cycle Length CL=1sec) was applied and a 16Hz or 32Hz MF was turned on at t=0 for 10min. MF exposure gradually decreased [Ca2+] due to KATP channel opening, more strongly at 16Hz. Additionally, a small negative diastolic shift was observed. These numerical results demonstrated similarity to published experimental data using similar 16Hz MF exposure. We conclude that 16Hz MF exposure increases the KATP channel open probability, lowering the cellular calcium load. Our model could be integrated in a tissue model to predict optimal MF parameters for future cardiac therapy devices.
Collapse
|
226
|
A Protective Role of Glibenclamide in Inflammation-Associated Injury. Mediators Inflamm 2017; 2017:3578702. [PMID: 28740332 PMCID: PMC5504948 DOI: 10.1155/2017/3578702] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 03/26/2017] [Accepted: 04/06/2017] [Indexed: 12/13/2022] Open
Abstract
Glibenclamide is the most widely used sulfonylurea drug for the treatment of type 2 diabetes mellitus (DM). Recent studies have suggested that glibenclamide reduced adverse neuroinflammation and improved behavioral outcomes following central nervous system (CNS) injury. We reviewed glibenclamide's anti-inflammatory effects: abundant evidences have shown that glibenclamide exerted an anti-inflammatory effect in respiratory, digestive, urological, cardiological, and CNS diseases, as well as in ischemia-reperfusion injury. Glibenclamide might block KATP channel, Sur1-Trpm4 channel, and NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome activation, decrease the production of proinflammatory mediators (TNF-α, IL-1β, and reactive oxygen species), and suppress the accumulation of inflammatory cells. Glibenclamide's anti-inflammation warrants further investigation.
Collapse
|
227
|
Abstract
BACKGROUND ATP-sensitive K+ (KATP) channels couple metabolic state to cellular excitability. Activation of neuronal and astrocytic mitochondrial KATP (mitoKATP) channels regulates a variety of neuronal functions. However, less is known about the impact of mitoKATP on tonic γ-aminobutyric acid (GABA) inhibition. Tonic GABA inhibition is mediated by the binding of ambient GABA on extrasynaptic GABA A-type receptors (GABAARs) and is involved in regulating neuronal excitability. METHODS We determined the impact of activation of KATP channels with diazoxide (DIZ) on tonic inhibition and recorded tonic current from rat cortical layer 5 pyramidal cells by patch-clamp recordings. RESULTS We found that neonatal tonic current increased with an increase in GABA concentration, which was partially mediated by the GABA A-type receptor (GABAAR) α5, and likely the δ subunits. Activation of KATP channels resulted in decreased tonic current in newborns, but there was increased tonic current during the second postnatal week. CONCLUSIONS These findings suggest that activation of KATP channels with DIZ regulates GABAergic transmission in neocortical pyramidal cells during development.
Collapse
|
228
|
Liu Y, Liu J, Li X, Wang F, Xu X, Wang C. Exogenous H 2 S prevents high glucose-induced damage to osteoblasts through regulation of KATP channels. Biochimie 2017; 137:151-157. [DOI: 10.1016/j.biochi.2017.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/27/2016] [Accepted: 03/13/2017] [Indexed: 11/30/2022]
|
229
|
Kang H, Oka S, Lee DY, Park J, Aponte AM, Jung YS, Bitterman J, Zhai P, He Y, Kooshapur H, Ghirlando R, Tjandra N, Lee SB, Kim MK, Sadoshima J, Chung JH. Sirt1 carboxyl-domain is an ATP-repressible domain that is transferrable to other proteins. Nat Commun 2017; 8:15560. [PMID: 28504272 PMCID: PMC5440690 DOI: 10.1038/ncomms15560] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 04/08/2017] [Indexed: 12/26/2022] Open
Abstract
Sirt1 is an NAD+-dependent protein deacetylase that regulates many physiological functions, including stress resistance, adipogenesis, cell senescence and energy production. Sirt1 can be activated by energy deprivation, but the mechanism is poorly understood. Here, we report that Sirt1 is negatively regulated by ATP, which binds to the C-terminal domain (CTD) of Sirt1. ATP suppresses Sirt1 activity by impairing the CTD's ability to bind to the deacetylase domain as well as its ability to function as the substrate recruitment site. ATP, but not NAD+, causes a conformational shift to a less compact structure. Mutations that prevent ATP binding increase Sirt1's ability to promote stress resistance and inhibit adipogenesis under high-ATP conditions. Interestingly, the CTD can be attached to other proteins, thereby converting them into energy-regulated proteins. These discoveries provide insight into how extreme energy deprivation can impact Sirt1 activity and underscore the complex nature of Sirt1 structure and regulation.
Collapse
Affiliation(s)
- Hyeog Kang
- Laboratory of Obesity and Aging Research, Genetics and Development Biology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Shinichi Oka
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers University, New Jersey Medical School, Newark, New Jersey 07101, USA
| | - Duck-Yeon Lee
- Biochemistry Core Facility, Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Junhong Park
- Tulane University School of Medicine, Department of Pathology, New Orleans, Louisiana 70112, USA
| | - Angel M. Aponte
- Proteomics Core Facility, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Young-Sang Jung
- Integrated Metabolomics Research Group, Western Seoul Center, Korea Basic Science Institute, Seoul 120-140, Republic of Korea
| | - Jacob Bitterman
- Laboratory of Obesity and Aging Research, Genetics and Development Biology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Peiyong Zhai
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers University, New Jersey Medical School, Newark, New Jersey 07101, USA
| | - Yi He
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Hamed Kooshapur
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Nico Tjandra
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sean B. Lee
- Tulane University School of Medicine, Department of Pathology, New Orleans, Louisiana 70112, USA
| | - Myung K. Kim
- Laboratory of Obesity and Aging Research, Genetics and Development Biology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Junichi Sadoshima
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers University, New Jersey Medical School, Newark, New Jersey 07101, USA
| | - Jay H. Chung
- Laboratory of Obesity and Aging Research, Genetics and Development Biology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| |
Collapse
|
230
|
Yildirim V, Bertram R. Calcium Oscillation Frequency-Sensitive Gene Regulation and Homeostatic Compensation in Pancreatic β-Cells. Bull Math Biol 2017; 79:1295-1324. [PMID: 28497293 DOI: 10.1007/s11538-017-0286-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/27/2017] [Indexed: 02/03/2023]
Abstract
Pancreatic islet [Formula: see text]-cells are electrically excitable cells that secrete insulin in an oscillatory fashion when the blood glucose concentration is at a stimulatory level. Insulin oscillations are the result of cytosolic [Formula: see text] oscillations that accompany bursting electrical activity of [Formula: see text]-cells and are physiologically important. ATP-sensitive [Formula: see text] channels (K(ATP) channels) play the key role in setting the overall activity of the cell and in driving bursting, by coupling cell metabolism to the membrane potential. In humans, when there is a defect in K(ATP) channel function, [Formula: see text]-cells fail to respond appropriately to changes in the blood glucose level, and electrical and [Formula: see text] oscillations are lost. However, mice compensate for K(ATP) channel defects in islet [Formula: see text]-cells by employing alternative mechanisms to maintain electrical and [Formula: see text] oscillations. In a recent study, we showed that in mice islets in which K(ATP) channels are genetically knocked out another [Formula: see text] current, provided by inward-rectifying [Formula: see text] channels, is increased. With mathematical modeling, we demonstrated that a sufficient upregulation in these channels can account for the paradoxical electrical bursting and [Formula: see text] oscillations observed in these [Formula: see text]-cells. However, the question of determining the correct level of upregulation that is necessary for this compensation remained unanswered, and this question motivates the current study. [Formula: see text] is a well-known regulator of gene expression, and several examples have been shown of genes that are sensitive to the frequency of the [Formula: see text] signal. In this mathematical modeling study, we demonstrate that a [Formula: see text] oscillation frequency-sensitive gene transcription network can adjust the gene expression level of a compensating [Formula: see text] channel so as to rescue electrical bursting and [Formula: see text] oscillations in a model [Formula: see text]-cell in which the key K(ATP) current is removed. This is done without the prescription of a target [Formula: see text] level, but evolves naturally as a consequence of the feedback between the [Formula: see text]-dependent enzymes and the cell's electrical activity. More generally, the study indicates how [Formula: see text] can provide the link between gene expression and cellular electrical activity that promotes wild-type behavior in a cell following gene knockout.
Collapse
Affiliation(s)
- Vehpi Yildirim
- Department of Mathematics, Florida State University, Tallahassee, FL, 32306, USA
| | - Richard Bertram
- Department of Mathematics and Programs in Molecular Biophysics and Neuroscience, Florida State University, Tallahassee, FL, 32306, USA.
| |
Collapse
|
231
|
Ashcroft FM, Puljung MC, Vedovato N. Neonatal Diabetes and the K ATP Channel: From Mutation to Therapy. Trends Endocrinol Metab 2017; 28:377-387. [PMID: 28262438 PMCID: PMC5582192 DOI: 10.1016/j.tem.2017.02.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 01/30/2017] [Accepted: 02/01/2017] [Indexed: 12/25/2022]
Abstract
Activating mutations in one of the two subunits of the ATP-sensitive potassium (KATP) channel cause neonatal diabetes (ND). This may be either transient or permanent and, in approximately 20% of patients, is associated with neurodevelopmental delay. In most patients, switching from insulin to oral sulfonylurea therapy improves glycemic control and ameliorates some of the neurological disabilities. Here, we review how KATP channel mutations lead to the varied clinical phenotype, how sulfonylureas exert their therapeutic effects, and why their efficacy varies with individual mutations.
Collapse
Affiliation(s)
- Frances M Ashcroft
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3PT, UK.
| | - Michael C Puljung
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3PT, UK
| | - Natascia Vedovato
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, OX1 3PT, UK
| |
Collapse
|
232
|
Wang S, Borschel WF, Heyman S, Hsu P, Nichols CG. Conformational changes at cytoplasmic intersubunit interactions control Kir channel gating. J Biol Chem 2017; 292:10087-10096. [PMID: 28446610 DOI: 10.1074/jbc.m117.785154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/17/2017] [Indexed: 02/02/2023] Open
Abstract
The defining structural feature of inward-rectifier potassium (Kir) channels is the unique Kir cytoplasmic domain. Recently we showed that salt bridges located at the cytoplasmic domain subunit interfaces (CD-Is) of eukaryotic Kir channels control channel gating via stability of a novel inactivated closed state. The cytoplasmic domains of prokaryotic and eukaryotic Kir channels show similar conformational rearrangements to the common gating ligand, phosphatidylinositol bisphosphate (PIP2), although these exhibit opposite coupling to opening and closing transitions. In Kir2.1, mutation of one of these CD-I salt bridge residues (R204A) reduces apparent PIP2 sensitivity of channel activity, and here we show that Ala or Cys substitutions of the functionally equivalent residue (Arg-165) in the prokaryotic Kir channel KirBac1.1 also significantly decrease sensitivity of the channel to PIP2 (by 5-30-fold). To further understand the structural basis of CD-I control of Kir channel gating, we examined the effect of the R165A mutation on PIP2-induced changes in channel function and conformation. Single-channel analyses indicated that the R165A mutation disrupts the characteristic long interburst closed state of reconstituted KirBac1.1 in giant liposomes, resulting in a higher open probability due to more frequent opening bursts. Intramolecular FRET measurements indicate that, relative to wild-type channels, the R165A mutation results in splaying of the cytoplasmic domains away from the central axis and that PIP2 essentially induces opposite motions of the major β-sheet in this channel mutant. We conclude that the removal of stabilizing CD-I salt bridges results in a collapsed state of the Kir domain.
Collapse
Affiliation(s)
- Shizhen Wang
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - William F Borschel
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Sarah Heyman
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Phillip Hsu
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Colin G Nichols
- From the Department of Cell Biology and Physiology and the Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| |
Collapse
|
233
|
Alvarez CP, Stagljar M, Muhandiram DR, Kanelis V. Hyperinsulinism-Causing Mutations Cause Multiple Molecular Defects in SUR1 NBD1. Biochemistry 2017; 56:2400-2416. [PMID: 28346775 DOI: 10.1021/acs.biochem.6b00681] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The sulfonylurea receptor 1 (SUR1) protein forms the regulatory subunit in ATP sensitive K+ (KATP) channels in the pancreas. SUR proteins are members of the ATP binding cassette (ABC) superfamily of proteins. Binding and hydrolysis of MgATP at the SUR nucleotide binding domains (NBDs) lead to channel opening. Pancreatic KATP channels play an important role in insulin secretion. SUR1 mutations that result in increased levels of channel opening ultimately inhibit insulin secretion and lead to neonatal diabetes. In contrast, SUR1 mutations that disrupt trafficking and/or decrease gating of KATP channels cause congenital hyperinsulinism, where oversecretion of insulin occurs even in the presence of low glucose levels. Here, we present data on the effects of specific congenital hyperinsulinism-causing mutations (G716V, R842G, and K890T) located in different regions of the first nucleotide binding domain (NBD1). Nuclear magnetic resonance (NMR) and fluorescence data indicate that the K890T mutation affects residues throughout NBD1, including residues that bind MgATP, NBD2, and coupling helices. The mutations also decrease the MgATP binding affinity of NBD1. Size exclusion and NMR data indicate that the G716V and R842G mutations cause aggregation of NBD1 in vitro, possibly because of destabilization of the domain. These data describe structural characterization of SUR1 NBD1 and shed light on the underlying molecular basis of mutations that cause congenital hyperinsulinism.
Collapse
Affiliation(s)
- Claudia P Alvarez
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6
| | - Marijana Stagljar
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.,Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| | - D Ranjith Muhandiram
- Department of Molecular Genetics, University of Toronto , 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
| | - Voula Kanelis
- Department of Chemical and Physical Sciences, University of Toronto Mississauga , 3359 Mississauga Road, Mississauga, Ontario, Canada L5L 1C6.,Department of Chemistry, University of Toronto , 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.,Department of Cell and Systems Biology, University of Toronto , 25 Harbord Street, Toronto, Ontario, Canada M5S 3G5
| |
Collapse
|
234
|
Yang JJ, Cheng RC, Cheng PC, Wang YC, Huang RC. K ATP Channels Mediate Differential Metabolic Responses to Glucose Shortage of the Dorsomedial and Ventrolateral Oscillators in the Central Clock. Sci Rep 2017; 7:640. [PMID: 28377630 PMCID: PMC5428822 DOI: 10.1038/s41598-017-00699-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/08/2017] [Indexed: 12/29/2022] Open
Abstract
The suprachiasmatic nucleus (SCN) central clock comprises two coupled oscillators, with light entraining the retinorecipient vasoactive intestinal peptide (VIP)-positive ventrolateral oscillator, which then entrains the arginine vasopressin (AVP)-positive dorsomedial oscillator. While glucose availability is known to alter photic entrainment, it is unclear how the SCN neurones respond to metabolic regulation and whether the two oscillators respond differently. Here we show that the ATP-sensitive K+ (KATP) channel mediates differential responses to glucose shortage of the two oscillators. RT-PCR and electrophysiological results suggested the presence of Kir6.2/SUR1 KATP channels in the SCN neurones. Immunostaining revealed preferential distribution of Kir6.2 in the dorsomedial subregion and selective colocalization with AVP. Whole cell recordings with ATP-free pipette solution indicated larger tolbutamide-induced depolarisation and tolbutamide-sensitive conductance in dorsal SCN (dSCN) than ventral SCN (vSCN) neurones. Tolbutamide-sensitive conductance was low under perforated patch conditions but markedly enhanced by cyanide inhibition of mitochondrial respiration. Glucoprivation produced a larger steady-state inhibition in dSCN than vSCN neurones, and importantly hypoglycemia via opening KATP channels selectively inhibited the KATP-expressing neurones. Our results suggest that the AVP-SCN oscillator may act as a glucose sensor to respond to glucose shortage while sparing the VIP-SCN oscillator to remain in synch with external light-dark cycle.
Collapse
Affiliation(s)
- Jyh-Jeen Yang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan
| | - Ruo-Ciao Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan
| | - Pi-Cheng Cheng
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan
| | - Yi-Chi Wang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan
| | - Rong-Chi Huang
- Department of Physiology and Pharmacology, College of Medicine, Chang Gung University, Tao-Yuan, 33305, Taiwan. .,Healthy Aging Research Center, Chang Gung University, Tao-Yuan, 33305, Taiwan. .,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, 33305, Taiwan.
| |
Collapse
|
235
|
Donnarumma E, Trivedi RK, Lefer DJ. Protective Actions of H2S in Acute Myocardial Infarction and Heart Failure. Compr Physiol 2017; 7:583-602. [PMID: 28333381 DOI: 10.1002/cphy.c160023] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hydrogen sulfide (H2S) was identified as the third gasotransmitter in 1996 following the discoveries of the biological importance of nitric oxide and carbon monoxide. Although H2S has long been considered a highly toxic gas, the discovery of its presence and enzymatic production in mammalian tissues supports a critical role for this physiological signaling molecule. H2S is synthesized endogenously by three enzymes: cystathionine β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. H2S plays a pivotal role in the regulation of cardiovascular function as H2S has been shown to modulate: vasodilation, angiogenesis, inflammation, oxidative stress, and apoptosis. Perturbation of endogenous production of H2S has been associated with many pathological conditions of the cardiovascular system such as diabetes, heart failure, and hypertension. As such, modulation of the endogenous H2S signaling pathway or administration of exogenous H2S has been shown to be cytoprotective. This review article will provide a summary of the current body of evidence on the role of H2S signaling in the setting of myocardial ischemia and heart failure. © 2017 American Physiological Society. Compr Physiol 7:583-602, 2017.
Collapse
Affiliation(s)
- Erminia Donnarumma
- Cardiovascular Center of Excellence Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - Rishi K Trivedi
- Cardiovascular Center of Excellence Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | - David J Lefer
- Cardiovascular Center of Excellence Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| |
Collapse
|
236
|
Kanelis V. From ions to insulin. eLife 2017; 6. [PMID: 28276322 PMCID: PMC5344668 DOI: 10.7554/elife.25159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 02/28/2017] [Indexed: 11/17/2022] Open
Abstract
Electron cryo-microscopy has revealed the three-dimensional structure of a potassium channel that has a central role in regulating the release of insulin from the pancreas.
Collapse
Affiliation(s)
- Voula Kanelis
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Canada.,Department of Chemistry, University of Toronto, Toronto, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, Canada
| |
Collapse
|
237
|
Emfinger CH, Welscher A, Yan Z, Wang Y, Conway H, Moss JB, Moss LG, Remedi MS, Nichols CG. Expression and function of ATP-dependent potassium channels in zebrafish islet β-cells. ROYAL SOCIETY OPEN SCIENCE 2017; 4:160808. [PMID: 28386438 PMCID: PMC5367309 DOI: 10.1098/rsos.160808] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/06/2017] [Indexed: 05/04/2023]
Abstract
ATP-sensitive potassium channels (KATP channels) are critical nutrient sensors in many mammalian tissues. In the pancreas, KATP channels are essential for coupling glucose metabolism to insulin secretion. While orthologous genes for many components of metabolism-secretion coupling in mammals are present in lower vertebrates, their expression, functionality and ultimate impact on body glucose homeostasis are unclear. In this paper, we demonstrate that zebrafish islet β-cells express functional KATP channels of similar subunit composition, structure and metabolic sensitivity to their mammalian counterparts. We further show that pharmacological activation of native zebrafish KATP using diazoxide, a specific KATP channel opener, is sufficient to disturb glucose tolerance in adult zebrafish. That β-cell KATP channel expression and function are conserved between zebrafish and mammals illustrates the evolutionary conservation of islet metabolic sensing from fish to humans, and lends relevance to the use of zebrafish to model islet glucose sensing and diseases of membrane excitability such as neonatal diabetes.
Collapse
Affiliation(s)
- Christopher H. Emfinger
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Alecia Welscher
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Zihan Yan
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Yixi Wang
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Hannah Conway
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
| | - Jennifer B. Moss
- Division of Endocrinology, Metabolism, and Nutrition and DMPI, Duke University Medical Center, Durham, NC, USA
| | - Larry G. Moss
- Division of Endocrinology, Metabolism, and Nutrition and DMPI, Duke University Medical Center, Durham, NC, USA
| | - Maria S. Remedi
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| |
Collapse
|
238
|
Martin GM, Yoshioka C, Rex EA, Fay JF, Xie Q, Whorton MR, Chen JZ, Shyng SL. Cryo-EM structure of the ATP-sensitive potassium channel illuminates mechanisms of assembly and gating. eLife 2017; 6. [PMID: 28092267 PMCID: PMC5344670 DOI: 10.7554/elife.24149] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 01/11/2017] [Indexed: 12/18/2022] Open
Abstract
KATP channels are metabolic sensors that couple cell energetics to membrane excitability. In pancreatic β-cells, channels formed by SUR1 and Kir6.2 regulate insulin secretion and are the targets of antidiabetic sulfonylureas. Here, we used cryo-EM to elucidate structural basis of channel assembly and gating. The structure, determined in the presence of ATP and the sulfonylurea glibenclamide, at ~6 Å resolution reveals a closed Kir6.2 tetrameric core with four peripheral SUR1s each anchored to a Kir6.2 by its N-terminal transmembrane domain (TMD0). Intricate interactions between TMD0, the loop following TMD0, and Kir6.2 near the proposed PIP2 binding site, and where ATP density is observed, suggest SUR1 may contribute to ATP and PIP2 binding to enhance Kir6.2 sensitivity to both. The SUR1-ABC core is found in an unusual inward-facing conformation whereby the two nucleotide binding domains are misaligned along a two-fold symmetry axis, revealing a possible mechanism by which glibenclamide inhibits channel activity. DOI:http://dx.doi.org/10.7554/eLife.24149.001 The hormone insulin reduces blood sugar levels by encouraging fat, muscle and other body cells to take up sugar. When blood sugar levels rise following a meal, cells within the pancreas known as beta cells should release insulin. In people with diabetes, the beta cells fail to release insulin, meaning that the high blood sugar levels are not corrected. When blood sugar levels are high, beta cells generate more energy in the form of ATP molecules. The increased level of ATP causes channels called ATP-sensitive potassium (KATP) channels in the membrane of the cell to close. This triggers a cascade of events that leads to the release of insulin. Some treatments for diabetes alter how the KATP channels work. For example, a widely prescribed medication called glibenclamide (also known as glyburide in the United States) stimulates the release of insulin by preventing the flow of potassium through KATP channels. It remains unknown exactly how ATP and glibenclamide interact with the channel’s molecular structure to stop the flow of potassium ions. KATP channels are made up of two proteins called SUR1 and Kir6.2. To investigate the structure of the KATP channel, Martin et al. purified channels made of the hamster form of the SUR1 protein and the mouse form of Kir6.2, which each closely resemble their human counterparts. The channels were purified in the presence of ATP and glibenclamide and were then rapidly frozen to preserve their structure, which allowed them to be visualized individually using electron microscopy. By analyzing the images taken from many channels, Martin et al. constructed a highly detailed, three-dimensional map of the KATP channel. The structure revealed by this map shows how SUR1 and Kir6.2 work together and provides insight into how ATP and glibenclamide interact with the channel to block the flow of potassium, and hence stimulate the release of insulin. An important next step will be to improve the structure to more clearly identify where ATP and glibenclamide bind to the KATP channel. It will also be important to study the structures of channels that are bound to other regulatory molecules. This will help researchers to fully understand how KATP channels located throughout the body operate under healthy and diseased conditions. This knowledge will aid in the design of more effective drugs to treat several devastating diseases caused by defective KATP channels. DOI:http://dx.doi.org/10.7554/eLife.24149.002
Collapse
Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, Oregon, United States
| | - Emily A Rex
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| | - Jonathan F Fay
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| | - Qing Xie
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| | - Matthew R Whorton
- Vollum Institute, Oregon Health and Science University, Portland, Oregon, United States
| | - James Z Chen
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, Oregon, United States
| |
Collapse
|
239
|
Isakova ZT, Talaibekova ET, Asambaeva DA, Kerimkulova AS, Lunegova OS, Aldashev AA. Association of the polymorphic marker Glu23Lys in the KCNJ11 gene with hypertension in Kyrgyz patients. TERAPEVT ARKH 2017; 89:14-17. [DOI: 10.17116/terarkh201789114-17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Aim. To study the association of the polymorphic marker Glu23Lys in the KCNJ11 with the development of hypertension in Kyrgyz patients. Subjects and methods. This case-control study enrolled 214 unrelated ethnic Kyrgyzes, in which a study group included 152 hypertensive patients (82 men and 70 women) and a control group consisted of 109 apparently healthy individuals (61 men and 48 women). The examinees’ mean age was 55.2±10.1 years. Hypertension was verified when blood pressure (BP) was above 140/90 mm Hg. Polymerase chain reaction-restriction fragment length polymorphism analysis was used to identify the polymorphic marker Glu23Lys in the KCNJ11 gene. Results. In the hypertension and control groups, the prevalence of 3 genotypes (Glu23Glu, Glu23Lys, and Lys23Lys) of the Glu23Lys polymorphism in the KCNJ11 gene differed significantly (χ2=8.04; p=0.018). The Lys23Lys and Glu23Lys genotypes were statistically more frequently recorded in the hypertension group and the homozygous Glu23Glu genotype was, on the contrary, more common in the control group than in the study one. In the hypertension group, the 23Lys allele frequency was statistically significantly higher than that in the control one (χ2=7.36; p=0.0067). The carriage of the 23Lys allele increased the risk of hypertension by 1.68 times (odds ratio (OR), 1.68; 95% confidence interval (CI), 1.17—2.41), that of the Glu23 allele had, on the contrary, a protective effect (OR, 0.60; 95% CI, 0.41—0.86). Conclusion. The polymorphic marker Glu23Lys in the KCNJ11 gene is associated with hypertension in the Kyrgyzes. The 23Lys allele is a marker for the higher risk of hypertension.
Collapse
|
240
|
Cooper PE, Sala-Rabanal M, Lee SJ, Nichols CG. Differential mechanisms of Cantú syndrome-associated gain of function mutations in the ABCC9 (SUR2) subunit of the KATP channel. ACTA ACUST UNITED AC 2017; 146:527-40. [PMID: 26621776 PMCID: PMC4664827 DOI: 10.1085/jgp.201511495] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutations that increase the activity of ATP-sensitive potassium channels through either enhanced activation by MgADP or decreased sensitivity to inhibition by ATP can lead to Cantú syndrome. Cantú syndrome (CS) is a rare disease characterized by congenital hypertrichosis, distinct facial features, osteochondrodysplasia, and cardiac defects. Recent genetic analysis has revealed that the majority of CS patients carry a missense mutation in ABCC9, which codes for the sulfonylurea receptor SUR2. SUR2 subunits couple with Kir6.x, inwardly rectifying potassium pore-forming subunits, to form adenosine triphosphate (ATP)-sensitive potassium (KATP) channels, which link cell metabolism to membrane excitability in a variety of tissues including vascular smooth muscle, skeletal muscle, and the heart. The functional consequences of multiple uncharacterized CS mutations remain unclear. Here, we have focused on determining the functional consequences of three documented human CS-associated ABCC9 mutations: human P432L, A478V, and C1043Y. The mutations were engineered in the equivalent position in rat SUR2A (P429L, A475V, and C1039Y), and each was coexpressed with mouse Kir6.2. Using macroscopic rubidium (86Rb+) efflux assays, we show that KATP channels formed with P429L, A475V, or C1039Y mutants enhance KATP activity compared with wild-type (WT) channels. We used inside-out patch-clamp electrophysiology to measure channel sensitivity to ATP inhibition and to MgADP activation. For P429L and A475V mutants, sensitivity to ATP inhibition was comparable to WT channels, but activation by MgADP was significantly greater. C1039Y-dependent channels were significantly less sensitive to inhibition by ATP or by glibenclamide, but MgADP activation was comparable to WT. The results indicate that these three CS mutations all lead to overactive KATP channels, but at least two mechanisms underlie the observed gain of function: decreased ATP inhibition and enhanced MgADP activation.
Collapse
Affiliation(s)
- Paige E Cooper
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Monica Sala-Rabanal
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Sun Joo Lee
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110 Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO 63110
| |
Collapse
|
241
|
Li N, Wu JX, Ding D, Cheng J, Gao N, Chen L. Structure of a Pancreatic ATP-Sensitive Potassium Channel. Cell 2017; 168:101-110.e10. [DOI: 10.1016/j.cell.2016.12.028] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 12/19/2016] [Accepted: 12/20/2016] [Indexed: 10/20/2022]
|
242
|
Udensi UK, Tchounwou PB. Potassium Homeostasis, Oxidative Stress, and Human Disease. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PHYSIOLOGY 2017; 4:111-122. [PMID: 29218312 PMCID: PMC5716641 DOI: 10.4103/ijcep.ijcep_43_17] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Potassium is the most abundant cation in the intracellular fluid and it plays a vital role in the maintenance of normal cell functions. Thus, potassium homeostasis across the cell membrane, is very critical because a tilt in this balance can result in different diseases that could be life threatening. Both Oxidative stress (OS) and potassium imbalance can cause life threatening health conditions. OS and abnormalities in potassium channel have been reported in neurodegenerative diseases. This review highlights the major factors involved in potassium homeostasis (dietary, hormonal, genetic, and physiologic influences), and discusses the major diseases and abnormalities associated with potassium imbalance including hypokalemia, hyperkalemia, hypertension, chronic kidney disease, and Gordon's syndrome, Bartter syndrome, and Gitelman syndrome.
Collapse
Affiliation(s)
- Udensi K. Udensi
- Molecular Toxicology Research laboratory, NIH RCMI-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, Jackson, Mississippi, MS 39217, USA
- Department of Pathology & Laboratory Medicine, Veterans Affairs Puget Sound Health Care System, 1660 S Columbian Way (S-113), Seattle, WA 98108, USA
| | - Paul B. Tchounwou
- Molecular Toxicology Research laboratory, NIH RCMI-Center for Environmental Health, College of Science, Engineering and Technology, Jackson State University, Jackson, Mississippi, MS 39217, USA
| |
Collapse
|
243
|
Atherton JF, McIver EL, Mullen MR, Wokosin DL, Surmeier DJ, Bevan MD. Early dysfunction and progressive degeneration of the subthalamic nucleus in mouse models of Huntington's disease. eLife 2016; 5. [PMID: 27995895 PMCID: PMC5199195 DOI: 10.7554/elife.21616] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/08/2016] [Indexed: 01/05/2023] Open
Abstract
The subthalamic nucleus (STN) is an element of cortico-basal ganglia-thalamo-cortical circuitry critical for action suppression. In Huntington's disease (HD) action suppression is impaired, resembling the effects of STN lesioning or inactivation. To explore this potential linkage, the STN was studied in BAC transgenic and Q175 knock-in mouse models of HD. At <2 and 6 months of age autonomous STN activity was impaired due to activation of KATP channels. STN neurons exhibited prolonged NMDA receptor-mediated synaptic currents, caused by a deficit in glutamate uptake, and elevated mitochondrial oxidant stress, which was ameliorated by NMDA receptor antagonism. STN activity was rescued by NMDA receptor antagonism or the break down of hydrogen peroxide. At 12 months of age approximately 30% of STN neurons had been lost, as in HD. Together, these data argue that dysfunction within the STN is an early feature of HD that may contribute to its expression and course. DOI:http://dx.doi.org/10.7554/eLife.21616.001
Collapse
Affiliation(s)
- Jeremy F Atherton
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Eileen L McIver
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Matthew Rm Mullen
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - David L Wokosin
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - D James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Mark D Bevan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| |
Collapse
|
244
|
|
245
|
Remedi MS, Friedman JB, Nichols CG. Diabetes induced by gain-of-function mutations in the Kir6.1 subunit of the KATP channel. J Gen Physiol 2016; 149:75-84. [PMID: 27956473 PMCID: PMC5217086 DOI: 10.1085/jgp.201611653] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 11/28/2016] [Indexed: 12/13/2022] Open
Abstract
Kir6.2-containing KATP channels are prominent in pancreatic β cells, and gain-of-function mutations in these channels are the most common cause of human neonatal diabetes mellitus. Remedi et al. find that Kir6.1 subunits are also present in pancreatic KATP channels and that gain-of-function mutations can also cause impaired glucose tolerance and insulin secretion. Gain-of-function (GOF) mutations in the pore-forming (Kir6.2) and regulatory (SUR1) subunits of KATP channels have been identified as the most common cause of human neonatal diabetes mellitus. The critical effect of these mutations is confirmed in mice expressing Kir6.2-GOF mutations in pancreatic β cells. A second KATP channel pore-forming subunit, Kir6.1, was originally cloned from the pancreas. Although the prominence of this subunit in the vascular system is well documented, a potential role in pancreatic β cells has not been considered. Here, we show that mice expressing Kir6.1-GOF mutations (Kir6.1[G343D] or Kir6.1[G343D,Q53R]) in pancreatic β cells (under rat-insulin-promoter [Rip] control) develop glucose intolerance and diabetes caused by reduced insulin secretion. We also generated transgenic mice in which a bacterial artificial chromosome (BAC) containing Kir6.1[G343D] is incorporated such that the transgene is only expressed in tissues where Kir6.1 is normally present. Strikingly, BAC-Kir6.1[G343D] mice also show impaired glucose tolerance, as well as reduced glucose- and sulfonylurea-dependent insulin secretion. However, the response to K+ depolarization is intact in Kir6.1-GOF mice compared with control islets. The presence of native Kir6.1 transcripts was demonstrated in both human and wild-type mouse islets using quantitative real-time PCR. Together, these results implicate the incorporation of native Kir6.1 subunits into pancreatic KATP channels and a contributory role for these subunits in the control of insulin secretion.
Collapse
Affiliation(s)
- Maria S Remedi
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110 .,Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Jonathan B Friedman
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| |
Collapse
|
246
|
Ritchie HE, Ragnerstam C, Gustafsson E, Jonsson JM, Webster WS. Control of the heart rate of rat embryos during the organogenic period. HYPOXIA 2016; 4:147-159. [PMID: 27878135 PMCID: PMC5108485 DOI: 10.2147/hp.s115050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The aim of this study was to gain insight into whether the first trimester embryo could control its own heart rate (HR) in response to hypoxia. The gestational day 13 rat embryo is a good model for the human embryo at 5–6 weeks gestation, as the heart is comparable in development and, like the human embryo, has no functional autonomic nerve supply at this stage. Utilizing a whole-embryo culture technique, we examined the effects of different pharmacological agents on HR under normoxic (95% oxygen) and hypoxic (20% oxygen) conditions. Oxygen concentrations ≤60% caused a concentration-dependent decrease in HR from normal levels of ~210 bpm. An adenosine agonist, AMP-activated protein kinase (AMPK) activator and KATP channel opener all caused bradycardia in normoxic conditions; however, putative antagonists for these systems failed to prevent or ameliorate hypoxia-induced bradycardia. This suggests that the activation of one or more of these systems is not the primary cause of the observed hypoxia-induced bradycardia. Inhibition of oxidative phosphorylation also decreased HR in normoxic conditions, highlighting the importance of ATP levels. The β-blocker metoprolol caused a concentration-dependent reduction in HR supporting reports that β1-adrenergic receptors are present in the early rat embryonic heart. The cAMP inducer colforsin induced a positive chronotropic effect in both normoxic and hypoxic conditions. Overall, the embryonic HR at this stage of development is responsive to the level of oxygenation, probably as a consequence of its influence on ATP production.
Collapse
Affiliation(s)
- Helen E Ritchie
- Discipline of Biomedical Science, Sydney Medical School, University of Sydney, Lidcombe
| | - Carolina Ragnerstam
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Elin Gustafsson
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Johanna M Jonsson
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - William S Webster
- Department of Anatomy and Histology, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| |
Collapse
|
247
|
Gooshe M, Tabaeizadeh M, Aleyasin AR, Mojahedi P, Ghasemi K, Yousefi F, Vafaei A, Amini-Khoei H, Amiri S, Dehpour AR. Levosimendan exerts anticonvulsant properties against PTZ-induced seizures in mice through activation of nNOS/NO pathway: Role for K ATP channel. Life Sci 2016; 168:38-46. [PMID: 27851890 DOI: 10.1016/j.lfs.2016.11.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Revised: 11/07/2016] [Accepted: 11/08/2016] [Indexed: 01/11/2023]
Abstract
AIMS Although approving new anticonvulsants was a major breakthrough in the field of epilepsy control, so far we have met limited success in almost one third of patients suffering from epilepsy and a definite and reliable method is yet to be found. Levosimendan demonstrated neuroprotective effects and reduced mortality in conditions in which seizure can be an etiology of death; however, the underlying neuroprotective mechanisms of levosimendan still eludes us. In the light of evidence suggesting levosimendan can be a KATP channel opener and nitrergic pathway activator, levosimendan may exert antiseizure effects through KATP channels and nitrergic pathway. MAIN METHODS In this study, the effects of levosimendan on seizure susceptibility was studied by PTZ-induced seizures model in mice. KEY FINDINGS Administration of a single effective dose of levosimendan significantly increased seizures threshold and the nitrite level in the hippocampus and temporal cortex. Pretreatment with noneffective doses of glibenclamide (a KATP channel blocker) and L-NAME (a non-selective NOS inhibitor) neutralize the anticonvulsant and nitrite elevating effects of levosimendan. While 7-NI (a neural NOS inhibitor) blocked the anticonvulsant effect of levosimendan, Aminoguanidine (an inducible NOS inhibitor) failed to affect the anticonvulsant effects of levosimendan. Cromakalim (a KATP channel opener) or l-arginine (an NO precursor) augmented the anticonvulsant effects of a subeffective dose of levosimendan. Moreover, co-administration of noneffective doses of Glibenclamide and L-NAME demonstrated a synergistic effect in blocking the anticonvulsant effects of levosimendan. SIGNIFICANCE Levosimendan has anticonvulsant effects possibly via KATP/nNOS/NO pathway activation in the hippocampus and temporal cortex.
Collapse
Affiliation(s)
- Maziar Gooshe
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Injury Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Students' Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran.
| | - Mohammad Tabaeizadeh
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Reza Aleyasin
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Payam Mojahedi
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Keyvan Ghasemi
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Injury Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Students' Scientific Research Center (SSRC), Tehran University of Medical Sciences, Tehran, Iran
| | - Farbod Yousefi
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Vafaei
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Hossein Amini-Khoei
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Department of Physiology and Pharmacology, School of Medicine, Shahrekord University of Medical Sciences, Shahrekord, Iran
| | - Shayan Amiri
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Ahmad Reza Dehpour
- Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Brain and Spinal Injury Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
248
|
Gupta P, Bala M, Gupta S, Dua A, Dabur R, Injeti E, Mittal A. Efficacy and risk profile of anti-diabetic therapies: Conventional vs traditional drugs—A mechanistic revisit to understand their mode of action. Pharmacol Res 2016; 113:636-674. [DOI: 10.1016/j.phrs.2016.09.029] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Revised: 09/23/2016] [Accepted: 09/23/2016] [Indexed: 12/17/2022]
|
249
|
Forte N, Medrihan L, Cappetti B, Baldelli P, Benfenati F. 2-Deoxy-d-glucose enhances tonic inhibition through the neurosteroid-mediated activation of extrasynaptic GABA A receptors. Epilepsia 2016; 57:1987-2000. [PMID: 27735054 DOI: 10.1111/epi.13578] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2016] [Indexed: 12/11/2022]
Abstract
OBJECTIVE The inhibition of glycolysis exerts potent antiseizure effects, as demonstrated by the efficacy of ketogenic and low-glucose/nonketogenic diets in the treatment of drug-resistant epilepsy. ATP-sensitive potassium (KATP ) channels have been initially identified as the main determinant of the reduction of neuronal hyperexcitability. However, a plethora of other mechanisms have been proposed. Herein, we report the ability of 2-deoxy-d-glucose (2-DG), a glucose analog that inhibits glycolytic enzymes, of potentiating γ-aminobutyric acid (GABA)ergic tonic inhibition via neurosteroid-mediated activation of extrasynaptic GABAA receptors. METHODS Acute effects of 2-DG on the ATP-sensitive potassium currents, GABAergic tonic inhibition, firing activity, and interictal events were assessed in hippocampal slices by whole-cell patch-clamp and local field potential recordings of dentate gyrus granule cells. RESULTS Acute application of 2-DG activates two distinct outward conductances: a KATP channel-mediated current and a bicuculline-sensitive tonic current. The effect of 2-DG on such GABAergic tonic currents was fully prevented by either finasteride or PK11195, which are specific inhibitors of the neurosteroidogenesis pathway acting via different mechanisms. Moreover, the oxidized form of vitamin C, dehydroascorbic acid, known for its ability to induce neurosteroidogenesis, also activated a bicuculline-sensitive tonic current in a manner indistinguishable from that of 2-DG. Finally, we found that the enhancement of KATP current by 2-DG primarily regulates intrinsic firing rate of granule cells, whereas the increase of the GABAergic tonic current plays a key role in reducing the frequency of interictal events evoked by treatment of hippocampal slices with the convulsive agent 4-aminopyridine. SIGNIFICANCE We demonstrated, for the first time, that 2-DG potentiates the extrasynaptic tonic GABAergic current through activation of neurosteroidogenesis. Such tonic inhibition represents the main conductance responsible for the antiseizure action of this glycolytic inhibitor.
Collapse
Affiliation(s)
- Nicola Forte
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.,Department of Experimental Medicine, University of Genova, Genova, Italy
| | - Lucian Medrihan
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy
| | - Beatrice Cappetti
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy
| | - Pietro Baldelli
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.,Department of Experimental Medicine, University of Genova, Genova, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.,Department of Experimental Medicine, University of Genova, Genova, Italy
| |
Collapse
|
250
|
Yang HQ, Subbotina E, Ramasamy R, Coetzee WA. Cardiovascular K ATP channels and advanced aging. PATHOBIOLOGY OF AGING & AGE RELATED DISEASES 2016; 6:32517. [PMID: 27733235 PMCID: PMC5061878 DOI: 10.3402/pba.v6.32517] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 09/12/2016] [Accepted: 09/14/2016] [Indexed: 12/20/2022]
Abstract
With advanced aging, there is a decline in innate cardiovascular function. This decline is not general in nature. Instead, specific changes occur that impact the basic cardiovascular function, which include alterations in biochemical pathways and ion channel function. This review focuses on a particular ion channel that couple the latter two processes, namely the KATP channel, which opening is promoted by alterations in intracellular energy metabolism. We show that the intrinsic properties of the KATP channel changes with advanced aging and argue that the channel can be further modulated by biochemical changes. The importance is widespread, given the ubiquitous nature of the KATP channel in the cardiovascular system where it can regulate processes as diverse as cardiac function, blood flow and protection mechanisms against superimposed stress, such as cardiac ischemia. We highlight questions that remain to be answered before the KATP channel can be considered as a viable target for therapeutic intervention.
Collapse
Affiliation(s)
- Hua-Qian Yang
- Department of Pediatrics, NYU School of Medicine, New York, NY, USA
| | | | - Ravichandran Ramasamy
- Department of Medicine, NYU School of Medicine, New York, NY, USA.,Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY, USA
| | - William A Coetzee
- Department of Pediatrics, NYU School of Medicine, New York, NY, USA.,Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, NY, USA.,Department of Physiology & Neuroscience, NYU School of Medicine, New York, NY, USA;
| |
Collapse
|