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https://www.readbyqxmd.com/read/27882143/expression-of-connexin-43-ion-channels-and-ca-2-handling-proteins-in-rat-pulmonary-vein-cardiomyocytes
#1
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
#2
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 to 4.1±0.29 bpm (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored...
November 21, 2016: Journal of Experimental Biology
https://www.readbyqxmd.com/read/27696527/differential-kv1-3-kca3-1-and-kir2-1-expression-in-classically-and-alternatively-activated-microglia
#3
Hai M Nguyen, Eva M Grössinger, Makoto Horiuchi, Kyle W Davis, Lee-Way Jin, Izumi Maezawa, Heike Wulff
Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) promote differentiation into classically activated M1-like microglia, which produce high levels of pro-inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL-4 in contrast induces a phenotype associated with anti-inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K(+) channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL-4) microglia and studying their K(+) channel expression by whole-cell patch-clamp, quantitative PCR and immunohistochemistry...
January 2017: Glia
https://www.readbyqxmd.com/read/27527100/structural-basis-of-control-of-inward-rectifier-kir2-channel-gating-by-bulk-anionic-phospholipids
#4
Sun-Joo Lee, Feifei Ren, Eva-Maria Zangerl-Plessl, Sarah Heyman, Anna Stary-Weinzinger, Peng Yuan, Colin G Nichols
Inward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP2) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(-)) with a distinct second site is required for high PIP2 sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP2 sensitivity, even in the absence of PL(-) Furthermore, high-resolution x-ray crystal structures of Kir2...
September 2016: Journal of General Physiology
https://www.readbyqxmd.com/read/27511995/effect-of-ethanol-and-acetaldehyde-at-clinically-relevant-concentrations-on-atrial-inward-rectifier-potassium-current-ik1-separate-and-combined-effect
#5
Z Horakova, P Matejovic, M Pasek, J Hosek, M Simurdova, J Simurda, M Bebarova
Atrial fibrillation is the most common arrhythmia at alcohol consumption. Its pathogenesis is complex, at least partly related to changes of cardiac inward rectifier potassium currents including IK1. Both ethanol and acetaldehyde have been demonstrated to considerably modify IK1 in rat ventricular myocytes. However, analogical data on the atrial IK1 are lacking. The present study aimed to analyse IK1 changes induced by ethanol and acetyldehyde in atrial myocytes. The experiments were performed by the whole cell patch-clamp technique at 23 ± 1°C on enzymatically isolated rat and guinea-pig atrial myocytes as well as on expressed human Kir2...
June 2016: Journal of Physiology and Pharmacology: An Official Journal of the Polish Physiological Society
https://www.readbyqxmd.com/read/27235552/hypoxic-stress-up-regulates-kir2-1-expression-and-facilitates-cell-proliferation-in-brain-capillary-endothelial-cells
#6
Hideto Yamamura, Yoshiaki Suzuki, Hisao Yamamura, Kiyofumi Asai, Yuji Imaizumi
The blood-brain barrier (BBB) is mainly composed of brain capillary endothelial cells (BCECs), astrocytes and pericytes. Brain ischemia causes hypoxic encephalopathy and damages BBB. However, it remains still unclear how hypoxia affects BCECs. In the present study, t-BBEC117 cells, an immortalized bovine brain endothelial cell line, were cultured under hypoxic conditions at 4-5% oxygen for 72 h. This hypoxic stress caused hyperpolarization of resting membrane potential. Patch-clamp recordings revealed a marked increase in Ba(2+)-sensitive inward rectifier K(+) current in t-BBEC117 cells after hypoxic culture...
August 5, 2016: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/27117805/pharmacological-inhibition-of-ik1-by-pa-6-in-isolated-rat-hearts-affects-ventricular-repolarization-and-refractoriness
#7
Mark A Skarsfeldt, Helena Carstensen, Lasse Skibsbye, Chuyi Tang, Rikke Buhl, Bo H Bentzen, Thomas Jespersen
The inwardly rectifying potassium current (IK 1) conducted through Kir2.X channels contribute to repolarization of the cardiac action potential and to stabilization of the resting membrane potential in cardiomyocytes. Our aim was to investigate the effect of the recently discovered IK 1 inhibitor PA-6 on action potential repolarization and refractoriness in isolated rat hearts. Transiently transfected HEK-293 cells expressing IK 1 were voltage-clamped with ramp protocols. Langendorff-perfused heart experiments were performed on male Sprague-Dawley rats, effective refractory period, Wenckebach cycle length, and ventricular effective refractory period were determined following 200 nmol/L PA-6 perfusion...
April 2016: Physiological Reports
https://www.readbyqxmd.com/read/27078635/optical-control-of-a-neuronal-protein-using-a-genetically-encoded-unnatural-amino-acid-in-neurons
#8
Ji-Yong Kang, Daichi Kawaguchi, Lei Wang
Photostimulation is a noninvasive way to control biological events with excellent spatial and temporal resolution. New methods are desired to photo-regulate endogenous proteins expressed in their native environment. Here, we present an approach to optically control the function of a neuronal protein directly in neurons using a genetically encoded unnatural amino acid (Uaa). By using an orthogonal tRNA/aminoacyl-tRNA synthetase pair to suppress the amber codon, a photo-reactive Uaa 4,5-dimethoxy-2-nitrobenzyl-cysteine (Cmn) is site-specifically incorporated in the pore of a neuronal protein Kir2...
2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27009332/complex-molecular-and-functional-outcomes-of-single-versus-sequential-cytokine-stimulation-of-rat-microglia
#9
Tamjeed A Siddiqui, Starlee Lively, Lyanne C Schlichter
BACKGROUND: Microglia are the "professional" phagocytes of the CNS. Phagocytosis is crucial for normal CNS development and maintenance, but it can be either beneficial or detrimental after injury or disease. For instance, white matter damage releases myelin debris that must be cleared by microglia in order for re-myelination to occur. However, phagocytosis can also produce damaging reactive oxygen species (ROS). Furthermore, microglia can acquire pro-inflammatory (M1) or anti-inflammatory (M2) activation states that affect cell functions...
2016: Journal of Neuroinflammation
https://www.readbyqxmd.com/read/27008341/whole-genome-and-exome-sequencing-realignment-supports-the-assignment-of-kcnj12-kcnj17-and-kcnj18-paralogous-genes-in-thyrotoxic-periodic-paralysis-locus-functional-characterization-of-two-polymorphic-kir2-6-isoforms
#10
Rolf M Paninka, Diego R Mazzotti, Marina M L Kizys, Angela C Vidi, Hélio Rodrigues, Silas P Silva, Ilda S Kunii, Gilberto K Furuzawa, Manoel Arcisio-Miranda, Magnus R Dias-da-Silva
Next-generation sequencing (NGS) has enriched the understanding of the human genome. However, homologous or repetitive sequences shared among genes frequently produce dubious alignments and can puzzle NGS mutation analysis, especially for paralogous potassium channels. Potassium inward rectifier (Kir) channels are important to establish the resting membrane potential and regulating the muscle excitability. Mutations in Kir channels cause disorders affecting the heart and skeletal muscle, such as arrhythmia and periodic paralysis...
August 2016: Molecular Genetics and Genomics: MGG
https://www.readbyqxmd.com/read/26960267/estrogen-ameliorates-microglial-activation-by-inhibiting-the-kir2-1-inward-rectifier-k-channel
#11
Shih-Ying Wu, Yun-Wen Chen, Sheng-Feng Tsai, Sheng-Nan Wu, Yao-Hsiang Shih, Ya-Fen Jiang-Shieh, Ting-Ting Yang, Yu-Min Kuo
Microglial activation is implicated in the pathogenesis of Parkinson's disease (PD). Although the etiology of PD remains unclear, age and male gender are known PD risk factors. By comparing microglia and dopaminergic (DA) neurons in the substantia nigra (SN) of male and female mice of different ages, we found that the degrees of microglial activation and DA neuron loss increased with age in both genders, but were more pronounced in males, as were peripheral lipopolysaccharide (LPS)-induced microglial activation and DA neuron loss...
2016: Scientific Reports
https://www.readbyqxmd.com/read/26934796/the-beneficial-effects-of-electro-acupuncture-at-pc6-neiguan-point-of-gene-and-protein-expressions-of-classical-inward-rectifier-potassium-channels-in-myocardial-ischemic-rats
#12
Ying Wang, Xiao-Lu Zhang, Wei Wang, Di Li, Jian-Yu Dai, Chun-Ri Li, Ji-Quan Li, Yi-Guo Chen, Pei-Jing Rong
This study is aim to investigate the effect of electro-acupuncture at PC6 (Neiguan-point) on the gene and protein expressions of classical inward-rectifier potassium channels (Kir) in myocardial ischemia (MI) rats induced by isoproterenol (ISO). With ten for each one, 50 rats were divided into 5 groups which were control group, MI group, PC6 group, LU7 (Lieque-point) group and non-acupoint group. The control group was injected normal saline solution (85 mg/kg), the other groups were injected ISO (85 mg/kg)...
2015: Acupuncture & Electro-therapeutics Research
https://www.readbyqxmd.com/read/26840527/inward-rectifier-potassium-kir2-1-channels-as-end-stage-boosters-of-endothelium-dependent-vasodilators
#13
Swapnil K Sonkusare, Thomas Dalsgaard, Adrian D Bonev, Mark T Nelson
KEY POINTS: Increase in endothelial cell (EC) calcium activates calcium-sensitive intermediate and small conductance potassium (IK and SK) channels, thereby causing hyperpolarization and endothelium-dependent vasodilatation. Endothelial cells express inward rectifier potassium (Kir) channels, but their role in endothelium-dependent vasodilatation is not clear. In the mesenteric arteries, only ECs, but not smooth muscle cells, displayed Kir currents that were predominantly mediated by the Kir2...
June 15, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/26702021/automated-patch-clamp-meets-high-throughput-screening-384-cells-recorded-in-parallel-on-a-planar-patch-clamp-module
#14
Alison Obergrussberger, Andrea Brüggemann, Tom A Goetze, Markus Rapedius, Claudia Haarmann, Ilka Rinke, Nadine Becker, Takayuki Oka, Atsushi Ohtsuki, Timo Stengel, Marius Vogel, Juergen Steindl, Max Mueller, Johannes Stiehler, Michael George, Niels Fertig
We have developed an automated patch clamp module for high-throughput ion channel screening, recording from 384 cells simultaneously. The module is incorporated into a laboratory pipetting robot and uses a 384-channel pipettor head for application of cells and compounds. The module contains 384 amplifier channels for fully parallel recordings using a digital amplifier. Success rates for completed experiments (1- to 4-point concentration-response curves for cells satisfying defined quality control parameters) of greater than 85% have been routinely achieved with, for example, HEK, CHO, and RBL cell lines expressing hNaV1...
December 2016: Journal of Laboratory Automation
https://www.readbyqxmd.com/read/26700160/inward-rectifier-k-currents-are-regulated-by-camkii-in-endothelial-cells-of-primarily-cultured-bovine-pulmonary-arteries
#15
Lihui Qu, Lei Yu, Yanli Wang, Xin Jin, Qianlong Zhang, Ping Lu, Xiufeng Yu, Weiwei Zhong, Xiaodong Zheng, Ningren Cui, Chun Jiang, Daling Zhu
Endothelium lines the interior surface of vascular walls and regulates vascular tones. The endothelial cells sense and respond to chemical and mechanical stimuli in the circulation, and couple the stimulus signals to vascular smooth muscles, in which inward rectifier K+ currents (Kir) play an important role. Here we applied several complementary strategies to determine the Kir subunit in primarily cultured pulmonary arterial endothelial cells (PAECs) that was regulated by the Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII)...
2015: PloS One
https://www.readbyqxmd.com/read/26631167/intracellular-spermine-blocks-trpc4-channel-via-electrostatic-interaction-with-c-terminal-negative-amino-acids
#16
Jinsung Kim, Sang Hui Moon, Young-Cheul Shin, Ju-Hong Jeon, Kyu Joo Park, Kyu Pil Lee, Insuk So
Transient receptor potential canonical (TRPC) 4 channels are calcium-permeable, nonselective cation channels and are widely expressed in mammalian tissue, especially in the GI tract and brain. TRPC4 channels are known to be involved in neurogenic contraction of ileal smooth muscle cells via generating cationic current after muscarinic stimulation (muscarinic cationic current (mIcat)). Polyamines exist in numerous tissues and are believed to be involved in cell proliferation, differentiation, scar formation, wound healing, and carcinogenesis...
April 2016: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/26484867/decrease-in-an-inwardly-rectifying-potassium-conductance-in-mouse-mammary-secretory-cells-after-forced-weaning
#17
Akihiro Kamikawa, Shota Sugimoto, Osamu Ichii, Daisuke Kondoh
Mammary glands are physiologically active in female mammals only during nursing. Immediately after weaning, most lactation-related genes are downregulated and milk production ceases. In our previous study, we have detected an inwardly rectifying potassium channel (Kir) 2.1-like current in mammary secretory (MS) cells freshly isolated from lactating mice. This current is highly sensitive to external Ba2+. The potassium permeability of the Kir channels may contribute to the secretion and/or preservation of ions in milk...
2015: PloS One
https://www.readbyqxmd.com/read/26324774/rise-and-fall-of-kir2-2-current-by-tlr4-signaling-in-human-monocytes-pkc-dependent-trafficking-and-pi3k-mediated-pip2-decrease
#18
Kyung Soo Kim, Ji Hyun Jang, Haiyue Lin, Seong Woo Choi, Hang Rae Kim, Dong Hoon Shin, Joo Hyun Nam, Yin Hua Zhang, Sung Joon Kim
LPSs are widely used to stimulate TLR4, but their effects on ion channels in immune cells are poorly known. In THP-1 cells and human blood monocytes treated with LPS, inwardly rectifying K(+) channel current (IKir,LPS) newly emerged at 1 h, peaked at 4 h (-119 ± 8.6 pA/pF), and decayed afterward (-32 ± 6.7 pA/pF at 24 h). Whereas both the Kir2.1 and Kir2.2 mRNAs and proteins were observed, single-channel conductance (38 pS) of IKir,LPS and small interfering RNA-induced knockdown commonly indicated Kir2.2 than Kir2...
October 1, 2015: Journal of Immunology: Official Journal of the American Association of Immunologists
https://www.readbyqxmd.com/read/26063437/identification-of-the-conformational-transition-pathway-in-pip2-opening-kir-channels
#19
Junwei Li, Shouqin Lü, Yuzhi Liu, Chunli Pang, Yafei Chen, Suhua Zhang, Hui Yu, Mian Long, Hailin Zhang, Diomedes E Logothetis, Yong Zhan, Hailong An
The gating of Kir channels depends critically on phosphatidylinositol 4,5-bisphosphate (PIP2), but the detailed mechanism by which PIP2 regulates Kir channels remains obscure. Here, we performed a series of Targeted molecular dynamics simulations on the full-length Kir2.1 channel and, for the first time, were able to achieve the transition from the closed to the open state. Our data show that with the upward motion of the cytoplasmic domain (CTD) the structure of the C-Linker changes from a loop to a helix...
2015: Scientific Reports
https://www.readbyqxmd.com/read/26042044/selectivity-filters-and-cysteine-rich-extracellular-loops-in-voltage-gated-sodium-calcium-and-nalcn-channels
#20
REVIEW
Robert F Stephens, W Guan, Boris S Zhorov, J David Spafford
How nature discriminates sodium from calcium ions in eukaryotic channels has been difficult to resolve because they contain four homologous, but markedly different repeat domains. We glean clues from analyzing the changing pore region in sodium, calcium and NALCN channels, from single-cell eukaryotes to mammals. Alternative splicing in invertebrate homologs provides insights into different structural features underlying calcium and sodium selectivity. NALCN generates alternative ion selectivity with splicing that changes the high field strength (HFS) site at the narrowest level of the hourglass shaped pore where the selectivity filter is located...
2015: Frontiers in Physiology
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