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https://www.readbyqxmd.com/read/28331977/role-of-plasma-membrane-associated-akaps-for-the-regulation-of-cardiac-ik1-current-by-protein-kinase-a
#1
Claudia Seyler, Daniel Scherer, Christoph Köpple, Martin Kulzer, Sevil Korkmaz, Panagiotis Xynogalos, Dierk Thomas, Ziya Kaya, Eberhard Scholz, Johannes Backs, Christoph Karle, Hugo A Katus, Edgar Zitron
The cardiac IK1 current stabilizes the resting membrane potential of cardiomyocytes. Protein kinase A (PKA) induces an inhibition of IK1 current which strongly promotes focal arrhythmogenesis. The molecular mechanisms underlying this regulation have only partially been elucidated yet. Furthermore, the role of A-kinase anchoring proteins (AKAPs) in this regulation has not been examined to date. The objective of this project was to elucidate the molecular mechanisms underlying the inhibition of IK1 by PKA and to identify novel molecular targets for antiarrhythmic therapy downstream β-adrenoreceptors...
March 22, 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28319610/capillary-k-sensing-initiates-retrograde-hyperpolarization-to-increase-local-cerebral-blood-flow
#2
Thomas A Longden, Fabrice Dabertrand, Masayo Koide, Albert L Gonzales, Nathan R Tykocki, Joseph E Brayden, David Hill-Eubanks, Mark T Nelson
Blood flow into the brain is dynamically regulated to satisfy the changing metabolic requirements of neurons, but how this is accomplished has remained unclear. Here we demonstrate a central role for capillary endothelial cells in sensing neural activity and communicating it to upstream arterioles in the form of an electrical vasodilatory signal. We further demonstrate that this signal is initiated by extracellular K(+) -a byproduct of neural activity-which activates capillary endothelial cell inward-rectifier K(+) (KIR2...
March 20, 2017: Nature Neuroscience
https://www.readbyqxmd.com/read/28301408/k-cl-cotransporter-2-mediated-cl-extrusion-determines-developmental-stage-dependent-impact-of-propofol-anesthesia-on-dendritic-spines
#3
Martin Puskarjov, Hubert Fiumelli, Adrian Briner, Timea Bodogan, Kornel Demeter, Claudia-Marvine Lacoh, Martina Mavrovic, Peter Blaesse, Kai Kaila, Laszlo Vutskits
BACKGROUND: General anesthetics potentiating γ-aminobutyric acid (GABA)-mediated signaling are known to induce a persistent decrement in excitatory synapse number in the cerebral cortex when applied during early postnatal development, while an opposite action is produced at later stages. Here, the authors test the hypothesis that the effect of general anesthetics on synaptogenesis depends upon the efficacy of GABA receptor type A (GABAA)-mediated inhibition controlled by the developmental up-regulation of the potassium-chloride (K-Cl) cotransporter 2 (KCC2)...
March 16, 2017: Anesthesiology
https://www.readbyqxmd.com/read/28289282/the-schizophrenia-and-autism-associated-gene-transcription-factor-4-regulates-the-columnar-distribution-of-layer-2-3-prefrontal-pyramidal-neurons-in-an-activity-dependent-manner
#4
S C Page, G R Hamersky, R A Gallo, M D Rannals, N E Calcaterra, M N Campbell, B Mayfield, A Briley, B N Phan, A E Jaffe, B J Maher
Disruption of the laminar and columnar organization of the brain is implicated in several psychiatric disorders. Here, we show in utero gain-of-function of the psychiatric risk gene transcription factor 4 (TCF4) severely disrupts the columnar organization of medial prefrontal cortex (mPFC) in a transcription- and activity-dependent manner. This morphological phenotype was rescued by co-expression of TCF4 plus calmodulin in a calcium-dependent manner and by dampening neuronal excitability through co-expression of an inwardly rectifying potassium channel (Kir2...
March 14, 2017: Molecular Psychiatry
https://www.readbyqxmd.com/read/28284503/renal-denervation-regulates-the-atrial-arrhythmogenic-substrates-through-reverse-structural-remodeling-in-heart-failure-rabbit-model
#5
Shinya Yamada, Li-Wei Lo, Yu-Hui Chou, Wei-Lun Lin, Shih-Lin Chang, Yenn-Jiang Lin, Shih-Ann Chen
BACKGROUND: Heart failure (HF) causes atrial remodeling and increases the incidence of atrial fibrillation (AF). Renal denervation (RDN) has been shown to decrease the development of AF. This study aimed to identify the effects of RDN on the atrial arrhythmogenic substrates in HF. METHODS: Rabbits were classified into four groups: control (n=9), RDN (n=10), HF (n=6) and HF-RDN (n=9). Surgical and chemical RDN was approached through bilateral retroperitoneal flank incisions in RDN and HF-RDN...
February 24, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28255076/beneficial-effect-of-renal-denervation-on-ventricular-premature-complex-induced-cardiomyopathy
#6
Shinya Yamada, Li-Wei Lo, Yu-Hui Chou, Wei-Lun Lin, Shih-Lin Chang, Yenn-Jiang Lin, Shin-Huei Liu, Wen-Han Cheng, Tsung-Ying Tsai, Shih-Ann Chen
BACKGROUND: Frequent ventricular premature complexes (VPCs) can lead to the development of dilated cardiomyopathy and sudden cardiac death. Renal artery sympathetic denervation (RDN) may protect the heart from remodeling. This study aimed to investigate the effect of frequent VPCs on structural and electrical properties and whether RDN can protect the heart from remodeling. METHODS AND RESULTS: Eighteen rabbits were randomized to control (n=6), VPC (n=6), and VPC-RDN (n=6) groups...
March 2, 2017: Journal of the American Heart Association
https://www.readbyqxmd.com/read/28235908/potencies-of-effector-genes-in-silencing-odor-guided-behavior-in-drosophila-melanogaster
#7
Tom Retzke, Michael Thoma, Bill S Hansson, Markus Knaden
The genetic toolbox in Drosophila offers a multitude of different effector constructs to silence neurons and neuron populations. In this study we investigated the potencies of several effector genes - when expressed in olfactory sensory neurons (OSNs) - to abolish odor-guided behavior in three different bioassays. We find that two of the tested effectors (tetanus toxin and Kir2.1) are capable of mimicking the Orco mutant phenotype in all of our behavioral paradigms. In both cases the effectiveness depended on effector expression levels as full suppression of odor-guided behavior was observed only in flies homozygous for both Gal4-driver and UAS-effector constructs...
February 24, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28216048/chloroquine-blocks-the-kir4-1-channels-by-an-open-pore-blocking-mechanism
#8
Leticia G Marmolejo-Murillo, Iván A Aréchiga-Figueroa, Eloy G Moreno-Galindo, Ricardo A Navarro-Polanco, Aldo A Rodríguez-Menchaca, Meng Cui, José A Sánchez-Chapula, Tania Ferrer
Kir4.1 channels have been implicated in various physiological processes, mainly in the K(+) homeostasis of the central nervous system and in the control of glial function and neuronal excitability. Even though, pharmacological research of these channels is very limited. Chloroquine (CQ) is an amino quinolone derivative known to inhibit Kir2.1 and Kir6.2 channels with different action mechanism and binding site. Here, we employed patch-clamp methods, mutagenesis analysis, and molecular modeling to characterize the molecular pharmacology of Kir4...
April 5, 2017: European Journal of Pharmacology
https://www.readbyqxmd.com/read/28188270/dual-mechanism-for-inhibition-of-inwardly-rectifying-kir2-x-channels-by-quinidine-involving-direct-pore-block-and-pip2-interference
#9
Christoph Koepple, Daniel Scherer, Claudia Seyler, Eberhard Scholz, Dierk Thomas, Hugo A Katus, Edgar Zitron
Class IA antiarrhythmic drug quinidine was one of the first clinically used compounds to terminate atrial fibrillation and acts as multichannel inhibitor with well-documented inhibitory effects on several cardiac potassium channels. In the mammalian heart, heteromeric assembly of Kir2.1-2.3 channels underlies IK1 current. While a low-affinity block of quinidine on Kir2.1 has already been described, a comparative analysis of effects on other Kir2.x channels has not been performed to date. Therefore, we analyzed the effects of quinidine on wild type and mutant Kir2...
February 10, 2017: Journal of Pharmacology and Experimental Therapeutics
https://www.readbyqxmd.com/read/28148533/inhibition-of-vascular-smooth-muscle-inward-rectifier-k-channels-restores-myogenic-tone-in-mouse-urinary-bladder-arterioles
#10
Nathan R Tykocki, Adrian D Bonev, Thomas Andrew Longden, Thomas J Heppner, Mark T Nelson
Prolonged decreases in urinary bladder blood flow are linked to overactive and underactive bladder pathologies. However, the mechanisms regulating bladder vascular reactivity are largely unknown. To investigate these mechanisms, we examined myogenic and vasoactive properties of mouse bladder feed arterioles (BFAs). Unlike similar-sized arterioles from other vascular beds, BFAs failed to constrict in response to increases in intraluminal pressure (5-80 mmHg). Consistent with this lack of myogenic tone, arteriolar smooth muscle cell membrane potential was hyperpolarized (-72...
February 1, 2017: American Journal of Physiology. Renal Physiology
https://www.readbyqxmd.com/read/28131627/down-regulation-of-kir2-6-channel-by-c-termini-mutation-d252n-and-its-association-with-the-susceptibility-to-thyrotoxic-periodic-paralysis
#11
Rolf Matias Paninka, Estevão Carlos-Lima, Susan C Lindsey, Ilda S Kunii, Magnus R Dias-da-Silva, Manoel Arcisio-Miranda
Inward rectifying potassium - Kir - channels drive the resting potential to potassium reversal potential and, when disrupted, might be related to muscular diseases. Recently, Thyrotoxic Periodic Paralysis (TPP) has emerged as a channelopathy related to mutations in KCNJ18 gene, which encodes Kir2.6 channel. TPP is a neuromuscular disorder characterized by a triad of muscle weakness, hypokalemia, and thyrotoxicosis, the latter being essential for the crisis. Direct sequencing revealed two heterozygous mutations - D252N and R386C - in two TPP patients...
January 25, 2017: Neuroscience
https://www.readbyqxmd.com/read/28112313/soluble-epoxide-hydrolase-inhibitors-might-prevent-ischemic-arrhythmias-via-microrna-1-repression-in-primary-neonatal-mouse-ventricular-myocytes
#12
Qiong Liu, Xuan Zhao, Ran Peng, Mi Wang, Wang Zhao, Ya-Jun Gui, Cai-Xiu Liao, Dan-Yan Xu
Ischemic arrhythmias are the main causes of sudden cardiac death. It has been reported that soluble epoxide hydrolase inhibitors (sEHis) could prevent arrhythmias; however, the underlying molecular mechanisms remain unclear. In recent years, the proarrhythmic role of microRNA-1 (miR-1) has been investigated. This study aimed to elucidate whether sEHis prevented ischemic arrhythmias by suppressing miR-1. The primary neonatal mouse ventricular myocyte model of miR-1 overexpression was established by incubating with agonist microONTM mmu-miR-1a-3p agomir (DAEDstain(TM) Dye) (agomiR-1)...
January 23, 2017: Molecular BioSystems
https://www.readbyqxmd.com/read/28007664/effects-of-seasonal-acclimatization-on-action-potentials-and-sarcolemmal-k-currents-in-roach-rutilus-rutilus-cardiac-myocytes
#13
Ahmed Badr, Minna Hassinen, Mohamed F El-Sayed, Matti Vornanen
Temperature sensitivity of electrical excitability is a potential limiting factor for high temperature tolerance of ectotherms. The present study examines whether heat resistance of electrical excitability of cardiac myocytes is modified by seasonal thermal acclimatization in roach (Rutilus rutilus), a eurythermal teleost species. To this end, temperature dependencies of ventricular action potentials (APs), and atrial and ventricular K(+) currents were measured from winter-acclimatized (WiR) and summer-acclimatized (SuR) roach...
March 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/28004830/fluid-flow-facilitates-inward-rectifier-k-current-by-convectively-restoring-k-at-the-cell-membrane-surface
#14
Jae Gon Kim, Sang Woong Park, Doyoung Byun, Wahn Soo Choi, Dong Jun Sung, Kyung Chul Shin, Hyun-Ji Kim, Young-Eun Leem, Jong-Sun Kang, Hana Cho, Bokyung Kim, Sung I Cho, Young Min Bae
The inward rectifier Kir2.1 current (IKir2.1) was reported to be facilitated by fluid flow. However, the mechanism underlying this facilitation remains uncertain. We hypothesized that during K(+) influx or efflux, [K(+)] adjacent to the outer mouth of the Kir2.1 channel might decrease or increase, respectively, compared with the average [K(+)] of the bulk extracellular solution, and that fluid flow could restore the original [K(+)] and result in the apparent facilitation of IKir2.1. We recorded the IKir2.1 in RBL-2H3 cells and HEK293T cells that were ectopically over-expressed with Kir2...
December 22, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27882143/expression-of-connexin-43-ion-channels-and-ca-2-handling-proteins-in-rat-pulmonary-vein-cardiomyocytes
#15
Yaqiong Xiao, Xue Cai, Andrew Atkinson, Sunil Jit Logantha, Mark Boyett, Halina Dobrzynski
Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF is thought to be triggered by ectopic beats, originating primarily in the myocardial sleeves surrounding the pulmonary veins (PVs). The mechanisms underlying these cardiac arrhythmias remain unclear. To investigate this, frozen sections of heart and lung tissue from adult rats without arrhythmia were obtained in different planes, stained with Masson's trichrome, and immunolabeled for connexin 43 (Cx43), caveolin-3 (Cav3), hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4), Nav1...
November 2016: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/27872214/effects-of-prolonged-anoxia-on-electrical-activity-of-the-heart-in-crucian-carp-carassius-carassius
#16
Elisa Tikkanen, Jaakko Haverinen, Stuart Egginton, Minna Hassinen, Matti Vornanen
The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 beats min(-1) to 4.1±0.29 beats min(-1) (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored...
February 1, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/27859264/inwardly-rectifying-k-channels-are-major-contributors-to-flow-induced-vasodilatation-in-resistance-arteries
#17
Sang Joon Ahn, Ibra S Fancher, Jing-Tan Bian, Chong Xu Zhang, Sarah Schwab, Robert Gaffin, Shane A Phillips, Irena Levitan
KEY POINTS: Endothelial inwardly rectifying K(+) (Kir2.1) channels regulate flow-induced vasodilatation via nitric oxide (NO) in mouse mesenteric resistance arteries. Deficiency of Kir2.1 channels results in elevated blood pressure and increased vascular resistance. Flow-induced vasodilatation in human resistance arteries is also regulated by inwardly rectifying K(+) channels. This study presents the first direct evidence that Kir channels play a critical role in physiological endothelial responses to flow...
November 17, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27849039/an-insecticide-resistance-breaking-mosquitocide-targeting-inward-rectifier-potassium-channels-in-vectors-of-zika-virus-and-malaria
#18
Daniel R Swale, Darren W Engers, Sean R Bollinger, Aaron Gross, Edna Alfaro Inocente, Emily Days, Fariba Kanga, Reed M Johnson, Liu Yang, Jeffrey R Bloomquist, Corey R Hopkins, Peter M Piermarini, Jerod S Denton
Insecticide resistance is a growing threat to mosquito control programs around the world, thus creating the need to discover novel target sites and target-specific compounds for insecticide development. Emerging evidence suggests that mosquito inward rectifier potassium (Kir) channels represent viable molecular targets for developing insecticides with new mechanisms of action. Here we describe the discovery and characterization of VU041, a submicromolar-affinity inhibitor of Anopheles (An.) gambiae and Aedes (Ae...
November 16, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27807980/convergence-and-sampling-in-determining-free-energy-landscapes-for-membrane-protein-association
#19
Jan Domanski, George Hedger, Robert B Best, Phillip James Stansfeld, Mark S P Sansom
Potential of mean force (PMF) calculations are used to characterize the free energy landscape of protein-lipid and protein-protein association within membranes. Coarse-grained simulations allow binding free energies to be determined with reasonable statistical error. This accuracy relies on defining a good collective variable describing the binding and unbinding transition, and upon criteria for assessing the convergence of the simulation toward representative equilibrium sampling. As examples, we calculate protein-lipid binding PMFs for ANT/cardiolipin and Kir2...
November 3, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27789106/reversible-dilated-cardiomyopathy-caused-by-a-high-burden-of-ventricular-arrhythmias-in-andersen-tawil-syndrome
#20
Saman Rezazadeh, Jiqing Guo, Henry J Duff, Raechel A Ferrier, Brenda Gerull
Andersen-Tawil syndrome (ATS) is caused by mutations in KCNJ2 (Kir2.1). It remains unclear whether dilated cardiomyopathy (DCM) is a primary feature of ATS. We studied a proband with typical physical features of ATS plus DCM and moderate to severe left ventricular dysfunction (left ventricular ejection fraction = 30.5%). Genetic screening revealed a novel mutation in Kir2.1 (c.665T>C, p.L222S). Functional studies showed that this mutation reduced ionic currents in a dominant-negative manner. Suppression of ventricular arrhythmias with bisoprolol led to normalization of left ventricular size and function...
July 27, 2016: Canadian Journal of Cardiology
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