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https://www.readbyqxmd.com/read/28863819/differential-effects-of-sterols-on-ion-channels-stereospecific-binding-vs-stereospecific-response
#1
Nicolas Barbera, Manuela A A Ayee, Belinda S Akpa, Irena Levitan
Numerous ion channels have been shown to be regulated by the level of membrane cholesterol, but the mechanisms responsible for these effects are still not well understood. The key question in the field is how to discriminate between the contributions of the two central mechanisms that might be responsible for the sensitivity of ion channels to cholesterol: specific sterol-protein interactions or regulation of channels by the bilayer physical properties. Comparative analysis of cholesterol and its isomers on the function of an ion channel is a powerful tool to achieve this goal...
2017: Current Topics in Membranes
https://www.readbyqxmd.com/read/28863816/insights-into-the-molecular-requirements-for-cholesterol-binding-to-ion-channels
#2
Avia Rosenhouse-Dantsker
The concept that cholesterol binds to proteins via specific binding motifs, and thereby modulates their function, has emerged two decades ago. When we recently embarked on studies to uncover the putative binding region(s) of cholesterol in the Kir2.1 channel, we carried out an unbiased approach that combines computational and experimental methods. This approach resulted in the identification of novel cholesterol-binding regions distinct from known cholesterol-binding motifs. In recent years, a plethora of structures of proteins complexed with cholesterol have been determined revealing variegated cholesterol-binding regions that can provide invaluable insights into the prerequisites for cholesterol binding...
2017: Current Topics in Membranes
https://www.readbyqxmd.com/read/28830445/responses-of-rat-and-mouse-primary-microglia-to-pro-and-anti-inflammatory-stimuli-molecular-profiles-k-channels-and-migration
#3
Doris Lam, Starlee Lively, Lyanne C Schlichter
BACKGROUND: Acute CNS damage is commonly studied using rat and mouse models, but increasingly, molecular analysis is finding species differences that might affect the ability to translate findings to humans. Microglia can undergo complex molecular and functional changes, often studied by in vitro responses to discrete activating stimuli. There is considerable evidence that pro-inflammatory (M1) activation can exacerbate tissue damage, while anti-inflammatory (M2) states help resolve inflammation and promote tissue repair...
August 22, 2017: Journal of Neuroinflammation
https://www.readbyqxmd.com/read/28812984/modelling-the-effects-of-quinidine-disopyramide-and-e-4031-on-short-qt-syndrome-variant-3-in-the-human-ventricles
#4
Cunjin Luo, Kuanquan Wang, Henggui Zhang
Short QT syndrome (SQTS) is an inherited cardiac channelopathy, but at present little information is available on its pharmacological treatment. SQT3 variant (linked to the inward rectifier potassium current IK1) of SQTS, results from a gain-of-function mutation (Kir2.1 D172N) in the KCNJ2-encoded channels, which is associated with ventricular fibrillation (VF). Using biophysically-detailed human ventricular computer models, this study investigated the potential effects of quinidine, disopyramide, and E-4031 on SQT3...
August 16, 2017: Physiological Measurement
https://www.readbyqxmd.com/read/28749940/upregulation-of-an-inward-rectifying-k-channel-can-rescue-slow-ca2-oscillations-in-k-atp-channel-deficient-pancreatic-islets
#5
Vehpi Yildirim, Suryakiran Vadrevu, Benjamin Thompson, Leslie S Satin, Richard Bertram
Plasma insulin oscillations are known to have physiological importance in the regulation of blood glucose. In insulin-secreting β-cells of pancreatic islets, K(ATP) channels play a key role in regulating glucose-dependent insulin secretion. In addition, they convey oscillations in cellular metabolism to the membrane by sensing adenine nucleotides, and are thus instrumental in mediating pulsatile insulin secretion. Blocking K(ATP) channels pharmacologically depolarizes the β-cell plasma membrane and terminates islet oscillations...
July 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28711067/pa-6-inhibits-inward-rectifier-currents-carried-by-v93i-and-d172n-gain-of-function-kir2-1-channels-but-increases-channel-protein-expression
#6
Yuan Ji, Marlieke G Veldhuis, Jantien Zandvoort, Fee L Romunde, Marien J C Houtman, Karen Duran, Gijs van Haaften, Eva-Maria Zangerl-Plessl, Hiroki Takanari, Anna Stary-Weinzinger, Marcel A G van der Heyden
BACKGROUND: The inward rectifier potassium current IK1 contributes to a stable resting membrane potential and phase 3 repolarization of the cardiac action potential. KCNJ2 gain-of-function mutations V93I and D172N associate with increased IK1, short QT syndrome type 3 and congenital atrial fibrillation. Pentamidine-Analogue 6 (PA-6) is an efficient (IC50 = 14 nM with inside-out patch clamp methodology) and specific IK1 inhibitor that interacts with the cytoplasmic pore region of the KIR2...
July 15, 2017: Journal of Biomedical Science
https://www.readbyqxmd.com/read/28660286/hydrocinnamic-acid-inhibits-the-currents-of-wt-and-sqt3-syndrome-related-mutants-of-kir2-1-channel
#7
Shuxi Ren, Chunli Pang, Yayue Huang, Chengfen Xing, Yong Zhan, Hailong An
Gain of function in mutations, D172N and E299V, of Kir2.1 will induce type III short QT syndrome. In our previous work, we had identified that a mixture of traditional Chinese medicine, styrax, is a blocker of Kir2.1. Here, we determined a monomer, hydrocinnamic acid (HA), as the effective component from 18 compounds of styrax. Our data show that HA can inhibit the currents of Kir2.1 channel in both excised inside-out and whole-cell patch with the IC50 of 5.21 ± 1.02 and 10.08 ± 0.46 mM, respectively...
June 28, 2017: Journal of Membrane Biology
https://www.readbyqxmd.com/read/28609477/atrial-arrhythmogenicity-of-kcnj2-mutations-in-short-qt-syndrome-insights-from-virtual-human-atria
#8
Dominic G Whittaker, Haibo Ni, Aziza El Harchi, Jules C Hancox, Henggui Zhang
Gain-of-function mutations in KCNJ2-encoded Kir2.1 channels underlie variant 3 (SQT3) of the short QT syndrome, which is associated with atrial fibrillation (AF). Using biophysically-detailed human atria computer models, this study investigated the mechanistic link between SQT3 mutations and atrial arrhythmogenesis, and potential ion channel targets for treatment of SQT3. A contemporary model of the human atrial action potential (AP) was modified to recapitulate functional changes in IK1 due to heterozygous and homozygous forms of the D172N and E299V Kir2...
June 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28592292/effects-of-amiodarone-on-short-qt-syndrome-variant-3-in-human-ventricles-a-simulation-study
#9
Cunjin Luo, Kuanquan Wang, Henggui Zhang
BACKGROUND: Short QT syndrome (SQTS) is a newly identified clinical disorder associated with atrial and/or ventricular arrhythmias and increased risk of sudden cardiac death (SCD). The SQTS variant 3 is linked to D172N mutation to the KCNJ2 gene that causes a gain-of-function to the inward rectifier potassium channel current (I K1), which shortens the ventricular action potential duration (APD) and effective refractory period (ERP). Pro-arrhythmogenic effects of SQTS have been characterized, but less is known about the possible pharmacological treatment of SQTS...
June 7, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28543529/kir2-1-and-k2p1-channels-reconstitute-two-levels-of-resting-membrane-potential-in-cardiomyocytes
#10
Dongchuan Zuo, Kuihao Chen, Min Zhou, Zheng Liu, Haijun Chen
KEY POINTS: Outward and inward background currents across the cell membrane balance, determining resting membrane potential. Inward rectifier K(+) channel subfamily 2 (Kir2) channels primarily maintain the resting membrane potential of cardiomyocytes. Human cardiomyocytes exhibit two levels of resting membrane potential at subphysiological extracellular K(+) concentrations or pathological hypokalaemia, however, the underlying mechanism is unclear. In the present study, we show that human cardiomyocytes derived from induced pluripotent stem cells with enhanced expression of isoform 1 of Kir2 (Kir2...
August 1, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28542320/the-ik1-kir2-1-channel-agonist-zacopride-prevents-and-cures-acute-ischemic-arrhythmias-in-the-rat
#11
Xu-Wen Zhai, Li Zhang, Yun-Fei Guo, Ying Yang, Dong-Ming Wang, Yan Zhang, Pan Li, Yi-Fan Niu, Qi-Long Feng, Bo-Wei Wu, Ji-Min Cao, Qing-Hua Liu
Arrhythmogenesis in acute myocardial infarction (MI) is associated with depolarization of resting membraine potential (RMP) and decrease of inward rectifier potassium current (IK1) in cardiomyocytes. However, clinical anti-arrhythmic agents that primarily act on RMP by enhancing the IK1 channel are not currently available. We hypothesized that zacopride, a selective and moderate agonist of the IK1/Kir2.1 channels, prevents and cures acute ischemic arrhythmias. To test this viewpoint, adult Sprague-Dawley (SD) rats were subjected to MI by ligating the left main coronary artery...
2017: PloS One
https://www.readbyqxmd.com/read/28452394/hierarchical-organization-and-genetically-separable-subfamilies-of-psd95-postsynaptic-supercomplexes
#12
René A W Frank, Fei Zhu, Noboru H Komiyama, Seth G N Grant
PSD95 is an abundant postsynaptic scaffold protein in glutamatergic synapses that assembles into supercomplexes composed of over 80 proteins including neurotransmitter receptors, ion channels and adhesion proteins. How these diverse constituents are organized into PSD95 supercomplexes in vivo is poorly understood. Here, we dissected the supercomplexes in mice combining endogenous gene-tagging, targeted mutations and quantitative biochemical assays. Generating compound heterozygous mice with two different gene-tags, one on each Psd95 allele, showed that each ~1...
August 2017: Journal of Neurochemistry
https://www.readbyqxmd.com/read/28446610/conformational-changes-at-cytoplasmic-intersubunit-interactions-control-kir-channel-gating
#13
COMPARATIVE STUDY
Shizhen Wang, William F Borschel, Sarah Heyman, Phillip Hsu, Colin G Nichols
The defining structural feature of inward-rectifier potassium (Kir) channels is the unique Kir cytoplasmic domain. Recently we showed that salt bridges located at the cytoplasmic domain subunit interfaces (CD-Is) of eukaryotic Kir channels control channel gating via stability of a novel inactivated closed state. The cytoplasmic domains of prokaryotic and eukaryotic Kir channels show similar conformational rearrangements to the common gating ligand, phosphatidylinositol bisphosphate (PIP2), although these exhibit opposite coupling to opening and closing transitions...
June 16, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28432059/increased-amplitude-of-inward-rectifier-k-currents-with-advanced-age-in-smooth-muscle-cells-of-murine-superior-epigastric-arteries
#14
Sebastien Hayoz, Jessica Pettis, Vanessa Bradley, Steven S Segal, William F Jackson
Inward rectifier K(+) channels (KIR) may contribute to skeletal muscle blood flow regulation and adapt to advanced age. Using mouse abdominal wall superior epigastric arteries (SEAs) from either young (3-6 mo) or old (24-26 mo) male C57BL/6 mice, we investigated whether SEA smooth muscle cells (SMCs) express functional KIR channels and how aging may affect KIR function. Freshly dissected SEAs were either enzymatically dissociated to isolate SMCs for electrophysiological recording (perforated patch) and mRNA expression or used intact for pressure myography...
June 1, 2017: American Journal of Physiology. Heart and Circulatory Physiology
https://www.readbyqxmd.com/read/28408648/azithromycin-causes-a-novel-proarrhythmic-syndrome
#15
Zhenjiang Yang, Joseph K Prinsen, Kevin R Bersell, Wangzhen Shen, Liudmila Yermalitskaya, Tatiana Sidorova, Paula B Luis, Lynn Hall, Wei Zhang, Liping Du, Ginger Milne, Patrick Tucker, Alfred L George, Courtney M Campbell, Robert A Pickett, Christian M Shaffer, Nagesh Chopra, Tao Yang, Bjorn C Knollmann, Dan M Roden, Katherine T Murray
BACKGROUND: The widely used macrolide antibiotic azithromycin increases risk of cardiovascular and sudden cardiac death, although the underlying mechanisms are unclear. Case reports, including the one we document here, demonstrate that azithromycin can cause rapid, polymorphic ventricular tachycardia in the absence of QT prolongation, indicating a novel proarrhythmic syndrome. We investigated the electrophysiological effects of azithromycin in vivo and in vitro using mice, cardiomyocytes, and human ion channels heterologously expressed in human embryonic kidney (HEK 293) and Chinese hamster ovary (CHO) cells...
April 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28389584/control-of-kir-channel-gating-by-cytoplasmic-domain-interface-interactions
#16
William F Borschel, Shizhen Wang, Sunjoo Lee, Colin G Nichols
Inward rectifier potassium (Kir) channels are expressed in almost all mammalian tissues and play critical roles in the control of excitability. Pancreatic ATP-sensitive K (KATP) channels are key regulators of insulin secretion and comprise Kir6.2 subunits coupled to sulfonylurea receptors. Because these channels are reversibly inhibited by cytoplasmic ATP, they link cellular metabolism with membrane excitability. Loss-of-function mutations in the pore-forming Kir6.2 subunit cause congenital hyperinsulinism as a result of diminished channel activity...
May 1, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/28383527/activation-of-the-hypoglossal-to-tongue-musculature-motor-pathway-by-remote-control
#17
Garret A Horton, Jimmy J Fraigne, Zoltan A Torontali, Matthew B Snow, Jennifer L Lapierre, Hattie Liu, Gaspard Montandon, John H Peever, Richard L Horner
Reduced tongue muscle tone precipitates obstructive sleep apnea (OSA), and activation of the tongue musculature can lessen OSA. The hypoglossal motor nucleus (HMN) innervates the tongue muscles but there is no pharmacological agent currently able to selectively manipulate a channel (e.g., Kir2.4) that is highly restricted in its expression to cranial motor pools such as the HMN. To model the effect of manipulating such a restricted target, we introduced a "designer" receptor into the HMN and selectively modulated it with a "designer" drug...
April 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28365825/inhibition-of-inwardly-rectifying-kir2-x-channels-by-the-novel-anti-cancer-agent-gambogic-acid-depends-on-both-pore-block-and-pip2-interference
#18
Daniel Scherer, Benedikt Schworm, Claudia Seyler, Panagiotis Xynogalos, Eberhard P Scholz, Dierk Thomas, Hugo A Katus, Edgar Zitron
The caged xanthone gambogic acid (GA) is a novel anti-cancer agent which exhibits anti-proliferative, anti-inflammatory and cytotoxic effects in many types of cancer tissues. In a recent phase IIa study, GA exhibits a favourable safety profile. However, limited data are available concerning its interaction with cardiac ion channels. Heteromeric assembly of Kir2.x channels underlies the cardiac inwardly rectifying IK1 current which is responsible for the stabilization of the diastolic resting membrane potential...
July 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28345117/inwardly-rectifying-k-currents-in-cultured-oligodendrocytes-from-rat-optic-nerve-are-insensitive-to-ph
#19
Alberto Pérez-Samartín, Edith Garay, Juan Pablo H Moctezuma, Abraham Cisneros-Mejorado, María Victoria Sánchez-Gómez, Guadalupe Martel-Gallegos, Leticia Robles-Martínez, Manuel Canedo-Antelo, Carlos Matute, Rogelio O Arellano
Inwardly rectifying K(+) (Kir) channel expression signals at an advanced stage of maturation during oligodendroglial differentiation. Knocking down their expression halts the generation of myelin and produces severe abnormalities in the central nervous system. Kir4.1 is the main subunit involved in the tetrameric structure of Kir channels in glial cells; however, the precise composition of Kir channels expressed in oligodendrocytes (OLs) remains partially unknown, as participation of other subunits has been proposed...
March 27, 2017: Neurochemical Research
https://www.readbyqxmd.com/read/28331977/role-of-plasma-membrane-associated-akaps-for-the-regulation-of-cardiac-ik1-current-by-protein-kinase-a
#20
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...
May 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
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