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Lee HM, Yoon SH, Kim MG, Hahn SJ, Choi BH. Effects of rosiglitazone, an antidiabetic drug, on Kv3.1 channels. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2023; 27:95-103. [PMID: 36575937 PMCID: PMC9806636 DOI: 10.4196/kjpp.2023.27.1.95] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/20/2022] [Accepted: 10/22/2022] [Indexed: 12/29/2022]
Abstract
Rosiglitazone is a thiazolidinedione-class antidiabetic drug that reduces blood glucose and glycated hemoglobin levels. We here investigated the interaction of rosiglitazone with Kv3.1 expressed in Chinese hamster ovary cells using the whole-cell patch-clamp technique. Rosiglitazone rapidly and reversibly inhibited Kv3.1 currents in a concentration-dependent manner (IC50 = 29.8 μM) and accelerated the decay of Kv3.1 currents without modifying the activation kinetics. The rosiglitazone-mediated inhibition of Kv3.1 channels increased steeply in a sigmoidal pattern over the voltage range of -20 to +30 mV, whereas it was voltage-independent in the voltage range above +30 mV, where the channels were fully activated. The deactivation of Kv3.1 current, measured along with tail currents, was also slowed by the drug. In addition, the steady-state inactivation curve of Kv3.1 by rosiglitazone shifts to a negative potential without significant change in the slope value. All the results with the use dependence of the rosiglitazone-mediated blockade suggest that rosiglitazone acts on Kv3.1 channels as an open channel blocker.
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Affiliation(s)
- Hyang Mi Lee
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Seong Han Yoon
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Min-Gul Kim
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Sang June Hahn
- Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Bok Hee Choi
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea,Correspondence Bok Hee Choi, E-mail:
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Serrano-Albarrás A, Cirera-Rocosa S, Sastre D, Estadella I, Felipe A. Fighting rheumatoid arthritis: Kv1.3 as a therapeutic target. Biochem Pharmacol 2019; 165:214-220. [DOI: 10.1016/j.bcp.2019.03.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/12/2019] [Indexed: 01/18/2023]
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Lee HM, Chai OH, Hahn SJ, Choi BH. Antidepressant drug paroxetine blocks the open pore of Kv3.1 potassium channel. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2017; 22:71-80. [PMID: 29302214 PMCID: PMC5746514 DOI: 10.4196/kjpp.2018.22.1.71] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Accepted: 10/27/2017] [Indexed: 12/20/2022]
Abstract
In patients with epilepsy, depression is a common comorbidity but difficult to be treated because many antidepressants cause pro-convulsive effects. Thus, it is important to identify the risk of seizures associated with antidepressants. To determine whether paroxetine, a very potent selective serotonin reuptake inhibitor (SSRI), interacts with ion channels that modulate neuronal excitability, we examined the effects of paroxetine on Kv3.1 potassium channels, which contribute to highfrequency firing of interneurons, using the whole-cell patch-clamp technique. Kv3.1 channels were cloned from rat neurons and expressed in Chinese hamster ovary cells. Paroxetine reversibly reduced the amplitude of Kv3.1 current, with an IC50 value of 9.43 µM and a Hill coefficient of 1.43, and also accelerated the decay of Kv3.1 current. The paroxetine-induced inhibition of Kv3.1 channels was voltage-dependent even when the channels were fully open. The binding (k+1) and unbinding (k−1) rate constants for the paroxetine effect were 4.5 µM−1s−1 and 35.8 s−1, respectively, yielding a calculated KD value of 7.9 µM. The analyses of Kv3.1 tail current indicated that paroxetine did not affect ion selectivity and slowed its deactivation time course, resulting in a tail crossover phenomenon. Paroxetine inhibited Kv3.1 channels in a usedependent manner. Taken together, these results suggest that paroxetine blocks the open state of Kv3.1 channels. Given the role of Kv3.1 in fast spiking of interneurons, our data imply that the blockade of Kv3.1 by paroxetine might elevate epileptic activity of neural networks by interfering with repetitive firing of inhibitory neurons.
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Affiliation(s)
- Hyang Mi Lee
- Department of Pharmacology, Institute for Medical Science, Chonbuk National University Medical School, Jeonju 54097, Korea
| | - Ok Hee Chai
- Department of Anatomy, Institute for Medical Science, Chonbuk National University Medical School, Jeonju 54097, Korea
| | - Sang June Hahn
- Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Bok Hee Choi
- Department of Pharmacology, Institute for Medical Science, Chonbuk National University Medical School, Jeonju 54097, Korea
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Pérez-Verdaguer M, Capera J, Serrano-Novillo C, Estadella I, Sastre D, Felipe A. The voltage-gated potassium channel Kv1.3 is a promising multitherapeutic target against human pathologies. Expert Opin Ther Targets 2015; 20:577-91. [DOI: 10.1517/14728222.2016.1112792] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Fu XX, Du LL, Zhao N, Dong Q, Liao YH, Du YM. 18β-Glycyrrhetinic acid potently inhibits Kv1.3 potassium channels and T cell activation in human Jurkat T cells. JOURNAL OF ETHNOPHARMACOLOGY 2013; 148:647-54. [PMID: 23707333 DOI: 10.1016/j.jep.2013.05.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 05/08/2013] [Accepted: 05/14/2013] [Indexed: 05/21/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Licorice has been extensively used in traditional medicines for treatment of many diseases, including inflammations and immunological disorders. Recent studies have shown that the anti-inflammatory and immunomodulation activities of licorice have been attributed to its active component, glycyrretinic acid (GA). GA consists of two isoforms, 18α- and 18β-. However, its mechanism remains poorly understood. AIM OF THE STUDY We compared the effects of two isoforms on Kv1.3 channels in Jurkat T cells and further characterized the inhibition of Kv1.3 channels by 18β-GA in CHO cells. In addition, we examined the effects of 18β-GA on Kv1.3 gene expression, Ca(2+) influx, proliferation, as well as IL-2 production in Jurkat T cells. MATERIALS AND METHODS Whole-cell patch-clamp technique was applied to record Kv1.3 currents in Jurkat T or CHO cells. Real-time PCR and Western blotting were used to detect gene expression. Fluo-4, CCK-8 kit and ELISA kit were used to measure Ca(2+) influx, proliferation, and IL-2 secretion in Jurkat T cells, respectively. RESULTS Superfusion of 18β-GA (10-100 µM) blocked Kv1.3 currents in Jurkat T cells, while 18α-GA at the same concentration had no effect. The 18β-GA induced inhibition had a voltage- and concentration-dependent manner with an IC50 of 23.9±1.5 µM at +40 mV in CHO cells. Furthermore, 18β-GA significantly inhibited Kv1.3 gene expression. In addition, paralleling Kv1.3 inhibition, 18β-GA also inhibited Ca(2+) influx, proliferation as well as IL-2 production in Jurkat T cells. CONCLUSION 18β-GA blocks Kv1.3 channels, which probably involves its anti-inflammatory and immunomodulation effects.
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Affiliation(s)
- Xiao-Xing Fu
- Ion Channelopathy Research Center, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, PR China
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Mello de Queiroz F, Ponte CG, Bonomo A, Vianna-Jorge R, Suarez-Kurtz G. Study of membrane potential in T lymphocytes subpopulations using flow cytometry. BMC Immunol 2008; 9:63. [PMID: 18980671 PMCID: PMC2584624 DOI: 10.1186/1471-2172-9-63] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 11/03/2008] [Indexed: 11/10/2022] Open
Abstract
Background Ion channels are involved in the control of membrane potential (ψ) in a variety of cells. The maintenance of ψ in human T lymphocytes is essential for T-cell activation and was suggested to depend mostly on the voltage-gated Kv1.3 channel. Blockage of Kv1.3 inhibits cytokine production and lymphocyte proliferation in vitro and suppresses immune response in vivo. T lymphocytes are a heterogeneous cell population and the expression of Kv1.3 varies among cell subsets. Oxonol diBA-C4-(3) was used to determine ψ by flow cytometry. The presence of distinct T cell subsets was evaluated by immunophenotyping techniques and the contribution of Kv1.3 channels for the maintenance of ψ was investigated using selective blockers. Results The distribution of ψ in T lymphocytes varied among blood donors and did not always follow a unimodal pattern. T lymphocytes were divided into CD3+/CD45RO- and CD3+/CD45RO+ subsets, whose peak channel values of ψ were -58 ± 3.6 mV and -37 ± 4.1 mV, respectively. MgTX (specific inhibitor of Kv1.3 channels) had no significant effect in the ψ of CD3+/CD45RO- subsets but depolarized CD3+/CD45RO+ cells to -27 ± 5.1 mV. Conclusion Combination of optical methods for determination of ψ by flow cytometry with immuophenotyping techniques opens new possibilities for the study of ion channels in the biology of heterogeneous cell populations such as T lymphocyte subsets.
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Affiliation(s)
- Fernanda Mello de Queiroz
- Molekulare Biologie Neuronaler Signale, Max-Planck-Institut für Experimentelle Medizin, Hermann-Rein-Strasse 3, 37075 Göttingen, Germany.
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Sung MJ, Ahn HS, Hahn SJ, Choi BH. Open channel block of Kv3.1 currents by fluoxetine. J Pharmacol Sci 2008; 106:38-45. [PMID: 18187934 DOI: 10.1254/jphs.fp0070759] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The action of fluoxetine, a serotonin reuptake inhibitor, on the cloned neuronal rat Kv3.1 channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. Fluoxetine reduced Kv3.1 whole-cell currents in a reversible, concentration-dependent manner, with an IC(50) value and a Hill coefficient of 13.4 muM and 1.4, respectively. Fluoxetine accelerated the decay rate of inactivation of Kv3.1 currents without modifying the kinetics of current activation. The inhibition increased steeply between 0 and +30 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +30 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance delta of 0.38. The binding (k(+1)) and dissociation (k(-1)) rate constants for fluoxetine-induced block of Kv3.1 were 5.7 microM(-1)s(-1) and 53.5 s(-1), respectively. The theoretical K(D) value derived by k(-1)/k(+1) yielded 9.3 microM. Fluoxetine did not affect the ion selectivity of Kv3.1. Fluoxetine slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of fluoxetine, were superimposed. Inhibition of Kv3.1 by fluoxetine was use-dependent. The present results suggest that fluoxetine acts on Kv3.1 currents as an open-channel blocker.
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Affiliation(s)
- Min Ji Sung
- Department of Pharmacology, Institute for Medical Sciences, Chonbuk National University Medical School, Jeonju, Chonbuk, Republic of Korea
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Kim SE, Ahn HS, Choi BH, Jang HJ, Kim MJ, Rhie DJ, Yoon SH, Jo YH, Kim MS, Sung KW, Hahn SJ. Open channel block of A-type, kv4.3, and delayed rectifier K+ channels, Kv1.3 and Kv3.1, by sibutramine. J Pharmacol Exp Ther 2007; 321:753-62. [PMID: 17312186 DOI: 10.1124/jpet.106.117747] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of sibutramine on voltage-gated K+ channel (Kv)4.3, Kv1.3, and Kv3.1, stably expressed in Chinese hamster ovary cells, were investigated using the whole-cell patch-clamp technique. Sibutramine did not significantly decrease the peak Kv4.3 currents, but it accelerated the rate of decay of current inactivation in a concentration-dependent manner. This phenomenon was effectively characterized by integrating the total current over the duration of a depolarizing pulse to +40 mV. The IC50 value for the sibutramine block of Kv4.3 was 17.3 microM. Under control conditions, the inactivation of Kv4.3 currents could be fit to a biexponential function, and the time constants for the fast and slow components were significantly decreased after the application of sibutramine. The association (k+1) and dissociation (k-1) rate constants for the sibutramine block of Kv 4.3 were 1.51 microM-1s-1 and 27.35 s-1, respectively. The theoretical KD value, derived from k-1/k+1, yielded a value of 18.11 microM. The block of Kv4.3 by sibutramine displayed a weak voltage dependence, increasing at more positive potentials, and it was use-dependent at 2 Hz. Sibutramine did not affect the time course for the deactivating tail currents. Neither steady-state activation and inactivation nor the recovery from inactivation was affected by sibutramine. Sibutramine caused the concentration-dependent block of the Kv1.3 and Kv3.1 currents with an IC50 value of 3.7 and 32.7 microM, respectively. In addition, sibutramine reduced the tail current amplitude and slowed the deactivation of the tail currents of Kv1.3 and Kv3.1, resulting in a crossover phenomenon. These results indicate that sibutramine acts on Kv4.3, Kv1.3, and Kv3.1 as an open channel blocker.
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Affiliation(s)
- Sung Eun Kim
- Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, Korea
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Liu SQJ, Kaczmarek LK. Aminoglycosides block the Kv3.1 potassium channel and reduce the ability of inferior colliculus neurons to fire at high frequencies. ACTA ACUST UNITED AC 2005; 62:439-52. [PMID: 15547932 DOI: 10.1002/neu.20112] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The Kv3.1 potassium channel is expressed at high levels in auditory nuclei and contributes to the ability of auditory neurons to fire at high frequencies. We have tested the effects of streptomycin, an agent that produces progressive hearing loss, on the firing properties of inferior colliculus neurons and on Kv3.1 currents in transfected cells. We found that in inferior colliculus neurons, intracellular streptomycin decreased the current density of a high threshold, noninactivating outward current and reduced the rate of repolarization of action potentials and the ability of these neurons to fire at high frequencies. Furthermore, potassium current in CHO cells transfected with the Kv3.1 gene was reduced by 50% when cells were cultured in the presence of streptomycin or when streptomycin was introduced intracellularly in the pipette solution. In the presence of intracellular streptomycin, the activation rate of Kv3.1 current increased and inhibition by extracellular TEA become voltage-dependent. The data indicate that streptomycin inhibits Kv3.1 currents by inducing a conformational change in the Kv3.1 channel. The hearing loss caused by aminoglycoside antibiotics may be partially mediated by their inhibition of Kv3.1 current in auditory neurons.
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Affiliation(s)
- Si-Qiong J Liu
- Department of Biology, Penn State University, 419 Mueller Lab, State College, Pennsylvania 16802, USA.
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Sipkema D, Snijders APL, Schroën CGPH, Osinga R, Wijffels RH. The life and death of sponge cells. Biotechnol Bioeng 2003; 85:239-47. [PMID: 14748078 DOI: 10.1002/bit.10886] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cell viability is an essential touchstone in the study of the effect of medium components on cell physiology. We developed a flow-cytometric assay to determine sponge-cell viability, based on the combined use of fluorescein diacetate (FDA) and propidium iodide (PI). Cell fluorescence measurements based on incubation of cells with FDA or PI resulted in a useful and reproducible estimate of the viability of primary sponge-cell cultures. We studied the effects of temperature, ammonium, and the fungicide amphotericin B on the viability of a primary-cell culture from the marine sponge Suberites domuncula using the aforementioned flow-cytometric assay. S. domuncula cells die rapidly at a temperature of >or=22 degrees C, but they are insensitive to ammonium concentrations of up to 25 mM. Amphotericin B, which is frequently used in sponge-cell culture media, was found to be toxic to S. domuncula cells.
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Affiliation(s)
- Detmer Sipkema
- Food and Bioprocess Engineering Group, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
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Choi BH, Choi JS, Yoon SH, Rhie DJ, Min DS, Jo YH, Kim MS, Hahn SJ. Effects of norfluoxetine, the major metabolite of fluoxetine, on the cloned neuronal potassium channel Kv3.1. Neuropharmacology 2001; 41:443-53. [PMID: 11543764 DOI: 10.1016/s0028-3908(01)00088-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effects of fluoxetine and its major metabolite, norfluoxetine, were studied using the patch-clamp technique on the cloned neuronal rat K(+) channel Kv3.1, expressed in Chinese hamster ovary cells. In whole-cell recordings, fluoxetine and norfluoxetine inhibited Kv3.1 currents in a reversible concentration-dependent manner, with an IC(50) value and a Hill coefficient of 13.11+/-0.91 microM and 1.33+/-0.08 for fluoxetine and 0.80+/-0.06 microM and 1.65+/-0.08 for norfluoxetine at +40 mV, respectively. In inside-out patches, norfluoxetine applied to the cytoplasmic surface inhibited Kv3.1 with an IC(50) value of 0.19+/-0.01 microM. The inhibition of Kv3.1 currents by both drugs was characterized by an acceleration in the apparent rate of current decay, without modification of the activation time course and with relatively fewer effects on peak amplitude. The degree of inhibition of Kv3.1 by norfluoxetine was voltage-dependent. The inhibition increased steeply between 0 and +30 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +30 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance delta of 0.31+/-0.05. The association (k(+1)) and dissociation (k(-1)) rate constants for norfluoxetine-induced inhibition of Kv3.1 were 21.70+/-3.39 microM(-1) s(-1) and 14.68+/-3.94 s(-1), respectively. The theoretical K(D) value derived by k(-1)/k(+1) yielded 0.68 microM. Norfluoxetine did not affect the ion selectivity of Kv3.1. The reversal potential under control conditions was about -85 mV and was not affected by norfluoxetine. Norfluoxetine slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of norfluoxetine, were superimposed. The voltage dependence of steady-state inactivation was not changed by the drug. Norfluoxetine produced use-dependent inhibition of Kv3.1 at a frequency of 1 Hz and slowed the recovery from inactivation. It is concluded that at clinically relevant concentrations, both fluoxetine and its major metabolite norfluoxetine inhibit Kv3.1, and that norfluoxetine directly inhibits Kv3.1 as an open channel blocker.
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Affiliation(s)
- B H Choi
- Department of Physiology, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, Seoul 137-701, South Korea
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Choi J, Choi BH, Hahn SJ, Yoon SH, Min DS, Jo Y, Kim M. Inhibition of Kv1.3 channels by H-89 (N--[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide) independent of protein kinase A. Biochem Pharmacol 2001; 61:1029-32. [PMID: 11286994 DOI: 10.1016/s0006-2952(01)00556-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide), a potent and selective inhibitor of protein kinase A (PKA), were examined on Kv1.3 channels stably expressed in Chinese hamster ovary (CHO) cells using the patch clamp technique. In whole-cell recordings, H-89 decreased Kv1.3 currents and accelerated the decay rate of current inactivation in a concentration-dependent manner with an IC(50) value of 1.70 microM. These effects were completely reversible after washout. Intracellular infusion with PKA inhibitors, adenosine 3', 5'-cyclic phosphorothioate-Rp (Rp-cAMPS) or protein kinase A inhibitor 5-24 (PKI 5-24) had no effect on Kv1.3 currents and did not prevent the inhibitory action of H-89 on the current. H-89 applied to the cytoplasmic surface also inhibited Kv1.3 currents in excised inside-out patches. These findings suggest that H-89 inhibits Kv1.3 currents independently of PKA.
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Affiliation(s)
- J Choi
- Department of Physiology, The Catholic University of Korea, College of Medicine, 505 Banpo-dong, Socho-gu, 137-701, Seoul, South Korea
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Jonas EA, Knox RJ, Kaczmarek LK. Giga-ohm seals on intracellular membranes: a technique for studying intracellular ion channels in intact cells. Neuron 1997; 19:7-13. [PMID: 9247259 DOI: 10.1016/s0896-6273(00)80343-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A method is outlined for obtaining giga-ohm seals on intracellular membranes in intact cells. The technique employs a variant of the patch-clamp technique: a concentric electrode arrangement protects an inner patch pipette during penetration of the plasma membrane, after which a seal can be formed on an internal organelle membrane. Using this technique, successful recordings can be obtained with the same frequency as with conventional patch clamping. To localize the position of the pipette within cells, lipophilic fluorescent dyes are included in the pipette solution. These dyes stain the membrane of internal organelles during seal formation and can then be visualized by video-enhanced or confocal imaging. The method can detect channels activated by inositol trisphosphate, as well as other types of intracellular membrane ion channel activity, and should facilitate studies of internal membranes in intact neurons and other cell types.
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Affiliation(s)
- E A Jonas
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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