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Piantoni C, Paina M, Molla D, Liu S, Bertoli G, Jiang H, Wang Y, Wang Y, Wang Y, DiFrancesco D, Barbuti A, Bucchi A, Baruscotti M. Chinese natural compound decreases pacemaking of rabbit cardiac sinoatrial cells by targeting second messenger regulation of f-channels. eLife 2022; 11:75119. [PMID: 35315774 PMCID: PMC8940175 DOI: 10.7554/elife.75119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 03/03/2022] [Indexed: 11/13/2022] Open
Abstract
Tongmai Yangxin (TMYX) is a complex compound of the Traditional Chinese Medicine (TCM) used to treat several cardiac rhythm disorders; however, no information regarding its mechanism of action is available. In this study we provide a detailed characterization of the effects of TMYX on the electrical activity of pacemaker cells and unravel its mechanism of action. Single-cell electrophysiology revealed that TMYX elicits a reversible and dose-dependent (2/6 mg/ml) slowing of spontaneous action potentials rate (−20.8/–50.2%) by a selective reduction of the diastolic phase (−50.1/–76.0%). This action is mediated by a negative shift of the If activation curve (−6.7/–11.9 mV) and is caused by a reduction of the cyclic adenosine monophosphate (cAMP)-induced stimulation of pacemaker channels. We provide evidence that TMYX acts by directly antagonizing the cAMP-induced allosteric modulation of the pacemaker channels. Noticeably, this mechanism functionally resembles the pharmacological actions of muscarinic stimulation or β-blockers, but it does not require generalized changes in cytoplasmic cAMP levels thus ensuring a selective action on rate. In agreement with a competitive inhibition mechanism, TMYX exerts its maximal antagonistic action at submaximal cAMP concentrations and then progressively becomes less effective thus ensuring a full contribution of If to pacemaker rate during high metabolic demand and sympathetic stimulation.
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Affiliation(s)
- Chiara Piantoni
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Manuel Paina
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - David Molla
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Sheng Liu
- Department of Physiology and Pathophysiology, School of Basic Medical Science, Tianjin Medical University, Tianjin, China
| | - Giorgia Bertoli
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Hongmei Jiang
- Department of Physiology and Pathophysiology, School of Basic Medical Science, Tianjin Medical University, Tianjin, China
| | - Yanyan Wang
- School of Integrative Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yi Wang
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yi Wang
- Institute of Traditional Chinese Medicine Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Dario DiFrancesco
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Andrea Barbuti
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Annalisa Bucchi
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
| | - Mirko Baruscotti
- Department of Biosciences, The Cell Physiology Lab and "Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata", Università degli Studi di Milano, Milano, Italy
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Calcium signaling mediated by aminergic GPCRs is impaired by the PI3K inhibitor LY294002 and its analog LY303511 in a PI3K-independent manner. Eur J Pharmacol 2020; 880:173182. [PMID: 32416185 DOI: 10.1016/j.ejphar.2020.173182] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 04/17/2020] [Accepted: 05/08/2020] [Indexed: 12/23/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (LY294) and its much less active analog LY303511 (LY303) constitute the paired probe that is commonly used to demonstrate the involvement of PI3K in intracellular signaling. We studied effects of LY294 and LY303 on Ca2+ signaling initiated by certain GPCR agonists in cells of several lines, including CHO cells expressing the recombinant serotonin receptor 5-HT2C and mesenchymal stromal cells derived from the human adipose tissue (AD-MSCs) and umbilical cord (UD-MSCs). The LY294/LY303 pair exerted apparently specific effects on responsiveness of AD-MSCs to ATP, suggesting the involvement of PI3K in ATP transduction. Surprisingly, LY303 inhibited Ca2+ transients elicited by histamine in the same cells, while LY294 was ineffective. This observation and other findings implicated a PI3K-unrelated mechanism in mediating effects of the LY compound on AD-MSC responsiveness to histamine. With LY303 in the bath, the dose dependence of histamine responses was shifted positively at the invariable number of responsive cells, as would be the case with a competitive antagonist of histamine receptors. Moreover, LY303 and LY294 inhibited Ca2+ transients elicited by acetylcholine and serotonin in UD-MSCs and CHO/5-HT2C cells, respectively. Our overall results argued for the possibility that LY294 and LY303 could directly affect activity of aminergic GPCRs. Thus, LY303511 and LY294002 should be used cautiously in studies of PI3K as a factor of GPCR signaling.
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Leist M, Rinné S, Datunashvili M, Aissaoui A, Pape HC, Decher N, Meuth SG, Budde T. Acetylcholine-dependent upregulation of TASK-1 channels in thalamic interneurons by a smooth muscle-like signalling pathway. J Physiol 2017; 595:5875-5893. [PMID: 28714121 DOI: 10.1113/jp274527] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 07/10/2017] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS The ascending brainstem transmitter acetylcholine depolarizes thalamocortical relay neurons while it induces hyperpolarization in local circuit inhibitory interneurons. Sustained K+ currents are modulated in thalamic neurons to control their activity modes; for the interneurons the molecular nature of the underlying ion channels is as yet unknown. Activation of TASK-1 K+ channels results in hyperpolarization of interneurons and suppression of their action potential firing. The modulation cascade involves a non-receptor tyrosine kinase, c-Src. The present study identifies a novel pathway for the activation of TASK-1 channels in CNS neurons that resembles cholinergic signalling and TASK-1 current modulation during hypoxia in smooth muscle cells. ABSTRACT The dorsal part of the lateral geniculate nucleus (dLGN) is the main thalamic site for state-dependent transmission of visual information. Non-retinal inputs from the ascending arousal system and inhibition provided by γ-aminobutyric acid (GABA)ergic local circuit interneurons (INs) control neuronal activity within the dLGN. In particular, acetylcholine (ACh) depolarizes thalamocortical relay neurons by inhibiting two-pore domain potassium (K2P ) channels. Conversely, ACh also hyperpolarizes INs via an as-yet-unknown mechanism. By using whole cell patch-clamp recordings in brain slices and appropriate pharmacological tools we here report that stimulation of type 2 muscarinic ACh receptors induces IN hyperpolarization by recruiting the G-protein βγ subunit (Gβγ), class-1A phosphatidylinositol-4,5-bisphosphate 3-kinase, and cellular and sarcoma (c-Src) tyrosine kinase, leading to activation of two-pore domain weakly inwardly rectifying K+ channel (TWIK)-related acid-sensitive K+ (TASK)-1 channels. The latter was confirmed by the use of TASK-1-deficient mice. Furthermore inhibition of phospholipase Cβ as well as an increase in the intracellular level of phosphatidylinositol-3,4,5-trisphosphate facilitated the muscarinic effect. Our results have uncovered a previously unknown role of c-Src tyrosine kinase in regulating IN function in the brain and identified a novel mechanism by which TASK-1 channels are activated in neurons.
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Affiliation(s)
- Michael Leist
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
| | - Susanne Rinné
- Institut für Physiologie und Pathophysiologie, AG Vegetative Physiologie, Philipps-Universität, Deutschhausstraße 1-2, D-35037, Marburg, Germany
| | - Maia Datunashvili
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
| | - Ania Aissaoui
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
| | - Hans-Christian Pape
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
| | - Niels Decher
- Institut für Physiologie und Pathophysiologie, AG Vegetative Physiologie, Philipps-Universität, Deutschhausstraße 1-2, D-35037, Marburg, Germany
| | - Sven G Meuth
- Department of Neurology, Westfälische Wilhelms-Universität, Albert-Schweitzer-Campus 1, D-48149, Münster, Germany
| | - Thomas Budde
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Robert-Koch-Str. 27a, D-48149, Münster, Germany
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Zhang Z, Huang TQ, Nepliouev I, Zhang H, Barnett AS, Rosenberg PB, Ou SHI, Stiber JA. Crizotinib Inhibits Hyperpolarization-activated Cyclic Nucleotide-Gated Channel 4 Activity. CARDIO-ONCOLOGY 2017; 3. [PMID: 28217366 PMCID: PMC5310672 DOI: 10.1186/s40959-017-0020-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Sinus bradycardia is frequently observed in patients treated with crizotinib, a receptor tyrosine kinase inhibitor used for the treatment of anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC). We investigated whether crizotinib could influence heart rate (HR) through direct cardiac effects. METHODS The direct effect of crizotinib on HR was studied using ECG analysis of Langendorff-perfused mouse hearts. The whole-cell patch clamp technique was used to measure the effects of crizotinib on the hyperpolarization-activated funny current, If, in mouse sinoatrial node cells (SANCs) and hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) activity in HEK-293 cells stably expressing human HCN4. RESULTS Crizotinib resulted in a dose-dependent reduction in HR in isolated intact mouse hearts with a half maximal inhibitory concentration (IC50) of 1.7 ± 0.4 μmol/L. Because ECG analysis revealed that crizotinib (0-5 μmol/L) resulted in significant reductions in HR in isolated mouse hearts without changes in PR, QRS, or QT intervals, we performed whole-cell patch clamp recordings of SANCs which showed that crizotinib inhibited If which regulates cardiac pacemaker activity. Crizotinib resulted in diminished current density of HCN4, the major molecular determinant of If, with an IC50 of 1.4 ± 0.3 μmol/L. Crizotinib also slowed HCN4 activation and shifted the activation curve to the left towards more hyperpolarized potentials. CONCLUSIONS Our results suggest that crizotinib's effects on HCN4 channels play a significant role in mediating its observed effects on HR.
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Affiliation(s)
- Zhushan Zhang
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Tai-Qin Huang
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Igor Nepliouev
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Hengtao Zhang
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Adam S Barnett
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Paul B Rosenberg
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
| | - Sai-Hong I Ou
- Department of Medicine, University of California Irvine School of Medicine, Orange, CA 92868
| | - Jonathan A Stiber
- Department of Medicine, Duke University Medical Center, Durham, NC USA 27710
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Scholz EP, Zitron E, Katus HA, Karle CA. Cardiovascular ion channels as a molecular target of flavonoids. Cardiovasc Ther 2010; 28:e46-52. [PMID: 20633021 DOI: 10.1111/j.1755-5922.2010.00212.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Flavonoids are a class of naturally occurring polyphenols abundant in edibles and beverages of plant origin. Epidemiological studies consistently associate high flavonoid intake with a reduced risk for the development of cardiovascular diseases. So far these beneficial effects have been mainly attributed to nonspecific antioxidant and antiinflammatory properties. However, there is an increasing body of evidence that flavonoids specifically target molecular structures including cardiovascular ion channels. Playing a pivotal role in the regulation of vascular tone and cardiac electric activity, ion channels represent a major target for the induction of antihypertensive and cardioprotective effects. Thus, pharmacological properties of flavonoids on cardiovascular ion channels, ion currents and tissue preparations are being increasingly addressed in experimental studies. Whereas it has become clear that cardiovascular ion channels represent an important molecular target of flavonoids, the published data have not yet been systematically reviewed.
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Affiliation(s)
- Eberhard P Scholz
- Department of Internal Medicine III (Cardiology), University Hospital Heidelberg, Heidelberg, Germany.
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Kim DJ, Seok SH, Baek MW, Lee HY, Na YR, Park SH, Lee HK, Dutta NK, Kawakami K, Park JH. Developmental toxicity and brain aromatase induction by high genistein concentrations in zebrafish embryos. Toxicol Mech Methods 2010; 19:251-6. [PMID: 19750021 PMCID: PMC2739649 DOI: 10.1080/15376510802563330] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Genistein is a phytoestrogen found at a high level in soybeans. In vitro and in vivo studies showed that high concentrations of genistein caused toxic effects. This study was designed to test the feasibility of zebrafish embryos for evaluating developmental toxicity and estrogenic potential of high genistein concentrations. The zebrafish embryos at 24 h post-fertilization were exposed to genistein (1 × 10−4 M, 0.5 × 10−4 M, 0.25 × 10−4 M) or vehicle (ethanol, 0.1%) for 60 h. Genistein-treated embryos showed decreased heart rates, retarded hatching times, decreased body length, and increased mortality in a dose-dependent manner. After 0.25 × 10−4 M genistein treatment, malformations of survived embryos such as pericardial edema, yolk sac edema, and spinal kyphosis were also observed. TUNEL assay results showed apoptotic DNA fragments in brain. This study also confirmed the estrogenic potential of genistein by EGFP expression in the brain of the mosaic reporter zebrafish embryos. This study first demonstrated that high concentrations of genistein caused a teratogenic effect on zebrafish embryos and confirmed the estrogenic potential of genistein in mosaic reporter zebrafish embryos.
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Affiliation(s)
- Dong-Jae Kim
- Department of Laboratory Animal Medicine, College of Veterinary Medicine, Seoul National University, Seoul, Korea
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Baruscotti M, Barbuti A, Bucchi A. The cardiac pacemaker current. J Mol Cell Cardiol 2009; 48:55-64. [PMID: 19591835 DOI: 10.1016/j.yjmcc.2009.06.019] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 06/15/2009] [Accepted: 06/26/2009] [Indexed: 12/17/2022]
Abstract
In mammals cardiac rate is determined by the duration of the diastolic depolarization of sinoatrial node (SAN) cells which is mainly determined by the pacemaker I(f) current. f-channels are encoded by four members of the hyperpolarization-activated cyclic nucleotide-gated gene (HCN1-4) family. HCN4 is the most abundant isoform in the SAN, and its relevance to pacemaking has been further supported by the discovery of four loss-of-function mutations in patients with mild or severe forms of cardiac rate disturbances. Due to its selective contribution to pacemaking, the I(f) current is also the pharmacological target of a selective heart rate-reducing agent (ivabradine) currently used in the clinical practice. Albeit to a minor extent, the I(f) current is also present in other spontaneously active myocytes of the cardiac conduction system (atrioventricular node and Purkinje fibres). In working atrial and ventricular myocytes f-channels are expressed at a very low level and do not play any physiological role; however in certain pathological conditions over-expression of HCN proteins may represent an arrhythmogenic mechanism. In this review some of the most recent findings on f/HCN channels contribution to pacemaking are described.
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Affiliation(s)
- Mirko Baruscotti
- Department of Biomolecular Sciences and Biotechnology, Laboratory of Molecular Physiology and Neurobiology, Università degli Studi di Milano, Centro Interuniversitario di Medicina Molecolare e Biofisica Applicata (CIMMBA), via Celoria 26, 20133 Milano, Italy.
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Rozario AO, Turbendian HK, Fogle KJ, Olivier NB, Tibbs GR. Voltage-dependent opening of HCN channels: Facilitation or inhibition by the phytoestrogen, genistein, is determined by the activation status of the cyclic nucleotide gating ring. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1939-49. [PMID: 19524546 DOI: 10.1016/j.bbamem.2009.06.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Revised: 05/29/2009] [Accepted: 06/08/2009] [Indexed: 11/27/2022]
Abstract
Investigation of the mechanistic bases and physiological importance of cAMP regulation of HCN channels has exploited an arginine to glutamate mutation in the nucleotide-binding fold, an approach critically dependent on the mutation selectively lowering the channel's nucleotide affinity. In apparent conflict with this, in intact Xenopus oocytes, HCN and HCN-RE channels exhibit qualitatively and quantitatively distinct responses to the tyrosine kinase inhibitor, genistein -- the estrogenic isoflavonoid strongly depolarizes the activation mid-point of HCN1-R538E, but not HCN1 channels (+9.8 mV + or - 0.9 versus +2.2 mV + or - 0.6) and hyperpolarizes gating of HCN2 (-4.8 mV + or - 1.0) but depolarizes gating of HCN2-R591E (+13.2 mV + or - 2.1). However, excised patch recording, X-ray crystallography and modeling reveal that this is not due to either a fundamental effect of the mutation on channel gating per se or of genistein acting as a mutation-sensitive partial agonist at the cAMP site. Rather, we find that genistein equivalently moves both HCN and HCN-RE channels closer to the open state (rendering the channels inherently easier to open but at a cost of decreasing the coupling energy of cAMP) and that the anomaly reflects a balance of these energetic effects with the isoform-specific inhibition of activation by the nucleotide gating ring and relief of this by endogenous cAMP. These findings have specific implications with regard to findings based on HCN-RE channels and kinase antagonists and general implications with respect to interpretation of drug effects in mutant channel backgrounds.
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Affiliation(s)
- Anjali O Rozario
- Department of Anesthesiology, Columbia University, New York, NY 10032, USA
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Kryukova Y, Rybin VO, Qu J, Steinberg SF, Robinson RB. Age-dependent differences in the inhibition of HCN2 current in rat ventricular myocytes by the tyrosine kinase inhibitor erbstatin. Pflugers Arch 2008; 457:821-30. [PMID: 18696104 DOI: 10.1007/s00424-008-0565-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 06/27/2008] [Accepted: 07/26/2008] [Indexed: 10/21/2022]
Abstract
Previously, we have shown that murine HCN2 channels over-expressed in newborn and adult cardiac myocytes produce currents with different biophysical characteristics. To investigate the role of tyrosine kinase modulation in these age-dependent differences, we employed the broad spectrum tyrosine kinase inhibitor erbstatin. Our results demonstrated distinct and separable effects of erbstatin on channel gating and current amplitude and a marked age dependence to these effects. In newborn myocytes, erbstatin decreased current amplitude, shifted the activation relation negative, and slowed activation kinetics. The effect on activation voltage but not that on amplitude was absent when expressing a cAMP-insensitive mutant (HCN2R/E), while a C-terminal truncated form of HCN2 (HCN2DeltaCx) exhibited only the voltage dependent but not the amplitude effect of erbstatin. Thus, the action of erbstatin on the activation relation and current amplitude are distinct and separable in newborn myocytes, and the effect on activation voltage depends on the cAMP status of HCN2 channels. In contrast to newborn myocytes, erbstatin had no effect on HCN2 under control conditions in adult myocytes but induced a negative shift with no change in amplitude when saturated cAMP was added to the pipette solution. We conclude that erbstatin's effects on HCN2 current magnitude and voltage dependence are distinct and separable, and there are fundamental developmental differences in the heart that affect channel function and its modulation by the tyrosine kinase inhibitor erbstatin.
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Affiliation(s)
- Yelena Kryukova
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, NY 10032, USA
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Regulation of two-pore-domain (K2P) potassium leak channels by the tyrosine kinase inhibitor genistein. Br J Pharmacol 2008; 154:1680-90. [PMID: 18516069 DOI: 10.1038/bjp.2008.213] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Two-pore-domain potassium (K2P) channels mediate potassium background (or 'leak') currents, controlling excitability by stabilizing membrane potential below firing threshold and expediting repolarization. Inhibition of K2P currents permits membrane potential depolarization and excitation. As expected for key regulators of excitability, leak channels are under tight control from a plethora of stimuli. Recently, signalling via protein tyrosine kinases (TKs) has been implicated in ion channel modulation. The objective of this study was to investigate TK regulation of K2P channels. EXPERIMENTAL APPROACH The two-electrode voltage clamp technique was used to record K2P currents in Xenopus oocytes. In addition, K2P channels were studied in Chinese hamster ovary (CHO) cells using the whole-cell patch clamp technique. KEY RESULTS Here, we report inhibition of human K2P3.1 (TASK-1) currents by the TK antagonist, genistein, in Xenopus oocytes (IC50=10.7 microM) and in CHO cells (IC50=12.3 microM). The underlying molecular mechanism was studied in detail. hK2P3.1 was not affected by genistin, an inactive analogue of genistein. Perorthovanadate, an inhibitor of tyrosine phosphatase activity, reduced the inhibitory effect of genistein. Current reduction was voltage independent and did not require channel protonation at position H98 or phosphorylation at the single TK phosphorylation site, Y323. Among functional hK2P family members, genistein also reduced K2P6.1 (TWIK-2), K2P9.1 (TASK-3) and K2P13.1 (THIK-1) currents, respectively. CONCLUSIONS AND IMPLICATIONS Modulation of K2P channels by the TK inhibitor, genistein, represents a novel molecular mechanism to alter background K+ currents.
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Genistein inhibits voltage-gated sodium currents in SCG neurons through protein tyrosine kinase-dependent and kinase-independent mechanisms. Pflugers Arch 2008; 456:857-66. [PMID: 18228037 DOI: 10.1007/s00424-008-0444-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Revised: 12/13/2007] [Accepted: 01/02/2008] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels play a crucial role in the initiation and propagation of neuronal action potentials. Genistein, an isoflavone phytoestrogen, has long been used as a broad-spectrum inhibitor of protein tyrosine kinases (PTK). In addition, genistein-induced modulation of ion channels has been described previously in the literature. In this study, we investigated the effect of genistein on voltage-gated sodium channels in rat superior cervical ganglia (SCG) neurons. The results show that genistein inhibits Na(+) currents in a concentration-dependent manner, with a concentration of half-maximal effect (IC(50)) at 9.1 +/- 0.9 microM. Genistein positively shifted the voltage dependence of activation but did not affect inactivation of the Na(+) current. The inactive genistein analog daidzein also inhibited Na(+) currents, but was less effective than genistein. The IC(50) for daidzein-induced inhibition was 20.7 +/- 0.1 microM. Vanadate, an inhibitor of protein tyrosine phosphatases, partially but significantly reversed genistein-induced inhibition of Na(+) currents. Other protein tyrosine kinase antagonists such as tyrphostin 23, an erbstatin analog, and PP2 all had small but significant inhibitory effects on Na(+) currents. Among all active and inactive tyrosine kinase inhibitors tested, genistein was the most potent inhibitor of Na(+) currents. These results suggest that genistein inhibits Na(+) currents in rat SCG neurons through two distinct mechanisms: protein tyrosine kinase-independent, and protein tyrosine kinase-dependent mechanisms. Furthermore, the Src kinase family may be involved in the basal phosphorylation of the Na(+) channel.
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Molecular basis for genistein-induced inhibition of Kir2.3 currents. Pflugers Arch 2007; 456:413-23. [DOI: 10.1007/s00424-007-0391-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 10/25/2007] [Accepted: 11/05/2007] [Indexed: 01/01/2023]
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