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Sample records for atp-sensitive potassium channel

  1. Differential effects of sulfonylurea derivatives on vascular ATP-sensitive potassium channels.

    NARCIS (Netherlands)

    Engbersen, R.H.G.; Masereeuw, R.; Gestel, M.A. van; Siero, H.L.M.; Moons, M.M.; Smits, P.; Russel, F.G.M.

    2012-01-01

    Sulfonylurea drugs exert their insulinotropic action by inhibiting ATP-sensitive potassium channels in the pancreas. However, these channels are also expressed in myocardial and vascular smooth muscle, implicating possible detrimental cardiovascular effects. Aim of the present study was to investiga

  2. Altered ATP-sensitive potassium channels may underscore obesity-triggered increase in blood pressure

    Institute of Scientific and Technical Information of China (English)

    Li-hong FAN; Hong-yan TIAN; Ai-qun MA; Zhi HU; Jian-hua HUO; Yong-xiao CAO

    2008-01-01

    Aim:To determine whether ATP-sensitive potassium channels are altered in VSMC from arotas and mesenteric arteries of obese rat,and their association with obesity-triggered increase in blood pressure.Methods:Obesity was induced by 24 weeks of high-fat diet feeding in male Sprague-Dawley rats.Control rats were fed with standard laboratory rat chow.Blood pressure and body weight of these rats were measured every 4 weeks.At the end of 24 weeks,KATP channel-mediated relaxation responses in the aortas and mesenteric arteries,KATP channel current,and gene expression were examined,respectively.Results:Blood pres-sure and body weight were increased in rats fed with high-fat diet.KATP channel-mediated relaxation responses,currents,and KATP expression in VSMC of both aortas and mesenteric arteries were inhibited in these rats.Conclusion:Altered ATP-sensitive potassium channels in obese rats may underscore obesity-triggered increase in blood pressure.

  3. Neuroprotective role of ATP-sensitive potassium channels in cerebral ischemia

    Institute of Scientific and Technical Information of China (English)

    Hong-shuo SUN; Zhong-ping FENG

    2013-01-01

    ATP-sensitive potassium (KATP) channels are weak,inward rectifiers that couple metabolic status to cell membrane electrical activity,thus modulating many cellular functions.An increase in the ADP/ATP ratio opens KATP channels,leading to membrane hyperpolarization.KATP channels are ubiquitously expressed in neurons located in different regions of the brain,including the hippocampus and cortex.Brief hypoxia triggers membrane hyperpolarization in these central neurons.In vivo animal studies confirmed that knocking out the Kir6.2 subunit of the KATP channels increases ischemic infarction,and overexpression of the Kir6.2 subunit reduces neuronal injury from ischemic insults.These findings provide the basis for a practical strategy whereby activation of endogenous KATP channels reduces cellular damage resulting from cerebral ischemic stroke.KATP channel modulators may prove to be clinically useful as part of a combination therapy for stroke management in the future.

  4. The molecular mechanisms and pharmacotherapy of ATP-sensitive potassium channel gene mutations underlying neonatal diabetes

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    Veronica Lang

    2010-11-01

    Full Text Available Veronica Lang, Peter E LightDepartment of Pharmacology and Alberta Diabetes Institute, Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, CanadaAbstract: Neonatal diabetes mellitus (NDM is a monogenic disorder caused by mutations in genes involved in regulation of insulin secretion from pancreatic β-cells. Mutations in the KCNJ11 and ABCC8 genes, encoding the adenosine triphosphate (ATP-sensitive potassium (KATP channel Kir6.2 and SUR1 subunits, respectively, are found in ~50% of NDM patients. In the pancreatic β-cell, KATP channel activity couples glucose metabolism to insulin secretion via cellular excitability and mutations in either KCNJ11 or ABCC8 genes alter KATP channel activity, leading to faulty insulin secretion. Inactivation mutations decrease KATP channel activity and stimulate excessive insulin secretion, leading to hyperinsulinism of infancy. In direct contrast, activation mutations increase KATP channel activity, resulting in impaired insulin secretion, NDM, and in severe cases, developmental delay and epilepsy. Many NDM patients with KCNJ11 and ABCC8 mutations can be successfully treated with sulfonylureas (SUs that inhibit the KATP channel, thus replacing the need for daily insulin injections. There is also strong evidence indicating that SU therapy ameliorates some of the neurological defects observed in patients with more severe forms of NDM. This review focuses on the molecular and cellular mechanisms of mutations in the KATP channel that underlie NDM. SU pharmacogenomics is also discussed with respect to evaluating whether patients with certain KATP channel activation mutations can be successfully switched to SU therapy.Keywords: neonatal diabetes, KCNJ11, ABCC8, ATP-sensitive potassium channels

  5. Inhibition of mitochondrial permeability transition pore contributes to the neuroprotection induced by activation of mitochondrial ATP-sensitive potassium channel

    Institute of Scientific and Technical Information of China (English)

    Li-pingWU; FangSHEN; QiangXIA

    2004-01-01

    AIM: To investigate whether the neuroprotection via activating mitochondrial ATP-sensitive potassium channel (mitoKTP) is mediated by the inhibition of mitochondrial permeability transition pore (MPTP). METHODS: Adult male Sprague-Dawleyrats were undergoing 90 min of middle cerebral artery occlusion(MCAO) by introducing a nylon monofilament through the external

  6. Localization and function of ATP-sensitive potassium channels in human skeletal muscle

    DEFF Research Database (Denmark)

    Nielsen, Jens Jung; Kristensen, Michael; Hellsten, Ylva;

    2003-01-01

    The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique...

  7. Intracellular signalling mechanism responsible for modulation of sarcolemmal ATP-sensitive potassium channels by nitric oxide in ventricular cardiomyocytes

    OpenAIRE

    Zhang, DM; Chai, Y.; Erickson, JR; Brown, JH; Bers, DM; Lin, YF

    2014-01-01

    Key points: Both the ATP-sensitive potassium (KATP) channel and the gaseous messenger nitric oxide (NO) play fundamental roles in protecting the heart from injuries related to ischaemia. NO has previously been suggested to modulate cardiac KATP channels; however, the underlying mechanism remains largely unknown. In this study, by performing electrophysiological and biochemical assays, we demonstrate that NO potentiation of KATP channel activity in ventricular cardiomyocytes is prevented by ph...

  8. Effects of mitochondrial ATP-sensitive potassium channels on the proliferation and secretion of human airway smooth muscle cells.

    OpenAIRE

    2014-01-01

    Bronchial asthma is the common chronic inflammatory disease and is characterized by chronic airway inflammation, airway remodeling, and airway hyperreactivity (AHR). Aim of this study was to investigate the effects of mitochondrial ATP-sensitive potassium channels (MitoKATP) on the proliferation and secretion of human airway smooth muscle cells (HASMCs). HASMCs were treated with the serum from asthmatic patients to establish HASMCs asthma model of passive sensitization. Rhodamine 123 (R-123) ...

  9. Sarcolemmal ATP-sensitive potassium channel protects cardiac myocytes against lipopolysaccharide-induced apoptosis.

    Science.gov (United States)

    Zhang, Xiaohui; Zhang, Xiaohua; Xiong, Yiqun; Xu, Chaoying; Liu, Xinliang; Lin, Jian; Mu, Guiping; Xu, Shaogang; Liu, Wenhe

    2016-09-01

    The sarcolemmal ATP-sensitive K+ (sarcKATP) channel plays a cardioprotective role during stress. However, the role of the sarcKATP channel in the apoptosis of cardiomyocytes and association with mitochondrial calcium remains unclear. For this purpose, we developed a model of LPS-induced sepsis in neonatal rat cardiomyocytes (NRCs). The TUNEL assay was performed in order to detect the apoptosis of cardiac myocytes and the MTT assay was performed to determine cellular viability. Exposure to LPS significantly decreased the viability of the NRCs as well as the expression of Bcl-2, whereas it enhanced the activity and expression of the apoptosis-related proteins caspase-3 and Bax, respectively. The sarcKATP channel blocker, HMR-1098, increased the apoptosis of NRCs, whereas the specific sarcKATP channel opener, P-1075, reduced the apoptosis of NRCs. The mitochondrial calcium uniporter inhibitor ruthenium red (RR) partially inhibited the pro-apoptotic effect of HMR-1098. In order to confirm the role of the sarcKATP channel, we constructed a recombinant adenovirus vector carrying the sarcKATP channel mutant subunit Kir6.2AAA to inhibit the channel activity. Kir6.2AAA adenovirus infection in NRCs significantly aggravated the apoptosis of myocytes induced by LPS. Elucidating the regulatory mechanisms of the sarcKATP channel in apoptosis may facilitate the development of novel therapeutic targets and strategies for the management of sepsis and cardiac dysfunction. PMID:27430376

  10. A role for ATP-sensitive potassium channels in the anticonvulsant effects of triamterene in mice.

    Science.gov (United States)

    Shafaroodi, Hamed; Barati, Saghar; Ghasemi, Mehdi; Almasirad, Ali; Moezi, Leila

    2016-03-01

    There are reports indicating that diuretics including chlorothiazide, furosemide, ethacrynic acid, amiloride and bumetanide can have anticonvulsant properties. Intracellular acidification appears to be a mechanism for the anticonvulsant action of some diuretics. This study was conducted to investigate whether or not triamterene, a K(+)-sparing diuretic, can generate protection against seizures induced by intravenous or intraperitoneal pentylenetetrazole (PTZ) models. And to see if, triamterene can withstand maximal electroshock seizure (MES) in mice. We also investigated to see if there is any connection between triamterene's anti-seizure effect and ATP-sensitive K(+) (KATP) channels. Five days triamterene oral administration (10, 20 and 40 mg/kg), significantly increased clonic seizure threshold which was induced by intravenous pentylenetetrazole. Triamterene (10, 20 and 40 mg/kg) treatment also increased the latency of clonic seizure and decreased its frequency in intraperitoneal PTZ model. Administration of triamterene (20 mg/kg) also decreased the incidence of tonic seizure in MES-induced seizure. Co-administration of a KATP sensitive channel blocker, glibenclamide, in the 6th day, 60 min before intravenous PTZ blocked triamterene's anticonvulsant effect. A KATP sensitive channel opener, diazoxide, enhanced triamterene's anti-seizure effect in both intravenous PTZ or MES seizure models. At the end, triamterene exerts anticonvulsant effect in 3 seizure models of mice including intravenous PTZ, intraperitoneal PTZ and MES. The anti-seizure effect of triamterene probably is induced through KATP channels. PMID:26855365

  11. Mouth breathing increases the pentylenetetrazole-induced seizure threshold in mice: a role for ATP-sensitive potassium channels.

    Science.gov (United States)

    Niaki, Seyed Esfandiar Akhavan; Shafaroodi, Hamed; Ghasemi, Mehdi; Shakiba, Bijan; Fakhimi, Ali; Dehpour, Ahamd Reza

    2008-08-01

    Nasal obstruction and consequent mouth breathing have been shown to change the acid-base balance, producing respiratory acidosis. Additionally, there exists a large body of evidence maintaining that acidosis affects the activity of ATP-sensitive potassium (K(ATP)) channels, which play a crucial role in the function of the central nervous system (CNS), for example, in modulating seizure threshold. Thus, in the study described here, we examined whether mouth breathing, induced by surgical ligation of nostrils, could affect the seizure threshold induced by pentylenetetrazole in male NMRI mice. Using the selective K(ATP) channel opener (diazoxide) and blocker (glibenclamide), we also evaluated the possible role of K(ATP) channels in this process. Our data revealed that seizure threshold was increased 6 to 72 hours after nasal obstruction, reaching a peak 48 hours afterward, compared with either control or sham-operated mice (Pmouth breathing, which could result in respiratory acidosis, increases seizure threshold in mice and K(ATP) channels may play a role in this effect.

  12. Nitric oxide activates ATP-sensitive potassium channels in mammalian sensory neurons: action by direct S-nitrosylation

    Directory of Open Access Journals (Sweden)

    Kwok Wai-Meng

    2009-03-01

    Full Text Available Abstract Background ATP-sensitive potassium (KATP channels in neurons regulate excitability, neurotransmitter release and mediate protection from cell-death. Furthermore, activation of KATP channels is suppressed in DRG neurons after painful-like nerve injury. NO-dependent mechanisms modulate both KATP channels and participate in the pathophysiology and pharmacology of neuropathic pain. Therefore, we investigated NO modulation of KATP channels in control and axotomized DRG neurons. Results Cell-attached and cell-free recordings of KATP currents in large DRG neurons from control rats (sham surgery, SS revealed activation of KATP channels by NO exogenously released by the NO donor SNAP, through decreased sensitivity to [ATP]i. This NO-induced KATP channel activation was not altered in ganglia from animals that demonstrated sustained hyperalgesia-type response to nociceptive stimulation following spinal nerve ligation. However, baseline opening of KATP channels and their activation induced by metabolic inhibition was suppressed by axotomy. Failure to block the NO-mediated amplification of KATP currents with specific inhibitors of sGC and PKG indicated that the classical sGC/cGMP/PKG signaling pathway was not involved in the activation by SNAP. NO-induced activation of KATP channels remained intact in cell-free patches, was reversed by DTT, a thiol-reducing agent, and prevented by NEM, a thiol-alkylating agent. Other findings indicated that the mechanisms by which NO activates KATP channels involve direct S-nitrosylation of cysteine residues in the SUR1 subunit. Specifically, current through recombinant wild-type SUR1/Kir6.2 channels expressed in COS7 cells was activated by NO, but channels formed only from truncated isoform Kir6.2 subunits without SUR1 subunits were insensitive to NO. Further, mutagenesis of SUR1 indicated that NO-induced KATP channel activation involves interaction of NO with residues in the NBD1 of the SUR1 subunit. Conclusion NO

  13. Hypoxic pulmonary hypertension and novel ATP-sensitive potassium channel opener: the new hope on the horizon

    Institute of Scientific and Technical Information of China (English)

    Yu JIN; Wei-ping XIE; Hong WANG

    2012-01-01

    Hypoxic pulmonary hypertension (HPH) is a syndrome characterized by the increase of pulmonary vascular tone and the structural remodeling of peripheral pulmonary arteries.The aim of specific therapies for hypoxic pulmonary hypertension is to reduce pulmonary vascular resistance,reverse pulmonary vascular remodeling,and thereby improving right ventricular function.Iptakalim,a lipophilic para-amino compound with a low molecular weight,has been demonstrated to be a new selective ATP-sensitive potassium (KATP) channel opener via pharmacological,electrophysiological,biochemical studies,and receptor binding tests.In hypoxia-induced animal models,iptakalim decreases the elevated mean pressure in pulmonary arteries,and attenuates remodeling in the right ventricle,pulmonary arteries and airways.Furthermore,iptakalim has selective antihypertensive effects,selective vasorelaxation effects on smaller arteries,and protective effects on endothelial cells,but no effects on the central nervous,respiratory,digestive or endocrine systems at therapeutic dose.Our previous studies demonstrated that iptakalim inhibited the effects of endothelin-1,reduced the intracellular calcium concentration and inhibited the proliferation of pulmonary artery smooth muscle cells.Since iptakalim has been shown safe and effective in both experimental animal models and phase I clinical trials,it can be a potential candidate of HPH in the future.

  14. Taurine blocks ATP-sensitive potassium channels of rat skeletal muscle fibres interfering with the sulphonylurea receptor

    OpenAIRE

    Tricarico, Domenico; Barbieri, Mariagrazia; Camerino, Diana Conte

    2000-01-01

    Taurine is a sulphonic aminoacid present in high amounts in various tissues including cardiac and skeletal muscles showing different properties such as antioxidative, antimyotonic and anti-schaemic effects. The cellular mechanism of action of taurine is under investigation and appears to involve the interaction of the sulphonic aminoacid with several ion channels.Using the patch-clamp technique we studied the effects of taurine in rat skeletal muscle fibres on ATP-sensitive K+ channel (KATP) ...

  15. Effects of mitochondrial ATP-sensitive potassium channels on the proliferation and secretion of human airway smooth muscle cells.

    Directory of Open Access Journals (Sweden)

    Changbiao Chen

    2014-12-01

    Full Text Available Bronchial asthma is the common chronic inflammatory disease and is characterized by chronic airway inflammation, airway remodeling, and airway hyperreactivity (AHR. Aim of this study was to investigate the effects of mitochondrial ATP-sensitive potassium channels (MitoKATP on the proliferation and secretion of human airway smooth muscle cells (HASMCs. HASMCs were treated with the serum from asthmatic patients to establish HASMCs asthma model of passive sensitization. Rhodamine 123 (R-123 and 2,7-dichloro-dihydrofluorescein diacetate (DCFH-DA fluorescence staining were used to detect mitochondrial membrane potential (Δψm and the content of reactive oxygen species (ROS in the cells, respectively. The cell counting was used to detect cell proliferation, and RT-PCR was used to detect the expression of TGF-β1 mRNA. In the normal + Diazoxide group, the fluorescence intensity of R-123, ROS content, cell proliferation and TGF-β1 expression were enhanced, compared with the normal control group (p<0.05. There were no significant differences between the normal + 5-hydroxydecanoate (5-HD group and the normal control group. In the asthma model control group, the fluorescence intensity of R-123, ROS content, cell proliferation and TGF-β1 expression were enhanced, compared with normal control group, (p<0.05. The aforementioned indices were enhanced in the asthma model + Diazoxide group, when compared with the asthma model control group, whereas these indices were attenuated in the asthma model + 5-HD group, when compared with the asthma model control group (p<0.05. In conclusion, asthma could activate MitoKATP channels in HASMCs, promote HASMC proliferation and TGF-β1 expression.

  16. Intracellular signalling mechanism responsible for modulation of sarcolemmal ATP-sensitive potassium channels by nitric oxide in ventricular cardiomyocytes.

    Science.gov (United States)

    Zhang, Dai-Min; Chai, Yongping; Erickson, Jeffrey R; Brown, Joan Heller; Bers, Donald M; Lin, Yu-Fung

    2014-03-01

    The ATP-sensitive potassium (KATP) channels are crucial for stress adaptation in the heart. It has previously been suggested that the function of KATP channels is modulated by nitric oxide (NO), a gaseous messenger known to be cytoprotective; however, the underlying mechanism remains poorly understood. Here we sought to delineate the intracellular signalling mechanism responsible for NO modulation of sarcolemmal KATP (sarcKATP) channels in ventricular cardiomyocytes. Cell-attached patch recordings were performed in transfected human embryonic kidney (HEK) 293 cells and ventricular cardiomyocytes freshly isolated from adult rabbits or genetically modified mice, in combination with pharmacological and biochemical approaches. Bath application of the NO donor NOC-18 increased the single-channel activity of Kir6.2/SUR2A (i.e., the principal ventricular-type KATP) channels in HEK293 cells, whereas the increase was abated by KT5823 [a selective cGMP-dependent protein kinase (PKG) inhibitor], mercaptopropionyl glycine [MPG; a reactive oxygen species (ROS) scavenger], catalase (an H2O2-degrading enzyme), myristoylated autocamtide-2 related inhibitory peptide (mAIP) selective for Ca2+ / calmodulin-dependent protein kinase II (CaMKII) and U0126 [an extracellular signal-regulated protein kinase 1/2 (ERK1/2) inhibitor], respectively. The NO donors NOC-18 and N-(2-deoxy-α,β-d-glucopyranose-2-)-N2-acetyl-S-nitroso-d,l-penicillaminamide (glycol-SNAP-2) were also capable of stimulating native sarcKATP channels preactivated by the channel opener pinacidil in rabbit ventricular myocytes, through reducing the occurrence and the dwelling time of the long closed states whilst increasing the frequency of channel opening; in contrast, all these changes were reversed in the presence of inhibitors selective for soluble guanylyl cyclase (sGC), PKG, calmodulin, CaMKII or ERK1/2. Mimicking the action of NO donors, exogenous H2O2 potentiated pinacidil-preactivated sarcKATP channel activity in

  17. SENSITIVE EFFECTS OF POTASSIUM AND CALCIUM CHANNEL BLOCKING AND ATP-SENSITIVE POTASSIUM CHANNEL ACTIVATORS ON SEMINAL VESICLE SMOOTH MUSCLE CONTRACTIONS

    Directory of Open Access Journals (Sweden)

    H SADRAEI

    2000-12-01

    Full Text Available Background. Seminal vesicle smooth muscle contraction is mediated through sympathetic and parasympathetic neurons activity. Although seminal vesicle plays an important role in male fertility, but little attention is given to mechanism involved in contraction of this organ.
    Methods. In this study effects of drugs which activate ATP - sensitive K channels and blockers of K and Ca channels were examined on contraction of guinea - pig isolated seminal vesicle due to electrical filled stimulation (EFS, noradrenaline, carbachol and KCI.
    Results. The K channel blocker tetraethyl ammonium potentate the EFS responses at all frequencies, while, the ATP - sensitive K channel inhibitor glibenclamide and the K channel opener levcromakalim, diazoxide, minoxidil and Ca channel blocker nifedipine all had relaxant effect on guinea - pig seminal vesicle.
    Discussion. This study indicate that activities of K and Ca channels is important in regulation of seminal vesicle contraction due to nerve stimulation, noradrenaline or carbachol.

  18. Dopamine midbrain neurons in health and Parkinson's disease: emerging roles of voltage-gated calcium channels and ATP-sensitive potassium channels.

    Science.gov (United States)

    Dragicevic, E; Schiemann, J; Liss, B

    2015-01-22

    Dopamine (DA) releasing midbrain neurons are essential for multiple brain functions, such as voluntary movement, working memory, emotion and cognition. DA midbrain neurons within the substantia nigra (SN) and the ventral tegmental area (VTA) exhibit a variety of distinct axonal projections and cellular properties, and are differentially affected in diseases like schizophrenia, attention deficit hyperactivity disorder, and Parkinson's disease (PD). Apart from having diverse functions in health and disease states, DA midbrain neurons display distinct electrical activity patterns, crucial for DA release. These activity patterns are generated and modulated by specific sets of ion channels. Recently, two ion channels have been identified, not only contributing to these activity patterns and to functional properties of DA midbrain neurons, but also seem to render SN DA neurons particularly vulnerable to degeneration in PD and its animal models: L-type calcium channels (LTCCs) and ATP-sensitive potassium channels (K-ATPs). In this review, we focus on the emerging physiological and pathophysiological roles of these two ion channels (and their complex interplay with other ion channels), particularly in highly vulnerable SN DA neurons, as selective degeneration of these neurons causes the major motor symptoms of PD.

  19. Molecular determinants of ATP-sensitive potassium channel MgATPase activity: diabetes risk variants and diazoxide sensitivity.

    Science.gov (United States)

    Fatehi, Mohammad; Carter, Chris R J; Youssef, Nermeen; Hunter, Beth E; Holt, Andrew; Light, Peter E

    2015-01-01

    ATP-sensitive K(+) (KATP) channels play an important role in insulin secretion. KATP channels possess intrinsic MgATPase activity that is important in regulating channel activity in response to metabolic changes, although the precise structural determinants are not clearly understood. Furthermore, the sulfonylurea receptor 1 (SUR1) S1369A diabetes risk variant increases MgATPase activity, but the molecular mechanisms remain to be determined. Therefore, we hypothesized that residue-residue interactions between 1369 and 1372, predicted from in silico modelling, influence MgATPase activity, as well as sensitivity to the clinically used drug diazoxide that is known to increase MgATPase activity. We employed a point mutagenic approach with patch-clamp and direct biochemical assays to determine interaction between residues 1369 and 1372. Mutations in residues 1369 and 1372 predicted to decrease the residue interaction elicited a significant increase in MgATPase activity, whereas mutations predicted to possess similar residue interactions to wild-type (WT) channels elicited no alterations in MgATPase activity. In contrast, mutations that were predicted to increase residue interactions resulted in significant decreases in MgATPase activity. We also determined that a single S1369K substitution in SUR1 caused MgATPase activity and diazoxide pharmacological profiles to resemble those of channels containing the SUR2A subunit isoform. Our results provide evidence, at the single residue level, for a molecular mechanism that may underlie the association of the S1369A variant with type 2 diabetes. We also show a single amino acid difference can account for the markedly different diazoxide sensitivities between channels containing either the SUR1 or SUR2A subunit isoforms. PMID:26181369

  20. Mice lacking sulfonylurea receptor 2 (SUR2) ATP sensitive potassium channels are resistant to acute cardiovascular stress

    OpenAIRE

    Stoller, Douglas; Kakkar, Rahul; Smelley, Matthew; Chalupsky, Karel; Earley, Judy U.; Shi, Nian-Qing; Makielski, Jonathan C.; McNally, Elizabeth M.

    2007-01-01

    Adenosine triphosphate sensitive potassium (KATP) channels are thought to mediate stress response by sensing intracellular ATP concentration. Cardiomyocyte KATP channels are composed of the pore-forming Kir6.2 subunit and the regulatory sulfonylurea receptor 2 (SUR2). We studied the response to acute isoproterenol in SUR2 null mice as a model of acute adrenergic stress and found that the episodic coronary vasospasm observed at baseline in SUR2 null mice was alleviated. Similar results were ob...

  1. Activation of Mitochondrial Uncoupling Protein 4 and ATP-Sensitive Potassium Channel Cumulatively Decreases Superoxide Production in Insect Mitochondria.

    Science.gov (United States)

    Slocińska, Malgorzata; Rosinski, Grzegorz; Jarmuszkiewicz, Wieslawa

    2016-01-01

    It has been evidenced that mitochondrial uncoupling protein 4 (UCP4) and ATP-regulated potassium channel (mKATP channel) of insect Gromphadorhina coqereliana mitochondria decrease superoxide anion production. We elucidated whether the two energy-dissipating systems work together on a modulation of superoxide level in cockroach mitochondria. Our data show that the simultaneous activation of UCP4 by palmitic acid and mKATP channel by pinacidil revealed a cumulative effect on weakening mitochondrial superoxide formation. The inhibition of UCP4 by GTP (and/or ATP) and mKATP channel by ATP elevated superoxide production. These results suggest a functional cooperation of both energy-dissipating systems in protection against oxidative stress in insects.

  2. Activation of ATP-sensitive potassium channels enhances DMT1-mediated iron uptake in SK-N-SH cells in vitro

    Science.gov (United States)

    Du, Xixun; Xu, Huamin; Shi, Limin; Jiang, Zhifeng; Song, Ning; Jiang, Hong; Xie, Junxia

    2016-01-01

    Iron importer divalent metal transporter 1 (DMT1) plays a crucial role in the nigal iron accumulation in Parkinson’s disease (PD). Membrane hyperpolarization is one of the factors that could affect its iron transport function. Besides iron, selective activation of the ATP-sensitive potassium (KATP) channels also contributes to the vulnerability of dopaminergic neurons in PD. Interestingly, activation of KATP channels could induce membrane hyperpolarization. Therefore, it is of vital importance to study the effects of activation of KATP channels on DMT1-mediated iron uptake function. In the present study, activation of KATP channels by diazoxide resulted in the hyperpolarization of the membrane potential and increased DMT1-mediated iron uptake in SK-N-SH cells. This led to an increase in intracellular iron levels and a subsequent decrease in the mitochondrial membrane potential and an increase in ROS production. Delayed inactivation of the Fe2+-evoked currents by diazoxide was recorded by patch clamp in HEK293 cells, which demonstrated that diazoxide could prolonged DMT1-facilitated iron transport. While inhibition of KATP channels by glibenclamide could block ferrous iron influx and the subsequent cell damage. Overexpression of Kir6.2/SUR1 resulted in an increase in iron influx and intracellular iron levels, which was markedly increased after diazoxide treatment. PMID:27646472

  3. Diazoxide Attenuates Postresuscitation Brain Injury in a Rat Model of Asphyxial Cardiac Arrest by Opening Mitochondrial ATP-Sensitive Potassium Channels.

    Science.gov (United States)

    Wu, Haidong; Wang, Peng; Li, Yi; Wu, Manhui; Lin, Jiali; Huang, Zitong

    2016-01-01

    Objective. We investigated whether and how diazoxide can attenuate brain injury after cardiopulmonary resuscitation (CPR) by selective opening of mitochondrial ATP-sensitive potassium (mitoKATP) channels. Methods. Adult male Sprague-Dawley rats with induced cerebral ischemia (n = 10 per group) received an intraperitoneal injection of 0.1% dimethyl sulfoxide (1 mL; vehicle group), diazoxide (10 mg/kg; DZ group), or diazoxide (10 mg/kg) plus 5-hydroxydecanoate (5 mg/kg; DZ + 5-HD group) 30 min after CPR. The control group (sham group, n = 5) underwent sham operation, without cardiac arrest. Mitochondrial respiratory control rate (RCR) was determined. Brain cell apoptosis was assessed using TUNEL staining. Expression of Bcl-2, Bax, and protein kinase C epsilon (PKCε) in the cerebral cortex was determined by Western blotting and immunohistochemistry. Results. The neurological deficit scores (NDS) in the vehicle group decreased significantly at 24 h and 48 h after CPR. Diazoxide significantly improved NDS and mitochondrial RCR after CPR at both time points; 5-HD cotreatment abolished these effects. Diazoxide decreased TUNEL-positive cells following CPR, upregulated Bcl-2 and PKCε, downregulated Bax, and increased the Bcl-2/Bax ratio; 5-HD cotreatment reversed these effects. Conclusions. Diazoxide attenuates postresuscitation brain injury, protects mitochondrial function, inhibits brain cell apoptosis, and activates the PKC pathway by opening mitoKATP channels. PMID:27648441

  4. Ocular Hypotensive Effects of the ATP-Sensitive Potassium Channel Opener Cromakalim in Human and Murine Experimental Model Systems.

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    Uttio Roy Chowdhury

    Full Text Available Elevated intraocular pressure (IOP is the most prevalent and only treatable risk factor for glaucoma, a leading cause of irreversible blindness worldwide. Unfortunately, all current therapeutics used to treat elevated IOP and glaucoma have significant and sometimes irreversible side effects necessitating the development of novel compounds. We evaluated the IOP lowering ability of the broad spectrum KATP channel opener cromakalim. Cultured human anterior segments when treated with 2 μM cromakalim showed a decrease in pressure (19.33 ± 2.78 mmHg at 0 hours to 13.22 ± 2.64 mmHg at 24 hours; p<0.001 when compared to vehicle treated controls (15.89 ± 5.33 mmHg at 0 h to 15.56 ± 4.88 mmHg at 24 hours; p = 0.89. In wild-type C57BL/6 mice, cromakalim reduced IOP by 18.75 ± 2.22% compared to vehicle treated contralateral eyes (17.01 ± 0.32 mmHg at 0 hours to 13.82 ± 0.37 mmHg at 24 hours; n = 10, p = 0.002. Cromakalim demonstrated an additive effect when used in conjunction with latanoprost free acid, a common ocular hypotensive drug prescribed to patients with elevated IOP. To examine KATP channel subunit specificity, Kir6.2(-/- mice were treated with cromakalim, but unlike wild-type animals, no change in IOP was noted. Histologic analysis of treated and control eyes in cultured human anterior segments and in mice showed similar cell numbers and extracellular matrix integrity within the trabecular meshwork, with no disruptions in the inner and outer walls of Schlemm's canal. Together, these studies suggest that cromakalim is a potent ocular hypotensive agent that lowers IOP via activation of Kir6.2 containing KATP channels, its effect is additive when used in combination with the commonly used glaucoma drug latanoprost, and is not toxic to cells and tissues of the aqueous humor outflow pathway, making it a candidate for future therapeutic development.

  5. Protective effects of iptakalim, a novel ATP-sensitive potassium channel opener, on global cerebral ischemia-evoked insult in gerbils

    Institute of Scientific and Technical Information of China (English)

    Hua CHEN; Yong YANG; Hong-hong YAO; Xing-chun TANG; Jian-hua DING; Hai WANG; Gang HU

    2006-01-01

    Aim: To investigate the protective role of iptakalim, a novel ATP sensitive potassium channel opener, on global cerebral ischemia-evoked insult in gerbils and glutamate-induced PC 12 cell injury. Methods: Global cerebral ischemia was induced by occluding the bilateral common carotid arteries in gerbils for 5 min. The open field maze and T-maze were employed to investigate the experimental therapeutic value of iptakalim on ischemic brain insult (n=8). The pyramidal cells in the hippocampal CA1 regions were counted to assess the protective effects of iptakalim. Glutamate released from the gerbil hippocampus and PC 12 cells were determined by HPLC. Intracellular calcium was measured by Fluo-3 AM with A Bio-Rad Radiance 2100TM confocal system in conjunction with a Nikon TE300 microscope. Astrocyte glutamate uptake measurements were determined by liquid scintillation counting. Results: Iptakalim (0.5-4.0 mg/kg per day, ip) could reduce the high locomotor activity evoked by ischemia and improve global cerebral ischemia-induced working memory impairments. Histological studies revealed that iptakalim could increase the survival neuron in the hippocampus CA1 zone in a dose-dependent manner. Moreover, iptakalim could reverse ischemia-evoked increases of glutamate in the hippocampus of gerbils. In an in vitro study, iptakalim protected PC 12 cells against glutamate-induced excitotoxicity, reduced the [Ca2+]; increases, and enhanced the glutamate uptake activity of primary cultured astrocytes. Conclusions: Iptakalim plays a key role in preventing global cerebral ischemia-evoked insults in gerbils and glutamate-induced PC12 cell injury by anti-excitotoxicity. Iptakalim might be a promising novel candidate for the prevention and/or treatment of stroke.

  6. Phosphatidylinositol 4,5-biphosphate (PIP2) modulates syntaxin-1A binding to sulfonylurea receptor 2A to regulate cardiac ATP-sensitive potassium (KATP) channels.

    Science.gov (United States)

    Xie, Li; Liang, Tao; Kang, Youhou; Lin, Xianguang; Sobbi, Roozbeh; Xie, Huanli; Chao, Christin; Backx, Peter; Feng, Zhong-Ping; Shyng, Show-Ling; Gaisano, Herbert Y

    2014-10-01

    Cardiac sarcolemmal syntaxin (Syn)-1A interacts with sulfonylurea receptor (SUR) 2A to inhibit ATP-sensitive potassium (KATP) channels. Phosphatidylinositol 4,5-bisphosphate (PIP2), a ubiquitous endogenous inositol phospholipid, known to bind Kir6.2 subunit to open KATP channels, has recently been shown to directly bind Syn-1A in plasma membrane to form Syn-1A clusters. Here, we sought to determine whether the interaction between Syn-1A and PIP2 interferes with the ability of Syn-1A to bind SUR2A and inhibit KATP channel activity. We found that PIP2 dose-dependently reduced SUR2A binding to GST-Syn-1A by in vitro pulldown assays. FRET studies in intact cells using TIRFM revealed that increasing endogenous PIP2 levels led to increased Syn-1A (-EGFP) cluster formation and a severe reduction in availability of Syn-1A molecules to interact with SUR2A (-mCherry) molecules outside the Syn-1A clusters. Correspondingly, electrophysiological studies employing SUR2A/Kir6.2-expressing HEK cells showed that increasing endogenous or exogenous PIP2 diminished the inhibitory effect of Syn-1A on KATP currents. The physiological relevance of these findings was confirmed by ability of exogenous PIP2 to block exogenous Syn-1A inhibition of cardiac KATP currents in inside-out patches of mouse ventricular myocytes. The effect of PIP2 on physical and functional interactions between Syn-1A and KATP channels is specific and not observed with physiologic concentrations of other phospholipids. To unequivocally demonstrate the specificity of PIP2 interaction with Syn-1A and its impact on KATP channel modulation by Syn-1A, we employed a PIP2-insensitive Syn-1A-5RK/A mutant. The Syn-1A-5RK/A mutant retains the ability to interact with SUR2A in both in vitro binding and in vivo FRET assays, although as expected the interaction is no longer disrupted by PIP2. Interestingly, at physiological PIP2 concentrations, Syn-1A-5RK/A inhibited KATP currents to a greater extent than Syn-1A-WT, indicating

  7. ATP sensitive potassium channels in the skeletal muscle functions : involvement of the KCNJ11(Kir6.2 gene in the determination of Warner Bratzer shear force

    Directory of Open Access Journals (Sweden)

    Domenico eTricarico

    2016-05-01

    Full Text Available The ATP-sensitive K+-channels (KATP are distributed in the tissues coupling metabolism with K+ ions efflux. KATP subunits are encoded by KCNJ8 (Kir6.1, KCNJ11 (Kir6.2, ABCC8 (SUR1 and ABCC9 (SUR2 genes, alternative RNA splicing give rise to SUR variants that confer distinct physiological properties on the channel. An high expression/activity of the sarco-KATP channel is observed in various rat fast-twitch muscles, characterized by elevated muscle strength, while a low expression/activity is observed in the slow-twitch muscles characterized by reduced strength and frailty. Down-regulation of the KATP subunits of fast-twitch fibres is found in conditions characterized by weakness and frailty. KCNJ11 gene knockout mice have reduced glycogen, lean phenotype, lower body fat, and weakness. KATP channel is also a sensor of muscle atrophy. The KCNJ11 gene is located on BTA15, close to a QTL for meat tenderness, it has also a role in glycogen storage, a key mechanism of the postmortem transformation of muscle into meat. The role of KCNJ11 gene in muscle function may underlie an effect of KCNJ11 genotypes on meat tenderness, as recently reported. The fiber phenotype and genotype are important in livestock production science. Quantitative traits including meat production and quality are influenced both by environment and genes. Molecular markers can play an important role in the genetic improvement of animals through breeding strategies. Many factors influence the muscle Warner-Bratzler shear force including breed, age, feeding, the biochemical and functional parameters. The role of KCNJ11gene and related genes on muscle tenderness will be discussed in the present review.

  8. Loss of ATP-Sensitive Potassium Channel Surface Expression in Heart Failure Underlies Dysregulation of Action Potential Duration and Myocardial Vulnerability to Injury.

    Science.gov (United States)

    Gao, Zhan; Sierra, Ana; Zhu, Zhiyong; Koganti, Siva Rama Krishna; Subbotina, Ekaterina; Maheshwari, Ankit; Anderson, Mark E; Zingman, Leonid V; Hodgson-Zingman, Denice M

    2016-01-01

    The search for new approaches to treatment and prevention of heart failure is a major challenge in medicine. The adenosine triphosphate-sensitive potassium (KATP) channel has been long associated with the ability to preserve myocardial function and viability under stress. High surface expression of membrane KATP channels ensures a rapid energy-sparing reduction in action potential duration (APD) in response to metabolic challenges, while cellular signaling that reduces surface KATP channel expression blunts APD shortening, thus sacrificing energetic efficiency in exchange for greater cellular calcium entry and increased contractile force. In healthy hearts, calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylates the Kir6.2 KATP channel subunit initiating a cascade responsible for KATP channel endocytosis. Here, activation of CaMKII in a transaortic banding (TAB) model of heart failure is coupled with a 35-40% reduction in surface expression of KATP channels compared to hearts from sham-operated mice. Linkage between KATP channel expression and CaMKII is verified in isolated cardiomyocytes in which activation of CaMKII results in downregulation of KATP channel current. Accordingly, shortening of monophasic APD is slowed in response to hypoxia or heart rate acceleration in failing compared to non-failing hearts, a phenomenon previously shown to result in significant increases in oxygen consumption. Even in the absence of coronary artery disease, failing myocardium can be further injured by ischemia due to a mismatch between metabolic supply and demand. Ischemia-reperfusion injury, following ischemic preconditioning, is diminished in hearts with CaMKII inhibition compared to wild-type hearts and this advantage is largely eliminated when myocardial KATP channel expression is absent, supporting that the myocardial protective benefit of CaMKII inhibition in heart failure may be substantially mediated by KATP channels. Recognition of Ca

  9. Loss of ATP-Sensitive Potassium Channel Surface Expression in Heart Failure Underlies Dysregulation of Action Potential Duration and Myocardial Vulnerability to Injury.

    Directory of Open Access Journals (Sweden)

    Zhan Gao

    Full Text Available The search for new approaches to treatment and prevention of heart failure is a major challenge in medicine. The adenosine triphosphate-sensitive potassium (KATP channel has been long associated with the ability to preserve myocardial function and viability under stress. High surface expression of membrane KATP channels ensures a rapid energy-sparing reduction in action potential duration (APD in response to metabolic challenges, while cellular signaling that reduces surface KATP channel expression blunts APD shortening, thus sacrificing energetic efficiency in exchange for greater cellular calcium entry and increased contractile force. In healthy hearts, calcium/calmodulin-dependent protein kinase II (CaMKII phosphorylates the Kir6.2 KATP channel subunit initiating a cascade responsible for KATP channel endocytosis. Here, activation of CaMKII in a transaortic banding (TAB model of heart failure is coupled with a 35-40% reduction in surface expression of KATP channels compared to hearts from sham-operated mice. Linkage between KATP channel expression and CaMKII is verified in isolated cardiomyocytes in which activation of CaMKII results in downregulation of KATP channel current. Accordingly, shortening of monophasic APD is slowed in response to hypoxia or heart rate acceleration in failing compared to non-failing hearts, a phenomenon previously shown to result in significant increases in oxygen consumption. Even in the absence of coronary artery disease, failing myocardium can be further injured by ischemia due to a mismatch between metabolic supply and demand. Ischemia-reperfusion injury, following ischemic preconditioning, is diminished in hearts with CaMKII inhibition compared to wild-type hearts and this advantage is largely eliminated when myocardial KATP channel expression is absent, supporting that the myocardial protective benefit of CaMKII inhibition in heart failure may be substantially mediated by KATP channels. Recognition of Ca

  10. Purinergic facilitation of ATP-sensitive potassium current in rat ventricular myocytes

    OpenAIRE

    Babenko, Andrey P.; Vassort, Guy

    1997-01-01

    The effects of different purinergic agonists on the cardiac adenosine 5′-triphosphate (ATP)-sensitive potassium current (IK(ATP)), appearing during dialysis of rat isolated ventricular myocytes with a low-ATP (100 μM) internal solution under whole-cell patch-clamp conditions, were examined in the presence of a P1 purinoceptor antagonist.The extracellular application of ATP in the micromolar range induced, besides known inward currents through cationic and chloride channels, the facilitation o...

  11. Effect of antihistaminic agents on the ATP-sensitive potassium channel activity in isolated mouse ventricular cardiomyocytes%组胺拮抗剂对小鼠ATP-敏感性钾离子通道的影响

    Institute of Scientific and Technical Information of China (English)

    朴伶华; 姜圣男; 柳贤德

    2013-01-01

    Objective The purpose of this study was to clarify the effect of the first generation histamine H1 receptor antagonists on adenosine triphosphate-sensitive potassium (KATP) channel in isolated mouse ventricular cardiomyocytes using excised inside-out and cell-attached patch clamp techniques. Methods Mouse heart ventricular cardiomyocytes were isolated, and excised inside-out and cell-attached patch clamp techniques were used to determine the effect of the antihistamines on the KATP channel activity. Results In the excised inside-out patch configuration, H1-antihistaminic agents (chlorpheniramine, pyrilamine and diphenhydramine), in a dose ranging from 1 to 100 μmol/L, inhibited KATP channel activity in a dose-dependent manner. The potency order reducing the channel activity was pyrilamine>diphenhydramine>chlorpheniramine. All the three antihistamines (100 μmol/L) also inhibited pinacidil-induced KATP channel activity in the cell-attached patch configuration. The potency order of the three antihistamines inhibiting KATP channel activity was pyrilamine>chlorpheniramine>diphenhydramine in the cell-attached configurations. Histamine did not affect the pinacidil-induced KATP channel activity by itself, in addition, did not influence the effects elicited by the three antihistamines on pinacidil-induced KATP channel activity in the cell-attached patches. Conclusions It is concluded that the first generation histamine H1 receptor antagonists are involved in the regulation of ATP-sensitive potassium channel activity in the mouse cardiac ventricular myocytes, and that the inhibitory action of the antihistaminic agents on the channel is not dependent on H1-receptors.%目的 观察比较3种组胺拮抗剂对缺血性心肌细胞的ATP-敏感性钾离子通道中的影响.方法 利用急性酶解法分离小鼠心室肌细胞.结果 组胺拮抗剂pyrilamine、chlorpheniramine及diphenhydramine均可抑制ATP-敏感性钾离子通道的活性,抑制程度为pyrilamine

  12. Targeting at SUR2B/Kir6.1 subtype of ATP-sensitive potassium channel opener natakalim improves pressure overload-induced heart failure

    Institute of Scientific and Technical Information of China (English)

    TANG Yuan; LONG Chao-liang; WANG Hai

    2008-01-01

    Objective To explore the new stratigies targeting at SUR2B/Kir6.1 subtype against pressure overload-induced heart failure. Methods Pressure overload-induced heart failure was induced in Wistar rat by abdominal aortic banding (AAB) .The effects of natakalim (1,3, 9 mg·kg-1·d-1, 10 weeks) were assessed on myocardial hypertrophy and heart failure, cardiac histology, vasoactive compounds, and gene expression. Isolated working heart and isolated tail artery helical strips were used to examine the influence of natakalim on heart and resistant vessels. Results Ten weeks after the onset of pressure overload, natakalim therapy potently inhibited cardiac hypertrophy and prevented heart failure. Natakalim inhibited the changes of left ventricular haemodynamic parameters, reversed the increase of heart mass index, left ventricular weight index and lung weight index remarkably. Histological examination demonstrated that there were no significant hypertrophy and fibrosis in hearts of pressure overload rat treated with natakalim. Ultrastructural examination of heart revealed well-organized myofibrils with mitochondria grouped along the periphery of longitudinally oriented fibers in natakalim group rats. The content of serum NO and plasma PGI2 was increased, while that of plasma ET-1 and cardiac tissue hydroxyproline, ANP and BNP mRNA was down-regulated in natakalim-treated rats. Natakalim at concentrations ranging from 0.01-100 μM had no effects on isolated working heart derived from Wistar rats; however, natakalim had endothelium-dependent vasodilation effects on the isolated tail artery helical strips precontracted with NE. Conclusions These results indicate that natakalim improves heart failure due to pressure overload by activating KATP channel SUR2B/Kir6.1 subtype and reversing endothelial dysfunction.

  13. dl-白花前胡甲素对人大脑皮层ATP敏感钾通道的作用%Effect of dl-praeruptorin A on ATP sensitive potassium channels inhuman cortical neurons

    Institute of Scientific and Technical Information of China (English)

    张沈丽; 李金鸣; 肖庆桓; 吴安华; 赵青; 杨国瑞; 张克义

    2001-01-01

    目的:研究白花前胡甲素(Pd-Ia)对人大脑皮层神经元ATP敏感钾通道的作用.方法:应用膜片箝全细胞记录技术,采用累积给药方式.箝制电压-40mV,指令电压-30到+100 mV,时程600 ms.结果:Pd-Ia以浓度依赖方式激活ATP敏感钾通道.当用含不同浓度的(0.001,0.01,0.1和1 μmol/L)Pd-Ia细胞外液灌流时,电流值分别从给药前的(0.9±0.4)nA增大到给药后的(1.0±0.4)nA,(1.1±0.4)nA,(1.2±0.4)nA和(1.3±0.4)nA(P<0.01,n=5).然后用含ATP敏感钾通道的特异抑制剂格列苯脲(10 μmol/L)的细胞外液冲洗,电流减小至(0.90±0.37)nA(P<0.01,n=5). 结论:Pd-Ia可开放ATP敏感钾通道,是一种钾通道开放剂.%AIM: To investigate the effect of dl-praeruptorin A (PdIa) on ATP sensitive potassium channels (KATP channel) in human cortical neurons. METHODS: Using standard whole cell recording method. Cell membranes were held at - 40 mV, commanding potential was - 30 to + 100 mV and duration was 600 ms. RESULTS: PdIa activated KATP channels in human cortical neurons in a concentration-dependent manner. After consecutive perfusion with extemal solution containing Pd-Ia 0.001,0.01, 0.1, and 1 μmol/L, currents increased from control (0.9±0.4) nAto (1.0±0.4) nA, (1.1±0.4) nA, (1.2±0.4) nA, and (1.3±0.4) nA (P<0.05 or P < 0.01, n = 5 ) respectively. Then the current decreased to (0.90±0.37) nA (P<0.01, n=5) after washout with glibenclamide (10 μmol/L ). The increscent part of the currents could nearly be inhibited by specific KATP channel inhibitor. CONCLUSION: Pd-Ia could open KATP channel and it is a kind of potassium channel opener.

  14. Cardiac ATP-sensitive K+ channels. Evidence for preferential regulation by glycolysis

    OpenAIRE

    1989-01-01

    The ability of glycolysis, oxidative phosphorylation, the creatine kinase system, and exogenous ATP to suppress ATP-sensitive K+ channels and prevent cell shortening were compared in patch-clamped single guinea pig ventricular myocytes. In cell-attached patches on myocytes permeabilized at one end with saponin, ATP-sensitive K+ channels were activated by removing ATP from the bath, and could be closed equally well by exogenous ATP or substrates for endogenous ATP production by glycolysis (wit...

  15. Effects of Exhaustive Exercise on the ATP-sensitive Potassium Channel in Sinoatrial Node of Rats%力竭运动对大鼠窦房结ATP-敏感型钾离子通道的影响

    Institute of Scientific and Technical Information of China (English)

    薄冰; 常芸

    2012-01-01

    目的:探讨两周力竭运动对大鼠窦房结ATP-敏感型钾离子通道(KATP通道)亚基Kir6.2mRNA表达及通道电流密度的影响.方法:健康雄性SD大鼠180只,8周龄,体重(220±8)g,共分9组,每组20只,包括安静对照组(C组)1组、一次力竭组(O组)4组、反复力竭组(R组)4组.安静对照组不进行任何运动.反复力竭组大鼠尾部负重3%体重,每天进行1次力竭游泳,每次约2小时,每周6天,共运动2周.一次力竭组大鼠在正常喂养2周后进行一次力竭游泳运动,运动方案同反复力竭组.运动组大鼠分别于运动后即刻、4小时、12小时、24小时不同时相取材,一次力竭运动各组大鼠分别以O-0h、O-4h、O-12h、O-24h命名,反复力竭运动各组大鼠分别以R-0h、R-4h、R-12h、R-24h命名,应用实时荧光定量PCR技术测定KATP通道亚基Kir6.2 mRNA表达变化,应用细胞急性分离及全细胞膜片钳技术测定通道电流密度变化,以观察力竭游泳运动对大鼠窦房结细胞膜上KATP通道的影响.结果:反复力竭运动各组Kir6.2 mRNA表达显著高于对照组(P<0.01).反复力竭各时相组KATP通道IK.ATP电流密度显著高于对照组及一次力竭组(P<0.01).结论:反复力竭运动可引起窦房结细胞膜KATP通道亚基Kir6.2 mRNA表达及IK,ATP电流密度增加,这可能引起窦房结细胞舒张期自动除极及自律活动减慢,提示反复力竭运动对于KATP通道的影响可能成为运动引发窦房结功能障碍及运动性心律失常的离子通道机制之一.%Objective This paper discusses the subunit mRNA and current density of ATP-sensitive potassium channel (KAtp channel) in sinoatrial node (SAN) at different time phrases after exhaustive exercise. Methods 180 healthy adult male SD rats were equally assigned into 9 groups ;1 control group (C) ,4 single exhaustive swimming groups (O-0hour,O-4hours,O-12hours,O-24hours) ,and 4 2-week repeated exhaustive swimming groups (R-0hour,R-4hours,R-12

  16. The ATP-sensitive K + channel and membrane potential in the pathogenesis of vascular hyporeactivity in severe hemorrhagic shock

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Objective: To elucidate the mechanism of vascular hyporeactivity following severe hemorrhagic shock (HS) by studying the changes of ATP-sensitive potassium channels'(KATP) properties and membrane potential of mesenteric arteriolar smooth muscle cells. Methods: Single channel currents were studied on cell-attached and inside-out patches of enzymatically isolated mesenteric arteriolar smooth muscle cells (ASMCs). Membrane potentials of arteriolar strips and ASMCs were recorded by intracellular membrane potential recording method and confocal microscopy, respectively. Results: KATP channels in ASMCs were activated,which induced smooth muscle hyperpolarization following vsscular hyporeactivity in HS. Conclusions: Hyperpolarizing effect of KATP channel activation plays an important role in low vasoreactivity during severe hemorrhagic shock.

  17. Role of mitochondrial ATP-sensitive potassium channel-mediated PKC-ε in delayed protection against myocardial ischemia/reperfusion injury in isolated hearts of sevoflurane-preconditioned rats

    International Nuclear Information System (INIS)

    This study aimed to determine the role of mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channels and protein kinase C (PKC)-ε in the delayed protective effects of sevoflurane preconditioning using Langendorff isolated heart perfusion models. Fifty-four isolated perfused rat hearts were randomly divided into 6 groups (n=9). The rats were exposed for 60 min to 2.5% sevoflurane (the second window of protection group, SWOP group) or 33% oxygen inhalation (I/R group) 24 h before coronary occlusion. The control group (CON) and the sevoflurane group (SEVO) group were exposed to 33% oxygen and 2.5% sevoflurane for 60 min, respectively, without coronary occlusion. The mitoKATP channel inhibitor 5-hydroxydecanoate (5-HD) was given 30 min before sevoflurane preconditioning (5-HD+SWOP group). Cardiac function indices, infarct sizes, serum cardiac troponin I (cTnI) concentrations, and the expression levels of phosphorylated PKC-ε (p-PKC-ε) and caspase-8 were measured. Cardiac function was unchanged, p-PKC-ε expression was upregulated, caspase-8 expression was downregulated, cTnI concentrations were decreased, and the infarcts were significantly smaller (P<0.05) in the SWOP group compared with the I/R group. Cardiac function was worse, p-PKC-ε expression was downregulated, caspase-8 expression was upregulated, cTnI concentration was increased and infarcts were larger in the 5-HD+SWOP group (P<0.05) compared with the SWOP group. The results suggest that mitoKATP channels are involved in the myocardial protective effects of sevoflurane in preconditioning against I/R injury, by regulating PKC-ε phosphorylation before ischemia, and by downregulating caspase-8 during reperfusion

  18. Role of mitochondrial ATP-sensitive potassium channel-mediated PKC-ε in delayed protection against myocardial ischemia/reperfusion injury in isolated hearts of sevoflurane-preconditioned rats

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C. [Department of Anesthesiology and Critical Care, The Second Affiliate Hospital, Soochow University, Suzhou (China); Institute of Neuroscience, Soochow University, Suzhou (China); Hu, S.M. [Institute of Neuroscience, Soochow University, Suzhou (China); Xie, H.; Qiao, S.G. [Department of Anesthesiology and Critical Care, The Second Affiliate Hospital, Soochow University, Suzhou (China); Liu, H. [Department of Anesthesiology and Pain Medicine, University of California Davis Health System, Davis, CA (United States); Liu, C.F. [Institute of Neuroscience, Soochow University, Suzhou (China)

    2015-03-27

    This study aimed to determine the role of mitochondrial adenosine triphosphate-sensitive potassium (mitoK{sub ATP}) channels and protein kinase C (PKC)-ε in the delayed protective effects of sevoflurane preconditioning using Langendorff isolated heart perfusion models. Fifty-four isolated perfused rat hearts were randomly divided into 6 groups (n=9). The rats were exposed for 60 min to 2.5% sevoflurane (the second window of protection group, SWOP group) or 33% oxygen inhalation (I/R group) 24 h before coronary occlusion. The control group (CON) and the sevoflurane group (SEVO) group were exposed to 33% oxygen and 2.5% sevoflurane for 60 min, respectively, without coronary occlusion. The mitoK{sub ATP} channel inhibitor 5-hydroxydecanoate (5-HD) was given 30 min before sevoflurane preconditioning (5-HD+SWOP group). Cardiac function indices, infarct sizes, serum cardiac troponin I (cTnI) concentrations, and the expression levels of phosphorylated PKC-ε (p-PKC-ε) and caspase-8 were measured. Cardiac function was unchanged, p-PKC-ε expression was upregulated, caspase-8 expression was downregulated, cTnI concentrations were decreased, and the infarcts were significantly smaller (P<0.05) in the SWOP group compared with the I/R group. Cardiac function was worse, p-PKC-ε expression was downregulated, caspase-8 expression was upregulated, cTnI concentration was increased and infarcts were larger in the 5-HD+SWOP group (P<0.05) compared with the SWOP group. The results suggest that mitoK{sub ATP} channels are involved in the myocardial protective effects of sevoflurane in preconditioning against I/R injury, by regulating PKC-ε phosphorylation before ischemia, and by downregulating caspase-8 during reperfusion.

  19. 肺动脉平滑肌细胞ATP敏感性钾通道研究进展%Research progress of ATP-sensitive potassium channels in pulmonary artery smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    朱煜明; 王虹

    2006-01-01

    ATP敏感性钾通道(KATP)是将细胞代谢与细胞膜电活动耦联在一起从而影响细胞功能的重要通道.KATP是由磺酰脲受体(sulfonylurea receptor,SUR)和内向整流钾通道亚单位(Kir6.x)组成的异源八聚体,其中肺动脉平滑肌细胞(pulmonary artery smooth muscle cell,PASMC)的KATP主要由SUR2B和Kir6.1形成.在某些病理条件下,KATP参与了肺血管张力的调节.KATP活性受多种因素的调控,胞内二磷酸核苷酸(NDPs)、钾通道开放剂(potassium channel opner,KCOs)等可激活该通道,而ATP和硫脲类药物则特异性抑制该通道的开放.对PASMC中KATP通道的结构及其调节机制的了解,为相关疾病的治疗与预防开辟了一条新的途径.

  20. Natriuretic peptides modulate ATP-sensitive K+ channels in rat ventricular cardiomyocytes

    OpenAIRE

    Burley, Dwaine S.; Charles D Cox; Zhang, Jin; Wann, Kenneth T.; Baxter, Gary F.

    2014-01-01

    B-type natriuretic peptide (BNP) and C-type natriuretic peptide (CNP), and (Cys-18)-atrial natriuretic factor (4–23) amide (C-ANF), are cytoprotective under conditions of ischemia–reperfusion, limiting infarct size. ATP-sensitive K+ channel (KATP) opening is also cardioprotective, and although the KATP activation is implicated in the regulation of cardiac natriuretic peptide release, no studies have directly examined the effects of natriuretic peptides on cardiac KATP activity. Normoxic cardi...

  1. Effects of the hypoglycaemic drugs repaglinide and glibenclamide on ATP-sensitive potassium-channels and cytosolic calcium levels in beta TC3 cells and rat pancreatic beta cells

    DEFF Research Database (Denmark)

    Gromada, J; Dissing, S; Kofod, Hans;

    1995-01-01

    -dependent increase in intracellular free Ca2+ concentration ([Ca2+]i) with a half-maximal effect at 0.5 nmol/l for both drugs in long-term experiments (30 min). The rise in [Ca2+]i results from Ca2+ entry through voltage-dependent L-type Ca(2+)-channels since it is inhibited by verapamil (10 mumol/l). The effect...

  2. Expression of ATP sensitive K+ channel subunit Kir6.1 in rat kidney

    Directory of Open Access Journals (Sweden)

    M Zhou

    2009-06-01

    Full Text Available ATP-sensitive K+ (KATP channels in kidney are considered to play roles in regulating membrane potential during the change in intracellular ATP concentration. They are composed of channel subunits (Kir6.1, Kir6.2, which are members of the inwardly rectifying K+ channel family, and sulphonylurea receptors (SUR1, SUR2A and SUR2B, which belong to the ATP-binding cassette superfamily. In the present study, we have investigated the expression and localization of Kir6.1 in rat kidney with Western blot analysis, immunohistochemistry, in situ hybridization histochemistry, and immunoelectron microscopy. Western blot analysis showed that Kir6.1 was expressed in the mitochondria and microsome fractions of rat kidney and very weakly in the membrane fractions. Immunohistochemistry revealed that Kir6.1 was widely distributed in renal tubular epithelial cells, glomerular mesangial cells, and smooth muscles of blood vessels. In immunoelectron microscopy, Kir6.1 is mainly localized in the mitochondria, endoplasmic reticulum (ER, and very weakly in cell membranes. Thus, Kir6.1 is contained in the kidney and may be a candidate of mitochondrial KATP channels.

  3. ATP-sensitive potassium channel opener protects PC12 Cells against ischemia/hypoxia-induced apoptosis through PI3K/Akt signaling pathway%ATP敏感性钾通道开放剂通过PI3K/Akt信号通路对缺血缺氧诱导PC12细胞凋亡发挥保护作用

    Institute of Scientific and Technical Information of China (English)

    张鸿; 贾春红; 赵丹阳; 王占强; 鲁阳; 王润玲

    2011-01-01

    目的 研究ATP敏感性钾通道(KATP)开放剂对缺血缺氧诱导PC12细胞凋亡及Akt蛋白和mRNA表达的影响.探讨KATP开放剂的保护作用机制.方法 取传代后3d Pc12细胞,分为对照组,缺血缺氧组,KATP通道开放剂组,KATP通道开放剂+阻断剂组.采用Annexin-v FITC/PI双染流式细胞分析仪检测凋亡率,应用免疫荧光染色和Western-blotting及RT-PCR方法检测P-Akt蛋白及mRNA表达水平.结果 缺血缺氧组细胞凋亡率高于对照组,24h达高峰,KATP开放剂组低于缺血缺氧组,KATP通道开放剂+阻断剂组高于KATP通道开放剂组(0.01).缺血缺氧后p-Akt蛋白及mRNA表达高于对照组,12h达高峰;KATP通道开放剂组高于缺血缺氧组,KATP通道开放剂+阻断剂组低于KATP通道开放剂组(P<0.01).结论 KATP开放剂可能通过激活PI3K/Akt信号通路,对缺血后PC12细胞凋亡发挥保护作用.%Objective To investigate the effect of ATP-sensitive potassium channel (KATP) openers on iscbemia-hypoxia-induced PC12 cell apoptosis and the expression of Akt mRNA and protein.Methods PC12 cells 3 days after passage were divided into control group, ischemia-hypoxia group, KATP channel opener group and KATP channel opener+blocker group.Apoptosis rate was detected using Annexin-v FITC/PI double staining flow cytometry, mRNA and protein levels of p-Akt were measured by immunofluorescent staining, Western-blotting and RT-PCR methods.Results The percentage of apoptotic PC12 cells is higher in iscbemia-hypoxia group than in control, peaked at 24h, lower in KATP channel opener group than in iscbemia-hypoxia 8roup, higher in KATP channel opener+blocker group than in KATP channel opener (P<0.01).The mRNA and protein levels of p-Akt were increased, reached peak at 12h, in ischemia-hypoxia group compared with control, higher in KATP channel opener group than in ischemia-hypoxia group, lower in KATP channel opener+blocker group than in KATP channel opener (P<0.01).Conclusion The

  4. 外源性硫化氢及KATP通道对大鼠慢性应激结肠高动力的调节%Effect of exogenous H2 S and ATP-sensitive potassium channels on colonic hypermotility in a rat model of chronic stress

    Institute of Scientific and Technical Information of China (English)

    刘颖; 全晓静; 夏虹; 罗和生

    2015-01-01

    目的:研究外源性硫化氢( hydrogen sulfide,H2 S)及ATP敏感性钾通道( ATP-sensitive potassium channels,KATP)在慢性应激结肠高动力中的作用。方法:制作慢性避水应激(water avoidance stress,WAS)和假避水应激( sham water avoidance stress,SWAS)大鼠模型,观察2组大鼠结肠肌条的收缩活性以及硫氢化钠( NaHS)和格列本脲预处理后对2组大鼠结肠肌条收缩影响并计算NaHS的半数抑制浓度( half maximal inhibitory concentration, IC50),使用免疫荧光及Western blotting法观察KATP通道各亚基在结肠中的分布及表达。结果:WAS组结肠肌条收缩活性明显高于SWAS组;NaHS浓度依赖性抑制2组大鼠纵行肌( longitudinal muscle,LM)和环形肌( circular mus-cle,CM)的收缩;WAS组LM和CM的NaHS IC50分别为0.2033 mmol/L和0.1438 mmol/L,均明显低于SWAS组(P<0.01);格列本脲明显增加2组大鼠肌条NaHS IC50(P<0.01);Kir6.1、Kir6.2和SUR-2B在2组大鼠结肠固有肌细胞膜均有分布;WAS组(去除黏膜及黏膜下层后)Kir6.1和SUR2B蛋白表达高于SWAS组(P<0.01)。结论:H2 S外源性供体NaHS对慢性应激结肠高动力具有潜在的治疗作用。 KATP通道亚基Kir6.1/SUR2B表达增加可能是慢性应激结肠动力紊乱的一种适应性反应。%[ ABSTRACT] AIM:To investigate the potential role of exogenous hydrogen sulfide ( H2 S) and ATP-sensitive po-tassium ( KATP ) channels in chronic stress-induced colonic hypermotility.METHODS:Male Wistar rats were divided into water avoidance stress ( WAS) group and sham WAS ( SWAS) group.Organ bath recordings were used to test the contrac-tile activity of colonic strips.The effects of H2 S donor NaHS and pretreatment with glibenclamide on the contractions of co-lonic smooth muscle were studied and the IC50 of NaHS was calculated.The localization and expression of the subunits of KATP channels were determined by

  5. Effects of iptakalim, a novel ATP-sensitive potassium channel opener, on the phosphorylation of ERK1/2 in primary cultured human pulmonary arterial smooth muscle cells%新型K_(ATP)开放剂埃他卡林对原代培养人肺动脉平滑肌细胞ERK1/2磷酸化的影响

    Institute of Scientific and Technical Information of China (English)

    梅宏波; 解卫平; 左祥荣; 王虹

    2009-01-01

    AIM: To study the effects of iptakalim , a novel ATP-sensitive potassium channel ( K_(ATP) ) opener, on the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) induced by endothelin-1(ET-1) in primary cultured human pulmonary arterial smooth muscle cells. METHODS: By Western blot analysis, the phosphorylation level of ERK1/2 was measured in primary cultured human pulmonary arterial smooth muscle cells. The cells were treated with ET-1 (10 nmol/L) for 0,1, 2, 5, 10, 30, 60 min, respectively. The cells were pretreated with 0.1, 1.0 and 10 μmol/L iptakalim respectively for 30 min prior to the treatment with ET-1 (10 nmol/L) for 10 min. The cells were pretreated with Glibenclamide( 10 jumol/L) for 30 min prior to the treatment with ET-1 (10 nmol/L) and iptakalim (10 μmol/L) for 10 min. RESULTS: ET-1 induced phosphorylation of ERK1/2 from 2 to 30 min with a peak response observed at 10 min in a time-dependent manner. Iptakalim inhibited ET-1-induced ERK1/2 phosphorylation in a concentration-dependent manner. Glibenclamide, a selective K_(ATP) channel antagonist, could antagonize the effects of iptakalim. CONCLUSION: Iptakalim inhibited ET-1-induced phosphorylation of ERK1/2 in primary cultured pulmonary arterial smooth muscle cells probably through activating K_(ATP) channel and would be a most promising candidate drug to treat the remodeling of pulmonary vasculature and pulmonary arterial hypertension.%目的:研究新型ATP敏感性钾通道(K_(ATP))开放剂埃他卡林(IPT)对内皮素-1(ET-1)诱导的原代培养人肺动脉平滑肌细胞细胞外信号调节激酶1和2(ERK1/2)磷酸化的影响.方法:原代培养人肺动脉平滑肌细胞,用Western blot方法检测磷酸化细胞外信号调节激酶1和2(p-ERK1/2).培养液中加入ET-1(10 nmol/L),孵育0、1、2、5、10、30、60 min.培养液中加入ET-1(10 nmol/L)前30 min分别加入0.1、1.0和10.0 μmol/L IPT,孵育10 min.培养液中加入ET-1(10 nmol/L)和IPT(10 μmol/L)前30 min

  6. Role of mitochondrial ATP sensitive potassium channel in delayed preconditioning with sevofiurane reducing myocardial ischemia-reperfusion injury in rats%ATP敏感性钾通道在七氟醚预处理延迟相减轻大鼠心肌缺血-再灌注损伤中的作用

    Institute of Scientific and Technical Information of China (English)

    肖艳英; 常业恬; 冉珂; 李双凤

    2011-01-01

    Objective To investigate the role of mitochondrial ATP sensitive potassium channel (mitoKATP) in the delayed cardioprotection produced by sevoflurane in ischemia-reperfusion(l-R) injured mts Methods Eighty male Sprague-Dawley rats were randomly divided into five groups: a sham operation group (group A); an ischemia-reperfusion injury group (group B), occlusion of left anterior descending coronary artery for 30 min and followed by 120rain of reperfusion; a sevoflurane preconditioning group (group C),breathing 2.5% sevoflurane for one hour 24 h before IR; a sevoflutane preconditioning+5-hydroxydecanoate (5-HD, a mito-KATP inhibitor) group (group D), 5-HD 5mg/kg was given before sevofiurane preconditioning;and a 5-HD group (group E). After 120 min of reperfusion, myocardial area at risk in ischemia and infarcted size (IS) were measured by double stain with evans blue and TTC Serum cTnl levels were detected with ELISA. The expression of Bcl-2 and Bax was measured with immunoblotting. Results Preconditioning with sevoflurane decreased the IS induced by I-R, reduced cTnI level, upregulated Bcl-2 protein and downregulated Bax expression (all P<0.05), but this effect was inhibited by 5-HD. Conclusion Delayed preconditioning with sevoflurane protects myocardial ischeaia-reperfusion injury by regulating Bcl-2 and Bax expression that may be associated with mito-KATP channel activation.%目的 探讨线粒体ATP敏感性钾通道(mito-KAar)在七氟醚预处理延迟相减轻大鼠心肌缺血-再灌注(I-R)损伤中的作用.方法 雄性SD大鼠80只随机均分为五组:假手术组(A组);I-R组(B组),左冠状动脉前降支结扎30 min后再灌注120 min;七氟醚预处理组(C组),I-R前24 h吸人2.5%七氟醚1 h;七氟醚预处理+mito-K抑制剂5-羟基癸酸(5-HD)组(D组),七氟醚预处理前尾静脉注射5-HD 5 mg/kg;单纯5-HD组(E组).再灌注120 min后各组取10只大鼠测定心肌缺血危险面积与梗死面积,酶联免疫吸附(ELISA)法检测血

  7. Effects of mexiletine on ATP sensitive K+ channel of rat skeletal muscle fibres: a state dependent mechanism of action

    OpenAIRE

    Tricarico, Domenico; Barbieri, Mariagrazia; Franchini, Carlo; Tortorella, Vincenzo; Conte Camerino, Diana

    1998-01-01

    The effects of mexiletine were evaluated on the ATP-sensitive K+ channel (KATP) of rat skeletal muscle fibres using patch clamp techniques. The effects of mexiletine were studied on macropatch currents 20 s (maximally activated), 8 min (early stage of rundown) and 15 min (late stage of rundown) after excision in the absence or in the presence of internal ADP (50–100 μM) or UDP (500 μM). In addition, the effects of mexiletine were tested on single channel.In the absence of ADP and UDP, mexilet...

  8. 线粒体ATP敏感性钾通道在七氟醚预处理减轻大鼠脑缺血再灌注损伤中的作用%Role of mitochondrial ATP-sensitive potassium channel in sevoflurane preconditioning-reduced focal cerebral ischemia-reperfusion injury in rats

    Institute of Scientific and Technical Information of China (English)

    叶治; 王锷; 潘韫丹; 郭曲练

    2009-01-01

    目的 探讨线粒体ATP敏感性钾通道(mito-K_(ATP)通道)在七氟醚预处理减轻大鼠脑缺血再灌注损伤中的作用.方法 健康雄性SD大鼠100只,体重250~300 g,随机分为5组(n=20):假手术组(S组)、缺血再灌注组(I/R组)、七氟醚预处理组(Sevo组)、mito-K_(ATP)通道阻断剂5-羟基葵酸(5-HD)组及5-HD+七氟醚预处理组(5-HD+Sevo组).采用线栓法制备大鼠局灶性脑缺血再灌注模型,七氟醚预处理方法:吸入2.4%七氟醚60 min后吸入纯氧洗脱15 min,停止吸入七氟醚后24 h时制备脑缺血再灌注模型.分别于再灌注6、24 h时进行神经功能损伤评分,计算脑梗死体积百分比,采用Western blot法测定蛋白激酶Cε(PKCε)膜转位水平.结果 与S组比较,其余各组大鼠再灌注6、24 h时神经功能损伤评分升高,脑梗死体积百分比及脑组织PKCε膜转位水平升高(P<0.05);与I/R组、5-HD组及5-HD+Sevo组比较,Sevo组大鼠再灌注6、24 h时神经功能损伤评分降低,脑梗死体积百分比降低,再灌注6 h时脑组织PKCε膜转位水平升高(P<0.05).结论 mito-K_(ATP)通道介导了七氟醚预处理减轻大鼠局灶性脑缺血再灌注损伤的作用,其机制可能与调控PKCε膜转位有关.%Objective To investigate the role of the mitochondrial ATP-sensitive potassium (mito-K_(ATP)) channel in sevoflurane preconditioning-reduced focal cerebral ischemia-reperfnsion (I/R) injury in rats. Methods One hundred healthy 3-4 month old male SD rats 250-300 g were randomly assigned into 5 groups (n = 20 each) : group Ⅰ sham operatiun (group S); group Ⅱ I/R; group Ⅲ sevoflurane preconditioning (group Sevo); group Ⅳ 5-hydroxydecannate (5-HD) and group Ⅴ 5-HD + Sevo. Focal cerebral I/R was produced by mid-cerebral artery occlusion (MCAO) in group Ⅱ-Ⅴ . Cerebral ischemia was maintained for 2 h followed by 6 and 24 h reporfnsiun. In group Ⅲ and Ⅴ 2.4% sevoflurane in 97.6% O_2 was inhaled for 60 min at 24 h before MCAO. In

  9. Role of mitochondrial ATP-sensitive potassium channels in attenuation of cerebral ischemia-reperfusion injury by dexmedetomidine in rats%线粒体ATP敏感性钾通道在右美托咪定减轻大鼠脑缺血再灌注损伤中的作用

    Institute of Scientific and Technical Information of China (English)

    袁峰; 付红光; 孙凯; 董铁立

    2014-01-01

    Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATe) channels in attenuation of cerebral ischemia-reperfusion (I/R) injury by dexmedetomidine in rats.Methods One hundred and twenty healthy male Wistar rats,weighing 290-340 g,were randomly assigned into 5 groups (n =24 each) using a random number table:sham operation group (group S) ; group I/R; dexmedetomidine group (group D) ; 5-HD (a specific blocker of mito-KATPchannel) group and 5-HD + dexmedetomidine group (group 5-HD + D).The rats were anesthetized with intraperitoneal chloral hydrate.Focal cerebral I/R was produced by 2 h middle cerebral artery occlusion followed by reperfusion.In group D,dexmedetomidine 50 μg/kg was injected intraperitoneally before ischemia and after onset of reperfusion.In group 5-HD,5-HD 30 mg/kg was injected intraperitoneally at 1 h before ischemia.In 5-HD + D group,5-HD 30 mg/kg was injected intraperitoneally at 1 h before ischemia and the other procedures were similar to those previously described in group D.Twelve rats were chosen at 24 and 48 h of reperfusion to assess the neurological deficit score (NDS).The animals were then sacrificed and brains were removed for determination of cerebral infarct size by TTC staining.Results Compared with S group,NDS and cerebral infarct size were significantly increased at each time point in the other four groups (P < 0.05).Compared with group I/R,NDS and cerebral infarct size were significantly decreased in D and 5-HD + D groups (P < 0.05),and no significant change was found in the parameters mentioned above in 5-HD group (P > 0.05).Compared with group D,NDS and infarct size were significantly increased in group 5-HD + D (P < 0.05).Conclusion Mito-KATP channels are involved in reduction of I/R-induced cerebral injury by dexmedetomidine in rats.%目的 评价线粒体ATP敏感性钾通道(mito-KATP通道)在右美托咪定减轻大鼠脑缺血再灌注损伤中的作用.方法

  10. Role of mitochondrial ATP-sensitive potassium channel in the mild head hypothermia induced attenuation of global cerebral ischemia-reperfusion injury in rats%线粒体ATP敏感性钾通道在头部浅低温减轻大鼠全脑缺血再灌注损伤中的作用

    Institute of Scientific and Technical Information of China (English)

    董振明; 薄立军; 韩建民; 黄立宁; 康荣田; 曹瑞旗; 吴文浩

    2009-01-01

    目的 评价线粒体ATP敏感性钾通道在头部浅低温减轻大鼠全脑缺血再灌注损伤中的作用.方法 健康雄性SD大鼠32只,体重200~250 g,随机分为4组(n=8):假手术组(S组)、全脑缺血再灌注组(I/R组)、头部浅低温组(H组)和5-羟基葵酸钠组(5-HD组).采用三血管阻断法建立大鼠全脑缺血再灌注模型.S组仅分离血管,不阻断;I/R组制备大鼠全脑缺血再灌注模型;H组于再灌注前即刻实施头部浅低温(使鼓膜温度在1 min内降至32~34℃),维持3 h后复温;5-HD组于缺血前30 min腹腔注射5-羟基葵酸钠10 mg/kg,于再灌注前即刻实施头部浅低温.于再灌注12 h时评估大鼠神经行为学(跨格次数和转体时间),采用EIJSA法测定血清神经元特异性烯醇化酶(NSE)的浓度,电镜下观察额叶皮质神经元的超微结构.结果 与S组比较,I/R组、H组和5-HD组跨格次数减少,转体时间延长,I/R组和5-HD组血清NSE浓度升高(P<0.05),H组血清NSE浓度差异无统计学意义(P0.05);与I/R组比较,H组跨格次数增多,转体时间缩短,血清NSE浓度降低,5-HD组转体时间缩短(P<0.05),其余指标差异无统计学意义(P0.05);与H组比较,5-HD组跨格次数减少,转体时间延长,血清NSE浓度升高(P<0.05).H组额叶皮质神经元病理学改变较I/R组和5-HD组减轻,5-HD组与I/R组损伤程度相似.结论 头部浅低温减轻大鼠全脑缺血再灌注损伤可能与开放线粒体ATP敏感性钾通道有关.%Objective To investigate the role of mitochondrial ATP-sensitive potassium channel (mito-KATP) in the mild head hypothermia induced attenuation of global cerebral ischemia-reperfusion (I/R) injury. Methods Thirty-two healthy male SD rats weighing 200-250 g were randomly divided into 4 groups (n=8each): group Ⅰ sham operation (S);group Ⅱ I/R;group Ⅲ mild head hypothermia + I/R (H) and group 5-HD + mild head hypothermia + I/R (5-HD). The animals were anesthetized with intraperitoneal 10% chloral

  11. Role of mitochondrial ATP-sensitive potassium channels in attenuation of renal ischemia-reperfusion injury by lidocaine pretreatment in rats%mito-KATP通道在利多卡因预先给药减轻大鼠肾脏缺血再灌注损伤中的作用

    Institute of Scientific and Technical Information of China (English)

    朱小兵; 刘志群; 吴论; 刘志龙; 卫毅; 石翊飒; 张喜洋

    2013-01-01

    Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in attenuation of renal ischemia-reperfusion (I/R) injury by lidocaine pretreatment in rats.Methods Sixty healthy male Wistar rats,weighing 300-350 g,were randomly assigned into 5 groups (n =12 each) using a random number table:sham operation group (group S); renal I/R group (group I/R); lidocaine pretreatment group (group L) ; 5-HD (a specific blocker of the mito-KATP channel) group and 5-HD + lidocaine pretreatment group (group 5-HD + L).Renal ischemia was induced by occlusion of bilateral renal arteries for 60 min with atraumatic microclips followed by 4 h reperfusion.At 60 min before renal ischemia,lidocaine 5 mg/kg was intravenously injected followed by continuous infusion at 2 mg· kg-1 · h-1 in group L.5-HD 10 mg/kg was injected intraperitoneally at 65 min before ischemia in group 5-HD.In 5-HD + L groups,5-HD 10 mg/kg was injected intraperitoneally at 65 min before ischemia and the other procedures were similar to those previously described in group L.In S and I/R groups,the animals received equal volumes of normal saline instead of lidocaine.Blood samples were obtained at 6 h of reperfusion for determination of serum creatinine (Cr) and urea mitrogen (BUN) concentrations.Bilateral kidneys were removed for determination of mitochondrial membrane potential in the renal tubular epidural cells,malondialdehyde (MDA) content,and superoxide dismutase (SOD) activity and for microscopic examination.Results Compared with group S,the serum Cr and BUN concentrations and MDA content were significantly increased,and SOD activity and mitochondrial membrane potential were decreased in I/R,L,5-HD and 5-HD + L groups (P < 0.05).Compared with group I/R,the serum Cr and BUN concentrations and MDA content were significantly decreased,and SOD activity and mitochondrial membrane potential were increased in L and 5-HD + L groups (P < 0.05),and no significant changes were found in the

  12. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  13. ATP敏感性钾通道突变与新生儿糖尿病iDEND综合征%Mutation of ATP-sensitive K+ channels and neonatal diabetes iDEND syndrome

    Institute of Scientific and Technical Information of China (English)

    邹颖颖; 张吉翔

    2012-01-01

    Activating mutation in the KCNJ11 gene encoding Kii6. 2 subunit of adenosine triphosphate ( ATP ) - sensitive potassium ( KATP ) channel gives rise to intermediate developmental delay, epilepsy and neonatal diabetes ( iDEND ) syndrome, a rare hereditary endocrine metabolic disorder characterized by neonatal diabetes accompanied by developmental delay and muscle weakness, but no epilepsy. The Kir6. 2 Val59 → Met59( V59M ) activating mutation is the common cause of iDEND syndrome ( >50% ). Activating mutation causes iDEND syndrome by inhibiting normal closure of ATP - sensitive K+ channel, which leads to reduce insulin secretion. Most of such patients are more sensitive to sulfony-lurea. High blood - brain barrier permeability and sulfonylurea receptor 1 ( SUR1 ) - specific drugs are expected to become a major therapy.%@@ ATP敏感性钾通道(ATP-sensitive K+ channels,KATP)由SUR1和Kir6.2亚基组成,是葡萄糖刺激胰岛β细胞分泌胰岛素的关键部位.新生儿糖尿病iDEND综合征(intermediate developmental delay, epilepsy, and neonatal diabetes syndrome)是由KATP通道突变引起的疾病.

  14. The modulation of vascular ATP-sensitive K+ channel function via the phosphatidylinositol 3-kinase-Akt pathway activated by phenylephrine.

    Science.gov (United States)

    Haba, Masanori; Hatakeyama, Noboru; Kinoshita, Hiroyuki; Teramae, Hiroki; Azma, Toshiharu; Hatano, Yoshio; Matsuda, Naoyuki

    2010-08-01

    The present study examined the modulator role of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway activated by the alpha-1 adrenoceptor agonist phenylephrine in ATP-sensitive K(+) channel function in intact vascular smooth muscle. We evaluated the ATP-sensitive K(+) channel function and the activity of the PI3K-Akt pathway in the rat thoracic aorta without endothelium. The PI3K inhibitor 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride (LY294002) (10(-5) M) augmented relaxation in response to the ATP-sensitive K(+) channel opener levcromakalim (10(-8) to 3 x 10(-6) M) in aortic rings contracted with phenylephrine (3 x 10(-7) M) but not with 9,11-dideoxy-11alpha,9alpha-epoxy-methanoprostaglandin F(2alpha) (U46619; 3 x 10(-8) M), although those agents induced similar contraction. ATP-sensitive K(+) channel currents induced by levcromakalim (10(-6) M) in the presence of phenylephrine (3 x 10(-7) M) were enhanced by the nonselective alpha-adrenoceptor antagonist phentolamine (10(-7) M) and LY294002 (10(-5) M). Levels of the regulatory subunits of PI3K p85-alpha and p55-gamma increased in the membrane fraction from aortas without endothelium treated with phenylephrine (3 x 10(-7) M) but not with U46619 (3 x 10(-8) M). Phenylephrine simultaneously augmented Akt phosphorylation at Ser473 and Thr308. Therefore, activation of the PI3K-Akt pathway seems to play a role in the impairment of ATP-sensitive K(+) channel function in vascular smooth muscle exposed to alpha-1 adrenergic stimuli.

  15. Regulation of ATP-sensitive K+ channels in insulinoma cells: Activation by somatostatin and protein kinase C and the role of cAMP

    International Nuclear Information System (INIS)

    The actions of somatostatin and of the phorbol ester 4β-phorbol 12-myristate 13-acetate (PMA) were studied in rat insulinoma (RINm5F) cells by electrophysiological and 86Rb+ flux techniques. Both PMA and somatostatin hyperpolarize insulinoma cells by activating ATP-sensitive K+ channels. The presence of intracellular GTP is required for the somatostatin effects. PMA- and somatostatin-induced hyperpolarization and channel activity are inhibited by the sulfonylurea glibenclamide. Glibenclamide-sensitive 86Rb+ efflux from insulinoma cells is stimulated by somatostatin in a dose-dependent manner (half maximal effect at 0.7 nM) and abolished by pertussis toxin pretreatment. Mutual roles of a GTP-binding protein, of protein kinase C, and of cAMP in the regulation of ATP-sensitive K+ channels are discussed

  16. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  17. Normal insulin release during sustained hyperglycaemia in hypokalaemic periodic paralysis : Role of the potassium channel opener pinacidil in impaired muscle strength

    NARCIS (Netherlands)

    Ligtenberg, JJM; VanHaeften, TW; VanderKolk, LE; Smit, AJ; Sluiter, WJ; Links, TP

    1996-01-01

    1. Hypokalaemic periodic paralysis is characterized by attacks of muscle weakness, Glucose, insulin and an abnormal regulation of ATP-sensitive potassium channels may be involved in these attacks, We studied the effect of hyperglycaemia and of the potassium channel opener pinacidil on insulin releas

  18. ATP-sensitive K+ channels that are blocked by hypoglycemia-inducing sulfonylureas in insulin-secreting cells are activated by galanin, a hyperglycemia-inducing hormone

    International Nuclear Information System (INIS)

    The action of the hyperglycemia-inducing hormone galanin, a 29-amino acid peptide names from its N-terminal glycine and C-terminal amidated alanine, was studied in rat insulinoma (RINm5F) cells using electrophysiological and 86Rb+ flux techniques. Galanin hyperpolarizes and reduces spontaneous electrical activity by activating a population of APT-sensitive K+ channels with a single-channel conductance of 30 pS (at -60 mV). Galanin-induced hyperpolarization and reduction of spike activity are reversed by the hypoglycemia-inducing sulfonylurea glibenclamine. Glibenclamide blocks the galanin-activated ATP-sensitive K+ channel. 86Rb+ efflux from insulinoma cells is stimulated by galanin in a dose-dependent manner. The half-maximum value of activation is found at 1.6 nM. Galanin-induced 86Rb+ efflux is abolished by glibenclamide. The half-maximum value of inhibition is found at 0.3 nM, which is close to the half-maximum value of inhibition of the ATP-dependent K+ channel reported earlier. 86Rb+ efflux studies confirm the electrophysiological demonstration that galanin activates and ATP-dependent K+ channel

  19. Common variants in the ATP-sensitive K channel genes KCNJ11 (Kir6.2) and ABCC8 (SUR1) in relation to glucose intolerance: population-based studies and meta-analyses

    NARCIS (Netherlands)

    Dam, van R.M.; Hoebee, B.; Seidell, J.C.; Schaap, M.M.; Bruin, de T.W.; Feskens, E.J.M.

    2005-01-01

    Abstract Aims To evaluate the relation between common variants in the ATP-sensitive K(+) channel genes and glucose intolerance. Methods We conducted a meta-analysis of reported association studies in Caucasian populations for common variants in the ABCC8 (exons 16 and 18) and the KCNJ11 (E23K) gene

  20. Dynamic imaging of free cytosolic ATP concentration during fuel sensing by rat hypothalamic neurones: evidence for ATP-independent control of ATP-sensitive K(+) channels.

    Science.gov (United States)

    Ainscow, Edward K; Mirshamsi, Shirin; Tang, Teresa; Ashford, Michael L J; Rutter, Guy A

    2002-10-15

    Glucose-responsive (GR) neurons from hypothalamic nuclei are implicated in the regulation of feeding and satiety. To determine the role of intracellular ATP in the closure of ATP-sensitive K(+) (K(ATP)) channels in these cells and associated glia, the cytosolic ATP concentration ([ATP](c)) was monitored in vivo using adenoviral-driven expression of recombinant targeted luciferases and bioluminescence imaging. Arguing against a role for ATP in the closure of K(ATP) channels in GR neurons, glucose (3 or 15 mM) caused no detectable increase in [ATP](c), monitored with cytosolic luciferase, and only a small decrease in the concentration of ATP immediately beneath the plasma membrane, monitored with a SNAP25-luciferase fusion protein. In contrast to hypothalamic neurons, hypothalamic glia responded to glucose (3 and 15 mM) with a significant increase in [ATP](c). Both neurons and glia from the cerebellum, a glucose-unresponsive region of the brain, responded robustly to 3 or 15 mM glucose with increases in [ATP](c). Further implicating an ATP-independent mechanism of K(ATP) channel closure in hypothalamic neurons, removal of extracellular glucose (10 mM) suppressed the electrical activity of GR neurons in the presence of a fixed, high concentration (3 mM) of intracellular ATP. Neurons from both brain regions responded to 5 mM lactate (but not pyruvate) with an oligomycin-sensitive increase in [ATP](c). High levels of the plasma membrane lactate-monocarboxylate transporter, MCT1, were found in both cell types, and exogenous lactate efficiently closed K(ATP) channels in GR neurons. These data suggest that (1) ATP-independent intracellular signalling mechanisms lead to the stimulation of hypothalamic neurons by glucose, and (2) these effects may be potentiated in vivo by the release of lactate from neighbouring glial cells.

  1. Dynamic imaging of free cytosolic ATP concentration during fuel sensing by rat hypothalamic neurones: evidence for ATP-independent control of ATP-sensitive K+ channels

    Science.gov (United States)

    Ainscow, Edward K; Mirshamsi, Shirin; Tang, Teresa; Ashford, Michael L J; Rutter, Guy A

    2002-01-01

    Glucose-responsive (GR) neurons from hypothalamic nuclei are implicated in the regulation of feeding and satiety. To determine the role of intracellular ATP in the closure of ATP-sensitive K+ (KATP) channels in these cells and associated glia, the cytosolic ATP concentration ([ATP]c) was monitored in vivo using adenoviral-driven expression of recombinant targeted luciferases and bioluminescence imaging. Arguing against a role for ATP in the closure of KATP channels in GR neurons, glucose (3 or 15 mm) caused no detectable increase in [ATP]c, monitored with cytosolic luciferase, and only a small decrease in the concentration of ATP immediately beneath the plasma membrane, monitored with a SNAP25–luciferase fusion protein. In contrast to hypothalamic neurons, hypothalamic glia responded to glucose (3 and 15 mm) with a significant increase in [ATP]c. Both neurons and glia from the cerebellum, a glucose-unresponsive region of the brain, responded robustly to 3 or 15 mm glucose with increases in [ATP]c. Further implicating an ATP-independent mechanism of KATP channel closure in hypothalamic neurons, removal of extracellular glucose (10 mm) suppressed the electrical activity of GR neurons in the presence of a fixed, high concentration (3 mm) of intracellular ATP. Neurons from both brain regions responded to 5 mm lactate (but not pyruvate) with an oligomycin-sensitive increase in [ATP]c. High levels of the plasma membrane lactate-monocarboxylate transporter, MCT1, were found in both cell types, and exogenous lactate efficiently closed KATP channels in GR neurons. These data suggest that (1) ATP-independent intracellular signalling mechanisms lead to the stimulation of hypothalamic neurons by glucose, and (2) these effects may be potentiated in vivo by the release of lactate from neighbouring glial cells. PMID:12381816

  2. Gastroprotective effects of thymol on acute and chronic ulcers in rats: The role of prostaglandins, ATP-sensitive K(+) channels, and gastric mucus secretion.

    Science.gov (United States)

    Ribeiro, Ana Roseli S; Diniz, Polyana B F; Pinheiro, Malone S; Albuquerque-Júnior, Ricardo L C; Thomazzi, Sara M

    2016-01-25

    Thymol, a monoterpene phenol derivative of cymene, is found in abundance in the essential oils of Thymus, Origanum, and Lippia species. The present study investigated the gastroprotective actions of thymol (10, 30, and 100 mg/kg, p.o.) in the acute (ethanol- and nonsteroidal anti-inflammatory drug-induced ulcers) and chronic (acetic acid-induced ulcers) ulcer models in rats. Some of the mechanisms underlying to the gastroprotective effect of thymol were investigated in the ethanol-induced ulcer model. Gastric secretion parameters (volume, pH, and total acidity) were also evaluated by the pylorus ligature model, and the mucus in the gastric content was determined. The anti-Helicobacter pylori activity of thymol was performed using the agar-well diffusion method. Thymol (10, 30, and 100 mg/kg) produced dose dependent reduction (P ulcer model. The gastroprotective response caused by thymol (30 mg/kg) was significantly attenuated (P ulcer index (P ulcer models, respectively. In the model pylorus ligature, the treatment with thymol failed to significantly change the gastric secretion parameters. However, after treatment with thymol (30 and 100 mg/kg), there was a significant increase (P ulcer models through mechanisms that involve increased in the amount of mucus, prostaglandins, and ATP-sensitive K(+) channels.

  3. Vascular potassium channels in NVC.

    Science.gov (United States)

    Yamada, K

    2016-01-01

    It has long been proposed that the external potassium ion ([K(+)]0) works as a potent vasodilator in the dynamic regulation of local cerebral blood flow. Astrocytes may play a central role for producing K(+) outflow possibly through calcium-activated potassium channels on the end feet, responding to a rise in the intracellular Ca(2+) concentration, which might well reflect local neuronal activity. A mild elevation of [K(+)]0 in the end feet/vascular smooth muscle space could activate Na(+)/K(+)-ATPase concomitant with inwardly rectifying potassium (Kir) channels in vascular smooth muscle cells, leading to a hyperpolarization of vascular smooth muscle and relaxation of smooth muscle actin-positive vessels. Also proposed notion is endothelial calcium-activated potassium channels and/or inwardly rectifying potassium channel-mediated hyperpolarization of vascular smooth muscle. A larger elevation of [K(+)]0, which may occur pathophysiologically in such as spreading depression or stroke, can trigger a depolarization of vascular smooth muscle cells and vasoconstriction instead. PMID:27130411

  4. The novel ATP-sensitive potassium channel opener iptakalim prevents insulin resistance associated with hypertension via restoring endothelial function

    Institute of Scientific and Technical Information of China (English)

    Yu WANG; Fu-hu ZENG; Chao-liang LONG; Zhi-yuan PAN; Wen-yu CUI; Ru-huan WANG; Guo-shu LIU; Hai WANG

    2011-01-01

    To investigate the effects of iptakalim on endothelial dysfunction induced by insulin resistance (IR) and to determine whether iptakalim improved IR associated with hypertension in fructose-fed rats (FFRs) and spontaneously hypertensive rats (SHRs).Methods:Human umbilical vein endothelial cells (HUVECs) were used for in vitro study.The levels of endothelial vasoactive mediators and eNOS protein expression were determined using radioimmunoassays,ELISAs,colorimetric assays or Western blotting.Sprague-Dawley rats were fed with a high-fructose diet.In both FFRs and SHRs,tail-cuff method was used to measure systolic blood pressure (SBP),and hyperinsulinemic-euglycemic clamp was used to evaluate IR states.Results:(1) Cultured HUVECs incubated with the PI3-kinase inhibitor wortmannin (50 nmol/L) and insulin (100 nmol/L) induced endothelial dysfunction characterized by significantly reduced release of NO and expression of eNOS protein,and significantly increased production of ET-1.Pretreatment with iptakalim (0.1-10 μmol/L) could prevent the endothelial dysfunction.(2) In FFRs,the levels of SBP,fasting plasma glucose and insulin were significantly elevated,whereas the glucose infusion rate (GIR) and insulin sensitive index (ISI) were significantly decreased,and the endothelium-dependent vascular relaxation response to ACh was impaired.These changes could be prevented by oral administration of iptakalim (1,3,or 9 mg-kg-1-d-1,for 4 weeks).The imbalance between serum NO and ET-1 was also ameliorated by iptakalim.(3) In 2-4 month-old SHRs (IR was established at the age of 4 months),oral administration of iptakalim (1,3,or 9 mg.kg-1.d-1,for 8 weeks) significantly ameliorated hypertension and increased the GIR to the normal level.Conclusion:These results demonstrate that iptakalim could protect against IR-induced endothelial dysfunction,and ameliorate IR associated with hypertension,possibly via restoring the balance between NO and ET-1 signaling.

  5. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  6. ATP-sensitive K/sup +/ channels that are blocked by hypoglycemia-inducing sulfonylureas in insulin-secreting cells are activated by galanin, a hyperglycemia-inducing hormone

    Energy Technology Data Exchange (ETDEWEB)

    de Weille, J.; Schmid-Antomarchi, H.; Fosset, M.; Lazdunski, M.

    1988-02-01

    The action of the hyperglycemia-inducing hormone galanin, a 29-amino acid peptide names from its N-terminal glycine and C-terminal amidated alanine, was studied in rat insulinoma (RINm5F) cells using electrophysiological and /sup 86/Rb/sup +/ flux techniques. Galanin hyperpolarizes and reduces spontaneous electrical activity by activating a population of APT-sensitive K/sup +/ channels with a single-channel conductance of 30 pS (at -60 mV). Galanin-induced hyperpolarization and reduction of spike activity are reversed by the hypoglycemia-inducing sulfonylurea glibenclamine. Glibenclamide blocks the galanin-activated ATP-sensitive K/sup +/ channel. /sup 86/Rb/sup +/ efflux from insulinoma cells is stimulated by galanin in a dose-dependent manner. The half-maximum value of activation is found at 1.6 nM. Galanin-induced /sup 86/Rb/sup +/ efflux is abolished by glibenclamide. The half-maximum value of inhibition is found at 0.3 nM, which is close to the half-maximum value of inhibition of the ATP-dependent K/sup +/ channel reported earlier. /sup 86/Rb/sup +/ efflux studies confirm the electrophysiological demonstration that galanin activates and ATP-dependent K/sup +/ channel.

  7. Researches toward potassium channels on tumor progressions.

    Science.gov (United States)

    Shen, Zheng; Yang, Qian; You, Qidong

    2009-01-01

    As trans-membrane proteins located in cytoplasm and organelle membrane, potassium (K(+)) channels are generally divided into four super-families: voltage-gated K(+) channels (K(v)), Ca(2+)-activated K(+) channels (K(Ca)), inwardly rectifying K(+) channels (K(ir)) and two-pore domain K(+) channels (K(2P)). Since dysfunctions of K(+) channels would induce many diseases, various studies toward their functions in physiologic and pathologic process have been extensively launched. This review focuses on the recent advances of K(+) channels in tumor progression, including the brief introduction of K(+) channels, the role of K(+) channels in tumor cells, the possible mechanism of action at cellular level, and the possible application of K(+) channel modulators in cancer chemotherapy.

  8. A conserved residue cluster that governs kinetics of ATP-dependent gating of Kir6.2 potassium channels

    DEFF Research Database (Denmark)

    Zhang, Roger S; Wright, Jordan; Pless, Stephan Alexander;

    2015-01-01

    that these residues play a role in lowering the transition state energy barrier between open and closed channel states. Using unnatural amino acid incorporation, we demonstrate the requirement for a planar amino acid at Kir6.2 position 68 for normal channel gating, potentially necessary to localize the ε-amine of Lys......ATP-sensitive potassium (KATP) channels are heteromultimeric complexes of an inwardly-rectifying Kir channel (Kir6.x) and sulfonylurea receptors (SUR). Their regulation by intracellular ATP and ADP generates electrical signals in response to changes in cellular metabolism. We investigated channel...... elements that control the kinetics of ATP-dependent regulation of KATP (Kir6.2 + SUR1) channels using rapid concentration jumps. WT Kir6.2 channels re-open after rapid washout of ATP with a time constant of approximately 60 ms. Extending similar kinetic measurements to numerous mutants revealed fairly...

  9. Potassium channels in pulmonary arterial hypertension.

    Science.gov (United States)

    Boucherat, Olivier; Chabot, Sophie; Antigny, Fabrice; Perros, Frédéric; Provencher, Steeve; Bonnet, Sébastien

    2015-10-01

    Pulmonary arterial hypertension (PAH) is a devastating cardiopulmonary disorder with various origins. All forms of PAH share a common pulmonary arteriopathy characterised by vasoconstriction, remodelling of the pre-capillary pulmonary vessel wall, and in situ thrombosis. Although the pathogenesis of PAH is recognised as a complex and multifactorial process, there is growing evidence that potassium channels dysfunction in pulmonary artery smooth muscle cells is a hallmark of PAH. Besides regulating many physiological functions, reduced potassium channels expression and/or activity have significant effects on PAH establishment and progression. This review describes the molecular mechanisms and physiological consequences of potassium channel modulation. Special emphasis is placed on KCNA5 (Kv1.5) and KCNK3 (TASK1), which are considered to play a central role in determining pulmonary vascular tone and may represent attractive therapeutic targets in the treatment of PAH. PMID:26341985

  10. A novel potassium channel in photosynthetic cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Manuela Zanetti

    Full Text Available Elucidation of the structure-function relationship of a small number of prokaryotic ion channels characterized so far greatly contributed to our knowledge on basic mechanisms of ion conduction. We identified a new potassium channel (SynK in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photosynthetic model organism. SynK, when expressed in a K(+-uptake-system deficient E. coli strain, was able to recover growth of these organisms. The protein functions as a potassium selective ion channel when expressed in Chinese hamster ovary cells. The location of SynK in cyanobacteria in both thylakoid and plasmamembranes was revealed by immunogold electron microscopy and Western blotting of isolated membrane fractions. SynK seems to be conserved during evolution, giving rise to a TPK (two-pore K(+ channel family member which is shown here to be located in the thylakoid membrane of Arabidopsis. Our work characterizes a novel cyanobacterial potassium channel and indicates the molecular nature of the first higher plant thylakoid cation channel, opening the way to functional studies.

  11. Molecular basis of potassium channels in pancreatic duct epithelial cells

    DEFF Research Database (Denmark)

    Hayashi, M.; Novak, Ivana

    2013-01-01

    Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K channels...

  12. Extracellular potassium inhibits Kv7.1 potassium channels by stabilizing an inactivated state

    DEFF Research Database (Denmark)

    Larsen, Anders Peter; Steffensen, Annette Buur; Grunnet, Morten;

    2011-01-01

    Kv7.1 (KCNQ1) channels are regulators of several physiological processes including vasodilatation, repolarization of cardiomyocytes, and control of secretory processes. A number of Kv7.1 pore mutants are sensitive to extracellular potassium. We hypothesized that extracellular potassium also...... modulates wild-type Kv7.1 channels. The Kv7.1 currents were measured in Xenopus laevis oocytes at different concentrations of extracellular potassium (1-50 mM). As extracellular potassium was elevated, Kv7.1 currents were reduced significantly more than expected from theoretical calculations based...... on the Goldman-Hodgkin-Katz flux equation. Potassium inhibited the steady-state current with an IC(50) of 6.0 ± 0.2 mM. Analysis of tail-currents showed that potassium increased the fraction of channels in the inactivated state. Similarly, the recovery from inactivation was slowed by potassium, suggesting...

  13. Studies of ATP sensitive potassium channels on 6 - hydroxydopamine and haloperidol rat models of Parkinson' s disease: Implications for treating Parkinson' s disease?

    Institute of Scientific and Technical Information of China (English)

    WANGSen; YANGYong; DINGJian-Hua; HUGang

    2004-01-01

    Parkinson' s disease is a common neurodegenerative movement disease that affects more than 1% of the elderly population, characterized by a preferential loss of the dopaminergic neurons of the substantia nigra pars compacta. Although during the past score, major biochemistry process such as mitochondrial dysfunction, oxidative stress and glutamate toxicity

  14. Chondriosome ATP sensitive potassium channel and myocardial precondition%线粒体ATP敏感性钾通道与心肌预适应

    Institute of Scientific and Technical Information of China (English)

    张新金; 肖践明

    2006-01-01

    预适应(preconditioning,PC)现象是1986年由Murry等首先报道的狗的一种心肌自我保护机制。是指预先给予短暂的几次非致死性缺血,可以提高心肌对后续的长时间的缺血及再灌注损伤的耐受性,这种现象称为缺血预适应(ischemia preconditioning,IPC)。随后这种现象在猫、鼠、猪、羊等不同的动物中观察到,在人冠心病患者中同样也得到证实。由于这种现象具有明显的临床价值,遂成为了近年来的研究热点。

  15. Bioinspired Artificial Sodium and Potassium Ion Channels.

    Science.gov (United States)

    Rodríguez-Vázquez, Nuria; Fuertes, Alberto; Amorín, Manuel; Granja, Juan R

    2016-01-01

    In Nature, all biological systems present a high level of compartmentalization in order to carry out a wide variety of functions in a very specific way. Hence, they need ways to be connected with the environment for communication, homeostasis equilibrium, nutrition, waste elimination, etc. The biological membranes carry out these functions; they consist of physical insulating barriers constituted mainly by phospholipids. These amphipathic molecules spontaneously aggregate in water to form bilayers in which the polar groups are exposed to the aqueous media while the non-polar chains self-organize by aggregating to each other to stay away from the aqueous media. The insulating properties of membranes are due to the formation of a hydrophobic bilayer covered at both sides by the hydrophilic phosphate groups. Thus, lipophilic molecules can permeate the membrane freely, while the small charged or very hydrophilic molecules require the assistance of other membrane components in order to overcome the energetic cost implied in crossing the non-polar region of the bilayer. Most of the large polar species (such as oligosaccharides, polypeptides or nucleic acids) cross into and out of the cell via endocytosis and exocytosis, respectively. Nature has created a series of systems (carriers and pores) in order to control the balance of small hydrophilic molecules and ions. The most important structures to achieve these goals are the ionophoric proteins that include the channel proteins, such as the sodium and potassium channels, and ionic transporters, including the sodium/potassium pumps or calcium/sodium exchangers among others. Inspired by these, scientists have created non-natural synthetic transporting structures to mimic the natural systems. The progress in the last years has been remarkable regarding the efficient transport of Na(+) and K(+) ions, despite the fact that the selectivity and the ON/OFF state of the non-natural systems remain a present and future challenge

  16. [Cardiac potassium channels: molecular structure, physiology, pathophysiology and therapeutic implications].

    Science.gov (United States)

    Mironov, N Iu; Golitsyn, S P

    2013-01-01

    Potassium channels and currents play essential roles in cardiac repolarization. Potassium channel blockade by class III antiarrhythmic drugs prolongs cardiac repolarization and results in termination and prevention of cardiac arrhythmias. Excessive inhomogeneous repolarization prolongation may lead to electrical instability and proarrhythmia (Torsade de Pointes tachycardia). This review focuses on molecular structure, physiology, pathophysiology and therapeutic potential of potassium channels of cardiac conduction system and myocardium providing information on recent findings in pathogenesis of cardiac arrhythmias, including inherited genetic abnormalities, and future perspectives. PMID:24654438

  17. Influence of Thromboxane A2 on the Regulation of Adenosine Triphosphate-Sensitive Potassium Channels in Mouse Ventricular Myocytes

    Science.gov (United States)

    Jeong, In Seok; Cho, Hwa Jin; Cho, Jeong Gwan; Kim, Sang Hyung; Na, Kook Joo

    2016-01-01

    Background and Objectives Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels play an important role in myocardial protection. We examined the effects of thromboxane A2 on the regulation of KATP channel activity in single ventricular myocytes. Subjects and Methods Single ventricular myocytes were isolated from the hearts of adult Institute of Cancer Research (ICR) mice by enzymatic digestion. Single channel activity was recorded by excised inside-out and cell-attached patch clamp configurations at −60 mV holding potential during the perfusion of an ATP-free K-5 solution. Results In the excised inside-out patches, the thromboxane A2 analog, U46619, decreased the KATP channel activity in a dose-dependent manner; however, the thromboxane A2 receptor antagonist, SQ29548, did not significantly attenuate the inhibitory effect of U46619. In the cell-attached patches, U46619 inhibited dinitrophenol (DNP)-induced KATP channel activity in a dose-dependent manner, and SQ29548 attenuated the inhibitory effects of U46619 on DNP-induced KATP channel activity. Conclusion Thromboxane A2 may inhibit KATP channel activity, and may have a harmful effect on ischemic myocardium. PMID:27482267

  18. Dynamical Properties of Potassium Ion Channels with a Hierarchical Model

    Institute of Scientific and Technical Information of China (English)

    ZHAN Yong; AN Hai-Long; YU Hui; ZHANG Su-Hua; HAN Ying-Rong

    2006-01-01

    @@ It is well known that potassium ion channels have higher permeability than K ions, and the permeable rate of a single K ion channel is about 108 ions per second. We develop a hierarchical model of potassium ion channel permeation involving ab initio quantum calculations and Brownian dynamics simulations, which can consistently explain a range of channel dynamics. The results show that the average velocity of K ions, the mean permeable time of K ions and the permeable rate of single channel are about 0.92nm/ns, 4.35ns and 2.30×108 ions/s,respectively.

  19. A novel potassium channel in skeletal muscle mitochondria.

    Science.gov (United States)

    Skalska, Jolanta; Piwońska, Marta; Wyroba, Elzbieta; Surmacz, Liliana; Wieczorek, Rafal; Koszela-Piotrowska, Izabela; Zielińska, Joanna; Bednarczyk, Piotr; Dołowy, Krzysztof; Wilczynski, Grzegorz M; Szewczyk, Adam; Kunz, Wolfram S

    2008-01-01

    In this work we provide evidence for the potential presence of a potassium channel in skeletal muscle mitochondria. In isolated rat skeletal muscle mitochondria, Ca(2+) was able to depolarize the mitochondrial inner membrane and stimulate respiration in a strictly potassium-dependent manner. These potassium-specific effects of Ca(2+) were completely abolished by 200 nM charybdotoxin or 50 nM iberiotoxin, which are well-known inhibitors of large conductance, calcium-activated potassium channels (BK(Ca) channel). Furthermore, NS1619, a BK(Ca)-channel opener, mimicked the potassium-specific effects of calcium on respiration and mitochondrial membrane potential. In agreement with these functional data, light and electron microscopy, planar lipid bilayer reconstruction and immunological studies identified the BK(Ca) channel to be preferentially located in the inner mitochondrial membrane of rat skeletal muscle fibers. We propose that activation of mitochondrial K(+) transport by opening of the BK(Ca) channel may be important for myoprotection since the channel opener NS1619 protected the myoblast cell line C2C12 against oxidative injury.

  20. Structural Determinants of Specific Lipid Binding to Potassium Channels

    NARCIS (Netherlands)

    Weingarth, M.H.; Prokofyev, A.; van der Cruijsen, E.A.W.; Nand, D.; Bonvin, A.M.J.J.; Pongs, O.; Baldus, M.

    2013-01-01

    We have investigated specific lipid binding to the pore domain of potassium channels KcsA and chimeric KcsAKv1.3 on the structural and functional level using extensive coarse-grained and atomistic molecular dynamics simulations, solid-state NMR, and single channel measurements. We show that, while K

  1. Clinical relevance of ATP-dependent potassium channels

    NARCIS (Netherlands)

    Ligtenberg, JJM; vanHaeften, TW; Links, TP; Smit, AJ

    1995-01-01

    Many cells are equipped with so-called potassium (K+) channels which have an important role in maintaining transmembrane potential. Closure of these channels leads to membrane depolarization, which can be followed by cell-specific activity such as contraction of vascular smooth muscle, or secretion

  2. Neuronal trafficking of voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Jensen, Camilla S; Rasmussen, Hanne Borger; Misonou, Hiroaki

    2011-01-01

    is regulated by voltage-gated potassium (Kv) channels, such as Kv4.2, which are specifically localized in the dendritic membrane. The synaptic potentials eventually depolarize the membrane of the axon initial segment, thereby activating voltage-gated sodium channels to generate action potentials. Specific Kv...

  3. The KCNQ1 potassium channel: from gene to physiological function

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Grunnet, Morten; Olesen, Søren-Peter

    2005-01-01

    The voltage-gated KCNQ1 (KvLQT1, Kv7.1) potassium channel plays a crucial role in shaping the cardiac action potential as well as in controlling the water and salt homeostasis in several epithelial tissues. KCNQ1 channels in these tissues are tightly regulated by auxiliary proteins and accessory...

  4. Permeation study of the potassium channel from streptomyces Lividans

    Institute of Scientific and Technical Information of China (English)

    XU Xiuzhi; ZHAN Yong; ZHAO Tongjun

    2004-01-01

    A three-state hopping model is established according to experiments to study permeation of an open-state potassium channel from Streptomyces Lividans (KcsA potassium channel). The master equations are used to characterize the dynamics of the system. In this model, ion conduction involves transitions of three states, with one three-ion state and two two-ion states in the selectivity filter respectively. In equilibrium, the well-known Nernst equation is deduced. It is further shown that the current follows Michaelis-Menten kinetics in steady state. According to the parameters provided by Nelson, the current-voltage relationship is proved to be ohmic and the current-concentration relationship is also obtained reasonably. Additional validation of the model in the characteristic time to reach the steady state for the potassium channel is also discussed. This model lays a possible physical basis for the permeation of ion channel, and opens an avenue for further research.

  5. Ropivacaine-Induced Contraction Is Attenuated by Both Endothelial Nitric Oxide and Voltage-Dependent Potassium Channels in Isolated Rat Aortae

    Directory of Open Access Journals (Sweden)

    Seong-Ho Ok

    2013-01-01

    Full Text Available This study investigated endothelium-derived vasodilators and potassium channels involved in the modulation of ropivacaine-induced contraction. In endothelium-intact rat aortae, ropivacaine concentration-response curves were generated in the presence or absence of the following inhibitors: the nonspecific nitric oxide synthase (NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, the neuronal NOS inhibitor Nω-propyl-L-arginine hydrochloride, the inducible NOS inhibitor 1400W dihydrochloride, the nitric oxide-sensitive guanylyl cyclase (GC inhibitor ODQ, the NOS and GC inhibitor methylene blue, the phosphoinositide-3 kinase inhibitor wortmannin, the cytochrome p450 epoxygenase inhibitor fluconazole, the voltage-dependent potassium channel inhibitor 4-aminopyridine (4-AP, the calcium-activated potassium channel inhibitor tetraethylammonium (TEA, the inward-rectifying potassium channel inhibitor barium chloride, and the ATP-sensitive potassium channel inhibitor glibenclamide. The effect of ropivacaine on endothelial nitric oxide synthase (eNOS phosphorylation in human umbilical vein endothelial cells was examined by western blotting. Ropivacaine-induced contraction was weaker in endothelium-intact aortae than in endothelium-denuded aortae. L-NAME, ODQ, and methylene blue enhanced ropivacaine-induced contraction, whereas wortmannin, Nω-propyl-L-arginine hydrochloride, 1400W dihydrochloride, and fluconazole had no effect. 4-AP and TEA enhanced ropivacaine-induced contraction; however, barium chloride and glibenclamide had no effect. eNOS phosphorylation was induced by ropivacaine. These results suggest that ropivacaine-induced contraction is attenuated primarily by both endothelial nitric oxide and voltage-dependent potassium channels.

  6. Tarantula toxins interacting with voltage sensors in potassium channels

    OpenAIRE

    Swartz, Kenton J.

    2006-01-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a process that is crucial for electrical signaling in the nervous system. The venom from many poisonous creatures contains a diverse array of small protein toxins that bind to voltage-activated channels and modify the gating mechanism. Hanatoxin and a growing number of related tarantula toxins have been shown to inhibit activation of voltage-activated potassium (Kv) channels by interacting with their vol...

  7. Potassium channels in prostate and colonic cancer

    OpenAIRE

    Ousingsawat, Jiraporn

    2007-01-01

    Large conductance Ca2+-activated K+ channels in human prostate cancer The KCNMA1 gene encoding the alpha-subunit of BK channels is amplified and BK channel expression is enhanced in late-stage, metastatic and hormone-refractory human prostate cancer tissues, whereas benign prostate tissues show only a weak expression of BK channels. PC-3 hormone-insensitive prostate cancer cells, but not hormone-sensitive prostate cancer cells (LNCaP) and benign prostate hyperplasia cells (BPH-1), show an ...

  8. Overexpression of potassium channel genes in rice plant

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    China′ s potassium fertilizer mainly depends on import and the utilization efficiency of K fertilizer was only 30% . So it is very important to enhance utilization efficiency and to reduce its applying amount by improving nutrition characteristics of plant with bioengineering techinques. Potassium channel genes AKT1 and KAT1 were the genes involved in K+ uptake. To investigate the role of heterogeneous K channel genes in the enhancement of K absorbing, genes AKT1 and KAT1 were transferred into four rice varieties, i.e. Zhonghua 8, Zhonghua 9, Zhonghua 13, and 8706.

  9. Effects of fractal gating of potassium channels on neuronal behaviours

    Science.gov (United States)

    Zhao, De-Jiang; Zeng, Shang-You; Zhang, Zheng-Zhen

    2010-10-01

    The classical model of voltage-gated ion channels assumes that according to a Markov process ion channels switch among a small number of states without memory, but a bunch of experimental papers show that some ion channels exhibit significant memory effects, and this memory effects can take the form of kinetic rate constant that is fractal. Obviously the gating character of ion channels will affect generation and propagation of action potentials, furthermore, affect generation, coding and propagation of neural information. However, there is little previous research on this series of interesting issues. This paper investigates effects of fractal gating of potassium channel subunits switching from closed state to open state on neuronal behaviours. The obtained results show that fractal gating of potassium channel subunits switching from closed state to open state has important effects on neuronal behaviours, increases excitability, rest potential and spiking frequency of the neuronal membrane, and decreases threshold voltage and threshold injected current of the neuronal membrane. So fractal gating of potassium channel subunits switching from closed state to open state can improve the sensitivity of the neuronal membrane, and enlarge the encoded strength of neural information.

  10. Potassium channels and human epileptic phenotypes: an updated overview

    Directory of Open Access Journals (Sweden)

    Chiara eVilla

    2016-03-01

    Full Text Available Potassium (K+ channels are expressed in almost every cells and are ubiquitous in neuronal and glial cell membranes. These channels have been implicated in different disorders, in particular in epilepsy. K+ channel diversity depends on the presence in the human genome of a large number of genes either encoding pore-forming or accessory subunits. More than 80 genes encoding the K+ channels were cloned and they represent the largest group of ion channels regulating the electrical activity of cells in different tissues, including the brain. It is therefore not surprising that mutations in these genes lead to K+ channels dysfunctions linked to inherited epilepsy in humans and non-human model animals.This article reviews genetic and molecular progresses in exploring the pathogenesis of different human epilepsies, with special emphasis on the role of K+ channels in monogenic forms.

  11. TRESK potassium channel in human T lymphoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Miguel, Dénison Selene, E-mail: amurusk@hotmail.com [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); García-Dolores, Fernando, E-mail: garciaddf@yahoo.com [Department of Pathology, Institute of Forensic Sciences, Av. Niños Héroes 130, Col. Doctores, C.P. 06720 Mexico, DF (Mexico); Rosa Flores-Márquez, María, E-mail: mariafo31@yahoo.com.mx [National Medical Center of Occident (CMNO) IMSS, Belisario Dominguez 735, Col. Independencia Oriente, C.P. 44340 Guadalajara, Jalisco (Mexico); Delgado-Enciso, Iván [University of Colima, School of Medicine, Av. Universidad 333, Col. Las Viboras, C.P. 28040 Colima (Mexico); Pottosin, Igor, E-mail: pottosin@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); Dobrovinskaya, Oxana, E-mail: oxana@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico)

    2013-05-03

    Highlights: • TRESK (KCNK18) mRNA is present in different T lymphoblastic cell lines. • KCNK18 mRNA was not found in resting peripheral blood lymphocytes. • Clinical samples of T lymphoblastic leukemias and lymphomas were positive for TRESK. • TRESK in T lymphoblasts has dual localization, in plasma membrane and intracellular. -- Abstract: TRESK (TWIK-related spinal cord K{sup +}) channel, encoded by KCNK18 gene, belongs to the double-pore domain K{sup +} channel family and in normal conditions is expressed predominantly in the central nervous system. In our previous patch-clamp study on Jurkat T lymphoblasts we have characterized highly selective K{sup +} channel with pharmacological profile identical to TRESK. In the present work, the presence of KCNK18 mRNA was confirmed in T lymphoblastic cell lines (Jurkat, JCaM, H9) but not in resting peripheral blood lymphocytes of healthy donors. Positive immunostaining for TRESK was demonstrated in lymphoblastic cell lines, in germinal centers of non-tumoral lymph nodes, and in clinical samples of T acute lymphoblastic leukemias/lymphomas. Besides detection in the plasma membrane, intracellular TRESK localization was also revealed. Possible involvement of TRESK channel in lymphocyte proliferation and tumorigenesis is discussed.

  12. Oxidative Stress and Maxi Calcium-Activated Potassium (BK Channels

    Directory of Open Access Journals (Sweden)

    Anton Hermann

    2015-08-01

    Full Text Available All cells contain ion channels in their outer (plasma and inner (organelle membranes. Ion channels, similar to other proteins, are targets of oxidative impact, which modulates ion fluxes across membranes. Subsequently, these ion currents affect electrical excitability, such as action potential discharge (in neurons, muscle, and receptor cells, alteration of the membrane resting potential, synaptic transmission, hormone secretion, muscle contraction or coordination of the cell cycle. In this chapter we summarize effects of oxidative stress and redox mechanisms on some ion channels, in particular on maxi calcium-activated potassium (BK channels which play an outstanding role in a plethora of physiological and pathophysiological functions in almost all cells and tissues. We first elaborate on some general features of ion channel structure and function and then summarize effects of oxidative alterations of ion channels and their functional consequences.

  13. Berberine induces pacemaker potential inhibition via cGMP-dependent ATP-sensitive K+ channels by stimulating mu/delta opioid receptors in cultured interstitial cells of Cajal from mouse small intestine.

    Science.gov (United States)

    Kim, Hyun Jung; Kim, Hyungwoo; Jung, Myeong Ho; Kwon, Young Kyu; Kim, Byung Joo

    2016-10-01

    Berberine is traditionally used to treat gastrointestinal (GI) motility disorders. The interstitial cells of Cajal (ICCs) are the pacemaker cells of the gastrointestinal tract, which are responsible for the production of gut movements. The present study aimed to investigate the effects of berberine on pacemaker potentials (PPs) in cultured ICC clusters from the mouse small intestine, and sought to identify the receptors involved and the underlying mechanisms of action. All experiments were performed on cultured ICCs, and a whole‑cell patch‑clamp configuration was used to record PPs from ICC clusters (current clamp mode). Under current clamp mode, berberine was shown to decrease the amplitude and frequency of PPs. However, these effects were suppressed by treatment with glibenclamide, a specific ATP‑sensitive K+ channel blocker. Nor‑binaltorphimine dihydrochloride (a kappa opioid receptor antagonist) did not suppress berberine‑induced PP inhibition, whereas ICI 174,864 (a delta opioid receptor antagonist) and CTOP (a mu opioid receptor antagonist) did suppress the inhibitory effects of berberine. Pretreatment with SQ‑22536 (an adenylate cyclase inhibitor) or with KT‑5720 (a protein kinase A inhibitor) did not suppress the effects of berberine; however, pretreatment with 1H‑[1,2,4] oxadiazolo [4,3‑a] quinoxalin‑1‑one (a guanylate cyclase inhibitor) or KT‑5823 [a protein kinase G (PKG) inhibitor] did. In addition, berberine stimulated cyclic guanosine monophosphate (cGMP) production in ICCs. These observations indicate that berberine may inhibit the pacemaker activity of ICC clusters via ATP‑sensitive K+ channels and the cGMP‑PKG‑dependent pathway by stimulating mu and delta opioid receptors. Therefore, berberine may provide a basis for the development of novel agents for the treatment of GI motility dysfunction. PMID:27601272

  14. Optogenetics. Engineering of a light-gated potassium channel.

    Science.gov (United States)

    Cosentino, Cristian; Alberio, Laura; Gazzarrini, Sabrina; Aquila, Marco; Romano, Edoardo; Cermenati, Solei; Zuccolini, Paolo; Petersen, Jan; Beltrame, Monica; Van Etten, James L; Christie, John M; Thiel, Gerhard; Moroni, Anna

    2015-05-01

    The present palette of opsin-based optogenetic tools lacks a light-gated potassium (K(+)) channel desirable for silencing of excitable cells. Here, we describe the construction of a blue-light-induced K(+) channel 1 (BLINK1) engineered by fusing the plant LOV2-Jα photosensory module to the small viral K(+) channel Kcv. BLINK1 exhibits biophysical features of Kcv, including K(+) selectivity and high single-channel conductance but reversibly photoactivates in blue light. Opening of BLINK1 channels hyperpolarizes the cell to the K(+) equilibrium potential. Ectopic expression of BLINK1 reversibly inhibits the escape response in light-exposed zebrafish larvae. BLINK1 therefore provides a single-component optogenetic tool that can establish prolonged, physiological hyperpolarization of cells at low light intensities.

  15. Pharmacodynamics of potassium channel openers in cultured neuronal networks.

    Science.gov (United States)

    Wu, Calvin; V Gopal, Kamakshi; Lukas, Thomas J; Gross, Guenter W; Moore, Ernest J

    2014-06-01

    A novel class of drugs - potassium (K(+)) channel openers or activators - has recently been shown to cause anticonvulsive and neuroprotective effects by activating hyperpolarizing K(+) currents, and therefore, may show efficacy for treating tinnitus. This study presents measurements of the modulatory effects of four K(+) channel openers on the spontaneous activity and action potential waveforms of neuronal networks. The networks were derived from mouse embryonic auditory cortices and grown on microelectrode arrays. Pentylenetetrazol was used to create hyperactivity states in the neuronal networks as a first approximation for mimicking tinnitus or tinnitus-like activity. We then compared the pharmacodynamics of the four channel activators, retigabine and flupirtine (voltage-gated K(+) channel KV7 activators), NS1619 and isopimaric acid ("big potassium" BK channel activators). The EC50 of retigabine, flupirtine, NS1619, and isopimaric acid were 8.0, 4.0, 5.8, and 7.8µM, respectively. The reduction of hyperactivity compared to the reference activity was significant. The present results highlight the notion of re-purposing the K(+) channel activators for reducing hyperactivity of spontaneously active auditory networks, serving as a platform for these drugs to show efficacy toward target identification, prevention, as well as treatment of tinnitus. PMID:24681057

  16. Pharmacodynamics of potassium channel openers in cultured neuronal networks.

    Science.gov (United States)

    Wu, Calvin; V Gopal, Kamakshi; Lukas, Thomas J; Gross, Guenter W; Moore, Ernest J

    2014-06-01

    A novel class of drugs - potassium (K(+)) channel openers or activators - has recently been shown to cause anticonvulsive and neuroprotective effects by activating hyperpolarizing K(+) currents, and therefore, may show efficacy for treating tinnitus. This study presents measurements of the modulatory effects of four K(+) channel openers on the spontaneous activity and action potential waveforms of neuronal networks. The networks were derived from mouse embryonic auditory cortices and grown on microelectrode arrays. Pentylenetetrazol was used to create hyperactivity states in the neuronal networks as a first approximation for mimicking tinnitus or tinnitus-like activity. We then compared the pharmacodynamics of the four channel activators, retigabine and flupirtine (voltage-gated K(+) channel KV7 activators), NS1619 and isopimaric acid ("big potassium" BK channel activators). The EC50 of retigabine, flupirtine, NS1619, and isopimaric acid were 8.0, 4.0, 5.8, and 7.8µM, respectively. The reduction of hyperactivity compared to the reference activity was significant. The present results highlight the notion of re-purposing the K(+) channel activators for reducing hyperactivity of spontaneously active auditory networks, serving as a platform for these drugs to show efficacy toward target identification, prevention, as well as treatment of tinnitus.

  17. Two-pore Domain Potassium Channels in Astrocytes

    Science.gov (United States)

    Ryoo, Kanghyun

    2016-01-01

    Two-pore domain potassium (K2P) channels have a distinct structure and channel properties, and are involved in a background K+ current. The 15 members of the K2P channels are identified and classified into six subfamilies on the basis of their sequence similarities. The activity of the channels is dynamically regulated by various physical, chemical, and biological effectors. The channels are expressed in a wide variety of tissues in mammals in an isoform specific manner, and play various roles in many physiological and pathophysiological conditions. To function as channels, the K2P channels form dimers, and some isoforms form heterodimers that provide diversity in channel properties. In the brain, TWIK1, TREK1, TREK2, TRAAK, TASK1, and TASK3 are predominantly expressed in various regions, including the cerebral cortex, dentate gyrus, CA1-CA3, and granular layer of the cerebellum. TWIK1, TREK1, and TASK1 are highly expressed in astrocytes, where they play specific cellular roles. Astrocytes keep leak K+ conductance, called the passive conductance, which mainly involves TWIK1-TREK1 heterodimeric channel. TWIK1 and TREK1 also mediate glutamate release from astrocytes in an exocytosis-independent manner. The expression of TREK1 and TREK2 in astrocytes increases under ischemic conditions, that enhance neuroprotection from ischemia. Accumulated evidence has indicated that astrocytes, together with neurons, are involved in brain function, with the K2P channels playing critical role in these astrocytes. PMID:27790056

  18. A review of potassium channels in bipolar disorder

    Directory of Open Access Journals (Sweden)

    Jennifer Toolan Judy

    2013-06-01

    Full Text Available Although bipolar disorder (BP is one of the most heritable psychiatric conditions, susceptibility genes for the disorder have yet to be conclusively identified. It is likely that variants in multiple genes across multiple pathways contribute to the genotype-phenotype relationship. Recent evidence from genome-wide association studies (GWAS implicates an entire class of genes related to the structure and regulation of ion channels, suggesting that the etiology of BP may arise from a channelopathy. In this review, we examine the evidence for this hypothesis, with a focus on the potential role of voltage gated potassium channels. We consider evidence from genetic and expression studies, and discuss the potential underlying biology. We consider animal models and treatment implications of the involvement of potassium ion channelopathy in BP. Finally, we explore intriguing parallels between BP and epilepsy, the signature channelopathy of the CNS.

  19. Engineering of an artificial light-modulated potassium channel.

    Directory of Open Access Journals (Sweden)

    Lydia N Caro

    Full Text Available Ion Channel-Coupled Receptors (ICCRs are artificial receptor-channel fusion proteins designed to couple ligand binding to channel gating. We previously validated the ICCR concept with various G protein-coupled receptors (GPCRs fused with the inward rectifying potassium channel Kir6.2. Here we characterize a novel ICCR, consisting of the light activated GPCR, opsin/rhodopsin, fused with Kir6.2. To validate our two-electrode voltage clamp (TEVC assay for activation of the GPCR, we first co-expressed the apoprotein opsin and the G protein-activated potassium channel Kir3.1(F137S (Kir3.1* in Xenopus oocytes. Opsin can be converted to rhodopsin by incubation with 11-cis retinal and activated by light-induced retinal cis→trans isomerization. Alternatively opsin can be activated by incubation of oocytes with all-trans-retinal. We found that illumination of 11-cis-retinal-incubated oocytes co-expressing opsin and Kir3.1* caused an immediate and long-lasting channel opening. In the absence of 11-cis retinal, all-trans-retinal also opened the channel persistently, although with slower kinetics. We then used the oocyte/TEVC system to test fusion proteins between opsin/rhodopsin and Kir6.2. We demonstrate that a construct with a C-terminally truncated rhodopsin responds to light stimulus independent of G protein. By extending the concept of ICCRs to the light-activatable GPCR rhodopsin we broaden the potential applications of this set of tools.

  20. The KCNQ5 potassium channel from mouse: a broadly expressed M-current like potassium channel modulated by zinc, pH, and volume changes

    DEFF Research Database (Denmark)

    Jensen, Henrik Sindal; Callø, Kirstine; Jespersen, Thomas;

    2005-01-01

    The KCNQ proteins compose a sub-group of the voltage-activated potassium channel family. The family consists of five members (KCNQ1 to 5--also named Kv7.1 to Kv7.5) encoded by single genes, which all give rise to proteins forming slowly activating potassium-selective ion channels. The physiological...

  1. A new pH-sensitive rectifying potassium channel in mitochondria from the embryonic rat hippocampus.

    Science.gov (United States)

    Kajma, Anna; Szewczyk, Adam

    2012-10-01

    Patch-clamp single-channel studies on mitochondria isolated from embryonic rat hippocampus revealed the presence of two different potassium ion channels: a large-conductance (288±4pS) calcium-activated potassium channel and second potassium channel with outwardly rectifying activity under symmetric conditions (150/150mM KCl). At positive voltages, this channel displayed a conductance of 67.84pS and a strong voltage dependence at holding potentials from -80mV to +80mV. The open probability was higher at positive than at negative voltages. Patch-clamp studies at the mitoplast-attached mode showed that the channel was not sensitive to activators and inhibitors of mitochondrial potassium channels but was regulated by pH. Moreover, we demonstrated that the channel activity was not affected by the application of lidocaine, an inhibitor of two-pore domain potassium channels, or by tertiapin, an inhibitor of inwardly rectifying potassium channels. In summary, based on the single-channel recordings, we characterised for the first time mitochondrial pH-sensitive ion channel that is selective for cations, permeable to potassium ions, displays voltage sensitivity and does not correspond to any previously described potassium ion channels in the inner mitochondrial membrane. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

  2. POTASSIUM CHANNELS AS DRUGS TARGETS IN THERAPY OF CARDIOVASCULAR DESEASES: 25 YEARS LATER

    Directory of Open Access Journals (Sweden)

    Protić Dragana

    2013-01-01

    Full Text Available Potassium channels are the most variable ion channel group. They participate in numerous cardiovascular functions, for example regulation of vascular tone, maintenance of resting cardiac membrane potential and excitability of cardiac conduction tissue. Both drugs and endogenous ligands could modulate potassium channel function, belonging to the potassium channel blockers or openers. Modulation of potassium channels could be a therapeutic or adverse drug action. Class III antiarrhythmic agents block the potassium channels, thereby prolonging repolarization phase of action potential with resulting prolongation of effective refractory period. Their effectiveness against supraventricular and ventricular arrhythmias should be weighted against their proarrhythmogenic potential. In addition, numerous other antiarrhythmic agents could modulate potassium channels as well. Diazoxide, minoxidil and nicorandil (well known arterial vasodilators, as well as numerous newly synthesized substances with still unknown therapeutic potential, belong to the potassium channel activators/ openers. Therapeutic use of such vasodilators may involve treatment of hypertension (diazoxide, minoxidil and stable angina (nicorandil. Their use might be accompanied with side effects, such as vasodilation, edema, hypotension and reflex tachycardia. Potassium channel openers have also an important role in the treatment of peripheral vascular disease and pulmonary hypertension. In the future, drugs with selective effects on the vascular or cardiac potassium channels could be useful therapeutic agents.

  3. Mitochondrial calcium-activated potassium channel:another potential target for neuroprotection?

    Institute of Scientific and Technical Information of China (English)

    FangSHEN; Li-pingWU; QianSHEN; QiangXIA

    2004-01-01

    AIM: It has recently been reported that large-conductance Ca2+activated potassium channel is present in the inner mitochondrial membrane (mitoKCa) of the neuron cell, which has been reported to have cardioprotective effect similar to that of mitochondrial ATP-sensitive K+ channel (mitoKATP). Hence the aim of this study was to clarify if mitoKCa is neuroprotective and compare thisnotantial affect with that of mitoK METHODS: Male

  4. Trypsin-Sensitive, Rapid Inactivation of a Calcium-Activated Potassium Channel

    Science.gov (United States)

    Solaro, Christopher R.; Lingle, Christopher J.

    1992-09-01

    Most calcium-activated potassium channels couple changes in intracellular calcium to membrane excitability by conducting a current with a probability that depends directly on submembrane calcium concentration. In rat adrenal chromaffin cells, however, a large conductance, voltage- and calcium-activated potassium channel (BK) undergoes rapid inactivation, suggesting that this channel has a physiological role different than that of other BK channels. The inactivation of the BK channel, like that of the voltage-gated Shaker B potassium channel, is removed by trypsin digestion and channels are blocked by the Shaker B amino-terminal inactivating domain. Thus, this BK channel shares functional and possibly structural homologies with other inactivating voltage-gated potassium channels.

  5. The neuroglial potassium cycle during neurotransmission: role of Kir4.1 channels.

    Directory of Open Access Journals (Sweden)

    Jérémie Sibille

    2015-03-01

    Full Text Available Neuronal excitability relies on inward sodium and outward potassium fluxes during action potentials. To prevent neuronal hyperexcitability, potassium ions have to be taken up quickly. However, the dynamics of the activity-dependent potassium fluxes and the molecular pathways underlying extracellular potassium homeostasis remain elusive. To decipher the specific and acute contribution of astroglial Kir4.1 channels in controlling potassium homeostasis and the moment to moment neurotransmission, we built a tri-compartment model accounting for potassium dynamics between neurons, astrocytes and the extracellular space. We here demonstrate that astroglial Kir4.1 channels are sufficient to account for the slow membrane depolarization of hippocampal astrocytes and crucially contribute to extracellular potassium clearance during basal and high activity. By quantifying the dynamics of potassium levels in neuron-glia-extracellular space compartments, we show that astrocytes buffer within 6 to 9 seconds more than 80% of the potassium released by neurons in response to basal, repetitive and tetanic stimulations. Astroglial Kir4.1 channels directly lead to recovery of basal extracellular potassium levels and neuronal excitability, especially during repetitive stimulation, thereby preventing the generation of epileptiform activity. Remarkably, we also show that Kir4.1 channels strongly regulate neuronal excitability for slow 3 to 10 Hz rhythmic activity resulting from probabilistic firing activity induced by sub-firing stimulation coupled to Brownian noise. Altogether, these data suggest that astroglial Kir4.1 channels are crucially involved in extracellular potassium homeostasis regulating theta rhythmic activity.

  6. Kv3.3 potassium channels and spinocerebellar ataxia.

    Science.gov (United States)

    Zhang, Yalan; Kaczmarek, Leonard K

    2016-08-15

    The voltage-dependent potassium channel subunit Kv3.3 is expressed at high levels in cerebellar Purkinje cells, in auditory brainstem nuclei and in many other neurons capable of firing at high rates. In the cerebellum, it helps to shape the very characteristic complex spike of Purkinje cells. Kv3.3 differs from other closely related channels in that human mutations in the gene encoding Kv3.3 (KCNC3) result in a unique neurodegenerative disease termed spinocerebellar ataxia type 13 (SCA13). This primarily affects the cerebellum, but also results in extracerebellar symptoms. Different mutations produce either early onset SCA13, associated with delayed motor and impaired cognitive skill acquisition, or late onset SCA13, which typically produces cerebellar degeneration in middle age. This review covers the localization and physiological function of Kv3.3 in the central nervous system and how the normal function of the channel is altered by the disease-causing mutations. It also describes experimental approaches that are being used to understand how Kv3.3 mutations are linked to neuronal survival, and to develop strategies for treatment. PMID:26442672

  7. Sleep disturbances in voltage-gated potassium channel antibody syndrome.

    Science.gov (United States)

    Barone, Daniel A; Krieger, Ana C

    2016-05-01

    Voltage-gated potassium channels (VGKCs) are a family of membrane proteins responsible for controlling cell membrane potential. The presence of antibodies (Ab) against neuronal VGKC complexes aids in the diagnosis of idiopathic and paraneoplastic autoimmune neurologic disorders. The diagnosis of VGKC Ab-associated encephalopathy (VCKC Ab syndrome) should be suspected in patients with subacute onset of disorientation, confusion, and memory loss in the presence of seizures or a movement disorder. VGKC Ab syndrome may present with sleep-related symptoms, and the purpose of this communication is to alert sleep and neurology clinicians of this still-under-recognized condition. In this case, we are presenting the VGKC Ab syndrome which improved after treatment with solumedrol. The prompt recognition and treatment of this condition may prevent the morbidity associated with cerebral atrophy and the mortality associated with intractable seizures and electrolyte disturbances.

  8. Upregulation of voltage-activated potassium channels in hippocampus of Aβ25.35-treated rats

    Institute of Scientific and Technical Information of China (English)

    Xiao-liangWANG; Ya-pingPAN

    2004-01-01

    AIM: Potassium channels dysfunction has been indicated in Alzheimer disease. In the present study, the mRNA and protein expression alterations and the functional changes ot VOltage- activated potassium channels were studied in rat hippocampus after a single intracerebro- ventricular injection of β-amyloid peptide 25-35 (Aβ25.35). METHODS: The expressions of mRNA

  9. KCNE3 is an inhibitory subunit of the Kv4.3 potassium channel

    DEFF Research Database (Denmark)

    Lundby, Alicia; Olesen, Søren-Peter

    2006-01-01

    The mammalian Kv4.3 potassium channel is a fast activating and inactivating K+ channel widely distributed in mammalian tissues. Kv4.3 is the major component of various physiologically important currents ranging from A-type currents in the CNS to the transient outward potassium conductance...

  10. Free RCK arrangement in Kch, a putative escherichia coli potassium channel, as suggested by electron crystallography.

    Science.gov (United States)

    Kuang, Qie; Purhonen, Pasi; Jegerschöld, Caroline; Koeck, Philip J B; Hebert, Hans

    2015-01-01

    The ligand-gated potassium channels are stimulated by various kinds of messengers. Previous studies showed that ligand-gated potassium channels containing RCK domains (the regulator of the conductance of potassium ion) form a dimer of tetramer structure through the RCK octameric gating ring in the presence of detergent. Here, we have analyzed the structure of Kch, a channel of this type from Escherichia coli, in a lipid environment using electron crystallography. By combining information from the 3D map of the transmembrane part of the protein and docking of an atomic model of a potassium channel, we conclude that the RCK domains face the solution and that an RCK octameric gating ring arrangement does not form under our crystallization condition. Our findings may be applied to other potassium channels that have an RCK gating ring arrangement.

  11. Potassium

    Science.gov (United States)

    ... stimulation and in the contraction of muscles. Cellular enzymes need potassium to work properly. A potassium deficiency ... or prune juice, honeydew melons, prunes, molasses and potatoes. Some foods high in potassium are also high ...

  12. Genetic Variations in the Kir6.2 Subunit (KCNJ11 of Pancreatic ATP-Sensitive Potassium Channel Gene Are Associated with Insulin Response to Glucose Loading and Early Onset of Type 2 Diabetes in Childhood and Adolescence in Taiwan

    Directory of Open Access Journals (Sweden)

    Yi-Der Jiang

    2014-01-01

    Full Text Available To investigate the role of E23K polymorphism of the KCNJ11 gene on early onset of type 2 diabetes in school-aged children/adolescents in Taiwan, we recruited 38 subjects with type 2 diabetes (ages 18.6 ± 6.6 years; body mass index percentiles 83.3 ± 15.4 and 69 normal controls (ages 17.3 ± 3.8 years; body mass index percentiles 56.7 ± 29.0 from a national surveillance for childhood/adolescent diabetes in Taiwan. We searched for the E23K polymorphism of the KCNJ11 gene. We found that type 2 diabetic subjects had higher carrier rate of E23K polymorphism of KCNJ11 gene than control subjects (P = 0.044. After adjusting for age, gender, body mass index percentiles, and fasting plasma insulin, the E23K polymorphism contributed to an increased risk for type 2 diabetes (P = 0.047. K23-allele-containing genotypes conferring increased plasma insulin level during OGTT in normal subjects. However, the diabetic subjects with the K23-allele-containing genotypes had lower fasting plasma insulin levels after adjustment of age and BMI percentiles. In conclusion, the E23K variant of the KCNJ11 gene conferred higher susceptibility to type 2 diabetes in children/adolescents. Furthermore, in normal glucose-tolerant children/adolescents, K23 allele carriers had a higher insulin response to oral glucose loading.

  13. 线粒体ATP敏感性钾通道对缺血性脑损伤的保护作用%Protective effects of mitochondrial ATP-sensitive potassium channels on ischemic cerebral injury

    Institute of Scientific and Technical Information of China (English)

    张俊杰; 李士通; 顾虎

    2003-01-01

    目的应用线粒体ATP敏感性钾通道(mito KATP)特异性的开放剂二氮嗪和阻断剂5-HD观察mito KATP对缺血性脑损伤的影响.方法成年健康雄性SD大鼠32只,随机分成四组:假手术组(n=8),行大脑中动脉栓塞(MCAO)的手术操作,但不插线;脑缺血组(n=8),MCAO前给予同等量生理盐水;二氮嗪组(n=8),MCAO前30 min二氮嗪5 mg/kg腹腔注射;5-HD复合二氮嗪组(n=8),5-HD 10 mg/kg静脉注射,15 min后二氮嗪5.0 mg/kg腹腔注射,30 min后再行MCAO.各组MCAO 2 h再灌注24 h后,应用Garcia评分法观察大鼠神经精神系统表现,大脑切片并行TTC染色,计算大脑梗死容积以及透射电镜观察线粒体超微结构的变化.结果应用二氮嗪后,相对脑缺血组大鼠的神经功能评分显著提高(P<0.01),大脑梗死容积明显减小(P<0.01).电镜下见脑缺血组线粒体肿胀混浊,呈空泡化,内嵴断裂,膜破损;二氮嗪组线粒体仅有轻度肿胀,基本结构完好,内膜间隙清晰.5-HD复合二氮嗪组表现与脑缺血组近似,二氮嗪的保护作用被取消.结论 mito KATP的开放可以对缺血性脑损伤产生保护作用.

  14. 刺五加叶皂苷对心肌ATP敏感性钾通道的作用%Effects of acanthopanax senticosus saponins on myocardial ATP sensitive potassium channel

    Institute of Scientific and Technical Information of China (English)

    周逸; 唐其柱; 史锡滕; 王滕

    2004-01-01

    目的:研究刺五加叶皂苷(ASS)对心肌线粒体ATP敏感性钾通道(mito KATP)和细胞膜ATP敏感性钾通道(sarcol KATP)的作用,探讨ASS对缺血心肌保护作用的机制.方法:用酶解法获取兔心室肌细胞,激光扫描共聚焦显微镜观察ASS对mito KATP的作用,全细胞膜片钳技术观察ASS对sarcol KATP的作用.结果:对照组观察 10min 线粒体荧光强度无明显变化.ASS 30、100和 300 mg·L-1 组均可见用药后线粒体荧光强度明显增加,分别增加(14.8±3.6)%、(30.4±4.3)%和(38.4±5.7)%.3 μmol·L-1格列本脲不影响线粒体荧光强度,但可以阻断ASS对线粒体荧光强度的作用.而对照组、ASS 10、100和 300μmol·L-1 组的IK-ATP峰值无明显差异.结论:ASS对mito KATP有开放作用,而对sarcol KATP没有作用.ASS通过开放mito KATP产生心肌保护作用.

  15. Mitochondrial ATP sensitive potassium channel: a new target for brain protection in hypoxic/ischemic preconditioning%线粒体ATP敏感性钾通道:脑缺氧/缺血预适应保护的新焦点

    Institute of Scientific and Technical Information of China (English)

    任双来; 高天明; 范明

    2005-01-01

    脑缺氧/缺血及药物等多种因素预适应对脑缺氧/缺血损伤有明显的保护作用.自Noma 1983年发现心肌细胞膜上存在ATP敏感性钾通道(KATP)以来,KATP被认为是介导脑缺氧/缺血预适应重要的效应器.随着研究的深入,Inoue等于1991年在线粒体内膜发现了KATP,线粒体内膜ATP敏感性钾通道(mito-KATP)则成了人们新的关注焦点.虽然mito-KATP还没有被克隆出来,但现有相关领域的研究结果暗示mito- KATP将在脑缺血/缺氧预适应的脑保护中占有越来越重要的地位.

  16. Advance in Research of Mitochondria ATP-sensitive Potassium Channels and Myocardial Preservation%线粒体ATP敏感性钾通道与心肌保护的研究进展

    Institute of Scientific and Technical Information of China (English)

    陈昆; 林乌拉

    2005-01-01

    缺血预处理对心肌的保护作用强大,但其机制复杂,涉及许多信号转导途径.目前认为线粒体ATP敏感性钾通道是其终末效应器.是细胞的一种重要离子通道,其结构复杂,功能多样,在细胞的生理、病理生理过程中起着重要作用.线粒体ATP敏感性钾通道的心肌保护机制主要涉及减轻缺血细胞钙超载,减轻自由基损伤,减少细胞凋亡及减轻远期心室重构.就线粒体ATP敏感性钾通道的结构及其心肌保护机制作一综述.

  17. Research Advancement of Cardioprotection of Exercise Preconditioning Mediated by ATP-Sensitive Potassium Channels%ATP敏感钾通道介导运动预适应对心肌保护作用的研究进展

    Institute of Scientific and Technical Information of China (English)

    王凯; 潘珊珊

    2011-01-01

    通过文献研究,对ATP敏感钾通道的生物学特征进行了分析,在总结心肌ATP敏感钾通道介导心肌保护作用机制的基础上,对ATP敏感钾通道介导运动预适应心肌保护作用的研究进展进行了综述,从不同的研究视角对ATP敏感钾通道介导运动预适应心肌保护作用的研究前景进行了展望.

  18. Effects of Taurine on ATP-sensitive Potassium Channel Activity during Hypoxia in Ventricular Muscle of Guinea Pig%牛磺酸对豚鼠心室肌细胞膜ATP敏感性钾电流的影响

    Institute of Scientific and Technical Information of China (English)

    祝芬; 张培华; 马季骅

    2002-01-01

    应用100%纯氮饱和灌流液建立低氧模型和膜片钳全细胞记录技术, 研究牛磺酸对单个豚鼠心室肌细胞膜上ATP敏感性钾电流IKATP的影响.结果表明:牛磺酸具有抑制豚鼠心室肌细胞膜上ATP敏感钾通道KATP开放的作用.从而推测出低氧心肌细胞内牛磺酸的耗竭,可能是促使KATP通道开放的机制之一.

  19. ATP sensitive K+ channel may be involved in the protective effects of preconditioning in isolated guinea pig cardiomyocytes%ATP敏感性钾通道可能参与对经预处理的离体豚鼠心肌细胞的保护作用

    Institute of Scientific and Technical Information of China (English)

    刘华军; 陈灏珠; 杨学义; 程介士

    2001-01-01

    目的 对离体豚鼠心肌细胞予以短时间的低氧建立细胞预处理模型,并以此判定ATP敏感性钾通道是否参与此缺氧(模拟缺血)的预处理。 方法 从成年豚鼠的心室分离出单个心肌细胞,进行实验的灌流槽容许这些细胞暴露于低氧灌流液从而处于低氧分压状态。在低氧预处理过程中,细胞先在正常溶液中平衡10分钟然后暴露于低氧灌流液中5分钟,随后给予10分钟的复氧。对这些经预处理的细胞给予低氧20-180分钟并再复氧。用斑片钳技术进行全细胞和单通道记录研究其离子流变化。 结果 5分钟的低氧预处理可对细胞低氧复氧所引起的损伤提供显著的保护作用。经15分钟以上的延迟后,低氧诱导出非时间依赖性的钾外流,此外向性电流可被5 μmol/L的格列本脲所阻断。在除极化至10 mV时,此电流从78±15 pA增至1581±153 pA(P<0.01,n=18)。然而,产生ATP敏感性钾通道电流的延迟时间在经预处理的细胞中大为缩短,并增高更快。在10 mV时超过4 nA。在单通道记录中,从第一个通道开放到最大开放的时距在预处理细胞中大为缩短。 结论 分离的豚鼠心肌细胞可用短时间的低氧作预处理。此低氧预处理可改变ATP敏感性钾通道,使之在再次低氧时更快开放。%Objective To develop a cellular model of preconditioning by a brief period of hypoxia in isolated guinea pig cardiomyocytes and to determine whether or not an ATP sensitive K+ (KATP) channel is involved in ischemic preconditioning. Methods Single myocytes were isolated from the ventricle of adult guinea pigs. The experimental chamber allowed the cells to be exposed to low O2 pressure. During hypoxic preconditioning, the cells were equilibrated with normaxic solution for 10 minutes and then exposed to hypoxia for 5 minutes, followed by 10 minutes of reoxygenation. The cells were then subjected to 20

  20. Acetylcholine modulates transient outward potassium channel in acutely isolated cerebral cortical neurons of rats

    Institute of Scientific and Technical Information of China (English)

    Lanwei Cui; Tao Sun; Lihui Qu; Yurong Li; Haixia Wen

    2009-01-01

    BACKGROUND:The neuronal transient outward potassium channel has been shown to be highly associated with acetylcholine.However,the influence of acetylcholine on the transient outward potassium current in cerebral cortical neurons remains poorly understood.OBJECTIVE:To investigate acetylcholine modulation on transient outward potassium current in rat parietal cortical neurons using the whole-cell patch-clamp technique.DESIGN,TIME AND SETTING:A neuroelectrophysiology study was performed at the Department of Physiology,Harbin Medical University between January 2005 and January 2006.MATERIALS:Wistar rats were provided by the Animal Research Center,the Second Hospital of Harbin Medical University;PC-IIC patch-clamp amplifier and IBBClamp data collection analysis system were provided by Huazhong University for Science and Technology,Wuhan,China;PP-83 microelectrode puller was purchased from Narrishage,Japan.METHODS:The parietal somatosensory cortical neurons were acutely dissociated,and the modulation of acetylcholine (0.1,1,10,100 μmol/L) on transient outward potassium channel was recorded using the whole-cell patch-clamp technique.MAIN OUTCOME MEASURES:Influence of acetylcholine on transient outward potassium current,potassium channel activation,and inactivation.RESULTS:The inhibitory effect of acetylcholine on transient outward potassium current was dose- and voltage-dependent (P<0.01).Acetylcholine was found to significantly affect the activation process of transient outward potassium current,i.e.,the activation curve of transient outward potassium current was left-shifted,while the inactivation curve was shifted to hyperpolarization.Acetylcholine significantly prolonged the time constant of recovery from inactivation of transient outward potassium current (P<0.01).CONCLUSION:These results suggest that acetylcholine inhibits transient outward potassium current by regulating activation and inactivation processes of the transient outward potassium channel.

  1. Immunolocalization and expression of small-conductance calcium-activated potassium channels in human myometrium

    DEFF Research Database (Denmark)

    Rosenbaum, Sofia T; Svalø, Julie; Nielsen, Karsten;

    2012-01-01

    Small-conductance calcium-activated potassium (SK3) channels have been detected in human myometrium and we have previously shown a functional role of SK channels in human myometrium in vitro. The aims of this study were to identify the precise localization of SK3 channels and to quantify SK3 mRNA...

  2. Potassium channels in airway smooth muscle and airway hyperreactivity in asthma

    Institute of Scientific and Technical Information of China (English)

    LIU Xian-sheng; XU Yong-jian

    2005-01-01

    @@ Our knowledge of the physiology of ion channels has increased tremendously during the past 20 years because of the advances of the single-channel recording and molecular cloning techniques. More than 50 different identified potassium channels have already been found.

  3. The Sodium-Activated Potassium Channel Slack Is Required for Optimal Cognitive Flexibility in Mice

    Science.gov (United States)

    Bausch, Anne E.; Dieter, Rebekka; Nann, Yvette; Hausmann, Mario; Meyerdierks, Nora; Kaczmarek, Leonard K.; Ruth, Peter; Lukowski, Robert

    2015-01-01

    "Kcnt1" encoded sodium-activated potassium channels (Slack channels) are highly expressed throughout the brain where they modulate the firing patterns and general excitability of many types of neurons. Increasing evidence suggests that Slack channels may be important for higher brain functions such as cognition and normal intellectual…

  4. Deubiquitylating enzyme USP2 counteracts Nedd4-2-mediated downregulation of KCNQ1 potassium channels

    DEFF Research Database (Denmark)

    Krzystanek, Katarzyna; Rasmussen, Hanne Borger; Grunnet, Morten;

    2012-01-01

    with the KCNQ1 potassium channel through a PY motif located in the C terminus of KCNQ1. This interaction induces ubiquitylation of KCNQ1, resulting in a reduced surface density of the channel. It was reported recently that the epithelial sodium channel is regulated by the reverse process...

  5. The voltage-gated potassium channel subunit, Kv1.3, is expressed in epithelia

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hanne B; Hay-Schmidt, Anders;

    2003-01-01

    The Shaker-type voltage-gated potassium channel, Kv1.3, is believed to be restricted in distribution to lymphocytes and neurons. In lymphocytes, this channel has gained intense attention since it has been proven that inhibition of Kv1.3 channels compromise T lymphocyte activation. To investigate...

  6. Adenosine triphosphate-sensitive potassium channel opener protects PC12 cells against hypoxia-induced apoptosis through PI3K/Akt and Bcl-2 signaling pathways

    Institute of Scientific and Technical Information of China (English)

    Hong Zhang; Chunhong Jia; Danyang Zhao; Yang Lu; Runling Wang; Jia Li

    2010-01-01

    Although previous studies have shown the neuroprotective effects of the adenosine triphosphate (ATP)-sensitive potassium (KATP) channel opener against ischemic neuronal damage, little is known about the mechanisms involved. Phosphatidylinositol-3 kinase (PI3K)/v-akt murine thy-moma viral oncogene homolog (Akt) and Bcl-2 are thought to be important factors that mediate neuroprotection. The present study investigated the effects of KATP openers on hypoxia-induced PC12 cell apoptosis, as well as mRNA and protein expression of Akt and Bcl-2. Results demon-strated that pretreatment of PC12 cells with pinacidil, a KATP opener, resulted in decreased PC12 cell apoptosis following hypoxia, as detected by Annexin-V fluorescein isothiocyanate/ propidium iodide double staining flow cytometry. In addition, mRNA and protein expression of phosphorylated Akt (p-Akt) and Bcl-2 increased, as detected by immunofluorescence, Western blot analysis, and reverse-transcription polymerase chain reaction. The protective effect of this preconditioning was attenuated by glipizide, a selective KATP blocker. These results demonstrate for the first time that the protective mechanisms of KATP openers on PC12 cell apoptosis following hypoxia could result from activation of the PI3K/Akt signaling pathway, which further activates expression of the downstream Bcl-2 gene.

  7. Differential blockage of two types of potassium channels in the crab giant axon.

    Science.gov (United States)

    Soria, B; Arispe, N; Quinta-Ferreira, M E; Rojas, E

    1985-01-01

    Measurements were made of the kinetic and steady-state characteristics of the potassium conductance in the giant axon of the crabs Carcinus maenas and Cancer pagirus. The conductance increase during depolarizing voltage-clamp pulses was analyzed assuming that two separate types of potassium channels exist in these axons (M.E. Quinta-Ferreira, E. Rojas and N. Arispe, J. Membrane Biol. 66:171-181, 1982). It is shown here that, with small concentrations of conventional K+-channel blockers, it is possible to differentially inhibit these channels. The potassium channels with activation and fast inactivation gating (m3h, Hodgkin-Huxley kinetics) were blocked by external application of 4 amino-pyridine (4-AP). The potassium channels with standard gating (n4, Hodgkin-Huxley kinetics) were preferentially inhibited by externally applied tetraethylammonium (TEA). The differential blockage of the two types of potassium conductance changes suggests that they represent two different populations of potassium channels. It is further shown here that blocking the early transient conductance increase leads to the inhibition of the repetitive electrical activity induced by constant depolarizing current injection in fibers from Cardisoma guanhumi.

  8. Comparison of Single Channel Potassium Current in Biological and Synthetic Systems - Dependence on Voltage

    International Nuclear Information System (INIS)

    The influence of an external field on an ion current pattern in biological and synthetic systems was investigated. The patch clamp recordings of potassium current through a big conductance locust potassium channel (BK-channel) and a track-etched polyethylene terephthalate membrane were examined by the power spectrum, fractal analysis and relative dispersion analysis. A similar dependence of potassium current behaviour on the external voltage in both systems was found. The generalized dimension formalism is redefined to make it applicable to the analysis of time series. (author)

  9. Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel

    Science.gov (United States)

    Zhang, Hongkang; Zou, Beiyan; Yu, Haibo; Moretti, Alessandra; Wang, Xiaoying; Yan, Wei; Babcock, Joseph J.; Bellin, Milena; McManus, Owen B.; Tomaselli, Gordon; Nan, Fajun; Laugwitz, Karl-Ludwig; Li, Min

    2012-01-01

    Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as IKs and IKr. The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of IKr by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if IKs is reduced. Using a unique specific chemical activator for IKr that has a primary effect of causing a right shift of V1/2 for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an IKr chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent. PMID:22745159

  10. Gating motions in voltage-gated potassium channels revealed by coarse-grained molecular dynamics simulations

    NARCIS (Netherlands)

    Treptow, W.; Marrink, S.J.; Tarek, M.

    2008-01-01

    Voltage-gated potassium (Kv) channels are ubiquitous transmembrane proteins involved in electric signaling of excitable tissues. A fundamental property of these channels is the ability to open or close in response to changes in the membrane potential. To date, their structure-based activation mechan

  11. Role of calcium activated potassium channels in atrial fibrillation pathophysiology and therapy

    DEFF Research Database (Denmark)

    Diness, Jonas G.; Bentzen, Bo H.; S. Sørensen, Ulrik;

    2015-01-01

    Small-conductance Ca2+-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels since they might constitute a relatively atrial selective target. The present review will give...

  12. Activation of ERG2 potassium channels by the diphenylurea NS1643

    DEFF Research Database (Denmark)

    Elmedyb, Pernille; Olesen, Søren-Peter; Grunnet, Morten

    2007-01-01

    Three members of the ERG potassium channel family have been described (ERG1-3 or Kv 11.1-3). ERG1 is by far the best characterized subtype and it constitutes the molecular component of the cardiac I(Kr) current. All three channel subtypes are expressed in neurons but their function remains unclear...

  13. NONLINEAR PROPERTY MEMBRANE RECTIFIER POTASSIUM CHANNEL AND INHIBITORY EFFECTS OF OXYGEN FREE RADICAL

    Institute of Scientific and Technical Information of China (English)

    鲍光宏; 于德洁; 刘宇; 刘东梅

    1996-01-01

    There are at least eight kinds of different potassium chennels on cardiac cell membrane. This paperpresents a nonlinear property membrane outward; current going rectifying potassium channel and the in-hibitory efeets of oxygen free radical on this channel. The current-vohage relation of this nonlimmr-mem-brahe can be defined by an equation I=8a3/(0.01v2+4a2)2 and the maximum conductance of this channel is-75.3pS.

  14. The role of potassium channels in the nitric oxide-induced relaxation of human airway smooth muscle of passively sensitization by serum from allergic asthmatic patients

    Institute of Scientific and Technical Information of China (English)

    Tao Ye; Yongjian Xu; Zhenxiang Zhang; Xiansheng Liu; Zhao Yang; Baoan Gao

    2006-01-01

    Objective: To investigate the role of large Ca2+-activated, delayed-rectifier and ATP-sensitive potassium channel in regulating the relaxation induced by nitric oxide (NO) in normal and passively sensitized human airway smooth muscle (HASM) with serum from asthmatic patients. Methods: The effects of NO or/and potassium channel blockers on the tensions of normal and passively sensitized HASM were measured by using nitric oxide donor and potassium blockers, with the isometric tension recording technique. Results: Showed that (1)In the control group and passively sensitized group, Kv blocker (4-AP) cause concentration-dependent augmentation in the contraction induced by histamine (1 ×10-4 mol/L), (P < 0.05), but Glib (1 × 10-2 mol/L)and TEA (1×10-3 mol/L) have no significant effects on the contraction induced by histamine (1×10-4 mol/L). The maximum tension induced by histamine in passively sensitized group is higher than that in the control group (P < 0.05). (2) NO-donor Sodium Nitroprusside (SNP) bring about significant relaxation in normal and passively sensitized HASM rings (P < 0.05). Relaxations of passively sensitized airway rings [ (29.4 ± 3.3)% ] were significant less than those of normal HASM rings [ (44.1 ± 10.2)% ], (P <0.05).(3) Glib(1×10-2 mol/L)have no significant effect on the relaxations induced by SNP(1×10-4 mol/L). 4-AP(1×10-2 mol/L) inhibited relaxation induced by SNP (1×10-4 mol/L), (P < 0.01). TEA (1×10-3 mol/L) inhibited relaxation induced by SNP (1×10-4mol/L) (P < 0.05), and the inhibiting effect in passively sensitized HASM rings were significant less than in normal HASM, (P <0.05). Conclusion: It was concluded that SNP(NO-donor) relaxed the contraction of HASM partly via BKca channel opening. In passively sensitized HASM in vitro, the relaxation of SNP decreased compared with control group, which might be associated with the down-regulating activity of BKca in passively sensitized HASM.

  15. Human α-endosulfine, a possible regulator of sulfonylurea-sensitive KATP channel: Molecular cloning, expression and biological properties

    OpenAIRE

    Heron, Lisa; Virsolvy, Anne; Peyrollier, Karine; Gribble, Fiona M.; Le Cam, Alphonse; Ashcroft, Frances M.; Bataille, Dominique

    1998-01-01

    Sulfonylureas are a class of drugs commonly used in the management of non-insulin-dependent diabetes mellitus. Their therapeutic action results primarily from their ability to inhibit ATP-sensitive potassium (KATP) channels in the plasma membrane of pancreatic β cells and thereby stimulate insulin release. A key question is whether an endogenous ligand for the KATP channel exists that is able to mimic the inhibitory effects of sulfonylureas. We describe here the cloning of the cDNA encoding h...

  16. Open State Destabilization by Atp Occupancy Is Mechanism Speeding Burst Exit Underlying KATP Channel Inhibition by Atp

    OpenAIRE

    Li, Lehong; Geng, Xuehui; Drain, Peter

    2002-01-01

    The ATP-sensitive potassium (KATP) channel is named after its characteristic inhibition by intracellular ATP. The inhibition is a centerpiece of how the KATP channel sets electrical signaling to the energy state of the cell. In the β cell of the endocrine pancreas, for example, ATP inhibition results from high blood glucose levels and turns on electrical activity leading to insulin release. The underlying gating mechanism (ATP inhibition gating) includes ATP stabilization of closed states, bu...

  17. The antifungal plant defensin AtPDF2.3 from Arabidopsis thaliana blocks potassium channels.

    Science.gov (United States)

    Vriens, Kim; Peigneur, Steve; De Coninck, Barbara; Tytgat, Jan; Cammue, Bruno P A; Thevissen, Karin

    2016-01-01

    Scorpion toxins that block potassium channels and antimicrobial plant defensins share a common structural CSαβ-motif. These toxins contain a toxin signature (K-C4-X-N) in their amino acid sequence, and based on in silico analysis of 18 plant defensin sequences, we noted the presence of a toxin signature (K-C5-R-G) in the amino acid sequence of the Arabidopsis thaliana defensin AtPDF2.3. We found that recombinant (r)AtPDF2.3 blocks Kv1.2 and Kv1.6 potassium channels, akin to the interaction between scorpion toxins and potassium channels. Moreover, rAtPDF2.3[G36N], a variant with a KCXN toxin signature (K-C5-R-N), is more potent in blocking Kv1.2 and Kv1.6 channels than rAtPDF2.3, whereas rAtPDF2.3[K33A], devoid of the toxin signature, is characterized by reduced Kv channel blocking activity. These findings highlight the importance of the KCXN scorpion toxin signature in the plant defensin sequence for blocking potassium channels. In addition, we found that rAtPDF2.3 inhibits the growth of Saccharomyces cerevisiae and that pathways regulating potassium transport and/or homeostasis confer tolerance of this yeast to rAtPDF2.3, indicating a role for potassium homeostasis in the fungal defence response towards rAtPDF2.3. Nevertheless, no differences in antifungal potency were observed between the rAtPDF2.3 variants, suggesting that antifungal activity and Kv channel inhibitory function are not linked. PMID:27573545

  18. Potassium

    Science.gov (United States)

    ... blackberries Root vegetables, such as carrots and potatoes Citrus fruits, such as oranges and grapefruit Your kidneys help to keep the right amount of potassium in your body. If you have chronic kidney disease, your kidneys may not remove extra potassium from ...

  19. Physiology of intracellular potassium channels: A unifying role as mediators of counterion fluxes?

    Science.gov (United States)

    Checchetto, Vanessa; Teardo, Enrico; Carraretto, Luca; Leanza, Luigi; Szabo, Ildiko

    2016-08-01

    Plasma membrane potassium channels importantly contribute to maintain ion homeostasis across the cell membrane. The view is emerging that also those residing in intracellular membranes play pivotal roles for the coordination of correct cell function. In this review we critically discuss our current understanding of the nature and physiological tasks of potassium channels in organelle membranes in both animal and plant cells, with a special emphasis on their function in the regulation of photosynthesis and mitochondrial respiration. In addition, the emerging role of potassium channels in the nuclear membranes in regulating transcription will be discussed. The possible functions of endoplasmic reticulum-, lysosome- and plant vacuolar membrane-located channels are also referred to. Altogether, experimental evidence obtained with distinct channels in different membrane systems points to a possible unifying function of most intracellular potassium channels in counterbalancing the movement of other ions including protons and calcium and modulating membrane potential, thereby fine-tuning crucial cellular processes. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-7, 2016', edited by Prof. Paolo Bernardi. PMID:26970213

  20. Potassium Channels Blockers from the Venom of Androctonus mauretanicus mauretanicus

    Directory of Open Access Journals (Sweden)

    Marie-France Martin-Eauclaire

    2012-01-01

    Full Text Available K+ channels selectively transport K+ ions across cell membranes and play a key role in regulating the physiology of excitable and nonexcitable cells. Their activation allows the cell to repolarize after action potential firing and reduces excitability, whereas channel inhibition increases excitability. In eukaryotes, the pharmacology and pore topology of several structural classes of K+ channels have been well characterized in the past two decades. This information has come about through the extensive use of scorpion toxins. We have participated in the isolation and in the characterization of several structurally distinct families of scorpion toxin peptides exhibiting different K+ channel blocking functions. In particular, the venom from the Moroccan scorpion Androctonus mauretanicus mauretanicus provided several high-affinity blockers selective for diverse K+ channels  (SKCa,  Kv4.x, and  Kv1.x K+ channel families. In this paper, we summarize our work on these toxin/channel interactions.

  1. G protein-coupled inwardly rectifying potassium channels in dorsal root ganglion neurons

    Institute of Scientific and Technical Information of China (English)

    Xiao-fei GAO; Hai-lin ZHANG; Zhen-dong YOU; Chang-lin LU; Cheng HE

    2007-01-01

    Aim: G protein-coupled inwardly rectifying potassium channels (GIRK) are important for neuronal signaling and membrane excitability. In the present study, we intend to find whether GIRK channels express functionally in adult rat dorsal root ganglion (DRG) neurons. Methods: We used RT-PCR to detect mRNA for4 subunits of GIRK in the adult DRG. The whole-cell patch clamp recording was used to confirm GIRK channels functionally expressed. Results: The mRNA for the 4 subunits of GIRK were detected in the adult DRG. GTPγS enhanced inwardly rectifying potassium (K+) currents of the DRG neurons, while Ba2+inhibited such currents. Furthermore, the GIRK channels were shown to be coupled to the GABAB receptor, a member of the G protein-coupled receptor family, as baclofen increased the inwardly rectifying K+ currents. Conclusion: GIRK channels are expressed and functionally coupled with GABAB receptors in adult rat DRG neurons.

  2. Interaction of C-70 fullerene with the Kv1.2 potassium channel

    DEFF Research Database (Denmark)

    Monticelli, L.; Barnoud, J.; Orlowskid, A.;

    2012-01-01

    is not understood, though. Meanwhile, fullerene is also known to interfere with the activity of potassium channel proteins, but the mechanisms of protein inhibition are not known. Here we consider the possibility that membrane protein function would be inhibited by C-70 and/or GA through direct contact or through...... lipid-mediated interactions. To this end, we use microsecond time scale atomistic simulations to explore (a) modifications of membrane properties in the presence of C-70 and/or GA, and (b) the possible conformational changes in Kv1.2, a voltage-gated potassium channel, upon exposure to C-70, or GA...

  3. Atomic basis for therapeutic activation of neuronal potassium channels

    DEFF Research Database (Denmark)

    Kim, Robin Y; Yau, Michael C; Galpin, Jason D;

    2015-01-01

    Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2-5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific...

  4. Potassium

    Science.gov (United States)

    ... Take all forms of potassium with a full glass of water or fruit juice.Add the liquid ... to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in ...

  5. Non-Michaelis-Menten kinetics model for conductance of low-conductance potassium ion channels.

    Science.gov (United States)

    Tolokh, Igor S; Tolokh, Illya I; Cho, Hee Cheol; D'Avanzo, Nazzareno; Backx, Peter H; Goldman, Saul; Gray, C G

    2005-02-01

    A reduced kinetics model is proposed for ion permeation in low-conductance potassium ion channels with zero net electrical charge in the selectivity filter region. The selectivity filter is assumed to be the only conductance-determining part of the channel. Ion entry and exit rate constants depend on the occupancy of the filter due to ion-ion interactions. The corresponding rates are assumed slow relative to the rates of ion motion between binding sites inside the filter, allowing a reduction of the kinetics model of the filter by averaging the entry and exit rate constants over the states with a particular occupancy number. The reduced kinetics model for low-conductance channels is described by only three states and two sets of effective rate constants characterizing transitions between these states. An explicit expression for the channel conductance as a function of symmetrical external ion concentration is derived under the assumption that the average electrical mobility of ions in the selectivity filter region in a limited range of ion concentrations does not depend on these concentrations. The simplified conductance model is shown to provide a good description of the experimentally observed conductance-concentration curve for the low-conductance potassium channel Kir2.1, and also predicts the mean occupancy of the selectivity filter of this channel. We find that at physiological external ion concentrations this occupancy is much lower than the value of two ions observed for one of the high-conductance potassium channels, KcsA.

  6. Combinatorial augmentation of voltage-gated KCNQ potassium channels by chemical openers

    Science.gov (United States)

    Xiong, Qiaojie; Sun, Haiyan; Zhang, Yangming; Nan, Fajun; Li, Min

    2008-01-01

    Noninactivating potassium current formed by KCNQ2 (Kv7.2) and KCNQ3 (Kv7.3) subunits resembles neuronal M-currents which are activated by voltage and play a critical role in controlling membrane excitability. Activation of voltage-gated potassium channels by a chemical opener is uncommon. Therefore, the mechanisms of action are worthy further investigation. Retigabine and zinc pyrithione are two activators for KCNQ channels but their molecular interactions with KCNQ channel remain largely elusive. Here we report that retigabine and zinc pyrithione recognize two different sites of KCNQ2 channels. Their agonistic actions are noncompetitive and allow for simultaneous binding of two different activators on the same channel complex, hence giving rise to combinatorial potentiation with characteristic properties of both openers. Examining their effects on mutant channels, we showed zinc pyrithione is capable of opening nonconductive channels and coapplication of zinc pyrithione and retigabine could restore a disease mutant channel similar to wild type. Our results indicate two independent activator binding sites present in KCNQ channels. The resultant combinatorial potentiation by multiple synthetic chemical openers indicates that KCNQ channels are accessible to various types and combinations of pharmacological regulation. PMID:18272489

  7. KCNQ Modulators Reveal a Key Role for KCNQ Potassium Channels in Regulating the Tone of Rat Pulmonary Artery Smooth Muscle

    OpenAIRE

    Joshi, Shreena; Sedivy, Vojtech; Hodyc, Daniel; Herget, Jan; Gurney, Alison M

    2009-01-01

    Potassium channels are central to the regulation of pulmonary vascular tone. The smooth muscle cells of pulmonary artery display a background K+ conductance with biophysical properties resembling those of KCNQ (KV7) potassium channels. Therefore, we investigated the expression and functional role of KCNQ channels in pulmonary artery. The effects of selective KCNQ channel modulators were investigated on K+ current and membrane potential in isolated pulmonary artery smoo...

  8. Astemizole Derivatives as Fluorescent Probes for hERG Potassium Channel Imaging.

    Science.gov (United States)

    Wang, Beilei; Liu, Zhenzhen; Ma, Zhao; Li, Minyong; Du, Lupei

    2016-03-10

    The detection and imaging of hERG potassium channels in living cells can provide useful information for hERG-correlation studies. Herein, three small-molecule fluorescent probes, based on the potent hERG channel inhibitor astemizole, for the imaging of hERG channels in hERG-transfected HEK293 cells (hERG-HEK293) and human colorectal cancer cells (HT-29), are described. These probes are expected to be applied in the physiological and pathological studies of hERG channels. PMID:26985309

  9. The mechanism of gentisic acid-induced relaxation of the guinea pig isolated trachea: the role of potassium channels and vasoactive intestinal peptide receptors

    Directory of Open Access Journals (Sweden)

    J.F. Cunha

    2001-03-01

    Full Text Available We examined some of the mechanisms by which the aspirin metabolite and the naturally occurring metabolite gentisic acid induced relaxation of the guinea pig trachea in vitro. In preparations with or without epithelium and contracted by histamine, gentisic acid caused concentration-dependent and reproducible relaxation, with mean EC50 values of 18 µM and Emax of 100% (N = 10 or 20 µM and Emax of 92% (N = 10, respectively. The relaxation caused by gentisic acid was of slow onset in comparison to that caused by norepinephrine, theophylline or vasoactive intestinal peptide (VIP. The relative rank order of potency was: salbutamol 7.9 > VIP 7.0 > gentisic acid 4.7 > theophylline 3.7. Gentisic acid-induced relaxation was markedly reduced (24 ± 7.0, 43 ± 3.9 and 78 ± 5.6% in preparations with elevated potassium concentration in the medium (20, 40 or 80 mM, respectively. Tetraethylammonium (100 µM, a nonselective blocker of the potassium channels, partially inhibited the relaxation response to gentisic acid, while 4-AP (10 µM, a blocker of the voltage potassium channel, inhibited gentisic acid-induced relaxation by 41 ± 12%. Glibenclamide (1 or 3 µM, at a concentration which markedly inhibited the relaxation induced by the opener of ATP-sensitive K+ channels, levcromakalim, had no effect on the relaxation induced by gentisic acid. Charybdotoxin (0.1 or 0.3 µM, a selective blocker of the large-conductance Ca2+-activated K+ channels, caused rightward shifts (6- and 7-fold of the gentisic acid concentration-relaxation curve. L-N G-nitroarginine (100 µM, a NO synthase inhibitor, had no effect on the relaxant effect of gentisic acid, and caused a slight displacement to the right in the relaxant effect of the gentisic acid curve at 300 µM, while methylene blue (10 or 30 µM or ODQ (1 µM, the inhibitors of soluble guanylate cyclase, all failed to affect gentisic acid-induced relaxation. D-P-Cl-Phe6,Leu17[VIP] (0.1 µM, a VIP receptor antagonist

  10. Calcium-Activated Potassium Channels at Nodes of Ranvier Secure Axonal Spike Propagation

    Directory of Open Access Journals (Sweden)

    Jan Gründemann

    2015-09-01

    Full Text Available Functional connectivity between brain regions relies on long-range signaling by myelinated axons. This is secured by saltatory action potential propagation that depends fundamentally on sodium channel availability at nodes of Ranvier. Although various potassium channel types have been anatomically localized to myelinated axons in the brain, direct evidence for their functional recruitment in maintaining node excitability is scarce. Cerebellar Purkinje cells provide continuous input to their targets in the cerebellar nuclei, reliably transmitting axonal spikes over a wide range of rates, requiring a constantly available pool of nodal sodium channels. We show that the recruitment of calcium-activated potassium channels (IK, KCa3.1 by local, activity-dependent calcium (Ca2+ influx at nodes of Ranvier via a T-type voltage-gated Ca2+ current provides a powerful mechanism that likely opposes depolarizing block at the nodes and is thus pivotal to securing continuous axonal spike propagation in spontaneously firing Purkinje cells.

  11. Pulmonary vasoconstrictor action of KCNQ potassium channel blockers

    Directory of Open Access Journals (Sweden)

    Balan Prabhu

    2006-02-01

    Full Text Available Abstract Background KCNQ channels have been widely studied in the nervous system, heart and inner ear, where they have important physiological functions. Recent reports indicate that KCNQ channels may also be expressed in portal vein where they are suggested to influence spontaneous contractile activity. The biophysical properties of K+ currents mediated by KCNQ channels resemble a current underlying the resting K+ conductance and resting potential of pulmonary artery smooth muscle cells. We therefore investigated a possible role of KCNQ channels in regulating the function of pulmonary arteries by determining the ability of the selective KCNQ channel blockers, linopirdine and XE991, to promote pulmonary vasoconstriction. Methods The tension developed by rat and mouse intrapulmonary or mesenteric arteries was measured using small vessel myography. Contractile responses to linopirdine and XE991 were measured in intact and endothelium denuded vessels. Experiments were also carried out under conditions that prevent the contractile effects of nerve released noradrenaline or ATP, or block various Ca2+ influx pathways, in order to investigate the mechanisms underlying contraction. Results Linopirdine and XE991 both contracted rat and mouse pulmonary arteries but had little effect on mesenteric arteries. In each case the maximum contraction was almost as large as the response to 50 mM K+. Linopirdine had an EC50 of around 1 μM and XE991 was almost 10-fold more potent. Neither removal of the endothelium nor exposure to phentolamine or α,β-methylene ATP, to block α1-adrenoceptors or P2X receptors, respectively, affected the contraction. Contraction was abolished in Ca2+-free solution and in the presence of 1 μM nifedipine or 10 μM levcromakalim. Conclusion The KCNQ channel blockers are potent and powerful constrictors of pulmonary arteries. This action may be selective for the pulmonary circulation as mesenteric arteries showed little response. The

  12. Mitochondrial KATP channel inhibition blunts arrhythmia protection in ischemic exercised hearts

    OpenAIRE

    Quindry, John C.; Schreiber, Lindsey; Hosick, Peter; Wrieden, Jenna; Irwin, J. Megan; Hoyt, Emily

    2010-01-01

    The mechanisms responsible for anti-arrhythmic protection during ischemia-reperfusion (IR) in exercised hearts are not fully understood. The purpose of this investigation was to examine whether the ATP-sensitive potassium channels in the mitochondria (mito KATP) and sarcolemma (sarc KATP) provide anti-arrhythmic protection in exercised hearts during IR. Male Sprague-Dawley rats were randomly assigned to cardioprotective treadmill exercise or sedentary conditions before IR (I = 20 min, R = 30 ...

  13. Characterization of potassium channel modulators with QPatch automated patch-clamp technology: system characteristics and performance

    DEFF Research Database (Denmark)

    Kutchinsky, Jonatan; Friis, Søren; Asmild, Margit;

    2003-01-01

    -cell configurations lasted for >20 min. Cells were maintained in suspension up to 4 h in a cell storage facility that is integrated in the QPatch 16. No decline in patchability was observed during this time course. A series of screens was conducted with known inhibitors of the hERG and KCNQ4 potassium channels. Dose...

  14. POTASSIUM CHANNEL MODULATION - EFFECT OF PINACIDIL ON INSULIN RELEASE IN HEALTHY-VOLUNTEERS

    NARCIS (Netherlands)

    LINKS, TP; SMIT, AJ; REITSMA, WD

    1995-01-01

    The effect of a potassium (K+) channel opener (pinacidil) on serum insulin levels and blood glucose levels was investigated in normal volunteers during glucose loading. An intravenous glucose load was used with and without oral pretreatment: pinacidil (25 mg) 11 hours and 1 hour before the 25-g gluc

  15. Treating a natural outbreak of columnaris in channel catfish with copper sulfate and potassium permanganate

    Science.gov (United States)

    An F. Columnare-exclusive epizootic occurred in fingerling channel catfish (Ictalurus punctatus) during normal tank culture practices at SNARC. Fish were transferred to the ultra low-flow system and 2.1 mg/L copper sulfate or 3 mg/L potassium permanganate was administered; an untreated control was ...

  16. The effect of copper sulfate, potassium permanganate, and peracetic acid on Ichthyobodo necator in channel catfish

    Science.gov (United States)

    Ichthyobodo necator is a single celled biflagellate that can cause significant mortalities in fish, particularly young, tank-reared fish. Copper sulfate (CuSO4), potassium permanganate (KMnO4) and peracetic acid (PAA) were evaluated for effectiveness against Ichthybodosis in juvenile channel catfis...

  17. Effectiveness of copper sulfate and potassium permanganate on channel catfish infected with Flavobacterium columnare

    Science.gov (United States)

    Copper sulfate (CuSO4) and potassium permanganate (KMnO4) were evaluated for their effectiveness to curtail mortality and decrease bacterial load in fish tissues and water in channel catfish Ictalurus punctatus naturally infected with Flavobacterium columnare, the causative agent of columnaris. Fis...

  18. PKC and AMPK regulation of Kv1.5 potassium channels

    DEFF Research Database (Denmark)

    Andersen, Martin Nybo; Skibsbye, Lasse; Tang, Chuyi;

    2015-01-01

    The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid rectifier K(+) current (IKur), is regulated through several pathways. Here we investigate if Kv1.5 surface expression is controlled by the 2 kinases PKC and AMPK, using Xenopus oocytes, MDCK cells and atrial derived HL-1 cells...

  19. Contributions of counter-charge in a potassium channel voltage-sensor domain

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Galpin, Jason D; Niciforovic, Ana P;

    2011-01-01

    in transmembrane segments S2 and S3, namely Glu293 and Asp316 in Shaker potassium channels, has little functional effect on conductance-voltage relationships, although Glu293 appears to catalyze S4 movement. Our results suggest that neither Glu293 nor Asp316 engages in electrostatic state-dependent charge...

  20. Role of Calcium-activated Potassium Channels in Atrial Fibrillation Pathophysiology and Therapy.

    Science.gov (United States)

    Diness, Jonas G; Bentzen, Bo H; Sørensen, Ulrik S; Grunnet, Morten

    2015-11-01

    Small-conductance Ca(2+)-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti-atrial fibrillation principle. PMID:25830485

  1. Role of Calcium-activated Potassium Channels in Atrial Fibrillation Pathophysiology and Therapy.

    Science.gov (United States)

    Diness, Jonas G; Bentzen, Bo H; Sørensen, Ulrik S; Grunnet, Morten

    2015-11-01

    Small-conductance Ca(2+)-activated potassium (SK) channels are relative newcomers within the field of cardiac electrophysiology. In recent years, an increased focus has been given to these channels because they might constitute a relatively atrial-selective target. This review will give a general introduction to SK channels followed by their proposed function in the heart under normal and pathophysiological conditions. It is revealed how antiarrhythmic effects can be obtained by SK channel inhibition in a number of species in situations of atrial fibrillation. On the contrary, the beneficial effects of SK channel inhibition in situations of heart failure are questionable and still needs investigation. The understanding of cardiac SK channels is rapidly increasing these years, and it is hoped that this will clarify whether SK channel inhibition has potential as a new anti-atrial fibrillation principle.

  2. Local Sequence Information-based Support Vector Machine to Classify Voltage-gated Potassium Channels

    Institute of Scientific and Technical Information of China (English)

    Li-Xia LIU; Meng-Long LI; Fu-Yuan TAN; Min-Chun LU; Ke-Long WANG; Yan-Zhi GUO; Zhi-Ning WEN; Lin JIANG

    2006-01-01

    In our previous work, we developed a computational tool, PreK-ClassK-ClassKv, to predict and classify potassium (K+) channels. For K+ channel prediction (PreK) and classification at family level (ClassK), this method performs well. However, it does not perform so well in classifying voltage-gated potassium (Kv) channels (ClassKv). In this paper, a new method based on the local sequence information of Kv channels is introduced to classify Kv channels. Six transmembrane domains of a Kv channel protein are used to define a protein, and the dipeptide composition technique is used to transform an amino acid sequence to a numerical sequence. A Kv channel protein is represented by a vector with 2000 elements, and a support vector machine algorithm is applied to classify Kv channels. This method shows good performance with averages of total accuracy (Acc), sensitivity (SE), specificity (SP); reliability (R) and Matthews correlation coefficient (MCC) of 98.0%, 89.9%, 100%, 0.95 and 0.94 respectively. The results indicate that the local sequence information-based method is better than the global sequence information-based method to classify Kv channels.

  3. Differential distribution of the sodium-activated potassium channels slick and slack in mouse brain.

    Science.gov (United States)

    Rizzi, Sandra; Knaus, Hans-Günther; Schwarzer, Christoph

    2016-07-01

    The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are high-conductance potassium channels of the Slo family. In neurons, Slick and Slack channels are involved in the generation of slow afterhyperpolarization, in the regulation of firing patterns, and in setting and stabilizing the resting membrane potential. The distribution and subcellular localization of Slick and Slack channels in the mouse brain have not yet been established in detail. The present study addresses this issue through in situ hybridization and immunohistochemistry. Both channels were widely distributed and exhibited distinct distribution patterns. However, in some brain regions, their expression overlapped. Intense Slick channel immunoreactivity was observed in processes, varicosities, and neuronal cell bodies of the olfactory bulb, granular zones of cortical regions, hippocampus, amygdala, lateral septal nuclei, certain hypothalamic and midbrain nuclei, and several regions of the brainstem. The Slack channel showed primarily a diffuse immunostaining pattern, and labeling of cell somata and processes was observed only occasionally. The highest Slack channel expression was detected in the olfactory bulb, lateral septal nuclei, basal ganglia, and distinct areas of the midbrain, brainstem, and cerebellar cortex. In addition, comparing our data obtained from mouse brain with a previously published study on rat brain revealed some differences in the expression and distribution of Slick and Slack channels in these species. J. Comp. Neurol. 524:2093-2116, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. PMID:26587966

  4. The calcium-activated potassium channels of turtle hair cells

    OpenAIRE

    1995-01-01

    A major factor determining the electrical resonant frequency of turtle cochlear hair cells is the time course of the Ca-activated K current (Art, J. J., and R. Fettiplace. 1987. Journal of Physiology. 385:207- 242). We have examined the notion that this time course is dictated by the K channel kinetics by recording single Ca-activated K channels in inside-out patches from isolated cells. A hair cell's resonant frequency was estimated from its known correlation with the dimensions of the hair ...

  5. Molecular diversity and functional evolution of scorpion potassium channel toxins.

    Science.gov (United States)

    Zhu, Shunyi; Peigneur, Steve; Gao, Bin; Luo, Lan; Jin, Di; Zhao, Yong; Tytgat, Jan

    2011-02-01

    Scorpion toxins affecting K(+) channels (KTxs) represent important pharmacological tools and potential drug candidates. Here, we report molecular characterization of seven new KTxs in the scorpion Mesobuthus eupeus by cDNA cloning combined with biochemical approaches. Comparative modeling supports that all these KTxs share a conserved cysteine-stabilized α-helix/β-sheet structural motif despite the differences in protein sequence and size. We investigated functional diversification of two orthologous α-KTxs (MeuTXKα1 from M. eupeus and BmP01 from Mesobuthus martensii) by comparing their K(+) channel-blocking activities. Pharmacologically, MeuTXKα1 selectively blocked Kv1.3 channel with nanomolar affinity (IC(50), 2.36 ± 0.9 nM), whereas only 35% of Kv1.1 currents were inhibited at 3 μM concentration, showing more than 1271-fold selectivity for Kv1.3 over Kv1.1. This peptide displayed a weak effect on Drosophila Shaker channel and no activity on Kv1.2, Kv1.4, Kv1.5, Kv1.6, and human ether-a-go-go-related gene (hERG) K(+) channels. Although BmB01 and MeuTXKα1 have a similar channel spectrum, their affinity and selectivity for these channels largely varies. In comparison with MeuTXKα1, BmP01 only exhibits a submicromolar affinity (IC(50), 133.72 ± 10.98 nM) for Kv1.3, showing 57-fold less activity than MeuTXKα1. Moreover, it lacks the ability to distinguish between Kv1.1 and Kv1.3. We also found that MeuTXKα1 inhibited the proliferation of activated T cells induced by phorbol myristate acetate and ionomycin at micromolar concentrations. Our results demonstrate that accelerated evolution drives affinity variations of orthologous α-KTxs on Kv channels and indicate that MeuTXKα1 is a promising candidate to develop an immune modulation agent for human autoimmune diseases. PMID:20889474

  6. Atomic basis for therapeutic activation of neuronal potassium channels

    Science.gov (United States)

    Kim, Robin Y.; Yau, Michael C.; Galpin, Jason D.; Seebohm, Guiscard; Ahern, Christopher A.; Pless, Stephan A.; Kurata, Harley T.

    2015-09-01

    Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2-5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific chemical interactions required for retigabine action. Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp. Supporting this model, substitution with fluorinated Trp analogues, with increased H-bonding propensity, strengthens retigabine potency. In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators. These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators.

  7. Distance-dependent homeostatic synaptic scaling mediated by A-type potassium channels

    Directory of Open Access Journals (Sweden)

    Hiroshi T Ito

    2009-11-01

    Full Text Available Many lines of evidence suggest that the efficacy of synapses on CA1 pyramidal neuron dendrites increases as a function of distance from the cell body. The strength of an individual synapse is also dynamically modulated by activity-dependent synaptic plasticity, which raises the question as to how a neuron can reconcile individual synaptic changes with the maintenance of the proximal-to-distal gradient of synaptic strength along the dendrites. As the density of A-type potassium channels exhibits a similar gradient from proximal (low-to-distal (high dendrites, the A-current may play a role in coordinating local synaptic changes with the global synaptic strength gradient. Here we describe a form of homeostatic plasticity elicited by conventional activity blockade (with TTX coupled with a block of the A-type potassium channel. Following A-type potassium channel inhibition for 12 hrs, recordings from CA1 somata revealed a significantly higher miniature excitatory postsynaptic current (mEPSC frequency, whereas in dendritic recordings, there was no change in mEPSC frequency. Consistent with mEPSC recordings, we observed a significant increase in AMPA receptor density in stratum pyramidale but not stratum radiatum. Based on these data, we propose that the differential distribution of A-type potassium channels along the apical dendrites may create a proximal-to-distal membrane potential gradient. This gradient may regulate AMPA receptor distribution along the same axis. Taken together, our results indicate that A-type potassium channels play an important role in controlling synaptic strength along the dendrites, which may help to maintain the computational capacity of the neuron.

  8. A review of potassium channels in bipolar disorder

    OpenAIRE

    Judy, Jennifer T.; Zandi, Peter P.

    2013-01-01

    Although bipolar disorder (BP) is one of the most heritable psychiatric conditions, susceptibility genes for the disorder have yet to be conclusively identified. It is likely that variants in multiple genes across multiple pathways contribute to the genotype–phenotype relationship in the affected population. Recent evidence from genome-wide association studies implicates an entire class of genes related to the structure and regulation of ion channels, suggesting that the etiology of BP may ar...

  9. A review of potassium channels in bipolar disorder

    OpenAIRE

    Jennifer Toolan Judy; Peter eZandi

    2013-01-01

    Although bipolar disorder (BP) is one of the most heritable psychiatric conditions, susceptibility genes for the disorder have yet to be conclusively identified. It is likely that variants in multiple genes across multiple pathways contribute to the genotype-phenotype relationship. Recent evidence from genome-wide association studies (GWAS) implicates an entire class of genes related to the structure and regulation of ion channels, suggesting that the etiology of BP may arise from a channelop...

  10. Molecular Diversity and Functional Evolution of Scorpion Potassium Channel Toxins*

    OpenAIRE

    Zhu, Shunyi; Peigneur, Steve; Gao, Bin; Luo, Lan; Jin, Di; Zhao, Yong; Tytgat, Jan

    2010-01-01

    Scorpion toxins affecting K+ channels (KTxs) represent important pharmacological tools and potential drug candidates. Here, we report molecular characterization of seven new KTxs in the scorpion Mesobuthus eupeus by cDNA cloning combined with biochemical approaches. Comparative modeling supports that all these KTxs share a conserved cysteine-stabilized α-helix/β-sheet structural motif despite the differences in protein sequence and size. We investigated functional diversification of two ortho...

  11. The acrylamide (S)-1 differentially affects Kv7 (KCNQ) potassium channels

    DEFF Research Database (Denmark)

    Bentzen, Bo Hjorth; Schmitt, Nicole; Calloe, Kirstine;

    2006-01-01

    The family of Kv7 (KCNQ) potassium channels consists of five members. Kv7.2 and 3 are the primary molecular correlates of the M-current, but also Kv7.4 and Kv7.5 display M-current characteristics. M-channel modulators include blockers (e.g., linopirdine) for cognition enhancement and openers (e.......g., retigabine) for treatment of epilepsy and neuropathic pain. We investigated the effect of a Bristol-Myers Squibb compound (S)-N-[1-(3-morpholin-4-yl-phenyl)-ethyl]-3-phenyl-acrylamide [(S)-1] on cloned human Kv7.1-5 potassium channels expressed in Xenopus laevis oocytes. Using two-electrode voltage...

  12. Voltage-gated potassium channel KCNV2 (Kv8.2) contributes to epilepsy susceptibility

    OpenAIRE

    Jorge, Benjamin S.; Campbell, Courtney M.; Miller, Alison R.; Rutter, Elizabeth D.; Gurnett, Christina A; Vanoye, Carlos G; George, Alfred L.; Kearney, Jennifer A.

    2011-01-01

    Mutations in voltage-gated ion channels are responsible for several types of epilepsy. Genetic epilepsies often exhibit variable severity in individuals with the same mutation, which may be due to variation in genetic modifiers. The Scn2aQ54 transgenic mouse model has a sodium channel mutation and exhibits epilepsy with strain-dependent severity. We previously mapped modifier loci that influence Scn2aQ54 phenotype severity and identified Kcnv2, encoding the voltage-gated potassium channel sub...

  13. Gain-of-Function Mutations in the KATP Channel (KCNJ11) Impair Coordinated Hand-Eye Tracking

    OpenAIRE

    James S McTaggart; Ned Jenkinson; John-Stuart Brittain; Greeley, Siri A. W.; Hattersley, Andrew T; Ashcroft, Frances M.

    2013-01-01

    Background Gain-of-function mutations in the ATP-sensitive potassium channel can cause permanent neonatal diabetes mellitus (PNDM) or neonatal diabetes accompanied by a constellation of neurological symptoms (iDEND syndrome). Studies of a mouse model of iDEND syndrome revealed that cerebellar Purkinje cell electrical activity was impaired and that the mice exhibited poor motor coordination. In this study, we probed the hand-eye coordination of PNDM and iDEND patients using visual tracking tas...

  14. A naturally occurring omega current in a Kv3 family potassium channel from a platyhelminth

    Directory of Open Access Journals (Sweden)

    Spencer Andrew N

    2008-06-01

    Full Text Available Abstract Background Voltage-gated ion channels are membrane proteins containing a selective pore that allows permeable ions to transit the membrane in response to a change in the transmembrane voltage. The typical selectivity filter in potassium channels is formed by a tetrameric arrangement of the carbonyl groups of the conserved amino-acid sequence Gly-Tyr-Gly. This canonical pore is opened or closed by conformational changes that originate in the voltage sensor (S4, a transmembrane helix with a series of positively charged amino acids. This sensor moves through a gating pore formed by elements of the S1, S2 and S3 helices, across the plane of the membrane, without allowing ions to pass through the membrane at that site. Recently, synthetic mutagenesis studies in the Drosophila melanogaster Shaker channel and analysis of human disease-causing mutations in sodium channels have identified amino acid residues that are integral parts of the gating-pore; when these residues are mutated the proteins allow a non-specific cation current, known as the omega current, to pass through the gating-pore with relatively low selectivity. Results The N.at-Kv3.2 potassium channel has an unusual weak inward rectifier phenotype. Several mutations of two amino acids in the voltage sensing (S4 transmembrane helix change the phenotype to a typical delayed rectifier. The inward rectifier channels (wild-type and mutant are sensitive to 4-aminopyridine (4-AP but not tetra-ethyl ammonium (TEA, whereas the delayed rectifier mutants are sensitive to TEA but not 4-AP. The inward rectifier channels also manifest low cation selectivity. The relative selectivity for different cations is sensitive to specific mutations in the S4 helix, Conclusion N.at-Kv3.2, a naturally occurring potassium channel of the Kv3 sequence family, mediates ion permeation through a modified gating pore, not the canonical, highly selective pore typical of potassium channels. This channel has evolved to

  15. Calcium-Activated Potassium Channels in Ischemia Reperfusion: A Brief Update

    Directory of Open Access Journals (Sweden)

    Jean-Yves eTano

    2014-10-01

    Full Text Available Ischemia and reperfusion (IR injury constitutes one of the major causes of cardiovascular morbidity and mortality. The discovery of new therapies to block/mediate the effects of IR is therefore an important goal in the biomedical sciences. Dysfunction associated with IR involves modification of calcium-activated potassium channels (KCa through different mechanisms, which are still under study. Respectively, the KCa family, major contributors to plasma membrane calcium influx in cells and essential players in the regulation of the vascular tone are interesting candidates. This family is divided into two groups including the large conductance (BKCa and the small/intermediate conductance (SKCa/IKCa K+ channels. In the heart and brain, these channels have been described to offer protection against IR injury. BKCa and SKCa channels deserve special attention since new data demonstrate that these channels are also expressed in mitochondria. More studies are however needed to fully determine their potential use as therapeutic targets.

  16. Effects of arsenic trioxide on voltage-dependent potassium channels and on cell proliferation of human multiple myeloma cells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jin; WANG Wei; WEI Qing-fang; FENG Tie-ming; TAN Li-jun; YANG Bao-feng

    2007-01-01

    @@ Arsenic trioxide (ATO) can induce cellular apoptosis and inhibit the activities of multiple myeloma (MM)cells in vitro,1 but how it works is not very clear. Recent studies showed that ATO worked on the voltagedependent potassium channel and L-type calcium channel in myocardial cells,2-5 but the effect of ATO on ion channels of tumor cells was rarely reported. As the potassium channel plays an important role in controlling cell proliferation,6 we studied the effects of ATO on the voltage-dependent potassium current (Ikv) of the voltage-dependent potassium channel in an MM cell line,and probed into the relationship between changes of the Ikv caused by ATO and cell proliferation.

  17. M-type potassium channels modulate Schaffer collateral-CA1 glutamatergic synaptic transmission.

    Science.gov (United States)

    Sun, Jianli; Kapur, Jaideep

    2012-08-15

    Previous studies have suggested that muscarinic receptor activation modulates glutamatergic transmission. M-type potassium channels mediate the effects of muscarinic activation in the hippocampus, and it has been proposed that they modulate glutamatergic synaptic transmission. We tested whether M1 muscarinic receptor activation enhances glutamatergic synaptic transmission via the inhibition of the M-type potassium channels that are present in Schaffer collateral axons and terminals. Miniature excitatory postsynaptic currents (mEPSCs) were recorded from CA1 pyramidal neurons. The M1 receptor agonist, NcN-A-343, increased the frequency of mEPSCs, but did not alter their amplitude. The M-channel blocker XE991 and its analogue linopirdine also increased the frequency of mEPSCs. Flupirtine, which opens M-channels, had the opposite effect. XE991 did not enhance mEPSCs frequency in a calcium-free external medium. Blocking P/Q- and N-type calcium channels abolished the effect of XE991 on mEPSCs. These data suggested that the inhibition of M-channels increases presynaptic calcium-dependent glutamate release in CA1 pyramidal neurons. The effects of these agents on the membrane potentials of presynaptic CA3 pyramidal neurons were studied using current clamp recordings; activation of M1 receptors and blocking M-channels depolarized neurons and increased burst firing. The input resistance of CA3 neurons was increased by the application of McN-A-343 and XE991; these effects were consistent with the closure of M-channels. Muscarinic activation inhibits M-channels in CA3 pyramidal neurons and its efferents – Schaffer collateral, which causes the depolarization, activates voltage-gated calcium channels, and ultimately elevates the intracellular calcium concentration to increase the release of glutamate on CA1 pyramidal neurons. PMID:22674722

  18. Potassium Channel Activator Attenuates Salicylate-Induced Cochlear Hearing Loss Potentially Ameliorating Tinnitus

    Directory of Open Access Journals (Sweden)

    Wei eSun

    2015-04-01

    Full Text Available High dose sodium salicylate causes moderate, reversible hearing loss and tinnitus. Salicylate-induced hearing loss is believed to arise from a reduction in the electromotile response of outer hair cells (OHCs and/or reduction of KCNQ4 potassium currents in OHCs which decreases the driving force for the transduction current. Therefore, enhancing OHC potassium currents could potentially prevent salicylate-induced temporary hearing loss. In this study, we tested whether opening voltage-gated potassium channels using ICA-105665, a novel small molecule that opens KCNQ2/3 and KCNQ3/5 channels, can reduce salicylate-induced hearing loss. We found that systemic application of ICA-105665 at 10 mg/kg prevented the salicylate-induced amplitude reduction and threshold shift in the compound action potentials recorded at the round window of the cochlea. ICA-105665 also prevented the salicylate-induced reduction of distortion products of otoacoustic emission (DPOAE. These results suggest that ICA-105665 partially compensates for salicylate induced cochlear hearing loss by enhancing KCNQ2/3 and KCNQ3/5 potassium currents and the motility of OHCs.

  19. The uniqueness of the plant mitochondrial potassium channel

    Directory of Open Access Journals (Sweden)

    Donato Pastore

    2013-08-01

    Full Text Available The ATP-inhibited Plant Mitochondrial K+ Channel (PmitoKATPwas discovered about fifteen years ago in Durum WheatMitochondria (DWM. PmitoKATP catalyses the electrophoreticK+ uniport through the inner mitochondrial membrane;moreover, the co-operation between PmitoKATP and K+/H+antiporter allows such a great operation of a K+ cycle tocollapse mitochondrial membrane potential (ΔΨ and ΔpH, thusimpairing protonmotive force (Δp. A possible physiological roleof such ΔΨ control is the restriction of harmful reactive oxygenspecies (ROS production under environmental/oxidative stressconditions. Interestingly, DWM lacking Δp were found to benevertheless fully coupled and able to regularly accomplish ATPsynthesis; this unexpected behaviour makes necessary to recastin some way the classical chemiosmotic model. In the whole,PmitoKATP may oppose to large scale ROS production bylowering ΔΨ under environmental/oxidative stress, but, whenstress is moderate, this occurs without impairing ATP synthesisin a crucial moment for cell and mitochondrial bioenergetics.[BMB Reports 2013; 46(8: 391-397

  20. Encephalitis due to antibodies to voltage gated potassium channel (VGKC with cerebellar involvement in a teenager

    Directory of Open Access Journals (Sweden)

    Megan M Langille

    2015-01-01

    Full Text Available Encephalitis due to antibodies to voltage gated potassium channel (VGKC typically presents with limbic encephalitis and medial temporal lobe involvement on neuroimaging. We describe a case of 13 year girl female with encephalitis due to antibodies to VGKC with signal changes in the cerebellar dentate nuclei bilaterally and clinical features that suggested predominant cerebellar involvement. These have never been reported previously in the literature. Our case expands the phenotypic spectrum of this rare condition.

  1. Encephalitis due to antibodies to voltage gated potassium channel (VGKC) with cerebellar involvement in a teenager.

    Science.gov (United States)

    Langille, Megan M; Desai, Jay

    2015-01-01

    Encephalitis due to antibodies to voltage gated potassium channel (VGKC) typically presents with limbic encephalitis and medial temporal lobe involvement on neuroimaging. We describe a case of 13 year girl female with encephalitis due to antibodies to VGKC with signal changes in the cerebellar dentate nuclei bilaterally and clinical features that suggested predominant cerebellar involvement. These have never been reported previously in the literature. Our case expands the phenotypic spectrum of this rare condition.

  2. Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease

    OpenAIRE

    Jammoul, Adham; Lederman, Richard J; Tavee, Jinny; Li, Yuebing

    2014-01-01

    Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is...

  3. Targeting solid tumours with potassium channel activators. A return to fundamentals?

    Science.gov (United States)

    Trechot, Philippe

    2014-01-01

    From a pharmacological point of view nicotinamide and minoxidil are potassium channel activators. Nicotinamide is used as a radiosensitizer in ARCON (accelerated radiotherapy combined with carbogen breathing and nicotinamide) therapeutic strategy with promising results but not confirmed so far. Minoxidil has never been considered by radiotherapists. Based from recent pathophysiological considerations we suggest a new perspective for the use of these two "old" molecules in order to target solid tumours. PMID:25371295

  4. Crystal structure of the PAS domain of the hEAG potassium channel.

    Science.gov (United States)

    Tang, Xue; Shao, Juan; Qin, Xiaohong

    2016-08-01

    KCNH voltage-gated potassium channels play critical roles in regulating cellular functions. The channel is composed of four subunits, each of which contains six transmembrane helices forming the central pore. The cytoplasmic parts of the subunits present a Per-Arnt-Sim (PAS) domain at the N-terminus and a cyclic nucleotide-binding homology domain at the C-terminus. PAS domains are conserved from prokaryotes to eukaryotes and are involved in sensing signals and cellular responses. To better understand the functional roles of PAS domains in KCNH channels, the structure of this domain from the human ether-à-go-go channel (hEAG channel) was determined. By comparing it with the structures of the Homo sapiens EAG-related gene (hERG) channel and the Drosophila EAG-like K(+) (dELK) channel and analyzing the structural features of the hEAG channel, it was identified that a hydrophobic patch on the β-sheet may mediate interaction between the PAS domain and other regions of the channel to regulate its functions. PMID:27487920

  5. Gain-of-function mutations in potassium channel subunit KCNE2 associated with early-onset lone atrial fibrillation

    DEFF Research Database (Denmark)

    Nielsen, Jonas Bille; Bentzen, Bo Hjorth; Olesen, Morten Salling;

    2014-01-01

    Aims: Atrial fibrillation (AF) is the most common cardiac arrhythmia. Disturbances in cardiac potassium conductance are considered as one of the disease mechanisms in AF. We aimed to investigate if mutations in potassium-channel β-subunits KCNE2 and KCNE3 are associated with early-onset lone AF. ...

  6. Histidine phosphorylation relieves copper inhibition in the mammalian potassium channel KCa3.1.

    Science.gov (United States)

    Srivastava, Shekhar; Panda, Saswati; Li, Zhai; Fuhs, Stephen R; Hunter, Tony; Thiele, Dennis J; Hubbard, Stevan R; Skolnik, Edward Y

    2016-01-01

    KCa2.1, KCa2.2, KCa2.3 and KCa3.1 constitute a family of mammalian small- to intermediate-conductance potassium channels that are activated by calcium-calmodulin. KCa3.1 is unique among these four channels in that activation requires, in addition to calcium, phosphorylation of a single histidine residue (His358) in the cytoplasmic region, by nucleoside diphosphate kinase-B (NDPK-B). The mechanism by which KCa3.1 is activated by histidine phosphorylation is unknown. Histidine phosphorylation is well characterized in prokaryotes but poorly understood in eukaryotes. Here, we demonstrate that phosphorylation of His358 activates KCa3.1 by antagonizing copper-mediated inhibition of the channel. Furthermore, we show that activated CD4(+) T cells deficient in intracellular copper exhibit increased KCa3.1 histidine phosphorylation and channel activity, leading to increased calcium flux and cytokine production. These findings reveal a novel regulatory mechanism for a mammalian potassium channel and for T-cell activation, and highlight a unique feature of histidine versus serine/threonine and tyrosine as a regulatory phosphorylation site. PMID:27542194

  7. Potassium channel blockers from the venom of the Brazilian scorpion Tityus serrulatus ().

    Science.gov (United States)

    Martin-Eauclaire, Marie-France; Pimenta, Adriano M C; Bougis, Pierre E; De Lima, Maria-Elena

    2016-09-01

    Potassium (K(+)) channels are trans-membrane proteins, which play a key role in cellular excitability and signal transduction pathways. Scorpion toxins blocking the ion-conducting pore from the external side have been invaluable probes to elucidate the structural, functional, and physio-pathological characteristics of these ion channels. This review will focus on the interaction between K(+) channels and their peptide blockers isolated from the venom of the scorpion Tityus serrulatus, which is considered as the most dangerous scorpion in Brazil, in particular in Minas-Gerais State, where many casualties are described each year. The primary mechanisms of action of these K(+) blockers will be discussed in correlation with their structure, very often non-canonical compared to those of other well known K(+) channels blockers purified from other scorpion venoms. Also, special attention will be brought to the most recent data obtained by proteomic and transcriptomic analyses on Tityus serrulatus venoms and venom glands. PMID:27349167

  8. Involvement of Potassium and Cation Channels in Hippocampal Abnormalities of Embryonic Ts65Dn and Tc1 Trisomic Mice

    Directory of Open Access Journals (Sweden)

    Shani Stern

    2015-09-01

    Numerical simulations reproduced the DS measured phenotype by variations in the conductance of the delayed rectifier and A-type, but necessitated also changes in inward rectifying and M-type potassium channels and in the hyperpolarization-activated cyclic nucleotide-gated (HCN channels. We therefore conducted whole cell patch clamp measurements of M-type potassium currents, which showed a ~90% decrease in Ts65Dn neurons, while HCN measurements displayed an increase of ~65% in Ts65Dn cells. Quantitative real-time PCR analysis indicates overexpression of 40% of KCNJ15, an inward rectifying potassium channel, contributing to the increased inhibition. We thus find that changes in several types of potassium channels dominate the observed DS model phenotype.

  9. Regulation of adenosine triphosphate-sensitive potassium channels suppresses the toxic effects of amyloid-beta peptide (25-35)

    Institute of Scientific and Technical Information of China (English)

    Min Kong; Maowen Ba; Hui Liang; Peng Shao; Tianxia Yu; Ying Wang

    2013-01-01

    In this study, we treated PC12 cells with 0-20 μM amyloid-β peptide (25-35) for 24 hours to induce cytotoxicity, and found that 5-20 μM amyloid-β peptide (25-35) decreased PC12 cell viability, but adenosine triphosphate-sensitive potassium channel activator diazoxide suppressed the decrease reactive oxygen species levels. These protective effects were reversed by the selective mitochondrial adenosine triphosphate-sensitive potassium channel blocker 5-hydroxydecanoate. An inducible nitric oxide synthase inhibitor, Nω-nitro-L-arginine, also protected PC12 cells from intracellular reactive oxygen species levels. However, the H2O2-degrading enzyme catalase could that the increases in both mitochondrial membrane potential and reactive oxygen species levels adenosine triphosphate-sensitive potassium channels and nitric oxide. Regulation of adenosine triphosphate-sensitive potassium channels suppresses PC12 cell cytotoxicity induced by amyloid-β

  10. Dynamic subunit stoichiometry confers a progressive continuum of pharmacological sensitivity by KCNQ potassium channels

    Science.gov (United States)

    Yu, Haibo; Lin, Zhihong; Mattmann, Margrith E.; Zou, Beiyan; Terrenoire, Cecile; Zhang, Hongkang; Wu, Meng; McManus, Owen B.; Kass, Robert S.; Lindsley, Craig W.; Hopkins, Corey R.; Li, Min

    2013-01-01

    Voltage-gated KCNQ1 (Kv7.1) potassium channels are expressed abundantly in heart but they are also found in multiple other tissues. Differential coassembly with single transmembrane KCNE beta subunits in different cell types gives rise to a variety of biophysical properties, hence endowing distinct physiological roles for KCNQ1–KCNEx complexes. Mutations in either KCNQ1 or KCNE1 genes result in diseases in brain, heart, and the respiratory system. In addition to complexities arising from existence of five KCNE subunits, KCNE1 to KCNE5, recent studies in heterologous systems suggest unorthodox stoichiometric dynamics in subunit assembly is dependent on KCNE expression levels. The resultant KCNQ1–KCNE channel complexes may have a range of zero to two or even up to four KCNE subunits coassembling per KCNQ1 tetramer. These findings underscore the need to assess the selectivity of small-molecule KCNQ1 modulators on these different assemblies. Here we report a unique small-molecule gating modulator, ML277, that potentiates both homomultimeric KCNQ1 channels and unsaturated heteromultimeric (KCNQ1)4(KCNE1)n (n < 4) channels. Progressive increase of KCNE1 or KCNE3 expression reduces efficacy of ML277 and eventually abolishes ML277-mediated augmentation. In cardiomyocytes, the slowly activating delayed rectifier potassium current, or IKs, is believed to be a heteromultimeric combination of KCNQ1 and KCNE1, but it is not entirely clear whether IKs is mediated by KCNE-saturated KCNQ1 channels or by channels with intermediate stoichiometries. We found ML277 effectively augments IKs current of cultured human cardiomyocytes and shortens action potential duration. These data indicate that unsaturated heteromultimeric (KCNQ1)4(KCNE1)n channels are present as components of IKs and are pharmacologically distinct from KCNE-saturated KCNQ1–KCNE1 channels. PMID:23650380

  11. [Inhibition of oxygen free radicals in potassium channels of cardiac myocytes and the action of salvianolic acid A].

    Science.gov (United States)

    Bao, G

    1993-10-01

    By using the patch clamp technique, the effect of oxygen free radicals on the single potassium channels of cardiac papillary muscle cells were studied, as well as the action of salvianolic acid A. It was found that xanthane-xanthane oxidase generated oxygen free radicals could apparently inhibited the unitary currents of the single potassium channel activity. This inhibition was reversed by salvianolic acid A, which is an effective component extracted from Salvia miltiorrhiza. PMID:8168213

  12. Differential effects of ethanol on electrical properties of various potassium channels expressed in oocytes.

    Science.gov (United States)

    Anantharam, V; Bayley, H; Wilson, A; Treistman, S N

    1992-09-01

    The effects of ethanol on a number of electrophysiological parameters were examined in 10 different voltage-gated potassium channels expressed in Xenopus oocytes. None of the channels examined was highly sensitive to ethanol, but there was significant variability among the channels tested at concentrations of ethanol of 200 mM and greater. The response to ethanol was not determined exclusively by membership in a genetic subfamily. In addition, the relative sensitivity among different channels could vary independently for different electrical parameters. For example, current amplitude in DRK1 was insensitive to ethanol, even at concentrations as high as 600 mM, whereas this was one of the more sensitive channels with respect to the kinetics of current inactivation. The opposite situation was true for ShA1. Therefore, ethanol at high concentrations may selectively perturb discrete regions of channel proteins. This is supported by the finding that removal of 318 amino acids from the cytoplasmic carboxyl terminus of DRK1 results in a channel whose current amplitude shows greater sensitivity to ethanol than does DRK1. Thus, the effects of ethanol on the channel may not be limited to interactions at the lipid-protein interface. PMID:1406600

  13. Identification of quaternary ammonium compounds as potent inhibitors of hERG potassium channels

    International Nuclear Information System (INIS)

    The human ether-a-go-go-related gene (hERG) channel, a member of a family of voltage-gated potassium (K+) channels, plays a critical role in the repolarization of the cardiac action potential. The reduction of hERG channel activity as a result of adverse drug effects or genetic mutations may cause QT interval prolongation and potentially leads to acquired long QT syndrome. Thus, screening for hERG channel activity is important in drug development. Cardiotoxicity associated with the inhibition of hERG channels by environmental chemicals is also a public health concern. To assess the inhibitory effects of environmental chemicals on hERG channel function, we screened the National Toxicology Program (NTP) collection of 1408 compounds by measuring thallium influx into cells through hERG channels. Seventeen compounds with hERG channel inhibition were identified with IC50 potencies ranging from 0.26 to 22 μM. Twelve of these compounds were confirmed as hERG channel blockers in an automated whole cell patch clamp experiment. In addition, we investigated the structure-activity relationship of seven compounds belonging to the quaternary ammonium compound (QAC) series on hERG channel inhibition. Among four active QAC compounds, tetra-n-octylammonium bromide was the most potent with an IC50 value of 260 nM in the thallium influx assay and 80 nM in the patch clamp assay. The potency of this class of hERG channel inhibitors appears to depend on the number and length of their aliphatic side-chains surrounding the charged nitrogen. Profiling environmental compound libraries for hERG channel inhibition provides information useful in prioritizing these compounds for cardiotoxicity assessment in vivo.

  14. Breathing Stimulant Compounds Inhibit TASK-3 Potassium Channel Function Likely by Binding at a Common Site in the Channel Pore.

    Science.gov (United States)

    Chokshi, Rikki H; Larsen, Aaron T; Bhayana, Brijesh; Cotten, Joseph F

    2015-11-01

    Compounds PKTHPP (1-{1-[6-(biphenyl-4-ylcarbonyl)-5,6,7,8-tetrahydropyrido[4,3-d]-pyrimidin-4-yl]piperidin-4-yl}propan-1-one), A1899 (2''-[(4-methoxybenzoylamino)methyl]biphenyl-2-carboxylic acid 2,4-difluorobenzylamide), and doxapram inhibit TASK-1 (KCNK3) and TASK-3 (KCNK9) tandem pore (K2P) potassium channel function and stimulate breathing. To better understand the molecular mechanism(s) of action of these drugs, we undertook studies to identify amino acid residues in the TASK-3 protein that mediate this inhibition. Guided by homology modeling and molecular docking, we hypothesized that PKTHPP and A1899 bind in the TASK-3 intracellular pore. To test our hypothesis, we mutated each residue in or near the predicted PKTHPP and A1899 binding site (residues 118-128 and 228-248), individually, to a negatively charged aspartate. We quantified each mutation's effect on TASK-3 potassium channel concentration response to PKTHPP. Studies were conducted on TASK-3 transiently expressed in Fischer rat thyroid epithelial monolayers; channel function was measured in an Ussing chamber. TASK-3 pore mutations at residues 122 (L122D, E, or K) and 236 (G236D) caused the IC50 of PKTHPP to increase more than 1000-fold. TASK-3 mutants L122D, G236D, L239D, and V242D were resistant to block by PKTHPP, A1899, and doxapram. Our data are consistent with a model in which breathing stimulant compounds PKTHPP, A1899, and doxapram inhibit TASK-3 function by binding at a common site within the channel intracellular pore region, although binding outside the channel pore cannot yet be excluded. PMID:26268529

  15. Characteristics of Transient Outward Potassium Channel Exposed to 3 mT Static Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LI Gang; CHENG Lijun; QIAO Xiaoyan; LIN Ling; ZHANG Lu; LI Yuanyuan

    2009-01-01

    Acutely isolated mouse hippocampai CA3 pyramidal neurons were exposed to 3 mT static magnetic field, and the characteristics of transient outward K+ channel were studied using the whole-cell patch-clamp tech-nique. The experiment revealed that the amplitude of transient outward potassium channel current was reduced. The maximum activated current densities of control group and exposure group were 163.62±20.68 pA/pF and 98.74±16.57 pA/pF(n=12, P0.05)and the slope factor of the inactivation curves from 8.69±0.80 mV to 10.87±1.02 mV(n=12, P<0.05). The results show that the static magnetic field can change the characteristics of transient outward K+ channel, and affect the physiological functions of neurons.

  16. Specific Sorting and Post-Golgi trafficking of Dendritic Potassium Channels in Living Neurons

    DEFF Research Database (Denmark)

    Jensen, Camilla Stampe; Watanabe, Shoji; Rasmussen, Hanne Borger;

    2014-01-01

    localization in distinct dendritic sub-compartments are largely unknown. Here, we developed a quantitative live-cell imaging method to analyze protein sorting and post-Golgi vesicular trafficking. We focused on two dendritic voltage-gated potassium channels which exhibit distinct localizations; Kv2.1 in......, cytoskeletal elements, and motor proteins. By live-cell and super-resolution imaging, we identified a novel trafficking machinery important for the localization of Kv2.1 channels. Particularly, we identified non-muscle myosin II as an important factor in Kv2.1 trafficking. These findings reveal that the...... sorting of ion channels at the Golgi apparatus and their subsequent trafficking by unique molecular mechanisms, are crucial for their specific localizations within dendrites....

  17. Ethanol affects network activity in cultured rat hippocampus: mediation by potassium channels.

    Directory of Open Access Journals (Sweden)

    Eduard Korkotian

    Full Text Available The effects of ethanol on neuronal network activity were studied in dissociated cultures of rat hippocampus. Exposure to low (0.25-0.5% ethanol concentrations caused an increase in synchronized network spikes, and a decrease in the duration of individual spikes. Ethanol also caused an increase in rate of miniature spontaneous excitatory postsynaptic currents. Higher concentrations of ethanol eliminated network spikes. These effects were reversible upon wash. The effects of the high, but not the low ethanol were blocked by the GABA antagonist bicuculline. The enhancing action of low ethanol was blocked by apamin, an SK potassium channel antagonist, and mimicked by 1-EBIO, an SK channel opener. It is proposed that in cultured hippocampal networks low concentration of ethanol is associated with SK channel activity, rather than the GABAergic receptor.

  18. Contributions of Counter-Charge in a Potassium Channel Voltage-Sensor Domain

    Science.gov (United States)

    Pless, Stephan A.; Galpin, Jason D.; Niciforovic, Ana P.; Ahern, Christopher A.

    2016-01-01

    Voltage-sensor domains couple membrane potential to conformational changes in voltage-gated ion channels and phosphatases. Highly co-evolved acidic and aromatic side-chains assist the transfer of cationic side-chains across the transmembrane electric field during voltage-sensing. We investigated the functional contribution of negative electrostatic potentials from these residues to channel gating and voltage-sensing with unnatural amino acid mutagenesis, electrophysiology, voltage-clamp fluorometry and ab initio calculations. The data show that neutralization of two conserved acidic side-chains in transmembrane segments S2 and S3, Glu293 and Asp316 in Shaker potassium channels, have little functional effect on conductance-voltage relationships, although Glu293 appears to catalyze S4 movement. Our results suggest that neither Glu293 nor Asp316 engages in electrostatic state-dependent charge-charge interactions with S4, likely because they occupy, and possibly help create, a water-filled vestibule. PMID:21785425

  19. PKC and AMPK regulation of Kv1.5 potassium channels.

    Science.gov (United States)

    Andersen, Martin Nybo; Skibsbye, Lasse; Tang, Chuyi; Petersen, Frederic; MacAulay, Nanna; Rasmussen, Hanne Borger; Jespersen, Thomas

    2015-01-01

    The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid rectifier K(+) current (IKur), is regulated through several pathways. Here we investigate if Kv1.5 surface expression is controlled by the 2 kinases PKC and AMPK, using Xenopus oocytes, MDCK cells and atrial derived HL-1 cells. By confocal microscopy combined with electrophysiology we demonstrate that PKC activation reduces Kv1.5 current, through a decrease in membrane expressed channels. AMPK activation was found to decrease the membrane expression in MDCK cells, but not in HL-1 cells and was furthermore shown to be dependent on co-expression of Nedd4-2 in Xenopus oocytes. These results indicate that Kv1.5 channels are regulated by both kinases, although through different molecular mechanisms in different cell systems. PMID:26043299

  20. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    Science.gov (United States)

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I.; Lindahl, Erik; Elinder, Fredrik

    2016-06-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions – a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel.

  1. Alteration in rectification of potassium channels in perinatal hypoxia ischemia brain damage.

    Science.gov (United States)

    Chen, Penghui; Wang, Liyan; Deng, Qiyue; Ruan, Huaizhen; Cai, Wenqin

    2015-01-15

    Oligodendrocyte progenitor cells (OPCs) are susceptible to perinatal hypoxia ischemia brain damage (HIBD), which results in infant cerebral palsy due to the effects on myelination. The origin of OPC vulnerability in HIBD, however, remains controversial. In this study, we defined the HIBD punctate lesions by MRI diffuse excessive high signal intensity (DEHSI) in postnatal 7-day-old rats. The electrophysiological functional properties of OPCs in HIBD were recorded by patch-clamp in acute cerebral cortex slices. The slices were intracellularly injected with Lucifer yellow and immunohistochemically labeled with NG2 antibody to identify local OPCs. Passive membrane properties and K(+) channel functions in OPCs were analyzed to estimate the onset of vulnerability in HIBD. The resting membrane potential, membrane resistance, and membrane capacitance of OPCs were increased in both the gray and white matter of the cerebral cortex. OPCs in both the gray and white matter exhibited voltage-dependent K(+) currents, which consisted of the initiated rectified potassium currents (IA) and the sustained rectified currents (IK). The significant alternation in membrane resistance was influenced by the diversity of potassium channel kinetics. These findings suggest that the rectification of IA and IK channels may play a significant role in OPC vulnerability in HIBD.

  2. Suppression of KV7/KCNQ potassium channel enhances neuronal differentiation of PC12 cells.

    Science.gov (United States)

    Zhou, Najing; Huang, Sha; Li, Li; Huang, Dongyang; Yan, Yunli; Du, Xiaona; Zhang, Hailin

    2016-10-01

    Membrane potential shift driven by electrical activity is critical in determining the cell fate of proliferation or differentiation. As such, the ion channels that underlie the membrane electrical activity play an important role in cell proliferation/differentiation. KV7/KCNQ potassium channels are critical in determining the resting membrane potentials in many neuronal cells. However, the role of these channels in cell differentiation is not well studied. In the present study, we used PC12 cells as well as primary cultured rat cortical neurons to study the role and mechanism of KV7/KCNQ in neuronal differentiation. NGF induced PC12 cell differentiation into neuron-like cells with growth of neurites showing typical growth cone-like extensions. The Kv7/KCNQ blocker XE991 promoted NGF-induced neurite outgrowth, whereas Kv7/KCNQ opener retigabine (RTG) inhibited outgrowth. M-type Kv7 channels are likely involved in regulating neurite growth because overexpression of KCNQ2/Q3 inhibited neurite growth whereas suppression of KCNQ2/Q3 with shRNA promoted neurite growth. Membrane depolarization possibly underpins enhanced neurite growth induced by the suppression of Kv7/KCNQ. Additionally, high extracellular K(+) likely induced membrane depolarization and also promoted neurite growth. Finally, T-type Ca(2+) channels may be involved in membrane-depolarization-induced neurite growth. This study provides a new perspective for understanding neuronal differentiation as well as KV7/KCNQ channel function. PMID:27450567

  3. Novel potassium channels encoded by the Shaker locus in Drosophila photoreceptors.

    Science.gov (United States)

    Hardie, R C; Voss, D; Pongs, O; Laughlin, S B

    1991-03-01

    The Shaker gene, responsible for A-type potassium channels in Drosophila muscle, encodes a large family of transcripts capable of generating a variety of kinetically distinct A channels when expressed in oocytes. We describe a distinct class of A channel encoded by the Shaker gene in a novel preparation of dissociated Drosophila photoreceptors. Whole-cell recordings reveal a rapidly inactivating A current that is absent in Shaker mutants and that can be readily isolated in cell-attached patches. Although very similar to their muscle counterparts, the photoreceptor A channels show a striking 40-50 mV negative shift in their voltage-operating range. Two mutations (ShE62 and T(1;Y)W32), which exclude only certain classes of Shaker transcripts, were used to show that photoreceptor A channels are encoded by multiple transcripts distinct from those encoding muscle A channels, while PCR techniques identified four transcripts (ShA1, ShA2, ShG1, and ShG2) in mRNA from dissected retina. PMID:2001287

  4. Scorpion Toxins Specific for Potassium (K+ Channels: A Historical Overview of Peptide Bioengineering

    Directory of Open Access Journals (Sweden)

    Zachary L. Bergeron

    2012-11-01

    Full Text Available Scorpion toxins have been central to the investigation and understanding of the physiological role of potassium (K+ channels and their expansive function in membrane biophysics. As highly specific probes, toxins have revealed a great deal about channel structure and the correlation between mutations, altered regulation and a number of human pathologies. Radio- and fluorescently-labeled toxin isoforms have contributed to localization studies of channel subtypes in expressing cells, and have been further used in competitive displacement assays for the identification of additional novel ligands for use in research and medicine. Chimeric toxins have been designed from multiple peptide scaffolds to probe channel isoform specificity, while advanced epitope chimerization has aided in the development of novel molecular therapeutics. Peptide backbone cyclization has been utilized to enhance therapeutic efficiency by augmenting serum stability and toxin half-life in vivo as a number of K+-channel isoforms have been identified with essential roles in disease states ranging from HIV, T-cell mediated autoimmune disease and hypertension to various cardiac arrhythmias and Malaria. Bioengineered scorpion toxins have been monumental to the evolution of channel science, and are now serving as templates for the development of invaluable experimental molecular therapeutics.

  5. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

    Science.gov (United States)

    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  6. A novel mechanism for fine-tuning open-state stability in a voltage-gated potassium channel

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Niciforovic, Ana P; Galpin, Jason D;

    2013-01-01

    Voltage-gated potassium channels elicit membrane hyperpolarization through voltage-sensor domains that regulate the conductive status of the pore domain. To better understand the inherent basis for the open-closed equilibrium in these channels, we undertook an atomistic scan using synthetic fluor...

  7. In vivo evidence for nitric oxide-mediated calcium-activated potassium-channel activation during human endotoxemia.

    NARCIS (Netherlands)

    Pickkers, P.; Dorresteijn, M.J.; Bouw, M.P.W.J.M.; Hoeven, J.G. van der; Smits, P.

    2006-01-01

    BACKGROUND: During septic shock, the vasoconstrictor response to norepinephrine is seriously blunted. Animal experiments suggest that hyperpolarization of smooth muscle cells by opening of potassium (K) channels underlies this phenomenon. In the present study, we examined whether K-channel blockers

  8. Spiro azepane-oxazolidinones as Kv1.3 potassium channel blockers - WO2010066840

    OpenAIRE

    Wulff, Heike

    2010-01-01

    This article evaluates a patent application from Solvay Pharmaceuticals, which claims spiro azepane-oxazolidinones as novel blockers of the voltage-gated potassium channel Kv1.3 for the treatment of diabetes, psoriasis, obesity, transplant rejection and T-cell mediated autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. The patent describes a new chemotype of Kv1.3 blockers and thus illustrates the growing interest of the pharmaceutical industry in Kv1.3 as a target of im...

  9. Effect of La3+ on myocardiac potassium channels revealed by patch-clamp technique

    Institute of Scientific and Technical Information of China (English)

    XUE Shaowu; YANG Pin

    2005-01-01

    The effect of La3+ on potassium channels in rat ventricular myocytes was investigated using the whole-cell patch-clamp recording mode. The Ca2+-independent voltage- activated outward K+ current was activated by the depolarizing pulse in enzymatically isolated rat ventricular myocytes. After addition of different concentrations La3+ to the bath solution, the outward K+ current was depressed gradually. The inhibition effect was in a concentration-dependent manner. The phenomena of the outward K+ current, being the main repolarizing current suppressed by La3+, suggest that the effect of lanthanides on myocardial function should be exploited further.

  10. MstX and a putative potassium channel facilitate biofilm formation in Bacillus subtilis.

    Directory of Open Access Journals (Sweden)

    Matthew E Lundberg

    Full Text Available Biofilms constitute the predominant form of microbial life and a potent reservoir for innate antibiotic resistance in systemic infections. In the spore-forming bacterium Bacillus subtilis, the transition from a planktonic to sessile state is mediated by mutually exclusive regulatory pathways controlling the expression of genes required for flagellum or biofilm formation. Here, we identify mstX and yugO as novel regulators of biofilm formation in B. subtilis. We show that expression of mstX and the downstream putative K+ efflux channel, yugO, is necessary for biofilm development in B. subtilis, and that overexpression of mstX induces biofilm assembly. Transcription of the mstX-yugO operon is under the negative regulation of SinR, a transcription factor that governs the switch between planktonic and sessile states. Furthermore, mstX regulates the activity of Spo0A through a positive autoregulatory loop involving KinC, a histidine kinase that is activated by potassium leakage. The addition of potassium abrogated mstX-mediated biofilm formation. Our findings expand the role of Spo0A and potassium homeostasis in the regulation of bacterial development.

  11. Heterozygous disruption of renal outer medullary potassium channel in rats is associated with reduced blood pressure.

    Science.gov (United States)

    Zhou, Xiaoyan; Zhang, Zuo; Shin, Myung Kyun; Horwitz, Sarah Beth; Levorse, John M; Zhu, Lei; Sharif-Rodriguez, Wanda; Streltsov, Denis Y; Dajee, Maya; Hernandez, Melba; Pan, Yi; Urosevic-Price, Olga; Wang, Li; Forrest, Gail; Szeto, Daphne; Zhu, Yonghua; Cui, Yan; Michael, Bindhu; Balogh, Leslie Ann; Welling, Paul A; Wade, James B; Roy, Sophie; Sullivan, Kathleen A

    2013-08-01

    The renal outer medullary potassium channel (ROMK, KCNJ1) mediates potassium recycling and facilitates sodium reabsorption through the Na(+)/K(+)/2Cl(-) cotransporter in the loop of Henle and potassium secretion at the cortical collecting duct. Human genetic studies indicate that ROMK homozygous loss-of-function mutations cause type II Bartter syndrome, featuring polyuria, renal salt wasting, and hypotension; humans heterozygous for ROMK mutations identified in the Framingham Heart Study have reduced blood pressure. ROMK null mice recapitulate many of the features of type II Bartter syndrome. We have generated an ROMK knockout rat model in Dahl salt-sensitive background by using zinc finger nuclease technology and investigated the effects of knocking out ROMK on systemic and renal hemodynamics and kidney histology in the Dahl salt-sensitive rats. The ROMK(-/-) pups recapitulated features identified in the ROMK null mice. The ROMK(+/-) rats, when challenged with a 4% salt diet, exhibited a reduced blood pressure compared with their ROMK(+/+) littermates. More importantly, when challenged with an 8% salt diet, the Dahl salt-sensitive rats with 50% less ROMK expression showed increased protection from salt-induced blood pressure elevation and signs of protection from renal injury. Our findings in ROMK knockout Dahl salt-sensitive rats, together with the previous reports in humans and mice, underscore a critical role of ROMK in blood pressure regulation.

  12. Importance of glycosylation on function of a potassium channel in neuroblastoma cells.

    Directory of Open Access Journals (Sweden)

    M K Hall

    Full Text Available The Kv3.1 glycoprotein, a voltage-gated potassium channel, is expressed throughout the central nervous system. The role of N-glycans attached to the Kv3.1 glycoprotein on conducting and non-conducting functions of the Kv3.1 channel are quite limiting. Glycosylated (wild type, partially glycosylated (N220Q and N229Q, and unglycosylated (N220Q/N229Q Kv3.1 proteins were expressed and characterized in a cultured neuronal-derived cell model, B35 neuroblastoma cells. Western blots, whole cell current recordings, and wound healing assays were employed to provide evidence that the conducting and non-conducting properties of the Kv3.1 channel were modified by N-glycans of the Kv3.1 glycoprotein. Electrophoretic migration of the various Kv3.1 proteins treated with PNGase F and neuraminidase verified that the glycosylation sites were occupied and that the N-glycans could be sialylated, respectively. The unglycosylated channel favored a different whole cell current pattern than the glycoform. Further the outward ionic currents of the unglycosylated channel had slower activation and deactivation rates than those of the glycosylated Kv3.1 channel. These kinetic parameters of the partially glycosylated Kv3.1 channels were also slowed. B35 cells expressing glycosylated Kv3.1 protein migrated faster than those expressing partially glycosylated and much faster than those expressing the unglycosylated Kv3.1 protein. These results have demonstrated that N-glycans of the Kv3.1 glycoprotein enhance outward ionic current kinetics, and neuronal migration. It is speculated that physiological changes which lead to a reduction in N-glycan attachment to proteins will alter the functions of the Kv3.1 channel.

  13. Altered potassium channel distribution and composition in myelinated axons suppresses hyperexcitability following injury.

    Science.gov (United States)

    Calvo, Margarita; Richards, Natalie; Schmid, Annina B; Barroso, Alejandro; Zhu, Lan; Ivulic, Dinka; Zhu, Ning; Anwandter, Philipp; Bhat, Manzoor A; Court, Felipe A; McMahon, Stephen B; Bennett, David L H

    2016-01-01

    Neuropathic pain following peripheral nerve injury is associated with hyperexcitability in damaged myelinated sensory axons, which begins to normalise over time. We investigated the composition and distribution of shaker-type-potassium channels (Kv1 channels) within the nodal complex of myelinated axons following injury. At the neuroma that forms after damage, expression of Kv1.1 and 1.2 (normally localised to the juxtaparanode) was markedly decreased. In contrast Kv1.4 and 1.6, which were hardly detectable in the naïve state, showed increased expression within juxtaparanodes and paranodes following injury, both in rats and humans. Within the dorsal root (a site remote from injury) we noted a redistribution of Kv1-channels towards the paranode. Blockade of Kv1 channels with α-DTX after injury reinstated hyperexcitability of A-fibre axons and enhanced mechanosensitivity. Changes in the molecular composition and distribution of axonal Kv1 channels, therefore represents a protective mechanism to suppress the hyperexcitability of myelinated sensory axons that follows nerve injury. PMID:27033551

  14. Structural analysis of the S4-S5 linker of the human KCNQ1 potassium channel.

    Science.gov (United States)

    Gayen, Shovanlal; Li, Qingxin; Kang, CongBao

    2015-01-01

    KCNQ1 plays important roles in the cardiac action potential and consists of an N-terminal domain, a voltage-sensor domain, a pore domain and a C-terminal domain. KCNQ1 is a voltage-gated potassium channel and its channel activity is regulated by membrane potentials. The linker between transmembrane helices 4 and 5 (S4-S5 linker) is important for transferring the conformational changes from the voltage-sensor domain to the pore domain. In this study, the structure of the S4-S5 linker of KCNQ1 was investigated by solution NMR, circular dichroism and fluorescence spectroscopic studies. The S4-S5 linker adopted a helical structure in detergent micelles. The W248 may interact with the cell membrane.

  15. High extracellular potassium ion concentration attenuates the blockade action of ketanserin on Kvl.3 channels expressed in xenopus oocytes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Background Ketanserin (KT), a selective serotonin (5-HT) 2-receptor antagonist, reduces peripheral blood pressure by blocking the activation of peripheral 5-HT receptors. In this study electrophysiological method was used to investigate the effect of KT and potassium ion on Kv1.3 potassium channels and explore the role of blocker KT in the alteration of channel kinetics contributing to the potassium ion imbalances. Methods Kvl.3 channels were expressed in xenopus oocytes, and currents were measured using the two-microelectrode voltage-clamp technique. Results KCI made a left shift of activation and an inactivation curve of Kv1.3 current and accelerated the activation and inactivation time constant. High extracellular [K+] attenuated the blockade effect of KT on Kv1.3 channels. In the presence of KT and KCI the activation and inactivation time constants were not influenced significantly no matter what was administered first. KT did not significantly inhibit Kv1.3 current induced by tetraethylammonium (TEA). Conclusions KT is a weak blocker of Kv1.3 channels at different concentrations of extracellular potassium and binds to the intracellular side of the channel pore. The inhibitor KT of ion channels is not fully effective in clinical use because of high [K+]o and other electrolyte disorders.

  16. Potassium channels in vascular smooth muscle and essential hypertension%血管平滑肌钾通道与原发性高血压

    Institute of Scientific and Technical Information of China (English)

    周述芝; 魏宗德

    2003-01-01

    Essential hypertension(EH)is characterized by an increased total peripheral resistance.There are four types of potassium channels in vascular smooth muscle cells,including Kca,Kv,Kir,KATP,which play an important role in regulating the diameter of vascular.The change of potassium channels may have something to do with the pathogenesis of hypertension.This article reviews the characters of potassium channels and their roles in EH.

  17. Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction.

    Directory of Open Access Journals (Sweden)

    Dong-Hai Liu

    Full Text Available Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (KV was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of KV activation was altered. The sensitivity of KV currents (IKV to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a KV blocker, stays the same. The protein levels of KV4.3 and KV2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of KV4.3 and KV2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of KV channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of KV4.3 and KV2.2 may be involved in this process.

  18. Effect of Nitric Oxide on Potassium Channels of Rat Airway Smooth Muscle Cells

    Institute of Scientific and Technical Information of China (English)

    高亚东; 徐永健; 熊盛道; 张珍祥; 刘先胜; 倪望

    2002-01-01

    Summary: The effect of nitric oxide donor sodium nitroprusside (SNP) on resting membrane potential (Em) and potassium currents of the bronchial smooth muscle cells from rats was investigated. All experiments were conducted in conventional whole-cell configuration. The changes of Em and potassium currents after addition of 0. 1 mmol/L SNP were measured under the current-clamp mode and the voltage-clamp mode respectively. Results showed that (1) SNP could decrease the Em from --33. 8±7.4 mV to -43. 7±6. 7mV (n=10, P<0. 01); (2) SNP could increase the Ca2+-activated K+ channel peak currents under ramp protocol from 466.9±180. 1 pA to 597. 7±237. 6 pA (n= 7, P<0. 01), and the currents under pulse protocol at +50 mV were increased from 544.2±145.4 pA to 678.1±206. 2 pA (n=6, P<0.05); (3) SNP also could increase voltage-gated K+ channel peak currents under ramp protocol from 389. 6±84. 1 pA to 526. 7±98. 7 pA (n=7, P<0. 01), the currents under pulse protocol at +50 mV were increased from 275.7±85.2 pA to 444.3±128.5 pA(n=6,P<0. 01). It was concluded that SNP increases the activities of Ca2+-activated K+ channels and voltage-gated K+ channels and leads to K+ efflux and hyperpolarization of the cell membrane, resulting in a decrease of the cell excitement.

  19. Changes of Ca2+ activated potassium channels and cellular proliferation in autogenous vein grafts

    Institute of Scientific and Technical Information of China (English)

    钱济先; 宋胜云; 马保安; 范清宇

    2003-01-01

    Objective: To investigate changes of Ca2+ activated potassium channels (KCa) in autogenous vein grafts. Methods: Contraction of venous ring was measured by means of perfusion in vitro. The intimal rabbits proliferation of vascular and proliferation of cultured smooth muscle cells(vascular smooth muscle cells, VSMCs)were observed by the means of computerised image analysis and MTT method respectively. Furthermore, whole cell mode of patch clamp was used to record KCa of VSMCs isolated from autogenous vein grafts. Results: One week after transplantation there were no significant differences of contraction and intimal relative thickness between autogenous vein grafts and control. Contraction and intimal relative thickness of autogenous vein graft were significantly increased 2 weeks after transplantation (P<0.05, n=8 vs control), and they was more enhanced 4 weeks after vein transplantation (P<0.01, n=8 vs control).TEA(blocker of Ca2+ activated potassium channels)increased MTT A490 nm value of VSMCs from femoral vein in a dose dependent manner(P<0.05, n=8). KCa current density was significantly attenuated in VSMCs from autogenous vein grafts (1-4) week after transplantation(P<0.05, n=5).Conclusion: KCa is inhibited in autogenous vein graft, which account for vasospasm and intimal proliferation.

  20. Huntington disease skeletal muscle is hyperexcitable owing to chloride and potassium channel dysfunction.

    Science.gov (United States)

    Waters, Christopher W; Varuzhanyan, Grigor; Talmadge, Robert J; Voss, Andrew A

    2013-05-28

    Huntington disease is a progressive and fatal genetic disorder with debilitating motor and cognitive defects. Chorea, rigidity, dystonia, and muscle weakness are characteristic motor defects of the disease that are commonly attributed to central neurodegeneration. However, no previous study has examined the membrane properties that control contraction in Huntington disease muscle. We show primary defects in ex vivo adult skeletal muscle from the R6/2 transgenic mouse model of Huntington disease. Action potentials in diseased fibers are more easily triggered and prolonged than in fibers from WT littermates. Furthermore, some action potentials in the diseased fibers self-trigger. These defects occur because of decreases in the resting chloride and potassium conductances. Consistent with this, the expression of the muscle chloride channel, ClC-1, in Huntington disease muscle was compromised by improper splicing and a corresponding reduction in total Clcn1 (gene for ClC-1) mRNA. Additionally, the total Kcnj2 (gene for the Kir2.1 potassium channel) mRNA was reduced in disease muscle. The resulting muscle hyperexcitability causes involuntary and prolonged contractions that may contribute to the chorea, rigidity, and dystonia that characterize Huntington disease.

  1. Channeling your inner ear potassium: K(+) channels in vestibular hair cells.

    Science.gov (United States)

    Meredith, Frances L; Rennie, Katherine J

    2016-08-01

    During development of vestibular hair cells, K(+) conductances are acquired in a specific pattern. Functionally mature vestibular hair cells express different complements of K(+) channels which uniquely shape the hair cell receptor potential and filtering properties. In amniote species, type I hair cells (HCI) have a large input conductance due to a ubiquitous low-voltage-activated K(+) current that activates with slow sigmoidal kinetics at voltages negative to the membrane resting potential. In contrast type II hair cells (HCII) from mammalian and non-mammalian species have voltage-dependent outward K(+) currents that activate rapidly at or above the resting membrane potential and show significant inactivation. A-type, delayed rectifier and calcium-activated K(+) channels contribute to the outward K(+) conductance and are present in varying proportions in HCII. In many species, K(+) currents in HCII in peripheral locations of vestibular epithelia inactivate more than HCII in more central locations. Two types of inward rectifier currents have been described in both HCI and HCII. A rapidly activating K(+)-selective inward rectifier current (IK1, mediated by Kir2.1 channels) predominates in HCII in peripheral zones, whereas a slower mixed cation inward rectifier current (Ih), shows greater expression in HCII in central zones of vestibular epithelia. The implications for sensory coding of vestibular signals by different types of hair cells are discussed. This article is part of a Special Issue entitled . PMID:26836968

  2. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  3. Expression of Potassium Channels in Uterine Smooth Muscle Cells from Patients with Adenomyosis

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    Jing-Hua Shi

    2016-01-01

    Full Text Available Background: Adenomyosis (AM has impaired contraction. This study aimed to explore the expression of potassium channels related to contraction in myometrial smooth muscle cells (MSMCs of AM. Methods: Uterine tissue samples from 22 patients (cases with histologically confirmed AM and 12 (controls with cervical intraepithelial neoplasia were collected for both immunohistochemistry and real-time polymerase chain reaction to detect the expression of large conductance calcium- and voltage-sensitive K + channel (BKCa-α/β subunits, voltage-gated potassium channel (Kv 4.2, and Kv4.3. Student′s t-test was used to compare the expression. Results: The BKCa-α/β subunits, Kv4.2, and Kv4.3 were located in smooth muscle cells, glandular epithelium, and stromal cells. However, BKCa-β subunit expression in endometrial glands of the controls was weak, and Kv4.3 was almost undetectable in the controls. The expression of BKCa-α messenger RNA (mRNA (0.62 ± 0.19-fold decrease, P < 0.05 and Kv4.3 mRNA (0.67 ± 0.20-fold decrease, P < 0.05 decreased significantly in the MSMCs of the control group compared with the AM group. However, there were no significant differences in BKCa-β subunit mRNA or Kv4.2 mRNA. Conclusions: The BKCa-α mRNA and the Kv4.3 mRNA are expressed significantly higher in AM than those in the control group, that might cause the abnormal uterus smooth muscle contractility, change the microcirculation of uterus to accumulate the inflammatory factors, impair the endometrium further, and aggravate the pain.

  4. Expression of Potassium Channels in Uterine Smooth Muscle Cells from Patients with Adenomyosis

    Institute of Scientific and Technical Information of China (English)

    Jing-Hua Shi; Li Jin; Jin-Hua Leng; Jing-He Lang

    2016-01-01

    Background:Adenomyosis (AM) has impaired contraction.This study aimed to explore the expression of potassium channels related to contraction in myometrial smooth muscle cells (MSMCs) of AM.Methods:Uterine tissue samples from 22 patients (cases) with histologically confirmed AM and 12 (controls) with cervical intraepithelial neoplasia were collected for both immunohistochemistry and real-time polymerase chain reaction to detect the expression of large conductance calcium-and voltage-sensitive K+ channel (BKCa)-α/β subunits,voltage-gated potassium channel (Kv) 4.2,and Kv4.3.Student's t-test was used to compare the expression.Results:The BKCa-α/β subunits,Kv4.2,and Kv4.3 were located in smooth muscle cells,glandular epithelium,and stromal cells.However,BKCa-β subunit expression in endometrial glands of the controls was weak,and Kv4.3 was almost undetectable in the controls.The expression of BKCa-α messenger RNA (mRNA) (0.62 ± 0.19-fold decrease,P < 0.05) and Kv4.3 mRNA (0.67 ± 0.20-fold decrease,P < 0.05) decreased significantly in the M SMCs of the control group compared with the AM group.However,there were no significant differences in BKCa-β subunit mRNA or Kv4.2 mRNA.Conclusions:The BKCa-α mRNA and the Kv4.3 mRNA are expressed significantly higher in AM than those in the control group,that might cause the abnormal uterus smooth muscle contractility,change the microcirculation of uterus to accumulate the inflammatory factors,impair the endometrium further,and aggravate the pain.

  5. 14-3-3θ is a binding partner of rat Eag1 potassium channels.

    Directory of Open Access Journals (Sweden)

    Po-Hao Hsu

    Full Text Available The ether-à-go-go (Eag potassium (K(+ channel belongs to the superfamily of voltage-gated K(+ channel. In mammals, the expression of Eag channels is neuron-specific but their neurophysiological role remains obscure. We have applied the yeast two-hybrid screening system to identify rat Eag1 (rEag1-interacting proteins from a rat brain cDNA library. One of the clones we identified was 14-3-3θ, which belongs to a family of small acidic protein abundantly expressed in the brain. Data from in vitro yeast two-hybrid and GST pull-down assays suggested that the direct association with 14-3-3θ was mediated by both the N- and the C-termini of rEag1. Co-precipitation of the two proteins was confirmed in both heterologous HEK293T cells and native hippocampal neurons. Electrophysiological studies showed that over-expression of 14-3-3θ led to a sizable suppression of rEag1 K(+ currents with no apparent alteration of the steady-state voltage dependence and gating kinetics. Furthermore, co-expression with 14-3-3θ failed to affect the total protein level, membrane trafficking, and single channel conductance of rEag1, implying that 14-3-3θ binding may render a fraction of the channel locked in a non-conducting state. Together these data suggest that 14-3-3θ is a binding partner of rEag1 and may modulate the functional expression of the K(+ channel in neurons.

  6. Membrane proteins involved in potassium shifts during muscle activity and fatigue

    DEFF Research Database (Denmark)

    Kristensen, Michael; Hansen, T.; Juel, C.

    2006-01-01

    for the ATP-sensitive K+ (KATP) channel. In the present experiments, we investigated the subcellular localizations of the strong inward rectifier 2.1 K+ (Kir2.1) channel and the Na+-K+-2Cl- (NKCC)1 cotransporter with Western blot analysis of different muscle fractions. Furthermore, muscle function was studied......Muscle activity is associated with potassium displacements, which may cause fatigue. It was reported previously that the density of the large-conductance Ca2+-dependent K+ (BKCa) channel is higher in the T tubule membrane than in the sarcolemmal membrane and that the opposite is the case...... while trying to manipulate the opening probability or transport capacity of these proteins during electrical stimulation of isolated soleus muscles. All experiments were made with excised muscle from male Wistar rats. Kir2.1 channels were almost undetectable in the sarcolemmal membrane but present...

  7. Effect of genistein on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    Shi-Ying Li; Bin-Bin Huang; Shou Ouyang

    2006-01-01

    AIM: To investigate the action of genistein (GST), a broad spectrum tyrosine kinase inhibitor, on voltagegated potassium channels in guinea pig proximal colon smooth muscle cells.METHODS: Smooth muscle cells in guinea pig proximal colon were enzymatically isolated. Nystatin-perforated whole cell patch clamp technique was used to record potassium currents including fast transient outward current (IKto) and delayed rectifier current (IKdr), two of which were isolated pharmacologically with 10 mmol/L tetraethylammonium or 5 mmol/L 4-aminopyridine.Contamination of calcium-dependent potassium currents was minimized with no calcium and 0.2 mmol/L CdCl2 in an external solution.RESULTS: GST (10-100 μmol/L) reversibly and dosedependently reduced the peak amplitude of IKto with an IC50value of 22.0±6.9 μmol/L. To a lesser extent, IKdr was also inhibited in both peak current and sustained current.GST could not totally block the outward potassium current as a fraction of the outWard potassium current,which was insensitive to GST. GST had no effect on the steady-state activation (n = 6) and inactivation kinetics(n =6) of IKto. Sodium orthovanadate (1 mmol/L), a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition (P< 0.05).CONCLUSION: GST can dose-dependently and reversibly block voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.

  8. Hexachlorophene Is a Potent KCNQ1/KCNE1 Potassium Channel Activator Which Rescues LQTs Mutants

    Science.gov (United States)

    Zheng, Yueming; Zhu, Xuejing; Zhou, Pingzheng; Lan, Xi; Xu, Haiyan; Li, Min; Gao, Zhaobing

    2012-01-01

    The voltage-gated KCNQ1 potassium channel is expressed in cardiac tissues, and coassembly of KCNQ1 with an auxiliary KCNE1 subunit mediates a slowly activating current that accelerates the repolarization of action potential in cardiomyocytes. Mutations of KCNQ1 genes that result in reduction or loss of channel activity cause prolongation of repolarization during action potential, thereby causing long QT syndrome (LQTs). Small molecule activators of KCNQ1/KCNE1 are useful both for understanding the mechanism of the complex activity and for developing therapeutics for LQTs. In this study we report that hexachlorophene (HCP), the active component of the topical anti-infective prescription drug pHisoHex, is a KCNQ1/KCNE1 activator. HCP potently increases the current amplitude of KCNQ1/KCNE1 expressed by stabilizing the channel in an open state with an EC50 of 4.61±1.29 μM. Further studies in cardiomyocytes showed that HCP significantly shortens the action potential duration at 1 μM. In addition, HCP is capable of rescuing the loss of function of the LQTs mutants caused by either impaired activation gating or phosphatidylinositol-4,5-bisphosphate (PIP2) binding affinity. Our results indicate HCP is a novel KCNQ1/KCNE1 activator and may be a useful tool compound for the development of LQTs therapeutics. PMID:23251633

  9. Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease.

    Science.gov (United States)

    Jammoul, Adham; Lederman, Richard J; Tavee, Jinny; Li, Yuebing

    2014-06-05

    Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is the rare instance when a positive VGKC complex antibody titre occurs in a definite case of prion disease. We present a pathologically and genetically confirmed case of CJD with elevated serum VGKC complex antibody titres. This case highlights the importance of interpreting the result of a positive VGKC complex antibody with caution and in the context of the overall clinical manifestation.

  10. High Grade Glioma Mimicking Voltage Gated Potassium Channel Complex Associated Antibody Limbic Encephalitis

    Directory of Open Access Journals (Sweden)

    Dilan Athauda

    2014-01-01

    Full Text Available Though raised titres of voltage gated potassium channel (VGKC complex antibodies have been occasionally associated with extracranial tumours, mainly presenting as Morvan's Syndrome or neuromyotonia, they have not yet been reported to be associated with an intracranial malignancy. This is especially important as misdiagnosis of these conditions and delay of the appropriate treatment can have important prognostic implications. We describe a patient with a high grade glioma presenting with clinical, radiological, and serological features consistent with the diagnosis of VGKC antibody associated limbic encephalitis (LE. This is the first association between a primary brain tumour and high titre of VGKC complex antibodies. Clinicoradiological progression despite effective immunosuppressive treatment should prompt clinicians to look for alternative diagnoses. Further studies to elucidate a possible association between VGKC complex and other surface antigen antibodies with primary brain tumours should be carried out.

  11. High grade glioma mimicking voltage gated potassium channel complex associated antibody limbic encephalitis.

    Science.gov (United States)

    Athauda, Dilan; Delamont, R S; Pablo-Fernandez, E De

    2014-01-01

    Though raised titres of voltage gated potassium channel (VGKC) complex antibodies have been occasionally associated with extracranial tumours, mainly presenting as Morvan's Syndrome or neuromyotonia, they have not yet been reported to be associated with an intracranial malignancy. This is especially important as misdiagnosis of these conditions and delay of the appropriate treatment can have important prognostic implications. We describe a patient with a high grade glioma presenting with clinical, radiological, and serological features consistent with the diagnosis of VGKC antibody associated limbic encephalitis (LE). This is the first association between a primary brain tumour and high titre of VGKC complex antibodies. Clinicoradiological progression despite effective immunosuppressive treatment should prompt clinicians to look for alternative diagnoses. Further studies to elucidate a possible association between VGKC complex and other surface antigen antibodies with primary brain tumours should be carried out.

  12. Mass spectrometry study of N-alkylbenzenesulfonamides with potential antagonist activity to potassium channels.

    Science.gov (United States)

    Martins, Carina C; Bassetto, Carlos A Zanutto; Santos, Jandyson M; Eberlin, Marcos N; Magalhães, Alvicler; Varanda, Wamberto; Gonzalez, Eduardo R Perez

    2016-02-01

    Herein, we report the synthesis and mass spectrometry studies of several N-alkylbenzenesulfonamides structurally related to sulfanilic acid. The compounds were synthesized using a modified Schotten-Baumann reaction coupled with Meisenheimer arylation. Sequential mass spectrometry by negative mode electrospray ionization (ESI(-)-MS/MS) showed the formation of sulfoxylate anion (m/z 65) observed in the mass spectrum of p-chloro-N-alkylbenzenesulfonamides. Investigation of the unexpected loss of two water molecules, as observed by electron ionization mass spectrometry (EI-MS) analysis of p-(N-alkyl)lactam sulfonamides, led to the proposal of corresponding fragmentation pathways. These compounds showed loss of neutral iminosulfane dioxide molecule (M-79) with formation of ions observed at m/z 344 and 377. These ions were formed by rearrangement on ESI(+)-MS/MS analysis. Some of the molecules showed antagonistic activity against Kv3.1 voltage-gated potassium channels.

  13. Basolateral localisation of KCNQ1 potassium channels in MDCK cells: molecular identification of an N-terminal targeting motif

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Rasmussen, Hanne B; Grunnet, Morten;

    2004-01-01

    KCNQ1 potassium channels are expressed in many epithelial tissues as well as in the heart. In epithelia KCNQ1 channels play an important role in salt and water transport and the channel has been reported to be located apically in some cell types and basolaterally in others. Here we show that KCNQ1...... channels are located basolaterally when expressed in polarised MDCK cells. The basolateral localisation of KCNQ1 is not affected by co-expression of any of the five KCNE beta-subunits. We characterise two independent basolateral sorting signals present in the N-terminal tail of KCNQ1. Mutation...

  14. Voltage-gated potassium channel-complex autoimmunity and associated clinical syndromes.

    Science.gov (United States)

    Irani, Sarosh R; Vincent, Angela

    2016-01-01

    Voltage-gated potassium channel (VGKC)-complex antibodies are defined by the radioimmunoprecipitation of Kv1 potassium channel subunits from brain tissue extracts and were initially discovered in patients with peripheral nerve hyperexcitability (PNH). Subsequently, they were found in patients with PNH plus psychosis, insomnia, and dysautonomia, collectively termed Morvan's syndrome (MoS), and in a limbic encephalopathy (LE) with prominent amnesia and frequent seizures. Most recently, they have been described in patients with pure epilepsies, especially in patients with the novel and distinctive semiology termed faciobrachial dystonic seizures (FBDS). In each of these conditions, there is a close correlation between clinical measures and antibody levels. The VGKC-complex is a group of proteins that are strongly associated in situ and after extraction in mild detergent. Two major targets of the autoantibodies are leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein 2 (CASPR2). The patients with PNH or MoS are most likely to have CASPR2 antibodies, whereas LGI1 antibodies are found characteristically in patients with FBDS and LE. Crucially, each of these conditions has a good response to immunotherapies, often corticosteroids and plasma exchange, although optimal regimes require further study. VGKC-complex antibodies have also been described in neuropathic pain syndromes, chronic epilepsies, a polyradiculopathy in porcine abattoir workers, and some children with status epilepticus. Increasingly, however, the antigenic targets in these patients are not defined and in some cases the antibodies may be secondary rather than the primary cause. Future serologic studies should define all the antigenic components of the VGKC-complex, and further inform mechanisms of antibody pathogenicity and related inflammation.

  15. Voltage-gated potassium channel-complex autoimmunity and associated clinical syndromes.

    Science.gov (United States)

    Irani, Sarosh R; Vincent, Angela

    2016-01-01

    Voltage-gated potassium channel (VGKC)-complex antibodies are defined by the radioimmunoprecipitation of Kv1 potassium channel subunits from brain tissue extracts and were initially discovered in patients with peripheral nerve hyperexcitability (PNH). Subsequently, they were found in patients with PNH plus psychosis, insomnia, and dysautonomia, collectively termed Morvan's syndrome (MoS), and in a limbic encephalopathy (LE) with prominent amnesia and frequent seizures. Most recently, they have been described in patients with pure epilepsies, especially in patients with the novel and distinctive semiology termed faciobrachial dystonic seizures (FBDS). In each of these conditions, there is a close correlation between clinical measures and antibody levels. The VGKC-complex is a group of proteins that are strongly associated in situ and after extraction in mild detergent. Two major targets of the autoantibodies are leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein 2 (CASPR2). The patients with PNH or MoS are most likely to have CASPR2 antibodies, whereas LGI1 antibodies are found characteristically in patients with FBDS and LE. Crucially, each of these conditions has a good response to immunotherapies, often corticosteroids and plasma exchange, although optimal regimes require further study. VGKC-complex antibodies have also been described in neuropathic pain syndromes, chronic epilepsies, a polyradiculopathy in porcine abattoir workers, and some children with status epilepticus. Increasingly, however, the antigenic targets in these patients are not defined and in some cases the antibodies may be secondary rather than the primary cause. Future serologic studies should define all the antigenic components of the VGKC-complex, and further inform mechanisms of antibody pathogenicity and related inflammation. PMID:27112678

  16. Voltage-dependent Ca2+ channels, not ryanodine receptors, activate Ca2+-dependent BK potassium channels in human retinal pigment epithelial cells

    OpenAIRE

    Wimmers, Sönke; Halsband, Claire; Seyler, Sebastian; Milenkovic, Vladimir; Strauß, Olaf

    2008-01-01

    Purpose In different tissues the activation of large conductance Ca2+-activated (BK) potassium channels has been shown to be coupled to voltage-gated Ca2+ channels as well as ryanodine receptors. As activation of BK channels leads to hyperpolarization of the cell, these channels provide a negative feedback mechanism for Ca2+-induced functions. Many cellular functions of the retinal pigment epithelium (RPE) are coupled to changes in [Ca2+]i. The aim of this study was to identify which Ca2+-ent...

  17. Potassium channel and NKCC cotransporter involvement in ocular refractive control mechanisms.

    Directory of Open Access Journals (Sweden)

    Sheila G Crewther

    Full Text Available Myopia affects well over 30% of adult humans globally. However, the underlying physiological mechanism is little understood. This study tested the hypothesis that ocular growth and refractive compensation to optical defocus can be controlled by manipulation of potassium and chloride ion-driven transretinal fluid movements to the choroid. Chicks were raised with +/-10D or zero power optical defocus rendering the focal plane of the eye in front of, behind, or at the level of the retinal photoreceptors respectively. Intravitreal injections of barium chloride, a non-specific inhibitor of potassium channels in the retina and RPE or bumetanide, a selective inhibitor of the sodium-potassium-chloride cotransporter were made, targeting fluid control mechanisms. Comparison of refractive compensation to 5 mM Ba(2+ and 10(-5 M bumetanide compared with control saline injected eyes shows significant change for both positive and negative lens defocus for Ba(2+ but significant change only for negative lens defocus with bumetanide (Rx(SAL(-10D = -8.6 +/- .9 D; Rx(Ba2+(-10D = -2.9 +/- .9 D; Rx(Bum(-10D = -2.9 +/- .9 D; Rx(SAL(+10D = +8.2 +/- .9 D; Rx(Ba2+(+10D = +2.8 +/- 1.3 D; Rx(Bum(+10D = +8.0 +/- .7 D. Vitreous chamber depths showed a main effect for drug conditions with less depth change in response to defocus shown for Ba(2+ relative to Saline, while bumetanide injected eyes showed a trend to increased depth without a significant interaction with applied defocus. The results indicate that both K channels and the NKCC cotransporter play a role in refractive compensation with NKCC blockade showing far more specificity for negative, compared with positive, lens defocus. Probable sites of action relevant to refractive control include the apical retinal pigment epithelium membrane and the photoreceptor/ON bipolar synapse. The similarities between the biometric effects of NKCC inhibition and biometric reports of the blockade of the retinal ON response, suggest a

  18. The potassium channel KCa3.1 as new therapeutic target for the prevention of obliterative airway disease

    DEFF Research Database (Denmark)

    Hua, Xiaoqin; Deuse, Tobias; Chen, Yi-Je;

    2013-01-01

    The calcium-activated potassium channel KCa3.1 is critically involved in T-cell activation as well as in the proliferation of smooth muscle cells and fibroblasts. We sought to investigate whether KCa3.1 contributes to the pathogenesis of obliterative airway disease (OAD) and whether knockout or p...

  19. Evaluation of potassium permanganate against an experimental subacute infection of Flavobacterium columnare in channel catfish, Icatlurus punctatus

    Science.gov (United States)

    The efficacy of potassium permanganate (KMnO4) as a prophylactic and therapeutic treatment for subacute infection of Flavobacterium columnare was demonstrated in experimentally infected channel catfish, Ictalurus punctatus. Catfish experimentally infected with F. columnare to mimic a subacute infec...

  20. Comparative effects of copper sulfate or potassium permanganate on channel catfish concurrently infected with Flavobacterium columnare and Ichthyobodo necator

    Science.gov (United States)

    An opportunistic study was conducted to determine the effects of two chemical therapeutants on channel catfish (CCF) Ictalurus punctatus concurrently infected Flavobacterium columnare and Ichthyobodo necator. Copper sulfate (CuSO4) and potassium permanganate (KMnO4) were investigated for their abil...

  1. Students' Understanding of External Representations of the Potassium Ion Channel Protein Part II: Structure-Function Relationships and Fragmented Knowledge

    Science.gov (United States)

    Harle, Marissa; Towns, Marcy H.

    2012-01-01

    Research that has focused on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This study focuses on students' understanding of three external representations (ribbon diagram, wireframe, and hydrophobic/hydrophilic) of the potassium ion channel protein. Analysis…

  2. Ether à go-go potassium channel expression in soft tissue sarcoma patients

    Directory of Open Access Journals (Sweden)

    Stühmer Walter

    2006-10-01

    Full Text Available Abstract Background The expression of the human Eag1 potassium channel (Kv10.1 is normally restricted to the adult brain, but it has been detected in both tumour cell lines and primary tumours. Our purpose was to determine the frequency of expression of Eag1 in soft tissue sarcoma and its potential clinical implications. Results We used specific monoclonal antibodies to determine the expression levels of Eag1 in soft tissue sarcomas from 210 patients by immunohistochemistry. Eag1 was expressed in 71% of all tumours, with frequencies ranging from 56% (liposarcoma to 82% (rhabdomyosarcoma. We detected differences in expression levels depending on the histological type, but no association was seen between expression of this protein and sex, age, grade or tumour size. Four cell lines derived from relevant sarcoma histological types (fibrosarcoma and rhabdomyosarcoma were tested for Eag1 expression by real-time RT-PCR. We found all four lines to be positive for Eag1. In these cell lines, blockage of Eag1 by RNA interference led to a decrease in proliferation. Conclusion Eag1 is aberrantly expressed in over 70% sarcomas. In sarcoma cell lines, inhibition of Eag1 expression and/or function leads to reduced proliferation. The high frequency of expression of Eag1 in primary tumours and the restriction of normal expression of the channel to the brain, suggests the application of this protein for diagnostic or therapeutic purposes.

  3. Effect of methamphetamine on the microglial damage: role of potassium channel Kv1.3.

    Directory of Open Access Journals (Sweden)

    Jun Wang

    Full Text Available Methamphetamine (Meth abusing represents a major public health problem worldwide. Meth has long been known to induce neurotoxicity. However, the mechanism is still remained poorly understood. Growing evidences indicated that the voltage-gated potassium channels (Kv were participated in neuronal damage and microglia function. With the whole cell patch clamp, we found that Meth significantly increased the outward K⁺ currents, therefore, we explored whether Kv1.3, one of the major K⁺ channels expressed in microglia, was involved in Meth-induced microglia damage. Our study showed that Meth significantly increased the cell viability in a dose dependent manner, while the Kv blocker, tetraethylamine (TEA, 4-Aminopyridine (4-AP and Kv1.3 specific antagonist margatoxin (MgTx, prevented against the damage mediated by Meth. Interestingly, treatment of cells with Meth resulted in increasing expression of Kv1.3 rather than Kv1.5, at both mRNA and protein level, which is partially blocked by MgTx. Furthermore, Meth also stimulated a significant increased expression of IL-6 and TNF-α at protein level, which was significantly inhibited by MgTx. Taken together, these results demonstrated that Kv1.3 was involved in Meth-mediated microglial damage, providing the potential target for the development of therapeutic strategies for Meth abuse.

  4. Phosphatidylinositol 4,5-bisphosphate alters pharmacological selectivity for epilepsy-causing KCNQ potassium channels

    Science.gov (United States)

    Zhou, Pingzheng; Yu, Haibo; Gu, Min; Nan, Fa-jun; Gao, Zhaobing; Li, Min

    2013-01-01

    Pharmacological augmentation of neuronal KCNQ muscarinic (M) currents by drugs such as retigabine (RTG) represents a first-in-class therapeutic to treat certain hyperexcitatory diseases by dampening neuronal firing. Whereas all five potassium channel subtypes (KCNQ1–KCNQ5) are found in the nervous system, KCNQ2 and KCNQ3 are the primary players that mediate M currents. We investigated the plasticity of subtype selectivity by two M current effective drugs, retigabine and zinc pyrithione (ZnPy). Retigabine is more effective on KCNQ3 than KCNQ2, whereas ZnPy is more effective on KCNQ2 with no detectable effect on KCNQ3. In neurons, activation of muscarinic receptor signaling desensitizes effects by retigabine but not ZnPy. Importantly, reduction of phosphatidylinositol 4,5-bisphosphate (PIP2) causes KCNQ3 to become sensitive to ZnPy but lose sensitivity to retigabine. The dynamic shift of pharmacological selectivity caused by PIP2 may be induced orthogonally by voltage-sensitive phosphatase, or conversely, abolished by mutating a PIP2 site within the S4–S5 linker of KCNQ3. Therefore, whereas drug-channel binding is a prerequisite, the drug selectivity on M current is dynamic and may be regulated by receptor signaling pathways via PIP2. PMID:23650395

  5. Dynamic memory of a single voltage-gated potassium ion channel: A stochastic nonequilibrium thermodynamic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Kinshuk, E-mail: kbpchem@gmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Kolkata 700 009 (India)

    2015-05-14

    In this work, we have studied the stochastic response of a single voltage-gated potassium ion channel to a periodic external voltage that keeps the system out-of-equilibrium. The system exhibits memory, resulting from time-dependent driving, that is reflected in terms of dynamic hysteresis in the current-voltage characteristics. The hysteresis loop area has a maximum at some intermediate voltage frequency and disappears in the limits of low and high frequencies. However, the (average) dissipation at long-time limit increases and finally goes to saturation with rising frequency. This raises the question: how diminishing hysteresis can be associated with growing dissipation? To answer this, we have studied the nonequilibrium thermodynamics of the system and analyzed different thermodynamic functions which also exhibit hysteresis. Interestingly, by applying a temporal symmetry analysis in the high-frequency limit, we have analytically shown that hysteresis in some of the periodic responses of the system does not vanish. On the contrary, the rates of free energy and internal energy change of the system as well as the rate of dissipative work done on the system show growing hysteresis with frequency. Hence, although the current-voltage hysteresis disappears in the high-frequency limit, the memory of the ion channel is manifested through its specific nonequilibrium thermodynamic responses.

  6. Targeting Potassium Channels for Increasing Delivery of Imaging Agents and Therapeutics to Brain Tumors

    Directory of Open Access Journals (Sweden)

    Nagendra Sanyasihally Ningaraj

    2013-05-01

    Full Text Available Every year in the US, 20,000 new primary and nearly 200,000 metastatic brain tumor cases are reported. The cerebral microvessels/ capillaries that form the blood–brain barrier (BBB not only protect the brain from toxic agents in the blood but also pose a significant hindrance to the delivery of small and large therapeutic molecules. Different strategies have been employed to circumvent the physiological barrier posed by blood-brain tumor barrier (BTB. Studies in our laboratory have identified significant differences in the expression levels of certain genes and proteins between normal and brain tumor capillary endothelial cells. In this study, we validated the non-invasive and clinically relevant Dynamic Contrast Enhancing-Magnetic Resonance Imaging (DCE-MRI method with invasive, clinically irrelevant but highly accurate Quantitative Autoradiography (QAR method using rat glioma model. We also showed that DCE-MRI metric of tissue vessel perfusion-permeability is sensitive to changes in blood vessel permeability following administration of calcium-activated potassium (BKCa channel activator NS-1619. Our results show that human gliomas and brain tumor endothelial cells that overexpress BKCa channels can be targeted for increased BTB permeability for MRI enhancing agents to brain tumors. We conclude that monitoring the outcome of increased MRI enhancing agents’ delivery to microsatellites and leading tumor edges in glioma patients would lead to beneficial clinical outcome.

  7. Comparison of the effects of DC031050,a class Ⅲ antiarrhythmic agent, on hERG channel and three neuronal potassium channels

    Institute of Scientific and Technical Information of China (English)

    Ping LI; Hai-feng SUN; Ping-zheng ZHOU; Chao-ying MA; Guo-yuan HU; Hua-liang JIANG; Min LI; Hong LIU; Zhao-bing GAO

    2012-01-01

    Aim:This study was conducted to test the selectivity of DC031050 on cardiac and neuronal potassium channels.Methods:Human ether-à-go-go related gene (hERG),KCNQ and Kv1.2 channels were expressed in CHO cells.The delayed rectifier potassium current (IK) was recorded from dissociated hippocampal pyramidal neurons of neonatal rats.Whole-cell voltage patch clamp was used to record the voltage-activated potassium currents.Drug-containing solution was delivered using a RSC-100 Rapid Solution Changer.Results:Both DC031050 and dofetilide potently inhibited hERG currents with IC50 values of 2.3±1.0 and 17.9±1.2 nmol/L,respectively.DC031050 inhibited the IK current with an IC50 value of 2.7±1.5 μmol/L,which was >1000 times the concentration required to inhibit hERG current.DC031050 at 3 μmol/L did not significantly affect the voltage-dependence of the steady activation,steady inactivation of IK,or the rate of IK from inactivation.Intracellular application of DC031050 (5μmol/L) was insufficient to inhibit IK.DC031050 up to 10μmol/L had no effects on KCNQ2 and Kv1.2 channel currents.Conclusion:DC031050 is a highly selective hERG potassium channel blocker with a substantial safety margin of activity over neuronal potassium channels,thus holds significant potential for therapeutic application as a class Ⅲ antiarrhythmic agent.

  8. Eliciting renal failure in mosquitoes with a small-molecule inhibitor of inward-rectifying potassium channels.

    Directory of Open Access Journals (Sweden)

    Rene Raphemot

    Full Text Available Mosquito-borne diseases such as malaria and dengue fever take a large toll on global health. The primary chemical agents used for controlling mosquitoes are insecticides that target the nervous system. However, the emergence of resistance in mosquito populations is reducing the efficacy of available insecticides. The development of new insecticides is therefore urgent. Here we show that VU573, a small-molecule inhibitor of mammalian inward-rectifying potassium (Kir channels, inhibits a Kir channel cloned from the renal (Malpighian tubules of Aedes aegypti (AeKir1. Injection of VU573 into the hemolymph of adult female mosquitoes (Ae. aegypti disrupts the production and excretion of urine in a manner consistent with channel block of AeKir1 and renders the mosquitoes incapacitated (flightless or dead within 24 hours. Moreover, the toxicity of VU573 in mosquitoes (Ae. aegypti is exacerbated when hemolymph potassium levels are elevated, suggesting that Kir channels are essential for maintenance of whole-animal potassium homeostasis. Our study demonstrates that renal failure is a promising mechanism of action for killing mosquitoes, and motivates the discovery of selective small-molecule inhibitors of mosquito Kir channels for use as insecticides.

  9. Suppression of the Eag1 potassium channel sensitizes glioblastoma cells to injury caused by temozolomide

    Science.gov (United States)

    Sales, Thais Torquato; Resende, Fernando Francisco Borges; Chaves, Natália Lemos; Titze-De-Almeida, Simoneide Souza; Báo, Sônia Nair; Brettas, Marcella Lemos; Titze-De-Almeida, Ricardo

    2016-01-01

    Glioblastoma multiforme (GBM) is the most aggressive type of human primary brain tumor. The standard treatment protocol includes radiotherapy in combination with temozolomide (TMZ). Despite advances in GBM treatment, the survival time of patients diagnosed with glioma is 14.5 months. Regarding tumor biology, various types of cancer cell overexpress the ether à go-go 1 (Eag1) potassium channel. Therefore, the present study examined the role of Eag1 in the cell damage caused by TMZ on the U87MG glioblastoma cell line. Eag1 was inhibited using a channel blocker (astemizole) or silenced by a short-hairpin RNA expression vector (pKv10.1-3). pKv10.1-3 (0.2 µg) improved the Eag1 silencing caused by 250 µM TMZ, as determined by reverse transcription-quantitative polymerase chain reaction and immunocytochemistry. Additionally, inhibiting Eag1 with the vector or astemizole (5 µM) reduced glioblastoma cell viability and sensitized cells to TMZ. Cell viability decreased by 63% for pKv10.1-3 + TMZ compared with 34% for TMZ alone, and by 77% for astemizole + TMZ compared with 46% for TMZ alone, as determined by MTT assay. In addition, both the vector and astemizole increased the apoptosis rate of glioblastoma cells triggered by TMZ, as determined by an Annexin V apoptosis assay. Collectively, the current data reveal that Eag1 has a role in the damage caused to glioblastoma by TMZ. Furthermore, suppression of this channel can improve the action of TMZ on U87MG glioblastoma cells. Thus, silencing Eag1 is a promising strategy to improve GBM treatment and merits additional studies in animal models of glioma.

  10. Expression of G-protein inwardly rectifying potassium channels (GIRKs in lung cancer cell lines

    Directory of Open Access Journals (Sweden)

    Schuller Hildegard M

    2005-08-01

    Full Text Available Abstract Background Previous data from our laboratory has indicated that there is a functional link between the β-adrenergic receptor signaling pathway and the G-protein inwardly rectifying potassium channel (GIRK1 in human breast cancer cell lines. We wanted to determine if GIRK channels were expressed in lung cancers and if a similar link exists in lung cancer. Methods GIRK1-4 expression and levels were determined by reverse transcription polymerase chain reaction (RT-PCR and real-time PCR. GIRK protein levels were determined by western blots and cell proliferation was determined by a 5-bromo-2'-deoxyuridine (BrdU assay. Results GIRK1 mRNA was expressed in three of six small cell lung cancer (SCLC cell lines, and either GIRK2, 3 or 4 mRNA expression was detected in all six SCLC cell lines. Treatment of NCI-H69 with β2-adrenergic antagonist ICI 118,551 (100 μM daily for seven days led to slight decreases of GIRK1 mRNA expression levels. Treatment of NCI-H69 with the β-adrenergic agonist isoproterenol (10 μM decreased growth rates in these cells. The GIRK inhibitor U50488H (2 μM also inhibited proliferation, and this decrease was potentiated by isoproterenol. In the SCLC cell lines that demonstrated GIRK1 mRNA expression, we also saw GIRK1 protein expression. We feel these may be important regulatory pathways since no expression of mRNA of the GIRK channels (1 & 2 was found in hamster pulmonary neuroendocrine cells, a suggested cell of origin for SCLC, nor was GIRK1 or 2 expression found in human small airway epithelial cells. GIRK (1,2,3,4 mRNA expression was also seen in A549 adenocarcinoma and NCI-H727 carcinoid cell lines. GIRK1 mRNA expression was not found in tissue samples from adenocarcinoma or squamous cancer patients, nor was it found in NCI-H322 or NCI-H441 adenocarcinoma cell lines. GIRK (1,3,4 mRNA expression was seen in three squamous cell lines, GIRK2 was only expressed in one squamous cell line. However, GIRK1 protein

  11. Expression of G-protein inwardly rectifying potassium channels (GIRKs) in lung cancer cell lines

    International Nuclear Information System (INIS)

    Previous data from our laboratory has indicated that there is a functional link between the β-adrenergic receptor signaling pathway and the G-protein inwardly rectifying potassium channel (GIRK1) in human breast cancer cell lines. We wanted to determine if GIRK channels were expressed in lung cancers and if a similar link exists in lung cancer. GIRK1-4 expression and levels were determined by reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR. GIRK protein levels were determined by western blots and cell proliferation was determined by a 5-bromo-2'-deoxyuridine (BrdU) assay. GIRK1 mRNA was expressed in three of six small cell lung cancer (SCLC) cell lines, and either GIRK2, 3 or 4 mRNA expression was detected in all six SCLC cell lines. Treatment of NCI-H69 with β2-adrenergic antagonist ICI 118,551 (100 μM) daily for seven days led to slight decreases of GIRK1 mRNA expression levels. Treatment of NCI-H69 with the β-adrenergic agonist isoproterenol (10 μM) decreased growth rates in these cells. The GIRK inhibitor U50488H (2 μM) also inhibited proliferation, and this decrease was potentiated by isoproterenol. In the SCLC cell lines that demonstrated GIRK1 mRNA expression, we also saw GIRK1 protein expression. We feel these may be important regulatory pathways since no expression of mRNA of the GIRK channels (1 & 2) was found in hamster pulmonary neuroendocrine cells, a suggested cell of origin for SCLC, nor was GIRK1 or 2 expression found in human small airway epithelial cells. GIRK (1,2,3,4) mRNA expression was also seen in A549 adenocarcinoma and NCI-H727 carcinoid cell lines. GIRK1 mRNA expression was not found in tissue samples from adenocarcinoma or squamous cancer patients, nor was it found in NCI-H322 or NCI-H441 adenocarcinoma cell lines. GIRK (1,3,4) mRNA expression was seen in three squamous cell lines, GIRK2 was only expressed in one squamous cell line. However, GIRK1 protein expression was not seen in any non-SCLC cells

  12. Conformational heterogeneity in closed and open states of the KcsA potassium channel in lipid bicelles.

    Science.gov (United States)

    Kim, Dorothy M; Dikiy, Igor; Upadhyay, Vikrant; Posson, David J; Eliezer, David; Nimigean, Crina M

    2016-08-01

    The process of ion channel gating-opening and closing-involves local and global structural changes in the channel in response to external stimuli. Conformational changes depend on the energetic landscape that underlies the transition between closed and open states, which plays a key role in ion channel gating. For the prokaryotic, pH-gated potassium channel KcsA, closed and open states have been extensively studied using structural and functional methods, but the dynamics within each of these functional states as well as the transition between them is not as well understood. In this study, we used solution nuclear magnetic resonance (NMR) spectroscopy to investigate the conformational transitions within specific functional states of KcsA. We incorporated KcsA channels into lipid bicelles and stabilized them into a closed state by using either phosphatidylcholine lipids, known to favor the closed channel, or mutations designed to trap the channel shut by disulfide cross-linking. A distinct state, consistent with an open channel, was uncovered by the addition of cardiolipin lipids. Using selective amino acid labeling at locations within the channel that are known to move during gating, we observed at least two different slowly interconverting conformational states for both closed and open channels. The pH dependence of these conformations and the predictable disruptions to this dependence observed in mutant channels with altered pH sensing highlight the importance of conformational heterogeneity for KcsA gating. PMID:27432996

  13. Targeting the Small- and Intermediate-Conductance Ca2+-Activated Potassium Channels: The Drug-Binding Pocket at the Channel/Calmodulin Interface

    Directory of Open Access Journals (Sweden)

    Meng Cui

    2014-10-01

    Full Text Available The small- and intermediate-conductance Ca2+-activated potassium (SK/IK channels play important roles in the regulation of excitable cells in both the central nervous and cardiovascular systems. Evidence from animal models has implicated SK/IK channels in neurological conditions such as ataxia and alcohol use disorders. Further, genome-wide association studies have suggested that cardiovascular abnormalities such as arrhythmias and hypertension are associated with single nucleotide polymorphisms that occur within the genes encoding the SK/IK channels. The Ca2+ sensitivity of the SK/IK channels stems from a constitutively bound Ca2+-binding protein: calmodulin. Small-molecule positive modulators of SK/IK channels have been developed over the past decade, and recent structural studies have revealed that the binding pocket of these positive modulators is located at the interface between the channel and calmodulin. SK/IK channel positive modulators can potentiate channel activity by enhancing the coupling between Ca2+ sensing via calmodulin and mechanical opening of the channel. Here, we review binding pocket studies that have provided structural insight into the mechanism of action for SK/IK channel positive modulators. These studies lay the foundation for structure-based drug discovery efforts that can identify novel SK/IK channel positive modulators. © 2014 S. Karger AG, Basel

  14. Protein expression of G-protein inwardly rectifying potassium channels (GIRK in breast cancer cells

    Directory of Open Access Journals (Sweden)

    Plummer Howard K

    2006-08-01

    Full Text Available Abstract Background Previous data from our laboratory has indicated that a functional link exists between the G-protein-coupled inwardly rectifying potassium (GIRK channel and the beta-adrenergic receptor pathway in breast cancer cell lines, and these pathways were involved in growth regulation of these cells. Alcohol is an established risk factor for breast cancer and has been found to open GIRK. In order to further investigate GIRK channels in breast cancer and possible alteration by ethanol, we identified GIRK channel protein expression in breast cancer cells. Results Cell pellets were collected and membrane protein was isolated to determine GIRK protein expression. GIRK protein was also analyzed by immuno-precipitation. GIRK protein was over-expressed in cells by transfection of GIRK plasmids. Gene expression studies were done by real-time RT-PCR. GIRK protein expression was identified in breast cancer cell lines. Expression of GIRK1 at the indicated molecular weight (MW (62 kDa was seen in cell lines MDA-MB-453 and ZR-75-1. In addition, GIRK1 expression was seen at a lower MW (40–42 kDa in MDA-MB-361, MDA-MB-468, MCF-7, ZR-75-1, and MDA-MB-453 cell lines. To prove the lower MW protein was GIRK1, MDA-MB-453 cells were immuno-precipitated. GIRK2 expression was seen in MDA-MB-468, MCF-7, and ZR-75-1 and was variable in MDA-MB-453, while GIRK4 protein expression was seen in all six cell lines tested. This is the first report indicating GIRK protein expression in breast cancer cells. To determine functionality, MDA-MB-453 cells were stimulated with ethanol. Decreased GIRK1 protein expression levels were seen after treatment with 0.12% ethanol in MDA-MB-453 breast cancer cells. Serum-free media decreased GIRK protein expression, possibly due to lack of estrogen in the media. Transfection of GIRK1 or GIRK4 plasmids increased GIRK1 protein expression and decreased gene expression in MDA-MB-453 breast cancer cells. Conclusion Our data indicates

  15. Interactions between β-catenin and the HSlo potassium channel regulates HSlo surface expression.

    Directory of Open Access Journals (Sweden)

    Shumin Bian

    Full Text Available BACKGROUND: The large conductance calcium-activated potassium channel alpha-subunit (Slo is widely distributed throughout the body and plays an important role in a number of diseases. Prior work has shown that Slo, through its S10 region, interacts with β-catenin, a key component of the cytoskeleton framework and the Wnt signaling pathway. However, the physiological significance of this interaction was not clear. METHODOLOGY/PRINCIPAL FINDINGS: Using a combination of proteomic and cell biology tools we show the existence of additional multiple binding sites in Slo, and explore in detail β-catenin interactions with the S10 region. We demonstrate that deletion of this region reduces Slo surface expression in HEK cells, which indicates that interaction with beta-catenin is important for Slo surface expression. This is confirmed by reduced expression of Slo in HEK cells and chicken (Gallus gallus domesticus leghorn white hair cells treated with siRNA to β-catenin. HSlo reciprocally co-immunoprecipitates with β-catenin, indicating a stable binding between these two proteins, with the S10 deletion mutant having reduced binding with β-catenin. We also observed that mutations of the two putative GSK phosphorylation sites within the S10 region affect both the surface expression of Slo and the channel's voltage and calcium sensitivities. Interestingly, expression of exogenous Slo in HEK cells inhibits β-catenin-dependent canonical Wnt signaling. CONCLUSIONS AND SIGNIFICANCE: These studies identify for the first time a central role for β-catenin in mediating Slo surface expression. Additionally we show that Slo overexpression can lead to downregulation of Wnt signaling.

  16. Function of the Shaw potassium channel within the Drosophila circadian clock.

    Directory of Open Access Journals (Sweden)

    James J Hodge

    Full Text Available BACKGROUND: In addition to the molecular feedback loops, electrical activity has been shown to be important for the function of networks of clock neurons in generating rhythmic behavior. Most studies have used over-expression of foreign channels or pharmacological manipulations that alter membrane excitability. In order to determine the cellular mechanisms that regulate resting membrane potential (RMP in the native clock of Drosophila we modulated the function of Shaw, a widely expressed neuronal potassium (K(+ channel known to regulate RMP in Drosophila central neurons. METHODOLOGY/PRINCIPAL FINDINGS: We show that Shaw is endogenously expressed in clock neurons. Differential use of clock gene promoters was employed to express a range of transgenes that either increase or decrease Shaw function in different clusters of clock neurons. Under LD conditions, increasing Shaw levels in all clock neurons (LNv, LNd, DN(1, DN(2 and DN(3, or in subsets of clock neurons (LNd and DNs or DNs alone increases locomotor activity at night. In free-running conditions these manipulations result in arrhythmic locomotor activity without disruption of the molecular clock. Reducing Shaw in the DN alone caused a dramatic lengthening of the behavioral period. Changing Shaw levels in all clock neurons also disrupts the rhythmic accumulation and levels of Pigment Dispersing Factor (PDF in the dorsal projections of LNv neurons. However, changing Shaw levels solely in LNv neurons had little effect on locomotor activity or rhythmic accumulation of PDF. CONCLUSIONS/SIGNIFICANCE: Based on our results it is likely that Shaw modulates pacemaker and output neuronal electrical activity that controls circadian locomotor behavior by affecting rhythmic release of PDF. The results support an important role of the DN clock neurons in Shaw-mediated control of circadian behavior. In conclusion, we have demonstrated a central role of Shaw for coordinated and rhythmic output from clock

  17. Supratentorial white matter blurring associated with voltage-gated potassium channel-complex limbic encephalitis

    Energy Technology Data Exchange (ETDEWEB)

    Urbach, H.; Mader, I. [University Medical Center Freiburg, Department of Neuroradiology, Freiburg (Germany); Rauer, S.; Baumgartner, A. [University Medical Center Freiburg, Department of Neurology, Freiburg (Germany); Paus, S. [University Medical Center, Department of Neurology, Bonn (Germany); Wagner, J. [University Medical Center, Department of Epileptology, Bonn (Germany); Malter, M.P. [University of Cologne, Department of Neurology, Cologne (Germany); Pruess, H. [Charite - Universitaetsmedizin Berlin, Department of Neurology, Berlin (Germany); Lewerenz, J.; Kassubek, J. [Ulm University, Department of Neurology, Ulm (Germany); Hegen, H.; Auer, M.; Deisenhammer, F. [University Innsbruck, Department of Neurology, Innsbruck (Austria); Ufer, F. [University Medical Center, Department of Neurology, Hamburg (Germany); Bien, C.G. [Epilepsy Centre Bethel, Bielefeld-Bethel (Germany)

    2015-12-15

    Limbic encephalitis (LE) associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) is frequently non-paraneoplastic and associated with marked improvement following corticosteroid therapy. Mesial temporal lobe abnormalities are present in around 80 % of patients. If associated or preceded by faciobrachial dystonic seizures, basal ganglia signal changes may occur. In some patients, blurring of the supratentorial white matter on T2-weighted images (SWMB) may be seen. The purpose of this study was to evaluate the incidence of SWMB and whether it is specific for VGKC-LE. Two experienced neuroradiologists independently evaluated signal abnormalities on FLAIR MRI in 79 patients with LE while unaware on the antibody type. SWMB was independently assessed as present in 10 of 36 (28 %) compared to 2 (5 %) of 43 non-VGKC patients (p = 0.009). It was not related to the presence of LGI1 or CASPR2 proteins of VGKC antibodies. MRI showed increased temporomesial FLAIR signal in 22 (61 %) VGKC compared to 14 (33 %) non-VGKC patients (p = 0.013), and extratemporomesial structures were affected in one VGKC (3 %) compared to 11 (26 %) non-VGKC patients (p = 0.005). SWMB is a newly described MRI sign rather specific for VGKC-LE. (orig.)

  18. Voltage-gated potassium channels autoantibodies in a child with rasmussen encephalitis.

    Science.gov (United States)

    Spitz, Marie-Aude; Dubois-Teklali, Fanny; Vercueil, Laurent; Sabourdy, Cécile; Nugues, Frédérique; Vincent, Angela; Oliver, Viviana; Bulteau, Christine

    2014-10-01

    Rasmussen encephalitis (RE) is a severe epileptic and inflammatory encephalopathy of unknown etiology, responsible for focal neurological signs and cognitive decline. The current leading hypothesis suggests a sequence of immune reactions induced by an indeterminate factor. This sequence is thought to be responsible for the production of autoantibody-mediated central nervous system degeneration. However, these autoantibodies are not specific to the disease and not all patients present with them. We report the case of a 4-year-old girl suffering from RE displaying some atypical features such as fast evolution and seizures of left parietal onset refractory to several antiepileptics, intravenous immunoglobulins, and corticosteroids. Serum autoantibodies directed against voltage-gated potassium channels (VGKC) were evidenced at 739 pM, a finding never previously reported in children. This screening was performed because of an increased signal in the temporolimbic areas on brain magnetic resonance imaging, which was similar to what is observed during limbic encephalitis. The patient experienced epilepsia partialis continua with progressive right hemiplegia and aphasia. She underwent left hemispherotomy at the age of 5.5 years after which she became seizure free with great cognitive improvement. First described in adults, VGKC autoantibodies have been recently described in children with various neurological manifestations. The implication of VGKC autoantibodies in RE is a new observation and opens up new physiopathological and therapeutic avenues of investigation.

  19. Voltage-Gated Potassium Channel Antibody Paraneoplastic Limbic Encephalitis Associated with Acute Myeloid Leukemia

    Directory of Open Access Journals (Sweden)

    Marion Alcantara

    2013-05-01

    Full Text Available Among paraneoplastic syndromes (PNS associated with malignant hemopathies, there are few reports of PNS of the central nervous system and most of them are associated with lymphomas. Limbic encephalitis is a rare neurological syndrome classically diagnosed in the context of PNS. We report the case of a 81-year-old man who presented with a relapsed acute myeloid leukemia (AML with minimal maturation. He was admitted for confusion with unfavorable evolution as he presented a rapidly progressive dementia resulting in death. A brain magnetic resonance imaging, performed 2 months after the onset, was considered normal. An electroencephalogram showed non-specific bilateral slow waves. We received the results of the blood screening of neuronal autoantibodies after the patient's death and detected the presence of anti-voltage-gated potassium channel (VGKC antibodies at 102 pmol/l (normal at <30 pmol/l. Other etiologic studies, including the screening for another cause of rapidly progressive dementia, were negative. To our knowledge, this is the first case of anti-VGKC paraneoplastic limbic encephalitis related to AML.

  20. Pungent agents from Szechuan peppers excite sensory neurons by inhibiting two-pore potassium channels.

    Science.gov (United States)

    Bautista, Diana M; Sigal, Yaron M; Milstein, Aaron D; Garrison, Jennifer L; Zorn, Julie A; Tsuruda, Pamela R; Nicoll, Roger A; Julius, David

    2008-07-01

    In traditional folk medicine, Xanthoxylum plants are referred to as 'toothache trees' because their anesthetic or counter-irritant properties render them useful in the treatment of pain. Psychophysical studies have identified hydroxy-alpha-sanshool as the compound most responsible for the unique tingling and buzzing sensations produced by Szechuan peppercorns or other Xanthoxylum preparations. Although it is generally agreed that sanshool elicits its effects by activating somatosensory neurons, the underlying cellular and molecular mechanisms remain a matter of debate. Here we show that hydroxy-alpha-sanshool excites two types of sensory neurons, including small-diameter unmyelinated cells that respond to capsaicin (but not mustard oil) as well as large-diameter myelinated neurons that express the neurotrophin receptor TrkC. We found that hydroxy-alpha-sanshool excites neurons through a unique mechanism involving inhibition of pH- and anesthetic-sensitive two-pore potassium channels (KCNK3, KCNK9 and KCNK18), providing a framework for understanding the unique and complex psychophysical sensations associated with the Szechuan pepper experience.

  1. Supratentorial white matter blurring associated with voltage-gated potassium channel-complex limbic encephalitis

    International Nuclear Information System (INIS)

    Limbic encephalitis (LE) associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) is frequently non-paraneoplastic and associated with marked improvement following corticosteroid therapy. Mesial temporal lobe abnormalities are present in around 80 % of patients. If associated or preceded by faciobrachial dystonic seizures, basal ganglia signal changes may occur. In some patients, blurring of the supratentorial white matter on T2-weighted images (SWMB) may be seen. The purpose of this study was to evaluate the incidence of SWMB and whether it is specific for VGKC-LE. Two experienced neuroradiologists independently evaluated signal abnormalities on FLAIR MRI in 79 patients with LE while unaware on the antibody type. SWMB was independently assessed as present in 10 of 36 (28 %) compared to 2 (5 %) of 43 non-VGKC patients (p = 0.009). It was not related to the presence of LGI1 or CASPR2 proteins of VGKC antibodies. MRI showed increased temporomesial FLAIR signal in 22 (61 %) VGKC compared to 14 (33 %) non-VGKC patients (p = 0.013), and extratemporomesial structures were affected in one VGKC (3 %) compared to 11 (26 %) non-VGKC patients (p = 0.005). SWMB is a newly described MRI sign rather specific for VGKC-LE. (orig.)

  2. Role of vascular KATP channels in blood pressure variability after sinoaortic denervation in rats

    OpenAIRE

    Yang, Zhong-Wei; Li, Dong-jie; Liu, Chong; Han, Ping; Yang, Yi-li; Su, Ding-Feng; Shen, Fu-Ming

    2011-01-01

    Aim: To investigate the role of ATP-sensitive potassium (KATP) channels on blood pressure variability (BPV) in sinoaortic denervated (SAD) rats. Methods: SAD was performed on male Sprague-Dawley rats 4 weeks before the study. mRNA expression of Kir6.1, Kir6.2 and SUR2 in aorta and mesenteric artery was determined using real-time quantitative polymerase chain reaction, and confirmed at the protein level using Western blotting and laser confocal immunofluorescence assays. Concentration-response...

  3. ATP interaction with the open state of the K(ATP) channel.

    OpenAIRE

    Enkvetchakul, D; Loussouarn, G.; Makhina, E; Nichols, C.G.

    2001-01-01

    The mechanism of ATP-sensitive potassium (K(ATP)) channel closure by ATP is unclear, and various kinetic models in which ATP binds to open or to closed states have previously been presented. Effects of phosphatidylinositol bisphosphate (PIP2) and multiple Kir6.2 mutations on ATP inhibition and open probability in the absence of ATP are explainable in kinetic models where ATP stabilizes a closed state and interaction with an open state is not required. Evidence that ATP can in fact interact wi...

  4. [Effects of beta-cypermethrin on voltage-gated potassium channels in rat hippocampal CA3 neurons].

    Science.gov (United States)

    Fu, Zhi-Yan; DU, Chun-Yun; Yao, Yang; Liu, Chao-Wei; Tian, Yu-Tao; He, Bing-Jun; Zhang, Tao; Yang, Zhuo

    2007-02-25

    The effects of beta-cypermethrin (consisting of alpha-cypermethrin and theta-cypermethrin) on the transient outward potassium current (I(A)) and delayed rectifier potassium current (I(K)) in freshly dissociated hippocampal CA3 neurons of rats were studied using whole-cell patch-clamp technique. The results indicated that alpha-cypermethrin increased the value of I(A) and theta-cypermethrin decreased the value of I(A), though both of them shifted steady activation curve of I(A) towards negative potential. theta-cypermethrin contributed to the inactivation of I(A). The results also showed that alpha-cypermethrin and theta-cypermethrin decreased the value of I(K), and shifted the steady state activation curve of I(K) towards negative potential. Both alpha-cypermethrin and theta-cypermethrin had no obvious effects on the inactivation of I(K). theta-cypermethrin prolonged recovery process of I(K). These results imply that both transient outward potassium channels and delayed rectified potassium channels are the targets of beta-cypermethrin, which may explain the mechanism of toxical effects of beta-cypermethrin on mammalian neurons.

  5. Solid-state NMR study and assignments of the KcsA potassium ion channel of S. lividans.

    Science.gov (United States)

    Varga, Krisztina; Tian, Lin; McDermott, Ann E

    2007-12-01

    The extraordinary efficiency and selectivity of potassium channels have made them ideal systems for biophysical and functional studies of ion conduction. We carried out solid-state NMR studies of the selectivity filter region of the protein. Partial site-specific assignments of the NMR signals were obtained based on high field multidimensional solid-state NMR spectra of uniformly (13)C, (15)N enriched KcsA potassium channel from Streptomyces lividans. Both backbone and sidechain atoms were assigned for residues V76-D80 and P83-L90, in and near the selectivity filter region of the protein; this region exhibits good dispersion and useful chemical shift fingerprints. This study will enable structure, dynamic and mechanistic studies of ion conduction by NMR.

  6. Pharmacological and molecular comparison of K(ATP) channels in rat basilar and middle cerebral arteries

    DEFF Research Database (Denmark)

    Ploug, Kenneth Beri; Edvinsson, Lars; Olesen, Jes;

    2006-01-01

    basilar and middle cerebral arteries using quantitative real-time PCR (Polymerase Chain Reaction) and Western blotting, respectively. In the perfusion system, we found no significant responses after luminal application of three K(ATP) channel openers to rat basilar and middle cerebral arteries......ATP-sensitive potassium (K(ATP)) channels play an important role in the regulation of cerebral vascular tone. In vitro studies using synthetic K(ATP) channel openers suggest that the pharmacological profiles differ between rat basilar arteries and rat middle cerebral arteries. To address this issue......, we studied the possible involvement of endothelial K(ATP) channels by pressurized arteriography after luminal administration of synthetic K(ATP) channel openers to rat basilar and middle cerebral arteries. Furthermore, we examined the mRNA and protein expression profile of K(ATP) channels to rat...

  7. Pharmacological and molecular comparison of K(ATP) channels in rat basilar and middle cerebral arteries

    DEFF Research Database (Denmark)

    Ploug, Kenneth Beri; Edvinsson, Lars; Olesen, Jes;

    2006-01-01

    ATP-sensitive potassium (K(ATP)) channels play an important role in the regulation of cerebral vascular tone. In vitro studies using synthetic K(ATP) channel openers suggest that the pharmacological profiles differ between rat basilar arteries and rat middle cerebral arteries. To address this issue......, we studied the possible involvement of endothelial K(ATP) channels by pressurized arteriography after luminal administration of synthetic K(ATP) channel openers to rat basilar and middle cerebral arteries. Furthermore, we examined the mRNA and protein expression profile of K(ATP) channels to rat...... basilar and middle cerebral arteries using quantitative real-time PCR (Polymerase Chain Reaction) and Western blotting, respectively. In the perfusion system, we found no significant responses after luminal application of three K(ATP) channel openers to rat basilar and middle cerebral arteries. In...

  8. Leucine-rich glioma inactivated-1 and voltage gated potassium channel autoimmune encephalitis associated with ischemic stroke; A Case Report

    Directory of Open Access Journals (Sweden)

    Marisa Patryce McGinley

    2016-05-01

    Full Text Available Autoimmune encephalitis is associated with a wide variety of antibodies and clinical presentations. Voltage gated potassium channel (VGKC antibodies are a cause of autoimmune non-paraneoplastic encephalitis characterized by memory impairment, psychiatric symptoms, and seizures. We present a case of VGKC encephalitis likely preceding an ischemic stroke. Reports of autoimmune encephalitis associated with ischemic stroke are rare. Several hypothesizes linking these two disease processes are proposed.

  9. Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA

    OpenAIRE

    Raja, M.M.; Spelbrink, R E J; de Kruijff, B.; Killian, J A

    2007-01-01

    In this study, we investigated how the presence of anionic lipids influenced the stability and folding properties of the potassium channel KcsA. By using a combination of gel electrophoresis, tryptophan fluorescence and acrylamide quenching experiments, we found that the presence of the anionic lipid phosphatidylglycerol (PG) in a phosphatidylcholine (PC) bilayer slightly stabilized the tetramer and protected it from trifluoroethanol- induced dissociation. Surprisingly, the presence of phosph...

  10. Kv7 potassium channels in airway smooth muscle cells: signal transduction intermediates and pharmacological targets for bronchodilator therapy

    OpenAIRE

    Brueggemann, Lioubov I.; Kakad, Priyanka P.; Robert B Love; Solway, Julian; Dowell, Maria L.; Cribbs, Leanne L.; Byron, Kenneth L.

    2011-01-01

    Expression and function of Kv7 (KCNQ) voltage-activated potassium channels in guinea pig and human airway smooth muscle cells (ASMCs) were investigated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), patch-clamp electrophysiology, and precision-cut lung slices. qRT-PCR revealed expression of multiple KCNQ genes in both guinea pig and human ASMCs. Currents with electrophysiological and pharmacological characteristics of Kv7 currents were measured in freshly isolated ...

  11. KCNE4 is an inhibitory subunit to Kv1.1 and Kv1.3 potassium channels

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hannne B; Hay-Schmidt, Anders;

    2003-01-01

    Kv1 potassium channels are widely distributed in mammalian tissues and are involved in a variety of functions from controlling the firing rate of neurons to maturation of T-lymphocytes. Here we show that the newly described KCNE4 beta-subunit has a drastic inhibitory effect on currents generated...... is detected in the heart and in five different parts of the brain. Having the broad distribution of Kv1 channels in mind, the demonstrated inhibitory property of KCNE4-subunits could locally and/or transiently have a dramatic influence on cellular excitability and on setting resting membrane potentials....

  12. Activation of human ether-a-go-go related gene (hERG) potassium channels by small molecules

    Institute of Scientific and Technical Information of China (English)

    Ping-zheng ZHOU; Joseph BABCOCK; Lian-qing LIU; Min LI; Zhao-bing GAO

    2011-01-01

    Human ether-a-go-go related gene (hERG) potassium (K+) channels play a critical role in cardiac action potential repolarlzatlon. Mutations that reduce hERG conductance or surface expression may cause congenital long QT syndrome (LQTS). Moreover, the channels can be inhibited by structurally diverse small molecules, resulting in an acquired form of LQTS. Consequently, small molecules that increase the hERG current may be of value for treatment of LQTS. So far, nine hERG activators have been reported. The aim of this review is to discuss recent advances concerning the identification and action mechanism of hERG activators.

  13. Inhibition of the human two-pore domain potassium channel, TREK-1, by fluoxetine and its metabolite norfluoxetine

    OpenAIRE

    Kennard, Louise E; Chumbley, Justin R.; Ranatunga, Kishani M.; Armstrong, Stephanie J; Veale, Emma L.; Mathie, Alistair

    2005-01-01

    Block of the human two-pore domain potassium (2-PK) channel TREK-1 by fluoxetine (ProzacR) and its active metabolite, norfluoxetine, was investigated using whole-cell patch-clamp recording of currents through recombinant channels in tsA 201 cells.Fluoxetine produced a concentration-dependent inhibition of TREK-1 current that was reversible on wash. The IC50 for block was 19 μM. Block by fluoxetine was voltage-independent. Fluoxetine (100 μM) produced an 84% inhibition of TREK-1 currents, but ...

  14. Identification of novel small molecule modulators of K2P18.1 two-pore potassium channel

    Science.gov (United States)

    Bruner, J. Kyle; Zou, Beiyan; Zhang, Hongkang; Zhang, Yixin; Schmidt, Katharina; Li, Min

    2014-01-01

    Two-pore domain potassium (K2P) channels are responsible for background potassium (K+) current, which is crucial for the maintenance of resting membrane potential. K2P18.1, also called TWIK-related spinal cord K+ channel (TRESK) or KCNK18, is thought to be a major contributor to background K+ currents, particularly in sensory neurons where it is abundantly expressed. Despite its critical role and potential therapeutic implication, pharmacological tools for probing K2P18.1 activity remain unavailable. Here, we report a high-throughput screen against a collection of bioactive compounds that yielded 26 inhibitors and 8 activators of K2P18.1 channel activity with more than 10-fold selectivity over the homologous channel K2P9.1. Among these modulators, the antihistamine loratadine inhibited K2P18.1 activity with IC50 of 0.49 ± 0.23 μM and is considerably more potent than existing K2P18.1 inhibitors. Importantly, the inhibition by loratadine remains equally efficacious upon potentiation of K2P18.1 by calcium signaling. Furthermore, the loratadine effect is dependent on transmembrane residues F145 and F352, providing orthogonal evidence that the inhibition is caused by a direct compound-channel interaction. This study reveals new pharmacological modulators of K2P18.1 activity useful in dissecting native K2P18.1 function. PMID:24972239

  15. In vitro and in vivo evaluation of potassium permanganate treatment efficacy for the control of acute experimental infection of flavobacterium columnare in channel catfish

    Science.gov (United States)

    An experimental trial was performed to evaluate the efficacy of potassium permanganate against an acute and systemic experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus. The infection was produced by waterborne exposure to the bacteria after mechanical cutaneo...

  16. Molecular basis for the toxin insensitivity of scorpion voltage-gated potassium channel MmKv1.

    Science.gov (United States)

    Zhang, Chuangeng; Xie, Zili; Li, Xinxin; Chen, Jing; Feng, Jing; Lang, Yange; Yang, Weishan; Li, Wenxin; Chen, Zongyun; Yao, Jing; Cao, Zhijian; Wu, Yingliang

    2016-05-01

    Scorpions are insensitive to their own venoms, which contain various neurotoxins specific for mammalian or insect ion channels, whose molecular mechanism remains unsolved. Using MmKv1, a potassium channel identified from the genome of the scorpion Mesobuthus martensii, channel kinetic experiments showed that MmKv1 was a classical voltage-gated potassium channel with a voltage-dependent fast activation and slow inactivation. Compared with the human Kv1.3 channel (hKv1.3), the MmKv1 channel exhibited a remarkable insensitivity to both scorpion venom and toxin. The chimaeric channels of MmKv1 and hKv1.3 revealed that both turret and filter regions of the MmKv1 channel were critical for the toxin insensitivity of MmKv1. Furthermore, mutagenesis of the chimaeric channel indicated that two basic residues (Arg(399) and Lys(403)) in the MmKv1 turret region and Arg(425) in the MmKv1 filter region significantly affected its toxin insensitivity. Moreover, when these three basic residues of MmKv1 were simultaneously substituted with the corresponding residues from hKv1.3, the MmKv1-R399T/K403S/R425H mutant channels exhibited similar sensitivity to both scorpion venom and toxin to hKv1.3, which revealed the determining role of these three basic residues in the toxin insensitivity of the MmKv1 channel. More strikingly, a similar triad sequence structure is present in all Shaker-like channels from venomous invertebrates, which suggested a possible convergent functional evolution of these channels to enable them to resist their own venoms. Together, these findings first illustrate the mechanism by which scorpions are insensitive to their own venoms at the ion channel receptor level and enrich our knowledge of the insensitivity of scorpions and other venomous animals to their own venoms. PMID:26951716

  17. Effects of arachidonic acid on ATP-sensitive K+ current in murine colonic smooth muscle cells.

    Science.gov (United States)

    Jun, Jae Yeoul; Yeum, Cheol Ho; Park, Yoo Whan; Jang, In Youb; Kong, In Deok; Sim, Jae Hoon; So, Insuk; Kim, Ki Whan; You, Ho Jin

    2002-09-01

    The effects of arachidonic acid (AA) and the mechanism through which it modulates ATP-sensitive K+ (K(ATP)) currents were examined in single smooth muscle cells of murine proximal colon. In the current-clamping mode, AA and glibenclamide induced depolarization of membrane potential. Using 0.1 mM ATP and 140 mM K+ solution in the pipette and 90 mM K+ in the bath solution at a -80 mV of holding potential, pinacidil activated the glibenclamide-sensitive inward current. The potential of these currents was reversed to near the equilibrium potential of K+ by 60 mM K+ in the bath solution. AA inhibited K(ATP) currents in a dose-dependent manner. This inhibition was not changed when 1 mM GDPbetaS was present in the pipette. Chelerythrine, protein kinase C inhibitor, did not block the AA effects. Superoxide dismutase and metabolic inhibitors (indomethacin and nordihydroguaiacretic acid) of AA did not affect the AA-induced inhibition. Eicosatetraynoic acid, a nonmetabolizable analogue of AA, inhibited the K(ATP) currents. These results suggest that AA-induced inhibition of K(ATP) currents is not mediated by G-protein or protein kinase C activation. The inhibitory action is likely to be a possible mechanism of AA-induced membrane depolarization. PMID:12396031

  18. The mechanism of KV4.3 voltage-gated potassium channel in arrhythmia induced by sleep deprivation in rat

    Directory of Open Access Journals (Sweden)

    Ya-jing ZHANG

    2011-03-01

    Full Text Available Objective To investigate the effect of sleep deprivation(SD on the changes in electrocardiogram and mRNA and protein expression of KV4.3 voltage-gated potassium channel in rats,and explore the related mechanisms of arrhythmia induced by SD.Methods A total of 48 adult male SD rats were randomly divided into 6 groups(8 each: normal control(CC group,tank control(TC group,1-,3-,5-and 7-day SD group.Animal model of SD was established by modified multiple platform method,and electrocardiogram was recorded on 1st,3rd,5th,and 7th of experiment.Protein and mRNA expressions of KV4.3 voltage-gated potassium channel were measured by real-time PCR and Western blotting analysis.Results The main changes on electrocardiogram following SD were arrhythmia.Compared with the CC group,rats in TC group showed sinus tachycardia in electrocardiogram: frequent atrial premature beats were observed one day after SD;ventricular arrhythmias,such as frequent polymorphic ventricular premature beats and paroxysmal ventricular tachycardia were observed three days after SD;incomplete right bundle branch block wave occurred five days after SD;the electrocardiogram showed third-degree atrioventricular(AV block wave seven days after SD,which indicated atrial arrhythmia and ventricular arrhythmia respectively.Ventricular escape beat,sinus arrest as well as the fusion of obviously elevated ST segment and T-wave were also observed.The expression levels of KV4.3 voltage-gated potassium channel decreased with prolongation of SD time.The expression of mRNA and protein of KV4.3 potassium channel in 7-day SD rats were only the one ninth and one fourth of levels in CC group.Conclusion Sleep deprivation can cause arrhythmia,and decreased expression of KV4.3 voltage-gated potassium channel may possibly be one of the reasons of arrhythmia induced by SD.

  19. Blockade of KCa3.1 potassium channels protects against cisplatin-induced acute kidney injury.

    Science.gov (United States)

    Chen, Cheng-Lung; Liao, Jiunn-Wang; Hu, Oliver Yoa-Pu; Pao, Li-Heng

    2016-09-01

    Tubular cell apoptosis significantly contributes to cisplatin-induced acute kidney injury (AKI) pathogenesis. Although KCa3.1, a calcium-activated potassium channel, participates in apoptosis, its involvement in cisplatin-induced AKI is unknown. Here, we found that cisplatin treatment triggered an early induction of KCa3.1 expression associated with HK-2 cell apoptosis, the development of renal tubular damage, and apoptosis in mice. Treatment with the highly selective KCa3.1 blocker TRAM-34 suppressed cisplatin-induced HK-2 cell apoptosis. We further assessed whether KCa3.1 mediated cisplatin-induced AKI in genetic knockout and pharmacological blockade mouse models. KCa3.1 deficiency reduced renal function loss, renal tubular damage, and the induction of the apoptotic marker caspase-3 in the kidneys of cisplatin-treated KCa3.1 (-/-) mice. Pharmacological blockade of KCa3.1 by TRAM-34 similarly attenuated cisplatin-induced AKI in mice. Furthermore, we dissected the mechanisms underlying cisplatin-induced apoptosis reduction via KCa3.1 blockade. We found that KCa3.1 blockade attenuated cytochrome c release and the increase in the intrinsic apoptotic mediators Bax, Bak, and caspase-9 after cisplatin treatment. KCa3.1 blocking inhibited the cisplatin-induced activation of the endoplasmic reticulum (ER) stress mediator caspase-12, which is independent of calcium-dependent protease m-calpain activation. Taken together, KCa3.1 blockade protects against cisplatin-induced AKI through the attenuation of apoptosis by interference with intrinsic apoptotic and ER stress-related mediators, providing a potential target for the prevention of cisplatin-induced AKI. PMID:26438401

  20. Comparative Effect of Type 1 and Type 2 Diabetes Mellitus on Vascular Responses of Rat Thoracic Aorta to Potassium Ion Channel Openers

    OpenAIRE

    Daniel U Owu; Orie, Nelson N.; Nwokocha, Chukwuemeka R.; Clapp, Lucie H.; Eme E. Osim

    2013-01-01

    Background: Diabetes mellitus is associated with many cardiovascular dysfunction and impairment of potassium channel function. Aim: We compared the vascular reactivity in aorta from streptozotocin-induced and Goto-Kakizaki (GK) diabetic rats to potassium channel openers. Methodology: Diabetes mellitus (DM) was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin (STZ) at 65 mg/kg body weight. After four weeks of DM, vascular reactivity of the aortic rings from STZ-ind...

  1. Neuroregulation of mucus secretion by opioid receptors and KATP and BKCa channels in ferret trachea in vitro

    OpenAIRE

    Ramnarine, Sean I; Liu, Yu-Chih; Rogers, Duncan F

    1998-01-01

    Opioid agonists inhibit neurogenic mucus secretion in the airways. The mechanism of the inhibition is unknown but may be via opening of potassium (K+) channels. We studied the effect on neurogenic secretion in ferret trachea in vitro of the OP1 receptor (formerly known as δ opioid receptor) agonist [D-Pen2,5]enkephalin (DPDPE), the OP2 receptor (formely κ) agonist U-50,488H, the OP3 receptor (formerly μ) agonist [D-Ala2, N-Me-Phe, Gly-ol5]enkephalin (DAMGO), the ATP-sensitive K+ (KATP) channe...

  2. Molecular determinants for the tarantula toxin jingzhaotoxin-I interacting with potassium channel Kv2.1.

    Science.gov (United States)

    Tao, Huai; Wu, Yuanyuan; Deng, Meichun; He, Juan; Wang, Meichi; Xiao, Yucheng; Liang, Songping

    2013-03-01

    With high binding affinity and distinct pharmacological functions, animal toxins are powerful ligands to investigate the structure-function relationships of voltage-gated ion channels. Jingzhaotoxin-I (JZTX-I) is an important neurotoxin from the tarantula Chilobrachys jingzhao venom that inhibits both sodium and potassium channels. In our previous work, JZTX-I, as a gating modifier, is able to inhibit activation of the potassium channel subtype Kv2.1. However, its binding site on Kv2.1 remains unknown. In this study, using Ala-scanning mutagenesis strategy, we demonstrated that four residues (I273, F274, E277, and K280) in S3b-S4 motif contributed to the formation of JZTX-I binding site. The mutations I273A, F274A, E277A, and K280A reduced toxin binding affinity by 6-, 10-, 8-, and 7-fold, respectively. Taken together with our previous data that JZTX-I accelerated channel deactivation, these results suggest that JZTX-I inhibits Kv2.1 activation by docking onto the voltage sensor paddle and trapping the voltage sensor in the closed state. PMID:23246579

  3. mito-KATP通道在利多卡因减轻肾缺血再灌注心肌损伤的作用%Role of mitochondrial ATP-sensitive potassium channels in myocardial damage induced by renal ischemia-reperfusion by lidocaine pretreatment in rats

    Institute of Scientific and Technical Information of China (English)

    朱小兵; 吴论; 刘志群; 王根宝

    2015-01-01

    目的 评价线粒体ATP敏感性钾(mito-KATP)通道在利多卡因预先给药减轻肾脏缺血再灌注致大鼠心肌损伤中的作用.方法 健康雄性Wistar大鼠60只,体重300~350 g,采用随机数字表法分为5组(n=12):假手术组(S组)、肾脏缺血再灌注组(I/R组)、利多卡因组(L组)、mito-KATP通道阻断剂5-羟葵酸组(5-HD组)和mito-KATP通道阻断剂5-羟葵酸+L组(5-HD+L组).夹闭双侧肾动脉60 min、恢复灌注4h建立大鼠肾脏缺血再灌注损伤模型,术后再灌注4h时,取心脏血样,测定血清Cr和BUN浓度,测定心肌肌钙蛋白I(cTnI)水平,取心肌组织,分别采用黄嘌呤氧化酶法、硫代巴比妥法测定超氧化物歧化酶(SOD)活性、丙二醛(MDA)含量.结果 与S组比较,I/R组、L组、5-HD组和5-HD+L组血清Cr、BUN浓度和MDA含量升高,SOD活性降低、cTnI浓度升高(P<0.05);与I/R组比较,L组和5-HD+L组血清Cr、BUN浓度和MDA含量降低,SOD活性升高、cTnI浓度降低(P<0.05),5-HD组血清Cr、BUN浓度和MDA含量,SOD活性、cTnI浓度差异无统计学意义(P>0.05);与L组比较,5-HD+L组血清Cr、BUN浓度和肾组织MDA浓度升高,SOD活性降低、cTnI浓度升高(P<0.05);L组心肌组织病理学损伤较I/R组和5-HD+L组减轻.结论 线粒体ATP敏感性钾通道参与了利多卡因预先给药减轻肾脏缺血再灌注致大鼠心肌损伤的过程.

  4. Current understanding of KATP channels in neonatal diseases: focus on insulin secretion disorders

    Institute of Scientific and Technical Information of China (English)

    Yi QUAN; Andrew BARSZCZYK; Zhong-ping FENG; Hong-shuo SUN

    2011-01-01

    ATP-sensitive potassium (KATP) channels are cell metabolic sensors that couple cell metabolic status to electric activity, thus regulating many cellular functions. In pancreatic beta cells, KATP channels modulate insulin secretion in response to fluctuations in plasma glucose level, and play an important role in glucose homeostasis. Recent studies show that gain-of-function and loss-of-function mutations in KATP channel subunits cause neonatal diabetes mellitus and congenital hyperinsulinism respectively. These findings lead to significant changes in the diagnosis and treatment for neonatal insulin secretion disorders. This review describes the physiological and pathophysiological functions of KATP channels in glucose homeostasis, their specific roles in neonatal diabetes mellitus and congenital hyperinsulinism, as well as future perspectives of KATP channels in neonatal diseases.

  5. KV1 and KV3 Potassium Channels Identified at Presynaptic Terminals of the Corticostriatal Synapses in Rat

    Science.gov (United States)

    Meneses, David; Vega, Ana V.; Torres-Cruz, Francisco Miguel; Barral, Jaime

    2016-01-01

    In the last years it has been increasingly clear that KV-channel activity modulates neurotransmitter release. The subcellular localization and composition of potassium channels are crucial to understanding its influence on neurotransmitter release. To investigate the role of KV in corticostriatal synapses modulation, we combined extracellular recording of population-spike and pharmacological blockage with specific and nonspecific blockers to identify several families of KV channels. We induced paired-pulse facilitation (PPF) and studied the changes in paired-pulse ratio (PPR) before and after the addition of specific KV blockers to determine whether particular KV subtypes were located pre- or postsynaptically. Initially, the presence of KV channels was tested by exposing brain slices to tetraethylammonium or 4-aminopyridine; in both cases we observed a decrease in PPR that was dose dependent. Further experiments with tityustoxin, margatoxin, hongotoxin, agitoxin, dendrotoxin, and BDS-I toxins all rendered a reduction in PPR. In contrast heteropodatoxin and phrixotoxin had no effect. Our results reveal that corticostriatal presynaptic KV channels have a complex stoichiometry, including heterologous combinations KV1.1, KV1.2, KV1.3, and KV1.6 isoforms, as well as KV3.4, but not KV4 channels. The variety of KV channels offers a wide spectrum of possibilities to regulate neurotransmitter release, providing fine-tuning mechanisms to modulate synaptic strength. PMID:27379187

  6. Expression of stretch-activated two-pore potassium channels in human myometrium in pregnancy and labor.

    Directory of Open Access Journals (Sweden)

    Iain L O Buxton

    Full Text Available BACKGROUND: We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P, TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor. METHODOLOGY: We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus. PRINCIPAL FINDINGS: TREK-1, but not TREK-2, channels are expressed in human myometrium and significantly up-regulated during pregnancy. Down-regulation of TREK-1 message was seen by Q-PCR in laboring tissues consistent with a role for TREK-1 in maintaining uterine quiescence prior to labor. The TRAAK channel was unregulated in the same women. Blockade of stretch-activated channels with a channel non-specific tarantula toxin (GsMTx-4 or the more specific TREK-1 antagonist L-methionine ethyl ester altered contractile frequency in a dose-dependent manner in pregnant myometrium. Arachidonic acid treatment lowered contractile tension an effect blocked by fluphenazine. Functional studies are consistent with a role for TREK-1 in uterine quiescence. CONCLUSIONS: We provide evidence supporting a role for TREK-1 in contributing to uterine quiescence during gestation and hypothesize that dysregulation of this mechanism may underlie certain cases of spontaneous pre-term birth.

  7. Modification of sodium and potassium channel kinetics by diethyl ether and studies on sodium channel inactivation in the crayfish giant axon membrane

    Energy Technology Data Exchange (ETDEWEB)

    Bean, Bruce Palmer

    1979-01-01

    The effects of ether and halothane on membrane currents in the voltage clamped crayfish giant axon membrane were investigated. Concentrations of ether up to 300 mM and of halothane up to 32 mM had no effect on resting potential or leakage conductance. Ether and halothane reduced the size of sodium currents without changing the voltage dependence of the peak currents or their reversal potential. Ether and halothane also produced a reversible, dose-dependent speeding of sodium current decay at all membrane potentials. Ether reduced the time constants for inactivation, and also shifted the midpoint of the steady-state inactivation curve in the hyperpolarizing direction. Potassium currents were smaller with ether present, with no change in the voltage dependence of steady-state currents. The activation of potassium channels was faster with ether present. There was no apparent change in the capacitance of the crayfish giant axon membrane with ether concentrations of up to 100 mM. Experiments on sodium channel inactivation kinetics were performed using 4-aminopyridine to block potassium currents. Sodium currents decayed with a time course generally fit well by a single exponential. The time constant of decay was a steep function of voltage, especially in the negative resistance region of the peak current vs voltage relation.The time course of inactivation was very similar to that of the decay of the current at the same potential. The measurement of steady-state inactivation curves with different test pulses showed no shifts along the voltage asix. The voltage-dependence of the integral of sodium conductance was measured to test models of sodium channel inactivation in which channels must open before inactivating; the results appear inconsistent with some of the simplest cases of such models.

  8. Ca2+- and voltage-gated potassium (BK) channel activators in the 5β-cholanic acid-3α-ol analogue series with modifications in lateral chain

    OpenAIRE

    Bukiya, Anna N.; Patil, Shivaputra; Li, Wei; Miller, Duane; Dopico, Alex M.

    2012-01-01

    Large conductance, calcium- and voltage-gated potassium (BK) channels regulate various physiological processes and represent an attractive target for drug discovery. Numerous BK channel activators are available. However, these agents usually interact with the ubiquitously distributed channel-forming subunit and thus cannot selectively target a particular tissue. Here, we performed structure-activity relationship study of lithocholic acid (LCA), a cholane that activates BK channels via the acc...

  9. Types of voltage—dependent calcium channels involved in high potassium depolarization—induced amylase secretion in the exocrine pancreatic tumour cell line AR4—2J

    Institute of Scientific and Technical Information of China (English)

    CUIZONGJIE

    1998-01-01

    In the perifused fura-2 loaded exocrine pancreatic acinar cell line AR4-2J pulses of high potassium induced repetitive increases in intracellular calcium,Attached cells when stimulated with high potassium secreted large amount of amylase.High potassium-induced secretion was dependent both on the concentration of potassium and duration of stimulation.High potassium induced increases in intracellular calcium were inhibited by voltage-dependent calcium channel anatagonists with an order of potency as follows:nifedipine>ω-agatoxin IVA>ω-conotoxin GVIA.In contrast,the L-type calcium channel anatagonist nifedipine almost completely inhibited potassium-induced amylase secretion,whereas the N-type channel antagonist ω-conotoxin GVIA was without effect.The P-type channel antagonist ω-agatoxin IVA had a small inhibitory effect,but this inhibition was not significant at the level of amylase secretion.In conclusion,the AR4-2J cell line posesses different voltage-dependent calcium channels(L,P,N)with the L-type predominantly involved in depolarization induced amylase secretion.

  10. CNTF-Treated Astrocyte Conditioned Medium Enhances Large-Conductance Calcium-Activated Potassium Channel Activity in Rat Cortical Neurons.

    Science.gov (United States)

    Sun, Meiqun; Liu, Hongli; Xu, Huanbai; Wang, Hongtao; Wang, Xiaojing

    2016-08-01

    Seizure activity is linked to astrocyte activation as well as dysfunctional cortical neuron excitability produced from changes in calcium-activated potassium (KCa) channel function. Ciliary neurotrophic factor-treated astrocyte conditioned medium (CNTF-ACM) can be used to investigate the peripheral effects of activated astrocytes upon cortical neurons. However, CNTF-ACM's effect upon KCa channel activity in cultured cortical neurons has not yet been investigated. Whole-cell patch clamp recordings were performed in rat cortical neurons to evaluate CNTF-ACM's effects upon charybdotoxin-sensitive large-conductance KCa (BK) channel currents and apamin-sensitive small-conductance KCa (SK) channel current. Biotinylation and RT-PCR were applied to assess CNTF-ACM's effects upon the protein and mRNA expression, respectively, of the SK channel subunits SK2 and SK3 and the BK channel subunits BKα1 and BKβ3. An anti-fibroblast growth factor-2 (FGF-2) monoclonal neutralizing antibody was used to assess the effects of the FGF-2 component of CNTF-ACM. CNTF-ACM significantly increased KCa channel current density, which was predominantly attributable to gains in BK channel activity (p  0.05). Blocking FGF-2 produced significant reductions in KCa channel current density (p > 0.05) as well as BKα1 and BKβ3 expression in CNTF-ACM-treated neurons (p > 0.05). CNTF-ACM significantly enhances BK channel activity in rat cortical neurons and that FGF-2 is partially responsible for these effects. CNTF-induced astrocyte activation results in secretion of neuroactive factors which may affect neuronal excitability and resultant seizure activity in mammalian cortical neurons. PMID:27097551

  11. Fine-tuning of voltage sensitivity of the Kv1.2 potassium channel by interhelix loop dynamics.

    Science.gov (United States)

    Sand, Rheanna; Sharmin, Nazlee; Morgan, Carla; Gallin, Warren J

    2013-04-01

    Many proteins function by changing conformation in response to ligand binding or changes in other factors in their environment. Any change in the sequence of a protein, for example during evolution, which alters the relative free energies of the different functional conformations changes the conditions under which the protein will function. Voltage-gated ion channels are membrane proteins that open and close an ion-selective pore in response to changes in transmembrane voltage. The charged S4 transmembrane helix transduces changes in transmembrane voltage into a change in protein internal energy by interacting with the rest of the channel protein through a combination of non-covalent interactions between adjacent helices and covalent interactions along the peptide backbone. However, the structural basis for the wide variation in the V50 value between different voltage-gated potassium channels is not well defined. To test the role of the loop linking the S3 helix and the S4 helix in voltage sensitivity, we have constructed a set of mutants of the rat Kv1.2 channel that vary solely in the length and composition of the extracellular loop that connects S4 to S3. We evaluated the effect of these different loop substitutions on the voltage sensitivity of the channel and compared these experimental results with molecular dynamics simulations of the loop structures. Here, we show that this loop has a significant role in setting the precise V50 of activation in Kv1 family channels.

  12. Localization of large conductance calcium-activated potassium channels and their effect on calcitonin gene-related peptide release in the rat trigemino-neuronal pathway

    DEFF Research Database (Denmark)

    Wulf-Johansson, H.; Amrutkar, D.V.; Hay-Schmidt, Anders;

    2010-01-01

    Large conductance calcium-activated potassium (BK(Ca)) channels are membrane proteins contributing to electrical propagation through neurons. Calcitonin gene-related peptide (CGRP) is a neuropeptide found in the trigeminovascular system (TGVS). Both BK(Ca) channels and CGRP are involved in migraine...

  13. Activation of human ether-a-go-go-related gene potassium channels by the diphenylurea 1,3-bis-(2-hydroxy-5-trifluoromethyl-phenyl)-urea (NS1643)

    DEFF Research Database (Denmark)

    Hansen, Rie Schultz; Diness, Thomas Goldin; Christ, Torsten;

    2005-01-01

    The cardiac action potential is generated by a concerted action of different ion channels and transporters. Dysfunction of any of these membrane proteins can give rise to cardiac arrhythmias, which is particularly true for the repolarizing potassium channels. We suggest that an increased repolari...

  14. Reversible dementia: two nursing home patients with voltage-gated potassium channel antibody-associated limbic encephalitis.

    Science.gov (United States)

    Reintjes, Wesley; Romijn, Marloes D M; Hollander, Daan; Ter Bruggen, Jan P; van Marum, Rob J

    2015-09-01

    Voltage-gated potassium channel antibody-associated limbic encephalitis (VGKC-LE) is a rare disease that is a diagnostic and therapeutic challenge for medical practitioners. Two patients with VGKC-LE, both developing dementia are presented. Following treatment, both patients showed remarkable cognitive and functional improvement enabling them to leave the psychogeriatric nursing homes they both were admitted to. Patients with VGKC-LE can have a major cognitive and functional improvement even after a diagnostic delay of more than 1 year. Medical practitioners who treat patients with unexplained cognitive decline, epileptic seizures, or psychiatric symptoms should be aware of LE as an underlying rare cause.

  15. Reversible dementia: two nursing home patients with voltage-gated potassium channel antibody-associated limbic encephalitis.

    Science.gov (United States)

    Reintjes, Wesley; Romijn, Marloes D M; Hollander, Daan; Ter Bruggen, Jan P; van Marum, Rob J

    2015-09-01

    Voltage-gated potassium channel antibody-associated limbic encephalitis (VGKC-LE) is a rare disease that is a diagnostic and therapeutic challenge for medical practitioners. Two patients with VGKC-LE, both developing dementia are presented. Following treatment, both patients showed remarkable cognitive and functional improvement enabling them to leave the psychogeriatric nursing homes they both were admitted to. Patients with VGKC-LE can have a major cognitive and functional improvement even after a diagnostic delay of more than 1 year. Medical practitioners who treat patients with unexplained cognitive decline, epileptic seizures, or psychiatric symptoms should be aware of LE as an underlying rare cause. PMID:26170033

  16. Potassium Channel, Ions, and Water: Simulation Studies Based on the High Resolution X-Ray Structure of KcsA

    OpenAIRE

    Domene, Carmen; Sansom, Mark S P

    2003-01-01

    Interactions of Na+, K+, Rb+, and Cs+ ions within the selectivity filter of a potassium channel have been investigated via multiple molecular dynamics simulations (total simulation time, 48 ns) based on the high resolution structure of KcsA, embedded in a phospholipid bilayer. As in simulations based on a lower resolution structure of KcsA, concerted motions of ions and water within the filter are seen. Despite the use of a higher resolution structure and the inclusion of four buried water mo...

  17. Effect of coriaria lactone on adenosine triphosphate-sensitive potassium channels in pyramidal neurons%马桑内酯对锥体神经元三磷酸腺苷敏感钾通道的作用

    Institute of Scientific and Technical Information of China (English)

    邹晓毅; 周华; 周树舜

    2005-01-01

    BACKGROUND: Abnormal neuronal discharge arose from the activation of cell membrane ion channels and transmembrane ion transport. The electric activity of the cells is associated with cell metabolism fundamentally through adenosine triphosphate (ATP)-sensitive potassium(KATP) channels.Currently the involvement of KATP channels in the pathogenesis of epilepsy and the regulation of KATP channels by coriaria lacton (EL) remain unknown.OBJETCIVE: To investigate the changes of cell membrane KATP channels in rat hippocampal neurons in response to CL as an epilepsy-inducing agent, and explore the role of KATP channels in the pathogenesis of epilepsy.DESIGN: Randomized controlled experiment.SETTING: Department of Neurology, West China Hospital Affiliated to Sichuan University, and Teaching and Research Section of Physiology,West China College of Preclinical Medicine and Forensic Medicine of Sichuan University.MATERIALS: This experiment was carried out at Luzhou Medical College between May and December 2000. Hippocampus pyramidal neurons were obtained from neonatal Wistar rats and randomized into normal control group, tetraethylammonium chloride (TEA) group, DNP group, CL group, and electric conductance and dynamics group.METHODS: The hippocampus of newborn Wistar rats was separated under aseptic condition and cultured for 24 hours prior to treatment with 10 μmol/L cytarabine for selective cell culture for 7-10 days. The cells in good growth exhibiting typical morphology of pyramidal neurons were then selected for patch-clamp experiment. The cells in the normal control group were treated with normal saline, which was replaced by 5 mmol/L TEA in TEA group, by 30 μmol/L DNP then 0.5 mol/L ATP in DNP group, and by 1.0 mL/L CL then 1 μmol/L glibenclamide in CL group. In electric conductance and dynamics group, the clamp voltage was firstly adjusted to investigate the channel opening before CL was added to the cells.MAIN OUTCOME MEASURES: ① Activity and curve of neuronal

  18. Regulation of Shaker-type potassium channels by hypoxia. Oxygen-sensitive K+ channels in PC12 cells.

    Science.gov (United States)

    Conforti, L; Millhorn, D E

    2000-01-01

    Little is known about the molecular composition of the O2-sensitive K+ (Ko2) channels. The possibility that these channels belong to the Shaker subfamily (Kv1) of voltage-dependent K+ (Kv) channels has been raised in pulmonary artery (PA) smooth muscle cells. Numerous findings suggest that the Ko2 channel in PC12 cells is a Kv1 channel, formed by the Kv1.2 alpha subunit. The Ko2 channel in PC12 cells is a slow-inactivating voltage-dependent K+ channel of 20 pS conductance. Other Kv channels, also expressed in PC12 cells, are not inhibited by hypoxia. Selective up-regulation by chronic hypoxia of the Kv1.2 alpha subunit expression correlates with an increase O2-sensitivity of the K+ current. Other Kv1 alpha subunit genes encoding slow-inactivating Kv channels, such as Kv1.3, Kv2.1, Kv3.1 and Kv3.2 are not modulated by chronic hypoxia. The Ko2 current in PC12 cells is blocked by 5 mM externally applied tetraethylammonium chloride (TEA) and by charydbotoxin (CTX). The responses of the Kv1.2 K+ channel to hypoxia have been studied in the Xenopus oocytes and compared to those of Kv2.1, also proposed as Ko2 channel in PA smooth muscle cells. Two-electrode voltage clamp experiments show that hypoxia induces inhibition of K+ current amplitude only in oocytes injected with Kv1.2 cRNA. These data indicate that Kv1.2 K+ channels are inhibited by hypoxia. PMID:10849667

  19. Effect of adenosine and adenosine receptor antagonist on Müller cell potassium channel in Rat chronic ocular hypertension models.

    Science.gov (United States)

    Yang, Zijian; Huang, Ping; Liu, Xiaohong; Huang, Shouyue; Deng, Lianfu; Jin, Zhe; Xu, Shuo; Shen, Xi; Luo, Xunda; Zhong, Yisheng

    2015-01-01

    Müller cells are principal glial cells in rat retina and have attracted much attention in glaucoma studies. However, it is not clear whether adenosine and adenosine receptor (AR) antagonists play any roles in the regulation of potassium channels in Müller cells and subsequently in the promotion of glutamine synthetase (GS) and L-Glutamate/L-Aspartate Transporter (GLAST) functions. We found that chronic ocular hypertension (COH) in rat down-regulated Müller cells Kir2.1, Kir4.1, TASK-1, GS and GLAST expressions and attenuated the peak of inward potassium current. Retinal ganglion cells (RGC) count was lower in the COH rats than that in the sham operation animals. Intravitreal injection of selective A2A AR antagonist SCH442416 up-regulated Müller cell Kir4.1, TASK-1, GS and GLAST expressions and enhanced inward potassium currents compared with those in the COH rats with vehicle control. Meanwhile, the RGC count was higher following intravitreal injection of SCH442416 in the COH rats than that after vehicle injection. The fact that PKA inhibitor H-89 blocked these SCH442416 effects suggested that the PKA signaling pathway was involved in the observed ocular responses following the intravitreal SCH442416 injection. PMID:26063641

  20. Role of calcium-activated potassium channels with small conductance in bradykinin-induced vasodilation of porcine retinal arterioles

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Bek, Toke;

    2009-01-01

    PURPOSE: Endothelial dysfunction and impaired vasodilation may be involved in the pathogenesis of retinal vascular diseases. In the present study, the mechanisms underlying bradykinin vasodilation were examined and whether calcium-activated potassium channels of small (SK(Ca)) and intermediate (IK......(Ca)) conductance are involved in regulation of endothelium-dependent vasodilation in retinal arterioles was investigated. METHODS: Porcine retinal arterioles (diameter approximately 112 microm, N = 119) were mounted in microvascular myographs for isometric tension recordings. The arterioles were contracted with...... the thromboxane analogue, U46619, and concentration-response curves were constructed for bradykinin and a novel opener of SK(Ca) and IK(Ca) channels, NS309. RESULTS: In U46619-contracted arterioles, bradykinin and NS309 induced concentration-dependent relaxations. In vessels without endothelium...

  1. Lack of potassium channel induces proliferation and survival causing increased neurogenesis and two-fold hippocampus enlargement

    DEFF Research Database (Denmark)

    Almgren, Malin; Persson, Ann-Sophie; Fenghua, Chen;

    2007-01-01

    The megencephaly mice show dramatic progressive increase in brain size and seizures. The overgrowth affects primarily the hippocampus and ventral cortex. The phenotype originates from a mutation in the Shaker-like voltage-gated potassium channel Kv1.1 brain, which results in a malfunctioning...... protein. A key question in elucidating the mechanism behind the unique brain overgrowth is whether it is caused by an increase in cell number. By applying stereological techniques, we found that the number of both neurons and astrocytes, as well as structure volume, was increased approximately two...... lower in mceph/mceph supporting additional overgrowth mechanism than induced by seizures. In conclusion, lack of a functional Kv1.1 ion channel subunit in the mceph/mceph mice causes a unique neuronal hyperplasia in distinct hippocampal regions and consequently hippocampal enlargement from 2 to 3 weeks...

  2. Docking ellipticine to the V-VI transmembrane domain of the Kv11.1 potassium channel

    Science.gov (United States)

    Lipscomb, Dawn; Brancaleon, Lorenzo; Gentile, S.

    2011-03-01

    Ellipticines such as 9-methoxy-N-2-methylellipticinium acetate (MMEA) and 9-hydroxy-N-2-methylellipticinium acetate (NMEA, Celiptium ) are antineoplastic drugs exerting their selective cytotoxicity against leukemia and endometrial carcinoma. Ellipticine's action is also related to severe physical side effects, but the link between undesired effects and pharmacological application is not well understood. We investigated the binding of Ellipticine derivatives with the Kv11.1 potassium ion channel using Autodock and revealed that hydroxyellipticinium derivatives provide binding configurations with Kv11.1, but the energy, location and estimated dissociation constant varied. The binding energy is as follows: Chloroceliptium (-6.60 kcal/mol) Celiptium (- 6.37 kcal / mol) > Methoxyceliptium (- 6.20 kcal / mol) Datelliptium (-6.08 kcal/mol). The data shows that some configurations enable these molecules to bridge among channel subunits, thus potentially inhibiting the flow of ions.

  3. Excessive blinking and ataxia in a child with occult neuroblastoma and voltage-gated potassium channel antibodies.

    LENUS (Irish Health Repository)

    Allen, Nicholas M

    2012-05-01

    A previously healthy 9-year-old girl presented with a 10-day history of slowly progressive unsteadiness, slurred speech, and behavior change. On examination there was cerebellar ataxia and dysarthria, excessive blinking, subtle perioral myoclonus, and labile mood. The finding of oligoclonal bands in the cerebrospinal fluid prompted paraneoplastic serological evaluation and search for an occult neural crest tumor. Antineuronal nuclear autoantibody type 1 (anti-Hu) and voltage-gated potassium channel complex antibodies were detected in serum. Metaiodobenzylguanidine scan and computed tomography scan of the abdomen showed a localized abdominal mass in the region of the porta hepatis. A diagnosis of occult neuroblastoma was made. Resection of the stage 1 neuroblastoma and treatment with pulsed corticosteroids resulted in resolution of all symptoms and signs. Excessive blinking has rarely been described with neuroblastoma, and, when it is not an isolated finding, it may be a useful clue to this paraneoplastic syndrome. Although voltage-gated potassium channel complex autoimmunity has not been described previously in the setting of neuroblastoma, it is associated with a spectrum of paraneoplastic neurologic manifestations in adults, including peripheral nerve hyperexcitability disorders.

  4. Mechanism of HERG potassium channel inhibition by tetra-n-octylammonium bromide and benzethonium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Long, Yan; Lin, Zuoxian [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China); Xia, Menghang; Zheng, Wei [National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892 (United States); Li, Zhiyuan, E-mail: li_zhiyuan@gibh.ac.cn [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China)

    2013-03-01

    Tetra-n-octylammonium bromide and benzethonium chloride are synthetic quaternary ammonium salts that are widely used in hospitals and industries for the disinfection and surface treatment and as the preservative agent. Recently, the activities of HERG channel inhibition by these compounds have been found to have potential risks to induce the long QT syndrome and cardiac arrhythmia, although the mechanism of action is still elusive. This study was conducted to investigate the mechanism of HERG channel inhibition by these compounds by using whole-cell patch clamp experiments in a CHO cell line stably expressing HERG channels. Tetra-n-octylammonium bromide and benzethonium chloride exhibited concentration-dependent inhibitions of HERG channel currents with IC{sub 50} values of 4 nM and 17 nM, respectively, which were also voltage-dependent and use-dependent. Both compounds shifted the channel activation I–V curves in a hyperpolarized direction for 10–15 mV and accelerated channel activation and inactivation processes by 2-fold. In addition, tetra-n-octylammonium bromide shifted the inactivation I–V curve in a hyperpolarized direction for 24.4 mV and slowed the rate of channel deactivation by 2-fold, whereas benzethonium chloride did not. The results indicate that tetra-n-octylammonium bromide and benzethonium chloride are open-channel blockers that inhibit HERG channels in the voltage-dependent, use-dependent and state-dependent manners. - Highlights: ► Tetra-n-octylammonium and benzethonium are potent HERG channel inhibitors. ► Channel activation and inactivation processes are accelerated by the two compounds. ► Both compounds are the open-channel blockers to HERG channels. ► HERG channel inhibition by both compounds is use-, voltage- and state dependent. ► The in vivo risk of QT prolongation needs to be studied for the two compounds.

  5. Phycodnavirus potassium ion channel proteins question the virus molecular piracy hypothesis.

    Directory of Open Access Journals (Sweden)

    Kay Hamacher

    Full Text Available Phycodnaviruses are large dsDNA, algal-infecting viruses that encode many genes with homologs in prokaryotes and eukaryotes. Among the viral gene products are the smallest proteins known to form functional K(+ channels. To determine if these viral K(+ channels are the product of molecular piracy from their hosts, we compared the sequences of the K(+ channel pore modules from seven phycodnaviruses to the K(+ channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced. C. variabilis is the host for two of the viruses PBCV-1 and NY-2A and E. siliculosus is the host for the virus EsV-1. Systematic phylogenetic analyses consistently indicate that the viral K(+ channels are not related to any lineage of the host channel homologs and that they are more closely related to each other than to their host homologs. A consensus sequence of the viral channels resembles a protein of unknown function from a proteobacterium. However, the bacterial protein lacks the consensus motif of all K(+ channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium. Collectively, our results indicate that the viruses did not acquire their K(+ channel-encoding genes from their current algal hosts by gene transfer; thus alternative explanations are required. One possibility is that the viral genes arose from ancient organisms, which served as their hosts before the viruses developed their current host specificity. Alternatively the viral proteins could be the origin of K(+ channels in algae and perhaps even all cellular organisms.

  6. Fractal analysis of a voltage-dependent potassium channel from cultured mouse hippocampal neurons.

    Science.gov (United States)

    Liebovitch, L S; Sullivan, J M

    1987-12-01

    The kinetics of ion channels have been widely modeled as a Markov process. In these models it is assumed that the channel protein has a small number of discrete conformational states and the kinetic rate constants connecting these states are constant. In the alternative fractal model the spontaneous fluctuations of the channel protein at many different time scales are represented by a kinetic rate constant k = At1-D, where A is the kinetic setpoint and D the fractal dimension. Single-channel currents were recorded at 146 mM external K+ from an inwardly rectifying, 120 pS, K+ selective, voltage-sensitive channel in cultured mouse hippocampal neurons. The kinetics of these channels were found to be statistically self-similar at different time scales as predicted by the fractal model. The fractal dimensions were approximately 2 for the closed times and approximately 1 for the open times and did not depend on voltage. For both the open and closed times the logarithm of the kinetic setpoint was found to be proportional to the applied voltage, which indicates that the gating of this channel involves the net inward movement of approximately one negative charge when this channel opens. Thus, the open and closed times and the voltage dependence of the gating of this channel are well described by the fractal model. PMID:2447974

  7. Expression of inwardly rectifying potassium channels (GIRKs and beta-adrenergic regulation of breast cancer cell lines

    Directory of Open Access Journals (Sweden)

    Cakir Yavuz

    2004-12-01

    Full Text Available Abstract Background Previous research has indicated that at various organ sites there is a subset of adenocarcinomas that is regulated by beta-adrenergic and arachidonic acid-mediated signal transduction pathways. We wished to determine if this regulation exists in breast adenocarcinomas. Expression of mRNA that encodes a G-protein coupled inwardly rectifying potassium channel (GIRK1 has been shown in tissue samples from approximately 40% of primary human breast cancers. Previously, GIRK channels have been associated with beta-adrenergic signaling. Methods Breast cancer cell lines were screened for GIRK channels by RT-PCR. Cell cultures of breast cancer cells were treated with beta-adrenergic agonists and antagonists, and changes in gene expression were determined by both relative competitive and real time PCR. Potassium flux was determined by flow cytometry and cell signaling was determined by western blotting. Results Breast cancer cell lines MCF-7, MDA-MB-361 MDA-MB 453, and ZR-75-1 expressed mRNA for the GIRK1 channel, while MDA-MB-468 and MDA-MB-435S did not. GIRK4 was expressed in all six breast cancer cell lines, and GIRK2 was expressed in all but ZR-75-1 and MDA-MB-435. Exposure of MDA-MB-453 cells for 6 days to the beta-blocker propranolol (1 μM increased the GIRK1 mRNA levels and decreased beta2-adrenergic mRNA levels, while treatment for 30 minutes daily for 7 days had no effect. Exposure to a beta-adrenergic agonist and antagonist for 24 hours had no effect on gene expression. The beta adrenergic agonist, formoterol hemifumarate, led to increases in K+ flux into MDA-MB-453 cells, and this increase was inhibited by the GIRK channel inhibitor clozapine. The tobacco carcinogen 4-(methylnitrosamino-1-(3-pyridyl-1-butanone (NNK, a high affinity agonist for beta-adrenergic receptors stimulated activation of Erk 1/2 in MDA-MB-453 cells. Conclusions Our data suggests β-adrenergic receptors and GIRK channels may play a role in breast cancer.

  8. Estrogens and human papilloma virus oncogenes regulate human ether-à-go-go-1 potassium channel expression.

    Science.gov (United States)

    Díaz, Lorenza; Ceja-Ochoa, Irais; Restrepo-Angulo, Iván; Larrea, Fernando; Avila-Chávez, Euclides; García-Becerra, Rocío; Borja-Cacho, Elizabeth; Barrera, David; Ahumada, Elías; Gariglio, Patricio; Alvarez-Rios, Elizabeth; Ocadiz-Delgado, Rodolfo; Garcia-Villa, Enrique; Hernández-Gallegos, Elizabeth; Camacho-Arroyo, Ignacio; Morales, Angélica; Ordaz-Rosado, David; García-Latorre, Ethel; Escamilla, Juan; Sánchez-Peña, Luz Carmen; Saqui-Salces, Milena; Gamboa-Dominguez, Armando; Vera, Eunice; Uribe-Ramírez, Marisela; Murbartián, Janet; Ortiz, Cindy Sharon; Rivera-Guevara, Claudia; De Vizcaya-Ruiz, Andrea; Camacho, Javier

    2009-04-15

    Ether-à-go-go-1 (Eag1) potassium channels are potential tools for detection and therapy of numerous cancers. Here, we show human Eag1 (hEag1) regulation by cancer-associated factors. We studied hEag1 gene expression and its regulation by estradiol, antiestrogens, and human papillomavirus (HPV) oncogenes (E6/E7). Primary cultures from normal placentas and cervical cancer tissues; tumor cell lines from cervix, choriocarcinoma, keratinocytes, and lung; and normal cell lines from vascular endothelium, keratinocytes, and lung were used. Reverse transcription-PCR (RT-PCR) experiments and Southern blot analysis showed Eag1 expression in all of the cancer cell types, normal trophoblasts, and vascular endothelium, in contrast to normal keratinocytes and lung cells. Estradiol and antiestrogens regulated Eag1 in a cell type-dependent manner. Real-time RT-PCR experiments in HeLa cells showed that Eag1 estrogenic regulation was strongly associated with the expression of estrogen receptor-alpha. Eag1 protein was detected by monoclonal antibodies in normal placenta and placental blood vessels. Patch-clamp recordings in normal trophoblasts treated with estradiol exhibited potassium currents resembling Eag1 channel activity. Eag1 gene expression in keratinocytes depended either on cellular immortalization or the presence of HPV oncogenes. Eag1 protein was found in keratinocytes transfected with E6/E7 HPV oncogenes. Cell proliferation of E6/E7 keratinocytes was decreased by Eag1 antibodies inhibiting channel activity and by the nonspecific Eag1 inhibitors imipramine and astemizole; the latter also increased apoptosis. Our results propose novel oncogenic mechanisms of estrogen/antiestrogen use and HPV infection. We also suggest Eag1 as an early indicator of cell proliferation leading to malignancies and a therapeutic target at early stages of cellular hyperproliferation. PMID:19351862

  9. Role of hydrophobic and ionic forces in the movement of S4 of the Shaker potassium channel.

    Science.gov (United States)

    Elliott, David J S; Neale, Edward J; Munsey, Tim S; Bannister, John P; Sivaprasadarao, Asipu

    2012-12-01

    Voltage-gated ion (K(+), Na(+), Ca(2+)) channels contain a pore domain (PD) surrounded by four voltage sensing domains (VSD). Each VSD is made up of four transmembrane helices, S1-S4. S4 contains 6-7 positively charged residues (arginine/lysine) separated two hydrophobic residues, whereas S1-S3 contribute to two negatively charged clusters. These structures are conserved among all members of the voltage-gated ion channel family and play essential roles in voltage gating. The role of S4 charged residues in voltage gating is well established: During depolarization, they move out of the membrane electric field, exerting a mechanical force on channel gates, causing them to open. However, the role of the intervening hydrophobic residues in voltage sensing is unclear. Here we studied the role of these residues in the prototypical Shaker potassium channel. We have altered the physicochemical properties of both charged and hydrophobic positions of S4 and examined the effect of these modifications on the gating properties of the channel. For this, we have introduced cysteines at each of these positions, expressed the mutants in Xenopus oocytes, and examined the effect of in situ addition of charge, via Cd(2+), on channel gating by two-electrode voltage clamp. Our results reveal a face of the S4 helix (comprising residues L358, L361, R365 and R368) where introduction of charge at hydrophobic positions destabilises the closed state and removal of charges from charged positions has an opposite effect. We propose that hydrophobic residues play a crucial role in limiting gating to a physiological voltage range.

  10. Kv7 potassium channels in airway smooth muscle cells: signal transduction intermediates and pharmacological targets for bronchodilator therapy.

    Science.gov (United States)

    Brueggemann, Lioubov I; Kakad, Priyanka P; Love, Robert B; Solway, Julian; Dowell, Maria L; Cribbs, Leanne L; Byron, Kenneth L

    2012-01-01

    Expression and function of Kv7 (KCNQ) voltage-activated potassium channels in guinea pig and human airway smooth muscle cells (ASMCs) were investigated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), patch-clamp electrophysiology, and precision-cut lung slices. qRT-PCR revealed expression of multiple KCNQ genes in both guinea pig and human ASMCs. Currents with electrophysiological and pharmacological characteristics of Kv7 currents were measured in freshly isolated guinea pig and human ASMCs. In guinea pig ASMCs, Kv7 currents were significantly suppressed by application of the bronchoconstrictor agonists methacholine (100 nM) or histamine (30 μM), but current amplitudes were restored by addition of a Kv7 channel activator, flupirtine (10 μM). Kv7 currents in guinea pig ASMCs were also significantly enhanced by another Kv7.2-7.5 channel activator, retigabine, and by celecoxib and 2,5-dimethyl celecoxib. In precision-cut human lung slices, constriction of airways by histamine was significantly reduced in the presence of flupirtine. Kv7 currents in both guinea pig and human ASMCs were inhibited by the Kv7 channel blocker XE991. In human lung slices, XE991 induced robust airway constriction, which was completely reversed by addition of the calcium channel blocker verapamil. These findings suggest that Kv7 channels in ASMCs play an essential role in the regulation of airway diameter and may be targeted pharmacologically to relieve airway hyperconstriction induced by elevated concentrations of bronchoconstrictor agonists. PMID:21964407

  11. Surface-enhanced IR absorption spectroscopy of the KcsA potassium channel upon application of an electric field.

    Science.gov (United States)

    Yamakata, Akira; Shimizu, Hirofumi; Oiki, Shigetoshi

    2015-09-01

    Surface-enhanced IR absorption spectroscopy (SEIRAS) is a powerful tool for studying the structure of molecules adsorbed on an electrode surface (ATR-SEIRA). Coupled with an electrochemical system, structural changes induced by changes in the electric field can be detected. All the membrane proteins are subjected to the effect of membrane electric field, but conformational changes at different membrane potentials and their functional relevance have not been studied extensively except for channel proteins. In this contribution, background information of potential-dependent functional and structural changes of a prototypical channel, the KcsA channel, is summarized, and SEIRAS applied to the KcsA channel under the application of the potential is shown. The potassium channels allow K(+) to permeate selectively through the structural part called the selectivity filter, in which dehydrated K(+) ions interact with backbone carbonyls. In the absence of K(+), the selectivity filter undergoes conformational changes to the non-conductive collapsed conformation. To apply the electric field, the KcsA channels were fixed on the gold surface in either upside or reverse orientation. The SEIRA spectrum in K(+) or Na(+) solution revealed both backbone structural changes and local changes in the OCO-carboxylate groups. Upon application of the negative electric field, the spectrum of OCO was enhanced only in the K(+) solution. These results indicate that the negative electric field accumulates local K(+) concentration, which turned the collapsed filter to the conductive conformation. ATR-SEIRA serves as an unprecedented experimental system for examining membrane proteins under an electric field.

  12. K+ CHANNELEPSY: progress in the neurobiology of potassium channels and epilepsy

    Directory of Open Access Journals (Sweden)

    Maria Cristina D'Adamo

    2013-09-01

    Full Text Available K+ channels are important determinants of seizure susceptibility. These membrane proteins, encoded by more than 70 genes, make the largest group of ion channels that fine-tune the electrical activity of neuronal and non-neuronal cells in the brain. Their ubiquity and extremely high genetic and functional diversity, unmatched by any other ion channel type, place K+ channels as primary targets of genetic variations or perturbations in K+-dependent homeostasis, even in the absence of a primary channel defect. It is therefore not surprising that numerous inherited or acquired K+ channels dysfunctions have been associated with several neurologic syndromes, including epilepsy, which often generate confusion in the classification of the associated diseases. Therefore, we propose to name the K+ channels defects underlying distinct epilepsies as K+ channelepsies, and introduce a new nomenclature (e.g. Kx.y-channelepsy, following the widely used K+ channel classification, which could be also adopted to easily identify other channelopathies involving Na+ (e.g. Navx.y-phenotype, Ca2+ (e.g. Cavx.y-phenotype, and Cl- channels. Furthermore, we discuss novel genetic defects in K+ channels and associated proteins that underlie distinct epileptic phenotypes in humans, and analyze critically the recent progress in the neurobiology of this disease that has also been provided by investigations on valuable animal models of epilepsy. The abundant and varied lines of evidence discussed here strongly foster assessments for variations in genes encoding for K+ channels and associated proteins in patients with idiopathic epilepsy, provide new avenues for future investigations, and highlight these proteins as critical pharmacological targets.

  13. Kv4 Potassium Channels Modulate Hippocampal EPSP-Spike Potentiation and Spatial Memory in Rats

    Science.gov (United States)

    Truchet, Bruno; Manrique, Christine; Sreng, Leam; Chaillan, Franck A.; Roman, Francois S.; Mourre, Christiane

    2012-01-01

    Kv4 channels regulate the backpropagation of action potentials (b-AP) and have been implicated in the modulation of long-term potentiation (LTP). Here we showed that blockade of Kv4 channels by the scorpion toxin AmmTX3 impaired reference memory in a radial maze task. In vivo, AmmTX3 intracerebroventricular (i.c.v.) infusion increased and…

  14. Frequency-dependent modulation of KCNQ1 and HERG1 potassium channels

    DEFF Research Database (Denmark)

    Diness, Thomas Goldin; Hansen, Rie Schultz; Olesen, Søren-Peter;

    2006-01-01

    To obtain information about a possible frequency-dependent modulation of HERG1 and hKCNQ1 channels, we performed heterologous expression in Xenopus laevis oocytes. Channel activation was obtained by voltage protocols roughly imitating cardiac action potentials at frequencies of 1, 3, 5.8, and 8.3...

  15. The sigma receptor as a ligand-regulated auxiliary potassium channel subunit.

    Science.gov (United States)

    Aydar, Ebru; Palmer, Christopher P; Klyachko, Vitaly A; Jackson, Meyer B

    2002-04-25

    The sigma receptor is a novel protein that mediates the modulation of ion channels by psychotropic drugs through a unique transduction mechanism depending neither on G proteins nor protein phosphorylation. The present study investigated sigma receptor signal transduction by reconstituting responses in Xenopus oocytes. Sigma receptors modulated voltage-gated K+ channels (Kv1.4 or Kv1.5) in different ways in the presence and absence of ligands. Association between Kv1.4 channels and sigma receptors was demonstrated by coimmunoprecipitation. These results indicate a novel mechanism of signal transduction dependent on protein-protein interactions. Domain accessibility experiments suggested a structure for the sigma receptor with two cytoplasmic termini and two membrane-spanning segments. The ligand-independent effects on channels suggest that sigma receptors serve as auxiliary subunits to voltage-gated K+ channels with distinct functional interactions, depending on the presence or absence of ligand.

  16. Calcium-activated potassium channels - a therapeutic target for modulating nitric oxide in cardiovascular disease?

    DEFF Research Database (Denmark)

    Dalsgaard, Thomas; Kroigaard, Christel; Simonsen, Ulf

    2010-01-01

    : Opening of SK and IK channels is associated with EDHF-type vasodilatation, but, through increased endothelial cell Ca(2+) influx, L-arginine uptake, and decreased ROS production, it may also lead to increased NO bioavailability and endothelium-dependent vasodilatation. TAKE HOME MESSAGE: Opening of SK and...... IK channels can increase both EDHF and NO-mediated vasodilatation. Therefore, openers of SK and IK channels may have the potential of improving endothelial cell function in cardiovascular disease.......-dependent vasodilatation is mediated by NO, prostacyclin, and an endothelium-derived hyperpolarising factor (EDHF), and involves small (SK) and intermediate (IK) conductance Ca(2+)-activated K(+) channels. Therefore, SK and IK channels may be drug targets for the treatment of endothelial dysfunction in cardiovascular...

  17. A heme-binding domain controls regulation of ATP-dependent potassium channels.

    Science.gov (United States)

    Burton, Mark J; Kapetanaki, Sofia M; Chernova, Tatyana; Jamieson, Andrew G; Dorlet, Pierre; Santolini, Jérôme; Moody, Peter C E; Mitcheson, John S; Davies, Noel W; Schmid, Ralf; Raven, Emma L; Storey, Nina M

    2016-04-01

    Heme iron has many and varied roles in biology. Most commonly it binds as a prosthetic group to proteins, and it has been widely supposed and amply demonstrated that subtle variations in the protein structure around the heme, including the heme ligands, are used to control the reactivity of the metal ion. However, the role of heme in biology now appears to also include a regulatory responsibility in the cell; this includes regulation of ion channel function. In this work, we show that cardiac KATP channels are regulated by heme. We identify a cytoplasmic heme-binding CXXHX16H motif on the sulphonylurea receptor subunit of the channel, and mutagenesis together with quantitative and spectroscopic analyses of heme-binding and single channel experiments identified Cys628 and His648 as important for heme binding. We discuss the wider implications of these findings and we use the information to present hypotheses for mechanisms of heme-dependent regulation across other ion channels.

  18. Role of vascular potassium channels in the regulation of renal hemodynamics

    DEFF Research Database (Denmark)

    Sørensen, Charlotte Mehlin; Braunstein, Thomas Hartig; von Holstein-Rathlou, Niels-Henrik;

    2012-01-01

    of one or more classes of K+ channels will lead to a change in hemodynamic resistance and therefore of renal blood flow and glomerular filtration pressure. Through these effects, the activity of renal vascular K+ channels influences renal salt and water excretion, fluid homeostasis, and ultimately blood......K+ conductance is a major determinant of membrane potential (Vm) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm through the action of voltage-operated Ca2+ channels (VOCC) in VSMC. Increased K+ conductance leads to hyperpolarization...... in K+ channel function, the role of renal vascular K+ channels in the control of salt and water excretion deserves attention....

  19. Classification of 2-pore domain potassium channels based on rectification under quasi-physiological ionic conditions.

    Science.gov (United States)

    Chen, Haijun; Zuo, Dongchuan; Zhang, Jianing; Zhou, Min; Ma, Liqun

    2014-01-01

    It is generally expected that 2-pore domain K(+) (K2P) channels are open or outward rectifiers in asymmetric physiological K(+) gradients, following the Goldman-Hodgkin-Katz (GHK) current equation. Although cloned K2P channels have been extensively studied, their current-voltage (I-V) relationships are not precisely characterized and previous definitions are contradictory. Here we study all the functional channels from 6 mammalian K2P subfamilies in transfected Chinese hamster ovary cells with patch-clamp technique, and examine whether their I-V relationships are described by the GHK current equation. K2P channels display 2 distinct types of I-V curves in asymmetric physiological K(+) gradients. Two K2P isoforms in the TWIK subfamily conduct large inward K(+) currents and have a nearly linear I-V curve. Ten isoforms from 5 other K2P subfamilies conduct small inward K(+) currents and exhibit open rectification, but fits with the GHK current equation cannot precisely reveal the differences in rectification among K2P channels. The Rectification Index, a ratio of limiting I-V slopes for outward and inward currents, is used to quantitatively describe open rectification of each K2P isoform, which is previously qualitatively defined as strong or weak open rectification. These results systematically and precisely classify K2P channels and suggest that TWIK K(+) channels have a unique feature in regulating cellular function.

  20. Apical Ca2+-activated potassium channels in mouse parotid acinar cells.

    Science.gov (United States)

    Almassy, Janos; Won, Jong Hak; Begenisich, Ted B; Yule, David I

    2012-02-01

    Ca(2+) activation of Cl and K channels is a key event underlying stimulated fluid secretion from parotid salivary glands. Cl channels are exclusively present on the apical plasma membrane (PM), whereas the localization of K channels has not been established. Mathematical models have suggested that localization of some K channels to the apical PM is optimum for fluid secretion. A combination of whole cell electrophysiology and temporally resolved digital imaging with local manipulation of intracellular [Ca(2+)] was used to investigate if Ca(2+)-activated K channels are present in the apical PM of parotid acinar cells. Initial experiments established Ca(2+)-buffering conditions that produced brief, localized increases in [Ca(2+)] after focal laser photolysis of caged Ca(2+). Conditions were used to isolate K(+) and Cl(-) conductances. Photolysis at the apical PM resulted in a robust increase in K(+) and Cl(-) currents. A localized reduction in [Ca(2+)] at the apical PM after photolysis of Diazo-2, a caged Ca(2+) chelator, resulted in a decrease in both K(+) and Cl(-) currents. The K(+) currents evoked by apical photolysis were partially blocked by both paxilline and TRAM-34, specific blockers of large-conductance "maxi-K" (BK) and intermediate K (IK), respectively, and almost abolished by incubation with both antagonists. Apical TRAM-34-sensitive K(+) currents were also observed in BK-null parotid acini. In contrast, when the [Ca(2+)] was increased at the basal or lateral PM, no increase in either K(+) or Cl(-) currents was evoked. These data provide strong evidence that K and Cl channels are similarly distributed in the apical PM. Furthermore, both IK and BK channels are present in this domain, and the density of these channels appears higher in the apical versus basolateral PM. Collectively, this study provides support for a model in which fluid secretion is optimized after expression of K channels specifically in the apical PM.

  1. Kinetic analysis of strontium and potassium sorption onto sands and gravels in a natural channel.

    Science.gov (United States)

    Bencala, K.E.; Jackman, A.P.; Kennedy, V.C.; Avanzino, R.J.; Zellweger, G.W.

    1983-01-01

    A kinetic, first-order mass transfer model was used to describe the sorption of strontium onto sand-and gravel-sized streambed sediments. Rate parameters, empirically determined for strontium, allowed for the prediction of potassium sorption with moderate success. The model parameters varied significantly with particle size. The sorption data were collected during an experimental injection of several elements into a small mountain pool-and- riffle stream. The sorption process onto sand- and gravel-sized sediment was relatively slow compared to changes in the dissolved concentrations. -Authors

  2. Hydrogen bonds as molecular timers for slow inactivation in voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Galpin, Jason D; Niciforovic, Ana P;

    2013-01-01

    the kinetics of this process remain obscure. Using a combination of synthetic amino acid analogs and concatenated channel subunits we establish two H-bonds near the extracellular surface of the channel that endow Kv channels with a mechanism to time the entry into slow inactivation: an intra-subunit H......-bond between Asp447 and Trp434 and an inter-subunit H-bond connecting Tyr445 to Thr439. Breaking of either interaction triggers slow inactivation by means of a local disruption in the selectivity filter, while severing the Tyr445-Thr439 H-bond is likely to communicate this conformational change to the adjacent...

  3. Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

    Institute of Scientific and Technical Information of China (English)

    LI Yan-feng; ZHUO Ye-hong; BI Wei-na; BAI Yu-jing; LI Yan-na; WANG Zhi-jian

    2008-01-01

    Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance.Ion channels play an important role in these processes.The main aim of this study was to determine whether the well-characterized members of the Kvl family (Kv1.3) contribute to the Kv currents in ciliary epithelium.Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle.Ciliary epithelium samples were isolated from the rabbits.We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium.Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium,however it seemed to express more in the apical membrane of the nonpigmented epithelial cells.One nmol/L margatoxin,a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential.The cytosotic calcium increased after NPE cell depolarization,this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine.These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.Conclusion Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

  4. Inhibition of hERG potassium channel by the antiarrhythmic agent mexiletine and its metabolite m-hydroxymexiletine.

    Science.gov (United States)

    Gualdani, Roberta; Tadini-Buoninsegni, Francesco; Roselli, Mariagrazia; Defrenza, Ivana; Contino, Marialessandra; Colabufo, Nicola Antonio; Lentini, Giovanni

    2015-10-01

    Mexiletine is a sodium channel blocker, primarily used in the treatment of ventricular arrhythmias. Moreover, recent studies have demonstrated its therapeutic value to treat myotonic syndromes and to relieve neuropathic pain. The present study aims at investigating the direct blockade of hERG potassium channel by mexiletine and its metabolite m-hydroxymexiletine (MHM). Our data show that mexiletine inhibits hERG in a time- and voltage-dependent manner, with an IC50 of 3.7 ± 0.7 μmol/L. Analysis of the initial onset of current inhibition during a depolarizing test pulse indicates mexiletine binds preferentially to the open state of the hERG channel. Looking for a possible mexiletine alternative, we show that m-hydroxymexiletine (MHM), a minor mexiletine metabolite recently reported to be as active as the parent compound in an arrhythmia animal model, is a weaker hERG channel blocker, compared to mexiletine (IC50 = 22.4 ± 1.2 μmol/L). The hERG aromatic residues located in the S6 helix (Tyr652 and Phe656) are crucial in the binding of mexiletine and the different affinities of mexiletine and MHM with hERG channel are interpreted by modeling their corresponding binding interactions through ab initio calculations. The simulations demonstrate that the introduction of a hydroxyl group on the meta-position of the aromatic portion of mexiletine weakens the interaction of the drug xylyloxy moiety with Tyr652. These results provide further insights into the molecular basis of drug/hERG interactions and, in agreement with previously reported results on clofilium and ibutilide analogs, support the possibility of reducing hERG potency and related toxicity by modifying the aromatic pattern of substitution of clinically relevant compounds. PMID:26516576

  5. S3-S4 linker length modulates the relaxed state of a voltage-gated potassium channel.

    Science.gov (United States)

    Priest, Michael F; Lacroix, Jérôme J; Villalba-Galea, Carlos A; Bezanilla, Francisco

    2013-11-19

    Voltage-sensing domains (VSDs) are membrane protein modules found in ion channels and enzymes that are responsible for a large number of fundamental biological tasks, such as neuronal electrical activity. The VSDs switch from a resting to an active conformation upon membrane depolarization, altering the activity of the protein in response to voltage changes. Interestingly, numerous studies describe the existence of a third distinct state, called the relaxed state, also populated at positive potentials. Although some physiological roles for the relaxed state have been suggested, little is known about the molecular determinants responsible for the development and modulation of VSD relaxation. Several lines of evidence have suggested that the linker (S3-S4 linker) between the third (S3) and fourth (S4) transmembrane segments of the VSD alters the equilibrium between resting and active conformations. By measuring gating currents from the Shaker potassium channel, we demonstrate here that shortening the S3-S4 linker stabilizes the relaxed state, whereas lengthening the linker or splitting it and coinjecting two fragments of the channel have little effect. We propose that natural variations of the length of the S3-S4 linker in various VSD-containing proteins may produce differential VSD relaxation in vivo.

  6. Study of the interaction of unaggregated and aggregated amyloid β protein (10-21) with outward potassium channel

    Institute of Scientific and Technical Information of China (English)

    ZHANG; ChaoFeng; FAN; Li; YANG; Pin

    2007-01-01

    Metal ion-induced aggregation of Aβinto insoluble plaques is a central factor in Alzheimer's disease. Zn2+ is the only physiologically available transition metal ion responsible for aggregating Aβ at pH 7.4. To make it clear that the neurotoxicity of Zn2+-induced aggregation of Aβ on neurons is the key to understand Aβ mechanism of action further. In this paper, we choose Aβ (10-21) as the model fragment to research hippocampal CA1 pyramidal neurons. For the first time, we adopt the combination of spectral analysis with patch-clamp technique for the preliminary study of the mutual relations of Zn2+, Aβ and ion channel from the cell level. The following expounds upon the effects and mode of action of two forms (unaggregated and aggregated) of Aβ (10-21) on hippocampus outward potassium channel three processes (activation, inactivation and reactivation). It also shows the molecular mechanics of AD from the channel level. These results are significant for the further study of Aβ nosogenesis and the development of new types of target drugs for the treatment of AD.

  7. Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA.

    Science.gov (United States)

    Raja, Mobeen; Spelbrink, Robin E J; de Kruijff, Ben; Killian, J Antoinette

    2007-12-11

    In this study, we investigated how the presence of anionic lipids influenced the stability and folding properties of the potassium channel KcsA. By using a combination of gel electrophoresis, tryptophan fluorescence and acrylamide quenching experiments, we found that the presence of the anionic lipid phosphatidylglycerol (PG) in a phosphatidylcholine (PC) bilayer slightly stabilized the tetramer and protected it from trifluoroethanol-induced dissociation. Surprisingly, the presence of phosphatidic acid (PA) had a much larger effect on the stability of KcsA and this lipid, in addition, significantly influenced the folding properties of the protein. The data indicate that PA creates some specificity over PG, and that it most likely stabilizes the tetramer via both electrostatic and hydrogen bond interactions. PMID:18036565

  8. Genetic variation in the two-pore domain potassium channel, TASK-1, may contribute to an atrial substrate for arrhythmogenesis

    DEFF Research Database (Denmark)

    Liang, Bo; Soka, Magdalena; Christensen, Alex Horby;

    2013-01-01

    The two-pore domain potassium channel, K2P3.1 (TASK-1) modulates background conductance in isolated human atrial cardiomyocytes and has been proposed as a potential drug target for atrial fibrillation (AF). TASK-1 knockout mice have a predominantly ventricular phenotype however, and effects of TASK......-1 inactivation on atrial structure and function have yet to be demonstrated in vivo. The extent to which genetic variation in KCNK3, that encodes TASK-1, might be a determinant of susceptibility to AF is also unknown. To address these questions, we first evaluated the effects of transient knockdown...... diameter (p=0.01) when compared with control-injected embryos. We next performed genetic screening of KCNK3 in two independent AF cohorts (373 subjects) and identified three novel KCNK3 variants. Two of these variants, present in one proband with familial AF, were located at adjacent nucleotides...

  9. Auditory hallucinations as ictal phenomena in a patient with voltage-gated potassium channel antibody-associated limbic encephalitis.

    Science.gov (United States)

    Boyd, Michael; Attarian, Hrayr; Raizer, Jeffrey; Kumthekar, Priya; Macken, Micheal P; Schuele, Stephan U; Gerard, Elizabeth

    2013-12-01

    Limbic encephalitis involving anti-voltage-gated potassium channel antibodies (VGKC-LE) has become increasingly recognised, with seizures and psychotic features, such as hallucinations being typical clinical manifestations. Though the literature supports auditory hallucinations as ictal phenomena, there are no reported cases of these hallucinations correlating with electrographic seizure for this disease entity. Early recognition of auditory hallucinations as seizures could alter treatment and subsequently affect short-term outcomes in these patients. We report the case of a patient with auditory hallucinations and progressive cognitive decline, as well as serological evidence of VGKC antibodies, in whom ictal hallucinations were identified by continuous video-EEG monitoring. This case highlights the subtlety of this entity, in both clinical and electrographic detection. [Published with video sequences]. PMID:24571022

  10. Sequence and functional expression in Xenopus oocytes of a human insulinoma and islet potassium channel

    International Nuclear Information System (INIS)

    Regulation of insulin secretion involves the coordinated control of ion channels in the β-cell membrane. The authors have isolated and characterized cDNA and genomic clones encoding a voltage-dependent K+ channel isoform expressed in human islets and in a human insulinoma. This K+ channel isoform, designated hPCN1, with a deduced amino acid sequence of 613 residues is related to the Shaker family of Drosophila K+ channels. hPCN1 is homologous to two other human K+ channel isoforms. They have isolated, hPCN2 and hPCN3, with 55% and 65% amino acid sequence identity, respectively. The electrophysiological characteristics of hPCN1 were determined after microinjuection of synthetic RNA into Xenopus oocytes. Two-microelectrode voltage-clamp recordings of oocytes injected with hPCN1 RNA revealed a voltage-dependent outward K+ current that inactivated slowly with time. Outward currents were inhibited by 4-aminopyridine with a Ki less that 0.01 mM and were relatively insensitive to tetraethylammonium ion or Ba2+. A delayed rectifier K+ channel such as hPCN1 could restore the resting membrane potential of β cells after depolarization and thereby contribute to the regulation of insulin secretion

  11. Modulation of Potassium Channel Activity in the Balance of ROS and ATP Production by Durum Wheat Mitochondria - An amazing defence tool against hyperosmotic stress

    Directory of Open Access Journals (Sweden)

    Daniela eTrono

    2015-12-01

    Full Text Available In plants, the existence of a mitochondrial potassium channel was firstly demonstrated about fifteen years ago in durum wheat as an ATP-dependent potassium channel (PmitoKATP. Since then, both properties of the original PmitoKATP and occurrence of different mitochondrial potassium channels in a number of plant species (monocotyledonous and dicotyledonous and tissues/organs (etiolated and green have been shown. Here, an overview of the current knowledge is reported; in particular, the issue of PmitoKATP physiological modulation is addressed. Similarities and differences with other potassium channels, as well as possible cross-regulation with other mitochondrial proteins (Plant Uncoupling Protein, Alternative Oxidase, Plant Inner Membrane Anion Channel are also described. PmitoKATP is inhibited by ATP and activated by superoxide anion, as well as by free fatty acids (FFAs and acyl-CoAs. Interestingly, channel activation increases electrophoretic potassium uptake across the inner membrane towards the matrix, so collapsing membrane potential (ΔΨ, the main component of the protonmotive force (Δp in plant mitochondria; moreover, cooperation between PmitoKATP and the K+/H+ antiporter allows a potassium cycle able to dissipate also ΔpH. Interestingly, ΔΨ collapse matches with an active control of mitochondrial reactive oxygen species (ROS production. Fully open channel is able to lower superoxide anion up to 35-fold compared to a condition of ATP-inhibited channel. On the other hand, ΔΨ collapse by PmitoKATP was unexpectedly found to not affect ATP synthesis via oxidative phosphorylation. This may probably occur by means of a controlled collapse due to ATP inhibition of PmitoKATP; this brake to the channel activity may allow a loss of the bulk phase Δp, but may preserve a non-classically detectable localized driving force for ATP synthesis. This ability may become crucial under environmental/oxidative stress. In particular, under moderate

  12. Development and Validation of Fluorescence-Based and Automated Patch Clamp–Based Functional Assays for the Inward Rectifier Potassium Channel Kir4.1

    OpenAIRE

    Raphemot, Rene; Kadakia, Rishin J.; Olsen, Michelle L.; Banerjee, Sreedatta; Days, Emily; Smith, Stephen S.; Weaver, C. David; Denton, Jerod S.

    2013-01-01

    The inward rectifier potassium (Kir) channel Kir4.1 plays essential roles in modulation of neurotransmission and renal sodium transport and may represent a novel drug target for temporal lobe epilepsy and hypertension. The molecular pharmacology of Kir4.1 is limited to neurological drugs, such as fluoxetine (Prozac©), exhibiting weak and nonspecific activity toward the channel. The development of potent and selective small-molecule probes would provide critically needed tools for exploring th...

  13. Plant adaptation to fluctuating environment and biomass production are strongly dependent on guard cell potassium channels

    Science.gov (United States)

    Lebaudy, Anne; Vavasseur, Alain; Hosy, Eric; Dreyer, Ingo; Leonhardt, Nathalie; Thibaud, Jean-Baptiste; Véry, Anne-Aliénor; Simonneau, Thierry; Sentenac, Hervé

    2008-01-01

    At least four genes encoding plasma membrane inward K+ channels (Kin channels) are expressed in Arabidopsis guard cells. A double mutant plant was engineered by disruption of a major Kin channel gene and expression of a dominant negative channel construct. Using the patch-clamp technique revealed that this mutant was totally deprived of guard cell Kin channel (GCKin) activity, providing a model to investigate the roles of this activity in the plant. GCKin activity was found to be an essential effector of stomatal opening triggered by membrane hyperpolarization and thereby of blue light-induced stomatal opening at dawn. It improved stomatal reactivity to external or internal signals (light, CO2 availability, and evaporative demand). It protected stomatal function against detrimental effects of Na+ when plants were grown in the presence of physiological concentrations of this cation, probably by enabling guard cells to selectively and rapidly take up K+ instead of Na+ during stomatal opening, thereby preventing deleterious effects of Na+ on stomatal closure. It was also shown to be a key component of the mechanisms that underlie the circadian rhythm of stomatal opening, which is known to gate stomatal responses to extracellular and intracellular signals. Finally, in a meteorological scenario with higher light intensity during the first hours of the photophase, GCKin activity was found to allow a strong increase (35%) in plant biomass production. Thus, a large diversity of approaches indicates that GCKin activity plays pleiotropic roles that crucially contribute to plant adaptation to fluctuating and stressing natural environments. PMID:18367672

  14. Dysfunction of the heteromeric KV7.3/KV7.5 potassium channel is associated with autism spectrum disorders

    DEFF Research Database (Denmark)

    Nielsen, Mette Gilling; Rasmussen, Hanne Borger; Callø, Kirstine;

    2013-01-01

    Heterozygous mutations in the KCNQ3 gene on chromosome 8q24 encoding the voltage-gated potassium channel KV7.3 subunit have previously been associated with rolandic epilepsy and idiopathic generalized epilepsy (IGE) including benign neonatal convulsions. We identified a de novo t(3;8) (q21;q24) t...

  15. Students' Understanding of External Representations of the Potassium Ion Channel Protein, Part I: Affordances and Limitations of Ribbon Diagrams, Vines, and Hydrophobic/Polar Representations

    Science.gov (United States)

    Harle, Marissa; Towns, Marcy H.

    2012-01-01

    Research on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This project focuses on students' understanding of three external representations of the potassium ion channel protein. This is part I of a two-part study, which focuses on the affordances and…

  16. Tyrosine phosphatases epsilon and alpha perform specific and overlapping functions in regulation of voltage-gated potassium channels in Schwann cells

    DEFF Research Database (Denmark)

    Tiran, Zohar; Peretz, Asher; Sines, Tal;

    2006-01-01

    Tyrosine phosphatases (PTPs) epsilon and alpha are closely related and share several molecular functions, such as regulation of Src family kinases and voltage-gated potassium (Kv) channels. Functional interrelationships between PTPepsilon and PTPalpha and the mechanisms by which they regulate K+ ...

  17. Evaluation of the therapeutic effect of potassium permanganate at early stages of an experimental acute infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus)

    Science.gov (United States)

    The efficacy of potassium permanganate (KMnO4) against early stages of an experimental acute infection of Flavobacterium columnare in channel catfish (Ictalurus punctatus) was evaluated. Fish were experimentally challenged, by waterborne exposure for 2 h to F. columnare after cutaneous abrasion, an...

  18. Association analysis of a highly polymorphic CAG Repeat in the human potassium channel gene KCNN3 and migraine susceptibility

    Directory of Open Access Journals (Sweden)

    Ovcaric Mick

    2005-09-01

    Full Text Available Abstract Background Migraine is a polygenic multifactorial disease, possessing environmental and genetic causative factors with multiple involved genes. Mutations in various ion channel genes are responsible for a number of neurological disorders. KCNN3 is a neuronal small conductance calcium-activated potassium channel gene that contains two polyglutamine tracts, encoded by polymorphic CAG repeats in the gene. This gene plays a critical role in determining the firing pattern of neurons and acts to regulate intracellular calcium channels. Methods The present association study tested whether length variations in the second (more 3' polymorphic CAG repeat in exon 1 of the KCNN3 gene, are involved in susceptibility to migraine with and without aura (MA and MO. In total 423 DNA samples from unrelated individuals, of which 202 consisted of migraine patients and 221 non-migraine controls, were genotyped and analysed using a fluorescence labelled primer set on an ABI310 Genetic Analyzer. Allele frequencies were calculated from observed genotype counts for the KCNN3 polymorphism. Analysis was performed using standard contingency table analysis, incorporating the chi-squared test of independence and CLUMP analysis. Results Overall, there was no convincing evidence that KCNN3 CAG lengths differ between Caucasian migraineurs and controls, with no significant difference in the allelic length distribution of CAG repeats between the population groups (P = 0.090. Also the MA and MO subtypes did not differ significantly between control allelic distributions (P > 0.05. The prevalence of the long CAG repeat (>19 repeats did not reach statistical significance in migraineurs (P = 0.15, nor was there a significant difference between the MA and MO subgroups observed compared to controls (P = 0.46 and P = 0.09, respectively, or between MA vs MO (P = 0.40. Conclusion This association study provides no evidence that length variations of the second polyglutamine array in

  19. Filter gate closure inhibits ion but not water transport through potassium channels.

    Science.gov (United States)

    Hoomann, Torben; Jahnke, Nadin; Horner, Andreas; Keller, Sandro; Pohl, Peter

    2013-06-25

    The selectivity filter of K(+) channels is conserved throughout all kingdoms of life. Carbonyl groups of highly conserved amino acids point toward the lumen to act as surrogates for the water molecules of K(+) hydration. Ion conductivity is abrogated if some of these carbonyl groups flip out of the lumen, which happens (i) in the process of C-type inactivation or (ii) during filter collapse in the absence of K(+). Here, we show that K(+) channels remain permeable to water, even after entering such an electrically silent conformation. We reconstituted fluorescently labeled and constitutively open mutants of the bacterial K(+) channel KcsA into lipid vesicles that were either C-type inactivating or noninactivating. Fluorescence correlation spectroscopy allowed us to count both the number of proteoliposomes and the number of protein-containing micelles after solubilization, providing the number of reconstituted channels per proteoliposome. Quantification of the per-channel increment in proteoliposome water permeability with the aid of stopped-flow experiments yielded a unitary water permeability pf of (6.9 ± 0.6) × 10(-13) cm(3)⋅s(-1) for both mutants. "Collapse" of the selectivity filter upon K(+) removal did not alter pf and was fully reversible, as demonstrated by current measurements through planar bilayers in a K(+)-containing medium to which K(+)-free proteoliposomes were fused. Water flow through KcsA is halved by 200 mM K(+) in the aqueous solution, which indicates an effective K(+) dissociation constant in that range for a singly occupied channel. This questions the widely accepted hypothesis that multiple K(+) ions in the selectivity filter act to mutually destabilize binding.

  20. Trafficking and intracellular regulation of Kv7.1 potassium channels in the heart

    DEFF Research Database (Denmark)

    Nielsen, Nathalie Hélix

    abnormalities induced by “loss of function” Kv7.1 mutations increase the risk of polymorphic ventricular arrhythmias. These cardiac arrhythmias, typically in the form of torsades de pointes, may underlie ventricular fibrillation, recurrent syncope, and sudden death. To date, nearly 300 Kv7.1 mutations have been...... to the regulation of the Kv7.1 channel, which displays a consensus site in the N-terminus for this kinase. Our study, with the support of others, tends to demonstrate that the Kv7.1 channel forms a macromolecular signaling complex with its interactions partners in order to allow a fast response to external signals....

  1. Antibodies to voltage-gated potassium and calcium channels in epilepsy.

    NARCIS (Netherlands)

    Majoie, H.J.; Baets, M.H.V. de; Renier, W.O.; Lang, B.; Vincent, A.

    2006-01-01

    OBJECTIVE: To determine the prevalence of antibodies to ion channels in patients with long standing epilepsy. BACKGROUND: Although the CNS is thought to be protected from circulating antibodies by the blood brain barrier, glutamate receptor antibodies have been reported in Rasmussen's encephalitis,

  2. Silencing of Kv4.1 potassium channels inhibits cell proliferation of tumorigenic human mammary epithelial cells

    International Nuclear Information System (INIS)

    Potassium channel activity has been shown to facilitate cell proliferation in cancer cells. In the present study, the role of Kv4.1 channels in immortal and tumorigenic human mammary epithelial cells was investigated. Kv4.1 protein expression was positively correlated with tumorigenicity. Moreover, transfection with siRNAs targeting Kv4.1 mRNA suppressed proliferation of tumorigenic mammary epithelial cells. Experiments using mRNA isolated from human breast cancer tissues revealed that the level of Kv4.1 mRNA expression varied depending on the stage of the tumor. Kv4.1 protein expression increased during stages T2 and T3 compared to normal tissue. These results demonstrated that Kv4.1 plays a role in proliferation of tumorigenic human mammary epithelial cells. In addition, elevated Kv4.1 expression may be useful as a diagnostic marker for staging mammary tumors and selective blockers of Kv4.1 may serve to suppress tumor cell proliferation.

  3. Intracellular potassium stabilizes human ether-à-go-go-related gene channels for export from endoplasmic reticulum.

    Science.gov (United States)

    Wang, Lu; Dennis, Adrienne T; Trieu, Phan; Charron, Francois; Ethier, Natalie; Hebert, Terence E; Wan, Xiaoping; Ficker, Eckhard

    2009-04-01

    Several therapeutic compounds have been identified that prolong the QT interval on the electrocardiogram and cause torsade de pointes arrhythmias not by direct block of the cardiac potassium channel human ether-à-go-go-related gene (hERG) but via disruption of hERG trafficking to the cell surface membrane. One example of a clinically important compound class that potently inhibits hERG trafficking are cardiac glycosides. We have shown previously that inhibition of hERG trafficking by cardiac glycosides is initiated via direct block of Na(+)/K(+) pumps and not via off-target interactions with hERG or any other protein. However, it was not known how pump inhibition at the cell surface is coupled to hERG processing in the endoplasmic reticulum. Here, we show that depletion of intracellular K(+)-either indirectly after long-term exposure to cardiac glycosides or directly after exposure to gramicidin in low sodium media-is sufficient to disrupt hERG trafficking. In K(+)-depleted cells, hERG trafficking can be restored by permeating K(+) or Rb(+) ions, incubation at low temperature, exposure to the pharmacological chaperone astemizole, or specific mutations in the selectivity filter of hERG. Our data suggest a novel mechanism for drug-induced trafficking inhibition in which cardiac glycosides produce a [K(+)](i)-mediated conformational defect directly in the hERG channel protein. PMID:19139152

  4. Mutation analysis of potassium channel genes KCNQ1 and KCNH2 in patients with long QT syndrome

    Institute of Scientific and Technical Information of China (English)

    刘文玲; 胡大一; 李翠兰; 李萍; 李运田; 李志明; 李蕾; 秦绪光; 董玮; 戚豫; 陈胜寒; 王擎

    2003-01-01

    Objective To determine mutations of two common potassium channel subunit genes KCNQ1, KCNH2 causing long QT syndrome (LQTS) in the Chinese.Methods Thirty-one Chinese LQTS pedigrees were characterized for mutations in the two LQTS genes, KCNQ1 and KCNH2, by sequencing.Results Two novel KCNQ1 mutations, S277L in the S5 domain and G306V in the channel pore, and two novel KCNH2 mutations, L413P in the transmembrane domain S1 and L559H in the transmembrane domain S5 were identified. The triggering factors for cardiac events developed in these mutation carriers included physical exercise and excitation. Mutation L413P in KCNH2 was associated with the notched T wave on ECGs. Mutation L559H in KCNH2 was associated with the typical bifid T wave on ECGs. Mutation S277L in KCNQ1 was associated with a high-amplitude T wave and G306V was associated with a low-amplitude T wave. Two likely polymorphisms, IVS11+18C>T in KCNQ1 and L520V in KCNH2 were also identified in two LQTS patients.Conclusions The mutation rates for both KCNQ1 (6.4%) and KCNH2 (6.4%) are lower in the Chinese population than those from North America or Europe.

  5. The pharmacology of three inwardly rectifying potassium Channels in neonatal rat cardiac myocytes.

    OpenAIRE

    Azam, R.

    1999-01-01

    The aim of the present study was to investigate the pharmacology of three inwardly rectifying K+-channels in neonatal rat cardiac myocytes, IKAch, IKI, IKAtp- using whole cell voltage clamp techniques. Cells were held at -50mV. A previous study has shown that clotrimazole, an antimycotic agent, and cetiedil, an antisickling agent are potent against the IKACch in atrial myocytes. Structural analogues of these compounds were tested on the three inward rectifiers. UCL1880, an a...

  6. Biophysical characterization of KV3.1 potassium channel activating compounds

    DEFF Research Database (Denmark)

    Taskin, Bahar; von Schoubye, Nadia Lybøl; Sheykhzade, Majid;

    2015-01-01

    The effect of two positive modulators, RE1 and EX15, on the voltage-gated K+ channel Kv3.1 was investigated using the whole-cell patch-clamp technique on HEK293 cells expressing Kv3.1a. RE1 and EX15 increased the Kv3.1 currents in a concentration-dependent manner with an EC50 value of 4.5 and 1.3...

  7. Discovery and characterisation of a novel toxin from Dendroaspis angusticeps, named Tx7335, that activates the potassium channel KcsA.

    Science.gov (United States)

    Rivera-Torres, Iván O; Jin, Tony B; Cadene, Martine; Chait, Brian T; Poget, Sébastien F

    2016-01-01

    Due to their central role in essential physiological processes, potassium channels are common targets for animal toxins. These toxins in turn are of great value as tools for studying channel function and as lead compounds for drug development. Here, we used a direct toxin pull-down assay with immobilised KcsA potassium channel to isolate a novel KcsA-binding toxin (called Tx7335) from eastern green mamba snake (Dendroaspis angusticeps) venom. Sequencing of the toxin by Edman degradation and mass spectrometry revealed a 63 amino acid residue peptide with 4 disulphide bonds that belongs to the three-finger toxin family, but with a unique modification of its disulphide-bridge scaffold. The toxin induces a dose-dependent increase in both open probabilities and mean open times on KcsA in artificial bilayers. Thus, it unexpectedly behaves as a channel activator rather than an inhibitor. A charybdotoxin-sensitive mutant of KcsA exhibits similar susceptibility to Tx7335 as wild-type, indicating that the binding site for Tx7335 is distinct from that of canonical pore-blocker toxins. Based on the extracellular location of the toxin binding site (far away from the intracellular pH gate), we propose that Tx7335 increases potassium flow through KcsA by allosterically reducing inactivation of the channel.

  8. Oxidation potentials of N-modified derivatives of the analgesic flupirtine linked to potassium KV 7 channel opening activity but not hepatocyte toxicity.

    Science.gov (United States)

    Lemmerhirt, Christian J; Rombach, Mirko; Bodtke, Anja; Bednarski, Patrick J; Link, Andreas

    2015-02-01

    Openers of neuronal voltage-gated potassium channels (KV ) are of interest as therapeutic agents for treating pain (flupirtine) and epilepsy (retigabine). In an effort to better understand the mechanisms of action and toxicity of flupirtine, we synthesized nine novel analogues with varying redox behavior. Flupirtine can be oxidatively metabolized into azaquinone diimines; thus, the oxidation potentials of flupirtine and its analogues were measured by cyclic voltammetry. KV 7.2/3 (KCNQ2/3) opening activity was determined by an established assay with HEK293 cells overexpressing these channels. A link was found between the oxidation potentials of the compounds and their EC50 values for potassium channel opening activity. On the other hand, no correlation was observed between oxidation potentials and cytotoxicity in cultures of transgenic mouse hepatocytes (TAMH). These results support the idea that oxidative metabolites of flupirtine contribute to the mechanism of action, similar to what was recently proposed for acetaminophen (paracetamol), but not to hepatotoxicity. PMID:25392984

  9. Developing a Comparative Docking Protocol for the Prediction of Peptide Selectivity Profiles: Investigation of Potassium Channel Toxins

    Directory of Open Access Journals (Sweden)

    Serdar Kuyucak

    2012-02-01

    Full Text Available During the development of selective peptides against highly homologous targets, a reliable tool is sought that can predict information on both mechanisms of binding and relative affinities. These tools must first be tested on known profiles before application on novel therapeutic candidates. We therefore present a comparative docking protocol in HADDOCK using critical motifs, and use it to “predict” the various selectivity profiles of several major αKTX scorpion toxin families versus Kv1.1, Kv1.2 and Kv1.3. By correlating results across toxins of similar profiles, a comprehensive set of functional residues can be identified. Reasonable models of channel-toxin interactions can be then drawn that are consistent with known affinity and mutagenesis. Without biological information on the interaction, HADDOCK reproduces mechanisms underlying the universal binding of αKTX-2 toxins, and Kv1.3 selectivity of αKTX-3 toxins. The addition of constraints encouraging the critical lysine insertion confirms these findings, and gives analogous explanations for other families, including models of partial pore-block in αKTX-6. While qualitatively informative, the HADDOCK scoring function is not yet sufficient for accurate affinity-ranking. False minima in low-affinity complexes often resemble true binding in high-affinity complexes, despite steric/conformational penalties apparent from visual inspection. This contamination significantly complicates energetic analysis, although it is usually possible to obtain correct ranking via careful interpretation of binding-well characteristics and elimination of false positives. Aside from adaptations to the broader potassium channel family, we suggest that this strategy of comparative docking can be extended to other channels of interest with known structure, especially in cases where a critical motif exists to improve docking effectiveness.

  10. Fluoxetine protection in decompression sickness in mice is enhanced by blocking TREK-1 potassium channel with the spadin antidepressant.

    Directory of Open Access Journals (Sweden)

    Nicolas eVallée

    2016-02-01

    Full Text Available In mice, disseminated coagulation, inflammation and ischemia induce neurological damages that can lead to the death. These symptoms result from circulating bubbles generated by a pathogenic decompression. An acute fluoxetine treatment or the presence of the TREK-1 potassium channel increased the survival rate when mice are subjected to an experimental dive/decompression protocol. This is a paradox because fluoxetine is a blocker of TREK-1 channels. First, we studied the effects of an acute dose of fluoxetine (50mg/kg in wild-type (WT and TREK-1 deficient mice (Knockout homozygous KO and heterozygous HET. Then, we combined the same fluoxetine treatment with a five-day treatment by spadin, in order to specifically block TREK-1 activity (KO-like mice. KO and KO-like mice could be regarded as antidepressed models.167 mice (45 WTcont 46 WTflux 30 HETflux and 46 KOflux constituting the flux-pool and 113 supplementary mice (27 KO-like 24 WTflux2 24 KO-likeflux 21 WTcont2 17 WTno dive constituting the spad-pool were included in this study. Only 7% of KO-TREK-1 treated with fluoxetine (KOflux and 4% of mice treated with both spadin and fluoxetine (KO-likeflux died from decompression sickness (DCS symptoms. These values are much lower than those of WT control (62% or KO-like mice (41%. After the decompression protocol, mice showed a significant consumption of their circulating platelets and leukocytes.Spadin antidepressed mice were more likely to declare DCS. Nevertheless, which had both blocked TREK-1 channel and were treated with fluoxetine were better protected against DCS. We conclude that the protective effect of such an acute dose of fluoxetine is enhanced when TREK-1 is inhibited. We confirmed that antidepressed models may have worse DCS outcomes, but a concomitant fluoxetine treatment not only decreases DCS severity but increases the survival rate.

  11. Calcium-activated potassium channels in insect pacemaker neurons as unexpected target site for the novel fumigant dimethyl disulfide.

    Science.gov (United States)

    Gautier, Hélène; Auger, Jacques; Legros, Christian; Lapied, Bruno

    2008-01-01

    Dimethyl disulfide (DMDS), a plant-derived insecticide, is a promising fumigant as a substitute for methyl bromide. To further understand the mode of action of DMDS, we examined its effect on cockroach octopaminergic neurosecretory cells, called dorsal unpaired median (DUM) neurons, using whole-cell patch-clamp technique, calcium imaging and antisense oligonucleotide strategy. At low concentration (1 microM), DMDS modified spontaneous regular spike discharge into clear bursting activity associated with a decrease of the amplitude of the afterhyperpolarization. This effect led us to suspect alterations of calcium-activated potassium currents (IKCa) and [Ca(2+)](i) changes. We showed that DMDS reduced amplitudes of both peak transient and sustained components of the total potassium current. IKCa was confirmed as a target of DMDS by using iberiotoxin, cadmium chloride, and pSlo antisense oligonucleotide. In addition, we showed that DMDS induced [Ca(2+)](i) rise in Fura-2-loaded DUM neurons. Using calcium-free solution, and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxy-phenyl)ethyl]-acetamide (LOE 908) [an inhibitor of transient receptor potential (TRP)gamma], we demonstrated that TRPgamma initiated calcium influx. By contrast, omega-conotoxin GVIA (an inhibitor of N-type high-voltage-activated calcium channels), did not affect the DMDS-induced [Ca(2+)](i) rise. Finally, the participation of the calcium-induced calcium release mechanism was investigated using thapsigargin, caffeine, and ryanodine. Our study revealed that DMDS-induced elevation in [Ca(2+)](i) modulated IKCa in an unexpected bell-shaped manner via intracellular calcium. In conclusion, DMDS affects multiple targets, which could be an effective way to improve pest control efficacy of fumigation. PMID:17942746

  12. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

    OpenAIRE

    Bo Hyung Lee; Pan Dong Ryu; So Yeong Lee

    2014-01-01

    The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv) channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G...

  13. Relevance of lysine snorkeling in the outer transmembrane domain of small viral potassium ion channels.

    Science.gov (United States)

    Gebhardt, Manuela; Henkes, Leonhard M; Tayefeh, Sascha; Hertel, Brigitte; Greiner, Timo; Van Etten, James L; Baumeister, Dirk; Cosentino, Cristian; Moroni, Anna; Kast, Stefan M; Thiel, Gerhard

    2012-07-17

    Transmembrane domains (TMDs) are often flanked by Lys or Arg because they keep their aliphatic parts in the bilayer and their charged groups in the polar interface. Here we examine the relevance of this so-called "snorkeling" of a cationic amino acid, which is conserved in the outer TMD of small viral K(+) channels. Experimentally, snorkeling activity is not mandatory for Kcv(PBCV-1) because K29 can be replaced by most of the natural amino acids without any corruption of function. Two similar channels, Kcv(ATCV-1) and Kcv(MT325), lack a cytosolic N-terminus, and neutralization of their equivalent cationic amino acids inhibits their function. To understand the variable importance of the cationic amino acids, we reanalyzed molecular dynamics simulations of Kcv(PBCV-1) and N-terminally truncated mutants; the truncated mutants mimic Kcv(ATCV-1) and Kcv(MT325). Structures were analyzed with respect to membrane positioning in relation to the orientation of K29. The results indicate that the architecture of the protein (including the selectivity filter) is only weakly dependent on TMD length and protonation of K29. The penetration depth of Lys in a given protonation state is independent of the TMD architecture, which leads to a distortion of shorter proteins. The data imply that snorkeling can be important for K(+) channels; however, its significance depends on the architecture of the entire TMD. The observation that the most severe N-terminal truncation causes the outer TMD to move toward the cytosolic side suggests that snorkeling becomes more relevant if TMDs are not stabilized in the membrane by other domains.

  14. Discovery and characterization of a potent and selective inhibitor of Aedes aegypti inward rectifier potassium channels.

    Directory of Open Access Journals (Sweden)

    Rene Raphemot

    Full Text Available Vector-borne diseases such as dengue fever and malaria, which are transmitted by infected female mosquitoes, affect nearly half of the world's population. The emergence of insecticide-resistant mosquito populations is reducing the effectiveness of conventional insecticides and threatening current vector control strategies, which has created an urgent need to identify new molecular targets against which novel classes of insecticides can be developed. We previously demonstrated that small molecule inhibitors of mammalian Kir channels represent promising chemicals for new mosquitocide development. In this study, high-throughput screening of approximately 30,000 chemically diverse small-molecules was employed to discover potent and selective inhibitors of Aedes aegypti Kir1 (AeKir1 channels heterologously expressed in HEK293 cells. Of 283 confirmed screening 'hits', the small-molecule inhibitor VU625 was selected for lead optimization and in vivo studies based on its potency and selectivity toward AeKir1, and tractability for medicinal chemistry. In patch clamp electrophysiology experiments of HEK293 cells, VU625 inhibits AeKir1 with an IC50 value of 96.8 nM, making VU625 the most potent inhibitor of AeKir1 described to date. Furthermore, electrophysiology experiments in Xenopus oocytes revealed that VU625 is a weak inhibitor of AeKir2B. Surprisingly, injection of VU625 failed to elicit significant effects on mosquito behavior, urine excretion, or survival. However, when co-injected with probenecid, VU625 inhibited the excretory capacity of mosquitoes and was toxic, suggesting that the compound is a substrate of organic anion and/or ATP-binding cassette (ABC transporters. The dose-toxicity relationship of VU625 (when co-injected with probenecid is biphasic, which is consistent with the molecule inhibiting both AeKir1 and AeKir2B with different potencies. This study demonstrates proof-of-concept that potent and highly selective inhibitors of mosquito

  15. Novel potassium channel blocker venom peptides from Mesobuthus gibbosus (Scorpiones: Buthidae).

    Science.gov (United States)

    Diego-García, Elia; Peigneur, Steve; Debaveye, Sarah; Gheldof, Eveline; Tytgat, Jan; Caliskan, Figen

    2013-01-01

    In the present study, we report for the first time, the molecular, biochemical and electrophysiological characterization of the components present in the soluble venom from Mesobuthus gibbosus (Brullé, 1832). According to the epidemiological and clinical situation of scorpion envenomation cases M. gibbosus scorpion is one of the most important health-threatening species of Turkey. Despite the medical importance reported for M. gibbosus, there is no additional information on toxin peptides and venom components to clarify the toxic effect of the M. gibbosus sting. Biochemical characterization of the venom was performed using different protocols and techniques following a bioassay-guided strategy (HPLC, mass spectrometry and Edman degradation sequencing). Venom fractions were tested in electrophysiological assays on a panel of six K(+) channels (K(v)1.1-1.6) by using the two-electrode voltage clamp technique. Three new α-KTx peptides were found and called MegKTx1, MegKTx2 and MegKTx3 (M. gibbosus, K(+) channel toxin number 1-3). A cDNA library from the telson was constructed and specific screening of transcripts was performed. Biochemical and molecular characterization of MegKTx peptides and transcripts shows a relation with toxins of three different α-KTx subfamilies (α-KTx3.x, α-KTx9.x and α-KTx16.x). PMID:23142506

  16. Complex N-Glycans Influence the Spatial Arrangement of Voltage Gated Potassium Channels in Membranes of Neuronal-Derived Cells.

    Directory of Open Access Journals (Sweden)

    M Kristen Hall

    Full Text Available The intrinsic electrical properties of a neuron depend on expression of voltage gated potassium (Kv channel isoforms, as well as their distribution and density in the plasma membrane. Recently, we showed that N-glycosylation site occupancy of Kv3.1b modulated its placement in the cell body and neurites of a neuronal-derived cell line, B35 neuroblastoma cells. To extrapolate this mechanism to other N-glycosylated Kv channels, we evaluated the impact of N-glycosylation occupancy of Kv3.1a and Kv1.1 channels. Western blots revealed that wild type Kv3.1a and Kv1.1 α-subunits had complex and oligomannose N-glycans, respectively, and that abolishment of the N-glycosylation site(s generated Kv proteins without N-glycans. Total internal reflection fluorescence microscopy images revealed that N-glycans of Kv3.1a contributed to its placement in the cell membrane while N-glycans had no effect on the distribution of Kv1.1. Based on particle analysis of EGFP-Kv proteins in the adhered membrane, glycosylated forms of Kv3.1a, Kv1.1, and Kv3.1b had differences in the number, size or density of Kv protein clusters in the cell membrane of neurites and cell body of B35 cells. Differences were also observed between the unglycosylated forms of the Kv proteins. Cell dissociation assays revealed that cell-cell adhesion was increased by the presence of complex N-glycans of Kv3.1a, like Kv3.1b, whereas cell adhesion was similar in the oligomannose and unglycosylated Kv1.1 subunit containing B35 cells. Our findings provide direct evidence that N-glycans of Kv3.1 splice variants contribute to the placement of these glycoproteins in the plasma membrane of neuronal-derived cells while those of Kv1.1 were absent. Further when the cell membrane distribution of the Kv channel was modified by N-glycans then the cell-cell adhesion properties were altered. Our study demonstrates that N-glycosylation of Kv3.1a, like Kv3.1b, provides a mechanism for the distribution of these

  17. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Becerra, Rocio [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Diaz, Lorenza, E-mail: lorenzadiaz@gmail.com [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Camacho, Javier [Department of Pharmacology, Centro de Investigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Av. Instituto Politecnico Nacional 2508, San Pedro Zacatenco 07360, Mexico, D.F. (Mexico); Barrera, David; Ordaz-Rosado, David; Morales, Angelica [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Ortiz, Cindy Sharon [Department of Pathology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Avila, Euclides [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Bargallo, Enrique [Department of Breast Tumors, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Arrecillas, Myrna [Department of Pathology, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Halhali, Ali; Larrea, Fernando [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico)

    2010-02-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  18. MicroRNA-Mediated Downregulation of the Potassium Channel Kv4.2 Contributes to Seizure Onset

    Directory of Open Access Journals (Sweden)

    Christina Gross

    2016-09-01

    Full Text Available Seizures are bursts of excessive synchronized neuronal activity, suggesting that mechanisms controlling brain excitability are compromised. The voltage-gated potassium channel Kv4.2, a major mediator of hyperpolarizing A-type currents in the brain, is a crucial regulator of neuronal excitability. Kv4.2 expression levels are reduced following seizures and in epilepsy, but the underlying mechanisms remain unclear. Here, we report that Kv4.2 mRNA is recruited to the RNA-induced silencing complex shortly after status epilepticus in mice and after kainic acid treatment of hippocampal neurons, coincident with reduction of Kv4.2 protein. We show that the microRNA miR-324-5p inhibits Kv4.2 protein expression and that antagonizing miR-324-5p is neuroprotective and seizure suppressive. MiR-324-5p inhibition also blocks kainic-acid-induced reduction of Kv4.2 protein in vitro and in vivo and delays kainic-acid-induced seizure onset in wild-type but not in Kcnd2 knockout mice. These results reveal an important role for miR-324-5p-mediated silencing of Kv4.2 in seizure onset.

  19. Effects of Acute Mechanical Stretch on the Expression of Mechanosensitive Potassium Channel TREK-1 in Rat Left Ventricle

    Institute of Scientific and Technical Information of China (English)

    ZHAO Fang; DONG Lijuan; CHENG Longxian; ZENG Qiutang; SU Fangcheng

    2007-01-01

    To explore the role of mechanosensitive potassium channel TREK-1, Western blot analysis was used to investigate the expression changes of TREK-1 in left ventricle in acute mechanically stretched heart. Forty Wistar rats were randomly divided into 8 groups (n=5 in each group),subject to single Langendorff perfusion for 0, 30, 60, 120 min and acute mechanical stretch for 0, 30,60, 120 min respectively. With Langendorff apparatus, an acute mechanically stretched heart model was established. There was no significant difference in the expression of TREK-1 among single Langendorff perfusion groups (P>0.05). As compared to non-stretched Langendorff-perfused heart, only the expression of TREK-1 in acute mechanically stretched heart (120 min) was greatly increased (P<0.05). This result suggested that some course of mechanical stretch could up-regulate the expression of TREK-1 in left ventricle. TREK-1 might play an important role in mechanoelectric feedback,so it could reduce the occurrence of arrhythmia that was induced by extra mechanical stretch.

  20. Statistical epistasis and functional brain imaging support a role of voltage-gated potassium channels in human memory.

    Directory of Open Access Journals (Sweden)

    Angela Heck

    Full Text Available Despite the current progress in high-throughput, dense genome scans, a major portion of complex traits' heritability still remains unexplained, a phenomenon commonly termed "missing heritability." The negligence of analytical approaches accounting for gene-gene interaction effects, such as statistical epistasis, is probably central to this phenomenon. Here we performed a comprehensive two-way SNP interaction analysis of human episodic memory, which is a heritable complex trait, and focused on 120 genes known to show differential, memory-related expression patterns in rat hippocampus. Functional magnetic resonance imaging was also used to capture genotype-dependent differences in memory-related brain activity. A significant, episodic memory-related interaction between two markers located in potassium channel genes (KCNB2 and KCNH5 was observed (P(nominal combined=0.000001. The epistatic interaction was robust, as it was significant in a screening (P(nominal=0.0000012 and in a replication sample (P(nominal=0.01. Finally, we found genotype-dependent activity differences in the parahippocampal gyrus (P(nominal=0.001 supporting the behavioral genetics finding. Our results demonstrate the importance of analytical approaches that go beyond single marker statistics of complex traits.

  1. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

    International Nuclear Information System (INIS)

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  2. Calcitriol inhibits Ether-à go-go potassium channel expression and cell proliferation in human breast cancer cells.

    Science.gov (United States)

    García-Becerra, Rocío; Díaz, Lorenza; Camacho, Javier; Barrera, David; Ordaz-Rosado, David; Morales, Angélica; Ortiz, Cindy Sharon; Avila, Euclides; Bargallo, Enrique; Arrecillas, Myrna; Halhali, Ali; Larrea, Fernando

    2010-02-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-à-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention. PMID:19932096

  3. KCNQ Potassium Channels Modulate Sensitivity of Skin Down-hair (D-hair) Mechanoreceptors.

    Science.gov (United States)

    Schütze, Sebastian; Orozco, Ian J; Jentsch, Thomas J

    2016-03-11

    M-current-mediating KCNQ (Kv7) channels play an important role in regulating the excitability of neuronal cells, as highlighted by mutations in Kcnq2 and Kcnq3 that underlie certain forms of epilepsy. In addition to their expression in brain, KCNQ2 and -3 are also found in the somatosensory system. We have now detected both KCNQ2 and KCNQ3 in a subset of dorsal root ganglia neurons that correspond to D-hair Aδ-fibers and demonstrate KCNQ3 expression in peripheral nerve endings of cutaneous D-hair follicles. Electrophysiological recordings from single D-hair afferents from Kcnq3(-/-) mice showed increased firing frequencies in response to mechanical ramp-and-hold stimuli. This effect was particularly pronounced at slow indentation velocities. Additional reduction of KCNQ2 expression further increased D-hair sensitivity. Together with previous work on the specific role of KCNQ4 in rapidly adapting skin mechanoreceptors, our results show that different KCNQ isoforms are specifically expressed in particular subsets of mechanosensory neurons and modulate their sensitivity directly in sensory nerve endings.

  4. Molecular modeling and structural analysis of two-pore domain potassium channels TASK1 interactions with the blocker A1899

    Directory of Open Access Journals (Sweden)

    David Mauricio Ramirez

    2015-03-01

    Full Text Available A1899 is a potent and highly selective blocker of the Two-pore domain potassium (K2P channel TASK-1, it acts as an antagonist blocking the K+ flux and binds to TASK-1 in the inner cavity and shows an activity in nanomolar order. This drug travels through the central cavity and finally binds in the bottom of the selectivity filter with some threonines and waters molecules forming a H-bond network and several hydrophobic interactions. Using alanine mutagenesis screens the binding site was identify involving residues in the P1 and P2 pore loops, the M2 and M4 transmembrane segments, and the halothane response element; mutations were introduced in the human TASK-1 (KCNK3, NM_002246 expressed in Oocytes from anesthetized Xenopus laevis frogs. Based in molecular modeling and structural analysis as such as molecular docking and binding free energy calculations a pose was suggested using a TASK-1 homology models. Recently, various K2P crystal structures have been obtained. We want redefined – from a structural point of view – the binding mode of A1899 in TASK-1 homology models using as a template the K2P crystal structures. By computational structural analysis we describe the molecular basis of the A1899 binding mode, how A1899 travel to its binding site and suggest an interacting pose (Figure 1. after 100 ns of molecular dynamics simulation (MDs we found an intra H-Bond (80% of the total MDs, a H-Bond whit Thr93 (42% of the total MDs, a pi-pi stacking interaction between a ring and Phe125 (88% of the total MDs and several water bridges. Our experimental and computational results allow the molecular understanding of the structural binding mechanism of the selective blocker A1899 to TASK-1 channels. We identified the structural common and divergent features of TASK-1 channel through our theoretical and experimental studies of A1899 drug action.

  5. Influence of epithelium on the inhibition of melittin-induced contraction of guinea-pig isolated trachea by the potassium channel opener NIP-121.

    OpenAIRE

    Shikada, K.; Tanaka, S

    1993-01-01

    1. We have investigated the effect of the potassium channel opener, NIP-121, on contraction elicited by melittin (a phospholipase A2 activator) in epithelium-intact and epithelium-denuded trachea isolated from guinea-pigs. The effects of NIP-121 were compared with those of isoprenaline, aminophylline and hydrocortisone. 2. In the presence of the cyclo-oxygenase inhibitor, indomethacin (5 microM), melittin (3 micrograms ml-1) caused time-dependent contraction. The melittin-induced contractile ...

  6. Therapeutic plasma exchange as a steroid-sparing therapy in a patient with limbic encephalitis due to antibodies to voltage-gated potassium channels.

    Science.gov (United States)

    Martin, Isabella W; Martin, Christi-Lynn B; Dunbar, Nancy M; Lee, Stephen L; Szczepiorkowski, Zbigniew M

    2016-02-01

    Autoantibodies to the voltage-gated potassium channel (VGKC) complex cause a spectrum of non-paraneoplastic neurologic syndromes including limbic encephalitis (LE). We report a case of a man with LE who underwent a course of therapeutic plasma exchange (TPE) in addition to other immunomodulatory therapies and experienced sustained clinical resolution of his symptoms. This report adds to the existing literature supporting TPE in cases of LE due to VGKC complex autoantibodies.

  7. Leucine-Rich Glioma Inactivated-1 and Voltage-Gated Potassium Channel Autoimmune Encephalitis Associated with Ischemic Stroke: A Case Report.

    Science.gov (United States)

    McGinley, Marisa; Morales-Vidal, Sarkis; Ruland, Sean

    2016-01-01

    Autoimmune encephalitis is associated with a wide variety of antibodies and clinical presentations. Voltage-gated potassium channel (VGKC) antibodies are a cause of autoimmune non-paraneoplastic encephalitis characterized by memory impairment, psychiatric symptoms, and seizures. We present a case of VGKC encephalitis likely preceding an ischemic stroke. Reports of autoimmune encephalitis associated with ischemic stroke are rare. Several hypotheses linking these two disease processes are proposed.

  8. Stimulation of beta-adrenoceptors inhibits calcium-dependent potassium-channels in mouse macrophages

    Energy Technology Data Exchange (ETDEWEB)

    Rosati, C.; Hannaert, P.; Dausse, J.P.; Braquet, P.; Garay, R.

    1986-12-01

    K/sup +/ efflux in mouse macrophages exhibited a rate constant (k/sub k/) of 0.67 +/- 0.04 (h)/sup -1/. This was strongly stimulated by increasing concentrations of the Ca/sup 2 +/ ionophore A23187 up to a maximal value of 4.01 +/- 0.25 (h)/sup -1/ with an IC/sub 50/ of 7.6 +/- 1.9 ..mu..M. Similar results were obtained with the Ca/sup 2 +/ ionophore ionomycin. Binding experiments with /sup 3/H-dihydroalprenolol revealed a high density of beta-adrenergic receptors with apparent dissociation constant of 2.03 +/- 0.06 nM. Isoproterenol at a concentration of 10/sup -6/ -10/sup -5/ M induced a two- to threefold stimulation of endogenous levels of cyclic AMP (cAMP). A23187-stimulated K/sup +/ efflux was partially inhibited by (i) stimulation of adenylate cyclase with isoproterenol, forskolin or, PGE/sub 1/; (ii) exogenous cAMP; and (iii) inhibition of phosphodiesterase with MIX (1-methyl-3-isobutylxanthine). Maximal inhibition of K/sup +/ efflux was obtained by simultaneous addition of isoproterenol and MIX. In dose-response curves, the isoproterenol-sensitive K/sup +/ efflux was half-maximally inhibited (IC/sub 50/) with 2-5 x 10/sup -10/ M of isoproterenol concentration. Propranolol was able to completely block the effect of isoproterenol, with an IC/sub 50/ of about 1-2 x 10/sup -7/ M. Isoproterenol and MIX did not inhibit A23187-stimulated K/sup +/ efflux in an incubation medium where NaCl was replaced by sucrose (or choline), suggesting the involvement of an Na/sup +/:Ca/sup 2 +/ exchange mechanism. The results show that stimulation of beta-adrenoceptors in mouse macrophages counter balances the opening of K/sup +/ channels induced by the calcium ionophore A23187. This likely reflects a decrease in cytoslic free calcium content via a cAMP-mediated stimulation of Na/sup +/:Ca/sup 2 +/ exchange.

  9. Aberrant expression of ether à go-go potassium channel in colorectal cancer patients and cell lines

    Institute of Scientific and Technical Information of China (English)

    Xiang-Wu Ding; Juan-Juan Yan; Ping An; Peng Lü; He-Sheng Luo

    2007-01-01

    AIM: To study the expression of ether à go-go (Eag1) potassium channel in colorectal cancer and the relation ship between their expression and clinico-pathological features.METHODS: The expression levels of Eag1 protein were determined in 76 cancer tissues with paired noncancerous matched tissues as well as 9 colorectal adenoma tissues by immunohistochemistry. Eag1 mRNA expression was detected in 13 colorectal cancer tissues with paired non-cancerous matched tissues and 4 colorectal adenoma tissues as well as two colorectal cancer cell lines (LoVo and HT-29) by reverse transcription PCR.RESULTS: The frequency of positive expression of Eag1 protein was 76.3% (58/76) and Eag1 mRNA was 76.9% (10/13) in colorectal cancer tissue. Expression level of Eag1 protein was dependent on the tumor size,lymphatic node metastasis, other organ metastases and Dukes' stage (P < 0.05), while not dependent on age,sex, site and degree of differentiation. Eag1 protein and mRNA were negative in normal colorectal tissue, and absolutely negative in colorectal adenomas except that one case was positively stained for Eag1 protein.CONCLUSION: Eag1 protein and mRNA are aberrantly expressed in colorectal cancer and occasionally expressed in colorectal adenoma. The high frequency of expression of Eag1 in tumors and the restriction of normal expression to the brain suggest the potential of this protein for diagnostic, prognostic and therapeutic purposes.

  10. Galanin Activates G Protein Gated Inwardly Rectifying Potassium Channels and Suppresses Kisspeptin-10 Activation of GnRH Neurons.

    Science.gov (United States)

    Constantin, Stephanie; Wray, Susan

    2016-08-01

    GnRH neurons are regulated by hypothalamic kisspeptin neurons. Recently, galanin was identified in a subpopulation of kisspeptin neurons. Although the literature thoroughly describes kisspeptin activation of GnRH neurons, little is known about the effects of galanin on GnRH neurons. This study investigated whether galanin could alter kisspeptin signaling to GnRH neurons. GnRH cells maintained in explants, known to display spontaneous calcium oscillations, and a long-lasting calcium response to kisspeptin-10 (kp-10), were used. First, transcripts for galanin receptors (GalRs) were examined. Only GalR1 was found in GnRH neurons. A series of experiments was then performed to determine the action of galanin on kp-10 activated GnRH neurons. Applied after kp-10 activation, galanin 1-16 (Gal1-16) rapidly suppressed kp-10 activation. Applied with kp-10, Gal1-16 prevented kp-10 activation until its removal. To determine the mechanism by which galanin inhibited kp-10 activation of GnRH neurons, Gal1-16 and galanin were applied to spontaneously active GnRH neurons. Both inhibited GnRH neuronal activity, independent of GnRH neuronal inputs. This inhibition was mimicked by a GalR1 agonist but not by GalR2 or GalR2/3 agonists. Although Gal1-16 inhibition relied on Gi/o signaling, it was independent of cAMP levels but sensitive to blockers of G protein-coupled inwardly rectifying potassium channels. A newly developed bioassay for GnRH detection showed Gal1-16 decreased the kp-10-evoked GnRH secretion below detection threshold. Together, this study shows that galanin is a potent regulator of GnRH neurons, possibly acting as a physiological break to kisspeptin excitation. PMID:27359210

  11. Protein self-assembly and lipid binding in the folding of the potassium channel KcsA.

    Science.gov (United States)

    Barrera, Francisco N; Renart, M Lourdes; Poveda, José A; de Kruijff, Ben; Killian, J Antoinette; González-Ros, José M

    2008-02-19

    Moderate concentrations of the alcohol 2,2,2-trifluoroethanol (TFE) cause the coupled unfolding and dissociation into subunits of the homotetrameric potassium channel KcsA, in a process that is partially irreversible when the protein is solubilized in plain dodecyl beta-d-maltoside (DDM) micelles [Barrera et al. (2005) Biochemistry 44, 14344-52]. Here we report that the transition from the folded tetramer to the unfolded monomer becomes completely reversible when KcsA is solubilized in mixed micelles composed of the detergent DDM and the lipids DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and DOPG (1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)]). This result suggests that lipids may act as effectors in the tetramerization of KcsA. The observed reversibility allowed the determination of the standard free energy of the folding reaction of KcsA: DeltaG = 30.5 +/- 3.1 kcal x mol-1. We also observed that, prior to the unfolding of the tetramer, the presence of lower TFE concentrations causes the disassembly of supramolecular clusters of KcsA into the individual tetrameric molecules. Within the limits of experimental resolution, this is also a reversible process, but unlike the tetramer to monomer transition from above, the level of clustering is not influenced by the presence of solubilized lipids. These observations suggest a distinct role of the lipids in the different in vitro assembly steps (folding/tetramerization and clustering) of KcsA. PMID:18205389

  12. Potassium Channel Interacting Protein 2 (KChIP2) is not a transcriptional regulator of cardiac electrical remodeling.

    Science.gov (United States)

    Winther, Sine V; Tuomainen, Tomi; Borup, Rehannah; Tavi, Pasi; Antoons, Gudrun; Thomsen, Morten B

    2016-01-01

    The heart-failure relevant Potassium Channel Interacting Protein 2 (KChIP2) augments CaV1.2 and KV4.3. KChIP3 represses CaV1.2 transcription in cardiomyocytes via interaction with regulatory DNA elements. Hence, we tested nuclear presence of KChIP2 and if KChIP2 translocates into the nucleus in a Ca(2+) dependent manner. Cardiac biopsies from human heart-failure patients and healthy donor controls showed that nuclear KChIP2 abundance was significantly increased in heart failure; however, this was secondary to a large variation of total KChIP2 content. Administration of ouabain did not increase KChIP2 content in nuclear protein fractions in anesthetized mice. KChIP2 was expressed in cell lines, and Ca(2+) ionophores were applied in a concentration- and time-dependent manner. The cell lines had KChIP2-immunoreactive protein in the nucleus in the absence of treatments to modulate intracellular Ca(2+) concentration. Neither increasing nor decreasing intracellular Ca(2+) concentrations caused translocation of KChIP2. Microarray analysis did not identify relief of transcriptional repression in murine KChIP2(-/-) heart samples. We conclude that although there is a baseline presence of KChIP2 in the nucleus both in vivo and in vitro, KChIP2 does not directly regulate transcriptional activity. Moreover, the nuclear transport of KChIP2 is not dependent on Ca(2+). Thus, KChIP2 does not function as a conventional transcription factor in the heart. PMID:27349185

  13. Research progress in drug reactions on hERG potassium channels%药物对hERG钾通道作用机制研究进展

    Institute of Scientific and Technical Information of China (English)

    林敏; 李泱; 张建成

    2012-01-01

    人ether-a-go-go-related gene (hERG)钾通道表达了延迟整流钾电流的快激活成分,对动作电位的复极至关重要.hERG钾电流不仅是抗心律失常作用的主要靶点,也是诸多药物增加尖端扭转型室速和心源性猝死风险的关键位点,而该电流的降低和(或)升高与基因突变或药物阻滞作用密切相关.随着对药物与hERG钾通道相互作用机制研究的深入,药物与通道孔道区蛋白结合位点的作用及其对通道转运的影响逐步被揭示,但这些药物对hERG作用的临床应用仍有待评价.%Human ether-a-go-go-related gene (hERG) potassium channels conduct the rapid component of the delayed rectifier potassium current ( Ikr). The reduction ( or increase ) of Ikr current due to either gene mutations or adverse drug effects would increase the risk of torsades de pointes and sudden cardiac death. This paper reviews various mechanisms of drug reactions of hERG potassium channels and the properties of major drug-protein reaction sites in the pore region and trafficking of hERG potassium channels under the influence of drugs. However, the effect of clinical administration of drugs on hERG remains unclear.

  14. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Directory of Open Access Journals (Sweden)

    Domenico Tricarico

    Full Text Available Emerging evidences suggest that Ca(2+activated-K(+-(BK channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L or hypokalemia (0.55 mEq/L conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293 in the presence or absence of BK channel modulators. The BK channel openers(10(-11-10(-3M were: acetazolamide(ACTZ, Dichlorphenamide(DCP, methazolamide(MTZ, bendroflumethiazide(BFT, ethoxzolamide(ETX, hydrochlorthiazide(HCT, quercetin(QUERC, resveratrol(RESV and NS1619; and the BK channel blockers(2 x 10(-7M-5 x 10(-3M were: tetraethylammonium(TEA, iberiotoxin(IbTx and charybdotoxin(ChTX. Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the

  15. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Science.gov (United States)

    Tricarico, Domenico; Mele, Antonietta; Calzolaro, Sara; Cannone, Gianluigi; Camerino, Giulia Maria; Dinardo, Maria Maddalena; Latorre, Ramon; Conte Camerino, Diana

    2013-01-01

    Emerging evidences suggest that Ca(2+)activated-K(+)-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10(-11)-10(-3)M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2 x 10(-7)M-5 x 10(-3)M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing

  16. Calcium-dependent modulation and plasma membrane targeting of the AKT2 potassium channel by the CBL4/ CIPK6 calcium sensor/protein kinase complex

    Institute of Scientific and Technical Information of China (English)

    Katrin Held; Jean-Baptiste Thibaud; J(o)rg Kudla; Francois Pascaud; Christian Eckert; Pawel Gajdanowicz; Kenji Hashimoto; Claire Corratgé-Faillie; Jan Niklas Offenborn; Beno(i)t Lacombe; Ingo Dreyer

    2011-01-01

    Potassium (K+) channel function is fundamental to many physiological processes. However, components and mechanisms regulating the activity of plant K+ channels remain poorly understood. Here, we show that the calcium (Ca2+)sensor CBL4 together with the interacting protein kinase CIPK6 modulates the activity and plasma membrane (PM)targeting of the K+ channel AKT2 from Arabidopsis thaliana by mediating translocation of AKT2 to the PM in plant cells and enhancing AKT2 activity in oocytes. Accordingly, akt2, cbl4 and cipk6 mutants share similar developmental and delayed flowering pheuotypes. Moreover, the isolated regulatory C-terminal domain of CIPK6 is sufficient for mediating CBL4- and Ca2+-dependent channel translocation from the endoplasmic reticulum membrane to the PM by a novel targeting pathway that is dependent on dual lipid modifications of CBL4 by myristoylation and palmitoylation. Thus, we describe a critical mechanism of ion-channel regulation where a Ca2+ sensor modulates K+ channel activity by promoting a kinase interaction-dependent but phosphorylation-independent translocation of the channel to the PM.

  17. Crystallization and preliminary X-ray diffraction studies of the tetramerization domain derived from the human potassium channel Kv1.3

    International Nuclear Information System (INIS)

    The tetramerization domain of human Kv1.3 was cloned, expressed, purified and crystallized. The crystals belonged to space group I4 and diffracted to 1.2 Å resolution using synchrotron radiation. The tetramerization domain (T1 domain) derived from the voltage-dependent potassium channel Kv1.3 of Homo sapiens was recombinantly expressed in Escherichia coli and purified. The crystals were first grown in an NMR tube in 150 mM potassium phosphate pH 6.5 in the absence of additional precipitants. The crystals showed I4 symmetry characteristic of the naturally occurring tetrameric assembly of the single subunits. A complete native data set was collected to 1.2 Å resolution at 100 K using synchrotron radiation

  18. Photobiomodulation on KATP Channels of Kir6.2-Transfected HEK-293 Cells

    Directory of Open Access Journals (Sweden)

    Fu-qing Zhong

    2014-01-01

    Full Text Available Background and Objective. ATP-sensitive potassium (KATP channel couples cell metabolism to excitability. To explore role of KATP channels in cellular photobiomodulation, we designed experiment to study effect of low intensity 808 nm laser irradiation on the activity of membrane KATP channel. Study Design/Materials and Methods. Plasmids encoding Kir6.2 was constructed and heterologously expressed in cultured mammalian HEK-293 cells. The patch-clamp and data acquisition systems were used to record KATP channel current before and after irradiation. A laser beam of Ga-As 808 nm at 5 mW/cm2 was used in experiments. A one-way ANOVA test followed by a post hoc Student-Newman-Keuls test was used to assess the statistical differences between data groups. Results. Obvious openings of KATP channels of Kir6.2-transfected HEK-293 cells and excised patches were recorded during and after low intensity 808 nm laser irradiation. Compared with the channels that did not undergo irradiation, open probability, current amplitude, and dwell time of KATP channels after irradiation improved. Conclusions. Low intensity 808 nm laser irradiation may activate membrane KATP channels of Kir6.2-transfected HEK-293 cells and in excised patches.

  19. Complex Membrane Channel Blockade: A Unifying Hypothesis for the Prodromal and Acute Neuropsychiatric Sequelae Resulting from Exposure to the Antimalarial Drug Mefloquine

    Directory of Open Access Journals (Sweden)

    Jane C. Quinn

    2015-01-01

    Full Text Available The alkaloid toxin quinine and its derivative compounds have been used for many centuries as effective medications for the prevention and treatment of malaria. More recently, synthetic derivatives, such as the quinoline derivative mefloquine (bis(trifluoromethyl-(2-piperidyl-4-quinolinemethanol, have been widely used to combat disease caused by chloroquine-resistant strains of the malaria parasite, Plasmodium falciparum. However, the parent compound quinine, as well as its more recent counterparts, suffers from an incidence of adverse neuropsychiatric side effects ranging from mild mood disturbances and anxiety to hallucinations, seizures, and psychosis. This review considers how the pharmacology, cellular neurobiology, and membrane channel kinetics of mefloquine could lead to the significant and sometimes life-threatening neurotoxicity associated with mefloquine exposure. A key role for mefloquine blockade of ATP-sensitive potassium channels and connexins in the substantia nigra is considered as a unifying hypothesis for the pathogenesis of severe neuropsychiatric events after mefloquine exposure in humans.

  20. Dendritic Kv3.3 potassium channels in cerebellar purkinje cells regulate generation and spatial dynamics of dendritic Ca2+ spikes.

    Science.gov (United States)

    Zagha, Edward; Manita, Satoshi; Ross, William N; Rudy, Bernardo

    2010-06-01

    Purkinje cell dendrites are excitable structures with intrinsic and synaptic conductances contributing to the generation and propagation of electrical activity. Voltage-gated potassium channel subunit Kv3.3 is expressed in the distal dendrites of Purkinje cells. However, the functional relevance of this dendritic distribution is not understood. Moreover, mutations in Kv3.3 cause movement disorders in mice and cerebellar atrophy and ataxia in humans, emphasizing the importance of understanding the role of these channels. In this study, we explore functional implications of this dendritic channel expression and compare Purkinje cell dendritic excitability in wild-type and Kv3.3 knockout mice. We demonstrate enhanced excitability of Purkinje cell dendrites in Kv3.3 knockout mice, despite normal resting membrane properties. Combined data from local application pharmacology, voltage clamp analysis of ionic currents, and assessment of dendritic Ca(2+) spike threshold in Purkinje cells suggest a role for Kv3.3 channels in opposing Ca(2+) spike initiation. To study the physiological relevance of altered dendritic excitability, we measured [Ca(2+)](i) changes throughout the dendritic tree in response to climbing fiber activation. Ca(2+) signals were specifically enhanced in distal dendrites of Kv3.3 knockout Purkinje cells, suggesting a role for dendritic Kv3.3 channels in regulating propagation of electrical activity and Ca(2+) influx in distal dendrites. These findings characterize unique roles of Kv3.3 channels in dendrites, with implications for synaptic integration, plasticity, and human disease. PMID:20357073

  1. Calcium- and voltage-gated potassium (BK) channel activators in the 5β-cholanic acid-3α-ol analogue series with modifications in the lateral chain.

    Science.gov (United States)

    Bukiya, Anna N; Patil, Shivaputra A; Li, Wei; Miller, Duane D; Dopico, Alex M

    2012-10-01

    Large conductance, calcium- and voltage-gated potassium (BK) channels regulate various physiological processes and represent an attractive target for drug discovery. Numerous BK channel activators are available. However, these agents usually interact with the ubiquitously distributed channel-forming subunit and thus cannot selectively target a particular tissue. We performed a structure-activity relationship study of lithocholic acid (LCA), a cholane that activates BK channels via the accessory BK β1 subunit. The latter protein is highly abundant in smooth muscle but scarce in most other tissues. Modifications to the LCA lateral chain length and functional group yielded two novel smooth muscle BK channel activators in which the substituent at C24 has a small volume and a net negative charge. Our data provide detailed structural information that will be useful to advance a pharmacophore in search of β1 subunit-selective BK channel activators. These compounds are expected to evoke smooth muscle relaxation, which would be beneficial in the pharmacotherapy of prevalent human disorders associated with increased smooth muscle contraction, such as systemic hypertension, cerebral or coronary vasospasm, bronchial asthma, bladder hyperactivity, and erectile dysfunction. PMID:22945504

  2. A whole-genome RNAi screen uncovers a novel role for human potassium channels in cell killing by the parasite Entamoeba histolytica.

    Science.gov (United States)

    Marie, Chelsea; Verkerke, Hans P; Theodorescu, Dan; Petri, William A

    2015-09-08

    The parasite Entamoeba histolytica kills human cells resulting in ulceration, inflammation and invasion of the colonic epithelium. We used the cytotoxic properties of ameba to select a genome-wide RNAi library to reveal novel host factors that control susceptibility to amebic killing. We identified 281 candidate susceptibility genes and bioinformatics analyses revealed that ion transporters were significantly enriched among susceptibility genes. Potassium (K(+)) channels were the most common transporter identified. Their importance was further supported by colon biopsy of humans with amebiasis that demonstrated suppressed K(+) channel expression. Inhibition of human K(+) channels by genetic silencing, pharmacologic inhibitors and with excess K(+) protected diverse cell types from E. histolytica-induced death. Contact with E. histolytica parasites triggered K(+) channel activation and K(+) efflux by intestinal epithelial cells, which preceded cell killing. Specific inhibition of Ca(2+)-dependent K(+) channels was highly effective in preventing amebic cytotoxicity in intestinal epithelial cells and macrophages. Blockade of K(+) efflux also inhibited caspase-1 activation, IL-1β secretion and pyroptotic death in THP-1 macrophages. We concluded that K(+) channels are host mediators of amebic cytotoxicity in multiple cells types and of inflammasome activation in macrophages.

  3. Morvan's syndrome with anti contactin associated protein like 2 – voltage gated potassium channel antibody presenting with syndrome of inappropriate antidiuretic hormone secretion

    Directory of Open Access Journals (Sweden)

    Anjani Kumar Sharma

    2016-01-01

    Full Text Available Morvan's syndrome is a rare autoimmune disorder characterized by triad of peripheral nerve hyperexcitability, autonomic dysfunction, and central nervous system symptoms. Antibodies against contactin-associated protein-like 2 (CASPR2, a subtype of voltage-gated potassium channel (VGKC complex, are found in a significant proportion of patients with Morvan's syndrome and are thought to play a key role in peripheral as well as central clinical manifestations. We report a patient of Morvan's syndrome with positive CASPR2–anti-VGKC antibody having syndrome of inappropriate antidiuretic hormone as a cause of persistent hyponatremia.

  4. [An autopsy case of amyotrophic lateral sclerosis with prominent muscle cramps, fasciculation, and high titer of anti-voltage gated potassium channel (VGKC) complex antibody].

    Science.gov (United States)

    Sato, Aki; Sakai, Naoko; Shinbo, Junsuke; Hashidate, Hideki; Igarashi, Shuichi; Kakita, Akiyoshi; Yamazaki, Motoyoshi

    2014-01-01

    The patient was a 55-year-old male who had prominent fasciculation and muscle cramps. Muscle weakness and atrophy of the trunk, respiratory system, and extremities gradually progressed. On the basis of these features, we diagnosed this patient as having amyotrophic lateral sclerosis (ALS), however, the upper motor neuron signs were not significant. Following the detection of the anti-voltage gated potassium channel (VGKC) complex antibody at 907.5 pM (normal VGKC complex antibody in the development of cramp-fasciculation syndrome has been speculated. In this ALS patient, the antibodies might be associated with pathomechanisms underlying the characteristic symptoms.

  5. Voltage gated potassium channel antibodies positive autoimmune encephalopathy in a child: A case report and literature review of an under-recognized condition

    Directory of Open Access Journals (Sweden)

    Subramanian Ganesan

    2013-01-01

    Full Text Available Autoimmune limbic encephalitis (LE associated with voltage gated potassium channel antibodies (VGKC-Abs in children is more common than previously thought and is not always paraneoplastic. Non-neoplastic, autoimmune LE associated with VGKC-Abs has been described recently. However, only few case reports in children as the disease is predominantly described in the adult population. It is likely that this type of autoimmune encephalitis is currently under-diagnosed and hence, under-treated, especially in children. We present a 13-year-old previously fit and healthy African girl diagnosed with LE and we reviewed the literature for its current management.

  6. Morvan's syndrome with anti contactin associated protein like 2 – voltage gated potassium channel antibody presenting with syndrome of inappropriate antidiuretic hormone secretion

    Science.gov (United States)

    Sharma, Anjani Kumar; Kaur, Manminder; Paul, Madhuparna

    2016-01-01

    Morvan's syndrome is a rare autoimmune disorder characterized by triad of peripheral nerve hyperexcitability, autonomic dysfunction, and central nervous system symptoms. Antibodies against contactin-associated protein-like 2 (CASPR2), a subtype of voltage-gated potassium channel (VGKC) complex, are found in a significant proportion of patients with Morvan's syndrome and are thought to play a key role in peripheral as well as central clinical manifestations. We report a patient of Morvan's syndrome with positive CASPR2–anti-VGKC antibody having syndrome of inappropriate antidiuretic hormone as a cause of persistent hyponatremia.

  7. Morvan's syndrome with anti contactin associated protein like 2 – voltage gated potassium channel antibody presenting with syndrome of inappropriate antidiuretic hormone secretion

    Science.gov (United States)

    Sharma, Anjani Kumar; Kaur, Manminder; Paul, Madhuparna

    2016-01-01

    Morvan's syndrome is a rare autoimmune disorder characterized by triad of peripheral nerve hyperexcitability, autonomic dysfunction, and central nervous system symptoms. Antibodies against contactin-associated protein-like 2 (CASPR2), a subtype of voltage-gated potassium channel (VGKC) complex, are found in a significant proportion of patients with Morvan's syndrome and are thought to play a key role in peripheral as well as central clinical manifestations. We report a patient of Morvan's syndrome with positive CASPR2–anti-VGKC antibody having syndrome of inappropriate antidiuretic hormone as a cause of persistent hyponatremia. PMID:27695240

  8. Chronic salt-loading downregulates large-conductance Ca~(2+)-activated potassium channel in mesenteric arterial smooth muscle cells from SD rats

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood pressure(BP),can regulate BKCa activity and then elevate blood pressure.Methods Male Sprague-Dawley rats aged 6 weeks were randomized into high salt diet group(HS)and control group,fed with high salt diet(containing 5% NaCl)and standard rat chow(containing 0.4% NaCl)respectively for 16 weeks.T...

  9. Selective inhibition of the Kir2 family of inward rectifier potassium channels by a small molecule probe: the discovery, SAR and pharmacological characterization of ML133

    Science.gov (United States)

    Wang, Hao-Ran; Wu, Meng; Yu, Haibo; Long, Shunyou; Stevens, Amy; Engers, Darren W.; Sackin, Henry; Daniels, J. Scott; Dawson, Eric S.; Hopkins, Corey R.; Lindsley, Craig W.; Li, Min; McManus, Owen B

    2011-01-01

    The Kir inward rectifying potassium channels have a broad tissue distribution and are implicated in a variety of functional roles. At least seven classes (Kir1 – Kir7) of structurally related inward rectifier potassium channels are known, and there are no selective small molecule tools to study their function. In an effort to develop selective Kir2.1 inhibitors, we performed a high-throughput screen (HTS) of more than 300,000 small molecules within the MLPCN for modulators of Kir2.1 function. Here we report one potent Kir2.1 inhibitor, ML133, which inhibits Kir2.1 with IC50 of 1.8 μM at pH 7.4 and 290 nM at pH 8.5, but exhibits little selectivity against other members of Kir2.x family channels. However, ML133 has no effect on Kir1.1 (IC50 > 300 μM), and displays weak activity for Kir4.1 (76 μM) and Kir7.1 (33 μM), making ML133 the most selective small molecule inhibitor of the Kir family reported to date. Due to the high homology within the Kir family, the channels share a common design of a pore region flanked by two transmembrane domains, identification of site(s) critical for isoform specificity would be an important basis for future development of more specific and potent Kir inhibitors. Using chimeric channels between Kir2.1 and Kir1.1 and site-directed mutagenesis, we have identified D172 and I176 within M2 segment of Kir2.1 as molecular determinants critical for the potency of ML133 mediated inhibition. Double mutation of the corresponding residues of Kir1.1 to those of Kir2.1 (N171D and C175I) transplants ML133 inhibition to Kir1.1. Together, the combination of a potent, Kir2 family selective inhibitor and identification of molecular determinants for the specificity provides both a tool and a model system to enable further mechanistic studies of modulation of Kir2 inward rectifier potassium channels. PMID:21615117

  10. Effects of helium-neon laser irradiation and local anesthetics on potassium channels in pond snail neurons.

    Science.gov (United States)

    Ignatov, Yu D; Vislobokov, A I; Vlasov, T D; Kolpakova, M E; Mel'nikov, K N; Petrishchev, I N

    2005-10-01

    Intracellular dialysis and membrane voltage clamping were used to show that He-Ne laser irradiation of a pond snail neuron at a dose of 0.7 x 10(-4) J (power density 1.5 x 10(2) W/m2) increases the amplitude of the potential-dependent slow potassium current, while a dose of 0.7 x 10(-3) J decreases this current. Bupivacaine suppresses the potassium current. Combined application of laser irradiation at a dose of 0.7 x 10(-3) J increased the blocking effect of 10 microM bupivacaine on the slow potassium current, while an irradiation dose of 0.7 x 10(-4) J weakened the effect of bupivacaine.

  11. Potassium Channelopathies and Gastrointestinal Ulceration

    Science.gov (United States)

    Han, Jaeyong; Lee, Seung Hun; Giebisch, Gerhard; Wang, Tong

    2016-01-01

    Potassium channels and transporters maintain potassium homeostasis and play significant roles in several different biological actions via potassium ion regulation. In previous decades, the key revelations that potassium channels and transporters are involved in the production of gastric acid and the regulation of secretion in the stomach have been recognized. Drugs used to treat peptic ulceration are often potassium transporter inhibitors. It has also been reported that potassium channels are involved in ulcerative colitis. Direct toxicity to the intestines from nonsteroidal anti-inflammatory drugs has been associated with altered potassium channel activities. Several reports have indicated that the long-term use of the antianginal drug Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, increases the chances of ulceration and perforation from the oral to anal regions throughout the gastrointestinal (GI) tract. Several of these drug features provide further insights into the role of potassium channels in the occurrence of ulceration in the GI tract. The purpose of this review is to investigate whether potassium channelopathies are involved in the mechanisms responsible for ulceration that occurs throughout the GI tract. PMID:27784845

  12. Docking Studies on the Interaction of Imidazolines and Potassium Ion Channel-Kir6.2%咪唑啉类药物与钾离子通道Kir6.2相互作用的分子对接研究

    Institute of Scientific and Technical Information of China (English)

    张蕊; 凌宝萍; 孟祥华; 王志国; 张长桥; 刘永军; 刘成卜

    2009-01-01

    Kir6.2, a key component of the ATP-sensitive potassium channel ( K_(ATP)),can directly interact with imidazolines, a kind of potential antidiabetic drug. This paper explored the interaction of Kir6.2 with im-idazoline molecules by applying AutoDock software. The docking results reveal the binding sites of the seven imidazolines on Kir6.2. For Efaroxan, Clonidine, Cibenzoline and 8111282, polar residues, H175, K67and W68, constitute the binding pocket; while Rx871024, Alinidine and Ly389382, lies in a hydrophobic pocket which is composed of nonpolar residues, F168, M169 and I296. Efaroxan, Clonidine, Cibenzoline and B111282 interact with Kir6.2 mainly by forming hydrogen bonds, but for Rx871024, Alinidine and Ly389382, the hydrophobic interaction is the most important mode of action. These binding sites and the interaction modes can interpret the inhibition of these imidazoline drugs to some extent, and this research may provide theoretical support in the pharmacological study of imidazolines regulating the secretion of insulin.%运用AutoDock4软件进行了分子对接研究, 得到了7种咪唑啉药物分子与Kir6.2的作用位点, 并发现了2个活性位点区域;依法可生(Efaroxan)、可乐定(Clonidine)、西苯唑啉(Cibenzoline)和Bl11282位于残基H175, K67和W68形成的活性口袋中, 主要作用方式为氢键相互作用;而Rx871024、烯丙尼定(Alinidine)和Ly389382位于残基F168, M169和I296形成的疏水口袋中, 在Kir6.2的通道孔中央, 没有氢键形成, 主要作用为疏水相互作用. 咪唑啉类药物与Kir6.2相互作用活性位点的理论预测将有助于该药物在胰腺β细胞中调控胰岛素分泌机制的研究.

  13. Inhibition of Schistosoma mansoni ether-a-go-go related gene-encoded potassium channels leads to hypermotility and impaired egg production.

    Science.gov (United States)

    Parker-Manuel, S J; Hahnel, S; Grevelding, C G

    2015-11-01

    The purpose of this work was to investigate the effect of ether-a-go-go related gene (ERG) potassium channel inhibition on Schistosoma mansoni. Use of dofetilide to block the schistosome ERGs resulted in a striking 'corkscrew' effect. The worms were unable to control their motility; they were hypermotile. The treated worms produced abnormal eggs, some of which consisted of little more than a spine. One of the S. mansoni ERGs (SmERGs), Smp_161140, was chosen for further study by RNAi. The transcript was knocked down to 50% compared to the controls. These RNAi-treated worms demonstrated seizure-like movements. In S. mansoni, as in other organisms, ERG channels seem to play a role in regulating muscle excitability. This work shows that egg production can be greatly reduced by effectively targeting muscle coordination in these important parasites. PMID:26188142

  14. Immunohistochemical investigation of voltage-gated potassium channel-interacting protein 1 in normal rat brain and Pentylenettrazole-induced seizures

    Institute of Scientific and Technical Information of China (English)

    Tao SU; Ai-Hua LUO; Wen-Dong CONG; Wei-Wen SUN; Wei-Yi DENG; Qi-Hua ZHAO; Zhuo-Hua ZHANG; Wei-Ping LIAO

    2006-01-01

    Objective To explore the possible role of voltage-gated potassium channel-interacting protein 1 (KChIP1) in the pathogenesis of epilepsy. Methods Sprague Dawley female adult rats were treated with pentylenettrazole (PTZ) to develop acute and chronic epilepsy models. The approximate coronal sections of normal and epilepsy rat brain were processed for immunohistochemistry. Double-labeling confocal microscopy was used to determine the coexistence of KChIP1 and gamma-aminobutyric acid (GABA). Results KChIP1 was expressed abundantly throughout adult rat brain.KChIP1 is highly co-localize with GABA transmitter in hippocampus and cerebral cortex. In the acute PTZ-induced convulsive rats, the number of KChIP1-postive cells was significantly increased especially in the regions of CA 1 and CA3 (P < 0.05); whereas the chronic PTZ-induced convulsive rats were found no changes. The number of GABA-labeled and co-labeled neurons in the hippocampus appeared to have no significant alteration responding to the epilepsy-genesis treatments. Conclusion KChIP1 might be involved in the PTZ-induced epileptogenesis process as a regulator to neuronal excitability through influencing the properties of potassium channels. KChIP1 is preferentially expressed in GABAergic neurons, but its changes did not couple with GABA in the epileptic models.

  15. Vitamin K3 inhibits mouse uterine contraction in vitro via interference with the calcium transfer and the potassium channels.

    Science.gov (United States)

    Zhang, Xian-Xia; Lu, Li-Min; Wang, Li

    2016-08-01

    Previous studies have demonstrated vitamin K3 had a great relief to smooth muscle spastic disorders, but no researches have yet pinpointed its possible anti-contractile activity in the uterus. Here, we evaluated the effect of vitamin K3 on myometrial contractility and explored the possible mechanisms of vitamin K3 action. Myograph apparatus were used to record the changes in contractility of isolated mouse uterine strips in a tissue bath. Uterine strips were exposed to vitamin K3 or vehicle. Vitamin K3 suppressed spontaneous contractions in a concentration dependent manner. It significantly decreased the contractile frequency induced by PGF2ɑ but not their amplitude (expect 58.0 μM). Prior incubation with vitamin K3 reduced the effectiveness of PGF2ɑ-induced contraction. The antispasmodic effect of vitamin K3 was also sensitive to potassium channel blockers, such as tetraethylammonium, 4-aminopyridine, iberiotoxin) but not to the nitric oxide related pathway blockers. High concentrations (29.0, 58.0 μM) of vitamin K3 weakened the Ca(2+) dose response and inhibited phase 1 contraction (intracellular stored calcium release). These dates suggest that vitamin K3 specifically suppresses myometrial contractility by affecting calcium and potassium channels; thus, this approach has potential therapy for uterine contractile activity related disorders. PMID:27237971

  16. Discovery of novel tetrahydroisoquinoline derivatives as orally active N-type calcium channel blockers with high selectivity for hERG potassium channels.

    Science.gov (United States)

    Ogiyama, Takashi; Inoue, Makoto; Honda, Shugo; Yamada, Hiroyoshi; Watanabe, Toshihiro; Gotoh, Takayasu; Kiso, Tetsuo; Koakutsu, Akiko; Kakimoto, Shuichiro; Shishikura, Jun-ichi

    2014-12-15

    N-type calcium channels represent a promising target for the treatment of neuropathic pain. The selective N-type calcium channel blocker ziconotide ameliorates severe chronic pain but has a narrow therapeutic window and requires intrathecal administration. We identified tetrahydroisoquinoline derivative 1a as a novel potent N-type calcium channel blocker. However, this compound also exhibited potent inhibitory activity against hERG channels. Structural optimizations led to identification of (1S)-(1-cyclohexyl-3,4-dihydroisoquinolin-2(1H)-yl)-2-{[(1-hydroxycyclohexyl)methyl]amino}ethanone ((S)-1h), which exhibited high selectivity for hERG channels while retaining potency for N-type calcium channel inhibition. (S)-1h went on to demonstrate in vivo efficacy as an orally available N-type calcium channel blocker in a rat spinal nerve ligation model of neuropathic pain. PMID:25456079

  17. A cell model study of calcium influx mechanism regulated by calcium-dependent potassium channels in Purkinje cell dendrites.

    Science.gov (United States)

    Chono, Koji; Takagi, Hiroshi; Koyama, Shozo; Suzuki, Hideo; Ito, Etsuro

    2003-10-30

    The present study was designed to elucidate the roles of dendritic voltage-gated K+ channels in Ca2+ influx mechanism of a rat Purkinje cell using a computer simulation program. First, we improved the channel descriptions and the maximum conductance in the Purkinje cell model to mimic both the kinetics of ion channels and the Ca2+ spikes, which had failed in previous studies. Our cell model is, therefore, much more authentic than those in previous studies. Second, synaptic inputs that mimic stimulation of parallel fibers and induce sub-threshold excitability were simultaneously applied to the spiny dendrites. As a result, transient Ca2+ responses were observed in the stimulation points and they decreased with the faster decay rate in the cell model including high-threshold Ca2+-dependent K+ channels than in those excluding these channels. Third, when a single synaptic input was applied into a spiny dendrite, Ca2+-dependent K+ channels suppressed Ca2+ increases at stimulation and recording points. Finally, Ca2+-dependent K+ channels were also found to suppress the time to peak Ca2+ values in the recording points. These results suggest that the opening of Ca2+-dependent K+ channels by Ca2+ influx through voltage-gated Ca2+ channels hyperpolarizes the membrane potentials and deactivates these Ca2+ channels in a negative feedback manner, resulting in local, weak Ca2+ responses in spiny dendrites of Purkinje cells.

  18. Activation of endothelial and epithelial K(Ca) 2.3 calcium-activated potassium channels by NS309 relaxes human small pulmonary arteries and bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Nielsen, Gorm;

    2012-01-01

    BACKGROUND AND PURPOSE: Small (K(Ca) 2) and intermediate (K(Ca) 3.1) conductance calcium-activated potassium channels (K(Ca) ) may contribute to both epithelium- and endothelium-dependent relaxations, but this has not been established in human pulmonary arteries and bronchioles. Therefore, we...... investigated the expression of K(Ca) 2.3 and K(Ca) 3.1 channels, and hypothesized that activation of these channels would produce relaxation of human bronchioles and pulmonary arteries. EXPERIMENTAL APPROACH: Channel expression and functional studies were conducted in human isolated small pulmonary arteries...... and bronchioles. K(Ca) 2 and K(Ca) 3.1 currents were examined in human small airways epithelial (HSAEpi) cells by whole-cell patch clamp techniques. RESULTS: While K(Ca) 2.3 expression was similar, K(Ca) 3.1 protein was more highly expressed in pulmonary arteries than bronchioles. Immunoreactive K(Ca) 2.3 and K...

  19. Determining Favorable Binding Configurations of the Anti-Cancer Drug Ellipticine to the KV11.1 Potassium Channel V-VI Transmembrane Domain Through Autodock Simulations

    Science.gov (United States)

    Lipscomb, Dawn; Gentile, Saverio; Brancaleon, Lorenzo

    2011-10-01

    Ellipticines such as 9-methoxy-N-2-methylellipticinium acetate (MMEA) and 9-hydroxy-N-2-methylellipticinium acetate (NMEA, Celiptium ) are antineoplastic drugs that exert their selective cytotoxicity against leukemia and endometrial carcinoma. Ellipticine's action is also related to severe physical side effects, but the link between undesired effects and pharmacological application is not well understood. We investigated the binding of Ellipticine derivatives with the Kv11.1 potassium ion channel using Autodock and revealed that hydroxyellipticinium derivatives provide binding configurations with Kv11.1, but the energy, location and estimated dissociation constant varied. The binding energy is as follows: Chloroceliptium (-6.60 kcal/mol) > Celiptium (- 6.37 kcal/mol) > Methoxyceliptium (- 6.20 kcal/mol) > Datelliptium (-6.08 kcal/mol). Autodock simulations demonstrate that binding affinity is high at opposing ends of the channel and low within the channel interior. These favorable binding configurations suggest that Ellipticine derivatives may bridge among end subunits of the channel and potentially inhibit the flow of ions.

  20. Inhibition of SK4 Potassium Channels Suppresses Cell Proliferation, Migration and the Epithelial-Mesenchymal Transition in Triple-Negative Breast Cancer Cells.

    Directory of Open Access Journals (Sweden)

    Panshi Zhang

    Full Text Available Treatments for triple-negative breast cancer (TNBC are limited; intermediate-conductance calcium-activated potassium (SK4 channels are closely involved in tumor progression, but little is known about these channels in TNBC. We aimed to investigate whether SK4 channels affect TNBC. First, by immunohistochemistry (IHC and western blotting (WB, increased SK4 protein expression in breast tumor tissues was detected relative to that in non-tumor breast tissues, but there was no apparent expression difference between various subtypes of breast cancer (p>0.05. Next, functional SK4 channels were detected in the TNBC cell line MDA-MB-231 using WB, real-time PCR, immunofluorescence and patch-clamp recording. By employing SK4 specific siRNAs and blockers, including TRAM-34 and clotrimazole, in combination with an MTT assay, a colony-formation assay, flow cytometry and a cell motility assay, we found that the suppression of SK4 channels significantly inhibited cell proliferation and migration and promoted apoptosis in MDA-MB-231 cells (p<0.05. Further investigation revealed that treatment with epidermal growth factor (EGF/basic fibroblast growth factor (bFGF caused MDA-MB-231 cells to undergo the epithelial-mesenchymal transition (EMT and to show increased SK4 mRNA expression. In addition, the down-regulation of SK4 expression inhibited the EMT markers Vimentin and Snail1. Collectively, our findings suggest that SK4 channels are expressed in TNBC and are involved in the proliferation, apoptosis, migration and EMT processes of TNBC cells.

  1. Ion channel therapy of ischemic heart disease%离子通道疗法在缺血性心脏病治疗中的应用

    Institute of Scientific and Technical Information of China (English)

    C.RichardConti; 陈丽竹; 丁荣晶

    2012-01-01

    Basic studies have shown a variety of ion channels are involved in the pathogenesis of ischemic heart disease,including L type Ca2+ channel,T type Ca2 + channel,ATP-sensitive potassium channel,If (funny) channel and late Na + channeL Clinical studies showed that the regulation of these channels function can improve myocardial blood supply and metabolism of myocardium.What is summarized below relates to the clinical usefulness of various ion channel antagonists reviewed by a clinical cardiologist,not a basic scientist working on ion channel biology.%基础研究显示有多种离子通道参与缺血性心脏病的发病机制,包括L型钙通道、T型钙通道、ATP敏感性钾通道、内向钠钾电流通道和晚钠电流通道.临床研究发现调控这些通道的功能可以改善心肌供血和心肌细胞代谢.本文对离子通道生物学研究作一简要论述,同时对不同离子通道阻滞剂缺血性心脏病治疗中的应用进行回顾总结,以期临床重视这类药物的研究和应用.

  2. Slack sodium-activated potassium channel membrane expression requires p38 mitogen-activated protein kinase phosphorylation.

    Science.gov (United States)

    Gururaj, Sushmitha; Fleites, John; Bhattacharjee, Arin

    2016-04-01

    p38 MAPK has long been understood as an inducible kinase under conditions of cellular stress, but there is now increasing evidence to support its role in the regulation of neuronal function. Several phosphorylation targets have been identified, an appreciable number of which are ion channels, implicating the possible involvement of p38 MAPK in neuronal excitability. The KNa channel Slack is an important protein to be studied as it is highly and ubiquitously expressed in DRG neurons and is important in the maintenance of their firing accommodation. We sought to examine if the Slack channel could be a substrate of p38 MAPK activity. First, we found that the Slack C-terminus contains two putative p38 MAPK phosphorylation sites that are highly conserved across species. Second, we show via electrophysiology experiments that KNa currents and further, Slack currents, are subject to tonic modulation by p38 MAPK. Third, biochemical approaches revealed that Slack channel regulation by p38 MAPK occurs through direct phosphorylation at the two putative sites of interaction, and mutating both sites prevented surface expression of Slack channels. Based on these results, we conclude that p38 MAPK is an obligate regulator of Slack channel function via the trafficking of channels into the membrane. The present study identifies Slack KNa channels as p38 MAPK substrates. PMID:26721627

  3. Airway Hydration, Apical K(+) Secretion, and the Large-Conductance, Ca(2+)-activated and Voltage-dependent Potassium (BK) Channel.

    Science.gov (United States)

    Kis, Adrian; Krick, Stefanie; Baumlin, Nathalie; Salathe, Matthias

    2016-04-01

    Large-conductance, calcium-activated, and voltage-gated K(+) (BK) channels are expressed in many tissues of the human body, where they play important roles in signaling not only in excitable but also in nonexcitable cells. Because BK channel properties are rendered in part by their association with four β and four γ subunits, their channel function can differ drastically, depending on in which cellular system they are expressed. Recent studies verify the importance of apically expressed BK channels for airway surface liquid homeostasis and therefore of their significant role in mucociliary clearance. Here, we review evidence that inflammatory cytokines, which contribute to airway diseases, can lead to reduced BK activity via a functional down-regulation of the γ regulatory subunit LRRC26. Therefore, manipulation of LRRC26 and pharmacological opening of BK channels represent two novel concepts of targeting epithelial dysfunction in inflammatory airway diseases. PMID:27115952

  4. Blockade of the intermediate-conductance calcium-activated potassium channel as a new therapeutic strategy for restenosis

    DEFF Research Database (Denmark)

    Köhler, Ralf; Wulff, Heike; Eichler, Ines;

    2003-01-01

    BACKGROUND: Angioplasty stimulates proliferation and migration of vascular smooth muscle cells (VSMC), leading to neointimal thickening and vascular restenosis. In a rat model of balloon catheter injury (BCI), we investigated whether alterations in expression of Ca2+-activated K+ channels (KCa......) channels. Two weeks after BCI, expression of BKCa was significantly reduced in neointimal VSMC, whereas expression of intermediate-conductance KCa (IKCa1) channels was upregulated. In the aortic VSMC cell line, A7r5 epidermal growth factor (EGF) induced IKCa1 upregulation and EGF-stimulated proliferation...

  5. Development and validation of fluorescence-based and automated patch clamp-based functional assays for the inward rectifier potassium channel Kir4.1.

    Science.gov (United States)

    Raphemot, Rene; Kadakia, Rishin J; Olsen, Michelle L; Banerjee, Sreedatta; Days, Emily; Smith, Stephen S; Weaver, C David; Denton, Jerod S

    2013-01-01

    The inward rectifier potassium (Kir) channel Kir4.1 plays essential roles in modulation of neurotransmission and renal sodium transport and may represent a novel drug target for temporal lobe epilepsy and hypertension. The molecular pharmacology of Kir4.1 is limited to neurological drugs, such as fluoxetine (Prozac(©)), exhibiting weak and nonspecific activity toward the channel. The development of potent and selective small-molecule probes would provide critically needed tools for exploring the integrative physiology and therapeutic potential of Kir4.1. A fluorescence-based thallium (Tl(+)) flux assay that utilizes a tetracycline-inducible T-Rex-HEK293-Kir4.1 cell line to enable high-throughput screening (HTS) of small-molecule libraries was developed. The assay is dimethyl sulfoxide tolerant and exhibits robust screening statistics (Z'=0.75±0.06). A pilot screen of 3,655 small molecules and lipids revealed 16 Kir4.1 inhibitors (0.4% hit rate). 3,3-Diphenyl-N-(1-phenylethyl)propan-1-amine, termed VU717, inhibits Kir4.1-mediated thallium flux with an IC50 of ∼6 μM. An automated patch clamp assay using the IonFlux HT workbench was developed to facilitate compound characterization. Leak-subtracted ensemble "loose patch" recordings revealed robust tetracycline-inducible and Kir4.1 currents that were inhibited by fluoxetine (IC50=10 μM), VU717 (IC50=6 μM), and structurally related calcium channel blocker prenylamine (IC50=6 μM). Finally, we demonstrate that VU717 inhibits Kir4.1 channel activity in cultured rat astrocytes, providing proof-of-concept that the Tl(+) flux and IonFlux HT assays can enable the discovery of antagonists that are active against native Kir4.1 channels. PMID:24266659

  6. Cutaneous blood flow during intradermal NO administration in young and older adults: roles for calcium-activated potassium channels and cyclooxygenase?

    Science.gov (United States)

    Fujii, Naoto; Meade, Robert D; Minson, Christopher T; Brunt, Vienna E; Boulay, Pierre; Sigal, Ronald J; Kenny, Glen P

    2016-06-01

    Nitric oxide (NO) increases cutaneous blood flow; however, the underpinning mechanism(s) remains to be elucidated. We hypothesized that the cutaneous blood flow response during intradermal administration of sodium nitroprusside (SNP, a NO donor) is regulated by calcium-activated potassium (KCa) channels and cyclooxygenase (COX) in young adults. We also hypothesized that these contributions are diminished in older adults given that aging can downregulate KCa channels and reduce COX-derived vasodilator prostanoids. In 10 young (23 ± 5 yr) and 10 older (54 ± 4 yr) adults, cutaneous vascular conductance (CVC) was measured at four forearm skin sites infused with 1) Ringer (Control), 2) 50 mM tetraethylammonium (TEA), a nonspecific KCa channel blocker, 3) 10 mM ketorolac, a nonspecific COX inhibitor, or 4) 50 mM TEA + 10 mM ketorolac via intradermal microdialysis. All skin sites were coinfused with incremental doses of SNP (0.005, 0.05, 0.5, 5, and 50 mM each for 25 min). During SNP administration, CVC was similar at the ketorolac site (0.005-50 mM, all P > 0.05) relative to Control, but lower at the TEA and TEA + ketorolac sites (0.005-0.05 mM, all P 0.05). Furthermore, TEA alone did not modulate CVC during any concentration of SNP administration in older adults (all P > 0.05). We show that during low-dose NO administration (e.g., 0.005-0.05 mM), KCa channels contribute to cutaneous blood flow regulation in young adults; however, in older adults, COX inhibition increases cutaneous blood flow through a KCa channel-dependent mechanism. PMID:27053645

  7. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

    Directory of Open Access Journals (Sweden)

    Bo Hyung Lee

    2014-01-01

    Full Text Available The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G1 phase. We also showed that Kv7.5 knockdown helps CCL-183 cells to proliferate. In an effort to find an endogenous regulator of Kv7.5, we used mithramycin A to reduce the level of the transcription factor Sp1, and it strongly inhibited the induction of Kv7.5 in CCL-183 cells. These results suggest that the activation of Kv7.5 by flupirtine may exert an anti-proliferative effect in canine osteosarcoma. Therefore, Kv7.5 is a possible molecular target for canine osteosarcoma therapy.

  8. Serum starvation-induced voltage-gated potassium channel Kv7.5 expression and its regulation by Sp1 in canine osteosarcoma cells.

    Science.gov (United States)

    Lee, Bo Hyung; Ryu, Pan Dong; Lee, So Yeong

    2014-01-01

    The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv) channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G1 phase. We also showed that Kv7.5 knockdown helps CCL-183 cells to proliferate. In an effort to find an endogenous regulator of Kv7.5, we used mithramycin A to reduce the level of the transcription factor Sp1, and it strongly inhibited the induction of Kv7.5 in CCL-183 cells. These results suggest that the activation of Kv7.5 by flupirtine may exert an anti-proliferative effect in canine osteosarcoma. Therefore, Kv7.5 is a possible molecular target for canine osteosarcoma therapy. PMID:24434641

  9. Structural Analysis and Deletion Mutagenesis Define Regions of QUIVER/SLEEPLESS that Are Responsible for Interactions with Shaker-Type Potassium Channels and Nicotinic Acetylcholine Receptors.

    Directory of Open Access Journals (Sweden)

    Meilin Wu

    Full Text Available Ly6 proteins are endogenous prototoxins found in most animals. They show striking structural and functional parallels to snake α-neurotoxins, including regulation of ion channels and cholinergic signaling. However, the structural contributions of Ly6 proteins to regulation of effector molecules is poorly understood. This question is particularly relevant to the Ly6 protein QUIVER/SLEEPLESS (QVR/SSS, which has previously been shown to suppress excitability and synaptic transmission by upregulating potassium (K channels and downregulating nicotinic acetylcholine receptors (nAChRs in wake-promoting neurons to facilitate sleep in Drosophila. Using deletion mutagenesis, co-immunoprecipitations, ion flux assays, surface labeling and confocal microscopy, we demonstrate that only loop 2 is required for many of the previously described properties of SSS in transfected cells, including interactions with K channels and nAChRs. Collectively our data suggest that QVR/SSS, and by extension perhaps other Ly6 proteins, target effector molecules using limited protein motifs. Mapping these motifs may be useful in rational design of drugs that mimic or suppress Ly6-effector interactions to modulate nervous system function.

  10. Regulation and function of the two-pore-domain (K2P) potassium channel Trek-1 in alveolar epithelial cells

    OpenAIRE

    Schwingshackl, Andreas; Teng, Bin; Ghosh, Manik; West, Alina Nico; Makena, Patrudu; Gorantla, Vijay; Sinclair, Scott E.; Waters, Christopher M.

    2011-01-01

    Hyperoxia can lead to a myriad of deleterious effects in the lung including epithelial damage and diffuse inflammation. The specific mechanisms by which hyperoxia promotes these pathological changes are not completely understood. Activation of ion channels has been proposed as one of the mechanisms required for cell activation and mediator secretion. The two-pore-domain K+ channel (K2P) Trek-1 has recently been described in lung epithelial cells, but its function remains elusive. In this stud...

  11. A clinico-radiological phenotype of voltage-gated potassium channel complex antibody-mediated disorder presenting with seizures and basal ganglia changes.

    Science.gov (United States)

    Hacohen, Yael; Wright, Sukhvir; Siddiqui, Ata; Pandya, Nikki; Lin, Jean-Pierre; Vincent, Angela; Lim, Ming

    2012-12-01

    In childhood, central nervous system (CNS) presentations associated with antibodies to voltage-gated potassium channel (VGKC) complex include limbic encephalitis, status epilepticus, epileptic encephalopathy, and autistic regression. We report the cases of two individuals (a 6-year-old male and an 11-year-old female) who presented with an acute-onset explosive seizure disorder with positive VGKC complex antibodies and bilateral basal ganglia changes on magnetic resonance imaging (MRI). Both patients made a complete clinical recovery, without immunotherapy, with resolution of the MRI changes and normalization of the antibody levels. Extended antibody testing, including testing for leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein 2, and contactin-2 was negative. This could suggest that the clinico-radiological phenotype in our patients may in fact be associated with a novel autoreactive target(s) within the VGKC complex, as may be the case in other children with VGKC complex-mediated CNS disorders.

  12. A Theoretical Model for Calculating Voltage Sensitivity of Ion Channels and the Application on Kv1.2 Potassium Channel

    Science.gov (United States)

    Yang, Huaiyu; Gao, Zhaobing; Li, Ping; Yu, Kunqian; Yu, Ye; Xu, Tian-Le; Li, Min; Jiang, Hualiang

    2012-01-01

    Voltage sensing confers conversion of a change in membrane potential to signaling activities underlying the physiological processes. For an ion channel, voltage sensitivity is usually experimentally measured by fitting electrophysiological data to Boltzmann distributions. In our study, a two-state model of the ion channel and equilibrium statistical mechanics principle were used to test the hypothesis of empirically calculating the overall voltage sensitivity of an ion channel on the basis of its closed and open conformations, and determine the contribution of individual residues to the voltage sensing. We examined the theoretical paradigm by performing experimental measurements with Kv1.2 channel and a series of mutants. The correlation between the calculated values and the experimental values is at respective level, R2 = 0.73. Our report therefore provides in silico prediction of key conformations and has identified additional residues critical for voltage sensing. PMID:22768937

  13. Identification of (R)-N-(4-(4-methoxyphenyl)thiazol-2-yl)-1-tosylpiperidine-2-carboxamide, ML277, as a novel, potent and selective Kv7.1 (KCNQ1) potassium channel activator

    Science.gov (United States)

    Mattmann, Margrith E.; Yu, Haibo; Lin, Zhihong; Xu, Kaiping; Huang, Xiaofang; Long, Shunyou; Wu, Meng; McManus, Owen B.; Engers, Darren W.; Le, Uyen M.; Li, Min; Lindsley, Craig W.; Hopkins, Corey R.

    2012-01-01

    A high-throughput screen utilizing a depolarization-triggered thallium influx through KCNQ1 channels was developed and used to screen the MLSMR collection of over 300,000 compounds. An iterative medicinal chemistry approach was initiated and from this effort, ML277 was identified as a potent activator of KCNQ1 channels (EC50 = 260 nM). ML277 was shown to be highly selective against other KCNQ channels (>100-fold selectivity versus KCNQ2 and KCNQ4) as well as against the distantly related hERG potassium channel. PMID:22910039

  14. Effects of Ginkgo biloba extracts with mirodenafil on the relaxation of corpus cavernosal smooth muscle and the potassium channel activity of corporal smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    Jung Jun Kim; Sung Won Lee; Deok Hyun Han; Soo Hyun Lim; Tae Hun Kim; Mee Ree Chae; Kyung Jin Chung; Sung Chul Kam; Ju-Hong Jeon; Jong Kwan Parks

    2011-01-01

    @@ In this study,we investigated the effects of a combination of Ginkgo biloba extracts (GBE) and phosphodiesterase type 5 (IRDE-5)inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells.Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies.After contraction with 1 x 10-5 mol I-1 norepinephrine,GBE (0.01-1 mg ml-1) and mirodenafil (0.01-100 nmoll-1) were added together into the organ bath.In electrophysiological studies,whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum.The corpus cavernosum was relaxed in response to GBE in a dose-dependent manner (from 0.64%a18.35% at 0.01 mg ml一'to 52.28%±11.42% at 1 mg ml-1).After pre-treatment with 0.03 mg ml-1of GBE,the relaxant effects of mirodenafil were increased at all concentrations.After tetraethylammonium (TEA) (1 mmoll-1) administration,the increased effects were inhibited (P<0.01).Extracellular administration of GBE increased the whole-cell K+ outward currents in a dose-dependent fashion.The increase of the outward current was inhibited by 1 mmoll-1 TEA.These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose.The K+ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.

  15. Application of a real-time PCR assay to detect BK potassium channel expression in samples from Atlantic salmon (Salmo salar and Rainbow trout (Oncorhynchus mykiss acclimated to freshwater#

    Directory of Open Access Journals (Sweden)

    CA Loncoman

    2015-01-01

    Full Text Available Atlantic salmon (Salmo salar and Rainbow trout (Oncorhynchus mykiss are two fish species that spawn in fresh water (FW and, during development, acclimate to seawater (SW by secreting excess NaCl to the environment. The salmon industry measures Na+/K+ ATPase (NKA activity as a molecular marker to determine the timing of smolt transfer from FW to SW. However, the lack of other accurate molecular markers of smoltification remains a major issue for the fish farming industry. The molecular mechanism of NaCl secretion in gills from SW-acclimated fish has a thermodynamic requirement to recycle K+ out of the cell via potassium channels therefore we hypothesised that potassium channel expression in gills may be a suitable candidate to monitor the smoltification process. In support of this hypothesis, we observed increased expression of BK potassium channel mRNA in gills from S. salar under conditions of high salinity (1.2% compared to animals in FW. In this work, we designed a real-time PCR analysis in order to quantify mRNA levels of BK potassium channels in S. salar organ samples. We found differences in mRNA expression among gills, kidney and intestine. We also found a unique real-time PCR product in S. salar gills through melting curve analysis, agarose gel electrophoresis and cDNA sequencing. This PCR product showed a 98% of identity with the BK channel portion recorded by the NCBI Database and was differentially expressed in gills, kidney and intestine. This real-time PCR assay may become an important tool to study BK potassium channels expressed in the gills of S. salar and its changes during smoltification as putative new candidate to monitor this process.

  16. GABA/sub B/ receptor activation inhibits Ca2+-activated potassium channels in synaptosomes: involvement of G-proteins

    International Nuclear Information System (INIS)

    86Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca2+-activated K+-channels. Depolarization of 86Rb-loaded synaptosomes in physiological buffer increased Ca2+-activated 86Rb-efflux by 400%. The 86Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La3+ indicating the involvement of Ca2+-activated K+-channels. (-)Baclofen inhibited Ca2+-activated 86Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but not by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca2+-activated K+-channels. These results suggest that baclofen inhibits Ca2+-activated K+-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology

  17. The Cyclooctadepsipeptide Anthelmintic Emodepside Differentially Modulates Nematode, Insect and Human Calcium-Activated Potassium (SLO Channel Alpha Subunits.

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    Anna Crisford

    Full Text Available The anthelmintic emodepside paralyses adult filarial worms, via a mode of action distinct from previous anthelmintics and has recently garnered interest as a new treatment for onchocerciasis. Whole organism data suggest its anthelmintic action is underpinned by a selective activation of the nematode isoform of an evolutionary conserved Ca2+-activated K+ channel, SLO-1. To test this at the molecular level we compared the actions of emodepside at heterologously expressed SLO-1 alpha subunit orthologues from nematode (Caenorhabditis elegans, Drosophila melanogaster and human using whole cell voltage clamp. Intriguingly we found that emodepside modulated nematode (Ce slo-1, insect (Drosophila, Dm slo and human (hum kcnma1SLO channels but that there are discrete differences in the features of the modulation that are consistent with its anthelmintic efficacy. Nematode SLO-1 currents required 100 μM intracellular Ca2+ and were strongly facilitated by emodepside (100 nM; +73.0 ± 17.4%; n = 9; p < 0.001. Drosophila Slo currents on the other hand were activated by emodepside (10 μM in the presence of 52 nM Ca2+ but were inhibited in the presence of 290 nM Ca2+ and exhibited a characteristic loss of rectification. Human Slo required 300 nM Ca2+ and emodepside transiently facilitated currents (100 nM; +33.5 ± 9%; n = 8; p<0.05 followed by a sustained inhibition (-52.6 ± 9.8%; n = 8; p < 0.001. This first cross phyla comparison of the actions of emodepside at nematode, insect and human channels provides new mechanistic insight into the compound's complex modulation of SLO channels. Consistent with whole organism behavioural studies on C. elegans, it indicates its anthelmintic action derives from a strong activation of SLO current, not observed in the human channel. These data provide an important benchmark for the wider deployment of emodepside as an anthelmintic treatment.

  18. Potassium Iodide

    Science.gov (United States)

    Potassium iodide is used to protect the thyroid gland from taking in radioactive iodine that may be ... damage the thyroid gland. You should only take potassium iodide if there is a nuclear radiation emergency ...

  19. Effect of beta-adrenoceptor blockers on human ether-a-go-go-related gene (HERG) potassium channels

    DEFF Research Database (Denmark)

    Dupuis, Delphine S; Klaerke, Dan A; Olesen, Søren-Peter

    2005-01-01

    Patients with congenital long QT syndrome may develop arrhythmias under conditions of increased sympathetic tone. We have addressed whether some of the beta-adrenoceptor blockers commonly used to prevent the development of these arrhythmias could per se block the cardiac HERG (Human Ether....... These data showed that HERG blockade by beta-adrenoceptor blockers occurred only at high micromolar concentrations, which are significantly above the recently established safe margin of 100 (Redfern et al., 2003).......-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride) blocked the HERG channel with similar affinity, whereas the beta1-receptor antagonists metoprolol and atenolol showed weak effects. Further, the four compounds blocked HERG channels expressed in a mammalian HEK293 cell line...

  20. The KCNQ1 potassium channel is down-regulated by ubiquitylating enzymes of the Nedd4/Nedd4-like family

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Membrez, Mathieu; Nicolas, Céline S;

    2007-01-01

    participate in controlling body electrolyte homeostasis. Several regulatory mechanisms of the KCNQ1 channel complexes have been reported, including protein kinase A (PKA)-phosphorylation and beta-subunit interactions. However, the mechanisms controlling the membrane density of KCNQ1 channels have attracted...... less attention. METHODS AND RESULTS: Here we demonstrate that KCNQ1 proteins expressed in HEK293 cells are down-regulated by Nedd4/Nedd4-like ubiquitin-protein ligases. KCNQ1 and KCNQ1/KCNE1 currents were reduced upon co-expression of Nedd4-2, the isoform among the nine members of the Nedd4/Nedd4-like...... by Nedd4-2, an increased ubiquitylation as well as a decreased total level of KCNQ1 proteins were observed in HEK293 cells. Pull-down and co-immunoprecipitation experiments showed that Nedd4-2 interacts with the C-terminal part of KCNQ1. The Nedd4/Nedd4-like-mediated regulation of the KCNQ1 channel...

  1. The Caenorhabditis elegans iodotyrosine deiodinase ortholog SUP-18 functions through a conserved channel SC-box to regulate the muscle two-pore domain potassium channel SUP-9.

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    Ignacio Perez de la Cruz

    2014-02-01

    Full Text Available Loss-of-function mutations in the Caenorhabditis elegans gene sup-18 suppress the defects in muscle contraction conferred by a gain-of-function mutation in SUP-10, a presumptive regulatory subunit of the SUP-9 two-pore domain K(+ channel associated with muscle membranes. We cloned sup-18 and found that it encodes the C. elegans ortholog of mammalian iodotyrosine deiodinase (IYD, an NADH oxidase/flavin reductase that functions in iodine recycling and is important for the biosynthesis of thyroid hormones that regulate metabolism. The FMN-binding site of mammalian IYD is conserved in SUP-18, which appears to require catalytic activity to function. Genetic analyses suggest that SUP-10 can function with SUP-18 to activate SUP-9 through a pathway that is independent of the presumptive SUP-9 regulatory subunit UNC-93. We identified a novel evolutionarily conserved serine-cysteine-rich region in the C-terminal cytoplasmic domain of SUP-9 required for its specific activation by SUP-10 and SUP-18 but not by UNC-93. Since two-pore domain K(+ channels regulate the resting membrane potentials of numerous cell types, we suggest that the SUP-18 IYD regulates the activity of the SUP-9 channel using NADH as a coenzyme and thus couples the metabolic state of muscle cells to muscle membrane excitability.

  2. The effects of beta-amyloid protein and presenilin on potassium channel%淀粉样蛋白及早老素对钾通道的影响

    Institute of Scientific and Technical Information of China (English)

    佟晓永; 王晓良

    2001-01-01

    Alzheimer病目前是痴呆的最常见原因,病理学特征是:神经纤维缠结,神经斑块,神经元丢失,淀粉样血管改变。临床上最显著的特点是学习记忆障碍。钾通道在学习记忆中起着重要作用。Alzheimer病人成纤维细胞以及嗅成纤维细胞113pS四已胺敏感的钾通道缺失。记忆相关蛋白Cp20以及与Alzheimer病遗传密切相关的淀粉样蛋白前体蛋白及早老素均能调节钾通道活性。Alzheimer病时钾通道亚型的改变尚需进一步的理论研究。钾通道在Alzhe imer病治疗方面有可能成为重要靶点。%Alzheimer disease(AD) is the most common cau se of dementia today. Th e characteristic histopathologic changes include neurofibrillary tangles, neurit ic plaques, neuronal loss, and amyloid angiopathy. The noted Alzheimer symptom is the dysfunction of learning a nd memory. Potassium channels play a key role in it. A 113-pS tetraethylammoniu m-sensitive potassium channel was consistently absent from AD fibroblasts and o lfactory neuroblasts. Cp20, a memory-associated protein, amyloid precuror prote in and presenilin which are all tightly associated with genetic Alzheimer diseas e can regulate the activities of potassium channels. The changes of potassium ch annels subtype need further study. Potassium channels are maybe the important dr ug targets in the treatment of Alzheimer disease.

  3. Relaxant effect of a novel calcium-activated potassium channel modulator on human myometrial spontaneous contractility in vitro

    DEFF Research Database (Denmark)

    Rosenbaum, S.T.; Larsen, T.; Joergensen, J.C.;

    2012-01-01

    . Simultaneous vehicle controls were performed for all experiments. The effects of drugs were studied on spontaneous contractions. Results: NS4591 exerted an inhibitory effect on myometrial contractions in muscle strips from non-pregnant and pregnant women. The contractility in non-pregnant and pregnant...... section at term (N=11) or hysterectomy (N=11). NS4591 was added cumulatively in the concentration range of 0.3-30μm. In separate experiments, the effects of pre-incubation of muscle preparation with the SK or IK channel blockers apamin (1μm) and TRAM34 (10μm) on the outcomes of NS4591 were evaluated...

  4. Effects of manipulating slowpoke calcium-dependent potassium channel expression on rhythmic locomotor activity in Drosophila larvae

    Directory of Open Access Journals (Sweden)

    Erin C. McKiernan

    2013-03-01

    Full Text Available Rhythmic motor behaviors are generated by networks of neurons. The sequence and timing of muscle contractions depends on both synaptic connections between neurons and the neurons’ intrinsic properties. In particular, motor neuron ion currents may contribute significantly to motor output. Large conductance Ca2+-dependent K+ (BK currents play a role in action potential repolarization, interspike interval, repetitive and burst firing, burst termination and interburst interval in neurons. Mutations in slowpoke (slo genes encoding BK channels result in motor disturbances. This study examined the effects of manipulating slo channel expression on rhythmic motor activity using Drosophila larva as a model system. Dual intracellular recordings from adjacent body wall muscles were made during spontaneous crawling-related activity in larvae expressing a slo mutation or a slo RNA interference construct. The incidence and duration of rhythmic activity in slo mutants were similar to wild-type control animals, while the timing of the motor pattern was altered. slo mutants showed decreased burst durations, cycle durations, and quiescence intervals, and increased duty cycles, relative to wild-type. Expressing slo RNAi in identified motor neurons phenocopied many of the effects observed in the mutant, including decreases in quiescence interval and cycle duration. Overall, these results show that altering slo expression in the whole larva, and specifically in motor neurons, changes the frequency of crawling activity. These results suggest an important role for motor neuron intrinsic properties in shaping the timing of motor output.

  5. Effect of osthole on potassium channels of cadiocytes in neonate rats in vitro%蛇床子素对体外培养大鼠乳鼠心肌细胞钾通道的影响

    Institute of Scientific and Technical Information of China (English)

    李树基; 袁春华

    2011-01-01

    Objective To investigate the effect of osthole on potassium channels electric current of cadiocytes in neo-nate rats in vitro. Methods The transient outward potassium currents and inward-rectifying potassium currents of cadiocytes in neonate rats were recorded by using whole cell patch clamp technique. The effects of osthole on potassium currents were investigated. Results Transient outward potassium currents were inhibited by osthole in a concentration-dependent manner,and the inhibition was fast and reversible. The half-effective concentration of the inhibition was( 101.1 ± 5. 2)μmol · L-1. Osthole showed no significant influence on the activation kinetics of transient outward potassium channel. Osthole showed depressant effect on inward-rectifying potassium currents,osthole reduced the inward-rectifying potassium currents by(68. 2 ±7. 5)% at the concentration of 200 μmol · L-1. Conclusion Osthole concentration-dependently decreased potassium currents of cadiocytes in neonate rats in vitro.%目的 研究蛇床子素对体外培养大鼠乳鼠心肌细胞钾通道电流的影响.方法 采用全细胞膜片钳技术,首先在乳鼠心肌细胞上诱导出内向整流钾电流和瞬时外向钾电流,然后观察蛇床子素对这2种钾电流的影响.结果 蛇床子素以浓度依赖的方式快速可逆地抑制心肌细胞瞬时外向钾电流,抑制的半有效浓度为(101.1±5.2)μmol·L-1,蛇床子素不改变瞬时外向钾通道的激活动力学.蛇床子素对内向整流钾电流有一定的抑制作用,在200 μmol·L-1的浓度下抑制(68.2±7.5)%的内向钾电流.结论 蛇床子素能够抑制乳鼠心肌细胞钾通道电流,并呈浓度依赖性.

  6. Comprehensive re-sequencing of adrenal aldosterone producing lesions reveal three somatic mutations near the KCNJ5 potassium channel selectivity filter.

    Directory of Open Access Journals (Sweden)

    Tobias Åkerström

    Full Text Available BACKGROUND: Aldosterone producing lesions are a common cause of hypertension, but genetic alterations for tumorigenesis have been unclear. Recently, either of two recurrent somatic missense mutations (G151R or L168R was found in the potassium channel KCNJ5 gene in aldosterone producing adenomas. These mutations alter the channel selectivity filter and result in Na(+ conductance and cell depolarization, stimulating aldosterone production and cell proliferation. Because a similar mutation occurs in a mendelian form of primary aldosteronism, these mutations appear to be sufficient for cell proliferation and aldosterone production. The prevalence and spectrum of KCNJ5 mutations in different entities of adrenocortical lesions remain to be defined. MATERIALS AND METHODS: The coding region and flanking intronic segments of KCNJ5 were subjected to Sanger DNA sequencing in 351 aldosterone producing lesions, from patients with primary aldosteronism and 130 other adrenocortical lesions. The specimens had been collected from 10 different worldwide referral centers. RESULTS: G151R or L168R somatic mutations were identified in 47% of aldosterone producing adenomas, each with similar frequency. A previously unreported somatic mutation near the selectivity filter, E145Q, was observed twice. Somatic G151R or L168R mutations were also found in 40% of aldosterone producing adenomas associated with marked hyperplasia, but not in specimens with merely unilateral hyperplasia. Mutations were absent in 130 non-aldosterone secreting lesions. KCNJ5 mutations were overrepresented in aldosterone producing adenomas from female compared to male patients (63 vs. 24%. Males with KCNJ5 mutations were significantly younger than those without (45 vs. 54, respectively; p<0.005 and their APAs with KCNJ5 mutations were larger than those without (27.1 mm vs. 17.1 mm; p<0.005. DISCUSSION: Either of two somatic KCNJ5 mutations are highly prevalent and specific for aldosterone producing

  7. Orientations and proximities of the extracellular ends of transmembrane helices S0 and S4 in open and closed BK potassium channels.

    Directory of Open Access Journals (Sweden)

    Xiaowei Niu

    Full Text Available The large-conductance potassium channel (BK α subunit contains a transmembrane (TM helix S0 preceding the canonical TM helices S1 through S6. S0 lies between S4 and the TM2 helix of the regulatory β1 subunit. Pairs of Cys were substituted in the first helical turns in the membrane of BK α S0 and S4 and in β1 TM2. One such pair, W22C in S0 and W203C in S4, was 95% crosslinked endogenously. Under voltage-clamp conditions in outside-out patches, this crosslink was reduced by DTT and reoxidized by a membrane-impermeant bis-quaternary ammonium derivative of diamide. The rate constants for this reoxidation were not significantly different in the open and closed states of the channel. Thus, these two residues are approximately equally close in the two states. In addition, 90% crosslinking of a second pair, R20C in S0 and W203C in S4, had no effect on the V50 for opening. Taken together, these findings indicate that separation between residues at the extracellular ends of S0 and S4 is not required for voltage-sensor activation. On the contrary, even though W22C and W203C were equally likely to form a disulfide in the activated and deactivated states, relative immobilization by crosslinking of these two residues favored the activated state. Furthermore, the efficiency of recrosslinking of W22C and W203C on the cell surface was greater in the presence of the β1 subunit than in its absence, consistent with β1 acting through S0 to stabilize its immobilization relative to α S4.

  8. Effect of nitric oxide-induced tyrosine phosphorylation of calcium-activated potassium channel α subunit on vascular hyporesponsiveness in rats

    Institute of Scientific and Technical Information of China (English)

    ZHOU Rong; LIU Liang-ming; HU De-yao

    2005-01-01

    Objective: To study the effect of nitric oxide-induced tyrosine phosphorylation of large-conductance calcium-activated potassium (BKCa) channel α subunit on vascular hyporesponsiveness in rats. Methods: A total of 46 Wistar rats of either sex, weighing 250 g±20 g, were used in this study. Models of vascular hyporesponsiveness induced by hemorrhagic shock (30 mm Hg for 2 hours) in vivo and by L-arginine in vitro were established respectively. The vascular responsiveness of isolated superior mesenteric arteries to norepinephrine was observed. Tyrosine phosphorylation of BKCa α subunit was evaluated with methods of immunoprecipitation and Western blotting. Results: In the smooth muscle cells of the superior mesenteric arteries, the expression of BKCa α subunit tyrosine phosphorylation increased following hemorrhagic shock, and L-arginine could induce BKCa channel α subunit tyrosine phosphorylation in a time- and dose-dependent manner. L-NAME (Nω-nitro-L-arginine-methyl-ester), a nitric oxide synthetase inhibitor, could partly restore the decreased vasoresponsiveness of the superior mesenteric arteries after hemorrhagic shock in rats. Down-regulating the protein tyrosine phosphorylation with genistein, a widely-used special protein tyrosine kinase inhibitor, could partly improve the decreased vasoresponsiveness of the superior mesenteric arteries induced by L-arginine in vitro, while up-regulating the protein tyrosine phosphorylation with Na3VO4, a protein tyrosine phosphatase inhibitor, could further decrease the nitric oxide-induced vascular hyporesponsiveness, which could be partly ameliorated by 0.1 mmol/L tetrabutylammonium chloride (TEA), a selective BKCa inhibitor at this concentration. Conclusions: Nitric oxide can induce the tyrosine phosphorylation of BKCa α subunit, which influences the vascular hyporesponsiveness in hemorrhagic shock rats or induced by L-arginine in vitro.

  9. Effects of genetic deletion of the Kv4.2 voltage-gated potassium channel on murine anxiety-, fear- and stress-related behaviors

    Directory of Open Access Journals (Sweden)

    Kiselycznyk Carly

    2012-03-01

    Full Text Available Abstract Background Potassium channels have been proposed to play a role in mechanisms of neural plasticity, and the Kv4.2 subunit has been implicated in the regulation of action-potential back-propagation to the dendrites. Alterations in mechanisms of plasticity have been further proposed to underlie various psychiatric disorders, but the role of Kv4.2 in anxiety or depression is not well understood. Methods In this paper, we analyzed the phenotype Kv4.2 knockout mice based on their neurological function, on a battery of behaviors including those related to anxiety and depression, and on plasticity-related learning tasks. Results We found a novelty-induced hyperactive phenotype in knockout mice, and these mice also displayed increased reactivity to novel stimulus such as an auditory tone. No clear anxiety- or depression-related phenotype was observed, nor any alterations in learning/plasticity-based paradigms. Conclusions We did not find clear evidence for an involvement of Kv4.2 in neuropsychiatric or plasticity-related phenotypes, but there was support for a role in Kv4.2 in dampening excitatory responses to novel stimuli.

  10. IgG and complement deposition and neuronal loss in cats and humans with epilepsy and voltage-gated potassium channel complex antibodies.

    Science.gov (United States)

    Klang, Andrea; Schmidt, Peter; Kneissl, Sibylle; Bagó, Zoltán; Vincent, Angela; Lang, Bethan; Moloney, Teresa; Bien, Christian G; Halász, Péter; Bauer, Jan; Pákozdy, Akos

    2014-05-01

    Voltage-gated potassium channel complex (VGKC-complex) antibody (Ab) encephalitis is a well-recognized form of limbic encephalitis in humans, usually occurring in the absence of an underlying tumor. The patients have a subacute onset of seizures, magnetic resonance imaging findings suggestive of hippocampal inflammation, and high serum titers of Abs against proteins of the VGKC-complex, particularly leucine-rich, glioma-inactivated 1 (LGI1). Most patients are diagnosed promptly and recover substantially with immunotherapies; consequently, neuropathological data are limited. We have recently shown that feline complex partial cluster seizures with orofacial involvement (FEPSO) in cats can also be associated with Abs against VGKC-complexes/LGI1. Here we examined the brains of cats with FEPSO and compared the neuropathological findings with those in a human with VGKC-complex-Ab limbic encephalitis. Similar to humans, cats with VGKC-complex-Ab and FEPSO have hippocampal lesions with only moderate T-cell infiltrates but with marked IgG infiltration and complement C9neo deposition on hippocampal neurons, associated with neuronal loss. These findings provide further evidence that FEPSO is a feline form of VGKC-complex-Ab limbic encephalitis and provide a model for increasing understanding of the human disease.

  11. Limbic encephalitis associated with anti-voltage-gated potassium channel complex antibodies as a cause of adult-onset mesial temporal lobe epilepsy.

    Science.gov (United States)

    Toyota, Tomoko; Akamatsu, Naoki; Tsuji, Sadatoshi; Nishizawa, Shigeru

    2014-06-01

    Recently, some reports have indicated that limbic encephalitis associated with anti-voltage-gated potassium channel complex antibodies (VGKC-Ab) is a cause of adult-onset mesial temporal lobe epilepsy (MTLE). We report a 53-year-old woman who had her first epileptic seizure at the age of 50 years old. Examination by 3-Tesla brain MRI revealed left hippocampal high signal intensity and swelling on fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging at 2 months after her first seizure. The patient received intravenous methylprednisolone and carbamazepine 300 mg/day. One month later, MRI revealed improvement of her left hippocampal abnormalities. Thereafter, she had no seizures, however, three years after her first seizure, EEG revealed a seizure pattern in the left temporal region. Brain MRI revealed left hippocampal high signal intensity and brain fluorodeoxyglucose positron emission tomography revealed hypermetabolism. Her serum VGKC-Ab levels were 118 pM(normal VGKC-Ab levels decreased to 4.4 pM. Remission of the epileptic seizures was also observed. This MTLE in the middle age was considered as limbic encephalitis associated with anti- VGKC-Ab. In cases of unexplained adult-onset MTLE, limbic encephalitis associated with anti-VGKC-Ab, which responds well to immunotherapy, should be considered in the differential diagnosis.

  12. Expression of T-cell KV1.3 potassium channel correlates with pro-inflammatory cytokines and disease activity in ulcerative colitis

    DEFF Research Database (Denmark)

    Koch Hansen, Lars; Møller, Linda Maria Sevelsted; Rabjerg, Maj;

    2014-01-01

    BACKGROUND AND AIMS: Potassium channels, KV1.3 and KCa3.1, have been suggested to control T-cell activation, proliferation, and cytokine production and may thus constitute targets for anti-inflammatory therapy. Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized...... with active UC (n=33) and controls (n=15). Protein and mRNA expression of KV1.3 and KCa3.1, immune cell markers, and pro-inflammatory cytokines were determined by quantitative-real-time-polymerase-chain-reaction (qPCR) and immunofluorescence, and correlated with clinical parameters of inflammation. In......% of CD8(+) T-cells. KV1.3 was virtually absent on infiltrating macrophages. KV1.3 mRNA expression correlated significantly with mRNA expression of pro-inflammatory cytokines TNF-α (R(2)=0.61) and IL-17A (R(2)=0.51), the mayo endoscopic subscore (R(2)=0.13), and histological inflammation (R(2)=0.23). In...

  13. KR-31378, a potassium-channel opener, induces the protection of retinal ganglion cells in rat retinal ischemic models.

    Science.gov (United States)

    Choi, Anho; Choi, Jun-Sub; Yoon, Yone-Jung; Kim, Kyung-A; Joo, Choun-Ki

    2009-04-01

    KR-31378 is a newly developed K(ATP)-channel opener. To investigate the ability of KR-31378 to protect retinal ganglion cells (RGC), experiments were conducted using two retinal ischemia models. Retinal ischemia was induced by transient high intraocular pressure (IOP) for acute ischemia and by three episcleral vein occlusion for chronic retinal ischemia. KR-31378 was injected intraperitoneally and administered orally in the acute and chronic ischemia models, respectively. Under the condition of chronic ischemia, RGC density in the KR-31378-treated group was statistically higher than that in the non-treated group, and IOP was reduced. In the acute retinal ischemia model, 90% of RGC were degenerated after one week in non-treated retina, but, RGC in KR-31378-treated retina were protected from ischemic damage in a dose-dependent manner and showed inhibited glial fibrillary acidic protein (GFAP) expression. Furthermore, the KR-31378 protective effect was inhibited by glibenclamide treatment in acute ischemia. These findings indicate that systemic KR-31378 treatment may protect against ischemic injury-induced ganglion cell loss in glaucoma.

  14. Potassium Channel Ether à go-go1 Is Aberrantly Expressed in Human Liposarcoma and Promotes Tumorigenesis

    Directory of Open Access Journals (Sweden)

    Jin Wu

    2014-01-01

    Full Text Available The ether à go-go1 (Eag1 channel is overexpressed in a variety of cancers. However, the expression and function of Eag1 in liposarcoma are poorly understood. In the present study, the mRNA expression of Eag1 in different adipose tissue samples was examined by real-time PCR. Then, the protein expression of Eag1 in 131 different adipose tissues from 109 patients was detected by immunohistochemistry. Next, the associations between Eag1 expression and clinicopathological features of liposarcoma were analyzed. In addition, the effects of Eag1 on liposarcoma cell proliferation and cycle were evaluated by CCK-8, colony formation, xenograft mouse model, and flow cytometry, respectively. Finally, the activation of p38 mitogen-activated protein kinase (MAPK was detected by Western blot analysis to explain the detailed mechanisms of oncogenic potential of Eag1 in liposarcoma. It was found that Eag1 was aberrantly expressed in over 67% liposarcomas, with a higher frequency than in lipoma, hyperplasia, inflammation, and normal adipose tissues. However, Eag1 expression was not correlated with clinicopathological features of liposarcoma. Eag1 inhibitor imipramine or Eag1-shRNA significantly suppressed the proliferation of liposarcoma cells in vitro and in vivo, accompanying with accumulation of cells in the G1 phase. These results suggest that Eag1 plays an important role in regulating the proliferation and cell cycle of liposarcoma cells and might be a potential therapeutic target for liposarcoma.

  15. ATP敏感钾通道在心血管系统中的作用%The role of ATP-sensitive K+ channels in the cardiovascular system

    Institute of Scientific and Technical Information of China (English)

    孟繁学; 焦晓慧; 韩大英

    2000-01-01

    @@ 1983年,Noma[1]首次报道细胞内ATP可抑制豚鼠心室肌选择性钾通道(即KATP),并推测KATP激活与心肌缺血时动作电位缩短有关,KATP激活可降低细胞内 ATP的消耗,避免细胞发生不可逆性损伤.近年来大量研究表明KATP在心血管系统的病理生理过程中具有重要作用.

  16. Expression and localization of inwardly rectifying potassium channel Kit2.1 in glia cells of native bovine retina

    Institute of Scientific and Technical Information of China (English)

    PAN Ai-hua; LUO Xue-gang

    2005-01-01

    Objective The purpose of this study is to identify the molecular basis of the contacting -neuron membrane K+ conductance in glia cells of native bovine retina. Methods RT-PCR, Northern blot and Western blot analyses were used to detect the expression of the inwardly rectifying K+ (Kir) channel subunits Kir2.1 in native bovine RPE and neural retina. The distribution of Kir2.1 protein was determined in frozen sections of bovine retina-RPEchoroid by indirect immunofluorescence analysis. Results RT-PCR analysis reveals Kir2.1 transcript in both RPE and neural retina. In Northern blots, Kir2.1 probe hybridizes to an appropriately sized-transcript in neural retina but not in RPE. In Western blots, Kir2.1 antibody recognizes a major monomer of about 60 kDa in neural retina but not in RPE. Immunofluorescence reveals that Kir2.1 immunostaining is expressed at many parts of Muller cells, especially in the membrane domains of Muller cells that contact retinal neurons, i. e. , along the two stem processes,over the soma, and in the side branches extending into the synaptic layers. No immunostaining is seen in RPE. Doubling staining shows that Kir2.1 proteins and glutamine synthetase proteins which are a marker of Muller cell co-localized well. Conclusions These results reveal that Kir2.1 is localized in the Muller cells, no Kir2.1 in RPE. These data suggests that Kir2.1 may be involved in the transport of K+ in the bovine neural retina.

  17. K(ATP) channel openers in the trigeminovascular system

    DEFF Research Database (Denmark)

    Ploug, K B; Amrutkar, D V; Baun, M;

    2012-01-01

    The ATP-sensitive K(+) (K(ATP)) channel openers levcromakalim and pinacidil are vasodilators that induce headache in healthy people. The neuropeptide calcitonin gene-related peptide (CGRP) induces headache in healthy people and migraine in migraineurs, potentially through a mechanism that involve...

  18. KIR4.1: K+ Channel Illusion or Reality in the Autoimmune Pathogenesis of Multiple Sclerosis

    Science.gov (United States)

    Gu, Chen

    2016-01-01

    Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Many believe autoimmune pathogenesis plays a key role in MS, but its target(s) remains elusive. A recent study detected autoantibodies against KIR4.1, an ATP-sensitive, inward rectifier potassium channel, in nearly half of the MS patients examined. KIR4.1 channels are expressed in astrocytes. Together with aquaporin 4 (AQP4) water channels, they regulate astrocytic functions vital for myelination. Autoantibodies against AQP4 have been established as a key biomarker for neuromyelitis optica (NMO) and contributed to diagnostic and treatment strategy adjustments. Similarly, identification of KIR4.1 autoantibodies could have high therapeutic values in treating MS. Consistent with its potential role in MS, KIR4.1 dysfunction is implicated in several neurological disorders. However, the enrichment of KIR4.1 autoantibodies in MS patients is questioned by follow-up studies. Further, investigations are needed to clarify this controversy and unravel the underlying mechanisms of MS pathogenesis. PMID:27729847

  19. Vascular KCNQ Potassium Channels as Novel Targets for the Control of Mesenteric Artery Constriction by Vasopressin, Based on Studies in Single Cells, Pressurized Arteries, and in Vivo Measurements of Mesenteric Vascular ResistanceS

    OpenAIRE

    Mackie, Alexander R.; Brueggemann, Lioubov I.; Henderson, Kyle K.; Shiels, Aaron J.; Cribbs, Leanne L.; Scrogin, Karie E.; Byron, Kenneth L.

    2008-01-01

    Pressor effects of the vasoconstrictor hormone arginine vasopressin (AVP), observed when systemic AVP concentrations are less than 100 pM, are important for the physiological maintenance of blood pressure, and they are also the basis for therapeutic use of vasopressin to restore blood pressure in hypotensive patients. However, the mechanisms by which circulating AVP induces arterial constriction are unclear. We examined the novel hypothesis that KCNQ potassium channels mediate the physiologic...

  20. Kv1.3钾离子通道及其与相关疾病的研究进展%Progresses of kv1.3 potassium channel and its related diseases

    Institute of Scientific and Technical Information of China (English)

    周倩兰

    2015-01-01

    Kvl.3 potassium channel plays a key role in T lymphocyte activation.In many diseases mediated by T lymphocytes, such as multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, anti-glomerular basement membrane glomerulonephritis, asthma, Kv1.3 potassium channel expression is up-regulated,closely related to the mechanism of those disease.In the cardiovascular system diseases, Kv1.3 potassium channel protein is related to the differentiation of monocyte derived macrophage into foam cells, and vascular remodeling.In addition Kv1.3 potassium channel plays a role in apoptosis.This paper provide new ideas for the diagnosis and treatment of T lymphocytes mediated disease, cardiovascular disease and neoplasms.%Kv1.3钾离子通道在T细胞活化中有着关键性作用,在T细胞介导的许多疾病中,如多发性硬化、风湿性关节炎、系统性红斑狼疮、抗肾小球基膜型肾小球肾炎、哮喘,发病时Kv1.3钾离子通道表达均上调,与其发病机制密切相关.在心血管系统疾病中,Kv1.3钾离子通道蛋白与单核细胞源性巨噬细胞向泡沫细胞分化过程以及血管重塑过程有关.此外Kv1.3钾离子通道参与细胞凋亡过程.为T细胞介导的系列疾病、心血管系统疾病以及肿瘤的诊治提供新思路.

  1. Chronic electroconvulsive stimulation but not chronic restraint stress modulates mRNA expression of voltage-dependent potassium channels Kv7.2 and Kv11.1 in the rat piriform cortex

    DEFF Research Database (Denmark)

    Hjæresen, Marie-Louise; Hageman, Ida; Plenge, Per;

    2008-01-01

    The mechanisms by which stress and electroconvulsive therapy exert opposite effects on the course of major depression are not known. Potential candidates might include the voltage-dependent potassium channels. Potassium channels play an important role in maintaining the resting membrane potential...... and controlling neuronal excitability. To explore this hypothesis, we examined the effects of one or several electroconvulsive stimulations and chronic restraint stress (6 h/day for 21 days) on the expression of voltage-dependent potassium channel Kv7.2, Kv11.1, and Kv11.3 mRNA in the rat brain using in situ...... hybridization. Repeated, but not acute, electroconvulsive stimulation increased Kv7.2 and Kv11.1 mRNA levels in the piriform cortex. In contrast, restraint stress had no significant effect on mRNA expression of Kv7.2, Kv11.1, or Kv11.3 in any of the brain regions examined. Thus, it appears that the investigated...

  2. Effects of potassium channel on shear stress - induced signal transduction in vascular endothelial cells%K离子通道在剪切力诱导血管内皮细胞信号转导中的作用

    Institute of Scientific and Technical Information of China (English)

    胡金麟

    1999-01-01

    Fluid shear stress play an important role in many physiological and pathophysiological processes of cardiovascular system. Shear stress - induced signal transduction throughout the vascular endothelial cell includes ion channels,G- protein linked receptors, tyrosine kinase receptors and integrins. The one impossible pathway of shear stress - induced signal transduction was biochemical reaction through second messenger, activating protein kinases and cytosolic transcription factors, and then regulating gene transcription . The other pathway was cytoskeletal system. This article reviewed the cellular and molecular mechanism of potassium channel signal transduction resulting from shear stress.

  3. Effect of low temperature on the transmembrane transport of potassium ion channel protein%温度变化对钾离子跨膜通道蛋白传输能力的影响

    Institute of Scientific and Technical Information of China (English)

    李代禧; 刘宝林; 乔勇进; 张燕; 翟振

    2012-01-01

    In order to investigate the effect of temperature changing on trans membrane transport in cells, the transport capability and mechanism of a potassium (K+) ion transmembrane channel protein was researched by means of molecular dynamic simulation and umbrella sampling with Gromacs software package and Gromo96 (53a6) forcefield at 300 K and 275 K, respectively. The potentials of mean force (PMF) during a potassium ion going through the potassium ion channel protein indicated that the decrease of temperature obviously affect the transport capability of a potassium ion channel protein. For example, the process of the K+ ion going through the potassium ion channel protein is completely spontaneous at 300 K on thermodynamics according to the results of PMF free energies. However, the PMF free energy of the cavum for trapping ions increases when the temperature decreases to 275 K, and therefore the capability to trap ions decreases. And the PMF free energy of the latter part of transport channel obviously increases. Thus the PMF free energy of exit became larger than those of entrance at 275 K. Finally, the process of the K+ ion going through the potassium ion channel protein became non-spontaneous at 275 K. Namely, the decrease of temperature from 300 K to 275 K reversed the transport direction of potassium ion channel protein, in summary, the transport capability of transmembrane channel protein would decrease, even vanish at low temperature. Those results were also expected to give a significant insight into the mechanism of chilling damage on fruits and vegetables. That is, the decrease or vanish of the transport capability of biomembrane is the mainly reason that results to the chilling damage at low temperature.%为了研究温度变化对生物膜跨膜传输能力的影响,本文以钾离子跨膜通道蛋白为研究对象,利用Gromacs分子生物学模拟软件包和Gromos96 (53a6)分子力场,通过分子动力模拟技术和伞

  4. The effect of protein kinase C on voltage-gated potassium channel in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia

    Institute of Scientific and Technical Information of China (English)

    张永昶; 倪望; 张珍祥; 徐永健

    2004-01-01

    Background Chronic hypoxia can cause pulmonary hypertension and pulmonary heart disease with high mortality.The signal transduction pathway of protein kinase C (PKC) plays an important role in chronic pulmonary hypertension. So it is necessary to investigate the effect of PKC on voltage-gated potassium (K+) channels in pulmonary artery smooth muscle cells of rats exposed to chronic hypoxia.Methods Male Wistar rats were randomly divided into a control group (group A) and a chronic hypoxia group (group B). Group B received hypoxia [oxygen concentration (10±1)%] eight hours per day for four consecutive weeks. Single pulmonary artery smooth muscle cells were obtained using an acute enzyme separation method. Conventional whole cell patch clamp technique was used to record resting membrane potential, membrane capacitance and voltage-gated K+ currents. The changes in voltage-gated K+ currents before and after applying paramethoxyamphetamine (PMA) (500 nmol/L), an agonist of PKC, and PMA plus carbohydrate mixture of glucose, fructose and xylitol (GFX) (30 nmol/L), an inhibitor of PKC, were compared between the two groups. Results The resting membrane potential in group B was significantly lower than that of group A: -(29.0±4.8) mV (n=18) vs -(42.5±4.6) mV (n=35) (P0.05). The voltage-gated K+ currents were significantly inhibited by PMA in group A, and this effect was reversed by GFX. However, the voltage-gated K+ currents in group B were not affected by PMA.Conclusions The resting membrane potential and voltage-gated K+ currents in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia decreased significantly. It seems that PKC has different effects on the voltage-gated K+ currents of pulmonary artery smooth muscle cells under different conditions.

  5. Potassium test

    Science.gov (United States)

    ... also be done if your provider suspects metabolic acidosis (for example, caused by uncontrolled diabetes) or alkalosis ( ... Hypoaldosteronism (very rare) Kidney failure Metabolic or respiratory acidosis Red blood cell destruction Too much potassium in ...

  6. New targets of inhalational anesthetics-two-pore-domain potassium channels%吸入麻醉药作用的新靶点——双孔钾通道

    Institute of Scientific and Technical Information of China (English)

    李世勇; 罗爱林

    2011-01-01

    背景尽管吸入麻醉药在临床上应用已久,但其作用的分子机制不是很清楚.双孔钾离子通道(two pore potassium channels,K2P)是新发现的钾通道超家族的一员,它被认为是吸入麻醉药敏感性钾通道的分子基础.目的 综合K2P通道相关文献,阐述K2P通道在吸入麻醉药作用机制中的研究进展.内容简要概述K2P通道结构、功能及分类,重点介绍吸入麻醉药敏感性钾通道作为吸入麻醉药作用靶点的实验室依据.趋向通过进一步阐释K2P通道在吸入麻醉药全身麻醉中的作用,有助于削明吸入麻醉药分子作用机制和开发作用于K2P的新麻醉药物.%Background The molecular mechanism of inhalational anesthetics is not fully understood, though it had been administrated clinically for a long time. Two -pore -domain potassium channels (K2P channels), a new member of K + channels superfamily, are deemed as molecular basis of inhalational anesthetics- sensitive K+ channels. Objective To elucidate the advance in inhalational anesthetics mechanism of K2P channels via summarizing the documents related to K2P channels. Content This review concisely outlines the structure, function and classification of K2P channels and thoroughly presents the experimental evidence that inhalational anesthetics-sensitive K+ channels are the target of inhalational anesthetics. Trend To further verify the role of K2P channels in general anesthesia of inhalational anesthetics would be helpful to expound the molecular mechanism of inhalational anesthetics and develop new anesthetic drugs acting on K2P channels.

  7. Stimulation of large-conductance calcium-activated potassium channels inhibits neurogenic contraction of human bladder from patients with urinary symptoms and reverses acetic acid-induced bladder hyperactivity in rats.

    Science.gov (United States)

    La Fuente, José M; Fernández, Argentina; Cuevas, Pedro; González-Corrochano, Rocío; Chen, Mao Xiang; Angulo, Javier

    2014-07-15

    We have analysed the effects of large-conductance calcium-activated potassium channel (BK) stimulation on neurogenic and myogenic contraction of human bladder from healthy subjects and patients with urinary symptoms and evaluated the efficacy of activating BK to relief bladder hyperactivity in rats. Bladder specimens were obtained from organ donors and from men with benign prostatic hyperplasia (BPH). Contractions elicited by electrical field stimulation (EFS) and carbachol (CCh) were evaluated in isolated bladder strips. in vivo cystometric recordings were obtained in anesthetized rats under control and acetic acid-induced hyperactive conditions. Neurogenic contractions of human bladder were potentiated by blockade of BK and small-conductance calcium-activated potassium channels (SK) but were unaffected by the blockade of intermediate calcium-activated potassium channels (IK). EFS-induced contractions were inhibited by BK stimulation with NS-8 or NS1619 or by SK/IK stimulation with NS309 (3µM). CCh-induced contractions were not modified by blockade or stimulation of BK, IK or SK. The anti-cholinergic agent, oxybutynin (0.3µM) inhibited either neurogenic or CCh-induced contractions. Neurogenic contractions of bladders from BPH patients were less sensitive to BK inhibition and more sensitive to BK activation than healthy bladders. The BK activator, NS-8 (5mg/kg; i.v.), reversed bladder hyperactivity induced by acetic acid in rats, while oxybutynin was ineffective. NS-8 did not significantly impact blood pressure or heart rate. BK stimulation specifically inhibits neurogenic contractions in patients with urinary symptoms and relieves bladder hyperactivity in vivo without compromising bladder contractile capacity or cardiovascular safety, supporting its potential therapeutic use for relieving bladder overactivity. PMID:24747752

  8. Effectiveness of copper sulfate, potassium permanganate, and peracetic acid to reduce mortality and infestation of Ichthyobodo nector in channel catfish Ictalurus punctatus (Rafinesque 1818)

    Science.gov (United States)

    Ichthyobodo necator is a single celled bi-flagellate parasite, and in high density can causes significant mortality in young fish. Copper sulfate (CuSO4), potassium permanganate (KMnO4) and peracetic acid (PAA) were evaluated for effectiveness against ichthyobodosis. Treatments were: untreated con...

  9. 运动与ATP-敏感型钾离子通道%Exercise and adenosine triphosphate-sensitive potassium channel

    Institute of Scientific and Technical Information of China (English)

    张如江; 宋永晶

    2014-01-01

    背景:在运动生理状态下,KATP 在调节冠状动脉张力、运动诱导心肌保护效应和延缓骨骼肌疲劳等多个方面具有重要作用。目的:对KATP在运动中的作用进行了综述和探讨,以期为深入了解运动调节机体代谢提供理论参考。方法:检索1991年1月至2014年6月 PubMed数据库及维普中文科技数据库文献。英文检索词为“KATP Channels;Adenosine Triphosphate;Sports;Myocardium;Ion Channels”,中文检索词为“KATP通道;三磷酸腺苷;运动;心肌;离子通道”。选择与KATP分子结构、生物学功能及调控相关,以及KATP与冠状动脉、心肌、骨骼肌疲劳及运动能力相关的文献42篇文献进行探讨。结果与结论:ATP敏感性钾离子通道可以偶联细胞内能量代谢和细胞膜兴奋性,在应对各种生理和病理应激时是保护心肌的效应器之一。长期的耐力训练则会增加骨骼肌和心肌KATP的表达,可能是心肌和骨骼肌对运动应激产生的一种适应性表现。KATP 可能参与冠状动脉血流量的调节。在运动诱导的减轻心肌缺血再灌注损伤的保护效应中,心肌KATP具有重要作用。当骨骼肌疲劳发生时,KATP的激活有利于防止ATP的过度消耗而造成肌纤维损伤和细胞死亡,有利于疲劳的快速恢复。关于KATP与运动能力的关系仍需进一步的研究。%BACKGROUND:In the condition of exercise physiology, adenosine triphosphate-sensitive potassium (KATP) channel plays an important role in many aspects, such as regulation of coronary artery tension, exercise-induced myocardial protection effect and delay of skeletal muscle fatigue. OBJECTIVE:To review and investigate the role of KATP in exercise in order to provide theoretical reference for understanding mechanism underlying exercise regulation of body’s metabolism. METHODS: A computer-based online search of PubMed and VIP databases was performed for articles

  10. Demonstration of physical proximity between the N terminus and the S4-S5 linker of the human ether-a-go-go-related gene (hERG) potassium channel.

    Science.gov (United States)

    de la Peña, Pilar; Alonso-Ron, Carlos; Machín, Angeles; Fernández-Trillo, Jorge; Carretero, Luis; Domínguez, Pedro; Barros, Francisco

    2011-05-27

    Potassium channels encoded by the human ether-à-go-go-related gene (hERG) contribute to cardiac repolarization as a result of their characteristic gating properties. The hERG channel N terminus acts as a crucial determinant in gating. It is also known that the S4-S5 linker couples the voltage-sensing machinery to the channel gate. Moreover, this linker has been repeatedly proposed as an interaction site for the distal portion of the N terminus controlling channel gating, but direct evidence for such an interaction is still lacking. In this study, we used disulfide bond formation between pairs of engineered cysteines to demonstrate the close proximity between the beginning of the N terminus and the S4-S5 linker. Currents from channels with introduced cysteines were rapidly and strongly attenuated by an oxidizing agent, this effect being maximal for cysteine pairs located around amino acids 3 and 542 of the hERG sequence. The state-dependent modification of the double-mutant channels, but not the single-cysteine mutants, and the ability to readily reverse modification with the reducing agent dithiothreitol indicate that a disulfide bond is formed under oxidizing conditions, locking the channels in a non-conducting state. We conclude that physical interactions between the N-terminal-most segment of the N terminus and the S4-S5 linker constitute an essential component of the hERG gating machinery, thus providing a molecular basis for previous data and indicating an important contribution of these cytoplasmic domains in controlling its unusual gating and hence determining its physiological role in setting the electrical behavior of cardiac and other cell types.

  11. Potassium clavulanate

    Directory of Open Access Journals (Sweden)

    Kotaro Fujii

    2010-08-01

    Full Text Available The title salt, K+·C8H8NO5− [systematic name: potassium (2R,5R,Z-3-(2-hydroxyethylidene-7-oxo-4-oxa-1-azabicyclo[3.2.0]heptane-2-carboxylate], a widely used β-lactam antibiotic, is usually chemically unstable even in the solid state owing to its tendency to be hydrolysed. In the crystal structure, the potassium cations are arranged along the a axis, forming interactions to the carboxylate and hydroxy groups, resulting in one-dimensional ionic columns. These columns are arranged along the b axis, connected by O—H...O hydrogen bonds, forming a layer in the ab plane.

  12. Characterization of hERG1a and hERG1b potassium channels-a possible role for hERG1b in the I (Kr) current

    DEFF Research Database (Denmark)

    Larsen, Anders Peter; Olesen, Søren-Peter; Grunnet, Morten;

    2008-01-01

    I (Kr) is the fast component of the delayed rectifier potassium currents responsible for the repolarization of the cardiac muscle. The molecular correlate underlying the I (Kr) current has been identified as the hERG1 channel. Recently, two splice variants of the hERG1 alpha-subunit, hERG1a and hERG......1b, have been shown to be co-expressed in human cardiomyocytes. In this paper, we present the electrophysiological characterization of hERG1a, hERG1b, and co-expressed hERG1a/b channels in a mammalian expression system using the whole-cell patch clamp technique. We also quantified the messenger RNA...... (mRNA) levels of hERG1a and hERG1b in human cardiac tissue, and based on the expressed ratios, we evaluated the resulting currents in Xenopus laevis oocytes. Compared to hERG1a channels, activation was faster for both hERG1b and hERG1a/b channels. The deactivation kinetics was greatly accelerated in...

  13. TLR2/MyD88/NF-κB pathway, reactive oxygen species, potassium efflux activates NLRP3/ASC inflammasome during respiratory syncytial virus infection.

    Directory of Open Access Journals (Sweden)

    Jesus Segovia

    Full Text Available Human respiratory syncytial virus (RSV constitute highly pathogenic virus that cause severe respiratory diseases in newborn, children, elderly and immuno-compromised individuals. Airway inflammation is a critical regulator of disease outcome in RSV infected hosts. Although "controlled" inflammation is required for virus clearance, aberrant and exaggerated inflammation during RSV infection results in development of inflammatory diseases like pneumonia and bronchiolitis. Interleukin-1β (IL-1β plays an important role in inflammation by orchestrating the pro-inflammatory response. IL-1β is synthesized as an immature pro-IL-1β form. It is cleaved by activated caspase-1 to yield mature IL-1β that is secreted extracellularly. Activation of caspase-1 is mediated by a multi-protein complex known as the inflammasome. Although RSV infection results in IL-1β release, the mechanism is unknown. Here in, we have characterized the mechanism of IL-1β secretion following RSV infection. Our study revealed that NLRP3/ASC inflammasome activation is crucial for IL-1β production during RSV infection. Further studies illustrated that prior to inflammasome formation; the "first signal" constitutes activation of toll-like receptor-2 (TLR2/MyD88/NF-κB pathway. TLR2/MyD88/NF-κB signaling is required for pro-IL-1β and NLRP3 gene expression during RSV infection. Following expression of these genes, two "second signals" are essential for triggering inflammasome activation. Intracellular reactive oxygen species (ROS and potassium (K(+ efflux due to stimulation of ATP-sensitive ion channel promote inflammasome activation following RSV infection. Thus, our studies have underscored the requirement of TLR2/MyD88/NF-κB pathway (first signal and ROS/potassium efflux (second signal for NLRP3/ASC inflammasome formation, leading to caspase-1 activation and subsequent IL-1β release during RSV infection.

  14. 电压依赖性钾离子通道在肺动脉高压发病过程中的作用%Role of voltage-gated potassium channels in the pathogenesis of pulmonary artery hypertension

    Institute of Scientific and Technical Information of China (English)

    李晶; 王军

    2011-01-01

    Pulmonary artery hypertension (PAH) is a syndrome induced by restricted flow of pulmonary artery, which leads to sustainable increases in pulmonary vascular resistance and pulmonary artery pressure and even right heart failure. The predominant pathogenic mechanisms of PAH are pulmonary vasoconstriction, vascular remodeling and in situ thrombus formation. Researches show that down-regulation of potassium channels especially voltage-gated potassium channels (Ky) is associated with the imbalance between proliferation and apoptosis in pulmonary artery smooth muscle cells, which in turn to pulmonary vascular remodeling. This review concentrates on the effect of Kv channels in leading to pulmonary artery remodeling in human PAH and its possible mechanism.%肺动脉高压是一种肺血流受限引起肺血管阻力和压力持续性增高,最终导致右心衰竭甚至死亡的综合征.病理生理学改变主要为肺血管收缩、重塑及原位血栓形成.研究表明,钾离子通道尤其电压依赖性钾离子通道功能与表达水平的降低是引起肺血管平滑肌细胞增殖和凋亡异常、肺血管重塑的关键因素.本文着重论述近年来有关电压依赖性钾离子通道与肺动脉高压肺血管重塑发生相关机制的研究进展.

  15. Effects of cisplatin on potassium currents in CT26 cells

    Directory of Open Access Journals (Sweden)

    Naveen Sharma

    2016-01-01

    Conclusion: Potassium currents were detected in CT26 cells and the currents were reduced by the application of tetraethylammonium (TEA chloride, iberiotoxin, a big conductance calcium-activated potassium channel blocker and barium. The potassium currents were enhanced to 192< by the application of cisplatin (0.5 mM. Moreover, the increase of potassium currents by cisplatin was further inhibited by the application of TEA confirming the action of cisplatin on potassium channels. In addition, relative current induced by cisplatin in CT26 cells was bit larger than in normal IEC-6 cells.

  16. Hydrophobic interactions between the S5 segment and the pore helix stabilizes the closed state of Slo2.1 potassium channels.

    Science.gov (United States)

    Suzuki, Tomoyuki; Hansen, Angela; Sanguinetti, Michael C

    2016-04-01

    Under normal physiological conditions, Slo2.1K(+) channels are in a closed state unless activated by an elevation in [Na(+)]i. Fenamates such as niflumic acid also activate Slo2.1. Previous studies suggest that activation of Slo2.1 channels is mediated by a conformational change in the selectivity filter, and not a widening of the aperture formed by the S6 segment bundle crossing as occurs in voltage-gated K(+) channels. It is unclear how binding of Na(+) or fenamates is allosterically linked to opening of the presumed selectivity filter activation gate in Slo2.1. Here we examined the role of the S5 transmembrane segment in the activation of Slo2.1. Channels were heterologously expressed in Xenopus laevis oocytes and whole cell currents measured with the voltage-clamp technique. Ala substitution of five residues located on a single face of the S5 α-helical segment induced constitutive channel activity. Leu-209, predicted to face towards Phe-240 in the pore helix was investigated by further mutagenesis. Mutation of Leu-209 to Glu or Gln induced maximal channel activation as did the combined mutation to Ala of all three hydrophobic S5 residues predicted to be adjacent to Phe-240. Together these results suggest that hydrophobic interactions between residues in S5 and the C-terminal end of the pore helix stabilize Slo2.1 channels in a closed state.

  17. Gating of a pH-sensitive K(2P potassium channel by an electrostatic effect of basic sensor residues on the selectivity filter.

    Directory of Open Access Journals (Sweden)

    Leandro Zúñiga

    Full Text Available K(+ channels share common selectivity characteristics but exhibit a wide diversity in how they are gated open. Leak K(2P K(+ channels TASK-2, TALK-1 and TALK-2 are gated open by extracellular alkalinization. The mechanism for this alkalinization-dependent gating has been proposed to be the neutralization of the side chain of a single arginine (lysine in TALK-2 residue near the pore of TASK-2, which occurs with the unusual pK(a of 8.0. We now corroborate this hypothesis by transplanting the TASK-2 extracellular pH (pH(o sensor in the background of a pH(o-insensitive TASK-3 channel, which leads to the restitution of pH(o-gating. Using a concatenated channel approach, we also demonstrate that for TASK-2 to open, pH(o sensors must be neutralized in each of the two subunits forming these dimeric channels with no apparent cross-talk between the sensors. These results are consistent with adaptive biasing force analysis of K(+ permeation using a model selectivity filter in wild-type and mutated channels. The underlying free-energy profiles confirm that either a doubly or a singly charged pH(o sensor is sufficient to abolish ion flow. Atomic detail of the associated mechanism reveals that, rather than a collapse of the pore, as proposed for other K(2P channels gated at the selectivity filter, an increased height of the energetic barriers for ion translocation accounts for channel blockade at acid pH(o. Our data, therefore, strongly suggest that a cycle of protonation/deprotonation of pH(o-sensing arginine 224 side chain gates the TASK-2 channel by electrostatically tuning the conformational stability of its selectivity filter.

  18. Pharmacologic inhibition of small-conductance calcium-activated potassium (SK) channels by NS8593 reveals atrial antiarrhythmic potential in horses

    DEFF Research Database (Denmark)

    Haugaard, Maria Mathilde; Hesselkilde, Eva Zander; Pehrson, Steen Michael;

    2015-01-01

    . METHODS: Cardiac biopsies were analyzed to investigate the expression level of the most prominent cardiac ion channels, with special focus on SK channels, in the equine heart. Subcellular distribution of SK isoform 2 (SK2) was assessed by immunohistochemistry and confocal microscopy......, and ventricular depolarization and repolarization times. RESULTS: Analysis revealed equivalent mRNA transcript levels of the 3 SK channel isoforms in atria compared to ventricles. Immunohistochemistry and confocal microscopy displayed a widespread distribution of SK2 in both atrial and ventricular cardiomyocytes...

  19. Dystrophin is required for the normal function of the cardio-protective K(ATP channel in cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Laura Graciotti

    Full Text Available Duchenne and Becker muscular dystrophy patients often develop a cardiomyopathy for which the pathogenesis is still unknown. We have employed the murine animal model of Duchenne muscular dystrophy (mdx, which develops a cardiomyopathy that includes some characteristics of the human disease, to study the molecular basis of this pathology. Here we show that the mdx mouse heart has defects consistent with alteration in compounds that regulate energy homeostasis including a marked decrease in creatine-phosphate (PC. In addition, the mdx heart is more susceptible to anoxia than controls. Since the cardio-protective ATP sensitive potassium channel (K(ATP complex and PC have been shown to interact we investigated whether deficits in PC levels correlate with other molecular events including K(ATP ion channel complex presence, its functionality and interaction with dystrophin. We found that this channel complex is present in the dystrophic cardiac cell membrane but its ability to sense a drop in the intracellular ATP concentration and consequently open is compromised by the absence of dystrophin. We further demonstrate that the creatine kinase muscle isoform (CKm is displaced from the plasma membrane of the mdx cardiac cells. Considering that CKm is a determinant of K(ATP channel complex function we hypothesize that dystrophin acts as a scaffolding protein organizing the K(ATP channel complex and the enzymes necessary for its correct functioning. Therefore, the lack of proper functioning of the cardio-protective K(ATP system in the mdx cardiomyocytes may be part of the mechanism contributing to development of cardiac disease in dystrophic patients.

  20. Opening of small and intermediate calcium-activated potassium channels induces relaxation mainly mediated by nitric-oxide release in large arteries and endothelium-derived hyperpolarizing factor in small arteries from rat

    DEFF Research Database (Denmark)

    Stankevicius, Edgaras; Dalsgaard, Thomas; Kroigaard, Christel;

    2011-01-01

    current, and NO release that were blocked by apamin and TRAM-34 or charybdotoxin. These findings suggest that opening of SK(Ca) and IK(Ca) channels leads to endothelium-dependent relaxation that is mediated mainly by NO in large mesenteric arteries and by EDHF-type relaxation in small mesenteric arteries......This study was designed to investigate whether calcium-activated potassium channels of small (SK(Ca) or K(Ca)2) and intermediate (IK(Ca) or K(Ca)3.1) conductance activated by 6,7-dichloro-1H-indole-2,3-dione 3-oxime (NS309) are involved in both nitric oxide (NO) and endothelium......-derived hyperpolarizing factor (EDHF)-type relaxation in large and small rat mesenteric arteries. Segments of rat superior and small mesenteric arteries were mounted in myographs for functional studies. NO was recorded using NO microsensors. SK(Ca) and IK(Ca) channel currents and mRNA expression were investigated in...

  1. Potassium Intake, Bioavailability, Hypertension, and Glucose Control

    Science.gov (United States)

    Stone, Michael S.; Martyn, Lisa; Weaver, Connie M.

    2016-01-01

    Potassium is an essential nutrient. It is the most abundant cation in intracellular fluid where it plays a key role in maintaining cell function. The gradient of potassium across the cell membrane determines cellular membrane potential, which is maintained in large part by the ubiquitous ion channel the sodium-potassium (Na+-K+) ATPase pump. Approximately 90% of potassium consumed (60–100 mEq) is lost in the urine, with the other 10% excreted in the stool, and a very small amount lost in sweat. Little is known about the bioavailability of potassium, especially from dietary sources. Less is understood on how bioavailability may affect health outcomes. Hypertension (HTN) is the leading cause of cardiovascular disease (CVD) and a major financial burden ($50.6 billion) to the US public health system, and has a significant impact on all-cause morbidity and mortality worldwide. The relationship between increased potassium supplementation and a decrease in HTN is relatively well understood, but the effect of increased potassium intake from dietary sources on blood pressure overall is less clear. In addition, treatment options for hypertensive individuals (e.g., thiazide diuretics) may further compound chronic disease risk via impairments in potassium utilization and glucose control. Understanding potassium bioavailability from various sources may help to reveal how specific compounds and tissues influence potassium movement, and further the understanding of its role in health. PMID:27455317

  2. Potassium Intake, Bioavailability, Hypertension, and Glucose Control.

    Science.gov (United States)

    Stone, Michael S; Martyn, Lisa; Weaver, Connie M

    2016-01-01

    Potassium is an essential nutrient. It is the most abundant cation in intracellular fluid where it plays a key role in maintaining cell function. The gradient of potassium across the cell membrane determines cellular membrane potential, which is maintained in large part by the ubiquitous ion channel the sodium-potassium (Na+-K+) ATPase pump. Approximately 90% of potassium consumed (60-100 mEq) is lost in the urine, with the other 10% excreted in the stool, and a very small amount lost in sweat. Little is known about the bioavailability of potassium, especially from dietary sources. Less is understood on how bioavailability may affect health outcomes. Hypertension (HTN) is the leading cause of cardiovascular disease (CVD) and a major financial burden ($50.6 billion) to the US public health system, and has a significant impact on all-cause morbidity and mortality worldwide. The relationship between increased potassium supplementation and a decrease in HTN is relatively well understood, but the effect of increased potassium intake from dietary sources on blood pressure overall is less clear. In addition, treatment options for hypertensive individuals (e.g., thiazide diuretics) may further compound chronic disease risk via impairments in potassium utilization and glucose control. Understanding potassium bioavailability from various sources may help to reveal how specific compounds and tissues influence potassium movement, and further the understanding of its role in health. PMID:27455317

  3. Potassium Intake, Bioavailability, Hypertension, and Glucose Control

    Directory of Open Access Journals (Sweden)

    Michael S. Stone

    2016-07-01

    Full Text Available Potassium is an essential nutrient. It is the most abundant cation in intracellular fluid where it plays a key role in maintaining cell function. The gradient of potassium across the cell membrane determines cellular membrane potential, which is maintained in large part by the ubiquitous ion channel the sodium-potassium (Na+-K+ ATPase pump. Approximately 90% of potassium consumed (60–100 mEq is lost in the urine, with the other 10% excreted in the stool, and a very small amount lost in sweat. Little is known about the bioavailability of potassium, especially from dietary sources. Less is understood on how bioavailability may affect health outcomes. Hypertension (HTN is the leading cause of cardiovascular disease (CVD and a major financial burden ($50.6 billion to the US public health system, and has a significant impact on all-cause morbidity and mortality worldwide. The relationship between increased potassium supplementation and a decrease in HTN is relatively well understood, but the effect of increased potassium intake from dietary sources on blood pressure overall is less clear. In addition, treatment options for hypertensive individuals (e.g., thiazide diuretics may further compound chronic disease risk via impairments in potassium utilization and glucose control. Understanding potassium bioavailability from various sources may help to reveal how specific compounds and tissues influence potassium movement, and further the understanding of its role in health.

  4. Estradiol rapidly induces the translocation and activation of the intermediate conductance calcium activated potassium channel in human eccrine sweat gland cells.

    LENUS (Irish Health Repository)

    Muchekehu, Ruth W

    2009-02-01

    Steroid hormones target K+ channels as a means of regulating electrolyte and fluid transport. In this study, ion transporter targets of Estradiol (E2) were investigated in the human eccrine sweat gland cell line NCL-SG3.

  5. Apamin-Sensitive Small Conductance Calcium-Activated Potassium Channels were Negatively Regulated by Captopril in Volume-Overload Heart Failure Rats.

    Science.gov (United States)

    Hongyuan, Bai; Xin, Dong; Jingwen, Zhang; Li, Gao; Yajuan, Ni

    2016-08-01

    In heart failure (HF), the malignant arrhythmias occur frequently; a study demonstrated that upregulation of I KAS resulted in recurrent spontaneous ventricular fibrillation in HF. However, the regulation of SK channels was poorly understood. The activation of SK channels depended on [Ca(2+)]i and PP2A; studies suggested that angiotensin II can regulate them. So, we hypothesized that in HF, the excess of angiotensin may regulate the SK channels and result in the remodeling of SK channels. To test the hypothesis, we used volume-overload-induced HF rat model, treated with captopril, performed whole-cell patch clamp to record apamin-sensitive currents (I KAS), and I-V curve was studied. The sensitivity of I KAS to [Ca(2+)]i was also explored by setting various [Ca(2+)]i (10, 100, 500, 900, 1000, and 10,000 nM), and the steady-state Ca(2+) response of I KAS was attained and performed Hill fitting with the equation (y = 1/[1 + (EC50/x) (n) ]). Immunofluorescent staining, real-time PCR, Western blot were also carried out to furtherly investigate the underlying molecular mechanisms of the regulation. Captopril significantly decreased the mean density of I KAS when [Ca(2+)]i was 500, 900, 1000, and 10000 nM. The Hill fitting showed significantly different EC50 values and the Hill coefficients and showed captopril significantly shifted rightward the steady-state Ca(2+) response of I KAS. The results of real-time PCR and Western blot demonstrated captopril decreased the mRNA and protein expression of SK3 channels. Captopril significantly downregulated the sensitivity of SK channels to [Ca(2+)]i and the SK3 channels expression in HF, and reversed the SK channels remodeling. PMID:26924798

  6. Effects of potassium channel and Na+-Ca2+ exchange blockers on the responses of slowly adapting pulmonary stretch receptors to hyperinflation in flecainide-treated rats

    OpenAIRE

    Matsumoto, Shigeji; Nishikawa, Toshimi; Yoshida, Shinki; Ikeda, Mizuho; Tanimoto, Takeshi; Saiki, Chikako; Takeda, Mamoru

    2001-01-01

    The effects of K+ channel blockers, such as 4-aminopyridine (4-AP) and tetraethylammonium (TEA), and a reverse-mode Na+ – Ca2+ exchange blocker, 2-[2-[4-(4-nitrobenzyloxyl) phenyl] ethyl] isothiourea methanesulphonate (KB-R7943), on the responses of slowly adapting pulmonary stretch receptor activity to hyperinflation (inflation volume=3 tidal volumes) were investigated in anaesthetized, artificially ventilated, unilaterally vagotomized rats after pretreatment with a Na+ channel blocker fleca...

  7. Expresion of A-type potassium channel Kv1. 4 in the hippocampi regions of epilepsy model%A型钾通道Kv1.4在致痫大鼠海马区的表达

    Institute of Scientific and Technical Information of China (English)

    李亚伟; 曾常茜; 邹飒枫; 胡波; 李冬平

    2011-01-01

    Objective This article aimed to check the expression of A-type potassium channel Kv1.4 in the hippocampi CA1 ,CA3 and DG regions of epilepsy model-induced by pentylenetetrazol (PTZ) ,and discuss the relation of A-type potassium channel to epilepsy.Methods Forty SD rats were divided randomly into control group and epilepsy groups ( 1h,24h and 72h after injecting PTZ) ,each group had ten rats.The rats models of epilepsy were established by injecting PTZ.Kv.1 4 protein were deteced at different times in the CA1 ,CA3 and DG regions of hippocampus,by using immunohistoehemical assay and Western Blot.Results PTZ-induced epilepsy caused a obvious decline in Kv1.4 protein at 1h,24h and 72h time point( P <0.05 ); the expressions of Kv1.4 protein among the experimental groups were not obviously different( P >0.05).Conclusions A-type potassium channel Kv1.4 had a wide distributing in the hippocampus of SD rats,expressed abundantly and especially in neuraxon.The expression of A-type potassium channel Kv1.4 protein in hippocampus of epileptic model was descendant, and this result clewed that the downregulation may be associated with epilepsy.%目的 通过检测A型钾通道Kv1.4在戊四唑(PTZ)致痈大鼠海马CA1、CA3及齿状同区的表达变化,探讨A型钾通道与癫痫发病的关系.方法 SD大鼠40只,随机分为对照组、致痫后1h、24h、72h组,每组各10只.腹腔注射PTZ制备大鼠癫痫模型,应用免疫组化及Western Blot技术检测Kv1.4在各时间段海马CA1、CA3及齿状回区的蛋白表达.结果 致痫组大鼠海马区Kv1.4蛋白水平在致痫后1h、24h、72h 3个时间段均明显低于正常组(P0.05).结论 (1)A型钾通道Kv1.4在SD大鼠海马中广泛分布.表达丰富,以轴突处最为明显.(2)大鼠癫痫模型海马区A型钾通道Kv1.4蛋白表达减少,提示Kv1.4的表达下调可能与癫痫的发病相关.

  8. Proapoptotic Role of Potassium Ions in Liver Cells

    Directory of Open Access Journals (Sweden)

    Zhenglin Xia

    2016-01-01

    Full Text Available Potassium channels are transmembrane proteins that selectively promote the infiltration of potassium ions. The significance of these channels for tumor biology has become obvious. However, the effects of potassium ions on the tumor or normal cells have seldom been studied. To address this problem, we studied the biological effects of L02 and HepG2 cells with ectogenous potassium ions. Cell proliferation, cell cycle, and apoptosis rate were analyzed. Our results indicated that potassium ions inhibited proliferation of L02 and HepG2 cells and promoted their apoptosis. Potassium ions induced apoptosis through regulating Bcl-2 family members and depolarized the mitochondrial membrane, especially for HepG2 cell. These biological effects were associated with channel protein HERG. By facilitating expression of channel protein HERG, potassium ions may prevent it from being shunted to procancerous pathways by inducing apoptosis. These results demonstrated that potassium ions may be a key regulator of liver cell function. Thus, our findings suggest that potassium ions could inhibit tumorigenesis through inducing apoptosis of hepatoma cells by upregulating potassium ions transport channel proteins HERG and VDAC1.

  9. Proapoptotic Role of Potassium Ions in Liver Cells.

    Science.gov (United States)

    Xia, Zhenglin; Huang, Xusen; Chen, Kaiyun; Wang, Hanning; Xiao, Jinfeng; He, Ke; Huang, Rui; Duan, Xiaopeng; Liu, Hao; Zhang, Jinqian; Xiang, Guoan

    2016-01-01

    Potassium channels are transmembrane proteins that selectively promote the infiltration of potassium ions. The significance of these channels for tumor biology has become obvious. However, the effects of potassium ions on the tumor or normal cells have seldom been studied. To address this problem, we studied the biological effects of L02 and HepG2 cells with ectogenous potassium ions. Cell proliferation, cell cycle, and apoptosis rate were analyzed. Our results indicated that potassium ions inhibited proliferation of L02 and HepG2 cells and promoted their apoptosis. Potassium ions induced apoptosis through regulating Bcl-2 family members and depolarized the mitochondrial membrane, especially for HepG2 cell. These biological effects were associated with channel protein HERG. By facilitating expression of channel protein HERG, potassium ions may prevent it from being shunted to procancerous pathways by inducing apoptosis. These results demonstrated that potassium ions may be a key regulator of liver cell function. Thus, our findings suggest that potassium ions could inhibit tumorigenesis through inducing apoptosis of hepatoma cells by upregulating potassium ions transport channel proteins HERG and VDAC1. PMID:27069917

  10. ATP敏感性钾通道对血管平滑肌张力的调控%The Control of ATP Sensitive Potassium Passage over the Tension of Blood-vessel Smooth Muscle

    Institute of Scientific and Technical Information of China (English)

    任雪平; 郭玉平

    2006-01-01

    ATP敏感性钾通道是一种受细胞内ATP浓度,NDPs,KCOs,SUs等多种因素调节启闭的钾通道.在生理状态下,KATP处于关闭状态;在缺血、缺氧等病理状态下KATP通道则激活开放,并通过改变细胞兴奋性,影响细胞功能而发挥重要的调节作用.

  11. Effect of mitochondrial potassium channel on the renal protection mediated by sodium thiosulfate against ethylene glycol induced nephrolithiasis in rat model

    Directory of Open Access Journals (Sweden)

    N. Baldev

    2015-12-01

    Full Text Available Purpose: Sodium thiosulfate (STS is clinically reported to be a promising drug in preventing nephrolithiasis. However, its mechanism of action remains unclear. In the present study, we investigated the role of mitochondrial KATP channel in the renal protection mediated by STS. Materials and Methods: Nephrolithiasis was induced in Wistar rats by administrating 0.4% ethylene glycol (EG along with 1% ammonium chloride for one week in drinking water followed by only 0.75% EG for two weeks. Treatment groups received STS, mitochondrial KATP channel opener and closer exclusively or in combination with STS for two weeks. Results: Animals treated with STS showed normal renal tissue architecture, supported by near normal serum creatinine, urea and ALP activity. Diazoxide (mitochondria KATP channel opening treatment to the animal also showed normal renal tissue histology and improved serum chemistry. However, an opposite result was shown by glibenclamide (mitochondria KATP channel closer treated rats. STS administered along with diazoxide negated the renal protection rendered by diazoxide alone, while it imparted protection to the glibenclamide treated rats, formulating a mitochondria modulated STS action. Conclusion: The present study confirmed that STS render renal protection not only through chelation and antioxidant effect but also by modulating the mitochondrial KATP channel for preventing urolithiasis.

  12. GABA/sub B/ receptor activation inhibits Ca/sup 2 +/-activated potassium channels in synaptosomes: involvement of G-proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ticku, M.K.; Delgado, A.

    1989-01-01

    /sup 86/Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca/sup 2 +/-activated K/sup +/-channels. Depolarization of /sup 86/Rb-loaded synaptosomes in physiological buffer increased Ca/sup 2 +/-activated /sup 86/Rb-efflux by 400%. The /sup 86/Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La/sup 3 +/ indicating the involvement of Ca/sup 2 +/-activated K/sup +/-channels. (-)Baclofen inhibited Ca/sup 2 +/-activated /sup 86/Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but not by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca/sup 2 +/-activated K/sup +/-channels. These results suggest that baclofen inhibits Ca/sup 2 +/-activated K/sup +/-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology.

  13. Reduced KCNQ4-encoded voltage-dependent potassium channel activity underlies impaired ß-adrenoceptor-mediated relaxation of renal arteries in hypertension

    DEFF Research Database (Denmark)

    Chadha, Preet S; Zunke, Friederike; Zhu, Hai-Lei;

    2012-01-01

    strategy, as well as pharmacological tools, to examine the hypothesis that Kv7.4 channels contribute to ß-adrenoceptor-mediated vasodilation in the renal vasculature and underlie the vascular deficit in spontaneously hypertensive rats. Quantitative PCR and immunohistochemistry confirmed gene and protein...... spontaneously hypertensive rats, which was associated with ˜60% decrease in Kv7.4 abundance. This study provides the first evidence that Kv7 channels contribute to ß-adrenoceptor-mediated vasodilation in the renal vasculature and that abrogation of Kv7.4 channels is strongly implicated in the impaired ß......-adrenoceptor pathway in spontaneously hypertensive rats. These findings may provide a novel pathogenic link between arterial dysfunction and hypertension....

  14. Underlying mechanism of regulatory actions of diclofenac, a nonsteroidal anti-inflammatory agent, on neuronal potassium channels and firing: an experimental and theoretical study.

    Science.gov (United States)

    Huang, C W; Hung, T Y; Liao, Y K; Hsu, M C; Wu, S N

    2013-06-01

    Diclofenac (DIC), a nonsteroidal anti-inflammatory drug, is known to exert anti-nociceptive and anti-convulsant actions; however, its effects on ion currents, in neurons remain debatable. We aimed to investigate (1) potential effects of diclofenac on membrane potential and potassium currents in differentiated NSC-34 neuronal cells and dorsal root ganglion (DRG) neurons with whole-cell patch-clamp technology, and (2) firing of action potentials (APs), using a simulation model from hippocampal CA1 pyramidal neurons based on diclofenac's effects on potassium currents. In the NSC-34 cells, diclofenac exerted an inhibitory effect on delayed-rectifier K⁺ current (I(KDR)) with an IC₅₀ value of 73 μM. Diclofenac not merely inhibited the I(KDR) amplitude in response to membrane depolarization, but also accelerated the process of current inactivation. The inhibition by diclofenac of IK(DR) was not reversed by subsequent application of either naloxone. Importantly, diclofenac (300 μM) increased the amplitude of M-type K⁺ current (I)(KM)), while flupirtine (10 μM) or meclofenamic acid (10 μM) enhanced it effectively. Consistently, diclofenac (100 μM) increased the amplitude of I(KM) and diminished the I(KDR) amplitude, with a shortening of inactivation time constant in DRG neurons. Furthermore, by using the simulation modeling, we demonstrated the potential electrophysiological mechanisms underlying changes in AP firing caused by diclofenac. During the exposure to diclofenac, the actions on both I(KM) and I(KDR) could be potential mechanism through which it influences the excitability of fast-spiking neurons. Caution needs to be made in attributing the effects of diclofenac primarily to those produced by the activation of I(KM). PMID:23959723

  15. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations.

    Science.gov (United States)

    Wu, Xiaokun; Han, Min; Ming, Dengming

    2015-10-01

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors. PMID:26450298

  16. Genetic deletion of TREK-1 or TWIK-1/TREK-1 potassium channels does not alter the basic electrophysiological properties of mature hippocampal astrocytes in situ

    Directory of Open Access Journals (Sweden)

    Yixing eDu

    2016-02-01

    Full Text Available We have recently shown that a linear current-to-voltage (I-V relationship of membrane conductance (passive conductance reflects the intrinsic property of K+ channels in mature astrocytes. While passive conductance is known to underpin a highly negative and stable membrane potential (VM essential for the basic homeostatic function of astrocytes, a complete repertoire of the involved K+ channels remains elusive. TREK-1 two-pore domain K+ channel (K2P is highly expressed in astrocytes, and covalent association of TREK-1 with TWIK-1, another highly expressed astrocytic K2P, has been reported as a mechanism underlying the trafficking of this heterodimer channel to the membrane and contributing to astrocytes’ passive conductance. To decipher the individual contribution of TREK-1 and address whether the appearance of passive conductance is conditional to the co-expression of TWIK-1/TREK-1 in astrocytes, TREK-1 single and TWIK-1/TREK-1 double gene knockout mice were used in the present study. The relative quantity of mRNA encoding other astrocyte K+ channels, such as Kir4.1, Kir5.1, and TREK-2, was not altered in these gene knockout mice. Whole-cell recording from hippocampal astrocytes in situ revealed no detectable changes in astrocyte passive conductance, VM, or membrane input resistance (Rin in either kind of gene knockout mouse. Additionally, TREK-1 proteins were mainly located in the intracellular compartments of the hippocampus. Altogether, genetic deletion of TREK-1 alone or together with TWIK-1 produced no obvious alteration in the basic electrophysiological properties of hippocampal astrocytes. Thus, future research focusing on other K+ channels may shed light on this long-standing and important question in astrocyte physiology.

  17. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaokun; Han, Min; Ming, Dengming, E-mail: dming@fudan.edu.cn [Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai (China)

    2015-10-07

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  18. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    Science.gov (United States)

    Wu, Xiaokun; Han, Min; Ming, Dengming

    2015-10-01

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  19. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    International Nuclear Information System (INIS)

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors

  20. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations.

    Science.gov (United States)

    Wu, Xiaokun; Han, Min; Ming, Dengming

    2015-10-01

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  1. Sine-wave electrical stimulation initiates a voltage-gated potassium channel-dependent soft tissue response characterized by induction of hemocyte recruitment and collagen deposition.

    Science.gov (United States)

    Franklin, Brandon M; Maroudas, Eleni; Osborn, Jeffrey L

    2016-06-01

    Soft tissue repair is a complex process that requires specific communication between multiple cell types to orchestrate effective restoration of physiological functions. Macrophages play a critical role in this wound healing process beginning at the onset of tissue injury. Understanding the signaling mechanisms involved in macrophage recruitment to the wound site is an essential step for developing more effective clinical therapies. Macrophages are known to respond to electrical fields, but the underlying cellular mechanisms mediating this response is unknown. This study demonstrated that low-amplitude sine-wave electrical stimulation (ES) initiates a soft tissue response in the absence of injury in Procambarus clarkii This cellular response was characterized by recruitment of macrophage-like hemocytes to the stimulation site indicated by increased hemocyte density at the site. ES also increased tissue collagen deposition compared to sham treatment (P astemizole decreased both hemocyte recruitment and collagen deposition compared to saline infusion (P < 0.05), whereas inhibition of calcium-permeable channels with ruthenium red did not affect either response to ES Thus, macrophage-like hemocytes in P. clarkii elicit a wound-like response to exogenous ES and this is accompanied by collagen deposition. This response is mediated by KV channels but independent of Ca(2+) channels. We propose a significant role for KV channels that extends beyond facilitating Ca(2+) transport via regulation of cellular membrane potentials during ES of soft tissue. PMID:27335435

  2. Effect of Heavy Metal Cadmium lon on Outward Potassium Channel in Cell%重金属Cd2+对细胞外向K+通道的影响

    Institute of Scientific and Technical Information of China (English)

    杜春蕾; 王丽红; 江娜; 黄晓华

    2011-01-01

    重金属镉(Cd)污染及其对动植物的伤害机理,已成为中外相关专家研究的热点,但是细胞毒害机理依然不清楚.分布于细胞膜上的通道蛋白,不仅是外来物质作用于生物体的首要位点,且会影响离子通道的功能.为阐释镉(Cd)污染致病与毒害的细胞学机理,选择具有重要生理功能的细胞钾离子(K+)通道为示踪,并应用全细胞膜片钳技术,研究了Cd2+对hERG(K+)通道电流的影响.结果表明:(1)Cd2+能显著抑制hERG K+通道的稳态电流和尾电流,干扰通道蛋白正常开关;(2)当10,50,200 μg/LCd2+作用细胞后,hERG(K+)通道激活曲线右移,斜率因子不变;(3)当10μg/L Cd2+作用细胞后,hERG K+通道电流迅速下降,且随Cd2+浓度增加,此抑制作用未发生明显改变.本工作从一新的角度揭示了Cd2+细胞毒性机理.结果提示,钾通道可作为镉污染致病与毒害的细胞学机理研究的靶点.%Cadmium (Cd) contamination leads to a variety of clinical diseases. Potassium ion (K+) channel is the most diverse and ubiquitous class of ion channels, and it plays the important physiological roles in human. In order to elucidate the cellular mechanism of the pathogenic and toxic effect of Cd2+pollution, the effects of Cd2+on the currents of a human ether-a-go-go related gene (hERG) K+channel was investigated by a whole-cell patch clamp method. The results indicated that Cd2+ significantly inhibited the steady-state and tail currents of hERG K+channel. When cells were treated with 10, 50, 200 μg/L Cd2+, the activation curve of hERG K+channel was right-shifted, and the slope factor was not changed. The currents of hERG K+ channel was not significantly changed with increasing the concentration of Cd2+. The results suggested that potassium channels can be used as the target of the research on the cellular mechanism of the pathogenic and toxic effect of Cd2+pollution.

  3. High-dose fasudil preserves postconditioning against myocardial infarction under hyperglycemia in rats: role of mitochondrial KATP channels

    Directory of Open Access Journals (Sweden)

    Ichinomiya Taiga

    2012-03-01

    Full Text Available Abstract Background The current study was carried out to determine whether fasudil hydrochloride (fasudil, a Rho-kinase inhibitor, has myocardial postconditioning (PostC activity under hyperglycemia as well as normoglycemia, and if so, whether the effects could be mediated by mitochondrial ATP-sensitive potassium (m-KATP channels. Methods Male Sprague-Dawley rats were anesthetized with sodium pentobarbital. After opening the chest, all rats underwent 30-min coronary artery occlusion followed by 2-h reperfusion. The rats received low-dose (0.15 mg/kg or high-dose (0.5 mg/kg fasudil or diazoxide, an m-KATP channel opener, at 10 mg/kg, just before reperfusion under normoglycemic or hyperglycemic conditions. In another group, rats received 5-hydroxydecanoic acid (5HD, an m-KATP channel blocker, at 10 mg/kg, before high-dose fasudil. Myocardial infarct size was expressed as a percentage of area at risk (AAR. Results Under normoglycemia, low-dose and high-dose fasudil and diazoxide reduced myocardial infarct size (23 ± 8%, 21 ± 9% and 21 ± 10% of AAR, respectively compared with that in the control (42 ± 7%. Under hyperglycemia, low-dose fasudil (40 ± 11% and diazoxide (44 ± 14% could not exert this beneficial effect, but high-dose fasudil reduced myocardial infarct size in the same manner as under normoglycemia (21 ± 13%. 5HD prevented fasudil-induced reduction of myocardial infarct size (42 ± 13%. Conclusion Fasudil induces PostC against myocardial infarction via activation of m-KATP channels in the rat. Although hyperglycemia attenuates the PostC, high-dose fasudil can restore cardioprotection.

  4. cAMP-independent dilation of coronary arterioles to adenosine : role of nitric oxide, G proteins, and K(ATP) channels.

    Science.gov (United States)

    Hein, T W; Kuo, L

    1999-10-01

    Adenosine is known to play an important role in the regulation of coronary blood flow during metabolic stress. However, there is sparse information on the mechanism of adenosine-induced dilation at the microcirculatory levels. In the present study, we examined the role of endothelial nitric oxide (NO), G proteins, cyclic nucleotides, and potassium channels in coronary arteriolar dilation to adenosine. Pig subepicardial coronary arterioles (50 to 100 microm in diameter) were isolated, cannulated, and pressurized to 60 cm H(2)O without flow for in vitro study. The arterioles developed basal tone and dilated dose dependently to adenosine. Disruption of endothelium, blocking of endothelial ATP-sensitive potassium (K(ATP)) channels by glibenclamide, and inhibition of NO synthase by N(G)-nitro-L-arginine methyl ester and of soluble guanylyl cyclase by 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one produced identical attenuation of vasodilation to adenosine. Combined administration of these inhibitors did not further attenuate the vasodilatory response. Production of NO from coronary arterioles was significantly increased by adenosine. Pertussis toxin, but not cholera toxin, significantly inhibited vasodilation to adenosine, and this inhibitory effect was only evident in vessels with an intact endothelium. Tetraethylammonium, glibenclamide, and a high concentration of extraluminal KCl abolished vasodilation of denuded vessels to adenosine; however, inhibition of calcium-activated potassium channels by iberiotoxin had no effect on this dilation. Rp-8-Br-cAMPS, a cAMP antagonist, inhibited vasodilation to cAMP analog 8-Br-cAMP but failed to block adenosine-induced dilation. Furthermore, vasodilations to 8-Br-cAMP and sodium nitroprusside were not inhibited by glibenclamide, indicating that cAMP- and cGMP-induced dilations are not mediated by the activation of K(ATP) channels. These results suggest that adenosine activates both endothelial and smooth muscle pathways to exert

  5. KCNQ4 channel activation by BMS-204352 and retigabine

    DEFF Research Database (Denmark)

    Schrøder, Rikke Louise K.; Jespersen, Thomas; Christophersen, P;

    2001-01-01

    Activation of potassium channels generally reduces cellular excitability, making potassium channel openers potential drug candidates for the treatment of diseases related to hyperexcitabilty such as epilepsy, neuropathic pain, and neurodegeneration. Two compounds, BMS-204352 and retigabine, prese...

  6. Model Vestibular Nuclei Neurons Can Exhibit a Boosting Nonlinearity Due to an Adaptation Current Regulated by Spike-Triggered Calcium and Calcium-Activated Potassium Channels

    Science.gov (United States)

    Schneider, Adam D.

    2016-01-01

    In vitro studies have previously found a class of vestibular nuclei neurons to exhibit a bidirectional afterhyperpolarization (AHP) in their membrane potential, due to calcium and calcium-activated potassium conductances. More recently in vivo studies of such vestibular neurons were found to exhibit a boosting nonlinearity in their input-output tuning curves. In this paper, a Hodgkin-Huxley (HH) type neuron model, originally developed to reproduce the in vitro AHP, is shown to produce a boosting nonlinearity similar to that seen in vivo for increased the calcium conductance. Indicative of a bifurcation, the HH model is reduced to a generalized integrate-and-fire (IF) model that preserves the bifurcation structure and boosting nonliearity. By then projecting the neuron model’s phase space trajectories into 2D, the underlying geometric mechanism relating the AHP and boosting nonlinearity is revealed. Further simplifications and approximations are made to derive analytic expressions for the steady steady state firing rate as a function of bias current, μ, as well as the gain (i.e. its slope) and the position of its peak at μ = μ*. Finally, although the boosting nonlinearity has not yet been experimentally observed in vitro, testable predictions indicate how it might be found. PMID:27427914

  7. Model Vestibular Nuclei Neurons Can Exhibit a Boosting Nonlinearity Due to an Adaptation Current Regulated by Spike-Triggered Calcium and Calcium-Activated Potassium Channels.

    Science.gov (United States)

    Schneider, Adam D

    2016-01-01

    In vitro studies have previously found a class of vestibular nuclei neurons to exhibit a bidirectional afterhyperpolarization (AHP) in their membrane potential, due to calcium and calcium-activated potassium conductances. More recently in vivo studies of such vestibular neurons were found to exhibit a boosting nonlinearity in their input-output tuning curves. In this paper, a Hodgkin-Huxley (HH) type neuron model, originally developed to reproduce the in vitro AHP, is shown to produce a boosting nonlinearity similar to that seen in vivo for increased the calcium conductance. Indicative of a bifurcation, the HH model is reduced to a generalized integrate-and-fire (IF) model that preserves the bifurcation structure and boosting nonliearity. By then projecting the neuron model's phase space trajectories into 2D, the underlying geometric mechanism relating the AHP and boosting nonlinearity is revealed. Further simplifications and approximations are made to derive analytic expressions for the steady steady state firing rate as a function of bias current, μ, as well as the gain (i.e. its slope) and the position of its peak at μ = μ*. Finally, although the boosting nonlinearity has not yet been experimentally observed in vitro, testable predictions indicate how it might be found. PMID:27427914

  8. Activation of SUR2B/Kir6.1-type KATP channels protects glomerular endothelial, mesangial and tubular epithelial cells against oleic acid renal damage

    Institute of Scientific and Technical Information of China (English)

    Ying ZHAO; Hai WANG

    2012-01-01

    Cumulative evidence suggests that renal vascular endothelial injury play an important role in initiating and extending tubular epithelial injury and contribute to the development of ischemic acute renal failure.Our previous studies have demonstrated that iptakalim's endothelium protection is related to activation of SUR2B/Kir6.1 subtype of ATP sensitive potassium channel (KATP) in the endothelium.It has been reported that SUR2B/Kir6.1 channels are widely distributed in the tubular epithelium,glomerular mesangium,and the endothelium and the smooth muscle of blood vessels.Herein,we hypothesized that activating renal KATP channels with iptakalim might have directly neroprotective effects.In this study,glomerular endothelial,mesangial and tubular epithelial cells which are the main cell types to form nephron were exposed to oleic acid (OA) at various concentrations for 24 h.0.25 μl/ml OA could cause cellular damage of glomerular endothelium and mesangium,while 1.25μl/ml OA could lead to the injury of three types of renal cells.It was observed that pretreatment with iptakalim at concentrations of 0.1,1,10 or 100 μmol/L prevented cellular damage of glomerular endothelium and tubular epithelium,whereas iptakalim from 1 to 100 μmol/L prevented the injury of mesangial cells.Our data showed iptakalim significantly increased survived cell rates in a concentration-dependent manner,significantly antagonized by glibenclamide,a KATP blocker.Iptakalim played a protective role in the main cell types of kidney,which was consistent with natakalim,a highly selective SUR2B/Kir6.1 channel opener.Iptakalim exerted protective effects through activating SUR2B/Kir6.1 channels,suggesting a new strategy for renal injury by its endothelial and renal cell protection.

  9. Regulation of cell proliferation of human induced pluripotent stem cell-derived mesenchymal stem cells via ether-à-go-go 1 (hEAG1) potassium channel.

    Science.gov (United States)

    Zhang, Jiao; Chan, Yau-Chi; Ho, Jenny Chung-Yee; Siu, Chung-Wah; Lian, Qizhou; Tse, Hung-Fat

    2012-07-15

    The successful generation of a high yield of mesenchymal stem cells (MSCs) from human induced pluripotent stem cells (iPSCs) may represent an unlimited cell source with superior therapeutic benefits for tissue regeneration to bone marrow (BM)-derived MSCs. We investigated whether the differential expression of ion channels in iPSC-MSCs was responsible for their higher proliferation capacity than BM-MSCs. The expression of ion channels for K(+), Na(+), Ca(2+), and Cl(-) was examined by RT-PCR. The electrophysiological properties of iPSC-MSCs and BM-MSCs were then compared by patch-clamp experiments to verify their functional roles. Significant mRNA expression of ion channel genes including KCa1.1, KCa3.1, KCNH1, Kir2.1, SCN9A, CACNA1C, and Clcn3 was observed in both human iPSC-MSCs and BM-MSCs, whereas Kir2.2 and Kir2.3 were only detected in human iPSC-MSCs. Five types of currents [big-conductance Ca(2+)-activated K(+) current (BK(Ca)), delayed rectifier K(+) current (IK(DR)), inwardly rectifying K(+) current (I(Kir)), Ca(2+)-activated K(+) current (IK(Ca)), and chloride current (I(Cl))] were found in iPSC-MSCs (83%, 47%, 11%, 5%, and 4%, respectively) but only four of them (BK(Ca), IK(DR), I(Kir), and IK(Ca)) were identified in BM-MSCs (76%, 25%, 22%, and 11%, respectively). Cell proliferation was examined with MTT or bromodeoxyuridine assay, and doubling times were 2.66 and 3.72 days for iPSC-MSCs and BM-MSCs, respectively, showing a 1.4-fold discrepancy. Blockade of IK(DR) with short hairpin RNA or human ether-à-go-go 1 (hEAG1) channel blockers, 4-AP and astemizole, significantly reduced the rate of proliferation of human iPSC-MSCs. These treatments also decreased the rate of proliferation of human BM-MSCs albeit to a lesser extent. These findings demonstrate that the hEAG1 channel plays a crucial role in controlling the proliferation rate of human iPSC-MSCs and to a lesser extent in BM-MSCs. PMID:22357737

  10. Coordination Numbers of K+ and Na+ Ions Inside the Selectivity Filter of the KcsA Potassium Channel: Insights from First Principles Molecular Dynamics

    OpenAIRE

    Bucher, Denis; Guidoni, Leonardo; Carloni, Paolo; Rothlisberger, Ursula

    2010-01-01

    Quantum mechanics/molecular mechanics (QM/MM) Car-Parrinello simulations were performed to estimate the coordination numbers of K+ and Na+ ions in the selectivity filter of the KcsA channel, and in water. At the DFT/BLYP level, K+ ions were found to display an average coordination number of 6.6 in the filter, and 6.2 in water. Na+ ions displayed an average coordination number of 5.2 in the filter, and 5.0 in water. A comparison was made with the average coordination numbers obtained from usin...

  11. Extracellular K(+) and opening of voltage-gated potassium channels activate T cell integrin function: physical and functional association between Kv1.3 channels and beta1 integrins.

    Science.gov (United States)

    Levite, M; Cahalon, L; Peretz, A; Hershkoviz, R; Sobko, A; Ariel, A; Desai, R; Attali, B; Lider, O

    2000-04-01

    Elevated extracellular K(+) ([K(+)](o)), in the absence of "classical" immunological stimulatory signals, was found to itself be a sufficient stimulus to activate T cell beta1 integrin moieties, and to induce integrin-mediated adhesion and migration. Gating of T cell voltage-gated K(+) channels (Kv1.3) appears to be the crucial "decision-making" step, through which various physiological factors, including elevated [K(+)](o) levels, affect the T cell beta1 integrin function: opening of the channel leads to function, whereas its blockage prevents it. In support of this notion, we found that the proadhesive effects of the chemokine macrophage-inflammatory protein 1beta, the neuropeptide calcitonin gene-related peptide (CGRP), as well as elevated [K(+)](o) levels, are blocked by specific Kv1.3 channel blockers, and that the unique physiological ability of substance P to inhibit T cell adhesion correlates with Kv1.3 inhibition. Interestingly, the Kv1.3 channels and the beta1 integrins coimmunoprecipitate, suggesting that their physical association underlies their functional cooperation on the T cell surface. This study shows that T cells can be activated and driven to integrin function by a pathway that does not involve any of its specific receptors (i.e., by elevated [K(+)](o)). In addition, our results suggest that undesired T cell integrin function in a series of pathological conditions can be arrested by molecules that block the Kv1.3 channels. PMID:10748234

  12. Expresión de canales de potasio voltaje dependientes en ovocitos de Xenopus laevis (Amphibia Voltage gated potassium channels expressed in Xenopus laevis(AMPHIBIA oocytes

    Directory of Open Access Journals (Sweden)

    Clavijo Carlos

    2003-06-01

    Full Text Available La expresión en sistemas heterólogos ha sido una herramienta ampliamente utilizada enlos últimos años para el estudio funcional y estructural de proteínas. Para la carac-terización de las propiedades biofísicas de canales, bombas y transportadores engeneral su expresión en ovocitos de Xenopus laevis, ha sido fundamental. Este estudioreporta la expresión de dos canales de potasio voltaje dependientes, Kv1.1y Shakerenovocitos de X. laevisusando un protocolo ajustado a las condiciones de latitud y altitudde Bogotá para la extracción, aislamiento, cultivo y microinyección de éstas células.Heterologous expression has been an important tool for structural and functionalcharacterization of proteins. The study of biophysical properties of ion channels,pumps and transporters has been possible thanks to their expression in Xenopuslaevisoocytes. Here we report the expression of two voltage gated channels, Kv1.1and Shaker, in X. laevisoocytes using a method for oocyte extraction, isolation, cul-ture, and microinjection adapted to the latitude and altitude conditions of Bogotá,Colombia.

  13. Isolation of proflavine as a blocker of G protein-gated inward rectifier potassium channels by a cell growth-based screening system.

    Science.gov (United States)

    Kawada, Hitoshi; Inanobe, Atsushi; Kurachi, Yoshihisa

    2016-10-01

    The overexpression of Kir3.2, a subunit of the G protein-gated inwardly rectifying K(+) channel, is implicated in some of the neurological phenotypes of Down syndrome (DS). Chemical compounds that block Kir3.2 are expected to improve the symptoms of DS. The purpose of this study is to develop a cell-based screening system to identify Kir3.2 blockers and then investigate the mode of action of the blocker. Chemical screening was carried out using a K(+) transporter-deficient yeast strain that expressed a constitutively active Kir3.2 mutant. The mode of action of an effective blocker was electrophysiologically analyzed using Kir channels expressed in Xenopus oocytes. Proflavine was identified to inhibit the growth of Kir3.2-transformant cells and Kir3.2 activity in a concentration-dependent manner. The current inhibition was strong when membrane potentials (Vm) was above equilibrium potential of K(+) (EK). When Vm was below EK, the blockage apparently depended on the difference between Vm and [K(+)]. Furthermore, the inhibition became stronger by lowering extracellular [K(+)]. These results indicated that the yeast strain serves as a screening system to isolate Kir3.2 blockers and proflavine is a prototype of a pore blocker of Kir3.2. PMID:27236080

  14. Distinct abscisic acid signaling pathways for modulation of guard cell versus mesophyll cell potassium channels revealed by expression studies in Xenopus laevis oocytes

    Science.gov (United States)

    Sutton, F.; Paul, S. S.; Wang, X. Q.; Assmann, S. M.; Evans, M. L. (Principal Investigator)

    2000-01-01

    Regulation of guard cell ion transport by abscisic acid (ABA) and in particular ABA inhibition of a guard cell inward K(+) current (I(Kin)) is well documented. However, little is known concerning ABA effects on ion transport in other plant cell types. Here we applied patch clamp techniques to mesophyll cell protoplasts of fava bean (Vicia faba cv Long Pod) plants and demonstrated ABA inhibition of an outward K(+) current (I(Kout)). When mesophyll cell protoplast mRNA (mesophyll mRNA) was expressed in Xenopus laevis oocytes, I(Kout) was generated that displayed similar properties to I(Kout) observed from direct analysis of mesophyll cell protoplasts. I(Kout) expressed by mesophyll mRNA-injected oocytes was inhibited by ABA, indicating that the ABA signal transduction pathway observed in mesophyll cells was preserved in the frog oocytes. Co-injection of oocytes with guard cell protoplast mRNA and cRNA for KAT1, an inward K(+) channel expressed in guard cells, resulted in I(Kin) that was similarly inhibited by ABA. However, oocytes co-injected with mesophyll mRNA and KAT1 cRNA produced I(Kin) that was not inhibited by ABA. These results demonstrate that the mesophyll-encoded signaling mechanism could not substitute for the guard cell pathway. These findings indicate that mesophyll cells and guard cells use distinct and different receptor types and/or signal transduction pathways in ABA regulation of K(+) channels.

  15. Regulation of action potential delays via voltage-gated potassium Kv1.1 channels in dentate granule cells during hippocampal epilepsy

    Directory of Open Access Journals (Sweden)

    Florian eKirchheim

    2013-12-01

    Full Text Available Action potential (AP responses of dentate gyrus granule (DG cells have to be tightly regulated to maintain hippocampal function. However, which ion channels control the response delay of DG cells is not known. In some neuron types, spike latency is influenced by a dendrotoxin (DTX-sensitive delay current (ID mediated by unidentified combinations of voltage-gated K+ (Kv channels of the Kv1 family Kv1.1-6. In DG cells, the ID has not been characterized and its molecular basis is unknown. The response phenotype of mature DG cells is usually considered homogenous but intrinsic adaptations likely occur in particular in conditions of hyperexcitability, for example during temporal lobe epilepsy (TLE. In this study, we examined response delays of DG cells and underlying ion channel molecules by employing a new combination of gramicidin-perforated patch-clamp recordings in acute brain slices and single-cell reverse transcriptase quantitative polymerase chain reaction (SC RT-qPCR experiments. An in vivo mouse model of TLE consisting of intrahippocampal kainate (KA injection was used to examine epilepsy-related plasticity. Response delays of DG cells were DTX-sensitive and strongly increased in KA-injected hippocampi; Kv1.1 mRNA was elevated 10-fold, and the response delays correlated with Kv1.1 mRNA abundance on the single cell level. Other Kv1 subunits did not show overt changes in mRNA levels. Kv1.1 immunolabeling was enhanced in KA DG cells. The biophysical properties of ID and the delay heterogeneity between inner and outer DG cell layer were characterized. Using organotypic hippocampal slice cultures (OHCs, where KA incubation also induced ID upregulation, reversibility and neuroprotective potential for DG cells were tested. In summary, the AP timing of DG cells is effectively controlled via scaling of Kv1.1 subunit transcription. With this antiepileptic mechanism, DG cells delay their

  16. Expression of the Small Conductance Ca(2+)-Activated Potassium Channel Subtype 3 (SK3) in Rat Uterus after Stimulation with 17β-Estradiol

    DEFF Research Database (Denmark)

    Rahbek, Mette; Nazemi, Sasan; Odum, Lars;

    2014-01-01

    Preterm births accounts for roughly 9% of all births worldwide and can have detrimental or even lethal consequences for the infant. However to develop new treatment that will lower the rate of preterm births, more knowledge is required on the factors contributing to the contraction and relaxation...... in the myometrium. Using Western blot the protein level of SK3 was found to increase in uteri from animals treated with 17β-estradiol, an effect that was not reflected at the mRNA level. The levels of mRNA for SK3 were significantly lower in the uterus of 17β-estradiol-treated animals than in the uterus...... of ovariectomized animals. We conclude that the SK channels are present in the endometrial epithelium, and possibly also in the myometrium of the rat uterus. Furthermore, the hormonal effect on SK3 caused by 17β-estradiol includes divergent regulation at mRNA and protein levels....

  17. A computational study of barium blockades in the KcsA potassium channel based on multi-ion potential of mean force calculations and free energy perturbation.

    Science.gov (United States)

    Rowley, Christopher N; Roux, Benoît

    2013-10-01

    Electrophysiological studies have established that the permeation of Ba(2+) ions through the KcsA K(+)-channel is impeded by the presence of K(+) ions in the external solution, while no effect is observed for external Na(+) ions. This Ba(2+) "lock-in" effect suggests that at least one of the external binding sites of the KcsA channel is thermodynamically selective for K(+). We used molecular dynamics simulations to interpret these lock-in experiments in the context of the crystallographic structure of KcsA. Assuming that the Ba(2+) is bound in site S(2) in the dominant blocked state, we examine the conditions that could impede its translocation and cause the observed "lock-in" effect. Although the binding of a K(+) ion to site S(1) when site S(2) is occupied by Ba(2+) is prohibitively high in energy (>10 kcal/mol), binding to site S0 appears to be more plausible (ΔG > 4 kcal/mol). The 2D potential of mean force (PMF) for the simultaneous translocation of Ba(2+) from site S(2) to site S(1) and of a K(+) ion on the extracellular side shows a barrier that is consistent with the concept of external lock-in. The barrier opposing the movement of Ba(2+) is very high when a cation is in site S(0), and considerably smaller when the site is unoccupied. Furthermore, free energy perturbation calculations show that site S(0) is selective for K(+) by 1.8 kcal/mol when S(2) is occupied by Ba(2+). However, the same site S(0) is nonselective when site S(2) is occupied by K(+), which shows that the presence of Ba(2+) affects the selectivity of the pore. A theoretical framework within classical rate theory is presented to incorporate the concentration dependence of the external ions on the lock-in effect. PMID:24043859

  18. Retigabine, a K(V)7 (KCNQ) potassium channel opener, attenuates L-DOPA-induced dyskinesias in 6-OHDA-lesioned rats.

    Science.gov (United States)

    Sander, S E; Lemm, C; Lange, N; Hamann, M; Richter, A

    2012-02-01

    L-DOPA-induced dyskinesias (LID) represent a severe complication of long-time pharmacotherapy in Parkinson's disease that necessitates novel therapeutics. The acute and chronic effects of K(V)7.2-7.5 channel openers (retigabine, flupirtine) on the severity of LID and parkinsonian signs were examined in comparison to the glutamate receptor antagonist amantadine (positive control) in a rat model of LID. Acute treatment with retigabine (2.5, 5 mg/kg i.p.) and flupirtine (5, 10 mg/kg i.p.) significantly reduced the severity of abnormal involuntary movements (AIM) to a comparable extent as amantadine (20, 40 mg/kg s.c.), but flupirtine delayed the disappearance of AIM. Chronic treatment with retigabine (daily 5 mg/kg i.p. over 19 days combined with l-DOPA 10 mg i.p.) did not prevent or delay the development of LID, but reduced the severity of AIM, while antidyskinetic effects of amantadine (40 mg/kg i.p.) were restricted to the first day of treatment. Retigabine caused sedation and ataxia which declined during the chronic treatment, but did not reduce the antiparkinsonian effects of l-DOPA in these experiments. Acute co-injections of retigabine (5 mg) together with l-DOPA (10 mg/kg) neither reduced the motor performance in the rotarod test nor exerted negative effects on the antiparkinsonian efficacy of l-DOPA in the block and stepping test. Nevertheless, the sedative effects of retigabine may limit its therapeutic potential for the treatment of LID. The present data indicate that K(V)7 channels deserve attention in the research of the pathophysiology of dyskinesias. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'. PMID:22079161

  19. Selective expression of KCNS3 potassium channel α-subunit in parvalbumin-containing GABA neurons in the human prefrontal cortex.

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    Danko Georgiev

    Full Text Available The cognitive deficits of schizophrenia appear to be associated with altered cortical GABA neurotransmission in the subsets of inhibitory neurons that express either parvalbumin (PV or somatostatin (SST. Identification of molecular mechanisms that operate selectively in these neurons is essential for developing targeted therapeutic strategies that do not influence other cell types. Consequently, we sought to identify, in the human cortex, gene products that are expressed selectively by PV and/or SST neurons, and that might contribute to their distinctive functional properties. Based on previously reported expression patterns in the cortex of mice and humans, we selected four genes: KCNS3, LHX6, KCNAB1, and PPP1R2, encoding K(+ channel Kv9.3 modulatory α-subunit, LIM homeobox protein 6, K(+ channel Kvβ1 subunit, and protein phosphatase 1 regulatory subunit 2, respectively, and examined their colocalization with PV or SST mRNAs in the human prefrontal cortex using dual-label in situ hybridization with (35S- and digoxigenin-labeled antisense riboprobes. KCNS3 mRNA was detected in almost all PV neurons, but not in SST neurons, and PV mRNA was detected in >90% of KCNS3 mRNA-expressing neurons. LHX6 mRNA was detected in almost all PV and >90% of SST neurons, while among all LHX6 mRNA-expressing neurons 50% expressed PV mRNA and >44% expressed SST mRNA. KCNAB1 and PPP1R2 mRNAs were detected in much larger populations of cortical neurons than PV or SST neurons. These findings indicate that KCNS3 is a selective marker of PV neurons, whereas LHX6 is expressed by both PV and SST neurons. KCNS3 and LHX6 might be useful for characterizing cell-type specific molecular alterations of cortical GABA neurotransmission and for the development of novel treatments targeting PV and/or SST neurons in schizophrenia.

  20. Selective expression of KCNS3 potassium channel α-subunit in parvalbumin-containing GABA neurons in the human prefrontal cortex.

    Science.gov (United States)

    Georgiev, Danko; González-Burgos, Guillermo; Kikuchi, Mitsuru; Minabe, Yoshio; Lewis, David A; Hashimoto, Takanori

    2012-01-01

    The cognitive deficits of schizophrenia appear to be associated with altered cortical GABA neurotransmission in the subsets of inhibitory neurons that express either parvalbumin (PV) or somatostatin (SST). Identification of molecular mechanisms that operate selectively in these neurons is essential for developing targeted therapeutic strategies that do not influence other cell types. Consequently, we sought to identify, in the human cortex, gene products that are expressed selectively by PV and/or SST neurons, and that might contribute to their distinctive functional properties. Based on previously reported expression patterns in the cortex of mice and humans, we selected four genes: KCNS3, LHX6, KCNAB1, and PPP1R2, encoding K(+) channel Kv9.3 modulatory α-subunit, LIM homeobox protein 6, K(+) channel Kvβ1 subunit, and protein phosphatase 1 regulatory subunit 2, respectively, and examined their colocalization with PV or SST mRNAs in the human prefrontal cortex using dual-label in situ hybridization with (35)S- and digoxigenin-labeled antisense riboprobes. KCNS3 mRNA was detected in almost all PV neurons, but not in SST neurons, and PV mRNA was detected in >90% of KCNS3 mRNA-expressing neurons. LHX6 mRNA was detected in almost all PV and >90% of SST neurons, while among all LHX6 mRNA-expressing neurons 50% expressed PV mRNA and >44% expressed SST mRNA. KCNAB1 and PPP1R2 mRNAs were detected in much larger populations of cortical neurons than PV or SST neurons. These findings indicate that KCNS3 is a selective marker of PV neurons, whereas LHX6 is expressed by both PV and SST neurons. KCNS3 and LHX6 might be useful for characterizing cell-type specific molecular alterations of cortical GABA neurotransmission and for the development of novel treatments targeting PV and/or SST neurons in schizophrenia.