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Fredrik Elinder, Michael Madeja, Hugo Zeberg, Peter Århem
The transmembrane voltage needed to open different voltage-gated K (Kv) channels differs by up to 50 mV from each other. In this study we test the hypothesis that the channels' voltage dependences to a large extent are set by charged amino-acid residues of the extracellular linkers of the Kv channels, which electrostatically affect the charged amino-acid residues of the voltage sensor S4. Extracellular cations shift the conductance-versus-voltage curve, G(V), by interfering with these extracellular charges...
October 18, 2016: Biophysical Journal
Jeroen I Stas, Elke Bocksteins, Camilla S Jensen, Nicole Schmitt, Dirk J Snyders
Enhancement of neuronal M-currents, generated through KV7.2-KV7.5 channels, has gained much interest for its potential in developing treatments for hyperexcitability-related disorders such as epilepsy. Retigabine, a KV7 channel opener, has proven to be an effective anticonvulsant and has recently also gained attention due to its neuroprotective properties. In the present study, we found that the auxiliary KCNE2 subunit reduced the KV7.2-KV7.3 retigabine sensitivity approximately 5-fold. In addition, using both mammalian expression systems and cultured hippocampal neurons we determined that low μM retigabine concentrations had 'off-target' effects on KV2...
October 13, 2016: Scientific Reports
Hongyuan Shen, Elke Bocksteins, Igor Kondrychyn, Dirk Snyders, Vladimir Korzh
The brain ventricular system is essential for neurogenesis and brain homeostasis. Its neuroepithelial lining effects these functions, but the underlying molecular pathways remain to be understood. We found that the K channels expressed in neuroepithelial cells determine formation of the ventricular system. The phenotype of a novel zebrafish mutant characterized by denudation of neuroepithelial lining of the ventricular system and hydrocephalus is mechanistically linked to Kcng4b, the homologue of the "silent" voltage-gated K channel alpha-subunit Kv6...
October 11, 2016: Development
Glenn Regnier, Elke Bocksteins, Waleed F Marei, Isabel Pintelon, Jean-Pierre Timmermans, Jo L M R Leroy, Dirk J Snyders
Electrically silent voltage-gated potassium (KvS) channel subunits (i.e. Kv5-Kv6 and Kv8-Kv9) do not form functional homotetrameric Kv channels, but co-assemble with Kv2 subunits, generating functional heterotetrameric Kv2--KvS channel complexes in which the KvS subunits modulate the Kv2 channel properties. Several KvS subunits are expressed in testis tissue but knowledge about their contribution to testis physiology is lacking. Here, we report that the targeted deletion of Kv6.4 in a transgenic mouse model (Kcng4-/-) causes male sterility as offspring from homozygous females were only obtained after mating with wild-type (WT) or heterozygous males...
September 28, 2016: Reproduction, Fertility, and Development
Robert H Cox, Samantha Fromme
We have shown that three components contribute to functional voltage gated K(+) (K v) currents in rat small mesenteric artery myocytes: (1) Kv1.2 plus Kv1.5 with Kvβ1.2 subunits, (2) Kv2.1 probably associated with Kv9.3 subunits, and (3) Kv7.4 subunits. To confirm and address subunit stoichiometry of the first two, we have compared the biophysical properties of K v currents in small mesenteric artery myocytes with those of Kv subunits heterologously expressed in HEK293 cells using whole cell voltage clamp methods...
September 16, 2016: Cell Biochemistry and Biophysics
Christoph Hönigsperger, Maximiliano J Nigro, Johan F Storm
The medial entorhinal cortex (mEC) is strongly involved in spatial navigation, memory, dementia and epilepsy. Although potassium channels shape neuronal activity, their roles in mEC are largely unknown. We used the new Kv2 blocker Guangxitoxin-1E (GTx, 10-100 nm) in rat brain slices to investigate Kv2 channel functions in mEC layer II stellate cells (SCs). These neurons project to the hippocampus and are thought to be grid cells representing space. Voltage clamp recordings from SCs nucleated patches showed that GTx inhibited a delayed rectifier K(+) current activating beyond -30 mV, but not transient, A-type current...
August 26, 2016: Journal of Physiology
Rym Hassiki, Alain J Labro, Zakaria Benlasfar, Cécile Vincke, Mahmoud Somia, Mohamed El Ayeb, Serge Muyldermans, Dirk J Snyders, Balkiss Bouhaouala-Zahar
Voltage-gated potassium (Kv) channels form cells repolarizing power and are commonly expressed in excitable cells. In non-excitable cells, Kv channels such as Kv2.1 are involved in cell differentiation and growth. Due to the involvement of Kv2.1 in several physiological processes, these channels are promising therapeutic targets. To develop Kv2.1 specific antibody-based channel modulators, we applied a novel approach and immunized a dromedary with heterologous Ltk- cells that overexpress the mouse Kv2.1 channel instead of immunizing with channel protein fragments...
June 16, 2016: International Journal of Biological Macromolecules
Yann Lanoiselée, Denis S Grebenkov
We propose the improved ergodicity and mixing estimators to identify nonergodic dynamics from a single particle trajectory. The estimators are based on the time-averaged characteristic function of the increments and can thus capture additional information on the process as compared to the conventional time-averaged mean-square displacement. The estimators are first investigated and validated for several models of anomalous diffusion, such as ergodic fractional Brownian motion and diffusion on percolating clusters, and nonergodic continuous-time random walks and scaled Brownian motion...
May 2016: Physical Review. E
Nicholas R Larson, Paul R Carlier, Aaron D Gross, Rafique M Islam, Ming Ma, Baonan Sun, Maxim M Totrov, Roopali Yadav, Jeffrey R Bloomquist
Potential targets for new vector control insecticides are nerve and muscle potassium channels. In this study, the activities of known potassium channel blockers (4-aminopyridine, quinidine, and tetraethylammonium) and the insecticide propoxur were compared to three experimental catechols and several other compounds against Anopheles gambiae and Aedes aegypti mosquitoes. Experimental catechol 1 was the most toxic experimental compound in all of the mortality assays conducted, but was at least 100-fold and 39-fold less toxic than propoxur against Ae...
June 1, 2016: Neurotoxicology
Da Hye Hong, Hongliang Li, Hye Won Kim, Han Sol Kim, Youn Kyoung Son, Se-Ran Yang, Jeong-Ran Park, Kwon-Soo Ha, Eun-Taek Han, Seok-Ho Hong, Amy L Firth, Sung Hun Na, Won Sun Park
This study investigated the alteration of voltage-dependent K(+) (Kv) channels in mesenteric arterial smooth muscle cells from control (Long-Evans Tokushima Otsuka [LETO]) and diabetic (Otsuka Long-Evans Tokushima Fatty [OLETF]) rats during the early and chronic phases of diabetes. We demonstrated alterations in the mesenteric Kv channels during the early and chronic phase of diabetes using the patch-clamp technique, the arterial tone measurement system, and RT-PCR in Long-Evans Tokushima (LETO; for control) and Otsuka Long-Evans Tokushima Fatty (OLETF; for diabetes) type 2 diabetic model rats...
September 2016: Clinical and Experimental Pharmacology & Physiology
Chin-Tsang Yang, Yuk-Man Leung, Sheng-Feng Hsu, Iona MacDonald, Mei-Ling Wang, Jaung-Geng Lin, Shih-Ya Hung, Yi-Hung Chen
Whole-cell patch-clamp recordings investigated the electrophysiological effects of 2'-hydroxy-4'-methoxyacetophenone (paeonol), one of the major components of Moutan Cortex, in hippocampal CA1 neurons and nucleus ambiguus (NA) neurons from neonatal rats as well as in lung epithelial H1355 cells expressing Kv2.1 or Kv1.2. Extracellular application of paeonol at 100μM did not significantly affect the spontaneous action potential frequency, whereas paeonol at 300μM increased the frequency of spontaneous action potentials in hippocampal CA1 neurons...
August 5, 2016: European Journal of Pharmacology
T T Zhou, L L Quan, L P Chen, T Du, K X Sun, J C Zhang, L Yu, Y Li, P Wan, L L Chen, B H Jiang, L H Hu, J Chen, X Shen
Kv2.1 as a voltage-gated potassium (Kv) channel subunit has a pivotal role in the regulation of glucose-stimulated insulin secretion (GSIS) and pancreatic β-cell apoptosis, and is believed to be a promising target for anti-diabetic drug discovery, although the mechanism underlying the Kv2.1-mediated β-cell apoptosis is obscure. Here, the small molecular compound, ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate (SP6616) was discovered to be a new Kv2...
2016: Cell Death & Disease
Federico Sesti
Reversible regulation of proteins by reactive oxygen species (ROS) is an important mechanism of neuronal plasticity. In particular, ROS have been shown to act as modulatory molecules of ion channels-which are key to neuronal excitability-in several physiological processes. However ROS are also fundamental contributors to aging vulnerability. When the level of excess ROS increases in the cell during aging, DNA is damaged, proteins are oxidized, lipids are degraded and more ROS are produced, all culminating in significant cell injury...
March 2016: Aging and Disease
Jun-Mei Lu, Chang-Ying Wang, Changlong Hu, Yan-Jia Fang, Yan-Ai Mei
GDF-15 (growth/differentiation factor 15) is a novel member of the TGF (transforming growth factor)-β superfamily that has critical roles in the central and peripheral nervous systems. We reported previously that GDF-15 increased delayed rectifier outward K(+) currents and Kv2.1 α subunit expression through TβRII (TGF-β receptor II) to activate Src kinase and Akt/mTOR (mammalian target of rapamycin) signalling in rat CGNs (cerebellar granule neurons). In the present study, we found that treatment of CGNs with GDF-15 for 24 h increased the intracellular Ca(2+) concentration ([Ca(2+)]i) in response to membrane depolarization, as determined by Ca(2+) imaging...
July 1, 2016: Biochemical Journal
J L Cadet, C Brannock, I N Krasnova, S Jayanthi, B Ladenheim, M T McCoy, D Walther, A Godino, M Pirooznia, R S Lee
Epigenetic consequences of exposure to psychostimulants are substantial but the relationship of these changes to compulsive drug taking and abstinence is not clear. Here, we used a paradigm that helped to segregate rats that reduce or stop their methamphetamine (METH) intake (nonaddicted) from those that continue to take the drug compulsively (addicted) in the presence of footshocks. We used that model to investigate potential alterations in global DNA hydroxymethylation in the nucleus accumbens (NAc) because neuroplastic changes in the NAc may participate in the development and maintenance of drug-taking behaviors...
April 5, 2016: Molecular Psychiatry
Autoosa Salari, Benjamin S Vega, Lorin S Milescu, Mirela Milescu
Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b-S4 "paddle motif," which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple toxin binding sites...
2016: Scientific Reports
Glenn Regnier, Elke Bocksteins, Gerda Van de Vijver, Dirk J Snyders, Pierre-Paul van Bogaert
Delayed rectifier voltage-gated K(+)(Kv) channels play an important role in the regulation of the electrophysiological properties of neurons. In mouse dorsal root ganglion (DRG) neurons, a large fraction of the delayed rectifier current is carried by both homotetrameric Kv2 channels and heterotetrameric channels consisting of Kv2 and silent Kv (KvS) subunits (i.e., Kv5-Kv6 and Kv8-Kv9). However, little is known about the contribution of Kv2-mediated currents during the postnatal development ofDRGneurons. Here, we report that the Stromatoxin-1 (ScTx)-sensitive fraction of the total outward K(+)current (IK) from mouseDRGneurons gradually decreased (~13%,P < 0...
March 2016: Physiological Reports
Melanie M Cobb, Daniel C Austin, Jon T Sack, James S Trimmer
No abstract text is available yet for this article.
March 11, 2016: Journal of Biological Chemistry
Shuai Zhang, Bo Liu, Zaiwen Fan, Dong Wang, Ying Liu, Jian Li, Ning Wang, Yi Liu, Bo Zhang
Hypoxic pulmonary hypertension (PH) is a common disease characterized by a disturbance to the balance of apoptosis and cell proliferation in pulmonary artery smooth muscle cells (PASMCs). The anti-apoptotic protein, survivin, has been observed to be upregulated in pulmonary arteries (PAs) of chronic hypoxia-induced PH rats. The present study aimed to investigate the therapeutic potential of sepantronium bromide (YM155), a selective survivin inhibitor, on hypoxic human PASMCs and examine the potential underlying mechanisms...
April 2016: Molecular Medicine Reports
Ivan Kopljar, Alessandro Grottesi, Tessa de Block, Jon D Rainier, Jan Tytgat, Alain J Labro, Dirk J Snyders
Marine ladder-shaped polyether toxins are implicated in neurological symptoms of fish-borne food poisonings. The toxin gambierol, produced by the marine dinoflagellate Gambierdiscus toxicus, belongs to the group of ladder-shaped polyether toxins and inhibits Kv3.1 channels with nanomolar affinity through a mechanism of gating modification. Binding determinants for gambierol localize at the lipid-exposed interface of the pore forming S5 and S6 segments, suggesting that gambierol binds outside of the permeation pathway...
August 2016: Neuropharmacology
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