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Potassium current voltage clamp

Armando Carpaneto, Antonella Gradogna
Plant two-pore channels (TPCs) are non-selective cation channels permeable both to monovalent potassium and divalent calcium. We previously developed a technique that allowed the simultaneous determination of the fluxes of these two ions across the channel by a combined use of patch-clamp and fluorescence. In this paper we studied how potassium and calcium fluxes were influenced by modification of cytosolic concentrations of K+ and Ca2+ . A decrease in cytosolic calcium from 2 to 0.5 mM led to a shift of the activation curve of about +60 mV; although at positive potentials currents were very similar, calcium ion permeation was significantly reduced and the ratio between the total and calcium-mediated current increased about two-fold...
February 24, 2018: Biophysical Chemistry
Jacqueline Gayet-Primo, Daniel B Yaeger, Roupen A Khanjian, Teresa Puthussery
Silent voltage-gated potassium channel subunits (KV S) interact selectively with members of the KV 2 channel family to modify their functional properties. The localization and functional roles of these silent subunits remain poorly understood. Mutations in the KV S subunit, KV 8.2 ( KCNV2 ), lead to severe visual impairment in humans, but the basis of these deficits remain unclear. Here, we examined the localization, native interactions and functional properties of KV 8.2-containing channels in mouse, macaque and human photoreceptors of either sex...
February 24, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Stefania Piscopo, Euan R Brown
Membrane-nanoparticle interactions are important in determining the effects of manufactured nanomaterials on cell physiology and pathology. Here, silica, titanium, zinc, and magnesium oxide nanoparticles are screened against human hERG (Kv 11.1) voltage-gated potassium channels under a whole-cell voltage clamp. 10 µg mL-1 ZnO uniquely increases the amplitude of the steady-state current, decreases the rate of hERG current inactivation during steady-state depolarization, accelerates channel deactivation during resurgent tail currents, and shows no significant alteration of current activation rate or voltage dependence...
February 26, 2018: Small
Hugo Zeberg, Johanna Nilsson, Peter Århem
Understanding the relationships between the rates and dynamics of current wave forms under voltage clamp conditions is essential for understanding phenomena such as state-dependence and use-dependence, which are fundamental for the action of drugs used as anti-epileptics, anti-arrhythmics, and anesthetics. In the present study, we mathematically analyze models of blocking mechanisms. In previous experimental studies of potassium channels we have shown that the effect of local anesthetics can be explained by binding to channels in the open state...
2018: Frontiers in Cellular Neuroscience
Roberta Costa, Davide Antonio Civello, Emanuele Bernardinelli, Simone Vanoni, Michaela Zopf, Giada Scantamburlo, Charity Nofziger, Wolfgang Patsch, Markus Paulmichl, Silvia Dossena
BACKGROUND/AIMS: In the human genome, more than 400 genes encode ion channels, which are ubiquitously expressed and often coexist and participate in almost all physiological processes. Therefore, ion channel blockers represent fundamental tools in discriminating the contribution of individual channel types to a physiological phenomenon. However, unspecific effects of these compounds may represent a confounding factor. Three commonly used chloride channel inhibitors, i.e. 4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid (DIDS), 5-nitro-2-[(3-phenylpropyl) amino]benzoic acid (NPPB) and the anti-inflammatory drug niflumic acid were tested to identify the lowest concentration effective on Cl- channels and ineffective on K+ channels...
February 2, 2018: Cellular Physiology and Biochemistry
Faisal Khan, Zafar Saeed Saify, Khawar Saeed Jamali, Saima Naz, Sohail Hassan, Sonia Siddiqui
Vitex negundo (Vn) extract is famous for the treatment of neurological diseases such as migraine and epilepsy. These neurological diseases have been associated with abnormally increased influx of sodium ions into the neurons. Drugs that inhibit voltage gated sodium channels can be used as potent anti-epileptics. Till now, the effects of Vn on sodium channels have not been investigated. Therefore, we have investigated the effects of methalonic fraction of Vn extract in Murine Neuro 2A cell line. Cells were cultured in a defined medium with or without the Vn extract (100 μg/ml)...
January 2018: Pakistan Journal of Pharmaceutical Sciences
Yuan Huang, Jiawei Yang, Wanyi Xie, Qince Li, Zhipeng Zeng, Haibo Sui, Zhonggui Shan, Zhengrong Huang
Atrial fibrillation (AF) is the most common arrhythmia in the clinic. While previous studies have identified AF-associated mutations in several genes, the genetic basis for AF remains unclear. Here, we identified a novel T361S missense mutation in potassium voltage-gated channel, shal-related subfamily, member 3 (KCND3) from a Chinese Han family ancestor with lone AF. The wild-type (WT) or mutant T361S of Kv4.3 protein (encoded by KCND3) were co-expressed with the auxiliary subunit K+ channel-Interacting Protein (KChIP2) in HEK293 cells, and transient outward potassium current (Ito) were recorded using patch-clamp methods, and the surface or total protein levels of Kv4...
December 29, 2017: Oncotarget
Ramazan Bal, Gurkan Ozturk, Ebru Onalan Etem, Aydin Him, Nurattin Cengiz, Tuncay Kuloglu, Mehmet Tuzcu, Caner Yildirim, Ahmet Tektemur
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...
January 29, 2018: Journal of Membrane Biology
Eric K Johnson, Steven J Springer, Wei Wang, Edward J Dranoff, Yan Zhang, Evelyn M Kanter, Kathryn A Yamada, Jeanne M Nerbonne
BACKGROUND: Myocardial, transient, outward currents, Ito, have been shown to play pivotal roles in action potential (AP) repolarization and remodeling in animal models. The properties and contribution of Ito to left ventricular (LV) repolarization in the human heart, however, are poorly defined. METHODS AND RESULTS: Whole-cell, voltage-clamp recordings, acquired at physiological (35°C to 37°C) temperatures, from myocytes isolated from the LV of nonfailing human hearts identified 2 distinct transient currents, Ito,fast (Ito,f) and Ito,slow (Ito,s), with significantly (P<0...
January 2018: Circulation. Arrhythmia and Electrophysiology
Alexander I Bondarenko, Olga Panasiuk, Iryna Okhai, Fabrizio Montecucco, Karim J Brandt, François Mach
Endothelial Ca2+-dependent K+ channels (KCa) regulate endothelial function. We also know that stimulation of type 2 cannabinoid (CB2) receptors ameliorates atherosclerosis. However, whether atherosclerosis is accompanied by altered endothelial KCa- and CB2 receptor-dependent signaling is unknown. By utilizing an in situ patch-clamp approach, we directly evaluated the KCa channel function and the CB2 receptor-dependent electrical responses in the endothelium of aortic strips from young ApoE-/- and C57Bl/6 mice...
January 3, 2018: Journal of Molecular and Cellular Cardiology
Hyang Mi Lee, Ok Hee Chai, Sang June Hahn, Bok Hee Choi
In patients with epilepsy, depression is a common comorbidity but difficult to be treated because many antidepressants cause pro-convulsive effects. Thus, it is important to identify the risk of seizures associated with antidepressants. To determine whether paroxetine, a very potent selective serotonin reuptake inhibitor (SSRI), interacts with ion channels that modulate neuronal excitability, we examined the effects of paroxetine on Kv3.1 potassium channels, which contribute to highfrequency firing of interneurons, using the whole-cell patch-clamp technique...
January 2018: Korean Journal of Physiology & Pharmacology
Zonglin Gu, Leigh D Plant, Xuanyu Meng, Jose Manuel Perez-Aguilar, Zegao Wang, Mingdong Dong, Diomedes E Logothetis, Ruhong Zhou
Molybdenum disulfide (MoS2) nanomaterial has recently found various applications in the biomedical field mainly due to its outstanding physicochemical properties. However, little is known about its interactions with biological systems at the atomic level, which intimately relates to the biocompatibility of the material. To provide insights into the effects of MoS2 in biological entities, we investigated the interactions of MoS2 with proteins from a functionally important membrane family, the ubiquitous potassium (K+) channels...
December 13, 2017: ACS Nano
Philipe R F Mendonça, Victoria Kyle, Shel-Hwa Yeo, William H Colledge, Hugh P C Robinson
KEY POINTS: Neurons in the hypothalamus of the brain which secrete the peptide kisspeptin are important regulators of reproduction, and normal reproductive development. Electrical activity, in the form of action potentials, or spikes, leads to secretion of peptides and neurotransmitters, influencing the activity of downstream neurons; in kisspeptin neurons, this activity is highly irregular, but the mechanism of this is not known. In this study, we show that irregularity depends on the presence of a particular type of potassium ion channel in the membrane, which opens transiently in response to electrical excitation...
March 1, 2018: Journal of Physiology
Anqi Sheng, Yan Zhang, Guang Li, Guangqin Zhang
Voltage-gated potassium (KV ) currents, subdivided into rapidly inactivating A-type currents (IA ) and slowly inactivating delayed rectifier currents (IK ), play a fundamental role in modulating pain by controlling neuronal excitability. The effects of Honokiol (Hon), a natural biphenolic compound derived from Magnolia officinalis, on KV currents were investigated in freshly isolated mouse dorsal root ganglion neurons using the whole-cell patch clamp technique. Results showed that Hon inhibited IA and IK in concentration-dependent manner...
February 2018: Neurochemical Research
Martin Nybo Andersen, Lasse Skibsbye, Arnela Saljic, Martin Zahle Larsen, Hanne Borger Rasmussen, Thomas Jespersen
Over the last years extensive kinase-mediated regulation of a number of voltage-gated potassium (Kv) channels important in cardiac electrophysiology has been reported. This includes regulation of Kv1.5, Kv7.1 and Kv11.1 cell surface expression, where the kinase-mediated regulation appears to center around the ubiquitin ligase Nedd4-2. In the present study we examined whether Kv1.4, constituting the cardiac Ito,s current, is subject to similar regulation. In the epithelial Madin-Darby Canine Kidney (MDCK) cell line, which constitutes a highly reproducible model system for addressing membrane targeting, we find, by confocal microscopy, that Kv1...
November 23, 2017: Channels
Makhala M Khammy, Sukhan Kim, Bo H Bentzen, Soojung Lee, Inyeoung Choi, Christian Aalkjaer, Thomas A Jepps
BACKGROUND AND PURPOSE: Kv7.4 and Kv7.5 channels are regulators of vascular tone. 4-aminopyridine (4-AP) is considered a broad inhibitor of voltage-gated potassium (KV ) channels, with little inhibitory effect on Kv7 family members at millimolar concentrations. However, the effect of 4-AP on Kv7 channels has not been systematically studied. The aim of this study was to investigate the pharmacological activity of 4-AP on Kv7.4 and Kv7.5 channels and characterise the effect of 4-AP on rat resistance arteries...
November 20, 2017: British Journal of Pharmacology
Hong Joon Lee, Jin-Sung Choi, Bok Hee Choi, Sang June Hahn
Quetiapine is an atypical antipsychotic drug that is widely used for the treatment of schizophrenia. It is mainly metabolized by a cytochrome P450 system in the liver. Norquetiapine is a major active metabolite in humans with a pharmacological profile that differs distinctly from that of quetiapine. We used the whole-cell patch-clamp technique to investigate the effects of norquetiapine on hERG channels that are stably expressed in HEK cells. Quetiapine and norquetiapine inhibited the hERG tail currents at -50mV in a concentration-dependent manner with IC50 values of 8...
January 18, 2018: Neuroscience Letters
Iván A Aréchiga-Figueroa, Rita Morán-Zendejas, Mayra Delgado-Ramírez, Aldo A Rodríguez-Menchaca
BACKGROUND: Phytochemicals are a large group of plant-derived compounds that have a broad range of pharmacological effects. Some of these effects are derived from their action on transport proteins, including ion channels. The present study investigates the effects of the phytochemicals genistein and capsaicin on voltage-gated potassium Kv2.1 channels. METHODS: The whole-cell patch clamp technique was used to explore the regulation of Kv2.1 channels expressed in HEK293 cells by genistein and capsaicin...
June 3, 2017: Pharmacological Reports: PR
Ying Dou, Logan C Macdonald, Yue Wu, David Fedida
Kv11.1 (hERG) is a voltage-gated potassium channel that shows very slow ionic current activation kinetics, and an unusual underlying biphasic gating charge movement with fast and slow components that differ greatly in time course. The structural basis and role of the fast component of gating charge (Qfast ) is unclear, and its relationship to the slow activation of hERG channels is not understood. In this study we have used the cut-open oocyte voltage-clamp technique to investigate the relationship of fast gating charge movement-to-residue interactions between D411 at the bottom of the S1, and lower S4 domain charged and uncharged residues...
November 7, 2017: Biophysical Journal
Erica S Levitt, John T Williams
Acute desensitization of mu opioid receptors is thought to be an initial step in the development of tolerance to opioids. Given the resistance of the respiratory system to develop tolerance, desensitization of neurons in the Kölliker-Fuse (KF), a key area in the respiratory circuit, was examined. The activation of G protein-coupled inwardly rectifying potassium current was measured using whole-cell voltage-clamp recordings from KF and locus coeruleus (LC) neurons contained in acute rat brain slices. A saturating concentration of the opioid agonist [Met5 ]-enkephalin (ME) caused significantly less desensitization in KF neurons compared with LC neurons...
January 2018: Molecular Pharmacology
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