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Patton BL, Zhu P, ElSheikh A, Driggers CM, Shyng SL. Dynamic duo: Kir6 and SUR in K ATP channel structure and function. Channels (Austin) 2024; 18:2327708. [PMID: 38489043 PMCID: PMC10950283 DOI: 10.1080/19336950.2024.2327708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 01/14/2024] [Indexed: 03/17/2024] Open
Abstract
KATP channels are ligand-gated potassium channels that couple cellular energetics with membrane potential to regulate cell activity. Each channel is an eight subunit complex comprising four central pore-forming Kir6 inward rectifier potassium channel subunits surrounded by four regulatory subunits known as the sulfonylurea receptor, SUR, which confer homeostatic metabolic control of KATP gating. SUR is an ATP binding cassette (ABC) protein family homolog that lacks membrane transport activity but is essential for KATP expression and function. For more than four decades, understanding the structure-function relationship of Kir6 and SUR has remained a central objective of clinical significance. Here, we review progress in correlating the wealth of functional data in the literature with recent KATP cryoEM structures.
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Affiliation(s)
- Bruce L. Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Phillip Zhu
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Assmaa ElSheikh
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Camden M. Driggers
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, USA
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2
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Abstract
BACKGROUND Atrial fibrillation (AF) is by far the most common cardiac arrhythmia. In about 3% of individuals, AF develops as a primary disorder without any identifiable trigger (idiopathic or historically termed lone AF). In line with the emerging field of autoantibody-related cardiac arrhythmias, the objective of this study was to explore whether autoantibodies targeting cardiac ion channels can underlie unexplained AF. METHODS Peptide microarray was used to screen patient samples for autoantibodies. We compared patients with unexplained AF (n=37 pre-existent AF; n=14 incident AF on follow-up) to age- and sex-matched controls (n=37). Electrophysiological properties of the identified autoantibody were then tested in vitro with the patch clamp technique and in vivo with an experimental mouse model of immunization. RESULTS A common autoantibody response against Kir3.4 protein was detected in patients with AF and even before the development of clinically apparent AF. Kir3.4 protein forms a heterotetramer that underlies the cardiac acetylcholine-activated inwardly rectifying K+ current, IKACh. Functional studies on human induced pluripotent stem cell-derived atrial cardiomyocytes showed that anti-Kir3.4 IgG purified from patients with AF shortened action potentials and enhanced the constitutive form of IKACh, both key mediators of AF. To establish a causal relationship, we developed a mouse model of Kir3.4 autoimmunity. Electrophysiological study in Kir3.4-immunized mice showed that Kir3.4 autoantibodies significantly reduced atrial effective refractory period and predisposed animals to a 2.8-fold increased susceptibility to AF. CONCLUSIONS To our knowledge, this is the first report of an autoimmune pathogenesis of AF with direct evidence of Kir3.4 autoantibody-mediated AF.
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Affiliation(s)
- Ange Maguy
- Institute of Physiology, University of Bern, Switzerland (A.M.)
| | | | - Jean-Claude Tardif
- Montreal Heart Institute, Université de Montréal, Canada (J.-C.T., D.B.)
| | - David Busseuil
- Montreal Heart Institute, Université de Montréal, Canada (J.-C.T., D.B.)
| | - Jin Li
- Department of Cardiology, University Heart Center, University Hospital Zurich, University of Zurich, Switzerland (J.L.)
- Center for Translational and Experimental Cardiology, Department of Cardiology, University Hospital Zurich, University of Zurich, Schlieren, Switzerland (J.L.)
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3
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Martin GM, Patton BL, Shyng SL. K ATP channels in focus: Progress toward a structural understanding of ligand regulation. Curr Opin Struct Biol 2023; 79:102541. [PMID: 36807078 PMCID: PMC10023423 DOI: 10.1016/j.sbi.2023.102541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/11/2022] [Accepted: 01/14/2023] [Indexed: 02/21/2023]
Abstract
KATP channels are hetero-octameric complexes of four inward rectifying potassium channels, Kir6.1 or Kir6.2, and four sulfonylurea receptors, SUR1, SUR2A, or SUR2B from the ABC transporter family. This unique combination enables KATP channels to couple intracellular ATP/ADP ratios, through gating, with membrane excitability, thus regulating a broad range of cellular activities. The prominence of KATP channels in human physiology, disease, and pharmacology has long attracted research interest. Since 2017, a steady flow of high-resolution KATP cryoEM structures has revealed complex and dynamic interactions between channel subunits and their ligands. Here, we highlight insights from recent structures that begin to provide mechanistic explanations for decades of experimental data and discuss the remaining knowledge gaps in our understanding of KATP channel regulation.
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Affiliation(s)
- Gregory M Martin
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Bruce L Patton
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health and Science University, Portland, OR, 97239, USA.
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4
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Liu Q, Sun J, Dong Y, Li P, Wang J, Wang Y, Xu Y, Tian X, Wu B, He P, Yu Q, Lu X, Cao J. Tetramisole is a new I K1 channel agonist and exerts I K1 -dependent cardioprotective effects in rats. Pharmacol Res Perspect 2022; 10:e00992. [PMID: 35880674 PMCID: PMC9316008 DOI: 10.1002/prp2.992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 06/22/2022] [Accepted: 07/04/2022] [Indexed: 11/30/2022] Open
Abstract
Cardiac ischemia, hypoxia, arrhythmias, and heart failure share the common electrophysiological changes featured by the elevation of intracellular Ca2+ (Ca2+ overload) and inhibition of the inward rectifier potassium (IK1 ) channel. IK1 channel agonists have been considered a new type of anti-arrhythmia and cardioprotective agents. We predicted using a drug repurposing strategy that tetramisole (Tet), a known anthelminthic agent, was a new IK1 channel agonist. The present study aimed to experimentally identify the above prediction and further demonstrate that Tet has cardioprotective effects. Results of the whole-cell patch clamp technique showed that Tet at 1-100 μmol/L enhanced IK1 current, hyperpolarized resting potential (RP), and shortened action potential duration (APD) in isolated rat cardiomyocytes, while without effects on other ion channels or transporters. In adult Sprague-Dawley (SD) rats in vivo, Tet showed anti-arrhythmia and anticardiac remodeling effects, respectively, in the coronary ligation-induced myocardial infarction model and isoproterenol (Iso, i.p., 3 mg/kg/day, 10 days) infusion-induced cardiac remodeling model. Tet also showed anticardiomyocyte remodeling effect in Iso (1 μmol/L) infused adult rat ventricular myocytes or cultured H9c2 (2-1) cardiomyocytes. Tet at 0.54 mg/kg in vivo or 30 μmol/L in vitro showed promising protections on acute ischemic arrhythmias, myocardial hypertrophy, and fibrosis. Molecular docking was performed and identified the selective binding of Tet with Kir2.1. The cardioprotection of Tet was associated with the facilitation of IK1 channel forward trafficking, deactivation of PKA signaling, and inhibition of intracellular calcium overload. Enhancing IK1 may play dual roles in anti-arrhythmia and antiventricular remodeling mediated by restoration of Ca2+ homeostasis.
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Affiliation(s)
- Qinghua Liu
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Jiaxing Sun
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Yangdou Dong
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Pan Li
- Department of PathophysiologyShanxi Medical UniversityTaiyuanChina
| | - Jin Wang
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Yulan Wang
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Yanwu Xu
- Department of BiochemistryShanghai University of Traditional Chinese MedicineShanghaiChina
| | - Xinrui Tian
- Department of Respiratory and Critical Care MedicineSecond Hospital of Shanxi Medical UniversityTaiyuanChina
| | - Bowei Wu
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
| | - Peifeng He
- Shanxi Key Laboratory of Big Data for Clinical Decision Research, School of ManagementShanxi Medical UniversityTaiyuanChina
| | - Qi Yu
- Shanxi Key Laboratory of Big Data for Clinical Decision Research, School of ManagementShanxi Medical UniversityTaiyuanChina
| | - Xuechun Lu
- Department of Hematology, The Second Medical Center, Chinese PLA General HospitalNational clinical research center for geriatric diseaseBeijingChina
| | - Jimin Cao
- Key Laboratory of Cellular Physiology, Ministry of EducationShanxi Medical UniversityTaiyuanChina
- Department of PhysiologyShanxi Medical UniversityTaiyuanChina
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Yang HQ, Echeverry FA, ElSheikh A, Gando I, Anez Arredondo S, Samper N, Cardozo T, Delmar M, Shyng SL, Coetzee WA. Subcellular trafficking and endocytic recycling of K ATP channels. Am J Physiol Cell Physiol 2022; 322:C1230-C1247. [PMID: 35508187 PMCID: PMC9169827 DOI: 10.1152/ajpcell.00099.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 04/27/2022] [Accepted: 04/30/2022] [Indexed: 11/22/2022]
Abstract
Sarcolemmal/plasmalemmal ATP-sensitive K+ (KATP) channels have key roles in many cell types and tissues. Hundreds of studies have described how the KATP channel activity and ATP sensitivity can be regulated by changes in the cellular metabolic state, by receptor signaling pathways and by pharmacological interventions. These alterations in channel activity directly translate to alterations in cell or tissue function, that can range from modulating secretory responses, such as insulin release from pancreatic β-cells or neurotransmitters from neurons, to modulating contractile behavior of smooth muscle or cardiac cells to elicit alterations in blood flow or cardiac contractility. It is increasingly becoming apparent, however, that KATP channels are regulated beyond changes in their activity. Recent studies have highlighted that KATP channel surface expression is a tightly regulated process with similar implications in health and disease. The surface expression of KATP channels is finely balanced by several trafficking steps including synthesis, assembly, anterograde trafficking, membrane anchoring, endocytosis, endocytic recycling, and degradation. This review aims to summarize the physiological and pathophysiological implications of KATP channel trafficking and mechanisms that regulate KATP channel trafficking. A better understanding of this topic has potential to identify new approaches to develop therapeutically useful drugs to treat KATP channel-related diseases.
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Affiliation(s)
- Hua-Qian Yang
- Cyrus Tang Hematology Center, Soochow University, Suzhou, People's Republic of China
| | | | - Assmaa ElSheikh
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
- Department of Medical Biochemistry, Tanta University, Tanta, Egypt
| | - Ivan Gando
- Department of Pathology, NYU School of Medicine, New York, New York
| | | | - Natalie Samper
- Department of Pathology, NYU School of Medicine, New York, New York
| | - Timothy Cardozo
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - Mario Delmar
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
- Department of Medicine, NYU School of Medicine, New York, New York
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon
| | - William A Coetzee
- Department of Pathology, NYU School of Medicine, New York, New York
- Department of Neuroscience & Physiology, NYU School of Medicine, New York, New York
- Department of Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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6
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Mishra P, Narayanan R. Ion-channel degeneracy: Multiple ion channels heterogeneously regulate intrinsic physiology of rat hippocampal granule cells. Physiol Rep 2021; 9:e14963. [PMID: 34342171 PMCID: PMC8329439 DOI: 10.14814/phy2.14963] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 06/13/2021] [Accepted: 06/21/2021] [Indexed: 01/09/2023] Open
Abstract
Degeneracy, the ability of multiple structural components to elicit the same characteristic functional properties, constitutes an elegant mechanism for achieving biological robustness. In this study, we sought electrophysiological signatures for the expression of ion-channel degeneracy in the emergence of intrinsic properties of rat hippocampal granule cells. We measured the impact of four different ion-channel subtypes-hyperpolarization-activated cyclic-nucleotide-gated (HCN), barium-sensitive inward rectifier potassium (Kir ), tertiapin-Q-sensitive inward rectifier potassium, and persistent sodium (NaP) channels-on 21 functional measurements employing pharmacological agents, and report electrophysiological data on two characteristic signatures for the expression of ion-channel degeneracy in granule cells. First, the blockade of a specific ion-channel subtype altered several, but not all, functional measurements. Furthermore, any given functional measurement was altered by the blockade of many, but not all, ion-channel subtypes. Second, the impact of blocking each ion-channel subtype manifested neuron-to-neuron variability in the quantum of changes in the electrophysiological measurements. Specifically, we found that blocking HCN or Ba-sensitive Kir channels enhanced action potential firing rate, but blockade of NaP channels reduced firing rate of granule cells. Subthreshold measures of granule cell intrinsic excitability (input resistance, temporal summation, and impedance amplitude) were enhanced by blockade of HCN or Ba-sensitive Kir channels, but were not significantly altered by NaP channel blockade. We confirmed that the HCN and Ba-sensitive Kir channels independently altered sub- and suprathreshold properties of granule cells through sequential application of pharmacological agents that blocked these channels. Finally, we found that none of the sub- or suprathreshold measurements of granule cells were significantly altered upon treatment with tertiapin-Q. Together, the heterogeneous many-to-many mapping between ion channels and single-neuron intrinsic properties emphasizes the need to account for ion-channel degeneracy in cellular- and network-scale physiology.
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Affiliation(s)
- Poonam Mishra
- Cellular Neurophysiology LaboratoryMolecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
| | - Rishikesh Narayanan
- Cellular Neurophysiology LaboratoryMolecular Biophysics UnitIndian Institute of ScienceBangaloreIndia
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7
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Sabouhanian A, Ameri S. Elucidating the role of K IR channels in rapid vasodilatation during transition in exercise intensity and different levels of muscle fibre recruitment. J Physiol 2020; 598:4451-4453. [PMID: 32715481 DOI: 10.1113/jp280187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 06/23/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Amir Sabouhanian
- Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
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8
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Terwoord JD, Hearon CM, Racine ML, Ketelhut NB, Luckasen GJ, Richards JC, Dinenno FA. K IR channel activation links local vasodilatation with muscle fibre recruitment during exercise in humans. J Physiol 2020; 598:2621-2636. [PMID: 32329892 DOI: 10.1113/jp279682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 04/17/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS During exercise, blood flow to working skeletal muscle increases in parallel with contractile activity such that oxygen delivery is sufficient to meet metabolic demand. K+ released from active skeletal muscle fibres could facilitate vasodilatation in proportion to the degree of muscle fibre recruitment. Once released, K+ stimulates inwardly rectifying K+ (KIR ) channels on the vasculature to elicit an increase in blood flow. In the present study, we demonstrate that KIR channels mediate the rapid vasodilatory response to an increase in exercise intensity. We also show that KIR channels augment vasodilatation during exercise which demands greater muscle fibre recruitment independent of the total amount of work performed. These results suggest that K+ plays a key role in coupling the magnitude of vasodilatation to the degree of contractile activity. Ultimately, the findings from this study help us understand the signalling mechanisms that regulate muscle blood flow in humans. ABSTRACT Blood flow to active skeletal muscle is augmented with greater muscle fibre recruitment. We tested whether activation of inwardly rectifying potassium (KIR ) channels underlies vasodilatation with elevated muscle fibre recruitment when work rate is increased (Protocol 1) or held constant (Protocol 2). We assessed forearm vascular conductance (FVC) during rhythmic handgrip exercise under control conditions and during local inhibition of KIR channels (intra-arterial BaCl2 ). In Protocol 1, healthy volunteers performed mild handgrip exercise for 3 min, then transitioned to moderate intensity for 30 s. BaCl2 eliminated vasodilatation during the first contraction at the moderate workload (ΔFVC, BaCl2 : -1 ± 17 vs. control: 30 ± 28 ml min-1 100 mmHg-1 ; n = 9; P = 0.004) and attenuated the 30 s area under the curve by 56 ± 14% (n = 9; P < 0.0001). In Protocol 2, participants performed two exercise bouts in which muscle fibre recruitment was manipulated while total contractile work was held constant via reciprocal changes in contraction frequency: (1) low fibre recruitment, with contractions at 12.5% maximal voluntary contraction once every 4 s and (2) high fibre recruitment, with contractions at 25% maximal voluntary contraction once every 8 s. Under control conditions, steady-state FVC was augmented in high vs. low fibre recruitment (211 ± 90 vs. 166 ± 73 ml min-1 ⋅100 mmHg-1 ; n = 10; P = 0.0006), whereas BaCl2 abolished the difference between high and low fibre recruitment (134 ± 59 vs. 134 ± 63 ml min-1 100 mmHg-1 ; n = 10; P = 0.85). These findings demonstrate that KIR channel activation is a key mechanism linking local vasodilatation with muscle fibre recruitment during exercise.
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Affiliation(s)
- Janée D Terwoord
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Christopher M Hearon
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Matthew L Racine
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Nathaniel B Ketelhut
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, CO, USA
| | - Jennifer C Richards
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
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9
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Yamada N, Asano Y, Fujita M, Yamazaki S, Inanobe A, Matsuura N, Kobayashi H, Ohno S, Ebana Y, Tsukamoto O, Ishino S, Takuwa A, Kioka H, Yamashita T, Hashimoto N, Zankov DP, Shimizu A, Asakura M, Asanuma H, Kato H, Nishida Y, Miyashita Y, Shinomiya H, Naiki N, Hayashi K, Makiyama T, Ogita H, Miura K, Ueshima H, Komuro I, Yamagishi M, Horie M, Kawakami K, Furukawa T, Koizumi A, Kurachi Y, Sakata Y, Minamino T, Kitakaze M, Takashima S. Mutant KCNJ3 and KCNJ5 Potassium Channels as Novel Molecular Targets in Bradyarrhythmias and Atrial Fibrillation. Circulation 2020; 139:2157-2169. [PMID: 30764634 DOI: 10.1161/circulationaha.118.036761] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Bradyarrhythmia is a common clinical manifestation. Although the majority of cases are acquired, genetic analysis of families with bradyarrhythmia has identified a growing number of causative gene mutations. Because the only ultimate treatment for symptomatic bradyarrhythmia has been invasive surgical implantation of a pacemaker, the discovery of novel therapeutic molecular targets is necessary to improve prognosis and quality of life. METHODS We investigated a family containing 7 individuals with autosomal dominant bradyarrhythmias of sinus node dysfunction, atrial fibrillation with slow ventricular response, and atrioventricular block. To identify the causative mutation, we conducted the family-based whole exome sequencing and genome-wide linkage analysis. We characterized the mutation-related mechanisms based on the pathophysiology in vitro. After generating a transgenic animal model to confirm the human phenotypes of bradyarrhythmia, we also evaluated the efficacy of a newly identified molecular-targeted compound to upregulate heart rate in bradyarrhythmias by using the animal model. RESULTS We identified one heterozygous mutation, KCNJ3 c.247A>C, p.N83H, as a novel cause of hereditary bradyarrhythmias in this family. KCNJ3 encodes the inwardly rectifying potassium channel Kir3.1, which combines with Kir3.4 (encoded by KCNJ5) to form the acetylcholine-activated potassium channel ( IKACh channel) with specific expression in the atrium. An additional study using a genome cohort of 2185 patients with sporadic atrial fibrillation revealed another 5 rare mutations in KCNJ3 and KCNJ5, suggesting the relevance of both genes to these arrhythmias. Cellular electrophysiological studies revealed that the KCNJ3 p.N83H mutation caused a gain of IKACh channel function by increasing the basal current, even in the absence of m2 muscarinic receptor stimulation. We generated transgenic zebrafish expressing mutant human KCNJ3 in the atrium specifically. It is interesting to note that the selective IKACh channel blocker NIP-151 repressed the increased current and improved bradyarrhythmia phenotypes in the mutant zebrafish. CONCLUSIONS The IKACh channel is associated with the pathophysiology of bradyarrhythmia and atrial fibrillation, and the mutant IKACh channel ( KCNJ3 p.N83H) can be effectively inhibited by NIP-151, a selective IKACh channel blocker. Thus, the IKACh channel might be considered to be a suitable pharmacological target for patients who have bradyarrhythmia with a gain-of-function mutation in the IKACh channel.
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Affiliation(s)
- Noriaki Yamada
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Yoshihiro Asano
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Masashi Fujita
- Department of Onco-cardiology, Osaka International Cancer Institute, Japan (M.F.)
| | - Satoru Yamazaki
- Departments of Cell Biology (S.Y.), National Cerebral and Cardiovascular Center, Suita, Japan
| | - Atsushi Inanobe
- Pharmacology (A.I., Y.K.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Norio Matsuura
- Departments of Health and Environmental Sciences (N.M.), Kyoto University Graduate School of Medicine, Japan
| | - Hatasu Kobayashi
- Department of Biomedical Sciences, College of Life and Health Sciences Chubu University, Kasugai, Japan (H. Kobayashi)
| | - Seiko Ohno
- Bioscience and Genetics (S.O.), National Cerebral and Cardiovascular Center, Suita, Japan.,Center for Epidemiologic Research in Asia (S.O., K.M., H.U., M.H.), Shiga University of Medical Science, Otsu, Japan
| | - Yusuke Ebana
- Life Science and Bioethics Research Center (Y.E.), Tokyo Medical and Dental University, Japan
| | - Osamu Tsukamoto
- Medical Biochemistry (O.T., H. Kato, Y.N., S.T.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Saki Ishino
- Center of Medical Innovation and Translational Research (S.I.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Ayako Takuwa
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Hidetaka Kioka
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Toru Yamashita
- Pharmaceuticals Division, Nissan Chemical Corporation, Tokyo, Japan (T.Y., N.H.)
| | - Norio Hashimoto
- Pharmaceuticals Division, Nissan Chemical Corporation, Tokyo, Japan (T.Y., N.H.)
| | - Dimitar P Zankov
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology (D.P.Z., A.S., H.O.), Shiga University of Medical Science, Otsu, Japan
| | - Akio Shimizu
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology (D.P.Z., A.S., H.O.), Shiga University of Medical Science, Otsu, Japan
| | - Masanori Asakura
- Cardiovascular Division, Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan (M.A.)
| | - Hiroshi Asanuma
- Department of Internal Medicine, Meiji University of Integrative Medicine, Nantan, Japan (H.A.)
| | - Hisakazu Kato
- Medical Biochemistry (O.T., H. Kato, Y.N., S.T.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Yuya Nishida
- Medical Biochemistry (O.T., H. Kato, Y.N., S.T.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Yohei Miyashita
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Haruki Shinomiya
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Nobu Naiki
- Departments of Cardiovascular Medicine (N.N., M.H.), Shiga University of Medical Science, Otsu, Japan
| | - Kenshi Hayashi
- Department of Cardiovascular and Internal Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., M.Y.)
| | - Takeru Makiyama
- Cardiovascular Medicine (T. Makiyama), Kyoto University Graduate School of Medicine, Japan
| | - Hisakazu Ogita
- Division of Molecular Medical Biochemistry, Department of Biochemistry and Molecular Biology (D.P.Z., A.S., H.O.), Shiga University of Medical Science, Otsu, Japan
| | - Katsuyuki Miura
- Center for Epidemiologic Research in Asia (S.O., K.M., H.U., M.H.), Shiga University of Medical Science, Otsu, Japan.,Public Health (K.M., H.U.), Shiga University of Medical Science, Otsu, Japan
| | - Hirotsugu Ueshima
- Center for Epidemiologic Research in Asia (S.O., K.M., H.U., M.H.), Shiga University of Medical Science, Otsu, Japan.,Public Health (K.M., H.U.), Shiga University of Medical Science, Otsu, Japan
| | - Issei Komuro
- Department of Cardiovascular Medicine, The University of Tokyo Graduate School of Medicine, Japan (I.K.)
| | - Masakazu Yamagishi
- Department of Cardiovascular and Internal Medicine, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (K.H., M.Y.).,Department of Human Sciences, Osaka University of Human Sciences, Settsu, Japan (M.Y.)
| | - Minoru Horie
- Center for Epidemiologic Research in Asia (S.O., K.M., H.U., M.H.), Shiga University of Medical Science, Otsu, Japan.,Departments of Cardiovascular Medicine (N.N., M.H.), Shiga University of Medical Science, Otsu, Japan
| | - Koichi Kawakami
- Division of Molecular and Developmental Biology, National Institute of Genetics, Mishima, Japan (K.K.).,Department of Genetics, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan (K.K.)
| | - Tetsushi Furukawa
- Department of Bioinformational Pharmacology (T.F.), Tokyo Medical and Dental University, Japan
| | - Akio Koizumi
- Public Interest Foundation Kyoto Hokenkai, Japan (A.K.)
| | - Yoshihisa Kurachi
- Pharmacology (A.I., Y.K.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Yasushi Sakata
- Departments of Cardiovascular Medicine (N.Y., Y.A., A.T., H. Kioka, Y.M., H.S., Y.S.), Osaka University Graduate School of Medicine, Suita, Japan
| | - Tetsuo Minamino
- Department of Cardiorenal and Cerebrovascular Medicine, Faculty of Medicine, Kagawa University, Japan (T. Minamino)
| | - Masafumi Kitakaze
- Clinical Medicine and Development (M.K.), National Cerebral and Cardiovascular Center, Suita, Japan
| | - Seiji Takashima
- Medical Biochemistry (O.T., H. Kato, Y.N., S.T.), Osaka University Graduate School of Medicine, Suita, Japan
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10
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Liu QH, Qiao X, Zhang LJ, Wang J, Zhang L, Zhai XW, Ren XZ, Li Y, Cao XN, Feng QL, Cao JM, Wu BW. I K1 Channel Agonist Zacopride Alleviates Cardiac Hypertrophy and Failure via Alterations in Calcium Dyshomeostasis and Electrical Remodeling in Rats. Front Pharmacol 2019; 10:929. [PMID: 31507422 PMCID: PMC6718093 DOI: 10.3389/fphar.2019.00929] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 07/22/2019] [Indexed: 01/08/2023] Open
Abstract
Intracellular Ca2+ overload, prolongation of the action potential duration (APD), and downregulation of inward rectifier potassium (IK1) channel are hallmarks of electrical remodeling in cardiac hypertrophy and heart failure (HF). We hypothesized that enhancement of IK1 currents is a compensation for IK1 deficit and a novel modulation for cardiac Ca2+ homeostasis and pathological remodeling. In adult Sprague-Dawley (SD) rats in vivo, cardiac hypertrophy was induced by isoproterenol (Iso) injection (i.p., 3 mg/kg/d) for 3, 10, and 30 days. Neonatal rat ventricular myocytes (NRVMs) were isolated from 1 to 3 days SD rat pups and treated with 1 μmol/L Iso for 24 h in vitro. The effects of zacopride, a selective IK1/Kir2.1 channel agonist, on cardiac remodeling/hypertrophy were observed in the settings of 15 μg/kg in vivo and 1 μmol/L in vitro. After exposing to Iso for 3 days and 10 days, rat hearts showed distinct concentric hypertrophy and fibrosis and enhanced pumping function (P < 0.01 or P < 0.05), then progressed to dilatation and dysfunction post 30 days. Compared with the age-matched control, cardiomyocytes exhibited higher cytosolic Ca2+ (P < 0.01 or P < 0.05) and lower SR Ca2+ content (P < 0.01 or P < 0.05) all through 3, 10, and 30 days of Iso infusion. The expressions of Kir2.1 and SERCA2 were downregulated, while p-CaMKII, p-RyR2, and cleaved caspase-3 were upregulated. Iso-induced electrophysiological abnormalities were also manifested with resting potential (RP) depolarization (P < 0.01), APD prolongation (P < 0.01) in adult cardiomyocytes, and calcium overload in cultured NRVMs (P < 0.01). Zacopride treatment effectively retarded myocardial hypertrophy and fibrosis, preserved the expression of Kir2.1 and some key players in Ca2+ homeostasis, normalized the RP (P < 0.05), and abbreviated APD (P < 0.01), thus lowered cytosolic [Ca2 +]i (P < 0.01 or P < 0.05). IK1channel blocker BaCl2 or chloroquine largely reversed the cardioprotection of zacopride. We conclude that cardiac electrical remodeling is concurrent with structural remodeling. By enhancing cardiac IK1, zacopride prevents Iso-induced electrical remodeling around intracellular Ca2+ overload, thereby attenuates cardiac structural disorder and dysfunction. Early electrical interventions may provide protection on cardiac remodeling.
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Affiliation(s)
- Qing-Hua Liu
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Xi Qiao
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Li-Jun Zhang
- Department of Pathophysiology, Shanxi Medical University, Taiyuan, China
| | - Jin Wang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Li Zhang
- Clinical Laboratory, Children's Hospital of Shanxi, Taiyuan, China
| | - Xu-Wen Zhai
- Clinical Skills Teaching Simulation Hospital, Shanxi Medical University, Taiyuan, China
| | - Xiao-Ze Ren
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Yu Li
- Department of Internal Medicine, The Hospital of Beijing Sports University, Beijing, China
| | - Xiao-Na Cao
- Department of Internal Medicine, The Hospital of Beijing Sports University, Beijing, China
| | - Qi-Long Feng
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Ji-Min Cao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Bo-Wei Wu
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, and the Department of Physiology, Shanxi Medical University, Taiyuan, China
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11
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Martin GM, Sung MW, Yang Z, Innes LM, Kandasamy B, David LL, Yoshioka C, Shyng SL. Mechanism of pharmacochaperoning in a mammalian K ATP channel revealed by cryo-EM. eLife 2019; 8:46417. [PMID: 31343405 PMCID: PMC6699824 DOI: 10.7554/elife.46417] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 07/22/2019] [Indexed: 01/03/2023] Open
Abstract
ATP-sensitive potassium (KATP) channels composed of a pore-forming Kir6.2 potassium channel and a regulatory ABC transporter sulfonylurea receptor 1 (SUR1) regulate insulin secretion in pancreatic β-cells to maintain glucose homeostasis. Mutations that impair channel folding or assembly prevent cell surface expression and cause congenital hyperinsulinism. Structurally diverse KATP inhibitors are known to act as pharmacochaperones to correct mutant channel expression, but the mechanism is unknown. Here, we compare cryoEM structures of a mammalian KATP channel bound to pharmacochaperones glibenclamide, repaglinide, and carbamazepine. We found all three drugs bind within a common pocket in SUR1. Further, we found the N-terminus of Kir6.2 inserted within the central cavity of the SUR1 ABC core, adjacent the drug binding pocket. The findings reveal a common mechanism by which diverse compounds stabilize the Kir6.2 N-terminus within SUR1’s ABC core, allowing it to act as a firm ‘handle’ for the assembly of metastable mutant SUR1-Kir6.2 complexes.
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Affiliation(s)
- Gregory M Martin
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Min Woo Sung
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Zhongying Yang
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Laura M Innes
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Balamurugan Kandasamy
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Larry L David
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
| | - Craig Yoshioka
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, United States
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, United States
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12
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Denton JS, Kharade SV. Plight of the pore polar bar(rier). Channels (Austin) 2017; 11:502-503. [PMID: 28806132 DOI: 10.1080/19336950.2017.1367234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Jerod S Denton
- a Department of Anesthesiology , Vanderbilt University Medical Center , Nashville , TN , USA.,b Department of Pharmacology , Vanderbilt University , Nashville , TN , USA
| | - Sujay V Kharade
- a Department of Anesthesiology , Vanderbilt University Medical Center , Nashville , TN , USA
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13
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Liu C, Liu E, Luo T, Zhang W, He R. Opening of the inward rectifier potassium channel alleviates maladaptive tissue repair following myocardial infarction. Acta Biochim Biophys Sin (Shanghai) 2016; 48:687-95. [PMID: 27486024 DOI: 10.1093/abbs/gmw060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 05/23/2016] [Indexed: 12/13/2022] Open
Abstract
Activation of the inward rectifier potassium current (IK1) channel has been reported to be associated with suppression of ventricular arrhythmias. In this study, we tested the hypothesis that opening of the IK1 channel with zacopride (ZAC) was involved in the modulation of tissue repair after myocardial infarction. Sprague-Dawley rats were subject to coronary artery ligation and ZAC was administered intraperitoneally (15 µg/kg/day) for 28 days. Compared with the ischemia group, treatment with ZAC significantly reduced the ratio of heart/body weight and the cross-sectional area of cardiomyocytes, suggesting less cardiac hypertrophy. ZAC reduced the accumulation of collagen types I and III, accompanied with decrease of collagen area, which were associated with a reduction of collagen deposition in the fibrotic myocardium. Echocardiography showed improved cardiac function, evidenced by the reduced left ventricular end-diastolic dimension and left ventricular end-systolic dimension, and the increased ejection fraction and fractional shortening in ZAC-treated animals (all P < 0.05 vs. ischemia group). In coincidence with these changes, ZAC up-regulated the protein level of the IK1 channel and down-regulated the phosphorylation of mammalian target of rapamycin (mTOR) and 70-kDa ribosomal protein S6 (p70S6) kinase. Administration of chloroquine alone, an IK1 channel antagonist, had no effect on all the parameters measured, but significantly blocked the beneficial effects of ZAC on cardiac repair. In conclusion, opening of the IK1 channel with ZAC inhibits maladaptive tissue repair and improves cardiac function, potentially mediated by the inhibition of ischemia-activated mTOR-p70S6 signaling pathway via the IK1 channel. So the development of pharmacological agents specifically targeting the activation of the IK1 channel may protect the heart against myocardial ischemia-induced cardiac dysfunction.
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Affiliation(s)
- Chengfang Liu
- Department of Human Anatomy, Shanxi Medical University, Taiyuan 030001, China
| | - Enli Liu
- Department of Physiology, Shanxi Medical University, Taiyuan 030001, China
| | - Tiane Luo
- Department of Health Statistics, Shanxi Medical University, Taiyuan 030001, China
| | - Weifang Zhang
- Department of Physiology, Shanxi Medical University, Taiyuan 030001, China
| | - Rongli He
- Department of Human Anatomy, Shanxi Medical University, Taiyuan 030001, China
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14
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Longden TA, Nelson MT. Vascular inward rectifier K+ channels as external K+ sensors in the control of cerebral blood flow. Microcirculation 2015; 22:183-96. [PMID: 25641345 PMCID: PMC4404517 DOI: 10.1111/micc.12190] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/16/2015] [Indexed: 12/25/2022]
Abstract
For decades it has been known that external K(+) ions are rapid and potent vasodilators that increase CBF. Recent studies have implicated the local release of K(+) from astrocytic endfeet-which encase the entirety of the parenchymal vasculature-in the dynamic regulation of local CBF during NVC. It has been proposed that the activation of KIR channels in the vascular wall by external K(+) is a central component of these hyperemic responses; however, a number of significant gaps in our knowledge remain. Here, we explore the concept that vascular KIR channels are the major extracellular K(+) sensors in the control of CBF. We propose that K(+) is an ideal mediator of NVC, and discuss KIR channels as effectors that produce rapid hyperpolarization and robust vasodilation of cerebral arterioles. We provide evidence that KIR channels, of the KIR 2 subtype in particular, are present in both the endothelial and SM cells of parenchymal arterioles and propose that this dual positioning of KIR 2 channels increases the robustness of the vasodilation to external K(+), enables the endothelium to be actively engaged in NVC, and permits electrical signaling through the endothelial syncytium to promote upstream vasodilation to modulate CBF.
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Affiliation(s)
- Thomas A Longden
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA
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15
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Meijer van Putten RME, Mengarelli I, Guan K, Zegers JG, van Ginneken ACG, Verkerk AO, Wilders R. Ion channelopathies in human induced pluripotent stem cell derived cardiomyocytes: a dynamic clamp study with virtual IK1. Front Physiol 2015; 6:7. [PMID: 25691870 PMCID: PMC4315032 DOI: 10.3389/fphys.2015.00007] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/07/2015] [Indexed: 12/11/2022] Open
Abstract
Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are widely used in studying basic mechanisms of cardiac arrhythmias that are caused by ion channelopathies. Unfortunately, the action potential profile of hiPSC-CMs-and consequently the profile of individual membrane currents active during that action potential-differs substantially from that of native human cardiomyocytes, largely due to almost negligible expression of the inward rectifier potassium current (IK1). In the present study, we attempted to "normalize" the action potential profile of our hiPSC-CMs by inserting a voltage dependent in silico IK1 into our hiPSC-CMs, using the dynamic clamp configuration of the patch clamp technique. Recordings were made from single hiPSC-CMs, using the perforated patch clamp technique at physiological temperature. We assessed three different models of IK1, with different degrees of inward rectification, and systematically varied the magnitude of the inserted IK1. Also, we modified the inserted IK1 in order to assess the effects of loss- and gain-of-function mutations in the KCNJ2 gene, which encodes the Kir2.1 protein that is primarily responsible for the IK1 channel in human ventricle. For our experiments, we selected spontaneously beating hiPSC-CMs, with negligible IK1 as demonstrated in separate voltage clamp experiments, which were paced at 1 Hz. Upon addition of in silico IK1 with a peak outward density of 4-6 pA/pF, these hiPSC-CMs showed a ventricular-like action potential morphology with a stable resting membrane potential near -80 mV and a maximum upstroke velocity >150 V/s (n = 9). Proarrhythmic action potential changes were observed upon injection of both loss-of-function and gain-of-function IK1, as associated with Andersen-Tawil syndrome type 1 and short QT syndrome type 3, respectively (n = 6). We conclude that injection of in silico IK1 makes the hiPSC-CM a more reliable model for investigating mechanisms underlying cardiac arrhythmias.
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Affiliation(s)
- Rosalie M E Meijer van Putten
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Isabella Mengarelli
- Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Kaomei Guan
- Department of Cardiology and Pneumology, Georg-August-University of Göttingen Göttingen, Germany
| | - Jan G Zegers
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Antoni C G van Ginneken
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Arie O Verkerk
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
| | - Ronald Wilders
- Department of Anatomy, Embryology and Physiology, Academic Medical Center, University of Amsterdam Amsterdam, Netherlands
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16
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Masia R, Krause DS, Yellen G. The inward rectifier potassium channel Kir2.1 is expressed in mouse neutrophils from bone marrow and liver. Am J Physiol Cell Physiol 2014; 308:C264-76. [PMID: 25472961 DOI: 10.1152/ajpcell.00176.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neutrophils are phagocytic cells that play a critical role in innate immunity by destroying bacterial pathogens. Channels belonging to the inward rectifier potassium channel subfamily 2 (Kir2 channels) have been described in other phagocytes (monocytes/macrophages and eosinophils) and in hematopoietic precursors of phagocytes. Their physiological function in these cells remains unclear, but some evidence suggests a role in growth factor-dependent proliferation and development. Expression of functional Kir2 channels has not been definitively demonstrated in mammalian neutrophils. Here, we show by RT-PCR that neutrophils from mouse bone marrow and liver express mRNA for the Kir2 subunit Kir2.1 but not for other subunits (Kir2.2, Kir2.3, and Kir2.4). In electrophysiological experiments, resting (unstimulated) neutrophils from mouse bone marrow and liver exhibit a constitutively active, external K(+)-dependent, strong inwardly rectifying current that constitutes the dominant current. The reversal potential is dependent on the external K(+) concentration in a Nernstian fashion, as expected for a K(+)-selective current. The current is not altered by changes in external or internal pH, and it is blocked by Ba(2+), Cs(+), and the Kir2-selective inhibitor ML133. The single-channel conductance is in agreement with previously reported values for Kir2.1 channels. These properties are characteristic of homomeric Kir2.1 channels. Current density in short-term cultures of bone marrow neutrophils is decreased in the absence of growth factors that are important for neutrophil proliferation [granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF)]. These results demonstrate that mouse neutrophils express functional Kir2.1 channels and suggest that these channels may be important for neutrophil function, possibly in a growth factor-dependent manner.
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Affiliation(s)
- Ricard Masia
- Department of Pathology and Laboratory Medicine, Massachusetts General Hospital, Boston, Massachusetts; and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
| | - Daniela S Krause
- Department of Pathology and Laboratory Medicine, Massachusetts General Hospital, Boston, Massachusetts; and
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
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17
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Chin C. Gold nanoparticle-spermidine complex blocks the inward rectifier potassium channel. Am J Cardiovasc Dis 2014; 4:34-46. [PMID: 25006531 PMCID: PMC4082228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 05/05/2014] [Indexed: 06/03/2023]
Abstract
A previous study showed that negatively charged gold nanoparticles block ion pores by binding to the sulfur group of the cysteine loop of the ion channel when small molecules like amine lead the nanoparticles inside the ion pore. Cells were voltage clamped at -100 mV. Subsequently a bath application of 30 μM Ach produced a current followed by the extracellular application of 100 mM spermidine and 50 nM of nanoparticle complex. Peak amplitude was then recorded. The addition of Ach (30 uM) reversed the effect, and we recorded inhibition of the peak amplitude. We also recorded electrocardiogram (EKG) and the atria effective refractory period (AERP) after treatment with the complex in the atrium of a rabbit heart in a Langendorff apparatus. Upon external application of the complex, the Ach-activated current was blocked by 48.8% ± 3.1% with 82.7% ± 3.1% reversal. In recording the EKG and the AERP after the addition of the complex including 30 mM spermidine with 50 nM nanoparticles, the complete resolution of atrial fibrillation at 50 s and the elongation of AERP from 46 to 52 was observed, which unveils a new class 3 anti arrythmic agent using gold nanoparticles with spermidine. Negatively charged gold nanoparticles (0.8 nm) block ion pores after penetrating the cell membrane with spermidine, thus entering the cells with a polyamine transporter and acting at the intracellular face of the channel via binding to the sulfur group of the human inward rectifying potassium channel- I(KAch).
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Affiliation(s)
- Chur Chin
- Department of Internal Medicine, School of Medicine, Gyeongsang National University Chilam-dong 90, Jinju, Gyeongsangnam-d, Korea
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18
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Csonka C, Kupai K, Bencsik P, Görbe A, Pálóczi J, Zvara A, Puskás LG, Csont T, Ferdinandy P. Cholesterol-enriched diet inhibits cardioprotection by ATP-sensitive K+ channel activators cromakalim and diazoxide. Am J Physiol Heart Circ Physiol 2013; 306:H405-13. [PMID: 24285110 DOI: 10.1152/ajpheart.00257.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been previously shown that hyperlipidemia interferes with cardioprotective mechanisms. Here, we investigated the interaction of hyperlipidemia with cardioprotection induced by pharmacological activators of ATP-sensitive K(+) (KATP) channels. Hearts isolated from rats fed a 2% cholesterol-enriched diet or normal diet for 8 wk were subjected to 30 min of global ischemia and 120 min of reperfusion in the presence or absence of KATP modulators. In normal diet-fed rats, either the nonselective KATP activator cromakalim at 10(-5) M or the selective mitochondrial (mito)KATP opener diazoxide at 3 × 10(-5) M significantly decreased infarct size compared with vehicle-treated control rats. Their cardioprotective effect was abolished by coadministration of the nonselective KATP blocker glibenclamide or the selective mitoKATP blocker 5-hydroxydecanoate, respectively. However, in cholesterol-fed rats, the cardioprotective effect of cromakalim or diazoxide was not observed. Therefore, we further investigated how cholesterol-enriched diet influences cardiac KATP channels. Cardiac expression of a KATP subunit gene (Kir6.1) was significantly downregulated in cholesterol-fed rats; however, protein levels of Kir6.1 and Kir6.2 were not changed. The cholesterol diet significantly decreased cardiac ATP, increased lactate content, and enhanced myocardial oxidative stress, as shown by increased cardiac superoxide and dityrosine formation. This is the first demonstration that cardioprotection by KATP channel activators is impaired in cholesterol-enriched diet-induced hyperlipidemia. The background mechanism may include hyperlipidemia-induced attenuation of mitoKATP function by altered energy metabolism and increased oxidative stress in the heart.
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Affiliation(s)
- Csaba Csonka
- Cardiovascular Research Group, Department of Biochemistry, University of Szeged, Szeged, Hungary
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19
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Hwang H, Yoon JY, Cho H, Kim BG. OsKAT2 is the prevailing functional inward rectifier potassium channels in rice guard cell. Plant Signal Behav 2013; 8:e26643. [PMID: 24103920 PMCID: PMC4091219 DOI: 10.4161/psb.26643] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 09/27/2013] [Indexed: 05/28/2023]
Abstract
AtKAT1 plays roles as a major channel to uptake K(+) in guard cell when stomata open in dicot model plant Arabidopsis. In a recent publication, we isolated 3 KAT-like potassium channels in rice. We expressed them in CHO cell to identify electrophysiological characteristics of the channels. OsKAT2 showed much bigger inwardly rectifying potassium channel activities among them. The histochemical X-glu staining of transgenic rice leaf blades expressing β-glucuronidase fused with OsKAT2 promoter showed that the OsKAT2 is dominantly expressed in rice guard cell. These findings indicate that OsKAT2 may be a functional ortholog of AtKAT1 in rice. Thus this gene will be the prime target for engineering the guard cell movement to improve drought tolerance in monocot plants, including most major crops.
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Affiliation(s)
- Hyunsik Hwang
- Department of Molecular Breeding; National Academy of Agricultural Science; Rural Development Administration; Suwon, Korea
| | - Jin-Young Yoon
- Department of Molecular Breeding; National Academy of Agricultural Science; Rural Development Administration; Suwon, Korea
| | - Hana Cho
- Department of Physiology; Sungkyunkwan University School of Medicine; Suwon, Korea
| | - Beom-Gi Kim
- Department of Molecular Breeding; National Academy of Agricultural Science; Rural Development Administration; Suwon, Korea
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